Process Selection
and
Facility Layout
Learning Objectives




Explain the strategic importance of process
selection.
Explain the influence that process selection
has on an organization.
Describe the basic processing types.
Discuss automated approaches to
processing.
Learning Objectives




List some reasons for redesign of layouts.
Describe the basic layout types.
List the main advantages and
disadvantages of product layouts and
process layouts.
Solve simple line-balancing problems.
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 Strategy
• Key aspects of process strategy
–
Capital intensive (mix of equipment/labor)
–
Process flexibility
–
–
Design
–
Volume
Technology
Kinds of Technology
 Operations management is primarily
concerned with three kinds of technology:
 Product and service technology
 Process technology
 Information technology
 All three have a major impact on:
 Costs
 Productivity
 Competitiveness
Technology Competitive
Advantage
 Innovations in
 Products and services
 Cell phones
 PDAs
 Wireless computing
 Processing technology
 Increasing productivity
 Increasing quality
 Lowering costs
Process Selection
 Variety
 How much
 Flexibility
Job Shop
 What degree
 Volume
 Expected output
Batch
Repetitive
Continuous
Process Types
 Job shop
 Small scale
 Batch
 Moderate volume
 Repetitive/assembly line
 High volumes of standardized goods or
services
 Continuous
 Very high volumes of non-discrete goods
Product and Service
Processes
High Volume
Process Type Low Volume
Job Shop
Appliance repair
Emergency
room
Ineffective
Commercial
baking
Batch
Classroom
Lecture
Automotive
assembly
Repetitive
Automatic
carwash
Continuous
(flow)
Ineffective
Steel Production
Water purification
Product – Process Matrix
Dimension
Job shop
Batch
Repetitive
Continuous
Job variety
Very High
Moderate
Low
Very low
Process
flexibility
Very High
Moderate
Low
Very low
Unit cost
Very High
Moderate
Low
Very low
Volume of
output
Very low
Low
High
Very High
Other issues; scheduling
work-in-process inventory
labor skill
Process and Product Profiling
 Process selection can involve substantial
investment in
 Equipment
 Layout of facilities
 Product profiling: Linking key product or service
requirements to process capabilities
 Key dimensions





Range of products or services
Expected order sizes
Pricing strategies
Expected schedule changes
Order winning requirements
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)
Facilities Layout
 Layout: the configuration of departments,
work centers, and equipment, with particular
emphasis on movement of work (customers
or materials) through the system
 Product layouts
 Process layouts
 Fixed-Position layout
 Combination layouts
Objective of Layout Design
1.
2.
3.
4.
Facilitate attainment of product quality
Use workers and space efficiently
Avoid bottlenecks
Minimize unnecessary material handling
costs
5. Eliminate unnecessary movement of
workers or materials
6. Minimize production time or customer
service time
7. Design for safety
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
The Need for Layout Design
Inefficient operations
For Example:
High Cost
Bottlenecks
Changes in the design
of products or services
Accidents
The introduction of new
products or services
Safety hazards
The Need for Layout Design
(Cont’d)
Changes in
environmental
or other legal
requirements
Changes in volume of
output or mix of
products
Morale problems
Changes in methods
and equipment
Basic Layout Types
 Product layouts
 Process layouts
 Fixed-Position layout
 Combination layouts
Basic Layout Types
 Product layout

Layout that uses standardized processing
operations to achieve smooth, rapid, highvolume flow
 Process layout

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
Used for Repetitive or Continuous Processing
Raw
materials
or customer
Material
and/or
labor
Station
1
Material
and/or
labor
Station
2
Material
and/or
labor
Station
3
Material
and/or
labor
Station
4
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
Routine accounting, purchasing and
inventory control
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
A U-Shaped Production Line
In
1
2
3
4
5
Workers
6
Out
10
9
8
7
 Ease to cross-travel of workers and vehicles
 More compact
 More communication between workers
Product Layout
Product Layout
(sequential)
Work
Station 1
Work
Station 2
Work
Station 3
Used for Repetitive Processing
or Continuous Processes
Process Layout
Process Layout
(functional)
Dept. A
Dept. C
Dept. E
Dept. B
Dept. D
Dept. F
Used for Intermittent processing
Job Shop or Batch Processes
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
Fixed Position Layouts
 Fixed Position Layout: Layout in which the
product or project remains stationary, and
workers, materials, and equipment are
moved as needed.
 Nature of the product dictates this type of
layout
 Weight
 Size
 Bulk
 Large construction projects
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
Functional vs. Cellular Layouts
Dimension
Functional
Cellular
Number of moves
between departments
many
few
Travel distances
longer
shorter
Travel paths
variable
fixed
Job waiting times
greater
shorter
Throughput time
higher
lower
Amount of work in
process
higher
lower
Supervision difficulty
higher
lower
Scheduling complexity
higher
lower
Equipment utilization
lower
higher
Service Layouts
 Warehouse and storage layouts
 Retail layouts
 Office layouts
Design Product Layouts: Line
Balancing
Line Balancing is the process of assigning
tasks to workstations in such a way that
the workstations have approximately
equal time requirements.
Cycle Time
Cycle time is the maximum time
allowed at each workstation to
complete its set of tasks on a unit.
Determine Maximum Output
OT
Output rate =
CT
OT  operating time per day
D = Desired output rate
OT
CT = cycle time =
D
Determine the Minimum Number
of Workstations Required
N=
(  t)
CT
 t = sum of task time
Precedence Diagram
Precedence diagram: Tool used in line balancing to
display elemental tasks and sequence requirements
0.1 min.
1.0 min.
a
b
c
0.7 min.
d
0.5 min.
A Simple Precedence
Diagram
e
0.2 min.
Example 1: Assembly Line
Balancing
 Arrange tasks shown in Figure 6.10 into
three workstations.


