MMU2s wont load filament after cutting, now stuck in a loop  

RE: MMU2s wont load filament after cutting, now stuck in a loop

Update

Ended up ending the print and troubleshooting. nothing worked, reconfiguring everything. Filament would not load.

Ended up reflashing both MMU and MK3S+.

Now working again. Will monitor and see what happens

Cheers

RE: MMU2s wont load filament after cutting, now stuck in a loop

I've been getting an insane amount of issues with my MMU2S lately(after flashing the updated firmware). I've gotten this exact issue along with a number of others. Its not my first MMU2S. Have you had any more issues with the MMU2S? I cannot get this to load to the nozzle or to even get my first layer calibration done. I've been at this for 3-4  days and I've tweaked EVERYTHING. I've added an updated buffer setup that works great on my other MMU2S along with 2.5mm ptfe. I've taken apart and reassembled this too many times. I usually handle these issues with these machines with a little patience and focus when debugging but this is pushing me to the end of the line with this MMU2S. I hope the PrusaXL doesn't give me this kind of heartache or that'll be the end for me. 

RE: MMU2s wont load filament after cutting, now stuck in a loop

We are having the same kind of problems. Once we have a filament crash it never recovers the right way. Ours will be sitting at number 4 position but the light will be on number 1 position but the whole time it should be on number 3 position. This is the 5th time we have tried to print a minion and it crashes around his eyes every time. If I reset the MMU the unit goes to number 1 position but should be at number 3. Sick of trying to print this thing for the grand kids. It has even printed the wrong color thinking it was in the right position which I think may have been from using the 2.4.3 beta slicer so went back to 2.4.0 and it seemed to fix the issue. Every thing is tweaked and updated. Can someone explain what is going on here. I'm just sick of getting 15 hours into a print and then MMU just goes nuts. We had 1 problem in 15 hours and we fixed it with out issue. Then all at once it does not know what it is doing. Have printed of 3 color coasters and no problem but doesn't print more than 5 or 6 hours but ever time its a long print then there is an issue. Sick of this thing!!!!!!!!!!!!!!!!

RE: MMU2s wont load filament after cutting, now stuck in a loop

Oh forgot that the heat bed will stay at 0 degrees after a recover which has happened a number of times. Wondering if it is a board issue? After having just added the MMU a few months ago but was purchased back in early 2020 with the MK3s probably will not get any help. 

RE: MMU2s wont load filament after cutting, now stuck in a loop

Forgot one more thing the minion printed fine using filament slot number 1.

RE: MMU2s wont load filament after cutting, now stuck in a loop

Now it is caught in a loop. Flashing all light goes flashes each green light but never moves. Then starts all over again. Calls for it to be at #1 position but stays at 3 and starts flashing all the lights again and just keeps doing it.  I just flashed both unit again to see if that fixes the problem. Any ideas why this is going on. It driving me nuts.

It sounds like your filament sensor is failing, most likely a loose connection or a fragment of filament dust/stringing caught in the sensor.

Cheerio,

RE: MMU2s wont load filament after cutting, now stuck in a loop

I've had the same issues I've calibrated, adjusted, replaced the filament sensor. I've disassembled and reassembled 5-7 times. I have another MMU2S and without any issues. I have maybe a dozen prints through it.  After flashing this a handful of times and struggling with multiple issues I was able to get it to print with single colors. I have two MMU2S and with the one that is giving me issues I have this buffer tube setup: https://www.prusaprinters.org/prints/56560-mmu2s-slot-buffer-holder/files and with the one that is working smoothly I have this: https://www.prusaprinters.org/prints/77054-mmu2s-buffer-inspired-by-rmu-buffer/files. Now before these I had my 2mm(=ID) PTFE strait from the Repbox The Repbox is mounted on the wall about 1-1.5 feet(.3 -.5 meters) from the top of the frame of the MK3S+. After discovering all the issues to come across and gaining a solid understanding of the small finicky points of stress I will say that the MMU2S buffer setup is key. This is after the filament sensor is calibrated, after the tension screws on the MMU2S(and the extruder tension screw) are all finely tuned according to the manual and the comments within that manual, after the gears are all lined up & all are clean, and after all the PTFE tubes heading into  the back of the MMU2S are inserted all the way properly(*Note: I use these: https://www.thingiverse.com/thing:3233579 but there are many like it with different fittings like these: https://www.prusaprinters.org/prints/35392-prusa-mmu2s-rear-ptfe-coupler using these https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2334524.m570.l1313&_nkw=+J%26J+Products+%5D+M5+Brass+Insert+40pcs%2C+7.1mm+OD%2C+7.1+mm&_sacat=0&LH_TitleDesc=0&_odkw=WMYCONGCONG+20+PCS+PC4-M5+Pneumatic+Air+Straight+Quick+Fitting&_osacat=0)  

After all that is checked and I was scratching my head. I went back to plugging the back of the MMU2S directly to the Repbox and its working. I think the first buffer setup I linked to should work but I have to adjust my setup to bring my RepBox down to the printer's level. It being too high (I believe) is causing the MMU2S gears to grind away at the filament. That and having a mile of PTFE for it to travel is not helping either. Then the filament goes to the nozzle and then goes back to the MMU2S. Its finicky... Its all finicky. But I can't help but continue to debug until its working. I'm printing our the second buffer setup that IS working for me and if that works then I will say that I am right(about my setup anyways).  These are my experiences after the long weekend of dealing with these issues. 

