Part design and the possibilities of production are disrupted by the increased usage of additive manufacturing (AM). Featuring excellent creative freedom due to the layer-by-layer buildup of components, AM leads to profound changes in future part design and enables previously impossible geometries. Laser powder bed fusion (LPBF) technology already allows to manufacture small quantities of parts with high productivity and material efficiency. Due to the specific process characteristics, the resulting surface finish of these parts is insufficient for a wide range of applications, and post-processing is usually unavoidable. Specifically for functional surfaces, this post-processing is often done by machining processes, which can pose challenges for intricate and complex AM parts due to excessive machining forces. In the present paper, the influence and the possibilities of the LPBF process parameters on the subtractive post-processing are shown. A novel weakened structure is developed to selectively reduce the strength of the material and improve the cutting conditions. Chip formation, cutting forces and vibrations during drilling as well as cutting forces during an orthogonal cut are examined. To quantify the differences, a comparison of the machinability between bulk material, standard support structures and the weakened structure is carried out.

In today’s manufacturing, additive manufacturing processes enable the production of complicated three-dimensional structures that are hard to be manufactured with traditional manufacturing processes. Due to its high build rate, the laser-based directed energy deposition (DED-LB) process is an attractive and versatile process to manufacture these kinds of components. In addition to the production of components, DED-LB is used for repair or coating applications. The DED-LB process consists of a multitude of complex thermal mechanisms with high heating and cooling rates of 5 × 102 up to 5 × 105 K/s. For materials with high hardness or low thermal conductivity like tool steels, cast iron, or tungsten carbide, these high cooling rates can lead to defects in the microstructure like cracks, pores, or delamination between the substrate and the deposited structures. By preheating the substrate, the cooling rates can be reduced and defects can be eliminated. In this paper, a preheating cycle was developed, which uses the laser of a DMG MORI LT 65 DED hybrid machine as a moving heat source for the substrate preheating. For this cycle, process parameters, a tool path strategy, and a temperature control system were developed. The impact of the elaborated concept was shown by depositing tungsten carbide in a nickel matrix on an S235 steel substrate.

In powder bed-based additive manufacturing (AM), complex geometries can be produced in a layer-wise approach. Results of material science experiments regarding material property identification, e.g., tensile strength, show interdependencies between the test load direction and the layer orientation. This goes hand-in-hand with the measured cutting force, changing with the relative angle between cutting direction and layer orientation in orthogonal cutting tests. However, due to the specific process characteristics, the layer orientation results in anisotropic material properties. Therefore, during machining, the material behaves depending on the buildup direction, which influences the cutting process. To predict this behavior, a simplified inverse approach is developed to determine the buildup direction-dependent parameters of a modified Johnson–Cook model for cutting simulation. To qualify these cutting models, mainly the cutting force and additionally the chip formation examined during orthogonal cuts are used. In the present paper, the influence of the laser-powder-bed-fusion (LPBF) process parameters on subtractive post-processing are shown. A good agreement between verification experiments and simulations is achieved.