Why I will never again use 3D printed pulleys

Although at first using a 3D printer pulley sounded like a good idea to me, considering many pulleys are made out of thermoplastics like ABS and Nylon, I was under the misguided conception that these parts would conform to the tolerance and temperature standards of an electric skateboard. After 5 to 10 minutes of riding, the pulley had been absolutely destroyed, resulting in something that looks like this:

Now, I’m not bashing @JuniorPotato93, being the grandmaster of 3D pulley design, but it does raise some serious considerations when building a board, along with the potential riding dangers, seeing as how this occurred while riding down the street at 30 mph. I looked down while riding to find a melted pulley which was hot to the touch and significantly pliable. I would have dismissed this most likely if the board had continued to function, but it took only 30 seconds more for the second pulley to melt and get pulled off as well. For this reason, I don’t see the benefit of using a 3D printer to make a pulley for an electric skateboard, or for any high-speed application for that matter.

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What type of plastic did you use to print the spur? I have printed my own custom modeled spur with the help of an scad template creator. It allows the teeth to be customized with a decimal value to ensure a perfect fit. Took me about 3 printed spurs to get the shape just right. I had one PLA printed spur that delaminated probably from a rock jamming it. Yours looks like it melted apart, so the fit was probably not proper causing excess friction and failure. I printed mine in PETG and it has held up 50 miles so far. It is all about fine tuning the tooth profile to fit.

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It was printed using PLA, the other using PETG, I was interested in testing the difference between the two, unfortunately, it seems that it was a friction problem, enough so that the belt actually felt HOT, which was very concerning. I ordered metal gears for the wheels which should improve the durability, I believe that 3D printed mounts can be durable, considering 3D printed polycarbonate can be shot out of a shotgun and it seems to hold up pretty well, it’s the tolerance issues that resulted in my near 30mph accident, when the pulley got ripped out. That being said, I still believe that 3D printed pulleys work better as a temporary solution rather than a finished product.

There’s something wrong with your system. It should not run that hot. If there is that much friction, switching to metal pulleys won’t help. Your belt will fail next. You need to fix whatever is causing the extra friction


Has anyone tried 3D printing with tough resin from formlabs? I just made some I believe I used junior potatoes design off of thingiverse I have not tried with my weight on them yet but they seem very promising I just spun the motor with them attached.

Just a pic of the setup not the pulleys

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I determined the problem was that that pulley was getting rubbed against the edge of a screw, a problem which I fixed by sanding down the edge of the pulley, but I guess the while the board was under load, it managed to brush up against the screw and create some heat, although I can not be assured that the metal mount will work better, the smaller gear on the metal pulley should prevent it from creating friction.

If the belt feels hot, it means either it is rubbing on something, or the belt/tooth mesh is poor. It could also be too high of a tension. On my $200 poor teenager board, I run barely any tension at all on a htd5m 15mm belt and I never get any skips. If I run more tension, everything gets this “bind” feeling and the belt gets to about 150f no load. If you want higher tolerances, print slower. With gears especially, you have to print very slow, about 25mm/s or under for most printers unless it’s one of those super speed deltas. Any faster with my setup, and the teeth started looking really bad.

I have a smaller resin printer which is designed for making small parts around 5 cm in diameter, but this is definitely something I’d love to try… Maybe it’s time to invest in an SLA. I would imagine the UV cure properties allow it to hold up to better temperatures, along with the better tolerances and layer adhesion. Very cool. Let me know how it goes.

I will make sure to let you know if it’s worth it or not.

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The gear was printed on a well tuned Makerbot which I ran calibration on before I printed. It’s definately friction created by the screw, but my point isn’t the source of the heat, rather the stability of the gear at high speed and how easily they melted.

Regarding your bind issue, THAT sounds concerning to me, have you figured out the source of it? The belt should spin freely both directions, especially a tight belt.

Nylon is the way to go. Also, aside from the screw rubbing. Having your belts too tight will cause over heating as well.


I’ve got some nylon kicking around in the back shelf, my main concern with nylon is that it absorbs water from the air which can cause some issues while printing. Some people like to stick the spool of filament in the oven to help dry it out a little, but I prefer not to put my plastics where my food goes. For now, I just keep it in a bag with some silica gel which hopefully will keep it pretty dried out. In the future, I’d be interested in doing a comparison of different materials for 3D printing pulleys if anyone would be interested I would be happy to throw together a video or something, and I’ll post my settings for those interested.

While that’s logical, I also would think that a loose belt is also capable of skipping and creating fiction on the teeth as well, I think it’s about finding the neutral zone where it works just right.

Not really sure, as of now I am not even going to bother checking because like I said, I have had no belt slippage before. There is sort of a relationship between the torque deliverable, width of the belt, and tension that I have found. With a wider belt, you need more tension in general which is more frictional loss but it has a higher capability. I have a relatively low powered board so I don’t really need a 15mm wide belt anyways, so I am able to run it on such a low tension with no issues at all.

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What’s your top speed?

If it’s 10+ mph I just don’t understand how you can experience zero slippage while riding using a loose belt, but I guess if it ain’t broke then don’t fix it. Lol

My belt slips sometimes even when it’s on tight.

I have, been about two weeks on this pulley. Previously I was using PCmax filament by polymaker printed on an ultimaker. They lasted a several months. I expect these to last longer as there is no delamination issues and the tooth profile is much more precise.

Also I would never us PLA for a pulley, it gets soft at too low of a temp. Minimum is ABS in my opinion.


That is awesome, are those made on a formlabs as well? Now I need to try one of these bad boys!

Yeah on a form 2. Print time was about 8 hours per piece though. Plus cleaning and post curing in a UV oven.

My top speed with my 12t pulley 31t printed spur is about 17mph flat ground. I am soon switching it out for a 10t but the chinese seller took 2 weeks to package it due to a chinese boat parade :frowning: 5mm pitch 15mm wide is pretty overkill and yeah somehow I get no slipping. The belt is loose enough to be able to slide on the pinion with no effort.

Word ok. If you modify the pulley and try a tighter belt let me know how that affects the riding. Very interesting.