1. Process Selection and Facility Layout
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CHAPTER 6
Process Selection and Facility Layout
Operations Management
BUS ADM 370

2. Agenda Process selection
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Agenda
Process selection
Process Type : Project , Job shop, Batch, Repetitive, Continuous
Automation : Fixed, Programmable, Flexible
Facilities layout
Product layout
Process layout
Others: Fixed position layout, Cellular production
Designing Product Layout
Line Balancing : cycle time

3. Process selection process types, and automation

4. 370-OperationsMgmt
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Process Selection
The ways organizations choose to produce or provide their goods and services. It involves choice of technology, type of processing, and so on. It influences
Capacity planning
Layout of facilities
Equipment
Design of work systems

5. Process Selection and System Design
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Process Selection and System Design
Figure 6.1
Forecasting
Facilities and Equipment
Capacity Planning
Layout
Product and Service Design
Process Selection
Work Design
Technological Change
Capacity is significantly impacted by process selection and facility layout.

6. Process Selection Key Questions
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Process Selection Key Questions
How much variety in products or services will the system need to handle?
What degree of equipment flexibility will be needed?
What is the expected volume of output?

7. Process Types Non-ongoing Operation On-going Operation
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Process Types
Non-ongoing Operation
Project: A nonrepetitive set of activities directed toward a unique goal within a limited time frame
Unique
Examples: Building a bridge, consulting
On-going Operation
Job shop: renders unit or lot production or service with varying specifications, according to customer needs
Small scale
Examples: Machine shop, dentist’s office
Batch: Produces many different products in groups (batches)
Low or moderate volume
Examples: Bakeries, movie theaters, classrooms

8. Process Types (Cont.) On-going Operation (Cont.)
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Process Types (Cont.)
On-going Operation (Cont.)
Repetitive / Assembly : renders one or a few highly standardized products or services
High volumes of standardized goods or services
Examples: automobiles, computers, cafeteria, car wash
Continuous: produces highly uniform products or continuous services, often performed by machines
Very high volumes of non-discrete goods
Examples: refineries, chemical plant, flour, sugar, electricity supplying and the internet

9. Product – Process Matrix
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Product – Process Matrix
Process Type
Low Volume
Moderate
High
Very High
Job Shop
Appliance repair Emergency room
Not feasible
Batch
Commercial bakery Classroom lecture
Repetitive
Automotive assembly
Continuous (flow)
Not feasible
Oil refinery Water purification
Dimension
Job Shop
Batch
Repetitive
Continuous
Job variety
Very high
Moderate
Low
Very low
Process flexibility
Unit cost
Volume of output
High

10. Process Choice Affects Activities/Functions
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Process Choice Affects Activities/Functions
Job Shop
Batch
Repetitive
Continuous
Projects
Cost estimation
Difficult
Somewhat routine
Routine
Simple to complex
Cost per unit
High
Moderate
Low
Very high
Equipment used
General purpose
Special purpose
Varied
Fixed costs
Variable costs
Very low
Labor skills
Low to high
Marketing
Promote capacities
Promote capacities; Semi-standard goods/ services
Promote standardized goods/ services
Scheduling
Complex
Moderately complex
Complex, subject to change
Work-in-process inventory

11. Self Test
Match the products in the first column with the manufacturing system which would probably be most appropriate for producing them.
Products Systems
Gasoline a. job shop
Bread b. batch processing
Pencils c. repetitive production
A muffler for a classic car d. continuous processing
Trucks
Light bulb d. b. c. a. c. c.

12. Standardized goods and services Examples:
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Automation
Automation: Machinery that has sensing and control devices that enables it to operate automatically
Standardized goods and services
Examples:
Goods: Automobile factories, semiconductors
Services: Package sorting, ATM, E-Z pass
Key Questions: automate or not? How much?

