How to Fuse Multiple Shapes in FreeCAD

This guide explains how to combine two or more 3D solids into a single, seamless object using the Union (Fuse) tool in the FreeCAD Part workbench. You will learn the exact steps to select your shapes, execute the boolean union operation, and clean up residual seam lines on the resulting geometry.

Step 1: Open the Part Workbench

  1. Launch FreeCAD and open your project containing the shapes you want to merge.
  2. In the workbench selector dropdown at the top of the interface, select Part.

Step 2: Select the Shapes to Fuse

  1. In the Tree View on the left panel (or directly within the 3D viewport), locate the shapes you want to combine.
  2. Hold down the Ctrl key (or Cmd on macOS) and click on each shape you want to include in the fusion.
  3. Ensure the shapes intersect or make direct contact. While disjoint shapes can be fused, the tool is primarily designed to merge overlapping solids.

Step 3: Execute the Union (Fuse) Operation

  1. Click the Union icon in the Part workbench toolbar. The icon resembles two overlapping blue spheres.
  2. Alternatively, go to the top menu and select Part > Boolean > Union.
  3. FreeCAD will hide the original individual shapes and generate a new object named Fusion in the Tree View. Expanding the Fusion object will show the original components nested beneath it.

Step 4: Remove Seam Lines (Refine Shape)

After a fusion, FreeCAD often leaves visible seam lines where the original geometries intersected coplanar faces. To create a clean, single surface:

  1. Select the newly created Fusion object in the Tree View.
  2. In the Property View below the Tree View, click the Data tab.
  3. Locate the Refine property and change its value from false to true.
  4. The redundant edges will disappear, leaving clean, continuous faces across the fused geometry.

Alternative Method: Using the Boolean Dialog

If you have a large number of shapes and prefer a checklist interface:

  1. Ensure nothing is selected, then navigate to Part > Boolean... in the top menu.
  2. In the Task panel, select Union as the Boolean operation.
  3. Check the boxes next to all the shapes you want to combine.
  4. Click Apply, then Close.