Modeling and simulation of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes, which produces a high level of surface quality and is primarily controlled by a magnetic field. In MAF, the workpiece is kept between the two poles of a magnet. The working gap between the workpiece and the magnet is filled with magnetic abrasive particles. A magnetic abrasive flexible brush (MAFB) is formed, acting as a multipoint cutting tool, due to the effect of the magnetic field in the working gap. This paper deals with the theoretical investigations of the MAF process. A finite element model of the process is developed to evaluate the distribution of magnetic forces on the workpiece surface. The MAF process removes a very small amount of material by indentation and rotation of magnetic abrasive particles in the circular tracks. A theoretical model for material removal and surface roughness is also proposed accounting for microcutting by considering a uniform surface profile without statistical distribution. Numerical experiments are carried out by providing different routes of intermittent motion to the tool. The simulation results are verified by comparing them with the experimental results available in the literature.     

磁力研磨加工永磁极设计及仿真研究

为进一步提高磁力研磨加工的表面质量和加工效率,基于平面磁力研磨装置,采用端面中心材料去除且开矩形槽的强永磁材料作为磁极,进行磁力研磨加工。利用ANSYS对磁极不同端面形状、开槽尺寸的磁力线分布和磁场强度分布进行模拟仿真,并通过磁力研磨加工试验验证设计磁极实际加工效果。结果表明:去除中心材料的磁极磁力线分布更加密集且增大了磁极中心处的磁场强度,从而提高研磨效率;通过仿真对比发现,当磁极中心去除材料半径与底面半径之比为1:3且开矩形槽深宽之比为1:1时研磨质量最佳。     

磁力光整加工平面磁极头设计及仿真

作为以提高表面质量的磁力光整加工技术,磁极的设计起着至关重要的作用.提出将永磁极设计为锥形以取代笨重的电磁极,仿真了磁极有无锥度的磁场强度分布,发现有锥度磁极的磁场分布较集中,可增加资源利用率且锥度为1∶0.6时磁场分布较强.分析了开槽能够改善磁场梯度分布,且开矩形槽和槽深宽之比为1∶1时产生的磁场效果最佳.并采用试验验证,磁极有锥度后工件表面质量改善效果要比无锥度磁极好.     

New iron-based SiC spherical composite magnetic abrasive for magnetic abrasive finishing

SiC magnetic abrasive is used to polish surfaces of precise, complex parts which are hard, brittle and highly corrosion-resistant in magnetic abrasive finishing(MAF). Various techniques are employed to produce this magnetic abrasive, but few can meet production demands because they are usually time-consuming, complex with high cost, and the magnetic abrasives made by these techniques have irregular shape and low bonding strength that result in low processing efficiency and shorter service life. Therefore, an attempt is made by combining gas atomization and rapid solidification to fabricate a new iron-based SiC spherical composite magnetic abrasive. The experimental system to prepare this new magnetic abrasive is constructed according to the characteristics of gas atomization and rapid solidification process and the performance requirements of magnetic abrasive. The new iron-based SiC spherical composite magnetic abrasive is prepared successfully when the machining parameters and the composition proportion of the raw materials are controlled properly. Its morphology, microstructure, phase composition are characterized by scanning electron microscope(SEM) and X-ray diffraction(XRD) analysis. The MAF tests on plate of mold steel S136 are carried out without grinding lubricant to assess the finishing performance and service life of this new SiC magnetic abrasive. The surface roughness(Ra) of the plate worked is rapidly reduced to 0.051 μm from an initial value of 0.372 μm within 5 min. The MAF test is carried on to find that the service life of this new SiC magnetic abrasive reaches to 155 min. The results indicate that this process presented is feasible to prepare the new SiC magnetic abrasive; and compared with previous magnetic abrasives, the new SiC spherical composite magnetic abrasive has excellent finishing performance, high processing efficiency and longer service life. The presented method to fabricate magnetic abrasive through gas atomization and rapid solidification presented can significantly improve the finishing performance and service life of magnetic abrasive, and provide a more practical approach for large-scale industrial production of magnetic abrasive.     

