We are a low budget team and i was wondering if 3d printing gearboxes would be viable with a strong filament like pa-cf. Parts like gears, shafts etc.
3d printing gearbox plates and housings is very viable and something weāve done for many years. Gears and shafts need to be metal though, or theyāll fail almost immediately in anything actually transmitting torque.
We tested 3d printed gears in a drivetrain many years ago and they literally lasted less than a minute.
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Agreed, wouldnāt expect that to work. But we have seen more and more teams adopt printed double-herringbone gears for things like intakes. Even PETG or PLA, with the right print settings, could get acceptable performance there. (Even if you had to change them once a day for whatever reason, thatās not that wild of a maintenance item.)
One resource a lot of teams ignore is that pile of AndyMark ToughBox parts lying around a lot of shops (or your neighborās shop). It may not be the most space-optimized or weight-optimized solution to use big steel gears in a gearbox, but if you canāt make a working gearbox out of those parts you probably need to stop and take in some fundamentals before throwing a ton of money at additional parts.
Iāve been mentioning Slant 3D on YouTube a fair bit lately. Theyāre a print farm growing a print-on-demand service and theyāre happy to remind you of that, but they do share a lot of tips that increase printability or make for better parts. Well worth a view.
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If you were going to print stuff for your robot I would recommend using them for proto typing or mounting things. And if you were to use them for just that I would recommend the bambu a1 with a .4 mm harden steel nozzle and some pla-cf.
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It can be, again as said above filament choice and the purpose of the gearing are the biggest factors. Is it a low torque application where thereās less strain on the teeth of the gear? Is it part of a planetary gearbox, if so itās spreading the force onto several gears. It all depends on how and where you use the gears.
Additionally the number of walls used for the print will greatly affect the strength around the perimeter and the outside edges of each tooth adding strength.
Final consideration is speed and friction. Gearboxes need grease to reduce friction, and greasing plastic gears and making them last long term is tough. They will delaminate, little bits can break off or at high temperature it can warp/melt so make sure they have adequate spacers at any rub points.
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Just a heads up, PLA-CF absolutely sucks for almost every application. CF is usually added for a decent stiffness increase and a mild increase in overall strength. With PLA already being incredible stiff/brittle you are going to be way better off with a reputable PLA+. PLA-CFās strength is a marginal increase from plain PLA.
There is virtually no use in FRC where PLA-CF would be any better than PLA, especially in gearboxes where abrasion is something to be avoided.
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Weāve had moderate to good success with 3D printed Belt Pulleys for intakes in the past. Allowed us to use some of the massive pile of random size belts we had lying around. These were low to medium speed, low torque applications and even the PLA ones we first made did āokā. (They break easily on impact tho.)
Eventually we moved them to PC-CF and even went as far as to take the spare we printed (and never needed) and let people hit it with a hammer at outreach events. The PC-CF ones were massive improvements to PLA, but require the correct setup to print.
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For a drive system, Iād personally be willing to consider printing gearbox housings (though I would probably print these with solid infill), and we have had good success with printing a variety of drive wheels before too. As otherās have pointed out though, I would strongly avoid drive gears or shafts, these are not applications for any kind of plastic, let alone 3D printed plastic.
That said, for lighter-duty or low-torque applications, there are all kinds of things you can use 3D printing for. Iāve seen lots of teams print gears for intakes, shooters, and other mechanisms. As long as you donāt need anything too detailed (weāve had limited success printing gears smaller than 20DP or pulleys smaller than 5mm HTD for instance), thereās a fair amount you can get away with, with the right print settings. A key thing to remember here is increasing the number of perimeters is a great way to add strength to a part like a gear, and if you need to, you can always print it solid.
A few years ago we had an adjustable-hood ball shooter that was almost entirely 3D printed, and it worked great for us. Building a more traditional aluminum/polycarbonate shooter would have taken much more design effort and manufacturing complexity, and buying an off the shelf solution can be quite expensive. Plus, 3D printing the mechanism allowed for easy iteration on the design throughout the season.
