Spring loaded bearing block (SC8UU replacement)

thingiverse

Update 28/9 -17: New base "v1.1 Spring Loaded SC8UU - Base". The bearing was found not centered on the rod in the original version; this issue has been corrected in the new release. I'd like to remix pparsniak's "Smart Bearing Block" design, which is a great idea that works surprisingly well. The original SC8UU/LM8UU bearing lacks sufficient preload and has poor tolerance fit between the rods and the bearing. In contrast, igus drylin bushings have this issue, but for me, they were actually worse than the original LM8UU bearings. The "smart" bearing design features adjustable preload, which means that the dimension and tolerance of the rod are less critical. I printed the original version, but I wasn't satisfied with using rubber bands or screws; therefore, the main change is that this base has a spring to set the preload. Along the way, I also made a few other improvements: * No washers are needed. * The same base-to-rod center as the SC8UU. * A thicker base to fit button head hex M3 bolts for the angled bearings. * A side surface for Y-axis limit switch to hit. * Optimized for 0.4 nozzle and 0.45 extrusion width. BOM: * 3x 623ZZ ball bearings * 1x Spring (OD 7.5-8mm, ID 5-6 mm, ~4 mm length) * 2x M3x8mm (minimum length) * 2x M3x16mm (minimum length) * 2x M3x25mm (minimum length) * 6x M3 nut (preferably Nyloc) * (4x M4 nuts for part assembly, min. M4x8mm or preferably M4x10mm bolts) The spring I used is the same as the one for the heat bed on Anet printers, cut down to length. It's recommended to use Nyloc nuts for the two nuts clamping the spring; washers and/or loctite thread-locker might also work. When setting the preload, a general tip is that it's fine if there is some resistance when moving the bearing, as long as the ball bearings are rolling and not slipping on the rod. The rods should be cleaned of any lubricant. I believe this solution is best suited for the Y-axis/bed, as the center of gravity is centered and the bed will rest down on the fixed ball bearings. For the A8 X-axis/hot end-carriage, the weight of the carriage may press partly on the spring-loaded bearings, which might be less rigid.