A practical approach to lot and setup scheduling at a textile firm

This is a study of scheduling of setups and production activities of a textile firm, located in North Carolina, USA. The firm faces the problem of scheduling customer orders on a number of knitting machines which can be configured differently by installing differnt knitting cylinders, to knot various types of greige cloth. Given a set of requirements for different styles of cloth, the problem is to decide on the specific configurations to be used on each machine and on the specific orders to be run on these configurations. The problem is formulated as an integer linear programming model. The objective is the maximization of total contribution of all the scheduled orders subject to capacity constraints of machines and that of tooling, which explicitly consider the effect of scheduled setups and constraints on customer orders. Various solution approaches are discussed. An approximate procedure is devised which incrementally adds new setups based on several heuristics by which the ‘value’ of candidate configurations for the machines are evaluated. These heuristics can either be developed into a self contained scheduling procedure or can interactively be utilized by a human scheduler in a microcomputer environment.