3D printing of polymers is today a well-implemented process for many applications, including rapid prototyping. Several tens of thousands of parts are produced every year in the 3D printing workshop at SPOT, EPFL's main student makerspace. Most of these parts are produced by FDM 3D printing, using PETG filament. Every year, around 20 kg of thermoplastic waste is thus generated.

As part of its sustainability approach, SPOT has acquired a recycling line (grinding, drying, extrusion) to recycle this waste and produce new 3D printing filaments in-house. Two previous semester projects have optimized the recycling process. However, the filaments obtained can still present random defects (inclusions, diameter variations) which make them unreliable for mass 3d printing. Thus, a device has been designed and built in a previous semester project in order to detect those defects in the filament.

This project aims to further develop the device in order to improve filament quality control and to facilitate the correction of detected defects.

The various steps in the project involves:

• Adding a spool defect mapping function to the existing device.
• Adding a semi-automatic defect correction function.
• Characterizing the entire process and evaluate the device's efficiency.

The student is expected to be rigorous and patient, and to have good programming and prototyping skills (mechanical design, 3D printing, laser cutting, etc). A previous experience prototyping at SPOT is required.