Now it is the photos time:
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| sun gear and bearing pressed onto the pin |
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| I know the surface of the motor is sloppy it was done by hand, will fix it next time ;p |
This part is the rotor extension so that I can press-fit a gear on it. The diameter step on the tip of the part is for bearing. It was milled from a 20mm PA6 aluminum cylinder.
Each 70mm cylinder slice was faced in order to get a flat reference point. Actually the one on the picture was earlier faced in the vice from other side, and this photo was made after facing from top side.
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| I mostly used screws to fix the material to the table, as it was the fastest way considering I do not own any good claps yet. |
This is the lower part with PCB cap and stator press-fitted onto the cylinder. Now it is time for the distancing cylinder:
This was the part that required the most coolant as it is relatively thin and a lot of material has to be removed around it. I did not noticed any problems caused by overheating whatsoever.
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| Probing the gearbox mount |
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| though the endmill was a bit to big it looks nice and fits tightly! |
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| lower planet carrier with additional sleeve for bearing ring |
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| gearbox mount, top planet carrier, lower planet carrier ready to be assembled |
And after milling the parts it was the time for assembling them:
I'm really happy with the result, considering it was machined on a low cost DIY CNC machine. Of course it works - for now only in spring/damper mode (and open loop d/q voltages mode), but I'm working on a FDCAN communication app and more features right now. Hope you enjoyed it, and see you next time.
I recently started documenting my projects on Instagram, so feel free to check it out: https://www.instagram.com/klonyyy/
This is encouraging. I’ve been developing a very similar module, except I have not reached a phase where I can machine anything yet, it’s all 3D printed, however a lot of vitamins are used to minimize the mechanical reliance on any plastic parts. Where did you source your gears?
ReplyDeleteThe gears come from a cordless drill, however, as expected, they have a fair amount of play. I plan to take advantage of the fact that the gearbox can be easily replaced and make a small gear ratio cycloidal reducer keeping the external gearbox dimensions.
DeleteNice!! I actually almost went that route! I even have a couple bins still sitting around somewhere with disassembled gearboxes from a couple different cheap drills but I ended up using 3d printed gears instead so that I could hit the ratio I was looking for, and while they aren’t as durable they seem to be holding up just fine for now. (Bearings inside each planet) Very interesting to me that your design looks similar to mine. How did you go about chopping down the ring gear, or was the drill in question only one stage? I’ll share a link once I get my blog in order it’s been a project of neglect lately :)
DeleteThe ring gear comes from the first stage of the drill gearbox, and it fits my design surprisingly well - it has 4 tabs that can be used to lock it in place and did not require chopping as it is like 4mm high :)
DeleteInteresting. So wait, your gearboxes had separated ring gears? What type of drill were they from? I just ended up with a lot of them pulled from “drill master” which I believe is a harbor freight drill, but they look identical to the wal mart drill gearboxes, in that both stages of the rings are one piece fused together.. you’ve inspired me to upgrade my gearboxes eventually though, as I’m not quite sure how long these nylon printed gears will hold up. Still haven’t gotten around to getting my blog up but will shoot you a link ASAP. It’s seriously oddly similar to your situation, sans the custom motor controller.
DeleteYeah the ring gear was a completely separate part with these additional tabs to hold it in the plastic case without rotating. In the second gearbox (single speed - the ones I use are double speed - I only make use of the first stage though) there was indeed a single long piece of internal gear and two stages were using it. I guess it depends on the manufacturer and if it is a single or double speed (in double speed there is a special "clutch" mechanism for changing the gear ratio, so a single long internal gear would probably not fit in there).
DeleteInteresting. I’m doing a side build of an actuator using both stages of the gearboxes I have on hand since these are somehow 9:1, across both which is closer to the 12:1 ratio my robot is currently fitted with. Thanks for reigniting my original plan, haha! One more question, how exactly did you go about pressing the steel pinion gear to the aluminum output flange on the motor? I keep reading that alu will react to steel in certain conditions when they are joined, but I’m doubtful in this application since salt normally plays a huge role in those situations. Curious what you did there and how well has it held up?
ReplyDeleteHi! Fixing the pinion gear to the aluminium flange is actually a subject for another writeup - I'm going to post it soon ;) For now I can say that this slight press-fit with epoxy method was not enough as the gear used to slip under heavy load.
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