EFFECT OF MAINTENANCE POLICIES ON THE JUST-IN-TIME PRODUCTION SYSTEM

Using simulation, experimental design, and regression analysis, mathem atical models are developed here to describe the effect that maintenan ce policy, machine unreliability, processing time variability, ratio o f preventive maintenance time to processing time, ratio of minimal rep air time to preventive maintenance time, and production line size have on various measures of performance, namely total production line outp ut and production line variability of the just-in-time production syst em. The analysis of the data shows that under different situations, di fferent maintenance policies do not have the same effect on the produc tion line performance. The following conclusions were obtained; when t he number of production machines is low (five machines or less), and/o r when the ratio of minimal repair time to preventive maintenance time is high, maintenance policy III leads to a higher performance than ma intenance policy II. Otherwise maintenance policy II, which is more se nsitive to the change of the ratio of minimal repair time to preventiv e maintenance time, leads to a higher performance. The results of the study can be utilized in choosing a maintenance policy as a function o f the production process parameters. Once a policy is chosen, the prac titioner can select the most important factors to control under that p olicy in order to minimize the machine idle time, maximize the product ion process reliability, improve productivity, and therefore increase the production line performance.