RE: Skewed XY-Plane (Z Rods, Heatbed)
Geometrically it doesn’t make sense to me that the trapezoidal nuts would be the problem since the nut is fixed and the leadscrew is what turns. I could see bad trapezoidal nuts causing binding and maybe “groaning”. But over the course of 260mm all three of my motors rotate exactly 130 times yet the right front corner ends up about 0.8mm higher than the left front corner. The only thing that can do this is a differential lead screw pitch.
I sent the pics of the leadscrew rubbings and the info using @Muk’s tool to tech support about two months ago but never heard back.
RE: Skewed XY-Plane (Z Rods, Heatbed)
Found some spare nuts I had on hand. Swapped out the left and right nuts, potentially made it slightly worse. Back to support chat and see if i can get some motors
Yeah they tried that with me first, even though I don't think anyones solved the issue without replacing 1 or in my case 2 motors. You have to be persistent with them, send them a link to this thread...they will send you out motors eventually.
Yeah first agent was fairly dismissive even when I linked this thread, second agent was great and disappeared for 15 minutes to read through this whole thing, then came back and started a case for my issue with the Coreone specialists and sadi to check back in after the holiday. He agreed with the motors being the issue although hard to say which one.
My back left bed is super high, front right low. I believe it to be the right motor, he thinks the back one
How I identified the culprits (I'm lazy and couldn't be bothered with tracing), was to print 3 cylinders, 260mm high, each as close to a lead screw as possible.make sure to label then before removing from plate.
The faulty ones in my case were measuring around 258.5mm, the 'good' one measured 260mm. I used a big tall ruler to measure them as my calibers only go to 150mm. But the difference is easy to see, especially when you stand the cylinders up against each other.
RE: Skewed XY-Plane (Z Rods, Heatbed)
Geometrically it doesn’t make sense to me that the trapezoidal nuts would be the problem since the nut is fixed and the leadscrew is what turns. I could see bad trapezoidal nuts causing binding and maybe “groaning”. But over the course of 260mm all three of my motors rotate exactly 130 times yet the right front corner ends up about 0.8mm higher than the left front corner. The only thing that can do this is a differential lead screw pitch.
I sent the pics of the leadscrew rubbings and the info using @Muk’s tool to tech support about two months ago but never heard back.
I was quite persistent knowing I was approaching the end of my warranty.
Always use the live chat, never email. Try not be an adversary.
Be firm but polite.
RE: Skewed XY-Plane (Z Rods, Heatbed)
A left front motor with a shorter pitch than standard could do that. Also, a right front motor with a longer pitch could do the same thing. You re going to have to measure each motor pitch. But if they send you new motor(s) how do they know what to send you unless they measure their motors in advance, which I doubt. You would hve to measure all your current lead screws plus the new lead screws and pick the best three that hopefully will match.
RE: Skewed XY-Plane (Z Rods, Heatbed)
A left front motor with a shorter pitch than standard could do that. Also, a right front motor with a longer pitch could do the same thing. You re going to have to measure each motor pitch. But if they send you new motor(s) how do they know what to send you unless they measure their motors in advance, which I doubt. You would hve to measure all your current lead screws plus the new lead screws and pick the best three that hopefully will match.
Yeah this is the main problem.
You'll hopefully end up with 3 motors that match, ideally you'll end up like myself with 3 that match and within tight enough tolerance that you can print tall, dimensionally accurate parts anywhere on the bed.
In the end I had 3 motors shipped to me separately by support.
I'm still of the opinion that many, many owners probably have this issue but arent aware.
RE: Skewed XY-Plane (Z Rods, Heatbed)
Printed 3 x 28mm diameter, 265mm tall hollow cylinders
One front left, front right, centre back
Measured with Mitutoyo 300mm calipers
Left = 265.85mm
Right = 265.00mm
Back = 265.85mm
RE: Skewed XY-Plane (Z Rods, Heatbed)
Temp fix I thought of while I wait for motors to arrive
When the beds level at the bottom, I manual twist my right thread/motor to offset the right at the bottom, then at the top everything is perfectly level and passes full bed probe
RE: Skewed XY-Plane (Z Rods, Heatbed)
Temp fix I thought of while I wait for motors to arrive
When the beds level at the bottom, I manual twist my right thread/motor to offset the right at the bottom, then at the top everything is perfectly level and passes full bed probe
That will work, as long as you only want to print objects which are not too tall or where dimensional accuracy is not critical.
If you want to avoid the manual correction step after the leveling, you can add shims -- various designs are available on Printables. Or insert M3 adjustment screws (with locking nuts) into the three holes which Prusa has conveniently provided in the base plate.
RE: Skewed XY-Plane (Z Rods, Heatbed)
Ah, well to keep the thread alive. I have a brand new Core One + Conversion from the MK4S, and noticed the bed moving up and down a ton on the first layer after calibration.
I threw the 3x M3 screws in the threaded holes at the bottom, locked them in with nuts and then got the bed much much more level on the first layer. Still not perfect, but then I found this thread.
I suppose I'll check my leadscrews and see what I learn.
RE: Skewed XY-Plane (Z Rods, Heatbed)
Front left motor replaced. All issues resolved