Experimental investigations into forces acting during a magnetic abrasive finishing process

A magnetic abrasive finishing (MAF) process is the one in which material is removed in such a way that surface finishing and deburring are performed simultaneously with the applied magnetic field in the finishing zone. Knowledge of forces acting during MAF is important to understand the mechanism of material removal. Forces have direct influence on the generation of a finished surface and accuracy of the workpiece. This paper reports the experimental findings about the forces acting during MAF and provides correlation between the surface finish and the forces. The resistance type force transducer (ring dynamometer) has been designed and fabricated. It is used to measure the normal magnetic force component responsible for microindentation into the workpiece and tangential cutting force component producing microchips. The force data have been recorded on-line by making use of virtual instruments (using Lab-View software). It is concluded that forces and change in surface roughness (ΔRa) increase with increase in current to the electromagnet (or magnetic flux density) and decrease in the working gap.On deputation from M.M.M.Engg. College, Gorakhpur (UP) India     

Development of a new magnetic abrasive finishing process with renewable abrasive particles using the circulatory system

In order to improve the finishing efficiency of the Magnetic Abrasive Finishing process, we proposed a new MAF process with renewable abrasive particles using compound magnetic finishing fluid circulatory system in this paper. This new finishing process has a circulating system that uses a conveyor belt to renew the mixed abrasive particles. This not only maintains the stability of the finishing but also ensures that the processing does not need to be interrupted. In this study, we investigated the magnetic field distribution, finishing force, and finishing behavior of the processing area. Furthermore, we designed experimental device to finish the sus304 stainless steel plate, to verify the feasibility of this process and understand its characteristics through processing experiments. Moreover, the influence of important process parameters, including magnetic particles, abrasive particles, conveyor belt line speed and working gap, on the surface quality of the workpiece is studied through the experiment. The experimental results indicate that the present process can achieve stable processing of the material surface without interruption, and the surface roughness of the sus304 stainless steel plate has been improved from 273 nm to 23 nm through this process.     

球形磁性磨料磁力研磨ZrO2材料机理研究

在磁力研磨加工ZrO 2材料过程中,分析了单颗磁性磨料在加工区域内的受力情况,并对研磨压力的形成进行探讨,利用公式推导计算研磨压力,通过研磨压力的大小分析了磁力光整加工中材料的去除机理,包括脆性断裂去除、塑性变形去除和粉末化去除。通过白光干涉仪、扫描电子显微镜等分析检测仪器对磁力研磨加工后的工件表面进行检测,可知在其他条件相同时,磁力研磨加工后的工件材料精度高于传统的草轮抛光精度,可达到0.59μm。     

Effect of temperature on the magnetic abrasive finishing process of Mg alloy bars

Experiments were conducted to evaluate the effect of temperature during magnetic abrasive finishing of Mg alloy bars. A magnetic abrasive finishing process is an unconventional finishing technique that has been used to achieve high-quality surfaces with dimensional accuracy. In this study, a Mg alloy bar, which is widely used in automobiles, aircraft, IT, and the defense industry, was chosen as a cylindrical workpiece. The workpiece was then finished with a magnetic abrasive finishing process at three different temperatures, i.e., a cryogenic temperature, room temperature, and high temperature. In the cryogenic temperature condition, liquid nitrogen and argon gas were used as the cryogenic cooling gases in the finishing process; the results from this treatment were compared with those obtained at room temperature and high temperature conditions. At the room temperature condition, the finishing process of the cylindrical workpiece was performed at 24 °C. To carry out the high temperature condition, a hot air dryer was used to maintain a finishing temperature of 112 °C. The experimental results show that the room and cryogenic temperatures could yield excellent performance in terms of the surface roughness. However, in terms of the removal weight and change in diameter, the high temperature condition was found to be superior. In the present research, the improvements of the surface roughness (Ra) at room temperature (24 °C) and cryogenic temperature (-120 °C) conditions were 84.21 % and 55 %, respectively.

