Assembly Lead Time Reduction in a Semiconductor Capital Equipment Plant
through Improved Material Kitting
by
Sonam Jain
Bachelor of Technology in Electronics and Electrical Communication Engineering
Indian Institute of Technology Kharagpur, 2008
Submitted to the Department of Mechanical Engineering
in Partial Fulfillment of the Requirements for the Degree of
O
INOLOGY
Master of Engineering in Manufacturing
LIBRARIES
at the
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
September 2014
( 2014 Sonam Jain
All rights reserved
The author hereby grants to MIT permission to reproduce and to
distribute publicly paper and electronic copies of this thesis document in whole or in part
in any medium now known or hereafter created.
redacted
Signature
.........................
Sig n at u re of A utho r.................. ........................................................
Sonam Jain
Department of Mechanical Engineering
August 15, 2014
Certified by.......................................
Signature redacted_
red acted_
Stephen C. Graves
Abraham Siegel Professor of Management Sciences
Thesis Supervisor
Signature redacted,
. ................................................................................
David E. Hardt
Ralph E. and Eloise F. Cross Professor of Mechanical Engineering
Chairman, Committee for Graduate Student
A cce pte d by...............................................................................
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2
Assembly Lead Time Reduction in a Semiconductor Capital Equipment Plant
through Improved Material Kitting
by
Sonam Jain
Submitted to the Department of Mechanical Engineering on August 15, 2014
in partial fulfillment of the requirements for the degree of
Master of Engineering in Manufacturing
Abstract
Manufacturing operations were studied at a semiconductor capital equipment manufacturing plant,
with an aim to reduce the production time of their longest lead time module.
Preliminary analysis was done by observing the assembly and test operations on the production floor,
and material handling operations at the warehouse. Detailed time studies were then performed on the
assembly and test processes, to establish baseline measurements and to gather in-depth information on
the value added and non-value added activities. It was found that 18% of the assembly activities were
non-value added activities, 28% of which were related to material handling on the production floor.
Based on the analysis a new kit design and kitting process were developed, which enabled parts to arrive
from the warehouse in kits specific to each assembly procedure performed on the module. A method of
indicating shortages was also proposed. The new design and process also facilitated Just-in-Time
ordering and arrival of parts.
The new kitting process was piloted, and based on two trial runs it was found that it reduced material
handling time on the production floor by 70% and overall time spent on non-value added assembly
operations was reduced by 20%.
Thesis Supervisor: Stephen C. Graves
Abraham Siegel Professor of Management Sciences
3
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4
Acknowledgements
I would like to express my sincere gratitude and thank everyone who made this thesis and my journey at
MIT possible.
First and foremost, I would like to thank MIT and Varian Semiconductor Equipment Associates for giving
me the opportunity to work on this project. I would like to thank my thesis advisor Professor Stephen C.
Graves, for his mentorship and guidance. The thesis would not have been possible without his invaluable
advice and feedback. I would also like to thank Jennifer Craig for reviewing my thesis and providing
insightful feedback.
I would like to thank my supervisor Daniel Martin at Varian Semiconductor Equipment Associates for
believing in my ideas, and for his support and help in implementing them. I would like to thank
Christopher Girardin, David Adkins, Jonathan Smith, Robbie Roberts, Vincent Cook, Brian McLaughlin,
and Maria Doyle, who were an integral part of my project and made it possible. I would also like to
thank Rusty Lake, Juan Sanchez-Caldero, Ryan Santos, Michael Ercolani, Robert Muise, Andrew
Steadman, Mark Tedesco, Anthony Ciaramitaro, Gary Hoyt and Cathy Cole for their help and feedback
on my project. I would also like to thank Debrework Legesse for all her help during my stay at Varian
Semiconductor Equipment Associates.
I would like to sincerely thank Blake Sedore, with whom I shared several successful collaborations at
MIT, this project being one of them. He was an awesome teammate and I am grateful for all his help and
support throughout my stay at MIT.
I would like to thank Professor David Hardt and Jose Pacheco for their guidance and help throughout the
program. This program provided me with a great learning opportunity and a platform to meet some
amazing people. I would like to thank the other members of the M.Eng cohort, with whom I worked and
socialized over the last year. They made my stay at MIT truly enjoyable. I would especially like to thank
Dale Thomas for being a great friend.
Most importantly, I would like to thank my husband for his unending support, encouragement, and
patience through this intense yet exciting period of my life. I would also like to thank my parents for
their love, support, and all the sacrifices they have made for me. I will be forever indebted to them.
5
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6
Table of Contents
Introduction...........................................................................................................................13
1.
1.1.
1.2.
1.3.
Sem iconductor M anufacturing .............................................................................................
13
1.1.1. Industry O verview ........................................................................................................
13
1.1.2. Sem iconductor Fabrication Process ................................................................................
14
1.1.3. Ion Implantation.................................................................................................................
15
Varian Sem iconductor Equipm ent Associates Background...................................................
15
1.2.1. Prod uct Line .......................................................................................................................
16
1.2.2. M achine Architecture.....................................................................................................
17
1.2.3. Universal End Station Architecture ................................................................................
20
Problem Statem ent ....................................................................................................................
21
1.3.1. M otivation ..........................................................................................................................
21
1.3.2. Problem Identification.....................................................................................................
21
1.3.3. Approach ............................................................................................................................
23
1.4. Thesis Organization....................................................................................................................
24
Description of Current Operations ......................................................................................
25
2.1.
UES Production Process Overview .........................................................................................
25
2.2.
W orkforce Scheduling................................................................................................................
26
2.3.
Assem bly and Test Process ....................................................................................................
27
2.4.
M aterial Inventory .....................................................................................................................
28
2.5.
Warehouse Operations ..............................................................................................................
29
2.
2.5.1. Overview ............................................................................................................................
29
................................................
30
2.5.2. Layout.............
2.5.3. Picking Process ...................................................................................................................
7
31
3.
Assem bly and Testing Time Studies ........................................................................................ 34
3.1.
Objectives ................................................................................................................................... 34
3.2.
M ethodology .............................................................................................................................. 34
3.3.
Assem bly Time Study ................................................................................................................. 36
3.3.1. Data and Observations ....................................................................................................... 36
3.3.2. Sum mary ............................................................................................................................ 39
3.4.
Testing Time Study ..................................................................................................................... 40
3.4.1. Data and Observations ....................................................................................................... 40
3.4.2. Sum mary ............................................................................................................................ 42
4.
Analysis of Non-Value Added Assembly Activities .................................................................. 43
4.1.
Objectives ................................................................................................................................... 43
4.2.
M ethodology .............................................................................................................................. 43
4.3.
Non-value Added Assem bly Activities ........................................................................................44
4.3.1. Analysis ............................................................................................................................... 44
4.3.2. Sum mary ............................................................................................................................ 47
4.4.
Existing M aterial Kitting Process ................................................................................................47
4.4.1. Analysis ............................................................................................................................... 50
4.4.2. S u m m a ry ............................................................................................................................ 51
5.
Theoretical Fram ework .......................................................................................................... 52
5.1.
Lean Philosophy ......................................................................................................................... 52
5.2.
M aterial Feeding Systems ..........................................................................................................53
5.3.
M aterial Kitting ..........................................................................................................................54
5.4.
Previous M IT Projects at VSEA .................................................................................................... 56
6.
New Kitting Process ............................................................................................................... 57
6.1.
Objectives ...................................................................................................................................57
6.2.
New Kit Design Features ............................................................................................................57
8
6.3.
Design Development M ethodology ........................................................................................... 59
6.3.1. Sorting Parts by Sub-module .............................................................................................. 60
6.3.2. Sorting Parts by Size ........................................................................................................... 62
6.3.3. Kit Design Selection ............................................................................................................ 65
6.3.4. Kit Design Development ..................................................................................................... 67
6.4.
New Kitting Process Flow ........................................................................................................... 68
6.5.
Advantages of the New Kit Design and Kitting Process .............................................................. 70
7.
Im plem entation and Results .................................................................................................. 72
7.1.
M ethodology .............................................................................................................................. 72
7.2.
Im plem entation: Phase I............................................................................................................ 73
7.2.1. Objectives ........................................................................................................................... 73
7.2.2. Im plementation Process .................................................................................................... 73
7.2.3. Results ................................................................................................................................ 74
7.2.4. Sum m ary ............................................................................................................................ 77
7.3.
Im plementation: Phase 11 ........................................................................................................... 77
7.3.1. Objectives ........................................................................................................................... 77
7.3.2. Im plem entation Process ....................................................................................................77
7 .3 .3 . R e su lts ................................................................................................................................ 80
7.3.4. Sum m ary ............................................................................................................................ 82
7.4.
Discussion ................................................................................................................................... 82
7.5.
Next Steps .................................................................................................................................. 84
Recom m endations ................................................................................................................. 86
9.
Conclusions ............................................................................................................................ 88
Appendix ............................................................................................................................................ 89
References ......................................................................................................................................... 91
9
List of Figures
Figure 1: V IlSta pro d uct line .......................................................................................................................
17
Figure 2: Schematic of ion implanter [6]................................................................................................
18
Figure 3: Universal End Station schematic [8].........................................................................................19
Figure 4: D M A IC m ethodology ...................................................................................................................
Figure 5
UES production process flow .................................................................................................
23
26
Figure 6: UES production floor layout ..................................................................................................
28
Figure 7: W arehouse layout .......................................................................................................................
31
Figure 8: Picking and consolidation process ...........................................................................................
33
Figure 9 : Logboo k structure .......................................................................................................................
35
Figure 10: Overall state of UES module during assembly [6]................................................................
37
Figure 11: Overall UES assembly active time vs inactive time (a) including unavailable production hours
(b) excluding unavailable production hours...........................................................................................
37
Figure 12: Overview of the assembly time study [6]..............................................................................
38
Figure 13: (a) Active and Inactive time during assembly; (b) Breakdown of Active time into VA, NVA-P,
and NVA-M time; (c) Breakdown of Inactive time into NVA-W and NVA-1 time..................
39
Figure 14: Overall state of the module during testing [6].....................................................................
40
Figure 15: Overall UES test active time vs inactive time (a) including ECO (b) excluding ECO............... 41
Figure 16: Overview of the testing time study [6] .................................................................................
41
Figure 17: (a) Active and Inactive time during testing; (b) Breakdown of Active time into VA, NVA-P, and
NVA-M time; (c) Breakdown of Inactive time into NVA-W and NVA-1 time...............................................42
Figure 18: Value added vs non-value added time per sub-module .......................................................
45
Figure 19: Non-value activities during assembly....................................................................................
46
Figure 20: Assembly production kit parts .............................................................................................
49
Figure 21: Staging of production kit parts on the kit rack on UES flowline ............................................
49
Figure 22 :N ew Kit D esign ...........................................................................................................................
58
Figure 23: Four phases of development of the new kitting process .....................................................
60
Figure 24: Parts distribution for existing sub-module structure ............................................................
61
Figure 25: Parts distribution for new sub-module structure...................................................................61
Figure 26: Parts sorted by sub-module and size for the current sub-module structure........................ 62
10
Figure 27: Parts sorted by sub-module and size for the new sub-module structure............................. 63
Figure 28: Bin-boxes on a rack system (a) Fixed bench rack [10] (b) Mobile rack [11].......................... 66
Figure 29: Bin-boxes on a cart system [12]...........................................................................................
67
Figure 30: Modified bin-boxes on a cart system ....................................................................................
68
Figure 31: Process Flow (a) Existing material handling process (b) New kitting process....................... 70
Figure 32: Implementation Methodology ..............................................................................................
72
Figure 33: Bin-boxes on a cart kit design ...............................................................................................
74
Figu re 34 : Final Kit D esign ..........................................................................................................................
76
Figure 35: Consolidation of parts into the kits at the warehouse ..........................................................
79
Figure 36: Cart strapped down to the truck for transportation ............................................................
80
Figure 37: Phases of implementation ....................................................................................................
84
11
List of Tables
Table 1: Assembly and test times for the different modules ................................................................
20
Table 2: Shift structure for the UES line ................................................................................................
27
Table 3: Order types and warehouse order fulfillment time targets .....................................................
32
Table 4: Z-pick kit codes for UES assembly ...........................................................................................
48
Table 5: Different Material Feeding Systems [16]..................................................................................
53
Table 5: Size classification of parts.............................................................................................................62
Table 6: Bin requirement per sub-module .............................................................................................
64
Table 7: Overall bin requirements for existing and new sub-module structures....................................64
Table 8: Changes in parts ordering ............................................................................................................
75
Table 9: Old kit olds and new kit codes..................................................................................................
78
12
1. Introduction
Varian Semiconductor Equipment and Associates (VSEA) is a wholly owned subsidiary of Applied
Materials based in Gloucester, Massachusetts that designs, manufactures, markets, and services ion
implantation systems, which are widely used in semiconductor fabrication. The ion implantation tool
manufactured at VSEA is broadly divided into four modules- the Source, the Analyzer, the Corrector and
Universal End Station (UES). These four modules are assembled and tested in parallel. The assembly and
test lead time of the UES module is significantly greater than that of the other three modules, making it
the bottleneck operation. This thesis describes the work done in analyzing the current assembly, test,
and warehouse operations, and the implementation of an improved material kitting process, which
significantly reduces the non-value added time in assembly, resulting in an overall lead time reduction of
the UES module.
This section of the thesis briefly describes the semiconductor industry, the wafer manufacturing process,
and the ion implantation process. It also gives a background of VSEA and describes the machine
architecture of the ion implantation machine and the UES module. Finally it discusses the advantages of
having a shorter lead time and the approach adopted to achieve this.
1.1. Semiconductor Manufacturing
Semiconductor manufacturing is a highly competitive business where each manufacturer seeks to
provide products that consume the least power and fastest processing speed at the least cost. The
industry is characterized by continuous growth, but in a cyclical pattern with high volatility with respect
to demand of the products. The industry also operates on high degrees of flexibility and innovation to
keep up with the rapid change of pace of the market.
1.1.1.
Industry Overview
The semiconductor industry can be divided into two segments - microchip manufacturers and capital
equipment manufacturers. The microchip segment produces microprocessor chips, memory chips,
system on chips (SOC), and other commodity integrated circuit chips. Companies in this segment include
Intel, Samsung, SK Hynix, Taiwan Semiconductor Manufacturing Company (TSMC), Analog Devices,
Global Foundries etc.
The capital equipment segment manufactures equipment used in the production of microchips. This
segment is further divided into two segments- Front End of the Line (FEOL) and Back End of the Line
13
(BEOL). In FEOL components like transistors, diodes, resistors, and capacitors are formed, while in BEOL
the wires and interconnects joining the front end components are formed. VSEA traditionally has
produced equipment that is used to form FEOL components. Other capital equipment manufacturers
include Tokyo Electron Ltd., Axcelis Technologies, SEN Corporation etc.
1.1.2.
Semiconductor Fabrication Process
Semiconductor fabrication is a complex multi-step process which involves creation of electronic circuits
on a silicon wafer. This process is performed in specialized facilities called 'fabs' and takes six to eight
weeks. The manufacturing process can be broadly divided into four steps- Wafer Processing, Die
Preparation, IC Packaging, and IC Testing.
