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iftibashir
(@iftibashir)
Honorable Member
Topic starter answered:
RE: Filament Sensor

This seems plausible. So if the tubular spacer doesn’t sit properly flush during step 4, it can cause the ball to dislodge, which explains why some users have been able to use a magnet to fix the issue - since it’s just pulling the ball back into position? 
May check and apply some glue to keep this part in place during my build so I don’t have to open everything back up afterwards! 

Posted by: @stepan-vesely

Hey, I had issues with my MK4 (built from kit) that, at some point, it asked me to change the filament every minute or so even though it was inserted. Eventually, it stopped detecting it whatsoever. After some digging, I figured out that "the tubular spacer" in Nextruder was a bit longer than it should be imho. Thus, the Nextruder didn't close fully, and eventually, it caused the filament sensor ball holder to pop out from the heatsink (I'm referring to Step 4).

I don't think I made any mistake building it, considering I reviewed everything twice, so I just used a bit of glue to hold the ball holder assembly in place. It's been working smoothly so far. 

 

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Posted : 03/08/2023 9:25 am
Paul Harbin
(@paul-harbin)
Trusted Member
RE:

I would just like to note: I had been using alpha 4 and running exclusive Input Shaping prints non-stop for nearly a week now.  Filament ran out, nothing happened when I tried to reload.  Went through all normal stuffs with support first blaming alpha firmware.  "Okay I will see and raise you a factory reset with the newest stable release. " Sensor calibration, NOPE nothing."   Make sure the sensor is plugged in. Okay then unplug it then plug it back in, (do that form the start?) Okay then, let's start taking it apart.  Okay, I should?  Didn't really give the directions "which screws should I take out?", but I know where it's going so, I took off the cover and the idler.  He actually replied that there is no guide for this at this time unfortunately =D Funny stuff, because he answered my next question very specifically without guidance. =D lol ANYWAYS, I have the transcript if anyone is privately curious.  

Not at one time was there any visible debris filament whatever. closest thing was some normal looking wear ooze on the gear-drive washer that came off.  I thought well, it's bad need a new one. We went further. I took out the ball housing the ball sprung out immediately. (I'm suggest here, make sure you use a VERY STRONG large rectangle one is maybe okay, I tried something else. magnet when you try this perhaps- More from the printer side of the extruder and away from yourself.)
When I put it back in, the first time, 1.5-2 seconds after I heard the ball spring into contact.  My opinion is this; there is a very small amount of play and or variance in this plastic housing. (I printed 3 weeks roll changes, etc no problem.) Perhaps, I didn't put it in perfect even-level-flush and after the filament ran out, the ball could not spring even though the sensor triggered the unload-for new roll properly in the first place, and this locked it in "on" afterwards. I feel this could easily be blamed on Input shaping, perhaps shaking the housing out of flush. 

My ball-spring housing goes in very smoothly and isn't tight and doesn't snap in. Perhaps this should be revisited, or I just got a normal manufacturing inconsistency. Anyhow, I think, if I had a stronger magnet, it might have worked.

I am printing the same file again, with alpha just because.  I have the urge to cut the filament and see what happens when it's close to the same area of the print where it ran out.

https://share.icloud.com/photos/04cf9psRnwsGEDGcwA-aFUCZg

Posted : 03/08/2023 2:16 pm
jmarler
(@jmarler)
Member
RE: Filament Sensor

I ran into trouble with my filament sensor, and I know exactly what happened. I had a filament snap mid print and subsequently the runout sensor caught it. However, the filament failed to unload. I accidentally selected "Yes" when asked if the unload was successful, and was left with about 2mm of filament sticking out, and the filament still loaded. I released the idler and was able to grab onto the filament with some pliers and pull it out. When I did, there was a small amount of PLA that was shredded off by the gear. I blew that out of the nextruder with compressed air, and tried to continue. I couldn't continue though, as the printer was waiting for the filament to be removed ... though it had been already. There was no option to go back, or retry. I had to reset the printer, causing the print to be aborted. However, the printer was convinced there was filament still loaded, even though there wasn't. 

Long story short, when I looked down into the hole the filament feeds in, I couldn't see the steel ball, but I could see a small amount of pink PLA where the ball should be. Some PLA had gotten jammed in there, preventing the ball from popping out. I used a small pick to remove the debris, and the ball popped right out. I ran a recalibration, and the sensor is working perfectly again.

If your filament sensor is falsely sensing that filament is inserted when it is not, look down the hole and see if the ball bearing is visible. If not, open the idler door, use some compressed air in the clearing hole under the idler tension screws, blow out the inside around the gears, and look for debris that could be blocking the sensor ball. If you can't see the sensor ball, use a pick and gently try to remove whatever is blocking the ball from extending fully until the ball does. If the ball doesn't appear, the sensor will never work properly. 

