DEVELOPMENT OF A LOT FORMATION SYSTEM FOR A FLOW SHOP LAYOUT LINE FOR SHIPBUILDING

摘要

The pipe shop of our shipbuilding yard is equipped with a flow shop production line in which pipe spools are fabricated and assembled. Some of the pipe spools are put together in a production lot, and each production lot is sent to several processing sites by a carriage which moves at a fixed pitch, known as the tact time. The length of time for fabrication and assembly vary depending on the type of pipe spools and it is necessary to form the production lot so that the idle time during the tact time in each process is kept to a minimum. Each pipe spool has its own delivery date and that date should, as much as possible, be met. To improve the productivity of the pipe shop, we developed a lot formation system by applying a genetic algorithm as a solution for the above combinatorial optimization problem. This system enables us to automatically form lots in considering production efficiency, management of delivery dates and stocks of parts which are needed for the manufacturing the pipe spools.