Transcript Process Selection and Facility Layout Chapter 6 Learning Objectives • You should be able to: 1.

Process Selection
and Facility Layout
Chapter 6
Learning Objectives
• You should be able to:
1. Explain the strategic importance of process selection
2. Describe the influence that process selection has on the
organization
3. Compare the basic processing types
4. Describe the basic layout types, and the main
advantages and disadvantages of each
5. Solve simple line-balancing problems
6. Develop simple process layouts
Instructor Slides
2
Process Selection
3
Process Selection
• Process selection
– Deciding on the way production of goods
or services will be organized
– Occurs when:
• Planning of new products or services
• Technological changes in product or equipment
• Competitive pressure
6-4
Process Selection
Process choice is demand driven:
1. Variety
– How much?
2. Equipment flexibility
– To what degree?
3. Volume
– Expected output?
6-5
Process Selection
• Goal:
• Have process capabilities match
product/service requirements.
• Major implications:
•
•
•
•
Capacity planning
Layout of facilities
Equipment
Design of work systems
6-6
Process Selection and System Design
Forecasting
Capacity
Planning
Product and
Service Design
Technological
Change
Facilities and
Equipment
Layout
Process
Selection
Work
Design
6-7
Process Types
• Job shop
– Small scale, intermittent
– e.g., doctor, tailor, veterinarian
• Batch
– Moderate volume
– e.g., bakery, cinema, airline
• Repetitive/assembly line
– High volumes of standardized goods or services
– e.g., automobiles
• Continuous
– Very high volumes of non-discrete goods
– e.g., petroleum products, steel, sugar, salt, electricity,
Internet
• Project (leave it to later chapter)
– Non-routine, with a unique set of objectives to be
accomplished in a limited time frame
– e.g., consulting, launching a new product, publishing a book,
building a bridge
6-8
Types of Processing
Repetitive/
Assembly
Job Shop
Batch
Continuous
Description
Customized
goods or
services
Semistandardized
goods or
services
Standardized
goods or
services
Highly standardized
Goods or services
Advantages
Able to handle a
wide variety
of work
Flexibility; easy
to add or change
products or
services
Low unit
cost, high volume,
efficient
Very efficient, very
high volume
Disadvantages
Slow, high cost
per unit,
complex
planning and
scheduling
Moderate cost
per unit,
moderate
scheduling
complexity
Low flexibility,
high cost of
downtime
Very rigid, lack of
variety, costly to
change, very high
cost of downtime
• Goal:
– Have process capabilities match product/service requirements.
6-9
Product-Process Matrix
Variety
Volume
• The diagonal represents the “ideal” match
• Hybrid process are possible (e.g., job-shop & batch)
• Process choice may change as products goes through its life-cycles
6-10
Process Choice Effects
Activity/
Function
Job Shop
Batch
Repetitive
Continuous
Projects
Cost estimation
Difficult
Somewhat routine
Routine
Routine
Simple to
complex
Cost per unit
High
Moderate
Low
Low
Very high
Equipment used
General
purpose
General purpose
Special purpose
Special purpose
Varied
Fixed costs
Low
Moderate
High
Very high
Varied
Variable costs
High
Moderate
Low
Very low
High
Labor skills
High
Moderate
Low
Low to high
Low to high
Marketing
Promote
capabilities
Promote
capabilities;
semistandardized
goods and
services
Promote
standardized
goods/service
s
Promote
standardized
goods/service
s
Promote
capabilities
Scheduling
Complex
Moderately
complex
Routine
Routine
Complex,
subject
to change
Work –in-process
inventory
High
High
Low
Low
Varied
6-11
Product and Service Profiling
 Product or service profiling
 Linking key product or service requirements to
process capabilities
 Key dimensions relate to





Range of products or services that will be processed
Expected order sizes
Pricing strategies
Expected frequency of schedule changes
Order-winning requirements
