Design and operation of dynamic assembly lines using work-sharing

Abstract

Dynamic line balancing (DLB) deals with dynamic shifting of assembly tasks (shared tasks) between consecutive stations during the operation of the assembly line. In traditional assembly lines, work-sharing is not allowed. Consequently, the cycle time is determined by the amount of work performed in the most loaded station. The DLB approach enables achieving a shorter cycle time and a higher throughput rate, as compared to the traditional lines. In the implementation of the DLB approach the following has to be determined: (1) the identity of the shared tasks, and (2) the operational task allocation rule. In some cases, the data regarding the percentage of cycles each shared task will be performed in a station is also required. We first analyse a case in which an initial task assignment to stations (line balance solution) and the identity of the shared tasks is known and given. Conditions for the balanceability (the ability of the DLB to achieve an equivalent performance to a perfect balanced line in the steady state) are developed, as well as the formulation for minimizing the cycle time. Next, the sharing costs are considered and approaches for minimizing the shared time and sharing cost are presented, based on the new concept of bottleneck segment. The operational aspect is also addressed, while examining the effect of several state-dependent and state-independent operating rules for task allocation on the cycle time and the system work in process.

Keywords:

• Work-sharing
• Assembly lines
• Dynamic line balancing
• Cross training