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First layer inconsistent extrusion... maybe?  

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marcel.w4
(@marcel-w4)
New Member
First layer inconsistent extrusion... maybe?

I have been having some issues with my prints, especially on the first layer, and I am not sure where to start to fix the issue of this "under extrusion".

The model in the picture was printer in the middle of the bed from left to right.

I have done all of the extruder calibration, z height adjustment. but I have not messed with the bed correction settings

It occurs with nearly every print, so I know the issue is not with the STL file I am using, but I would be happy to provide it if needed.

This model was printed in PLA with a majority of the default PLA settings in slic3r, printing on the glossy PEI powdercoated surface

Some of the things I did change was the steps per mm (in gcode)
the linear advance K value set to 45 from testing
extrusion multiplier set to 0.96

Looking at the heatmap from octoprint, it looks like the bed is a fair amount higher in the middle, which should mean that the print comes out more squished in the middle. I have tighted the screws as much as possible on the bed, but not so much that there is a potential to strip the screws or break them.

Any advice on where to start would be appreciated

Thanks in advance,

Marcel

Posted : 28/09/2018 7:26 am
leif.s
(@leif-s)
Eminent Member
Re: First layer inconsistent extrusion... maybe?

I have also been having issues with this since mk2.5 upgrade. I have printed first layer test squares on the various points on the print bed. Okay so my print bed isn't perfectly level, so left side was perfectly laid down then right side had gaps (z too high).

I did live z adjust to get as good first layer squish i can, but there was still inconsistency from left to right. I tweaked the z bed correction settings, but it seems they have no effect. The resulting test prints are always the same. Nozzle too high on the one side.
My conclusion was the auto bed levelling & bed correction settings weren't working!

What I have resorted to doing was manually turning the lead screw on the one side, do a z-level reading, and compare with the octoprint bed level readings until i get a result that was as level as possible. Of course this way I can only make adjustments on left/right side - fortunately my front/back results were almost perfect from the get go.

Yeah I know its a hack - but it was the only way I could get consistent first layer!

btw, my xyz calibration results in a "congrats, all perpendicular" even before the hack. so i really don't know whats up with auto bed levelling?

...
Posted : 28/09/2018 12:35 pm
RufusClupea
(@rufusclupea)
Reputable Member
Re: First layer inconsistent extrusion... maybe?

I've got similar issues on my MK3. I've called it a "washboard effect" for lack of a better term.
Like you guys, I've done all the calibrating & corrections.
Joan.t provided me with a list of possibles to check out, which I'm only partway through.

That's "MISTER Old Fart" to you!...
Posted : 29/09/2018 9:06 pm
vinic
(@vinic)
New Member
Re: First layer inconsistent extrusion... maybe?

Hi,

I was looking for solutions for exact same problem on my mK3... And found solution!

I did tests printing this file : https://www.thingiverse.com/thing:2838514
I was getting hairy/non-squashed squares around the center of the bed.

Then read few posts on this forum and found this one : https://shop.prusa3d.com/forum/hardware-firmware-and-software-help-f64/bed-level-calibration-t15517.html#p76866

I did a 10~15 minutes preheat and now I get perfect squares everywhere...

Even if it doesn't fully solve your problem, it sounds like a "must perform" operation in order to allow the bed to evenly warm!

Hope this helps

Posted : 02/10/2018 2:28 pm
randolph.l
(@randolph-l)
Honorable Member
Re: First layer inconsistent extrusion... maybe?

Looking at the heatmap from octoprint, it looks like the bed is a fair amount higher in the middle, which should mean that the print comes out more squished in the middle. I have tighted the screws as much as possible on the bed, but not so much that there is a potential to strip the screws or break them.

heatmap.png

Any advice on where to start would be appreciated

Thanks in advance,

Marcel

do you have to have a raspberry π with octoprint running on your printer to generate that heat map or can you get just from the Octoprint software fork for the Prusa machines?

Posted : 02/10/2018 4:42 pm
Mike01Hu
(@mike01hu)
Active Member
Re: First layer inconsistent extrusion... maybe?

My build resulted in a perfect alignment result but I still had inconsistent first layer results. After trying so many of the listed possible here, I did a detailed check of bed level using my own first layer test piece. From this I determined that as well as front to back and side to side errors there was a pronounced dip in the middle of the bed that made me think about distortion due to heat. With this in mind, I loosened the bed fixing screws and heated the bed to 65 degrees and re-tightened the screws while hot. The result was that the dip was no longer there but the other height differences were, so I then resorted to the bed level adjustments via the LCD, based on the measurements from my test piece but I found no correlation between the menu settings, that i assumed were in microns, and the measured differences. Nevertheless, after several iterations, I have achieved fair level across the bed, within 10microns except for the rear right corner that is around 20microns. All measurements were made using a micrometer, not calipers. I have yet to test with PETG but that will have to wait until I can get to my stock.

Posted : 04/10/2018 10:41 pm
marcel.w4
(@marcel-w4)
New Member
Topic starter answered:
Re: First layer inconsistent extrusion... maybe?


Looking at the heatmap from octoprint, it looks like the bed is a fair amount higher in the middle, which should mean that the print comes out more squished in the middle. I have tighted the screws as much as possible on the bed, but not so much that there is a potential to strip the screws or break them.

heatmap.png

Any advice on where to start would be appreciated

Thanks in advance,

Marcel

do you have to have a raspberry π with octoprint running on your printer to generate that heat map or can you get just from the Octoprint software fork for the Prusa machines?

Yes indeed, octoprint running Prusa Mesh Leveling 🙂

Posted : 15/10/2018 12:51 am
Daniele (Jollino)
(@daniele-jollino)
Active Member
Re: First layer inconsistent extrusion... maybe?


Then read few posts on this forum and found this one : https://shop.prusa3d.com/forum/hardware-firmware-and-software-help-f64/bed-level-calibration-t15517.html#p76866

I did a 10~15 minutes preheat and now I get perfect squares everywhere...

Where do you keep the nozzle during the preheat? I'm wondering if this helps you by taking the PINDA probe to a higher temperature, or just sort of helps the bed itself get into place, for lack of a better term.

Posted : 14/11/2018 10:01 pm
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