13. Automation Types Fixed automation Programmable automation
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Automation Types
Fixed automation
Specialized equipment for a fixed sequence of operations
Programmable automation
Computer-aided design and manufacturing systems (CAD/CAM)
Numerically controlled (NC) machines: Machines that perform operations by following mathematical processing instructions.
Robot: A machine consisting of a mechanical arm, a power supply and a controller
Flexible automation
Evolved from programmable automation
Key difference: significantly less changeover time than programmable automation

14. Advantages and Disadvantages of Automation
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Advantages and Disadvantages of Automation
Advantages
Low variability
No requirements
Reduction of variable costs
Disadvantages
Costly
Less flexible
Adverse effect on morale and productivity

15. The term “automation,” refers soley to manufacturing (T/F)
Self Test
A project approach is often the best choice when a complex set of tasks has a limited life span. (T/F)
The term “automation,” refers soley to manufacturing (T/F)
Equipment flexibility is generally low in a job shop (T/F)
Product variety in a job shop tends to be:
A. high. B. moderate.
C. low. D. very low. T F F

16. Classification of production systems and types of layouts

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Facilities Layout
the configuration of departments, work centers, and equipment, with particular emphasis on movement of work (customers or materials) through the system.

18. Importance of Layout Decisions
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Importance of Layout Decisions
Requires substantial investments of money and effort
Involves long-term commitments, which makes difficult to overcome
Has significant impact on cost and efficiency of short-term operations
Poor layout example: Minneapolis-St. Paul airport security check

19. 370-OperationsMgmt
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Basic Layout Types
Product Layouts most conducive to repetitive processing
Process Layouts used for intermittent processing
Fixed-position layouts used when large construction projects require layouts
Hybrid layouts combinations of these pure types
Cellular manufacturing
Group technology
Flexible Manufacturing Systems

20. Comparison of Product and Process Layouts

21. Product Layouts – Repetitive Processing
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Product Layouts – Repetitive Processing
Product layout: Layout that uses standardized processing operations to achieve smooth, rapid, high-volume flow
Made possible by highly standardized goods or services that allow highly standardized, repetitive processing
The work is divided into a series of standardized tasks, permitting specialization of equipment and division of labor
The large volumes handled by these systems usually make it economical to invest substantial sums of money in equipment and in job design.

22. Production/Assembly Line
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Production/Assembly Line
Figure 6.4
Raw materials
or customer
Station 1
Station 2
Station 3
Station 4
Finished item
Materials
and/or labor
Materials
and/or labor
Materials
and/or labor
Materials
and/or labor
Used for Repetitive or Continuous Processing
Example: automobile assembly lines, cafeteria serving line

23. A U-Shaped Production Line
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A U-Shaped Production Line
Figure 6.6 1 2 3 4 5 6 7 8 9 10 In
Out
Workers

24. Advantages of Product Layouts
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Advantages of Product Layouts
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

25. Disadvantages of Product Layouts
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Disadvantages of Product Layouts
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

26. Process Layouts – Non-repetitive Processing
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Process Layouts – Non-repetitive Processing
Process layouts: Layouts that can handle varied processing requirements
The layouts feature departments or other functional groupings in which similar kinds of activities are performed
Examples: Machine shops usually have separate departments for milling, grinding, drilling, and so on
Different products may present quite different processing requirements and sequences of operations

27. Process Layout - work travels to dedicated process centers
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Process Layout
Process Layout - work travels to dedicated process centers
Milling
Assembly & Test
Grinding
Drilling
Plating

28. Advantages of Process Layouts
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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

29. Disadvantages of Process Layouts
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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, inventory control and purchasing are more involved

30. Self Test
One drawback of process layout is that equipment utilization rates are lower than in a product layout (T/F)
Which one of the following is not generally regarded as an advantage of product layouts?
Material handling costs per unit are low
Labor costs are low per unit
The system is fairly flexible to changes in the design of the product
Accounting, purchasing, and inventory control are fairly routine.
There is high utilization of labor and equipment. T

31. Designing Product Layouts: Line Balancing

32. 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.
Tasks are grouped into manageable bundles and assigned to workstations with one or two operators
Goal is to minimize idle time along the line, which leads to high utilization of labor and equipment
Perfect balance is often impossible to achieve
Operation 1 20 units/hr.
Operation 2 10 units/hr.
Operation 3 15 units/hr.
Output rate:10/hr.
Processing time:
Cycle Time: 6 mins
3 mins/unit
6 mins/unit
4 mins/unit

33. Cycle time is the maximum time allowed
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Cycle Time
Cycle time is the maximum time allowed
at each workstation to complete its set
of tasks on a unit.

