3D Printed Parts on an FRC Robot?

[Why_A_Username?]

Hey CD,

when I first started on my team, one of the many things that fascinated me was 3D Printing. The concept of additive manufacturing opens up a world of new possibilities for designing and creating intricate parts, but are they useful in FRC?

I would argue yes (though that may be somewhat biased, as I own a 3D Printer), but I've heard many argue against it. my reasons for why it's useful are as follows (In Relation to Fused-Deposition Modeling only):

1. In recent years, material choice has expanded hugely, ballooning from just PLA and ABS, to HTPLA, Carbon Fibre, Flexible materials, HIPS, Nylon, PETG, metal fill... etc.

2. People often assume that 3D printed parts are too weak or too brittle. largely this is a myth sprouting from basic PLAs which are extremely brittle. Nylon, ABS, and PETG are all viable alternatives which are much stronger and more shock-resistant.

3. 3D Printed parts offer shorter wait times than ordering parts from online retailers

4. printed parts are easily replaced when broken because they can be inexpensively replaced, and custom parts can be made easily, often in a shorter time period than if they were manufactured conventionally.

5. they can be used as quick and dirty spare parts in the event that an ordered part fails. (Team 2910 had several Rhino Track Pulleys printed out in case we had parts break during competition)

Obviously, I'm not advocating for printing things like motor mounts and chassis components, which are subject to incredibly high stresses during the game. But in the case of things such as custom sensor mounts, passive gears , and other relatively low stress positions, like turret ring-gears, printed parts can often be the way to go.

I'd love to hear your thoughts on printing parts, both for and against. My biggest issue on the subject is the 3D printing Phobia I see in many FIRST teams. I believe it has its uses and, when an option, should be exploited as a cheap and fast method of production.

[guniv]

Team 3824 in our region prints their entire chassis. Oak Ridge National Laboratories has been sort of a pioneer in large scale additive manufacturing, and 3824 gets to work out of their facility with a lot of mentor support. You can read about them in the book that came with kickoff kits last year (Behind the Design). Here's a video of them printing in 2014: https://www.youtube.com/watch?v=dvLxsRnA0Y0

[MailmanDelivers]

We [The LigerBots] love 3D Printed Parts! I've attached a document that describes most of our 3D Printed Parts from last year.

The file looks a little odd when opened it word as it is made from google docs.

If you have any questions I'd be happy to answer.

[BrendanB]

Spacers are a good part to use a printer for. Its nice for some of the more arbitrary sizes you need based on CAD files to just hit print and have a ton made consistently.

This year we printed a ton of 1/2" hex spacers in 1/8th increments. We had a box full and it made last minute additions and testing pain free.

We also used them to save some money in our drivebase. Instead of spending almost $100 on sprocket spacers we just printed them to cut costs.

[lorykzarr]

This year, we were having trouble getting hubs to fit our pneumatic tires. Our solution was to modify the AndyMark hub to fit our tires as a center piece then use 2 milled aluminum plates as beadlock rings to sandwich the tire and inner tube together. We printed several full sets as backups but at the competition we attended didn't need to change a single one. Even now, after doing numerous demonstrations they've held up very well. In addition to our wheels, we also printed some pieces to join tubing on our superstructure. These proved to be fairly strong but were reinforced with some gussets.

[Cothron Theiss]

I think more FRC teams are using additive manufacturing on their robots than you realize. Search around the forums here, and talk to all the teams when you go to competitions. I think you'll be pleasantly surprised.

Originally Posted by guniv

Team 3824 in our region prints their entire chassis. Oak Ridge National Laboratories has been sort of a pioneer in large scale additive manufacturing, and 3824 gets to work out of their facility with a lot of mentor support. You can read about them in the book that came with kickoff kits last year (Behind the Design). Here's a video of them printing in 2014: https://www.youtube.com/watch?v=dvLxsRnA0Y0

Case in point. From 2012-2015, 3824 printed just about every component of their robots, especially the structural components. Even before ORNL developed their Big Area Additive Machine, 3824 used a Fortus printer to print their robots. Many of the surrounding Knoxville teams use those printers as well.

[ollien]

Originally Posted by MailmanDelivers

We [The LigerBots] love 3D Printed Parts! I've attached a document that describes most of our 3D Printed Parts from last year.

The file looks a little odd when opened it word as it is made from google docs.

If you have any questions I'd be happy to answer.

Would you mind posting the CAD for those Talon brackets? They sound awesome.

[tpvagnini]

3D printing definitely has it's place in frc and in the build season, but it shouldn't be used for everything and it's very easy to get carried away and 3d print too much.

My team uses professional Stratasys 3d printers, a uPrint, objet 30, and a new Fortus for this year. We print the majority of our parts in ABS with about 90% infill.

Like people have mentioned before, 3d printers are great for spacers, ball/object guide rails, and even lightweight mounting brackets.

