Chapter 6
Process Selection and
Facility Layout
Introduction

Process selection


Deciding on the way production of goods or
services will be organized
Major implications




Capacity planning
Layout of facilities
Equipment
Design of work systems
Process Selection and System Design
Forecasting
Capacity
Planning
Product and
Service Design
Technological
Change
Facilities and
Equipment
Layout
Process
Selection
Work
Design
Process Selection
Batch

Variety


Flexibility


How much
Job Shop
What degree
Volume

Repetitive
Expected output
Continuous
Types of Operations
Project/
Job Shop
Unit or Batch
Mass/
Continuous
Assembly
INCREASED VOLUME
Process Design




Project Processes (Fixed Position)
Intermittent Flow Processes (Batch
Shops)
Continuous Flow Processes (Flow
Shops)
Processing Industries (Continuous)
Job Shop (Fixed Position)




People and material move
Have limited duration
Small scale
Examples




Housing
Ship building
Dam
Appliance Repair
Intermittent Flow Processes
(Batch Shops)




No pattern exists between process of
different products
Appropriate to service organizations
Moderate volume
Example:




Machine Shops
Auto Repair Shops
Commercial Bakery
Classroom Lecture
Continuous Flow Processes
(Flow Shops)



Sequences are the same (Standard
Routes)
High volumes of standardized goods or
services
Examples:


Assembly Lines
Car Wash
Processing Industries (Continuous
Flow)



One primary input (gas, wheat, etc) is
converted to multiple outputs
Very high volumes of non-discrete
goods
Example:



Petroleum
Chemicals
Food Industries
Process Characteristics
Characteristics Project
Intermittent Continuous
PRODUCT
Order Type
Single Unit
Batch
Continuous or
large batch
Flow of Product
None
Jumbled
Sequence
Product Variety
Very High
High
Low
Market type
Unique
Custom
Mass
Volume
Single Unit
Medium
High
Process Characteristics
Characteristics Project
Intermittent Continuous
CAPITAL
Inventory
Medium
High
Low
Equipment
General
Purpose
General
Purpose
Special
Purpose
High
High
Low
Non-routine
Non-routine
Repetitive
LABOR
Skills
Task Type
Process Characteristics
Characteristics Project
Intermittent Continuous
CONTROL
Production
Difficult
Difficult
Easy
Quality
Difficult
Difficult
Easy
Inventory
Difficult
Difficult
Easy
EQUIPMENT
General
Purpose
General
Purpose
Special
Purpose
Automation

Automation: Machinery that has sensing
and control devices that enables it to
operate


Fixed automation
Programmable automation
Automation
• Computer-aided design and
manufacturing systems (CAD/CAM)
• Numerically controlled (NC) machines
• Robot
• Manufacturing cell
• Flexible manufacturing systems(FMS)
• Computer-integrated manufacturing (CIM)
Functional Areas Being Linked to
Manage the Flow of Information




Design
Handling of Materials
Storage and Retrieval of Information
Control of Machine Tools
Design

CAD





No longer limited to the top, side and front
views
Can observe the rotation of the part about any
axis on the screen
Generally, improves productivity in the drafting
room by a factor of 3 or more
At GM, the redesign of a single auto model
requires 14 months instead of 24 months
The time needed to design custom values
reduced from six months to one
Handling of Materials

Data processing technology can be
applied to the control of 3 general kids
of machines in the factory:



Machines that store, retrieve, or transport
materials
Machines that process the materials
Robots
Handling of Materials

Automatic storage and retrieval systems
transfer pallets of material into or out of
storage rack up to 100 feet high

Mini Loaders


Hold drawers of small parts
Automatic Warehouse

Automatic shuttle takes the place of the fork-lift
truck and its human operations
Storage and Retrieval
of Information

GT




The formation of part families based on design or
manufacturing similarities (or both)
Classification of parts speed up the design of
similar parts in the company
Only 20% of the parts actually need new design.
40% could be built from an existing design and
the other 40% could be created by modifying an
existing design.
Automatic guided vehicle
Control of Machine Tools

NC


Machine tools run by programs
DNC


Direct numerically controlled machine tools
Several computerized, NC machine tools
are linked by a hierarchy of computers
Control of Machine Tools



FMS
Flexible Manufacturing System
It consists of an integrated collection of:

Automated Production Processes



NC
Robots
A material transport system


An automated transfer line
Robots
Control of Robots

Robots


Main features:



A programmable machine capable of moving
materials and performing repetitive tasks.
They are flexible
They eliminate the need for operators
Applications


Loading and unloading of machine tools
Jobs that are dirty, hazardous, unpleasant, or
monotonous
The Operating Capabilities of
the Factory of the Future





Economic order quantity approaches 1
Variety has no cost penalty (economy of slope)
Rapid response to changes in product design, market
demand, and production mix
Unmanned and continuous operation is standard
Consistent high levels of quality and accuracy and
repeatability introduce higher levels of certainty into
the production planning and control activity
Facilities Layout

