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BrutusBoots
(@brutusboots)
Trusted Member
Filament sensor issues? (possible fix)

So I've had an MK4 for almost two months.. about a month into it I had a filament run out and from that point on my filament sensor wouldn't properly detect filament.  I wasn't able to calibrate the sensor and had to leave it disabled.  I could get it to detect filament if I really jiggled the filament around so I was guessing I had some debris in there somewhere.

I went through all the steps with support to troubleshoot and they wanted me to wait for the assembly manual so I could open things up.  I reached out to chat today since the manuals are now available and the agent had an additional troubleshooting step that I hadn't tried.  On the extruder there is a small hole.  I unloaded the filament, opened the idler door and blew compressed air into that hole as I poked a piece of filament in and out of the filament path.  Looking at the manual, it looks like the hole is meant for this very purpose.  In any case, it worked and my filament sensor is working again.  Just wanted to share in case it helps anyone else out.

Hole circled in green:

This topic was modified 11 months ago by BrutusBoots
Posted : 14/06/2023 1:21 pm
Tom, _FirstLayer, PointNemo and 6 people liked
maltvat
(@maltvat)
Member
RE: Filament sensor issues? (possible fix)

Thanks for posting this!  My filament sensor pretty much just stopped working.  I may have had a runout, not sure.  but now even swapping filament is a hassle because it does not detect when the old filament has been unloaded or the new one loaded, and there is no way to bypass is on the screen.  I'll try what you said tonight, and hopefully have a properly working printer again.

Posted : 10/08/2023 12:38 pm
PapaBearAZ
(@papabearaz)
Member
RE: Filament sensor issues? (possible fix)

Thanks for this for sure! I had the same issue about 15 mins ago due to this. Was printing out old filament, prolly too much dust on it that caused the sensor to fail. Canned air and some in-n-out in the path and all good now! Thanks!

Posted : 11/08/2023 12:12 am
thomers
(@thomers)
Active Member
RE:

Thanks a lot, that saved my day! Had the same issue. It started after printing carbon filament. Seems like there were a lot of fibres inside, clogging the sensor! The new magnetic filament sensor seems to be less resilient than expected...

Posted by: @brutusboots

I went through all the steps with support to troubleshoot and they wanted me to wait for the assembly manual so I could open things up.  I reached out to chat today since the manuals are now available and the agent had an additional troubleshooting step that I hadn't tried.  On the extruder there is a small hole.  I unloaded the filament, opened the idler door and blew compressed air into that hole as I poked a piece of filament in and out of the filament path.  Looking at the manual, it looks like the hole is meant for this very purpose.  In any case, it worked and my filament sensor is working again.  Just wanted to share in case it helps anyone else out.

Posted : 12/08/2023 8:15 am
David H. Brown
(@david-h-brown)
Eminent Member
RE: Filament sensor issues? (possible fix)

😢📖💨😄🙏👍🙇‍♂️

On a more technical note, the filament sensor status (Info/Sensor Info)was reporting around 1.40m with filament inserted and 670k with no filament ("INS" displayed in both cases). A couple very gently puffs from a can of compressed air (with the tube bent so I could keep the can vertical and not dump liquified gas into it and possible crack parts!) and it's reading 1.5m with filament ("INS") and as little as 50k without ("NINS"). (It reports jittery and inconsistent values to single digits, so I rounded.) Inserting filament very slowly while watching the display, I think that the transition point is around 620,000.

I don't know whether the printer had detected the problem or if triggering the filament sensor while monitoring it turned it off, but I had to disable and reenable the filament sensor before it would auto-load again. (Indeed, auto-loading would have been annoying while I was playing with the sensor readings.)

https://www.thingiverse.com/davidhbrown/designs
Posted : 06/09/2023 3:00 am
BrutusBoots
(@brutusboots)
Trusted Member
Topic starter answered:
RE: Filament sensor issues? (possible fix)

 

Posted by: @david-h-brown

😢📖💨😄🙏👍🙇‍♂️

On a more technical note, the filament sensor status (Info/Sensor Info)was reporting around 1.40m with filament inserted and 670k with no filament ("INS" displayed in both cases). A couple very gently puffs from a can of compressed air (with the tube bent so I could keep the can vertical and not dump liquified gas into it and possible crack parts!) and it's reading 1.5m with filament ("INS") and as little as 50k without ("NINS"). (It reports jittery and inconsistent values to single digits, so I rounded.) Inserting filament very slowly while watching the display, I think that the transition point is around 620,000.

