Ninjaflex, Universal Joint

I am working on a project that requires a univeral joint (i.e. I’m printing in ABS. The joint is a weak part in the design, as it has a relatively thin structure compared to other parts. Anyway, was wondering if anybody has tried designing some kind of alternative universal joint using ninjaflex. Seems like there might be a way to use ninjaflex to make such a joint be less fragile.

Ninjaflex is awesomely flexible. I have not tried universal joints out of it, but it would be a very cool thing to try and test out. You could probably achieve what you want to with just one piece as your joint, sort of like a regular shaft, but flexible. (You can probably just heat/friction weld together the three parts; rigid shaft to flexible shaft to rigid shaft)

The trick will be to get enough flexibility to achieve your shaft-misalignment, but enough rigidity to transmit your forces.

The more infill, the more rigid your part will be.

Alternatively, you can try printing out your current design in Nylon. Compared to ABS, Nylon is basically indestructible (within reason, tiny little parts are still tiny little parts). I recently printed a replacement set of herringbone gears out of Taulman Bridge. I printed an additional set because I was curious what kind of beating they could take. After several furious whacks with a hammer, no damage to the part (it was printed at 50% infill and 2 0.5mm wide perimeters).

The great thing about nylon is that it starts off strong, but gets stronger as it deforms. As nylon is cold formed, its tensile strength increases. And it will elongate to approximately two times it’s length before a nylon test sample will break in tension.

Thanks for the suggestion, I’d been thinking about ordering some nylon, guess I’ll go ahead and do that.

Yeah, the issue of flexibility versus rigidity was what I was wondering about. Since I don’t have a flexystruder, I’ve not had a chance to play with ninjaflex, so wasn’t sure how it would work for this. I wonder if it would work for the joint to consist of a series of alternating discs of rigid and non-rigid material.

Any pics of the project? Is it just a hinge or do you need multi-axis rotation? I take it size is a factor…

Ninjaflex would be a good option, but its as matter of attaching to your project. Search Thingiverse for universal joints… Maybe a ball mount could work…

Not at a point right now where I can make a good pic that shows the need for the u-joint. If I get to that point soon, I’ll post something. But yes, multi-axis rotation is critical. A universal joint or some variant of that is pretty much required.