Having a bear of a time with PLA adhesion after using PETG
I seem to have noticed that after I switch from PETG to PLA I'm having a bear of a time getting prints to adhere to the bed. Usually visible right away when corners in the skirt go funny - no matter how much I clean with IPA (91%) it just will not stick. No amount of z adjust helps either.
Has anyone experienced this with their prints, or is it common knowledge? I noticed some weird residue after removing the first failed layer, almost like a thin plastic film that remained behind when the PLA was gone. That vanished pretty quick, but I'd answered "no" several times after the colour was good (as in 4-5 times) when loading the PLA to ensure all the PETG was gone. I also did a cold-pull on the PLA in case there was junk in the nozzle. No dice.
Note I wasn't using the same side of the bed- I'd flipped it after the PETG print, so there already should not have been any chance of windex residue.
Bed only has a handful of prints on it so it's unlikely to be time for the acetone treatment; I did try a blue "safe for non-stick" scrubby to no avail; I finally had to resort to gluestick... which just seems wrong since PEI is supposed to help avoid the need for surface prep voodoo.
One thing I did notice was in the right light I can still see streaks after wiping down with the IPA. It only lists purified water under additives, so I doubt there is anything else there - but I have heard of folks having issues. So some 99.9% stuff is on the way.
Re: Having a bear of a time with PLA adhesion after using PETG
Unfortunately soap and water are the best cure for this. Most people report using a drop or two of Dawn dish detergent on a paper towel and washing the bed well in a sink; then a good rinse, and drying with a fresh paper towel. After the bed is on the printer, use a new paper towel to wipe the bed with 90%+ alcohol; or a light scrub with acetone is sometimes needed.
It also depends what you used to keep the PETG from sticking to the bed. If gluestick or Windex, both need water to wash clean.
BTW, streaks is a clue there is something on the bed the alcohol isn't lifting off. 91% is fine. People often forget that hands are oily, and alcohol will transfer oils from your hands to the paper towel and to the bed: so it's a good idea to wash and dry your hands before cleaning the bed.
Re: Having a bear of a time with PLA adhesion after using PETG
You may be on to something there; I've tried to keep the PLA on one side and the PETG on the other so I had to worry less about making sure I got all the windex off. But perhaps there is something on it that the 9% water in the IPA isn't enough to take care of.
Back to the PETG purge aspect - what is considered a good length of filament to extrude to ensure the previous material type has been thoroughly purged?
Re: Having a bear of a time with PLA adhesion after using PETG
The times I change from PET to PLA I generally end up doing a cold pull. Just good luck on my part, I guess. But I try to run at least 50mm of PLA at 250c through before printing PLA at 210c. This usually works and avoids plugs. But eventually a chip of PET (or who knows what) finds it's way to the nozzle and I end up doing a cold pull.
Re: Having a bear of a time with PLA adhesion after using PETG
Makes sense. Guess I'll start doing PETG cold pulls.
Re: Having a bear of a time with PLA adhesion after using PETG
😛
Makes sense. Guess I'll start doing PETG cold pulls.
I recommend cleaning filament. It is formulated to stick well to other filament, but more importantly will extrude over a wide range of temps. If a bit gets stuck, it won't jam the next time you print at lower temps.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
Re: Having a bear of a time with PLA adhesion after using PETG
Thanks for the tip!
Re: Having a bear of a time with PLA adhesion after using PETG
😛
Makes sense. Guess I'll start doing PETG cold pulls.
I recommend cleaning filament. It is formulated to stick well to other filament, but more importantly will extrude over a wide range of temps. If a bit gets stuck, it won't jam the next time you print at lower temps.
How do you use them?
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Chuck H
3D Printer Review Blog
Re: Having a bear of a time with PLA adhesion after using PETG
How do you use them?
Just heat up above normal printing temps and feed the cleaning filament like any other until the nozzle runs clear. Let the nozzle cool with the cleaning filament loaded, loosen the extruder screws, and then set a print temp and gently pull the cleaning filament out as the temp hits 90C for a cold pull.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
Re: Having a bear of a time with PLA adhesion after using PETG
How do you use them?
