Simple Toy Robot Arm 5DoF

myminifactory

I've been wanting to create a fully actuated robot arm using print-in-place techniques for a while. Here is the first stage, a simple toy knocked up real quick like. If you are interested in these elbow joints I am starting to tidy up the code. There's also an updated version. In future I'd like to progress to an improved version with elbow mounted pancake motors or similar leading onto a more precise version incorporating some kind of bearings (preferably common 608 type) and an anti-backlash mechanism (eg. spring). At least this will give the kids something to play with as I iterate the design. Not a terribly demanding print but you do need to have your tolerances dialled in. I advise printing the gears as tight as they can be while still separating cleanly. Perhaps try a clearance gauge or printing just the grip alone as a test piece. Another tip for checking tolerances is to submerge it below the build plate (move it in the negative Z direction) for quick partial prints. Tweak flow rate, temperature or horizontal expansion to fine tune. I print this on a stock standard Ender3 with the corresponding profile that comes with Cura just fine without any such tweaks. Similar to my previous gearbox designs, print at 0.2mm layer height and ensure there is a 1-layer gap in the ring gears after slicing. Use a sharpened spatula, razor or hobby knife to de-laminate the 1-layer gaps (watch fingers and listen for the "crack"), then turn the knob just a little to get the gears moving (these knobs are a little small, a 14mm socket might give a bit more leverage) taking care not to break the knob off, once you see a little movement, work it back and forth gently rather than apply more force. Now "crack" the jaws apart manually by back-driving by a few mm (there should be a little backlash) or give the elbow a tap with a rubber mallet. Now all the parts are free, it will be a bit stiff at first but opening and closing a few times will loosen it up. Then apply petroleum jelly or lubricant of choice to gears and work it in (again by opening and closing a few times).