Comparison of DBR with CONWIP in an unbalanced production line with three stations

TLDR

DBR and CONWIP are modern push/pull production control systems that combine MRP‑style push with Kanban‑style pull, moving materials into the shop and then pushing them to subsequent workstations. The study aims to analyze and compare the performance of DBR and CONWIP on a three‑stage unbalanced tandem line by proposing optimization models for each system. A continuous Markov process model is used to derive steady‑state probability distributions, enabling evaluation of performance measures and supporting the optimization models for both systems. Sensitivity analysis validates the models and shows that DBR outperforms CONWIP under the evaluated performance measures.

Abstract

The recently developed alternatives to traditional production planning and control systems such as material requirement planning (MRP) and Kanban are the drum–buffer–rope (DBR) and CONWIP (CONstant Work In Process) systems. Each system is best described as a combination push (like an MRP)/pull (like a Kanban) logistical procedure. Materials are pulled into the shop via the appropriate logic, and once released, materials are then pushed to subsequent workcentres. The performance of the DBR and CONWIP control policies are analysed and compared in a three-stage unbalanced tandem production line. Using a continuous Markov process model, steady-state probability distributions for the systems are derived, and then the performance measures of the systems can be evaluated. To compare the two systems, an optimization model for each system is proposed. From sensitivity analyses for the optimization models, the proposed models are validated, the differences of the two systems are investigated, and it is found that DBR is better than CONWIP under the proposed performance measures.