Posted : 03/08/2023 9:29 pm
MarcWinNJ
(@marcwinnj)
Active Member
RE: Filament Sensor

Have to be honest here and I hope Prusa support is in this forum.  I have gotten the clear filament sensor many times and have wasted too many hours and filament. After a 2 hour print has to be thrown away because I could not clear the error I reached out to support. I provided several links to forums including this one and the rep still played it like this was new news to him.  The second time it happened today I saw on here that a magnet will fix it and sure enough it did.  I ran the filament sensor calibration afterwards as well.  After the magnet fixed the issue I reached back out to support and again crickets on this issue.  All I got was go back to the 4.7.2 release and do a hard reset.  Sorry Prusa that isn't happening. I am on the IS 5 RC release.  This is either a hardware or software issue but it is a Prusa issue and they need to step up and acknowledge it and fix it.  My Mk4 is a factory assembled. 

 

Posted : 22/08/2023 12:11 am
Jon916 liked
Philipp
(@philipp-8)
Active Member
RE: Filament Sensor

I've also got that problem sometimes, I could always clear the ball by sticking a piece of PLA in, poking at the hole. This will be a Problem when running the MMU though. Accessing the whole from the top is going to be harder then.

Posted : 28/08/2023 12:35 pm
MarcWinNJ
(@marcwinnj)
Active Member
RE: Filament Sensor

That was the first thing I tried.  I read elsewhere here about using a magnet reset it. That worked. I recalibrated it. I haven’t printed all that much since then, but the last couple of times the issue did not reoccur.

Posted : 28/08/2023 12:45 pm
cwbullet
(@cwbullet)
Member
RE: Filament Sensor

If that does not work, try a hard reset.  After which, the calibration works.  

Posted by: @marcwinnj

That was the first thing I tried.  I read elsewhere here about using a magnet reset it. That worked. I recalibrated it. I haven’t printed all that much since then, but the last couple of times the issue did not reoccur.

 

--------------------
Chuck H
3D Printer Review Blog

Posted : 28/08/2023 5:01 pm
Fabrice Lebas
(@fabrice-lebas)
Member
RE: Filament Sensor

Yes, the magnet trick works for some of us. But that will not prevent the steel ball to get stuck anytime soon and the whole detector to get faulty. Murphy's law call for that to happen when we will run out of filament. 

Has Joseph and team produced a new design for this part? Are the shipments on their way? 🤨

Posted : 28/08/2023 7:59 pm
iftibashir
(@iftibashir)
Honorable Member
Topic starter answered:
RE: Filament Sensor

OK so my first thought was the steel ball gets stuck - hence the magnet moves back and triggers the filament sensor. Since teh magnet stays in that position teh sensor continually thinks filament is still inserted, hence teh issue. This is why using some more filament in and out, or using an external magnet, will help dislodge and release the ball back into position. The way to fix this properly would be to disassemble the extruder somewhat and reseat the plastic part that holds the magnet/ball setup (which needs to be perfectly lined up with the heatsink it sits inside). It doesn’t necessarily mean a new part is required - it could just be a current part not perfectly aligned and fit. 

However, if this was actually the case, it does not explain why a printer reset, or power cycle, would fix the issue. This of course cannot fix a hardware issue ie releasing the ball, so my assumption is that there could possibly be two separate problems entirely, leading to the same outcome? So it’s best to try all the listed ‘fixes’ in order to determine the root cause, before implementing any fix…..

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Posted : 28/08/2023 8:50 pm
iftibashir
(@iftibashir)
Honorable Member
Topic starter answered:
RE: Filament Sensor

Where exactly do you place the magnet to fix the issue? On the opposite side to the ball, in order to pull it back out?

Posted by: @marcwinnj

Have to be honest here and I hope Prusa support is in this forum.  I have gotten the clear filament sensor many times and have wasted too many hours and filament. After a 2 hour print has to be thrown away because I could not clear the error I reached out to support. I provided several links to forums including this one and the rep still played it like this was new news to him.  The second time it happened today I saw on here that a magnet will fix it and sure enough it did.  I ran the filament sensor calibration afterwards as well.  After the magnet fixed the issue I reached back out to support and again crickets on this issue.  All I got was go back to the 4.7.2 release and do a hard reset.  Sorry Prusa that isn't happening. I am on the IS 5 RC release.  This is either a hardware or software issue but it is a Prusa issue and they need to step up and acknowledge it and fix it.  My Mk4 is a factory assembled. 

 

 

ORIGINAL PRUSA MK4 KIT - Full step-by-step video assembly guide!

>ORIGINAL PRUSA MINI+ Full video assembly guide!

Posted : 28/08/2023 8:54 pm
MarcWinNJ
(@marcwinnj)
Active Member
RE: Filament Sensor

I just moved it around near the filament feed, top center of the motor and the error cleared.  

Posted : 29/08/2023 12:58 am
Steve
(@steve-28)
Member
RE: Filament Sensor

Hi folks -- Just adding my experience on the filament sensor / jammed steel ball issue. For me, the issue happened when my spool ran out and auto-ejected the filament. That part went as expected but the sensor wouldn't detect my attempts to insert new filament. The magnet trick previously described in this thread didn't work for me and in the end I had to take off the gear box and pull out the ball holder assembly when I discovered a small sliver of filament had jammed itself inside.

