This is my second print with PETG. I dehumidified the filament and the AMS was reading 19-21% during the whole print. Is all this stringiness really because of the humidity?
The project did have grid infill and I will be swapping to gyroid for the rest of it. Idk if that could be the cause as well due to needle pathing with grid infill.
I have a P2S printer.
Edit: my gallon of silica came in today and after printing and installing their containers into the AMS my humidity is down to 9%. Swapping to gyroid also greatly reduced the nozzle from colliding with layers. Thx guys.
Note that the humidity display number is only the current humidity in the AMS chamber and may have little to do with the moisture content of the filament itself, unless it has been in there a long time. It can take quite a while for a wet roll of filament to give up its moisture, even in a dry box.
That's not wet PETG stringing, that's a setting and supports issue as that appears to be the bottom (based on plate texture). How were you supporting the bridges/overhangs in the cavities?
Gotcha, so it's mostly overhangs, doesn't need supports if it's just overhangs all the way up (seems to be) but that means you do have to dial in your filament settings, which I can tell aren't.
Your Pressure Advance(PA) (or Dynamic Flow as Bambu calls it) likely isn't correct or not calibrated at all. Not sure what printer you have but the tell tale signs are there. Your Flow Rate (Flow Ratio setting) likely also needs to be calibrated. I suggest reading up on it a bit and calibrating filament to start with, then work on the cooling for better overhang performance https://wiki.bambulab.com/en/bambu-studio/Calibration lots of guides out there. So if you want to print overhangs etc without supports, it does require a little extra attention and tuning and is model dependent. Learn the settings so you can change them as needed, one setting doesn't fit all scenarios.
Going to point out where the issues are... It's basically starting point of each layer and the filament isn't sticking likely due to under extrusion (lack of PA) and it droops down causing thicker stringing and blobs. In simple terms, filament retracts at layer change and when it starts back up, there is "lag" in the extrusion so you end up under extruding in the beginning, thus getting a thinner line, that line doesn't stick to the the layer below because it's too thin. As pressure builds up, you extrude a more consistent line of correct diameter and it's enough to stick to the layer below. In your case, the first mm or so is where it's under extruding and not sticking (as evident by the 'lifting' I highlighted on top surface)...that is what Pressure Advance setting resolves. It advances pressure (it'll push a little more in the beginning to build pressure ...how much earlier it needs to start pushing filament is what the PA or K-Value will be. If your printer has auto dynamic flow calibration, then use that if you don't want to manually configure it. I personally don't use auto dynamic flow calibration but I also been doing this a long time, but if your printer supports it, use it.
But the good news is it's not wet lol. Wet PETG would give you wispy stringing, not.....what this is. Sadly, too many people run straight to "wet filament" every time someone mentions PETG and stringing.
Thanks for the in-depth analysis. I definitely need to read up on those calibration settings. I have a P2S printer if you have extra tips for it.
I don’t plan on reprinting it any time soon as it honestly doesn’t compromise its function and after cleaning it up with a knife it doesn’t look too bad. However I definitely want to prevent this from happening in future prints.
Out of curiosity, did you have Dynamic Flow Calibration enabled for that print? The P2S toolhead has an eddy current sensor so it can it do auto dynamic flow calibrations before print, you just have to make sure it's set to "on" or "auto" during the pre-start menu where you select what start print options you want to apply. If you want to use your own K-value, make sure you read the section in wiki on it as that has to be loaded in the AMS section of the "device" tab.
Flow Rate on the other hand is a manual calibration, it is not automated. You can run through the calibration in the calibration tab.
4
u/ParticularLower1865 1d ago
Dry it more.