chap006 - process selection and facility layout
TRANSCRIPT
S P CHHEDA & CO.
6-1 Process Selection and Facility Layout
William J. Stevenson
Operations Management
8th edition
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6-2 Process Selection and Facility Layout
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6-3 Process Selection and Facility Layout
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
Introduction
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6-4 Process Selection and Facility Layout
Forecasting
Product andService Design
TechnologicalChange
CapacityPlanning
ProcessSelection
Facilities andEquipment
Layout
WorkDesign
Figure 6.1
Process Selection and System Design
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6-5 Process Selection and Facility Layout
• Key aspects of process strategy– Capital intensive – equipment/labor
– Process flexibility
– Adjust to changes
– Design
– Volume
– technology
Process Strategy
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6-6 Process Selection and Facility Layout
Variety How much
Flexibility What degree
Volume Expected output
Job Shop
Batch
Repetitive
Continuous
Process Selection
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6-7 Process Selection and Facility Layout
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
Process Types
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6-8 Process Selection and Facility Layout
Process Type
Job Shop Appliance repairEmergency
room
Not feasible
Batch Commercialbakery
ClassroomLecture
Repetitive Automotiveassembly
Automaticcarwash
Continuous(flow)
Notfeasible
Oil refineryWater purification
Figure 6.2Product – Process Matrix
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6-9 Process Selection and Facility Layout
Dimension
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 High Low High Very low
Figure 6.2 (cont’d)Product – Process Matrix
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6-10 Process Selection and Facility Layout
Automation: Machinery that has sensing and control devices that enables it to operate Fixed automation Programmable automation
Automation
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6-11 Process Selection and Facility Layout
• Computer-aided design and manufacturing systems (CAD/CAM)
• Numerically controlled (NC) machines
• Robot
• Manufacturing cell
• Flexible manufacturing systems(FMS)
• Computer-integrated manufacturing (CIM)
Automation
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6-12 Process Selection and Facility 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
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6-13 Process Selection and Facility Layout
Requires substantial investments of money and effort
Involves long-term commitments Has significant impact on cost and
efficiency of short-term operations
Importance of Layout Decisions
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6-14 Process Selection and Facility Layout
Inefficient operations
For Example:
High CostBottlenecks
Changes in the designof products or services
The introduction of newproducts or services
Accidents
Safety hazards
The Need for Layout Decisions
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6-15 Process Selection and Facility Layout
Changes inenvironmentalor other legalrequirements
Changes in volume ofoutput or mix of
products
Changes in methodsand equipment
Morale problems
The Need for Layout Design (Cont’d)
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6-16 Process Selection and Facility Layout
Product layouts
Process layouts
Fixed-Position layout
Combination layouts
Basic Layout Types
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6-17 Process Selection and Facility Layout
Product layout Layout that uses standardized processing
operations to achieve smooth, rapid, high-volume 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
Basic Layout Types
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6-18 Process Selection and Facility Layout
Raw materialsor customer
Finished item
Station 2
Station 2
Station 3
Station 3
Station 4
Station 4
Material and/or labor
Station 1
Material and/or labor
Material and/or labor
Material and/or labor
Used for Repetitive or Continuous Processing
Figure 6.4Product Layout
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6-19 Process Selection and Facility 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
Advantages of Product Layout
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6-20 Process Selection and Facility 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
Disadvantages of Product Layout
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6-21 Process Selection and Facility Layout
1 2 3 4
5
6
78910
In
Out
Workers
Figure 6.6A U-Shaped Production Line
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6-22 Process Selection and Facility Layout
Dept. A
Dept. B Dept. D
Dept. C
Dept. F
Dept. E
Used for Intermittent processingJob Shop or Batch
Process Layout(functional)
Figure 6.7Process Layout
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6-23 Process Selection and Facility Layout
Work Station 1
Work Station 2
Work Station 3
Figure 6.7 (cont’d)
Product Layout(sequential)
Used for Repetitive ProcessingRepetitive or Continuous
Product Layout
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6-24 Process Selection and Facility Layout
Can handle a variety of processing requirements
Not particularly vulnerable to equipment failures
Equipment used is less costly Possible to use individual incentive plans
Advantages of Process Layouts
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6-25 Process Selection and Facility Layout
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
Disadvantages of Process Layouts
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6-26 Process Selection and Facility Layout
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
Cellular Layouts
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6-27 Process Selection and Facility Layout
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
Table 6.3Functional vs. Cellular Layouts
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6-28 Process Selection and Facility Layout
Warehouse and storage layouts Retail layouts Office layouts
Other Service Layouts
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6-29 Process Selection and Facility Layout
Line Balancing is the process of assigning tasks to workstations in such a way that the workstations have approximately equal time requirements.
