Figure 1: Scrappy is a system that lets users use scrap objects as infll to reduce time, cost, and material: (a) a library tracks scrap objects, like an old print, as well as other common objects; (b) an add-in for Fusion 360 suggests scraps from the library that can ft into a model, sorted by saved printing time; (c) an algorithm fnds the best scrap placement and generates a modifed model; (d) a custom slicer optimizes infll and adds machine commands to pause the printer with instructions how to insert the scrap into the object; (e) the fnal printed object has the scrap inside, reducing the material, time, and energy needed to print.