UM3 and dual extrusion/dual material alignment

[paoletto 3]

Hi, so a question from a first timer in dual extrusions here:

I tried to print a model of mine setting a cutting mesh for using the second extruder.
First extruder is PLA, second extruder is TPU.

The final result is pretty good, however i feel a misalignment between the two extruders: Cura shows perfect alignment in the preview, yet in the final model there seems to be a shift in the TPU part, leaving some sort of step on one side, and spilling out on the other. Is this a known problem of any sort? I thought of maybe printing it in another orientation, to see if that shift is also present in a different direction..
The printer is configured to do calibration before every print.

Pictures: https://imgur.com/a/6WBm8OC  (somehow ffox/linux messes up with images uploaded directly to the forum)

Edit: should i perhaps do XY calibration? (never done..)
Edit2: I see that the calibration submenu has a "change xy offset" where i have +14 xoffset and +0  yoffset. Not sure if these are factory default or what. I will try to change the xoffset and try again. I assume these values in millimeters?
 

Edited December 9, 2022 by paoletto

[gr5 2,224]

14 is a lot.  You could try zero.  Or do the XY calibration.  Doing the XY calibration is the proper way.  Do you have the calibration sheet?  After it lays down material from both cores you are supposed to remove the glass and place on a piece of paper so you know which lines are +1,+2,+3, etc for each axis.

 

See these instructions

 

https://support.makerbot.com/s/article/1667410778876?utm_id=UMa1709000000F48h

 

[leonhart88 2]

I'm also curious what units the XY calibration numbers represent because it doesn't seem like they are a mm value like on many other printers (usually 0.1mm increments).

 

Is there a way to manually view or edit the offset in mm units?

[gr5 2,224]

Yes you can edit the offset directly without doing the calibration and I believe when you do that it shows you the old values.