磁性研磨在模具曲面抛光中的应用

针对大型模具曲面精整加工的问题,探讨采用磁性研磨加工模具曲面的工艺。根据磁性研磨加工原理,基于数控铣床研制了磁性研磨实验装置,采用工具旋转的磁性研磨加工方式,磁性磨料受到磁场约束力和离心力的作用,成为影响加工过程正反两方面的因素。对模具曲面进行磁性研磨加工实验,针对模具曲面研磨量不均匀问题,分析了影响曲面研磨量的主要因素,提出了从磁极形状和研磨轨迹等方面控制研磨量的方法。     

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.     

磁极形状对磁粒研磨工艺影响的数值分析

利用有限元的方法对磁粒研磨中的关键技术———磁极的形状做了全面的分析计算 ,得到适合磁粒研磨的最佳磁极形状 ,解决了在磁粒研磨中经常出现的“磁滞”现象 ,不仅改善工件的质量、提高加工的效率 ,同时也延长磁极的使用寿命。这给磁粒研磨技术在生产中的应用提供了重要的理论依据     

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。     

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.     

Study of magnetic abrasive finishing in free-form surface operations using the Taguchi method

This study employed magnetic abrasive finishing (MAF) to conduct free-form surface abrasion of stainless SUS304 material operations. The operations were demonstrated using a permanent magnetic finishing mechanism installed at the CNC machining center. The operations were performed using the Taguchi experimental design, considering the effects of magnetic field, spindle revolution, feed rate, working gap, abrasive, and lubricant. Furthermore, the experimental data was collected using the Taguchi experimental design. The optimal parametric conditions for processing stainless SUS304 material were applied in a two-stage process comprised of rough finishing that involved MAF followed by a precise finishing of the surface. Prior to rough finishing, the R_max value was 2.670 μm; after rough finishing, the value was 0.158 μm. Precise finishing yields an even lower value of 0.102 μm similar to that of the mirror surface. Therefore, the results revealed that MAF provides a highly efficient way of obtaining surface finish.     

磁力研磨加工参数的定量分析

对磁力研磨光整加工所涉及的加工工艺力进行研究 ,给出相应的数学表达式 ,对磁力研磨在生产中的应用提供了重要的理论依据。     

磁力研磨头形状对研磨效果的影响

磁力研磨是利用磁性磨料和磁场作用进行研磨加工的一种研抛技术．讨论了不同研磨头形状对磁力研磨的影响以及研磨头设计的要点．在五自由度并联机床上利用不同形状磨头对自由曲面的模具进行了磁力研磨试验．开槽研磨头比不开槽研磨头的研磨效果要好得多．实验分析了利用球型磨头对工件磁力研磨时,磁场强度、研磨间隙、研磨时间等因素对自由曲面模具表面研磨质量的影响．利用五自由度并联机床不仅可以去除自由曲面模具表面的切削残留痕迹,降低模具的表面粗糙度,还可解决传统手工研磨方式所引起的工件研磨质量不一致的缺陷。     

Improving Electrical Discharge Machined Surfaces Using Magnetic Abrasive Finishing

Abstract

A recast layer is invariably present on surfaces produced by electrical discharge machining (EDM). For some metals with high hardness, the recast layer may contain micro-cracks. This damaged layer can affect the service life of the parts produced by this method. This investigation demonstrates that magnetic abrasive finishing (MAF) process using unbonded magnetic abrasives (UMA), can improve the quality of EDM machined surfaces effectively. The UMA used herein is a mechanical mixture of steel grit and SiC abrasive. SKD11 tool steel was used as the workpiece. Experimental results show that the recast layer and micro-cracks on EDM machined surfaces can be completely removed and a new surface of roughness on the order of 0.04 μm Ra can be produced. Additionally, experiments using the Taguchi method and L₁₈ orthogonal array enable the determination of the optimum process conditions for improving the surface finish. Further, the significance of the control factors was identified with the assistance of analysis of variance (ANOVA), and the optimum combination of the process parameters was verified by conducting several confirmatory experiments.     