During the build season it's fine to prototype anything with the 3d printer, but from experience, any criticals part should be replaced with stronger parts before competition.

For any 3d printed parts that make it to competition, make sure you 3d printed them properly, (correct orientation, infill, material) and made plenty of extras.

[cbale2000]

The only 3D Printed part we ever had an issue with was a PLA "spindle" we made for the elastic bands on the shooter of our 2014 robot (it prevented the bands from rubbing against the sharp 90 degree corners of the 1"x1" aluminum tube they attached to).

Needless to say our shooter was WAY over-tensioned for what it needed to be, so the part kept being crushed under the force of the elastic bands. After replacing it twice we finally just printed one at 100% infill and never had another problem with it (we had one of the free Cube printers, so our only options were basically: "no fill", "some fill", and "ALL THE FILL").


As long as the part itself is not too small for the application, when in doubt, add more infill.

[The Ginger]

3840 in MN has used 3D printed parts since 2014 with great success. this year they made a incredible tank suspension system with all drive and running wheels printed. I would love to see more teams, including my own, utilizing this great technology.

[Bryce Clegg]

3196 uses 3D printed parts for prototyping, but when it comes to our robot competing we use ordered on milled parts. Since 3D printing with material used in FRC is becoming more available, I think we'll definitely see an increase in the future.

[Michael Hill]

I've been toying around with the idea of using 3D printed turret parts. I generated a large (either HTD or GT2) sprocket, put a hole in it and split it into 6 sections. Those six sections get 3D printed and then bolted onto aluminum.

Check out screenshots here (obviously I need a gearbox on the lower section to drive the belt, but that wasn't part of this exercise):
http://imgur.com/a/0ZGUS

I had one of the sections printed up by shapeways with their white, strong & flexible material (the section isn't flexible at all, they only call it that for thin parts). It's really just a nylon I believe. We had 3mm GT3 belt at our shop that seemed to mesh fine with the section, though I am a bit concerned that the printed part seems to be very slightly undersized, so if I stuck 6 of them together, I'm not a fan of how those errors are going to stack up and possibly ratchet my belt.

[Cothron Theiss]

Originally Posted by Michael Hill

I've been toying around with the idea of using 3D printed turret parts. I generated a large (either HTD or GT2) sprocket, put a hole in it and split it into 6 sections. Those six sections get 3D printed and then bolted onto aluminum.

That looks really interesting! Does it have to be 6 sections though? I feel like the fewer sections you can make it out of, the tighter your tolerances will be. Also, you might want to add in a different way of aligning and piloting your sprocket sections. It looks like you're just using the bolt holes, but those will not hold very tight tolerances, from the printer and to the actual fit. Maybe design in a boss or something similar to the Versakey pattern, or something where the edges of the sections meet so that they fit like puzzle pieces. Make it tight enough so it's a light press fit on an arbor press, and they'll align much more true to your design.

[Michael Hill]

Originally Posted by Cothron Theiss

That looks really interesting! Does it have to be 6 sections though? I feel like the fewer sections you can make it out of, the tighter your tolerances will be. Also, you might want to add in a different way of aligning and piloting your sprocket sections. It looks like you're just using the bolt holes, but those will not hold very tight tolerances, from the printer and to the actual fit. Maybe design in a boss or something similar to the Versakey pattern, or something where the edges of the sections meet so that they fit like puzzle pieces. Make it tight enough so it's a light press fit on an arbor press, and they'll align much more true to your design.

I used 6 sections to keep the physical size of the part small so it would be more economical to print. I'm not sure if making larger sections would make the tolerance situation any better (or worse). The overall size seemed to be around 98% of what the actual size should be, and with their printing process, dimensional stability isn't an exact science. The overall sizes can change due to temperature, humidity and other factors. But I would like to get 6 of them printed to see if it really is an issue though.

I'all have to check on adding a boss. The aluminum would get waterjet anyway, so adding holes in there to fit a boss wouldn't be too hard.

[Kevin Kolodziej]

FRC1675 has used 3d printed parts for 4 years now. Most of our parts have been done on a Stratasys Dimension 1200 but we have also had limited success with the the Ekocycle printers that were given out a couple of years ago.

Most of our parts are small, including spacers, sensor mounts, camera holders, etc. One innovative solution mated with a versablock to mount an encoder.

In 2014, we printed quite a few versablocks for quick prototyping. We did not use any printed versablocks on the competition robot, but I don't see any problem with it for certain applications.

We have also done a LOT of pulleys and sprockets for HTD belt and Vex EDR chain for intakes and sensors. We have used a 2-part pulley (ranging from 12 to 30 teeth) to eliminate the need for overhang printing on the flanges that fit together using steel dowel pins.

In 2013, we printed the plates for our custom drive gearboxes. They weren't very optimized, but it was our only way (at the time) to create high tolerance bearing holes. They were two stage reductions from Mini CIMs into 6" wheels with aluminum standoffs between the plates. Had zero issues with those over the course of the season.