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

Abstract

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.

Keywords:

• AMHS
• buffer
• CONWIP
• lean-pull strategy
• simulation optimisation
• TFT-LCD

Acknowledgements

The anonymous reviewers provided helpful comments that greatly improved the manuscript. The authors thank the anonymous company for the collaboration of this study. This work was supported, in part, by the National Science Council of Taiwan, Republic of China, under grant NSC-98-2221-E-006-100-MY3.