The process starts with growing an ingot of pure silicon, by placing a perfectly structured silicon seed
into molten silicon. The molten silicon forms a chemical bond with the seed and an ingot of pure silicon,
mimicking the properties of the seed, can then be pulled out as the silicon cools down. The diameter of
the ingot is typically 200 mm or 300 mm. The ingot is then sawed into thin wafers and made ready for
further processing.
Wafer Processing involves creation of the integrated circuits on the silicon wafer. This includes creation
of transistors, capacitors, resistors, diodes, wires, and interconnects. There are several different steps
and processes involved in Wafer Processing, which can be grouped into four categories- Deposition,
Removal, Patterning, and Modification of Electrical Properties. Deposition involves growing, coating, or
transferring material onto the wafer. Processes include Physical Vapor Deposition (PVD), Chemical Vapor
Deposition (CVD), Atomic layer Deposition (ALD), and Molecular Beam Epitaxy (MBE). Removal process
removes material from the wafer and includes processes like Wet Etching, Dry Etching, and Chemical
Mechanical Planarization (CMP). Patterning involves shaping or altering the deposited material and is
also known as Lithography. Modification involves creating transistor sources and drains through doping.
Processes involved here are Ion Implantation, Furnace Annealing, and Rapid Thermal Annealing (RTA).
After wafer processing the wafer is put through testing to check for damage.
Die Preparation is the step where the wafer is prepared for IC packaging and testing. It involves two
steps - Wafer Mounting and Wafer Dicing. In wafer mounting the wafer is mounted on a plastic tape
attached to a ring, which is then followed by wafer dicing where the wafer is cut into multiple identical
rectangular pieces called dies.
14
IC packaging involves encasing the die in a supporting case to prevent physical damage. The case also
supports the electrical contacts that connect the device to a circuit board. The packaged chips are then
put through further IC Testing to ensure that there was no damage during packaging [1].
1.1.3.
Ion Implantation
Ion Implantation is a method of introducing dopants in the wafer. The purpose of doping is to introduce
impurities into pure silicon that will modulate its electrical properties. A hole can be created using a ptype dopant like boron and electrons can be created by using n-type dopants like arsenic and
phosphorous. Ion implantation is used to create p-n junctions, sources, and drains of transistors, which
are the building blocks of all electronic circuits.
Ion implantation starts with creating ions of the desired element from its gas form to ensure high levels
of purity. The ions are then electrostatically accelerated to high energy and made to impinge with the
substrate, onto which they get implanted.
An implant is characterized by the dose and the depth of the penetration of the dopant. The dose is the
integral over time of the ion current.
The depth of penetration of the ions is determined by the energy
of the ions, the ion species, and the composition of the substrate. Typical ion energies are in the range
of 10 -500 keV and the depth of penetration is 10 nanometer to 1 micrometer [2].
1.2.Varian Semiconductor Equipment Associates Background
Varian Associates was founded in 1948, in San Carlos, California, by brothers Russell and Sigurd Varian,
with the aim to commercialize the klystron technology developed by them. Klystrons are specialized
linear beam vacuum tubes, used as amplifiers for electromagnetic waves at high frequencies. In 1975, it
acquired Extiron Corporation, based in Gloucester, Massachusetts, which was founded in 1971 and
manufactured ion implantation equipment. In 1999, the company spun out the Gloucester facility into
Varian Semiconductor Equipment Associates (VSEA) [3].
Applied Materials, Inc. is a leading producer of equipment, services, and software that enable
manufacture of semiconductor chips, flat panel displays, energy efficient glass, and solar photovoltaic
cells. It was founded in 1967 in Santa Clara, California. Applied Materials's initial efforts were focused on
developing Chemical Vapor Deposition equipment, but over the years the company has developed a
wide portfolio of product offerings. In 2011, Applied Materials acquired Varian Semiconductor
Equipment Associates [4].
15
1.2.1.
Product Line
VSEA offers five different single wafer implanter products, which cover the full range of dose and energy
requirements of semiconductor doping applications. These are medium current, high current, high
energy, ultra high dose, and Solion
TM
[5].
Medium Current implanters are characterized by low dose and very low energy of the dopant. These
implanters are widely used in logic and memory chips. They provide superior overall throughput,
precision doping, and high levels of contamination control.
High Current implanters are characterized by high dose and low energy of the dopant. They provide high
levels of implant angle accuracy, beam steering correction, and tilt angle capability in addition to high
productivity and contamination control. High current implanters are used in logic, memory, and foundry
applications, especially in advanced device fabrication. High Current implanters have the highest
demand among all the implanters and a steady increase in demand is anticipated, given its use in
advanced microchip fabrication. In 2010 a new version of the high current implanter called the Trident
was introduced, which provides high device performance, energy purity, micro-uniformity, and tight
angle control.
High Energy implanters are used for low dose and very high energy applications. These implanters are
primarily used in memory chip manufacturing, where increased device packing density is required.
Ultra High Dose implanters are characterized by very high dose and very low energy of the dopant. This
category of implanters uses a technology different from the medium current, high current, and high
energy tools, in which a focused ion beam is used. Here, a plasma of the dopant is created in the
chamber where the wafer is held. A pulsed DC voltage is then applied to the wafer platen which draws
ions into the wafer proportional to the DC pulse. Ultra high dose doping is required in DRAM and flash
memory chip fabrication.
Solion
TM
ion implanters were introduced in 2010 for use in solar cell manufacturing. They differ from
regular ion implanters as they handle square solar wafers, instead of round wafers. These implanters
enable high throughput, in-situ patterning, and junction engineering capabilities- all of which are critical
for high efficiency solar cell design.
All the products use the same software platform called VIlSta and allow for high degree of commonality
in subsystems and overall architecture. The entire VlISta product family can be seen in Figure 1.
16
VllSta PLATFORM
Medium Current
High Current
High Energy
Ultra High Dose
Sol ion TM
VIISta 810XP
VIISta 81OXE
VIISta 900XPT
VIISta H CS
VIISt a T ride nt
VIISta H E
VIISta 3000
VIISta PLAD
VIISta Solion TMV
Figure 1: VllSta product line
Demand for High Current ion implanters is the highest, followed by Medium Current and then High
Energy; and within the High Current category, the Trident model is the most popular. The Trident
assembly and test process is also more complex and labor intensive as compared to the other models.
For these reasons, the project and thesis focus specifically on the Trident model, however the proposed
improvements can be easily extended and applied to all other models.
1.2.2.
Machine Architecture
VSEA's ion implanters are automated production tools that enable implantation of a single dopant
species onto a silicon wafer, one wafer at a time. The ion beam is produced to a specific design criteria
or process recipe using the control system. The system allows for the selection of the dopant species,
dose, beam energy, implant angle, and the number of processing steps. The ion implanter consists of
five modules- the Source module, the Analyzer module, the Corrector module, and the Universal End
Station module, and the Equipment Front End Module (EFEM) as seen in Figure 2.
The Source module extracts and focuses the ions. Boron Trifluoride, Arsine, and Phosphine are the
standard gases used by VSEA implanters to generate dopant ions. The ions are produced in a cathode
source, and then extracted by creating a voltage difference between two power supplies. The ion beam
is focused vertically and spread horizontally during extraction, to allow for better beam transmission to
the Beamline [7].
17
I
I
Beam Line
Corrector
Analyzer
=
90
Magnet
Beam Path
I*Magnet
Wafer Path
4
Facilities
Gas Box
Process
Facilites
Chamber
I
Source
4-j
I
Source
i
|
Wafer
H
II
g
System
Universal End Station
I
I
0
Equipment Front
End Module
Figure 2: Schematic of ion implanter [6]
The Beamline is where the ion beam is decelerated, focused, analyzed, measured, and made parallel.
The Beamline consists of two modules- the Analyzer module and the Corrector module. In the Analyzer
module, the beam leaving the source module is passed through a quad lens which focuses the beam.
This focused beam then passes through the 90 degree analyzer magnet. This electromagnet creates a
strong field that bends the beam by 90 degrees, to allow for the ions traveling at correct speeds (beam
energy) to make it through, while eliminating undesired ions. The analyzed beam passes through two
more lenses for focusing, before entering the Corrector module. This module houses a 55 degree
magnet, which bends the beam by 55 degrees, so that it enters the process chamber and strikes the
wafer at a 90 degree angle [7].
The Universal End Station (UES) consists of two sections - the wafer handling section and the process
control section. The wafer handling section moves wafers from atmosphere to high vacuum, orients the
wafer, and places it on the platen for implantation. The process control chamber interfaces with the
Beamline module and is where the beam is profiled and measured, and this is where the implantation
takes place. A schematic diagram of the UES module can be seen in Figure 3.
18
Equipment Front End Module
Loadport
Loadport
Universal End Station
I
I
I
Loadlock
I
(Left)
Wafer Handler
Robot (Left)
I
Transfer
I
Roplat
RobprtOrienter
Loadport
Loadport
II
B:em
Wafer Handler
Robot (Right)
Loadlock
(Right)
1 -Figure 3: Universal End Station schematic [8]
The wafer transport section of the UES uses the buffer robot located in the Equipment front End Module
(EFEM) to transport wafers to the load locks. The wafers are placed in the EFEM either manually or
through an automated delivery system. A mapping laser on the buffer transport robot determines the
presence of wafers and then delivers them to the pass through cassette in the left or right load lock.
After the mapped wafers are loaded, the load lock door closes and the load lock is pumped to high
vacuum. After the high vacuum state is reached, the load lock isolation valve opens up to the wafer
transfer chamber. Here another robot picks up a single wafer and transfers it onto an orienter, where
the notch on the wafer is repositioned to align the crystal orientation to match the process recipe. The
opposite robot arm then moves the wafer from the orienter to the platen, where it is electrostatically
clamped for implantation. After implantation, the wafer is placed back in the load lock, and after all
wafers in the cassette are implanted, the load lock isolation valve closes and is vented to the
atmosphere. The buffer transfer robot then transfers the wafers back to the EFEM [8].
The Source, Analyzer, Corrector, and UES module are assembled and tested in parallel, and shipped
separately due to size constraints. They get integrated directly at the client site, unless the client
specifically requests a complete functional test, in which case they are integrated and tested at the
Gloucester facility and then again broken down to the four modules for shipment. The EFEM module is a
vendor supplied assembly and is not built by VSEA. The average lead times for assembly and test for
each of the modules can be seen in Table 1 (the averages are based on lead times of the Tridents built
between November 2013 and July 2014). UES production is evidently the bottleneck process, as its lead
time is significantly larger than that of the other three modules.
19
Table 1: Assembly and test times for the different modules
1.2.3.
Module
Assembly Lead Time
Testing Lead Time
Total Lead Time
Source
2 days
2 days
4 days
Analyzer
0.6 days
0.4 days
1 day
Corrector
1.2 days
0.6 days
1.8 days
UES
5.5 days
5.4 days
10.9 days
Universal End Station Architecture
The Universal End Station consists of six major assemblies: the Frame, Top Process Chamber, Bottom
Process Chamber, Wafer Handler, Electronics Control Rack, and Tool Control Rack. These assemblies are
built independently and then integrated to form the complete UES module. After integration, the UES
module is put through a series of functional tests for qualification.
Frame: The weldment frame forms the base of the UES module onto which the remaining assemblies
are mounted. The frame is a High Level Assembly (HLA) that is outsourced to an external supplier. It
comes with all of the harnessing and routing done, however, some re-routing is required.
Top Process Chamber: The Top Process Chamber houses the cryo pumps (two for Trident and three in
other models) that are required to create high vacuum in the process chamber. The top process
chamber also houses gate valves that are used to regulate the cryo pumps.
Bottom Chamber: The bottom process chamber houses the rotating platen (roplat). The roplat is
mounted to the tilter assembly that provides X-axis movement to adjust the implant angle. The tilter
and the platen are mounted on an air bearing that provides for Y-axis movement and provides
functionality for incident angle correction and multiple angle implants. The wafer is secured to the
platen through electro-static clamping.
Wafer Handler: The wafer handler has three major components: the load locks, robotic arms, and the
orienter. The left and right load locks are used to hold wafers. Each load lock contains a wafer cassette
platform which holds up to 25 wafers, wafer mapping lasers to detect the location of wafers in the
cassette, an elevator drive to move the cassette through the laser beam for wafer mapping, a load lock
isolation valve to separate the load locks from the high vacuum area of the wafer handler, and a turbo
pump to create vacuum in the load locks. The robotic arms are used to move individual wafers from the
cassette in the load lock to the orienter, then from the orienter to the platen for implant, and then back
20
to the cassette after implantation. The robot arms are driven by theta and radial motors with optical
encoders for precise and repeatable positioning. The purpose of the orienter is to determine wafer
eccentricity and notch position. The orienter then re-positions the notch so that the crystal orientation
of the wafer matches the implant recipe. The orienter uses LEDs to establish the rotational position of
the notch.
Electronics Rack: The chassis of the electronics rack is supplied with the Frame HLA. It is then removed
from the frame and built separately. It houses special power supplies and Analog-Digital-Input-Output
interface modules (ADIO).
Tool Control Rack: The tool control rack houses specific control computers and control modules for the
process chamber and wafer handler.
1.3. Problem Statement
1.3.1.
Motivation
The UES module is the longest lead time module in the ion implanter production process. Its lead time is
significantly greater than the lead times of the other three modules, and lowering it will have several
benefits.
Firstly, lowering lead time of the UES module will reduce the overall lead time of the entire machine.
This will result in shorter delivery and response times to clients, making the production process more
efficient.
Secondly, it will reduce the work in process inventory (WIP). The machines are high in cost and have
expensive parts.
Reducing WIP will result in less money tied up in in-process inventory. It will also
reduce clutter on the shop floor and offer more visibility of the production flow process. Furthermore, it
will reduce the risks associated with obsolescence and engineering changes.
Thirdly, in order to offer high levels of customer service, VSEA allows its customers to change or cancel
their orders at any point in the production process without any penalty. Short lead times will help in
reducing the risks associated with such changes.
1.3.2.
Problem Identification
The problem identification process started with observing the UES production process and conducting
interviews with people involved. This included the production manager, production supervisor,
21
production lead, production controller, manufacturing engineers, UES assemblers, UES technicians, and
material handlers. Detailed time studies were then carried out to develop a deeper understanding of the
process and the challenges associated with it. The details of the time studies and the observations are
documented in Chapter 3 of this thesis. Analysis of the time study data resulted in identification of three
major areas of improvement, each of which independently contributes towards reduction of UES lead
time. The three projects werei)
Reduction of assembly lead time through improved material kitting
ii)
Reduction of assembly lead time through constraint based scheduling
iii)
Reduction of testing lead time through optimized testing protocols
This thesis documents the work done in reduction of non-value added assembly time through kitting of
parts received from the warehouse. The time study showed that 18% of the assembly labor hours are
spent in non-value added activities. Of this, 28% of the time is spent in looking for parts. Approximately
200 parts are delivered from the warehouse for assembly, and these parts are not sorted by procedure
or operation. Also, if there are any shortages, it is not known until the assembler specifically looks for
that part. The goal of this project was to design and implement a new kitting process which would
address these issues and ultimately result in reduction of the overall lead time.
