So far I printed 2 of 6 big gear segments, and by tomorrow the missing ones will be finished. The motor mount and the small gear look good. For sideways support I'm using 608ZZ bearings and a small base. A 45-mm long screw holds the gear in place.
I'm thinking about painting the table surface but I'm not sure if it's worth the effort.
Turns out the Gear library I am using creates weird geometry if the bore of a gear is too close to its diameter. As a workaround, I create a gear with a small bore and then cut out the inner part. It's being printed now!
I bought a used 600 mm diameter table for 10 € and transported it back home on the train... Ü
I designed retainer rings for the bearing balls in OpenSCAD and printed them out of PLA. I'm sure it'll be up for the job strength-wise; the component doesn't carry any significant weight, only keep the balls in place. See the diagram:
The .scad file is uploaded in case anyone else wants to build it. As always, it is fully parametric.
Instead of trying to make an axle and make sure it's centered, I figured I just create my own bearing by putting balls between two wooden surfaces and supporting it at 3 points around the circumference to restrict its movement on the XY plane to a circular one.
So I was looking for bearing balls to make this big bearing, and I figured that it is not economical to order 200 pieces of 15mm balls through Aliexpress because balls are heavy. Probably steel isn't much cheaper in China either. So I found a company in this very same city Wien which sells all kings of spherical things, and they sell "polishing quality" steel balls for 8 € per kilo. I estimated that I need about one kilo of 15 mm balls in order to get a single line of balls around the 600 mm diameter table.
When I was in the shop, it turned out that they charge you 10 € extra for any orders below 50 €. So instead of getting 2 kilo of steel balls, I bought 6 kilo - I didn't wanted to pay this handling fee. I bought 5.56mm, 12.7mm and 15mm diameter steel balls, 2 kilo each, so I now have about 3000 pieces, give or take a few hundred.
Long-term dream is to add a robotic arm and a camera, machine vision, and then we can ask the robot to clean up the bench and put back everything to where it belongs. Or save state of the bench and reload later. Etc.