In the press or molding process, a multi-cavity product is one in which multiple pieces of the same material can be obtained with a single shot, while a product that can be obtained in a left and right set with a single shot is a left and right set or a co-attached product.
When setting up a two-piece item in the BOM (Bill of Materials) of the production control system from the viewpoint of the expansion of the required quantity, it is set that 0.5 items (children) immediately before being divided into two pieces are required for one item (parent) immediately after being divided into two pieces, but this can also be expressed as requiring one child for two parents.
In the case of car door parts, which is a typical left and right set, it is called RL (Right-Left), but unlike a two-piece set, the item code of the item (parent) immediately after it is divided into left and right is different from that of a two-piece set, and because the customer receives an order for the left and right separately, the production quantity changes depending on the combination pattern of the order quantity.
- If the order has only "R"
- If the order only has "L"
- If you have the same number of orders for both "R/L"
- If you have different number of orders for each "R/L"
In the case of 1 to 3, the production quantity on the left and right is the same, and in the case of 4, in order to ensure that there is no shortage of both, it is necessary to develop the one with the higher order quantity as the requirement.
The expansion of the required quantity when an order of 100 pieces each is received is shown in the figure below.
If we summarize this as the requirements for each item, we can see that the requirements are correctly developed on a one-to-one basis from the products of the left and right sets to the work-in-progress items.
How to handle main and byproducts in the system
Goods that are necessarily derived from the manufacturing process of the main product are called byproducts, but I think in general the higher value is the main product and the lower value is the byproduct.
However, if tofu, the main product produced from soybeans, were to boom in the market for okara, a byproduct, it is possible that the positions of byproduct and main product could be reversed.
There are cases where the parent and child requirements of the BOM of a production management system or production scheduler can be used, and there are cases where the parent and child requirements of the BOM alone cannot be used to develop requirements on a one-to-one basis, and there are cases where the requirements are not registered in the BOM from the beginning but are capitalized in the accounting process.
- Can be accommodated by the parent and child requirements of the BOM.
- Multi-cavity (general molding and pressing)
- Adjust the number of orders to be developed according to the requirements, as it is not possible to meet the parent and child requirements of the BOM.
- Sets (RL products, stickers cut out of sheets)
- Actual results are recorded as assets for accounting purposes without being set in the BOM.
- Main and byproducts (coke and coal tar from coal)
- Scrap (burrs and scraps of reusable value)
The difference between a production control system and a production scheduler master
As mentioned above, in the BOM of the production control system, the two-piece batch was expressed as 0.5 child requirement for parent requirement 1 or 1 child requirement for parent requirement 2.
The master of the production control system is expressed in terms of the parent and child requirements of the BOM for requirements expansion (number of pieces), and the standard load (cycle time) is set in the item line master for load calculation, and the standard capacity of the entire line (capacity per day) is set in the line master, so that the masters for requirements expansion and load calculation are managed separately.
This originates from the idea that the MRP of the production management system is based on the standard capacity of the line master, but piles up the load at an infinite capacity without considering the order quantity, and emphasizes the development of requirements, on the premise that the overload is leveled out by manual adjustment.
On the other hand, the production scheduler integrates the BOM, process information and capacity as a view and treats requirement expansion and load calculation as inseparable by making it look like the capacity is set in the BOM or item process master.
This is based on the basic production scheduler philosophy of developing requirements according to order quantities so that resource capacity does not exceed 100% based on cycle time.