Search Results (27)

Surface defects in additively manufactured internal channels limit their practical applications. Conventional post-processing methods suffer from limited accessibility and a tendency toward over-polishing, whereas magnetic abrasive finishing (MAF) offers high adaptability and precise process controllability. This study systematically investigates the material removal mechanisms in magnetic abrasive polishing and clarifies the distinctions and transitions between two-body and three-body wear modes. Based on these findings, a rolling removal model grounded in rough surface contact theory and a sliding removal model incorporating correction factors are established. Experiments were conducted on AlSi10Mg internal channels fabricated via selective laser melting (SLM) using a composite magnetic field polishing apparatus. The results verify the accuracy of the proposed models and demonstrate that the process effectively reduces surface defects and surface roughness. Although some deviations arise from model idealization and non-uniform magnetic field distribution, this study establishes a systematic theoretical framework for material removal in additively manufactured complex internal channels. Full article

As semiconductor devices continue to scale down and integrate more densely, the atomic-level planarization of metal interconnects and dielectric layers is critical. Consequently, the development of chemical mechanical planarization (CMP) materials must address both high polishing performance and environmental sustainability. In this study, γ-Fe₂O₃@SiO₂ core–shell abrasive particles were designed to overcome the performance and recyclability limitations of conventional SiO₂ abrasives. The γ-Fe₂O₃ core enables an efficient magnetic separation from spent slurry, while the tunable SiO₂ shell enhances the dispersion stability and modulates the polishing characteristics. When applied to the CMP of tungsten (W) thin films, the optimized γ-Fe₂O₃@SiO₂ abrasives achieved a higher removal rate and lower surface roughness than commercial SiO₂-based slurries. Notably, the abrasives maintained a high performance even after 10 reuse cycles through simple magnetic recovery. This demonstrates a highly efficient and sustainable design strategy for next-generation CMP materials. Full article

316L stainless steel slender tubes with smooth inner surfaces play an important role in fields such as aerospace and medical testing. In order to solve the challenge of difficult machining of their inner surfaces, this paper introduces a novel rotary magnetorheological finishing (RMRF) method specifically designed for processing the inner surfaces of slender tubes. This method does not require frequent replacement of the polishing medium during the processing, which helps to simplify the processing technology. By combining the rotational motion of a magnetic field with the linear reciprocating movement of the workpiece, uniform material removal on the inner surfaces of 316L stainless steel tubes was achieved. Initially, a finite element model coupling the magnetic and flow fields was developed to investigate the flow behavior of the MPF under a rotating magnetic field, to examine the theoretical feasibility of the proposed polishing principle. Subsequently, experimental validation was performed using a custom-designed polishing apparatus. Through processing experiments, with surface quality designated as the index, the influences of key parameters such as the volume content and sizes of carbonyl iron particles and abrasive particles in the MPF were comprehensively evaluated, and the composition and ratio of the MPF were optimized. Based on the optimized formulation, the optimal processing time was established, reducing the inner surface roughness from an initial Sa of approximately 320 nm to 28 nm, and effectively eliminating the original defects. Full article

The dual-pole magnetic abrasive finishing (DMAF) method was proposed to achieve a smooth surface on TC4 titanium alloy. Firstly, both the distribution of the magnetic field and the intensity of magnetic induction produced by nine combinations of magnetic poles of different shapes were simulated using Ansys Maxwell software (2024R2). According to the results of the simulation, the optimal combination of magnetic poles was determined. Then, the machining parameters of multi-stage DMAF were optimized through comparative experiments on major single factors. Finally, combinations of the mixed magnetic abrasive in three polishing stages were obtained as follows: #100 electrolytic iron powder (Fe₃O₄) + #2000 white abrasive (WA), #200 Fe₃O₄ + #8000 WA, and #450Fe₃O₄ + #w1 diamond (DMD). The gap between the upper and lower magnetic poles was set to 5 mm, the rotational speed of the magnetic pole was set to 300 rpm, and the quality ratio of the abrasive was 2:1. The experiments indicated that the average surface roughness Ra was reduced from an initial value of 0.433 μm to 8 nm after 30 min of multi-stage DMAF, and a nano-level mirror polishing effect was essentially achieved in the polishing zone. Full article

