When it comes to making gearboxes, 3D printing has the benefit that it lets you whip up whatever strange gears you might need without a whole lot of hunting around at obscure gear suppliers. This is particularly good for those outside the limited radius served by McMaster Carr. When it came to 3D printed gears though, [Michael Rechtin] wondered whether PLA or resin-printed gears performed better, and decided to investigate.
The subject of the test is a 3D-printed compound planetary gearbox, designed for a NEMA-17 motor with an 80:1 reduction. The FDM printer was a Creality CR10S, while the Creality LD02-H was on resin duty.
The assembled gearboxes were tested by using a 100 mm arm to press against a 20 kg load cell so that their performance could be measured accurately. By multiplying the force applied to the load cell by the length of the arm, the torque output from the gearbox can be calculated. A rig was set up with each gearbox pushing on the load cell in turn, with a closed-loop controller ensuring the gearbox is loaded up to the stall torque of the stepper motor before letting the other motor take over.
The resin gearbox failed relatively quickly, and dissection indicated some of the internal gears had failed. A reprint with stronger resin was done, and the test begun again. This time, each gearbox lasted over 500 cycles without issues, but the resin gearbox failed shortly after, wiggling about before jamming up for good. Opening the gearbox led to broken teeth and powdered resin falling out. Meanwhile, the PLA gearbox showed very little wear despite the repetitive test.
Thus, if you’re looking to put serious loads through your 3D printed gearbox, you probably want to go with PLA or another FDM material rather than resin. This result is unsurprising, as a general rule of thumb is that resin prints are more brittle than their FDM counterparts. Of course, the exact plastic or resin you print with will vary this result however, so don’t take it as a hard-and-fast rule, more of a general guide. Video after the break.
[Thanks to Zane Atkins for the tip!]