I'm done  

RE: I'm done

I'm curious, have you ever contacted Prusa support via chat?

RE: I'm done

i'm there with you. I finally got tired. I even tried "skindiping" approach of prusaslicer. I got the situation a little better but i still get same situation as you where the mmu unit is stuck at the needs attention message. No filament in the pathway  and nothing that makes sense. And at that point i cannot see the sensors to see whats wrong. I dont know if i have a faulty mmu unit. I chatted with prusa and they send me a new finda probe but the problem i still there. My suspicion is that the finda is stuck showing one and it cannot change filament position. I really got tired to. I tried almost everything. I even printed out this https://www.thingiverse.com/thing:3688458 .

I got mmu2 for printing with soluble and breakable support. No luck.

I left it on thought. Maybe in a new firmware update thinks will get better.

RE: I'm done

Been there done that.  I am just coming back from a hiatus and giving it another try.  I got some fantastic prints early on which suckered me in and then I filled up a 5 gallon bucket with failures. I am reading through the posts to see if I can improve my results.  Take a break and come back in 3 to 6 months.

RE: I'm done

I feel your pain. Took mine off a couple of weeks ago and now I love my printer again.

The first two weeks after assembly it would fail to load to the nozzle constantly. Finally figured out the IR sensor has a blind spot or something and had to shim it up so that it would "see" the arm that moves when filament loads. To this day I am not sure if the tab is supposed to go between the two parts on the sensor or what. It's not even very close to it at all currently. Was finally able to get that to read a "1" when it was supposed to and moved on to the nightmare of the actual MMU2S.

Had the same issues described in this thread with the MMU2S and just couldn't take it anymore. So frustrating. I got a few really nice multi color prints but it seemed to work most reliably with two colors. I gave up when it just stopped being able to load any filament for no apparent reason. In my case it was like the selector was not lining up correctly with the filament holes other than the first one. It would also not unload completely out of the selector and when it moved to the next filament it would drag the previous filament and jam it under the selector. 

Also - I am a big fan of proto-pasta HTPLA filament and it's not usable with the MMU2S or even the stock heatbreak used on the Prusa MK3/S due to the slightly larger diameter in one half of the Prusa heatbreak to accomodate the unload/load of the MMU2S. So to use that filament you basically need to swap the heatbreak out for a stock E3D heatbreak...which may impair the MMU's load/unload action according to the Internet.

RE: I'm done

I tried that selector as well.  No meaningful improvements. I was on my 3rd custom selector when I gave up.  I thought the problem was the IR sensor as well, I even mounted an LED on it so I could see when it was activating.  As far as I could tell, it was not the IR sensor.

I came to the conclusion that it was the way the MMU was communicating with the printer.  Like I said, after months, I just decided that I wanted to actually print things and not spend all my time trying to make the MMU work.  Even using the MMU in single color mode was problematic. The printer would ask me what filament to load, then the MMU would try to load a different one.  Sometimes it worked, sometimes it didn't.

Since I've removed it, I feel like a great weight was lifted from my shoulders.  

Maybe I'll try again in 6 months when, hopefully, Prusa releases something that is more reliable.

I know there are some out there that say "well, it is a hobbyist device, don't expect perfection".  I get it and I approached it with that in mind, but after reading endless forums, printing numerous modified parts and tweaking everything I could, I just got tired of it...it stopped being fun.  When friends asked me to print things for them and I kept saying "well, my printer is down right now" over and over, I realized that enough was enough.

I know other have had successful with the thing, but I tried everything they suggested and still failed.  Either others are much better than me at troubleshooting, or there is a fatal flaw in the design of the device; I suspect it is a little of both.

Thanks to everyone who contributed to the forums and offered condolences.  I'm glad I'm not alone in this.

RE: I'm done

Starting to feel the same, to be honest. How much is the process to remove the MMU2S? Just disconnect from the board or is it also removal of the IR tower etc?

RE: I'm done

Mine is running as a Mk3s but with the Sensor tower...   

I don't use  Auto Load 

and I haven't relied on filament runout... but I just slice as a Mk3S and set it off

regards Joan   (not using my MMU2)at the motor, because I have a potentially faulty motor  so I need to swap it out with another motor off the MMU1...   (I got the MMU1 to MMU2 upgrade)

regards Joan

RE: I'm done

Finally after 3 months of starting the 3D printer by hand because the IR sensor is getting on an off for no reason I have finally fixed my issue !

RE: I'm done

Posted by: @chris-b59

Finally after 3 months of starting the 3D printer by hand because the IR sensor is getting on an off for no reason I have finally fixed my issue !

 

Please describe in more detail what exactly you have fixed. That might help others.

RE: I'm done

I have the 2 screw IR holder, I will put in the .STL files I have used to fix my issues later today.

which I have moved a little bit to the right just to have it pickup the IR 1 when filament goes through and 0 when filament goes out.

RE: I'm done

Posted by: @chris-b59

I have the 2 screw IR holder, I will put in the .STL files I have used to fix my issues later today.

which I have moved a little bit to the right just to have it pickup the IR 1 when filament goes through and 0 when filament goes out.

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

Just print the items and rebuild your printer with in then attach the 2 screws and use the one on the right side to get the 1 with very little tention.

Then the loading and unloading works perfectly.

I am now printing the 3D bug from FAB365 and have already printed 3 other parts without any manual intervention.

I am finally glad that I took the time to rebuild it with these parts.

