Example Y motion bearing

thingiverse

Uploading the example as I strongly disagree with claims that "plastic bushings do not work" when using unsuitable designs. This piece of folklore has been debunked in my experience. You must use a design suited to the task and means of fabrication. I'm not inventing anything here; these are old ideas from examples I saw many years ago, though probably not made of plastic. They date back too far for me to recall the source. Most 3D FDM printers lack the accuracy needed to fabricate bearings requiring tight tolerances. However, you can achieve close tolerance with careful design. There are two design tricks here. First, there are three lines of contact along the rod. Three points are sufficient to force exact placement of the rod within the bearing. As the upper two points are offset, the weight of the build plate also forces exact placement. Second, the slot/plug in the bottom allows fabrication with less precision. When assembled, a hand clamp or any substantial weight forces the plug tightly against the rod. The bolt locks the plug in place but does not press against the rod. This is how we achieve very tight tolerances when our method of fabrication is less precise. Note that the design is for a 10mm rod, and the test rod (sawed from an old printer) is actually 9.5mm. The bearing works fine as it is tolerant of small differences in dimension. I soaked these in light spray oil (something generic from the local hardware store that also claims to contain Teflon and Silicone). The slightly porous nature of FDM is advantageous in this case. Tried both longer and shorter variants. The longer had more static friction, and I don't see any advantage; therefore, only uploaded the shorter one. This example does not fit any specific printer (I have an i3 clone, but the bearings are adequate, so there's no immediate need to replace).