Reduction of idle time through improved sequencing and scheduling of operations was looked into and
documented by Sedore in his thesis [6]. The assembly time study indicated that the current grouping of
tasks is not ideal, leading to dependencies between tasks across groups. Since dependencies are not
clearly known, critical scheduling of tasks to achieve minimum lead time is also not known. Sedore's
research focuses on re-organizing and re-grouping tasks to optimize their sequencing, and then
developing build schedules for different production rates, with an aim to reduce idle time, WIP, and
overall assembly the lead time.
Reduction of non-value added testing time was looked into and documented by Bhadauria in her thesis
[9]. Since most activities during testing are performed to ensure compliance and do not change the
form, fit, or function of the machine, these can be considered to be non-value added. Bhaduaria
evaluates the possibility of introducing automated testing, parallel testing, and simultaneous build and
test as a means to reduce the testing lead time.
22
1.3.3.
Approach
The team adopted the DMAIC methodology as a tool for problem solving. DMAIC is a data-driven lean
tool that is used to improve existing processes and is widely used in the industry. This methodology
breaks down the problem solving process into five discrete ordered phases- Define, Measure, Analyze,
Improve, and Control. See Figure 4.
-
-
-
---
INDIVIDUAL
----------------------------
--
-
-
-
-
-
-
-
-
-
--
-
-
-
-
-
-
-
-
-
-
GROUP
Figure 4: DMAIC methodology
In the Define phase, the problem was identified and the goal was defined. The project scope and
resource constraints were also identified.
In the Measure phase, the existing process was studied and data was gathered to establish the baseline
for future improvement. Historical data was gathered, process flow maps and value stream maps (VSM)
were drawn, and detailed time studies were performed for the assembly and test processes. The Define
and Measure milestones of the project were accomplished as a group, at the end of which three
potential areas of improvement were identified.
In the Analyze phase, each team member picked an area of focus and thoroughly analyzed the data
gathered in the Measure phase. Gantt charts, pareto charts, and other statistical analysis tools were
used, and root causes of problems were identified.
In the
Improve
phase, process improvement
ideas were generated, developed, tested, and
implemented. This included implementing a new material kitting procedure, which reduced the nonvalue added spent in searching and sorting parts at the production floor and the warehouse;
implementing a new build schedule, which optimized sequencing of tasks and reduced idle time; and
proposing a set of recommendations to reduce non-value activities in testing.
In the Control phase, measures were implemented to sustain the proposed changes. This involved
creating reference documents, and updating existing documents and business systems.
23
1.4. Thesis Organization
The thesis has been structured in keeping with the DMAIC methodology discussed in the previous
section.
Chapter 2 forms the Define section and describes the current UES production operations. It briefly
describes the assembly and test process, the material flow, the workforce schedule, and the warehouse
operations.
Chapter 3 forms the Measure section of the thesis and documents the time studies performed on the
assembly and test processes. It states the objectives and describes the methodology for the time
studies, and then presents the data gathered and observations made.
Chapter 4 forms the Analysis section of the thesis and documents the analysis of the non-value added
operations in UES assembly. It analyzes the various non-value added activities with an aim to find
specific areas for improvement. After establishing that material handling is the most significant nonvalue added activity, it analyzes the existing material handling process and identifies the inefficiencies in
it.
Chapter 5 documents the literature review performed prior to proposing and implementing any
improvement steps.
Chapter 6 forms part of the Improve section and proposes a new kit design and a new kitting process.
The goals for the new kitting process are defined, and the methodology used for developing it is
discussed. The features of the proposed kit design and the potential advantages of the new kitting
process are also discussed.
Chapter 7 forms the Improve and Control sections of the thesis. It documents the procedure followed for
the implementation of the new kitting process and discusses the results. It also describes the next steps
in the implementation process which need to be carried out by VSEA.
The thesis concludes with recommendations for further improvement of operations at VSEA.
24
2. Description of Current Operations
2.1. UES Production Process Overview
The production process starts with establishing a build start date, also known as the 'lay-down' date.
The Material Resource Planning (MRP) system back calculates this date based on the delivery date
specified by the customer and the average lead time information that is entered into the system based
on historical data. The lead time of the build is measured from the lay-down date to the date that it
completes testing. The lay-down rate can vary from 1 machine per day in high season to 1 machine per
week in the low season.
Each machine is built-to-order and the details of the build are documented in a 'production build order'
(PBO). The machines can have special features called 'options', in addition to the basic features.
Machines also have 'selects', where typically one out of two available features needs to be selected. The
options and selects are documented in the PBO, and the assemblers and testers use this document to
build the tool. A PBO can be changed upon customer request up to 10 days before the ship date and
such changes are very common.
Material inventory is stored at five different locations, and centrally coordinated using the MRP system.
The inventories that feed the production line are: Supplier-managed Inventory, Warehouse Inventory,
Supermarket Inventory, Gold-Square Inventory and In-line Inventory. The production lead places the
order for the warehouse parts 24 hours before the scheduled laydown, and up to 5 days ahead for the
supermarket parts. The supplier inventory and gold square inventory are managed through a Kanban.
On the lay-down date, building of all six assemblies starts in parallel, depending on the availability of the
assemblers. Once the six assemblies are built, they are integrated, and this is followed by testing. This
entire process for the Trident machine currently averages 10.9 days, with assembly and integration
taking an average of 5.5 days and testing averaging 5.4 days. Once the machine completes testing, it is
sent to the packaging and shipping department. The different modules - Source, Analyzer, Corrector,
UES, and the Equipment Front End Module are packaged and shipped separately. This method of
separate shipping is called 'Smart Ship'.
The Value Stream Map (VSM) for the current UES production process can be seen in Figure 5. It shows
the process flow, material flow, and information flow during the complete UES production cycle.
25
Production Control
Customer
Buid
Suppliers
Bottom
Integration
Warehouse
Supermarket
Gold
Square
I
Inline
Inventory
Testing
Prep/Ship
Wafer
Handler
E-CR,L
__-___ _i'
Asebyand
Test Lead Time
I
6 days
5.8fdas
Figure 5 : UES production process flow
2.2. Workforce Scheduling
Production takes place in four shifts. On weekdays there are two 8.5 hour shifts and one 10.5-hour shift
on each day, except for Friday when there are only the first two shifts. On weekends there is one 12hour shift on each day. Each shift has a production supervisor, assemblers, and technicians. The workforce is a mix of full-time workers and contractors. The shift structure and the workforce distribution for
the UES line can be seen in Table 2.
26
Table 2: Shift structure for the UES line
No. of Test Technicians
Hours
Days
No. of
N.o
Assemblers
Dedicated
1
7am - 3:30pm
Mon -Fri
9
1
6
Final Test
2
2
3pm - 11:30pm
Mon -Fri
5
0
4
4
3
9pm - 7:30am
Mon - Thu
5
2
0
2
4
7am-7pm
Sat- Sun
Seka Sun+_4 0 4
1 weekday
+
Shift
Numer
Number
____
Floating
________
7
Due to the high variability in demand of the product, the company prefers to have its assemblers and
technicians cross-trained and capable of working across different assemblies and modules. For example,
within the UES cell an assembler can work on any of the assemblies- Top Chamber, Bottom Chamber,
Wafer Handler, Frame etc. The testing workforce distribution is even more complicated. The testing
crew is divided into three categories- technicians dedicated to the UES line, technicians that float
between UES line and the 'Mixed-Mod' line where the Source, Analyzer, and Converter modules are
built, and final test technicians who primarily work in the clean room but can also work on the UES line if
needed. At a given point, any mix of these three categories of technicians can be assigned to work on
testing of the UES module. While this structure benefits the company by enabling them to maintain a
smaller work force and offering flexibility, it also makes resource planning and scheduling very
challenging.
2.3. Assembly and Test Process
UES production is broadly divided into two phases: assembly and testing. Assembly can be further
broken down into build and integration. In the build phase the six assemblies (HLA Frame, Top Chamber,
Bottom Chamber, Wafer Handler, ECR, and TCR) are built in parallel, typically with one assembler
working on one assembly. This is followed by integration, where the built assemblies are mounted onto
the frame and integrated electrically and mechanically with each other. Integration is performed by up
to three assemblers, depending on their availability and workload. Assembly requires approximately 174
labor hours. Integration is followed by testing, where the module is put through a series of functional
tests. This process requires approximately 59 labor hours. The average lead time for the assembly and
testing of the UES is currently 10.9 days. After testing, the U ES module is sent for packaging and crating.
The UES line functions as a flow line. It has designated areas for build, integration, and testing. There are
two bays each for the Top Chamber build, Bottom Chamber build, and Wafer Handler build; three bays
27
for integration, which are also used for the frame lay-down and buildup; and nine bays for testing. Only
six test bays are shown in UES production floor layout in Figure 6, as three bays are in a different
location. Also, the ECR and TCR are built in a separate area on the production floor.
PICK STORAGE
I
GOLD SQUARE
I INTEGRATION
I --- -- --
-
-
INTl
1
TH1i
BUILD
___
TH2
INT2
WHi
WH2
BC1
BC2
I
TB2
I
TB4
---
TBl
2C
INT3
I
I
I
TESTING
TB5
TB6
--
I-0
I
---- -- --i
LnL- -
K
-
STAG ING
AR EA
TB3
L-----
I
0 FT l
Figure 6 : UES production floor layout
2.4. Material Inventory
The raw material inventory for production is divided into five categories: supplier-managed inventory,
warehouse inventory, supermarket inventory, Gold-Square inventory, and in-line inventory.
These
inventories are managed through the MRP system.
Supplier-managed inventory is the inventory of parts that are delivered directly from the supplier to the
shop floor. The supplier-managed inventory is managed through a supplier kanban and includes
complex HLA's such as the Frame, castings for the top chamber, bottom chamber, and wafer handler,
and TCR. Suppliers for these parts are mostly local and have a turn-around time of around 2 days. The
delivery of these parts is scheduled through MRP, but the production supervisor can also directly place
an order for these parts with the supplier in case of an emergency.
28
Warehouse inventory is parts that are stored at the warehouse (Building 80) on the VSEA campus. These
include large, medium and small parts that are required at the Supermarket and the assembly lines.
Parts required from the warehouse are pulled 24 hours before the laydown by the production lead and
production controller, through Z-picks orders and shop orders respectively. Bulk of the material required
for assembly comes from the warehouse.
Supermarket inventory is inventory of the sub-assemblies built in the supermarket. These subassemblies get assembled into the top level assemblies. The demand for these parts is driven by shop
orders. The supermarket is fed by the warehouse and also through direct deliveries from the suppliers.
The supermarket in-turn feeds the gold-squares.
Gold Square inventory is the inventory of parts that are made-to-stock by the Supermarket. These are
typically high volume- fast moving subassemblies and are stored in the assembly area on special racks
called Gold Squares. This inventory is controlled through a visual Kanban system, managed by the
planners.
In-line inventory is the inventory of parts that are stored at the assembly line. In-line inventory is further
divided into two categories: 'Free Stock' or 'min-max' parts and 'Line-side' parts. Free Stock is primarily
hardware parts like screws, washers, nuts, 0-rings etc., while Line-side parts are bigger parts like harness
assemblies, ADIOs etc. This inventory is replenished by the warehouse. All in-line parts have a bin and a
barcode associated with them. Each part also has a fixed 'order quantity' on the system depending on
usage. The production lead performs a visual check of the line side bins and if the bins require more
parts, he scans the barcode on them, which places an order equal to the order quantity for
replenishment.
2.5. Warehouse Operations
2.5.1.
Overview
The warehouse is a separate building on the VSEA campus, and is commonly referred to as 'Building 80'.
It is VSEA's primary storage location and it houses large, medium, and small parts. It is responsible for
fulfilling production orders, sales orders, kit room orders, window requisitions, and replenishment
orders.
Production orders are orders for parts required for assembly and testing of machines at the main
building (Building 5). These are further divided into shop orders- parts required to build the base
29
module, and production kit orders -parts required to build a module which mostly consist of options
and selects.
Sales Orders are orders for parts directly placed by the customers. These are further classified as
international, domestic, or emergency orders. Sales orders are typically prioritized over other types of
orders, with emergency orders being given the highest priority.
Kit Orders are orders for parts like upgrade kits, service kits, and other kits which are shipped as
accessories with the ion implant machine.
Window requisitions are orders for one-off parts, such as in the case of a failure on the production floor
or to replace damaged parts. Replenishment orders are used to replenish small parts stored in the main
building, like in the supermarket area or in the in-line inventory on the production floor.
2.5.2.
Layout
Parts are received at the warehouse from suppliers and other VSEA buildings on campus. These parts
are unloaded and staged in the receiving area. Bulk parts are unloaded in the bulk staging area,
barcoded, and then put away in their designated storage location. Smaller boxes are sent to the
conveyor belt, where they are checked against the purchase orders. They are then either sent to the
sorting and de-trash area, QA rack, or Check 80 racks. At sorting and de-trash area, the quantities are
checked and the parts are made ready to be sent to the storage locations. The parts going through the
QA racks are checked at the Quality and Inspection department, before being sent for storage. Parts
which come in with missing dimensional or weight information are sent to Check 80 racks for
measurement before being sent to storage.
Building 80 has three primary storage locations- Warehouse (WH), General Location (GL), and VLM
(Vertical Lift Module). WH holds the large and medium sized parts and is fork-lift accessible. It is further
divided into sub areas called Rack (RK), Cantilever Rack (CK), and Bulk. GL holds small parts on racks,
which need to be manually accessed. VLM is an automated storage system that holds fast moving small
parts. It consumes very little real estate, but because of its height and design, can densely store a very
large quantity of parts. See Figure 7.
30
VLM
I
GL
KIT ROOM
G
BULK KITTING
WH
SALES
it
CONSOLIDATION AREA
il
[Ll
I
[EU
El
SHIPPING
L-1
QUALITY AND
INSPECTION
RECEIVING
I
Figure 7: Warehouse layout
There is a consolidation area with four bays. Each bay corresponds to a particular active order, and parts
corresponding to this order are picked from different locations of Building 80 and dropped off here by
the pickers. The parts are then consolidated, binned, and made ready for shipment. There is currently
one consolidator working one regular shift in this area.
The kit room handles all kit orders, while the sales department is responsible for handling all the sales
orders. They receive orders, consolidate the parts, and then complete the transaction once the orders
are ready.
2.5.3.
Picking Process
The picking process starts by the generation of a 'wave'. At the beginning of each shift, the warehouse
coordinator checks for the open orders and generates waves for these orders based on predetermined
priority. Each order type has an associated priority and a target fulfillment time. Fulfillment time is
measured from the time the order is received at the warehouse to the time it takes to ship it out. The
different order types, their priority, and their target fulfillment times can be seen in
31
Table 3.
Table 3: Order types and warehouse order fulfillment time targets
Priority
.
.
Order Type
Fulfillment
Time
t
Time Target
5 hours
2
Sales - Emergency Order
Sales - International Orders
3
Sales - Domestic Orders
5 hours
4
Production- Kit Orders
24 hours
5
Production- Shop Orders
24 hours
6
Window Requisitions
48 hours
7
Transfer Orders
48 hours
1
5 hours
UES production orders are placed 24 hours before the scheduled laydown date through the MRP
system. The production controller places the shop orders while the production lead places the orders for
the production kits. The production kits are ordered and picked using Z-pick kit codes. There are 8 pick
codes associated with the UES module. Of these, 6 correspond to parts required for assembly and 2 for
testing. Typically all parts associated with assembly are ordered together, as are parts for testing.