To solve the manufacturing problem of the efficient removal of multi-scale surface defects (wrinkles, cracks, scratches, etc.) on the inner wall of MP35N cobalt–chromium alloy vascular stents, this study proposes a collaborative optimization strategy of magnetic abrasive polishing (MAF) based on a new type of magnetic abrasive. In response to the unique requirements for the inner wall processing of high aspect ratio microtubes, metal-based Al₂O₃ magnetic abrasives with superior performance were prepared by the plasma melt powder spraying method. A special MAF system for the inner wall of the bracket was designed and constructed. The four-factor and three-level Box–Behnken response surface method was adopted to analyze the influences and interactions of tube rotational speed, magnetic pole feed rate, abrasive filling amount, and processing clearance on surface roughness (Ra). The significance order of each parameter for Ra is determined as follows: processing clearance > tube rotational speed > abrasive filling amount > magnetic pole feed rate. Using the established model and multiple regression equations, the optimal parameters were determined as follows: a tube rotational speed of 600 r/min, a magnetic pole feed rate of 150 mm/min, an abrasive filling amount of 0.50 g, and a processing clearance of 0.50 mm. The optimized model predicted an Ra value of 0.104 μm, while the average Ra value verified experimentally was 0.107 μm, with the minimum error being 2.9%. Compared with the initial Ra of 0.486 μm, directly measured by the ultra-depth-of-field 3D microscope of model DSX1000, the surface roughness was reduced by 77.98%. MAF effectively eliminates the surface defects and deteriorated layers on the inner wall of MP35N tubes, significantly improving the surface quality, which is of great significance for the subsequent preparation of high-quality vascular stents and their clinical applications. Full article

This study addresses the critical challenge of precise control over active abrasive particles in magnetorheological polishing (MRP) through innovative core–shell particle engineering. A sol–gel synthesized CIP@SiO₂ magnetic composite abrasive with controlled SiO₂ encapsulation (20 nm shell thickness) was developed using tetraethyl orthosilicate (TEOS) as the silicon precursor, demonstrating significant advantages in optical-grade fused silica finishing. Systematic polishing experiments reveal that the core–shell architecture achieves a remarkable 20.16% improvement in surface quality (Ra = 1.03 nm) compared to conventional CIP/SiO₂ mixed abrasives, with notably reduced surface defects despite a modest 8–12% decrease in material removal rate. Through synergistic analysis combining elastic microcontact mechanics modeling and molecular dynamics simulations, we establish that the SiO₂ shell mediates stress distribution at tool–workpiece interfaces, effectively suppressing deep subsurface damage while maintaining nano-scale material removal efficiency. The time-dependent performance analysis further demonstrates that extended polishing durations with CIP@SiO₂ composites progressively eliminate mid-spatial frequency errors without introducing new surface artifacts. These findings provide fundamental insights into designed abrasive architectures for precision finishing applications requiring sub-nanometer surface integrity control. Full article

Additive manufacturing (AM) has revolutionized the production of complex geometrical parts with metals; however, the usual layer-by-layer deposition results in poor surface quality and unpredictable surface integrity. Abrasive machining and finishing techniques play vital roles in counteracting these challenges and qualifying AM parts for practical applications. This review aims to present recent research developments concerning the machining of additively manufactured metal parts via both conventional and nonconventional abrasive machining methods. Conventional methods such as grinding, milling, polishing, honing, and sandblasting have been widely investigated for their ability to enhance the surface finish, dimensional accuracy, and mechanical properties of AM metal components. However, the characteristic features of various AM processes, such as porosity, microstructural features, and residual stresses, can significantly influence the machinability of the produced parts. Nonconventional methods such as abrasive flow machining, electrochemical machining, magnetic abrasive finishing, and vibratory bowl finishing, on the other hand, have shown potential in addressing the difficulties associated with internal machining geometries and hard-to-machine material combinations that are typical for many AM parts. This review also highlights some challenges and future trends in the machining of AM metal parts and emphasizes that further research is required in the direction of combinations of various postprocessing techniques, machinability regarding new alloy compositions, and the integration of AI for process optimization. As the demand for high-precision AM parts grows across various industries, the advancement of abrasive machining and finishing techniques is crucial for driving the wider adoption of AM technologies. Full article

