Terrible under-extrusion with TPU
Stock V Minion: bondtech lgx lite, dragonfly BMO. I can't even extrude more than 50mm before it either clogs or just slows down to a halt, but then if I request another extrusion, it'll squirt out a little bit more. It's not a smooth extrusion, it speeds up and slows down. I'm extruding at 3 mm/s at 240C. I've also put the extruder tension in the flexible setting.
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Very strange how it just keeps slowing down and speeding up. 3 mm/s isn't too fast to test the extrusion multiplier is it? Especially at 240c
Don't use a guide tube with TPU it creates drag and causes under extrusion. Best solution is to put the spool directly above the center of the bed and drop it down to the extruder with nothing but air around it. If that is not physically possible or easy you need to run the filament over a series of pulleys that are on bearings until it can drop down to the extruder.