Layer shifting in in Y-axis
Hello everyone,
I repeatedly experienced an issue with layer shifting of about 5mm in Y-direction that always occured in the same printing height of about 2mm (layer 11). Just before the problem occurs, I could hear a rattling noise which was probably belt skipping, but could not find out what caused it. There were no visible collisions of nozzle and parts.
To gid rid of this, I tried the follwing without success:
- Checked all belt tensions
- Checked that motor pulley screws are tightened
- Checked printer for foreign object that might cause collisions (screws, ...)
- Checked if bearings move freely without resistance
- Checked cables and connections on Y-axis motor
- Fell back from firmware 5.0 to 4.7
- Checked for protruding bearings and tightness of bearing fixations
- Removed and re-attached Y-axis belt tensioner parts
The problem persisted. When I was assembling the Y-belt tensioners, I had an idea, but that is probably far fetched. Let me know what you think. From the parts, I could see that the last time I printed it occured when I was printing in the lower right corner (front right) of the printbed, that means the printbed goes all the way to the back. Checking the Y-belt tensioner I saw that the fixed side of the tensioner parts collides with the Y-motor holder at the far end of movement. So could it be that when the buildplate moves to the back too fast, it collides on the tensioner, which applies a short momentum to the part which results in a very short loss of belt tension which makes the belt skip a short distance on the pulley (see illustration)?
RE: Layer shifting in in Y-axis
I have a CAD file with a complete MK4 and it in fact seems that the tensioner bangs to the motor holder.
Strange thing this was not seen.
Just tried to modify the motorholder a bit so that this problem should be solverd.
RE:
STL file was not attached to the mail, trying again ....
Why does that refuse to work? Trying a zipped file .....
RE: Layer shifting in in Y-axis
So do you think the collision at this area is not intended by design? In my opinion it does not help to keep a constant belt tension at least.
RE: Layer shifting in in Y-axis
I in fact can not imagine that this was not intended to be so. Can something like this be overseen?
At least the Y-Axis must hit some point on each side to stop, if it is the rod holder or the motor holder.
But hiting the motor holder means to lose some mm in Y direction.
Who knows .....
RE: Layer shifting in in Y-axis
Just had a look at my MK4 after I made the modification only in CAD.
Yes, the tensioner hits the motor holder before the bearings hit the rod holders.
I think that must be inteded to be so. If I would use the modified motor holder instead the bed will go some mm more to the printers back. But at the same time the nozzle may come over the printbed on the front side.
The space should be enough to avoid this, but I would not use my modified motor holder indeed.
So I do not think that this is the reason for the layer shift. Must be the firmware.
RE: Layer shifting in in Y-axis
I am having the same problem. Did you ever figure out what the issue was?
Same issue as here it seems. https://www.reddit.com/r/prusa3d/comments/14wcxnt/yaxis_bedmotor_mount_interference/