3D Printed Parts on an FRC Robot?

[nuclearnerd]

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.

[Chris is me]

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.

[AdamHeard]

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.

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.

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.

[Brandon Holley]

Originally Posted by nuclearnerd

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.

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

[Cothron Theiss]

Originally Posted by nuclearnerd

An FDM printed roller would have cracked or crushed in this application for sure.

Are you sure?

[Sam Skoglund]

Originally Posted by Kevin Kolodziej

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.

I have never seen 3D parts used for this before! A couple of questions: Were the 3D printed plates proving any structure for the robot frame? Or were they just mounted onto the frame? Also, how thick did you print them?

[Michael Hill]

Originally Posted by AdamHeard

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.

First off, the aluminum rings haven't been made. I just did a 3D printing test as a proof of concept.

During the regular season, I don't know the exact model our sponsor uses, but I believe it's somewhat older machine (from what I was told, there's no head tilting for taper removal). If you can tell from a close-up picture, this is the machine (and sponsor) that does our waterjet work: http://www.rpgindustries.com/11301/11385.html

If there really is no taper reduction, I'm a little cautious about having gear teeth cut. He could do wire EDM (he's cut some gears for us in the past), but I really don't like to use up his machine time since he already loans us our build space. So we try to limit ourselves to just a single waterjet job per season, and it's usually a 1/4" plate job. Though I'm sure he'd do more for us if we asked.

The other thing 3D printing lets me do that waterjet wouldn't is adding the belt flange directly on the 3D printed part. It's not a huge deal though because it can always be added on after the fact. It's just another part I don't have to worry about making.

In the end, I've just made it sound like I need to send our sponsor an e-mail

[rch328]

3D printed motor mounts on a horizontal flywheel shooter for stronghold held up fine. In my experience, problems with 3D printing models strength is usually a design flaw; though they are inherently weaker than non-3D printed parts, especially with ABS filament or stronger they are plenty strong, if well designed, for anything in FRC.

[AdamHeard]

Originally Posted by Michael Hill

First off, the aluminum rings haven't been made. I just did a 3D printing test as a proof of concept.

During the regular season, I don't know the exact model our sponsor uses, but I believe it's somewhat older machine (from what I was told, there's no head tilting for taper removal). If you can tell from a close-up picture, this is the machine (and sponsor) that does our waterjet work: http://www.rpgindustries.com/11301/11385.html

If there really is no taper reduction, I'm a little cautious about having gear teeth cut. He could do wire EDM (he's cut some gears for us in the past), but I really don't like to use up his machine time since he already loans us our build space. So we try to limit ourselves to just a single waterjet job per season, and it's usually a 1/4" plate job. Though I'm sure he'd do more for us if we asked.

The other thing 3D printing lets me do that waterjet wouldn't is adding the belt flange directly on the 3D printed part. It's not a huge deal though because it can always be added on after the fact. It's just another part I don't have to worry about making.

In the end, I've just made it sound like I need to send our sponsor an e-mail

We've cut numerous gears (12-32DP) on a regular waterjet w/ the taper and it's worked out fine.

I'd recommend 20DP here bc vexpro product. It certainly does add waterjet runtime, but completely eliminates the printed part.

[Kevin Kolodziej]

Originally Posted by Sam Skoglund

I have never seen 3D parts used for this before! A couple of questions: Were the 3D printed plates proving any structure for the robot frame? Or were they just mounted onto the frame? Also, how thick did you print them?

I'll have to get some better pictures after Thanksgiving when we start meeting again, but no, the gearbox did not provide any structure for the frame. The output shaft ran through a bearing on the chassis and the motor was clamped to the top rail of the chassis - the plates were only holding the gears. Here is a preliminary version of the gearbox: https://www.chiefdelphi.com/media/photos/38361

They were printed solid ABS, 1/4" thick.

[Michael Hill]

Originally Posted by AdamHeard

We've cut numerous gears (12-32DP) on a regular waterjet w/ the taper and it's worked out fine.

I'd recommend 20DP here bc vexpro product. It certainly does add waterjet runtime, but completely eliminates the printed part.

I was a bit dissuaded by Cory's post, which is why I started looking into 3D printing an alternative.

[Bluman56]

For the past couple of years, 334 has used 3D printing (Ultem specifically) extensively. In this picture you can see their two front drive wheels as well as their shooter wheel/hood adjustment mechanism and turret gear all 3D printed.

[fargus111111111]

We 3D print quite a few components, mostly spacers and battery trays. In 2016 we tried printing the pulleys for our track drive and we did shatter several of them after lots of use, but we did not fill them fully and we were not nice to them. (repeated full speed over the rock wall did them no favors) We love to print with bright orange plastic so we can easily show it off. Our printed rollers on the sliding part of our 2015 arm, which supported the weight of a full stack held out past the frame of the robot, have never had any problems. That being said, I think that 3D printed parts are better used for more constant stress situations rather than high shock situations.

[Why_A_Username?]

Originally Posted by Brandon Holley

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.


-Brando

You guys made that roller on an FDM printer? Did you vapour smooth them? That is a super smooth and clean finish on them.

[Munchskull]

How do people model custom HTD 5 pulleys for 3d printing?