This thesis explores the modification of a 4-axis 3D printer by FullControl, with a particular focus on enabling non-planar and non-horizontal printing through the implementation of a B-axis slicing pipeline. A Python Jupyter Notebook is developed to generate the corresponding G-code, utilizing all four axes. The work presents the conceptual design, implementation process, and technical challenges involved in creating a slicer for this type of 3D printer. Additionally, the study investigates the complexity, capabilities, and limitations of non-planar fused filament fabrication (FFF) by comparing it with conventional planar printing techniques. A series of experiments are conducted to evaluate the differences and potential benefits of non-planar 4-axis printing.