How to secure a rotating disc so that it has no wobble

For a 3D printing application, I need to have a spinning disc(that I will rotate via geared stepper motors) that will wobble as little as possible. By wobble, I mean that it will only rotate around it's axis and not shift side to side.

The goal is to build a 3d printer that uses polar coordinates rather than traditional Cartesian coordinates. Instead of using leadscrews, I want to instead rotate two discs. Disc 1 is mounted to disc 2 which is mounted to an immobile surface. If I can precisely rotate both, I should be able to 3d print. So the question is how can I mount them such that they don't require much torque to spin and also spin accurately around their axis?

I have ordered some lazy Susan type bearings from McMasterCar, but they wobble too much under use. I've heard that there are axial and thrust bearings and that the ones I ordered are thrust. Should I use a combination of the two (and how would you suggest mounting it?) or should I use the diagonal type that has both combined in one assembly?

The disc is 8 inches in diameter and I would like to keep the assembly thin. The disc is spinning parallel to the ground; if I were to mount the bearing underneath, it would be in compression.

Here is a sketch showing one of the axis:

This sketch shows an overview of the whole system:

• @James For future reference, you can add images to your posts by editing them. I've done it for you this time. Commented Jan 13, 2016 at 14:04
• As the DataMunger Guru always says: What is the problem you are trying to solve? Tell us what you need to do, not how you want to solve it Given that 3D printers have rather accurate X-Y-Z positioners, why would you want to move the platen? Commented Jan 13, 2016 at 15:17