Can someone get into some details as how the Z calibration or XYZ calibration works for a MK2S? I really want to get my printer printing and am quite frustrated at this point because it wasn’t as straight fw as I wanted it to be and that i managed to scratch my printbed in the process of the XYZ calibration, where it searches for the circles on the bed going many times left and right the circle and up and down on Z…
I have noticed that when homing, it does it ok, it goes just above the bed when homing Z. Then the same goes for Z calibration, when it probes 9 points on the bed, the first (front) row is ok-ish but second (middle) and back row it presses hard on the bed.
Is there a hardcoded value of Z height because when it asks you to go up till the motors skip and then it goes down towards the bed, if the X axis wasn’t atop it goes straight through the bed, pressing terribly on the bed with the nozzle, just like the probe is Off and not triggering. How can I check the probe works well?
Thanks.
https://is.gd/cPKSwX
Your X axis is slanted. By moving it to the top of the frame, this corrects the tilt. When the X axis is tilted, the left side is usually lower because the hotend homes there and the left side has the X motor. This causes the Z probe to be higher than the expected position, causing the nozzle to hit the bed.
I don’t trust those flimsy clamps, they bend when X hits them. I stopped the X axis somewhere at near bottom and measured with caliper tail and compensated by manually rotating one or the other leadscrews until I got the same reading on both sides of the X axis. Then Homed. But when trying this trick with the Calibration routines it badly slams the Z axis into the bed like there is a hardcoded value that it goes down from atop… strange behavior :-/
What’s the Z gap between the bottom of your PINDA probe and the bottom of your nozzle?
I have has problems similar to yours, and it turned out the PINDA probe needs to be significantly nearer the bed than Prusa advises, for my printer at least – try lowering your PINDA probe so that when the nozzle is touching the bed, the PINDA probe is only, say, 1.5mm off the bed – see if that fixes it.
I lowered it once … but I believe it is higher than 1.5mm … will have to check that thanks.
@Mark_Wheadon they now recommend placing it a zip tie’s thickness from the bed, so roughly 1.5mm.
@Adam_Steinmark Ah, OK then mine must be closer than that. I started with the zip tie distance but have had to go closer to the bed to avoid the printer doing its level best to destroy the bed.
I used the ziptie to set the distance so if that’s an issue than the 1.5mm is too high. I will try even 0.5mm and see what’s what but first I will take some time to re-check the proper construction, measure again everything and maybe re-fasten some parts … because I don’t want other scratches on the bed …
What could I lay on the printbed to protect it from other mishaps that would end in the nozzle scratching my PEI? Maybe some thin alu sheeting?
I’d just recommend hitting the tops of the Z axis, the system is bound to work that way. It’s the only way to guarantee the X axis is perpendicular to the Z and to have both motors at the end/beginning of a step. That’s what I always do. They shouldn’t really deform the motors don’t have enough torque to cause any permanent damage.
Yeah no damage but the plastic bends visibly (elastic deformation not plastic). I assube the motors, being identical, bend them the same way so the X axis should still be horizontal but if one bends a little more than the other then the X axis is not parallel anymore. This has been solved by various people with reprinting thicker versions of the pieces that will not bend.
Now how do you ensure the ZFramePlate is perfectly perpendicular with the bed in bot axes? I thought that having the Y-Rods firmly pressed at the bottoms of the ZFramePlate’s notches ensures that the plate is not rotated around the Y axis. But do the nuts on the Y-Rods alone ensure the ZPlate is perpendicular to the Y Axis? I seem to have issues where the nozzle is flush with the front row of calibration points then it is increasingly forced into the bed suggesting the bed is slanted, lower at the front and higher at the back, which to me means that the ZPlate is actually slanted. I have seen on Thingiverse diagonal rods that are used to stabilize and (maybe) adjust the ZPlate being slightly leaned to the front or back…
You shouldn’t be having as much trouble as you are. Make sure the Y rods are fully pushed into the printed corner feet. Otherwise you may have a damaged PINDA probe. I would contact Prusa support though if you haven’t already. The live chat is very helpful.
I thought I wouldn’t have as much trouble as I have, heard about others having but I followed the instructions as close as I could and didn’t expect this … now I am very angry for that scratch but I hope that is the worst that will happen 
… Anyhow next calibrations I want to have some sort of sheet on the bed to protect it…at least until I become confident it will not get damaged.
Oh one more, how can I test the PINDA? Place some metal under it when it homs Z? It should stop the X axis from descending right away right?
Did you ever flip your Z nuts? I saw and commented on your other post.
Yes, turned them the right way how did I ever miss that one :/ - and also made the plastic holders atop flush with the ZPlate. Measured the ZPlate distance from the back feet and it is 100.83mm on both sides (I could make that 100.00 but it’s so difficult to get to the nuts between all kind of cables).
I am still wondering why the nozzle tries to go under the bed and it is not stopping when the PINDA triggers … will have to get the probe down a bit though and try to trigger it during Auto Home with a metal thing before it reaches the bed … if it stops then it is working.
Your board might be faulty or the firmware might be corrupt if you’re SURE the probe is triggering. Best bet is to contact the live support.
I will contact them and I agree it shouldn’t be this difficult to get going a printer praising itself with auto-calibration and axies-orientation defects compensation…
Time is at a premium unfortunately…
One thing … I just realized this might be a problem. I have noticed that the PINDA led is always-on but it didn’t click until a workmate mentioned that it should only turn on when it reads metal. Is that true for the rest of you MK2S owners?
It works the other way. The LED is always on and turns off momentarily when sensing metal.