Practical Methods to Check Undercuts in Mold Design

In mold design, detecting undercuts early—and verifying again after completion—is critical. Undercuts can cause ejection issues, increase complexity, or even make molding impossible without special mechanisms.

Here are six practical methods we use to efficiently identify undercuts:

1. Draft (Slope) Analysis

Run a draft analysis: if blue surfaces appear within red regions (or vice versa), it indicates an undercut relative to the parting direction.

2. Use “Check Region” Tool

This built-in function highlights areas where undercuts exist—look specifically for flagged “undercut” zones.

3. Inspect via the “Face” Panel

Go to the Faces interface, select “Undercut Area”, and the software will directly show you which faces are undercut.

4. Enable “Wireframe with Faded Edges” View

First, go to Preferences > Visualization Preferences, and set the hidden geometry color to a highly visible color (e.g., red).

5. Check Slider/Core Pull Direction

Orient the part along the slider’s ejection direction. In wireframe with faded edges mode, look for red lines (hidden edges). If none appear, the slider area is undercut-free.

6. Check Cavity/Core Parting Direction

Align the cavity insert along its opening direction. If red lines appear in this view, it means there’s still an undercut on the cavity side—requiring a lifter, slide, or other mechanism for release.

Key Takeaway: The best method isn’t the fanciest—it’s the one that works reliably in your workflow. Combine visual inspection with software analysis for maximum confidence.