烧结法与雾化法制备磁性磨料的形貌及研磨性能

分析了烧结法和雾化法制备磁性磨料的工艺过程、特点,并对磁性磨料的形貌、研磨性能进行了对比。结果表明:与烧结法相比,雾化法制备磁性磨料的磨粒相均匀地分布在铁基体上,具有较长的使用寿命,研磨性能更加优良。     

Improving Electrical Discharge Machined Surfaces Using Magnetic Abrasive Finishing

A recast layer is invariably present on surfaces produced by electrical discharge machining (EDM). For some metals with high hardness, the recast layer may contain micro-cracks. This damaged layer can affect the service life of the parts produced by this method. This investigation demonstrates that magnetic abrasive finishing (MAF) process using unbonded magnetic abrasives (UMA), can improve the quality of EDM machined surfaces effectively. The UMA used herein is a mechanical mixture of steel grit and SiC abrasive. SKD11 tool steel was used as the workpiece. Experimental results show that the recast layer and micro-cracks on EDM machined surfaces can be completely removed and a new surface of roughness on the order of 0.04 μm Ra can be produced. Additionally, experiments using the Taguchi method and L₁₈ orthogonal array enable the determination of the optimum process conditions for improving the surface finish. Further, the significance of the control factors was identified with the assistance of analysis of variance (ANOVA), and the optimum combination of the process parameters was verified by conducting several confirmatory experiments.     

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.     

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.     

Comprehensive performance evaluation of the magnetic abrasive particles

Magnetic abrasive finishing (MAF) is one of the nontraditional machining processes that have been studied to improve the surface quality and deburr the workpiece. The magnetic abrasive particles (MAPs) as the machining tool of MAF influence the finishing efficiency and the final surface quality. In this study, in order to evaluate the comprehensive performance of the sintered MAPs with the simply mixed MAPs, the surface morphologic structure and the particulate compositions of the sintered MAPs were observed and tested by scanning electron microscopy with energy spectrum analysis. The M–H curves of the two kinds of MAPs were tested through a superconducting quantum interference device. The actual magnetic flux density in the working gap was measured by Gauss meter, and the results showed that the magnetic properties of the sintered MAPs are superior to the simply mixed MAPs. At last, through the different finished surface texture and motion analysis combining with all the measurements, results proved that the finishing ability of sintered MAPs is greater than simply mixed MAPs.     

磁力光整加工铝镁合金永磁极研究

以主轴改造后的XK7136C数控铣床为平台,以AZ31系镁合金与7075-T651铝合金为研究对象,通过理论计算与磁场仿真,设计出适用于加工铝镁合金结构材料平面的强永磁材料磁极,并采用雾化快凝球形磁性磨粒进行试验,以验证该种光整加工方法的可行性及球形磨粒性能。使用“米字槽”与“田字槽”两种磁极分别对两种材料进行研磨实验。实验结果表明：两种端面开槽方式均可防止磨料的局部堆积,保证磨料的流动性,并使端面磁通密度增大,磁场强度梯度增大,提高研磨效率。两种磁极所研磨表面粗糙度分别为0.126 μm和0.148 μm,端面拥有更大磁通密度的“田字槽”磁极前期研磨效率更佳。     

Two-dimensional vibration-assisted magnetic abrasive finishing of stainless steel SUS304

Traditional magnetic abrasive finishing (MAF) involves unidirectional polishing of surface but suffers the drawback of forming deep scratches, resulting in poor surface quality. This study attempts to enhance the polishing efficiency of MAF by adding vibration to the platform, focusing on the fabrication of the two-dimensional vibration-assisted MAF (2D VAMAF) setup. Experiments are conducted with variations in parameter levels of 2D VAMAF. Comparison of finished surface results shows superiority of 2D VAMAF in obtaining lower surface roughness and mirror surface quality. In addition, this study uses the Taguchi experimental design method to obtain the optimal parameter combination of 2D VAMAF for surface roughness improvement. The optimal combination obtained includes working gap (1 mm) and weight of SiC, steel particles, and machining fluid (1 g, 1.5 g and 3 g, respectively); frequency of vibration along X and Y directions (16.67 Hz); rotational speed of magnet (500 rpm); and size of SiC and steel particles (8000 and #120, respectively). With 5-min 2D VAMAF under optimal parameter combination, the surface roughness of a stainless steel SUS304 workpiece can be reduced from 0.13 to 0.03 μm, an improvement of 77 %. Experimental results reveal that 2D VAMAF can indeed improve surface quality with a shorter processing time and a smaller amount of abrasives required, both of which contribute to cost reduction. With less pollution incurred, 2D VAMAF is a more environmental friendly machining method in industry.     

