3D Printer Runout Sensor (Low Friction)

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.