34. Example 1: Cycle Times With 5 workstations, CT =
0.5 min.
1.0 min.
0.7 min.
0.1 min.
0.2 min.
With 5 workstations, CT =
Output rate = 60 units/hr
Efficiency = = 2.5/(5*1) = 50%
1.0 minute.
å t
Nactual × CT
Cycle time of a system = longest processing time in a workstation.

35. Output rate = 60/2.5 = 24 units/hr Efficiency = 100%
Example 1: Cycle Time
0.5 min.
1.0 min.
0.7 min.
0.1 min.
0.2 min.
With 1 workstation, CT =
2.5 minutes.
Output rate = 60/2.5 = 24 units/hr Efficiency = 100%
With 3 workstations, can CT = 1.0 minute, i.e., output rate = 60 units/hr?
0.5 min.
1.0 min.
0.7 min.
0.1 min.
0.2 min.
Workstation 1
Workstation 2
Workstation 3

36. Example 1: Cycle Time
0.5 min.
1.0 min.
0.7 min.
0.1 min.
0.2 min.
With 5 workstations, CT = 1.0 min. Efficiency = 2.5/5 = 50%
With 3 workstations, CT = 1.0 min. Efficiency = 2.5/3 = 83.3%
0.5 min.
1.0 min.
0.7 min.
0.1 min.
0.2 min.
Workstation 1
Workstation 2
Workstation 3

37. Output Capacity OT Output capacity = CT OT = operating time per day
CT = cycle time
Example: 8 hours per day
OT = 8 x 60 = 480 minutes per day
Cycle Time = CT = 1.0 min
Output = OT/CT = 480/1.0 = 480 units per day
Cycle Time = CT = 2.5 min
Output = OT/CT = 480/2.5 = 192 units per day

38. Cycle Time Determined by Desired OutputOT D
CT = cycle time =
D = Desired output rate
Example: 8 hours per day
OT = 8 x 60 = 480 minutes per day
D = 480 units per day
CT = OT/D = 480/480 = 1.0 Minute

39. Theoretical Minimum Number of Stations Required
Nmin = CT å t =
sum of task times
Nmin = theoretical Minimum Number of
Workstations Required
Example: 8 hours per day, desired output rate is 480 units per day
CT = OT/D = 480/480 = 1.0 Minute
Nmin = ∑t /CT = 2.5/1.0 = 2.5 stations
≈ 3 stations

40. Nmin cannot always be met
Drying
2 min.
Rinsing
4 min.
Scrubbing
Assume that Cycle time = 4 min
Nmin = å t = 8 min = 2 stations are needed
CT min
But we cannot achieve a cycle time of 4 with N=2.

41. a b c d e Precedence Diagram
Tool used in line balancing to display elemental tasks and sequence requirements.
Figure 6.11
0.1 min. a b c d e
0.7 min.
1.0 min.
0.5 min.
0.2 min.
A Simple Precedence
Diagram

42. Some Heuristic (intuitive) Rules
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 the task times for itself and all its following tasks

43. Line Balancing Procedure (textbook page 264)
1. Identify the cycle time and determine the minimum number of workstations.
2. Make assignments to workstations in order, beginning with Station 1.
Tasks are assigned based on one of the two heuristic rules (most following tasks or greatest positional weight) to workstations moving from left to right through the
precedence diagram.
3. Before each assignment, use the following criteria to determine which tasks are eligible to be assigned to a workstation :
a. All preceding tasks in the sequence have been assigned.
b. The task time does not exceed the time remaining at the workstation.
If no tasks are eligible, move on to the next workstations.
4. After each task assignment, determine the time remaining at the current workstation by subtracting the sum of times for tasks already assigned to it from the cycle time.
5. Break ties that occur using one of these rules:
a. Assign the task with the longest task time
b. Assign the task with the greatest number of followers
If there is still a tie, choose one task arbitrarily
6. Continue until all tasks have been assigned to workstations.
7. Compute appropriate measures (e.g., percent idle time, efficiency) for the set of assignments.

