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Fast progress in near-net-shape production of parts has attracted vast interest in internal surface finishing. Interest in designing a modern finishing machine to cover the different shapes of workpieces with different materials has risen recently, and the current state of technology cannot satisfy the high requirements for finishing internal channels in metal-additive-manufactured parts. Therefore, in this work, an effort has been made to close the current gaps. This literature review aims to trace the development of different non-traditional internal surface finishing methods. For this reason, attention is focused on the working principles, capabilities, and limitations of the most applicable processes, such as internal magnetic abrasive finishing, abrasive flow machining, fluidized bed machining, cavitation abrasive finishing, and electrochemical machining. Thereafter, a comparison is presented based on which models were surveyed in detail, with particular attention to their specifications and methods. The assessment is measured by seven key features, with two selected methods deciding their value for a proper hybrid machine.

Magnetic abrasive finishing (MAF) has attracted much attention as an advanced nano-finishing technology in achieving high-quality surface for finishing superalloys, composites, and ceramics. This paper provides a comprehensive review on MAF process which is mainly organized by different six sections, including MAF principles, magnetic abrasive preparation, MAF tools, MAF modeling and simulation, MAF characteristics, and challenges and future directions. The principle of MAF for internal workpiece and flat workpiece is mainly introduced. Magnetic preparation methods, including simply mixing method, bonding method, sintering method, gas atomization, and rapid solidification method, are described in detail. The design of MAF tools for outer surface and inner surface is summarized. It also covers some models and simulations to predict optimal processing parameters. Force measurement and material removal mechanism to explore the MAF processes are performed. Finally, challenges and future directions are provided. This review is beneficial to researchers and practitioners in the MAF-related fields.

The geometric complexity of 3D-printed parts increases the difficulty of surface finishing with the conventional grinding technique. In this study, a rotary ultrasonic-assisted abrasive flow finishing (RUA-AFF) method is proposed towards improving the performance of the AFF process by providing rotary motion and ultrasonic vibration to the equipment. Finishing experiments are carried out involving Al6061 to investigate the capabilities of the proposed RUA-AFF. The obtained results show that (1) the higher ultrasonic vibration amplitude results in the greatest improvement in the work surface quality and a higher increase in material removal rate (MRR); (2) with the higher ultrasonic frequency and rotational speed, the surface roughness and MRR are decreased marginally; (3) there are two material remove modes in the RUA-AFF process: abrasive impingement and micro-cutting. These indicate that the high efficiency and high-quality finishing of Al6061 can be performed with the proposed RUA-AFF technique.

As an advanced precision machining process, magnetic abrasive finishing (MAF) technology can be applied to grind complex workpieces. However, it is not conducive to formulate an appropriate processing that MAF processing on tubular workpiece has a severe lack of a well-defined material removal rate model. In order to solve this problem, the contact form between the magnetic abrasive and the workpiece surface was simplified, and the force analysis of the magnetic abrasive in the magnetic field was performed. Furthermore, an ideal predictive model on material removal rate was proposed, which was based on both the quantity of active abrasives in the processing area and the depth at which magnetic abrasive was pressed into the workpiece. The correction factor 'k' was determined based on the comparison and analysis of experimental results and theoretical predictions. What is more, the accuracy of the revised model on material removal rate was confirmed. The surface roughness of the workpiece was reduced from 0.213 to 0.058 μm after undergoing 19 cycles of processing under the conditions of spindle speed of 104.7 rad/s, abrasive mass of 3.5 g, processing distance of 2 mm, and a feed rate of 3 mm/s. The material removal rate was 0.140 μm/min, which exhibits an absolute error of 7.675% in comparison to the predicted value of 0.152 μm/min. The results indicate that the model can meet the prediction requirements of material removal rate in the MAF process, and MAF technology can effectively achieve finishing on the inner surface of the tube.

In response to the shortcomings of existing bonded magnetic abrasives, such as poor finishing performance, short service life, and insufficient mechanical properties of the binder, a preparation method for the nanoparticle-enhanced bonded magnetic abrasive (NEBMA) was proposed, and its morphology and composition were analyzed. The finishing characteristics and service life of the novel and traditional bonded magnetic abrasives were compared through planar magnetic abrasive finishing experiments. Under the same process conditions, the quality of magnetic abrasive finishing for the 3D printed AlSi10Mg, aluminum alloy A12A, aluminum alloy 7075, and 304 stainless steel was evaluated using NEMBA as a tool. The results show that the NEBMA has a higher finishing efficiency and a longer lifespan than the conventional bonded magnetic abrasive. After finishing, the surface roughness Ra of 3D printed AlSi10Mg, aluminum alloy A12A, aluminum alloy 7075, and 304 stainless steel can be reduced by 94.21%, 91.25%, 83.33%, and 48.89%, respectively. The research results can provide an effective theoretical basis and technical reference for developing new magnetic abrasives.

