One of the biggest problem i have with my bowden tube feed extruder is plastic that has kinks or bends in to, this gets stuck in my feeder and causes the filament to grind. So taken from the idea of a wire straightener , here is my filament straightener. i haven't had any grinding problem since starting to use it. I find that after slicing my object, I then know how much filament is needed and then pull that amount through and then back and recoil it on the spool. When using semi translucent plastics, running them through the straightener will turn them slightly white as is bends the plastic. But this colouration goes away after the plastic has been heated. Bom: 6x m3 20mm 6x m3 nuts 6x m4 washers 6x u grooved bearings, id 3.5/4mm, od 25.5, od inside the groove is 19.5 I picked up these bearings from my local surplus store, they were 2$ each and they had hundreds of them. These particular bearing fit snugly around 3mm filament. Im currently using just 5 bearings in my configuration, this gives me the curve i want for my filament, to feed nicely through the bowden tube.