Just heat up above normal printing temps and feed the cleaning filament like any other until the nozzle runs clear. Let the nozzle cool with the cleaning filament loaded, loosen the extruder screws, and then set a print temp and gently pull the cleaning filament out as the temp hits 90C for a cold pull.
Thanks. I will give it a try.
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Chuck H
3D Printer Review Blog
Re: Having a bear of a time with PLA adhesion after using PETG
How do you use them?
Just heat up above normal printing temps and feed the cleaning filament like any other until the nozzle runs clear. Let the nozzle cool with the cleaning filament loaded, loosen the extruder screws, and then set a print temp and gently pull the cleaning filament out as the temp hits 90C for a cold pull.
Hi Bob, I have a question on the filament used for „cleaning“ ... in your Project Notebook (which is a great help and compendium for me by the way) you mention ABS or eSUN cleaning filaments - would white PC filament also work? Or are there some constraints that I am missing?
I have a roll of PolyMaker PCmax for temp sensitive parts, that‘s the background ...
Cheers,
Mark
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MK3 kit B7-R3 / custom FW v3.5.1 with 7x7 MBL
Slic3r PE v1.41.2
Re: Having a bear of a time with PLA adhesion after using PETG
Thanks! Glad it's useful.
[...] in your Project Notebook (which is a great help and compendium for me by the way)
you mention ABS or eSUN cleaning filaments - would white PC filament also work? Or are there some constraints that I am missing?
For doing a cold pull, any filament that can get hotter than whatever else you print can work. Some will work better than others. The idea is that you get the hotend hot enough to melt anything that might be stuck inside and fill it with hot filament, then let it cool. With any luck, the trapped stuff hardens inside the new filament, and when you pop it out, the crud will be pulled out.
White is recommended for visibility to see what's coming out (useful if you need more than one pull). ABS is recommended for high print temps and strength. I'd expect PC to work the same way. So long as it doesn't snap when you pull up at 90C it should work. The reasons I recommend cleaning filament are:
If you already have suitable filament, definitely try it. I like the eSun product because it handles well and will work from 200-265C well.
and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan
Re: Having a bear of a time with PLA adhesion after using PETG
Thanks! Glad it's useful.
[...] in your Project Notebook (which is a great help and compendium for me by the way)
you mention ABS or eSUN cleaning filaments - would white PC filament also work? Or are there some constraints that I am missing?
For doing a cold pull, any filament that can get hotter than whatever else you print can work. Some will work better than others. The idea is that you get the hotend hot enough to melt anything that might be stuck inside and fill it with hot filament, then let it cool. With any luck, the trapped stuff hardens inside the new filament, and when you pop it out, the crud will be pulled out.
White is recommended for visibility to see what's coming out (useful if you need more than one pull). ABS is recommended for high print temps and strength. I'd expect PC to work the same way. So long as it doesn't snap when you pull up at 90C it should work. The reasons I recommend cleaning filament are:
If you already have suitable filament, definitely try it. I like the eSun product because it handles well and will work from 200-265C well.
Thanks Bob, appreciated! I will try with my PC but the cleaning filament advantages are understood ...
———————————————
MK3 kit B7-R3 / custom FW v3.5.1 with 7x7 MBL
Slic3r PE v1.41.2
Re: Having a bear of a time with PLA adhesion after using PETG
Quick follow-up: I think it is an additive in my 91%. I just used the 99% I ordered and it wiped clean without any streaks, and the pad had a faint brown blotch when done.
Re: Having a bear of a time with PLA adhesion after using PETG
The 91% is the alcohol, and that other the 9% is almost always distilled water, unless of course, you dip things into the bottle to clean them 🙄 .
As for cold pulls, a major reason for them isn't only getting rid of higher melt point plastics. It's also crucial for when you are using plastics with high melt-point additives: copper and other metal fills, carbon fill, glow in the dark sand, glitter, pigments (try melting titanium dioxide), etc. Because some of these materials have an affinity to copper/brass, several pulls might be necessary to get it all. e.g., If any dark patches are on the pull, there is more crud to remove.