Metal Additive Manufacturing Conference - MAMC 2022

Additive manufacturing (AM) has developed very dynamically in recent years and is becoming increasingly popular. For AM in metal, laser powder bed fusion (LPBF) is the most commonly used process and has been successfully applied in many industrial applications. It allows the fabrication of complex structures, but is time consuming, expensive and limited in build volume. To date, no AM technology for large-volume metallic components has been established on an industrial scale like LPBF. This paper presents a new process approach to fabricate larger metallic structures from steel by inductive melting of a continuously fed wire. The presented method is characterized by the comparatively low energy input in contrast to comparable processes for AM, such as arc, laser or electron beam. Previously published work is based on the principle of a melt reservoir of low-melting alloys and droplet delivery using gas pressure or vibration. In contrast, the approach described here is to transfer the material directly from the end of the wire to the substrate by continuous drop deposition. However, to avoid a stochastic material transition, a suitable process strategy has to be chosen. This challenge is met by a pulsed coil current and the resulting periodically varying Lorentz forces in order to achieve regular and forced droplet detachment. Using the FEA software COMSOL Multiphysics, different coil geometries were investigated in order to determine the Lorentz forces and the temperature distribution in the moving wire. For the experiments, a suitable coil was manufactured and connected to a high frequency induction power supply. The generator power was controlled with a sinusoidal oscillation of 4 Hz. Tests confirm the principle of controlled droplet detachment and reveal the great potential of this technological approach.