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

We present a software system for 3D printing that replaces infill material with scrap to reduce material and energy consumption. Using this system, you can insert unused 3D prints, household waste like coffee cups, and off-cuts from other projects into a 3D printed object.

Consumer 3D Printing machines that create objects by depositing material layer by layer rely on depositing material inside the printed object. These internal structures provide a foundation for the subsequent print lines to stick to. This infill material makes the printing process more reliable and provides mechanical strength. Depositing infill however consumes printing material and increases the time it takes to finish the print. 

We present a software tool called Scrappy that integrates into the existing workflow for modelling objects for 3D printing as an add-in for Fusion 360. Scrappy assists the user in reducing the amount of infill material by recommending scrap objects that can replace infill. Scrappy makes sure that the recommended scrap fits inside the model without intersections and that it can be inserted into the model during the fabrication process.

Scrappy pauses the printing process to allow the user to insert the scrap at the appropriate time. The scrap acts much in the same way as the infill that it replaces by providing a foundation to print on and mechanical strength. After inserting the scrap, printing continues as normal. Inserting just one scrap object using our system can save up to 50% printing time and material.

Scrappy keeps track of available scrap objects, such as (a) old discarded prints, (b) common household waste, (c) broken tools and (d) recurring prints. It works with a variety of different material types and allows repurposing many different types of household waste.

To make sure that recommended scrap objects such as (a) an old Pikachu print can be inserted during fabrication, (b) the scrap model is inflated to account for printer inaccuracies. (c) The scrap mesh is projected towards the insertion plane (d) to generate a mesh of the cavity that has to be removed from the model mesh to allow the scrap insertion.


Ludwig Wilhelm Wall, Alec Jacobson, Daniel Vogel, Oliver Schneider, "Scrappy: Using Scrap Material as Infill To Make Fabrication More Sustainable", CHI ‘21: Proceedings of the 2021 CHI Conference on Human Factors in Computing Systems.

Last updated: March 21, 2021

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