RE: MMU2s wont load filament after cutting, now stuck in a loop

@LMJ - yes issues started again, MMU2s won’t change and will only print in one colour at the moment, filament will retract start loading the next and start looping then fail and sit there. 
unforunatelynj have now been travelling for work in the last two weeks and the printer is powered down til I get home to work on it again. 

@Diem - I have tested and tested and tested the sensors and they all go to 1 and 0 as expected when filament is installed/removed. When the mmu2s pushes filament into the sensor, as soon as the sensor changes state the filament is retracted. I have also reconfigured the ptfe length from mmu2 to hot end with no change in behaviour. 

@joeybronzini - thanks, that is a lot of information to read through. I will look at all of that as soon as I get back and start further troubleshooting on the printer. 

thanks again all. 

RE: MMU2s wont load filament after cutting, now stuck in a loop

I LIED... I cannot figure this out. The MMU2S is toast. I'm printing out new parts and I'm going to order a new board for it. I've tried everything else. Everything. If I solve one issue I get hammered with another issue. This is nuts. 

RE: MMU2s wont load filament after cutting, now stuck in a loop

I'm almost there.... almost to where I'm going to through this MMU2S out with the rubbish. I'll drop the $53 on a new control board and see if that "fixes" this. After that if I get the same thing I'm sending it sea worthy.... I haven't been this frustrated over something I can't "fix"/get-to-work in a long time. 

RE: MMU2s wont load filament after cutting, now stuck in a loop

Ok I'm back. I've cooled off a bit. I can't believe how finicky this MMU2S got. My first one worked really well. Then the second one started just fine. What I've noticed is that while I installed them I was specific with the instructions and beyond that maybe I just got a little lucky in the sense that I had no idea about the small details of how things worked. I haven't had nozzle clogs, my tension screws were typically good, by gears were all lined up properly, and the bearings and belts were greased, level, and just tight enough.  But this past week of troubleshooting I've adjusted and tweaked all of those things. 

 I have the Mini+ and those are just little workhorse that I never have had to even touch, tweak, or handle. They just work. So back to the MMU2S. I found this buffer to work great. But I guess there's a buffer from Wedge Group that I'll suggest. They created it and if you could afford it its worth it for what you get. Regardless, I have both my MMU2S printing as I type. The first one is printing a multi color item that is 50% through a 4 hour print. The second one(the one that near pushed me out my window dreaming of taking a sailor dive into my driveway) is now printing a 40hour single print(which failed <10% into the print the last 4 attempts. But its 35% and looking good. ... ... ... (a few hours later... ...) And we're back... back to erratic behavior That print 60% through the print all of a sudden stopped for a filament change... and then continued to make one single move and loop on filament change. I tried to save the print but couldn't(tried flashing the MMU2S too). I don't understand the firmware under the hood. I haven't ever looked, that might change. And what does that possibly mean? A continuous loop on filament  change after reloading and making one single move. This isn't a multicolored print its a single.  

RE: MMU2s wont load filament after cutting, now stuck in a loop

Ok, I have look the MMU over again while it was printing and when it crashed. The f.i.n.d.a. is reading N/A during a print. It will run for an hour then crash. Any one know why it doing this. Do I need a new Finda or a new MMU board. There hasn't been to many prints thru the MMU unit so why is it crashing. Right now Finda is reading 1 and the Pinda is reading 0 but the filament sensor  is reading 1. I have to push the reset on the MMU unit every color change. This is driving me crazy Help!!!!

RE: MMU2s wont load filament after cutting, now stuck in a loop

Just found the part in the help area that the Finda will read N/A during filament load and unload so this isn't the problem. I did look at my filament again and the MMU doesn't like the RapRapper filament at all as it grinds it badly this could be part of the issue. This stuff very soft and then dries out in the tubes if it sits over night which makes it very brittle. So I'm back the the drawing board. 

RE: MMU2s wont load filament after cutting, now stuck in a loop

Yea much of the same here. Lucky if I had a dozen prints through it before the 7-8 failed prints this past week. I have a new board coming so I'll let you know if that fixes anything. In the meantime I found this old post here and this other reddit and I have taken apart the filament sensor and vacuumed and compressed aired it clean, made sure the gears were 100% lined up, triple checked the F.I.N.D.A probe and watched this 10 times already. Now I have the 8th or 9th attempt on this 25+hour print(tried it a few different ways) and I turned the filament sensor off via the settings menu. I am also printing out those modified "selectors" and that filament LED mod and will add those. But as for now the print is running 5% through.It has gotten as far as 60% and then the looping begins. I'll keep you posted with those other mods and the new board. I have another MMU2S that I got when it was released and I never have problems like this. TBC...

RE: MMU2s wont load filament after cutting, now stuck in a loop

Also what is get upset about if you kill the power and turn it back on the light will go on in the #1 position but it will be at number #2 slot or another slot. I have had it sitting at #2 slot and it will be loading #4. Very strange design of this unit.

RE: MMU2s wont load filament after cutting, now stuck in a loop

Here are some links that I think are helpful. The MMU2S is "touchy" for sure. There's just a lot of information to take in concerning how the MMU2S works. Part-1 Part-2 Part-3 .  

RE: MMU2s wont load filament after cutting, now stuck in a loop

Looked at the links which are funny to me as he had the same problems as a lot of us. Now we had a problem where it wouldn't load the filament and got some error 258 or 285. Not 100% sure of the number so we had to turn it off. Just wonder if the board or the finda is causing the problems.

RE:

Yea at this point I have no idea. Ever since the latest  firmware upgrade for me. Extremely frustrating. I don't think Prusa has the MMU2S as a top priority with the XL coming out later this year. Had I known then what I know now.