Delta 3D printers work with the Fused Deposition Modeling (FDM) process. Here, a filament serves as the starting material and is wound on a spool and pushed through an extruder into a print head. The molten filament is then applied to a usually heated print bed and expanded layer by layer. In the course of printing, the material cools down so that gradually different layers can be applied and the printing can be finished.