After the waves are generated at the warehouse, picking tasks are batched based on warehouse
location. Pickers login to their designated zones using their scanning 'guns'. The location and quantity of
the items to be picked is displayed on the gun, zone by zone. Pickers use forklifts to access parts in WH
and walk to the racks in the GL location. VLM operates differently from WH and GL. There is a bin
corresponding to a particular order and the all parts stored in the first VLM station are picked, and then
the bin is passed onto the next station. There are 13 VLM stations in all.
32
I
Warehouse
0
Shipping
Consolidator
Picker
Co-ordinator
Waves
X
--
-------
_Z-pick Kit
piKtod
---------
------------------------------------
-A-
Production Lead
---
Receiveing
Material Flow
Information Flow
Figure 8: Picking and consolidation process
Parts are picked and dropped off at the consolidation area. The consolidator then sorts these parts
based on the 'Consolidation Codes'. Consolidation Codes are codes corresponding to a particular kit
code, i.e. every part associated with a given kit code has the same Consolidation Code; however each
production order has a unique set of Consolidation Codes. Each production order also has unique set of
'Handling Units ' that are used for ensuring the completeness of a pick. Each kit code has three different
Handling Units corresponding to the WH, GL, and VLM picks under it. If a pick is not complete, the
Handling Unit flashes as 'open' on the scanning guns. Once all Handling Units are closed, it indicates that
picking is complete, and final consolidation can be done. After consolidation the parts are moved to the
Truck 35 staging area and made ready to be sent to Building 35 on the next available truck. Figure 8
summarizes the picking and consolidation process.
33
3. Assembly and Testing Time Studies
3.1.Objectives
Preliminary analysis of the UES production process based on interviews and first person observations
indicated that there were several inefficiencies in the process. It was decided that an in-depth time
study would be required to develop a better understanding of the process and the issues involved. This
study had three key objectives.
The first objective was to capture the time durations for each of the tasks involved in the assembly and
test processes. This was necessary in order to establish baseline metrics for further analysis. The
company was also interested in documenting these times in their standard work instructions.
The second objective was to observe the process and determine the time spent in value added activities
and non-value added activities, and also the time that the machine was inactive during the lead time
due to labor constraints or due to material shortages and failures.
The third objective was to determine the dependencies between the different tasks, in order to come up
with a better grouping structure and sequence of tasks, which would maximize labor utilization and
reduce idle time. This would also help determine the theoretical minimum lead time for the entire
process.
3.2. Methodology
Two time studies were performed - one for assembly and another for testing. These were performed
independently on two different Trident machines due to availability constraints. The time studies
involved observing the complete assembly and test cycles from start to finish, by having at least one
member of the team on the shop floor at any given point, throughout the duration of the study. The
assembly test study took place over 6 days and the testing time study took place over 5 days.
VSEA documents its standard work instructions on a platform called Lotus Notes. Each machine has a
specific set of work instructions generated for it based on the PBO, and it is called the 'logbook'. The
logbook also serves as a signoff document for the assemblers and technicians, where their signatures
are captured electronically. A logbook has instructions broken down by 'modules', which are further
broken down into 'sub-modules'. The sub-modules are further broken down into 'tasks'. The assemblers
34
and technicians sign off on individual tasks under the sub-modules. There is often a detailed procedure
linked to every task for reference. Each task is accomplished through several 'steps'.
The UES module is broken down into 21 assembly sub-modules and 61 test sub-modules. The number
of tasks within each sub-module varies, but there are 198 tasks in all for assembly and 1297 for testing.
For the purpose of further analysis, the assembly sub-modules will be referred to as A1,A2,..,A21; and
the testing sub-modules will be referred to as T1,T2,..T61. The tasks within the sub-module Al will be
referred to as A1.01, A1.02, etc., and so on. See Figure 9.
TASKS
A1.01
A1.02
A1.03
SUB-MODULES
ASSEMBLY
A2.01
A2.02
A2.03
Al-
A2-
A21-
-'
A21.02
L
MODULE
2
.
TEST
T1.01
T1.02
-
T1.03
-
T1T2
LA 1.03
T2.01
T2.02
T2.03
T61
-
UES
-
--
L.
Figure 9: Logbook structure
35
T3.01
T3.02
T3.03
For the purpose of the time study, five terms were definedValue Added Process (VA): These were processes that changed the form, fit, and function of the
machine. Examples included - installing parts and subassemblies, making internal connections,
calibrations etc.
Non- Value Added Process (NVA-P): These were processes that did not change the form, fit, or function
of the machine. All rework was classified as NVA-P. Other examples included - searching for parts,
unpacking parts, cleaning parts, making facilities connections for testing, inspections and verifications
etc.
Non-Value Added Movement (NVA-M): Any movement that was significant enough, during the assembly
or test process was captured as NVA-M. Examples included - movement of sub-modules or the machine
itself from one part of the floor to another, movement of assembler for fetching parts that were stored
far away etc.
Idle Time (/T): This was the time that a sub-module was not being worked on, once it was started. This
included scheduled and unscheduled breaks, and worker unavailability.
Wait Time (WT): This was the time the sub-module was not being worked on, once it was started,
because it was waiting on parts due to material shortages or quality issues.
During the time studies, the steps performed by the assemblers and technicians were documented, and
the following information was capturedi.
Start and end times of steps
ii.
Category of steps -VA,NVA-P, NVA-M, IT, or WT
iii.
Dependencies between tasks
iv.
Recommendations for improvement based on observation and interviews
3.3.Assembly Time Study
3.3.1.
Data and Observations
The time study captured the start and end times of tasks, dependencies between them, and their
classification (VA,NVA-P,NVA-M,IT, WT). This information was analyzed at task level and at sub-module
level and it led to five key observations.
36
The first observation was that the UES module overall was in an 'active' state for majority of the
assembly process, as can be seen in Figure 10. The module was considered to be active when at least
one of the twenty one sub-modules was being worked on. The inactive periods were attributed to
unavailable production hours on weekends, overlapping breaks, and inefficient scheduling of submodule operations. Figure 11(a) and Figure 11(b) show the percentage of active and inactive time for
the overall assembly process, including unavailable production hours and excluding unavailable
production hours respectively.
Overall State of the Machine During Assembly
0
1
3
2
4
Active
Inactive
5
6
Time from Start of Build (Days)
Figure 10: Overall state of UES module during assembly [6]
Act
(a)
*Aie
(b)
0 Active
NJ Inactive
Active
Inactive
Figure 11: Overall UES assembly active time vs inactive time (a) including unavailable production hours (b) excluding
unavailable production hours
37
The second observation was that there was a significant amount of 'inactive' time within the submodule, i.e. the sub-module was not being worked on after it was started. Figure 12 shows the different
assembly sub-modules, their relative start and end times, the active and inactive time within them, and
also the dependencies between them. This inactive time within the sub-module was primarily attributed
to dependencies between tasks across sub-modules which caused one module to become inactive when
the prerequisite task from another sub-module was being performed. Extended breaks, part shortages,
and unavailability of personnel also contributed to the inactive time.
Assembly Time Study: Trident ES131234
= Active
Inactive
Laydown and Prep Frame
Wafer Handler/Load Lock Buildup
Bottom Hat Buildup
ECR Build
Bottom Hat installation to Frame
Wafer Handler/Load Lock Installation
_7K
TCR Build
Top Hat Buildup
Roplat installation
Process Chamber Liners
Top Hat to Bottom Hat Installation
Trough and Manifolding
Tool and Electronics Rack Installation
Process Chamber Buildup
Scan Rotate Harness
Load Lock Additions
Tubing, Harnessing, and Light Links
Misc End Station Items
B
Gas Control
Final Steps
0
1
3
2
4
5
6
Time from Start of Build (Days)
Figure 12: Overview of the assembly time study [6]
The third key observation was that on an average 82% of the active time within sub-modules was spent
on value added processes (VA), while 18% was spent on non-value added activities (NVA-P and NVAM);and 97% of the inactive time was attributed to labor unavailability (IT), while only 3% was attributed
to material unavailability (WT). See Figure 13.
38
* VA
NVA-P
NVA-M
N Active
Inactive
(a)
U
WT
IT
(c)
(b)
Figure 13: (a) Active and Inactive time during assembly; (b) Breakdown of Active time into VA, NVA-P, and NVA-M time; (c)
Breakdown of Inactive time into NVA-W and NVA-I time
The fourth observation was that the current grouping of tasks into sub-modules was not ideal. This led
to interdependencies between tasks across sub-modules, leading to inactive time on one sub-module
while the other was being worked on.
The fifth observation was that there was no optimized order for the scheduling of sub-modules. The
sub-module procedures were scheduled in an ad-hoc manner, as there was no understanding of the
critical sequence of operations in the assembly process. This led to a lot of idle time during the build
because a sub-module was often waiting on another sub-module to be completed.
3.3.2.
Summary
The time study showed that the long lead time of the assembly can primarily be attributed to two major
causes. The first cause is the idle time due to improper grouping of tasks, un-optimized scheduling of
operations, and unavailability of work-force. The improper grouping of tasks arises from limited
understanding of dependencies between tasks; the un-optimized scheduling of operations can be
attributed to not having an understanding of the critical path of operations; and unavailability of
workforce is mostly caused by poor line-balancing and task scheduling, and not necessarily due to being
understaffed. Sedore further analyzes the inefficiencies in grouping and sequencing of operations, and
proposes an improved task grouping and sequencing structure within the current labor constraints [6].
The second major contributor to the long lead time is non-value added activities. 18% of the sub-module
active time is spent in non-value added activities like rework, searching for parts, unpacking parts,
39
cleaning parts, and moving parts. If time spent on these non-value added processes could be reduced,
this would not only reduce the lead time, but also make the assembly process more lean. This thesis
documents the work done in reducing time spent on searching for parts, through an improved material
kitting process.
3.4.Testing Time Study
Data and Observations
3.4.1.
Similar to the assembly time study, the start and end times of the tasks, the dependencies between
tasks, and their classification (VA, NVA-P, NVA-M, IT, WT) were captured for the test cycle. The data was
captured at task level and analyzed both at task and sub-module level. Three key observations were
made.
The first observation was that the UES module overall was in an active state during the test process for
majority of the time as seen in
Figure 14. The two instances when the machine was inactive for a long period of time- one was when a
test technician was absent from work and no replacement was available, and another was when testing
had to be halted for an assembly related Engineering Change Order (ECO) to be implemented. Figure
15(a) and Figure 15(b) show the active and inactive periods for the UES module including the period the
ECO was being implemented and excluding the period the ECO was being implemented respectively.
Active
Overall State of Machine During Testing
I
aInctive
0
0
1
2
3
Time from Start of Buld (Days)
Figure 14: Overall state of the module during testing [6]
40
4
5
* Active
9 Inactive
0 Active
N Inactive
(a)
(b)
Figure 15: Overall UES test active time vs inactive time (a) including ECO (b) excluding ECO
The second observation was that if the ECO implementation period and the absence of the test
technician were ignored, the inactive time within a sub-module was insignificant, unlike in case of UES
assembly. This difference can be explained by the fact that testing is predominantly a serial process and
sequencing of tasks is straightforward, unlike in the case of assembly where a lot of sub-modules can be
worked on in parallel and optimized sequencing of these sub-modules is critical to reduce inactive time.
Figure 16 shows the relative start and end times of the testing sub-modules, and the active and inactive
time within each.
Testing Ti me Study: Trident E S 1312 5 6
=
Active
-
1
= Inactive
-
4
7
10
13
16
19
22
1.. 25
2 28
E 31
= 34
U
=
ECO
M37
040
E43
.46
49
52
55
58
61
0
0.5
1
1.5
2
2.5
3
3.5
Time from Start (Days)
Figure 16: Overview of the testing time study [6]
41
4
4.5
5
The third key observation was that on an average 90% of the active sub-module time was spent on nonvalue added activities. This was expected because by definition all testing is considered non-value
added, as it does not change the form, fit or function of the machine. The 10% of active time which was
considered value added involved calibrations, software downloads, and installation of parts. Of the
inactive time, 65% was attributed to the machine being idle due to unavailability of work-force, and 35%
to waiting on parts- which in this case was waiting on the ECO to be implemented. See Figure 17.
0.4%
1VA
* Active
* Inactive
NVA-P
* NVA-M
M WT
m IT
Figure 17: (a) Active and Inactive time during testing; (b) Breakdown of Active time into VA, NVA-P, and NVA-M time; (c)
Breakdown of Inactive time into NVA-W and NVA-I time
3.4.2.
Summary
The testing time study indicated that significant period of the time was spent in non-value added
activities. These activities included making and breakdown of facilities connections for testing, tests
themselves, and software verifications. Part installations, calibrations, and software downloads were
considered value-added, as they changed the form, fit, and function of the machine, and formed only a
small fraction of the testing process.
The main purpose of testing is to ensure that the assembled product is meeting specifications and is in
conformance with the customer requirements. If it can be shown through analysis of historical data, that
the process is in statistical control and the failure rate during testing is insignificant, then there is an
opportunity to reduce testing. Also, if the sequential testing process can be broken down into parallel
steps and if automated testing can be introduced, the testing lead time can be significantly reduced.
Bhadauria further studies the testing process and proposes an improved testing protocol which reduces
the non-value added time spent on testing [9].
42
4. Analysis of Non-Value Added Assembly Activities
A central focus of lean manufacturing is to reduce or eliminate activities that consume resources
without adding any value to the overall process. The assembly time study showed that on average 18%
of the time that a sub-module was being worked on, was spent on non-value added activities. Reducing
the time spent on non-value added activities will contribute to reducing the overall lead time of the UES
module.
The time study data was analyzed to identify the different non-value added activities and determine the
major contributors. It was found that gathering parts for assembly was the most time consuming nonvalue added activity and this was attributed to the inadequate kitting process.
This chapter documents the analysis of the non-value added activities during the assembly process and
summarizes the findings. It then describes the existing material kitting process and identifies the
inadequacies in it.
4.1. Objectives
The objective was to analyze the non-value added activities in the assembly process, with an aim to
-
determine the potential areas of improvement. The specific objectives were to
L.
Identify the different non-value added activities
ii.
Find the time spent on the non-value added activities and determine the major contributors
iii.
Identify potential areas of improvement
4.2. Methodology
The assembly time study data formed the basis of this analysis. As mentioned in Section 3.2, the time
study captured the assembly steps, their durations, and their classification- VA, NVA-P, NVA-M, IT, or
WT.
The NVA-P and NVA-M steps constituted the non-value added activities during assembly. These were
further analyzed, by reviewing each one of these steps and then grouping them into six broad
categories- gathering parts, rework, fixturing and lifting, general setup, and necessary processes.
Gathering parts involved activities like locating parts on the production floor, searching for parts in the
production kits, and searching for missing parts. It also included laying out and organizing parts.
43
Rework involved troubleshooting failures, uninstalling failed parts, reworking defective parts, and reinstalling fixed or replaced parts. It also included routine rework like re-routing harnesses on the frame,
which is done on every single build.
Fixturing involved attaching and detaching fixtures used during the build phase; while lifting involved
attaching and detaching lifting gear used to move the wafer handler, top hat, and bottom chamber to
the frame during the integration phase. Activities like clearing and sealing off the production area prior
to lifting and moving were also grouped into this category.
