MK4S->CoreOne+ : Z treaded axis off-centered
Hello all,
I encounter an annoying issue with the printer.
Both of the three Z axis are lightly off-centered of the respective end parts.
The two front axis are grinding inside the aluminium fixing parts when moving up and down.
And the rear axis is rumbling inside the Bed-stop at some different positions.
i have double (triple) check the assembly and there is no visible problem at this side.
Is there any tip to solve this issue regarding your own experience ?
Other than that, the print quality is pretty good…
Thank you in advance !
RE:
Drive the heatbed to its lowest position, then loosen the M3 screws which hold the three black trapezoidal nuts that travel on the lead screws. Loosen all six screws at once, then re-tighten them. Do not overtighten since the nuts are made of POM, i.e. plastic.
This will allow the nuts to settle into a strain-free lateral position. (The heatbed's lateral position is defined by the smooth rods, and the nuts & lead screws must align to that.) It avoids lateral forces on the lead screws, and should leave their top ends reasonably centered.
Printables has a handful of mods which add bearings at the top end of the lead screws, to force them to a centered position there. I do not recommend these. They will over-constrain the lead screws, causing increased mechanical tension and friction.
RE: MK4S->CoreOne+ : Z treaded axis off-centered
Printables has a handful of mods which add bearings at the top end of the lead screws, to force them to a centered position there. I do not recommend these. They will over-constrain the lead screws, causing increased mechanical tension and friction.
Agree on this point, however I think I saw a photo of the Core One L that has a bearing for the back lead screw? I'm not going to do this for my Core One but curious none the less.
RE: MK4S->CoreOne+ : Z treaded axis off-centered
As described above, you can adjust the nuts, but I'd take it a step further. Spin the nuts up the screws a bit so nothing is affecting the position of the screws. They should be centered in the pockets in front (or at least not be rubbing much) and the rear plastic piece should be adjusted so the rear screw is centered. If that condition doesn't exist, something else is wrong, maybe something bent or not seated where the motors mount. If all is good, you should then adjust the nuts and possible other local parts. Note that the nuts are supposed to be rotated to a certain position per the assembly instructions. I think that has to do with the bed zeroing out cleanly with the natural stepper detents, but not sure.
RE: MK4S->CoreOne+ : Z treaded axis off-centered
Note that the nuts are supposed to be rotated to a certain position per the assembly instructions.
Huh? I don't remember that from my build, and checking the instructions, all I can find is: "Align the holes in the trapezoidal nut with those in the plastic part. Either pair of holes can be used." Which step in the instructions are you referring to specifically?
RE: MK4S->CoreOne+ : Z treaded axis off-centered
My mind goes a little bit day by day! You're right, but the way I read it, the bed should be resting on the base or screws or whatever it hits, and the nuts should be screwed down so everything is in contact. Then the closest pair of holes should be used, regardless of which pair. I think anybody doing this would just naturally do it that way. Now I'm curious enough to go check and see if it makes a difference in how the bed contacts in relation to the motor detent positions. Because the system relies on contact for the zero position, it seems desirable that it not happen in a less stable position of the stepper. But, I could be over thinking it.
RE: MK4S->CoreOne+ : Z treaded axis off-centered
It's confirmed, I'm a few card short of a full deck. The motor detents are too small for this to matter. What I did discover was that I could improve the friction by readjusting the nuts, in spite of believing I had it as good as possible when I built it. I doubt anything moved, maybe it wore in a bit. At any rate, the lead screws should move fairly easily by hand over a short range. Not a fan of the idea of lubricating it to correct a problem. It should work fine dry.
RE: MK4S->CoreOne+ : Z treaded axis off-centered
It's confirmed, I'm a few card short of a full deck. The motor detents are too small for this to matter. What I did discover was that I could improve the friction by readjusting the nuts, in spite of believing I had it as good as possible when I built it. I doubt anything moved, maybe it wore in a bit. At any rate, the lead screws should move fairly easily by hand over a short range. Not a fan of the idea of lubricating it to correct a problem. It should work fine dry.
Many thanks for testing this -- and I am happy to read that you got smoother Z movement out of the effort as a side effect! 😊
I would also prefer to run the lead screws without lubrication, but did lubricate mine right after I built the kit in April. With the "relaxed" nut positions the Z drive never lost steps, but made that "Chewbacca noise" during extended moves. Lubrication with the grease included in the kit fixed that, and I have not noted any detrimental effects yet. Fingers crossed!
RE: MK4S->CoreOne+ : Z treaded axis off-centered
We have a surface profilometer at work that uses a similar lead screw system for its motion. It's a crazy precise machine and the manufacturer specifies Castrol Brayco 1624 lubricant for the screws. It's stupidly expensive at about $75 for an ounce or so, but if I were going to lube my screws, I'd be very tempted to use that. Inert and lasts for a long time. Quite thin. I complain about costs, but that Kluber lube they want for the X rail isn't cheap either.