Filament tips with long strings
Hi,
I wonder if anyone is also experiencing this problem. When the MMU3 pulls back the filament from the extruder (for a filament change or just at the end of the print), the tip has a string of about 30 mm. That string keeps in the way of the moving head of the MMU3 which I'm afraid can cause problems and also leaves some filament debris in that area.
How to avoid this long string?
In a related question, since the MMU3 have two blades inside, wasn't it supposed to make a clean cut of the filament's tip after each filament change? If not, what's the purpose of those blades?
The picture shows that long string at the filament's tip. I've pulled it a bit from the MMU3 to be more easily seen, but at normal operation the only thing that protrudes form the filament hole is the long string, not the filament itself.
RE: Filament tips with long strings
the cutter blades are used during load attempts, not unloads.
I suspect the extruder is a bit hot. try reducing the extruder temperature.
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
RE: Filament tips with long strings
Thank you for your help, but the extruder is not too hot. I'm printing at 225ºC.
You say that the blades are used for loading filament. I don't understand how. I always cut the tip before pre-loading the filament into the MMU3. During printing, after filament changes, the long string stays there as a filament is re-loading into the extruder (one can see it through the transparent PTFE tube).
So, at least in my case, it looks like the blades are never used.
Am I interpreting things in a wrong way or is something not right with my MMU3?
Thanks!
RE: Filament tips with long strings
Did you ever work this out?
Thank you for your help, but the extruder is not too hot. I'm printing at 225ºC.
You say that the blades are used for loading filament. I don't understand how. I always cut the tip before pre-loading the filament into the MMU3. During printing, after filament changes, the long string stays there as a filament is re-loading into the extruder (one can see it through the transparent PTFE tube).
So, at least in my case, it looks like the blades are never used.
Am I interpreting things in a wrong way or is something not right with my MMU3?
Thanks!
RE: Filament tips with long strings
I have seen this also, that the tassels on the filament seems rather exaggerated. I adjusted the temperature to reduce the fluidity of the filament which shortened it slightly. However, the design of the MMU3 also complicates it's own process of preparing a new end when loading. So should the software not get two successful resistance checks at the extruder it will unload the filament and do a cut cycle. But if the filament has a pronounced tail the filament end will cut and the tail will wrap around the selector head, in the standard configuration the MMU3 tilts backwards and gravity holds that tail in the mechanism doing the cutting and feeding. In my case my MMU3 is tilted at a 45 degree angle towards the extruder which allows most times for the cut end to fall away, but in some instances when the filament is very dry it generates static which sticks the cuttings to the selector cutting assembly and dust to the filament holes, and then when the selector returns to the hole in question the cuttings will be rammed into the hole for filament, plug the ball, and grind up filament into powder. What I am contemplating doing is including either a brush that cleans the selector face and cutter or a air jet like what is done in industry for exactly this issue. The other issue I have found is during extent ended cycles the extruder nip area (extruder cavity around the gears) can get built up with pulled off filament tassels, and get to the point of spreading the filament gears apart. This was a really poor design as it wound encapsulate any and all dust or cuttings when the gear abrade the filament to push it into the hot end. I have not thought yet about how to redesign the filament door to allow ejection of the dust and trimmings. But yet again in industry these kinds of things are always addressed with systems to eject dust.