Material Removal in Ultrasonic Abrasive Polishing of Additive Manufactured Components

Abstract

Featured Application: The study of the material removal mechanisms in ultrasonic abrasive polishing provides technical support for the surface modification of metal-based additive manufactured components which have poor surface quality. In addition, the technology can be further applied to smoothing various complex shapes and the internal features of both metal and non-metal parts, due to the use of loose abrasive particles and the possibility of uniform material removal process.Abstract: Powder-based layered Additive Manufacturing (AM) techniques lead to high surface roughness, due to the balling and partial melting of powders, which cannot satisfy the requirements of design and practical use. Consequently, until there is a significant step-change in the resolution of AM technology, finishing processes will be a necessary step in the additive manufacturing process. In this work, ultrasonic abrasive polishing experiments are conducted with the aim of improving the surface quality of additive manufactured components. The roles of cavitation bubbles and abrasive particles in material removal are discussed. The impact action of abrasive particles is simulated using the Smoothed Particle Hydrodynamics (SPH) method. The effects of ultrasonic output power and the concentration of abrasive suspension on machining characteristics are also examined. It is found that the cavitation bubble collapse in ultrasonic polishing can remove the partially melted structures efficiently, and further roughness improvement could be obtained using the micro-cut and impact of abrasive particles in the slurry. An increase in the ultrasonic output power and abrasive concentration within a certain range lead to a more desirable polishing effect.Additive Manufacturing (AM) technology has developed rapidly over the past two decades. Metal-based AM techniques represented by Powder Bed Fusion (PBF) have advantages, including the production of fine features with great geometrical accuracy and high-strength-to-weight ratios. However, its forming mechanism, based on the melting of metal powders, induces the agglomeration of partially melted powders and a balling phenomenon in the process [1]. Therefore, the average roughness (Ra) of metal-based AM parts is generally higher than 10 µm [2], which not only affects the appearance, but also greatly influences several functional properties, including fatigue resistance, friction performance and heat transfer [3][4][5]. Accordingly, post-process finishing is required to improve the surface quality of AM parts [6,7]. AM parts always have complex shapes and features, which makes the finishing process difficult. Several surface modification processes for AM parts have been reported in the literature. However, each process has limitations and complexities. Implementing hand polishing as one of the main finishing processes for AM parts would increase the labor cost and time, and the surface quality would be poor. Laser polishing, chemical polishing, electrochemical polishing, and abrasive flow polishing have s...

Influence of Postprocessing on Wear Resistance of Aerospace Steel Parts Produced by Laser Powder Bed Fusion

“…Furthermore, the methods based on mechanical machining often leave cutting traces or traces of erosion such as those from cavitation-abrasive finishing that can dramatically influence the functional surfaces' wear resistance. At the same time, the positive influence of local heating and remelting with the formation of a more fine-grained submicron structure while avoiding volumetric spreading and high quenching temperatures of the sample during laser-plasma, ion-plasma, and electron beam polishing, and while strengthening the surface and subsurface layers through plastic deformation, vibratory tumbling [30][31][32][33][34] for large-scale parts, and etching [35][36][37], in combination with reduced roughness can significantly improve the wear resistance of the surfaces in the friction pair [38,39] and ensure tight contact with detachable fasteners of parts when subsequent heat treatment reduces anisotropy of the exploitation properties [40][41][42][43][44]. Surface roughness parameters of additively manufactured parts are critical for the nuclear industry to provide smooth contact between rods and volumetric mesh structures [45,46] to ensure smooth surfaces of nozzles and dies [47,48].…”

Applications of Additively Manufactured Tools in Abrasive Machining—A Literature Review

“…Other difficulties are associated with effective machining of parts with internal complex geometries, including metal-bonded abrasive tools. Currently, some non-conventional finishing techniques are proposed to improve the surface quality of 3D printed metal parts, like abrasive flow machining (AFM) and ultrasonic abrasive polishing [ 64 ]. Considering the high surface roughness resulting from powder-based AM techniques, much more attention should be paid to studying the influence of abrasive tool surfaces on the obtained technological effects, including the quality of the workpiece surfaces.…”

“…Laser polishing, chemical polishing, electrochemical polishing and abrasive machining have shown great potential for AM surface treatment. In powder bed fusion, for instance, laser polishing uses a direct laser source in the laser melting deposition equipment, but this technique may cause thermal damage [ 64 ].…”

A Review of Post-Processing Technologies in Additive Manufacturing

“…However, the process parameters should be well-selected to prevent strut damage. Wang et al [135] investigated the effects of ultrasonic abrasive polishing on the surface quality of AM parts. The impact action of abrasive particles was simulated with the Smoothed Particle Hydrodynamics (SPH) methodology.…”