How to identify Undercuts relative to a workplane

Identifying undercut geometry can influence your manufacturing process. Could you quickly show any areas that cannot be machined to determine what steps need to be taken to manufacture your part?


I need to find out if undercuts exist on a part relative to my setup.


Use Draft Angle Shade to determine areas that are undercut.

Draft Angle Shade allows you to set an undercut and warning angle to determine undercuts and areas with a draft.


  1. Change the View mode to Draft Angle Shade.
    View > Appearance > Shade > Draft Angle Shade
  2. Open the Model Drawing Options.
    View > Appearance > Model Drawing Options
  3. The Draft Angle value should be zero, and Warning Angle is your preference.
    1. Draft Angle Shading determines that any angle with this angle or less relative to the active workplane will be identified as an undercut. A value of zero means perpendicular or less will be identified.

Inspect the model to determine areas that are Undercut or drafted as Warning.

We have created a macro that simplifies these steps and can be downloaded here.
This macro will do the following:
  • Deactivate all entities except Workplane and Stock Model
  • Change the view to Draft Angle Shade
  • Sets Undercut Angle to zero
  • Sets Warning Angle to five
  • Selects all perpendicular surfaces to the workplane and blanks them
  • Shows only undercut surfaces relative to the workplane