Measured correlation between layer height, first layer calibration, and bed level correction?
 
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Measured correlation between layer height, first layer calibration, and bed level correction?  

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bumgarb42
(@bumgarb42)
Active Member
Measured correlation between layer height, first layer calibration, and bed level correction?

I'm brand new to 3D printing and just built my first Prusa i3 MK3S+.  I'm trying to get the first layer calibrated to close to .20mm across most of the surface, primarily because my first couple of projects are going to be clock faces that I'd want as smooth as possible across 8 inches (~200 mm).  

I know visual is the suggestion, but the small incremental adjustments I'm making seem to be wasting a lot of filament.   I got the first layer calibration print at .20mm for that small square in the front left, but printing Benchy and the Prusa badge showed the center of my surface had a first layer height with gaps and measured .28mm with calipers.  Further adjustment to get the center down to .20mm has put my left, right and front too smashed and well below .20mm - the 3x3 squares have lots of scarring.

I've tried searching but I cannot find anything that verifies a true MEASURED relationship between the layer height of .20mm, the first layer calibration adjustments (#.### in unknown units) and the bed level correction (+/-100 microns) so that I can make sense of the incremental changes I'm making. 

I'm hoping someone can verify if this is correct...

If the first layer height target is .20mm, then we are talking about 2 x 10^-4, were mm would be 10^-3.

From a Prusa video or website, I saw that the first layer calibration is usually between -0.400 and -1.500 AND that going to -2.000 means you need to adjust the PINDA or other hardware.  SO, I've been assuming that for the first layer calibration setting, where we have digits for w.xyz , that:

  • "w" is also 10^-4
  • "x" is 10^-5
  • "y is 10^-6 (or microns)"
  • "z" is 10^-7

Is this correct?

I saw the bed level correction can be +/-100 microns or 10^-6, is that correct?

I'm trying to figure out how I can adjust out a center measurement of .28mm if my left, right, and front are measuring below .20mm because adjusting z down in the center by -0.08mm would move my left, right, and front down to around .1omm... and adjusting the bed level correction would only allow an adjustment of +/-0.01mm, not the +/-.08mm that I'd need to bring the left, right, and front closer to the center.

Any confirmation on the calibration measurement correlations or suggestions on getting  a smooth as possible first layer across most of the print surface would be greatly appreciated!

Thanks!

 

Posted : 24/07/2021 5:13 pm
fuchsr
(@fuchsr)
Noble Member
Live z

I think the consensus is that live z is essentially millimeters although to my knowledge Prusa has never officially confirmed this. But it's easy to verify. The textured sheets are about 0.4 mm thinner than the smooth sheets, and they require live Z to be adjusted down by about o.4.  

Posted : 25/07/2021 11:08 pm
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