MMU load fail 3 times forward and retract. Better error coding required.  

RE: MMU load fail 3 times forward and retract. Better error coding required.

Posted by: @jeremy-d9

It looks like there are lots of problems with this. Mine seems to be a little different as it does not require a shut down of the machine.

My MMU2S repeatedly fails on loading the filament. It makes 3 attempts, it actually goes into the extruder head and then reverses back out.

I have checked the condition of the tip and its 'textbook' perfect as per the pictures in the manual, no tails just a neat little tip. It moves freely in the tube. I have verified that it is actually going into the tube in the extruder head - but then it retracts???????? why???

To correct it. I have to remove the tube, cut the filament and then press the middle button and then the third button. 

I think there are two things here. 1) its a guessing game as to why the printer is actually going to an error state. We need to know which element specifically is firing the error code.... why arent there E1/E2/E3 numerical codes that we can reference to find out specifically which sensor/ measurement is failing?

2) why does the middle button have to be pressed AND ALSO then the 3rd button, surely if the middle button shows the MMU is okay, why have an additional action?

I am getting really fed up with my MMU - I appreciate this is groundbreaking technology but the amount of babysitting I have to do just to get a print to even complete is intensive to say the least. I think with better error reporting and failure recovery a lot of these problems could be really improved. Either that or I bring it in a baby stroller with a 12V car battery power supply everywhere i go so i can wipe the milk off its lips????

Have you ever checked the functionality of the sensors. With the MMU2S it is important that both sensors switch correctly. I would observe the switching state on the LCD (filament loaded =1, unloaded=0).

RE: MMU load fail 3 times forward and retract. Better error coding required.

Hi thanks for getting back to me.... are you referring to the 3rd line down where it says 'F1' in the centre? - is there a way to tell which sensor thinks its loaded and unloaded? 

Cheers

Jerry

RE: MMU load fail 3 times forward and retract. Better error coding required.

i have the exact same problem and its driving me insane.

sometimes it will work, many times it loks like this printer has some self desctruct preferences as it drives me crazy enough to willing to throw it out of the window...

I got a tip to implement a 5v led on the ir filament sensor of the extruder in order to see if it works properly. (in the menu it does when testing, but when loading/printing you cant check, rediculous...).

i dont think its this sensor, buti can only make sure if the led is soldered.

In the meanwhile, if someone would like to chime in, feel free to assist.

RE: MMU load fail 3 times forward and retract. Better error coding required.

@dutch

The IR sensor is in the MMU2 extruder version the very same PITA as in the i3MK3s version. You can adjust all day long in accordance with the manual, only to find that once you fully tightened the top screws the setting goes down the drain again. The LED will help significantly to see whether the IR sensor acts as needed, eliminating the necessity to check back deep in the menu over and over, which is not even possible once the MMU2s goes into "needs user action" mode.

Regards

Chris

RE: MMU load fail 3 times forward and retract. Better error coding required.

@dutch

here a simple instruction for the assembly of the IR sensor with LED SMD elements:

I have installed it on all printers and it works fine. For the Mini I changed the pre-resistors to 2 x 47 ohms.

RE: MMU load fail 3 times forward and retract. Better error coding required.

@karl-herbert

Nice - where does this come from?

Thanks
Chris

RE: MMU load fail 3 times forward and retract. Better error coding required.

This looks like a nice workaround, but it seems like a common problem and I would like Prusa to jump in here and make their direction on how to permanently resolve this issue with a firmware upgrade or hardware upgrade pack - in my view it should be FOC because to be honest, out of the box - this MMU2s just aint working..... its painful to use and i want to throw it out of the window 🙁

RE: MMU load fail 3 times forward and retract. Better error coding required.

@decotopian

There are those who think of the MMU2s as a product, ready to go out of the box, as you say, and then there are those who think of the MMU2s as a project for early adopters in a still young 3D printing scene. I´m part of the second group - which I believe is far bigger than the first group - and thus I don´t see an added LED not as a workaround but as an improvement in an ongoing project. I for one gave money to Joe for sharing a bunch of parts in a project he continues to work on,  not for a final, perfectly aligned product. Having said that the MMU2s can work great, if one brings the necessary time and flexibility to really get into it. Being in the first group is fine, but maybe some of those in that group have not made an educated decision when they ordered.