Magnetic abrasive finishing of hardened AISI 52100 steel

Surface finish has a vital influence on functional properties such as wear resistance and power loss due to friction on most of the engineering components. Magnetic abrasive finishing (MAF) is one of the advanced finishing process in which a surface is finished by removing the material in the form of microchips by abrasive particles in the presence of magnetic field in the finishing zone. In this study an electromagnet with four poles has been used which was found to give better performance in terms of achieving surface quality in lesser processing time. Voltage, mesh number, revolutions per minute (rpm) of electromagnet, and percentage weight of abrasives have been identified as important process parameters affecting surface roughness. The experiments were planned using response surface methodology and percentage change in surface roughness (??Ra) was considered as response. Analysis of experimental data showed that percentage change in surface roughness (??Ra) was highly influenced by mesh number followed by percentage weight of abrasives, rpm of electromagnet, and voltage. In this study, the least surface roughness value obtained was as low as 51?nm in 120?s processing time on a hardened AISI 52100 steel workpiece of 61 HRC hardness. In order to study the surface texture produced and to identify finishing mechanism, scanning electron microscopy and atomic force microscopy were also conducted. Shearing and brittle fracture of small portion of peaks of grounded workpiece have been found to be finishing mechanisms during MAF of AISI 52100 steel.     

超声磁力复合研磨钛合金锥孔的试验研究

为了提高钛合金锥孔的研磨质量和研磨效率,提出了采用超声波振动辅助磁力研磨的复合加工方案。加工时,磨粒在磁场束缚下切削锥孔表面,并对其进行不断撞击,且因为磁场力、超声振动力和离心力等综合影响的原因,磨粒的切削轨迹呈现明显的多向性。针对钛合金锥孔,与传统磁力研磨法进行试验对比,并分析研磨后试件的材料去除量、表面粗糙度和表面形貌等来验证超声磁力复合研磨的效果。结果表明：超声磁力复合研磨加工效率得到提高;锥孔的材料去除量增加至1.6倍;研磨后锥孔平均表面粗糙度由原始的R_a1.23 μm降至R_a0.25 μm,下降率是传统工艺的1.3倍;试件表面的微波峰、凹坑和加工纹理均被去除,锥孔表面质量得到显著提高,且试件形状精度得到改善。     

一种基于气压悬浮磨料池光整加工方法的研究

针对复杂曲面难加工零件,提出一种基于气压悬浮磨料池光整加工方法:采用气压悬浮磨料的混合方式,工件表面与流态化磨料产生相对运动速度,从而使固体颗粒与工件表面发生微观二体磨料磨损.通过对磨粒进行动力分析以及气固二相流加工机理分析,揭示了磨料池内部气体和磨料混合及扩散规律.利用光整加工实验确定了光整加工过程中最佳的主轴转速和...     

旋转磁场在微小工件磁力研磨加工中的应用

微小工件在工业产品中的应用日益增多,相对于其他工件的加工,微小工件由于在加工过程中装夹困难,至今缺少高效的加工手段。磁力研磨加工中使用旋转磁场被认为是解决微小工件加工困难的有效手段。介绍了磁力研磨技术在应用领域的最新成果,总结了产生旋转磁场几种的方法,分析了磁力研磨加工的加工原理和技术特点。讨论了影响磁力研磨加工质量的几个因素,解释了影响因素的作用原理。最后指出了在磁力研磨加工存在的问题,展望了旋转磁场在微小工件磁力研磨加工中的发展前景。