General setup involved activities like checking the PBO, signing off on the routings, handover, verifying
the work, cleaning up at the end of the shift, and unpacking parts.
Necessary processes were processes which despite being non-value added, were essential to the
assembly process. These included processes like levelling the frame, inspecting mating surfaces,
inspecting and cleaning parts, detaching and re-attaching the ECR and trough cover etc.
Movement included movement of assemblies and sub-assemblies using the overhead crane or using
pallets.
After the steps were grouped into these five categories, the total time associated with each category
was determined. Each of the five categories was analyzed in detail to identify inefficiencies and the
scope for improvement.
4.3. Non-value Added Assembly Activities
4.3.1.
Analysis
The data was first analyzed at sub-module level and it was observed that sub-modules corresponding to
sub-assembly build and installation had relatively more non-value added activities (NVA-P and NVA-M),
than the sub-modules corresponding to integration. This can be seen in Figure 18, where sub-modules
A1-A7 correspond to sub-assembly build, AS-A16 correspond to sub-assembly installation on to the
frame, and A17-A21 correspond to integration.
44
Value Added vs Non Value Added Time per Submodule
21:36
19:12
16:48
-
14:24
5-12:00
w
E
---
--1 NVA-M
9:36
M NVA-P
7:12
EVA
4:48
2:24
0:00
Al A5 A6 A7 A8 A9 AlOAllA12 A13 A14 A15 A16 A17 A18 A19 A20 A21
Sub-module
Figure 18: Value added vs non-value added time per sub-module
The non-value added activities across all sub-modules were then grouped into the six categories for
further analysis - gathering parts, rework, general setup, fixturing and lifting, necessary processes, and
movement. Figure 19 shows the time consumed by each of these activities. It was found that gathering
parts was the most time consuming non-value added activity, while movement was the least time
consuming. This also explains the previous observation of sub-modules corresponding to build and
install phases having a higher percentage of non-value added time, as these phases involve a lot more
part handling than the integration phase.
45
NVA Activities during Assembly
7:12
-
6:00
E 4:48
E 2:24
-
3:36
1:12
0:00
Gathering
Parts
Rework
Necessary
Processes
General Setup
Fixturing and
Lifting
Movement
Task Category
Figure 19: Non-value activities during assembly
Time study data showed that gathering parts required an average of 17 minutes per sub-module. This is
attributed to the existing inadequate kitting procedure. Approximately 200 parts are received from the
warehouse under six Z-pick kit codes. These parts arrive in seven big bins and are not sorted according
to order of use or procedure. Also, if there are any shortages it is not immediately known, as there is no
way to indicate it. Parts from one machine's kit often get stolen to fulfill a shortage on another machine,
without indication or proper transaction. This results in the assemblers having to spend a lot of time in
locating and gathering parts. Improving the kitting process can result in significant reduction of time
spent in gathering parts.
Rework was found to be the second major non-value added activity. Rework could further be classified
into routine rework and failure rework. Routine rework is rework that happens on every machine
assembly, for example re-routing the harness on the frame, re-labeling parts, etc. For a Trident model
routine rework is approximately 2.5 hours, and is fairly constant across builds. This rework can be
eliminated by having the parts built to exact specification at the supplier end or at super market. There
are currently two ongoing projects, one is to change the routing on the HLA frame and another is to
update the labeling on the ECR harnesses, so that no additional rework is required at the facility. Failure
rework is the rework due to failures. This is different for different machines, depending on the number
and severity of failures it encounters, and was approximately 2 hours for the machine observed during
46
the time study. Most of the failures observed were one-off failures and there is no history of repeated
failures.
Necessary non-value added processes like inspecting and cleaning mating surfaces, verifying the build,
levelling the frame, removing the ECR and then re-attaching after populating it etc. are processes that
are essential to the assembly process and cannot entirely be eliminated. There is little scope for
reduction of these non-value added activities.
General setup involves activities like signing off on the routings, handovers, clean up at the end of the
shift, unpacking, and trashing waste. These processes do not contribute to the assembly process
directly, but are required to maintain the company's 6S standards, and hence cannot be eliminated.
Fixturing, lifting, and movement are already being done in a very lean and optimized manner, and again
there is little scope for improvement.
4.3.2.
Summary
Analysis of the non-value added activities and times showed that activities like fixturing, lifting and
movement are being done in a fairly optimized manner, with little scope for improvement. Certain other
non-value added activities are essential either to the assembly itself or to maintain 6S standards, and
hence cannot be eliminated. Historically there have not been any repeated failures resulting in excessive
rework, and most failures are one-off. There are ongoing projects which aim at reducing the routine
rework by enabling parts to be built to exact specification at the supplier.
The non-value added activity that consumes the most time and has the most scope for improvement is
gathering of parts. The existing kitting process is inadequate and makes locating parts very time
consuming. An improved material kitting process can significantly reduce the time spent on gathering
parts, which in turn will reduce the assembly lead time. The following section describes the existing
kitting process and highlights the inefficiencies in it.
4.4. Existing Material Kitting Process
The raw material inventory for production is divided into five categories: supplier-managed inventory,
warehouse inventory, supermarket inventory, Gold Square inventory, and in-line Inventory. All inventory
is tracked and maintained through the MRP system.
47
The supplier-managed inventory, supermarket inventory, Gold Square inventory, and in-line inventory is
maintained in the main building (building 35). The warehouse inventory is maintained in a separate
building (building 80) and is ordered 24 hours ahead of the scheduled lay-down. Warehouse parts that
are required for production are pulled either as shop orders or production kits.
Shop orders are orders for parts that are used on a basic machine build or are required to build subassemblies at the super-market. Once these sub-assemblies are built, they get sent over to the UES
production line and can be installed onto the machine. The shop order for a machine is placed 24 hours
ahead of the lay-down by the production controller.
Production kits are orders for parts which get directly installed onto the machine. They include parts
that are options and selects. The production lead places the order for these parts 24 hours ahead of the
lay-down, and these parts get directly delivered to the UES line. There are 6 production kits that get
ordered prior to assembly, and 2 kits get ordered just before testing. Each of these kits has a kit code
associated with it called the Z-pick kit code, which is used to place orders.
The 6 assembly production kits contain approximately 200 parts in all. The number of parts varies
depending on the options and selects on that particular build. Table 4 shows the various kit codes
associated with the UES module.
Table 4: Z-pick kit codes for UES assembly
Kit Code
1LA1
1LA2
1LA4
1LA7
LAWH
RACK
Description
Assembly
Assembly
Assembly
Assembly
Wafer Handler Assembly
ECR and TCR Assembly
These kits contain small, medium, and bulk sized parts. The six kits arrive in the UES staging on two
pallets. One pallet holds all thp bulks parts and the other pallet holds the remaining parts which are
typically packed into seven bins, as seen in Figure 20 . These bins are not labeled, and are not specific to
the UES line. Additionally there is no picklist or BOM sent with these kits, so it is not known if there is a
shortage. The production lead places the seven bins on the pick rack and often spreads the parts out for
easy accessibility, as seen in Figure 21. The bulk parts are retained in the main UES staging area.
48
Figure 20: Assembly production kit parts
Figure 21: Staging of production kit parts on the kit rack on UES flowline
49
As and when assemblers need parts for assembly, they fetch parts from the kit rack. As the parts are not
staged in a sorted or organized manner, it can take the assembler up to 30 minutes per sub-module to
locate the required parts.
4.4.1.
Analysis
The kitting process at the warehouse and the staging process at the production floor were studied, with
an aim to understand the inefficiencies and find avenues for improvement. Four key problems were
found with the existing process.
The first issue with the existing kitting process is that parts are not organized or sorted according to submodules. Assembly consists of 129 tasks grouped into 21 sub-modules, that get worked on over a
period of 6 days. Parts for all these sub-modules arrive at the same time on the production floor,
randomly grouped in seven bins, as per the consolidator's discretion. This results in the assemblers
spending a lot of time locating parts that they require for the particular sub-module that they are
working on. Further analysis of the parts showed that some parts used in testing and shipment have also
been wrongly grouped into the assembly kits.
The second major issue with the kitting process is that shortages are not made known. There is no
picklist accompanying the kits indicating if any parts are missing. Also, since the parts arrive grouped in
large bins, it's difficult to visually spot shortages. This often results in the assemblers starting a submodule and then realizing mid-way that a part is missing, making the sub-module go idle thereafter. If
the shortages were known before hand, the assemblers could work on another sub-module which didn't
have any shortages. Also, replacement parts could be ordered and procured sooner if shortages were
known.
Thirdly, due to lack of organization and control, parts from one machine's kits often get stolen to fulfill
shortages on another machine. There is no way to know if a part is unavailable because it was a
shortage or if it was used up on another machine.
Fourthly, because of the large size of the kits and the ad-hoc distribution of parts, all assembly kits need
to be ordered at the same time. If the kits could be broken into smaller kits, with each kit corresponding
to specific procedures, fewer kits could be ordered at a given time, allowing for better work leveling at
the warehouse and also shorter order fulfillment times. Order fulfillment time is measured from the
time the order has been received by the warehouse to the time it takes to ship the order out.
50
In addition, the existing kitting and staging process does not comply with the company's 6S standards as
the parts are not sorted and organized, and there is no standard way of consolidating or staging the
parts.
4.4.2.
Summary
In summary, part sorting, organization, and shortage indication are the main issues with the existing
kitting process. These result in a lot of time being wasted in locating parts during assembly. An improved
kitting process is required to address these issues and to make the assembly process more lean and 6S
compliant.
51
5. Theoretical Framework
5.1. Lean Philosophy
The principles of lean manufacturing were first introduced and implemented by the Japanese car
manufacturer Toyota in the early 1940's. The term 'lean production' however, was introduced in 1988
by Krajick [10] to describe the Toyota Production System, and subsequently the principles were
documented by Womack, Jones, and Roos [11] in 1990. Ever since, these principles have been widely
adopted by several industries to improve their efficiency, productivity, and quality of service.
Toyota's 3M model forms the basis of Lean Manufacturing. The 3M's stand for Muda, Mur, and Muri.
Muda in Japanese means waste, Mura means variability, and Muri means overburden. The goal of lean
is to eliminate the 3Ms, in order to make the system more efficient.
Muda or waste, in lean thinking, is defined as anything that adds cost to a system without adding any
value to it. Waste can be further classified into seven categories- Transport, Inventory, Motion, Waiting,
Over-production, Over-processing, and Downtime. Lean tools like error proofing, standardized work,
one-piece-flow, Kanban, line balancing, and 65 are used to reduce waste [12].
Mura or variability can be found in the form of fluctuating process times, operator times, quality of the
product, customer demand etc.
Hopp & Spearman [13] observe that production variance leads to
performance degradation of a production system and variability is buffered by some combination of
inventories, capacity, or time. It is therefore essential to reduce Mura. Variance in a process can be
reduced through reducing variation in product architecture through modular designs; by production
leveling in production planning; by building flow at production level through capacity planning; and by
using standard work instructions and a 6S system [14].
Muri or overburden is observed in the form of overburdened machines and workers. Overburdened
machines result in wear outs and breakdowns, while overburdening workers leads to defects, low
motivation, and absenteeism. Preventative maintenance and autonomous maintenance help minimize
machine related Muri, while implementing 6S and using standard work instructions helps reduce people
related Muri [15].
6S forms the foundation of lean manufacturing as it helps in reducing all the 3 M's - Muda, Mura, and
Muri. 6S stands for Sort, Straighten, Shine, Standardize, Sustain, and Safety. Sort involves ensuring that
only items necessary to perform relevant tasks are stored at every work station. Straighten involves
52
storing parts in an organized manner at the work station so that time and effort spent on locating parts
is minimized. Shine involves cleaning the work stations not only to make the workspace visually pleasing,
but also to maintain a safe and hygienic work environment, and to prevent equipment deterioration.
Standardize involves uniformly implementing the sort, straighten, and shine steps across all work
stations. Sustain involves setting up a system which ensures that the sort, shine, straighten, and
standardize operations are being performed in a regular and sustainable manner. Safety involves
eliminating hazards and unsafe practices in the workplace.
Just-in-Time (JIT) production is another key element of lean manufacturing. JIT production is
characterized by eliminating overproduction by producing to customer demand, leveling demand so that
work flows smoothly through the plant, linking all processes to customer demand through visual tools,
and maximizing flexibility of people and machinery. This approach significantly reduces inventory and
WIP, and also the holding costs associated with them. Kanban is a system of visual tools that
synchronizes and controls the logistical chain for material and production flow, and is an integral
component of JIT production.
This thesis aims at reducing non-value added assembly time, which in lean thinking is a type of Muda, as
a means to increase the productivity and efficiency of the production process. It uses the 65
methodology to reduce waste associated with material handling, and sets up a process which facilitates
JIT ordering of parts.
5.2. Material Feeding Systems
Johansson [16] categorizes the material feeding systems to manual assembly stations into three types,
based on whether a selection of part numbers or all parts are displayed at the assembly stations, and
whether the components are sorted by part numbers or assembly objects. The three categories of
material supply are -continuous supply, batch supply, and kitting. See Table 5.
Table 5: Different Material Feeding Systems [16]
Selection of Part Numbers
All Part Numbers
Sorted by Part Number
BATCH
CONTINUOUS
Sorted by Assembly Object
KITTING
53
Continuous supply is when materials are supplied to the assembly line in units suitable for handling and
&
the units are replaced when empty. This type of supply has been referred to as 'line stocking' by Bozer
McGinnis [17]. Every part number used on the line is stored on the line and the stock is replenished once
everything is used up. The advantage of this system is that material is always available, no preprocessing
is required, and if there is a defect or failure a replacement is easily available. The disadvantage is that
this leads to poor inventory control, a lot of capital tied up in stock, and over-crowding on the
production floor.
In batch supply, the materials are supplied for multiple assembly objects. The batch can be a batch of
necessary part numbers or a batch of these part numbers in requisite quantity [16].
In kitting, only the requisite part numbers in the requisite quantity for a single assembly are supplied.
Kitting is advantageous when the total number of components and the product variants are high.
In practice pure systems rarely exist. Generally, all three systems co-exist and complement each other.
The UES assembly line at VSEA is also fed through a combination of continuous supply, batch supply, and
kitting.
5.3. Material Kitting
Bozer & McGinnis [17] define kitting as the practice of delivering components and subassemblies to the
shop floor in predetermined quantities that are placed in specific containers. A kit can be viewed as a
container that holds a specific assortment of parts used in one or more assembly operations.
Kitting as an operational strategy remains a point of debate among researchers as well as industry
experts. While kitting has several advantages, it also has some serious limitations.
