A simple idea for automatic power off on ender 3 Remove filament, cooldown and shut down

Just put on the right side of your x axis

I used a stock screw and a simple light switch

Use with this gcode: G91 ; Set coordinates to relative G1 F1800 E-3 ; Retract filament 3 mm to prevent oozing G1 F3000 Z20 ; Move Z Axis up 20 mm to allow filament ooze freely G1 F1800 E-100 ; Retract all filament G1 F1800 E-100 ; Retract all filament G1 F1800 E-100 ; Retract all filament G1 F1800 E-100 ; Retract all filament G1 F1800 E-100 ; Retract all filament G90 ; Set coordinates to absolute G1 X0 Y200.0 F1000 ; Move Heat Bed to the front for easy print removal M116 ; wait for temperatures M140 S0 ; turn off heated bed M106 S255 ; set fan to 100 M109 R35 ; cool down hot end to 35 G1 X230.5 Y200.0 F1000 ; Automatic shut down M84 ; Disable stepper motors ; End of custom end GCode