If you are to throw the MMU2s out of the window if it does not work flawlessly out of the box, well, then I guess we can´t be of much help here. For those in the second group who do want to get into the MMU details, there are a number of very good videos on YT about careful calibration, do´s and don´ts and other learnings.

RE: MMU load fail 3 times forward and retract. Better error coding required.

@justme3d

A bit of tinkerin and optimising is something way far other that the nesessity you have to do at the moment to even get it to work.

It is to be expected not to have two left hands when buying something like this, but to be a graduate university technician to get a print out of this, is far more that to be expected...

Any way; i think your comment is way off.

The current state the MMU2 is delivered in, is pathetic and not something to be expected from a reputable company like prusa.

last thing i want to say about this, is when the product is on the market for over a year, it IS to be expected to work right out of the box, yes...

RE: MMU load fail 3 times forward and retract. Better error coding required.

@justme3d

Just to be clear - I am an experienced mechanical engineer and product designer - im not a numpty who went out an bought this expecting it to work first time.

I have spent ..... weeks........ tweaking, watching YouTubes, experimenting. Sometimes it has worked but the vast majority of times - ie 95% it doesn't and it requires constant intervention every time there is a colour transition.  But life goes on and unless you live in a box, have no life/wife/kids then the MMU2S is perfect for you and thumbs up for being JP's best buddy for supporting open source. But no..... this isn't good enough even for group 1 or group 2. It has been been out in various guises for what 3 years now?

From my perspective I think a lot of these issue are caused by poor sensor / software routines and lack of an operator being able to clearly see what the error state is - as I said I think a system of Error codes always available on the front screen with flashing LCD pixels indicating faults would actually be preferable to LEDs having to be hand soldered onto PCB and drilled into position.

It seems pretty obvious to me that this could and should happen - so why is it left up to us to solve this????

Any comments from Prusa here????

PS - JP you are a legend xx - there's no doubting that, but please step up here and get this fixed for all of us.

RE: MMU load fail 3 times forward and retract. Better error coding required.

@decotopian

just to be clear - your posting I referred to did in my (potentially misguided) view indicate not much other than the impression of someone asking Prusa to ship a €0,03 LED free of charge around the world to thousands of users, which is not necessary to run the MMU2s or to even check on the IR sensor status but a mere convenience. No harm intended. 😉

RE: MMU load fail 3 times forward and retract. Better error coding required.

Posted by: @justme3d

@decotopian

just to be clear - your posting I referred to did in my (potentially misguided) view indicate not much other than the impression of someone asking Prusa to ship a €0,03 LED free of charge around the world to thousands of users, which is not necessary to run the MMU2s or to even check on the IR sensor status but a mere convenience. No harm intended. 😉

 

And again; you're completely missing the point here.

You are correct; they shouldnt' have to ship the LED, but should ship the revised sensor and cap with the led built in to everyone.

Please explain to me how to check the ir sensor status when a print or a load - to - nozzle is initiated. i do am really curious!

One cannot expect everyone to have soldering skills, electronic skills, and the correct equipment in order to operate a machine...

RE: MMU load fail 3 times forward and retract. Better error coding required.

ps. i do like the SMD option the best, but already ordered the 5v LED's 5mm.

RE: MMU load fail 3 times forward and retract. Better error coding required.

@Dutch

You're apparently trying to getting me into an argument which I did not intend nor have an interest in to continue. Have a good day 😉

RE: MMU load fail 3 times forward and retract. Better error coding required.

@dutch

Whether a control LED makes sense or not is another question. I find the LED very helpful for quick error analysis. Even though my MMU2 runs very well and I have no problems with it, no matter what material I print with, I still installed the LED's, because it was the same with me, that at the beginning not everything ran perfectly. Especially for beginners it is often quite difficult to attribute some filament load or unload errors to incorrectly adjusted sensors. If a LED lights up or does not light up from the beginning, the cause is more quickly manageable for many users.
Furthermore the installation is quite simple and the necessary parts cost almost nothing.