RE: I'm done

I'm at very same position as you are right now. It has been two weeks since I finally got it fixed and been printing almost everyday. Till two days ago, my printer started to having issue with sensor as it went back to "0" "1" shuttering. Today, I tried to do what I did two weeks ago and still failed. /rant It's stupid single positioned chimney that won't let us adjust/calibrate in proper position./end rant 

I'm seriously considering reverse back to MK3S and put MMU2S in storage.

After reading this, I'm going to try final time with mods that Chris's posted. If it failed, it's good bye to MMU2S. 

RE: I'm done

I just upgraded to TZB MK3S and MMU2S firmware as I had again a fillament load issue with Prusa 3.8.0 Firmware

Upgraded the Prusa firmware towards TZB 3.0.0 and MMU2S as well restarted and works like a sharm now with this firmware.

https://github.com/TheZeroBeast/TZB-MMU2S-Firmware/

RE: I'm done

I got fed up with trying to get the MMU2S to work with multicolor/multi-material prints too and dumped it.

Since I was lazy, I first figured I'd just keep it mounted and only print single color stuff. But the printer behavior with the unit attached kept driving me crazy: Stopping a print would also retract the filament from the extruder back to the MMU unit, even if I explicitly loaded a certain filament before starting that print (print file was created using the MK3S base profile, without MMU). That led to a much longer downtime between stopping a print and restarting, since I had to feed the filament to the nozzle again.

This led to me not using the "safe" stop print functionality, but pressing the reset button instead... which then led to me damaging one of my smooth steel sheets as the hot nozzle was too close to the sheet for too long, while the printer was rebooting. That was the final straw for me, now the MMU unit is dismounted, extruder rebuilt to the base MK3S version (as the filament runout detection does not work at all with the chimney version without MMU unit attached!).

Now even if I had gotten the MMU to work properly... there still is a huge issue: print time. Single nozzle with filament changes nonstop is simply a bad solution, unless all you want to do is print with multiple colors of the same material, and not use soluble supports at all. But I typically create mechanical parts. I don't need to print with 4 or 5 materials... all I really need is two - the part material and soluble material. And I'd rather prefer not waiting half a day for a simple tiny model to print just because there are a lot of material changes.

300 bucks gone to waste, sadly.

That being said, if Prusa came out with a dual-nozzle printer design, I would be very tempted to buy that.

It must not be a basic dual-nozzle design though, as that leads to low quality prints (smearing). Either have the unused nozzle slightly lifted up (compare with Raise3D), or use independent print heads (compare with Flashforge Creator 3). The reasons why I don't simply go and buy one of those two printers are that Raise3D is crazy expensive and the Creator 3 is an extremely bulky, heavy box I just don't have enough space for at home (the Raise3D is bulky and heavy too, but Creator 3 at least halfway reasonably priced). Plus, I really like Prusa's magnetic print bed with the spring steel sheets. They are miles ahead of the competition here and I really don't want to miss it when buying a different-brand printer.

What I've also noticed with the recent "upgrade" of PrusaSlicer to 2.1.0... the new algorithm for placing objects on the print bed made me realize none of my steel sheets is perfectly flat but has slight ridges and valleys placed randomly across the whole surface, so no Z adjust value will ensure a perfect first layer across the whole print bed but only ever a small part of it. Previously, I was only using sort of the center of the print bed plus a little to the front and back where it all was fine, but I kept getting screwed up first layers with the new object placement. The printer has an automatic compensation for general skew of the whole print bed, but apparently not for this. Should definitely be a high priority feature to add, although you'd need additional sensor hardware on the extruder to measure the distance to the steel sheet at different points (instead of the heatbed). For the meantime I've reverted back to PrusaSlicer 2.0.0...

RE: I'm done

It has been awhile since I started this thread.  I still have the MMU2s removed and I could not be happier. 

I've been focusing on optimizing my single-color-experience.  I replaced my extruder with a Bondtech extruder, installed new belts, feet, and a bunch of other little improvements.

The joy of being able to start a print, go to work (or sleep) and not have to worry about the print failing has reignited my love of 3d printing.

I still wish I could do muti-color prints (especially soluble material), but until the technology improves dramatically, I'm not going back to the MMU any time soon.

My hat is off to those who made it work. 

Cory

RE: I'm done

I decided to gut MMU2S from my original MK3. I don't take the decision very lightly. If there a new version of MMU and it's better than MMU2S, I might reconsider. 

Now that I have two single color printers. lol 

RE: I'm done

Look at this video it might save all your trouble...

RE: I'm done

This is the post I wish I'd read months ago. I too have tried everything. The MMU2S (or any so far) isnt a "tinkerer's" product, it's just not sufficiently engineered. There's a difference between giving up and recognizing a problem; I bought it to solve my problems, not to be a volunteer engineer. 

It got to a point where i was going to buy another printer so I had a working one, after several months of already troubleshooting, for me to realize how bad this is. To those who have it working reliably (and by that I mean not erroring, not "only requiring manual intervention a few times per print"), I'm impressed. I'm starting to doubt that many of these people actually exist however.

My mmu2s comes off today. Maybe I'll check back in a few months for an update

RE: I'm done

Posted by: @drew-b4

To those who have it working reliably (and by that I mean not erroring, not "only requiring manual intervention a few times per print"), I'm impressed. I'm starting to doubt that many of these people actually exist however.

In FB groups you will find more happy MMU2 user then here.

My definition of reliable MMU2 is: no failed prints. Manual intervention is part of this design. Some people are dialing in each filament and/or using methods to make "perfect" filament tip (i.e. dribbling) in order to minimize those. I don't have any issues (>1000 changes) with Polyalchemie PLA and for other filaments is usually one intervention per 300 changes (with default PS settings).