beyond frustrated  

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chris.b65
(@chris-b65)
Active Member

I'm about to downgrade this upgrade because it's a waste of time and money.  Has anyone actually got this printer to work reliably? 

I've spent hours with the online chat, to the point where I couldn't touch the printer for days, cause I'm so sick of dealing with the issues.

  1. filament won't load. Ever. It's detected, but won't actually go into the extruder. Sometimes it appears that the extruder motor is spinning the wrong direction. After a while, it gives up and blames the MMU as it " needs attention". MMU took the filament to the extruder extruder just wouldn't accept. 
  2. IR filament detection can only been seen if you are in support, sensors. If you are actually trying to print something, you have no clue if the filament is being detected or not. So you have no clue which part to blame.
  3. buttons on the MMU are not labeled, and the instructions to use them https://help.prusa3d.com/en/article/mmu-needs-user-attention_2139 don't seem to match what actually happens.  How much would it have cost to put a screen on here so you can actually give feedback to the user. 
  4. My printer now beeps when it's warming up. I've no idea why. It stays beeping until the filament gets to around 170 deg. Chat people don't seem to know why either.

 

Posted : 11/09/2020 10:02 pm
joan.t
(@joantabb)
Veteran Member Moderator

I fitted a 5volt LED to both of my mk3s printers 
it gives immediate status indication

this is the LED on the MMU2S printer...


this shows how th 5volt LED conects to the IR Filament sensor board on my normal Mk3s...    the LED is the same for both printers, but the sensor for the MMU2 is mounted in a tower.

Regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 12/09/2020 5:51 pm
fionnbharre.s2
(@fionnbharre-s2)
New Member

Hi Chris,

Yes people have been able to get it to work... I had difficulties too but slowly I am getting it figured out.  It might help if you change one way you are looking at this situation.  I expected it to just work perfect out of the box.  There are little things to tweak and adjust.  I too was frustrated but then I started to just look at it as an opportunity to learn... and be curious as to what is happening and do some research as to what other people experienced.  There are some youtube videos that help but I dont have those links.  Also look in other areas of this forum many people have similar problems to yours.  Dont give up just try to be curious and you will get it figured out.  I hope that helps...

https://www.antalife.com/2020/07/project-prusa-i3-mk3s-mmu2s.html

 

Posted : 12/09/2020 7:36 pm
chris.b65
(@chris-b65)
Active Member

@joantabb

Hi, it looks like you didn't use a resistor on the led, and you've connected it from the 5V to the signal. Is that right? 

Posted : 13/09/2020 8:57 pm
chris.b65
(@chris-b65)
Active Member

OK, so I added the LED, (with resistor) and it's been very "enlightening". 

step 1. The printer feeds filament to the extruder.

step 2. The extruder detects it, (light goes on).

step 3. Printer takes filament back from extruder. 

this happens 3(?) times and then it gives up giving an mmu error.

I know that the controller can see the filament, because when I re-assmebled it all I tested it. The sensor and the light both corresponded correctly.

So I'm thinking it's software now. (AND I'M A PROGRAMMER). 

Why would it be giving up when the filament is sensed?

 

Posted : 13/09/2020 9:58 pm
matt.b.atkinson
(@matt-b-atkinson)
New Member

@joantabb

What a great little idea! Thanks, for sharing. 🙂

Posted : 11/10/2020 6:55 pm
flowerroads
(@flowerroads)
New Member

I have the same issues, drive rollers spinning in opposite directions, will not print and no response from the support @prusa.  This is an expensive upgrade, and the rest of the printer is great, supported by the best build instructions ever.

Seriously considering going back to single filament.

In response to a comment above, yes I would expect something at this price to work correctly and have the bugs ironed out, we are not beta testers.  I am a professional engineer and need this to rapid prototype, it is not a hobby item or I would have bought a Chinese copy.

Posted : 13/10/2020 12:34 pm
Pavel
(@ruhkukah)
Active Member
Posted by: @chris-b65

So I'm thinking it's software now. (AND I'M A PROGRAMMER). 

Why would it be giving up when the filament is sensed?

