Testing 3D Printed Worm Gears

Worm gears are great if you have a low-speed, high-torque application in which you don’t need to backdrive. [Let’s Print] decided to see if they could print their own worm gear drives that would actually be usable in practice. The testing is enlightening for anyone looking to use 3D printed gearsets. (Video, embedded below.)

The testing involved printing worm gears on an FDM machine, in a variety of positions on the print bed in order to determine the impact of layer orientations on performance. Materials used were ABS, PLA and PETG. Testing conditions involved running a paired worm gear and worm wheel at various rotational speeds to determine if the plastic parts would heat up or otherwise fail when running.

The major upshot of the testing was that, unlubricated, gears in each material failed in under two minutes at 8,000 RPM. However, with adequate lubrication from a plastic-safe grease, each gearset was able to run for over ten minutes at 12,000 RPM. This makes sense, given the high friction typical in worm gear designs. However, it does bear noting that there was little to no load placed on the gear train. We’d love to see the testing done again with the drive doing some real work.

It also bears noting that worm drives typically don’t run at 12,000 RPM, but hey – it’s actually quite fun to watch. We’ve featured some 3D printed gearboxes before too, pulling off some impressive feats. Video after the break.

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7000 RPM On A 3D-Printed Gearbox

[Steven] at the 3D Printer Academy has been working on a variety of different gear designs. He recently embarked on a series of experiments to see how fast he can spin a 3D-printed gearbox.

After testing several kinds of gear teeth, gear diameters, and gear spacing, he finally struck upon an 81:1 ratio gearbox. It has six gears: five stepped gears and one drive gear on the input shaft. First tests are accomplished with a 3D-printed handle, similar to a hand crank used to start really old cars. But unlike those cranks, [Steven]’s doesn’t have any release provision. While the handle can be removed, it can’t be removed while spinning.

We think it would be helpful to revise the drive shaft coupling method, allowing the handle or drill to be easily removed from the gearbox once it’s attained speed. This would be more convenient, and it seems prudent from the workbench safety point of view as well.

Example of a crank quick release mechanism

[Steven] manages to get the final gear spinning at 7000 RPM in video #2 of the series by hand cranking it “as fast as he can”, a speed measured by using the metronome app on his smartphone. He begins driving the gearbox with an electric drill in video #3, with some mixed but promising results. We think he will ultimately succeed in his goal of a high-speed, electric-drill-driven gearbox after a few more tests. If you want to have a go at this yourself, the design files are posted online.

How fast do you think he can eventually get this gearbox spinning? Are there any physical limitations of the assembly or due to the 3D printing materials/process? We certainly know that high torque can tear 3D-printed gearboxes apart, but how does the speed affect things? Let us know in the comments below.

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Express Your Love With Candy And Engineering

Still don’t have anything for Valentine’s Day? We wholeheartedly suggest that you fire up that printer and get ready to fall in love with engineering all over again, because [JBV Creative] has designed a super-sweet piece of machinery that would turn the gears of anyone’s heart. He calls this the most overly-engineered candy dispenser ever, and we have to agree. It’s certainly one of the most beautiful we’ve ever seen.

There’s no electronics at all in this elegant design, just purely mechanical, hand-cranked fun. Turning the crank does two things at once — it moves a little access panel back and forth underneath the chute that governs the number of candies given, and at the same time, moves the conveyor belt along to deliver the goods to the receiving area.

This entire design is absolute genius, especially the decoupling mechanism that shuts off the flow of candy but allows the belt to keep moving. Be sure to watch the build video where [JBV Creative] effortlessly snap-fits the machine together without a single tool, and stay for the follow-up video where he discusses the engineering challenges and shows just how much work went into it.

Of course, there’s more than one way to overly-engineer a candy dispenser. Here’s one that finds the holy grail of peanut M&Ms — the ones that didn’t get a peanut.

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