Mitsushi Tamaki

Suppose that a job-shop production system consist of a sales center with order-selection and a production center with switch-over. Job orders have variable estimated prices and arrive frequently at irregular or random intervals under a changeable production capacity. The macro-level problem considered is summarized as follows. Accepting all orders is not always the best option due to changeable capacity considerations. A manager of job shops is faced with the problem of selecting and processing the orders according to some decision rule, and that of increasing the idle (opportunity) cost of a job shop. We will here decide the structure of the best decision rule under a dynamic job-shop production system. This paper discusses a typical dynamic job-shop model, in the case where fixed switching costs are assumed when two processing types are switched between each other. Four control variables are introduced : two selection criteria (c_1,c_2) and two control levels (i_1,i_2). First, a stochastic model is proposed to derive the two sub-objective functions : the mean accepted price and mean operating cost of the long-run average. Next, by numerical considerations, a cooperative vs.non-cooperative problem of sales and production centers and a periodic vs.dynamic model are discussed. Finally, a revised version of dynamic job-shop production is proposed, and the non-monotonicity of selection criteria (c^*_1,c^*_2) is pointed out.