EA ZC412 / MM ZC412 / DM ZC412
FLEXIBLE MANUFACTURING
SYSTEMS
BITS Pilani
Pilani Campus
Girish Kant Garg
Department of Mechanical Engineering
1
Review
 Manufacturing Models and Metrics (Ch-3)
 Manufacturing Costs
– Fixed and Variable Costs
– Direct Labor, Material and Overhead
 Computer Numerical Control (Ch-7)
 Fundamentals of NC Technology
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-6, 10/9/22
BITS Pilani, Pilani Campus
Learning Objectives
 Computer Numerical Control (Ch-7)
 Analysis of Positioning Systems
 Review (Lecture 1-8)
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-6, 10/9/22
BITS Pilani, Pilani Campus
BITS Pilani
Pilani Campus
Computer Numerical Control (Ch-7)
Numerical Control (NC) Defined
•
•
•
Form of programmable automation in which the mechanical
actions of a machine tool or other equipment are controlled
by a program containing coded alphanumeric data
The alphanumeric data represent relative positions
between a workhead (e.g., cutting tool) and a work part
When the current job is completed, a new program can be
entered for the next job
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-7, 11/9/22
BITS Pilani, Pilani Campus
Common NC Machining
Operations
a)
b)
c)
d)
Turning
Drilling
Milling
Grinding
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-7, 11/9/22
BITS Pilani, Pilani Campus
Calculation of Machining Time
(Operations on Lathe)
• A 150 mm long, 12 mm diameter stainless steel rod is to be
reduced in diameter to 10 mm by turning on a lathe in one pass.
The spindle rotates at 500 rpm, and the tool is moving at an axial
speed of 200 mm/min. Calculate material removal rate and time
required for machining the steel rod.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-7, 11/9/22
BITS Pilani, Pilani Campus
Calculation of Machining Time
(Operations on Lathe)
• A small scale industry received an order to do the machining of
stainless steel shafts of 75 mm diameter and 200 mm long, with
one cut each, using a carbide cutting tool. The spindle speeds
available are 140, 200, 280, 400, 560 and 800 rpm. The
suggested feed and speed for the above job-tool combination are
0.25
mm/rev
and
100
m/min
respectively.
Estimate
the
manufacturing time required for turning 1000 shafts allowing one
minute for the center hole drilling and 2 minutes for handling of
each workpiece.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-7, 11/9/22
BITS Pilani, Pilani Campus
Calculation of Machining Time
(Operations on Lathe)
• Calculate the time required to machine a workpiece 170 mm long,
60 mm diameter to 165 mm long, 50 mm diameter. The workpiece
rotates at 440 rpm, feed is 0.3 mm/rev and maximum depth of cut
is 2 mm. Assume approach and over-travel distance each as 5
mm for turning operation.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-7, 11/9/22
BITS Pilani, Pilani Campus
Calculation of Machining Time
(Operations on Lathe)
A XYZ company wants to manufacture washers of external diameter
=40 mm, internal diameter = 35 mm and thickness =5 mm on a lathe
machine. The raw material is available in the form of hollow mild steel
pipe of external diameter 40 mm, internal diameter 35 mm and length
1000 mm. The operator can move the HSS cutting tool at a speed of 20
mm/min along the axis of rotation of raw material and at a speed of 10
mm/min perpendicular to the axis of rotation of raw material. Assume
the spindle is rotating at 750 rpm, and number of passes as equal to one.
Determine the minimum time to cut one washer.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-7, 11/9/22
BITS Pilani, Pilani Campus
Basic Components of an NC
System
1. Program of instructions
 Called a part program in machining
2. Machine control unit
 Controls the process
3. Processing equipment
 Performs the process
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Basic Components of an NC
System
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Analysis of Positioning NC
Systems
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Analysis of Positioning NC
Systems
Two types of NC positioning systems:
1. Open-loop - no feedback to verify that the actual
position achieved is the desired position
2. Closed-loop - uses feedback measurements to confirm
that the final position is the specified position
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Open Loop Positioning
systems
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Open Loop Positioning
systems
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Open Loop Positioning
systems
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Open Loop Positioning
systems
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Open Loop Positioning
systems
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Example-1
The worktable of a positioning system is driven by a ball screw
whose pitch=6 mm. The screw is connected to the output
of a stepper motor through a gearbox whose ratio is 5:1.
