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XYZ Calibration details

Relevant for

MK2.5
MK2.5S
MK3
MK3S
MK3S+
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Starting with the firmware version 3.0.12, more detailed information about XYZ calibration results becomes available. This feature can be found in LCD menu -> Support -> XYZ cal. details.

The first screen tells you the distance of the “perfect” position of your front 1st, 2nd, and 3rd calibration points. Ideally, all of these are positive and at least 0.5 mm or more. If the margin is between 0 and 0.4 mm, then there is a chance that your calibration will not be successful ("XYZ calibration failed" error). 

For the Original Prusa MK2/S, in order to improve your results, you should adjust the threaded rods of the frame so that all of the points can be reached during the calibration process.

To achieve the best results, aim for the smallest possible difference between Left and Right numbers. A difference of up to 0.1mm is considered good.

Pressing the knob will take you to the second screen. This screen identifies how far you are from the perfect perpendicularity. It is measuring the skew of your X/Y axis.

  • Over 0.25° = Severe skew compensating for the offset of 1.1 mm on 250 mm length 
  • Between 0.25° and 0.12° = Slight skew compensating for the offset of 0.5 mm on 250 mm length 
  • Under 0.12° = No need to compensate, X and Y axis are perpendicular. Congratulations! 

It may seem that the compensations are not that significant. However, if we take into consideration the 250 mm X-axis length, 1.1 mm is a large margin. In order to improve your axis perpendicularity, make sure the difference in the front calibration points distance is minimal.

When you get your axes perpendicular or just slightly skewed, nothing needs to be tweaked as the printer will perform with the best accuracy.

 

4 comments

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RD
My first layer calibration prints are good around the edges, but not in the center.  The center is farther away from the print head.  Based upon comments, I reseated and tightened the bed using the suggested tightening sequence (middle last).  Then I redid the XYZ calibration.  This is an Original Prusa i3 MK3S+ printer.Question, I have the following info from XYZ Cal Details, but I don't understand what these numbers mean.  Please help. Y distance from min;  Left 10.74mm, Right 10.45mmSkew 0.02 degrees[0;0] pt offset;  X 0.07mm, Y 0.26mm TIA
William H. - Official Prusa

Did you try to start with the middle screw, as is instructed in the assembly manual?

3k334tb
I also started with the middle screw and have the same issue. The center is farther from the extruder than the sides. My skew is 0.02 degrees. I have it working for the most part, however I am not the only one with this issue while following instructions.
bedesten
I have the latest firmware so am seeing  Y distance from minimum of left 10.53mm and  right 10.54mm  Skew of 0.15 degrees Slight skew 0.12  severe skew 0.25 [0;0] point offset of x -0.41  and  y -0.03 can you point me in the direction of the thing(s) i need to adjust please?
David

Hi! If you are using the MK2/2.5/S printer, ensure you are running the stock unmodified setup and try to square the frame by adjusting the threaded rods so that the frame is perfectly squared. A square gauge might be helpful in this case.

Tomaitch
I have had to dismantle my printer to replace the Y belt but now keep failing the XYZ calibration. I have the latest firmware so am seeing 
Y distance from minimum of left 9.99mm and  right 9.73mm
Skew of 0.15 degrees
[0;0] point offset of x -2.22 and y -0.49.
can you point me in the direction of the thing(s) i need to adjust please?
David

Hi! Check the pulley on the motor is installed correctly.
Check the y-belt-holder and y-belt-tensioner parts have the correct orientation, the heatbed cable does not hit the wall behind the printer and there is nothing disabling the heatbed from reaching the furthermost position. Keep watching if the PINDA probe isn't giving you an intermittent signal :)

Tomaitch
I think you found my error(s). I had refitted the y belt too tight so I added a washer between the idler and the frame. this was enough to skew my calibration so Many Thanks :-)
Beech76
"In order to improve your results, you should adjust your threaded rods so that all of the points can be reached during the calibration process."I am not sure what this means. I am having problems with the 4th point failing the calibration with the usual XYZ calibration fail?
William H. - Official Prusa
That was referring the threaded rods of the MK2 frame. Did not make much sense before that. Updated:)