3d printed wheels & treads

For those who have pursued or used 3D printed wheels in the past, what are some tips you may have for a team looking into this? what material works best? (I’d assume Onyx, but lmk if i’m wrong). assuming the printer can, is using things such as continuous fiberglass within the print necessary? Do you use heat set threaded inserts for screws? what is the best method to attach treads to the wheel?

also, as a side question, what’s the best way to mount treads, such as blue nitrile, without having the screw head or rivet head stick out too much?

We made ABS wheels for an 8-wheel west coast drive a few years back, with outside corner wheels at 1" x 4", center wheels 3" wide (going for a hexagonal robot for defensive reasons). Tread was riveted on the same way you would with aluminum wheels, but you couldn’t re-use the same hole twice. We recessed the rivet into the tread by removing some of the tread with a drill bit. I don’t think I would have trusted these wheels to not start failing at the 1/2" hex under the conditions of a typical frc match, which is why they never made it past use one the practice field. One could probably epoxy a 1/2" hex hub made of aluminum into a wheel instead of what we did.

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Team Tators, 2122, showed me their 3d printed wheels at Houston this year. They used 2 cnc cut aluminum discs on the outside to hold it together and for hex axle strength. And they used brass inserts with screws for the tread instead of rivets. They also used these inserts and screws to hold the aluminum plates onto either side. I’ll see if I can find the pic I took. Here it is! image|375x500

Do you know what kind of plastic they used on the wheels.

We made ABS 3D printed wheel hubs for ~9in pneumatic wheels in 2016. We had to use COTS aluminum hex hubs but surprisingly never had any failures despite 2016 being a pretty brutal year for wheels. If i remember correctly we used geometry very similar to Andymark’s HiGrip design. if you want to make the lightest wheel possible you could probably use stronger materials and a more optimized design.

I can’t recall, honestly. I think it was either ABS or PLA+ though.

2767 went down this road for the sake of repeatability in movements in auto. Other than Onyx being used for its excellent mechanical properties in this area, most of the development was in over-molding various durometer compounds as for compliant treads. This took more than a few refinement cycles to dial in. I’ll let someone a little more familiar with the exact process chime in with more details.

Didn’t 2767 since switch to threading into the onyx wheel to attach tread to the onyx wheels instead of the overmold?

Someone from 2767 can correct me if I’m wrong but this is what Cory and I had talked about a couple of times including at IRI where I believe they were running these versions.

Yup, we have some experiments w/ rough top on onyx rims. Really liking the direction of this development though.

For some reason I thought overmolding was in the OP, but I guess I was mistaken.

However, as I am not really involved in this aspect I will let others from the team comment on the specifics.

We did a urethane over mold over an onyx wheel and ran that design through worlds. They looked a lot like a colson. Pre 2019 season we experimented with over mold knobbys also. Can’t say we were happy with their durability so we went back to the tried and true method by putting belting on a wheel.

3" x .75" onyx rim
SBR 2 ply rough top conveyor belting
6-32 x .5 flat head screws screwed directly into the onyx

This picture was taken after IRI and they look pretty much the same after 2 more invitationals.

I’ve heard others having issues with rough top tread but so far we’ve been really happy with this one.

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We’ve used 3D printed wheels for the past two years and have been very happy with the results.
In 2018 we made these 4" diameter wheels to replace some of our existing traction wheels for weight reduction. In 2019, we used these 6" diameter wheels right from the start of the season and they held up pretty well.

Both wheels used eSUN PLA+ filament and were printed with 25% infill and 5x outside perimeters. The only significant wear we observed was the lip of the wheel (that prevents the tread from slipping off), though we concluded this was generally aesthetic damage and didn’t usually merit replacing the wheel. Fully assembled, both wheels were lighter than their VEX and AndyMark counterparts (which is what they were replacing for us). The effective cost for each wheel was <$5.

We used standard Blue Nitrile traction tread, attached with screws and lock nuts (one of the benefits of our wheel design is it allows for the easy use of locknuts with the included holes and “slots”). I don’t personally recommend using pop-rivets for attaching tread to 3D printed wheels as it tends to cause layer separation.

@GalactechGoat Check this out!

A trick I’ve heard (pretty sure from Allen Gregory) is to use McM 9063T33 to step up to .75" hex in the wheel to resist stripping.

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Ewww. @Mark_Wasserman your modules are covered with grime and are disgusting. #dirtyswerve

:smirk:

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Whenever we have had printed pulleys on 3/8" hex shaft, we have pressed a 3/8"-1/2" hex adapter into them so they are less likely to strip. This sounds like a similar practice for a drive wheel that we would take if we printed a alive axle wheel.

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To the OP,

Onyx wheel.
Carbon fiber around the hex shaft area for hoop strength.
Carbon fiber around the spokes.
All screws are tapped directly into the onyx, no inserts. This includes the screws that hold on the gear. Good practice is at least a 3:1 length to dia ratio even then the threads are weak and tend to cold flow after a while

Gut feel, if the wheel is less than 4" and not too narrow and you’re smart on your spoke geometry (wide spokes, wide hub) I don’t think the continuous fiber is necessary. No proof, just gut.

How were they screwed into the Onyx? Did you print the threading? Tap into the Onyx? Use a self-threading screw?

How is the .75" hex secured in the wheel? Or is it just used as a spacer, and floated between shaft collars/retaining clips?

Thanks!

Do the threads on your wheels ever wear out? I’m surprised a bit that tapping it works well over time.

We ran PETG 3D printed wheels on our offseason swerve. As the kids say, it was “super gucci.” Print those puppies at 40% gyroid infill and you’ve got a wheel stronger than my morning coffee. We use a bolt pattern to affix a bevel gear, and so far, we haven’t seen any significant deformation or failure.

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