MMU2S Print Failure and Firmware Update Failure
I have a MK3S+ with a MMU2S that has been working fine for the last two years. Recently I have been getting a failure on the MMU2S where all five LEDs flash green and red at the same time - this normally happens about 2 hours into a two material print. I tried the rest button and then all flashed red (This was in the middle of a print, which the troubleshoot video says is not possible). I pulled all filament out of the MMU2S and cleared the flashing lights (manually reloading filament), but when it started printing again it used the wrong color.
I followed through the video on how to troubleshoot the five flashing lights. I checked all connections, blew out all connections with compressed air, updated the printer firmware (MK3S_MK3S+_FW_3.14.1_MULTILANG.hex). I tried printing after this and it when through the start of the print cycle, zeroing the bed, but it never attempted to load filament. I then reflashed the MMU2S (MMU2S_MMU3_FW3.0.3+896.hex) and now I have three green light hold steady, one slow flashes red, the last flashes fast green. The main shaft spins one way fast and the other way fast until it jams, then all lights go out. The MMU2S's lights only turns back on when I hit the rest button but it goes through that whole process again. It only responds to the center button on the MMU being pressed - the idler spins fast one way and fast the other until it jams. The printer does not recognize it as being attached. I recorded a video of the error.
It does not make a difference if filament is loaded (i.e. the finda probe is triggered).
Anyone know how to fix this?
RE: MMU2S Print Failure and Firmware Update Failure
Update 1:
I worked through the issues with the Prusa 24/7 Chat. The issue connecting to the printer has been resolved – I reconnected to the MMU in the settings feature (the connection was lost when the printer firmware was updated.
However, the MMU still fails about one hour into the print, same error that sent me down this rabbit hole. All five LEDs flash green and red at the same time 2 hours into a two material print. Now this time it shows an error code 4306.
https://help.prusa3d.com/article/mmu-mcu-error-04306-mmu_492340
As noted above, I went through every cable connection, took them apart, cleaned them, and put them back together. But this is the same error.
RE: MMU2S Print Failure and Firmware Update Failure
Update 2:
I was successfully able to run the two-material print (PETG). In the past I have been running the printer in the Prusa enclosure with the doors closed and the top panel two thirds of the way on. This time I ran it with the doors open and the enclosure fan running (top panel still two thirds on). This was the only change I made from the last failure. It seems like the MMU is failing due to the temperature the MMU board sees, which is a problem for when I want to print ABS. I don’t suppose anyone has any recommendations? I find it surprising that the MMU is failing now after two years – it has been running in the enclosure for close to a year without any issue (without the enclosure fan running or the doors open and generally with the top panel mostly closed).
RE: MMU2S Print Failure and Firmware Update Failure
Update 3
I successfully completed a 16 hour print with two color changes every layer and another three hour print with two color changes every layer without issue. On my third print, I got four hours into an eight hour print before the same error occurred (4306) with both red and green lights flashing. I followed the video instruction for troubleshooting the issue, clicked the reset button, and the MMU reset. However, I noticed that instead of going to filament slot #1 or #3 after the reset that it tried to pull from filament slot #2 (the print was only using filament slots #1 & #3). There is no filament there so it failed and the same 4306 error occurred. I then manually loaded filament in slot #2 and reset the MMU. It tried again to pull filament from slot #2 but it failed. I have no idea why it tried to pull from slot #2 as that is not a filament I included in the file. Nothing I try to do lets me recover the print, the error message stays.
Can someone please help?
RE: MMU2S Print Failure and Firmware Update Failure
Update 4
Prusa Customer Support directed me to reflash the firmware on the MMU per the article 2187 ( https://help.prusa3d.com/article/mmu2s-leds-meaning_2187). I reflashed only the MMU with a fresh copy of MMU2S_MMU3_FW3.0.3+896.hex, reconnected the printer to the MMU in settings since it disconnected with the new firmware. It still doesn’t work, same error (4306), but a new failure method. I tried to load filament - it loaded the first filament but when loading the second it failed and went to the green and red blocking light error immediately. Nothing except a MMU reset recovered it but it continued to happen. I tried to tune (the idler) in the 4306 error window but it never went to the tune window, just popped right back to the supremely annoying beeping error window (beeping as in the sound it makes while displaying the error message, not an expletive on what I think about the error window).