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Z-height and first layer issue:  

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TimW
 TimW
(@timw-3)
Active Member
Z-height and first layer issue:

I have been been very satisfied user of an MK3S for several years.  However, I have recently been printing some small parts which have highlighted a Z-scale problem. In summary my X and Y dimensions are within the measurable tolerances of my vernier caliper.  However, the Z-dimension is consistently 0.1mm to 0.2mm too high.  This is not a slicing problem as my test models are an integral number of my layer height ( e.g. Model 20mm / layer 0.2mm ).  I have printed test models from single layer ( 0.2mm ) up to 20mm high.  All have the same issue.  As the error is more or less constant I thought that this must be some sort of problem with my Z-axis offset.  I checked the calibration and printed a single layer model.  The results can be seen in the attached photo.

The first layer calibration print, on the left, looks good to me and has strong lateral strength which shows that the individual lines are uniform and well bonded together. 
The single layer print ( 0.2 mm ), on the right, looks completely different with significant gaps between the lines.  As the thickness of the single layer is > 0.2mm I checked the Live Z Adjustment and that was the same as the calibration setting.

I have also attached the g-code for the single layer print.

I would appreciate any thoughts on:

1) Why my printed Z-dimensions are 0.1 - 0.2mm too high, irrespective of the overall model height.
2) The loose unbonded nature of my single layer print.

Thanks.

Tim

Posted : 14/05/2022 3:02 pm
Diem
 Diem
(@diem)
Noble Member

Please re-run your first layer Z calibration and show us the print *on the print-sheet*

The g-code isn't a lot of use...

Please save your project as a .3mf file

Files > Save Project as

Zip the .3mf and post it here. It will contain both your part and your settings for us to diagnose.

Cheerio,

Posted : 14/05/2022 7:07 pm
TimW
 TimW
(@timw-3)
Active Member
Topic starter answered:
RE: Z-height and first layer issue:

Diem, thanks for your help.  Attached is a zip file containing the 2 files you requested.

 

Posted : 15/05/2022 8:29 am
fuchsr
(@fuchsr)
Noble Member
RE: Z-height and first layer issue:

I'd be more inclined to trust the calibration square than the in-built first layer calibration method (even though that rectangle looks pretty good) and adjust live z until the square comes out okay.

As far as the Z issue is concerned, curious. I saw the M92 gcode in your custom start-up code and thought that was it—but it's commented out. 

Posted : 15/05/2022 10:28 am
TimW
 TimW
(@timw-3)
Active Member
Topic starter answered:
RE: Z-height and first layer issue:

fuchsr, I will try what you have suggested.  A simple, but almost certainly incorrect, explanation of what I am observing is that no account is being taken of the calibrated Z-offset when printing.

Posted : 15/05/2022 10:49 am
TimW
 TimW
(@timw-3)
Active Member
Topic starter answered:
RE: Z-height and first layer issue:

"A simple, but almost certainly incorrect, explanation of what I am observing is that no account is being taken of the calibrated Z-offset when printing." This is obviously not right because my Z dimension would be ~1mm too high instead of ~0.1mm too high.

Posted : 15/05/2022 11:36 am
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