iPhone drawn concept: “Swiper”
I sketched up a quick idea for a mechanical oozebane. This sketch is obviously not dimension or positional accurate.
The concept: Have a arc of very thin, rigid metal (or other material that can handle a lot of heat) that covers the end of the extruder nozzle of a Makerbot Cupcake CNC, a Reprap, or any other plastic-extruder-based CNC machine. The metal will get hot with the extruder and hold the molten plastic in and molten.
It works like this:
Before the extruder starts to extrude, the electromagnet will charge pulling the swiper around and out of the way of extrusion.
When the extruder stops, the magnet will be shut off and the springs will both cut the filament and stop the oozing.
The common solution to this is to run the extruder backwards for a small period of time after stopping. This works a lot better if you have a stepper motor or other means of precisely controlling the motor, but still has a few drawbacks:
The first is that the filament still has a string out of the nozzle that is dragging more of the molten filament out the further you get from the stopping point. Since the motor is off, this molten filament won't be completely replaced and will cause a gap the next time the extruder starts.
The second is that the filament will have a small portion that is exposed to cool air, making a hardened “booger” that will be dropped as soon as the extruder starts again. There's also a widening bubble of air between where the last of the filament hits the melting zone and that is falling slowly. These two things will make a lump followed by a gap after every stop/start of the extruder.
So, this swiper aims to solve both of these. First by cutting the filament off clean and second by keeping the filament hot and ready without forming a bubble.
I am yet to make a prototype, but I think I'm close. I'm totally open to any ideas.
-Rob
Sent from my iPhone.
