Design Rules for Hybrid Additive Manufacturing Combining Selective Laser Melting and Micromilling

Abstract

We report on a comprehensive study to evaluate fundamental properties of a hybrid manufacturing approach, combining selective laser melting and high speed milling, and to characterize typical geometrical features and conclude on a catalogue of design rules. As for any additive manufacturing approach, the understanding of the machine properties and the process behaviour as well as such a selection guide is of upmost importance to foster the implementation of new machining concepts and support design engineers. Geometrical accuracy between digitally designed and physically realized parts made of maraging steel and dimensional limits are analyzed by stripe line projection. In particular, we identify design rules for numerous basic geometric elements like walls, cylinders, angles, inclinations, overhangs, notches, inner and outer radii of spheres, chamfers in build direction, and holes of different shape, respectively, as being manufactured by the hybrid approach and compare them to sole selective laser melting. While the cutting tool defines the manufacturability of, e.g., edges and corners, the milling itself improves the surface roughness to Ra < 2μm. Thus, the given advantages of this hybrid process, e.g., space-resolved and custom-designed roughness and the superior geometrical accuracy are evaluated. Finally, we exemplify the potential of this particular promising hybrid approach by demonstrating an injection mold with a conformal cooling for a charge socket for an electro mobile.

Tool Wear and Milling Characteristics for Hybrid Additive Manufacturing Combining Laser Powder Bed Fusion and In Situ High-Speed Milling

“…The advancement of such hybrid approaches requires a thorough understanding of the fundamental properties of these new technologies, their restrictions and requirements. The specific hybrid approach under investigation in this study has recently been investigated with respect to design rules [ 19 ] and fundamental properties [ 12 , 20 ]. In addition, different applications as the generation of medical parts with superior surface roughness and fitting accuracy have been demonstrated [ 21 , 22 , 23 , 24 ].…”

The State of the Art in Machining Additively Manufactured Titanium Alloy Ti-6Al-4V

“…To solve this bottleneck problem, a new type of “hybrid manufacturing” machine has been developed recently by integrating the machining and AM process together [ 29 , 30 ]. The machining of internal surfaces is conducted during the AM process before the surfaces become inaccessible after the AM process is finished ( Figure 21 ) [ 180 ].…”

“…A significant number of studies have been carried out on the machining of wrought Ti alloys in the past decades. These studies have focused either on the development of specially designed cutting tools and new tool materials [ 23 , 24 ], optimisation of cutting parameters, application of new cooling media and tribology theories [ 25 ], or on the investigation of hybrid machining processes such as thermal-assisted machining (TAM) [ 26 , 27 , 28 , 29 , 30 ]. Since Ti-6Al-4V is the most widely used titanium alloy constituting 50% of total titanium alloy production worldwide, the machining of Ti-6Al-4V has become one of the most widely studied subjects [ 31 , 32 , 33 ].…”

Optimization of mechanical properties of additive manufactured IN 718 parts combining LPBF and in-situ high-speed milling

“…Due to an in-situ 3-axis milling process, the surface quality is improved as well as the fitting accuracy can keep up with conventional fabrication processes. 18,19 Further, heat treatment processes are used for the post processing of additive manufactured components. Using solution and ageing treatments or hot isostatic pressing, internal voids can be reduced, residual stress can be minimized, and mechanical load behaviour can be modified, respectively improved.…”