Guiding improvement programs towards lead time reduction in a single-machine environment

Abstract

The main goal of this paper is to study the effect of six shop-floor improvement programs on lead time for several production system characteristics. The improvement programs studied were: improvement in setup time, defect rate, repair time, time between failures, processing time variability, and arrival variability. The research tools used were a system dynamics–factory physics hybrid model and design for experiments technique. All the improvement programs present statistically significant contribution for lead time reduction in at least some production environment studied, except improvement in arrival cv. The experimental results also showed that improvement in time between failures was the program that presented significant positive effect on lead time reduction for the greater number of environments studied (12 environments in 20 possibles). Repair time improvement presented significant positive effect on lead time reduction in 11 environments (from 20 possibles), setup time improvement in 9 environments (from 20 possibles), process variability in 6 environments (from 16 possibles), and defect rate only in 5 environments (from 20). These findings can help practical managers to choose the better improvement options aimed at lead time reduction accordingly to their production system characteristics. In addition, some practical implications could be drawn from this study: (1) managers should know that, when improvement in some shop-floor variable is difficult to achieve, it is also possible to get lead time reduction by means of choosing alternative improvement programs; (2) managers should take advantage of a positive synergic effect that it was found between some of the improvement programs studied; (3) managers should notice that, before implementing an improvement program on the shop-floor level aiming at lead time reduction, it is very important analyzing carefully the characteristics of the production environment, once even some well-known improvement program will lose their efficiency in lead time reduction if they are used in a nonfavorable production environment.