Task and worker assignment in the shared-machine U-shaped assembly line

This study presents a new approach on a U-shaped line namely, task and worker (double) assignment in the shared-machine U-shaped assembly line. A case study was done on a garment manufacturing company in Thailand. In order to revolutionize and consider the lean concept of waste reduction and synchronous move, three objective functions were considered: minimizing the number of workstations (workers), minimizing walking time, and maximizing full work. The results showed that the shared-machine U-shaped line has the same number of workstations (or workers) as the straight line and traditional U-line but the walking time is less than the latter while the utilization of worker is satisfying. In addition, the utilization of machine is better than other lines. Hence, the proposed model can help improve the double assignment and increase machine and worker utilization of a manufacturing company.