But as I said, whether one needs such a thing is another question. I like to make things more comfortable for myself.

I myself preferred the SMD version because it takes up very little space and is easy to install. At the sensor cover I only drilled a small hole for the SMD LED.

RE: MMU load fail 3 times forward and retract. Better error coding required.

@karl-herbert

Just a note, thank you very much for that second picture. It put me on a quest for a better designed IR tower. 🙂 I made a few changes and then botched somethings up, I have had some success with the MMU2, but it still required a watchful eye. Most of my issues were IR detection. I removed the MMU and unplugged it from the board. Then changed the nozzle and a few other mods. Well the executive summary is I'm really good at dealing with leaking extruders. ANYWAY, After a number of months I was left with just this IR problem, and if this works, I will next take up re tuning the MMU2/ Thank you!

RE: MMU load fail 3 times forward and retract. Better error coding required.

My comments here are with respect to the Prusa Firmware 3.9.2 MK3S 1.0.6 MMU2S. After upgrading the MK3 with the MMU2S I experienced problems causing lot of frustrations o me. Now I'd like to report my experiences which may help other people.

Please note that I carefully did the IR filament sensor calibration. Inserting the Allen key always showed me a 1 and taking it out took it back t0 0.

Trying to print the sheep example I first observed that the filament was retracted 3 times during the loading phase and the the machine stopped. I thought this was caused by the excessive tightening of the idler screw, so I decided to loosen it a bit. Then the first loading went fine and the machine ran fine until the first color change. The retraction of the old filament worked fine. The loading of the new color also, but the extruder did not start moving. I heard that the MMU kept on pushing the filament fast into the tube - after a couple of seconds I decided to stop the system and moved the extruder manually away. Then I saw that quite a lot of melted filament has been ejected building a blob I was lucky that I attended the print otherwise large amounts of melted filament would have covered my MK3. I cleaned up everything and rerun the print, but got exactly the same result again. I think the firmware should catch this condition and stop the ejection of filament after a reasonable amount of time.

To avoid this I tightened the idler screw again, but then I ran into the 3-times filament retraction issue again. Doing the IR filament sensor calibration again did not fix anything.

After reading your posts I got suspicious and inserted an Allen key and then wiggled on the IR sensor tower a bit. That caused the IR sensor readout to toggle between 0 and 1 (which I did not anticipate before). So my guess is now that when the MMU pushes the filament into the extruder it first moves the extruder idler, so that the IR sensor changes to 1. But later on the force of the pushed filament causes the signal to toggle back to 0 which triggers the firmware to retract the filament again.

I then separated the FS-cover-mmu2s and the IR-sensor-holder-mmu2s. I had to used some force to due this, because these two parts really did stick together. During re-assembling I observed that I now could move these part a bit - something which was proposed in the IR filament sensor calibration procedure.

That made the trick! Now the color changes worked fine - even hundreds of them and I was finally able to print the sheep using 3 colors.

Many thanks for all your comments in this post that helped me a lot.

RE: MMU load fail 3 times forward and retract. Better error coding required.

@reifo

I had similar issues and setting the IR sensor with filament instead of the hex key resolved it. I also set the IR sensor to be less sensitive by moving the tower to the right. As soon as I adjusted that the load/unload issue resolved itself and the printer started printing as I thought it should. 

Thanks for the hints!

RE: MMU load fail 3 times forward and retract. Better error coding required.

I am having a similar, but not the same load issue: It only occurs when using soluble support profiles (either one). The printer prints fine with any of the filaments in lines 1-4, but for the soluble filament in line 5 it will load it to within 2 cm of the extruder (it never has actually gotten it into the extruder). It will stop then unload the soluble filament, then reload it to within 2 cm of the extruder body then repeat the process, until it fails out. Most of the aids for filament loading errors seem to be to check the IR sensor, but this never even gets to the IR sensor. Again this only happens with the soluble print profiles.

Any ideas to fix this?