Articulated hands

Overview:

Many collectible toys have good overall articulation, but poor hand articulation. Many adult collectors purchase articulation upgrades for their favourite figures, so with this project I set out to develop an unbeatable articulated hand, which could be used as an aftermarket upgrade across toylines.

Goals:

- Maximum articulation and quality

To set these hands apart from potential competitors, they needed to have the maximum possible articulation, however the bottom end needs to be able to handle the stresses and complexity involved.

- Ease of production

Since collectors are unlikely to spend $60+ on upgraded hands, production needs to be kept simple and repeatable.

- Proportional accuracy

The hands need to match the proportions of human hands in a variety of poses so that they look good on camera.

Due to the size of the hand, there wasn’t enough space for snap-fit tolerances to work without weakness, or frustration from parts popping off. For maximum solidity I went with a print-in-place approach. Normally print-in-place parts are completely loose, but I used a range of tricks to give the fingers rigidity. One was variable tolerance connections- instead of circular hinges, the pins/holes were oval-shaped, and when moved into position the joints self-tightened. Additionally, I added slightly thicker geometry just barely outside the hinge- when the joint moved, the geometry slid into the joint, adding tightness.

For production I developed a novel print automation system. The hands print lying flat and so were difficult/unreliable to eject traditionally. So this time, when the print finished the toolhead would stay in place, cooling the part & nozzle and forming a bond between the two. After a few minutes, once the part delaminated from the build plate, the printhead would lift up with the part still attached, then off to the side to bump-release the part.

Reflection:

I sold over 600 hands during this design’s run without a single breakage report. Some early customers did comment about needing more grip, so I adjusted the tolerances to be tighter from then on.

Tolerance tuning did end up playing a huge part- at points I was moving individual polygons by 50 microns to see what worked best. The big issue was slight differences between materials- if I were to switch colours, even within the same material brand, I’d have to tune the print to account for slight differences in consistency.

The print in place system was successful for the hands themselves, however as an overall product they suffered due to the constant tuning required to maintain close tolerances. That was the big killer for this product- there was too much work involved behind each batch, which prevented me from being able to offer these at a sensible price. I do have a V2 in the works which will be a self-assemble kit. In order for it to work I’ll use a 0.2mm nozzle, and I’ll need to rethink the palm mechanism to retain both articulation and strength without being fully print-in-place.

Designs

Articulated hands