Filament Sensor (IR) problem
Hi,
I'm, having problems with the filament sensor and i've been looking through the forum but haven't find a similar problem so i've been looking also in the knowledge database and i've found this article: https://help.prusa3d.com/article/43mduc4zdn-ir-sensor-troubleshooting
I haven't dismantle the extruder yet, think i may have to do it at some point but would like to avoid since everything it's working pretty good right now.
Checks i've done previous to dismantle anything:
- Check Support -> Sensors with filament inserted. It has a 1 value so it's OK
- Check Support -> Sensors with filament removed. It has a 1 value so it's NOT OK
Ok then, the problem seems to be in the detection since it always think there's filament inserted (value 1), so i did a quick test, remove the upper cup of the extruder so i could see the sensor and removed the screw to take out the sensor and dis the same test passing an orange filament (the one i had at hand) in and out, the results:
- Check Support -> Sensors with filament inserted. It has a 1 value so it's OK
- Check Support -> Sensors with filament removed. It has a 0 value so it's OK
So, this is valuable info since the sensor seems to be working just fine, 1 when the filament goes in, 0 when there's no filament.
Having that input i tried the next piece, the movable piece using the magnets looking it through the hole left once the sensor was out of it's place, so i was looking it from above prior to dismantling all the extruder part
- Magnets are just fine, they are repelling each other, the moving part is always getting away as soon as i take the filament out
- The piece moves softly when i insert the filament, doesn't seem to be any problem there
- The steel ball is on place and moves fine
Separately both pieces work fine so i put the sensor in place without the screw and inserted the filament moving the black piece and it worked... :-/ so i took the filament out and the sensor value went to 0, ok seems to work, started to tighten the screw and... value 1.. :'( if i tighten and move with the hand the sensor, very little as it has little place, goes from 0 to 1, i can even find spots were it works as expected but as soon as i tighten the screw it moves to 1. I tried to left it not completely tighten and put the cover but as soon as the cover was on top the sensor move back to 1.
All in all i have no idea whats going on, i can only think of 2 plausible explanations
- The piece is not the correct size and it's maybe just a mm longer than expected which triggers the sensor when in place with the screw
- The screw that holds the moving piece (figure 3C of https://help.prusa3d.com/article/43mduc4zdn-ir-sensor-troubleshooting ) is to tighten, it might but it seems to move fine, maybe it just affects the last bit of movement.
Temporarily i have move filament Autoload to false until a find a solution but both problems would imply disassembling the extruder to access the screw and i would like to avoid it if possible
Sorry for the long text but i wanted to explain everything the best i could in order to have all the facts, if anyone can help me or have any idea of what could be happening it would be really appreciated.
Thanks!
RE: Filament Sensor (IR) problem
Filament sensor false positives seem to be a common issue, especially with self printed parts. Disable the sensor until you get it figured out and you'll avoid most of the glitches the sensor can cause.
Causes range from too small a flag, too large a flag, burrs that catch and jam the flag arm, assembling the flag arm "axle" screw too tight etc. Even misplaced magnets.
And, yes, disassembly is required to resolve.
But - triple check the EINSY end and verify you have the sensor plugged in correctly. There is plenty of room for error.
RE: Filament Sensor (IR) problem
Filament sensor false positives seem to be a common issue, especially with self printed parts. Disable the sensor until you get it figured out and you'll avoid most of the glitches the sensor can cause.
Causes range from too small a flag, too large a flag, burrs that catch and jam the flag arm, assembling the flag arm "axle" screw too tight etc. Even misplaced magnets.
And, yes, disassembly is required to resolve.
But - triple check the EINSY end and verify you have the sensor plugged in correctly. There is plenty of room for error.
Thanks for the input 🙂
I'll triple check the INSY connection but i'm pretty sure it's fine since the sensor works once i move it or take it out of it's place 👍
The self printed parts not so sure about it, i didn't print the parts, those are the ones included in the kit, i guess you mean those regardless who printed them
About disassembling it i guess i have no other option, but not so sure how to do it, what worries me is that seems like i have to dismantle everything up to step 14 ( https://manual.prusa3d.com/Guide/5.+E-axis+assembly/1055?lang=en )... is there a way to access this part without dismantling everything? Seems like sections 1 through 2 should be enough but not so sure....
RE: Filament Sensor (IR) problem
Somewhere I read a post that claimed he didn't have to do a full tear down - just logically took off parts as needed to reach the sensor parts. I haven't done it personally so can't really help.
RE: Filament Sensor (IR) problem
I'll give it a try this weekend and keep you posted, thanks! 👍
RE: Filament Sensor (IR) problem
Ok, i've fix it and i could avoid tearing it down ! 🤗 🤩 😎
Due to my initial test i was pretty sure the sensor worked just fine because it worked when i took it out, also the ball was in place and the lever moved smooth, although i was unsure if it was moving all the way due to a too tight screw. Yesterday took out the sensor and tried to move the lever manually and moved all the way so it didn't seemed to be the issue. My last guess would be that the piece is 1mm or so wider than it should.
Before tearing it apart i tried to moved the sensor a little bit from the moving lever, just a bit. To do that i took the square printed from z calibration and cut a little piece and folded it once or twice and put in under the left side of the sensor in a way that it would be slightly inclined to the rigth leaving the sensor away from the lever, this did the trick and now it's working perfectly.
