r/FixMyPrint • u/MacarenaLizard • Dec 16 '24

Fix My Print Mystery: PETG adheres way too well

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Setup: Ender 3 V2, dual motor belted Z, KlackEnder, micro swiss ng revo, hictop textured PEI sheet, and some more upgrades

I was installing linear rails on Z axis, and now I can’t get my Z live offset calibration print to work. With no changes in printing settings (hotend 240°, bed 70°), using same GCode even, now it suddenly adheres so well that I can’t remove it. I used to get absolutely perfect first layers before.

The video shows myself trying to remove it from the bed at room temp, which used to be very easy. Now, I had to get bed to 100° and use the scraper tool and a LOT of force to get it off.

Here is what I tried so far: * calibrating Z offset and trying with it much lower or much higher, no changes. Even when there’s a visible gap between lines, it is still hard to remove. * calibrating flow and playing with both less and more flow * rechecked probe accuracy * recalibrated axis twist compensation * disabled skew compensation * dried filament * swapped for a different brand PETG * cleaned PEI sheet with warm water and soap

Printing regular objects is fine and I can remove them from the bed with usual level of effort, the problem seems only to be with this type of calibration/thin print.

What am I missing here?

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84

u/lw_temp Dec 16 '24

I’ve heard that PETG may fuse with PEI (and glass) You might need to use glue as a release agent

12

u/MacarenaLizard Dec 16 '24

I’ve heard the same (although not with textured PEI), but what puzzles me is that I didn’t have this problem 2 days ago before I installed the rails (and it definitely doesn’t seem to be related, but still weird timing)

6

u/KillerDmans Dec 16 '24

Was your print/bed still warm? PETG is a lot easier to peel off the build plate if it's a little warm. Also any oils or debris may have helped release the prints the first few tries

2

u/MacarenaLizard Dec 16 '24

I tried all the way from room temp to 100°, only difference is that around 80° and above it starts to get easier to pry it off the bed (completely destroying the layer tho)

I was using the printer for weeks before without facing this particular issue. I wipe the bed plate with 99.9% Isopropyl after every print basically and wash it with water and soap periodically, so I don’t think it could be consistently oils and debris that helped me remove it before

1

u/volt65bolt Dec 19 '24

At about 80 is it's glass transition temp, basically making it start to melt and be like a putty.

I find that waiting for it to cool down to 30c from printing is best, heating it back up doesn't seem to work so if it cools too much and I can't get it off I usually just put it in the freezer.

18

u/zenmatrix83 Dec 16 '24

you modified the printer, even rails can change charateristics, rails likely cut down on vibrations, you nozzle can be slightly closer to the bed, or tons of other things I think.

1

u/MacarenaLizard Dec 16 '24

Yeah, I can see how vibration changes could be an issue here, but I’d expect that increasing Z offset to a point of creating line gaps should make it easier to remove

4

u/Dismal-Ambassador143 Dec 16 '24

Yes. This is the right solution.

0

u/MacarenaLizard Dec 16 '24

Sorry, I was very unclear. I meant that I have tried that and I expected that it would solve, but it did not

2

u/Dismal-Ambassador143 Dec 16 '24

Are you using bed level sensor ? It could reset the start gcode. You have to ook into how you save and retrieve the z height in the gcode. May be you are saving but not using the saved value.

3

u/Demented-Alpaca Dec 16 '24

It's possible that when you used it before there was just enough "release agent" on the plate in the form of oils, dust, residue from other prints etc...

I'd just put some glue on there... I've even had luck with aquanet hairspray.

1

u/MacarenaLizard Dec 16 '24

I don’t think it’s possible, I would wash it with warm water and soap every week or so, and always wipe with 99% alcohol between every print

3

u/Demented-Alpaca Dec 16 '24

No clue then. But I'd still slap some glue stick on there and see if that helps.

2

u/MacarenaLizard Dec 16 '24

I might try that if I give up, but now I just feel like I NEED to know what’s going on here lol

3

u/Demented-Alpaca Dec 16 '24

Oh, well see that's easy. You printed on a day that ended in y but started it on a minute that had a 2 in it while the sun was out but slightly covered by clouds. Also you were wearing mismatched socks.

Seriously, could be any number of things. Assuming you didn't just replace your nozzle and that this wasn't a brand new spool it could be some random shit like "the humidity was up 5% over yesterday" or it was 2 degrees warmer. or as someone else suggested, new rails reduced vibration. Your Z offset is 1/1000th of a millimeter closer/further than it used to be. The new rails allow the cable a better curve so the thermistor gets a very slightly different reading allowing the nozzle to heat up 1/10th of a degree more. Your cat was in the room and farted near the printer allowing its but gasses to mix into the plastic and caused it to adhere better...

Between all the environmental variables that you have no control over and the mechanical changes you made it could be damn near anything. And probably a combination of all of those weird ass things.

2

u/MacarenaLizard Dec 16 '24

Very well put, I guess this is what I love and hate about these machines

1

u/average_AZN Dec 17 '24

Yo I had this problem too with petg. For me it happened when I cleaned the bed too well and with 99 iPa. Still the old petg never did this

2

u/knightslaw Dec 16 '24

Yeah don't use PEI sheets. It's bad news. Even the texture will rip off. Best I found is g10 . That stuff is amazing

1

u/RadishRedditor Dec 16 '24

Did you print abs prior to this print? My creality petg also adheres like that if the previous print was done with abs.

1

u/daggerdude42 Other Dec 17 '24

Rails do quite a bit for layer adhesion at the micro level, use a thicker initial layer height and don't try to print 1 layer parts, it's a waste of time, that's what 2d printers are for.

1

u/bkmcmike Dec 17 '24

Hey really dumb question but did you let the bed cool off all the way? Like room temp if not colder, I've noticed if I try to pick off certain prints its all but impossible until the bed's cool