The stepper motor has 48 step angles. The table must
move a distance of 250 mm from its present position at a
linear velocity = 500 mm/min. Determine
(a) How many pulses are required to move the table the
specified distance
(b) The required motor speed and pulse rate to achieve the
desired table velocity.
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Example-2
A stepper motor with 50 step angles is coupled to a
leadscrew through a gear reduction of 5:1 (5 rotations of the
motor for each rotation of the leadscrew). The leadscrew
has 1.25 threads/cm. The worktable driven by the leadscrew
must move a distance = 40.0 cm at a feed rate = 90 cm/min.
Determine (a) the number of pulses required to move the
table, (b) required motor speed
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Motion Control Systems
Closed loop
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
Optical Encoder
Device for measuring rotational position and speed:
(a) apparatus and
(b) series of pulses to measure rotation
Common feedback sensor for closed-loop NC control
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-8, 17/9/22
BITS Pilani, Pilani Campus
BITS Pilani
Pilani Campus
Review Lecture – 1
Introduction to FMS
What is Manufacturing?
 Manufacturing (Latin word): Manus + Factus : Made by hands
 A value addition process by which raw materials are
converted into finished product.
Definition of manufacturing
as a technological process
Definition of manufacturing
as an economic process
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
Importance of Manufacturing
 Manufacturing (Latin word): Manu + Factus : Made by hands
 A value addition process by which raw materials are
converted into finished product.
 GDP of a country is a function of manufacturing. Higher the
level of manufacturing higher the standard of living. (In U.S,
manufacturing contributes more than 12% to GDP, employ
18% of workforce and 40% of export).
 Manufacturing accounts for 37% of global energy demand.
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
Importance of Manufacturing
Manufacturing
37%
Machine tools
75%
Mining, construction
and others
63%
Casting, forming and others
25%
Global Energy Demand
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
Importance of Manufacturing

Provides the hand on experience about different processes
required for production of different products.

A value addition process by which raw materials are converted
into finished product.

GDP of a country is a function of manufacturing. Higher the level
of manufacturing higher the standard of living. (In U.S,
manufacturing contributes more than 12% to GDP, employ 18% of
workforce and 40% of export).

Manufacturing accounts for 37% of global energy demand.

Manufacturing cost represent about 40% of a product’s selling
price.
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
Importance of Manufacturing
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
Importance of Manufacturing
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
Importance of Manufacturing
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
Importance of Manufacturing
Casting
Processes
Forming
Processes
Metal Cutting
Processes
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
Joining
Processes
BITS Pilani, Pilani Campus
Importance of Manufacturing
 Melting material and pouring it into a cavity of
desired shape.
– (Casting)
 Removing unnecessary material (-).
– (Metal cutting or Machining)
 Moving material from one region to another (0).
– (Forming)
 Putting materials together (+).
– (Joining)
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
What is Flexible Manufacturing
System
 Flexible + Manufacturing + System
 Manufacturing System
 It is a collection of people, equipment and procedures
organized to perform the manufacturing operations of a
company.
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
What is Flexible Manufacturing
System
 Manufacturing System
Manual Work
System
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
What is Flexible Manufacturing
System
 Manufacturing System
Worker Machine
System
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
What is Flexible Manufacturing
System
 Manufacturing System
Automated
System
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
What is Flexible Manufacturing
System
 Manufacturing Support System
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
What is Flexible Manufacturing
System
 A flexible manufacturing system (FMS) consists of a group of
processing workstations, interconnected by an automated
material handling and storage system, and controlled by a
distributed computer system.
