About this project
A print-in-place ball bearing. Outer race, inner race, cage and balls all come off the bed as one assembly that frees itself with a twist — no post-assembly, no steel balls.
Sizing it
Set the outside diameter, the bore and the height. Everything else is derived: the ball pitch circle sits at od/2 - ball_od/2 - cage_wall, so raising the ball diameter or the cage wall eats into the outer race and pushes the balls inwards.
The Info panel reports the two numbers that actually decide whether it works: the wall left on each race, and the gap between neighbouring balls.
The three tolerances
These are what separate a bearing that spins from a solid lump:
- Ball tolerance — clearance around each ball. The single most important number; start at 0.2 mm.
- Ball track tolerance — clearance in the race groove itself.
- Cage ring tolerance — clearance between the cage and the races.
All three are printer-dependent. If the first print seizes, raise ball tolerance in 0.05 mm steps before touching anything else.
Cage
The cage keeps the balls evenly spaced so they do not bunch up and jam. Cage slots opens the sides so trapped material can be cleared. Turn the cage off entirely for a full-complement bearing — more load capacity, more friction.
Printing
Flat, no supports, no brim. Slow the first few layers. Do NOT use ironing or any "detect thin walls" setting — both bridge the clearances shut. Once it is off the bed, twist the races against each other until the balls break free; that takes some force the first time.