Productivity improvement by reduction of idle time through application of queuing theory

Abstract

In Lean Six Sigma one of the primary objectives is to identify and eliminate the waiting or idle time for enhancing productivity and reducing production cost. However, in some situations it is better to replace ‘elimination’ by ‘optimization’ due to the presence of conflicting requirements. Optimization techniques in the form of queuing models are quite useful to resolve this conflict. In an Indian textile manufacturing plant, the waiting (idle) time in the winding process is identified as a reason for high production cost. In this situation, it is to be determined as to how many machines are to be assigned to an operator for reducing waiting or idle time of both the operators and the machines leading to reduced production cost. The situation can be compared and contrasted to a machine repairman problem aiming for optimizing the number of machines per operator. The various process parameters have been estimated and suitably modified or derived to serve as inputs to the Queuing Model. Sensitivity analysis has been carried out to identify and control the significant factors. The objective of this paper is to demonstrate through an application of queuing models the procedure of optimizing the waiting or idle time. Consequently, the focus is on the application of optimization techniques like Queuing Theory and Simulation while implementing lean six sigma.