Spool Rollers (F695 Bearings)

I have been holding my spools on a piece of PVC pipe for several years now (https://www.printables.com/model/433471-diy-filament-dry-box-simple-cheap) and it was annoying removing the entire pipe and wrangling spools around to re-dry my desiccant, swap colors, etc., so I decided to make some rollers for the spools to rest on. I had some F695 bearings (which should be more than able to tolerate the loads involved) but couldn't find a design online that made use of them (everyone seems to be using 608 bearings) so I decided to design my own.

Printing

No support material required for any parts. I used generic PLA on an Ender 3 v2 with a 0.6mm nozzle. 3MF files with my print settings are included. STEP files and the Fusion 360 project file are also included in case you wish to make modifications. There are lots of bodies that overlap with the base; these are there to use as modifiers with 0 top and bottom layers, 0 perimeters, and 15-20% hexagonal infill.

Inner Pin

make sure to slice with lots of perimeters (I used 6 perimeters with 0.7mm line width) and do not print outer perimeters first. The goal is for the sliced gcode to print a series of concentric circles outwards from the middle, with the last two overhanging circles being supported by the inner circles. I printed these at around 40 mm/s and found printing multiple instances at once helped with layer cooling and minimized warping. I'm not sure how well this will work with a 0.4mm nozzle.

I am impatient and like to pop parts off as soon as the print finishes. IF YOU DO THIS WITH THESE PINS YOU WILL RUIN THEM. They will warp and loose their roundness and straightness. Let them sit for several minutes before removing from the bed. If you can remove the build surface from your bed, I recommend doing so to allow the bottoms of the pins to cool as well (as opposed to waiting for the entire thermal mass of the bed to return to ambient temperature).

Base

I printed base.stl with each “mod#.stl” file added as a modifier with 0 top and bottom layers, 0 perimeters, and 20% hex infill. This saves about 10 minutes and about 7 grams of filament per base (not as much as I expected!) but it looks cool so whatever.

Rollers

The bulk of the filament usage is in the rollers. I printed them vertically, which allows for finer control over the bearing press fit, but puts stresses across layers instead of within layers and reduces specific strength. To compensate, I used 4 perimeters (at about 0.7mm line width) which resulted in about 2/3 of build filament consumed by the rollers. Infill was 5% gyroid for most of the part, except for the ends (where the bearings are) as these portions will experience the majority of the shear stress. I printed these sections with 20% gyroid infill.

I am not sure if thinner walls would be strong enough as I didn't have the opportunity to test. Just based on handling the parts, with my print settings they are almost certainly way overbuilt. This is also very filament and print setting specific. (I used PLA at about 70 mm/s; more layer adhesion via a different material or slower printing would improve specific strength across layers and require less material for equivalent strength.)

In order to facilitate printing overhanging circular profiles, one end of the roller has a hexagonal pattern slightly indented into the outer surface of the narrow bearing sleeve. Print this part with the hex pattern end facing down and no support material is required.

I am not sure why, but the fit on the bottom bearing press fit seem much tighter than the top. It is unrelated to first layer squish. I found a few passes with a circular file around the inside of the bottom hole was necessary to press in the bearing. These dimensions will very likely need to be adjusted for other printers.