工件組合對生產效率之影響與上下游排程整合

Abstract

機台製程能力的限制可由機台能力矩陣表示，當工作站面對的WIP到達組合與機台能力矩陣不一致時，機台之間工作負載分配會不均，工作站Throughput受到限制。本研究提出WIP分配方法，可推測最佳的WIP分配概率，使機台工作負載平衡，從中發現工作負載平衡存在極限，故WIP到達組合與機台能力矩陣不一致可能發生；並可利用此方法得到機台能力矩陣偏好的WIP組合。 因上下游工作站機台能力矩陣相異，下游工作站面對的WIP到達組合為上游工作站排入排程的WIP組合，若此組合與下游工作站的機台能力矩陣不一致時，上游的排程限制了下游的Throughput，導致上游的Throughput較下游的Throughput高。本研究針對上下游Throughput失衡的問題，提出排程整合方法，整理上下游排程資訊，發展集合運算模型能協助找到所有改進途徑，可供下游工作站選擇成為改進方案以要求上游工作站微調排程的WIP組合，以改進下游工作站的Throughput。利用只考慮WIP到達為隨機過程的實驗，數據顯示原先上游的Throughput較下游的Throughput高；經由改進方案後，上游僅降低些微的Throughput，而下游的Throughput明顯改進，表示此方法可消弭上下游Throughput失衡的問題。

Machine capability matrix can be used to express the differences in capability between parallel machines. When the WIP arrival mix does not match the machine capability matrix, the workload of parallel machines cannot be balanced. Thus, the throughput of the shop composed of parallel machines is constrained. This research proposes WIP allocation method which can conjecture the optimal WIP allocation likelihood. However, there’s limit that the balanced workload cannot be reached. This method can help to derive the WIP mix preferred by the machine capability matrix. Belonging to different processes, shops have difference in machine capability matrix. The WIP arrival mix downstream shop faced with are what upstream shop scheduled to process. If the WIP mix that upstream shop scheduled does not match the machine capability matrix of downstream shop, the throughput is constrained by the schedule of upstream shop. Thus, the throughput in upstream shop is higher than that in downstream shop. This research points out the problem and proposes an integration method on upstream and downstream scheduling. It can help to find the way to improve the throughput of downstream shop. The downstream shop can select the improving policy to request the upstream shop to change the scheduled WIP mix. We performed an experiment by considering only the stochastic processes of WIP Arrivals. The results indicate that the throughput of upstream shop is higher than that in downstream shop before using the improving policy. It also shows that the throughput of upstream shop may be decreased slightly by using improving policy. However, the throughput of downstream shop may be increased significantly. Thus, this method can mitigate the imbalanced throughput between upstream and downstream shop.