If one day i have to dismantle the extruder i'll try to check everything is ok from the inside but at this moment it works with this little tweak
Thanks!
RE: Filament Sensor (IR) problem
Thanks a lot for your post !
I've encountered the same issue with IR Sensor, I've realised the same tests as you and then leave the sensor screw loose. It works fine ... for the moment ...
Thanks again
RE: Filament Sensor (IR) problem
Glad it could help 😀
RE: Filament Sensor (IR) problem
I had the very same problem: IR sensor always returned 1 (filament loaded). I got confident that I could fix it myself after reading this, so here are my findings:
It turned out that the sensor just needs to have more distance to the trigger: I achieved that by putting some plastic (I used a a piece of the included zip ties) between tip of sensor and its bed, that raised it by ~1mm. It was a bit of fiddling and testing out, but when screwed together it worked reliably. The only problem was that the extruder/sensor cover has a too small cutout for the sensor board: It actually covers part of the board that normally would have been sunken in.
In my eyes Prusa has to check the tolerances for those parts (including their housings) to be more robust. And the cover could get a bigger cutout, so that it never pushes pressure on the board, even if raised a little. As a first solution, a chapter should be added to the manual that tests the sensor while unassembled, to make sure nobody ever needs to disassemble the extruder again just because of that.
PS: Oh, fyi, I printed all related parts myself. And testing the filament sensor was easy, with just cover off, printer on, going into Support > Sensor Info.
RE: Filament Sensor (IR) problem
Hi,
Had similar problems with my Mk3s upgrade kit. Seem that Prusa has had some problems with the length of the filament sensor lever. The FS lever when printed from downloaded Prusa G code was 1.5 mm too short. They had updated the .stl codes with a longer FS lever (but forgot to update G code). The length of the lever seems critical. I found it difficult to stop the sensor toggling when wriggling the filament. I ended up loosening the IR sensor screw and found a position where the sensor did not toggle and then glued the IR board on with hot glue gun.
If you want to check the mechanism an FS lever length just remove filament cover and remove IR sensor and the lever height and operation can be checked.
RE: Filament Sensor (IR) problem
Hi,
Had problem to and tried something similar but it did not work.
I found that fs lever and extruder motor plate did not fit together, pushing lever to the left and i solved the problem by printing a new lever and use à lime to adjust the motor plate.
RE: Filament Sensor (IR) problem
Seems to be an usual problem, there's another thread about it ( https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/prusa-mk3s-ir-sensor-lever-issue/ )
Either way it seems like the solution it's either use something to move the sensor or use a lime to adjust the lever or the motor plate, whatever works best 🙂
RE: Filament Sensor (IR) problem
Hey, that sounds like qczek actually found the culprit. Would make sense for me too: the lever had a very short path to travel for me, maybe that's why. It was pushed into something like a %50 percent open position, which was enough for me to always have a "1".
I hope that is researched by Prusa Research... 😉
RE: Filament Sensor (IR) problem
Prusa have realised that there is a problem with the filament sensor. They would not have gone to the trouble of writing the following procedure to debug it.
https://help.prusa3d.com/article/43mduc4zdn-ir-sensor-troubleshooting
I suggested to a Prusa developer that this procedure should be included in the MK3S extruder upgrade build instructions so that any problem can be identified at an early stage so that a major dissassembly can be avoided later. They thought it was a good idea.
Just to let you know that I have started printing with carbon filled nylon and for some reason with this filament the filament sensor has become unstable.
I have now turned the filament sensor off. So much for upgrading the MK3S with an improved filament sensor. Had no problems with the MK3.
RE: Filament Sensor (IR) problem
I agree that they stumbled over some issues with the new sensor already, but the existing tutorial does not talk about the same problem at all, it puts all problems to assembly failures (customer) and at last it could mean Prusa is done looking at those problems because there is this guide now (last update of this guide was 3 weeks ago).
But I am convinced that this is a construction issue that leads to several assembly issues. Any tutorial to help assembling it is just a temporary workaround until someone finds out what exactly makes assembling so error prone and fixes that within the parts.
RE: Filament Sensor (IR) problem
The problem with the filament sensor design is that the lever has no mechanical advantage and therefore to part that moves across the IR sensor can only move a maximum of 1.7mm or maybe even a bit less if you take into acount wriggling the filament.
This distance makes the lenght of the lever and the position of the IR sensor absolutely critical- hence the numerous problems people (myself included) are having.
I am going to design my own sensor and fit it into a modified extruder cover using a lever with about 2:1 mechanical advantage.
RE: Filament Sensor (IR) problem
yeah, need a lever to amplify the movement.
also, if the firmware would just try to load a couple more times before giving up, it would save me a lot of getting up.
RE: Filament Sensor (IR) problem
I had this same issue with the IR sensor on brand new printer I assembled. I used a shim under the sensor to fix. Thanks!
RE: Filament Sensor (IR) problem
@masterhead
I'm having a terrible time visualizing the "fix." Would you please post photo or drawing of where to place the "shim?"
RE: Filament Sensor (IR) problem
Hi, i do not have access to the printer right now but the idea is to take out the screw so you can remove the IR-Sensor, put some little plastic or paper on either side, wheter you need it to move to the left or to the right, and put the sensor and tight it up again with the screw
