Chap015 Scheduling

7/28/2019 Chap015 Scheduling

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15-1 Scheduling

William J. Stevenson

Operations Management

8th edition


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15-2 Scheduling

CHAPTER

15

Scheduling

McGraw-Hill/Irwin

Operations Management, Eighth Edition, by William J. StevensonCopyright 2005 by The McGraw-Hill Companies, Inc. All rights reserved.


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15-3 Scheduling

Scheduling: Establishing the timing of theuse of equipment, facilities and human

activities in an organization

Effective scheduling can yield

Cost savings

Increases in productivity

Scheduling


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15-4 Scheduling

High-Volume SystemsFlow system: High-volume system with

Standardized equipment and activities

Flow-shop scheduling: Scheduling for high-

volume flow system

WorkCenter #1 Work Center#2

Output


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15-5 Scheduling

Bui ld A

A Done

Bui ld B

B Done

Bui ld C

C Done

Bui ld D

Ship

JAN FEB MAR APR MAY JUN

On time!

Scheduling Manufacturing OperationsHigh-volume

Intermediate-

volume

Low-volume

Service

operations


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15-6 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


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15-7 Scheduling

Intermediate-Volume Systems Outputs are between standardized high-

volume systems and made-to-order job shops

Run size, timing, and sequence of jobs

Economic run size:

Q

DS

H

p

p u0

2


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15-8 Scheduling

Scheduling Low-Volume SystemsLoading- assignment of jobs to process

centers

Sequencing- determining the order inwhich jobs will be processed

Job-shop scheduling

Scheduling for low-volumesystems with many

variationsin requirements


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15-9 Scheduling

Gantt Load Chart Gantt chart- used as a visual aid for loading

and scheduling

Work

Center

Mon. Tues. Wed. Thurs. Fri.

1 Job 3 Job 4

2 Job 3 Job 7

3 Job 1 Job 6 Job 7

4 Job 10

Figure 15.2


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15-10 Scheduling

Infinite loading

Finite loading

Vertical loading

Horizontal loading

Forward scheduling

Backward scheduling

Schedule chart

Loading

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15-11 Scheduling

Sequencing Sequencing: Determine the order in whichjobs at a work center will be processed.

Workstation: An area where one personworks, usually with special equipment, on a

specialized job.

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15-12 Scheduling

SequencingPriority rules: Simple heuristics

used to select the order inwhich jobs will be processed.

Job time: Time needed forsetup and processing of a job.

Everything is

#1 Priority

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15-13 Scheduling

Priority Rules

FCFS - first come, first served SPT - shortest processing time

EDD - earliest due date

CR - critical ratio

S/O - slack per operation

Rush - emergency Top Priority

Table 15.2

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15-14 Scheduling

3.249.6722.17CR

2.686.3318.33EDD

2.636.6718.00SPT

2.939.0020.00FCFS

AverageNumber of

Jobs at the

Work Center

Average

Tardiness

(days)

Average

Flow Time

(days)Rule

Example 2Table 15.4

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15-15 Scheduling

Two Work Center SequencingJohnsons Rule: technique for minimizingcompletion 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

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15-16 Scheduling

Johnsons 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 firstwork center before moving to second

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15-17 Scheduling

Johnsons Rule Optimum Sequence

1. List the jobs and their times at each workcenter

2. Select the job with the shortest time

3. Eliminate the job from further consideration4. Repeat steps 2 and 3 until all jobs have been

scheduled

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15-18 Scheduling

Scheduling Difficulties

Variability in Setup times

Processing times

Interruptions Changes in the set of jobs

No method for identifying optimal schedule

Scheduling is not an exact science

Ongoing task for a manager

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15-19 Scheduling

Minimizing Scheduling Difficulties

Set realistic due dates Focus on bottleneck operations

Consider lot splitting of large jobs

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15-20 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

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15-21 Scheduling

Cyclical Scheduling

Hospitals, police/fire departments, restaurants,supermarkets

Rotating schedules

Set a scheduling horizon Identify the work pattern

Develop a basic employee schedule

Assign employees to the schedule

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15-22 Scheduling

Service Operation Problems Cannot store or inventory services Customer service requests are random

Scheduling service involves

Customers Workforce

Equipment

15-23 Scheduling


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15 23 Scheduling

Service Scheduling

SSU1

Overview

United Airlines

15-24 Scheduling


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15 24 Scheduling

Service Scheduling

SSU2

United Airlines Flight Schedule

15-25 Scheduling


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15 25 Scheduling

Schedule

PS8

Painting Example (Washburn Guitar)

Documents

Chap015 Scheduling