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The screw

Initially all the parts were intended to be printed on desktop 3D printer. This is good approach taken from e-Nable organization – they print prosthetic hands for kids out of charge. Beside being easily available everywhere around the world (thanks for printing services like eg. 3D Hubs) and being relatively cheap desktop 3D printing has its weakness: limited quality. While in most usual cases it’s not the problem (believe me, for most applications desktop printer quality is just great), in arm exoskeletons is one of main factors responsible for locking and jerky movement. Iteration after iteration it was clearly visible that I wouldn’t design another clone of 3D printed WREX. And it wouldn’t have been even possible…
Always focused on users comfort and fun of wearing supportive exoskeleton I’ve been trying to keep it slick and friendly. That’s why I reduced number of components and screws to minimum. The less screws means other joining methods must be utilized and this is the reason of parts internal complexity (while still maintain external simplicity). Such complex parts couldn’t be 3D printed on desktop printer with required tolerances and surface quality. Keeping above in mind leaded me to the point where whole device was fastened with one metal screw which additionally acts as a tensioner.

At this point it was obvious I had to print them on professional SLS 3D printer. I contacted local manufacturer Sinterit and they agreed to print the parts on their model Lisa.

The quality was perfect. The parts fits incredibly well to each other, to previous resin parts, to bearings and to aluminum pipes. After combining them I saw the proof of concept. They moved freely and almost friction-less, exactly how they should.
  

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