3D Printed Parts on an FRC Robot?


#1

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.


#2

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


#3

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. :smiley:

CadModelSheet3Dprintedpartsonrobot.docx (678 KB)


CadModelSheet3Dprintedpartsonrobot.docx (678 KB)


#4

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.


#5

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.


#6

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.

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.


#7

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


#8

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.


#9

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. :rolleyes:


#10

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.


#11

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.


#12

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):

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.


#13

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.


#14

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.


#15

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.


#16

This may not interest you, because it requires a specialized machine, but our local community college (Mohawk) printed our intake rollers from nylon powder using the “Selective Laser Sintering” process (SLS). We were worried these wouldn’t perform, but after a season of smashing the intake rollers against defense dividers, I can report that the rollers were tougher than the hex shaft that ran through them. An FDM printed roller would have cracked or crushed in this application for sure. We were very pleased, and hope to work with Mohawk again next year to print more SLS parts.

IMG_20160312_093447.jpg


IMG_20160312_093447.jpg


#17

3D printed parts are absolutely valid in FRC, it’s just a matter of knowing when and where to use them, and how to design and manufacture them such that they do not see excessive loading.

Printing is particularly useful in FRC:

  • When parts don’t see significant load. 3D printed parts can be used with load as well, but that requires more active effort or reinforcement.

  • When you need a specific geometry of part that is a pain to make through other methods. Things like electronics brackets, camera mounts, eccentric spacers, gearbox shields, even internal ball cradles can be printed to easily achieve a specific size and shape.

  • When your other manufacturing resources are tied up, or needed for more valuable things. Spacers and standoffs are a common 3D printed part, not because the technology is required for it, but because the 3D printer has more downtime than the lathe and these parts are just boring to make by hand.

  • When you are stuck in CAD at 2 AM trying to interface two internal assemblies and need to bridge some oddly specific gap between two parts. Personal experience on this one.

Honestly, if you get and have a printer, you’ll find ways to use it. You can even make composites out of it, using the 3d printed geometry for shape and adding metal components for structure. It’s just too handy.


#18

What machine did you use to cut the two (presumably) aluminum rings?

If you lasered or waterjetted the plate, you can cut gearteeth directly into it and skip the printing portion.


#19

SLS is definitely a really cool technology that makes great parts. Unfortunately, most teams will not have access to SLS parts as the technology is considerably more expensive than an FDM printer. FDM parts are plenty robust enough for that application you described.

We used FDM to print our intake roller, among other parts this year and had no issues. We actually played all of our ~160 matches with the same roller this year, so it took a beating, but held up considerably well.

As with everything, its about using the technology and material smartly. We printed the ‘shell’ of the part we wanted because of its complex shape. FDM allowed us to make this helical screw type of intake that would be unachievable otherwise. We liked this because it was a lot less complex and a lot lighter than a row of mecanums. It also would also be way more maintenance friendly than adhering a strip of something to a cylinder.

We took our shell and epoxied it to a very thin wall aluminum pipe, and printed some endcaps to plug into the ends, complete with thunder hex pattern.

The other parts you see in the below picture, particularly the drums are our hanging drum/winch for our robot. We used these drums to wind the winch up and scale the castle. Easiest winch drums we ever made!

-Brando


#20

Are you sure?