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MK3S/MMU2S not loading filament on print  

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mkopack
(@mkopack)
Eminent Member
RE: MK3S/MMU2S not loading filament on print

But they claim that the calibration doesn't do anything anymore??? Or at least that it isn't needed??

Respondido : 29/06/2019 3:03 pm
Sneaks
(@sneaks)
Eminent Member
RE: MK3S/MMU2S not loading filament on print

This calibration determines where the MMU2 feeds the filament to. If you don’t have it adjusted correctly, your filament won’t make it to the bondtech gear and therefore won’t load. 

Respondido : 29/06/2019 3:30 pm
gnat
 gnat
(@gnat)
Noble Member
RE: MK3S/MMU2S not loading filament on print
Posted by: sneaks

This calibration determines where the MMU2 feeds the filament to. If you don’t have it adjusted correctly, your filament won’t make it to the bondtech gear and therefore won’t load. 

Actually mkopack is correct. It auto calibrates now by coordinating with the IR sensor. The MMU will just keep feeding until the IR sensor trips or it runs out of filament. 

What it does is the "fast load" which is a preset value that should get it to the IR sensor. If the sensor doesn't trip, then it starts "searching" by advancing a few centimeters at a time until the sensor trips. 

As a test I replaced the MMU->extruder tube with a 1m tube. Other than making a 13 minute print take 30 due to all the "searching" the print ran with no issues. 

MMU tips and troubleshooting
Respondido : 29/06/2019 4:44 pm
Sneaks
(@sneaks)
Eminent Member
RE: MK3S/MMU2S not loading filament on print

Sounds like something is wrong on my machine then.  After I did the upgrade, I had non stop issues with my MMU2 loading (it wouldn't load properly).  I ran the calibration in the link above, and then I never had an issue again.

Maybe I'm using old firmware?

Respondido : 29/06/2019 4:56 pm
mkopack
(@mkopack)
Eminent Member
RE: MK3S/MMU2S not loading filament on print

Yeah, well, I tried doing the calibration - when I do the calibration routine, it was driving the filament all the way down past the bondtechs into the tube below (and even a little past that....)

So I adjusted the calibration so it goes just to the middle of the gears.

Same effect, whether I have the IR sensor turned on or off, I get the same behavior as before...

There's a video of what I'm experiencing at:

Doesn't seem to matter how tight or loose I set the idler screw..

Anybody have any other ideas??

Respondido : 29/06/2019 5:07 pm
xenotrax me gusta
Sneaks
(@sneaks)
Eminent Member
RE: MK3S/MMU2S not loading filament on print

I just watched your video.  Are you using Prusa's extruder-idler-mmu2s1 part or my modified one

I had a TON of issues with that door!  Even once I thought I had it right (watching 1/0 on support screen) it still was not right.  If you've tried everything else, maybe this will solve it for you. 

 

Most recent comment posted on part:  "I was curiously doubtful upon stumbling across this print. People here had already claimed it was a cure-all, and I have been struggling with my MMU2/S for nearly 6 months. Yet lo and behold, upon removing the old idler door and replacing it with this one... everything has miraculously fixed itself and I haven't had a single jam! I have no idea how it made that much of a difference as upon observing the functionality of the original idler door it didn't appear (to me) to be in the way as the poster suggested. Well, for some reason, it worked. Thank you."

 

Respondido : 29/06/2019 7:00 pm
mkopack
(@mkopack)
Eminent Member
RE: MK3S/MMU2S not loading filament on print

Prusa's part... Unfortunately, without my printer working I have no way to print a replacement part (argh!!!!)

SOOOOOO frustrating...

Respondido : 29/06/2019 7:48 pm
A.Dorn
(@a-dorn)
Eminent Member
RE: MK3S/MMU2S not loading filament on print
Posted by: mkopack

There's a video of what I'm experiencing at:

Yeah, I know that feeling...

I currently try to get a 2-color benchy with the new 3.7.2 firmware. And just now tried to rescue a print that was in the 3rd hour from this situation.

There are many possible sources of the problem. I tried the following:

- cutting the tip of the filament (didn't help)

- checked that loading at the selector was working as expected (no grinding there)

- checked if IR Sensor was ok.  I checked the sensor-Info in the menu - and saw, that it was changing correctly - also it reacted fine when I removed the tube and inserted a piece of filament into the extruder / I removed the tube, pushed the screw to get past the resistance and inserted a piece of filament manually.

- fiddled a bit with idler tension (didn't help - changed it back to normal)

- checked the bondtech gear - removed the door (2 screws) - gear is fine, grub screw is good, no debris, no trouble when inserting filament manually

- checked for a clog (pushing the filament even deeper worked fine)

- checked for other symptoms (only noticed that the extruder motor was quite hot - waiting a bit to let everything cool down a bit didn't help)

- Finally I noticed a hard physical resistance in the extruder festo whenever I try to insert the filament that doesn't work. The pieces of filament I inserted manually didn't get stuck there.