Advantages of Kitting:
(i)
Saves manufacturing space by reducing inventory stored at the production floor and allows
for a better organized shop floor [17]
(ii)
Ensures that latest bill of materials is used [18]
(iii)
Allows for error proofing in case of similar looking components by only supplying the correct
component [18]
(iv)
Ensures correct assembly by presenting components in sequential or assembly order [18]
54
(v)
Allows for early identification of low quality components [17]
(vi)
Increases workstation product quality and productivity, by making required parts readily
available[17]
(vii)
Provides better control and visibility of high cost and perishable components [17]
(viii)
Allows for ensuring that all parts required for a certain assembly are available prior to
scheduling work [18]
(ix)
Allows for easy changeover as components are not staged at the work stations [17]
(x)
Serves as a training aid for new assemblers [19]
(xi)
Allows for easy identification of missing components if kits are appropriately designed [18]
Limitations of Kitting:
(i)
Kit preparation consumes time and effort, with little or no value added to the product [17]
(ii)
Temporary shortage of a single part leads to the entire kit being flagged short [17]
(iii)
Wrong or defective parts in the kit may disrupt assembly, as procuring replacement parts
takes time [17]
(iv)
Part shortages may lead to 'cannibalization' of kits, where short parts are removed from
existing kits. This could lead to further complication of the shortage and problems with
accountability [17]
(v)
Increased instances for part handling increases the probability of damaging components
[20]
Research literature suggests that kitting has its advantages and disadvantages. Several factors like the
type of components, the type of assembly, and the variation in products, the quantity of parts required
for assembly etc. need to be considered to determine whether kitting is a suitable method of material
supply for a particular application. The goal of this thesis is not to introduce kitting as a new method of
material supply at VSEA, but to improve the already existing kitting process by removing the
inefficiencies and addressing the inadequacies in it.
55
5.4. Previous MIT Projects at VSEA
Daneshmand [21] studied the assembly and test operations in the Mixed-Mod line at VSEA in 2011, and
found searching of parts to be a major non-value added activity. She suggested using a better kitting
process where parts are organized by procedure, have labels for kit codes and procedure names, and
have shortage indicators, as a means to reduce the non-value added effort on the production floor.
Although her research was focused on the Mixed-Mod line, her findings and suggestions are also
applicable to the UES line.
56
6. New Kitting Process
Analysis of the existing kitting process showed that the process had several inadequacies. The parts that
arrived from the warehouse were not sorted and organized according to sub-module procedures, which
resulted in a lot of time being spent on looking for parts on the production floor. Also, the consolidation
process at the warehouse and the staging process on the floor were not standardized and depended on
the discretion of the consolidator and production lead respectively. In addition, the large size of the kits
and ad-hoc grouping of parts did not facilitate Just -in- Time (JIT) arrival of parts, resulting in cluttering
on the production floor and long order fulfillment time for the warehouse.
This chapter documents the process of development of the new kit design and the kitting process
accompanying it. It states the objectives and the methodology adopted for the development process,
and then briefly discusses the proposed kit design and the new kitting process. It also discusses the
advantages of adopting this new kitting system.
6.1.Objectives
The goal of the project was to develop a kit design and a kitting process that would:
i)
Enable grouping and sorting of parts according to sub-modules, so that time spent by the
assembler on locating and gathering parts would be reduced
ii)
Reduce time spent by the production lead on staging parts on the production floor
iii)
Reduce time spent by the consolidator on consolidation of parts at the warehouse
iv)
Make shortages known before start of assembly
v)
Facilitate JIT arrival of parts and shorter warehouse order fulfillment times
6.2. New Kit Design Features
A new kit design was developed to address the inadequacies in the current kitting process. The
proposed design can be seen in Figure 22. It consists of bin-boxes stacked on a mobile cart, where each
bin-box corresponds to a particular sub-module. Each bin box is labeled with a kit code and procedure
name. Shortages are indicated using a shortage list and stickers. This design has the following four key
-
features
57
I Kit
7
Code
Labels
Shortage List
Figure 22:New Kit Design
Parts grouped by sub-module:
Each sub-module has a bin of parts associated with it. Sub-modules which have no parts associated with
them do not have a bin. Each bin is labeled with the procedure name to enable easy locating of parts by
assemblers and the kit code to enable easy consolidation of parts by the consolidator.
Stackable bins on a mobile cart system:
All parts except for the bulk parts are housed on a single mobile bin-box system. The system consists of
stackable bins placed on a cart. It is intended that the system will be stored in the warehouse and will be
populated each time a Z-pick order is placed. It will then be sent over to the main building on a truck and
wheeled in to the staging area. With this new system, no additional re-organization or staging is
required by the production lead.
58
New kit codes:
The 6 old assembly kit codes have been replaced by 17 new kit codes. Each sub-module that has Z-pick
parts associated with it, has been given a new kit code. The kit code has the format 'LA##', where 'LA'
represents the UES flowline area and the two digits following it represent the sub-module number
proposed by Sedore[6].
Shortage indicators:
A new shortage indication method is proposed, where a list of part shortages is generated using MRP
and attached to the cart by the production lead after the cart arrives in the staging area. The generated
shortage list consists of shortages seen on the entire machine (Source, Analyzer, Corrector, and UES).
The missing parts corresponding to UES assembly (kit codes LA01-LA31) are highlighted on the shortage
list and the bins with shortages are indicated using red stickers. If an assembler sees a shortage sticker
on the bin corresponding to the sub-module he is working on, he needs to refer to the shortage list to
see what part is missing.
6.3. Design Development Methodology
The kit design and kitting process was developed in four phases. The first phase involved sorting the
warehouse parts used on a Trident model, based on the sub-module they get used on. The second phase
involved sorting the parts within each sub-module based on size. This was required to determine the
size of the bin needed for kitting that particular sub-module. The third phase involved evaluating several
kit designs and selecting the most appropriate design, and the fourth phase involved further developing
and customizing the selected design for this specific use. See Figure 23.
59
Sort parts by sub-module
Sort parts by size
Kit design selection
Kit design development
Figure 23: Four phases of development of the new kitting process
6.3.1.
Sorting Parts by Sub-module
The first step of developing the new kitting process involved sorting the parts according to the submodules. This was accomplished by generating a list of parts that were used in the existing assembly
production kits- 1LA1, 1LA2, 1LA4, 1LA7, LAWH, and RACK, and then using the logbooks and the MRP
system to determine in which sub-module they get used. Approximately 200 unique parts were sorted
and grouped by sub-module. Parts that got used on multiple sub-modules were grouped into a separate
category called 'Multiple'. These parts were mostly screws, nuts, and washers, which were eventually
made in-line inventory.
During the sorting process it was also discovered that some parts were wrongly grouped into the
assembly production kits. There were three parts that got used in testing, two in final assembly, and two
in shipping that are wrongly grouped into assembly kits.
Figure 24 shows the distribution of parts for the existing sub-module structure. Here the parts are
grouped into 22 groups - 21 corresponding to the sub-modules A1-A21, and an additional group for
parts that are used on multiple sub-modules. Figure 25 shows the distribution of parts for the new submodule structure proposed by Sedore [6]. In this case the parts are divided into 32 groups - 31
corresponding to the new sub-modules B1-B31, and an additional group for parts that get used on
multiple sub-modules.
60
~
q-4-4T(ri-4
V-4
C
4
N
.
Parts Distribution : Current Sub-module Structure
50
45
40
35
M
a
30
'4-
0
25
6
z
20
15
10
5
0
Sub-module
Figure 24: Parts distribution for existing sub-module structure
Parts Distribution : New Sub-module Structure
60
50
t
'+-
40
30
d
z
20
10
0
Iiiiljiilii
i- .NI
I . I~
D
c
i
I
,I I
' Im
.~
In
In
I-
o o
_______________
v -I
IN
v
4
1n
1n
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co
(U-
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73
Sub-module
Figure 25: Parts distribution for new sub-module structure
61
6.3.2.
Sorting Parts by Size
The next step after sorting parts by sub-modules, was to determine the size of the parts in order to
come up with a suitable kit design. Since there was a large range in the size of the parts, the parts were
classified into five sizes - very small, small, medium, large, and bulk. The parts were visually checked at
the warehouse and classified into one of the five categories. Table 6 shows the maximum dimension of
parts and the typical parts that fell into the size categories.
Table 6: Size classification of parts
Very Small
Dimensions
(w x d x h)
< 1" x 1" x 1"
Parts
screws, nuts, washers
Small
< 3" x 3" x 3"
fittings, sensors, o-rings, labels
Medium
harnesses, PCBs, o-rings
Large
< 8" x 8" x 8"
< 20" x 20" x20"
Bulk
> 20" x 20" x 20"
frame, chassis
Size Category
liners, harnesses
Figure 26 shows parts sorted by size within the different sub-modules, based on the existing sub-module
structure. Figure 27 shows parts sorted by size within different sub-modules based on the new submodules proposed by Sedore [6]. The sub-modules which did not have any parts associated with them
have not been shown in these figures.
Parts Sorted by Sub-module and Size : Current Sub-module Structure
50
45
40
35
30
0 Bulk
6
Z 20
15
10
5
0
I 6
~I
I
0 Large
N Medium
U Small
-I
-
m
-
5 25
,I
VN
Sub-module
Figure 26: Parts sorted by sub-module and size for the current sub-module structure
62
EVery Small
Parts Sorted by Sub-module and Size: New Sub-module Structure
-
60
-
50
140
-
'I
t
C
0 Bulk
~0-
-
C 30
N Large
C
z
10
-
-
20
0
lmlhiji
-
I
I
* Medium
U Small
I
I=
SiinmI
wI
EVery Small
Sub-module
Figure 27: Parts sorted by sub-module and size for the new sub-module structure
After the parts were sorted by size, the overall bin size for each sub-module was determined based on
the size of the largest part and the quantity of parts in it. Table 8 shows the number of large, medium,
and small bins required for the existing sub-module structure and the new sub-module structure [6].
63
Table 7: Bin requirement per sub-module
Existing Sub-modules
New Sub-modules
Sub-module
Bin Size
Quantity
Sub-module
Bin Size
Quantity
Al
Large
1
B1
Large
1
A2
Medium
1
B2
Large
1
A4
Small
1
B3
Medium
1
AS
Large
1
B4
Small
1
A6
Medium
1
B5
Medium
1
A7-E
Large
1
B6
Medium
1
A7-T
Large
1
B7
Large
1
A10
Large
1
B15
Medium
1
A12
Large
3
B19
Large
3
A13
Large
1
B21
Medium
1
A14
Small
1
B22
Medium
1
A15
Medium
1
B23
Large
1
A17
Small
1
B25
Small
1
A18
Small
1
B29
Small
1
A20
Medium
1
B30
Medium
1
A21
Multiple
Small
Medium
1
1
B31
Multiple
Small
Medium
1
1
Table 8: Overall bin requirements for existing and new sub-module structures
Size
Existing sub-modules
Large
7
7
Medium
7
8
Small
5
4
Total
19
19
64
New sub-modules
6.3.3.
Kit Design Selection
The third step of the kitting process development was selecting the kit design. Various kit designs were
evaluated with respect to four key features- modularity, size flexibility, mobility, and safety.
Modularity:
The design would have to be modular, so that the parts could be separated and kitted by sub-module.
Also, it would be ideal if the modular bins or boxes were removable instead of fixed, so that the
assemblers could carry all the parts to their workspace in the bin.
Size Flexibility:
The kit design would have to be able to accommodate different bin or box sizes, as different submodules had different sized parts and different quantities of parts.
Mobility:
It would be ideal to have a kit system that would be mobile. A kit system on wheels would obviate the
need for pallets and forklifts, and make moving parts around easy.
Safety:
The kit system will have to be able to safely carry the weight of the parts and also allow for easy
transportation of parts without dropping or damaging them.
Several different ideas were explored before two designs were shortlisted for final consideration. The
two designs considered were : bin- boxes on a louvered rack system and bin-boxes on a cart system.
Both these designs consisted of modular bin-boxes mounted on to a frame, where each of the bin-boxes
would correspond to a particular sub-module kit.
Bin-boxes on a Louvered Rack System:
This design consists of two components- the hangable bin-boxes and the louvered rack. The hangable
bin-boxes are available in several different sizes. The louvered rack can either be mobile or fixed. See
Figure 28.
65
(b)
Figure 28: Bin-boxes on a rack system (a) Fixed bench rack [22] (b) Mobile rack [23]
In case of the fixed rack system, the rack would be placed on the UES production line and the bins would
be populated at the warehouse and brought over to the main building on pallets. The production lead
would then have to load the bins onto the rack. This process would be similar to the existing process
with the only added advantage of the parts being sorted according to sub-modules and being better
visually organized. However, recycling of the bins between the production floor and the warehouse
would be challenging, due to the risk of the bins getting lost or misplaced.
In case of the mobile rack system, the bin-boxes would be populated and loaded onto the rack at the
warehouse, and then the entire system would be shipped over to the main building on the truck. The
advantage of this system would be that there would be less probability of bins getting misplaced.
However, transporting the loaded rack from the warehouse to the main building on a truck could be
challenging, with the possibility of the bins and parts falling off the rack.
Bin-boxes on a Cart System:
Bin-boxes on a cart system consists of twelve large bin-boxes stacked in three rows on a cart. The bins
and cart are of a standard size, with the bins being approximately the same size as the bins that are
currently used for kitting. The advantage of this system is that it is sturdier than the bin-boxes on a rack
66
system and that the probability of bins getting lost or misplaced is much less. The limitation of this
system is that it can house only twelve bins and the bins are all of the same size. See Figure 29.
Figure 29: Bin-boxes on a cart system [241
A meeting was held between all stakeholders - the operations manager, the manufacturing manager,
the warehouse manager, the consolidator, the manufacturing engineer, and the production lead, and it
was decided that a bin-box on a cart system would be most suitable for UES kitting, given its ability to be
easily transported and less risk of parts and bins falling off. However, modification would be required to
make it hold 19 bin-boxes in three different sizes, instead of the standard 12 same sized bins.
Size specifications, cost, and vendor information for the bin-boxes on a cart system can be found in the
appendix of this thesis.
6.3.4.
Kit Design Development
Kit design development phase involved using the off-the-shelf bin-boxes on cart system and customizing
it to suit the needs of the UES production kits. As discussed in section 6.3.2, 19 bins - 7 large, 8 medium,
and 4 small are required to kit the UES Trident parts according to the new sub-module structure
proposed by Sedore [6]. To enable this, the standard bin-boxes on cart system was modified as shown in
Figure 30. Four of the large bins were made to hold two medium sized bins each, and one large bin was
67
made to house four small bins. The figure shows the very first design that was proposed, however this
went through minor changes during the implementation phase.
Kit
Code
Shortage List
Labels
Figure 30: Modified bin-boxes on a cart system
New kit codes were proposed to enable the kitting process. The new kit codes were LA01, LA02, LA03 so
on, where 'LA' represents the UES flow line location and the two digit number following LA represents
the sub-module number. Sub-modules that did not have parts associated with them were not assigned
kit codes. Labels indicating the kit codes and procedure names were placed on the bin-boxes.
6.4. New Kitting Process Flow
The process flow for the new kitting process will be similar to the old process, with two key differences.
The process will start as usual with the production lead placing the order for the kits 24 hours before the
scheduled lay down. The new Z-pick kit codes will be used for this purpose, instead of the old codes. The
warehouse coordinator on receiving the order request will release the waves for picking the kits. Waves
for other orders may be released at the same time, and the MRP system will batch and optimize the pick
list for the pickers. The pickers will then pick parts from the different warehouse locations and drop it off
68
in the consolidation area. In the existing process, the consolidator attempts to separate parts out
according to the 6 kit codes, while the pickers are dropping parts off. Once all parts have been picked,
he scans them based on handling units, and then finally packs them into bins. In the new process, the
consolidator will be able to drop parts into bins corresponding to the kit codes, as soon as they arrive.
