Statistical control of manufacturing cycle time and project time: Lessons from statistical process control

A manufacturing cycle includes all activities from order processing to shipping. The benefits of reducing cycle time includes increased productivity and added competitive advantage. This paper proposes a new approach to the control of cycle time variability in the short-term and the reduction of cycle time in the long-term. It has been said that when the control and stability of a variable is a matter of interest, as in the case of cycle time, control charts similar to those used for controlling product quality can be used as long as the challenge of developing appropriate tolerance limits for the variable can be overcome. The authors make use of three propositions to implement this rationale. The challenge to establishing tolerance limits to cycle time is overcome by the use of desired worst-case cycle time. Step-by-step application of the principles of statistical cycle time control at A.B. Chance Company is used to illustrate the practical viability of this new procedure. The principles of this study may be extended to the statistical control of activity times on a PERT network to improve the on-time completion of activities and to increase the accuracy of activity-time estimates.