Use a cycle time of 1.0 minute
Assign tasks in order of the most number of
followers
Example 1 Solution
Eligible
Revised
Assign Time
Task
Remaining
1.0
0.9
0.2
a, c
c
none
a
c
-
0.9
0.2
2
1.0
b
b
0.0
3
1.0
0.5
0.3
d
e
-
d
e
-
0.5
0.3
Time
Workstation Remaining
1
Station
Idle Time
0.2
0.0
0.3
0.5
Calculate Percent Idle Time
Idle time per cycle
Percent idle time =
(N)(CT)
Efficiency = 100 – Percent idle time
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.
Example 2
Plan to produce 400 units in 1 day (8 hours)
Task
0.2
a
a
b
c
d
0.8
e
c
f
g
h
Immediate
follower
0.3
b0.2
e
eb
d
f0.6
fd
f
g
1.0
h
end
Task time
(min)
0.2
0.2
0.8
0.6
0.3
g
h
1.0
0.4
0.3
0.4
0.3
Solution to Example 2
Station 1
a
b
Station 2
Station 3
e
f
c
Station 4
d
g
h
Bottleneck Workstation
1 min.
30/hr.
1 min.
30/hr.
Bottleneck
2 min.
30/hr.
1 min.
30/hr.
Parallel Workstations
30/hr.
1 min.
60/hr.
2 min.
30/hr.
1 min.
1 min.
30/hr.
2 min.
Parallel Workstations
30/hr.
60/hr.
Copier Example
Performance
Time
Task
(minutes)
A
10
B
11
C
5
D
4
E
12
F
3
G
7
H
11
I
3
Total time 66
Task Must Follow
Task Listed
Below
—
A
B
B
A
C, D
F
E
G, H
This means that
tasks B and E
cannot be done
until task A has
been completed
Copier Example
Performance
Time
Task
(minutes)
A
10
B
11
C
5
D
4
E
12
F
3
G
7
H
11
I
3
Total time 66
Task Must Follow
Task Listed
Below
—
A
B
B
A
C, D
F
E
G, H
5
10
11
A
B
C
3
7
F
G
4
12
E
D
3
11
I
H
Figure 9.13
Copier Example
Performance
Time
Task
(minutes)
A
10
B
11
C
5
D
4
E
12
F
3
G
7
H
11
I
3
Total time 66
480 available
mins per day
40 units required
Task Must Follow
Task Listed
Below
—
A
Production time
B
available per day
Cycle
B time = Units required per day
A
= 480 / 40
5
C, D
= 12 minutes per unit
C
F
10
11
3
7
n
E
for taskFi
A ∑ Time
B
G
Minimum
G, H
i=1
4
number of =
workstations
Cycle Dtime
12
11
3
I
= 66 / 12
E
H
= 5.5 or 6 stations
Figure 9.13
Copier Example
Line-Balancing Heuristics
1. Longest task time
Choose the available
with
480task
available
Performance Task Must
Follow
the longest task time mins per day
Time
Task Listed
Task2. Most
(minutes)
40 task
units
following tasks Below
Choose the available
withrequired
of following
A
10
—the largest number
Cycle
time = 12 mins
B
11
Atasks
Minimum
= 5.5 or 6
C 3. Ranked5 positional
BChoose the available
workstations
task for
D
Bwhich the sum of following task
weight 4
E
12
Atimes is the longest
5
F
3
C, D
the available
C task with
G 4. Shortest
7 task time
FChoose
10
11
3
7
the shortest
task
time
H
11
E
A
B
G
F
I 5. Least number
3
G,
H
of
Choose the available
4 task with
3
the least number ofDfollowing
Totalfollowing
time 66 tasks
I
12
11
tasks
E
H
Table 9.4
Figure 9.13
Copier Example
Performance
Time
Task
(minutes)
480 available
mins per day
40 units required
Task Must Follow
Task Listed
Below
A
10
B
11
Station
C
52
D
4
11
E 10
12
F A
3
B
G
7
H
11
I
3
12
Stationtime 66
Total
E
1
Station
3
—
A
5 B
C B
A
C, D
4
F
D E
G, H
Cycle time = 12 mins
Minimum
workstations = 5.5 or 6
3
7
F
G
Station 4
3
I
11
Station 6
H
Station
5
Figure 9.14
Copier Example
Performance
Time
Task
(minutes)
Task Must Follow
Task Listed
Below
480 available
mins per day
40 units required
A
10
—
Cycle time = 12 mins
B
11
A
Minimum
C
5
B
workstations = 5.5 or 6
D
4
B
E
12
A
F
3
C, D
∑ Task times
G
7
F
Efficiency =
(actual number ofE workstations) x (largest cycle time)
H
11
I
3
G, H
= 66 minutes / (6 stations) x (12 minutes)
Total time 66
= 91.7%
Example 1
Performance
Time
Task
(minutes)
1
2
3
4
5
6
7
8
9
10
11
12
Total time
0.20
0.40
0.70
0.10
0.30
0.11
0.32
0.60
0.27
0.38
0.50
0.12
4 min.
Task Must Follow
Task Listed
Below
1
1,2
2
3
3
3,4
6,7,8
5,8
9,10
11
Balance by
1 Longest task time
method
2 RPW method
Example 2
Performance
Time
Task
(minutes)
1
2
3
4
5
6
7
8
9
10
Total time
0.5
0.3
0.8
0.2
0.1
0.6
0.4
0.5
0.3
0.6
4.3
Task Must Follow
Task Listed
Below
1
1
2
2
3
4,5
3,5
7,8
6,9
min.
Balance by
1 Longest task time
method
2 RPW method
Designing Process Layouts
Information Requirements:
1. List of departments
2. Projection of work flows
3. Distance between locations
4. Amount of money to be invested
5. List of special considerations
6. Location of key utilities
Example 3: Interdepartmental Work
Flows
for Assigned Departments
30
1
A
170
B
3
10
0
C
2
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
2222
Mill
3333
Lathe Mill
4444
Drill
Mill
Heat
treat
Gear
-1111
cut
Heat
treat
Grind - 2222
Heat
treat
Grind - 3333
Drill
Gear - 4444
cut
Assembly
Cellular Manufacturing Layout
Linear Programming
 Used to obtain optimal solutions to
problems that involve restrictions or
limitations, such as:




