PETG newbie: Major issues with uneven extrusion, can't even get to a Live Z test
 
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PETG newbie: Major issues with uneven extrusion, can't even get to a Live Z test  

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NeoMobius
(@neomobius)
Active Member
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:

  1. 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". 
  2. 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:

  1. Washed the textured steel sheet with soap and a lot of hot water.
  2. Tried different settings (up to 245 / 80 deg, lowered speed to 40 mm/s)
  3. 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!

 

Posted : 06/03/2023 7:41 pm
fuchsr
(@fuchsr)
Famed Member
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. 

Posted : 06/03/2023 11:49 pm
NeoMobius
(@neomobius)
Active Member
Topic starter answered:
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. 

Posted : 07/03/2023 1:33 am
fuchsr
(@fuchsr)
Famed Member
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)

Posted : 07/03/2023 2:00 am
NeoMobius
(@neomobius)
Active Member
Topic starter answered:
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!

Posted : 07/03/2023 3:54 am
NeoMobius
(@neomobius)
Active Member
Topic starter answered:
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

This post was modified 1 year ago by NeoMobius
Posted : 09/03/2023 9:39 pm
fuchsr
(@fuchsr)
Famed Member
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.

This post was modified 1 year ago by fuchsr
Posted : 09/03/2023 10:02 pm
NeoMobius
(@neomobius)
Active Member
Topic starter answered:
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!

Posted : 11/03/2023 5:55 pm
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