"Perfect first layer" issues  

RE: "Perfect first layer" issues

It is the back, but also the right. Does back left exhibit the same issue?

I had a poorly assembled X axis mount which resulted in my X axis not being parallel to the bed. You may be experiencing the same thing. Check for any gaps between the plastic parts at either end of the X axis and the carriage of the Y axis. 

RE: "Perfect first layer" issues

I have similar issue just close to the front, can you elaborate or take a photo what is required, I do not understand, sorry ^ ^

Posted by: @flynny75

It is the back, but also the right. Does back left exhibit the same issue?

I had a poorly assembled X axis mount which resulted in my X axis not being parallel to the bed. You may be experiencing the same thing. Check for any gaps between the plastic parts at either end of the X axis and the carriage of the Y axis. 

RE: "Perfect first layer" issues

I am having a similar issue in the back of the bed.  

RE: "Perfect first layer" issues

I am also having this issue with the first layer calibration. The back left corner seems to have a sag. The rest of the print adheres great, just that back left corner. I've cleaned the bed and addressed any other adhesion troubleshooting I can think of. All I can think that is left is that the heatbed panel is crooked. 

RE: "Perfect first layer" issues

I'm having a similar issue at times the printer tries to print right aginst the print bed. Running the factory reset and tests will only move the issue to a different spot on the bed.

RE: "Perfect first layer" issues

@CWBullet is one of the most c0mpetent and trustworthy posters on this site. If he is having issues with his bed (along with all the others' troubles that are posted), I am really worried. I have a 5 head on the waitlist, and it is a lot of money for a machine of dubious quality.

RE: "Perfect first layer" issues

I was able to get a print after setting the z offset in Prusa Slicer to 2.5 and re-slicing.  Not a great solution to something that should be adjusted on the printer it's self.

RE: "Perfect first layer" issues

I'm getting the same thing across the rear of the bed. Factory-assembled 5-head XL

It's about the rear 1/4 across the back

RE: "Perfect first layer" issues

So far it's been all of the back bed, no matter what orientation I print the part. Since I've started this thread, I don't believe that the issue has been fixed...
Developers dont seem to want to get involved either, or when I ask, I am getting pretty generic answers.

RE:

Considering that the bed of the XL is made from 16 different panels of PCB, it’s not surprising that the overall flatness of the assembly is often less than perfect. Not easy to manufacture PCB boards flat to 1/100 of mm and even more difficult to assemble 16 of these boards making them coincide on the same plane. Printing small objects shouldn’t be much of an issue but long parts taking most of the width/length of the bed are another story.

It would seem logic that bed mesh leveling takes care of the problem but, in my experience with the MK3S, this isn’t always the case. Bed mesh corrects quite well overall slanting or warping, but it doesn’t does much good if there’re irregular bumps or hollows along the bed.

That said, for sure some XL beds will be flatter than others so the issue is much less apparent. We only can hope to stumble into one of the ‘good’ ones.

RE: "Perfect first layer" issues

What is the regular 1st layer height for the XL? I would add 0.1 mm layer height, just to the first layer. That is also what many do with large Vorons, which also do bed mesh levelling. This can substantially increase the tolerance for slight errors in the bed mesh without having a lot of other downsides. (That only works if you regular layers aren't already at the max for the chosen nozzle diameter of course)

RE: "Perfect first layer" issues

Which surface are you using?

Posted by: @kurzawa

So far it's been all of the back bed, no matter what orientation I print the part. Since I've started this thread, I don't believe that the issue has been fixed...
Developers dont seem to want to get involved either, or when I ask, I am getting pretty generic answers.

RE: "Perfect first layer" issues

textured - with PETG.

I also note the textured sheet has inconsistent z height. Due to the bumps most likely. It'll get good height at random, otherwise it's scrape off the print, start over and over. I've been adding -0.1 to the Z height in the slicer to try and help with this. 

