TABLE OF CONTENTS Infinite capacity analysis can provide some insights at the planning level, but provides little help for the detailed scheduling and dispatching tasks.
Finite capacity analysis is a core element for any improvement in planning and scheduling.
The standard MRP approach to scheduling is useful in some plants, but not too many.
Almost all factories have some kind of MRP running. Either a legacy MRP, an updated MRP-II, or ERP. The program might be home grown, heavily customized, or off the shelf. The internal concepts will be largely the same. They have been the same since the early 1960s. There might be some new options and some new fields, but the philosophy and techniques have been mature for a long time. In this chapter, we will briefly describe the main concepts behind the MRP approach to capacity analysis.
Traditional MRP logic and capacity planning tools use backward scheduling and infinite loading when generating scheduled receipts and requirements. At the top level of the bill of material, the requirements may be driven by a specific demand or the desire to maintain a specified minimum level of inventory. This sets the due date and quantities. The release or start date, or due date for subcomponents at the next level of the bill of material, is determined by either a fixed lead time or a calculation that uses setup and processing time. A queue time or movement time can also be included to move...
