InMoov No Longer InPieces

Over the past couple of months my build of the InMoov robotic arm has continued to progress slowly in the background, until now I find myself near the end. So about time for a little update on the build since my last post where I only had the arm and wrist pieces printed and partially assembled.

Now that the hand and fingers are assembled this is really starting to look cool, with a good range of movement and nice details controlling these movements. Let me say (if I haven’t before) that this is really not a project for the feint of heart – sure you might get lucky and be able to 3D print all of the parts without a hitch (although if you 3D print as much as me you know that for all of these successful prints assembled into the hand, there are many more failures!), but much of the challenge is in having the tools and patience to assemble them together properly. Each joint has needed filing, drilling of holes, gluing, even some acetone to clean up some of the rough surfaces to save reprinting, and of course these processes have been repeated numerous times. But that’s what I love about a project like this, you get to understand how every piece works.

Threading the Spectra braided line (I found a roll of 180lb 0.7mm Spectra quite cheap on Ebay) again requires the patience of a surgeon and a nice pointy set of tweezers, but I’m really loving how I can already start manually controlling the fingers by pulling on the lines. When doing this I found that some of the fingers were stiff and required a lot of force to move, so again you need to be prepared to take things apart and file them down before gluing anything into place, or the servo’s just won’t cope. I’ve found a little bit of lithium grease to be useful to help prevent binding of a few of the joints, but most of them are working quite smoothly without, pinned together with 3mm filament as suggested in the build instructions (so simple if you have access to some of the larger diameter stuff).

Next step is to connect the Spectra lines to the servo’s, which I’ll admit I’ve been nervous about since getting this right is critical, and then it should be up and running! I’ve bought an adjustable power supply to give the servo’s the power they need, seems like they can draw a lot of current when they move, far more than the Arduino/computer can give, so hopefully my next post will have a video of it moving 😀

– Posted by James Novak

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