Did you print your new piece with the wooden spindle holder hanging on the wall already? Sometimes it helps to unroll a good chunk of filament and reroll it so no jamming will happen. The on and off switching of the fan is nothing to worry about. I guess it is only really needed to prevent warping of the cool layers when a new layer gets printed on top. PLA likes to warp a little when it gets hot. --Matthias.breuer 11:07, 19 November 2010 (CET)