I found serious design error in MMU2 electronics hardware  

RE: I found serious design error in MMU2 electronics hardware

It's not a revers polarity protection. It's a flow back protection. if the USB voltage is more than the main voltage, you have a risk to have a flow back courant in the main board and damage the 5V power supply of the main board.

After several issu in my MMU2 in a 2 year of try (max 1000 fillament change with no issu if i have a big luck) i have unmounted the MMU2 defenitively... and wait the Prusa XL with great anticipation 🙂 My prusa is "vanilla" (Linear rail in X and Y, all part in PC and a box + regulated heater).

RE: I found serious design error in MMU2 electronics hardware

Could you replace the diode in it with one with a lower voltage drop? Or even just wire a second diode with a lower voltage drop in parallel with the original? I'm definitely not an expert, but my understanding is this would lower the overall voltage drop, while still providing the protection.

RE: I found serious design error in MMU2 electronics hardware

The diode is there to prevent a USB cable connection’s 5V supply from back driving /shorting the 5V supply from the Einsy. 

Your best bet, IMHO, is to disconnect the 5V supply from the Einsy, and provide an adjustable 5V supply to the MMU2S.  Adjust to get 5V on the on the opposite side of the diode, and life with the MMU2S will be better.   It has been for me at least. 

RE: I found serious design error in MMU2 electronics hardware

Posted by: @kg

The diode is there to prevent a USB cable connection’s 5V supply from back driving /shorting the 5V supply from the Einsy. 

Your best bet, IMHO, is to disconnect the 5V supply from the Einsy, and provide an adjustable 5V supply to the MMU2S.  Adjust to get 5V on the on the opposite side of the diode, and life with the MMU2S will be better.   It has been for me at least. 

So the advice is to disconnect the internal power and plug the MMU2 into the wall through the USB port, to get it 5v? 

RE: I found serious design error in MMU2 electronics hardware

I haven't had the best results.. so far still happening a fair bit with the USB power source.

RE: I found serious design error in MMU2 electronics hardware

Is there already a new version of this board? seems the repository is not updated for the last four years although there is a 0.4 version in production. Is this version more stable and not having this reset problem?

RE: I found serious design error in MMU2 electronics hardware

Posted by: @cowboyhenk

Is there already a new version of this board? seems the repository is not updated for the last four years although there is a 0.4 version in production. Is this version more stable and not having this reset problem?

No. If there would be, I would have bought it myself as well. The original reporter mentions that the issue exists on board revision 0.4.4 and that's in my understanding the latest revision as absolutely nothing has been done by prusa to this issue. Even the ticket is still open at https://github.com/prusa3d/MM-control-2.0/issues/15 and there is absolutely no progress in there either. Looks like this product has been abandoned for good long time ago.

RE: I found serious design error in MMU2 electronics hardware

Well, about a year ago in this thread @same-old-shane said otherwise… But it surely does not look like Prusa still puts much effort into the MMU2 project.

RE: I found serious design error in MMU2 electronics hardware

I think Prusa shut down the project a long time ago and is not developing much there due to low priorities.

wbr,

Karl

RE: I found serious design error in MMU2 electronics hardware

I just find it very annoying that the upgrade is still being sold, although it was never fixed to work properly. I have to say that I am disappointed how this particular upgrade has been ignored from the beginning and except of a few firmware upgrades in the beginning, it has been ignored completely by prusa.

Somehow I have the feeling that even the Voron ERCF might be better "supported" in the near future as there is at least some development going on.

RE: I found serious design error in MMU2 electronics hardware

I removed the MMU2S from my mk3s+....happy with a reliable printing workhorse once again....

RE: I found serious design error in MMU2 electronics hardware

Posted by: @cowboyhenk

I removed the MMU2S from my mk3s+....happy with a reliable printing workhorse once again....

I use the machine primarily as a single-medium printer, but I do have the MMU2S still in place if needed, which lately has been rarely since I got a dual-extruder Ultimaker early in 2021 and only use the MMU when I need three or more media.

I added a switch to take the MMU out of the circuit when not needed.  The little enclosure is in the Prints section (excuse me, on the 'Printables' site) and there are two tapped holed in the Prusa frame that look like they were already intended for something like that.

I also added a few other tweaks, such as the thumb screw extensions and quick-release fittings for the Bowden tubes.

RE:

Months later, and I've had zero instances of the all lights blinking, after adding in the DC-DC.  But I primarily do single extruder mode.

RE: I found serious design error in MMU2 electronics hardware

I created this thread.

I am quite disapointed with Prusa - no response at all.

