Hi there! I’ve just assembled my new K8400, print quality, etc. is perfectly fine but every print has shifting layers. Sometimes it’s just one or two millimetres, sometimes as much as 5 cm. The shifts always occur after a weird sound coming from somewhere around the axis or the motors, then the printer stops for a second and continues to print the layer, but somewhere else. I’ve tightened all the screws on the axis, used Slic3r and Cura with different models, I have even switched the motors to see if it’s a motor problem… Nothing seems to help.
are the x y rods properly aligned?
Thanks for your reply! Yes indeed, all the rods are aligned properly and parallel to the respective sides.
Check if the stepper drivers are correctly set.
Instructions can be found here =>http://manuals.velleman.eu/article.php?id=39#SHIFTEDLAYERS
Shifting layers (especially after a ‘weird’ sound) almost always means incorrectly aligned axis (even if they look correct). Check the procedure in the Wiki. And you often need to fine tune things a second time as it’s hard to get the perfect alignment right away.
Thank you very much raby. I’ve just reassembled the whole axis apparatus. Now I get the weird sound when I move the Y axis to the rear, so it seems that the incorrectly aligned axis are the problem; I guess you’re right! I will try aligning them again 
Thanks for the link to the wiki!!