Materials
Budgets
Labor
Machine time
Linear Programming Model
 Objective Function: mathematical statement
of profit or cost for a given solution
 Decision variables: amounts of either inputs
or outputs
 Feasible solution space: the set of all
feasible combinations of decision variables as
defined by the constraints
 Constraints: limitations that restrict the
available alternatives
 Parameters: numerical values
Graphical Linear Programming
Graphical method for finding optimal
solutions to two-variable problems
1.Set up objective function and
constraints in mathematical format
2.Plot the constraints
3.Identify the feasible solution space
4.Plot the objective function
5.Determine the optimum solution
Linear Programming Example
 Objective - profit
Maximize Z=60X1 + 50X2
 Subject to
Assembly 4X1 + 10X2 <= 100 hours
Inspection 2X1 + 1X2 <= 22 hours
Storage
3X1 + 3X2 <= 39 cubic feet
X1, X2 >= 0
Linear Programming Example
Product X1
24
22
20
18
16
14
12
10
8
6
4
2
12
10
8
6
4
2
0
0
Product X2
Assembly Constraint
4X1 +10X2 = 100
Linear Programming Example
Add Inspection Constraint
2X1 + 1X2 = 22
20
15
10
5
Product X1
24
22
20
18
16
14
12
10
8
6
4
2
0
0
Product X2
25
Linear Programming Example
Add Storage Constraint
3X1 + 3X2 = 39
Product X2
25
Inspection
20
Storage
15
Assembly
10
5
Feasible solution space
Product X1
24
22
20
18
16
14
12
10
8
6
4
2
0
0
Linear Programming Example
Add Profit Lines
Product X2
25
20
Z=900
15
10
5
Z=300
Z=600
Product X1
24
22
20
18
16
14
12
10
8
6
4
2
0
0
Solution
 The intersection of inspection and storage
 Solve two equations in two unknowns
2X1 + 1X2 = 22
3X1 + 3X2 = 39
X1 = 9
X2 = 4
Z = $740
Solutions and Corner Points
 Feasible solution space is usually a polygon
 Solution will be at one of the corner points
 Enumeration approach: Substituting the
coordinates of each corner point into the
objective function to determine which corner
point is optimal.
Simplex Method
 Simplex: a linear-programming
algorithm that can solve problems
having more than two decision
variables
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