2018/2019 Printed Parts - PLA, ABS, Nylon, PETG

In the works right now

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Gearbox and wheel holder
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Planetary in a wheel
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Double Rack with 2 pinions.

Stls etc for the new stuff on request as for now that new stuff is untested and fresh of the printer More as it will be developed and check the youtube channel (search for Martin Pirringer)

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How did printing the robot work out for you? what material and printer did you use etc. We (team 1989) are in the process of doing that and would like to know what to watch out for

Nice herringbone gears! How did you generate the tooth pattern on the pinions: did you just mirror a standard helical gear?

The hatch claws that we used for our hatch intake for our first two events were printed out of TPU. (We switched to a wheeled hatch-intake design for DCMP and CMP)

Our robot radio case was also printed out of TPU.

First we design a true involute helical gear and then mirror it

As our school uses inventor this is what we use. I gave some team members a what you could call “extra credit” Team 1989 homework to figure out to do a true involute herring bone bevel gear set in inventor. Will see what they come up with after the AP tests and finals are over

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Not sure if this is the type of thing you are looking for, but we used mostly printed swerve drives this year.

We used all PLA on a makerbot rep+, Taz 4, and Kossel mini… Nothing special. Your Prusa will be more than adequate if you can design well enough (to an extent, you need a markforged to do crazy 2471 stuff).
In our adventures in printing crucial mechanisms, we’ve picked up a few guidelines

  • Reinforce any crucial part with aluminum or threaded rod (although you can get away with more if you aren’t using PLA
  • Make sure to keep large parts inside frame perimeter (Even within bumper perimeter, things get hit)
  • Things will break, so make sure the part that breaks is easily reparable (fuse parts)
  • Don’t print massive parts, it’s not worth it. Could this part be split in to more smaller parts?
  • Don’t forget about the grain of the print, planes of weakness are your first design consideration
  • Will 3d printing be lighter than Lexan/Plexi/Coroplast? for long, linear parts it can be better/cheaper, and a jigsaw and drill press do an ok enough job
  • Can the part you want to print be made strong enough? Some parts can’t be printed (mainly elevator stuff, so y’all should be good next year)
  • This is more of a fun design tip, but sink 3/8 hex bores to capture nylocks, it makes assembly a breeze!

Above all else, don’t be afraid to iterate.
There’s no shame in taking another run at it. It took 14 revisions (full re-prints) to get to our hatch gripper this year. 3d printing makes it easy to iterate, so iterate. Four hours of print time seems like nothing when a part breaking mid-match ends your season.

You seem to have the design part down, good luck Martin and 1989! I can’t wait to see what you come up with!

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thanks - we do a lot of that and we are trying to standardize parts like for the frame etc. And we are trying to elevator too with a rack and pinion setup. As for Markforged - well out of our price range

Keep us updated on the elevator, I’d love to see a partially printed elevator! We used more printed parts in our 2019 elevator (2018 had a double climb, so it needed to be very robust), but our moving parts were mostly aluminum… :cry:

Something you might find helpful is our gusset sandwich from our elevator (we build everything out of 1" square stock). We used a printed spacer in between two gussets, but looking back, we could’ve put spacers around a single gusset. This uses the sunk nut process I described earlier


We laser cut the gusset, but I’m sure there’s acceptable COTS gussets out there.

If Markforged is out of the question (Heaven knows it is for us…), enforcement is the way to go, and after your posts on the rack, I’m fairly certain I don’t need to give too many pointers :laughing:

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Regarding 3D printed elevators, I know 179 used 3D printed PETG 254-style bearing blocks when I saw their bot at champs. They seemed to hold up fairly well, despite their aggressive driving.

Also regarding 3D printed elevators, we printed all the blue pieces in the bearing blocks here for our prototype’s elevator. The only other pieces were 1/4"-20 bolts, 3/16" rivets, and R4 bearings. We didn’t break any of the blocks, even when we tipped over once going off level 2.

The other bearings in the slots are for running the belt through the 2x1 for powering the elevator

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Thanks - interesting - we will definitely keep everyone updated. We just got a bunch of CIM Motors from 1533 (THANK YOU) so we are going to redesign the elevator to take a CIM The rack and pinion are strong enough so far and quite impact resistent as one of our mentors proved when trying to insert the 1/2 in square aluminum stock to Join multiple racks together

This is the rack and pinion

Its a herring bone double rack to cancel out deflection forces so the only deflection you get is on the shaft that holds the pinions. The gear pair below the rack mesh so that torque goes to both sides of the rack evenly There is another pair about 6 in down the rackand a gear that will be connecting them between that gear will be the output of the gear box that is driven by the CIM probably somewhere in the Neighborhood of 20 to 50 to one most likely a compound planetary. This is what we had 3d printed on our robot this year. The rack and pinion setup worked once. we did not get it finished until about the middle of our 2nd competition and in our first test we misdeploid and a team member tried to help us by crashing full speed into them. That is the reason why its being replaced with a bigger stronger one. This one has a 1.840 mm pitch with a 14.5 deg pressure angle and a 30 deg helix and has the support in the middle between the 2 racks. The help from our team mate not only broke the racks but also the hex aluminum shafts mounted in support. Anyway here is a short video of what we used this year and where we are going

I wanted to revive this again as the summer is almost over and we are getting back into the swing of things. DId anyone have cool 3D printing projects over the summer? Any updates to existing projects @mpirringer?