Prusa: [BEEEP] the community 😉

I guess this is just $$$ after all 🙁

RE: I found serious design error in MMU2 electronics hardware

Is this device officially out of support?

RE: I found serious design error in MMU2 electronics hardware

I do not know, and I do not care.

I Strongly dislike companies that does not "own" their mistakes - after all: we all make them from time to time...

And this is a 100% clear case: the MCU producer says: "you can not do this".

🙂

RE: I found serious design error in MMU2 electronics hardware

Hello all; 

Posted by: @robin

Well, about a year ago in this thread @same-old-shane said otherwise… But it surely does not look like Prusa still puts much effort into the MMU2 project.

First off, I apologize not for paying more attention to this thread, that is my fault. From that lack of attention I can see why some of you think the MMU project is dead. I can still assure you that it is not, but I can not go into details (NDA agreements and such). What I can tell you is to keep an eye out in the next several months to see about the MMU. I will answer what I can for you now. 

I think Prusa shut down the project a long time ago and is not developing much there due to low priorities.

I can assure you it's not a dead project, it has always been an active project. 

I created this thread.

I am quite disapointed with Prusa - no response at all.

Prusa: [BEEEP] the community 😉

I guess this is just $$$ after all 🙁

Your post was forwarded over to the developers when it was created. One thing with developers is that they can not spend time on the forums. Normally the process for them is that they respond to issues brought up on github as those tickets go directly to them. I am not saying you did not submit anything to github, I am letting you know of the usual process for them. 

For the other 2 comments. I can understand the frustration and anger. I can tell you that it is not the case. If they didn't care about the community and their customers, I wouldn't have done the things I did before. I used to work for Prusa's support department for a few years. I left the Czech and went back to the U.S. and eventually I left the company and worked for a few other places within the "trade". I ended up returning to Prusa as I found that other places didn't have the same level of commitment to their community and customers and I ended up returning to the Czech all together. Now you can call me a fanboy and the usual stuff, but I can honestly tell you without any hesitation or deception that if the company didn't care about the customers and it was all a cash grab, I wouldn't be here. 

I just find it very annoying that the upgrade is still being sold, although it was never fixed to work properly. I have to say that I am disappointed how this particular upgrade has been ignored from the beginning and except of a few firmware upgrades in the beginning, it has been ignored completely by prusa.

Let me say this before I answer this one, I am NOT saying anything like "Oh it's the customer / users fault". I do know that there are people who have / had issues with their MMU's, and on the flip side there are others that it works without issues (or issues that others experience). Situations like these have been looked into and data was gathered and was not ignored. 

Is this device officially out of support?

Nope, it is not.

As far as the rest of the concerns on here. I will try and see what I can do about getting more direct answers. I do understand your concerns and your frustration and it has not been ignored. Just keep one thing in mind. I am NOT a highly technical guy / developer / or engineer. So with some of the comments and such I would need to consult with others and see. What I can get answers for, I will. What I can't, I will need to work on further. I know you guys have been patient with things and I hope that you can be a bit more patient a bit longer. 

RE: I found serious design error in MMU2 electronics hardware

Thank you for the explanation. We will see what the future will offer. Some improvements could still be made to the mechanics. Perhaps it would also be conceivable to use a different board. On my old MK3, a mechanically modified MMU2 runs quite stable so far, but I only use it as a "tool changer".

wbr,

Karl

RE: I found serious design error in MMU2 electronics hardware

Yes, thank you for updating us, Shane.  I did get the impression that the MMU2S was, or was soon to be a dead product.

RE: I found serious design error in MMU2 electronics hardware

I've been using an MMU for close to a year and generally had good success with it - the only real issue has been periodically it starting to throw under voltage errors, sometimes before the print starts and sometimes (much worse) during the print as it tries to change filament. But I've had hundreds of successful prints from it and the issues had been relatively rare.

But...

Last week I was totally unable to get a print started because every time it did the limit check it would do each of the expected moves, move to the correct filament slot and then start flashing under voltage. After a few seconds it tries again and errors out again.

It had done this before but usually turning the entire machine off for a few seconds then back on would fix it but on this particular day it refused to start working.

I got so frustrated with it that I literally ripped the unit off the machine (damaging a bunch of stuff in the process as you can imagine) - I've since fixed everything but not re-installed the MMU2 and likely wont unless I can find a way to prevent the issue.

What's sad is that the actual filament changing has worked really well for me, it's just the voltage issue that kills it.

The under voltage (all lights flashing both colours) has gotten progressively worse/more frequent recently leading to the day where I just couldn't get it to work at all. Does the problem discussed in this thread seem like what could be the cause of my issues? or something else

Ta.