Benny Schacht

Bio: Benny Schacht is an academic researcher from Katholieke Universiteit Leuven. The author has contributed to research in topics: Electrical discharge machining & Surface roughness. The author has an hindex of 6, co-authored 12 publications receiving 377 citations.

Surface and Sub-Surface Quality of Steel after EDM†

Abstract: This paper deals with the influence of electrical discharge machining (EDM) on surface and sub-surface quality in the manufacturing of mould and tool steel. The thermal nature of material removal by EDM yields a thermally affected zone at the surface of the manufactured part. This zone consists of a molten and resolidified layer, and a heat affected zone, showing properties that differ considerably from the base material. Based on experimental investigations with three types of EDM processes (sinking EDM, wire EDM and milling EDM), the influence of process parameters on surface and sub-surface properties is discussed. These include surface roughness, sub-surface micro-structure and composition, micro-hardness and residual stresses. Attention goes to the dangers of surface degradation, yet also to the opportunities to use the EDM process for surface improvement.

The skin-effect in ferromagnetic electrodes for wire-EDM

Abstract: In wire electrical discharge machining (wire-EDM) material is removed by the thermal energy of an electric spark that has been initiated between two electrodes (the wire and the workpiece), submerged in demineralised water. The use of high frequency current pulses for sparking leads to excellent machining performance, in terms of the work piece roughness, the material integrity of the cut and the material removal rate. To reach the highest frequencies, the wire-EDM generator mostly consists of a voltage source with an as low as possible internal inductance. The working current delivered to the spark and, hence, the material removal rate of the process depends on the total impedance of the electrical circuit. In this article the importance of the wire’s impedance will be shown. Due to the skin-effect, this impedance depends on the frequency of the current signal, especially for ferromagnetic wires, such as steel wire. Coatings will prove to be primordial to prevent the machining speed from dropping significantly.

Interaction between workpiece and CMM during geometrical quality control in non-standard thermal conditions

Abstract: Industrial quality demands have resulted in increasing attention towards the thermal behavior of coordinate measuring machines. The influence of the workpiece on the measurement accuracy is hereby often disregarded. This can lead to significant measurement errors. The described research examines the interaction between the measurement device and the measured object. Four distinct measurement error types that result from non-standard temperatures are listed. Temperature variations during the measurement lead to the most challenging situation. The key to measurement accuracy lies in linking the measurement time to the accompanying temperature variation. The possibilities of this methodology are indicated by an experiment on a reference object.

An Experimental Investigation into Additive Manufacturing-Induced Residual Stresses in 316L Stainless Steel

Abstract: Additive manufacturing (AM) technology provides unique opportunities for producing net-shape geometries at the macroscale through microscale processing. This level of control presents inherent trade-offs necessitating the establishment of quality controls aimed at minimizing undesirable properties, such as porosity and residual stresses. Here, we perform a parametric study into the effects of laser scanning pattern, power, speed, and build direction in powder bed fusion AM on residual stress. In an effort to better understand the factors influencing macroscale residual stresses, a destructive surface residual stress measurement technique (digital image correlation in conjunction with build plate removal and sectioning) has been coupled with a nondestructive volumetric evaluation method (i.e., neutron diffraction). Good agreement between the two measurement techniques is observed. Furthermore, a reduction in residual stress is obtained by decreasing scan island size, increasing island to wall rotation to 45 deg, and increasing applied energy per unit length (laser power/speed). Neutron diffraction measurements reveal that, while in-plane residual stresses are affected by scan island rotation, axial residual stresses are unchanged. We attribute this in-plane behavior to misalignment between the greatest thermal stresses (scan direction) and largest part dimension.