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Do a temp tower. Find one hottest to coolest (260 to 220) and see where the sweet spot is. Going coolest to hottest could cause clogging.
And when in doubt make sure you PETG is dry. Likes to pull in the moisture. Tell-a-tale is popping and hissing.
Others: correct if I’m wrong but black PETG tends to be on the warmer side then other colours?
I did two temp towers: 260-225
And
280-235
Although my printer didn’t want to go above 260, so the first layers are all 260.
Yikes! Are you sure you sliced the temp tower for PETG profile? (as others have inquired)
Update: replaced the nozzle, heat block (heating element, sensor, PTFE) and fan duct. Did two new temp towers:
Left tower is 235 (top) to 260 (layers labeled 280-260 are all 260). Right is 220-240.
https://i.imgur.com/1MQkStE.jpg
https://i.imgur.com/HDWq19A.jpg
I definitely feel like 220 is the right temp for this.
Huge difference!
Yeah I have Prusament Jet Black and 220/225 is the sweet spot for it on my setup.
That’s a shame you have to do all of the replacements but looks to solve all sorts of things for you.
I selected PETG filament profile in prusaslicer.
I wrote the custom layer change temp code to switch temps and checked in prusaslicer that temp changes occur the right places. (Using the color preview thing)
While printing I also saw that the temp did change where it should.
I think I’ll do a calibration of the feeding, or whatever you call it, where you measure how much filament is extruded. During some of the bridging, it looked like nothing got extruded.
It almost looks like 260 is the best temp. While extruding at this temp, I did heat lots of popping noise, which makes me believe the filament is wet. The noise did not occur at lower temps.
Kinda annoying when it’s a brand new roll.
What's your print fan set to? I've had better results with fixed fan speed and much higher than default, but I use an enclosure. Is it popping or skipping? You'll hear clicking if the filament skips, happens if you feed too fast, partial clogs etc. What brand petg? 260 seems high-ish, I tend to print hot in general but petg is usually 245-250 depending on the filament. What's your speed like? If you're enclosed definitely crank the print fan and maybe try slowing down.
Is your hotend clogged? Petg is the only filament I've had clogging issues with in the past. While printing, is it trying to cling to the nozzle? I've also found petg can try to climb up the nozzle, solved with a sock.
Update: replaced the nozzle, heat block (heating element, sensor, PTFE) and fan duct. Did two new temp towers:
Left tower is 235 (top) to 260 (layers labeled 280-260 are all 260). Right is 220-240.
https://i.imgur.com/1MQkStE.jpg
https://i.imgur.com/HDWq19A.jpg
I definitely feel like 220 is the right temp for this.
In regards to the fan, I actually read a post saying PETG wants almost no fan, so I just left it on default but maybe I should try a fixed fan speed.
I’m pretty sure the popping noise was clogged PLA burning like crazy at 260c…
I've always understood petg to really like cooling but I print in an enclosure so YMMV, it's absolutely awful for bridges without cooling. Another thing to check would be extrusion multiplier and retraction. I get nozzle buildup if it's overextruding which leads to blobs and stringing, worth tuning that anyhow
Been doing a couple of test prints with 30-80% variable fan speed and it’s actually pretty good looking with almost no stringing.
I unfortunately don’t have an enclosure, else I would for sure try and higher fan speed. Ad a slight draft this morning and my calibration cube print popped off half way through.