“3D Printing of Large Objects with PET Flakes” is the Graduation project of Daniël Eikelenboom of the Faculty of Industrial Design Engineering of the TU Delft for the Rotterdam based company 3D Robotprinting. The project focusses on the development and implementation of an ‘all-inclusive’ PET bottle recycling unit containing a large-scale 3D printer as made by 3D Robotprinting and the development of a preliminary set of guidelines for manufacturing products using the 3D printer. The aim is to enable the 3D printer to use PET flakes gained from bottles as feedstock. Therefore, the 3D printer was adapted and guidelines for manufacturing were developed. An iterative approach is followed, in which the exploration of the ‘novel’ source material and defining the design guidelines for manufacturing are at the heart of the project. After defining the context, the 3D printer was analysed and a literature study was performed, from which was concluded that the current polymer extrusion machine is likely too small to process the initial flake sample. With an initial sample of the material, experiments were performed in order to examine directions for a possible solution and to determine the most important properties, like flake material density, particle size distribution and funnel flow behaviour. By increasing the polymer extrusion screw channel depth at the feeding zone to 8 mm and compression ratio to 4:1 (resulting in a screw diameter of 30,4 mm), the 3D printer should be able to process PET flakes with a diameter up to 4 mm. To ensure the material does not contain particles larger than 4 mm in diameter, it should be shredded, granulated with a 3 mm mesh and sifted using a 4 mm sieve consecutively. Using literature of previous experiments, preliminary design guidelines for creating products with the 3D printer from 3D Robotprinting were set up. From a set of ideas gained from context analysis, a children’s slide was chosen to experiment on. Multiple prototyping rounds were done to perfect the slide’s printing performance and to refine the design guidelines. The project’s final results are: • Advised dimensions on the most important part of the system: the polymer extruder. • A list of preliminary design guidelines for optimizing a product for manufacturing on the 3D printer. • A children’s slide showing the application of the design guidelines.