=> My filament is bending the wrong way right where the tube and festo meet.

After bending the tube a bit while the filament was entering the festo the print simply continued...

 

 

Well, 3 layers after that the benchy came loose from the bed. While checking for the clog I also used "load to nozzle" a few times - and I preheated the nozzle and before resuming the print I let it cool down a few seconds.

Continuing the print heated the nozzle, but most likely didn't cancel my cool down of the bed temperature. The bed temperature went to 30°C - and the benchy just came off...

Next try I have to be more careful...

Respondido : 29/06/2019 8:05 pm
gnat
 gnat
(@gnat)
Noble Member
RE: MK3S/MMU2S not loading filament on print
Posted by: mkopack

Prusa's part... Unfortunately, without my printer working I have no way to print a replacement part (argh!!!!)

SOOOOOO frustrating...

If you want to print parts to try to solve issues, disconnect the MMU from the Rambo and remove the festo from the extruder. Then you can print as a MK3S. If the IR sensor is giving you trouble, you can disable it, though that's a good chance to go through troubleshooting such issues. 

MMU tips and troubleshooting
Respondido : 29/06/2019 8:22 pm
Dave Avery
(@dave-avery)
Honorable Member
RE: MK3S/MMU2S not loading filament on print

it sure sounds like your IR sensor is not working all the time. the sensor adjustment is very sensitive and easy to get it partly working. if it's a little off it can go on and off as the head or filament moves.

i modified mine and added a LED and resistor to the sensor board. makes it easy to see it blink is the alignment is a bit off

https://bunnyscience.dozuki.com/Guide/Bunny+and+Bear+(BNBSX)+MKS3+Geared+Extruder+Assembly/2?lang=en#s84

is the mod i followed

you could do the same thing with non-surface mount components by splicing into the sensor wires behind the plug 

Esta publicación ha sido modificada el hace 5 years por Dave Avery
Respondido : 29/06/2019 9:50 pm
mkopack
(@mkopack)
Eminent Member
RE: MK3S/MMU2S not loading filament on print

Ok, THINK I found my problem...

Turns out the set screw for the bondtech on the extruder motor was loose and it was just spinning freely, so it was never actually pulling the filament down in. Just tightened it up after removing the MMU2's wire from the Einsy board and printing out the upgraded idler part now (4 of them just to be safe).

Respondido : 30/06/2019 2:24 pm
Samaker
(@samaker)
New Member
RE: MK3S/MMU2S not loading filament on print
Posted by: christian.h7

The culprit indeed is the IR sensor. Try the self test, it probably will fail.

What happens is: It may show 0 when the extruder is not moving, when the extruder moves it may switch to 1 because of the vibrations.

There's very little tolerance here, I did not get my chimney to move further to the left of the extruder.

I fixed the issue for me using the following method (no guarantee that it works for you, please be careful and do small iterations):

  • go into the support menu, find the sensor info and select it (we'll need that the whole time)

  • unscrew the spring-screw of the extruder-door (side of the extruder)

  • unscrew the screw holding the door in place (back side of the extruder) but keep it close to you

  • use the file to remove a bit of the material (just a few micrometers) => green arrow

  • put the door back in and use the holding screw to fix (tighten it like it was before and be aware that the door can still move) the door again

  • apply pressure directly on the nut using your finger => blue arrow

  • use your finger and apply very gentle pressure on the lever (opposite of the green arrow, ATTENTION: the door should not move)

  • repeat the steps until your IR shows 0 even if you have followed the last step

  • use the selftest to check if the IR works even if the extruder is loading

 

repeat those steps until the self-tests pass and you can load your filament to the extruder using the menu.

Again, attention: If you remove too much of the material, the IR sensor will not get a "1" again.
In this case you can either move the chimney a bit to the right or reprint the part and start from scratch.

Hope this helps you as well.

BR,
Christian

Could you please upload pictures? I have the same issue here. Thanks!

Respondido : 16/08/2019 6:14 am
Paul Mullen
(@paul-mullen)
Active Member
RE: MK3S/MMU2S not loading filament on print

I started to follow the procedure for Bowden length calibration.  The instructions say to open the idler door to do the calibration.  In fact, it requires more disassembly than that.  Stick that interacts with the IR sensor keeps you from "just opening" the idler door.  Am I missing something?

Respondido : 21/08/2019 4:33 pm
JMH714
(@jmh714)
Estimable Member
RE: MK3S/MMU2S not loading filament on print

Seems like I'm having similar issue. It seems like MMU2S and Extruder are doing tug of war after few seconds of loading filament. I couldn't pinpoint which MMU2S or new Extruder that caused the issue.

