Influence of LPBF parameters and strategies on fine machining of pre-built bores

Additive manufacturing changes the classical possibilities of production. However, post-processing is usually unavoidable for these components to achieve functional performance. To obtain an optimum product, knowledge of the characteristics of the additive manufactured part and the machining mechanisms depending on these characteristics is required. In this paper, the influence and the interaction of the laser powder bed fusion process parameters on the subtractive post-processing are shown. The effects of the parameters on the geometry of bores are examined and subsequently the precision machinability is analysed using reaming. In addition, a process simulation is carried out to correlate the simulated deformation to the required machining allowance for subsequent reaming. The aim of this investigation is to examine the capabilities of the laser powder bed fusion process to produce bores at angles of 90° (vertical), 60° and 45° that can be machined directly with a reaming tool without the need for drilling

Inverse Determination of Johnson–Cook Parameters of Additively Produced Anisotropic Maraging Steel

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

The additive-subtractive process chain – a review

In recent years, metal additive manufacturing developed intensively and became a relevant technology in industrial production of highly complex and function integrated parts. However, almost all additively manufactured parts must be post-processed in order to fulfil geometric tolerances, surface quality demands and the desired functional properties. Thus, additive manufacturing actually means the implementation of additive-subtractive process chains. Starting with the most relevant additive processes (powder-based PBF-LB, LMD-p and wire-based WAAM and LMD-w/WLAM), considering intermediate process steps (heat treatment and shot peening) and ending up with post-processing material removal processes (with defined and undefined cutting edges), this paper gives an overview of recent research findings with respect to a comprehensive scientific investigation of influences and interactions within the additive-subtractive process chain. This includes both the macroscopic geometric scale and the microscopic scale of the material structure. Finally, conclusions and future perspectives are derived and discussed

Prediction of the shape accuracy of parts fabricated by means of FLM process using FEM simulations

The prediction of component properties from the Additive manufacturing (AM) process poses a challenge. Therefore, this paper presents the development of a novel machine data (G-Code) based procedure as well as its programming implementation of a process simulation in ANSYS Mechanical for the fused layer modelling (FLM) process. For this purpose, an investigation of additively produced components with varying parameters made of polylactic acid (PLA) is carried out and simulated by means of the developed method. Application of the developed method makes it possible to predict the thermally induced distortion of PLA-Parts based on the machine data from the FLM process before production

Influence of the support structure on the bandsawing process when separating lpbf components from the building platform

The method of laser powder bed fusion (LPBF) is an additive manufacturing process and allows great freedom of component geometry due to the layer-by-layer structure. The LPBF components are printed on a substrate plate and must be separated from the plate afterwards. Support structures are used to attach LPBF components to the substrate plate and to sustain overhanging parts. The cutting of the components is mainly carried out by means of a sawing process using the support structure. The forces occurring during this process are very challenging because the component has to be cut off without damage or deformation. The present study investigates and discusses the resultant forces and vibrations during the sawing of LPBF components made of titanium alloy Ti6Al4V using two different support structures. The components were arranged on the substrate plate at angles of 0°, 5°, 10°, 15°, 45° and 90° to the direction of primary motion