Josef Prusa  is a mod here,

3D Printing
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@Josef_Prusa is a mod here, but I don’t think he even uses G+ that often. Regardless, he looks like he’s been busy and making his own guide videos.

Originally shared by Prusa 3D by Josef Prusa
https://www.youtube.com/watch?v=wqTrT6dM1Nw&feature=autoshare

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When things are running right, there is almost no buildup of material on the hobbed pulley.

My experience has shown that junk on the hobbed pulley/bolt is a result of (pre)jamming.

When my hot end is starting to jam (temp too low, unlevel bed blocking tip, feed rate too high), the hobbed pulley will grind on the filament.

So while inspecting and cleaning are good routine tasks, I would add that if you are regularly cleaning material off the hobbed pulley, you should investigate the root cause.

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@Alex_Wiebe I’ve also seen plastic shredded into the hobbled pulley by having the bearing pressing too tight or too loose.