Bottleneck shifting in production lines: Impact of variability, new detection method and control strategies

Abstract

One of the main causes for degrade in the performance of a production line is bottleneck machine. To improve system performance, bottleneck (BN) is one of the critical factors that need to be addressed. Most of the researchers focus on long term bottlenecks in the system. From other researches, it is evident that detection and elimination of short term BNs is more efficient than long term BNs. Till now, there is no generic method to identify bottlenecks in production lines with and without buffer. Proposed inactive duration method for identification of BNs detects both short term and long term bottlenecks. In production lines, bottlenecks can be classified into buffer bottlenecks and machine bottlenecks. Machine BNs are mainly due to variability in the system. There is always strong relationship between variability and machine BN. Due to dynamic nature of manufacturing lines, there will be frequent shifting of BN between different machines. In this research, BN characteristics are proposed to analyze the critical nature of BN and BN shifting. In production lines with buffer, buffer bottlenecks are eliminated by placing optimal buffer size before each machine. This thesis presents a two step heuristic procedure for optimal buffer size determination. Case studies were conducted for both production lines with optimal buffer and without buffer. Results from case studies proved that increase in variability increases BN time and BN shifting between different machines.