Clicking coming from filament sensor?  

New Member

Everything has been printing well on my new Mini+ until about a week ago. I’ve taken apart the extruder assembly to clean it out. I’ve used a needle in the heated hotend. I’ve done several cold pulls.


Despite all that, I am getting an occasional clicking, which *sounds* like it’s coming from the filament runout sensor. Here’s a video that has the sound. After this video is when I put my hands on both the extruder assembly and the filament sensor, which is why I bring that up at all.   (hopefully that works....)


Two concerns: not knowing exactly how tight/loose to have the extruder idler screw, and not knowing how tight/loose to have the screw for the tubing at the filament sensor.

Posted : 03/01/2021 9:08 pm
Eminent Member

maybe clicking form extruder?

someone used grease,

and on the forum is information to tension the idler-spring on the extruder.

maybe this - or cleaning - will help?

Posted : 06/01/2021 9:16 am
Active Member

My filament sensor is clicking too!
It is NOT the extruder. I can stop the clicking noise by holding the filament sensor. It sounds as if there is a lot of resistance in the sensor and the filament can not go through smoothly but skips along the way. I loosened the screw holding the PTFE tube as much as possible but it is still clicking.
I will try to disassemble it as soon as the print is done...

Posted : 22/01/2021 6:27 am
Active Member

Made a 6 second video of the filament sensor clicking: 

It is not on the video, but when I hold the sensor thightly in my fingers the clicking stops.

I have 3 Mini+ standing in a row. This one is the only one clicking like this.

This post was modified 1 month ago by WorstCase
Posted : 22/01/2021 6:46 am
Eminent Member
Posted by: @jasonfornelli

Two concerns: not knowing exactly how tight/loose to have the extruder idler screw, and not knowing how tight/loose to have the screw for the tubing at the filament sensor.


The following PRUSA article has guidelines for the idler adjustment for each of their printers.  Side note: I only get the occasional clicking when I have PLA loaded.  PETG seems to feed much smoother on my Mini+.  I had to correct the ilder adjustment when I received the Mini+ (too loose). It would only feed PLA and didn't feed PETG.  After adjusting it works fine with PETG.  I adjusted it so the idler screw was flush with the housing.


Idler screw adjustment:


Filament sensor tubing screw:  On my MINI+ the slotted hole for the PTFE tube was too tight even with the screw removed. I had to spread the slot slightly in order to fully insert the tube.  The screws should only be tight enough to keep the tube from coming out.  It should not be so tight as too restrict/deform the tube diameter so that the filament is pinched in the tube.

Posted : 22/01/2021 8:14 am
toz liked

The clicking could be also caused by retracts (backward filament extruder move) during print. The filament tries to move backward also in FS. The ptfe tube inside FS consists of two separated parts which can bump to each other. 

Each filament has different friction factor, so the PLA could have higher.

This post was modified 1 month ago by Zoltan
even an old man can learn new things 🙂
Standard I3 mk3s, FW 3.9.1, no closed box, sketchup , fusion 360, PrusaSlicer, Windows 10
PRUSA MINI FW 4.3.0 RC1, technical background...
Posted : 22/01/2021 6:35 pm
New Member

I ended up tightening the extruder idler screw much more than I would have thought it should be. In addition to that, I'm running temps slightly higher for both nozzle and bed. It seems I am only hearing the clicking sound now when I use a particular filament (Sunlu Marble PLA). When I use that filament, I keep checking on the extruder gears to see if they're starting to grind the filament down. If so, I use some compressed air to clean it out, then come back in another hour or so (unless I hear clicking before that).

Oh, and I'm also running my filament through a heater/dryer before (and while) it feeds in.

Posted : 22/01/2021 6:44 pm
Prominent Member

Filament sensor is partially mechanical - there's a steel ball hitting on a lever which blocks or allows a light from LED to the sensor. Ball rattles there. As long as it is working, I would not worry about it, but of course you can disassemble it and take a look inside.

Posted : 25/01/2021 11:16 am
Active Member


I did open it up. I removed everything, cleaned out some stringing (probably from the original printing) and reassembled everything. Now there is not more noise! Still no idea what really caused it, but it is gone!

Posted : 25/01/2021 2:01 pm

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