 It is capable of processing a variety of different parts
simultaneously and quantity of production can be adjusted in
response to changing demand patterns.
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-1, 23/7/22
BITS Pilani, Pilani Campus
Review (Lecture - 2)
 Introduction to Production or Manufacturing Systems (Ch-1)
– Manufacturing Systems
– Automation in Manufacturing Systems
– Manual Labor in Manufacturing Systems
– Automation Principle and Strategies
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Automation in Production
Systems
 Two categories of automation in the production system:
 Automation of manufacturing systems in the factory
 Computerization of the manufacturing support systems
 The two categories overlap because manufacturing
support
systems
are
connected
to
the
factory
manufacturing systems.
 Computer-Integrated Manufacturing (CIM)
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Computer-Integrated
Manufacturing (CIM)
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Automated Manufacturing
Systems
Automated Manufacturing Systems operate in the factory on the
physical product.
Examples:
 Automated machine tools that process parts.
 Transfer lines that performs a series of machining
operations.
 Automated assembly systems.
 Industrial robots that perform processing or assembly
operations.
 Automated material handling and storage systems to
integrate manufacturing operations.
 Automatic inspection systems for quality control.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Automated Manufacturing
Systems
Three basic types:
1. Fixed automation
2. Programmable automation
3. Flexible automation
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Fixed Automation
A system in which the sequence of processing (or
assembly) operations is fixed by the equipment
configuration.
Typical features:
 Suited to high production quantities.
 High initial investment for custom-engineered equipment.
 High production rates.
 Relatively inflexible in accommodating product variety.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Programmable Automation
A system designed with the capability to change the
sequence of operations to accommodate different
product configurations.
Typical features:
 High investment in general purpose equipment.
 Lower production rates than fixed automation.
 Flexibility to deal with variations and changes in product
configuration.
 Most suitable for batch production.
 Physical setup and part program must be changed
between jobs (batches).
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Flexible Automation
 An extension of programmable automation in which the
system is capable of changing over from one job to
the next with no time lost between jobs.
Typical features:
 Flexibility to deal with soft product variety.
 High investment for custom-engineered system.
 Continuous production of variable mixtures of products.
 Medium production rates.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Computerized Manufacturing
Support Systems
 To reduce the amount of manual and clerical effort in
product design, manufacturing planning and control, and
the business functions.
 Integrates computer-aided design (CAD) and computeraided manufacturing (CAM) in CAD/CAM.
 CIM includes CAD/CAM and the business functions of
the firm.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Reasons for Automating








To increase labor productivity.
To reduce labor cost.
To mitigate the effects of labor shortages.
To reduce or remove routine manual and clerical tasks.
To improve worker safety.
To improve product quality.
To reduce manufacturing lead time.
To accomplish processes what cannot be done
manually.
 To avoid the high cost of not automating.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Manual Labor in Production
Systems
Is there a place for manual labor in the modern
production system?
– Answer: YES
Two aspects:
1. Manual labor in factory operations
2. Labor in manufacturing support systems
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Manual Labor in Factory
Operations
 The long term trend is toward greater use of automated
systems to substitute for manual labor.
When is manual labor justified?
– Some countries have very low labor rates and automation
cannot be justified.
– Task is too technologically difficult to automate.
– Short product life cycle.
– Customized product requires human flexibility.
– To cope with ups and downs in demand.
– To reduce risk of product failure.
– Lack of capital
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Labor in Manufacturing
Support Systems
Product designers who bring creativity to the
design task.
Manufacturing engineers who
– Design the production equipment and tooling
– And plan the production methods and routings
 Equipment maintenance.
 Programming and computer operation.
 Engineering project work.
