环形生产线的生产率估算

Production Rate Evaluation of Closed-loop Production Line

摘要:

环形生产线中的托盘数(在制品数)恒定，因此生产率指标不仅与工位中设备可靠性和工位间缓冲区容量有关，还与恒定的托盘数量相关.针对各工位作业时间确定、包含多种故障状态、故障率和修复率为负指数分布的有限缓冲区环形生产线，利用分解方法将整线分解为多个两工位单缓冲区的生产单元，并根据恒定的托盘数量划分故障传递区间，即界定每个生产单元的虚拟故障状态，再利用连续型生产线生产率计算方法获得两工位单缓冲区的生产率估算值，然后利用流失效与流修复方程迭代求解出整线生产率.最后，进行算例分析和实例求解，利用仿真软件进行对比分析，验证了本文方法的有效性，尤其是对于工位时间不同的非平衡生产线，该方法亦具有较高准确性.

Abstract:

A closed-loop production line has a constant number of pallets (work in process, WIP) flowing through its workstations and buffers. The performance of a closed-loop production line depends not only on the machines’ reliabilities and buffers’ capacities, but also on the constant number of pallets. This paper presents an analytical method to approximate the production rate of an unbalanced closed-loop production line with finite buffers. The machines have deterministic processing times and multiple failure modes. A decomposition method was used to divide the whole line into multiple two-machine-one-buffer blocks, and the failure modes influencing the blocks are related with the constant number of pallets. An exact algorithm to calculate the production rate for continuous systems was introduced to approximate the production rate of the discrete systems. Then, interruption of flow equations and resumption of flow equations were used to iterate the whole line production rate until converging. At last, cases analysis and comparison with simulation results were used to validate the method. Especially for unbalanced closed-loop production line with different workstation time, the method also has high accuracy.