Implementation of hybrid additive manufacturing based on extrusion of feedstock and milling

Abstract

Abstract In the current industry, fabrication of metallic and ceramic artifacts by means of feedstock extrusion additive manufacturing is receiving attention because of the capacity of this technology to deal with low costs and materials that possess a low Additive Manufacturability Index when treated with high power beam technologies. However, the extrusion additive manufacturing lacks in achievable accuracy and productivity therefore techniques that can improve the overall performances are required to increase the impact that this technology can have on industry. This paper demonstrates how extrusion additive technology of metals and ceramics can be enhanced by integrating green-state milling into the manufacturing cycle. In the hybrid cycle, the additive and subtractive processes act alternatively on the green-state part to shape its near-net form. This work shows how this innovative method, that integrates cutting and micro-cutting operations on the feedstock, allows compensating the lack of accuracy and micro reachability that characterize the extrusion-based additive manufacturing method. In the manuscript, the promising aspects of the hybrid concept are presented and discussed. Some examples of manufactured parts are illustrated showing how complex geometries, with good surface quality can be addressed with higher production flexibility. The developed hybrid machine prototype adopted for that scope is described along with the AISI316L parts that are obtained by depositing, green-state milling, debinding and sintering the feedstock. Another contribution is provided regarding the feedstock machinability that is studied under different cutting conditions. The feasibility of the hybrid implementation is confirmed and future steps to improve the process are discussed.