This book provides an in-depth exploration of process planning steps required for Directed energy deposition (DED) processes and their automation during the data preparation stage. DED is a resource-efficient, tool-less manufacturing method with high deposition rates and larger build volumes. Their flexibility, enabled by 6-axis industrial robots, allows fabrication of complex geometries, but poses challenges in data preparation and build strategy definition due to software limitations and lack of standards. This thesis thereby deals with the development of a STEP file format-based slicing framework with toolpath generation algorithms specific to build geometries clustered under six categories. Thin-wall components cluster, an important part category in the aerospace sector, is being further examined because of its industrial relevance.