 Plant management.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Automation Principles and
Strategies
1. The USA Principle
2. Ten Strategies for Automation and Process
Improvement
3. Automation Migration Strategy
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
U.S.A Principle
1. Understand the existing process
–
–
–
Input/output analysis
Value chain analysis
Charting techniques and mathematical modeling
2. Simplify the process
–
Reduce unnecessary steps and moves
3. Automate the process
–
–
Ten strategies for automation and production systems
Automation migration strategy
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Ten Strategies for Automation
and Process Improvement
1. Specialization of operations
2. Combined operations
3. Simultaneous operations
4. Integration of operations
5. Increased flexibility
6. Improved material handling and storage
7. On-line inspection
8. Process control and optimization
9. Plant operations control
10. Computer-integrated manufacturing
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Automation Migration Strategy
for Introduction of New Products
Phase 1 – Manual production
–
–
Single-station manned cells working independently
Advantages: quick to set up, low-cost tooling
Phase 2 – Automated production
–
–
Single-station automated cells operating independently
As demand grows and automation can be justified
Phase 3 – Automated integrated production
–
Multi-station system with serial operations and automated
transfer of work units between stations
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Automation Migration Strategy
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-2, 30/7/22
BITS Pilani, Pilani Campus
Review (Lecture - 3)
Case Study
– Optimization of Machining Parameters for Improving Energy Efficiency
using Integrated Response Surface Methodology and Genetic
Algorithm Approach
– Optimization of tool geometry parameters for turning operations based
on the response surface methodology
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-3, 20/8/22
BITS Pilani, Pilani Campus
BITS Pilani
Pilani Campus
Review Lecture 4-5
Group Technology and Cellular Manufacturing (Ch-18)
Overview of Group
Technology
•
•
Parts in the medium production quantity range are
usually made in batches
Disadvantages of batch production:
– Downtime for changeovers
– High inventory carrying costs
•
GT minimizes these disadvantages by recognizing that
although the parts are different, there are groups of
parts that possess similarities
60
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Production Facilities
 A manufacturing company attempts to organize its
facilities in the most efficient way to serve the particular
mission of the plant.
 Certain types of facilities are recognized as the most
appropriate way to organize for a given type of
manufacturing.
The most appropriate type depends on:
 Types of products made
 Production quantity
 Product variety
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Production Quantity
Number of units of a given part or product
produced annually by the plant.
Three quantity ranges:
1. Low production – 1 to 100 units
2. Medium production – 100 to 10,000 units
3. High production – 10,000 to millions of
units
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Product Variety
Refers to the number of different product or part designs or
types produced in the plant.
Inverse relationship between production quantity and
product variety in factory operations.
Product variety is more complicated than a number.
 Hard product variety – products differ greatly.
Few common components in an assembly
Ex: Difference between car and truck.
 Soft product variety – small differences between products.
Many common components in an assembly
Difference between car models in same production
line.
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Product Variety vs. Production
Quantity
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Low Production Quantity
Job shop – makes low quantities of specialized and
customized products
Also includes production of components for these products
Products are typically complex (e.g., specialized
machinery, prototypes, space capsules)
Equipment is general purpose
Plant layouts:
 Fixed position
 Process layout
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Fixed-Position Layout
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Process Layout
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Medium Production Quantities
1. Batch production – A batch of a given product is
produced, and then the facility is changed over to
produce another product.
–
–
–
Changeover takes time – setup time
Typical layout – process layout
Hard product variety
2. Cellular manufacturing – A mixture of products is
made without significant changeover time between
products.
–
–
Typical layout – cellular layout
Soft product variety
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Cellular Layout
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
High Production
1. Quantity production – Equipment is dedicated to the
manufacture of one product.
–
–
Standard machines tools for high production (e.g., stamping presses, molding
machines)
Typical layout – process layout
2. Flow line production – Multiple workstations arranged
in sequence.