Silicon nitride (Si₃N₄) is used for high-speed rotating bearings in machine tools, aircraft, and turbo pumps due to its excellent material properties such as high-temperature strength, hardness, and fracture toughness. Grinding with fixed abrasives enables high shape accuracy and high efficiency in machining brittle materials. However, it is difficult to completely remove surface damage, which limits its use in products requiring a nano surface. These defects also result in reduced reliability and shortened lifespan. Magnetic-assisted polishing (MAP) is a technology that can achieve a fine surface by using a mixture of iron powder and abrasives, but it requires a lot of time due to the low material removal rate (MRR). Therefore, this study developed a hybrid processing technology using a metal-bonded grinding wheel and a slurry with hard abrasives for the high precision of silicon nitride ceramic ball bearings. Experiments were conducted in order to compare and analyze the surface roughness and material removal rate. Through MAP, using a grinding wheel with low grit (#325), high-efficiency machining performance was confirmed with a maximum material removal rate of 1.193 mg/min. In MAP, using a grinding wheel with high grit (#2000), a nano-level surface roughness of 6.5 nm Ra was achieved. Full article

To extend the working life of products made of titanium alloy, it is necessary to improve the polishing method to diminish the remaining defects on the workpiece surface. The Halbach array-assisted magnetic abrasive particle polishing method for titanium alloy was employed in this work. The distribution of magnetic field strength was simulated and verified at first to learn the characteristics of the Halbach array used in this work. Then, the polishing performance of the polishing tool was studied by conducting the polishing test, which aimed to display the relationship between shear force and surface roughness with polishing time, and the surface morphology during polishing was also analyzed. Following the establishment of the response surface model, a study on the optimal polishing parameters was conducted to obtain the suitable parameters for maximum shear force and minimum surface roughness. The results show that the maximum shear force 6.11 N and minimum surface roughness S_a 88 nm can be attained, respectively, under the conditions of (1) polishing tool speed of 724.254 r·min⁻¹, working gap of 0.5 mm, and abrasive particle size of 200 μm; and (2) polishing tool speed of 897.87 r·min⁻¹, working gap of 0.52 mm, and abrasive particle size of 160 μm. Full article

To enhance the surface quality of metal 3D-printed components, magnetic abrasive finishing (MAF) technology was employed for post-processing polishing. Experimental investigation employing response surface methodology was conducted to explore the impact of processing gap, rotational speed of the magnetic field, auxiliary vibration, and magnetic abrasive particle (MAP) size on the quality enhancement of internal surfaces. A regression model correlating roughness with crucial process parameters was established, followed by parameter optimization. Ultimately, the internal surface finishing of waveguides with blind cavities was achieved, and the finishing quality was comprehensively evaluated. Results indicate that under optimal process conditions, the roughness of the specimens decreased from Ra 2.5 μm to Ra 0.65 μm, reflecting a reduction rate of 74%. Following sequential rough and fine processing, the roughnesses of the cavity bottom, side wall, and convex surface inside the waveguide reduced to 0.59 μm, 0.61 μm, and 1.9 μm, respectively, from the original Ra above 12 μm. The findings of this study provide valuable technical insights into the surface finishing of metal 3D-printed components. Full article

This study explores a super-fast magnetic abrasive finishing (MAF) process for polishing the surface of an Inconel 625 bar workpiece for a hydrogen solenoid valve stem. The Inconel 625 bar was chosen to replace the existing STS 316 bar material, previously used for a hydrogen solenoid valve stem. The cylindrical surface of Inconel 625 bars was polished by a super-fast MAF process with high rotational speeds of 1000, 5000, 15,000, and 25,000 RPM and a super-strong magnetic field of 550 mT. The polishing characteristics of this process were evaluated according to the type of abrasives, rotational speeds of the workpiece and processing time. As a result, a super-smooth Inconel 625 bar was successfully achieved, with a surface roughness (Ra) reduced from 0.31 μm to 0.02 μm under the optimal conditions (15,000 RPM, CNT particles (0.04 μm), PCD diamond abrasive (1 μm), Fe (#200), 0.5 g of light oil, and 16 min of processing time). Also, the Ansys analysis results showed suitable strain, equivalent stress, and safety factor of the Inconel 625 bar. This confirmed that, after a super-fast MAF process, an Inconel 625 bar is feasible for application in Hydrogen (H₂) tanks instead of a conventional STS 316 bar. Full article