Clearing that out and re-running through the gears calibration and sensor calibration resolved the issue.

Posted : 30/08/2023 8:31 pm
Bruce Farquhar
(@bruce-farquhar)
New Member
RE: Filament Sensor

There seems to be a firmware issue, or a chronic problem with the sensor that affects a lot of printers.  I noticed it the first time I ran out a spool of filament.  It detected that it ran out, but never could find the new filament. I think I got it to recognize new filament once, but had to fiddle with it a lot.  This approach seems random.  The printer is pre-assembled, I have cleaned the intake area, reset, powered off/on, calibrated the sensor, calibrated the printer, and the issue remains.  This sort of issue is not something I expect from Prusa.

My firmware is 4.7.2.  I hope this bug is fixed in the next release.

Posted : 01/09/2023 6:12 pm
John
 John
(@john-34)
Eminent Member
RE: Filament Sensor

I've been having a ton of issues with the filament sensor on one (of three) of my MK4s, and it's getting old fast. It isn't a firmware issue, it's absolutely hardware as this design is just not as robust and is prone to sticking.

It consistently "sticks" in the back or filament-loaded position, so doesn't notice when filament is not inserted. It also makes it impossible to do a filament change, as it always thinks filament is loaded. Yes, it's clean of any debris (and was factory-assembled). 

Having a similar issue with the side filament sensor on the Prusa XL, but it actually does the opposite where it can't detect that filament is loaded. That one might be a firmware issue. Support has passed it back to their Development team, but no updates in over a week. 

Frankly, I'm pretty disappointed as the quality of the MK4 and XL have been substandard, and I have to sit here and wait 25+ minutes just to talk to someone on support chat instead of firing off an email. Prusa is also incredibly resistant to sending replacements or addressing the issue.

Posted : 02/09/2023 7:10 pm
Pintie liked
wikallen
(@wikallen)
Member
RE: Filament Sensor

Will add my experience with my sensor issues today.  I printed the mk4 filament guide but I did not install the intended 10mm ptfe tubes into the holes on the guides.  Today the extruder started making  a terrible noise. When removed the cover and gear, I thought I had cat hair (cat bed near the printer) jammed in the feed and in the ball socket.  I removed the ball retainer and cleaned it all out, reassembled and calibrated, then resumed printing. An hour later, it started the noise again.  This time the filament was nearly locked in place. I was like no way cat hair got in there and jammed it up. I did an inspection and it was then I noticed grooves in the PETG filament guide. It appears that filament was slowly wearing a groove into the guide and PETG particles and strings were stuck to the filament as it fed into the extruder. It was nearly a powder. It was getting jammed into the sensor ball, into the feed holes, into everything. Some of it was white strings that looked like my cat's hair, but it was petg.  I printed some adapters to fit some regular 4x2mm ptfe tube into the guide.  So far no more noise, not more sensor errors. If you get a sensor errors, open the release on the extruder. Look into the incoming hole and inspect the ball. 

Posted : 05/09/2023 5:03 am
v68AQP
(@v68aqp)
Active Member
RE: Filament Sensor

I've been having this issue as well. MK4 on 5.0.0 RC
My filament sensor triggers mid-print, telling me that my filament is out, despite there being 80% of a spool remaining.

This already happened 2 times during a 1h30m print that I'm currently running.

Posted : 11/09/2023 6:17 pm
ad.lamy
(@ad-lamy)
Estimable Member
RE: Filament Sensor

As I read it seems that it mainly affects pre-assembled printers, or I'm wrong ? I have a self assembled MK4 with firmware 5.0.0-rc, printing since 13 days continuously fell twice out of filament, feed with a new spool and the print resume.

If not an improper assembly of the ball, magnet and spring assembly, it could be the sensor itself or rather a poor electrical contact between the connector and the "love board", certainly not a firmware issue.

Posted : 11/09/2023 6:59 pm
ad.lamy
(@ad-lamy)
Estimable Member
v68AQP
(@v68aqp)
Active Member
RE: Filament Sensor

 

Posted by: @ad-lamy

As I read it seems that it mainly affects pre-assembled printers, or I'm wrong ? I have a self assembled MK4 with firmware 5.0.0-rc, printing since 13 days continuously fell twice out of filament, feed with a new spool and the print resume.

If not an improper assembly of the ball, magnet and spring assembly, it could be the sensor itself or rather a poor electrical contact between the connector and the "love board", certainly not a firmware issue.

Mine is a kit: self-assembled.

Posted : 11/09/2023 7:27 pm
Robiscash
(@robiscash)
Member
RE: Filament Sensor

Just had the same error, tried spraying compressed air, using a magnet, what I did that actually got it to reset was inserting a very small allen key into the filament hole, "Jimmying" it a little bit and voila it registered the key as the filament being removed. 

I think the error was issued in the first place after I did not follow the prompts and just pulled the filament out like I'd do in the past with my Mk3 (also has a broken sensor)

Hopefully someone tries this as well and it works 🙂  

Posted : 15/09/2023 9:23 pm
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