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Z-Level not consistent on multiple prints  

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screw_ball69
(@screw_ball69)
Eminent Member
Z-Level not consistent on multiple prints

For some strange reason my printer has developed a bug as of late.

I basically have to print two calibration squares before doing any print, the first one will barley stick and be as if the nozzle is way to high off the build surface. modifying the Live Z also changes nothing.
However once the first one is done and I start the next one without altering the Z-Height at all it prints the calibration near perfect and will only need fine adjustment depending on the filament.

I would like to fix this since its A) very wasteful and B) extremely hard to tune

Napsal : 03/04/2019 7:19 pm
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(@)
Illustrious Member
Re: Z-Level not consistent on multiple prints

There are so many variables in what you just said. Where did the calibration squares come from? Sliced yourself, are the two sets the same gcode? Do you home the printer at any time? Etc. And when you adjust Z-level, where do you do the adjustment at (firmware, external software, first layer cal, Z-level tune??

Napsal : 03/04/2019 9:58 pm
screw_ball69
(@screw_ball69)
Eminent Member
Topic starter answered:
Re: Z-Level not consistent on multiple prints

The calibration squares are the ones from here:
https://shop.prusa3d.com/forum/assembly-and-first-prints-troubleshooting-f62/life-adjust-z-my-way-t2981.html

The same G-code has lived on my sdcard for over a year now and its the one I use both times.

When I am adjusting Z level its the live Z adjust on the printer

Napsal : 03/04/2019 10:12 pm
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(@)
Illustrious Member
Re: Z-Level not consistent on multiple prints

Have you cleaned the bed? Silly question I know, but it fixes so may adhesion & bad first layer problems I have to ask.

My logic is the first test patches remove the finger prints you left removing the last part. The second test patches stick well enough... and finish the cleaning, sort of.

Along this line of thought, older PEI can oxidize and become less tacky to PLA. A good soap and water wash and then acetone scrub can help refresh the tack.

Napsal : 04/04/2019 6:18 am
screw_ball69
(@screw_ball69)
Eminent Member
Topic starter answered:
Re: Z-Level not consistent on multiple prints

Yes I am cleaning between prints with 99% alcohol and occasionally with acetone when stuff doesn't stick.

I dont think its a adhesion issue because the first test patch I still have to peel off the print bed. The whole thing is stuck down but each individual line is loose after I peel it off.

Napsal : 04/04/2019 7:02 pm
screw_ball69
(@screw_ball69)
Eminent Member
Topic starter answered:
Re: Z-Level not consistent on multiple prints

Here is print 1 vs print 2. No settings changed and cleaned between prints same gcode for both.

https://imgur.com/2PnMTXP

I'm also not sure if there is something weird going on with my bed maybe?
One half of this is over extruded and the other half is fine

https://imgur.com/sMOk0iw

https://imgur.com/F3LT0GZ

Napsal : 04/04/2019 9:31 pm
Mustrum Ridcully
(@mustrum-ridcully-2)
Honorable Member
Re: Z-Level not consistent on multiple prints

Knock off using ISO and especially acetone, over time it will make the bed material brittle

the best prep for your bed is to wash it with warm water and dawn dish soap (in the UK use Fairy liquid) by using a wad of clean kitchen paper towel dampen with warm water and put a dollop of Dawn on the pad and scrub (i do it twice at 90 deg to each other holding the plate by the edge as it is a phonograph record rinse under running water and dry with clean paper towel keep touching only by the edge... I do this every other day of printing with both kinds of plate.

Napsal : 04/04/2019 11:32 pm
screw_ball69
(@screw_ball69)
Eminent Member
Topic starter answered:
Re: Z-Level not consistent on multiple prints

I understand that overuse of acetone will make PEI britle which is why I rarely ever use it but damn near everyone uses ISO or denatured.

Napsal : 05/04/2019 12:33 am
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(@)
Illustrious Member
Re: Z-Level not consistent on multiple prints

re: Alcohol -- it doesn't remove fingerprints very well, soap and water is best. Acetone is to remove PE oxide build up.

I am thinking you have an uncompensated PINDA ...

Add this line to your Printer Custom GCODE ... before the G80 commands, something like this.

