print causes denting in heated bed?
I made a pretty normal PLA print with default PLA heat settings, and when I took it off (carefully pried one edge up with my very thin letter opener), I saw a ring under the print. Passing my finger over the print reveals that the ring is an impression into the flat surface of the bed. The print itself came out just fine, so I'm not sure how this happened. Did my prying cause it? Has anyone else seen this?:
Bottom left is the bottom of the print, with no apparent flaws:
The ring:
I can see that when I print over this ring that the filament has to bridge over the ditch, so it could lead to some minor imperfections.
Re: print causes denting in heated bed?
Seems to be severe wrong y-axis-alignment due to wrong or not done calibration.
Do the xyz calibration from the calibration menue and after that the 1st layer calibration as shown in your manual.
Your PEI sheet still is messed up and if you want to use that particular space needs to be replaced as is well described here.
http://manual.prusa3d.com/c/English_manuals
Re: print causes denting in heated bed?
That's really weird that it would drop calibration like that. I did a few prints before and after with no issue.
I did XYZ and Z calibration after that series of prints was done, though, and the Z offset seems to be the same, about -0.35 for me.
Is the heated bed sold separately? In case I don't wanna dip my toes into the world of replacing just the PEI sheet.
e: for my own reference later:
http://manual.prusa3d.com/Guide/Replacing+the+PEI+sheet/133?lang=en
Re: print causes denting in heated bed?
See this thread about the PEI sheet "healing" when it's heated:
https://shop.prusa3d.com/forum/original-prusa-i3-mk2-f23/blister-on-print-bed-t12841.html#p57987
Can't verify this myself, but perhaps you won't have to replace your PEI sheet.
-Kevin
Re: print causes denting in heated bed?
That's really weird that it would drop calibration like that. I did a few prints before and after with no issue.
Another reason could be that it is something mechanical that came loose.
I can confirm the self-healing capability of the sheet. Could certainly be worth a try to wait some prints and See how far that dent dissapoears. I fear not completely, though...
Re: print causes denting in heated bed?
the only scenario, about what happened, that I can imagine is the following:
you've previously printed a version of "the knob" (or something similar) at exactly the same spot.
the pei sheet lifted a little bit after removing the previous print (maybe while removing the print as the heatbed hasn't cooled down).
you then printed the knob a second time, over exactly the same location.... while the tip of the nozzle touched* the somehow uplifted pei at the location where it carved the crescend now into the surface.
*) or you've printed the first layer too slow, so that the pei reached glass transition temperature without touching the nozzle.
a hot nozzle touching the surface is really dangerous for the pei, because the glass transition temperature of it is 213°C.
dem inscheniör is' nix zu schwör...
Re: print causes denting in heated bed?
the only scenario, about what happened, that I can imagine is the following:
you've previously printed a version of "the knob" (or something similar) at exactly the same spot.
the pei sheet lifted a little bit after removing the previous print (maybe while removing the print as the heatbed hasn't cooled down).
you then printed the knob a second time, over exactly the same location.... while the tip of the nozzle touched* the somehow uplifted pei at the location where it carved the crescend now into the surface.
The prior 3 prints were very small test fitment prototypes, so not nearly at that radius. 2 of those are in my hand in the top pic.
I'm not sure if any of the prints I've done in the past have been circular like that.
In any case, I'm now disposed to printing future things off center so as to not go right over this area. I'll see if the heated bed will anneal itself back to more usable flatness over the next few prints.