Free Engineering Tool
Draft Angle Calculator
Determine the optimal draft angle for your injection molded parts based on material properties, surface texture specifications, and part depth.
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Surface Texture Reference Guide
Common injection mold surface finishes with texture depths and minimum draft angles.
| Finish | Group | Depth (mm) | Min Draft (°) |
|---|---|---|---|
| SPI A-1 (Diamond Buff) | SPI Polish | 0.000 | 0.25 |
| SPI A-2 (High Polish) | SPI Polish | 0.000 | 0.25 |
| SPI A-3 (Standard Polish) | SPI Polish | 0.000 | 0.5 |
| SPI B-1 (Fine Paper) | SPI Semi-Gloss | 0.005 | 0.5 |
| SPI B-2 (Medium Paper) | SPI Semi-Gloss | 0.008 | 0.5 |
| SPI B-3 (Coarse Paper) | SPI Semi-Gloss | 0.010 | 0.75 |
| SPI C-1 (Fine Stone) | SPI Matte | 0.013 | 1 |
| SPI C-2 (Medium Stone) | SPI Matte | 0.018 | 1 |
| SPI C-3 (Coarse Stone) | SPI Matte | 0.025 | 1.5 |
| SPI D-1 (Fine Blast) | SPI Textured | 0.030 | 1.5 |
| SPI D-2 (Medium Blast) | SPI Textured | 0.050 | 2 |
| SPI D-3 (Coarse Blast) | SPI Textured | 0.080 | 3 |
| VDI 12 (600 Grit) | VDI 3400 | 0.001 | 0.25 |
| VDI 15 (400 Grit) | VDI 3400 | 0.002 | 0.5 |
| VDI 18 (Matte) | VDI 3400 | 0.004 | 0.5 |
| VDI 21 (Light Texture) | VDI 3400 | 0.006 | 0.75 |
| VDI 24 (Medium Texture) | VDI 3400 | 0.009 | 1 |
| VDI 27 (Standard Texture) | VDI 3400 | 0.014 | 1 |
| VDI 30 (Coarse Texture) | VDI 3400 | 0.020 | 1.5 |
| VDI 33 (Heavy Texture) | VDI 3400 | 0.030 | 2 |
| VDI 36 (Very Heavy) | VDI 3400 | 0.040 | 2.5 |
| VDI 39 (Extra Heavy) | VDI 3400 | 0.056 | 3 |
| VDI 42 (Deep Etch) | VDI 3400 | 0.080 | 3.5 |
| VDI 45 (Deepest Etch) | VDI 3400 | 0.112 | 5 |
| MT-11010 (Fine Leather) | Mold-Tech | 0.025 | 1.5 |
| MT-11020 (Med Leather) | Mold-Tech | 0.050 | 2.5 |
| MT-11030 (Deep Leather) | Mold-Tech | 0.076 | 3 |
| MT-11040 (Heavy Leather) | Mold-Tech | 0.100 | 4 |
| MT-11510 (Fine Geometric) | Mold-Tech | 0.025 | 1.5 |
| MT-11520 (Med Geometric) | Mold-Tech | 0.050 | 2.5 |
| MT-11540 (Deep Geometric) | Mold-Tech | 0.076 | 3 |
How to Use the Draft Angle Calculator
Choose Material
Different plastics have different coefficients of friction and shrinkage rates that directly affect ejection requirements.
Select Texture
Pick the surface finish specification. Deeper textures require significantly more draft to prevent drag marks and part damage during ejection.
Enter Part Depth
The deeper the draw, the more draft you need. Very deep parts (over 50 mm) get an automatic adder to the recommendation.
Need Expert Help?
Optimize Your Part Design
Draft angles are critical, but they are just one piece of the DFM puzzle. Let our engineers review your part design for optimal manufacturability.