Purpose: The purpose of this study is the introduction and validation of a new technique for process monitoring during electron beam melting (EBM). Design/methodology/approach: In this study, a backscatter electron detector inside the building chamber is used for image acquisition during EBM process. By systematic variation of process parameters, the ability of displaying different topographies, especially pores, is investigated. The results are evaluated in terms of porosity and compared with optical microscopy and X-ray computed tomography. Findings: The method is capable of detecting major flaws (e.g. pores) and gives information about the quality of the resulting component. Originality/value: Image acquisition by evaluating backscatter electrons during EBM process is a new approach in process monitoring which avoids disadvantages restricting previously investigated techniques.

In order to understand the absorption characteristic, a ray trace model is developed by taking into account the reflection, absorption and refraction. The ray paths are resolved on a sub-powder grid. For validation, the simulation results are compared to analytic solutions of the irradiation of the laser beam onto a plain surface. In addition, the absorptance, reflectance and transmittance of PA12 powder layers measured by an integration sphere setup are compared with the numerical results of our model. It is shown that the effective penetration depth can be lower than the penetration depth in bulk material for polymer powders and, therefore, can increase the energy density at the powder bed surface. The implications for modeling of the selective laser sintering (SLS) process and the processability of fine powder distributions and high powder bed densities are discussed.

Purpose: Selective electron beam melting (SEBM) is a highly versatile powder bed fusion additive manufacturing method. SEBM is characterized by high energy densities which can be applied with nearly inertia free beam deflection at high speeds (<8.000 m/s). This paper aims to determine processing maps for Ti-6Al-4V on an Arcam Q10 machine with LaB6 cathode design. Design/methodology/approach: Scan line spacings of 100, 50 and 20 µm in a broad parameter range, focusing on high deflection and build speeds are investigated. Findings: There are broad processing windows for dense parts without surface flaws for all scan line spacings which are defined by the total energy input and the area melting velocity. Originality/value: The differences and limitations are discussed taking into account the beam properties at high beam energy and velocity as well as evaporation related loss of alloying components.