MK3S/MMU3 extruder not loading  

RE: MK3S/MMU3 extruder not loading

Same for me on my MK4 that I just installed the MMU3 on. The filament is never straight enough off the spool to go straight through. I pull the PTFE tube and push it up and if it curves, I use a small screwdriver to guide it into the hole. After that it loads perfectly. I have tried tighter and less tight on the Idler with no change, so I left the Idler relatively loose and it seems just fine.

RE: MK3S/MMU3 extruder not loading

interesting. yeah, the  end of the filament often has a curve to it doesn't it! I'll often remove that if I can - but it's wound around a spool so it always has some curvature.

I'll mess with idler tension some more. and of course the sensor.

RE: MK3S/MMU3 extruder not loading

I know my pulleys on the motor are perfectly aligned, it may just be the tension of the idler ones. The filament shoots off to the side, instead of going into the next hole, due to the cast of it being on a spool. I don't feel the sensor is the issue, the filament is not to that point yet. I have gotten used to popping the tube out and feeding it through with a screwdriver to aim it to the second hole. 

Overall, I love my Prusa MK4. 

RE:

I was having the same issue (one of many with the MMU3 over the MMU2). One of the things I tried was to replace the idler with this one https://www.printables.com/model/892876-rattle-freequiet-prusa-mmu3-idler

It fixed the main reason I was trying it and also fixed the misfeed issue I was having.

I think part of the cause of the misfeed is the Pulley body has wider channels before and after the gear than they did with the MMU2 Pulley body.

RE: MK3S/MMU3 extruder not loading

Posted by: @rgordon0

Have upgraded an Mk3s/MMU2s (which barely got use because it was so problematic) to an mk3s(+ appropriate parts)/MMU3.

MMU selector/FINDA sensor working well, Filament sensor calibrated per manual. But most of the time the extruder isn't getting the filament - requiring me to remove the PTFE tube and hand-feed the filament in. As you can imagine, that's not going to scale out of test modes!

I've played with extruder idler tension, and recalibrated the filament sensor, multiple times. Looking for clues or further debugging info.

I had the same error too and I solved it. I my case it was an calibration error of the filament sensor from the extruder: The sensor was calibrated "too good/fast" and for this the MMU motor stopped when the extruder catched only the tip of the filament. This was not enough to catch it completely. So I recalibrated it to react much slower and it now works very fine. Be careful when you turn the screw to tighten the calibrated sensor. Tighten the screw will always change the calibration a bit. You have to calculate this.

RE: MK3S/MMU3 extruder not loading

well, I think I have the calibration correct now, it's loading much better. 

Charging the channels with new filament the first time is still something of a challenge, I often have to open up the top and make sure the filament is all the way through into the channel on the other side. Curvature of filament I suspect.

Have had a few hundred cycles now, with only 1 error - when the tip of filament somehow got rammed into something too wide to be withdrawn back up out of the extruder! Not sure what caused that - it's only happened once so far. (Is it just me or is white PLA filament just more temperamental than other colors?)

RE: MK3S/MMU3 extruder not loading

I had the problem only on slot 5. found the upper motor screw a bit loose. I untight all 3 screws, push the motor  up in direction to selector and tightend the 3 motor screws  again. After that i perfom a filament load on slot 5 and it work's 100% on the first try.