A bill of materials looks like a simple table.
But if the BOM is wrong, the entire assembly can become wrong.
## Part numbers must be controlled
Avoid creating multiple names for the same physical component.
A consistent part-number system helps purchasing, production and engineering communicate.
## Quantity matters
Check whether the quantity is per assembly, subassembly or complete product.
A simple “2” can mean different things depending on the BOM level.
## Match the drawing revision
If the drawing is Rev B and the BOM points to Rev A information, someone will eventually notice—and usually not at a convenient time.
## Separate purchased and manufactured parts
The purchasing team needs different information from the manufacturing team.
Purchased components may require:
– Manufacturer – Supplier part number – Specification – Approved alternatives
Manufactured parts need drawing and production information.
## Watch for duplicate components
A duplicate line can cause over-ordering.
Compare the assembly tree with the BOM before release.
## Check units
A quantity of 10 pieces is very different from 10 metres or 10 kilograms.
Make units obvious.
## The final BOM check
Before releasing an assembly:
– Open the top-level assembly. – Review every component. – Compare against the BOM. – Verify quantities. – Verify revisions. – Check purchased components. – Check suppressed or hidden components. – Confirm drawing references.
A good BOM quietly prevents a lot of expensive mistakes.