How to Extrude a Sketch Symmetrically in FreeCAD

Extruding a sketch symmetrically across its base plane is a fundamental operation in FreeCAD used to create balanced, centered 3D geometry. This guide outlines the straightforward steps to perform a symmetric extrusion in two opposite directions using both the Part Design Workbench (Pad tool) and the Part Workbench (Extrude tool), as well as how to extrude custom, unequal lengths in both directions.

Method 1: Using the Part Design Workbench (Pad)

The Part Design Workbench is the standard environment for parametric, sketch-based modeling in FreeCAD.

  1. Select the Sketch: In the tree view or the 3D viewport, click on the sketch you want to extrude.
  2. Activate the Pad Tool: Click the Pad icon in the toolbar, or go to the top menu and select Part Design > Create a sub-feature > Pad.
  3. Enable Symmetry: In the Tasks panel on the left side of the screen, locate the Type settings and check the box labeled Symmetric to plane.
  4. Define the Length: Enter the desired dimension in the Length field. FreeCAD will distribute this total length equally on both sides of the sketch plane (for example, entering 20 mm will extrude 10 mm in each direction).
  5. Apply: Click OK to complete the pad.

Method 2: Using the Part Workbench (Extrude)

If you are working with direct CSG modeling in the Part Workbench, you can achieve a symmetrical extrusion using the standard Extrude tool.

  1. Select the Sketch: Highlight your sketch in the tree view.
  2. Activate the Extrude Tool: Switch to the Part Workbench and click the Extrude icon (or choose Part > Extrude from the menu).
  3. Configure the Extrusion: In the Tasks panel, specify the direction (typically normal to the sketch) and enter the total extrusion length.
  4. Enable Symmetry: Check the Symmetric option. FreeCAD will split the defined length equally in both positive and negative normal directions.
  5. Apply: Click OK to generate the solid.

Extruding Asymmetrically in Opposite Directions

If your design requires different lengths in each direction rather than equal symmetry:

  1. Open the Pad tool within the Part Design Workbench.
  2. Change the Type dropdown from Dimension to Two dimensions.
  3. Enter your primary dimension in the Length field.
  4. Enter the opposite direction's dimension in the Second length field.
  5. Click OK to apply.