3DPrinting

What I am about to say will probably go against what at least a few people on here will say, but I've been printing PETg (and PLA, ABS, tpu, etc...) for about 5 years now on 6 different machines. It all started where you are now, on a stock (besides a microswiss hotend) ender 3 and a glass bed.

For me PETg Prints as easily as PLA every time by following these guidelines.

• 1. This is the number one most important thing when printing PETg. MAKE SURE IT'S DRY. PETg is very hygroscopic, which means it absorbs moisture from the air like crazy. It's a requirement (IMO) to get a filament dryer, or food dehydrator to dry your PETg. I dry it at 120°F for 6-12 hours in a modified flld dehydrator. Even when stored in a vacuum bag with desiccant PETg will still not stay 100% dry. Wer filament will bubble and make it weak, make it stringy as a guitar, and lead to weak parts.
• 2. Invest in a PEI coated spring steal build surface. Smooth and textured both work awesome. It just depeton what surface finish you want. Personally, I would start with one that is powder coated with a textured finish, as it's more forgiving to uneven beds and also releases super easy once it cools off, usually the part will self release so you can just grab it right off.
• 3. Don't use any type of adhesives on the PEI. We use PEI on our high dollar, over engineerd Voron printers for a reason. When you heat it up to the proper temp, prints stick to it like theres no tomorrow, As long as you keep it clean! I don't even bother with isopropyl alcohol anymore, use blue dawn and a paper towel in the kitchen sink. Dish soap is a surfactant, which means it washes contaminates away, instead of just moving them around like a solvent does (isopropyl). From talking to people online about it, some of those adhesives can actually cause adhesion issues.

Temp: I print PETg at 245° first layer and 240° after that. I run 75° on all of my beds with PEI sheets and have great adhesion.

Part Cooling: PETg doesn't tolerate part cooling as well as PLA. I run my 5015 setups at about 30% fan speed which delivers a good balance of print quality and strength.

It should also be noted that you should really invest in an all metal hotend when printing above above 230°C. The PTFE tubing in the stock lined creality hotendt begins to break down above this temp and puts off some really bad chemicals, like chemicals that are said to eat holes in your brain amd stuff... Also, you will have less headaches with an all metal hotend, just be sure to lower your retraction accordingly.

Well, this has turned into a wall of text so I'm going to stop here. If anything I said doesn't make sense justlet me know and I'll be happy to clarify. Cheers.

I pretty much only use petg and abs. Petg really likes to ooze, I put a retract of 10-15mm at print end, I'd recommend bringing up to print temp only when you need to (heatup bed and set the nozzle to 150, do your bed level, then heat to print temp, my voron does that and has way less ooze). It also, at least for me, loves to cling to the nozzle so nozzle cleanliness is key, I use a sock that covers all but the very tip of the nozzle which made a world of difference. First layer height is really important with that as well, too high and it just sticks to itself and makes a mess.

Check your filament as well, I personally like to go as hot as possible with petg as it seems to flow better, the one I have right now is 230-250 with a bed of 70-90, 245 and 80 works well for that. Bridging and overhangs can be not great, had better luck with faster bridge speeds and high fan speeds.

Keep your surface clean, light brushing with warm soapy water is good periodic maintenance, I wipe down with 99 ipa to keep my sheet clean, ipa isn't the best degreaser but it's good to keep it maintained. Windex and then a wipe down with ipa has worked for me too.

I don't recommend printing directly on PEI, at least the prusa PEI sheet, it adheres extremely well to the point of tearing off PEI chunks, gluestick works well as a release agent. Textured sheets are nice and they self release when cold.

Key take aways though, keep everything super clean as bad adhesion is a bad time. I have had better luck with running things on the hotter end and turn up the cooling as I print in an enclosure. Get a dry box, I have a few desicant filled boxes as it really likes moisture.

Qucik edit: Prusa has some solid material guides for recommendations and things to know about different materials. Petg will adhere to surfaces strongly, I just saw you use a glass sheet and I've read some annedotal stories of people literally pulling chunks of glass off with a petg print, definitely use a gluestick or some other material for bed release, make your life easier.

Textured print surface and enclosure a must for me.

Prusament PETG I use the Prusa PETG profile (230-240 nozzle, 85-90 bed). (First layer - remaining print)

Overture PETG I've found I need 250-260 nozzle and 85-90 bed, but had to decrease retraction, increase deretraction and increase flow rate to 1.01

I use some glue stick if it still lifts off on a cleaned textured plate, needs cleaning off and refreshing every few prints. If its still bad or you have a small connection area, add a brim in the slicer

You need to raise your z-offset. PLA should be squished onto the bed. PET-G needs to be laid down neatly. If you try to squish it then the next layer snags on it because it's tacky and it causes it to lose adherence. Raise your z-offset by 0.02-0.15mm. It'll require some experimentation.

You also need a much hotter bed. I use 60c for PLA and 90c for the first layer of PET-G and then 85c for every other layer.

Ultimately what worked best for me was getting a spring steel bed surface. I never had much luck with PET-G on the glass or default bed surface. As soon as I got a spring steel bed all of my problems were solved.

That's really hot. I print at 70 and 230

Make sure is dry as well. I just opened a fresh Prusament PETG Black and it was popping and hissing. Stopped the print. Got my food dehydrator and dried it. Prints well now.

The other advise here is good. I'll also add that PETG really likes to pop of the bed if the temp changes. Even the breeze of someone swiftly walking by the printer could be enough to get a corner to lift.

An enclosure or tent may help; as a test maybe try a big cardboard box set over it carefully while printing.

I would recommend a textured bed. I also tried PETG on glass but the adhesion is better on a textured bed. I've been able to print at 240/70 on a PEI sheet. I have an Ender 3 S1

I've been using textured PEI sheets on the bed, and apart from where I had completely wrong first layers or parts with very little bed contact, adhesion has been great.

i've got basically the exact same setup as you, other than flipping the bed upside down to use the smooth side, and having the base ender3 instead of the pro (only difference there, given we're both on mini e3v2's is the y axis rail).

a little spritz of aquanet on the nontextured side, and blocking out potential drafts can go a long way. also your first layer thickness is larger than your nozzle diameter, try bringing that down to at most 3/4ths, or 0.3 in this instance.

all that out of the way, i'm printing 230/70 extruder/bed with petg and having no real issues to speak of.

Bed and extruder both seem too hot for PETG, but it depends on your exact brand/type of filament. Are you using a textured/satin sheet? Glue stick on a smooth sheet is pretty unreliable. Some brands of PETG seem more prone to contracting while cooling than others too (avoid "Kaaber" on Amazon, it was pretty bad hah).

Also make super sure your bed is clean. Washing with dawn liquid dish soap, drying carefully, then wiping with high-roof rubbing alcohol works best for a new sheet.

It's very sensitive to temperature so try running with the fan off or at a very low setting. You can also try stuff like hairspray to promote adhesion, or a textured buildplate/sticker

I was pulling my hair out over poor bed adhesion with PETG while I was having no issues with PLA. As in, completely failing a first layer test with PETG turning into spaghetti while PLA printed perfectly.
Turns out that PETG seems to be more sensitive when it comes to how clean the bed is. Scrubbed the bed with water and dish soap and the same gcode that was producing spaghetti was now printing without any issues.

I like to drop my cooling fan down to 10% and drop my layer hieght slightly for the first 3-5 layers of the prints for PETG. It tends to like to shift a bunch if cooled too quickly. I also have better results on a textured print surface.