MMU 2 failure on first print.  

RE: MMU 2 failure on first print.

The MMU needs to be dialed in and calibrated and as an operator you also need to get to know how to interpret things when stuff doesn't work as intended. That can take a bit but if you make it through that it is a pretty reliable machine for the filaments you know to work. 

In order that it makes sense to work on the MMU your printer needs into perfect operating condition.  If that is the case, test that both filament sensors work reliably by manually sticking a piece of filament into both, while watching the sensor readings in the respective display menu. 0 and 1 need to be correct and most importantly stable. If they aren't the MMU does all sorts of crazy things. 

The MMU is also fairly cryptic regarding output. Have a look at the manual to learn what all the light signals mean exactly, that is quite important, and how to load filaments into the MMU, if you haven't done so already. 

I am not sure what you mean by having to confirm color changes when the MMU went to lane 1. Did you start a print with colour changes and the MMU did not always go to the correct lane during color change or something else? Can you elaborate what is exactly happening when and what kind of error messages you recieve (lights, display, weird sounds etc). If I have to guess it seems you have an issue with the selector. Make sure the maggot screws are really tightened properly, that's a problem I had and it was notoriously difficult to figure out as the selector moved too little just ever so slightly until dozens of colour changes in it failed. If they are, test the selector using the buttons on the MMU (moving it to all 5 positions) and verify that both the head as well as the selector wheel move into the correct position each time. If they are, try a test print and observe exactly at which point things go wrong and what exactly can be observed then (lights, messages, sounds, what exactly goes wrong). 

RE: MMU 2 failure on first print.

PS: During manual check you can also test load filament for each position. Move with buttons manually to the lane of choice, press the middle button and then the filament should be fed to the MMU filament sensor and as soon as the sensor triggers the filament is moved back to the waiting position. Succesful loading is indicated by a green light (if you get a persistent red blinking light which doesn't go away anymore the loading failed). 

Oh and never press the reset on the MMU unless you are fine with ending the print. Sometimes reset is necessary but it basically always screws up your print and confuses the MMU and also can lead to those misalignment errors. 

RE: MMU 2 failure on first print.

Thank you for your response.  When I went to calibrate the MMU I went thru all the lanes and the filament did it's the thing without error  The filament went into the MMu and was pulled back out.   .  At the end of the calibration when the lane 5 LED was flashing quicky I could not get the calibration to save.  I'm thinking that's my  first problem.    The exact issue I am having is illustrated in the picture.   I'm hoping you have a some suggestions.  Thanks

RE: MMU 2 failure on first print.

I am not sure I understand what you mean by calibration. There is the option to load all five lanes subsequently in one go on the screen. Do you mean that? There is nothing to save there. I never load the filaments into the MMU like that. I always use the 3 buttons directly on the MMU with those buttons you can load any lane you want individually or just check if a loaded lane is still working fine (it can happen that filament is getting pulled out slightly over time and then the MMU can't grip it anymore and then you also get an error).

I am not entirely sure about the context of that error message but if you get that message even though you verified that there is no filament left in the channel, it looks as if your filament sensor (I assume the one on the MMU) is showing a false positive signal. The usual culprit is some fine filament strings block the selector and preventing the metal ball to move fully to the down position again. You can test that by removing the PTFE tubing between MMU and extruder and inserting manually a piece of filament into the selector until you hit the ball, if you move back and forth, do you hear the ball falling back when you move out and in the screen menu you can also see the sensor state, do you get 0 and 1 at the appropriate time?

RE: MMU 2 failure on first print.

Good evening

Thank you for the help.  I was able to get the MMU to load and do automatic filament changes.  My sheep failed half way thru because the filament was/is stuck and the MMU gears stripped it.  

I was very happy to make some progress even with the failure.  I will have to attend to the failure tomorrow,  and make some adjustments.

Thanks again.  

RE:

Very good, you are making progress. 

Too high friction in the filament path is a common issue and can have several causes. First, check the filament path from spool to extruder. Are there some harsh bends?Try the filament movement manually by uncuppling the tube from the extruder and moving the filament coming from the spool by hand. Is it relatively easy going or can you feel a lot of friction? If the latter, you either should have a look at the filament both, maybe your screws at the back of the MMU, holding the tubes are too tight or there is some issue in the MMU. If it moves nicely, you might have an issue either with stringing or filament tip shape. 

Have a look at the tip shape during unloading steps. There is also a chapter in the manual. Do you have stringing on your tip? Stringing doesn't lead to loading/unloading failures immediately but usually increase risk of issues the longer it goes. The other issue can be that your tip is simply too "fat". My go to solution for the latter, making my friction issues simply go away, never to come back is to buy a PTFE tube with an ID of 2.5 mm instead of 2.0 mm and replace the tube connecting MMU with Extruder (but keep the tubes at the back at 2 mm ID). I have not experienced any downside from that and it makes your system much more tolerant towards "fat tips", ie tips which have a proper shape but are simply a bit too wide in diameter. 

A topic that comes with tip shape are filament type (brand, material type) and slicer profiles. This is an endless pit. In your case I would stay with Prusament PLA for the time being, while are still trying to dial your MMU in. That filament is very MMU friendly and the profiles in the slicer are very well adapted. If you can print with that flawlessly you can try out other brands and filaments, suitability for the MMU varies. 

RE: MMU 2 failure on first print.

PS: Occasional load/unload issues can also occur in a dialed in MMU. It is advisable to learn how one can resolve those issues, mid-print, without trashing the print. If it is just a bad tip or some stringing blocking the PTFE tube, one can usually resolve those issues in less than a minute and then simply resume if you know what you are doing. 

