3D Printer Runout Sensor (Low Friction)

thingiverse

I had first cobbled together a simple runout sensor using a "roller" style microswitch that worked okay but induced a lot of drag on the filament passing through it. To address this problem, I designed this new sensor based on commonly available Optical Limit Switch modules (readily sourced from eBay or Amazon). It includes a 3d printed "Spring-Sensing-Arm" that exerts just enough force on the filament to sense a break but not so much as to cause excessive friction on the filament passing through the sensor. Furthermore, the "Sensor Arm" protrudes slightly through the case to provides both a visual indicator of a filament break PLUS an easy touch point that is used to gently push arm "open" when sliding new filament through the sensor body. The design consists of 3 printed parts plus the Optical Limit switch. 1. CASE BOTTOM HALF 2. CASE TOP HALF 3. SPRING SENSING ARM9-17-2020: One 4-40 or M3 screw is used to attache the Optical Limit Switch into the case. While a second 4-40/M3 Screw can be used to fasten the case halves together, I have found that by just putting four short lengths of 1.75mm filament into the case corner locating holes, the whole assembly will just snap together! A small hole is provided in the TOP HALF of the case in the event that you'd like to add an optionsl indicator LED. All printed parts can be printed in about an hour using PLA or PETG at a .2 mm or .3 mm layer height. RECOMMENDATION ADDED 9-20-2020: WHILE PLA CAN BE USED, THE SENSOR-ARM WILL BE MORE ROBUST IF PRINTED USING PETG - PETG WILL ALSO PROVIDE A LITTLE MORE "SPRING-ACTION" TO THE SENSOR ARM.