The Advantages of Z Fade Height

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The Advantages of Z Fade Height

Postby cbxbiker61 » 2018-Jan-Sun-03-Jan

The advantage of Z fade height (ENABLE_LEVELING_FADE_HEIGHT, M420)
in Marlin on AVR printer boards.

Joseph Prusa had pointed out in one of his youtube videos that the firmware
was doing bed leveling compensation throughout the print process and seemed to
be soliciting solutions. This motivated me to look into an option that would
allow you to fade out bed compensation at a predetermined level. After I had
proof of concept code done I emailed him and asked him if he was interested.
He said yes, so I sent him the patch and he forwarded it to one of his main coders.

I then contacted thinkyhead (Marlin main man) and told him about my contact
with Joseph and asked him if he was interested. He said, yes so I put together
a pull request to get feedback. This seemed to get thinkyhead motivated to
implement fade height for most of the bed leveling algorithms, although he didn't
implement it for the mode I was using on my PrintrBot Simple (AUTO_BED_LEVELING_LINEAR),
so I cleaned up my code and did an external patch to implement the missing code:

Since my initial code I had figured out a much cleaner way of doing it,
and the bed leveling overhead disappears once you reach the fade height.
I use 3mm. This would mostly be academic if there wasn't tangible evidence
of the advantages on AVR micros.

I started a print on both my Prusa MK2 and my PrintrBot Simple of the Sine Cube Vase using Slic3rPE 1.38.5 using the
same print settings for both (0.20mm 100mms Linear Advance, PLA 20% infill).
This model is quite challenging for the printer due to the number of small
moves required.

You would naturally think the MK2 would do a faster/better job. But no,
that's not the case. Prusa Firmware 3.1.0 has not incorporated fade height -
M420 yet. It seems to slow down as the z height goes up.

Both models printed with the same plastic - 3d Solutech PLA.

Slic3rPE 1.38.5 using same settings on both printers:
0.20mm 100mms Linear Advance, PLA 20% infill

Prusa MK2 printing the blue model:
print failed at 48+ hours 88% complete
Prusa Firmware 3.1.0

PrintrBot Simple with stock PrintrBoard printing the green model:
total print time 38 hours
patched Marlin 1.0.8
the patch allows fade height to be used with linear bed leveling and some other fixes ... 1227.patch
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Waiting for printbed temp...
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The Advantages of Z Fade Height



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