This project involved the design and simulation of a manually operated shredder for PLA plastic, aimed at being low-cost, easily manufacturable, and structurally reliable. Drawing on the CDIO framework, the team researched existing shredders and PLA material properties, selecting Bambu Lab’s PLA for its consistency and documented mechanical performance. Several conceptual designs were explored, including motorised and manual options, before settling on a dual-barrel, gear-driven hand-crank design that combined effective shredding performance with manufacturing simplicity.

The final design features custom-fabricated steel components—including blades, spacers, and casing—cut via laser or plasma, with all mechanical parts simulated using Autodesk Inventor and Fusion 360 to ensure they could withstand the expected stresses. The blade geometry was optimised for torque transfer and cutting efficiency, and tolerances were chosen for a balance of reliability and manufacturability. The gear train multiplies user input torque to exceed the PLA’s required failure stress.

3D-printed elements were used for non-structural parts like the drawer and gear cover, while the core mechanism was built around durable steel and hex shafts for easy alignment and assembly. Simulations demonstrated that components would perform under load, and an exploded and animated CAD model was produced to demonstrate assembly and function. Due to cost we where not able to manufacture all spacers and blades but a small portion were created with a large spacer to hold them to allow testing of the device.

In reflection, the design proved effective in concept and simulation, with the use of common materials and repeatable manufacturing methods being a key strength. Future iterations may explore a motorised version for efficiency, but the project successfully met its goal of designing a practical, hand-powered shredder for PLA recycling.