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Shadows on PEI Sheet showing up in first layer of print  

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Grendelrt
(@grendelrt)
Eminent Member
Shadows on PEI Sheet showing up in first layer of print

I have shadows of previous PLA prints on my smooth PEI sheet and it doesnt bother me at all because you can not feel them in any way, not do they affect adherence. But I noticed the same shadow now shows up in my first layer on my prints (you still can't feel it). Any way to correct this? I tried a wipe down of acetone, didn't seem to help. Pics attached

 

 

Posted : 17/11/2020 6:52 pm
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(@)
Illustrious Member
RE: Shadows on PEI Sheet showing up in first layer of print

Hard to tell from a photo - so I'll throw out a few ideas. 

Generally the oxides I've encountered on the PEI don't affect prints. It might be the glue under the PEI is somehow deforming and not coming back as fast as it usually does. This would be pretty rare with 60c PLA bed temps - more common at 80c+.  Try flipping the sheet over between prints. The extra heat on the bed side might help equalize the glue layer better/faster.

If it is an oxide layer - which I doubt - when I get oxide build up, I generally have to scrub the sheet with copious amounts of acetone, then wash in soap and water to remove the film the acetone leaves. A dampened paper towel with only a few drops of acetone doesn't do much. Again - I've never had (or never noticed) oxides or prior print plastic residue mark prints.

You can also try using a lot of 91% alcohol to scrub the sheet. And I mean a lot - pour a 150mm puddle mid sheet and scrub with a paper towel. This will remove some PEI residuals that collect. Maybe you are using a brand of plastic that has a lot of additives that stick to the bed? I've had a few rolls that seemed to do similar. Never caused problems tho.

The only thing that has ever left a mark on prints is the donut hole I made when I was fighting bed level issues on broken firmware. lol.

Posted : 17/11/2020 10:03 pm
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(@)
Illustrious Member
RE: Shadows on PEI Sheet showing up in first layer of print

Something else to try: try wiping the new part with the markings with a paper towel wet with alcohol. Does the mark go away? If it does, try a different brand of PLA.

Posted : 17/11/2020 10:07 pm
Grendelrt
(@grendelrt)
Eminent Member
Topic starter answered:
RE: Shadows on PEI Sheet showing up in first layer of print

@tim-m30

Thanks, I tried scrubbing the printed part with some isopropyl but its still there. Its affecting all PLA I put on the sheet I believe, not just this one. I will try giving the sheet a super scrub with acetone, I tend to very light on the acetone so maybe that is it. 

Posted : 17/11/2020 10:11 pm
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(@)
Illustrious Member
RE: Shadows on PEI Sheet showing up in first layer of print

I pour a puddle, about 50 mm, then scrub. I usually get a whitish film - not sure it's oxides or PEI I'd rather keep. But, once I've scrubbed the sheet fairly well, I mop up the acetone that I can then take it to the sink and use soap and water to do the final clean. 

If I use too little acetone, the paper towel will abrade the PEI. So I scrub more like I am wet sanding. 

ps: acetone is hard on the PEI: so it is only something I do every few months.

This post was modified 2 years ago by --
Posted : 17/11/2020 10:25 pm
Tech Guy
(@tech-guy)
New Member
RE: Shadows on PEI Sheet showing up in first layer of print

Could this be a result of weak IPA? I had 70% laying around my house and still waiting on the 99% I ordered online, am getting these exact shadows OP posted in their image. Trying to figure if my z is too low or the IPA is too weak to clean old PLA residues... washing by hand and soap did not make any difference. I'm doubting its z squish because if i raise it any more then center of the bed there is almost no squish

Posted : 30/09/2022 6:43 pm
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