Layout: the configuration of
departments, work centers, and
equipment, with particular
emphasis on movement of work
(customers or materials) through
the system
Importance of Layout Decisions



Requires substantial investments of
money and effort
Involves long-term commitments
Has significant impact on cost and
efficiency of short-term operations
Basic Layout Types

Product layout


Process layout


Layout that uses standardized processing
operations to achieve smooth, rapid, highvolume flow
Layout that can handle varied processing
requirements
Fixed Position layout

Layout in which the product or project
remains stationary, and workers, materials,
and equipment are moved as needed
Product Layout
Raw
materials
or customer
Material
and/or
labor
Station
1
Material
and/or
labor
Station
2
Material
and/or
labor
Station
3
Station
4
Material
and/or
labor
Used for Repetitive or Continuous Processing
Finished
item
Advantages of Product Layout







High rate of output
Low unit cost
Labor specialization
Low material handling cost
High utilization of labor and equipment
Established routing and scheduling
Routing accounting and purchasing
Disadvantages of Product Layout






Creates dull, repetitive jobs
Poorly skilled workers may not maintain
equipment or quality of output
Fairly inflexible to changes in volume
Highly susceptible to shutdowns
Needs preventive maintenance
Individual incentive plans are impractical
Assembly Line Balancing

Cycle time


The time required to produce one part is
called the cycle time, or the maximum time
allowed at any one work station
Assembly Line Balancing

Given a cycle time, find the minimum
number of work stations or minimize the
cycle time for a given number of work
stations
Assembly Line Balancing - Example
Task
Time (min)
Immediate Predecessors
A
B
0.2
0.3
----A
C
D
E
0.2
0.25
0.15
A
A
B,C
F
0.3
D,E
Total
1.4
Assembly Line Balancing
Assembly Line Balancing
CYCLE TIME
.30 C  1.40
C = productive time/output rate
C = (8hr x 60min) =.5 min
960
Number of work stations, N = total time/C
N = 140 = 2.8 =3
.5
Solution to Assembly Line
Balancing Problem
Station
Time
1
2
3
Tasks Assigned Total Task Time Idle
A, B
C, D
E, F
TOTAL
0.5
0.45
0.45
1.4
0
0.05
0.05
0.1
Line Balancing Rules
Some Heuristic (intuitive) Rules:

Assign tasks in order of most following
tasks.


Count the number of tasks that follow
Assign tasks in order of greatest
positional weight.
 Positional
weight is the sum of each task’s
time and the times of all following tasks.
Assembly Line Balancing Solution



Line Efficiency = Total Work Content
CxN
Efficiency = 1.40 = .93 or 93%
.5 x 3
Balance Delay = 1 – efficiency = 1-.93
= 7%
Example 2
0.2
0.2
0.3
a
b
e
0.8
0.6
c
d
f
g
h
1.0
0.4
0.3
Solution to Example 2
Station 1
a
b
Station 2
Station 3
e
f
c
Station 4
d
g
h
A U-Shaped Production Line
In
1
2
3
4
5
Workers
6
Out
10
9
8
7
Process Layout (functional)

Assume we have the following
departments:





Accounting (A)
Production Planning (P)
Customer Service (C)
Sales (S)
What arrangement would be better?
Used for Intermittent processing
Job Shop or Batch
A P
C S
S C
A P
Intermittent Process

Criteria



Desirability ranking
Volume of interaction
Cost of interaction




Distance
Time
Safety
Facility Limitations
Advantages of Process Layouts




Can handle a variety of processing
requirements
Not particularly vulnerable to equipment
failures
Equipment used is less costly
Possible to use individual incentive plans
Disadvantages of Process Layouts







In-process inventory costs can be high
Challenging routing and scheduling
Equipment utilization rates are low
Material handling slow and inefficient
Complexities often reduce span of
supervision
Special attention for each product or
customer
Accounting and purchasing are more
involved
Cellular Layouts

Cellular Production


Layout in which machines are grouped into a
cell that can process items that have similar
processing requirements
Group Technology

The grouping into part families of items with
similar design or manufacturing
characteristics
Process Layout - Example
Milling
Assembly
& Test
Grinding
Drilling
Plating
Process Layout - work travels
to dedicated process centers
Functional Layout
222
444
Mill
111 333
111
333
Lathes
222
111
444
222
Drill
Grind
3333
1111 2222
Heat
treat
Assembly
111
Gear
cutting
111
444
-1111
Lathe
Mill
Drill
222222222
Mill
3333333333
Lathe Mill
44444444444444
Drill
Mill
Heat
treat
Gear
-1111
cut
Heat
treat
Grind - 2222
Heat
treat
Grind - 3333
Drill
Gear - 4444
cut
Assembly
Cellular Manufacturing Layout –
Group Technology