What matters
- Draft every surface that slides against steel during ejection.
- Depth, texture, resin shrinkage, and steel condition affect the required angle.
- Specify which side holds the nominal dimension so draft does not quietly break the assembly.
Find draft from the pull direction
Set the mold-opening direction, then inspect every face parallel or nearly parallel to it. Outer walls, inner walls, ribs, bosses, louvers, pockets, and shutoffs all need deliberate treatment. An automatic draft analysis is useful, but it cannot decide where the part should stay on opening or which face may show an ejector mark.
Use a range, then confirm the surface
One degree per side is a common early modeling allowance for an untextured wall, not a universal requirement. Deep features and textured surfaces often need more. Some polished or specially designed features can work with less, but the ejection margin becomes sensitive to resin, shrinkage, pressure, and steel finish.
Texture suppliers publish depth-based draft guidance for their own patterns. Put the selected texture code and the agreed draft on the same review; otherwise the texture may be specified after the geometry can no longer release cleanly.
Decide where the dimension is held
A drafted wall has different dimensions at its two ends. For an external enclosure, the parting-line edge may be the controlled silhouette. For an internal fit, the dimension at an assembly plane may matter more. Mark the hold point and use profile or explicit dimensions that describe function without over-constraining the rest of the face.
Draft review checklist
- Confirm opening direction, core/cavity split, and the side intended to retain the part.
- Run positive and negative draft analysis with small faces visible.
- Check deep ribs, boss interiors, snap pockets, vents, lettering, and textured walls.
- Review shutoff angles and steel strength at thin edges.
- Recheck mating dimensions at the correct height after draft is applied.
Use this as a design review, not a production release
These guides support early planning. The selected resin supplier, toolmaker, and molder still need to confirm the final geometry, process window, tolerances, safety factors, validation plan, and commercial assumptions for your application.