First Layer Cal, Went from 0.0 to -0.9 Z-axis biased and not working
 
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First Layer Cal, Went from 0.0 to -0.9 Z-axis biased and not working  

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nameo0.lsk
(@nameo0-lsk)
Active Member
First Layer Cal, Went from 0.0 to -0.9 Z-axis biased and not working

Hello fellow 3D printers,

I recently obtained my i3 MK3 printer and assembled the printer with no issues. I had no issues working through set-up with the exception of the filament auto load which I disabled and First Layer Calibration.

 

For 1st Layer Cal, I have tried everything (see below) and I still can't get the right outcome. The result sometimes attaches itself to the nozzle and creates a blob on the nozzle since the PLA is not adhering to the textured plate but it always results in the lines being "high" and never printing "flat." I am using the gray PLA that was shipped with the printer and default PLA grey, the textured steel plate, and the printer's default temps for PLA

  • Changing the z-axis bias from 0.0 to just under -0.9 (Any lower and the nozzle will come in contact with the bed)
  • Cleaning the bed with 91% IPA (not the beer variant though)
  • Cleaning the nozzle with a bristle brush while the nozzle is still warm but not hot.

I still have my 1st Layer Cal print coming out as if the nozzle is too high.

 

The image below is two (2) of the best strips that are printed as the first thing during 1st Layer Cal. Note how they have a flatness to them on the left but after the print starts, they change to be more cylindrical and high almost as if the nozzle is to high at that point even though nothing changes.Two of the best strips that are printed as the first thi g during 1st Layer Cal

Here is an example of one of the better finales for the 1st Layer Cal1st Layer Cal finale

Below is an illustration I made for what I can observe happening when I get the nozzle above the printer surface.My illustration

I am tired of shooting in the dark and not getting any results.

 

My next intuition is to start messing with temps but I don't have any hands-on experience with a 3d printer besides printing this 1st Layer Cal.

 

Sincerely,

-Me

Posted : 12/02/2020 5:01 pm
Steve
(@steve-5)
Trusted Member
RE: First Layer Cal, Went from 0.0 to -0.9 Z-axis biased and not working

First, welcome aboard me.  You are off on an exciting journey.  I too am a new MK3S owner and you will learn a lot just following these forums.

To your problem.  I see two things in the pictures that you posted. First you, like me, opted for the textured PEI build sheet with your printer.  You will see on the forum many discussions regarding difficulty getting PLA prints to stick well to these sheets.  The first thing that nearly all of the experienced users will tell you is CLEAN YOUR SHEET! Most of the users who successfully print PLA on the textured sheet start with a thorough scrubbing under HOT water with a dish soap free of perfumes, moisturizers, etc.  A favorite recommendation in the United States is Dawn.  Wash the sheet using a little soap and copious amounts of water as hot as you can stand using only clean paper towels to scrub and dry.  The key is to remove all potential contaminants, primarily skin oils from the surface. Be extremely careful not to touch the surface from now on with your bare hands!

The second issue is that your live-Z is still much too high.  The nozzle must be close enough to the bed surface to "squish" the filament into the textured surface of the build plate.  So, now that you have a clean build plate, the next recommendation is to ignore the built in first layer calibration routine in favor of the method outlined in this extremely popular post:

https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/

Using this method will allow you a much better opportunity to observe what is happening with the filament while you make your adjustments to the "live-Z" setting as it is printing a much larger test "coupon".  Once you have a test sample that you think is good you can upload a picture in the forums and several people will likely evaluate it and provide feedback.

A couple of notes for you.  The first "strip" of plastic laid down at the beginning of the print is known as the purge line.  The purpose of this extrusion is to make certain that the filament is flowing well from the extruder, do not attempt to adjust live-Z here as this line has no relation to the actual printing thickness to come.

Second, you may want to revisit the setting of the height of the PINDA sensor in the build instructions prior to resuming your attempts to calibrate the first layer.  The PINDA sensor height is set using the thickness of a "zip tie" but the instructions are somewhat ambiguous about how close to the build plate you should position the nozzle tip before using the "zip tie".  I found that placing a piece of paper between the nozzle tip and the bed surface and then slowly adjusting Z down until the nozzle just started to touch the paper (indicated by a slight friction when trying to slide the paper around under the nozzle) put the nozzle in a position where using the "zip tie" allowed me to get the PINDA sensor well postioned.

Finally, the printer firmware is capable of storing different live-Z values for up to 3 different build sheets.  Make certain that you have selected the desired build sheet from the printer menus before beginning the adjustment procedure or, like me, you will have to learn how to rename the sheets or re-run the live-Z procedure.

Good luck and report back either success or failure.

Regards,

Steve

This post was modified 2 years ago by Steve
Posted : 13/02/2020 5:07 am
rmm200
(@rmm200)
Noble Member
RE: First Layer Cal, Went from 0.0 to -0.9 Z-axis biased and not working

Answer bot approves of that post.

I would have said the same.

Posted : 13/02/2020 5:28 am
nameo0.lsk
(@nameo0-lsk)
Active Member
Topic starter answered:
RE: First Layer Cal, Went from 0.0 to -0.9 Z-axis biased and not working

[SOLVED]

 

I wanted to update this post since the issue was me.

 

I didn't know that the nozzle had to be about a paper's thickness away from the print bed. I was also worried about damaging the nozzle due to all of the warnings that were made during the earlier calibration steps about not having the nozzle come in contact with the bed.

 

Thanks for everyone's help! =D

Posted : 17/02/2020 3:48 am
Steve
(@steve-5)
Trusted Member
RE: First Layer Cal, Went from 0.0 to -0.9 Z-axis biased and not working

Glad you got it working for you.  I agree that this is one slight bump in the otherwise excellent build instructions for this printer.  That is why I used the online build manual and read all of the comments when I built my kit.  The opportunity to learn from others about their trials was valuable. I do wish that Prusa would update this step though.  I think many builders end up with the PINDA probe set far too high initially which leads to either difficulty with even detecting the bed or worse to live-Z settings that are extremely close to or exceeding the -2.00mm recommended limit.

Regards,

Steve

Posted : 18/02/2020 2:04 am
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