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Unread 16-01-2017, 18:19
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Re: FRC Bearing Load Ratings (Climber Winch)

Quote:
Originally Posted by Ari423 View Post
Slightly off-topic but does anyone have experience using 3D printed bushings? We want to 3D print a 5mm hex bushing to interface with REV Robotics' 5mm hex shaft[1], but we want to make sure the 3D printed bushing won't crack under load[3]. We are planning on printing a few and testing them by hand, but if anyone has any info on this, I would appreciate it.[4]



[1]http://www.revrobotics.com/rev-41-1349/[2]
[2]I know they sell bushings for that purpose, but we don't want to have to wait for them to ship overseas.
[3]To be clear, this is not the load of the climber. This is a small flap we are actuating with a REV Smart Robot Servo. The flap is only taking a few pounds of force total.
[4]Both empirical and anecdotal information is welcome. If anyone has any ideas on how to lathe and mill that small of a hex bushing that would be welcome too.
While 3D printed bushings with a hex bore are viable, I'm not sure if I'd go this route. That would mean the bushing would be rotating with the hex shaft, making the OD of the bushing the bearing material. Regardless of the bearing material, this is typically not the best idea. I'd either turn down or file down the corners of the hex shaft to round so you can just use normal sleeve bearings, or I'd make a plug at some sort that has a hex bore and just converts it to a larger round diameter and use a proper bearing. But if you have to use a hex bore 3D printed bearing, there are definitely some extra things you can do to reduce friction and make it more wear resistant.



Quote:
Originally Posted by JamesCH95 View Post
To directly answer your question, I recall seeing a team last year with 3D-printed wheel hubs, so printed parts can be used in high-stress situations. Your success will depend on the printer, materials, and printing pattern, not simply that its 3D printed. You can also do fun things like soaking the part in epoxy to make it ~100% dense and thus stronger.
I would not recommend using epoxy infiltration on 3D printed parts to increase the structural integrity. Epoxy infiltration is intended to increase the sealing capacity and fluid pressure capacity of printed parts. Also, it's extremely difficult to achieve 100% penetration and even more difficult to confirm the penetration of the epoxy for an average FRC team. There are plenty of ways to make 3D printed parts more successful that are far easier than epoxy infiltration.

Quote:
Originally Posted by Cog View Post
Yeah, as a team who used (or at least attempted to use) 3d printed wheel hubs I'd recommend steering clear of 3d printing for high stress applications. It went pretty terribly for us, and we had to switch out everything last minute. The type of hubs we used were just the VEX Versa hubs. I think the material was ABS but I can't be sure.
Without giving more information on what specifically went wrong, I'm not sure if it's wise to just advise people to steer clear of additive manufactured parts for structural parts. There are plenty of teams that use additive manufacturing with success in all sorts of applications.
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