Ender 3 Filament Roller

I couldn't find the bearings I bought for projects like this, but I had some extra 1/4 inch slingshot ammo I used in one of [Tulio's 3d printable marble mazes](https://www.thingiverse.com/thing:1385312), and I was impatient. So I created this roller for my Ender 3's filament spool holder.

I made it for my eSun PETG spools, and the fit is perfect. For wider spools like Hatchbox you can probably print 3 of the center spacers (yellow) and only one of the end spacers (blue), and the end spacer may need to be thinner.

It has 4 channels of 18-19 balls. The tops of rollers face out, and they are designed to be printed without support. Originally I didn't have the center spacer, but the balls were moving around too much. The end spacers could have a larger diameter, but this size allows me to slide the spool on without removing the end cap and the spacer. They should still stay in the track if you have to remove the spacer and don't move it around too much.

Update: I reduced the width