     

Effect of working gap and circumferential speed on the performance of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes in which workpiece is kept between two magnets, and cutting force is controlled by working gap and magnetic field between the two magnets. MAF setup is designed for finishing cylindrical workpieces and it is mounted on lathe machine. The loosely bounded powder is prepared for experimentation by homogeneous mixing of magnetic powder (Fe powder of 300 mesh size (51.4 μm)), abrasive powder (Al₂O₃ of 600 mesh size (25.7 μm), and lubricant called servospin-12 oil. To investigate the effects of working gap and circumferential speed on material removal, change in surface finish and percent improvement in surface finish, a series of experiments have been conducted using in-house fabricated setup. Based upon the results, in general, material removal decreases by increasing working gap or decreasing circumferential speed of the workpiece. Change in surface finish increases by increasing circumferential speed of the workpiece.     

Optimizing multi-requirements of surface finishing in magnetic abrasive cutting process using grey relational analysis

Journal of Mechanical Science and Technology - Mechanical machining inevitably generates undesirable parts on the surface of workpieces. It brings adverse effects in terms of manufacturing cost,...     

实用型磁力研磨装置的设计与研究

研究永磁极头磁场的控制技术 ,加工区磁通密度及磁场梯度符合技术要求。永磁极头简化了装置 ,降低成本 ,易维护 ,通用性好。可根据用户的需求改装在不同的机床上 ,成为一类高精度、复杂难加工零件的重要加工设备。     

On the effect of relative size of magnetic particles and abrasive particles in MR fluid-based finishing process

Magnetorheological fluid-based finishing (MRFF) process is widely used for fabrication of optical material such as glasses, lenses, mirrors, etc. Performance of the process is significantly affected by the properties (size, concentration, hardness, etc.) of the constituents of MR fluid. MR fluids have been prepared by varying three abrasive particles mean sizes (4 µm, 6 µm and 9 µm) with carbonyl iron particles (CIPs) having average particles size of 6 µm. Yield stress of MR fluids is measured using a rheometer. The composition of the fluid has CIPs of 25%, abrasive 10% (by volume) and rest of the base medium (liquid). The yield stress was evaluated at magnetic flux density of 0.33 Tesla. It is observed that MR fluid having the same particle size of CIPs and abrasive particles exhibits higher yield stress as compared to other combinations. The lowest yield stress is observed in case of 9 µm abrasive particles size. A set of finishing experiments is carried out to understand the effect of relative size of magnetic particles and abrasive particles on surface roughness values.     

磁性磨粒的制备工艺及其研磨性能研究

针对研磨效率低,磁性磨粒制备困难,比较了热压烧结、放电等离子烧结(SPS)烧结和粘结磁性磨粒等方法,发现SPS烧结磁性磨粒虽然成本较高,但改善了粘结磨粒和热压烧结磨粒的缺陷,且耐用度很高,加工效率和加工性能比较好.     

Polishing of the aluminum sheets with magnetic abrasive finishing method

Recent needs to superfinished surfaces have motivated researchers to study on modern methods of polishing. Magnetic-assisted finishing is one of those methods which can generate mirror-like finished surfaces. This paper investigates the effects of some parameters, i.e., rotational speed of the permanent magnetic pole, working gap between the permanent pole and the workpiece, number of cycles, and the weight of the abrasive particles on aluminum surface finishing. Three-level full factorial method was used as design of experiments technique to study the selected factors. A total of 54 designed tests were done on aluminum sheet using an innovative material removal mechanism. Analysis of variance was used to determine significant factors and also to obtain an equation based on data regression. Experimental results indicate that the number of cycles and working gap are the most significant parameters on surface roughness change (?Ra), followed by rotational speed and then weight of powder.