–
–
Product requires multiple processing or assembly steps
Product layout is most common
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Product Layout
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Relationships between Plant Layout
and Type of Production Facility
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Overview of Group
Technology
•
•
Parts in the medium production quantity range are
usually made in batches
Disadvantages of batch production:
– Downtime for changeovers
– High inventory carrying costs
•
GT minimizes these disadvantages by recognizing that
although the parts are different, there are groups of
parts that possess similarities
73
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Group Technology (GT)
Defined
 A manufacturing philosophy in which similar parts are
identified and grouped together to take advantage of
their similarities in design and production
 Similarities among parts permit them to be classified
into part families
– In each part family, processing steps are similar
 The improvement is typically achieved by organizing the
production facilities into manufacturing cells that
specialize in production of certain part families
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
When to Use GT and
Cellular Manufacturing
1. The plant currently uses traditional batch production
and a process type layout
–
This results in much material handling effort, high in-process inventory, and
long manufacturing lead times
2. The parts can be grouped into part families
–
–
A necessary condition to apply group technology
Each machine cell is designed to produce a given part family, or a limited
collection of part families, so it must be possible to group parts made in the
plant into families
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Problems in Implementing GT
1. Identifying the part families
–
Reviewing all of the parts made in the plant and grouping them into part
families is a substantial task
2. Rearranging production machines into GT cells
–
It is time-consuming and costly to physically rearrange the machines into cells,
and the machines are not producing during the changeover
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Part Families and
Cellular Manufacturing
 GT exploits the part similarities by utilizing similar
processes and tooling to produce them
 Machines are grouped into cells, each cell specializing
in the production of a part family
– Called cellular manufacturing
 Cellular manufacturing can be implemented by manual
or automated methods
– When automated, the term flexible manufacturing
system is often applied
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Part Family
•
•
A collection of parts that possess similarities in
geometric shape and size, or in the processing steps
used in their manufacture
Part families are a central feature of group technology
– There are always differences among parts in a family
– But the similarities are close enough that the parts can be grouped into the same
family
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Part Families
Two parts that are identical in shape and size but quite
different in manufacturing: (a) 1,000,000 units/yr, tolerance
= 0.010 inch, 1015 CR steel, nickel plate; (b) 100/yr,
tolerance = 0.001 inch, 18-8 stainless steel
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EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-4, 27/8/22
BITS Pilani, Pilani Campus
Part Families
•
•
Ten parts are different
in size, shape, and
material, but quite
similar in terms of
manufacturing
All parts are
machined from
cylindrical stock by
turning; some parts
require drilling and/or
milling
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Traditional Process Layout
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Cellular Layout Based on GT
Each cell
specializes in
producing one or
a limited number
of part families
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Ways to Identify Part Families
1. Intuitive grouping (aka visual inspection)
–
Using best judgment to group parts into appropriate families, based on the
parts or photos of the parts
2. Parts classification and coding
–
Identifying similarities and differences among parts and relating them by means
of a coding scheme
3. Production flow analysis
–
Using information contained on route sheets to classify parts
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Intuitive Grouping
•
•
•
Least sophisticated and least expensive method
Involves the classification of parts into families by
experienced technical staff in the plant who examine
either the physical parts or their photographs and
arrange them into groups having similar features.
Least accurate out of three methods.
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Intuitive Grouping
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Parts Classification and
Coding
•
•
•
•
Identification of similarities among parts and relating the
similarities by means of a numerical coding system
Most time consuming of the three methods
Must be customized for a given company or industry
Reasons for using a coding scheme:
– Design retrieval
– Automated process planning
– Machine cell design
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Features of Parts Classification
and Coding Systems
Most classification and coding systems are based on one
of the following:
– Part design attributes
– Part manufacturing attributes
– Both design and manufacturing attributes
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Parts Classification and
Coding
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Parts Classification and
Coding
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Parts Classification and
Coding
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Production Flow Analysis
(PFA)
•
•
•
Method for identifying part families and associated
machine groupings based on production route sheets
rather than part design data
Workparts with identical or similar route sheets are
classified into part families
Advantages of using route sheet data
– Parts with different geometries may nevertheless require the same or similar
processing
– Parts with nearly the same geometries may nevertheless require different
processing
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Steps in Production Flow
Analysis
1. Data collection – operation sequence and machine
routing for each part
2. Sortation of process routings – parts with same
sequences and routings are arranged into “packs”
3. PFA chart – each pack is displayed on a PFA chart
–
Also called a part-machine incidence matrix
4. Cluster analysis – purpose is to collect packs with
similar routings into groups
–
Each machine group = a machine cell
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Steps in Production Flow
Analysis
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Production Flow Analysis
Chart
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Part and Machine Groupings
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Rank Order Clustering
•
•
•
•
•
•
In each row of the matrix, read the series of 1s and 0s
(blank) from left to right as a binary number. Rank the rows
in order of decreasing value.
