Hi everyone,

I’m reaching out to get some insight on a very specific and recurring clogging issue I’m facing with my Creality K1C using a 0.8 mm nozzle and the KREI APEX CARBON HF filament. I'm printing engineering parts and experiencing clogs at a very consistent point during the first layer.

• The printer always clogs at the end of the first layer and right after sparse infill finishes, as the top layers begin.
• The extruder gear grinds the filament and extrusion completely stops.

Material:

• KREI APEX CARBON HF
• Requires 260–300 °C hotend
• Has high viscosity, carbon-fiber reinforced
• I'm drying it at 65 °C for 4–6 hours

Printer & Setup:

• Creality K1C
• Nozzle: 0.8 mm (hardened steel)
• Bed: 90 °C
• Hotend Temp: tried 275, 280, and even 290 °C
• Fan: OFF for first layer, then 50%
• Filament dried for 2h, then 4h, then 6h
• Slicer: creality slicer

Print Settings:

• Layer height: 0.2 mm
• Line width: 0.8 mm
• Volumetric speed: tested 6 mm³/s, 10 mm³/s, and 12 mm³/s
• Flow rate: tested 0.98, then 1.0
• Retraction: OFF for first layer
• Sparse infill speed: limited to ~60–70 mm/s

Tests & Observations:

• A small cube (20×20×20 mm) prints perfectly.

• A larger flat test part (100×100×5 mm) prints the first infill area, but clogs at the very end of sparce infill, right as it transitions to the top walls.

• Tried 290 °C hotend – no improvement.

• When printing PLA and ABS afterward, I can print fine.

• I cleaned the nozzle, did cold pulls, and inspected for debris.

What else can I try? running out of ideas here, Thanks in advance to anyone willing to share insights or success stories. I’ll try any suggestion you throw at me.