The effects of flexibility in machine selection on job shop scheduling.

Abstract

This paper describes the effectiveness of flexibility in the choice of machines. In job shop where there is flexibility, an alternate machine can be used if one machine is overloaded while another is idle. This allows balancing of the workloads of all machines. But generally, the primary machine is more efficient than the alternate machine, so alternate machines typically perform with some time penalty. To show these relations, a model which represents the flexibility in machine selection is proposed, and two measures of the degree of flexibility in machine selection are derived. The simulation results show that the effects of flexibility in machine selection on job shop scheduling are dependent primarily upon the efficiency of alternate machines, rather than on the number of alternate machines, and the appropriate use of alternate machines can reduce flow time.