Scrappy: Using Scrap Material as Infill to Make Fabrication More Sustainable

We present a software system for fused deposition modelling 3D printing that replaces infill material with scrap to reduce material and energy consumption. Example scrap objects include unused 3D prints from prototyping and calibration, household waste like coffee cups, and off-cuts from other fabrication projects. To achieve this, our system integrates into an existing CAD workflow and manages a database of common items, previous prints, and manually entered objects. While modelling in a standard CAD application, the system suggests objects to insert, ranked by how much infill material they could replace. This computation extends an existing nesting algorithm to determine which objects fit, optimize their alignment, and adjust the enclosing mesh geometry. While printing, the system uses custom tool-paths and animated instructions to enable anyone nearby to manually insert the scrap material.