A bill of materials, or BOM, lists what goes into one unit of a product: each material, the quantity, the unit and the expected loss. It is the factory's recipe. Without it, purchase is guesswork, costing is a rough figure, and stock of raw material never matches the books.
01What a good BOM holds
Take a steel almirah as an example.
| Material | Quantity per unit | Loss allowed |
|---|---|---|
| CRCA sheet, 0.8 mm | 38 kg | 6% |
| Hinges | 4 nos | 0% |
| Lock set | 1 set | 0% |
| Powder coat | 1.2 kg | 10% |
| Packing carton | 1 nos | 2% |
Add the output: one almirah, plus the scrap you expect to sell. Scrap has value and should be counted.
02Levels
Many products are made from parts you also make. A pump has a motor, a casing and an impeller; the casing has its own BOM of casting, machining and paint. Keep each part's BOM separate and link them, so a change in the casing shows up in every pump that uses it.
03What the BOM drives
- Purchase
- orders for the next two weeks multiplied by the BOM give the material you need. Subtract stock and open orders, and the rest is your purchase list.
- Issue to the floor
- material is issued against a production order, at BOM quantity. Anything more needs a reason.
- Costing
- BOM quantity times the latest purchase rate gives material cost per unit. See costing a product.
- Yield checks
- compare actual use with BOM each week. A gap that grows points to waste, wrong entries or theft.
04Keep it current
A BOM written once and never changed is worse than none, because people trust it. Give one person ownership. When the design, supplier or process changes, the BOM changes the same day, with the date it took effect.
In MatruOS, factories start with BOMs for their kind of product, which they correct to match their own, and production orders issue material against them.