Ender 3 bed leveling sensor

Use this to get almost free automatic mesh bed levelling for the ender 3. The only extra parts you need are perhaps some m3 bolts, an sg90 servo and some glue. This design is better than directly attaching the micro switch to the arm because the wires connecting to the micro switch don't get bent every time the servo rotates. I originally used a design where the micro switch was attached to the servo arm, but every couple of prints, the wires would break and I would need to re-solder. This one lasts much much longer and works just as well. You will need to sand down the inside of the track and the outside of the piston so that the piston slides down the track in a smooth, play-free manner.