Adaptive Design Strategies for a Dual-Shaft PVC Shredder

This capstone project involved the design and development of a mid-size plastic shredder, created to process strong, ductile PVC sheets up to ½” thick. This application falls between the capabilities of consumer grade plastic shredders and heavy-duty industrial machines. Over 400 million tons of plastic produced annually and less than 10% of it is recycled; there is an ever-growing need for plastic recycling accessibility and infrastructure. This project aimed to create a compact dual-shaft shredder that can shred thick PVC sheets while being powered by a 120V outlet. Research into blade geometry and orientations aided an iterative design process driven by industry sponsor Ichor Systems, resulting in blades with removable key stock tips and star patterned cutouts that allowed for the greatest flexibility and replaceability of components. Theoretical analysis of shear punchout and orthogonal cutting methods showed that conventional shredding machines for this application would exceed feasible torque limits for a 2-3 hp motor. This resulted in a pivot toward small chip formation which reduced force requirements. A refurbished gearbox with a maximum torque output of around 600 ft-lbs was selected, and custom flanged shaft collars enabled transmission of torque between differently sized shafts. The final design aims to integrate mechanical and electrical systems to deliver a safe and effective shredder. Fabrication is ongoing at time of writing; the shredder is expected to achieve at least partial success in processing thick PVC sheets, with potential challenges in blade engagement and material retention. Future work includes performance testing and model validation.