Modelling and implementation of manufacturing direct labour allocation: a case study in semiconductor production operations

In many current semiconductor manufacturing operations, headcount is manually allocated periodically based on man-machine ratio. Attributed to non-optimised allocation of direct labour to operations/machines, considerable productivity loss occurs. The problem is further complicated by some dynamic and uncertain factors such as constantly changing production targets and work in progress, overlapped labour skills, and variability in manufacturing operations and labour absenteeism rates. Motivated by the needs in real practice, this study aims to develop a model for allocating a direct workforce among semiconductor manufacturing operations to meet production targets and maximise labour productivity. This paper presents a two-stage goal programming model for the headcount allocation problem. To enhance the model's pragmatic use, a queueing module is introduced to account for the interferences among the multi-machine operations. Computational experiments are carried out to evaluate the performances of the proposed algorithms and pilot runs are implemented in a factory. Finally, a prototype system is developed and has been proved to be useful in practice.