A Solid Solution to Plastic Waste

After printing a 3DBenchy and a calibration cube, every owner of a 3D printer will move on to some more complex designs. As the designs increase in complexity, the pile of scrap materials from parts that are not quite the right size, and from failed prints, grows in size. The consequences of that growing pile of junk extends beyond just wasted cash — the petroleum-based plastic filaments commonly used in 3D printing leech chemicals into the environment after they wind up in a landfill.

There are more eco-friendly filaments, generally made from biodegradable or recycled materials, available on the market today. But these existing options are not very widely used because they do not have the strength of standard plastic filaments. Since we do not presently have a material that is both eco-friendly and strong for use with 3D printers, a group led by engineers at MIT CSAIL has come up with a stopgap solution that could significantly reduce the environmental hazards associated with our scrap piles.

The team calls their approach SustainaPrint, and it is a system that combines software, hardware, and testing tools to help users strategically blend eco-friendly and conventional filaments in a single print. Instead of choosing one material for an entire object, SustainaPrint analyzes how a model will bear stress and determines which regions must be reinforced with tougher plastics. The rest of the structure can be fabricated with weaker, greener filament, cutting down on petroleum-based plastic use while preserving functionality.

To accomplish this, SustainaPrint relies on finite element analysis, a simulation method engineers often use to predict how objects deform under pressure. The software lets a user upload their 3D model, specify where forces will act, and then visualize a map of stress distribution. SustainaPrint applies heuristics to decide which sections of the design require reinforcement. According to the team, just 20% reinforcement with tough PLA was often enough to recover as much as 70% of the strength of a part printed entirely from strong plastic.

The group tested their method by fabricating dozens of everyday items from rings, beams, wall hooks, and plant pots, to headphone stands. Each item was produced three times: once entirely in eco-friendly filament, once entirely in strong PLA, and once using the hybrid SustainaPrint configuration. Mechanical stress tests revealed that the hybrid prints often matched or even outperformed full-strength versions, especially in cases where stress distribution mattered more than raw material strength.

Recognizing that many hobbyists and small labs lack access to expensive testing machines, the researchers also developed a DIY strength-testing toolkit. This 3D-printable device includes modules for tensile and flexural strength tests and works with common household items like pull-up bars or digital scales. While not lab-grade, the results proved accurate enough to guide filament choice — particularly for recycled materials that may lack datasheets or vary in quality from batch to batch.

Currently, SustainaPrint works best with dual-extrusion printers, though the team notes it could be adapted for single-extruder machines with some manual filament swapping. The system is intentionally designed to be simple, supporting one applied force and one fixed boundary per simulation. In the future, the researchers hope to expand the software to handle more complex load conditions and perhaps even use AI to infer intended use directly from an object’s geometry.