Automated bed levelling - i don't get it?  

RE: Automated bed levelling - i don't get it?

Is the printer simply moving from left to right? OR
Is it PRINTING, as it moves from left to right? 

If it's only moving, I expect it will not follow the mesh deviations.
200 x 4 x .2 mm stl

Try the attached file, it should give you a long thin strip, across the buildplate. which will hopefully encourage the demonstration of Mesh Bed Levelling

regards Joan

RE: Automated bed levelling - i don't get it?

Thank you Joan. The printer is actually printing. Tonight i will do your little test. I also re-install the firmware on the machine.

I will report back.

Regards,

Eric

RE: Automated bed levelling - i don't get it?

Good Luck

Joan

RE: Automated bed levelling - i don't get it?

Hi Joan, i re-installed the printers firmware 3x and after that i printed your file where the printerjead moved completeley from left to right. And i was able to see the printer correcting my somewhat crappy build plate! So solved this - check. Why you can make corrections in the software i still don't understand but hey -it works

Thanks for your support!

Eric.

RE: Automated bed levelling - i don't get it?

Cheers Eric,

Could the ability to correct in software, be a facility for printers which do not self correct?  Prusa slicer supports many non prusa printers.

regards Joan

RE: Automated bed levelling - i don't get it?

But this functionality is in the MK3s+ menu - not in Prusaslicer. That is what confuses me.

Regards,

Eric.

RE: Automated bed levelling - i don't get it?

Posted by: @eric-25

Hi Joan, i re-installed the printers firmware 3x and after that i printed your file where the printerjead moved completeley from left to right. And i was able to see the printer correcting my somewhat crappy build plate! So solved this - check. Why you can make corrections in the software i still don't understand but hey -it works

Thanks for your support!

 

Eric.

You need to be more specific about what you do not understand, software could mean basically everything... Are you talking about the bed level correction in the MK3 LCD menu? Also you need to use the correct terms to differentiate different things without confusion. Starting with the thing you refer to as "automated bed leveling" is called "mesh bed leveling" in the prusa documentation.

RE: Automated bed levelling - i don't get it?

@ Robin, thank you for your responce. I get it totally, reading my reply to Yoan in the middle of a conversation. Let me rephrase based on my initial post text;

So i just don't get it: every print i start the printer runs a 7x7 mesh bed levelling routine. Storing the z-level at a certain point of the bed. The Prusa firmware let's you correct the mesh in its's LCD menu(front,back, left, right etc.), which gets me puzzled because the printer corrects small variances in the z-height of the bed level automatically - based on its mesh measured by the Pinda probe.

 So i cannot figure out why you would want to adjust the mesh values via the LCD menu, when the printer corrects the right z-height automatically while printing?

I hope i made myself clear using the correct terminology.

Thank you, Eric.

RE: Automated bed levelling - i don't get it?

the Mk1 Prusa  and many other non prusa printers don't have automatic mesh bed levelling, 
Bed level correction has been in the firmware for a long time. 

Many people who play with Bed level correction mess things up... 

There are many features in Prusa slicer, you don't have to use them all. 

Do you believe that you have a mesh bed levelling issue? 

the 7x7 Mesh bed levelling process has 11 test points that are corrupted by magnets beneath the build plate, 
It is wise to leave Magnet compensation on. this reduces the active points to 38. but it's still better than 9

https://www.prusa3d.com/downloads/manual/prusa3d_manual_mk3s_en.pdf  
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RE: Automated bed levelling - i don't get it?

Posted by: @eric-25

@ Robin, thank you for your responce. I get it totally, reading my reply to Yoan in the middle of a conversation. Let me rephrase based on my initial post text;

So i just don't get it: every print i start the printer runs a 7x7 mesh bed levelling routine. Storing the z-level at a certain point of the bed. The Prusa firmware let's you correct the mesh in its's LCD menu(front,back, left, right etc.), which gets me puzzled because the printer corrects small variances in the z-height of the bed level automatically - based on its mesh measured by the Pinda probe.

 So i cannot figure out why you would want to adjust the mesh values via the LCD menu, when the printer corrects the right z-height automatically while printing?

I hope i made myself clear using the correct terminology.

Thank you, Eric.

 

 

You are on to something there. I am completely on your side, it really helps to understand what is happening and why.

First of all, Joan is right, if you use 7x7 you need to switch magnet compensation on, otherwise you would have a problem, to be honest I do not understand why it can be switched off in the first place… Anyway.

