Traditional bushing 8x15x45mm (LM8LUU)

thingiverse

Traditional bushings for 8mm rods: A Long Version Don't use MoS2 grease on printed bushings; it's a total failure. PTFE spray can oil works with PETG bushings if you wipe them dry after saturation. I haven't tested silicon-based or lithium-based lubricants, but I did look for graphite dry lubricant spray as my first choice and couldn't find any in my area, so I chose PTFE spray can oil instead, and it seems to work if wiped dry after saturation. My first attempt at greasing the Y-axis used MoS2 dark grey grease, which worked fine for the linear ball bearings. However, when I tried using MoS2 dark grey grease on printed bushings made of PLA or PETG, it didn't work at all. They seemed to work initially but got stuck after just one day or less, and the stepper motor struggled with resistance to move. MoS2 grease is a NO GO for printed bushings! I printed a new batch of PETG bushings and tried them with sprayed PTFE oil (with tens of thousands of PTFE balls per mm² and micro gap fillers). I used a threaded rod to grind the bushings to tolerance, moving the bushing back and forth along the threaded rod while slowly rotating them both under pressure (an 8mm drill bit might work better). Grind for a while, check the bushing against the bearing rod, grind some more, etc., until satisfied with the tolerance. I found it sufficient if the bushing slides easily along the rod when dry but sticks to the rod when saturated with PTFE spray can oil. I ground the bushings until they just slid easily by gravity on the rods but stuck to the rod when wet with PTFE oil. When satisfied with tolerance, I saturated both the rods and bushings with PTFE spray can oil, moved the bushings along the rods for a while, and then thoroughly wiped them all dry with toilet paper, inside and out. Lesson 1: MoS2 dark gray grease works well with linear ball bearings if applied inside the bearings. The linear ball bearings run quiet and smooth with MoS2 dark gray grease (bearing quality may vary). Lesson 2: MoS2 grease doesn't work at all for printed bushings, neither PLA nor PETG! At least not with fine tolerances between the rod and bushing. Lesson 3: PLA might be partially dissolved by MoS2 and refined oils; I don't know, but it could be why smoothness feels okay the first day but not the next day. PETG is resistant to oils and greases, or so they say. Lesson 4: PTFE spray can oil works with PETG bushings if you saturate the inside of the bushings and on the rods with PTFE oil, move them back and forth rapidly by hand for a while, and when done wipe them completely dry inside and out. Important to understand that if wet by oil (or grease), the bushings stick to the rod by viscosity and boundary layer adhesion. Wipe everything dry using fresh toilet paper after saturated with PTFE spray can oil, remount, and realign carefully, and you should end up with a quiet linear PETG bushing heatbed; I did. From my trial-and-error practical experience.