The bill of materials — the BOM — is the structured list of every material and process needed to make a product. In metal fabrication it is the single most important document there is, because every accurate quote depends on how precise it is.
What a bill of materials contains
For each component of the product, the BOM sets out: the material (type, section, thickness), the quantity needed, the expected waste percentage, and the processes to apply (cutting, bending, welding, coating) with an estimated time for each. A simple sliding gate might run to a dozen lines across sections, plates, hinges and processes; an industrial door many more.
The problem with made-to-measure work
Most fabrication products have no fixed size: a gate may be 3 metres wide or 5, 1.80 tall or 2.20. A static bill of materials, written for one specific size, has to be redone every time the dimensions change — repetitive work, and easy to get wrong.
The answer: a parametric BOM
A parametric bill of materials replaces fixed quantities with formulas tied to the product's dimensions: the length of a section becomes a function of the gate's width, the number of welds a function of the perimeter. Once the right formula is built for a product, the same BOM automatically produces the correct quantity of materials and hours for any size the customer asks for — with no need to rewrite it each time.
Why the time invested pays back
Building a parametric BOM for your best-selling products takes an upfront investment of time, but it repays quickly: every subsequent quote for that kind of product is generated in seconds, with materials and hours correct automatically, and with far less room for error than repeated manual calculation. It is the step that turns quoting from a craft activity into a process that scales.