Learning Objectives
LO 8s-1: Explain the concepts of job scheduling in both product- and process-focused systems.
The objective of job scheduling in product focused systems is to ensure a smooth or consistent flow of goods; therefore, enabling equipment and labor utilization to remain high. The objective of job scheduling in process-focused systems is to ensure WIP inventories are kept to a minimum and customer jobs are completed on time. These objectives can be accomplished through the use of input–output controls, forward scheduling, and Gantt chart scheduling.
LO 8s-2: Apply various machine-level dispatch rules.
There are six common dispatch rules designed to help prioritize jobs and continually manage work at each machine. In the shortest process time (SPT) dispatch rule the job with the shortest process time is selected first. In the earliest due date (EDD) dispatch rule, the job with the earliest due date is processed first. In the minimum slack time per operation (MINSOP) dispatch rule, the job with the minimum slack time per remaining operation is selected first. Critical ratio (CR) dispatch rule selects the job with the smallest ratio. First come first served (FCFS) dispatch rule processes the job that arrived first at the facility. Finally, the most important job first dispatch rule prioritizes jobs based in the importance of the customer.
LO 8s-3: Demonstrate several vehicle scheduling and routing heuristics.
The type of vehicle scheduling and routing heuristic used depends on the organization’s objective. The traveling salesman problem technique addresses the best delivery route for one vehicle in order to minimize time, mileage, or cost. The Clark and Wright savings heuristic is often used to solve the traveling salesman problem. It calculates the savings in miles or cost by combining two nodes into one tour. For more general vehicle, routing problems the cluster first-route-second heuristic can be used. Finally, there is the concurrent scheduler approach. Basically, this approach puts the pickups and deliveries in order by their promised arrival times.
Chapter Outline
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