Is there any known bug around wrong live Z after switching sheet?
 
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KjsiderPrinter
(@kjsiderprinter)
Eminent Member
Is there any known bug around wrong live Z after switching sheet?

I’ve been leaving some imprints of objects onto my smooth PEI sheet when printing with PLA. I’ve had three objects do this and after this third time I’m starting to think it’s because I was printing with a textured sheet and PETG on the previous print. I don’t print with PETG often. When doing continuous PLA and smooth sheet, the objects don’t leave imprints. 

The latest sequence was print on textured, which has a lower live z. Unload Filament. Printer cools down and I turn it off. 
Later on at night, I turn it back on. Swap out the sheet to smooth, clean it with ipa 99%. I actually started a print but as it was warming up, I realized I didn’t change the sheet. Hit the abort button. After printer boots back up, I switch the sheet to Smooth, and start up the print again.

And... I come back to a nice imprint of the object on my smooth PEI sheet. Sigh. This was the same object I printed the night before with no issue. 

 1) Has anything like this happen to anyone else?

2) Does this imprint comprimise my sheets ability? It’s a 2x2 inch square right in the middle. 

Posted : 03/03/2021 9:03 am
cwbullet
(@cwbullet)
Member
RE: Is there any known bug around wrong live Z after switching sheet?

I have not seen this.  I have been able to change sheets in the firmware successfully.  What version of firmware?

--------------------
Chuck H
3D Printer Review Blog

Posted : 03/03/2021 10:54 am
fuchsr
(@fuchsr)
Famed Member
RE: Is there any known bug around wrong live Z after switching sheet?

Can you get the imprint off by cleaning the sheet with soapy hot water? Then don't worry about this. I occasionally find imprints on my smooth sheet. They don't affect its performance and when they begin to bother me, I just clean the sheet with soapy water. 

I am not sure I always followed you in your narrative... Did you change live Z when you switched between smooth and textured sheets, and PLA and PETG?

Posted : 03/03/2021 2:53 pm
bobstro
(@bobstro)
Illustrious Member
RE: Is there any known bug around wrong live Z after switching sheet?

Following up on @fuchsr's comments, unless the PEI is physically damaged, the imprint shouldn't cause any problems. Over time, minor indentations may fade away through many heating cycles. If there's actually PLA stuck on the PEI, I find a wipe with acetone works far better than trying to sand or scrape it off. More than once I've thought I permanently damaged my print surface, only to be surprised when the "damage" wipes off. Acetone can cause the PEI to become brittle with over-use, but I figure PEI that can be used again is better than not using acetone and marring future prints.

I still follow up with a wash with Dawn under the sink to restore adhesion.

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Posted : 03/03/2021 3:57 pm
KjsiderPrinter
(@kjsiderprinter)
Eminent Member
Topic starter answered:
RE: Is there any known bug around wrong live Z after switching sheet?
Posted by: @cwbullet

What version of firmware?

3.9.3-3556. It was updated late Jan or early Feb, when I got the printer.

 

Can you get the imprint off by cleaning the sheet with soapy hot water?

Only partially. The previous ones still seem to leave the area a bit lighter. 

My issue seems more that a lot of prints in a row end up fine but someone when switching sheets, the live Z calibration does not return to what it was or it runs a print at the wrong setting (seems like it ran my texture sheet -1.800 instead of my smooth sheet -1.518) even though I changed the setting. 

Do I need to power off and on? Or anything I can check to ensure that the printer actually changed the live z to the one I calibrated for the sheet?

Posted : 03/03/2021 4:46 pm
fuchsr
(@fuchsr)
Famed Member
RE: Is there any known bug around wrong live Z after switching sheet?

I’m still a tiny bit confused about your process. Running a textured sheet at -1.8 and a smooth sheet at -1.5 seems reasonable—the textured sheet is about 0.4 mm thinner. I guess what you’re saying is that you put the smooth sheet on and it used the -1.8 setting of the textured sheet. Okay. I assume you’ve stored the sheet profiles as in  https://help.prusa3d.com/en/article/steel-sheet-profiles_1955, with a profile for smooth and a profile for textured. So if you put the smooth sheet on and select the corresponding profile, will it go to the correct Live Z (I think you can check under the Tune menu; I’m not near my printers right now)? There’s no need to turn it off and on. This should work, as long as you’re not manually changing live z while a profile is selected as that will override the previous setting for that sheet. 

Posted : 03/03/2021 6:02 pm
KjsiderPrinter
(@kjsiderprinter)
Eminent Member
Topic starter answered:
RE: Is there any known bug around wrong live Z after switching sheet?

@fuchsr

That is the process I’m following but I’ve noticed after switching sheets physically and by selecting the right sheet profile, the next print doesn’t perform as I think it should. In this case, the results seem to indicate the Z was too low when I’ve been printing at this Z for the smooth sheet the previous few days with no issue. No imprints previous 5 days (no petg printing in this timeframe). 

I’m not sure if this is coincidence or not but I wanted to see if anyone has come across this scenario. 

Posted : 03/03/2021 6:06 pm
fuchsr
(@fuchsr)
Famed Member
RE: Is there any known bug around wrong live Z after switching sheet?

Not me. I have found the printer to reset the stored live z accurately. And I frequently switch plates, sometimes multiple times a day. 
At this point I guess I’m out of ideas and would suggest you get on the chat with Prusa support, to see what they say. I would be curious to know what the outcome of this is. 

Posted : 03/03/2021 6:16 pm
KjsiderPrinter
(@kjsiderprinter)
Eminent Member
Topic starter answered:
RE: Is there any known bug around wrong live Z after switching sheet?

@fuchsr

Thanks for taking the time. I'll try the support route to see if they can identify anything weird with my process. 

I guess a related question is what causes imprinting? And why does it only sometimes happen even with the same object/gcode, same filament, same room conditions and time of day? Is this some kind of random occurrence or could this be an indication of something else. I've only gotten imprints on maybe 5 prints out of the hundred+ or so small prints i've done the last 1.5 months. 

Posted : 03/03/2021 6:23 pm
cwbullet
(@cwbullet)
Member
RE: Is there any known bug around wrong live Z after switching sheet?

@fuchsr

I concur.  Chat may have a wider view.  

--------------------
Chuck H
3D Printer Review Blog

Posted : 03/03/2021 6:23 pm
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