BY AMT ERP Research Group)
Basic MRP's operational logic
Basic MRP's operational logic map shown in the figure:
Figure 1 MRP calculation logic
Next, the example will be described below to explain the operational logic step of the MRP. As shown in Figure 2, the structure diagram of the product a.
Figure 2 A product structure diagram
So, now we can calculate the demand for each product and corresponding components.
It is to be noted that due to the presence of the advance period, the time of the material plan delivery time and the net demand will sometimes be inconsistent. In addition, in order to simplify the calculation, we have not considered safe inventory.
Table 1 Demand calculation of product A (product A, advance period = 2, batch = 10)
The above calculation process shows that although A is required 1, 2, 4, 6, but actual A can be delivered within 3 and 4 weeks. This plan is time and quantity of time and quantity of components B and C.
Table 2 Demand Calculation of Parts B (Part B, Advanced During Period = 1, Batch = 20, 1A = 2B = 2'10 = 20)
Table 3 Demand Calculation of Parts C (Parts C, Advanced Period = 3, Batch = 60, 1A = 3c = 3'10 = 30)
From the decomposition of this layer, it can be seen that for the component B, it is still required to deliver 10 on the third week, and we must also explore the next layer according to the product structure. The decomposition method and steps are as before, we will not be unnamed.
After the above development calculations, we can derive the relevant needs of the parts of the product A. However, the situation in reality is far from simple, in many machining and manufacturing companies, due to the wide variety of products, not just product A to use parts B, components C, and parts D and E, there may be other products It also needs to be used, or the parts D, E have a certain independent requirement (such as a part as a server, etc.). Therefore, the work to be MRP is to first summarize the company's Mao demand for the same parts in a certain period, and then calculate their net demand and plan delivery volume in each period, and arrange production Plan and procurement plan. Here, in order to explain its principles, we can assume that companies also have product X to use parts D, in addition, parts D have a certain independent requirement. The total demand for the part D is calculated as shown in Figure 3.
We can obtain the total demand for parts D, we can further calculate the total net demand and plan delivery volume of the part according to the principles described above, thereby, the relevant production plan and procurement plan will be given appropriate time arrangement. In this way, we have completed a basic MRP calculation cycle. Of course, all this is with the help of the computer, follow the hierarchical processing principle (the ERP system starts from MPS, then performs the calculation of related requirements by layers by the BO-layer layer, until the low layer) . It should be said that this calculation of material demand for advanced computer technology and management software, compared with traditional manual methods, the calculated time is greatly shortened, and the accuracy of the calculation is also greatly improved.
Demand calculation of related requirements and independent needs
