MPS with multiple freeze fences in multi-product multi-level MRP systems
本文提出一种在物料清单的每个物料上设置冻结时界的新方法，允许在传统单一冻结时界内根据组件供应调整计划，从而提升主生产计划的灵活性，并通过仿真模型验证其在客户服务水平和成品库存方面的优势。
In the current severe competitive marketplace, customers are now expecting better quality, price and service, and demanding higher flexibility. To survive in this highly demanding and competitive manufacturing environment, many manufacturers are forced to improve flexibility in their manufacturing management systems. Traditionally, manufacturers use a single freeze fence in their master production schedule (MPS). Within the single freeze fence, even if a more accurate sales forecast is available, no schedule change is allowed. This paper introduces a new approach to improve MPS flexibility by imposing a freeze fence on each item in the bill of materials (BOM). This new approach allows schedule changes within certain periods of the traditional single freeze fence subject to the availability of component supply. It allows manufacturers to react more quickly to market trends. When applying multiple freeze fences, allocating limited component supply is required. In this study, a mathematical model for allocating limited component supply is developed and a simulation model is built to study the performance of multiple freeze fences. In terms of customer service level, the results show that the multiple freeze fences approach performs equally well and even better in certain manufacturing environments compared with the single freeze fence. In terms of end-item inventory, using the multiple freeze fences approach can achieve much lower end-item inventory. It is intuitively believed that higher commonality will result in a higher service level. However, the results of the simulation experiment show that higher commonality may lead to a lower customer service level, except for the case where all components are common.