Filament Width Sensor - Prototype 2

thingiverse

Prototype 2 of an optical sensor for measuring plastic filament width in real-time during 3D printing is now available. The prototype includes a custom PCB and housing design, with a modified Marlin firmware that utilizes the sensor data to adjust extrusion flow based on filament width changes. A video showcasing the sensor's operation can be found at http://www.youtube.com/watch?v=HHjDG1jdv5o. The latest update includes refinements to the case design for improved screw holes and PCB fit. This prototype is now integrated into the Lyman extruder design, with Hugh assisting in controller building and sensor integration. In this version of the optical sensor, the case has been improved to guide filament closer to the sensor while blocking out external light. The CAD work for the case was done using Cubify Invent software, and the PCB was designed using Eagle. The system employs an 8-bit Freescale SG8 microcontroller, with Seeed Studio handling board production. The code has been ported from the previous proof of concept, incorporating a sub-pixel edge detection algorithm to improve measurement accuracy by a factor of 2-10. New pictures and a video showcasing sensor attachment to a 3D printer and filament width measurements are available, along with a graph demonstrating the sensor's performance on various diameter rods. Marlin firmware has been updated to read real-time filament diameter measurements via an A-D channel on the board (Printrboard) and adjust extrusion rate accordingly based on calculated cross-sectional area of the filament. Additional M-codes have been added for filament sensor control, including M404 for nominal filament width input or display, M405 for enabling Filament Sensor extrusion control with optional delay setting, and M406 for disabling the feature. The compensation functionality is demonstrated in a photo showcasing successful print completion despite a measured filament diameter lower than the nominal value. Future prototypes will focus on measuring complete cross-sectional area by scanning filament at multiple angles to calculate a cross-section. Firmware updates are also in progress, including support for M404, M405, and M406 M-codes for Filament Sensor control. For instructions on sensor terminals and calibration, refer to Board Instructions v3.pdf.