6-12
Product and Service Profiling
Product/Service
Process
Ice-cream manufacturer
Batch
Automatic carwash
Repetitive
Steel
Continuous
Books
Batch
Cafeteria line
Repetitive
Airlines
Batch
Veterinarian
Job-shop
Movie theater
Batch
Sugar
Continuous
TVs
Repetitive
Cookies
Batch
Flour
Continuous
6-13
Facilities Layout
14
Facilities Layout
• Layout
– the configuration of departments, work
centers, and equipment, with particular
emphasis on movement of work (customers or
materials) through the system
– Facilities layout decisions arise when:
• Designing new facilities
• Re-designing existing facilities
6-15
The Need for Layout Planning
• Inefficient operations
 High cost
 Bottlenecks
Accidents or safety hazards
Changes in product or service design
Introduction of new products or services
Changes in output volume or product mix
Changes in methods or equipment
Changes in environmental or other legal
requirements
• Morale problems
•
•
•
•
•
•
6-16
Layout Design Objectives
 Basic Objective
 Facilitate a smooth flow of work, material, and
information through the system
 Supporting objectives:
1. Facilitate product or service quality
2. Use workers and space efficiently
3. Avoid bottlenecks
4. Minimize material handling costs
5. Eliminate unnecessary movement of workers or
material
6. Minimize production time or customer service time
7. Safety
6-17
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
6-18
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
Combination layouts
6-19
Repetitive Processing: Product
Layout (repetitive and
continuous processes)
20
Product Layouts
• Product layout
– Layout that uses standardized processing
operations to achieve smooth, rapid, highvolume flow
http://www.youtube.com/watch?v=uVoQJrz0sH8
Raw materials
Station
Station
Station
Station
or customer
–
1
Material
and/or
labor
Material
and/or
labor
2
Material
and/or
labor
3
4
Finished
item
Material
and/or
labor
Used for Repetitive Processing
Repetitive or Continuous
6-21
A U-Shaped Production Line
In
1
2
3
4
5
Workers
6
Out
10
9
8
7
6-22
• An operation in a
sequence of
operations whose
capacity is lower
than that of the
other operations
Bottleneck
Operation 1
20/hr
(3 min/unit)
Operation 2
10/hr
(6 min/unit)
Operation 3
15/hr
(4 min/unit)
Maximum output rate
limited by bottleneck
10/hr
(6 min/unit)
5-23
Line Balancing
 Line balancing
 The process of assigning tasks to workstations in
such a way that the workstations have
approximately equal time requirements
 Goal:
 Obtain task grouping that represent
approximately equal time requirements:
 minimizes idle time along the line
 results in a high utilization of equipment and labor
 Input
 Tasks sequencing (precedence diagram)
 Tasks time
 Operating time
6-24
Real-World Case
Instructor Slides
25
Precedence Diagram
• Precedence diagram
– A diagram that shows elemental tasks and
their precedence requirements
Task
Duration
(min)
Immediate
predecessor
a
serve
main
0.1
-
b
serve
side
1.0
a
c
serve
drink
0.7
-
d
wrap
0.5
b, c
e
bill
0.2
d
6-26
Cycle Time
• Cycle time
– The maximum time allowed at each workstation to
complete its set of tasks on a unit
• Minimum Cycle Time = longest task time = 1.0 min
• Maximum Cycle Time = Σt = sum of task time = 2.5 min
6-27
Desired Output Rate
• Establishing the desired output rate of a
line:
Operating time per day
Output rate 
Cycle time
Operating time per day
Cycle time 
Desired output rate
6-28
How Many Workstations are Needed?
• The required number of workstations is a
function of:
– Desired output rate
– The ability to combine tasks into a workstation
• (theoretical) Minimum number of stations
N min 
t
Cycle time
where
N min  theoretica l minimum number of stations
 t  Sum of task time s
6-29
Assigning Tasks to Workstations
 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.
6-30
Example 1: Assembly Line Balancing
• Arrange tasks shown the figure into
workstations.
