With the spread of intraoral scanners and three-dimensional (3D) printers in the orthodontic practice, it is possible to realise a complete digital workflow for the production of aligners in the laboratory. Both intraoral scanners and cast scanners provide highly accurate virtual models for diagnosis and further use as virtual working models with reduced horseshoe base. Using appropriate software, the teeth can be segmented after tooth repair of the STL file and tooth movements simulated. This defines treatment goals (visual treatment objective). After disassembly into individual steps (staging), the individual working models can be produced with a 3D printer. For this purpose, digital light processing (DLP) or fused filament fabrication (FFF) printers can be used. The latter have specific advantages and disadvantages, but are seen as an interesting alternative. Further technical aspects and printing materials in FFF printing are discussed in detail. Clinical case studies illustrate the technical explanations. These show that FFF printers are suitable for the production of working models for aligner technology. Keywords: 3D printing, aligner, CAD/CAM, fused filament fabrication, in-office workflow, intraoral scanning