I am in the process of building my MK2S but hit what could be a showstopper. While building the Z axis I inserted the linear rods through the LM8UUs and walked the rod back and forth a few times just to notice that it was rotating in my hand. Tried it with the other smooth rod and that one stayed in place. What gives? Bent rod? Bad bearings? (they are quite loud and I don’t quite like the sound they make) …
Here’s the link to the Album which I add photos to as I go to keep track of everything: https://photos.google.com/share/AF1QipPGWcEvr_cwz1tIPW1kafq8Nj9xP-6achNLEY2NpL2vp0zNqPlWdOSs3_ZqSRADEQ?key=TWFyYzh2RjZTNDBfVHRKcE5aR0IwdGlVTFExQlJn
roll the smooth rod on a table. Then you should see if it is bent or not.
Might be one bearing tilted in the housing/carriage. Take the bearings out (if you can) and try them one at a time.
In the possible scenario of bad bearings, the guiding rod would of gotten stuck and damaged. There is a slight chance that the bearing chamber might not be centric. However, if going to work with 0,01 to 0.001 micron you will absolutely need to control the setup if it’s precise
Took X axis assembly apart, rolled the rod on the aluminum frame, seen no light through the rolling contact, took the bearings out, tried them individually, no turning of the rod inside, put one bearing in the plastic holder, rod sliding smoothly, put the other one in just 1mm or 2 so I can slide the rod through it and then worked my way down until I got it completely inserted, flush with the plastic part’s lip… I noticed that as I went in it started to fell more and more willing to rotate around its axis. When completely in, it doesn’t seem to be as bad as the first time but still perhaps 85% of the initial turning still happens.
Probably a slight off center of the housing. Try to assemble everything on a slip. Move the parts evenly on a flat surface. This should adjust everything evenly. But there is also a chance that you might have to retrofit in order to have some part mounted in the end.
I think I’ll go with this as is now, otherwise I’ll just waste more time. If the 3D-printed part is slightly warped/off-center/whatever, then that’s it, I don’t have another one until I can print it or somebody else can print it for me … but I don’t think this will translate to errors down the road -might be wrong about that though…
If the axis give a slight delay in directional position, there is a chance of having a print blob.
Ok, took the bearings out and put them in again and agan, at 45 degree angle between ball races, until I got to a lucky position when I felt the rotation tendency was at a minimum and left it like that. I believe few would even notice it as is right now.
Try to assemble everything on a slip ( not firmly fastened ). Once everything is aligned, use a torque ratchet to fasten all bolts or screws with the same torque force.
I don’t think it’ll actually be a big problem if the rod wants to rotate a bit but it’s a weird issue.
