A comparative study of just-in-time (JIT) and theory of constraints (TOC) systems with varying constraint locations and operational characteristics

Various researchers have extolled the benefits of Theory of Constraints (TOC), Just-in-Time (JM, and other manufacturing strategies. Some supporters of JIT argue it is the least costly, while others point to the overall benefits of TOC. There are conflicting claims as to the best manufacturing philosophies which is compounded by the fact that no one system is best in every situation. The success of a production system truly depends on the manufacturing environment rather than the philosophy being used. This study uses computer simulations of differing manufacturing environments to compare Just-in-Time (JM and Theory of Constraints (TOC) philosophies over two response variables, make span and work-in-process (WIP).; Results showed significant differences favoring both TOC and JIT in different manufacturing environments with respect to both make span and work-in-process (WIP). The study showed evidence that both JIT and TOC are essentially the same when a production system has a bottleneck located at the last station. However, the performance of TOC could equal that of JIT with less inventory.; This supports the concept of strategic inventory use for the constrained resource in TOC over the JIT concept of having at least two Kanban cards at each workstation. Different process structures showed different performance for the two strategies used. The study suggested that higher setup and process variation did not have much effect on WIP level, but they did have a significant effect on the make span variable. In conclusion, the study proved that not one system is best in every condition. Each manufacturing environment will be best served by a unique manufacturing strategy.