Nextruder filament sensor / flexible filament
I can't get Filaflex40 to pass the filament sensor in the heatsink.
No problem to pass the side sensor.
Any idea what to do?
Best Answer by Etadriver:
Hello, yes, this is a known problem. The filament is so soft that the force of the spring and ball of the Nextruder filament sensor compresses it to the point where it's in the off state. With this type of filament, you can deactivate the Nextruder filament sensor. Alternatively, you can switch to a mod with a magnet.
RE: Nextruder filament sensor / flexible filament
Well, after several attempts the filament gets through the heatsink sensor.
But the sensor does not activate loading the filament.
Using PLA there's no problem.
RE: Nextruder filament sensor / flexible filament
Hello, yes, this is a known problem. The filament is so soft that the force of the spring and ball of the Nextruder filament sensor compresses it to the point where it's in the off state. With this type of filament, you can deactivate the Nextruder filament sensor. Alternatively, you can switch to a mod with a magnet.
RE: Nextruder filament sensor / flexible filament
I'm printing rather soft TPE83A and everything works OK, but I have to pull the Teflon tube, cram the stuff through the sensor with my fingers right at the fitting, then replace the tube. It can't go around the bend and overcome the sensor. I should probably top-feed anyway, but this works for now.
RE: Nextruder filament sensor / flexible filament
There is probably some history to this -- but why is Prusa using the mechanical ball & spring sensor? Shouldn't an optical sensor do the job nicely, without exerting any mechanical force on the filament? Just an LED on one side of the filament path, photo-diode on the opposite side, and some apertures to define the light path.
I realize there are transparent filaments too, but they will strongly diffract the light. So a simple optical arrangement with slit apertures on both sides should work, I'd think.
RE: Nextruder filament sensor / flexible filament
Thank you. Very helpful 👍
RE: Nextruder filament sensor / flexible filament
This is exactly the solution used on the first MK3s and was very quickly thrown into the dustbin of history precisely because of its absolute unreliability!
RE: Nextruder filament sensor / flexible filament
This is exactly the solution used on the first MK3s and was very quickly thrown into the dustbin of history precisely because of its absolute unreliability!
That's what I was suspecting when I mentioned "history" -- they must have tried that before; it's such an obvious solution. But why couldn't they get it to work?! My old Anycubic i3 used such an optical filament sensor, and while it was a rather simplistic printer with various issues, the filament sensor worked just fine. Including with transparent filaments.
I wonder whether Prusa gave up too early on optimizing the optical sensor. It's easy to say "let's solve this once and for all" and go for the mechanical ball & spring (or magnet) solution, to decouple the sensing from the optical properties of the filament. But then, when you replace the direct filament feed of the Mk3 and 4 with a long Bowden tube, you realize that it was not "once and for all"...
Curious to see what solution we will find in the Bondtech INDX!
RE: Nextruder filament sensor / flexible filament
The current mod/solution that works quite well is to replace the spring with a magnet. This makes it much easier to push soft filament past it. The second is to replace the idler bogie and main plate so it doesn't get squashed and wrapped around the nextruder gear.
RE: Nextruder filament sensor / flexible filament
It doesn't seem like a terribly difficult problem. I'd think just a slightly lighter spring would do the trick.
The Mk3 optical sensor failed with certain colours, mostly greens and some pastels - in retrospect I suspect that these matched gaps in the light spectrum of 'white' LEDS - a related problem on ships at sea mean that until recently LED lamps couldn't be used for chart tables as maritime charts use colours that the lamps didn't have - newer combination lamps and induced florescence have solved the problem for large vessels but most yachts are still advised to use simple incandescents.
Cheerio,
RE: Nextruder filament sensor / flexible filament
Pretty sure I've read Josef mention that it was proving very hard to make it reliable with translucent filaments, and I've noticed that many filaments, even those that from a quick glance look opaque, still allow a certain amount of light pass through.
RE: Nextruder filament sensor / flexible filament
Hello, yes, this is a known problem. The filament is so soft that the force of the spring and ball of the Nextruder filament sensor compresses it to the point where it's in the off state. With this type of filament, you can deactivate the Nextruder filament sensor. Alternatively, you can switch to a mod with a magnet.
Is this the magnet mod? https://www.printables.com/model/1263406-nextruder-filament-sensor-magnet-mod
Thank you. Very helpful 👍
Have you tried this? I had a fillament accessories kit on hand so they're all matching magnets, no idea if that will be good or not, the ones the creator is suggesting don't seem to list their power, so I don't know. I'm still building my CoreOne atm, so I've not tested it.
RE: Nextruder filament sensor / flexible filament
Is this the magnet mod?
Hello, yes this what i meaned.
RE: Nextruder filament sensor / flexible filament
The power of the magnets is listet to be N52 for the mod.