Parametric TPU Bellows: Custom Dust Boots & Covers

Press the Customize button to customize!

Looking for a 3D printed bellows or a custom TPU dust boot? This OpenSCAD parametric generator creates perfectly sized flexible covers for mechanical parts, linear rails, and joints. Optimized for Bambu Lab TPU and other flexible filaments, this script allows you to generate a professional-grade flexible joint cover with full support for circular, rectangular, and mixed geometries.

Why use this Parametric Bellows Generator?

Finding a replacement dust boot or mechanical bellows that fits your specific project is nearly impossible. Off-the-shelf parts are rigid in sizing. This OpenSCAD script solves that by letting you define exact cuff sizes, total travel length, and fold geometry. It automatically handles the transition between cuffs and folds, calculating the perfect transition length based on your fold_angle to ensure a seamless flow that respects your chosen style (smooth S-curves for rounded bellows or sharp tapers for zigzag).

Key Features for 3D Printing

• Automated & Style-Matched Transitions: Transitions automatically match the selected bellows style. Rounded bellows get smooth S-curve transitions, while zigzag styles get sharp linear tapers. The steepest point is always calculated to obey your fold_angle.
• Smooth Wall Ramping: The wall thickness ramps smoothly from the (often thicker) cuff wall to the flexible bellows wall. This eliminates weak points and stress concentrations where the cuff meets the body.
• Mixed Geometry Support: Mix and match circular and rectangular shapes for the top cuff, bottom cuff, and the bellows body itself.
• Fully Parametric Body: Choose between a circular or rectangular bellows body with independent width and depth control.
• Decoupled Cuff Sizing: Specify cuff diameters and widths independently from the bellows opening for a perfect fit on any hardware.
• Support-Free 3D Printing: Designed with a 40-degree fold angle to ensure clean prints in flexible filament without internal or external supports.
• Split Bellows with Sealing Lip: Includes a "Split" toggle for wrap-around installations on existing machinery. Two sealing lip styles are available: Wraps Over (default) generates a curved flap, arc-shaped for circular bellows so it conforms to the outer surface, that bridges the gap and laps over the opposite edge, and Sticks Out places a traditional radial flange on each split edge. Both styles respect user-set lip length and wall thickness.
• Axle Boot Clamp Slots: Independently enable a circumferential clamp groove on the bottom and/or top cuff to seat standard axle boot band clamps. User-configurable slot width, depth, and position from the cuff's free end. Depth is automatically capped at 80 % of cuff wall thickness. When a clamp slot is active, the split sealing lip automatically terminates at the inner edge of that slot so it never interferes with the clamp.
• Durable TPU Folds: Features a rounded wave profile that distributes mechanical stress more evenly than traditional zig-zags, significantly increasing the fatigue life of your 3D printed flexible cover. (Zig-zag style still available as an option).

How To Use

• Press the customize button
• Change the parameters to your specifications
• Download as STL
• Download the sample print profile which has been highly optimized for TPU
• Delete the samples off the plate
• Import your STL to the print profile

Troubleshooting: "Holes" or Missing Segments

If you see holes or missing sections in the preview (especially with extreme diameter differences), it usually means the geometry is "crushed."

• Increase Total Length: Give the transitions more room to breathe.
• Adjust Fold Angle: A steeper or shallower angle can help the transition fit within the available vertical space, although if it's too low you'll need supports.
• Increase Fold Depth: Sometimes deeper or shallower folds provide more stability in the mathematical model.

Common Use Cases

• CNC & Linear Rail Protection: Custom rectangular dust boots for square linear rails and lead screws.
• Automotive Boots: CV joint, steering rack, and shifter boots with clamp slot grooves for proper band-clamp retention.
• RC Car Suspension: Protective covers for shocks and linkages.
• Robotics & Animatronics: Flexible joint covers and cable conduits.
• Workshop Tools: Replacement boots for old or custom machinery, including circular-to-rectangular adapters.