# Filament melting against hobbed bolt

**URL:** <https://forum.lulzbot.com/t/filament-melting-against-hobbed-bolt/5179>\
**Category:** LulzBot Mini\
**Created:** [August 29, 2017, 10:45pm UTC](https://forum.lulzbot.com/t/filament-melting-against-hobbed-bolt/5179 "2017-08-29T22:45:52Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![rastoboy](https://avatars.discourse-cdn.com/v4/letter/r/e19b73/32.png) [@rastoboy](https://forum.lulzbot.com/u/rastoboy)\
**Post date:** [August 29, 2017, 10:45pm UTC](https://forum.lulzbot.com/t/filament-melting-against-hobbed-bolt/5179/1 "2017-08-29T22:45:52Z")

</div>

I have problem that wasn’t happening, and now is happening regularly, so I think perhaps a fan is failing? When I put some new filament in, it prints fine. But when I try to do a second print, extrusion doesn’t happen. When I remove the filament, I see a little melted crescent in it, right about where the hobbed bolt is in the head (see green box on attachement).

I lowered the temperature, and it helped for several prints, but now it’s back to doing it after every print. What could be causing this? Any input would be greatly appreciated!

 ![20170821_193724.jpg](https://us1.discourse-cdn.com/flex020/uploads/lulzbot/original/2X/7/7ee27e0a1a3ebe7d6db326ad7d35eca983e31a74.jpeg)

---

<div class="post-metadata">

**Author:** ![Orias](https://sea2.discourse-cdn.com/flex020/user_avatar/forum.lulzbot.com/orias/32/3_2.png) [@Orias](https://forum.lulzbot.com/u/Orias)\
**Post date:** [August 31, 2017, 6:35pm UTC](https://forum.lulzbot.com/t/filament-melting-against-hobbed-bolt/5179/2 "2017-08-31T18:35:53Z")

</div>

What material are you using? Do you feel resistance at specific points when feeding in filament? Some things to check:

[_]The always on hot end cooling fan (middle or small fan pointed at the hot end cooling fins) should continuously spin when the 3D printer is powered on.  
[_]The hobbed bolt teeth should be clean and free from ground up or impacted plastic. Use the metallic brush or **sharp** dental pic to clean the hobbed bolt. Spin the large 3D printed herringbone gear to reach all the teeth.  
[\*]Make sure you’re using the latest version of [Cura LulzBot Edition](https://lulzbot.com/cura)

If the above doesn’t help, contact the support team by emailing [Support@LulzBot.com](mailto:Support@LulzBot.com) with information on filament used, filament vendor, Cura LulzBot Edition slicing profile selected, and fixes attempted.

---

<div class="post-metadata">

**Author:** ![kcchen\_00](https://avatars.discourse-cdn.com/v4/letter/k/9dc877/32.png) [@kcchen\_00](https://forum.lulzbot.com/u/kcchen_00)\
**Post date:** [September 1, 2017, 6:12am UTC](https://forum.lulzbot.com/t/filament-melting-against-hobbed-bolt/5179/3 "2017-09-01T06:12:20Z")

</div>

Also try tightening the idler to increase the pressure against the hobbed bolt. This will help push the filament through any friction in the filament path.

FWIW, the filament probably isn’t melting to against the hobbed bolt. The teeth are grinding through the filament because the filament has stopped moving…