Having some time to actually attempt the calibration of the MKS2 … so while the Selftest went OK (apart from the blower fan showing some noisy defect - see video) the Z calibration goes well for the front calibration points (I move back and forth a piece of paper under the nozzle so I can feel the pressure on the bed).
BUT when it gets to the middle points it really presses the bed down a lot for the right point, again in the middle where there is no room to press down and also to some extent on the left side.
The back row of calibration points doesn’t get any better but it’s worse on the right side as far as I can tell compared to the left side…
It’s like the probe doesn’t trigger in those points but it does ok for the first row
… Is the back of the bed upper? Is the Upright Frame Plate leaned to the back -which would bring that side of the bed upper relative to the frame… What gives? :-ss
If the PINDAR probe has sufficient space, move the end slightly closer to the bed. This may change the sensor’s ability to detect the bed and perform suitable compensation. If that doesn’t help or otherwise solve the problem, read onward.
Consider to perform a test with a good known straight edge. With the bed cold, place the edge across the bed in all eight directions, while shining a bright light (torch/flashlight) from behind. If your bed is warped, you will see irregular shape to the light under the edge.
If you find a warp, use the method above to determine rough shape. You may be able to tighten the bed bolts near the high spots, or add a shim of a tenth of a millimeter under the bed at the low spots.
If the warp is too severe, you may be able to get a replacement under warranty.
After the above test with cold bed, perhaps to heat bed to 70°C and check again.
Actually the bed is slightly warped but very little as far as I can tell. The Autohome function does its job and the PINDA probe seems to stop the nozzle at the right height (I can insert the paper under the nozzle and it slightly scratches it). I can’t imagine why during the Z or XYZ calibration when going on the second and third row it plunges the nozzle into the bed puressing it down visibly and worryingly… the YtoZ might really be not perpendicular.
That’s a good line of thought. Many locations to confirm with that in mind. Check the placement of the Z screw guides as they are the “calibration stops” when raising the carriage to the top. If one is lower than the other, it throws off the reference point.
@Fred_U Oh those flimsy parts that are bending as I do the suggested steps in the manual (raise Z until motors skip). I don’t trust those, I measure with caliper distance from bed to X rods or from upper frame to X rods … when I get the same measurements at both ends I call it parallel.
I believe that the powersource fastening is pulling the Z Upright clockwise to the back and so the back of the bed comes up as a relative positioning between Z and Y …
But the PINDA should stop when it triggers, it shouldn’t consider the Z height it finds for the homing position the refference Z …Is the probe inactive but at the homing procedure?
Crap, l managed to scratch my PEI sheet :(( … this is so frustrating. Frankly the way this Prusa is built makes it so difficult to get inside it and re-fasten nuts and re-do some parts of the assembly I am amazed people manage to make it print.
You’re missing zip ties most noticeably, so quite possibly your linear rails aren’t seated. I’d look for other assembly mistakes. Now, if it came assembled, you probably cut them accidentally.
Don’t be so quick to blame a product thousands swear by.
@Rob_Nance I left out the zipties on purpose, put them on and took them out after measuring there was no difference … I could put them back just to rule out the possibility but that is not what I believe is the problem.
By your train of thought there are also thousands that “swear at” but I am not trying to say Prusa made a shitty product, just that it is pretty difficult to redo some assembly just to make sure everything is straight - just as you thought it was when doing it the first time.
Anyway… thanks for your input I hope to put it end to end at some point.
but I am not trying to say Prusa made a shitty product, just that it is pretty difficult to redo some assembly just to make sure everything is straight - just as you thought it was when doing it the first time.