A study on line operation planning for sewing works

This paper focuses.on multi-product sewing shops, in which there are various products and the operations combination for completing each product differs largely among products, and in which skill levels differ largely among workers. As basic research, this paper discusses one sub-problem of multi-product line operation planning: the single-product line operation planning problem, which includes not only the operation assignment problem but also the worker allocation problem for a product. Firstly, from a survey of the literature and investigation of real sewing shops, we clarify that there are two typical line operation planning methods. Both of them determine the above two problems separately, and the difference between them is the solving procedure: one method first assigns operations and then allocates workers to the workstations of the line (Method A), while the other takes the opposite procedure (Method B). Secondly, we carry out numerical experiments and clarify that Method A will cause large line balance loss when the varieties of operation and worker ability are large. Thirdly, in order to implement Method B under the new production environment, algorithms for worker allocation are proposed and discussed. The effects of Method B on decreasing line balance loss and cycle time are confirmed. We also point out that Method B can still be improved. In order to obtain a good operation plan for such lines, methods which can solve these two problems together should be developed, instead of solving them separately.