Evaluation of improvement programmes in a job-shop context by simulation models

The continuous improvement is important to increase the company’s competitiveness in today's market. The decision on the improvement programs areas is relevant to improve the enterprises’ performance. It is essential where to focus the investment efforts available among the different areas of the manufacturing system. In this paper, the main areas considered are: process time variability, reliability of the machines, set-up times and product defects. This paper tests the improvement programmes centralised, distributed and proposes a proportional policy by simulation models in a job shop context. The simulation experiments consider the following issues: the process time of the bottleneck, the number of bottlenecks, the degree of variation in process time, the average utilisation of the manufacturing system and the process time of the bottlenecks. The simulation results highlight how the choice of the improvement policy is not relevant when the manufacturing system has a low or high utilisation. The centralised approach leads to better results, while the proposed approach is competitive when the bottleneck may shift from one machine to another.