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Extruder not gripping Well (Kossel Mini)

Posted by ANgelHun 
Extruder not gripping Well (Kossel Mini)
July 24, 2018 05:18PM
Hello All!

I have a Kossel Mini (think3dprint3d) running:

Firmware Name: RepRapFirmware for Duet
Firmware Version: 1.21.2beta1 (2018-06-23b1)
Web Interface Version: HTML: 1.11, JS: 1.11

I am having issues with the extruder inconsistently gripping and pulling filament (Hatchbox 1.75mm PLA) into the bowden tube and thus it starves the hot end during printing causing failures. Is there any way to adjust the tension or increase the force of the gripper gears? Any other solutions to remedy this? It is the release 3 variant with the spindle on top.
Re: Extruder not gripping Well (Kossel Mini)
July 24, 2018 06:21PM
If the motor is skipping steps, increase extruder motor current (M906 in config,g) or increase extrusion temperature. If the hobbed insert is losing its grip on the filament, AFAIR the extruder drive has a screw to adjust the clamping force. Also check that the bearing that presses the filament against the hobbed insert rotates freely.

HTH David



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Extruder not gripping Well (Kossel Mini)
July 24, 2018 07:37PM
Is there a recommended step increase for M906? I'll give that a try. I think I may have identified the screw that adjusts clamp force. Thanks for the help.
Re: Extruder not gripping Well (Kossel Mini)
July 25, 2018 01:34AM
Thinking back a bit more, AFAIR the extruder on that machine has 5:1 gearing and a 48mm long motor, assuming that they didn't change it between version 1 of that kit and later versions. So you are unlikely to need more motor current.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: Extruder not gripping Well (Kossel Mini)
August 06, 2018 04:25PM
I got rid of varying layers on my printer by changing spool holders, went from a solid plastic one to one with bearings embedded into it. Turns out there was enough friction to interfere with smooth extruder movements.
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