FreeCAD SheetMetal: How to Add Flanges and Bend Lines

Designing sheet metal components in FreeCAD requires the dedicated SheetMetal workbench to model manufacturing-ready features like folds, tabs, and flat projections. This guide covers the process of generating flanges from existing edges, folding flat plates along dedicated bend lines using sketches, and exporting an unfolded pattern displaying your bend centerlines for fabrication.

Installing the SheetMetal Workbench

Before beginning, ensure the SheetMetal add-on is installed:

  1. Open FreeCAD and navigate to Tools > Addon manager.
  2. Locate SheetMetal in the workbenches list, select it, and click Install.
  3. Restart FreeCAD and select SheetMetal from the workbench dropdown menu.

Method 1: Adding Flanges from Edges

The standard way to extend walls and form bends is by adding flanges directly to existing geometry.

  1. Create a Base Plate: Start in the Part Design or Sketcher workbench. Create a 2D sketch of your base profile, then use the Make Base Wall tool from the SheetMetal workbench to give it a defined sheet thickness.
  2. Select an Edge: Click on the specific top or bottom edge of the plate where you want the bend to originate. To add multiple identical flanges simultaneously, hold Ctrl and select multiple edges.
  3. Generate the Flange: Click the Make Bend (Edge Bend) icon on the toolbar.
  4. Adjust Parameters: Select the newly created Bend object in the tree view and open the Data tab in the Property View to configure dimensions:
    • Radius: Sets the internal bend radius (ensure this matches your tooling).
    • Length: Sets the total extension of the new flange.
    • Angle: Changes the bend angle (default is 90°).
    • Relief Type: Changes corner cutouts (e.g., Rectangle, Round) to avoid material tearing.
    • Invert: Flips the direction of the bend if necessary.

Method 2: Adding Bends along a Sketch Line

If you have a flat plate and need to fold it across an arbitrary line, use the bend-on-line workflow:

  1. Select the Plate Surface: Click on the flat face of the sheet metal body where the fold should occur.
  2. Create a Bend Line Sketch: Click the New Sketch tool. Draw a single open line across the face representing the axis of the bend, then close the sketch.
  3. Execute the Fold:
    • Select the flat face of your plate.
    • Hold Ctrl and select the sketch containing the bend line.
    • Click the Bend on a line tool from the SheetMetal toolbar.
  4. Configure the Fold: In the Property View, adjust the Angle, Radius, and choose which side of the line moves by toggling the Invert parameter.

Generating Flat Patterns and Bend Lines for Production

To view and export the flattened sheet displaying the tangent and center bend lines for CNC or laser cutting:

  1. Select the main base face of your finished model.
  2. Click the Unfold tool on the SheetMetal toolbar.
  3. In the tree view, expand the resulting Unfold object to view the generated flat geometry.
  4. In the Property View under the Unfold object, ensure Bend Lines is set to True.
  5. Export the flat pattern:
    • Select the unfolded object, navigate to File > Export, and choose DXF to export cut lines and bend lines for manufacturing.
    • Alternatively, send the unfolded shape to the TechDraw workbench to generate an engineering drawing with dimensioned bend positions and angles.