Design for manufacturability (DFM) changes product geometry and specifications so required function can be produced reliably with appropriate processes and cost.

DFM starts from manufacturing capability rather than asking production to reproduce arbitrary geometry exactly.

Typical questions include:

• Is the selected material compatible with the intended process?
• Are tolerances tighter than function requires?
• Can tools, dies, electrodes or inspection probes reach the features?
• Can near-net geometry replace unnecessary material removal?
• Are wall thicknesses, radii and draft compatible with the selected shaping process?
• Can several setups be eliminated by changing datum or feature layout?
• Does the design require expensive finishing only because of a local specification?

For example, specifying $R_a=0.4\ \mu\mathrm m$ on every surface of a housing may force an additional precision-finishing operation even if only a sealing land needs that texture. Moving the tight requirement to the functional surface can preserve performance while removing needless operations.

DFM is not permission to weaken requirements. It asks which requirements are genuinely functional and then chooses geometry, tolerances, materials and processes that satisfy them robustly.

The final design is therefore a negotiated object between function and realization:

functional requirements
       ↕
product geometry / tolerances / material
       ↕
process capability / tooling / inspection / cost

Good manufacturing design makes those three layers consistent before production begins.