Chap 17 Scheduling
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Transcript of Chap 17 Scheduling
17-1
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Chapter 17
Scheduling
17-2
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
• Scheduling: Establishing the timing of the use of equipment, facilities and human activities in an organization
Scheduling
17-3
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Build A
A Done
Build B
B Done
Build C
C Done
Build D
Ship
JAN FEB MAR APR MAY JUN
On time!
Scheduling Manufacturing Operations
High-volume
Intermediate-volume
Low-volume
Service operations
17-4
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
High-Volume Systems
• Flow system: High-volume system with Standardized equipment and activities
• Flow-shop scheduling: Scheduling for high-volume flow system
Work Center #1 Work Center #2 Output
17-5
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
High-Volume Success Factors
• Process and product design
• Preventive maintenance
• Rapid repair when breakdown occurs
• Optimal product mixes
• Minimization of quality problems
• Reliability and timing of supplies
17-6
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Intermediate-Volume Systems
• Outputs are between standardized high-volume systems and made-to-order job shops
• Economic run size:
QDS
H
p
p u0
2
17-7
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Scheduling Low-Volume Systems
• Loading - assignment of jobs to process centers
• Sequencing - determining the order in which jobs will be processed
17-8
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Gantt Load Chart
• Gantt chart - used as a visual aid for loading and scheduling
WorkCenter
Mon. Tues. Wed. Thurs. Fri.
1 Job 3 Job 42 Job 3 Job 73 Job 1 Job 6 Job 74 Job 10
Figure 17-2
17-9
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
• Infinite loading
• Finite loading
• Vertical loading
• Horizontal loading
• Forward scheduling
• Backward scheduling
• Schedule chart
Loading
17-10
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Sequencing
• Sequencing: Determine the order in which jobs at a work center will be processed.
• Workstation: An area where one person works, usually with special equipment, on a specialized job.
17-11
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Sequencing
• Priority rules: Simple heuristics used to select the order in which jobs will be processed.
• Job time: Time needed for setup and processing of a job.
Everything is#1 Priority
17-12
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Priority Rules
• FCFS - first come, first served• SPT - shortest processing time• DD - due date• CR - critical ratio• S/O - slack per operation• Rush - emergency
Top Priority
Table 17-2
17-13
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
3.9014.1726.67CR
2.686.3318.33DD
2.636.6718.00SPT
2.939.0020.00FCFS
AverageNumber ofJobs at theWork Center
AverageTardiness(days)
AverageFlow Time(days)Rule
Example 2Table 17-4
17-14
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Two Work Center Sequencing
• Johnson’s Rule: technique for minimizing completion time for a group of jobs to be processed on two machines or at two work centers.
• Minimizes total idle time
• Several conditions must be satisfied
17-15
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Johnson’s Rule Conditions
• Job time must be known and constant
• Job times must be independent of sequence
• Jobs must follow same two-step sequence
• Job priorities cannot be used
• All units must be completed at the first work center before moving to second
17-16
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Scheduling Service Operations
• Appointment systems– Controls customer arrivals for service
• Reservation systems– Estimates demand for service
• Scheduling the workforce– Manages capacity for service
• Scheduling multiple resources– Coordinates use of more than one
resource
17-17
McGraw-Hill/IrwinOperations Management, Seventh Edition, by William J. StevensonCopyright © 2002 by The McGraw-Hill Companies, Inc. All rights reserved.
Scheduling
Service Operation Problems
• Cannot store or inventory services
• Customer service requests are random
• Scheduling service involves– Customers– Workforce– Equipment