RE: "Perfect first layer" issues

My understanding of mesh levelling is that it would compensate for these bed variations. Is it just me or does this not really work perfectly? I've noticed it on other printers too. 

RE: "Perfect first layer" issues

 

textured - with PETG.

I also note the textured sheet has inconsistent z height. Due to the bumps most likely. It'll get good height at random, otherwise it's scrape off the print, start over and over. I've been adding -0.1 to the Z height in the slicer to try and help with this. 

That has been my experience too. On satin sheet and textured sheet (which are the only ones I use ☹️) I've learned to manually add -0.1 to -0.25 on my Mk4 and XL.  In fact, this weekend I had one filament that gave me so much grief that I ended up actually running a calibration strip and testing a range of offsets to find one that finally worked. 

So much for an "always perfect" first layer. The longer I use my Mk4, the happier I am that I kept one of my Mk3S's. That thing is just a workhorse. Once Live Z is set properly, it just prints and prints and prints…. No need to babysit the first layer.

RE: "Perfect first layer" issues

Exactly my point....

These perfect layer issues requires something more - at least permanent Z offset I can set.
All my PLA print are unsticking and un-warping from the textured sheet on MK4. While the all the same sheets work like charm on my MK3s - no unstick, no warp - prefect flat surface..  With the same material

Posted by: @fuchsr

 

textured - with PETG.

I also note the textured sheet has inconsistent z height. Due to the bumps most likely. It'll get good height at random, otherwise it's scrape off the print, start over and over. I've been adding -0.1 to the Z height in the slicer to try and help with this. 

That has been my experience too. On satin sheet and textured sheet (which are the only ones I use ☹️) I've learned to manually add -0.1 to -0.25 on my Mk4 and XL.  In fact, this weekend I had one filament that gave me so much grief that I ended up actually running a calibration strip and testing a range of offsets to find one that finally worked. 

So much for an "always perfect" first layer. The longer I use my Mk4, the happier I am that I kept one of my Mk3S's. That thing is just a workhorse. Once Live Z is set properly, it just prints and prints and prints…. No need to babysit the first layer.

RE: "Perfect first layer" issues

So much for an "always perfect" first layer. The longer I use my Mk4, the happier I am that I kept one of my Mk3S's. That thing is just a workhorse. Once Live Z is set properly, it just prints and prints and prints…. No need to babysit the first layer.

That's really weird. I have no problem with it at all on my MK4. I used the smooth and satin. I have never changed my sheets that much.

Do you guys have this mainly with big parts or in general?

RE: "Perfect first layer" issues

no matter what size of "bed touch" the print has, if it is small it unstick, if it is large it just warp and unstick later. while the same print on the same sheet on MK3 prints perfectly. Issue is that the Z height is not low enough, and manually setting it up during each print is pain in the arse.

Posted by: @rainer-2

So much for an "always perfect" first layer. The longer I use my Mk4, the happier I am that I kept one of my Mk3S's. That thing is just a workhorse. Once Live Z is set properly, it just prints and prints and prints…. No need to babysit the first layer.

That's really weird. I have no problem with it at all on my MK4. I used the smooth and satin. I have never changed my sheets that much.

Do you guys have this mainly with big parts or in general?

RE: "Perfect first layer" issues

Two issues going on here:

1. Too high Z-offfset overall, at random, on the textured sheet.
   My theory, since I have so much trouble with the textured sheet and not the satin, is that the tiny bumps on the textured sheet cause enough of an issue with the probing that it makes the end result random. When the nozzle probes the bed, it touches down randomly on top of a bump or down in the "valley" between bumps. It's my opinion that Prusa needs to add sheet profiles to the printer, then when textured is chosen, do more probes at each spot, with slightly varying X and Y offsets, and then taking the average.
2. Too high Z across the back side of the bed.  I am not sure about the cause of this.

I only use PETG, which works best on textured sheets. So I hope to get this solved.