Effective layout designs for the Shojinka control problem for a TFT-LCD module assembly line

Attaining flexibility in the number of workers in a workshop to adapt to demand changes is termed Shojinka, and this is often combined with cellular layout design configuration. The machine layout for Shojinka must be appropriately designed to enable workers to walk easily between machines within a cell. This paper analyzes a problem of how to attain Shojinka under the limitations of a process where operators have restricted movement within a cell. The study is motivated by a practical flow shop problem with different machine rates among workstations. We first consider the decision of Shojinka to develop the cellular layout design under the limitations of a process. Next, we propose a mixed integer programming formulation to minimize the total number of operators. Taguchi's signal-to-noise (SN) ratios are used to compare the robustness of different layouts when the demand changes. The present study uses a thin-film-transistor liquid-crystal display (TFT-LCD) module assembly line as a case study to illustrate the effectiveness of the proposed approaches. The results show that the proposed layout can decrease manpower and labor idle time ratio by 15.02% and 12.48% on average, respectively.