Which rule establishes priorities on the basis of the due date for the jobs?

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Scheduling -- determine the timing and order of operations to optimize the use of resources to meet production requirements

n jobs 1 machine case

Priority rules (pg.590)

First Come First Serve (FCFS)
Shortest Processing Time (SPT)
Earliest Due Date (EDD)
Slack Time Remaining (STR) = time remaining before due date - remaining processing time
    The shortest STR goes first
Critical Ratio (CR) = Time remaining before due date/Remaining processing time
    The smallest CR goes first

Comparison of priority rules

Average Completion time/Mean flow time =(Total processing time + total waiting time)/Number of jobs
Average lateness = total late days/number of jobs

Example

Given:

Comparing the priority rules

Exercises

Pg. 607 Problem 5, 13

Flow shop scheduling

n jobs two machines: all jobs require the same sequence/order in visiting the machines

Johnson's rule

If the shortest time is for the first machine, do the job first
If the shortest time is for the second machine, do the job last

Example

Job sequence: B à E à D à C à A

Gantt Chart representation

Exercises

Pg. 606 Problem 3, 9, 12, 14

Job sequencing rules determine the priority for processing jobs. They address scheduling problems that generally lead to inefficient performance in assigning jobs and completing them. Of central importance is job flow time, which is the amount of time a job spends in a shop from order placement to its completion and release. The average time taken to complete jobs is one way of measuring a job shop's performance.

Earliest Due Date

Some shops sequence jobs by earliest due date. Sometimes called due date assignment, it places the highest priority on processing jobs with the earliest due dates. Job shop quality performance can be measured by the number of late jobs, the average tardiness across late jobs or the average tardiness across all jobs.

Longest Processing Time

The longest processing time approach to job sequencing assigns the highest priority to jobs with the longest processing time. By scheduling the longest job first, schedulers are able to reduce the number of outstanding long jobs at the end of the job schedule. The completion time for the last jobs—which are among the shortest in length—is also reduced.

Shortest Processing Time

Another method of job sequencing based on job completion time, the shortest processing time method assigns jobs with the shortest processing time first. Like the LPT scheduling method, SPT requires an initial time estimation for each job. SPT reduces average flow time for jobs, according to Kenneth R. Baker in "Management Science."

First-Come, First-Serve

Many shope employ the first-come, first-served job sequencing method, which processes job orders in the order of their arrivel at the production center. Arrival time is the determinative factor in this scheduling rule, which is also referred to as first-in, first-out. It is sometimes described as the simplest job sequencing rule. For example, unlike SPT and LPT scheduling methods, no time estimation is required for FCFS scheduling.

Preferred Customer Order

The preferred customer order approach prioritizes jobs from preferred customers, and can be useful tool for building customer loyalty.

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