Scheduling – Day 2

Production Planning Process Process Planning Strategic Capacity Planning Aggregate Planning Master Production Scheduling Material Requirements Planning Order Scheduling Weekly Workforce & Customer Scheduling Daily Workforce & Customer Scheduling Long Range Medium Range Short Range Manufacturing Services

Outline Scheduling Recap Sequencing rules Single resource Global Multiple resources

Scheduling Deals with the timing of operations Specifies when resources are needed to produce a product or provide a service Helps us decide what order to perform jobs All organizations perform scheduling to some extent… All organizations perform scheduling to some extent…

Sequencing Rules Determine the order jobs are processed by a resource Determine the order jobs are processed by a resource

Types of Sequencing Rules Sequencing jobs at a single resource Sequencing jobs across multiple resources

Sequencing Rules (Single Resource) Local First Come First Served Last Come First Served Shortest Processing Time Longest Processing Time Earliest Due Date Global Slack Per Remaining Operation Critical Ratio Last class

Sequencing Rules (Single Resource) Local First Come First Served Last Come First Served Shortest Processing Time Longest Processing Time Earliest Due Date Global Slack Per Remaining Operation Critical Ratio

Global Rules Consider more than current operation Look at work at other work centers that needs to be completed before the job is done

Types of Sequencing Rules Sequencing jobs at a single resource Sequencing jobs across multiple resources

Scheduling Across Multiple Resources Previous rules considered scheduling (sequencing) jobs at one resource How can we schedule jobs across multiple resources??

Two resource problems Suppose you work with a classmate, Kim on all projects Management Marketing Finance Accounting English In each project you do the research, then Kim writes the report Processing time (you): Processing time (Kim): You want to complete all projects asap What should be the order for the projects?

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Find the smallest processing time If its on the 1st machine, assign the task at the beginning of the sequence and eliminate it from further consideration Processing time (you): Processing time (Kim): What order should you do the projects in? If its on the 2nd machine, assign the task at the end of the sequence and eliminate it from further consideration 2. Repeat step 1 for all unassigned tasks Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Find the smallest processing time If its on the 1st machine, assign the task at the beginning of the sequence and eliminate it from further consideration Processing time (you): Processing time (Kim): If its on the 2nd machine, assign the task at the end of the sequence and eliminate it from further consideration 2. Repeat step 1 for all unassigned tasks Sequence English Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Find the smallest processing time If its on the 1st machine, assign the task at the beginning of the sequence and eliminate it from further consideration Processing time (you): Processing time (Kim): If its on the 2nd machine, assign the task at the end of the sequence and eliminate it from further consideration 2. Repeat step 1 for all unassigned tasks Sequence English Management Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Find the smallest processing time If its on the 1st machine, assign the task at the beginning of the sequence and eliminate it from further consideration Processing time (you): Processing time (Kim): If its on the 2nd machine, assign the task at the end of the sequence and eliminate it from further consideration 2. Repeat step 1 for all unassigned tasks Sequence English Management Finance Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Find the smallest processing time If its on the 1st machine, assign the task at the beginning of the sequence and eliminate it from further consideration Processing time (you): Processing time (Kim): If its on the 2nd machine, assign the task at the end of the sequence and eliminate it from further consideration 2. Repeat step 1 for all unassigned tasks Sequence English Management Finance Marketing Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Find the smallest processing time If its on the 1st machine, assign the task at the beginning of the sequence and eliminate it from further consideration Processing time (you): Processing time (Kim): If its on the 2nd machine, assign the task at the end of the sequence and eliminate it from further consideration 2. Repeat step 1 for all unassigned tasks Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Sequences tasks to minimize makespan

Two resource problems Johnson’s Rule Management Marketing Finance Accounting English Processing time (you): Processing time (Kim): Sequence English Management Finance Marketing Accounting Idle time Sequences tasks to minimize makespan

More Than 2 Resources Optimal methods don’t exist to minimize makespan Heuristics CDS Heuristic

Sequencing Rules Local FCFS LCFS SPT LPT EDD Global SPO CR Single ResourceMultiple Resources 2 resources Johnson’s rule > 2 resources heuristics When should you choose one rule over another??

Guidelines for Selecting a Sequencing Rule 1.SPT most useful when shop is highly congested 2.Use SPO for periods of normal activity 3.Use EDD when only small tardiness values can be tolerated 4.Use FCFS when operating at low-capacity levels

Employee Scheduling Labor is very flexible resource Labor is very flexible resource Scheduling workforce is complicated repetitive task Scheduling workforce is complicated repetitive task Heuristics commonly used Heuristics commonly used We’ll cover one simple one today…

Employee Scheduling Heuristic Let N = no. of workers available D i = demand for workers on day i 1.Assign the first N - D 1 workers day 1 off. Assign the next N - D 2 workers day 2 off. Continue in a similar manner until all days are scheduled. 2.If number of workdays for full time employee < 5, assign remaining workdays so consecutive days off are possible. Assign any remaining work to part-time employees. Assign any remaining work to part-time employees. 3.If consecutive days off are desired, consider switching schedules among days with the same demand requirements.

Example DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED TaylorSmithSimpsonAllenDickerson

DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED TaylorSmithSimpsonAllenDickerson N = 5 D 1 =D 2 =D 3 =D 4 = D 5 =D 6 =D 7 = N – D 1 =5 – 3 =2 X = day working O = day off 1.Assign the first N - D1 workers day 1 off. Assign the next N - D2 workers day 2 off. Continue in a similar manner until all days are have been scheduled.

DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED TaylorOXXOXXX SmithOXXOXXX SimpsonXOXXOXX AllenXOXXXXO DickersonXXOXXXO 1.Assign the first N - D1 workers day 1 off. Assign the next N - D2 workers day 2 off. Continue in a similar manner until all days are have been scheduled. N – D 2 =5 – 3 =2

DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED TaylorOXXOXXX SmithOXXOXXX SimpsonXOXXOXX AllenXOXXXXO DickersonXXOXXXO Work days 2.If number of workdays for full time employee < 5, assign remaining workdays so consecutive days off are possible.

DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED TaylorOXXOXXX SmithOXXOXXX SimpsonXOXXOXX AllenXOXXXXO DickersonXXOXXXO 3.If consecutive days off are desired, consider switching schedules among days with the same demand requirements. Completed schedule satisfies requirements but has no consecutive days off.

DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED TaylorOXXOXXX SmithOXXOXXX SimpsonXOXXOXX AllenXOXXXXO DickersonXXOXXXO 3.If consecutive days off are desired, consider switching schedules among days with the same demand requirements.

DAY OF WEEKMTWTHFSASU MIN NO. OF WORKERS REQUIRED TaylorOOXXXXX SmithOOXXXXX SimpsonXXXOOXX AllenXXXOXXO DickersonXXOXXXO The revised schedule satisfies requirements with consecutive days off for most employees. 3.If consecutive days off are desired, consider switching schedules among days with the same demand requirements.