operations management stevenson chapter06
TRANSCRIPT
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McGraw-Hill/Irwin Copyright © 2007 by The McGraw-Hill Companies, Inc. All rights reserved.
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Process Selection and Facility Layout
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Learning ObjectivesLearning 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. Explain the need for management of
technology.
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Learning ObjectivesLearning 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. Develop simple process layouts.
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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
IntroductionIntroduction
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Forecasting
Product andService Design
TechnologicalChange
CapacityPlanning
ProcessSelection
Facilities andEquipment
Layout
WorkDesign
Figure 6.1
Process Selection and Process Selection and System DesignSystem Design
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• Key aspects of process strategy– Capital intensive – equipment/labor
– Process flexibility
– Technology
– Adjust to changes
– Design
– Volume
– technology
Process StrategyProcess Strategy
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TechnologyTechnology
Technology: The application of scientific discoveries to the development and improvement of products and services and operations processes.
Technology innovation: The discovery and development of new or improved products, services, or processes for producing or providing them.
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Kinds of TechnologyKinds 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
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Technology Competitive Technology Competitive AdvantageAdvantage
Innovations in Products and services
Cell phones PDAs Wireless computing
Processing technology Increasing productivity Increasing quality Lowering costs
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Technology AcquisitionTechnology Acquisition
Technology can have benefits but … Technology risks include:
What technology will and will not do Technical issues Economic issues
Initial costs, space, cash flow, maintenance Consultants and/or skilled employees Integration cost, time resources Training, safety, job loss
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Variety How much
Flexibility What degree
Volume Expected output
Job Shop
Batch
Repetitive
Continuous
Process SelectionProcess Selection
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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 TypesProcess Types
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Process Type
Job Shop Appliance repairEmergency
room
Ineffective
Batch Commercialbaking
ClassroomLecture
Repetitive Automotiveassembly
Automaticcarwash
Continuous(flow)
Ineffective Steel ProductionWater purification
Figure 6.2
Product and Service Product and Service ProcessesProcesses
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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 MatrixProduct – Process Matrix
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Product and Process ProfilingProduct and Process 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
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Automation: Machinery that has sensing and control devices that enables it to operate Fixed automation Programmable automation
AutomationAutomation
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• Computer-aided design and manufacturing systems (CAD/CAM)
• Numerically controlled (NC) machines
• Robot
• Manufacturing cell
• Flexible manufacturing systems(FMS)
• Computer-integrated manufacturing (CIM)
AutomationAutomation
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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
Facilities LayoutFacilities Layout
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Objective of Layout DesignObjective of Layout Design
1. Facilitate attainment of product or service quality
2. Use workers and space efficiently3. Avoid bottlenecks4. Minimize unnecessary material handling
costs5. Eliminate unnecessary movement of workers
or materials6. Minimize production time or customer service
time7. Design for safety
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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 Importance of Layout DecisionsDecisions
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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 DecisionsThe Need for Layout Decisions
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Changes inenvironmentalor other legalrequirements
Changes in volume ofoutput or mix of
products
Changes in methodsand equipment
Morale problems
The Need for Layout Design The Need for Layout Design (Cont’d)(Cont’d)
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Product layouts
Process layouts
Fixed-Position layout
Combination layouts
Basic Layout TypesBasic Layout Types
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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 TypesBasic Layout Types
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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 LayoutProduct Layout
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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 LayoutAdvantages of Product Layout
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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 LayoutDisadvantages of Product Layout
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1 2 3 4
5
6
78910
In
Out
Workers
Figure 6.6A U-Shaped Production LineA U-Shaped Production Line
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Dept. A
Dept. B Dept. D
Dept. C
Dept. F
Dept. E
Used for Intermittent processingJob Shop or Batch Processes
Process Layout(functional)
Figure 6.7Process LayoutProcess Layout
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Work Station 1
Work Station 2
Work Station 3
Figure 6.7 (cont’d)
Product Layout(sequential)
Used for Repetitive ProcessingRepetitive or Continuous Processes
Product LayoutProduct Layout
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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 LayoutsAdvantages of Process Layouts
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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 Disadvantages of Process LayoutsLayouts
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Fixed Position LayoutsFixed 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
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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 LayoutsCellular Layouts
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Dimension Functional CellularNumber 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 LayoutsFunctional vs. Cellular Layouts
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Warehouse and storage layouts Retail layouts Office layouts Service layouts must be aesthetically
pleasing as well as functional
Service LayoutsService Layouts
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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 Design Product Layouts: Line BalancingBalancing
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Cycle time is the maximum time allowed at each workstation tocomplete its set of tasks on a unit.
Cycle TimeCycle Time
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D
OT = timecycle = CT
rateoutput Desired= D
dayper timeoperating OT
CT
OT = rateOutput
D
OT = timecycle = CT
rateoutput Desired= D
dayper timeoperating OT
CT
OT = rateOutput
Determine Maximum OutputDetermine Maximum Output
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task timeof sum = t
CT
t)( =N
Determine the Minimum Number Determine the Minimum Number
of Workstations Requiredof Workstations Required
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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 6.11Precedence DiagramPrecedence Diagram
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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 Example 1: Assembly Line BalancingBalancing
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Workstation
TimeRemaining Eligible
AssignTask
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 SolutionExample 1 Solution
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Percent idle time = Idle time per cycle
(N)(CT)
Efficiency = 1 – Percent idle time
Calculate Percent Idle TimeCalculate Percent Idle Time
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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 RulesLine Balancing Rules
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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 2Example 2
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Station 1 Station 2 Station 3 Station 4
a b ef
d
g h
c
Solution to Example 2Solution to Example 2
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1 min.2 min.1 min.1 min. 30/hr. 30/hr. 30/hr. 30/hr.
Bottleneck
Bottleneck WorkstationBottleneck Workstation
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Parallel WorkstationsParallel Workstations
1 min.
2 min.
1 min.1 min. 60/hr.
30/hr. 30/hr.
60/hr.
2 min.
30/hr.30/hr.
Parallel Workstations
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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 LayoutsDesigning Process Layouts
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1 3 2
30
170 100
A B C
Figure 6.13
Example 3: Interdepartmental Work Example 3: Interdepartmental Work FlowsFlows
for Assigned Departmentsfor Assigned Departments
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PowerPoint Author’s note: The following three slides are not in the 9e
text, but I like to use them for alternate examples.
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Process Layout - work travels to dedicated process centers
Milling
Assembly& Test Grinding
Drilling Plating
Process LayoutProcess Layout
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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 LayoutFunctional Layout
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-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 LayoutCellular Manufacturing Layout
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Video: Process DesignVideo: Process Design
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Video: Process ImplementationVideo: Process Implementation
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Video: Process MappingVideo: Process Mapping