6-1
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Chapter 6
Process Selection and
Facility Layout
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Process Selection and System Design
Forecasting
Product and service design
Capacity planning
Facilities andEquipment
Layout
Work design
Processselection
Technologicalchange
Technologicalchange
Process selection defines the way production is organized, how things will be done
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Process Strategy
• How an organization approaches the process selection process
• Important concerns:– Make or buy?– Capital intensity– Process flexibility
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Introduction
• Make or Buy?– Available capacity
– Expertise
– Quality Consideration
– The nature of demand
– Cost
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
• Product Variety– How much
• Process Flexibility– What degree will be required
• Volume – Expected output
Process Selection
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Process Types• Job Shops
– Small runs, high variety– Requires skilled labor and flexible
equipment
• Batch Processing– Moderate volume, moderate variety,
moderate skill
• Repetitive/Assembly– Semicontinuous– Higher volume, more standardized, less
flexibility and skill required
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Process Types
• Continuous Processing– High volume, highly standardized
• Projects– Nonroutine jobs, limited duration– Large products like buildings
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
ProductVariety
High Moderate Low Very Low
Equipmentflexibility
High Moderate Low Very Low
LowVolume
ModerateVolume
HighVolume
Very highVolume
ProductVariety
High Moderate Low Very Low
Equipmentflexibility
High Moderate Low Very Low
LowVolume
ModerateVolume
HighVolume
Very highVolume
JobShop
Batch
Repetitiveassembly
ContinuousFlow
Variety, Flexibility, & Volume
Job Shop
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
• Automation: Machinery that operates automatically, with little or no human intervention• Advantages:
– Consistency– Elimination of negative human factors– Reduced variable costs
• Disadvantages– High initial investment– High fixed costs– Requires high volume to offset costs– Less flexible than human labor– Can hurt worker morale
Automation
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Automation
• Computer-aided design and manufacturing systems (CAD/CAM)
• Numerically controlled (NC) machines
• Robot
• Manufacturing cell
• Flexible manufacturing systems
• Computer-integrated manufacturing (CIM)
6-11
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Management of Technology
• Potential effects of new technology:– Improved quality– Increased productivity– Reduced production times– Increased customer satisfaction– Reduced flexibility– Increased fixed costs– Short-term disruptions– Increased training costs– Difficult integration with existing systems
6-12
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
• Service blueprint: A method used in service design to describe and analyze a proposed service.
• Steps:– Establish boundaries and determine the required level of detail– Identify and describe the steps of a process– Flowchart key process steps– Identify potential failure points– Establish a time frame for service execution and estimate variability– Analyze profitability and zero in on process steps with the biggest impact
Service Blueprint
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
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
• Important because:– Require substantial investments of time and
money– Involve long-term commitments– Significant impact on cost and efficiency
Layout
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Layout
• Reasons to redesign an existing layout:– Inefficiency– Accidents or safety hazards– Changes in product design– Introduction of new products– Changes in output volume or mix– Changes in regulations
6-15
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Basic Layout Types
• Product Layouts
• Process Layouts
• Fixed-Position
• Combination Layouts
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Product Layout• Work divided into a series of standard tasks that every unit goes through• Often uses fixed-path material handling• Entire line can be shut down by one mechanical failure• Advantages:
– High output– Low unit cost– Labor specialization reduces training costs– High utilization rate of labor and equipment
• Disadvantages– Dull, repetitive jobs– Not very flexible to product design or volume changes– Susceptible to shutdowns
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
A Flow Line for Production or Service
Flow Shop or Assembly Line Work Flow
Raw materialsor customer
Finished item
Station 2
Station 3
Station 4
Material and/or labor
Station 1
Material and/or labor
Material and/or labor
Material and/or labor
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
A U-Shaped Production Line
1 2 3 4
5
6
78910
In
Out
Workers
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Process Layout• Work divided into departments, each of which handles a given
process• Products follow different paths depending on processing
requirements• Equipment must be more general-purpose• Advantages:
– More flexible– Not as vulnerable to shutdowns– General-purpose equipment often cheaper than specialized
• Disadvantages:– Routing and scheduling can be difficult– Low utilization rates– More costly material handling– Complex jobs can lead to higher supervision costs
6-20
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Process Layout
Process Layout - work travels to dedicated process centers
Milling
Assembly& Test Grinding
Drilling Plating
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Functional 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
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Fixed Position Layout
• Layout in which the product or project remains stationary, and workers, materials, and equipment are moved as needed
• Requires special attention to time materials and workers to prevent clogging up the jobsite
6-23
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
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.
6-24
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Cycle Time
Cycle time is the maximum time allowed at each workstation tocomplete its set of tasks on a unit.
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Determine Maximum Output
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
6-26
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Determine the Minimum Number of Workstations Required: Efficiency
N = (D)( t)
OT
t = sum of task times
6-27
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Precedence Diagram
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.
6-28
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Example 1: Assembly Line Balancing
• Arrange tasks shown in the previous slide into workstations.– Use a cycle time of 1.0 minute– Assign tasks in order of the most number of
followers
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Solution to Example 1
W o r k -S t a t i o n
T i m eR e m a i n i n g E l i g i b l e
A s s i g nT a s k
S t a t i o nI d l e T i m e
1 1 . 0. 9. 2
ac
n o n e
ac- . 2
2 1 . 00
bn o n e
b- 0
3 1 . 0. 5. 3
de-
de- . 3
. 5
W o r k -S t a t i o n
T i m eR e m a i n i n g E l i g i b l e
A s s i g nT a s k
S t a t i o nI d l e T i m e
1 1 . 0. 9. 2
ac
n o n e
ac- . 2
2 1 . 00
bn o n e
b- 0
3 1 . 0. 5. 3
de-
de- . 3
. 5
6-30
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Calculate Percent Idle Time
Percent idle time = Idle time per cycle
(N)(CT)
6-31
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Line Balancing Rules
• Assign tasks in order of most following tasks.
• 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:
6-32
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Solution to Example 2
Station 1 Station 2 Station 3 Station 4
a b ef
d
g h
c
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McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
Parallel Workstations
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
6-34
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Process Selection and Facility Layout
• Requirements:– List of departments– Projection of work flows– Distance between locations– Amount of money to be invested– List of special considerations
Designing Process Layouts