SAP_MRP详解

在文西的鼓励下开始着手准备写一点MRP的东西，本想着其实也不会太难吧，可是越到后面越艰难丫，MRP博大精深，但是要做到狠精确是不能的，要不我们自己的饭碗都没得鸟，本着这个伟大的精神，文西们开始了。

其实有一部电影叫：……文西VS文西……MRP流程可分为两种处理方式：基于消耗的计划、物料需求计划（MRP），而基于消耗的计划可有三种处理方式：Forecast-based Planning这三种处理方式都是基于物料消耗历史数据的，唯一有一点区别的是时间段计划，根据历史值预测估算未来需求的时候，只根据预先定制好的具有特殊规律的时间间隔来计划运行。

基于消耗的计划不参照生产计划，换言之，净需求计算不会被独立或非独立需求触发，其要不就被可用库存水平低于再订货点触发，要不就被预测根据历史数据计算需求而触发。

一般情况下只有低于再订货点，在Reorder point planning时输入计划文件（planning file Entry），这时才会触发净需求计划，为了避免计划过剩，销售订单、预留等不包含在净需求计算中，但在特定的环境中要考虑在Reorder point planning的净需求计算时同样必须考虑外部需求，你可以让销售订单、预留等外部需求包含在。

<In Customizing for Materials Management underConsumption-Based Planning Master Data Check MRP Types, use the indicator Include ext. requirements for the MRP type in reorder point planning to determine whether external requirements (sales orders and manual reservations) are considered.>如图：而物料需求计划（MRP）与基于消耗的计划则相反……1、要使物料参与MRP流程处理，首先要在物料主数据中建立相关MRP参数，同时由于MRP计划物料众多，其中有很多物料运用到的参数具有相通点，因此会涉及到一个MRP参数文件MRP Profile,其作用就是可以将在参数文件中设置好的值直接带到物料主数据的MRP视图字段中。

这些参数文件可以创建也可以修改：（用修改示一下）选好参数文件后点击此按钮3121：固定值，若将有关字段设成固定值，则在建物料主数据的MRP视图时运用MRP参数文件，这些字段Copy过去后不能更改2：与1相反，即使默认值copy过去了但还是能再进行更改3：相对应的，在固定值和默认值中勾选了多少个字段，在数据屏幕1、2中就会显示多少个相应的字段在数据屏幕1中的字段和值同时这个T-code可以查看MRP参数文件的使用情况：选好参数文件后执行，也可更精确的查询某一工厂下，或是某一MRP控制者的使用情况查询VB01参数文件，结果如下：那这些参数文件中的值可不可以改呢，是可以的，改了之后有什么影响呢？例如，改了VB01这个参数文件的某一个或某些值，系统不仅会自动在后台创建一个工作<background job (PROFILE) >更改用到这个参数文件的物料主数据，还会自动创建一个物料主数据的更改记录。

如图：在此定义工作时间，到点自动运行如由于任何原因造成background job (PROFILE)终止，则要手动从program RMMM0001建立一个后台工作，输入项目名RMMM0001 然后点击闹钟执行，再一次执行。

之后，会有一个消息通知你物料已改变。

如图：其创建的更改记录可在此看：点击执行2、净需求计算(书本上讲的很粗略，也没有具体例子，这是我在yahoo 上搜到的，供参考)FOR EXAMPLE:The Master Production Schedule shows we have to make 400 scissors during the 3 rd week, in the 4 th week 600, in the 6 th week 800, and in the 7 th week 300 scissors.We will name (GR) Gross Requirements to the demand of fabrication of the products, the final products (in this case the scissors) correspond to the quantity appeared in the MPS. To the intermediate products (in this case the screws) you have to multiply the necessary quantity to make the final product with its demand.Gross Requirements of the MRPInventory Master FileThe file indicated us that we have since the first week 550 scissors in stock, also it indicates that the security stock do not have to be less than 50 scissors.We will name Availability (A) to the initial stock of the final product we have to satisfy the before mentioned necessities.We Will name Security Stock (SS) to the final quantity of the final product that cannot be use to satisfy the necessities.We will denominate Net Requirements (NR) to the quantity that we really need to satisfy the Gross Requirements (GR), taking into account the Availability (A) and the Security Stock (SS), the calculations will be the following:1. If the availability is more than 0 , NR = GR-A+ SS2. If the availability is equal to 0 , NR = GRNet Requirements of the MRPWeek 1: Gross Requirements are invalid, the availability is of 550 units, inside the security stock is 50, and therefore if we do not have Gross Requirements there are not also Net Requirements.GR = 0 A= 550, SS = 50 NR = 0Week 2: the same as the week 1, so we have an Availability of 550 units and the Security Stock is 50 units.Week 3: The Gross Requirements are 400 units, but we have an Availability of 550 inherited of the last week, so we can satisfy the 400 units with the 550 available and we make sure that 50 we have 50 units for the Security Stock.NR = GR- A + SS; NR = 400- 550 + 50; NR = - 100It is important to realise that the result is negative, that means that we do not need to make more scissors,because there are 150 available. 550-400 = 150Week 4: We need to make 600 scissors but we only have 150 units that were left the weeks before, sothe Nets Requirements are:NR = GR- A + SS; NR= 600-150+50; NR = 500We have to make during the 4 th week 500 scissors; we ensure that the Security Stock has 50 units.Week 5: The GR are invalid, we do not need to fabricate more because the NR are also invalid.Week 6: The Gross Requirements are 800 units, the Availability is invalid so,NR= GR, NR=800We have to fabricate 800 units during the 6 th week, and our security stock is 50 units.Week 7: The same as in the week 6, our Net Requirements are 300 units,NR= GR, NR=300Net Requirements of the MRP其实这个例子很简单易懂，运用两个公式算净需求：1. If the availability is more than 0 , NR = GR-A+ SS2. If the availability is equal to 0 , NR = GR3、replenishment lead time:包括三个部分，如图：其中采购处理时间没有在主数据中，在这里设置：而计划交货时间和收货处理时间在物料主数据中的MRP2视图中：4、让外部需求也包含在重订货点计划中：5、计划运行全部运行 total planningsingle-item planning看看物料主数据里相关的参数设置：Planning file entry一般来说，只要在后台激活了MRP，当建立MRP物料的主数据时（MRP view），这个物料就会被自动规划到计划文件中了。