In this chapter, the following content will be discussed: What imbalance does the existence of a waiting line reveal? What causes waiting lines to form, and why is it impossible to eliminate them completely? What causes waiting lines to form, and why is it impossible to eliminate them completely?. | Manufacturing Planning and Control MPC 6th Edition Chapter 8a Advanced Scheduling Detailed scheduling of individual jobs through work centers in a shop has been the focus of numerous researchers. Focusing on some basic concepts and results and relating them to some newer manufacturing approaches can show how to apply results in different operating situations. Agenda Scheduling Research Framework A schedule is a plan for the sequence of time allotted for and operations necessary to complete an item The schedule has several inputs Sequential constraints Time estimates for each operation Required resources for each operation Scheduling Research The One-Machine Case Problem of how to best schedule a fixed set of jobs through a single machine All jobs are available at the start of the period Setup times are independent of the sequence Objectives Minimize total time–all sequences are equal Minimize average time–process shortest jobs first Minimize average number of jobs in the . | Manufacturing Planning and Control MPC 6th Edition Chapter 8a Advanced Scheduling Detailed scheduling of individual jobs through work centers in a shop has been the focus of numerous researchers. Focusing on some basic concepts and results and relating them to some newer manufacturing approaches can show how to apply results in different operating situations. Agenda Scheduling Research Framework A schedule is a plan for the sequence of time allotted for and operations necessary to complete an item The schedule has several inputs Sequential constraints Time estimates for each operation Required resources for each operation Scheduling Research The One-Machine Case Problem of how to best schedule a fixed set of jobs through a single machine All jobs are available at the start of the period Setup times are independent of the sequence Objectives Minimize total time–all sequences are equal Minimize average time–process shortest jobs first Minimize average number of jobs in the system–process shortest jobs first The Two-Machine Case More complex than the one-machine case Must consider job routings Minimum total time (make span) depends upon sequencing Two-machine case can be used as an approximation of the M-machine problem (where M > 2) Dispatching Approaches Dispatching approaches allow analysis of dynamic problems (where randomness in inter-arrival times and service times are considered) Uses logic rules to guide the prioritizing of jobs at a work center (sequencing rules) Often uses simulation methodology to study realistic problems Sequencing Rules Sequencing rules provide guidelines to the wide range of possible sequencing options With n jobs and m machines, there are (n!)m possible ways to schedule the system Sequencing Rules Random–pick any job with equal probability. Used as a benchmark for other rules. First-come/first-served–jobs are processed in the order they arrive Shortest processing time–reduces work-in-process, average completion time, and average .
