MMU2 Pulley Running in the wrong direction  

Active Member

Good day,
We purchased a MK3S printer with the MMU2 multi material loader. The printer came assembled. We added the expansion kit here. I ran the machine with only one color for a couple weeks and it performed perfectly although each time I would load a program it would say it was for a different printer. (I had selected the correct model for the G-code creation each time)

 As it turns out the guy that added the expansion kit had inadvertently switched the MMU2 connector (three wires: white, black and red) with the 4 wire connector (brown, green, white & blue) position on the RAMbo board. When I discovered the problem I switched the plug positions and put them where they are supposed to be. The MMU connector toward the bottom of the RAMbo board and the 4 wire connector above it. Now that the things are straight I get a few different selections in my LCD panel when I start the printer up however I have a problem that I have not been able to overcome.
The pulley on the MMU2 that feeds the filament into the selector and down the tube into the extruder is rotating in the wrong direction. When I tell it to load a filament it does a couple different things. Sometimes it just clicks and all 5 red lights start flashing. Other times it will try to load the filament but the MMU2 pulley is turning in the UNLOAD direction and the pulley on the extruder is turning in the LOAD direction. Then I get an error that says the MMU2 needs user attention.

 Only one time did the MMU actually start to feed the filament in the right direction but then half way thru getting the filament to the hot end extruder it suddenly unloaded the filament rapidly and then I got the error 'MMU needs user attention'. Can someone please tell me if I will be able to get this problem corrected? I've read all the forums and have only found one person who had this problem. And there was no real solution offered and the original poster did not say if they ever got the problem corrected. I would appreciate any help that can be offered.

Posted : 29/12/2020 10:24 pm
Noble Member

If a stepper motor runs the wrong direction, it's most likely that (some of) the wires from the motor are not connected to the proper connections on the driver board.  Check the wiring carefully.

Posted : 29/12/2020 11:24 pm
Active Member


I agree. However I've checked and double checked all the wiring. Hence finding the issue with the connectors being switched. But beyond that I can't find anything that is not connected correctly.  The wiring to the board on the  MMU has connectors that have a notch allowing them to only be plugged in in one position.

Posted : 30/12/2020 12:35 am

If this were a mmu1 to mmu2 upgrade the motor for the filament feed and the motor for the selector drum, would be re purposed extruder motors. If you are concerned about the motor rotation direction, you could temporarily connect the filament pulley motor in place of the mk3 Extruder motor and see if it turns the same way when instructed to load filament.     
If it rotates the other way, then the motor wiring is wrong,  if it turns the same way, the issue is in the MMU2 controller. 

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 : 30/12/2020 12:48 am
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