How to Model a Spring in FreeCAD Part Design

This guide explains how to model a 3D spring or coil using the Part Design workbench in FreeCAD. By creating a wire profile sketch and utilizing the native Additive Helix tool, you can quickly generate parametric compression, extension, or custom coil springs without switching workbenches.

Step 1: Set Up the Body and Sketch

  1. Open FreeCAD and switch to the Part Design workbench.
  2. Click Create body, then click Create sketch.
  3. Choose a vertical plane (such as the XZ-Plane or YZ-Plane) and click OK.

Step 2: Draw the Wire Profile

  1. Select the Circle tool from the sketcher toolbar.
  2. Draw a circle off to one side of the vertical axis. The circle's diameter represents the wire thickness, while the distance from the vertical axis to the circle's center represents the mean radius of the spring.
  3. Apply constraints to define:
    • The diameter of the circle (wire diameter).
    • The horizontal distance from the vertical axis to the center of the circle (spring radius).
    • The vertical distance from the horizontal axis (optional, to position the base of the spring).
  4. Click Close to exit the sketcher.

Step 3: Apply the Additive Helix Tool

  1. With the sketch selected, click the Additive helix tool in the Part Design toolbar.
  2. In the Tasks panel, configure the helix parameters:
    • Axis: Choose the axis of revolution (typically the Vertical sketch axis or Base Z axis).
    • Mode: Select how you want to define the spring dimensions:
      • Pitch-Height-Angle: Set the distance between coils and total height.
      • Pitch-Turns-Angle: Set the distance between coils and total turn count.
      • Height-Turns-Angle: Set the total height and turn count.
    • Pitch: The distance between each coil loop.
    • Height / Turns: Define the total length or number of rotations according to your selected mode.
    • Cone Angle: Keep at 0° for a standard cylindrical spring, or enter an angle to create a conical spring.
    • Left handed: Check this box if you need a reverse-wound spring.
  3. Click OK to generate the solid spring.

Step 4: Flatten the Spring Ends (Optional)

If you are designing a compression spring that requires ground, flat ends:

  1. Create a sketch on a plane perpendicular to the spring's axis (such as the XY-Plane).
  2. Draw a large rectangle that covers the protruding tip of the spring wire.
  3. Close the sketch and use the Pocket tool through all to slice the end flat.
  4. Repeat the process for the opposite end using a parallel datum plane positioned at the top of the spring.