Module 9

Question 1

Backward Scheduling

Answer 1

begins with the due date, scheduling the final operation first

Question 2

Loading

Answer 2

the process of assigning jobs to work stations or processes

Question 4

finite loading

Answer 4

Scheduling techniques that load (or assign) work only up to the capacity of the process

Question 5

Input-Output Control

Answer 5

technique that allows operations personnel to manage facility work flows.

Question 6

ConWIP card

Answer 6

cards that control the amount of work in a work center; aiding input-output control

Question 7

assignment method

Answer 7

a special class of linear programming models that involves assigning tasks or jobs to resources

Question 8

Sequencing

Answer 8

determining the order in which jobs should be done at each work center

also called dispatching

Question 10

Priority Rules

Answer 10

rules for determining the sequence of jobs in process oriented facilities

Question 11

Priority Rules Examples

Answer 11

FCFS: first come, first served. Jobs are completed in the order they arrived.

            ◆ SPT: shortest processing time. Jobs with the shortest processing times are assigned first.
          
            ◆ EDD: earliest due date. Earliest due date jobs are assigned first.
          
            ◆ LPT: longest processing time. Jobs with the longest processing time are assigned first.

Question 12

flow time

Answer 12

the time between the release of a job to a work center until the job is finished

Question 13

Critical Ratio

in job sequencing

Answer 13

a sequencing rule that is an index number computed by dividing the time remaining until due date by work time remaining

Question 14

Johnson’s Rule

Answer 14

an approach that minimizes the total time for sequencing a group of jobs through two work centers while minimizing total idle time in the work centers

Question 15

4 Steps of Johnson’s Rule

Answer 15

1. All jobs are to be listed, and the time that each requires on a machine is to be shown.

           2. Select the job with the shortest activity time. If the shortest time lies with the first machine, the job is scheduled first. If the shortest time lies with the second machine, schedule the job last. Ties in activity times can be broken arbitrarily.
             
        3.    Once a job is scheduled, eliminate it.
             
          4.  Apply steps2 and 3 to the remaining jobs, working toward the center of the sequence.

Question 16

Limitations of rule based scheduling techiques

Answer 16

1. scheduling is dynamic - rules need revised
2. rules do not look upstream or downstream
3. Rules do not look beyond due dates - ie which job due at same time is more important

Question 17

Finite capacity scheduling

Answer 17

a computerized short term scheduling that overcomes the disadvantages of rule based systems by providing the user with graphical interactive computing