A slight taper angle applied to vertical walls of a molded or cast part to allow clean release from the mold: also used in 3D printing to avoid overhangs.
Draft angle (α) is a small taper angle (typically 1–5°) applied to walls that are parallel to the mold pull direction. Without draft, molded parts stick to the mold due to friction and suction. In 3D printing, draft angles on downward-facing walls keep surfaces within the self-supporting angle (usually ≤45° from horizontal), eliminating the need for supports. Draft is also used in SLA printing to reduce peel forces on the FEP membrane.
For injection molding design: use 1–2° draft on smooth surfaces, 2–5° on textured surfaces. In FDM design, applying 45° draft on overhanging features (like ears or tabs) eliminates supports and improves surface finish on the underside. Fusion 360's Draft feature applies uniform or parting-line draft. Use the 'Overhang Analysis' visualization in slicers to confirm which faces benefit from added draft.
Insufficient draft (< 0.5°) on tall mold features causes drag marks and part deformation on release. Asymmetric draft on mating parts causes assembly misalignment. In 3D printing, excessive draft angle on structural walls reduces the effective wall thickness at the base: verify minimum wall thickness at the widest draft point. Zero-draft vertical walls in SLA prints can lock against the tank bottom.
Related terms: Fillet, Chamfer, Wall Thickness
| Field | 3D design, engineering, mechanics |
|---|---|
| Also called | taper angle, demolding angle, draft |
Engineer, author of The Big Book of 3D Printing and additive manufacturing expert