MMU2S keeps resetting/Red & Green LED's flashing at once.  

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

Unfortunately it is really a painful process that I'm not at all certain to have overcome yet. Here's what I have learned and done so far. 

• The previous version of the selector's knife cut into the parts so I removed it until a new selector came out. 
• That selector had a problem where the filament got stuck on the festo and wouldn't feed, I've printed one that's on thingiverse that has a magnet working in conjunction with the FINDA probe, I'm not yet certain about the knife yet.
• The original idler barrel had a minor warp which caught on the filament by changing its alignment, a second one that I had printed snapped during a filament feed, the third one is in place I have a fourth one printed as a spare in ASA,  which being smoother may work better, as long as the layers do not separate.
• When I changed the selector piece I noticed it's difficult movement left to right. I then bored the rod holes slightly to straighten the path and allow the selector to move freely.
• The Bondtech grub screw came loose, misaligned the filament path causing multiple feed failures. With a, successful feed the extruder made a clicking noise and printed an MMU failure on the LCD. The grub screw's  head was ever so  slightly stripped I ordered new ones from Bondtech

• The cables loosened since I'd 
  opened the unit several times
   making for poor connectivity at 
  the connectors, reseating the 
  connectors cleared that error.
  
  

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

I also had a lot of trouble...but figured out some things...:

My setup is in the V2 lack enclosure; the Idler wore out as well so I've printed this replacement: https://www.prusaprinters.org/prints/5297-prusa-stronger-mmu2s-idler

I've replaced the following parts since they where Updated:

https://github.com/prusa3d/Original-Prusa-i3/blob/MMU2/STL/mmu2-blade-holder.stl

https://github.com/prusa3d/Original-Prusa-i3/blob/MMU2/STL/mmu2-front-PTFE-holder.stl

https://github.com/prusa3d/Original-Prusa-i3/blob/MMU2/STL/mmu2-selector-finda.stl

also as a more convenient PTFE connector at the back I installed this: https://www.prusaprinters.org/prints/6605-prusa-mmu2-ptfe-holder-m10-passthrough-adapter

Also I disconnected and reconnected al wiring and am happy to report that this seemed to have done the trick and I have printed 3 5 colour prints with no problems anymore....

Running an MK3s with MMU2s, latest firmware in an Ikea Lack enclosure V2. Black PSU, MMU2s and printer in normal mode, spools are above the printer.

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@chris-p14

My solution has been to reset the MMU unit prior to every print.  That seems to have fixed the issue, leading me to believe it's a firmware issue, not mechanical.

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

Halleluja, dan-patell,

I mentioned quite some time ago, that whenever I did something from a "cold" machine (meaning just having powered-up the printer previous to the print), it would work flawlessly.
However if I worked on a "hot" machine (meaning continuing with a different print after completing one without resetting or powering down) I would have a quite high rate of failure.

I would also imagine the problem is from the firmware. Or it could be some sensor-value in the software that gets distorted by a wrongly applied correction or calibration over time.

But when I spoke to support and laid down what I found, I was basically told that it has to be friction, or some connectors that are only halfway connected, or wiring that's hooked up the wrong way, or some other basic error someone could do. Well, I personally would not mind to check any connector for proper installation, as it really sounds like a plausible explanation, but in this case I simply said no to disconnect and reconnect all involved connections for the 143rd time...

At this time, I really do wonder whether the MMU is still something that Prusa stands behind, or if it has become some hollow symbolic item which is kept alive so they can separate themself from the rest. After all, if it was really such a success, how come the chinese-clones haven't caught up with it yet...?

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@joe_prints

Hi Joe, has lowering the current of the MMU idler motor resolved this issue for you since? Also, do you change the current in the MMU firmware or the printer firmware? 

Been having this issue for a few months now, been getting around the issue by disconnecting then connecting the signal cable each time.

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

Hi Joe, 

I'm concerned about the fact that you reduce current to make your unit work. This only makes sense if you have some mechanical drag in the unit.

Try taking off the selector motor and see if the selector carriage moves freely without releasing the brass bushings. The two rods should go from the right hole to the left without forcing the rod vertically. 

The idler barrel should also roll freely with the stepper motors off or the unit powered down. 

If either doesn't move correctly you should take pictures and contact Tech support. 

Best Regards 

Phil

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

Following. I’ve been having similar serious issues with my MMU2S since I moved the unit into the V2 enclosure and updated the firmware from 1.02 to 1.06.
The printer was working perfectly. Now it’ll do these weird resets on start up until I juggled the connectors in the MMU board.  This seems to do the trick. The other problem I’ve been having is with MMU2S unloading filaments. The filament will always get stuck in the tube and require manual intervention. Either the standard ramming is too much or my E3D 0.6mm nozzle is have issues. At this stage it’s closer to a mK3S than MMU2S 

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

Guys like someone said before: "Disconnect that piece of shit and be happy" !!!!

I followed everything here! I even soldered 2 BIG FAT cables directly to the board and connected then with my printer. 3 days fine ... then EVERY DAMN DAY a blinking piece of shit with a LOT LOT more issues (as you know!)

