K40 Y axis idler pulley

prusaprinters

After a few months of work my K40 was acting up, not moving smoothly and the belt tension could not remedy this. I removed the whole laser gantry and found that the two pulleys on the Y axis were twisted and rubbing against the belt and the holder. The reason is that the pulleys have a single 3x8x4 bearing in the middle and that's not enough to keep the bearing aligned. You can buy replacement pulleys but in my case the axle had worn a groove in the middle and the pulley itself was actually fine. Couldn't find the axle and didn't want to install a flimsy arrangement again. My solution was to replace the pulleys with printed pulleys that can hold 2 bearings for better support. My pulleys are slightly narrower in the middle because my belt is only 8mm wide. Check yours before you print, you can always stretch the Z axis when you slice because the space between the arms of the holder is about 18mm, lots of space for expansion You could drill the existing pulleys out to 8mm and insert bearings at each end, this would work fine but I wanted to keep them intact in case my idea wouldn't work. FocusMiah has a similar system, they printed the holder too I but wasn't sure that would be strong enough, even with PLA, theirs was resin printed. K40 y-axis belt tensioner and pulley replacement Remove the gantry 693ZZ Bearings K40 Laser Cutter Alignment I ordered these metal pulleys complete with bearings but they arrived too late In the end it works fine, I think a toothed pulley would be smoother and these you can buy or print. Print Settings Printer Brand: Creality Printer: Ender 3 Rafts: No Supports: Yes Resolution: .2 Infill: 50 Filament: Amz PETG/PLA Blue Notes: You can use concentric supports, I suggest only in contact with the bed because the pulley will have support around the outside and that will need to be cut off, not at all difficult with wire cutters, but they didn't improve the top flange quality at all. I increased the wall count and density to add rigidity, this may not be necessary Post-Printing Insert the bearings Bearing need to be pressed in, remove any elephants foot spread from the bottom layer first and press them in evenly one at a time. They are fragile so don't force anything too much. I used a small vice but some pliers would probably work as well. You can easily press it in against a wooden surface too. I used washers on either side to prevent the plastic from rubbing against the metal You can use the existing axle but one end is 3.1mm and you will have to reduce that with a file or fine sandpaper. I made a new U shaped bracket and used a M3x20mm screw as an axle. If you want to use a screw you will have to enlarge the hole to 3mm and use a nut to hold the screw in place. Category: Parts