Analyzing the time buffer in the Theory of Constraints based lean operations

Abstract

This paper uses quantitative methods to estimate the size of the time buffer in lean operations controlled by the Theory of Constraints (TOC). The main focus of the operations system of TOC is the identification and management of constraints. To protect the constraints, they should be buffered with time buffers, which protecting the system's output from disruptions and fluctuations. Despite the importance of time buffers, the approaches to identifying the size of the time buffer in literature are very empirical. In this paper, a queuing-theory based method is applied to calculate the time buffer sizes. It provides a mathematically exact expression for the coefficient of variation of waiting time for Markov queues. It then applies the concept of isomorphism to approximate the variance of customer waiting time in a general queue. Simulation experiments are conducted to verify the accuracy of approximation.

Keywords:

• Theory of Constraints
• lean operations
• queuing theory
• time buffer