Missing steps on left Z axis motor  

Missing steps on left Z axis motor

Looking for advice and suggestions if anyone has had a similar issue. Thanks!

My kit i3 has gone together and passes self-test and xyz calibration with flying colours. I am running the latest firmware 3.1.1 RC4 B143 (DECEMBER 30, 2017)

When I run first layer calibration or attempt to print anything I now appear to be missing steps on the left z-axis motor when the extruder rises at the end of the print. Have not tried to print anything tall yet. This issue is always happening in the first 20-30 mm of travel up from the print bed. My x-axis ends up at an angle (left end low, right end high) and bed level calibration fails next time I try to print anything. Running z-axis calibration again will level the x-axis but the problem is occurring after every print.

I have swapped the z-axis connections to the einsy board around and this has had no effect (left motor still missing steps) so the problem does not appear to be with the controller board.

Everything appears to be lined up well, the threaded rod on the left z-axis motor does not appear to be out of alignment at top or bottom of z-axis travel. Manual control of the z-axis via the LCD appears to work fine and there is no noticeable difference in torque required to rotate the leadscrews manually when the printer is turned off. I have checked that the motor shield is not binding to the top of the motor. The motor does not feel hot when running.

Anyone else encountered this issue? Any suggestions? I am not going to redo z-axis calibration after every print and am not confident at all that I could print anything tall without steps being missed during layer changes.

I am assuming that the motors from an i3 mk2 should be identical to those on the mk3? My next attempt at diagnosing the issue is to switch out the motor for the one from my mk2 and see what happens.