Sources and scope for this page: Industry convention — no single governing standard (conventional usage, definitions vary between sources), covering the definition of design for manufacturability (dfm). No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. How sources, methods and updates are recorded.
Definition
DFM is a review performed before release, checking that the design respects the process it will be made by. For machining that means avoiding deep narrow pockets, sharp internal corners that cannot be cut because of tool radius, and tolerances tighter than the process can hold.
The internal-corner rule is the one that catches most designs: a pocket corner cannot be sharper than the radius of the end mill that cuts it, so a square corner means either a relief hole or a change to the drawing.
Common misuse
Specifying sharp internal corners. Every cutter has a radius, and a corner sharper than it requires either an EDM operation or a design change.