You are right, mesh bed leveling should take care of a not completely flat bed and everything should be fine. But, as a matter of fact, it does not,  or not for everybody, so what is the problem and what to do about it? First thing: inconsistency in PINDA measurement. Nothing you can don about that, if you compensate for it you might just screw up the next print, because it is an inconsistency which will be - well - inconsistent. But since there are quite a lot of people printing consistently well with Prusa MK3 printers, let‘s just rule this out. Next thing is: something PINDA can not detect. And this might be a thing, PINDA reacts strongly to the Metall plate and not so strongly to the coating. Meaning if - and that‘s a big if - your PEI sheet‘s coating is not evenly thick, there is something to additionally compensate for with bed level correction - but, if you think about it, it might be less complicated to switch of mesh bedleveling completely, home at a specific point of the bed and adjust the rest with bed level correction and be done in this case. Third an last thing to consider is the temperature and what it does to the bed and PINDA measurements, and this is, what -  imho - has the biggest effect, which can not be compensated for by messing with bed level correction, just preheat the bed for a reasonable time with the extruder at a reasonable height above and then start mesh bed levelling and printing, and in my experience you will get pretty good results without compensating for anything else…

RE: Automated bed levelling - i don't get it?

I after about a year I noticed 1 side of one of my PEI sheets in particular always had crappy first layers.  I flip the sheet over and it's perfect.  So I marked that bad side and don't use it anymore. 

I also recently did the Nylock mod to level the bed and my first layers are way better than they ever have been.  This tells me that the software bed level correction can only do so much due to all of those variables Robin listed above. 

If your decide to do the Nylock mod I definitely recommend letting your heat bed warm up for at least 30 minutes prior because it definitely moves at it warms up.  I also recommend leveling it at the temperature you most often print at.  For me that was 90°C for PETG.

I also have never messed with the leveling feature on the printer itself.  I think mechanically leveling the bed is your best bet as it will produce the flattest parts.  If you only use software to compensate you an unlevel bed then all of the unevenness will be on the bottom of your part.

Good luck. 

RE: Automated bed levelling - i don't get it?

Since you use the PINDA mesurements to calibrate your Nylock-mod all the variables still apply 🙂

You are right of course that the bed should be as flat as possible before the software compensation by mesh bed leveling and everthing that is compensated by mesh bed leveling is "deforming" your printed part - but with all the sheet changeing and turning the error introduced by that might be bigger than the few microns you are compensating with the Nylock-mod.

In the end it's pretty irrelevant how you got a consistent first layer as long as it worked for you. As a matter of fact - as Joan pointed out - messing with to much of the variables, in particular with bed level correction, will most likely make things worse. Most people are happy with the stock MK3 bed and it's slight imperfections and the ones of the sheet used beeing compensated by mesh bed leveling. I am one of them, I use a stock MK3 bed with 3 diffenrent PEI sheets (each of them stored with a profile), no bed level correction at all and 3x3 mesh bed leveling and I have a very consitent first layer all over my bed.

RE: Automated bed levelling - i don't get it?

Robin that's awesome that you've had no issues.  

I can say for fact that the Nylock mod has improved my first layers.   Prior to making the change you could see in some areas where the nozzle was too close and in others too far away.  This would rarely lead to a print failure, but would make obvious imperfections on the bottom of the part.  The larger the part, the more noticable this was.

Since completing the Nylock mod this has disappeared completely.  Maybe my bed was not as flat as yours from the factory.

Appreciate your feedback. 

RE: Automated bed levelling - i don't get it?

Yes, you are probably right about that, and the Nylock-mod seems to help a lot of users with first layer problems... I'd just recommend to factory reset, clean and first layer calibrate the preheated bed before start using bed level correction or modding the printer.

RE: Automated bed levelling - i don't get it?

Definitely preheat your bed before printing if you want a consistent first layer.  Not my picture but I keep this around to show as an example of the difference it makes

RE: Automated bed levelling - i don't get it?

First of all many thanks for these valuable insights. I am a great fan of Prusa printers, but i definitely can now see why they changed/improved mesh bed levelling in the MK4. It seems that i am not completely stupid afterall 😉

I do print a lot -having quite some experience. I feel that printing single and small things the stock bed and its mesh bed levelling does its job fine. Once you start printing a fully ocupied printbed with multiple parts and large prints you might end-up with challenges to have a succesfull print. I say might, because some area's print just fine as where other are not, i am gratefull for Robins explanation now i know why. I ended up modding my printer also with the nylock mod, and i must admit greatly improving my first layer issues (for multi-part and large prints in my case).

I thank you all for your input.

Regards, Eric.