In my last project, I tackled the daunting task of building a hybrid cross-roller bearing. The biggest challenge was coiling incredibly springy, high-tensile piano wire to the perfect diameter to form the bearing's raceway. The solution to that specific problem, however, ended up being a versatile tool in its own right: a 3D printed wire bender. Today, I'm sharing the build of this neat little machine, which is designed to coil wire to precise diameters, and I'll see what else it can handle.

The Wire Bender's Anatomy

The wire bender's core mechanics are a brilliant exercise in elegant simplicity. The design features a central pulley and two carriages, one with a right-hand threaded insert and the other with a left-hand threaded insert. A single threaded rod runs through both, so when you turn the rod, the carriages move in opposite directions, either towards or away from the central pulley. This keeps the distance to the centre equal on both sides, ensuring the wire bends into a perfect circle.

The build relies on a few key components. I used a 10mm x 10mm Maker Beam for the guideway of the sleds, which is a scaled-down version of a 2020 aluminium extrusion. This provided great rigidity and kept the sleds constrained to one dimension. The sleds themselves, along with the central housing, were printed in polycarbonate. This was a crucial choice, as the bending forces are high and perpendicular to the print layers—an earlier PLA version of a similar part failed spectacularly.

Putting It All Together

With the parts printed and gathered, assembly was straightforward. The base holds the bearing blocks, the central housing, and the Maker Beam guideways. The carbon fibre axle, with its accompanying bearings, sits in the centre The two sleds are attached to the threaded rod, and the system is secured with retainers and grommets. The whole process took no time at all.

The Bending Test

After assembly, it was time for the fun part: seeing what this little machine could do. I gathered a few different materials that might appear in future projects.

1. Springy 1.2mm Piano Wire: This was the original reason for the tool, and it performed its job perfectly, creating a consistent, uniform coil.

2. Ductile 3mm Anodized Aluminum Wire: This craft wire was much softer and easier to bend. The bender handled it well, but for this kind of material, it might be just as easy to wrap it around a correctly-sized rod by hand if you don't need a perfectly-tuned diameter.

3. Soft Copper Tubing: I tested a piece of 3mm ID copper tubing, and the bender successfully coiled it into a uniform shape. This is especially useful for creating perfect coils for things like heat exchangers or custom cooling solutions.

Final Thoughts

The bender performed well across the board, though its true value lies in the precision and repeatability it offers. For springy, high-tensile materials like piano wire, it's a necessity. For more ductile materials like the aluminium and copper, its main advantage is the ability to precisely fine-tune the final diameter, which is a big plus for projects that require exact measurements. This tool is a great example of how building one solution can lead to another, and I'm excited to see what other uses I can find for it.