Number from top to bottom
Reorder the rows in part machine incidence matrix by
listing them in the decreasing rank order.
In each column of the matix, read the series of 1s and 0s
from top to bottom as a binary number. Rank the columns
in order of decreasing value.
Number from left to right
Reorder the columns in part machine incidence matrix by
listing them in the decreasing rank order, starting with left
column
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Rank Order Clustering
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Problem-1
Apply the rank order clustering technique to the part machine incidence matrix in
the following table to identify logical part families and machine groups. Parts are
identified by letters and machines are identified numerically.
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Problem-2
Apply the rank order clustering technique to the part machine incidence matrix in
the following table to identify logical part families and machine groups. Parts are
identified by letters and machines are identified numerically.
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Cellular Manufacturing
•
•
Application of group technology in which dissimilar
machines or processes are aggregated into cells, each
of which is dedicated to the production of a part family
or limited group of families
Typical objectives of cellular manufacturing:
–
–
–
–
–
To shorten manufacturing lead times
To reduce WIP
To improve quality
To simplify production scheduling
To reduce setup times
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Composite Part Concept
•
•
•
•
A composite part for a given family is a hypothetical part
that includes all of the design and manufacturing
attributes of the family
In general, an individual part in the family will have
some of the features of the family, but not all of them
A production cell for the part family would consist of
those machines required to make the composite part
Such a cell would be able to produce any family
member, by omitting operations corresponding to
features not possessed by that part
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Composite Part Concept
Composite part concept: (a) the composite part for a family
of machined rotational parts, and (b) the individual
features of the composite part
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Part Features and Corresponding
Manufacturing Operations
Design feature
1. External cylinder
2. Face of cylinder
3. Cylindrical step
4. Smooth surface
5. Axial hole
6. Counter bore
7. Internal threads
Corresponding operation
Turning
Facing
Turning
External cylindrical grinding
Drilling
Counterboring
Tapping
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Machine Cell Designs
1. Single machine
2. Multiple machines with manual handling
–
Often organized into U-shaped layout
3. Multiple machines with semi-integrated handling
4. Automated cell – automated processing and integrated
handling
–
–
Flexible manufacturing cell
Flexible manufacturing system
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Machine Cell with Manual
Handling
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Machine Cell Layouts
In-line layout using mechanized work handling between
machines
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Cell with Semi-Integrated
Handling
Loop layout allows variations in part routing between
machines
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Four Types of Part Moves in
Cellular Manufacturing
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Other factors for machine cell
design layout
 Amount of the work to be done by the cell
 Part size, shape, weight and other physical attributes
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Arranging Machines in a GT cell
•
•
After part machine groupings have been identified, the next
work is to organize the machines into logical sequence.
Hollier method is used, which uses the data contained in
from-to charts to place the machines in an order that
maximizes the proportion of in-sequence moves within the
cell.
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Hollier Method
 Develop the from-to chart.
Data contained in the chart indicates the number of parts moves between the
machines in the cell. Moves into and out of the cell are not included in the chart.
 Determine the from-to ratio for each machine
This is done by summing all the From trips and To trips for each machine. The
From sum for a machine is determined by adding the entries in the
corresponding row and the To sum is determined by adding the entries in the
corresponding column. For each machine, the From-to ratio is calculated by
taking the From sum for each machine and dividing by the respective To sum.
 Arrange machines in order of decreasing from-to ratio.
