MMU2S filament feed / Self Check Errors  

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matthew.b17
(@matthew-b17)
New Member

Hi Group, I am having issues with the Mk3 / MMU2 to Mk3s / MMU2s upgrade. I've been through any forum posts that look like they could be associated, but I'm officially stuck still.

1. It appears I had an IR sensor functionality issue, but through modifying the "chimney" location and shaving the piece that swings in and out of the IR beam I believe that's fixed (it now appears to consistently show 1 if there is no filament in, and 0 if there is filament in).

2. Problem 1 is that I cannot complete a self-test. It fails every time when testing filament sensor and says "self test failed". It heats up the the nozzle, then pushes a tiny bit of filament (I don't think it's enough to even reach the FINDA sensor) and then says "self test failed" with no further information. I am thinking it might tie together with item 3/4.

3. If I try to load filament to nozzle it acts wacky. It pushes the filament to the extruder, the extruder picks it up, but then as the extruder tries to pull it in it can't BECAUSE THE MMU2 still has the bearing pushing down on the MMU2 Bondtech gear. This locks the filament so the extruder can't move it and I can hear it skipping as it tries to push it towards the hot end, but the filament doesn't move at all.

4. There is another crazy behavior I've seen sometimes. At times when I try to load the filament by hand (just as a test, pull out the MMU2S to extruder tube and feed a separate piece of filament by hand into the extruder) just as the extruder takes the filament and starts to feed it the extruder goes into a high speed load mode (feeding filament a bit faster than the hot end can heat it) while the MMU2S goes into a high speed RETRACT mode. The several times this happened in which I wasn't feeding it by hand it took up all slack in the filament between the MMU & the extruder in a second or so and then I hit the reset or the filament broke.

I'm officially stuck folks. I've tried factory resets on both the MK3s and the MMU2s. I have loaded what I believe to be the latest firmwares on both (FW_MK3S-EINSy10a.hex & prusa3d_fw_MMU2board_1_0_5.hex). I've got the majority of my weekend spent just trying to solve this problem... Any advise/help greatly appreciated.

Regards,
Matt

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Posted : 21/04/2019 11:10 pm
randy.h3
(@randy-h3)
Trusted Member

I just finished my build so I'm probly not the best person but according the mmu2 handbook it should be reading 0 with no filament and 1 when loaded. Could you have the connector flipped on the board or sensor?

Posted : 22/04/2019 6:33 pm
toby.e
(@toby-e)
Active Member

I'm having exactly the same issue. I have checked the orientation of the ir sensor cable and I'm fairly sure I have that right but self test calibration fails after heating the hot end. The first test seems to pass but not the second. The problem is that the error message is so generic I'm not entirely sure if it's the ir sensor it complaining about.

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Posted : 22/04/2019 7:11 pm
toby.e
(@toby-e)
Active Member

I wonder if it's related to this

https://shop.prusa3d.com/forum/assembly-and-first-prints-troubleshooting-f54/mk3s-mmu2s-not-loading-filament-on-print-t28447.html

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Posted : 22/04/2019 9:37 pm
toby.e
(@toby-e)
Active Member

I have now fixed my issue. It was the ir sensor which seems very fussy. if you go to Support/sensors you'll see the state of the IR sensor. It should be 1 when there is filament in the extruder and 0 when it's empty. It took quite a bit of fiddling to get it to report the presence of filament correctly. I unscrewed the tube that feeds the extruder so I could push filament in and out. The trick was to experiment until it was reporting correctly. I had to shave some of the chimney off (as described in the link above) and experiment with the tension in the two screws that hold the idler door in. Eventually I got to a state where pushing the filament in turned the sensor from 0 to 1. I was then able to finish calibration without an error.

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Posted : 23/04/2019 3:10 am
matthew.b17
(@matthew-b17)
New Member

Based on these replies there is yet the chance that the issue is a relatively easily addressed case of stupidity rather than machine error...I believe I managed to adjust the IR sensor such that it reliably triggered exactly the opposite of what it was supposed to do. Luckily I have another mk3 running a replacement part I hope to try tonight 🙂

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Posted : 23/04/2019 3:31 am
matthew.b17
(@matthew-b17)
New Member

Yep, definitely an ID10T error. I had an iffy IR sensor reading, then adjusted so that it read backwards (0 with filament in extruder, 1 with filament out). Duh.

It did throw me off that in calibration it failed when it appeared that it was testing the FINDA rather than the IR sensor, and the error gave no information at all... In that will State it would be super helpful if the massage at least hinted at an unexpected IR reading.

Anyways, it has now passed the self test as in on to standard calibration... And I did a few filament change rest and they were gorgeous and smooth sounding.

Looking forward to a likely first test print tonight :). Thanks for the input you all.

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Posted : 23/04/2019 4:47 am
timothy.r2
(@timothy-r2)
New Member

@matthew-b17

I've had a trouble with the IR sensor tower ... First figured out for me by chat support (thanks!) but I've had to readjust it several times. The whole process gets pretty mucked up when this is out of whack.

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Posted : 30/06/2020 3:32 am
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