Laser polishing of 3D printed mesoscale components

Laser polishing of various engineered materials such as glass, silica, steel, nickel and titanium alloys, has attracted considerable interest in the last 20 years due to its superior flexibility, operating speed and capability for localised surface treatment compared to conventional mechanical based methods. The paper initially reports results from process optimisation experiments aimed at investigating the influence of laser fluence and pulse overlap parameters on resulting workpiece surface roughness following laser polishing of planar 3D printed stainless steel (SS316L) specimens. A maximum reduction in roughness of over 94% (from ∼3.8 to ∼0.2 μm Sa) was achieved at the optimised settings (fluence of 9 J/cm2 and overlap factors of 95% and 88–91% along beam scanning and step-over directions respectively). Subsequent analysis using both X-ray photoelectron spectroscopy (XPS) and glow discharge optical emission spectroscopy (GDOES) confirmed the presence of surface oxide layers (predominantly consisting of Fe and Cr phases) up to a depth of ∼0.5 μm when laser polishing was performed under normal atmospheric conditions. Conversely, formation of oxide layers was negligible when operating in an inert argon gas environment. The microhardness of the polished specimens was primarily influenced by the input thermal energy, with greater sub-surface hardness (up to ∼60%) recorded in the samples processed with higher energy density. Additionally, all of the polished surfaces were free of the scratch marks, pits, holes, lumps and irregularities that were prevalent on the as-received stainless steel samples. The optimised laser polishing technology was consequently implemented for serial finishing of structured 3D printed mesoscale SS316L components. This led to substantial reductions in areal Sa and St parameters by 75% (0.489–0.126 μm) and 90% (17.71–1.21 μm) respectively, without compromising the geometrical accuracy of the native 3D printed samples

Benchmarking of three processes for producing castings incorporating micro/meso-scale features with a high aspect ratio

This paper investigates the capabilities of three different process chains for vacuum investment casting of parts incorporating micro/mesoscale features. The first two process chains employ the classical Lost Wax Process and make use of layer-based manufacturing technologies, ThermoJet and PatternMaster respectively, to create patterns out of a thermoplastic material, while the third one, Fcubic, produces directly a casting tree in zirconia ceramics. The study involves the manufacture of test parts in aluminium/zinc alloys and stainless steel with microfeatures in the range of 250 to 700 μm and aspect ratios up to 50. The dimensional accuracy, surface quality, and production costs of the investigated manufacturing routes are compared. A metallographic analysis is performed on castings in aluminium to investigate the evolution of the dendrite structure and eutectic clusters of microfeatures as a function of their aspect ratios together with their influence on the parts' mechanical properties. Conclusions are drawn about the applicability of the studied three processes for casting parts with micro/mesoscale features

Indoor Received Power Prediction Based on Physical Optics (PO): Simulations and Experimental Validation in Industrial Environment

This study presents an approach based on Physical Optics computations to predict the receive signal power in an indoor environment. The application in focus pertains the development of highly reliable manufacturing industry processes where wireless communications plays a key role. Our proposed numerical method shows a good agreement with measurement data. It is therefore suggested that Electromagnetic modelling based on computationally efficient Physical Optics algorithms can be used as a complement, an alternative or even a replacement for empirical models requiring time consuming measurement campaigns