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Ghosting on surface of PETG  

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RickSeiden
(@rickseiden)
Eminent Member
Ghosting on surface of PETG

Hello,

I have this weird thing happening when I print PETG. I get what I'll call "ghosting" on the surface that touches the bed.  I can see outlines of previous prints.  This picture here shows what I mean.  I've got a very smooth surface on the first layer, which is great, but I can see lines from when I printed the master spool a few prints ago.

I have an MK3S that was upgraded from an MK3 kit.  I am printing on the PEI sheet spring steel. I use 91% rubbing alcohol with a paper towel before every print to clean the bed.  This print here is printed with the small roll of PETG that came with the upgrade kit.  I've also seen it with the role of PETG I bought from Prusa in the past. It was sliced with PrusaSlicer 2.1 with the default Prusament PETG settings (except I went for 15% infill).

The masterspool print you can see was printed in PLA.  I don't remember the brand of PLA that I used, but it wasn't Prusament. It was sliced using the default Generic PLA settings in PrusaSlicer 2.0 (except I went for 15% infill).

Whenever I print with PETG, which is not very often, I try to catch the print just as it finishes, and get it off the print bed right away.  I find that if I let it cool, it is very hard to get off, and I've actually had some PEI come off with it.

This time, I was distracted, and I missed the end of the print, and everything cooled to room temperature.   I tried to get it off, and it didn't want to come off, so I put the spring steel back, and pre-heated the machine so the print would come off easier.

Is there anything I can do to stop this from happening/fix this.  It's a great print surface, but it looks like crap with that ghosting on there.

Thanks

Rick

Posted : 22/09/2019 3:58 pm
Bunny Science
(@bunny-science)
Noble Member
RE: Ghosting on surface of PETG

If your PEI surface has been physically etched, there isn't much you can do other than sanding the PEI surface. However, if your surface is not etched, I would Dawn & water scrub to remove PLA residue. Switching between PETG and PLA should always include a Dawn scrub. The two material are not particularly compatible with each other when sharing a print surface. A good dawn scrub is needed to remove their mutually incompatible residue.

The brand of PETG can greatly change how easily it releases with a cool plate. Overture, Amazon Basic, Stronghero, Paramount all release with practically zero effort when plate is cool. In contrast, Priline will be stuck as you describe. For brands that are super adherent, windex coating plate before print is good release agent.

Posted : 22/09/2019 8:07 pm
RickSeiden
(@rickseiden)
Eminent Member
Topic starter answered:
RE: Ghosting on surface of PETG

It sounds like a Dawn and water scrub is in order between prints, as I've seen different patterns on the PETG before.  I didn't know that about PLA and PETG.

It's pretty obvious that you mean Dawn soap and water, but I have  a few questions.  Hot, warm or cold water? (I'm guessing the hotter the better.)  Hot or cold bed? How much Dawn to how much water? (I'm guessing a few drops to a cup full of water would do.) And finally, do I wet down the paper towel with the Dawn and soap mix and let it sit on the bed for a little bit, or can I just scrub the bed with the wet paper towel right away?

Thanks!

Posted : 22/09/2019 9:26 pm
Bunny Science
(@bunny-science)
Noble Member
RE: Ghosting on surface of PETG

Put 2-3 ml Dawn on surface of PEI. I simply wet with hot (but not scalding hot) water and scrub with cotton ball to spread detergent and water mixture over entire surface. No need to carefully meter out nor premix the detergent. It will rinse off. Then rinse with running hot water while continue to scrub. If very severe contamination, a Mr. Clean magic eraser may be needed instead of cotton ball. Rinse well. Immediately dry with paper towels taking care to avoid touching surface with fingers. Dry on hot head bed 80 to 100C for a few minutes until completely dry.

Posted : 22/09/2019 9:45 pm
RickSeiden
(@rickseiden)
Eminent Member
Topic starter answered:
RE: Ghosting on surface of PETG

Thanks!  I'll give it a shot and report back.  I have a big PLA print going on right now, and a big PETG one that will follow it, so I'll get to test it really soon.

Posted : 23/09/2019 12:29 am
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(@)
Illustrious Member
RE: Ghosting on surface of PETG

The trick with soap and water is to use a SINK so you have the benefit of gallons of hot water rinse.   This is why soap and water works when alcohol fails.  Removing oils and sugar residuals from PLA printing require volume.  A few ml of alcohol simply can't dilute oils well enough compared to gallons of water, and the risk of adding oil when using bare fingers to dab alcohol makes it worse.

 

This post was modified 2 years ago by --
Posted : 23/09/2019 4:01 pm
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