Filament sensors not coordinating?
I had a problem with a print last night where after a filament change, the machine apparently didn’t know that the filament was in the hot end, so it just kept extruding filament until there was a massive ball of molten filament around the nozzle. This morning I replaced the hot end, calibrated the IR sensor and cleaned everything, but it still is doing this. It seems like the machine doesn’t know that the filament is already at the hot end, so it keeps on extruding. And it’s making a grinding sound as well - sounds like it’s coming from the extruder on the MMU.
IR sensor
That looks like the IR sensor on the extruder is not triggered. In this case the MMU continues pushing the filament even though the extruder gears are allready engaged, that's causing the grinding sound. You can test that by pressing in the little lever on the extruder's chimney to trigger the IR sensor (do that after the filament reaches the extruder and the grinding sound begins), if that is causing the MMU to stop feeding and the MMU idler to disengage you have found the problem: recalibrate the IR sensor (again). The LED mod of the extruder helps to diagnose this cases a lot...
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RE: Filament sensors not coordinating?
Thank you! I have been thinking about doing an LED mod - I have a bunch of spare through-hole and smd leds I could use - can you send me a link to the led mod you used?
RE:
No, I can't - I build my own little mod because I did not want to modify the extruder. I split the signal of the IR Sensor from the cable to the extruder (near the Einsy enclosure) with a transistor and did the same with the FINDA signal from the MMU and fixed 2 LEDs, one red one green to the frame next to the MMU. It works like a little traffic light. Red only when no filament detected, red and green when filament in transit between FINDA and extruder and green only when filament successfully loaded and detected in the extruder. Looks like this:
Basically like this: https://www.prusaprinters.org/prints/42893-prusa-mmu2s-finda-troubleshooting-aid but twice..
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