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I'm doing something wrong; can't print this PETG (imgur.com)
submitted 2 months ago* (last edited 2 months ago) by csm10495@sh.itjust.works to c/3dprinting@lemmy.world
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I have this PETG; its Kingroon Blue PETG. I can't get it to print nicely no matter what I do. Been testing with benchy over and over.

The filament is as dry as I can make it. It's been in the dryer for at least 12 hours before each print. I even have tried snipping the part of the filament not in the dryer to start from a dried state. The Relative Humidity doesn't drop anymore at this point (from 19ish).

I've tried different temperatures from 220 to 260. I've tried different retraction lengths and speeds. I've tried with the cooling fan on/off and at a couple middling percentages. Also different speeds from 30mm/s to 45 to 60.

I tried printing a retraction tower and it fell apart after the first level.

The first layer prints more/less fine, then eventually it either just falls apart (most of the time) or produces something in awful quality.

I've attached images of everything I can think of from the way it looks on the first layer, to the case where its a benchy out of a horror film, to when it just fails miserably.

Printer Elegoo Neptune 3 Plus. .4mm nozzle (i've tried both copper and hardened steel). Besides the nozzle its stock. If I swap to PLA it prints generally fine.

I feel like I'm missing something obvious. Everyone says dry the filament, but I can't dry it anymore 😢 .

Thanks folks (and if you celebrate: Happy Turkey Day!)

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[-] csm10495@sh.itjust.works 1 points 2 months ago* (last edited 2 months ago)

Holy crap. So I tried a pack of the Green PETG (still Kingroon) and the first print didn't go well. It didn't like .3mm on a .4mm nozzle.

This happened:

Image

A bit of a clog and other weirdness.

I took the default Cura PETG settings for .4mm nozzle, swapped to .2mm (fast) default settings then set fan to 50% and temperature to 230C.. I got a beautiful benchy:

Image

It's beautiful.

I guess it seems like maybe something is just wrong with that roll of blue..

Makes me wonder if a Bambu or some other more set/forget kind of printer would have been able to print it somehow. Maybe I'll try again one day.

Thanks everyone so much for all.

[-] jokeyrhyme@lemmy.ml 1 points 2 months ago* (last edited 2 months ago)

i've had a cursed spool of filament, too

same brand and type as known-good spools, but it was extremely resistant to me actually getting any results at all

i've not had anywhere near this level of trouble with a spool before or since

[-] IMALlama@lemmy.world 1 points 2 months ago

You're severely under-extruding. This may sound weird, but try a warmer temp tower without any extrusion. You might be developing a clog mid print.

[-] csm10495@sh.itjust.works 0 points 2 months ago

What's the recommendation to fix under extrusion? I tried changing the flow in cura to 102 then later to 118.. no obvious differences.

[-] IMALlama@lemmy.world 0 points 2 months ago

PETG isn't very tolerant of too much retraction. Given your fine first layer I suspect you're developing a clog as the print goes on, which would result in under extrusion. Turning retraction completely off will make it very easy to rule out as a possibility.

[-] csm10495@sh.itjust.works 0 points 2 months ago

What should I see differently with retraction off? Like it failed but what should I look for then try next?

[-] IMALlama@lemmy.world 0 points 2 months ago

Did it look more solid or did print quality basically remain the same?

[-] csm10495@sh.itjust.works 0 points 2 months ago

It pretty much self clogged a few layers in. So about the same?

[-] IMALlama@lemmy.world 0 points 2 months ago

Sorry to hear that. The only thing that comes to mind is potentially print speed. Your first layer is probably pretty slow. Are your subsequent layers much faster?

[-] csm10495@sh.itjust.works 1 points 2 months ago

It must be just the blue. I figured out green: https://sh.itjust.works/comment/22401881

[-] papalonian@lemmy.world 0 points 2 months ago

As others have said, you are severely under-extruding.

Looking at your pictures, I do see a potentially major issue that nobody has addressed: the taughtness of the filament between your hot end and runout sensor. It does not look like filament is being fed to the extruder easily enough for the extruder gears to grip the filament. If you're able to print other filaments, it's possible that this one has a harder or slicker surface than say PLA.

I would try temporarily disabling the runout sensor, and routing the filament under the top bar, directly to the hotend, to test this.

[-] csm10495@sh.itjust.works 1 points 2 months ago

I instead tried printing directly from the spool holder immediately after taking it out of the dryer. Same thing happened. I doubt it could have moisture-d up that fast for it to make a difference

[-] csm10495@sh.itjust.works 0 points 2 months ago

For good measure I tried going direct from the dryer to the hot end (and just left a piece in the runout sensor to have it not trip). More/less the same problems: https://imgur.com/a/65jzAQv .. I stopped it early since it was failing terribly. Otherwise was using default cura generic PETG settings on .3mm per layer with .4mm nozzle.

[-] papalonian@lemmy.world 1 points 2 months ago

0.3mm layers seems kinda high for a 0.4mm nozzle (I usually try to keep layer height ≤1/2 nozzle diameter), could be your hotend is having a hard time melting PETG that quickly?

[-] csm10495@sh.itjust.works 1 points 2 months ago

This may have been it. Thanks! ref: https://sh.itjust.works/comment/22401881

[-] papalonian@lemmy.world 2 points 2 months ago

Awesome! One of the biggest advantages of switching to a larger nozzle diameter is being able to print those larger layers. Cuts print time dramatically

this post was submitted on 28 Nov 2025
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