Slew bearings, Slewing bearings, and cross-roller bearings are all the same thing. The unique advantage is that they can take forces in every direction. Some bearings you can pop out the center if you push wrong. Some you can't use like a car wheel. Some you can't put a pencil in the hole and bend. Slew bearings can take a (relatively) large amount of all these forces, and do it in a really low profile (thin design).
I wanted a slew bearing for my robot. One slew bearing can replace about 6 parts in my current design and takes up a lot less room. Online slew bearings cost $120 before $60 shipping. No thank you! I got 100pc 1/8" ball bearings from Aliexpress for $10. This is a job for my 3D printer.
PS: There are four steps to this instructable but only 3 are displayed on the main page. Step 4 has the STL files and more.
Step 1: Design
I searched for "slew bearing cross section" and found http://www.sbibearing.com/userfiles/zp01.JPG
I modified the design to suit my tastes. The inside is two identical pieces. In the picture the inside and outside sit flush. In the photos I didn't plan so well and I had to chase bearings all over the place during assembly.
Based on the design I knew I would need 70 balls. In the end I used 68 to leave a bit more room for movement.
Dear Solidworks: please come out with a $500 edition for hobbyists. Sincerely, everybody.
Step 2: Print
Printing large shapes tend to "curl up" and peel right off the bed.
Lately I've been experimenting with the ABS slurry method to hold my prints down: mix some old ABS and some acetone in a glass jar, seal it tight, give it a swirl, and let it sit overnight. The goo you find in the morning can be applied in a thin coat to the glass of your printer and it makes your prints stick like contact cement.
Looks like garbage on the bed and it fixes the problem.
Time to print my parts was about 40 minutes for the exterior and 15 for each interior. My bed is 86 degrees celcius and my nozzle is 207.
Step 3: Assembly
I put the exterior and one interior on a cookie sheet to prevent bearings from escaping. Then I dumped a whole bunch in the center and scooped them with a spoon, sometimes pressing with a finger. for the final few i used a pair of pliers to pick and place.
I used M3x10 screws to attach the two halves together. No nuts were needed, the teeth of the screw bite into the plastic and hold great.
In the other four interior holes I put M3x25 screws so I could attach the bearing to my robot.
Step 4: Final Thoughts
You may wish to try printing this bearing with gear teeth on either side. GT2 timing belt teeth would be great. A parametric version of this model would be more gooder.
Download the STL files for yourself here: http://www.thingiverse.com/thing:321679
I would dearly love to see someone make inexpensive slew bearings. If you know of someone who can make this happen, please contact me.
If you've enjoyed this tutorial, you may enjoy some of my other creations. Check 'em out at http://marginallyclever.com
Thanks for reading!