Design for slicing in large format fused filament fabrication

Slicing is the process of converting a computer aided design file (CAD) to G-Code instructions. The G-Code is then interpreted by a 3D printer to produce a part. The slicing software has no process feedback, so the user needs to properly design the part and configure the slicing parameters for a successful print. Slicing is primarily a geometric approach to creating machine instructions. Slicing starts with a stereolithography file (STL), which uses triangles to approximate the CAD part. The STL is intersected with a plane to “slice” it into layers. The resultant slices are polygon representations of the area(s) to be printed. The slicing software fits toolpaths to the polygons and turns them into G-Code. These toolpaths assume a perfect world where the machine outputs exactly what is instructed. If the machine outputs more or less material than the slicer expects, then the part will not meet the desired specifications because of over- or underfilling. This limitation of the slicing software can lead to unsatisfactory results and prevent the end user from achieving the part exactly as desired. However, the limitation can be accounted for with proper front-end design and in some cases can even be completely mitigated by intentional designing. In certain situations, such as the hollowing of a part, slicing can be used to ease or speed up the design process by offloading repetitive and tedious tasks from the CAD designer to the slicing software. This paper will address how intentional design can promote desirable results in slicer output and in the final product. Learning objectives include an overview of how slicing works, how to design for the slicing process, and how to configure slicing for the ideal output.