Design and simulation of multi-CONWIP into a Make-To-Order firm with general job shop configuration

This paper presents a general approach for designing and implementing a multi-loop CONWIP system in a complex make-to-order (MTO) firm (i.e. multi-product and multi-routing). The approach was illustrated and then directly simulated in the general job shop of an Italian manufacturer of oil hydraulics products. Firstly, the approach was briefly described, and a case study follows to depict the steps of the implementation. The chosen system consists of a dual-loop CONWIP with cluster type cards and pull-from-the-bottleneck method. Also, a customized dispatching rule and the common unit to measure WIP were chosen according to the firm’s needs and strategy. After designing, this system was simulated and compared with the performances of the current one; it shows lower average values and standard deviations of WIP and flow times, without affecting throughput rate. Finally, the simulated system will also have much lower weighted lateness, to the slight detriment of job tardiness and wait-to-match times for purchase orders. However, multi-CONWIP is an appealing solution for job shop MTO environments.