I use speed, temperature and retraction according to what colorfabb suggested ( http://learn.colorfabb.com/how-to-print-with-woodfill/ ). I am using 0.4mm Nozzle, 0.27mm layerheight, 105% material flow, 205C nozzle temperature, 70mm/s speed. The first 3 prints are printed fine, however, when the 4th one is printing, the printer suddenly stopped extruding and black liquid came out after more than 5 hours had passed. So, I cleaned it using the atomic method and the charred part comes out of the nozzle. The STL files has been checked, it’s water-tight, no errors. So, it might be the nozzle problem, but we are not exactly sure about it. Does anyone know why this is happening?