Filament fails to unload after runout
When filament runs out on the MMU3 the print stops as it should and tries to unload, but the filament fails to reach the pulley wheel. It stops maybe 2mm short. So I have to disconnect the PTFE tube from the extruder and push the filament the last millimetre or so.. Seems like the FINDA sensor is placed too far from the pulley, or it simply is too slow to trigger when the filament runs out? In the pictures you can see the yellow filament as far back as it gets without manual help.
RE: Filament fails to unload after runout
I just completed the assembly of my new MMU3. I bought the model that I had to assemble myself so I don't know if this makes it different than your but I had an issue that looked and sounded just like yours. Here is what I did to troubleshoot it.
1. I looked at everything in the filament path from the Hot End to the spool and I determined it was somewhere in the MMU3 device.
2. I saw several posts that discussed cleaning out the pathway holes in the MMU3 and some that even said to drill them out and make them wider. I chose not to do any of this.
3. I openened the top of the MMU3 and pressed the middle button to make it act like it was loading filament into slot 1 and I noticed the filament in slot 5 moved a tiny bit at the same time.
4. I knew nothing was engaged to push the filament so the pressure to move the filament had to be coming from upstream of the MMU3.
5. I noticed the Filament Buffer Assembly was attached to the printer, but it was sitting on my desk. As I watched the filament unload, I saw the filament hit the bottom of the Buffer and that created enough pressure to push the filament back up the tube toward the MMU3.
6. I raised the Filament Buffer up to give the filament just enough room to hand out the bottom of the Buffer assembly. This removed the pressure and things started working.