The importance of the filament detection sensor calibration (MK3S) and other problems
 
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The importance of the filament detection sensor calibration (MK3S) and other problems  

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Nico2126
(@nico2126)
Active Member
The importance of the filament detection sensor calibration (MK3S) and other problems

This is an absolutely fundamental step for the MMU3 to function correctly, and the explanation in the manual is extremely poor. Using words like 'slightly' or 'tighten it a little bit' is not serious, to be honest. Beyond the fact that the explanation could have more concise steps, there is a serious problem in the design of the 'Chimney' and the 'Chimney-base' parts.

 Speaking in detail, the 'Chimney-base' has only one gripping screw to the extruder, meaning that while it is adjusted, it has a slight angular movement that affects the indication of filament presence. It is also possible to displace it linearly, which sometimes happens when adjusting the calibration screw.
 Then, in the 'Chimney' (referring to calibration point 9: 'Now you need to start loosening the calibration screw as much as possible but the Fil. sensor value should still say "1". If it switches to "0", tighten it a little bit.'), when loosening the screw, there is no mechanical movement produced. This is because there should be a spring that pushes it, so as we loosen the screw, it is necessary to push it manually and check the state of the sensor. In addition to all this, the sensor is extremely sensitive. Even if we use the 1.5 mm hex key and correctly check the state of the sensor, it is necessary to perform many load tests to verify its proper functioning, which can take a really long time and is quite tedious.

The issue with the high sensitivity of the sensor is that the loading and unloading of filament in Prusa Slicer are designed and tested with their own filaments. I had to find the exact configuration for the filaments I can buy in my country. It was trial and error after another until I found a correct setting that doesn't jam the extruder with every filament change because of a bad filament tip

As a piece of advice, two things that helped me a lot to achieve satisfactory prints were: enabling automatic filament cutting after 2 failed loading attempts and activating "High current on filament swap" in Prusa Slicer.

This topic was modified 1 month ago by Nico2126
Posted : 17/04/2024 7:06 pm
JoanTabb
(@joantabb)
Veteran Member Moderator
RE: The importance of the filament detection sensor calibration (MK3S) and other problems

i had MMU3 with Mk3s, and I used a filament sensor with a 5 volt LED soldered between the +5 volt pin and the output pin, to give immediate indication of operation. 
it has worked well with my noname filaments.

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK

Posted : 17/04/2024 8:36 pm
Nico2126 liked
Thejiral
(@thejiral)
Noble Member
RE: The importance of the filament detection sensor calibration (MK3S) and other problems

My filament sensor also gave me troubles originally. It did not reliably detect the filament as the tolerance of the latch was a tad too high for my build at least. What I did was to modify the sensor latch, extruding the tip that triggers the sensor in 100 µm steps and testing a few alternative versions. I can't remember witch which version I settled but it was extending maybe 200 µm further than the original. With that sensor it has worked reliably ever since, no matter what filament I am throwing at it (ok, the MMU absolutely hates flexibles but that has other reasons). 

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 18/04/2024 7:14 am
Nico2126 liked
Nico2126
(@nico2126)
Active Member
Topic starter answered:
RE: The importance of the filament detection sensor calibration (MK3S) and other problems

Thanks! May be I'll do it to save time when I calibrate

Posted : 19/04/2024 2:11 am
Nico2126
(@nico2126)
Active Member
Topic starter answered:
RE: The importance of the filament detection sensor calibration (MK3S) and other problems

 

Posted by: @thejiral

My filament sensor also gave me troubles originally. It did not reliably detect the filament as the tolerance of the latch was a tad too high for my build at least. What I did was to modify the sensor latch, extruding the tip that triggers the sensor in 100 µm steps and testing a few alternative versions. I can't remember witch which version I settled but it was extending maybe 200 µm further than the original. With that sensor it has worked reliably ever since, no matter what filament I am throwing at it (ok, the MMU absolutely hates flexibles but that has other reasons). 

 

Thanks for your answer! Did you modify the extruder idler? Anyway, after proper calibration and with the correct PrusaSlicer parameters, I've been getting good prints. But, well... I don't like the calibration procedure.

Posted : 19/04/2024 2:20 am
Thejiral
(@thejiral)
Noble Member
RE: The importance of the filament detection sensor calibration (MK3S) and other problems

Yes I modified the tip of the idler a tiny bit, just where it triggers the sensor. Extended that part maybe by 200µm. Then it reliably blocked the light path of the sensor, when filament was loaded, no matter the tensioning or filament type but also reliably kept it free when no filament was loaded. 

That was a bit quick and dirty and non-adjustable but very easy to do. 

Mk3s MMU2s, Voron 0.1, Voron 2.4

Posted : 19/04/2024 7:17 am
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IG
 IG
(@ig)
Eminent Member
RE: The importance of the filament detection sensor calibration (MK3S) and other problems

I've noticed intermittent issues with loading to fsensor when using one filament (so far.) All I can attribute this to would be that the filament is less dimensionally accurate in some spots. All my sensor calibrations have been fine.

When it cries at me, I squeeze the fsensor screws with my finger/thumb while it loads. That being said, I am still working on a permanent solution, and I think making a new MK4 nextruder fsensor idler like @Thejiral said is a great idea.

X marks the spot.

Posted : 19/04/2024 7:22 pm
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