- Assign tasks in order of the most number
of followers
6-31
Determine the Minimum Number
of Workstations Required
Assume:
OT (Operations Time per Day)=8 hours=8*60=480 minutes
D (Desired output rate)=480 units
CT (Cycle Time)=OT/D=480/480=1.0 minutes per unit
( t)
(0.1  1  0.7  0.5  0.2)
N=

 2.5  3stations
CT
1.0
 t = sum of task time
6-32
Example 1 Solution
Assign tasks in order of the most number of followers
Time
Workstation Remaining
1
1.0
Eligible
Revised
Assign Time
Task
Remaining
Station
Idle Time
a, c
2
3
6-33
Example 1 Solution
Assign tasks in order of the most number of followers
Time
Workstation Remaining
1
1.0
Eligible
Revised
Assign Time
Task
Remaining
a, c
a
Station
Idle Time
0.9
2
3
6-34
Example 1 Solution
Time
Workstation Remaining
1
1.0
0.9
Eligible
a, c
c, b
Revised
Assign Time
Task
Remaining
a
Station
Idle Time
0.9
2
3
6-35
Example 1 Solution
Time
Workstation Remaining
1
1.0
0.9
Eligible
Revised
Assign Time
Task
Remaining
a, c
c, b
a
c
Station
Idle Time
0.9
0.2
2
3
6-36
Example 1 Solution
Time
Workstation Remaining
1
1.0
0.9
0.2
Eligible
a, c
c, b
b
Revised
Assign Time
Task
Remaining
a
c
Station
Idle Time
0.9
0.2
2
3
6-37
Example 1 Solution
Time
Workstation Remaining
1
1.0
0.9
0.2
Eligible
Revised
Assign Time
Task
Remaining
a, c
c, b
b
a
c
-
Station
Idle Time
0.9
0.2
0.2
2
3
6-38
Example 1 Solution
Eligible
Revised
Assign Time
Task
Remaining
1.0
0.9
0.2
a, c
c
none
a
c
-
1.0
b
Time
Workstation Remaining
1
2
Station
Idle Time
0.9
0.2
0.2
3
6-39
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
1.0
b
b
0.0
Time
Workstation Remaining
1
2
Station
Idle Time
0.2
0.0
3
6-40
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
d
d
0.5
Time
Workstation Remaining
1
Station
Idle Time
0.2
0.0
6-41
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
d
e
d
e
0.5
0.3
Time
Workstation Remaining
1
Station
Idle Time
0.2
0.0
6-42
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
Idle time per cycle=0.5
6-43
Example - Layout
Task
a&c
b
d&e
(0.1+0.7)
(1.0)
(0.5+0.2)
Duration
(min)
Immediate
predecessor
a
serve
main
0.1
-
b
serve
side
1.0
a
c
serve
drink
0.7
-
d
wrap
0.5
b, c
e
bill
0.2
d
6-44
Measuring Effectiveness
• Balance delay (percentage of idle time)
– Percentage of idle time of a line
Idle time per cycle
Balance Delay 
 100
N actual  Cycle time
where
N actual  Actual number of stations
• Efficiency
– Percentage of busy time of a line
Efficiency  100% - Balance Delay
6-45
Example - Measuring Effectiveness
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
Percent idle time =
X 100  16.7%
(3)(1.0)
Efficiency = (1– 0.167)x100=83.3%
6-46
Product Layouts
Advantages
Disadvantages
High rate of output
Low unit cost
Labor specialization
Low material handling cost per
unit
 High utilization of labor and
equipment
 Established routing and
scheduling
 Routine accounting,
purchasing, and inventory
control
 Creates dull, repetitive jobs
 Poorly skilled workers may
not maintain equipment or
quality of output
 Fairly inflexible to changes in
volume or product or process
design
 Highly susceptible to
shutdowns
 Preventive maintenance,
capacity for quick repair and
spare-parts inventories are
necessary expenses
 Individual incentive plans are
impractical




6-47
Non-repetitive Processing:
Process Layout (Job Shop and
Batch Processes)
48
Process Layouts
• Process layouts (Non-repetitive Processing)
– Layouts that can handle varied processing
requirements
Dept. A
Dept. C
Dept. E
Dept. B
Dept. D
Dept. F
Used for Intermittent processing
Job Shop or Batch
6-49
Information Requirements
• In designing process layouts, the following
information is required:
1. A list of departments to be arranged and their
dimensions
2. A projection of future work flows between the pairs of
work centers
3. The distance between locations and the cost per unit
of distance to move loads between them
4. The amount of money to be invested in the layout
5. A list of any special considerations
6. The location of key utilities, access and exit points,
etc.
6-50
Designing Process Layouts
• The main issue in designing process layouts
concerns the relative placement of the
departments
• Measuring effectiveness
– A major objective in designing process layouts is
(trying) to minimize:
• Transportation cost
• Distance
• Time
6-51
Designing Process Layouts
Minimize Transportation Costs
• Goal:
– Assign departments 1, 2, 3 to locations A, B, C in a way
that minimizes transportation costs.
A
B
C
• Heuristic:
– Assign departments with the greatest
interdepartmental work flow first to locations
that are closet to each other.