I don't know whether the printer had detected the problem or if triggering the filament sensor while monitoring it turned it off, but I had to disable and reenable the filament sensor before it would auto-load again. (Indeed, auto-loading would have been annoying while I was playing with the sensor readings.)

did you blow the air down the cleanout hole or the filament path?

Posted : 06/09/2023 12:25 pm
mm404
(@mm404)
New Member
RE: Filament sensor issues? (possible fix)

I hit this issue on my MK4 after only a few months of printing (stats: 20days print time, 1.7km filament).

At first I tried the same trick as described above. A tiny white piece of filament came out at one point and I was able to get it working. But it lasted only one or two filament changes. So I decided to take the Nextruder apart.

(using the naming as described in https://help.prusa3d.com/guide/5-nextruder-assembly_434014 )

Removing the "Prusa ball holder" was a bit tricky. I used a piece of filament fed through the regular input to push the Steel ball in. Then I used some pliers to wiggle the holder out enough for me to get a grip with my nails. See the photo below of what came out (2.5mm hex key for scale). Assembled it all back together, recalibrated and all good now. 

 

For those needing to take apart extruder, a couple hints:

1. Start with filament unloaded

2. Make sure you have the "PG assembly adapter" handy

3. Consider re-printing the "Main plate", if you have PETG on hand. Mine OEM piece was looking like a bit like rough printout. The replacement turned out noticeably nicer looking.

4. After assembling it together, use the proper steps from Nextruder assembly manual, but don't tighten the screws

5. First thing after powering it on, go to menus and run Nextruder calibration (follow the steps) and then Filament sensor calibration.

Posted : 05/10/2023 11:38 pm
David H. Brown
(@david-h-brown)
Eminent Member
RE:
Posted by: @brutusboots

did you blow the air down the cleanout hole or the filament path?

What, that wasn't clear from the string of emoji? 😉 I pretty much blew air everywhere that seemed relevant.... mostly the filament path because it's easiest, but I tried to get a fair number of puffs into the cleanout hole, too. Thank you very much for taking the time to point it out so clearly.

(Sorry for the slow reply. I will check to see if this forum does email notifications.)

This post was modified 6 months ago by David H. Brown
https://www.thingiverse.com/davidhbrown/designs
Posted : 20/10/2023 9:39 pm
Joker
(@joker)
New Member
RE: Filament sensor issues? (possible fix)

i got same issue after + - 600 meters of filament... i must open it and clean.... this is extremly anoyng. now i must clean it second time, but blowing with air is not working for me. this need better solution for cleaning... maybe some kind of cutout on extruder gearbox cover, or something

Posted : 15/11/2023 11:40 am
MichalDruciak
(@michaldruciak)
Member
RE:

Thanks! The compressed air worked for me! This occured after the filament ended (during print) and printer initiated reload. I might have removed it too fast though.

This post was modified 5 months ago by MichalDruciak
Posted : 19/11/2023 12:19 am
bbmester
(@bbmester)
Member
RE: Filament sensor issues? (possible fix)

After new sefttest, filamet sensor stopped working/calibration failed. It was working fine before that. With 5,0,1 it doesnt register when i press  in the filament.  But when i go to sensor it shows 1478844 whitout filament and 1838750 with filament pushed in. So sensor is working but keeps failing. Tried updating to 5,1,0 beta and doing calibration again. It sees the filament and i get the green tick. But when i press the knob, it failes?

Tryed compressed air in small hole, no help.

Posted : 23/11/2023 8:25 am
bbmester
(@bbmester)
Member
RE: Filament sensor issues? (possible fix)

Well, did the only thing that I should have startet with. Took  the filament sensor apart. And behold, I had 2 magnets between spring and ball!!!!! My fault. How come it have worked until now, I don`t know. Did the filament calibration and all worked out fine. 

Posted : 23/11/2023 2:15 pm
Tom
 Tom
(@tom-42)
Member
RE: Filament sensor issues? (possible fix)

Thanks for this tip. I didn't have any compressed air so I blew into the hole and poked some filament into the filament path. This fixed the problem immediately.

Thanks again for posting

Posted : 28/03/2024 6:57 pm
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