MBOM BASICS · UPDATED 10 OCTOBER 2026

What is an MBOM?

An MBOM, or manufacturing bill of materials, lists what the factory needs to make a product as it is actually built: the components, how many of each and, for many products, the sizes to cut them to.

A parts list for making, not designing

Designers describe a product as it is engineered. The factory needs it described as it is made: stock lengths cut to size, fixings counted, sheets cut into panels. The MBOM is that view. In many businesses it also feeds purchasing, kitting, cutting and labelling.

What an MBOM line usually holds

A component, by part code and revision.
A quantity for each unit made.
Where it applies, a size: a cut length for linear stock, or width and height for sheet and panel parts.
Enough description for the shop floor to recognise it.

Larger systems add structure on top, such as subassemblies, operations and work centres. Those belong to routings and production planning. The core is still the same: which parts, how many and what size.

Why configured products are different

For a fixed product, the MBOM is written once. For a configured or made-to-measure product, every order has its own. A wider unit has longer rails and may need an extra support, a different finish changes the part codes, and some combinations cannot be made at all. The MBOM has to be worked out from rules, unit by unit.

That working-out is the hard part, and it is often spread across spreadsheets, notes and the memory of a few experienced people.

Generating the MBOM from rules

FactorySpec holds those rules in one reviewed model for each product family: the inputs, deductions, tables and conditions your product expert approves. Each unit’s dimensions and options go in, and its MBOM comes out, with a trace showing how every line was reached. See how it works.

What FactorySpec’s MBOM covers

A flat list of components for one unit, with whole counts.
Cut lengths, and panel width and height, in millimetres.
The checks that decide whether the unit can be made at all.

It does not hold subassemblies, routings, operations, prices or stock. Those stay in your ERP, planning or order systems. EBOM vs MBOM explains where it fits.

Questions

Is an MBOM the same as a BOM?

An MBOM is one kind of BOM. “BOM” on its own can mean the engineering view, the manufacturing view or a sales parts list. The MBOM is the one the factory builds from.

Does every unit need its own MBOM?

For a fixed product, no: one MBOM serves every unit. For a product made to size or with options, each distinct configuration has its own, which is why it is worth generating from rules.

Does this match how you make your products?

Start with a short description of what you make and how each unit’s parts are worked out.

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