What is a ʼDraftʼ angle in plastic parts in SolidWorks?
Short Answer
A draft angle in plastic parts in SolidWorks is the intentional taper added to faces so the molded part releases cleanly from the mold. The most common professional method is the Draft feature, usually applied from a neutral plane or parting line. Too little draft can still cause sticking or surface drag.
What You Need to Know Before
Warning: If you add draft after complex fillets, ribs, or shutoff geometry, SolidWorks may fail to rebuild or create distorted faces near the parting direction. A wrong pull direction is a common real-world mistake that makes a part look correct but impossible to eject from the mold.
How to Add a Draft Angle in SolidWorks
Command: Draft
Shortcut: No default keyboard shortcut
Quick Steps:
- Go to Features tab > Draft on the CommandManager.
- In the PropertyManager, choose the most common method: Neutral Plane, then select the neutral face or plane and set the Draft Angle.
- Select the faces to draft, confirm the Direction of Pull arrow is correct, and click OK.
Use the fastest common workflow for molded parts: apply draft early in the feature tree, before nonessential fillets.
Variables & Settings
Key Setting: Draft Angle / Neutral Plane / Direction of Pull
Expert Setting: The Neutral Plane controls which face stays fixed while adjacent faces taper. If the pull direction is flipped incorrectly, the draft may go inward instead of outward, creating undercuts or reducing wall thickness beyond molding limits.
Why it Fails
Cause 1 (Geometry): Tangent or highly curved faces may not support the requested draft angle without self-intersecting or collapsing the surface.
Cause 2 (layers/Locks): If the body is imported, featureless, or affected by external references, selecting the correct faces or pull reference can become unreliable.
Cause 3 (Command/Logic): Using the wrong draft type, such as Neutral Plane instead of Parting Line, can fail when the model has multiple pull regions or complex shutoff conditions.
Quick Fix & Best Practice
Quick Fix: Edit the feature and reduce the Draft Angle, then verify the Direction of Pull and switch to Parting Line Draft if the geometry crosses the mold split.
Manager’s Verdict: Use draft as early as possible in plastic part modeling and validate it against the true mold pull direction. Avoid leaving draft to the end, especially on production parts with ribs, bosses, and cosmetic surfaces.
FAQ
What draft angle is typically used for plastic parts?
Usually 1° to 3° per side, depending on material, texture, and depth.
Can I add draft to existing solid geometry in SolidWorks?
Yes, the Draft feature is commonly used to add taper to an already modeled solid.
What is the best draft method for simple molded parts?
Neutral Plane Draft is the most common and fastest method for standard plastic features.
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