Problems getting PETG to extrude properly

[43915 9]

Hello,

 

We have an UM2+ at work and I just received a spool of Polymaker Polylite PETG and decided to try it out. I unloaded the PLA I was printing with before with a pull and tried to load the PETG.

However, when the filament reached the nozzle it just barely managed to squeeze a tiny bit of filament out very slowly and after a while stopped all together while the extruder started carving away at the filament. I figured that there had to be something clogging the nozzle, so I did a few pulls to clean the inside of the nozzle (with no signs of any debris or dirt) as well as wiping off the outside of it and sticking a small needle through the hole to clean it out.

 

I tried loading the PETG again but the same thing happened again. When I helped push the filament behind the extruder it managed to slowly extrude a little bit of filament, but still basically nothing. I adjusted the tension in the extruder in case it wasn't getting a good enough grip, but even at the highest tension the problem persisted.

 

After that I tried adjusting the nozzle temp to see if it would make a difference, but going from 10C below the recommended temperature to 10C above it still didn't solve it. I then tried switching to a new nozzle and while I had the old nozzle removed I took a bit of filament and tried to push it through the print head. I went through, but it wanted to catch on to some edge down inside the head after entering the teflon coupler, and when I got it past that point it felt like something was scraping against the filament and making some resistance on the way through. I changed the teflon coupler a few weeks ago making sure to use the printhead spacer, so I doubt that that's the issue. But given the distance I could feed the filament before it hit the edge I mentioned I would like to think that it's right where the teflon coupler connects to hot end isolator. As if they aren't entirely flush on the inside. Is this something that can happen or could something else be causing this?

 

Anyway, after mounting the new nozzle I tried again with the PETG but the problem persisted. I then unloaded the PETG and loaded regular PLA again, and it prints perfectly right away. I'm having a hard time figuring out why PLA (and also ABS) works just fine while the PETG is a total failure. I can't even start a print with it since the prime blob basically just becomes a 4-5mm long string instead of a blob on the bed, and then the print gets heavily under extruded to the point where there's basically no printing getting done.

I guess there must be something wierd with the printhead given what I found when changing nozzles, but since both PLA and ABS prints normally I don't understand why the PETG is having so much trouble. Has someone else had similar problems, or can someone help me troubleshoot this?

 

Regards,

Jocke

[dsp 18]

try and load the PETG as CPE+ the nozzle gets a bit hotter, we already used this before there was an ultimaker petg profile and still do because it works. 

 

We noticed that PETG prints better at the top end of the temperature 245 to 250 °C .

Also we noticed PETG prints better on simple Painters tape than on glass

(but I must say I use an S5 and not a UM2+ perhaps that makes a difference in printing with PETG)

[43915 9]

I tried your suggestion and loaded the PETG at 250C and raised it to 252-253C when starting the first print, and it actually does print now. Funnily enough, now that it loaded properly at the higher temp I could lower the temp all the way to 225C during the first print without problem. Strange since it basically refused to extrude at all at 240C at earlier tries without any signs of a clogged nozzle. Not sure why it works fine at lower temps now after loading it at a much higher temp first.

 

But I'm not complaining, it seems to work and I'm getting great prints out of it now. Thank you for the help!

[dsp 18]

You're welcome