G28 W ; home all without mesh bed level (hot)
M860 S35 ; wait for PINDA temp to stabilize
G80 ; mesh bed leveling

https://github.com/PrusaOwners/prusaowners/blob/master/Manual_print_based_PINDA_temperature_calibration.md

Napsal : 05/04/2019 1:14 am
screw_ball69
(@screw_ball69)
Eminent Member
Topic starter answered:
Re: Z-Level not consistent on multiple prints

Ah good to know , I generally try not to touch the bed itself but I'll keep that in mind for the future.

I'll see if I can try this and report back

Napsal : 05/04/2019 1:42 am
JBinFL
(@jbinfl)
Reputable Member
Re: Z-Level not consistent on multiple prints

Joe:

After cleaning the bed with Dish soap and water, if it does not fix it, you may want to try a 9 square bed calibration check if you have not already - e.g. 9 squares across the bed covering the corners and center. you can make one from your calibration square STL or download one from thingiverse...

I know it sounds strange, but changes to the firmware and or Slic3rPE can cause bed leveling issues out of the blue. If that is the case, the bed level correction can fix minor issues...

Just a suggestion.

Strange women, laying in ponds, distributing swords, is hardly a basis for a system of governance!

Napsal : 05/04/2019 2:03 am
screw_ball69
(@screw_ball69)
Eminent Member
Topic starter answered:
Re: Z-Level not consistent on multiple prints

I'll give it a shot.

curious how do you do 7x7 mesh leveling that was added in the last firmware? the wizard only does 3x3.

Napsal : 05/04/2019 5:17 am
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(@)
Illustrious Member
Re: Z-Level not consistent on multiple prints

As far as I know (I haven't upgraded to 3.7 yet) there is a function in the LCD menu to select 7x7, and a few "speed" options for it (one pass, 3, passes, 5 passes or something similar)... a few people are having issues with the fast setting, and there is a "magnet" comp setting. My older patched fw uses 3 or 4 passes (repeats a measurement of each location then averages), and no magnet compensation and I am extremely happy. And the extra time for the extra steps is well worth it.

Napsal : 05/04/2019 9:31 pm
JBinFL
(@jbinfl)
Reputable Member
Re: Z-Level not consistent on multiple prints

The 7X7 Mesh bed level is under a new menu in settings called Mesh bed level. Lots of options in that menu.

I like it and it is very fast. I do the 7X7 with 5 points and it is not much more than the original 3X3 mesh bed level.

Strange women, laying in ponds, distributing swords, is hardly a basis for a system of governance!

Napsal : 06/04/2019 12:52 am
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(@)
Illustrious Member
Re: Z-Level not consistent on multiple prints

And - if the PINDA is temperature sensitive, it won't matter how many spots you test if each is using a sample taken at a different PINDA temp.

Napsal : 06/04/2019 5:56 am
chris.k26
(@chris-k26)
Active Member
Re: Z-Level not consistent on multiple prints

I had the same problem. I switched off magnet compensation & it seems to be ok now. I was using the patched firmware for a month without issue with 7x7 bed levelling. I noticed with the magnet compensation on, every time I use Z home the nozzle would be higher and would need the live Z adjusting I would start at -0.150 and end near -0,700. Drove me crazy for a couple of days. Is this a firmware bug?

Napsal : 07/04/2019 8:44 pm
chris.k26
(@chris-k26)
Active Member
Re: Z-Level not consistent on multiple prints

Problem is back today. Just tried printing and the Z position is very inconsistent. Tried going back a firmware version same thing. Any help appreciated!

Napsal : 08/04/2019 10:23 am
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(@)
Illustrious Member
Re: Z-Level not consistent on multiple prints

@chris, have you ran the PINDA temp calibration or added the PINDA temp wait command?

Napsal : 08/04/2019 8:35 pm
chris.k26
(@chris-k26)
Active Member
Re: Z-Level not consistent on multiple prints

I have added the PINDA wait command but haven't tried temperature calibration, I wasn't sure what it did actually?

Napsal : 09/04/2019 6:51 pm
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(@)
Illustrious Member
Re: Z-Level not consistent on multiple prints

8.2 P.I.N.D.A. probe calibration / Temp. calibration
(Experimental/Optional)
All induction proximity probes drift the sensing distance with increased temperature. This might affect the quality of the first printed layer. P.I.N.D.A. v2 probe, included in the MK3, has an embedded thermistor inside its body to measure the temperature and fully compensate for the drift. A pre-calibrated data table is stored in the printer and the temperature calibration is active by default.

Napsal : 09/04/2019 9:53 pm
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