Fully parametric roller bearing

Non-print-in-place, i.e. the parts are printed separately and assembled. While print-in-place bearings makes for a nice 3d printing demo, they must necessarily be rather loose to not fuse together. If it instead is assembled from parts it can be made really tight, almost approaching a real bearing.

Printing

No support. Print the rollers with a brim if you have problems getting them to stick to the bed. Small bearings could have this problem, larger shouldn't. Set 'seam position' to random to make the parts as round as possible. If you have problems with an 'elephant foot', i.e. the first layer sticking out due to being squashed against the plate, then you might need to trim it away from the roller ends and the cage holes so they roll freely inside the cage. Any obvious blobs should be trimmed away from the races and the rollers before assembling.

Assembling

1. Put the rollers side by side against the outer ring. Then fit the inner ring into the bearing, also against the outer ring.
2. Press the inner ring sideways into it's place in the center of the outer ring
3. Spread out the rollers evenly
4. Put the cage in place
5. Snap the cage top onto the cage 'pillars'.

FreeCAD model

The main settings are provided in a spreadsheet. The model works down to 22mm diameter with 8mm hole.The clearance needed for a perfect fit is very dependent on the printer, so some experimentation is probably needed.

For small bearings, check out this model instead: https://www.thingiverse.com/thing:3593568

8x32x8 bearing

An 8x32x8 bearing with 0.04mm clearance is included as stl files.

UPDATE 2019-04-26

I tweaked the FreeCAD model so it works down to 608 size, or 8x22x7

UPDATE 2019-04-28

Fixed a problem that made the model unstable when resizing, also switched to freecad 0.18

UPDATE 2020-04-14

One sketch in the freecad model was overconstrained, which prevented the model from resizing correctly when changing parameters. Fixed by removing the unnecessary constraint.