RE: Problems with PETG first layer
Great thread. Here's what helped for me, as I have struggled with PETG first layers also. Now I'm getting consistently good prints. Everything I did was with the Satin sheet, so this may not fully apply to using the other sheets.
1. The satin sheet is best cleaned with hot water and dish soap. I use IPA most times, but if it's been a while since I printed or I have done several prints, I find I need to use hot water and dish soap to clean the sheet (I take it to the sink and use paper towel, then really use a lot of hot water -- as hot as I can get -- to rinse off the soap).
2. Filament brand matters! I have had good luck with Hatchbox PETG. At one point Amazon was out of stock of the color I wanted and I was impatient, so I bought a roll of Overture PETG. I could never get this stuff to give me decent first layers, ever, despite days of adjusting things. Finally switched back to Hatchbox and everything was great again. I'm in the USA so brands available elsewhere might vary. If you just can't get your first layer to stick, try a better brand of filament.
3. For settings, I found adjusting the following settings from the default useful: First layer speed: 25%, First layer acceleration: 200, Small perimeters speed: 15. Support material contact Z distance: about 75% of the layer height (.15 for .2 layer height, .20 for .3 layer height); otherwise the supports won't detach from the main print. I also add a few more loops to the skirt to really get any blobs out of the way and get the filament flowing consistently.
4. I found a hot bed temperature useful, about 90-95 degrees.
5. PETG was more sensitive to the first layer Z calibration than PLA. I used the following variation of the system often touted on the forums: using Prusa slicer (right click, add shape, box), I created a model with 4 50mm squares, 0.2mm thick. I printed these, changing the live Z value at the diagonal, so I had 8 different live Z values, and adjusted by 0.020 each time. I could really see both too low (wavy pattern in the layers) and too high (you can see light between the lines of filament), and could find the perfect intermediate spot. If you are a perfectionist, you can then redo another set of 8 around the sweet spot, varying by 0.010 or even 0.005 each time to completely dial it in.
6. Finally -- don't leave your print alone until you are sure that the first few layers have stuck. A giant ball of PETG around your extruder really sucks (but this page really helps if this happens: https://help.prusa3d.com/en/article/extruder-blob_2005)
RE:
Thank y'all, this solved my problems with first layer laying down like crap/ripping up. The .3mm first layer worked like a charm, turned first layer heat from 230 to 240•C—this form is why the internet is amazing.
RE: Problems with PETG first layer
After even more work with PETG, elaborating slightly on my previous suggestions:
1. Clean your sheet well! Flowing hot water in the sink with a little dish soap (Dawn is good), and use a fresh paper towel to scrub thoroughly. Rinse with hot water for at least a minute. Touch only from the edges from there on. You don't need to IPA immediately after a soap/hot water cleaning.
2. In between hot water/soap washings, IPA with a fresh paper towel before every print. Before heating, pour a puddle of IPA directly onto the sheet straight from the bottle, tear off a piece of fresh paper towel, being sure to only touch one side of the paper towel, and wipe down thoroughly. DO NOT use a piece of cloth or pour the IPA into another dish first -- this will contaminate it -- I learned this the hard way. Just IPA poured directly on the sheet and a brand new piece of paper towel. I can't emphasize this enough. This is important for PLA also.
3. Slow down the first layer a lot. Putting "20%" (not 20 mm/s) as the first layer speed seems to do it for me.
4. I found the Prusa Slicer defaults not hot enough. I've had good luck with first layer of 240/92 and other layers 225/95 (nozzle temp / bed temp).
5. If all that doesn't work, try glue stick (Elmer's disappearing purple is cheap and effective). After IPA, but before heating, thoroughly glue stick the sheet (I like to do two layers so I don't miss anywhere, one horizontally, one vertically). There is no shame in using glue stick if you can't get things to stick directly to the sheet. It's often faster than constantly tweaking parameters.
RE: Problems with PETG first layer
I wanted to re-print the PLA parts I had done for my MK3S clone, but was nervous as I had never dealt with PETG before. So, I read all I could and grabbed some windex. Cleaned bed real good with alcohol, then heated bed up. Sprayed some windex and spread it out on the smooth PEI sheet. Let it evaporate (didn't wipe anything off.)
Started my PETG print and worked great. Printed all the parts I needed and they popped off after the bed cooled. Had a little stringing (none with PLA) but I haven't tuned anything for PETG, so it wasn't a big deal. Now to rebuild the clone with PETG parts.....