Is it possible to 3D print a joint or blunt?

Short answer: Blunt objects are incredibly easy to 3D print. Movable parts, such as joints and gear bearings, are a little more complicated, and occasionally require assembly after the fact. If you are specifically interested in printing replacement human joints such as a knee or shoulder, it’s an ongoing area of research.

Long answer: 3D printers are really cool- they take a filament of plastic on spool, like a wound up thread, and melt very small amounts and extrude them through a nozzle, so that they cool and freeze rapidly into the desired shape. Things are printed by laying down layer after layer of this plastic. The printer is like an cake icing nozzle, but instead of laying down icing to make cakes, it lays down plastic to make the future.

Blunt and rounded objects are easy to make. Most modern 3D printers generally have micron-scale resolution. This, for example, is a 3D printed ball bearing- no assembly required:


3D printed ball bearing - by RenatoT via Thingiverse

3D printed ball bearing – by RenatoT via Thingiverse


You’ll notice that the parts come out quite smooth, and in one piece.

By layering the plastic and building things from the bottom up 3D printers can actually make solid pieces intertwined with other solid pieces that would otherwise be impossible to connect without a seam or other assembly. My second favorite example of this is this planetary gear system which is effectively a ball bearing (my top favorite is my own 3D printed blocks of nuclear pasta):

3D printed planetary gear system - by emmett via Thingiverse

3D printed planetary gear system – by emmett via Thingiverse


You can see one of those gear systems being printed in action here. You’ll notice that the gears are actually helical, so that they can’t actually be taken apart – the gears won’t slide past each other, so it can handle an axial load! Check this video. This is pretty fantastic- you can 3D print gadgets with working, moving parts all with the push of a button.

But you asked, specifically, about joints.


3D printed joint- by PrintTo3D via Thingiverse

3D printed joint – by PrintTo3D via Thingiverse


I don’t know if I’ve seen many designs that allow you to print the joint pre-assembled like the bearings, but the ‘snap and click’ kind of joints are very easy to print as separate pieces, and are really quite robust. For example, this chess set is designed with joints in place so that the pieces can be assembled into fighting robots.

3D printed fighting robot chess set - by cymon via Thingiverse

3D printed fighting robot chess set – by cymon via Thingiverse


Of course, that’s all plastic ‘toy’ joints. What about joints of a more medicinal persuasion? It turns out that recently doctors were able to successfully design and print a replacement knee joint. It’s basically a biodegradable scaffolding that is inserted surgically into the joint. The doctors were even able to make them custom to the individual by basing the size of the joint off MRI images. Admittedly, these tests were done in sheep, but human trials are the next step.

We’re quickly entering a time when 3D printers can make things beyond plastic toys, and the possibilities are limited only by your imagination.





asked by /u/InteNsReddit

cover image credit: Wikimedia Commons



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