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Example
•
•
Suppose that four machines, 1, 2, 3, and 4 have been identified as belonging in
a GT machine cell. An analysis of 50 parts processed on these machines has
been summarized in the From-To chart presented below. Additional information
is that 50 parts enter the machine grouping at machine 3, 20 parts leave after
processing at machine 1, and 30 parts leave after machine 4. Determine a
logical machine arrangement using Hollier method.
Compute the (a) the percentage of in-sequence moves (b) the percentage of bypassing moves (c) the percentage of backtracking moves
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Problem-3
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Problem-4
•
In problem-2, two logical machine groups are identified. For each group
determine the (a) the most logical sequence of machines for this data (b)
Construct the network diagram for the data (c) Compute the percentage of insequence moves, by-passing moves and backtracking moves.
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Review (Lecture 6-7)
Manufacturing Models and Metrics (Ch-3)
Operation Cycle Time
Cycle time:
 Time that one work unit spends being processed or assembled.
 It is the time between when one work unit begins processing
(assembly) and when the next unit begins.
Typical cycle time for a production operation:
Tc = To + Th + Tt
where
Tc = cycle time,
To = processing time for the operation,
Th = work part handling time (e.g., loading and unloading the production
machine), and
Tt = average tool handling time (e.g., time to change tools)
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-6, 10/9/22
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Production rate (Rp)
Work units completed per hour (pc/hr)
• Batch production
• Job shop production
• Mass production
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Types of discrete production
(a) Job shop, Q = 1, (b) batch production, sequential, (c) batch production,
simultaneous, (d) quantity mass production, (e) flow line mass production
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Production Rate
Batch production:
Batch time in min,
Tb = Tsu + QTc
Tb = Batch processing time (min/batch)
Tsu = Setup time to prepare for the batch (min/batch).
Q = Batch quantity (pc/batch).
Tc = Cycle time per work unit (min/cycle).
Average production time per work unit
Tp = Tb/Q
Production rate
Rp = 1/Tp
Rp = 60/Tp
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Production Rate
Job shop production:
For job shop production, when Q = 1,
Production time per work unit
Tp = Tsu + Tc
For job shop production, when Q > 1,
Tb = Tsu + QTc
Mass production
As quantity is very high, setup time becomes insignificant.
For quantity high production:
Rp = Rc = 60/Tp since Tsu/Q  0
For flow line production
Tc = Tr + Max To and
Rc = 60/Tc
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-6, 10/9/22
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Ex:1
A batch of parts is produced on a semi-automated production
machine. Batch size is 250 units. Setup requires 50 min. A
worker loads and unloads the machine each cycle, which
takes 0.40 min. Machine processing time is 2.50 min/cycle,
and tool handling time is negligible. One part is produced
each cycle. Determine (a) cycle time, (b) time to complete the
batch, and (c) average production rate.
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Ex:2
In a batch machining operation, setup time is 1.5 hours and
batch size is 80 units. The cycle time consists of part handling
time of 30 sec and processing time of 1.37 min. One part is
produced each cycle. Tool changes must be performed every
10 parts and this takes 2.0 min. Determine (a) cycle time, (b)
time to complete the batch, and (c) average production rate.
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Ex:3
A batch production operation has a machine setup time of 3.0
hours and a processing time of 1.60 min per cycle. Two parts are
produced each cycle. No tool handling time is included in the
cycle. Part handling time each cycle is 45 sec. It consists of the
worker obtaining two starting work units from a parts tray,
loading them into the machine, and then after processing,
unloading the completed units and placing them into the same
tray. Each tray holds 24 work units. When all of the starting work
units have been replaced with completed units, the tray of
completed parts is moved aside and a new tray of starting parts
is moved into position at the machine. This irregular work
element takes 3.0 min. Batch quantity is 2400 units. Determine
(a) average cycle time, (b) time to complete the batch, and (c)
average production rate.
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Ex:4
A flow line mass production operation consists of eight manual
workstations. Work units are moved synchronously and
automatically between stations, with a transfer time of 15 sec.
