3D Printed Parts on an FRC Robot?

[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.

[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.

[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

[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?

[lorykzarr]

Originally Posted by Munchskull

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

You could try using the model of some pulley stock (with the correct tooth count, profile and pitch of course) so that you don't need to draw out the profile in a sketch. Then add whatever bolt holes or bores you need.

[Munchskull]

Originally Posted by lorykzarr

You could try using the model of some pulley stock (with the correct tooth count, profile and pitch of course) so that you don't need to draw out the profile in a sketch. Then add whatever bolt holes or bores you need.

Thanks, however part of my motivation is learning how pulleys are designed from the ground up.

[Cothron Theiss]

Originally Posted by Munchskull

Thanks, however part of my motivation is learning how pulleys are designed from the ground up.

Check out the Gates belts and metals design manual. Gates has lots of information about the design of timing belts and pulleys. Also, Gates refers to their pulleys as "metals." Just a little tip to navigate their site.

[cbale2000]

Originally Posted by Munchskull

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

I can't speak for everyone else, but I do know that Autodesk Inventor has a tool that allows you to generate standard sprockets/gears/pulleys of various sizes and tooth counts.

[troy_dietz]

Originally Posted by Why_A_Username?

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

It looks like it may be a combination of a lower layer height, high quality filament, and possibly the way the picture is taken. (you could also have the layers start on the inside of the roller to prevent Z-scar from showing)

I'm not saying it isn't vapor smoothed ABS, but there are other ways to get that effect.

[Cothron Theiss]

Originally Posted by nuclearnerd

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

Are you sure?

[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.

[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?