As can be seen from the figure 1, it has input social demand master file, product structure file, production capacity file, logistics capacity file, production cost file, supplier supply file, etc. And form product production plan, production capacity demand plan, delivery plan and order purchase plan, transportation plan, logistics capacity demand plan, etc. , and perform cost accounting. However, the main file of social demand (that is, social orders) is always supplied from inventory first, and the warehouse is not enough. Different from general MRP, the input of MRP here is a part of the order purchase plan P(t) generated by DRP, that is, the order for the production department, and its output is not only the product production plan T(t) generated by general MRP, but also the outsourcing plan D3 (t) input to DRP. MRP executes MRP according to DRP's purchase plan of production order, formulates production task list, and generates processing task list for production department to process. The purchased parts are added to the requirement document of DRP system, which is processed by DRP. DRP still supplies goods from the warehouse first, and the warehouse is not enough to purchase goods from the order purchase plan to the resource market.
The concrete implementation can be divided into the following three steps:
In step 1, run the main products and parts that can be produced by the enterprise in the master demand plan D(t) separately (determined according to the product catalogue of the enterprise) D 1(t), and get the purchase plan P 1(t) that needs to be ordered from the production department of the enterprise. The internal master demand plan D 1(t) is the master demand document D (d). In DRP processing, the part is always supplied from the warehouse inventory first, and then the order is issued to the production department when the inventory drops to the safety inventory.
At this time, the parameters are determined according to the following formula: q (t) = q (t-1)-d1(t); p(t)= Q0； P 1(t)=P(t-tP), where Q(t) is the ending inventory of the current period; Q(t- 1) is the inventory at the end of the previous period; Q0(t) is the ordered quantity; P(t) is the planned arrival quantity of this period; TP is the lead time of the order.
Step 2: Run MRP from the production order plan P 1(t) to get the product production plan T(t) and its parts outsourcing plan D3(t).
Step 3: Input the part D2(t) in the main demand document D(t) that the enterprise cannot produce and the outsourced part D3(t) obtained by MRP into the DRP for calculation, and obtain the order purchase plan P(t) and the delivery plan S(t) from the market. Among them, goods in transit are divided into OS(t) and OP(t) and Q, and P(t) is determined as follows: When Q(t) drops to the order point (or below the safety stock), the goods will be delivered, and the size of the goods will be equal to an order quantity Q0, that is, P(t)=Q0. And the order purchase plan P(t)=P(t-tP). The delivery plan S(t) is S(t-tS)=D(t), where tS is the delivery lead time.
Through these three steps, we can get the order purchase plan, purchase plan, production plan and delivery plan. In fact, if we input the logistics capacity conditions (storage and transportation conditions, etc.). ), logistics optimization model and cost documents, we can also get logistics capacity plan, unified transportation plan and logistics cost.