General MRP Calculation Formula

General MRP calculation formula: Net demand = gross demand + allocated volume + safety stock-plan in transit-actual in transit-available stock
Gross demand: the demand for inventory, manufacturing, and procurement is not considered, relative to the net demand. If it is an independent demand, then the gross demand = the main production plan demand/(1-The expected product is not enough ). For related requirements, the Mao demand is equal to the upper layer.
Releases of materials. Independent requirement means that the demand of an inventory item is not associated with that of other items.

MRP Concept
General MRP calculation formula: Net demand = gross demand + allocated volume + safety stock-plan in transit-actual in transit-available stock
Gross demand: the demand for inventory, manufacturing, and procurement is not considered, relative to the net demand. If it is an independent demand, then the gross demand = the main production plan demand/(1-The expected product is not enough ). For related requirements, the Mao demand is equal to the volume of upper-level materials. An independent requirement means that the demand of an inventory item is not associated with that of other items, such as the final product produced, A product project that can be sold by an enterprise is usually located at the top of the product structure table. The related demand refers to the demand of a certain inventory item, which is related to the demand of another project and can be calculated accordingly, such as semi-finished products and raw materials. It calculates the demand for semi-finished products and raw materials based on the demand of final products. The gross demand of finished products is the amount of overdue orders (the amount of production in arrears ). The first-stage semi-finished products or materials require the final products. The gross demand for second-or lower-order semi-finished products or materials is the net demand for second-or upper-order semi-finished products.
Quantity allocated: The quantity of items that have been saved in the warehouse (hypothetical full database) But allocated to the ticket. It is actually the amount of overdue payments in the material control file. That is, the quantity allocated = the quantity to be sent-the quantity to be sent.
Safety inventory: to avoid additional demand caused by various exceptions, it can also be understood as the number of spare parts.
Planned amount in transit: the actual amount of procurement required for the intermediate process from the generated procurement plan to the generated procurement order after running out of MRP: divided into procurement in transit and manufacturing in transit. Procurement in transit: Number of unpaid tickets that have not been reviewed. Manufacturing in transit: number of unfinished manufacturing orders reviewed and closed
Available stock: generally refers to the quantity of good physical stock available in all warehouses (available stock = inventory-safety stock .) however, the available stock in the formula used for running MRP is the expected settlement of the previous order (manufacturing order), which is the theoretical available stock! In fact, it is assumed that there are three orders (manufacturing orders) A, B, and C in the order of date. The expected settlement of a is the available inventory of B, b's estimated inventory is the available inventory of C. the following push means that the available stock of the materials used during the MRP operation is the estimated deposit amount of the previous order or manufacturing order of the materials used or produced.
Estimated amount of inventory: Estimated amount of inventory = issued amount + available stock + in-transit volume + planned amount in transit-gross demand-allocated amount, which is the overall stock settlement of Materials
Net demand: the quantity calculated based on the MRP formula.
Planned amount: the total number of planned materials in transit after the material demand date.
Overdue amount: the total number of materials in transit purchased after the material demand date.
Release volume: refers to the actual release volume of materials, usually the actual release demand of the net demand. The data source is the net demand, however, there may be some differences with the net demand due to different ordering rules.

Calculation Method of Material Ordering rules
1. Net demand volume = net demand
2 According to the fixed batch release volume = sum (net demand/batch) * batch order is more than one
3. Pay-as-you-go = net demand during a fixed period
4 according to the main production plan issued volume = net Demand Note: (inventory = 0, allocated volume = 0) its meaning is not to consider inventory
And allocated quantity
5. Based on the minimum batch size, if the net demand <batch size = Batch Size
If the net demand is greater than the batch demand, the volume is equal to the net demand.
Note:
(1) The accuracy of BOM (production-oriented material list) should reach 95%
(2) The inventory accounting accuracy of the primary inventory file (stock records of materials) should reach 95%
(3) the daily settlement rate of all documents reaches 95%.
(4) Each item shall be informed of its lead time (pre-release period) and set in the main document of the item (ordering lead time and inspection lead time)
Period and preparation period)
(5) The MRP operation is based on the material, rather than the batch number! The allocated amount during calculation is that the item is in the item
All (demand date of all batches of materials <= demand date of the current batch of materials) in the control file are not released
The accumulation amount is the same as the on-the-way, on-the-way, and available stock!
(6) MRP features: the first MRP corresponding to the order for this material/semi-finished product is to capture all the allocated quantity, all available stock, all in-transit (purchase/manufacture) of the material) all plans are on the way. the second order used for this material/semi-finished product, except that the available stock is the expected settlement of the MRP calculation result of the first order used for this material/semi-finished product, the other values are 0. and so on, except that the first order that uses this item is to capture all items, the other is the available stock of the next order to capture the expected deposit of the previous order, and the other amount is 0, this is also true for the assigned quantity. for finished products, the amount in transit is also the first order to grasp all in transit, and the other is the available stock of the next order to grasp the expected settlement of the previous order.