Abstract This work aims to reveal the action mechanism of multi-abrasive particles in finishing the complex inner cavity. The body force function of particles and the particle–wall contact model were developed based on the theories of the magnetic field and the discrete element method (DEM). The particle motion and the wall-wear mode were simulated, revealing the influences of abrasive particle size, magnetic pole speed, and processing clearance on the finishing quality. Experiments verified the feasibility of the simulation. The result showed that when the processing clearance was 1 mm, the magnetic pole speed was 800 r/min, the finishing time was 40 min, and the steel grit (SG) diameter was 1 mm, the Ra was decreased by 89.3%. And then, 0.6 mm SGs were switched to perform the secondary polishing remaining other process parameters unchanged, and the Ra could be reduced to 0.95 μm. The result can provide a practical research idea for polishing the inner cavity of special-shaped parts.

In order to obtain a high accuracy with high machining efficiency for finishing hard alloy metal material, we proposed a hybrid finishing method which is electrochemical (ECM) effects assisted magnetic abrasive finishing (MAF). In this study, the electrochemical magnetic abrasive finishing (EMAF process) was divided into EMAF stage and MAF stage. The metal surface can be easily finished with the passive films formed in electrochemical reactions. Simultaneously, the passive films can be removed by frictional action between magnetic brush and workpiece surface. Thus, the essence of EMAF process is to form and remove the passive films on the workpiece surface. This study focused on investigating the finishing mechanism and finishing characteristics of EMAF process. Compared with traditional MAF process, it can be confirmed that the finishing efficiency is remarkably improved more than 75% by EMAF process, and the surface roughness is also lower in EMAF process. The optimal experimental result of EMAF process showed that the surface roughness was reduced to less than 30 nm from the original surface roughness 178 nm after 4 min in EMAF stage, and the surface roughness was finally reduced to 20 nm after 10 min in MAF stage. The material removal rate in hybrid finishing stage was nearly 7 times than that in MAF stage. Additionally, the effective finishing area in EMAF process was about 70% of that in MAF process.

Due to the high hardness and brittleness of zirconia ceramic (ZrO2), it is difficult to generate a good surface integrity by traditional grinding. The surface quality of ZrO2 can be greatly improved by magnetic abrasive finishing (MAF) with spherical CBN/Fe-based magnetic abrasive particles (MAPs) prepared by gas atomization. In this study, it was found that the difference of machining gap in MAF would seriously affect the surface integrity of ZrO2. The grinding pressure of CBN MAPs on ZrO2 under different machining gaps was analyzed theoretically. The surface morphology, surface roughness Ra and material removal amount MR, grinding pressure, surface temperature and residual stress, subsurface damage and the morphology of MAPs adsorbed by magnetic pole after grinding were studied under different machining gaps (3 mm to 1 mm). The results show that when the machining gap is large, the grinding pressure is small, the number of MAPs involved in grinding is small, and the surface integrity of ZrO2 do not change significantly. When the machining gap is small and the grinding pressure is too large, a large number of MAPs are extruded from the machining area, the magnetic abrasive brush is changed from flexible to rigid, and the ceramic surface is mainly removed by brittleness. After grinding, many cracks and pits are generated on the ceramic surface, and cracks are also produced on the subsurface, which destroys the surface integrity of the workpiece. Under the appropriate machining gap, it can not only ensure that the grinding pressure is large, but also make the ZrO2 surface mainly plastic removal, and finally obtain the best surface integrity. The optimal machining gap in this experiment is 2 mm.

Selective laser melting (SLM) technology is playing an increasingly important role in today’s manufacturing industry. However, the surface quality of SLM samples is relatively poor and cannot be directly applied to industrial production. Therefore, this paper focuses on the post-treatment process of SLM AlSi10Mg alloy. First, the rough machining is performed by a grinding process (GP), and then, the magnetic abrasive finishing (MAF) is used for finish machining. The experiment results show that the combination of GP and MAF can effectively reduce the surface roughness and improve the surface quality of SLM AlSi10Mg alloy. The GP reduced the surface roughness to drop from 7 μm (after SLM forming) to about 0.6 μm, and the rough surface with defects such as spheroids and pits evolved into the fine surface with scratches and pores. The MAF reduced the surface roughness to a minimum of 0.155 μm, which resulted in excellent surface morphology. The surface hardness after the GP was higher, and the MAF reduced the hardness of the GP surface.

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.