Additive manufacturing using material extrusion enables both the fast and cost- effective production of functional prototypes (rapid prototyping) and ready-to-use plastic products (rapid manufacturing). In addition to the processing of plastic wires, also known as filament, the direct processing of plastic granulate using the Fused Granular Fabrication process is also a practicable method. In this case, the cost- intensive production of filament can be dispensed with, and an even wider range of materials can be processed. The design of the extrusion unit is similar to that of standard screw extruders, although a wide variety of different screw geometries can be found on the market. The motivation for the investigation in this paper is the design, development and construction of an extrusion unit with subsequent benchmarking of different geometries. A standard three-zone screw is used, which should make it possible to process the widest possible range of plastics. In addition to standard plastics (e.g. polypropylene), technical plastics (e.g. polyamide 6) are also used to analyse their processability and thus draw conclusions about the usability of the extrusion unit. The aim of the investigations is to determine the production quality depending on the material to be processed. In addition to the general appearance, the focus is particular on the stringing behaviour of the materials to be examined. The results obtained will be used to determine the extent to which a standard three-zone screw is suitable for additive manufacturing using the Fused Granular Fabrication process. It can be determined that materials such as high impact polystyrene (HIPS), polylactide (PLA), acrylonitrile butadiene acrylic ester (ABS) and polypropylene (PP) exhibit little to no stringing, while polyamide 6 (PA) and polyethylene terephthalate glycol (PET-G) show higher stringing.
