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I’m getting defects when using PETG. They look like this:
Lots of boogers get left all over the print bed when this is happening.
I’m using Prusament on a Bambu X1C. This was a box with 0.1" thick vertical walls. No support, just a hollow box. Print bed adhesion was fine. I dried the filament for 5 hours at 50 degrees C prior to printing. I have also used different brands of filament (Matterhackers and Creality) and they had the same problem. At first I used the default PETG settings in Bambu Studio. Then ChatGPT recommended a bunch of stuff that was probably nonsense; at any rate, it didn’t fix it.
I don’t know what the name for this failure is, which makes it hard to research. It doesn’t seem to quite match the common PETG failures I saw when looking around, but I’m pretty new to this so who knows
My first guess is you are having nozzle issues. It looks like your nozzle is clogging and then un clogging. I print a lot of PETG and dealt with my fair share of cold pulling. What temps are you running? and is that nozzle temperature fluctuating throughout the print?
Always in the same place? Or different places with different models?
Not enough to ensure it’s dry. 8+ hours at 65ºC. But I don’t think this is your problem, since I’d expect to see effects everywhere and not just in one specific area.
Also, it’s pretty amazing the rest of the print completed cleanly with that amount of disruption at lower layers.
Try putting a prime tower at the corner. What I mean is just a small rectangular shape that is trash. Only as tall as needed.
My first guess was that corner lifted a little. But you said no. The shape you described creates the classic problem for shrinkage.
Is your chamber closed? front door and top glass.
IMO you are running that filament too fast, you can see the rippled area on the high speed areas along that entire wall. It’s at the absolute threshhold, and something tipped it over into pure failure in that spot. As the nozzle slows down to round the curve, the ripples fade away and it looks like neatly stacked lines. Too fast.
You either need to recalibrate your pressure advance AT THE SPEED you are running this filament, or you need to just simply slow down.
Nozzle temps are 255 °C for the first layer and 265 °C after. Max volumetric speed is set to 12 mm³/s. Initial layer speed is 50 mm/s; outer walls 200 mm/s; inner walls 350 mm/s; sparse infill 450 mm/s; internal solid infill 350 mm/s; vertical shell speed is 80%.
The failures don’t occur at a consistent Z height — I’ve seen them in different locations and on different models.
The chamber is closed (front door and top glass), though I didn’t record chamber temperature during the print.
I haven’t yet tried significantly slowing the print or lowering volumetric speed, but that’s something I can test next.
And there’s no Aux fan being turned on at any time?
What size nozzle? 0.4mm?
These noodles look quite a bit bigger than 0.4mm, so if that’s the nozzle size you’re using, I’m inclined to go back to “drying” since moisture can make oozed filament “swell”.
The rippling of the walls that otherwise printed cleanly are probably due to slightly exceeding the flow of the filament. Assuming it’s not something you’ve done intentionally. It’s kind of a cool effect…
Again, post a screen grab of the sliced model on the build plate, positioned so Z seam is visible (assuming you’re not doing “random”). Are there any features inside the box in this area?
I’ve started a new print with a lower speed and temperature. I’ll watch to see if the Aux fan comes on. Here is a screenshot of the slicer - the seam is on the rightmost edge of the box in the screenshot, and the damage is on the wall in the northeast quadrant of the box in the screenshot, adjacent to the northern edge: https://postimg.cc/XGnNpFKs
The rough part is not near any interior features (which are minimal, just some short pieces on the bottom of the box).
Should change one parameter at a time. You lowered the speed because at the temperature you’re running it’s not flowing good enough. So also lowering the temperature, which will reduce maximum flow, is counter to your objective. Should have left temperature alone.
Worth noting, I run my MatterHacker PETG at 270ºC when I run in Sport. It’s not fast enough for Ludicrous at even higher temps.
I caught it in the act. First, there were some stringy bits that didn’t adhere properly. Then when it tried to print over them, a booger formed on the nozzle that got dragged around until it got big enough to fall off.
a simple test is set the speed to silent during the build. It is my impression that halfs all the speeds. Not the same as setting the speed pre slice but a simple test.
I think your drying could be the issue. You say you dried it at 50C for 5 hours, on my Creality dryer its preset is 65C for 8 hours. So perhaps to cold for not long enough?
I always get excellent prints using Bambu Lab PETG-HF with a 0.6mm nozzle. It prints fast and the results are predictable across hundreds of hours. As long as the Filament is dry!
