A filament runout sensor for any printer running a RAMBo / Mini RAMBo board, or if you have one of their endstops laying around. This part is designed to work on an MTW MendelMax 3, but I have included the .STEP and Fusion 360 files for anyone who needs to make modifications. This works for 1.75mm filament, but the actual endstop may need some adjusting to work right. Please note that there is only one direction the endstop switch can be mounted inside the piece, as the channel is slanted to keep filament from coming off track.
**IMPORTANT:** Before installing and using this on your printer, assemble it completely and run some spare filament through it to make sure it clicks on ONLY when the filament is fully inserted, and clicks off ONLY when the filament is completely taken out. You can very slightly bend the arm of the endstop with a pair of pliers to adjust the gap and dial the sensor in. Also make sure the screws holding the endstop in the printed part are very snug.