Prusa MK3 not homing correctly/ failing z calibration

I've finally got my home built (clone) to pass almost all its self tests. My issue now is that it dosnt "auto home" correctly. It dosnt land in the spot on the heatbed that it should. the probe works, it senses when to stop, it has done the 9 point calibration and passed that. But for some reason when i try to do the wizard or manually go to the z calibration it fails. Im assuming because its not aligning with the spot on the heat bed but i dont know why its not aligning to it correctly is the issue.

the bot should be to spec now, im using einsy rambo, mk3 frame etc...every thing else is passing besides Z calibration and the auto home seems off to me.

Are you 100% sure the leadscrews are correct?

3 common lead-screws used on 3d printers
TR8x2: 2mm pitch, 2mm of linear movement per rotation. 8mm wide
TR8x4: 2mm pitch, 4mm of linear movement per rotation. 8mm wide
TR8x8: 2mm pitch, 8mm of linear movement per rotation. 8mm wide

MK3 uses TR8x8: 2mm pitch, 8mm of linear movement per rotation. 8mm wide

yeah i have the correct lead screws. Mine are built in to the motors. I have both Z motors tied in to each other, I forgot why i had to do this but it was for a different bot so im going to pull them apart and run them individually. I feel like this could be the issue.

ok so i double checked the lead screw specs and they are correct. i split the Z motors apart and still no change. I don't get it cause it passes homing calibration but wont pass z calibration.

heres the z motors im using but im pretty sure there fine


[www.amazon.com]

ok, so when i do "auto home" it some times lands in the circle on the heatbed and some times it dosnt. Every time i do the Z calibration it never ends up in the circle. I dont understand this because when i do the self test and it does the "homing calibration" it passes that....

just wanted to give you a shout out for all your help Dust, I really appreciate it. I figured out my issue. It seems either some binding or maybe a bad bearing is causing the Z axis to stop early. If i manual move it to the top then do Z calibration it works, but if i just hit the Z calibration it does not rise all the way to the top. I noticed this after looking at some videos of others doing the z calibrating on their printers on youtube.

I believe it is binding, I think that my 3D printed parts are not 100% accurate because of the printer i printed them on is a little rough around the edges.

Edited 1 time(s). Last edit at 08/06/2019 12:45PM by cevans9921.

I should be able to get this printer to print all of its own parts out now tho, I have a handful more of prusa MK3 Frames in boxes that I now get to assemble since I now am a little more familiar with how this bot works. Again thanks for all your awesome time and help!