Summer science: Rethinking 3D printing with recycled filament

This summer, summer lab students dove into making 3D printing more sustainable by recycling existing filament. We spoke with senior Tanner Wit about his team’s project, which focused on recycling 3D printer filament. Their goal was to turn discarded prints back into usable filament, instead of using new materials, and test its strength for viability.

The process began with printing various rectangular shapes to be ground into shreds. They found a clever trick, “rectangles with a larger infill and no exterior layers, though harder to shred, produced the smallest pieces that fit best into the extruder.”

The extrusion process itself was a significant learning curve for Witt, who is on track to graduate with a degree in chemical engineering from the University of Wisconsin-Madison in December 2025. “Using the extruder took a lot of trial and error,” he admitted. “Getting the temperature and speed of both the extruder and the reeling machine just right for the correct filament thickness was a challenge. Optimizing it in just a few days was challenging, especially with recycled filament being harder to work with than virgin pellets!”

Putting it to the test

To understand the viability of their recycled filament, Witt’s team conducted strength tests. They created small, standardized testing blocks, which had a close resemblance to a classic dog bone shape. These “dog bones” were then taken to the materials lab upstairs. “They have a machine that clamps onto each end of the bone and slowly pulls it apart,” Witt described, “recording the applied force and elongation over time.”

While the project aimed to test various compositions of recycled material, time constraints limited their scope. And while they were successfully able to make a few samples out of 50% recycled filament, the testing was less successful. The samples made out of 50% recycled filament performed worse on the strength tests than samples that used new filament. This finding highlights the ongoing need for optimization and research in this area.

Beyond the technical hurdles, the project offered invaluable lessons in adaptability. “We were only able to do a very small portion of what we planned over the four days of work we had,” Witt reflected. They also learned how complicated the extrusion of the polymers was and therefore had delays.

This unexpected turn taught him a crucial skill. “We were constantly adjusting our plan when things didn’t go well and we were running out of time,” he explained. “I think it taught me how to be more flexible and adjust when things don’t go as we expected originally.”

The Path to Chemical and Biological Engineering

When asked about his draw to chemical and biological engineering, Witt recalls how much he liked his chemistry and engineering classes in high school. On the other hand, his choice of UW-Madison was both personal and academic. “My mom went here for grad school,” Wit shared, “it was a great chemical engineering school, amazing campus, and still close to home.”

Looking ahead, Witt’s passion for hands-on work shines through. “I would love to go into research or a position where I am in the field taking data and measurements often,” he enthusiastically stated. “I love hands-on work and don’t do great just sitting doing desk work.”

This summer project is a fantastic example of how students at UW-Madison are engaging with real-world problems, pushing the boundaries of sustainable technology, and gaining invaluable experience.