In my opinion nail it on the wall an piss over it !

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@ka-wai-lawrence

My recent experience with this unit, and I too have it in an enclosed cabinet, is that friction plays mayhem on the selector body's tolerances. Heat causes expansion making marginal parts bind during travel. That along with temperature expansion in the manufacturing process causing minor layer shift of the parts may be the cause of the flashing christmas lights.

As far as the filament ends, I'm also using a 0.6mm nozzle. Since I don't mostly use Prusa filament, due to shipping costs, I've had to dial in each filament seperately. Some people use oversized Teflon tubing, I opted for Capricorn PTFE in between the selector and the extruder as well as in the heat sink assembly.

Best Regards, 

Phil

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@ka-wai-lawrence-w

At this point it appears that walking the firmware back to 1.05 has fixed my issues! Regarding the filament failing to retract, I suspect that your Bowden tube from the MMU to the extruder body is too short. That was the case with mine, and once I added some extra tube and calibrated the new length it stopped getting hung up at the too-extreme bend just south of the ferrule on the selector.

I enjoy tinkering with this stuff, but I must admit that the MMU has pushed past enjoyment into frustration territory in some cases. I forget all of that when it 'just works" for a print or 3, but it all comes crashing down when I check in on a print 3 hours later and the extruder is hovering over the wipe tower with a warning on the screen and blinking lights on the MMU.

My business requires the MMU capability to be set apart from alternatives. I'll keep on keeping on with this thing.

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@joe_prints

Hello,

I've been having this issue a lot lately. How would you go about changing the current of the idler motor?

I assume it has to be done in the firmware. I appreciate it!

Thanks,

Jon

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

Put the MMU in stealth mode. 

Phil

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@pcweber

Hi Phil,

Has stealth been working better for you? Early on, stealth seemed to be causing more issues than standard mode.

Thanks,

Jon

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@s-g-2008

I am not far from reverting the unit back to Mk3s. I am so sick of spending more time working on the printer than printing. The Mk3 was so reliable. The MMU2 makes it worse than the Anet A6 I started with. 

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@dan-patell

I'll give that a try. I am always reluctant to update firmware for these exact reasons. Every time I service/fix/update the printer it just gets worse and worse. The printer and MMU2 was working fine on 1.02 (for me anyway) until I updated to 1.06. All hell broke loose after that. 

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@jonathan-h27

I've used stealth mode in the past but I am a fervent believer that placing the unit into stealth mode only masks the underlying issue.

Firstly I am starting to get the feeling that the MMU if it's in an enclosure it requires cooling, I'll probably place an extractor above it. 

Secondly I had errors from the outset that were probably exacerbated by placing the mmu2s into an enclosure. I get a rare red green blinking after printing as the temperature gets warmer.

I got the unit with two critical parts having minor level shifting. The warmer temperatures may have made the problem worse. 

Check that the selector carriage moves without binding, you need to remove the motor to do this. 

Roll the idler with the power off or the steppers disabled, verify there's no binding or wobble. If you loosen the idler motor and the section that it mounts to wobbles then there's an alignment issue which may well be the idler barrel.

I hope that this helps, 

Regards, 

Phil 

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

I think I have resolved my MMU2s issues.  I am currently running Firmware 1.05, I backed off my FINDA about 1/16", and re-adjusted my IR sensor assembly ("chimney?") on my extruder. 

It appears the FINDA was too far in, causing excessive interference when loading filament which caused insurmountable jamming.  It also seems that there was excessive drag due to the misalignment of the Bowden connector at the top of the extruder to the PTFE leading to the extruder gears.  This caused some pretty serious "shaving" of the filament upon retraction, which would ultimately accumulate in the brass fitting.  This accumulation would cause excessive drag when retracting, or it would prevent filament from ever getting to the extruder gears.

I think that I am now ready to retry the firmware update to 1.06. I have a nice backlog of orders that don't require filament swaps, so I'll get those done before I take the leap.

Thanks for all of the input! It would appear that the fix was simpler than I anticipated.  Knock on wood...

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

@joe_prints

I know this is old, but how did you implement that code? in the slicer?

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

About two weeks ago I downgraded to older firmware and the issues I’ve been having with the MMU2S disappeared for a while before it started randomly occurring again. I started taking the MMU2S apart today and found the two screws holding the idler to the idler motor were completely loose. This would explain why sometimes the idler can’t seem to get into the correct position and the unit having issues with unloading operations as the idle came loose from the motor and cannot apply the correct pressure to press the filament against the gear.

RE: MMU2S keeps resetting/Red & Green LED's flashing at once.

This problem is comming back to me on a regular basis and when it does it doesnt really seem to help doing anything. MMU2S continues to flash with all leds after power on when doing the move to find position.

Not in Stealth mode(but I have tried it and it dont get better or worse).

Cables released and rescrewed confirming good contact quite some times now, but no joy.

Today I litterally torned the MMU2S from the mk3s. Not happy and I dont have the time to continue searching problem fixes for no gain.