Scheduling in the Textile Industry

Abstract

The Textile Industry faces specific and critical scheduling difficulties along with the planning and control of production in the weaving sections. Generally the textiles are produced to order and the whole production must observe the times of delivery agreed with the clients. Therefore it is necessary to allocate the existing looms to the processing of tasks, the fabric types to be produced. The case of one of the largest Portuguese textile companies (manufacturing mainly for exportation) is presented. The situation involves more than 100 looms with different characteristics. The parallel machines scheduling problems are complex due to various reasons such as: specific sets of fabric can only be produced on certain looms, depending on the equipment - a specific warp chain; there are limits on the length of the threads to wind round the cylinders of the looms - setups must be taken into account; a certain loom may used to produce various fabric types, but then its configuration must be changed, another (external) setup occurs due to the replacement of a warp chain, which may take at least 5 hours, and so on. The problems were modelled as Combinatorial Optimisation and several criteria were discussed. Feasible solutions were generated to test all the conditions and restrictions and to facilitate the discussion with the technicians of the company. The optimisation procedure is based on Tabu Search - the procedure will be described. Computational results will also be presente