First layer issue  

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Archetrico
(@archetrico)
Active Member

Hi,

I got and set up a MK3S printer and im not having any problem with the prints, everything is printing with no issues, but just i am having a bad looking first layer, it doesnt affect the rest of the print, its just stetical issue and i dont know why it's happening. Any clues?

I am slicing with PrusaSlicer 2.0 in defaults for prusament and printing with prusament...

I tryed live adjusting the z but in the first tests i had a perfect first layer, its after some prints that it got looking like this:

Best Answer by Miguel:

Posted by: adrianmartinezmorcillo

Thank you so much for your answer!

I will indeed try to raise the extruder before printing and see if that solves the issue, otherwise a slight live z adjustment should do it.

The “problem” of live z is that in this video “original prusa i3 mk3 guide for new user” it is mentioned that the z should be somewhere around -1mm, and mine wasnt reaching that level, it is around -0.8, so setting it farther away from that distance didn’t sound reasonable, but maybe it is if the pinda doesnt measure properly due to heat.

Thank you joantabb, i will try and find a solution

Not so sure about that, in the video they say that you have to adjust the level and they got a 1.150, if i recall correctly, but this is the value they got and it may, most likely, be different in your printer since it depends on the position you tighten the pinda screw, what they say is that if you need mora than -2000 adjustment means you have to lower the pinda physically so a -0.800 value should be correct, nothing wrong with it

In my opinion, still new here, you have plenty of room, up and down, to play with the Z correction 

 

 

Posted : 02/06/2019 1:10 pm
JoanTabb
(@joantabb)
Moderator

that effect is because the extruder is too low.

Live Z is too big a negative number...

I come from Mk1, mk2 and mmuv1 .
the mk1 didn't have auto bed levelling, so the Mk2's bed levelling was a massive step forward...   BUT, there was an issue...  the Pinda version 1 (three wire) as used on the mk2, was temperature sensitive... 
this lead to different performance if the pinda was close to the heatbed during preheating, or further away.

it was common for live Z adjustment to give different results if the extruder was low (Say after doing a failed live z test,)if the extruder was high after doing a successful print.
I found that always raising the extruder to about 60mm reduced the issue.

The Mk3, has a version2 Pinda (4 wire) with integrated thermistor, to reduce these thermal differences... 

But it doesn't always work. 

I still tend to raise the extruder before heating the printer, and I don't get the issue,  you might find this simple exercise helps.

other people set the printer to wait until the pinda reaches a set temperature before starting mesh bed levelling...  a common temperature is 30Centigrade!

regards Joan.

.

This post was modified 2 years ago by JoanTabb
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 02/06/2019 11:08 pm
Archetrico
(@archetrico)
Active Member

Thank you so much for your answer!

I will indeed try to raise the extruder before printing and see if that solves the issue, otherwise a slight live z adjustment should do it.

The “problem” of live z is that in this video “original prusa i3 mk3 guide for new user” it is mentioned that the z should be somewhere around -1mm, and mine wasnt reaching that level, it is around -0.8, so setting it farther away from that distance didn’t sound reasonable, but maybe it is if the pinda doesnt measure properly due to heat.

Thank you joantabb, i will try and find a solution

Posted : 04/06/2019 7:27 am
Miguel
(@miguel-6)
Eminent Member
Posted by: adrianmartinezmorcillo

Thank you so much for your answer!

I will indeed try to raise the extruder before printing and see if that solves the issue, otherwise a slight live z adjustment should do it.

The “problem” of live z is that in this video “original prusa i3 mk3 guide for new user” it is mentioned that the z should be somewhere around -1mm, and mine wasnt reaching that level, it is around -0.8, so setting it farther away from that distance didn’t sound reasonable, but maybe it is if the pinda doesnt measure properly due to heat.

Thank you joantabb, i will try and find a solution

Not so sure about that, in the video they say that you have to adjust the level and they got a 1.150, if i recall correctly, but this is the value they got and it may, most likely, be different in your printer since it depends on the position you tighten the pinda screw, what they say is that if you need mora than -2000 adjustment means you have to lower the pinda physically so a -0.800 value should be correct, nothing wrong with it

In my opinion, still new here, you have plenty of room, up and down, to play with the Z correction 

 

 

Posted : 05/06/2019 9:17 am
johannes.m
(@johannes-m)
Eminent Member

In your case i would try setting it to ~ -0.750 or try to set it to -0.700 and dial it in from there.

Posted : 05/06/2019 12:22 pm
DarcShadow
(@darcshadow)
Trusted Member

Just for reference, the printer I use the live z is -0.4. It's just a matter of where the height of probe ended up during build.

Posted : 05/06/2019 2:27 pm
johannes.m
(@johannes-m)
Eminent Member

I see, yes it depends on the PINDA height. He wrote in his post above that he is at about -0,800 so I from his pictures I thought it would be a good start to raise 100.

Posted : 05/06/2019 2:52 pm
Archetrico
(@archetrico)
Active Member

Thank you all for your reply,

 

I was indeed mistaken thinking that -0,800 wasn’t enoug. It makes sense that is up to how close the pinda sensor was located during build.

 

Unfortunately i’m far from home this week and i couldn’t check your advices yet. So as soon as i get there i will try and adjust a new live z (thank for the advice of starting around -0,700, johannes-m)

 

I will post again if the problem is solved 😊

Posted : 05/06/2019 3:20 pm
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 --
(@-2)
Illustrious Member

The PINDA is temperature sensitive, and while Prusa provides a calibration for it, the best way to minimize that dependency is to use the M860 command to allow time for the PINDA to warm to a set temperature:  this way each run will be much more consistent.

M860 S35 ; wait until PINDA is >= 35C
G80 ; mesh bed leveling

The PINDA is set about 1.2 mm above the nozzle if you use a cable tie as a reference. It senses the bed at about 2 mm. So it needs to be "adjusted" a fraction of a millimeter downward.  Hence the -0.800 typical range.  

This post was modified 2 years ago by --
It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 05/06/2019 5:20 pm
Archetrico
(@archetrico)
Active Member

Great info, thanks for the tip!

anyhow my live z adjustment was lower than necessary:

My live z was -850, and i decided to start at -800 to test (you can see at the center part it wasn’t enough) and i modified it after a while to -750 and then it was perfect, now i can get a decent first layer.

So the only thing left to do is to use the command m860 as tim-m30 mentioned to avoid any kind of irregularity (the very first line of the first layer is always still more down that it should be)

 

Thank you all for your replies 

Posted : 08/06/2019 7:01 pm
--
 --
(@-2)
Illustrious Member

The -0.750 looks good.  No over extrusion as the layer fills in. 

The first few mm of layer 1 extrusion is usually thicker than expected.  Purge and skirt are there to help with that "artifact" of the heating process.  There are ways to tune it out, but each has negative affects, too. 

Also - the M860 doesn't cure everything, but it will help run to run consistency.   Another place to improve is setting the printer to use the 7x7 mesh bed cal instead of the 3x3.  But honestly, your layer one looks pretty consistent and I'd not change anything until needed.

It is always wise to get more than one opinion... as for trusting Prusa? No way man....
Posted : 08/06/2019 10:36 pm
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