In the JIT System: Effects of Processing Time and Set-up Time

The presence of variance, processing time and setup time reductions can have “detrimental” effects on the WIP (world in process) inventory in both pull systems and push systems. In this context, we point out that the merits of such a warning for Just in Time manufacturing systems are questionable. If we deal setup time as PERT network, it is very complex to accept claim that waiting queues can grow without bound when setup time minimized. In addition, we show that the amount of setup cut and the level of variance can determine whether waiting time grows or not. This result may help in planning a viable setup minimization project and we use example to show that, even when the variances are not minimized proportionately, the expected waiting time does not necessarily increase.