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Weird PETG Printing Behavior
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this post was submitted on 18 Oct 2024
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Did you notice a difference in print speed when you slowed down? As this is a small print, it could already be as slow as it will be due to minimum layer times.
It could also be that the nozzle spends too much close to the print. What happens if you print 2 or 3 of them?
This is typically more of an issue with PC where you don’t have a part cooling fan running, but maybe it’s the case here too?
Honestly not very different timing: maybe 25 minutes instead of 20 to be failing.
Trying more than 1 is an interesting idea. Too bad I don't need more than 1 lol. Maybe I'll print a benchy elsewhere on the plate. Though why wouldn't more cooling help offset similarly?
It could be a case of too much cooling, while simultaneously being too much heat.
If you’re blowing so much air that the filament instantly solidifies when it leaves the nozzle, it’s not going to bond with anything else. It’s also interesting that the first layers are fine (when the part cooling fan is typically not running), but problems start when the part cooling fan turns on.
Have you tried without part cooling at all? Another thing is that your part cooling might be cooling down the tip of the nozzle, causing tiny partial clogs, which are cleared every so often by friction.
Weird as heck but without any cooling it printed fully just fine. Thanks for the advice!
FWIW the default PETG profile on my printer doesn't even run the part cooling fan at all except during bridges. PETG has a very narrow window of suitable temperatures typically between 240 and 260° C, and if you're printing with your nozzle at 240 you're already scraping the lower end of that range. And unlike PLA, especially the modern blends we have now that are full of additives to make the stuff easier to print, there is no leeway. PETG will essentially solidify instantly once it falls below that critical temperature point. Not only underextruding severely (or not extruding at all) but likely also failing to bond to the layer underneath with whatever does manage to make it out of the nozzle.
On my machine you can hear it when this happens, a least. The extruder gears click like mad whenever there's a failure to extrude at any significant volume.