Dispatching Issues in Job Shop Scheduling

Abstract

In this paper we develop a framework for dispatching rules suitable for a scheduling system in a specific type of job shop. In this type of job shop, each lot undergoes many operations. At various points during the process, sublots are merged into a single lot. The precedence constraints on the operations of a particular order take the form of an intree. An order, sometimes referred to as a lot, may consist of one or more sublots. The path of any sublot or lot may pass a given machine several times. When a machine is freed and there are several lots waiting for processing, a decision has to be made which (sub)lot has the highest priority. These competing lots may be sublots of either the same order or different orders. We suggest factors that should be included in a priority function. These factors are considered from both resource perspectives as well as order perspective.