Production Scheduling Production Planning Process Planning Long Range

Production Planning Process Planning Long Range Medium Range Strategic Capacity Planning Aggregate Planning Manufacturing

Outline n Scheduling ü Recap ü Sequencing rules n Single resource ü Global n

Scheduling ü Deals with the timing of operations ü Specifies when resources are needed

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

Types of Sequencing Rules n Sequencing jobs at a single resource n Sequencing jobs

Sequencing Rules (Single Resource) n Local ü ü ü First Come First Served Last

Global Rules n Consider more than current operation n Look at work at other

Scheduling Across Multiple Resources n Previous rules considered scheduling (sequencing) jobs at one resource

Two resource problems Suppose you work with a classmate, Kim on all projects In

Two resource problems Sequences tasks to minimize makespan Johnson’s Rule 1. Find the smallest

Two resource problems Sequences tasks to minimize makespan Processing time (Kim): 4 3 5

Two resource problems Sequences tasks to minimize makespan Johnson’s Rule Processing time (Kim): 4

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

Sequencing Rules Single Resource Multiple Resources n Local n 2 resources ü ü ü

Guidelines for Selecting a Sequencing Rule 1. 2. 3. SPT most useful when shop

Employee Scheduling ü Labor is very flexible resource ü Scheduling workforce is complicated repetitive

Employee Scheduling Heuristic Let N = no. of workers available Di = demand for

Example DAY OF WEEK MIN NO. OF WORKERS REQUIRED Taylor Smith Simpson Allen Dickerson

X = day working O = day off 1. Assign the first N -

1. Assign the first N - D 1 workers day 1 off. Assign the

2. If number of workdays for full time employee < 5, assign remaining workdays

3. If consecutive days off are desired, consider switching schedules among days with the

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Production Scheduling

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

Outline n Scheduling ü Recap ü Sequencing rules n Single resource ü Global n Multiple resources

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

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

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

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

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

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

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

Two resource problems Suppose you work with a classmate, Kim on all projects In each project you do the research, then Kim writes the report Processing time (Kim): 4 3 5 4 2 ting Eng oun anc Fin Ma Acc Ma lish 1 ting 5 e 3 rke 6 nag Processing time (you): 2 em ent You want to complete all projects asap What should be the order for the projects?

Two resource problems Sequences tasks to minimize makespan Johnson’s Rule 1. Find the smallest processing time • If its on the 1 st machine, assign the task at the beginning of the sequence and eliminate it from further consideration • If its on the 2 nd machine, assign the task at the end of the sequence and eliminate it from further consideration 2. Repeat step 1 for all unassigned tasks Processing time (Kim): 4 3 5 4 2 Eng oun Acc anc Fin rke Ma nag Ma lish 1 ting 5 e 3 ting 6 em ent Processing time (you): 2 What order should you do the projects in?

Two resource problems Sequences tasks to minimize makespan Johnson’s Rule 1. Find the smallest processing time • If its on the 1 st machine, assign the task at the beginning of the sequence and eliminate it from further consideration • If its on the 2 nd machine, assign the task at the end of the sequence and eliminate it from further consideration Processing time (Kim): 4 3 5 4 2 ting Eng oun anc Fin Ma Acc Ma lish 1 ting 5 e 3 rke 6 nag Processing time (you): 2 em ent 2. Repeat step 1 for all unassigned tasks Sequence English Management Finance Accounting Marketing

Two resource problems Sequences tasks to minimize makespan Processing time (Kim): 4 3 5 4 2 ting Eng oun anc Fin Ma Acc Ma lish 1 ting 5 e 3 rke 6 nag Processing time (you): 2 em ent Johnson’s Rule Sequence English Management Finance Accounting Marketing

Two resource problems Sequences tasks to minimize makespan Johnson’s Rule Processing time (Kim): 4 3 5 4 2 ting Eng oun anc Fin Ma Acc Ma lish 1 ting 5 e 3 rke 6 nag Processing time (you): 2 em ent Idle time Sequence English Management Finance Accounting Marketing

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

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

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

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

Employee Scheduling Heuristic Let N = no. of workers available Di = 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. 3. If consecutive days off are desired, consider switching schedules among days with the same demand requirements.

Example DAY OF WEEK MIN NO. OF WORKERS REQUIRED Taylor Smith Simpson Allen Dickerson M T W TH F SA SU 3 3 4 5 3

X = day working O = day off 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 have been scheduled. DAY OF WEEK M T W TH F SA SU MIN NO. OF WORKERS REQUIRED D 1 = 3 D 2 = 3 D 3 = 4 D 4 = 3 D 5 =4 D 6 = 5 D 7 = 3 N=5 Taylor Smith Simpson Allen Dickerson N – D 1 = 5 – 3 = 2

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 have been scheduled. DAY OF WEEK MIN NO. OF WORKERS REQUIRED Taylor Smith Simpson Allen Dickerson M T W TH F SA SU 3 3 4 5 3 O O X X X X X O O O X X X X O O N – D 2 = 5 – 3 = 2

2. If number of workdays for full time employee < 5, assign remaining workdays so consecutive days off are possible. DAY OF WEEK MIN NO. OF WORKERS REQUIRED Taylor Smith Simpson Allen Dickerson M T W TH F SA SU 3 3 4 5 3 O O X X X X X O O O X X X X O O Work days 5 5 5

3. If consecutive days off are desired, consider switching schedules among days with the same demand requirements. DAY OF WEEK MIN NO. OF WORKERS REQUIRED Taylor Smith Simpson Allen Dickerson M T W TH F SA SU 3 3 4 5 3 O O X X X X X O O O X X X X O O Completed schedule satisfies requirements but has no consecutive days off.

3. If consecutive days off are desired, consider switching schedules among days with the same demand requirements. DAY OF WEEK MIN NO. OF WORKERS REQUIRED Taylor Smith Simpson Allen Dickerson M T W TH F SA SU 3 3 4 5 3 O O X X X X X O O X X X X O O The revised schedule satisfies requirements with consecutive days off for most employees.