Lesson 2 of 6
Bills of material
9 min
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A bill of material (BOM) lists the components and quantities needed to make a product. SAP Learning puts it simply: planning uses the BOM to work out what to buy or make, and production orders use it to know which components to stage and issue. For Contoso, the alternator BOM in plant 1710 decides how many rotors MRP orders from Lakeside Components.
| Item | Component | Quantity | Item category | Notes |
|---|---|---|---|---|
| 0010 | CMC-RTR-200 rotor | 1 pc | L (stock item) | Purchased from Lakeside Components |
| 0020 | CMC-STA-300 stator core | 1 pc | L (stock item) | Wound in operation 0010 of the routing |
| 0030 | CMC-HSG-400 housing | 1 pc | L (stock item) | Purchased |
| 0040 | CMC-FST-010 fastener kit | 1 kit | L (stock item) | Backflushed at assembly |
| 0050 | Assembly instruction | – | T (text item) | Not planned, not costed |
Contoso's production BOM for CMC-ALT-100 in plant 1710 (base quantity 1 pc). Component numbers other than the rotor are introduced for this course.
Header: plant, usage, base quantity
A material BOM is created for a material, a plant and a BOM usage, in transaction CS01 (change with CS02, display with CS03) or the equivalent Fiori app. The usage says what the BOM is for. Usage 1 is production; others include engineering/design, sales and costing. Production orders and MRP look for a production-relevant BOM, so a BOM that exists only as an engineering BOM plans nothing.
The base quantity is the quantity of the parent the component quantities refer to. A base quantity of 100 with 100 fasteners means one fastener per alternator; change the base quantity to 1 and forget the items, and you have just ordered a hundred times the fasteners.
Items and item categories
Each item has an item category. L (stock item) is planned and issued from stock. N (non-stock item) is bought directly for the order. T (text item) carries instructions. Items can carry component scrap or operation scrap percentages, and an explosion type that changes how MRP treats them, for example to plan a component as a collective requirement regardless of its own master data.
Validity and change control
BOM items have a valid-from date. When engineering replaces the housing with a lighter version from 1 March, you do not edit the item in place; you add the new item valid from 1 March and delimit the old one. With engineering change management, a change number carries the date and the reason, and you can see the BOM as it was on any date. MRP and order creation explode the BOM valid on the order's explosion date.
- Until 28 FebOld housing validPlanned orders dated before 1 March explode CMC-HSG-400
- 1 MarchChange number effectiveNew lighter housing item valid from this date; old item delimited
- From 1 MarchNew housing validMRP plans the new housing for orders exploded on or after 1 March
- Run-outOld stockRemaining old housings used up or scrapped by decision, not by accident
Alternative BOMs
One material can have several alternative BOMs for the same plant and usage, for example one for the automated line and one for a manual cell that uses a different fastener kit. Which alternative production uses is decided by the production version, covered later in this course. Multi-level structures (an assembly that has its own BOM) are exploded level by level; transaction CS11 shows the multi-level explosion and CS15 shows where a component is used.
- Is the BOM for the right plant?Yes → continue · No → plant 1720 needs its own BOM (or a plant assignment)
- Is the usage production-relevant?Yes → continue · No → MRP and orders will not find it
- Is every item valid on the planned date?Yes → continue · No → check change numbers and valid-from dates
- Is the base quantity consistent with item quantities?Yes → BOM is ready · No → correct before MRP runs
What would you do?
A probe production order for CMC-ALT-100 in plant 1710 shows the rotor, housing and fasteners but no stator core. The BOM in CS03 shows the stator item. What should you check first?
- A material BOM is per material, plant and usage; production and MRP need a production-relevant usage.
- Base quantity scales every item; item category L items are planned and issued from stock.
- Validity dates and change numbers control which items explode on a given date.
- Alternative BOMs exist side by side; the production version decides which one production uses.
Check your understanding · not graded
Lesson check
1. Which BOM usage do production orders and MRP normally need?
2. A component is replaced from 1 March. What is the correct BOM change?
3. What does item category T mean?
4. What decides which alternative BOM production uses?