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Trim by Plane

In one sentence: Trim the mesh at a plane defined by three picked points, discarding one half and keeping the other.

Overview

Workbench: Mesh
Menu: Mesh → Meshes → Cutting → Trim by Plane
Command: Mesh_TrimByPlane
Shortcut: none

Trims the mesh by a plane you define interactively by picking three points in the 3-D view. One side of the plane is kept; the other is discarded.

Intuition

Trim by Plane is like using a bandsaw with a flat blade aligned to any arbitrary plane: you define the plane by picking three points, choose which half to keep, and the operation cuts the mesh cleanly at that plane.

Unlike Cut by Polygon (a 2-D screen-space operation), Trim by Plane works in 3-D space and can cut at any angle.

When to use it

  • Removing the bottom of a scan mesh to create a flat base.
  • Cutting a mesh at a parting plane for mould analysis.
  • Trimming excess scan data above or below a reference plane.

Step-by-step

  1. Select the mesh.
  2. Choose Mesh → Meshes → Cutting → Trim by Plane.
  3. Pick three points in the 3-D view to define the cutting plane.
  4. FreeCAD previews the plane and asks which side to keep.
  5. Click Above or Below to discard one side.

Common mistakes and pitfalls

Result has an open boundary

Trimming leaves an open mesh edge at the cut plane. Use Fill Up Holes to close it.

Three-point plane definition can be imprecise

Picking points on a curved or noisy mesh surface may produce a slightly tilted plane. For a precise axis-aligned cut, place datum points at known coordinates first.

See also