Once all parts are picked, he will scan all parts in the bins, one bin at a time. The new process will reduce
one step in the consolidation process. After the parts have been consolidated, they will be shipped out
from the warehouse to the main building on the earliest available truck, as per existing protocols. Once
the cart has been received, the receiver will wheel in the cart into the staging area. In contrast to the
existing process, no additional staging or organization will be required by the production lead. Figure 30
shows the existing and new process flow maps and highlights the two key differences between them.
EXISTING PROCESS FLOW
oPlace
organize
order
Issue pick
waves
0
P kpat
Drop-off
parts
cc
-ru
0
n partsts-----
0
Truck
parts
U
Receive
parts
Warehouse
(a)
69
Main Building
NEW PROCESS FLOW
z
0
B0
Place order
for kits
Issue pick
waves
Pick artsDrop-off
.
.. . . ... . .. . .
Pick
ppasrts
pr
0
parrts
Bin ~prt
patsndnpat
st.g
Warehouse
(b)
Main Building
Figure 31: Process Flow (a) Existing material handling process (b) New kitting process
6.5. Advantages of the New Kit Design and Kitting Process
The new kit design and kitting process will offer five key advantages over the existing process.
The first main advantage is that it will reduce non-value added assembly time, by reducing the time
spent by the assemblers on locating parts. Since the parts will be grouped by sub-module and all parts
corresponding to a sub-module will be placed in a single bin (with the exception of sub-module A12 or
B19, where three bins will be used), the assembler will only need to locate the bin corresponding to the
sub-module he is working on, instead of having to locate individual parts. The bin-boxes will also be
labeled with the kit codes and sub-module names to aid the assemblers. The modular nature of the bins
will allow the assemblers to pick the bins off the cart and stage it near their work area, and then put it
back on the cart at the end of the sub-module. Overall, this kit design will save time spent on searching,
locating, gathering, and organizing parts.
The second advantage is that this kitting process will standardize and reduce consolidation time.
Currently the consolidator has to wait on all parts to be picked and dropped off, before he can start
70
consolidation. Once all parts are picked, he groups them according to kit codes, and then places them
into bins. There is no standardized procedure for consolidation, and the consolidator has developed an
optimized way of doing it through trial and error. The new process will allow for 'consolidation while
picking'. As and when the picker drops off the parts, the consolidator will be able to scan the kit code
and place the part in the corresponding bin on the cart. He will no longer have to wait for all parts to be
picked, before he can start the consolidation process. The process can be further developed to enable
the pickers to directly scan and drop the parts off into the bins, further simplifying the consolidator's
job. Also, the bin-boxes on a cart system will eliminate the time spent in searching for available bins,
pallets, and pallet jacks.
The third advantage is that it will save time spent on staging the parts on the production floor.
Currently, the production lead receives the parts and then places the bins on the racks. He also
rearranges and spreads out the parts to enable easy access. With the new system, the cart will be
wheeled into a designated area on the production floor, and no additional re-organization or staging will
be required.
The fourth advantage is that it will facilitate Just-in-Time ordering and arrival of parts. Currently, all parts
for assembly are ordered at the same time and get used up over a period of five days. The large batch
size results in a long warehouse fulfillment time of 24 hours. Breaking up the large kits into smaller submodule specific kits will allow for fewer kits to be ordered at a given time, which will result in reduction
of warehouse fulfillment time. For example, it will be possible to have all kits corresponding to build and
install sub-modules arrive on the cart on the day of the laydown, and all the integration kits arrive on
pallets on the second day and then get loaded onto the cart. After the assembly is complete, the entire
system could be sent back to the warehouse to be populated for the next machine.
The fifth advantage is that the new kitting process will be more 6S compliant than the existing process.
In the new process, the parts will be sorted by procedure and the consolidation process and staging
process will be more standardized. Staging of parts using the bin-boxes on cart system will also allow for
better visual management of parts. For example, a full bin on the cart will indicate that the
corresponding sub-module has not been started; an empty slot on the cart will indicate that a procedure
is being worked on; and an empty bin on the cart will indicate that the procedure is complete. Also,
transporting parts on the cart will be safer than transporting parts on a pallet.
71
7. Implementation and Results
This chapter documents the methodology, objectives, and the procedure followed for implementation
of the new kitting process. It then discusses the results and the work that needs to be done in future to
fully implement the process.
7.1. Methodology
The implementation was carried out in two phases and each phase had distinct objectives. See Figure
32. The first phase focused on testing out the physical kit design. Here the parts were received from the
warehouse in the main building through the usual Z-pick process using the old kit codes, and then they
were manually kitted into the bin-boxes on a cart system. A trial run was performed on a Trident
assembly. The part sorting was verified and the adjustments to the part distribution and physical kit
design were made. Feedback from the floor personnel was taken into account before moving to the
second phase.
SVerify part distribution and sorting
STest out physical kit design
SUpdate MVRP system with new kit codes
eTest out the new kitting process
Figure 32: Implementation Methodology
The second phase involved testing out the kitting process. After modifications to the physical kit design
were made and the sorting was fine-tuned in Phase I, the Z-pick kit codes were updated on the MRP
system. A second trial run was performed on another Trident assembly, and in this run the parts were
sorted and kitted according to the new procedure at the warehouse. The entire process was MRP
driven, with no manual intervention. Adjustments to the process flow were made based on the feedback
from the warehouse personnel.
72
7.2. Implementation: Phase I
7.2.1.
Objectives
The objectives of Phase I were to:
i)
Test out the physical kit design and make necessary modifications
ii)
Test out the part distribution and usage, and make necessary adjustments, prior to making
any changes on the MRP system
iii)
7.2.2.
Get feedback from the assemblers on the kit design and the part distribution
Implementation Process
The implementation process started with ordering the bin-boxes on a cart system. Once the order
arrived from the supplier, it was assembled and labeled with the new kit codes and the sub-module
names. The parts for the Trident assembly were Z-picked at usual from the warehouse, using the 6 old
kit codes, 24 hours ahead of the laydown. Once these parts arrived at the main building, they were
manually sorted into the bin-boxes according to the new sub-modules and kit codes. Few changes were
made to the organization of bins, in order to neatly accommodate all the parts. After being fully
populated, the bin-boxes on a cart system was staged in the UES production line. A form was placed in
each bin, with instructions for the assemblers to capture the part numbers of the missing parts and
excess parts. The bulk parts associated with the Z-picks were left in the bulk staging area. A meeting
was held on the day prior to the laydown and everyone involved was made aware of the new kitting
system and the information capture forms. See Figure 33.
73
Figure 33: Bin-boxes on a cart kit design
Once assembly started, the part usage was continuously monitored. Missing parts, wrongly grouped
parts, and excess parts were tracked. At the end of the two day assembly cycle, the information on the
forms and additional information captured through interviews was consolidated and used to update the
sorting list and the kit design.
7.2.3.
Results
The Phase I trial run resulted in several key findings with respect to parts usage, parts ordering, parts
distribution, and the physical kit design. This information was used to update the MRP system in Phase 11
to call out the correct parts, to prevent double-picking of parts, to reassign parts to correct kit codes,
and to improve the physical kit design.
Improvement in Part Ordering:
The parts distribution by sub-module was fairly accurate and minimal redistribution had to be done.
However, the key observation was that approximately a third of the parts picked for assembly were
excess parts that did not get used in assembly. These excess parts fell into three categories -doublepicked parts, parts no longer being installed, and wrongly grouped parts.
74
54 unique parts were identified that were being Z-picked at the warehouse, under the 6 old kit codes,
which were already part of the in-line inventory on the UES line. The double picking of parts not only
resulted in wasted effort on part of the pickers and consolidator at the warehouse, but also resulted in
wasted effort by the production lead on the assembly floor, because typically he would have to go place
these excess parts in the in-line racks at the end of each assembly cycle. The MRP system was updated
in Phase 11, to stop driving demand for these parts to the warehouse.
6 parts were identified that were always Z-picked, but never got installed on the machine. These parts
were installed in the past, but were no longer required in the newer revisions of the UES. The BOM and
the MRP system had not been updated when the revisions were made. Most of these parts were low
cost parts and were typically thrown away. These parts were removed from the BOM during Phase 11.
7 parts were identified - 3 parts which were used in testing, 2 parts in final assembly, and 2 parts in
shipping - that were wrongly grouped under the 6 old kit codes. These parts were assigned to the
already existing kit codes for testing, final assembly, and shipping respectively during Phase II of the
implementation.
Finally, 11 parts which were not part of the in-line inventory on the UES line, but were small hardware
parts like nuts, screws, and washers, were identified td be made in-line inventory. The MRP system was
updated and parts were procured for the line side inventory in Phase I of the implementation.
A summary of all the findings with respect to parts usage, ordering, and distribution, along with action
items for Phase I of implementation can be seen in Table 9.
Table 9: Changes in parts ordering
Double-picked parts
54
Action Items for Phase 11
Update MRP to stop driving demand to the warehouse
Unused parts
6
Remove from BOM and update MRP system
Wrongly grouped parts
7
Reassign to correct kits
Potential line side parts
11
Remove from kits and add to in-line inventory
Parts Category
Quantity
75
Improvement in Kit Design:
were made while
The Phase I trial run resulted in a few changes in the kit design. Some changes
the trial run but prior to
populating the bins during the trial run, and some changes were made after
beginning of Phase 11.
requirements for the kits. For
Adjustments to sorting of parts resulted in some changes in the bin size
kit code LA20 had to be
example, LA04 now needed a large bin instead of a small bin. Also, an additional
removed and
created for sub-module B20 which was earlier missed due to error in sorting. Kit LA23 was
assigned to subreplaced with LA24, as the parts assigned to sub-module B25 initially should have been
module B24. The final kit design can be seen in Figure 34.
and this kit code
All parts in the 'MULT' kit code were made in-line inventory at the end of the trial run
was made redundant.
Figure 34: Final kit design
76
7.2.4.
Summary
Phase I successfully accomplished the objectives of testing out the kit design and the parts distribution.
The physical kit design was tested out and minor modifications were made during the trial run, while
changes which were more significant were implemented in Phase 11. Minor redistribution of parts and
reorganization of kits was done.
78 parts were identified, which were being unnecessarily picked at the warehouse. These included parts
which were no longer being installed on the tool, parts which already existed as in-line inventory and
were being double picked at the warehouse, parts that were wrongly grouped into assembly kits, and
parts that could be made in-line inventory. Phase I concluded with identifying these inefficiencies and
proposing changes to be made to the MRP system in Phase 11, so that only the right parts and right
quantities of parts were pulled from the correct locations.
7.3. Implementation: Phase II
7.3.1.
Objectives
The objectives of Phase II were to:
i)
Update the MRP system to reflect the new kit codes, which would in turn drive the picking
and consolidation process at the warehouse
ii)
Address inefficiencies identified in Phase I with respect to excess parts getting ordered
iii)
Test out the proposed kitting process at the warehouse
iv)
Get feedback from the warehouse personnel on the new kitting process
7.3.2.
Implementation Process
Phase 11 started with updating the MRP system with new kit codes and location codes for the parts. The
parts distribution and sorting list that was generated using the logbooks and MRP, was verified and finetuned during Phase I of the implementation process. This information was used to change the kit codes
on the system. The assembly parts that were earlier associated with 6 kit codes, were now distributed
over 17 new kit codes. See Table 10.
77
Table 10: Old kit olds and new kit codes
Old Assembly Kit Codes
New Assembly Kit Codes
ILA1
LA01
LA19
1LA2
LA02
LA20
1LA4
LA03
LA21
1LA7
LA04
LA22
LAWH
LA05
LA24
RACK
LA06
LA25
LA07
LA29
LA15
LA30
LA31
Also, the MRP system was updated to ensure that the 78 excess parts identified in Phase 1, would not
get picked from the warehouse in future. The location codes for the 54 parts that already existed as inline inventory on the UES line were changed on the MRP system. This ensured that parts would not get
picked at the warehouse, and be flagged as floor stock. The BOM was updated to remove the 6 parts
that are no longer used on UES. The 7 parts that were wrongly grouped under assembly were reassigned
to correct kit codes corresponding to testing, shipping, and final assembly. Also, the 11 parts which were
found to be suitable for in-line storage were made in-line inventory by updating the system with new
location codes and re-order quantities. These parts were also physically procured and placed on the line
side racks.
The modified bin-box on a cart system was sent to the warehouse two days before the scheduled
laydown. 24 hours before the laydown, the production lead placed the order for the Z-picks using the
new and old kit codes. Z-picks orders for the old kit codes were placed in addition to the new kit codes,
to ensure that all parts required for assembly got picked, in case some parts got missed during the initial
sorting. The system was allowed to generate the pick list, consolidation codes, and handling units based
on the new kit codes, and there was no manual intervention. Waves for these kit codes were generated
as usual by the warehouse coordinator, and the parts were picked by the pickers as usual. Consolidation
was done under moderate supervision and the process followed was slightly different than usual. The
consolidator dropped the parts into the corresponding bins as and when they arrived. Once all parts had
arrived, he scanned the parts in each of the bins, one bin at a time, and closed out all the handling units.
78
A top level handling unit was generated for each kit code and a sticker corresponding to it was placed on
each bin. See Figure 35. After this process was complete the bin-box system was sent over to the main
building in the regular fashion on a truck. The cart strapped down to the truck, to prevent it from
moving. See Figure 36. The parts were received at the main building and were transacted by the
receivers using the handling units.
Figure 35: Consolidation of parts into the kits at the warehouse
79
Figure 36: Cart strapped down to the truck for transportation
The cart was then wheeled in to the staging area in preparation for the laydown. The shortage list was
printed out by the production lead and placed on the rack. The bins with shortages were highlighted
with red stickers.
7.3.3.
Results
Phase I of the implementation proved that the process could be successfully implemented at the
warehouse, with the MRP system driving the picking and consolidation of parts, according to the new kit
codes. The benefits of this process were observed both at the warehouse and production floor.
Warehouse:
The entire picking and consolidation process took 1.5 hours with no other orders in the system. Since
the picking and consolidation time is primarily driven by the number of orders in the system, a fair
comparison of consolidation times between the new and kitting processes could not be made. However,
an interview with the consolidator confirmed that the new process did not increase the complexity of
the consolidation process, and with a few more iterations and increased familiarization with the new
process, the consolidation time could be significantly reduced.
80
The change in picking time with the new process could not be estimated, because as mentioned earlier,
it depends on the number of orders in the system. All orders are batched and the system optimizes the
picking order and work distribution between the pickers.
However, an interview with the picker
suggested that breaking up of the old kits into smaller kits, allowed for better workload distribution
between pickers. For example, the picking of liners which is the most time consuming and physically
demanding process, could now be distributed between two pickers and could be worked on in parallel.
Removing the line side parts from the Z-picks that were being double picked at the warehouse resulted
in time savings from reduced number of picks. Only two thirds of the original number of parts had to be
picked. Since picking is the bottleneck step in the picking and consolidation process, this significantly
reduced the overall material handling time at the warehouse.
Material movement post consolidation was also simplified, as a pallet and forklift were no longer
required. The cart was easily wheeled in to the truck and strapped down. Strapping required less than 3
minutes. No parts fell off or got damaged during the transportation process.