 

It's because it uses an algorithm to detect a block in your hotend. Since you can read the code, check out mmu.cpp here: https://github.com/prusa3d/Prusa-Firmware/blob/MK3/Firmware/mmu.cpp

You need can_load() function. As you can see, it moves a filament 60mm forward, then moves 52 backwards, then moves by increments and checks whether IR sensor is still on. If during the 60mm forward move the filament slipped on the Bondtech gears because of a friction or a block in the hotend, it will be pulled out from the IR sensor completely and this will indicate to the firmware that the extruder can't load the filament reliably to the hotend. It tries to do 3 times because of "const uint_least8_t max_retry = 3".

Troubleshooting is difficult in this case: I would check that a path to the hotend is clear and the filament can move free all the way to the nozzle; check Bondtech gears tension - if it is too low, you may encounter issues inserting the filament. If this problem only happens with a filament that was previously pulled from your extruder then there may be an issue with your tips. If this only happens with freshly cut filament tips, then increase friction or hotend blockage is the answer

Prusa Bear MK3S + MMU2S. Hotend: TriangleLab Dragon Hotend + Rubber Sock.
TheZeroBeast MMU2S firmware...
Posted : 14/10/2020 10:38 pm
Pavel
(@ruhkukah)
Active Member
Posted by: @chris-b65

How much would it have cost to put a screen on here so you can actually give feedback to the user. 

 

Indeed. That's why I choose to use a modded firmware which provides more clues as to what's going on with the MMU:

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

It works great so far. Yesterday I finished a 340 color changes print with a single issue in the beginning

Prusa Bear MK3S + MMU2S. Hotend: TriangleLab Dragon Hotend + Rubber Sock.
TheZeroBeast MMU2S firmware...
Posted : 14/10/2020 10:46 pm
fromprusa
(@fromprusa)
Member Admin

@chris-b65

Stupid question, did you double check to make sure the filament sensor on the extruder is still properly aligned?

If you think its a software issue, you could try and write down your live Z settings, then reflash the printer firmware and also the MMU2 firmware and do a factory reset to clear out any settings, and then redo the first layer calibration.

If you are still having issues... you can try recalibrating the length of travel the filament goes from the MMU into the Extruder.

It can be found here .

https://help.prusa3d.com/en/guide/service-menu-individual-filament-calibration_86376

 

But in general, the MMU2 does take time to get it sorted and can be frustrated, I always tell people to take a lot of breaks and to step away from the machine and try to go back with a clear head...

Can you either try or confirm you did try these before so we can see what can be done.

Thanks

Shane

 

Posted : 15/10/2020 3:30 pm
chris.b65
(@chris-b65)
Active Member

@fromprusa

The filament sensor and alignment is what I've been working with mainly.  I've recently taken apart the extruder and found a clog so that was part of the problem. The problems started before the clog but the clog didn't help. I've stepped away for about a month. I just feel sick when I think of how reliable it used to be and now can't do the most basic of things. I just can't force myself to get back into it.

Posted : 15/10/2020 4:03 pm
fuchsr
(@fuchsr)
Trusted Member

@chris-65:

I'm in a similar place. Yesterday, I decided to give up. I uninstalled the MMU and I couldn't be a happier person. Not that it never worked. But it's just way too temperamental to be relied upon. I don't mind tinkering but not all the time. When I realized that I ended up doing mostly single material prints with Load to Nozzle, hey, then why do I need the MMU at all? One of those cold and long winter nights I'll be reverting the extruder back to the original Mk3S design and put this whole experience behind me. And yes, I'm sure that with a lot of hours invested I could have made it more reliable, but my primary interest is in designing and printing, not hardware and software debugging. The Mk3S was such a revelation -- none of the stuff I had to do with my other printers to make them do what I wanted them to do was necessary with this marvel of a printer. The MMU -- felt like a throwback to those dark times 🙂

Posted : 28/10/2020 10:51 am
flowerroads
(@flowerroads)
New Member

@fuchsr

Same here, just removed the MMU but left the extruder with the modification, I see no reason to change back.  Prusa support have been great but I want to print not fettle.  The only regret is the cost.

Posted : 28/10/2020 2:48 pm
chris.b65
(@chris-b65)
Active Member

My printer has sat idle for 2 months, bought a replacement from aliexpress.

Posted : 28/10/2020 3:48 pm
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