DFM

DFM (design for manufacturing) is reviewing a design through the eyes of whoever will make it. Many decisions that cost a lot on the shop floor (an inside radius too small, a tight tolerance with no reason, a hard-to-source material) can be changed in CAD with no harm to the part’s function.

How it works

A DFM review looks at process (machining, sheet metal, casting, 3D printing), geometry (inside radii that fit end mills, thin walls, deep holes, tool access), tolerances (only where function demands), material and treatment (availability, machinability) and workholding (how many setups the part needs). The result is usually fewer operations, fewer setups and fewer rejected parts.

Practical example

A machined bracket had sharp inside corners, ±0.02 on every dimension and needed three setups. In the DFM review, the corners got a 3 mm radius, general tolerance moved to ISO 2768-m with ±0.02 only on the dowel holes, and the part now takes two setups: price dropped 35%.

Common mistakes

• Designing sharp inside corners on milled parts.
• Applying tight tolerances to the whole drawing.
• Picking a material from a table without checking availability and lead time.