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1-2 2 Work Center A work center is an area in a business in which productive resources are organized and work is completed Can be a single machine, a group of machines, or an area where a particular type of work is done

1-3 3 Typical Scheduling and Control Functions Allocating orders, equipment, and personnel Determining the sequence of order performance Initiating performance of the scheduled work Shop-floor control

1-4 4 Work-Center Scheduling Objectives Meet due dates Minimize lead time Minimize setup time or cost Minimize work-in-process inventory Maximize machine utilization

1-5 5 Priority Rules for Job Sequencing 1. First-come, first-served (FCFS) 2. Shortest operating time (SOT) 3. Earliest due date first (DDate) 4. Slack time remaining (STR) first 5. Slack time remaining per operation (STR/OP)

1-6 6 Example of Job Sequencing: First-Come First-Served Answer: FCFS Schedule Suppose you have the four jobs to the right arrive for processing on one machine What is the FCFS schedule? No, Jobs B, C, and D are going to be late Do all the jobs get done on time?

1-7 7 Example of Job Sequencing: Shortest Operating Time Answer: Shortest Operating Time Schedule Suppose you have the four jobs to the right arrive for processing on one machine What is the SOT schedule? No, Jobs A and B are going to be late Do all the jobs get done on time?

1-8 8 Example of Job Sequencing: Earliest Due Date First Answer: Earliest Due Date First Suppose you have the four jobs to the right arrive for processing on one machine What is the earliest due date first schedule? No, Jobs C and B are going to be late Do all the jobs get done on time?

1-9 9 Performance Measures Comparison Avg. flow timeAvg. lateness FCFS SPT EDD

1-10 10 Scheduling n Jobs on 2 Machines Johnson’s Rule (minimize flow time): 1. List all the jobs and processing times on the two machines. 2. Select the job with the shortest processing time. If the time is on the first machine, schedule the job first. If the time is on the second machine, schedule the job last. Ties can be broken arbitrarily. 3. Eliminate this job. Repeat Step 2.

1-11 11 Johnson’s Rule-Example