OPERATIONS SCHEDULING

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SUPPLEMENT J

OPERATIONS SCHEDULING

LEARNING GOALS
After reading this supplement, you should be able to:
1. Define new performance measures (beyond flow time and past due) for evaluating a schedule. 2. Describe the decision rules (beyond FCFS and EDD) to sequence jobs.
3. Determine schedules for single and multiple workstations.

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his supplement focuses on operations scheduling, which involves assigning jobs to workstations or employees to jobs for specified time periods. Effective scheduling helps managers achieve the full potential of their supply chains. Chapter 14, “Operations Planning and
Scheduling,” covers the basics of scheduling—Gantt charts, workforce scheduling, two rules (FCFS and
EDD) for sequencing work at a single workstation, and two commonly used performance measures
(flow time and past due). Here we deepen your understanding with additional performance measures and priority sequencing rules, a discussion of scheduling multiple workstations, and a discussion of scheduling a two-station flow shop.

myomlab and the Companion Website at www.pearsonhighered.com contain many tools, activities, and resources designed for this supplement.

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SUPPLEMENT J

OPERATIONS SCHEDULING

operations scheduling
A type of scheduling in which jobs are assigned to workstations or employees are assigned to jobs for specified time periods. Scheduling Service and Manufacturing
Processes
The scheduling techniques we discuss in this supplement cut across the various process types found in services and manufacturing. Many service firms are characterized by a front-office process with high customer contact, divergent work flows, customization, and, consequently, a complex scheduling environment. Often customer demands are difficult to predict, which puts a high premium on scheduling employees to handle the varied needs of customers. At the other extreme in the service industry, a back-office process has low customer involvement, uses more line work flows, and provides standardized services. Inanimate objects are processed; these processes take on the appearance of manufacturing processes.
Manufacturing processes also benefit from operations scheduling techniques. Our discussion of the operations scheduling techniques in this supplement has application for job, batch, and line processes in services as well as in manufacturing. Schedules for continuous processes can be developed with linear programming (see Supplement E,
“Linear Programming”). Although the scheduling techniques in this chapter provide some structure to the selection of good schedules, many alternatives typically need to be evaluated. We begin by looking at the performance measures managers use to select good schedules.

Performance Measures
We already covered two important performance measures in Chapter 14, “Operations
Planning and Scheduling.” Flow time is the time a job spends in the service or manufacturing system, and past due (tardiness) is the amount of time by which a job missed its due date. In this regard, a job is the object receiving service or being manufactured. For example, a job may be a customer waiting for service at a state licensing bureau or it may be a batch of pistons waiting for a manufacturing process. These two performance measures can be insufficient, depending on the competitive priorities of a process. Additional performance measures follow: makespan The total amount of time required to complete a group of jobs.

total inventory
The sum of scheduled receipts and onhand inventories.

½ Makespan. The total amount of time required to complete a group of jobs is called makespan. Minimizing makespan supports the competitive priorities of cost (lower inventory) and time (delivery speed).
Makespan = Time of completion of last job - Starting time of the first job
½ Total Inventory. This performance measure is used to measure the effectivness of schedules for manufacturing processes. The sum of scheduled receipts