Ringing Part 3: Belt re-tensioning and bearing replacement
Still chasing ringing.
I noticed some serious rattling whenever the fan started spinning up. This seems to be caused by the way the fan is mounted to the extruder; PETG is too flexible for that kind of thing.
The spring went back onto the X belt fine. I evened-out both Z towers by manually cranking them to the top and aligning their flanges with the end of the Z lead screws, and then I ran it through four or five cycles of going to Z+150 and Z0. Never locked up or grinded, so this seems acceptable.
The spring also went onto the Y belt fine, and I was able to reinstall the belt without too much trouble. I’ve noticed that the idler is under tension, so it might be a good idea to print a better-designed idler. Also a good time to buy some metric thread taps.
Before putting the old linear bearings back onto the rods, I test-fitted each bearing on both rods. 3 bearings ran freely on the left rod and only 1 ran freely on the right, but I made a combination of bearings + rods where they ran smoothly and with more-or-less equal friction. Again, I installed the bearing blocks by tightening the screws until I just felt the head touch down onto the plate.
I have replaced the screws on the rod mounting flanges with nylon M3 philips-head screws because the original M3 countersunk screws used a crappy little 2 mm hex wrench, and the hex holes were already getting stripped despite my best efforts. I briefly considered socket head M3 cap screws, but I guess I wanted the vibration-resistance of the nylon. This part is easy enough to replace when I do the test prints anyway.
Checked the rods for wind by putting a sharpening stone at each end (the closest thing to a winding stick I have) and sighting alone the stones and the bed (no springs installed). Tightened all of the rod set screws down to the point of first friction, and then had to tighten the rear-left one just a bit more to get it looking parallel.
Checked the spacing between the rods in the X direction by taking an inside measurement with my calipers hard against the mounting flanges. The front separation was 141.88 mm, the rear separation was 141.68 mm. I tapped both sides to around 141.70 mm. This spacing probably will not survive the machine being moved around, but I thought that I may as well do it while I’m there.
Final test of the bed, and it looks like everything is okay. Even friction throughout, no grinding sound, no catching, takes little effort to start it moving.
Did a double-check of the bearing blocks before I installed the springs, and some of them had begun to come loose. I tightened them all just a bit more than previously, and the sound of the bed traversing is now a bit rougher. What can I do?
Spring washers? I have 5 mm ID ones, but they aren’t engaging with the M4 screws properly. Bunnings run?
I’ve just noticed that there is a bearing mount between the two that are on the right rod. What if I just use a single bearing and got rid of that rough-running one? My guess is that the bed would have more of a tendency to twist, especially because the belt attachment is on that side.
Nylon washers? They’re good with vibrations, after all. I only have M3, but I can drill them out if it saves me a Bunnings run.
Nylon washers can be drilled 2 at a time by threading them onto a 3 mm hex wrench, using the wrench to load them into a vice, and then holding them down with your fingers while drilling.
Initial success using only 8 mounting screws (in the diagonals of the blocks, pointing to the center) because it’s fiddly to drill those washers out. The traversing bed sounds (and most importantly feels) the same with finger-tight nylon washered screws as it does with completely loose screws. Will add all the screws and see if it’s still good.
All the screws are in and it is looking good! I will check back in a week or so to see if the screws have loosened. If they have, then perhaps the simplest solution is a non-permanent Loctite.