Bearing for Printrbot Metal Plus Filament Spool Holder

thingiverse

Taking inspiration from BiZaRrO_John's bushings, I chose to upgrade real rolling bearings onto my Printrbot Metal Plus spool holder (http://www.thingiverse.com/thing:675439) to ensure really smooth filament feeding. Starting with unitconversion's parametric ball bearing design, I revised it, optimized it for 3/16-inch balls, and added the cap piece that transforms it into a wheel for PVC tubes. Instructions Print four of these per spool (so eight if you have dual extruders). Load twenty 3/16-inch balls through the feed hole (while the inner ring is in place), and then attach the cap piece on top. The cap fit should be tight enough that no glue is required. Don't forget to print my original spool holder first! You can easily find the ball bearings at any bike store, but I bought a pack of 144 for $5.45 from Amazon (http://www.amazon.com/gp/product/B000AO5KOW/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1). I will actually need to buy some more, as I'll need 160 for my dual-extruder setup. I printed with a layer height of 0.25mm. If you need to tweak the fit for your specific printer, adjust these parameters in the OpenSCAD model: ball_spacing_ratio - clearance around the balls in the raceway [one of unitconversion's original variables], cap_clearance - gap between outer wall of the bearing and the cap, bead_radius - (scroll down to find this variable) radius of the friction fit beads on the inside wall of the cap. These control the snugness of the cap press fit. This was my first time using OpenSCAD, so apologies for any untidiness in the code; I was learning as I went along.