This study investigates the intricate process of surface polishing for ITO-coated Pyrex glass utilizing magnetic abrasive polishing (MAP) while employing acoustic emission (AE) sensors for real-time defect monitoring. MAP, known for its versatility in achieving nanoscale thickness processing and uniform surfaces, has been widely used in various materials. However, the complexity of the process, influenced by multiple variables like cutting conditions, material properties, and environmental factors, poses challenges to maintaining high surface quality. To address this, a sensor monitoring system, specifically one that uses AE sensors, was integrated into the MAP process to detect and confirm defects, providing real-time insights into machining conditions and outcomes. AE sensors excel in identifying material deterioration, microcrack formation, and wear, even in cases of minor damage. Leveraging AE sensor data, this study aims to minimize surface defects in ITO thin films during MAP while optimizing surface roughness. The investigation involves theoretical validation, magnetic density simulations, and force sensor pressure measurements to identify factors influencing surface roughness. ANOVA analysis is employed to determine optimal processing conditions. Additionally, this study compares the identified optimal roughness conditions with those predicted by AE sensor parameters, aiming to establish a correlation between predicted and achieved surface quality. The integration of AE sensor monitoring within the MAP process offers a promising avenue for enhancing surface quality by effectively identifying and addressing defects in real time. This comprehensive analysis contributes to advancing the understanding of surface polishing methodologies for ITO-coated Pyrex glass, paving the way for improved precision and quality in thin-film surface processes. Full article

This study proposed a new magnetic abrasive finishing (MAF) method, in which a 6-axis robot with a magnetic machining tool was used to polish the inner surfaces of curved tubes. We have also developed a magnetic machining tool jig, which can be fixed at the front of the 6-axis robot, rotating freely and suitable for polishing the inner surfaces of curved tubes. In this study, we focused on investigating the machining parameters in the initial machining stage and precision finishing stage. Based on the characteristics of machining parameters, a multi-stage MAF process was conducted to obtain an inner surface with high quality and high efficiency. The experimental results showed that both the roughness Ra and Rz of inner surface in the initial machining stage significantly decreased with the increase in the mixed magnetic abrasives, to as low as less than 20 nm Ra in the precision finishing stage when the machining parameters were appropriately adjusted. In addition, the roughness Ra of inner surface could be further reduced to less than 10 nm Ra in the multi-stage MAF process. Finally, the magnetic flux density cloud map and the magnetic field line distribution map were analyzed in Ansys Maxwell. Full article

The internal wall of cardiovascular stent tubing produced by a drawing process has defects such as pits and bumps, making the surface rough and unusable. In this research, the challenge of finishing the inner wall of a super-slim cardiovascular stent tube was solved by magnetic abrasive finishing. Firstly, a spherical CBN magnetic abrasive was prepared by a new method, plasma molten metal powders bonding with hard abrasives; then, a magnetic abrasive finishing device was developed to remove the defect layer from the inner wall of ultrafine long cardiovascular stent tubing; finally, response surface tests were performed and parameters were optimized. The results show that the prepared spherical CBN magnetic abrasive has a perfect spherical appearance; the sharp cutting edges cover the surface layer of the iron matrix; the developed magnetic abrasive finishing device for a ultrafine long cardiovascular stent tube meets the processing requirements; the process parameters are optimized by the established regression model; and the inner wall roughness (Ra) of the nickel–titanium alloy cardiovascular stents tube is reduced from 0.356 μm to 0.083 μm, with an error of 4.3% from the predicted value. Magnetic abrasive finishing effectively removed the inner wall defect layer and reduced the roughness, and this solution provides a reference for polishing the inner wall of ultrafine long tubes. Full article

Nitinol (NiTi), an alloy of nickel and titanium, wires are an important biomedical material that has been used in catheter tubes, guidewires, stents, and other surgical instruments. As such wires are temporarily or permanently inserted inside the human body, their surfaces need to be smoothed and cleaned in order to prevent wear, friction, and adhesion of bacteria. In this study, NiTi wire samples of micro-scale diameters (i.e., Ø 200 μm and Ø 400 μm) were polished by an advanced magnetic abrasive finishing (MAF) process using a nanoscale polishing method. Furthermore, bacterial adhesion (i.e., Escherichia coli (E. coli), and Staphylococcus aureus (S. aureus)) to the initial and final surfaces of NiTi wires were investigated and compared in order to assess the impact of surface roughness on bacterial adhesion to the surfaces of NiTi wires. The finding revealed that the surfaces of NiTi wires were clean and smooth with a lack of particle impurities and toxic components on the final surface polished using the advanced MAF process. The surface roughness Ra values of the Ø 200 μm and Ø 400 μm NiTi wires were smoothly enhanced to 20 nm and 30 nm from the 140 nm and 280 nm initial surface roughness values. Importantly, polishing the surfaces of a biomedical material such as NiTi wire to nano-level roughness can significantly reduce bacterial adhesion on the surface by more than 83.48% in the case of S. aureus, while in the case of E. coli was more than 70.67%. Full article