RE: MMU 2 failure on first print.

I have not been using Prusamant filament.  I have been using Zyltech PETG, due to it's abilities to withstand the heat of direct sunlight.   I'm not a big fan of PLA.   I may have some PLA stashed somewhere.    The issue was exactly a fat tip issue in the tube between the MMU and the extruder.  I am going to get the fatter PTFE tube and go with that.  Thank you.  

Also I am working on how to fix issues mid print,  I haven't figured it out yet,  I will get their.

Thanks for helping I do appreciate it.

Bob

RE: MMU 2 failure on first print.

I mean you don't have to use PLA. My first print on my MMU was with PETG as well after all 😉 Generally speaking PETG works fine with the MMU too, not just PLA.
I would just recommend using Prusament in the beginning (there is also Prusament PETG), simply because it is the in house filament and the profiles are the most solid ones for those in my experience. 

If you get to manage with Zyltech PETG, no need to do that though. Just keep an eye out for stringy tips. Those can take a while until they are becoming a problem, maybe a few hours into a print or so. If you can't get good looking tips with your current filament, then it would be certainly a good idea to try it with a Prusament filament and see if you can manage there. Unless you live somwhere where it is prohibitively expensive to buy that stuff due to shipping or tariffs. 

RE: MMU 2 failure on first print.

Thank you.  I will try the Prusament filament that I have here in the house.    I'll see if I can make this work.  GO  ME!!!

RE: MMU 2 failure on first print.

@thejiral is right, use filaments that have an MMU profile in PrusaSlicer, they work best. Personally I never had any stringing problems using Prusament PETG and the default profiles with my MMU2.

Regarding the friction problem: At first make sure that the PTFE inside your hot end is the right one, there are spare ones coming with the MMU2 kit and they are very special (1.85mm ID I think) and essential in building not to fat tips.
Second: I recommend 2.5 mm and 3mm ID PTFEs for everything else, 2.5mmID for the small ones inside the MMU2 and from selector to extruder, and 3mm ID for the whole feeding towards the MMU2. I use 3mm from dry boxes to the buffer and from buffer to MMU2.

That together with the pass through adaptor ( https://www.printables.com/model/6605-prusa-mmu2-ptfe-holder-m10-passthrough-adapter ) has significantly reduced friction in the filament path and made my MMU2 very reliable.

RE: MMU 2 failure on first print.

Now that you say it. I replaced that tube leading to the hotend already once and honestly I have no idea which one I got there now. But given that I have the 2.5 mm tube leading to the extruder, it is not an issue anyway. 

Regarding the tubes feeding to the MMU I'd say, one needs to decide based on the concrete setup. You definitely want to enough friction in your path leading to the MMU that the filament doesn't easily slide back out of the MMU by itself. You do not want more friction either though. One can fine tune that with the screws at the back entry point. I installed the pass through adapter here though. Simply because with my enlcosure the stock option was a real pain to work with. I am rather on the low side of friction so every once in a while a filament might slip back out a bit. But failures due to that are very rare. So I could not be bothered to add something back to fine tune friction. 

So yes, you can also have too little friction as well, but I guess that's a much rarer issue than too much friction. 

RE: MMU 2 failure on first print.

So yes, you can also have too little friction as well, but I guess that's a much rarer issue than too much friction. 

true

One addition to mounting of the PTFEs in the back of the MMU2 (pass through or original): It' s essential to push the PTFEs all the way in until you can see them clearly inside the MMU through the little windows which are there for exactly that reason. 

RE: MMU 2 failure on first print.

Thank you for the kind words.  I got my sheep to print.   I'm very excited.  I changed the PTFE tube and the nozzle in the hot end,  I got the 2.5mm ID PTFE tube for the MMU to the extruder.   Now I'm trying to figure out how to add support material from a separate lane to my print.  I'm going to print a black clip and I need to use the Dissolvable filament to give it support.  

Thanks again guys you are the best!!!

RE:

A kind word of advice. Stay away from dissolveable filament until you are confidently and successfully printing with PLA or PETG alone. The MMU is primarely a multi-colour unit, not quite the "multi-material" that is in its name. Printing with soluble support is possible with the MMU, but it is much more challenging than single material prints with multiple colours. Soluble material has a strong tendency for stringing and for successful prints it might be necessary to fine tune or even radically change the unloading process and tip formation settings. That is a true rabbit hole. To make things more complicated, the problems with solubles often phase in only slowly during print, that means the first few hours may look fine and it only then starts to get problem ridden due increasing stringing. Also one has to flush the nozzle a lot more with solubles, much more than the default settings.

Don't do it unless you've figured everything out for basic operation of the MMU and are looking for a new challenge. For a start, simply use regular supports with the material you print with. 

RE: MMU 2 failure on first print.

@thejiral is right, don‘t try it at this stage. 
If you want to anyway, there are pre configured profiles (called soluble support) in slicer. Don‘t print the supports faster than 10 or they will loose adherence. Use a drybox to print directly from there.

RE: MMU 2 failure on first print.

Oh,  Ok  I will heed your words and hold off.   I do have some things I'd like to eventually print that may need supports.  I made some eggs in Fusion 360 that I'd like to print and sell for easter.

RE: MMU 2 failure on first print.

It looks like that egg has a flat bottom. That will probably print ok without any supports. If it‘s completely round you will need some support but with the right settings just very few. 

RE: MMU 2 failure on first print.

It is round.  Now that I've been fooling around in Prusaslicer I think the real issue is going to be getting the different colors into the model.  I need to learn more about supports I think