After reading this thread, so, it's extruder idler for not being trigger sensor properly. I got the upgrade (MMU2 to MMU2S) just few weeks ago and I'm surprised that they (Prusa) didn't update the idler or fix it. :-/

I can see Sneaks shared the modified version of idler in STL file. I'm not expert on converting STL into G-code file (I'm still very beginner 3D printer...). 

Respondido : 08/09/2019 2:58 am
Samaker
(@samaker)
New Member
RE: MK3S/MMU2S not loading filament on print

I fixed the problem. Seems that the 4 screw that are holding the extruded motor were too tight and were blocking the IR sensor on reading the filament.

Respondido : 08/09/2019 3:51 am
Sneaks
(@sneaks)
Eminent Member
RE: MK3S/MMU2S not loading filament on print
Posted by: john.h63

Seems like I'm having similar issue. It seems like MMU2S and Extruder are doing tug of war after few seconds of loading filament. I couldn't pinpoint which MMU2S or new Extruder that caused the issue.

After reading this thread, so, it's extruder idler for not being trigger sensor properly. I got the upgrade (MMU2 to MMU2S) just few weeks ago and I'm surprised that they (Prusa) didn't update the idler or fix it. :-/

I can see Sneaks shared the modified version of idler in STL file. I'm not expert on converting STL into G-code file (I'm still very beginner 3D printer...). 

I used to upload Gcode files as well, however, they are so machine-specific that many people ran into issues with my Gcode files and I quit including them.  I have attached a Gcode file for you: PET, .20mm Layer, Grid, MK3S Single Extruder.  I don't think this will print on MMU2 (not 100%).  I also added the GCODE to the Part page

Esta publicación ha sido modificada el hace 5 years por Sneaks
Respondido : 08/09/2019 12:09 pm
JMH714
(@jmh714)
Estimable Member
RE: MK3S/MMU2S not loading filament on print
Posted by: sneaks
Posted by: john.h63

Seems like I'm having similar issue. It seems like MMU2S and Extruder are doing tug of war after few seconds of loading filament. I couldn't pinpoint which MMU2S or new Extruder that caused the issue.

After reading this thread, so, it's extruder idler for not being trigger sensor properly. I got the upgrade (MMU2 to MMU2S) just few weeks ago and I'm surprised that they (Prusa) didn't update the idler or fix it. :-/

I can see Sneaks shared the modified version of idler in STL file. I'm not expert on converting STL into G-code file (I'm still very beginner 3D printer...). 

I used to upload Gcode files as well, however, they are so machine-specific that many people ran into issues with my Gcode files and I quit including them.  I have attached a Gcode file for you: PET, .20mm Layer, Grid, MK3S Single Extruder.  I don't think this will print on MMU2 (not 100%).  I also added the GCODE to the Part page

Thank you. I do have another MK3S here that I can print it off. 👍 

Respondido : 08/09/2019 2:26 pm
JMH714
(@jmh714)
Estimable Member
RE: MK3S/MMU2S not loading filament on print

Um... printed out Sneaks modified version and installed. And it still does not work - the issue remains same.

I put together my new MK3S (strictly single color printer) just last weekend and it prints flawless. 

I don't understand why I'm having issue with my old printer (MK3) MMU2S. 

If I told it load to nozzle, it does load to nozzle as it goes out of nozzle. It continues for 2 or 3 seconds and it stopped. The screen says "loading filament" but nothing coming out of nozzle. But I can see extruder bondtech spinning counterclockwise (as filament should go to nozzle) and MMU2S bondtech shows spinning counterclockwise (as filament should go back to filament spool). It's like extruder and MMU2S doing tug of war game. 

Why is it doing that? I was hoping that the extruder sensor issue as description above and it doesn't seems to fix after Sneaks print. I must have flawed sensor or something or I missed a step somewhere. 

Respondido : 08/09/2019 8:13 pm
Sneaks
(@sneaks)
Eminent Member
RE: MK3S/MMU2S not loading filament on print

Aw man, so sorry to hear that!  If you haven't already, look through all the solutions in this post.  When I did my MK3S upgrade, it took me a day and a half to get everything working and I had a couple of issues.  Outside of the Idler door, my bondtech gear wasn't tightened all the way down to the shaft.  Keep at it - you'll figure it out.

Respondido : 08/09/2019 9:12 pm
Golden snake
(@golden-snake)
New Member
RE: MK3S/MMU2S not loading filament on print

I just finished assembly my new MMU2S and had been testing it with a small testing gcode from Prusa from 2 to 5 filaments over a day. I had been facing all kind of problems like everyone does. Finally, I get it to work perfectly now. I learned that calibrating/adjusting on FINDA and IR sensors and making sure they are reliably detection a filament by using "sensor information" while printing. MMU2S are using the sensors to detect a filament load/unload correctly. I successfully printed a print with 3 colors in 9 hours. Now I have a second print with 5 colors in 26 hours and will see the result in 24 hours....

Respondido : 09/09/2019 4:30 am
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