Lean-pull strategy in a re-entrant manufacturing environment: a pilot study for TFT-LCD array manufacturing

The increase of a panel's size in thin film transistor - liquid crystal display (TFT-LCD), results in an increase in stock space and increased cost from work-in-process (WIP). This paper proposes a lean-pull strategy, combining buffers with CONWIP (CONstant work-in-process), which results in shared resources to a re-entrant process in TFT-LCD manufacturing. The buffer size and CONWIP levels are the decision variables and are solved by simulation optimisation. The proposed procedure is applied to a factory that manufactures TFT-LCD. The study shows that the proposed lean-pull strategy can reduce the cycle time and achieve a reduction of 34.57% in WIP. The automated material handling systems (AMHS) stocker utilisation can be reduced from 62.13% to 18.49% without additional investment or facilities. Sensitivity analysis indicates the maximum daily throughput will achieve over 10% improvement. The empirical results from this pilot study provide useful managerial insights for the production control of array manufacturing.