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The screw mechanism they describe is quite a bit different than an injection molding screw. The screw in an injection molder is like an auger, designed to push
by TD-Linux 9y ago
The screw mechanism they describe is quite a bit different than an injection molding screw. The screw in an injection molder is like an auger, designed to push plastic pellets. A hobbed bolt is not an option because it can't pick up the pellets. Here they are grabbing the filament from the outside with threads, kind of like rifling.
Reading the paper, it seems like they managed to double the force compared to a traditional pinchwheel. However, there are now extruders that used geared pinchwheels on both sides of the filament, doubling the force without requiring threading the filament.
- Animats 9y agoThat's what the article says, but there must be some trick to make that work. Trying to drive a filament just by threading it and running it through a rotating nut will mostly twist the filament or tear off the threads. Maybe an inside conical thread, like the negative of a wood screw...
- lylecheatham 9y agoIt's actually just a standard 4-40 thread cut into the filament. They use rollers to prevent rotation of the thread when cutting the threads into the filament, and then when they actually use the nut it's got enough thread engagement that it's better than a hobbed gear. If you think about it, it's almost like a hobbed gear that attacks from all sides instead of one or two. Feel free to ask me questions on it, I work in the industry and have spoken with one of the authors of the paper, it's a shame it's behind a paywall.