PETG newbie: Major issues with uneven extrusion, can't even get to a Live Z test
Printer: Mk3S+ in an enclosure
Material: Prusament Recycled PETG (Black) (freshly opened 2 kg spool)
Steel sheet: Textured
Temp: 230-245 / 80-85 (no fan on first layer)
Hi folks,
I'm new to 3D printing. I started with some Prusament PLA on a PEI sheet and printed a dozen or so model with minimal difficulty using standard settings. The problem started when I switched to Prusament PETG on a textured sheet. Since it's the first time I've used the textured sheet, I tried to do a first layer calibration in the HW menu using (PET setting), but it was a mess. I lowered the head down to -0.300 and again at different heights all the way down to -0.700 (which was too low). I also tried to the print the Live Z 3x3 test and got another mess (see pictures).
Issues:
- The extruded filament looks very uneven (see third pic). There are tiny popping sounds while the extruder is running and the material comes out "dented".
- The PETG doesn't adhere very well to the textured sheet. When the printer makes a 90 deg turn, the recently extruded material gets pulled diagonally. It can't even draw the initial rectangles correctly.
What I've tried:
- Washed the textured steel sheet with soap and a lot of hot water.
- Tried different settings (up to 245 / 80 deg, lowered speed to 40 mm/s)
- Made sure the spool was turning freely
I want to figure out what's causing the problems. Tinkering with temp and Z axis hasn't improved the results.
Any pointers are very appreciated!
RE: PETG newbie: Major issues with uneven extrusion, can't even get to a Live Z test
From the last picture I'd say your live z is not negative enough. The textured (and satin) sheets are about 0.4 mm thinner than the smooth PEI sheet so your live z would be somewhere around -0.4 more negative. Example, if it was -1.0 for the smooth sheet you would end up somewhere around -1.4 for the textured sheet.
The popping sounds could indicate damp filament. Just because you just opened the box doesn't mean it wasn't sitting in a warehouse for months. I'd try drying it.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: PETG newbie: Major issues with uneven extrusion, can't even get to a Live Z test
Excellent information. Thank you. I ordered a filament dryer from Amazon (the Sunlu one that seems popular). I will also redo my Z live adjust for the textured sheet. The PEI one was -1.9, so it sounds like the textured sheet will be -2.3 or so.
RE: PETG newbie: Major issues with uneven extrusion, can't even get to a Live Z test
The PEI one was -1.9, so it sounds like the textured sheet will be -2.3 or so.
In that case, I would strongly advise you to reposition your PINDA sensor a bit higher. Ideally, you want to be somewhere around -1.000 when your Live Z is optimal. That gives you plenty of wiggle room up and down. With greater than -2 you're kinda pushing it (the Prusa Mini wouldn't even allow you to go beyond -2.0).
You can just eyeball it by simply loosening the screw that holds it and move it up a bit, then retighten. Or print one of these babies https://www.printables.com/model/57192 to get the ideal distance between PINDA and nozzle (1.5 mm)
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: PETG newbie: Major issues with uneven extrusion, can't even get to a Live Z test
When I assembled the printer I think I just eyeballed the sensor height but I prefer to use something more standardized like your model. I'll use it then rerun the Live Z with the textured sheet. Fingers crossed!
RE:
@fuchsr I followed your recommendations. With the spacer you linked to reposition the PINDA, I got the PEI Z-offset to -1.0. The textured sheet took some fine tuning but seemed to look best at -1.35. The filament is finally looking neater and adheres to the sheet.
I'm running a test print and it's much better than before, but the surface still looks off. Does it still look like a moisture issue? I couldn't dry the filament because the 2 kg spool won't fit in the standard Sunlu dryer. If it's not moisture, can you recommend any improvements?
Here are some pics of the current print: Imgur
RE:
From the last picture, I'd say the nozzle is too low. Those ridges you see are very typical for a Live Z that's a bit too low.
Everything else still looks like damp filament to me.
One more thing: I just looked at your original post and saw you mention an enclosure. For PLA and PETG, I don't close the doors, as I found doing so can cause print artifacts and/or heat creep. But I don't think that's related to the problem you're seeing.
Edit: Some of the pictures look like my favorite villain Prusament Neon Green. I can dry it overnight and it will print fine for a few hours and then it starts looking like your filament. I ended up printing it directly from a dry box.
I wouldn't buy 2kg spools unless you know you will go through it in a couple of days. Most dryers are not set up to do a decent job with such large spools.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE: PETG newbie: Major issues with uneven extrusion, can't even get to a Live Z test
I'm happy to report your recommendations got things on the right path. I raised the Z offset a bit and am now working my way through my first PETG models. My next issue to resolve is that even small overhangs look frayed with a lot of filament pieces I have to cut off. I noticed a similar appearance with PLA overhangs but it seems worse in PETG.
As far as the 2kg spool, I might try to respool half of it onto a standard sized spool so I can dry it in the dryer. And that Neon Green Prusament looks like a fun color for prints.
Thanks for all your useful tips!