I am trying to print Benchy at 50% scale out of nylon (trimmer line). And all is ok, but there is under-extrusion when the boards are already printed, but before printing the roof. Sometimes it is so severe that the roof comes off under slight pressure.
I tried temperatures of 250, 255 and 263 degrees, 0.45 * 0.2 and 0.6 * 0.3 extrusion size, no fan and slight cooling, and have seen no difference except sometimes under-extrusion occurs at the window level, but sometimes slightly higher (but not at the roof).
I left nylon overnight in oven at 60 - 65 degrees, but it had not dried completely, as the hairs tell. The speed was 30 - 40 mm/s, the slicer is Prusa slicer, the printer is Kingroon KP3S.
Full sized Benchy prints perfectly, except it bends due to thermal shrinking. I printed it at 250 degrees, 0.6 * 0.3 extrusion and 80 speed, so the extruder is totally fine.
The small layer size itself is also not the cause, as the smoke stack prints ok (at least when cooled). It could be extrusion of the nylon during head movement due to water boiling and therefore insufficient amount of plastic where it should be, but I can not see any significant lumps of plastic anywhere else.
What it can be and how can I overcome this?