Design Product Layouts: Line Balancing
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6-30 Process Selection and Facility Layout
Cycle time is the maximum time allowed at each workstation tocomplete its set of tasks on a unit.
Cycle Time
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6-31 Process Selection and Facility Layout
O utput capac ity = O T
C T
O T operating tim e per day
D = D es ired output ra te
C T = cyc le tim e = O T
D
O utput capac ity = O T
C T
O T operating tim e per day
D = D es ired output ra te
C T = cyc le tim e = O T
D
Determine Maximum Output
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6-32 Process Selection and Facility Layout
N = (D)( t)
OT
t = sum of task times
Determine the Minimum Number of Workstations Required
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6-33 Process Selection and Facility Layout
Precedence diagram: Tool used in line balancing to display elemental tasks and sequence requirements
A Simple Precedence Diagrama b
c d e
0.1 min.
0.7 min.
1.0 min.
0.5 min. 0.2 min.
Figure 6.10Precedence Diagram
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6-34 Process Selection and Facility Layout
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: Assembly Line Balancing
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6-35 Process Selection and Facility Layout
Workstation
TimeRemaining
EligibleAssignTask
RevisedTime Remaining
StationIdle Time
1 1.0
0.9
0.2
a, c
c
none
a
c
-
0.9
0.2
0.2
2 1.0 b b 0.0 0.0
3 1.0
0.5
0.3
d
e
-
d
e
-
0.5
0.3 0.3
0.5
Example 1 Solution
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6-36 Process Selection and Facility Layout
Percent idle time = Idle time per cycle
(N)(CT)
Efficiency = 1 – Percent idle time
Calculate Percent Idle Time
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6-37 Process Selection and Facility Layout
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.
Some Heuristic (intuitive) Rules:
Line Balancing Rules
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6-38 Process Selection and Facility Layout
c d
a b e
f g h
0.2 0.2 0.3
0.8 0.6
1.0 0.4 0.3
Example 2
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6-39 Process Selection and Facility Layout
Station 1 Station 2 Station 3 Station 4
a b ef
d
g h
c
Solution to Example 2
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6-40 Process Selection and Facility Layout
1 min.2 min.1 min.1 min. 30/hr. 30/hr. 30/hr. 30/hr.
1 min.
1 min.
1 min.1 min. 60/hr.
30/hr. 30/hr.
60/hr.
1 min.
30/hr.30/hr.
Bottleneck
Parallel Workstations
Parallel Workstations
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6-41 Process Selection and Facility Layout
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
Designing Process Layouts
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6-42 Process Selection and Facility Layout
1 3 2
30
170 100
A B C
Figure 6.12
Example 3: Interdepartmental Work Flowsfor Assigned Departments
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6-43 Process Selection and Facility Layout
Author’s note: The following three slides are not in the 8e,
but I like to use them for alternate examples.
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6-44 Process Selection and Facility Layout
Process Layout - work travels to dedicated process centers
Milling
Assembly& Test Grinding
Drilling Plating
Process Layout
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6-45 Process Selection and Facility Layout
Gearcutting
Mill Drill
Lathes
Grind
Heattreat
Assembly
111
333
222
444
222111444
111 3331111 2222
222
3333
111
444111
333333333
44444
3333
3322
222
Functional Layout
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6-46 Process Selection and Facility Layout
-1111 -1111
222222222 - 2222
Ass
emb
ly
3333333333 - 3333
44444444444444 - 4444
Lathe
Lathe
Mill
Mill
Mill
Mill
Drill
Drill
Drill
Heat treat
Heat treat
Heat treat
Gear cut
Gear cut
Grind
Grind
Cellular Manufacturing Layout