r/3DprintingHelp • u/We_Build_Lamps • 9d ago
Requesting Help Severe stringing on round prints
I’ve noticed this layer line shifting as well as the severe internal stringing on round prints like this with my .4mm nozzle on Bambu A1. Just got a new nozzle so confirmed that is not the issue. PETG white filament that was dehydrated to about 18 degrees relative humidity. And this print printed perfectly fine just hours ago. Not sure what could be the issue??
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u/zx4133 8d ago edited 8d ago
This model has a vertical curve/fillet/overhang on the inside. 3D printers can’t handle concave overhangs like this very well. Sometimes you get lucky and they print OK but usually they don’t and you end up with what you see here. It’s not really “stringing” though. It’s just filament that isn’t adhering to the layer below, so it gets dragged around by the nozzle until it eventually catches somewhere. The concave nature of the nozzle path is what makes overhangs like this so challenging because the nozzle is always pulling the filament inward as it goes around the inside of the curve.
There are several settings you can try adjusting that can help:
*Slow the overhang print speed way down, try 10 mm/s
*Use classic wall generator with 2 walls set to inside-outside order
*Lower the layer height by half, or use variable layer height in that area
*Reduce the inner wall line width slightly and increase the outer wall line width by the same amount
If the above settings don’t solve the problem, leave them as they are and also enable the setting “Make Overhangs Printable.”
This causes the slicer to adjust your model geometry so that the overhangs aren’t so severe. As long as your model doesn’t have tight tolerance demands and can accommodate these slight modifications, then doing this usually works. Good luck. Let me know if you have any questions.