Mmu2s not swapping filaments
I have been having a problem with filament reaching the extruder. The mmu2s and hotend don't seem to work well together sometimes and lately filament has been getting snagged it seems just before extrusion I'm causing the mmu2s to load and unload over and over.
Physically pushing the filament once it's at the hotend and at the end of the mmu2s feed, it seems to work and print just fine. Having to do this for every filament swap is unrealistic and defeats the purpose of the mmu2s.
I have checked all screws to be tight or loose enough swapped PTFE tubes from the OGs to after market and back. Nothing seems to make it work other than physically forcing the filament to load.
Ive also disassembled it and pushed filament through to ensure it all lines up as it should with no noticable issues.
If I had to take a shot in the dark it seems like the filament gets stuck on the top of the PTFE tube that is in the hotend heat sink but I'm using new prusament filament with the correct size tubes and a nice clean it tip. Tubes are well organized with no hard bends.
Thanks in advance for any and all help!
RE: Mmu2s not swapping filaments
I have some of the same issues. Have you had any resolution? Sometimes it will load/unload fine, and then I'm having to give it a push to get it through the extruder idler at other times. My filament tips are how they should look. I've had success printing some MMU prints with no interventions, and then others..... With the small test print I was running to try and dial in my MMU settings, doing an intervention every half dozen color changes is beyond annoying.
RE: Mmu2s not swapping filaments
So today I noticed that the idler barrel in the mmu2s had both screws loose causing misalignment issues and trouble pushing the filament at times. Beyond that I have installed Sneaks extruder idler door to better trigger the IR sensor ( https://www.prusaprinters.org/prints/3417-mk3smmu2s-modified-extruder-idler-mmu2s1-solves-ir ) and the magnet mod for the FINDA sensor by 78zeros ( https://www.prusaprinters.org/prints/25169-mmu2s-r2-selector-finda-remix-with-magnet ) . I have increased the length of the PTFE tube between the mmu2s and the extruder a little bit (didnt even measure) as well as replaced it with wider inner diameter tube. I then made my own tube for the inside of the extruder that is maybe .5mm longer than the stock one with the same bevel on both edges. I also beveled the brass push fittings that screw into the extruder and mmu2s to ensure there is no snag. I also noticed that tightening the extruder housing that holds the hotend in place too much can cause a clamping force on the ptfe tube in the extruder. Finally I had to retighten my extruders gear shaft tension screw and even used locktite on it this time as it had become loose too. After all of this, i am roughly 30 unassisted tool swaps into a test print as of typing this response.
i also installed my own LED to show when the IR sensor is being triggered so i can rule that out as an issue. here is a picture of my temporary and removable solution as well as a diagram to install a cleaner more permanent LED for the IR sensor. For my version its just a 5 volt LED with a 1k resistor on the cathode jammed into the back of the connector on the sensor. Cathode to white wire anode to red wire.
Prusa support has been extremely helpful in my efforts. When they link you an article asking you to check the assembly or whatever it may be, its not just a general article and telling you to go over each little screw and bolt to rebuild it. they link you right to what they think the issue may be and how to fix it and wait for you to attempt the fix they suggest before moving forward without rushing you. I genuinely like using the support system they have here.
RE: Mmu2s not swapping filaments
it randomly did a full blown filament swap mid print including the beginning of the print purge blob on the purge tower. it prompted me to remove old filament and hit the button. it then resumed printing at the correct layer. no idea what thats about. no obvious reason what prompted that as i had not touched the printer in almost an hour
RE: Mmu2s not swapping filaments
it randomly did a full blown filament swap mid print including the beginning of the print purge blob on the purge tower. it prompted me to remove old filament and hit the button. it then resumed printing at the correct layer. no idea what thats about. no obvious reason what prompted that as i had not touched the printer in almost an hour
This happens when FINDA triggers the filament runout procedure. You probably should recalibrate FINDA.
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