Production Floor:
Receiving of parts was simplified as a forklift was not required. Scanning in the handling units was also
made simpler as all the handling units were easily visible and accessible on the cart, as opposed to the
earlier system where the receiver had to find all the bins associated with the order and then find where
the handling unit was placed on each bin.
The new kitting process saved the production lead an hour's worth of effort spent on staging, reorganizing parts, and handling extra parts. It saved 30 minutes of time spent on redistributing parts and
putting the parts away on racks, and it saved another 30 minutes of effort on putting back excess parts
into line side bins.
The biggest advantage observed was that the new kits saved the assemblers a lot of time and effort
spent on locating and gathering the right parts required for the sub-module they were working on.
Interviews suggested that on an average 10-12 minutes per sub-module were saved, and an overall
saving of 4 labor hours per machine. The production lead also indicated that this system would greatly
help new assemblers on the line, who were not familiar with the parts.
81
7.3.4.
Summary
Phase II of the implementation focused on updating the MRP system with the new kit codes and trialing
the picking and consolidation process at the warehouse, in accordance with the new process.
Inefficiencies in material handling that were identified in Phase I, like ordering of excess and
unnecessary parts, were also addressed.
Benefits of the new process were observed and acknowledged at the warehouse and the production
floor. Increasing the number of kit codes did not affect the complexity of the consolidation process and
breaking up the kits into smaller kit codes enabled better workload distribution amongst pickers.
Eliminating excess parts and unnecessary parts resulted in pickers having to perform fewer picks. The
material shipping and receiving process was also simplified. The process resulted in time savings on the
production floor through elimination of non-value added activities like staging, re-organizing, searching,
and gathering of parts.
7.4. Discussion
The overall goal of implementation was to test and prove out the new kit design and the new kitting
process. This was successfully accomplished over the two phases of implementation. In addition, several
inefficiencies in the material handling process, which were not very obvious, came to light and were
addressed during this process.
Carrying out the implementation in two phases had several advantages. Firstly, it was possible to have
specific focused goals for each phase. The first phase was focused on verifying the part sorting and
testing out the physical kit design. To verify the sorting, the parts were manually kitted into the
proposed kit codes, and their usage was tracked. The assembly process was closely monitored and any
instances of missing or misplaced parts were noted. Also, at the end of each sub-module the excess
parts were noted. This information was used not only to fine-tune the part sorting list, but also to
determine and address the root cause of the inefficiencies. This phase also helped verify that all parts
for assembly could be fit on to a single cart system. The second phase focused on testing out the kitting
process at the warehouse. To enable this, the MRP system had to be updated with the new kit code and
location codes. This was followed by trying out the picking and consolidation process at the warehouse
using the new kit codes. The entire process was system driven, with minimal manual intervention. This
phase proved out the concept and the merits of consolidation while picking.
82
The second advantage of phase-wise implementation was that it allowed for incremental changes and
improvements to be made between phases. In phase I the errors in sorting were identified and
addressed before the kit codes were changed on the system. Also, this allowed for a design iteration of
the physical kit after making changes to the part distribution and by incorporating feedback from the
assemblers.
The third advantage of breaking down the implementation into two phases was that it gave an
opportunity to capture inefficiencies in the process that were earlier not identified and implement
corrective measures, prior to making major changes on the MRP system. The trial run in Phase I led to
the finding that approximately 67 parts picked and delivered from the warehouse are excess parts. The
root causes and action items were determined, and the MRP system was updated to stop having these
parts pulled from the warehouse. Implementing these change prior to the Phase II trial run at the
warehouse saved the pickers and consolidator a lot of effort, as they now had to handle only two-thirds
of the original quantity of parts.
The biggest advantage observed with this new process was the time savings from reduced non-value
added activities. The implementation showed that the new production kits saved the assemblers a lot of
time and effort spent on locating and gathering parts, as the parts were sorted by procedure and the
bins were clearly labeled to facilitate easy spotting. These kits also saved the production lead a lot of
time spent on staging parts.
Prior to the trial runs there was concern that breaking up kit codes would increase the workload of the
pickers and the complexity of the consolidation process. However, it was found that breaking up the kit
codes allowed for better workload distribution amongst pickers and multiple picks could be done in
parallel. Also, the complexity of the consolidation process did not increase due to the additional kit
codes. With increased familiarization with the new process, it is expected that the consolidation time
will be reduced.
Phase I and Phase 11 proved that the proposed kit design and kitting process were feasible ideas that
worked both on the production floor and the warehouse, and could be widely implemented across all
lines at VSEA.
83
7.5. Next Steps
Phase I and Phase I of implementation proved out the concepts for the kit design and the kitting
process. These were successfully accomplished by performing trial runs on two Trident assemblies, using
a prototype kit system. This kitting process now needs to be fully implemented on the UES line for the
Trident model. Also, the proposed kitting system is applicable to all other non- Trident UES assemblies,
and to other modules like the Source, Analyzer, and Corrector, and needs to eventually be extended to
them. Figure 37 shows the proposed plan to fully implement the kitting process across the VSEA
production facility.
"
Verify part distribution and sorting for Trident UES
" Test out physical kit design
* Update MRP system with new kit codes for Trident UES
* Test out the new kitting process
*
Fully implement the kitting process for all Trident UES assemblies
11
" Extend the kitting process to other non-Trident UES assemblies
" Extend the kitting process to Mix-Mod line
E
Complete
In process
E
Not started
Figure 37: Phases of implementation
Phase III of implementation would focus on fully implementing this kitting system on all Trident UES
assemblies. This would require procuring more cart systems, and customizing them for UES assembly as
described in Section 6.3.4. The number of carts required would depend on the maximum lay-down rate
and the average assembly time for the UES assembly. It is recommended to maintain some spares too.
Also, initially parts will have to ordered using both old and new kit codes, to prevent missing parts like
special options and selects which are occasionally used, and may not have been captured during the
84
initial sorting and part distribution exercise. Such parts associated with old kit codes will have to be
identified during each assembly and be assigned to the appropriate new kit code. It is recommended
that the system be updated after every assembly to reflect this change, however the parts could be
identified and the system could be updated after every few assembly cycles. It is expected that over the
next 4 or 5 builds all the stray parts will be captured and assigned to the new kit codes, and the old kit
codes could be made obsolete. This phase of implementation is currently in-process.
Phase IV of implementation would focus on extending the kitting process to the non-Trident UES
assemblies, like the other High Current assemblies and Medium Current assemblies. This would require
going through the entire process of sorting by procedure, recording size requirements, and modifying
the physical kit design as documented in sections 6.3.1, 6.3.2, and 6.3.4 respectively, for the parts
specific to High Current and Medium Current UES assemblies. The process however, will not be as
involved as the initial process, as majority of the parts picked at the warehouse are expected to be
common to all flavors of the UES.
Phase V of implementation would focus on extending the kitting process to other modules like the
Source, Analyzer, and Corrector in the Mixed-Mod line. This would require sorting parts by procedure,
recording size requirements, evaluating kit designs, and customizing kit design for each module, as
documented in section 6.3. This would require significant amount of effort, resources, and time to
implement.
85
8. Recommendations
In this thesis it was shown that an improved kitting process can greatly reduce time spent on non-value
added activities by the assemblers, production lead, and the consolidator. In addition to implementing
the proposed kitting process, there are several other steps that VSEA can take to improve their material
handling process.
Existing Z-pick kit codes for all the modules- Source, Analyzer, Corrector, and UES should be reviewed
and evaluated. Most kit codes have parts grouped in an ad-hoc manner. These kit codes need to be
replaced with new kit codes, which have parts grouped by procedure or sub-module. Also, the kit code
names need to be made more representative of the module and sub-module that they are associated
with.
Logbooks should be updated with the correct sequence of sub-modules and tasks, and should have the
corresponding kit code mentioned at the start of each sub-module, to make it easier for the assembler
to identify the kit required for the sub-module that he is working on.
The line side inventory for each of the UES and Mixed-Mod lines needs to be reviewed. During the trial
run it was observed that 54 parts which were already a part of the in-line inventory were being doublepicked at the warehouse through Z-picks. Such parts need to be identified on all the lines and the MRP
system needs to be updated to change the location code, to ensure that the parts do not get picked at
the warehouse. Also, small hardware parts that are not already part of the in-line inventory and get
picked at the warehouse, need to be identified and made in-line. This will greatly reduce the workload
of the pickers and consolidators at the warehouse, and also reduce the order fulfillment time.
Currently there is no way for the warehouse to see or indicate shortages associated with a Z-pick order.
The shortage list can only be generated once the parts have been received at the main building. It would
be beneficial to develop a way for the EWM (Extended Warehouse Management) system to generate a
list of shortages, which could be attached to the Z-pick parts after consolidation. This would save the
assemblers and production lead a lot of time and effort spent on figuring out shortages.
Shortages related to any given module on the production floor are tracked by multiple different people
in an informal manner, and there is no place where this information is consolidated. The production lead
tracks the shortages associated with the Z-picks, by performing a visual check of all the parts arrived.
The production controller tracks the shortages associated with the shop orders by using the MRP
86
system. The production supervisor tracks the shortages associated with the supplier managed parts,
through communication with the buyers. The communication between these three people regarding
shortages is again very informal. It would be advisable to adopt a more formal way of documenting and
communicating the shortages. One easy way could be maintaining a spreadsheet on a shared server,
where the production lead, supervisor, and controller document the shortages they track for each
machine. This will not only make the information available to everyone, but will also allow for
documentation of shortages which could be analyzed in future.
Just-in-Time ordering and receiving of parts can be piloted using the new kitting process. As the new
kitting system has kits broken down by sub-module, only the kits required for a day's worth of assembly
activities could be ordered at a time. Currently the order fulfillment time from the warehouse is 24
hours, but with smaller batches of parts being ordered at a given time, this can be reduced to a much
smaller period. This will not only help the warehouse meet its fulfilment time reduction goals, but also
lead to less clutter and material inventory being held on the production floor.
The new ktting process can also be used to further reduce the workload of the consolidator, by training
the pickers to pick and drop off parts into the bins corresponding to the kit codes. This would then allow
the consolidator to focus on just scanning the parts and closing out the order once picking is complete.
Currently there is only one consolidator and multiple pickers. This will allow for workload levelling
between pickers and the consolidator.
It is also recommended to have a second consolidator at the warehouse. It could be a picker or mover
who is cross trained to help out on busy days. Currently there is only one person who consolidates all
production orders. His workload can be very high on busy days, and sometimes picks have to be
performed much ahead of time to accommodate his availability.
87
9. Conclusions
Production floor and warehouse operations at VSEA were studied with an aim to reduce the lead time of
the UES module. Through detailed time studies and data analysis it was found that 18% of the activities
were non-value added activities, of which 28% were related to material handling.
A new kitting process was developed which enabled parts to arrive to the production floor sorted by
sub-modules. A method to indicate shortages was also proposed. This kit design and process also
enabled Just-in-Time ordering of parts from the warehouse and made the material handling process
more 6S compliant.
The new process was implemented and two trial runs were performed. It was shown the new process
reduced time spent on parts handling by 70%, and overall non-value added activities on the production
floor by 20%.
The proposed kitting process was developed for a Trident UES, but can be easily extended to other
modules like the Source, Analyzer, and Corrector on the Mixed-Mod line.
88
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References
[1] Wikipedia, 2014, "Semiconductor Device Fabrication", from
http://en.wikipedia.org/wiki/Semiconductordevicefabrication [Accessed: 16- May-2014].
[2] Hamm, R. W. and Hamm, M. E., 2012, Industrial Accelerators and their Applications, World Scientific,
,Hackensack, NJ.
[3] Varian Semiconductor Equipment Associates, 2012, "Varian Services Company History", from
https://www.vsea.com/company.nsf/docs/history
[4] Applied Materials, 2014, "1967-1979: The Early Years", from
http://www.appliedmaterials.com/company/about/history/early-years
[5] Varian Semiconductor Equipment Associates, 2010, "10-K Annual Report" from
http://www.appliedmaterials.com/sites/default/files/vsea20lO.pdf [Accessed: 16- May-2014].
[6] Sedore, B., 2014, "Assembly Lead Time Reduction through Constraint Based Scheduling", M.Eng.
Thesis, Massachusetts Institute of Technology.
[7] Applied Materials,2014, "Trident- Theory of Operations", AMAT Confidential Document.
[8] Applied Materials, 2010, "Universal End Station - Theory of Operation", AMAT Confidential
Document.
[9] Bhadauria, A., 2014, "Production Lead Time Reduction through Improved Testing Protocols", M.Eng.
Thesis, Massachusetts Institute of Technology.
[10] Krafcik, J.F., 1988, "The Triumph of the Lean Production System", Sloan Management Review (Fall),
pp. 41-52.
[11] Womack, J.P., Jones, D.T., and Roos, D., 1990, The Machine That Changed the World, Rawson
Associates, New York, NY.
[12] Panview, 2013, "Finding Muda in your Process", from http://www.panview.nl/en/lean-productiontoyota-3m-model/finding-muda-waste-your-process
[13] Hopp, W.J. and Spearman, M.L., 1996, Factory Physics, Irwin/McGraw-Hill, New York, NY.
[14] Panview, 2013, "Finding Mura in your Process", from http://www.panview.nl/en/lean-productiontoyota-3m-model/finding-mura-variation-your-process
[15] Panview, 2013, "Finding Muri in your Process", from http://www.panview.nl/en/lean-productiontoyota-3m-model/finding-muri-overburden-your-process
91
[16] Johansson, M.I., 1991, "Kitting Systems for Small Parts in Manual Assembly Systems" in Pridham, M.
and O'Brien C., 1991, Production Research: Approaching the
2 1't
Century, Taylor & Francis, London, pp.
225-230.
[17] Bozer, Y.A. and McGinnis, L.F, 1992, "Kitting versus Line Stocking: A Conceptual Framework and a
Descriptive Model", International Journal of Production Economics, pp. 1-19.
[18 ] Schwind, G.F., 1992, "How Storage Systems Keep Kits Moving", Material Handling Engineering,
pp.43-45.
[19] Ding, F.Y. and Balakrishnan, P., 1990, "Kitting in JIT Production", Production and Inventory
Management Journal, 31, pp. 25-28.
[20] Johansson, E. and Johansson, M.I., 2006, "Materials Supply Systems Design in Product Development
Projects", International Journal of Operation and Product Management, 26, 4, pp.371-393.
[21] Daneshmand, M., 2011, "Lean Manufacturing in a Mass Customization Plant: Improved Efficiencies
in Raw Material Presentation", M.Eng. Thesis, Massachusetts Institute of Technology.
[22] McMaster-Carr, 2014, "Design-Your-Own Louvered Bin-Box Systems- Bench Racks", from
http://www.mcmaster.com/#bin-box-racks/=sxb7s0
[23] McMaster-Carr, 2014, "Design-Your-Own Louvered Bin-Box Systems- Double Sided Floor Rack",
from http://www.mcmaster.com/#bin-box-racks/=sxb9wx
[24] McMaster-Carr, 2014, "Jumbo Bin-Box Carts- 12 Bin-Boxes", from
http://www.mcmaster.com/#bin-box-racks/=sxbayy
92