The advantages of using short cycle time manufacturing (SCM) instead of continuous flow manufacturing (CFM)

Abstract

Over the past two decades, continuous flow manufacturing (CFM) has been the principal operational tool to manage and improve manufacturing asset usage. CFM measures and manages throughput of the tools/toolsets that comprise the manufacturing line. Various systems have been proposed to help manage throughput (e.g. PUSH, PULL, theory of constraints) with their attendant control methodologies (e.g. MRP, KANBAN, drum-buffer-rope). This paper explores how the X-factor (normalized cycle time) rather than throughput is used as the prime line control and analysis parameter; hence, the name short cycle time manufacturing (SCM). As manufacturing lines have both throughput and X-factor commitments, it is essential to understand the fundamental relationships between throughput, capacity and X-factor. This paper also shows that X-factor is a much more sensitive indicator of capacity problems than throughput, as X-factor increases rapidly as throughput approaches effective capacity. This X-factor sensitivity can be used as a diagnostic tool to uncover unforeseen capacity issues. Short cycle time manufacturing (SCM) allows each tool/toolset to be analyzed depending on its demonstrated X-factor and capacity versus target to determine which tools/toolsets need improvement, as the overall X-factor of the line is just the weighted sums of the component toolset X-factors. This paper also analyzes the impact of mix and volume with a cycle time constraint on the capacity of tools that are affected by batch or train size. SCM provides significant advantages over CFM in helping to manage and improve manufacturing asset utilization.