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How to fix the IR Filament Sensor?  

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thedevilsjester
(@thedevilsjester)
Eminent Member
How to fix the IR Filament Sensor?

I "upgraded" my MK3S with the MMU2S a few months ago, and to-date have not been able to get a single multi-color print to work, and in fact, the success of my single color prints has plummeted, to the point where its almost impossible for me to get a single color print that last more than an hour or so.

From all my investigation, it seems to be the filament sensor.  No amount of adjustment is reliably getting the sensor to report accurately.  I tried printing the cover that has a larger flag, but that one was even worse.  I don't think the sensor itself is faulty, when I manually move the (stock) flag back and forth, it turns on/off exactly as desired. 

When I have it in the best state I can get it (where it says 0 when there is no filament, and 1 when there is), if I slide the filament back and forth, it toggles between 0 and 1 even though there is filament in it.

I have the latest (and correct) firmware for the MK3S and the MMU2S

Is there a known solution to this or has someone designed a better chimney that is reliable?

Posted : 13/10/2019 4:52 pm
petr.f12
(@petr-f12)
Active Member
RE: How to fix the IR Filament Sensor?

I am very satisfied with this alternative sensor chimney.

https://www.thingiverse.com/thing:3554066

Posted : 13/10/2019 6:38 pm
ad.lamy
(@ad-lamy)
Estimable Member
RE: How to fix the IR Filament Sensor?

This append when the lever is just on the edge of the IR sensor, but  I think you're already aware of that.

I never used the original Prusa extruder design, before I got my MMU2S upgrade' I designed my own extruder, the adjustment is more precise, on one side you have to insert shim if needed or use the mordiev chimney.

Take a look to my design and to the remix of the chimnay

https://www.thingiverse.com/thing:3467644

https://www.thingiverse.com/thing:3850541

Posted : 13/10/2019 6:40 pm
shilbert liked
shilbert
(@shilbert)
Active Member
RE: How to fix the IR Filament Sensor?

@andre-l9

I am using these mods successfully.

Posted : 13/10/2019 9:19 pm
ad.lamy liked
thedevilsjester
(@thedevilsjester)
Eminent Member
Topic starter answered:
RE: How to fix the IR Filament Sensor?

Thank you both, I will try these out and see if they make a difference!

 

One question about the links that @andre-l9 provided: where do you get the extra tensioner spring if you only have a MMU2S?

This post was modified 3 years ago by thedevilsjester
Posted : 14/10/2019 12:49 am
ad.lamy
(@ad-lamy)
Estimable Member
RE: How to fix the IR Filament Sensor?
Posted by: @thedevilsjester

Thank you both, I will try these out and see if they make a difference!

 

One question about the links that @andre-l9 provided: where do you get the extra tensioner spring if you only have a MMU2S?

Hi, the springs comes from the MK3 with 2 springs idler door, but you can use only one spring like the stock MK3S if you want.

Don't mix MK3 and MK3S, the latter is harder.

Posted : 14/10/2019 4:45 pm
shilbert
(@shilbert)
Active Member
RE: How to fix the IR Filament Sensor?

@thedevilsjester

In one of the bags there was a spring that fits. It might be a bit harder but you can alway work on different tension for both springs. Works for me but also works with only one spring.

Posted : 15/10/2019 4:47 pm
Marino
(@marino)
Active Member
RE: How to fix the IR Filament Sensor?

I know it is an old post but I faced the very same problem now.

I would like to add my small grain of sand. What I noticed is that the sensor is loose in its support (the chimney) no matter how much tight is the screw. It is the possible that, on the occasion of some fast movement of the extruder, the sensor moves and detects lack of filament, etc.

What I did, although I consider very valuables and helpful the proposal made in this post, was to sand a little bit the top of the chimney and add a thin paper washer between the top cover and the sensor.

This helps to keep the sensor quite steady in its place and now I do not face any problem.

Another solution would be to design the top of the chimney with less clearance with the sensor PB..

Posted : 24/11/2020 4:45 pm
lcdguy
(@lcdguy)
Eminent Member
RE: How to fix the IR Filament Sensor?

I was also having issues with the IR sensor not reliably detecting filament, i had a thought that maybe the sensor was moving around inside the chimney, just enough to miss the blade, i used the tip of a spare tie wrap to act as a shim to keep it pressed up against the idler side (right side) of the chimney then tested this using a 1.5mm allen key, and this seemed to have solved the issue (tried about 7-9 times inserting and removing).

Not sure if that will help anyone, but it's a cheap fix to try 🙂

Posted : 03/12/2020 3:42 pm
thedevilsjester
(@thedevilsjester)
Eminent Member
Topic starter answered:
RE: How to fix the IR Filament Sensor?

I am still struggling with this issue.  The various after market chimneys have helped somewhat; but even so it's not reliable enough to use the MMU2s with a single color, no changes; let alone actually use it for its intended purpose.

