Seven key variables of the MRP processing logic

Gross demand/total demand GR (gross requirement)
Dependency requirements (related requirements) caused by one or more direct upper-order materials (parent parts) in MRP) and the sum of other independent requirements of the material itself is the gross demand/total demand of the material.

Sr (scheduled receipts)
The amount scheduled to be obtained at a certain time in the future is a future inventory, which is considered usable during the delivery period.

Estimated amount of Poh (projected on-hand)
The estimated number of databases at the end of a certain period (time period) without considering whether there are plans to receive porc orders. MRPProgramPoh is used to determine whether there is a net requirement Nr in a certain period. Note that the Intermediate Value of Poh is only used.

Net requirement NR (net requirement)
When the inventory quantity is insufficient to meet the required requirements, a net demand is generated. More precisely: In the MRP logic, if the expected Poh in the database volume is smaller than the security stock SS, the difference is Nr.

Planned order receiving porc (planned order receipts)
If a certain material requires a certain amount of net resources, we need to make a production or purchase to supplement it. Planned order receiving refers to the quantity of materials to be added in a certain period after the net demand is adjusted according to certain batch rules. This volume is porc before the production or purchase order is issued. After it is issued, it becomes Sr. After receiving, it is converted to OH.

Expected PAB (projected available balance)
The estimated number of databases at the end of a certain period (time period) when the planned order receiving PORC is considered. That is to say, the original expected Poh in a certain period plus the expected porc number of planned orders in this period is equal to the expected amount available in this period. If the production and procurement supplies work properly as planned, this value is the real end-time inventory of a certain item in a certain period.

Issue POR (planned order releases)
It takes some time (that is, the lead time of a job) to complete an order, the planned order receiving porc of the item in a certain period needs to be moved forward by a lead time, so that the Plan Order of the item in the corresponding period is issued by por. The planned order (por) of the parent component is expanded by the material table to the total amount (GR) of all its child parts ). when a plan order is issued, the Plan Order receiving will become in transit, instead of generating the total demand for its subparts.

In addition, there is a"Overdue amountThe concept involves both MRP input and MRP logic operations.

Overdue past due

The MRP of the material demand plan is implemented on a regular basis, and a new material demand document is generated upon each execution, and the phase 1 of the period covered by the planning horizon is moved back during the planning period, for example, the planned period of the previous MRP covers period 1 to 12, and the actual period 2 to 13 is covered next time. This is the "rolling scheduling ). When MRP is executed, the number that has not been reversed in the previous period will be rolled into the overdue period, which is called the overdue amount. There are three key variables: GR, Sr, and por.

The amount of GR overdue for Mao demand
If the source is an independent requirement, the operation layer feedback is directly input. In this case, the production efficiency is poor and the customer's needs cannot be met. When a customer makes an order, the order will be removed from the customer's order file or marked as delivered. If a customer's order needs to be satisfied after the delivery period expires, the quantity will fall into the overdue period of the gross demand.
If it comes from the relevant requirements, it is the first step of logical operation. The child part gr should be calculated by the parent component POR (expired ). For example, if a POC in the MRP calculation result of a persistent connected item has a positive value in the overdue period, the por will trigger the relevant requirements of the item. Most of the calculation results in the first step will be overdue, that is, the gr of this item is overdue.

Overdue amount of Sr in transit
Because the SR in transit belongs to the input information, the overdue amount is no exception. This indicates the supplier supply delay or workshop production delay, and the manager must step up the supervision. The MRP processing assumes that the overdue amount can be supplemented in the current period (1st period). If it is determined that the amount cannot be supplemented in the current period, the order delivery period should be modified based on the actual situation, that is, the quantity and duration of the corresponding amount in transit.

Number of overdue por orders issued
The calculation of the scheduled order to issue a por is the last step of the MRP logic operation. The number of overdue orders is no exception, but the calculation formula is different. In this case, it indicates that the publication date of the recommended purchase or manufacturing of MRP has expired. The available time is less than the pre-period. If the manager does not issue the ticket quickly, make an emergency purchase or work overtime, most orders are destined to be delayed.

Finally, in order to determine the order of material demand calculation, the system automatically calculates the minimum order of each item based on the BOM.