The manual processing operations performed at the eight
stations take 40 sec, 52 sec, 43 sec, 48 sec, 30 sec, 57 sec,
53 sec, and 49 sec, respectively. Determine (a) cycle time for
the line, (b) time to process one work unit through the eight
workstations, (c) average production rate, and (d) time to
produce 10,000 units.
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Production Capacity
 Production capacity is the maximum rate of output that a production
facility is able to produce under a given set of operating conditions.
Plant capacity for facility in which parts are made in one operation
PC = n Hpc Rp
where
PC = Production capacity, pc/period.
n = Number of machines or work centers in the facility.
Hpc = number of hours in the period
Rp = Hourly production rate of each work center.
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Ex:1
The automatic lathe department has five machines, all
devoted to the production of the same part. The machines
operate two 8-hr shifts, 5 days/week, 50 weeks/year. Average
production rate of each machine is 15 unit/hour. Determine
the weekly production capacity of the automatic lathe
department.
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Utilization
Utilization:
It refers to the amount of output of a production facility
relative to its capacity.
where
Q = quantity actually produced,
PC = production capacity
Utilization can be defined as the proportionate of time that
the facility is operating relative to the time available under
the definition of capacity.
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Ex:2
A production machine operates 80 hours/week (2 shifts, 5
days) at full capacity. Its production rate is 20 unit/hour.
During a certain week, the machine produced 1000 parts and
wad idle the remaining time. (a) Determine the production
capacity of the machine (b) What was the utilization of the
machine during the week under consideration?
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Availability
Availability:
It is a common measure of reliability for equipment.
It can be defined using two reliability terms mean time
between failures (MTBF) and mean time to repair (MTTR).
MTBF: Average length of time the piece of equipment
runs between breakdowns.
MTTR: Average time required to service the equipment
and put it back into operation when a breakdown occurs.
Calculation of availability:
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Availability-MTBF and MTTR
Defined
EA ZC412 / MM ZC412/DM ZC412, FMS, Lecture-6, 10/9/22
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Ex:3
The turret lathe section has six machines, all devoted to the
production of the same part. The section operates 10
shifts/week. The number of hours per shift averages 8.0.
Average production rate of each machine is 17 unit/hour.
Determine the weekly production capacity of the turret lathe
section. If the availability of the machines (A) = 90% and the
utilization of machines U=80%. Determine the expected plant
output.
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Manufacturing Costs
Two major categories of manufacturing costs:
1.
2.
Fixed costs - remain constant for any output level
Variable costs - vary in proportion to production output level
Adding fixed and variable costs
TC = FC + VC(Q)
where TC = total costs, FC = fixed costs (e.g.,
building, equipment, taxes), VC = variable costs
(e.g., labor, materials, utilities), Q = output level.
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Fixed and Variable Costs
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Manufacturing Costs
Alternative classification of manufacturing costs:
1. Direct labor - wages and benefits paid to workers
2. Materials - costs of raw materials
3. Overhead - all of the other expenses associated with
running the manufacturing firm
• Factory overhead
• Corporate overhead
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Manufacturing Costs
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Typical Manufacturing Costs
(J Black)
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Overhead Rates
Factory overhead rate:
FOHR = FOHC
DLC
Corporate overhead rate:
COHR = COHC
DLC
where DLC = direct labor costs
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Example1
 Suppose that all costs have been compiled for a certain
manufacturing firm for last year. The summary is shown in
table below. The company operates two different
manufacturing plants plus a corporate headquarter.
Determine (a) the factory overhead rate for each plant, and
(b) the corporate overhead rate.
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Example2
 A customer order of 50 parts is to be processed
thorough plant 1 the previous example. Raw materials
and tooling are supplied by the customer. The total time
for processing the parts (including setup and other direct
labor) is 100 hr. Direct labor cost is $15.00/hr. The
factory overhead rate is 250% and the corporate
overhead rate is 600%. (a) Compute the cost of the job.
(b) What price should be quoted to a potential customer
if the company uses a 10% markup?
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Thanks
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