6-52
Example: Minimize Transportation Costs
40
Distance
Trip
Location
From\
To
A
A
B
C
A-B
20
-
20
40
B-C
30
-
30
A-C
40
B
C
closest A
20
B
30
C
Place dept. 1&3
in A&B
-
Work flow
From\
1
2
3
To
Department
Pair
Work flow
1
2
3
1-3
170
-
30
170
2-3
100
-
100
1-2
30
Highest work flow
6-53
Example: Minimize Transportation Costs
40
• Place departments 1&3 in A&B
• 2&3 have higher work flow than 1&2 (100>30)
A
• 2&3 should be located closer than 1&2
• B closer to C than to A (30<40)
20
Trip
• Solution:
B
30
C
Pair
Work flow
A-B
20
1-3
170
B-C
30
2-3
100
A-C
40
1-2
30
30
1
A
170
3
B
100
2
C
6-54
Closeness Ratings
(Relationship Diagramming)
• Allows the considerations of
multiple qualitative criteria.
• Input from management or
subjective analysis.
• Indicates the relative
importance of each
combination of department
pairs.
Muther’s grid
6-55
Closeness Ratings
A
E
I
O
U
X
Production
O
A
Offices
U
Shipping and
receiving
I
E
O
Stockroom
Absolutely necessary
Very important
Important
Ordinary importance
Unimportant
Undesirable
A
A
X
U
U
U
O
O
Locker room
O
Toolroom
6-56
Closeness Ratings : Example
Dept. 1
A
Dept 2.
E
Dept 3.
Dept 4.
X
O
Dept. 5
A
A
U
A
A
X
I
X
U
A
O
Dept 6.
Assign department using the heuristic:
Assign critical departments first (they are most important)
6-57
Closeness Ratings : Example
1. List critical departments (either A or X):
Dept. 1
A
X
1-2
1-4
Dept 2.
1-3
3-6
Dept 3.
2-6
3-4
Dept 4.
3-5
4-6
5-6
Dept. 5
Dept 6.
A
A
E
X
U
U
X
O
I
A
A
O
X
A
A
6-58
Closeness Ratings : Example
2. Form a cluster of A links
(beginning with the
department that appears
most frequently)
A
1-2
Dept. 1
1-3
Dept 2.
2-6
3-5
4
2
4-6
5-6
6
5
3. Take the remaining A links in
order and add them to this cluster
where possible (rearranging as
necessary)
Form separate clusters for
departments that do not link with
the main cluster.
A
A
E
X
U
U
X
O
I
A
A
O
X
A
A
Dept 3.
Dept 4.
Dept. 5
Dept 6.
4
2
1
6
5
3
6-59
Closeness Ratings : Example
4. Graphically portray the
X links
1
3
4
X
1-4
Dept. 1
3-6
Dept 2.
3-4
A
E
X
U
U
X
O
I
A
A
O
X
A
A
Dept 3.
Dept 4.
6
Dept. 5
Dept 6.
5. Adjust A cluster as
necessary.
(in this case, the A cluster
also satisfies the X cluster).
A
4
2
1
6
5
3
6-60
Closeness Ratings : Example
4
2
Dept. 1
6
1
5
Dept 2.
1
3
3
4
Dept 3.
Dept 4.
6
6. Fit cluster into arrangement
(e.g., 2x3)
may require some trial and error.
Dept. 5
Dept 6.
A
A
E
X
U
U
X
O
I
A
A
O
X
A
A
Departments are considered close not only when they touch
side to side but also when they touch corner to corner.
1
2
6
3
5
4
7. Check for possible
improvements
6-61
Process Layouts
Advantages
 Can handle a variety of
processing requirements
 Not particularly vulnerable
to equipment failures
 General-purpose equipment
is often less costly and
easier and less costly to
maintain
 It is possible to use
individual incentive
systems
Disadvantages
 In-process inventories can
be high
 Routing and scheduling
pose continual challenges
 Equipment utilization rates
are low
 Material handling is slow
and inefficient
 Complicates supervision
 Special attention
necessary for each
product or customer
 Accounting, inventory
control, and purchasing
are more complex
6-62
Fixed Position Layouts
• Fixed Position layout
–
Layout in which the product or project remains
stationary, and workers, materials, and
equipment are moved as needed
Dam
Ship
6-63
Combination Layouts
• Some operational environments use a
combination of the three basic layout types:
– Hospitals
• process + fixed
– Supermarket
• process + product
• Some organizations are moving away from
process layouts in an effort to capture the
benefits of product layouts
– Cellular manufacturing
– Flexible manufacturing systems
6-64
Service Layout
• Service layouts can be categorized as:
– product
– process
– fixed position
• Other common service layouts:
– Warehouse and storage layouts (easy access to items in high
demand)
– Retail layouts (influence sales, customer attitude, customer
flow, avoid customer confusion)
– Office layouts
6-65