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Bumble Bot is coming along

The scateboard version drove at the sussex county fair. and is in the progress in getting an elevator/climber we intend to use it in an off season competition in November


These are the unassembled parts for a 70:1 gearbox its a planetary inside a harmonic gearbox where the planetary takes up the role of the elliptical bearing
Here are some pictures of it partially assembled.


There are still a couple of problems with it like right now I am reprinting the sun as its supposed to be a very tight fit on the cim shaft and key and the current one is so “tight” it does not go on (too small) We are also looking for a better way to assemble it as putting the motor on has to be dead on aligned. We also started design and print on a robot we will use as a display/test platform for all kinds of ideas non FRC style optimized for cool looks to maybe roam the pits and events and being used at presentations. Smokey ran into some programming/electronics problems that are being worked on and we got about 300-500 bucks to build a CNC it s going to be inspired by the MPCNC (Mostly 3d printed CNC) and we are shooting for 36x36 in on it. And some of our freshmen are working on sticking a gearbox inside a wheel so there hopefully will be some things to report soon. The harmo-planetary is work in progress and no one knows if its going to work so I was hesitant posting about it before. What you see is actually prototype 2.0 as 1.0 - well all it did was tell us to make 2.0 (Flexor was to stiff and thick and the toothcount of the flexor and stator was too close and the direction of the herring bone of the inside of the flexor was facing the wrong way and was causing structural problems - so not worth showing. This one works when turned by hand, runs smothly so there is hope …

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@mpirringer, your team’s 3D printing experimentation is amazing! Thanks for sharing. I’m really interested in the rack & pinion actuator shared in the past. A design like that, with modular rack gear elements to allow for whatever actuation distance is needed, would be a great option to have on hand. For many purposes, pneumatics will be simpler, but a scalable rack & pinion would be great when the positional flexibility and precision of a controlled motor solution are required.

-+IDK which one I posted but we designed a heavier one than the one we had last year and will use it as a climber on bumblebot.

And here is one of our teachers “testing” it for durability

The rack survived even though it was found to not be usable due to a calculation error. The engineer in training took the numbers from the gear generator in inventor and did not realize that they were based on diameter and for the rack you need radius so she did not divide by 2 and it made it all the way through 3DP and the error was discovered when the gears did not mesh and fit due to the profile being off (2x to tall) So redesign - reprint

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This seems to be an appropriate place to (re)post this. Not sure about the practicality of this mechanism in an FRC environment and I have yet to test at speed or for torque. This project was my own and done on my home printer, I am working to introduce more things like this to my team as we’re soon acquiring a Markforged printer.

My closest to a finished project, the one I have the best grasp on is a 50:1 cyclo speed reducer that I was able to simulate (new to me) , 3D print, and assemble. I have yet to test it under load but I am working on plans to set that up.

Lesson learned on this one, I had to measure the OD and ID of the pin pattern, resize and reprint the main “gears”.

I’m also introducing bearing races into my design work. This is the outer race of an angular contact bearing set (one on each hub) with the principles of a gothic/2 point contact geometry built-in.

I’m also using this project to introduce heat-set inserts into my printable designs. This hub features the ‘standard’ 1.875" bolt pattern found on most FRC COTS hubs. I made the mistake of freehanding the first one and let the inserts cause protrusions on the OD that I then had to sand back down. The second hub I wrapped in Kapton tape (high heat polyamide?) and the inserts went in “flawlessly”.

The other patent that piqued my interest was for an internally self-recirculating, ball driven, double enveloping (globoid) worm. I only have the model of the worm and the wheel (gear) on this one and I am currently running into walls for how to print this without supports. I’ll likely split it into two halves and use pins and a chemical weld for PETG (if they make one?) to put the two halves together. I’m not sure how applicable it would ever be to FRC use but I thought it to be cool as hell and something I could scale to FRC size regardless. It uses two technologies that I am familiar with at work as well which is always a nice connection (we use ‘Cone-Drive’ products in a few of our machine axes and we have/had a patent on the Internal Return Ball Nut).

Four-point contact on a gothic arch profile

Internal return, self-circulating path

1/2" hex for scale

That is all for now, I likely won’t advance much further with either project at this point in the summer. I usually feel the need to scratch that mechanical itch in short bursts and I think I’m all out for now. Perhaps I go back and finish one of the other 100 projects I started in the last few years. Maybe something with an artistic flourish, like finishing and painting this.

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Here is the camera mount we used on this year’s robot. It attached to a 7/8" round tube that was mounted on our carriage. It allowed us to get the right height for the camera above our intake and below our limelight.

https://grabcad.com/library/spectrum-elp-usb-camera-mount-1

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