Slew8, Cross Roller Bearing

A Cross Roller Bearing, intended to use as a slewing ring.

This is more of a demonstration than a useful part, but should be easy to customize.
The default settings are the only ones that have been well tested. If you change the parameters be sure to have a good look at the resulting model. I am not sure that all the dimensions will scale correctly.

The high and low inner races are threaded together so you can set the tension on the rollers. There is a set of holes on the inner bore that can be used to lock the thread in place. Use a raw bit of 1.75 mm fiber to make the locking pin. The holes go all the way through the low part so you should be able to remove the pin using a paperclip to push it back out of the hole. The third photo shows the pin in place.

Print instructions

Unassociated tags: cross roller

Category: Parts Summary

A Cross Roller Bearing, intended to use as a slewing ring.

This is more of a demonstration than a useful part, but should be easy to customize.
The default settings are the only ones that have been well tested. If you change the parameters be sure to have a good look at the resulting model. I am not sure that all the dimensions will scale correctly.

The high and low inner races are threaded together so you can set the tension on the rollers. There is a set of holes on the inner bore that can be used to lock the thread in place. Use a raw bit of 1.75 mm fiber to make the locking pin. The holes go all the way through the low part so you should be able to remove the pin using a paperclip to push it back out of the hole. The third photo shows the pin in place.

Print Settings

Printer Brand: Prusa

Printer: i3 MK3 MMU 2

Rafts: No

Supports: No

Resolution: See notes below

Infill: 20%

Filament: generic PLA or PetG tested any
Notes:

Print the bearing races and rollers at 0.1 mm for best smoothness. If you have adaptive layer height it can speed up the print by making all the non-race layers at 0.3 mm.

IMPORTANT: Do not print a bunch of rollers at the same time. When the hotend moves from one roller to the next at each layer it will leave a little bit of tail sticking off the roller horizontally. If you print each roller by itself this tail will be vertical and will get covered over by the next layer. You may still print a bunch of rollers in one job if your slicer supports finishing each piece before beginning the next. In the Prusa slicer this is a checkbox under Output Options called Complete Individual Objects.

Let the parts cool before removing them from the build plate to avoid bending the still soft plastic. Any deformation will make the bearing wobble.

Post-Printing

To assemble the bearing put the outer race on top of the lower inner race. Add the carrier. Then insert the rollers into the carrier. You will need to lift the carrier up slightly to get all the rollers in place. Give it a spin with the high inner race still off. It should turn very easily. See the second photo.

Then screw the inner high race into place. Adjust the tension on the rollers by screwing or unscrewing the top race. Use a short bit of raw 1.75 mm fiber to lock the high and low inner races together. There are a bunch of holes for this locking pin, so you should be able to find one that suits your desired tension.

You can check the rollers for any bits of excess plastic by rolling them across your build plate. See if they roll smoothly or stick in one place. An emery board is pretty good for removing any rough spots.

How I Designed This

This was designed in OpenScad. Its revision 8 of this design. The .scad files are included so you can customize it.

Thanks to Dan Kirshner for the threads.scad design file!