We use eSUN PLA+ for basically all of our printing, with a handful of parts being made on our Markforge with Carbon Fiber Nylon. Weāve tried printing with Polycarbonate filament too, but these parts often come out too brittle for practical uses.
I cannot say enough good things about this.
Using the MkCAD generator in OnShape to make custom pulley sizes, then exporting the STL for printing easy peasy. Itās the closest thing to having a Star Trek replicator for FRC as I can find.
Our main āconveyor/feedingā system was driven by a metal gearbox on bottom for the intake, tied to the first 3Dp pulleys along the chain of 4. This brought the notes up to the shooter and we could index it properly to let the shooter get to the correct RPM.
We learned during testing to leave space between the pulley nubs and the plexi glass side panels. They would melt together after enough run time without a break
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Iām going to put my standard plug in for Ninjatek Armadillo. Itās strong and abrasion-resistant. Yes, itās a TPU, but with a 75D hardness, its rigidity is on par with PETG and PLA. One downside is that it really, really, really sticks to itself ā you cannot use it for support, because youāll never be able to detach the support.
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The only problem with custom pulleys weāve encountered is that our printers tend to under-size them, which can make the fit problematic and result in increased resistance and/or belt skipping. Our Markforge definitely handles it better than our other printers (it tends to be more dimensionally accurate in general), but itās still a problem to be aware of and something that youāll probably have to calibrate differently depending on your printer.
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I guess it depends on the load and speed. Iāve seen planetary gearboxes with PET-CF on YouTube.
On our Off Season Bot, we used tons of 3D printed PLA+ Pulleys for our Shooter and its been working great.
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Calibrate and if itās slightly undersized or very tight you could run a hex broach through it to clean the first wall layer lines up. We did that when we didnt have time to reprint, a students home printer made spares were better than nothing.
Still better to get it right to begin with. Donāt expect a perfect fit first time through.
Would you all recomend just PLA+ for most applications on the printer? Our team is going to be ordering some filament soon so itād be nice to know if thereās any other materials that might work better, or if thereās some we might not use all the time but might want to have on hand for the ocassional thing.
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These are gold. Use these to keep the hex from rounding out.
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To be clear, Iām not referring to the hex being undersized, but rather the pulley itself being undersized due to material shrinkage which affects the spacing of the teeth. When printing gears, if the material shrinks, it just results in a slightly larger gap between gears, but when pulleys shrink it throws off the teeth mesh of the belts and can cause a bunch of issues.
PLA+ (or equivalent, it sometimes goes by āPro PLAā or other similar names) is by far the most versatile, easy to use filament on the market right now, and it has enough strength for many FRC applications. If you have to pick one material, I would definitely start with PLA+.
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Agree, during the start of 2024 season prototyping was ten times faster and more effective, due to how quickly they were to make.
The main places we used fully 3D printed pulleys were on the intake and storage, only downside of them were the fact that in the intake due to the speed eventually replacements were needed but over all they work pretty great and last quite a while if printed with the right settings.
Side note; always make sure to leav space between rapidly moving 3D printed parts and surfaces since they belt and get stuck.
I think a lot of people are making overly broad and incorrect statements about what you can do with 3D printing because of bad experiences due to poor designs. Shafts are not a good use due to expected cross sectional areas, but geartrains are well within the realm of printing. You can even create high torque capable gears with appropriate material selection and more importantly sizing. Plastic simply requires substantially larger and wider teeth for the same use cases as metal. There is no inherent limitation with plastic except for volumetric constraints in your robot.
It also opens some interesting possibilities without adding manufacturing difficulties, such as TPU gears that deform and slip under hard impacts to limit damage (like a built-in clutch), nautilus gears, single piece geared assemblies, etc.
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Some of these never Overture PLA filaments are pretty phenomenal as well