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