Once you have a set idea of what you’ll be 3D printing, the next step is to consider what material works best. Depending on the application, you’ll need think about what filament material is compatible, whether it’s for structural support, used as a heat-regulator, or even expandable fillers. Some of these specific filaments are difficult to find on the market or might not even exist (yet). Thus, the creation of a custom type of filament is the only solution for some projects. Filament extrusion, therefore, is the process through which raw plastic pellets (and additivities) are converted into filament wires for 3D printers to use.