Mini Filament Sensor

Q: Why another filament sensor?
A: Well, why not?


Q: What is wrong with a simple limit-switch one?
A: Nothing. But if you need something else that adds very little drag on the filament and is dimensioned differently than a limit-switch, then this might be useful ...


The metal piece of a limit-switch is basically a spring and springs have the "feature" that the force they push back with increases as you push them away from their normal position. For a filament sensor that typically means that the limit-switch will be pushing your filament against a wall of your sensor body, causing drag en possibly erosion over time.


Magnets are like inverse springs: the force they exert gets lower the further you move the magnets apart. In the design here you can feel this very well: you feel the effort it takes to pull the magnets apart to get the holes - lined with PTFE tube - to align and allow the filament through, but when those holes do align, the magnets are so far apart that