44. Example 2: Assembly Line Balancing
Using the Figure 6.11, do each of the following:
Assuming an eight-hour workday, compute the cycle time needed to obtain an output of 480 units per day.
0.1 min. a b c d e
0.7 min.
1.0 min.
0.5 min.
0.2 min.
= 1 min per cycle
OT min per day
D units per day
CT = =

45. Example 2: Assembly Line Balancing cont.
2. Determine the minimum number of workstations required.
0.1 min. a b c d e
0.7 min.
1.0 min.
0.5 min.
0.2 min.
å t min
Nmin = =
= stations are needed
CT min

46. Example 2: Assembly Line Balancing cont.
0.1 min. a b c d e
0.7 min.
1.0 min.
0.5 min.
0.2 min.
3. Assign tasks to workstations using the greatest positional weight
a: 1.8 mins= ;
b: 1.7 mins; c: 1.4 mins; d: 0.7 mins; e: 0.2 mins
Workstation
Time Remaining
Eligible
Assign Task
Revised Time Remaining
Station Idle Time 1
1.0
0.9
0.2
a, c c
none a - 2 b
0.0 3
0.5
0.3 d e

47. Example 2: Assembly Line Balancing cont.
0.1 min. a b c d e
0.7 min.
1.0 min.
0.5 min.
0.2 min.
Station1
Station2
Station3

48. Two widely used measures of effectiveness
Balance Delay
The percentage of idle time of the line.
Nactual = actual number of stations
Efficiency
Percent idle time =
Idle time per cycle
Nactual × CT
å t
Efficiency = 1 – Percent idle time =
Nactual × CT

49. Two widely used measures of effectiveness
0.1 min. a b c d e
0.7 min.
1.0 min.
0.5 min.
0.2 min.
Station1
Station2
Station3
( )min
Efficiency = = = 0.833
3 × 1 min
3 × 1 min

50. Example 3: a b c d e f g h - 0.2 0.8 0.6 0.3 1.0 0.4 å t=3.8
Task Immediate Task Time
Follower (in minutes)

51. 1. Draw a precedence diagram
Solution to Example 3 a b c d e f g h -
0.2
0.8
0.6
0.3
1.0
0.4
Task Immediate Task Time
Follower (in minutes)
1. Draw a precedence diagram
0.2
0.3
0.8
0.6
1.0
0.4 a b e c d f g h

52. Solution to Example 3
Assuming an eight-hour workday, compute the cycle time needed to obtain an output of 400 units per day.
Determine the minimum number of workstations required.
CT = OT = 480 min per day = 1.2 min per cycle
D units per day
Nmin = å t = 3.8 min = stations are needed
CT min

53. Solution to Example 3 (Cont.)
Assign tasks to workstations using this rule: Assign tasks according to greatest number of following tasks. In case of a tie, use the tiebreaker of assigning the task with the longest processing first.
Workstation
Time Remaining
Eligible
Assigned Task
Station Idle Time 1
1.2
1.0
0.2
0.0
a, c
c, b b -
a (0.2)
c (0.8)
b (0.2) -
0.0 2
1.2
0.6
0.3
e, d e -
d (0.6)
e (0.3) -
0.3 3 4
1.2
0.2
0.8
0.5 f - g h
f (1.0) -
g (0.4)
h (0.3)
0.2
0.5

54. Solution to Example 3 (Cont.)
Station 1
Station 2
Station 3
Station 4 a b e f d g h c
Efficiency = 1 - ( )min = = 79.2%
4 × 1.2 min

55. Example 4: Parallel Workstations
Bottleneck
1.0 min.
2.0 min.
30/hr.
Output Rate = units/hr
Parallel Workstations
1 min.
2 min.
60/hr.
30/hr.
Output Rate = units/hr