Comparison of DBR with CONWIP in a Production Line with Constant Processing Times

Abstract

We compared a DBR(drum-buffer-rope) system with a CONWIP(constant work-in-process) system in a production line with constant processing times. Based on the observation that a WIP-controlled line production system such as DBR and CONWIP is equivalent to a m-node tandem queue with finite buffer, we applied a max-plus algebra based solution method for the tandem queue to evaluate the performance of two systems. Numerical examples with 6 workstations were also used to demonstrate the proposed analysis. The mathematical analyses support that CONWIP outperforms DBR in terms of expected waiting time and WIP. Unlike the CONWIP case, sequencing workstations in a DBR affects the performance of the system. Delaying a bottleneck station in a DBR reduces expected waiting time.

Explicit Expression for Moment of Waiting Time in a DBR Line Production System with Constant Processing Times Using Max-plus Algebra

“…[1,3,7] provided the basic max-plus algebra and some preliminaries on the waiting times in MPLs. Taking into consideration DBR WIP-control policy, we introduce explicit expressions for higher moments of stationary waiting times in  -node tandem systems with constant processing times.…”