Design for Release: Draft Angle Basics That Pay Off
Why draft is not optional
Molten alloy shrinks onto the die cores as it solidifies. Without taper, ejection drags, galls and tears the surface — and the die needs more frequent polishing. Draft is the difference between a clean release and a maintenance headache.
Draft also affects porosity: poor release can smear and fold surface defects into the skin.
Typical minimums
External walls often release with minimal draft; internal features, bosses and pockets need substantially more because shrinkage grips them. Textured surfaces need extra draft proportional to texture depth so the pattern releases without dragging.
The exact numbers depend on depth, alloy and die polish — your caster will quote draft from the 3D model, so leave it negotiable early.
Where draft costs hide
Insufficient draft shows up not as a scrapped part but as slower cycles, more die maintenance and higher reject rates — costs buried in unit price. Adding one more degree to a deep boss often pays for itself in the first production run.
FAQ
Do external surfaces need draft?
Usually far less than internal features, but some taper still improves release and surface quality.
How much draft for a textured surface?
Draft increases with texture depth; align texture direction with pull direction and add draft per your finisher's guidance.
Can draft be zero?
Only with sliding cores or special die actions, all of which add tooling cost — rarely worth it for non-critical surfaces.
When should draft be decided?
At the initial 3D model stage. Changing draft late means tooling changes and re-quotes.
All figures above refer to standard product data sheets; final confirmation is subject to written quotation.