To use the printer right now I have to keep power disconnected from the MMU2s, and turn off the filament sensor in the settings, bypassing the whole thing to feed filament directly to the extruder.

I have considered removing the MMU2s entirely and abandon it; but I keep holding out hope that there will be another revision, or someone will come up with a more reliable sensor setup.

This post was modified 2 years ago by thedevilsjester
Posted : 03/12/2020 4:33 pm
Marino
(@marino)
Active Member
RE: How to fix the IR Filament Sensor?

@lcdguy

I realized that the IR PCB is 8 mm wide and the slot of the chimney is 8.5 mm wide.

I modified the original stl file (ir-sensor-holder-mmu2s) adding a 0,4x1 mm spacer on the side opposite to the opening of the shutter (the red portion of the picture. Printed the part in in black PETG, smoothly sand the top to allow the cover to hold in place the IR PCB. In a different way is what you did.

Posted : 03/12/2020 4:38 pm
lcdguy
(@lcdguy)
Eminent Member
RE: How to fix the IR Filament Sensor?

yup, seems that way 🙂 if you have a link to an stl with that modification maybe i will print one out instead of my ghetto zip tie shim 🙂

Posted : 04/12/2020 1:16 pm
Marino
(@marino)
Active Member
RE: How to fix the IR Filament Sensor?

@lcdguy

This is the file created with FreeCad. Hope it helps you.

Do not forget to smoothly sand the top of the chimney to better host the cover (only few strokes). I have used a P360 grade sand paper (I am an Italian living in Spain therefore my references are European) over a mirror/glass (cheap solution for a flat surface).

Posted : 04/12/2020 2:54 pm
lcdguy
(@lcdguy)
Eminent Member
RE: How to fix the IR Filament Sensor?

hmm, i don't see a link or attachement ?.

I also have started to see the issue return unfortunately. I am going to try printing out a new idler door with a slightly longer blade, then trim it a bit to see if it works more reliably.

This post was modified 2 years ago by lcdguy
Posted : 04/12/2020 7:56 pm
lcdguy
(@lcdguy)
Eminent Member
RE: How to fix the IR Filament Sensor?

printed my modified door idler cover, and seems to be working better, i now don't need to position it all the way to the right as far as it will go to get the sensor to trigger reliably, once i get some more parts i was planning to upgrade i will run a full multicolour print to see if it works better, but so far single filament mode seems to be working well. I can post the 3mf here if other people wanted to print it out and give it a try.

Posted : 04/12/2020 11:53 pm
Marino
(@marino)
Active Member
RE: How to fix the IR Filament Sensor?

@lcdguy

Happy to know you managed to solve the problem.

In my previous post I attached the stl file using the Attach file at the bottom of the reply box.  It is only 138Kb therefore less than the maximum allowed.

But or I am not capable to use it or something went wrong.

I just realized that apparently stl files cannot be attached for security reasons.

This post was modified 2 years ago 2 times by Marino
Posted : 05/12/2020 8:02 am
lcdguy
(@lcdguy)
Eminent Member
RE: How to fix the IR Filament Sensor?

well i remain cautiously optimistic that it's "fixed" i still think the mmu2s/mmu2s+ is inherently flawed and don't expect prusa to fix this anytime soon, especially with them looking at tool changing on the xl, whenever it get's released.

Posted : 05/12/2020 9:24 pm
lcdguy
(@lcdguy)
Eminent Member
RE: How to fix the IR Filament Sensor?

and, it broke again, i'm giving up on this mmu2 malarky. it's far to finnicky and sensitive for my taste. Maybe it will get another look at if it's design ever get's updated by prusa (not holding my breath).

Posted : 06/12/2020 2:35 am
Marino
(@marino)
Active Member
RE: How to fix the IR Filament Sensor?

@lcdguy

Sorry to know it did not work.

After I made my modification I printed a gecko modified for 5 colors and except some loading issues due to my MMU assembly mistakes (not proper alignment  of the pulleys) I did not face any problem.

If you are still interested in trying my solution send me your E-mail and I'll mail you the stl file. This is all what I can do.

Posted : 06/12/2020 9:05 am
shilbert
(@shilbert)
Active Member
RE: How to fix the IR Filament Sensor?

I have not read the entire thread but can add this. I had loads of problems. Tried everything. MMU2 mods, much more. Most of my problems came from the the filament not going in and out of the extruder properly.I was about to completely remove the MMU2

Eventually I fixed this completely by changing the extruder assembley to this

https://www.prusaprinters.org/de/prints/7690-tzb-mk3smk25smmu2s-extruder-mmu2s-no-tower-v2

I have not looked back. Ever. It just works. I assume it has to do with much improved filament path an more reliable filament detection.

I run this with stock firmware, even though there is a special TZB firmware.

Posted : 06/12/2020 9:28 am
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