Problems with Jamming of new filament extruder

[cliffwarner]

My original extruder cracked recently when I had a failure of the thermistor on my V3B hotend. The temp was reading fine when in reality it was too low and the part cracked with the forces applied. I was lucky to be in the room when things went bad, and was able to shut it down. But the crunch was a nasty sound. After a long evening sorting out what went wrong, I figured out it was the thermistor and swapped out the hot end with my backup. I was able to hold the extruder together with a zip tie until last night when I printed a new one (silvers model on thingiverse: http://www.thingiverse.com/thing:267137) out of ColorFabb XT. Today I put it on my system and have one printer jam after another. I have carefully drilled out the filament path with a 2.0mm drill bit and made sure the path is smooth. However, that did not do anything to fix the problem and it jams constantly. I have played extensively with the tension bolt to no avail.

So a couple questions.

1: What diameter do people clean out the filament holes to?

2: Does one need a larger diameter than 2.0mm for the filament path?

3: Is the ColorFabb XT not a good material choice for a filament drive? Is it inherently sticky with itself?

4: Any other ideas???

Thanks
Cliff

[jimc]

cliff i cant say as to how the xt works as a filament drive. i would think it would be ok but you never know i guess. i clean the filament path with a 2mm drill bit just like you. i have done that on every drive i have made for the past year. in most cases the hole in most hot ends are 2mm so no need to go bigger. the v3b brass tube is 2mm bore. i know the rsilvers filament drive is probably the most popular of any drive for m2 owners. one thing i have found is that you dont need almost any tension on the screw. with pla it doesnt matter much because its so hard but with pet, nylon and maybe some abs if you tighten the screw you can actually squish the filament flat or into an oval making it too wide to feed into the lower hole. try removing all tension from the screw.

[cliffwarner]

I had done that and oscillated between the extruder gear machining away the filament so it would not move and immediately jamming.

Interestingly, I tried running ColorFabb PLA/PHA through it tonight at it works flawlessly. So I must have a problem with the compression of the PET. I will need to exeriment further.