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.     

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.     

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.     

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     

ON THE PERFORMANCE ANALYSIS OF FLEXIBLE MAGNETIC ABRASIVE BRUSH

ABSTRACT

Magnetic abrasive finishing (MAF) of alloy steel workpiece with unbounded magnetic abrasive particles (UMAPs) indicates that the surface finish in the range of nanometer can be achieved. Important controllable four process parameters have been identified which are as current to the electromagnet, machining gap, abrasive size (mesh number), and number of cycles. Experiments have been planned using design of experiments technique. Based upon the results of response surface methodology and analysis of variance (ANOVA), it is concluded that magnetic flux density that depends on current to the electromagnet and machining gap, is most influencing parameter followed by grain size and number of cycles. The surface roughness profile generated during the MAF process has been discussed. To understand the cutting mechanism of magnetic abrasive finishing process, scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the machined surfaces have been carried out. The correlation between surface finish and material removal has also been established.     

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。     

ON THE PERFORMANCE ANALYSIS OF FLEXIBLE MAGNETIC ABRASIVE BRUSH

Magnetic abrasive finishing (MAF) of alloy steel workpiece with unbounded magnetic abrasive particles (UMAPs) indicates that the surface finish in the range of nanometer can be achieved. Important controllable four process parameters have been identified which are as current to the electromagnet, machining gap, abrasive size (mesh number), and number of cycles. Experiments have been planned using design of experiments technique. Based upon the results of response surface methodology and analysis of variance (ANOVA), it is concluded that magnetic flux density that depends on current to the electromagnet and machining gap, is most influencing parameter followed by grain size and number of cycles. The surface roughness profile generated during the MAF process has been discussed. To understand the cutting mechanism of magnetic abrasive finishing process, scanning electron microscopy (SEM) and atomic force microscopy (AFM) of the machined surfaces have been carried out. The correlation between surface finish and material removal has also been established.     

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.     

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.     

Multiagent-based scheduling optimization for Intelligent Manufacturing System

The magnetic pole is an important finishing tool in magnetic abrasive finishing (MAF). This study used finite element method to analyze magnetic field characteristics for three different magnetic poles such as solid cylindrical pole, hollow cylindrical pole, and hollow cylindrical pole with grooves design. The results showed that the hollow cylindrical with grooves can generate the better surface roughness in MAF. The operations were demonstrated using a permanent magnetic polishing mechanism installed at a CNC machining center. The operations were performed using Taguchi experimental design, considering the effects of magnetic field, pole rotational speed, feed rate, working gap, abrasive, and lubrication. The optimal parameter conditions was obtained after experimental data analysis, the quality surface roughness (R _max = 0.1 mm) which is similar to a mirror surface was obtained after confirmatory tests. The optimal parameter conditions for material removal weight were also obtained in MAF. The results showed that MAF technique can meet customer requirement and raise the value-added products simultaneously.     

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。     

ABRASIVE-BASED NANO-FINISHING TECHNIQUES: AN OVERVIEW

The surface finishing techniques can be divided into two categories: traditional and advanced. To overcome some of the problems of traditional finishing techniques, hybridized processes have been evolved by the researchers. Some of the advanced finishing processes that have been reviewed are abrasive flow machining (AFM), magnetorheological finishing (MRF), magnetorheological abrasive flow finishing (MRAFF), magnetic abrasive finishing (MAF), chemo mechanical polishing (CMP), etc. Most of these processes have been developed in the recent past and they can be employed to produce optical, mechanical, and electronic components with micrometer or sub-micrometer form accuracy and surface roughness within nanometer range with hardly any surface defects. However for large size flat components, MAF seems to be the most suitable finishing process. In MAF, DC power supply is given to the electromagnet hence intermixing of ferromagnetic abrasive particles during the process does not take place and the worn out cutting edges keep interacting with the workpiece surface. As a result, the finishing rate is quite low. The use of pulsed DC power supply to the electromagnet results in pulsating flexible magnetic abrasive brush (P-FMAB), which substantially enhances the finishing rate. The on-line measurement of the forces has helped in understanding the mechanism of material removal during Static-FMAB (S-FMAB) and Pulsating-FMAB. The magnitude of normal magnetic force (originating indentations) in P-FMAB has been found to be dynamic in nature and substantially high in magnitude as compared to S-FMAB.     

集群磁流变变间隙动压平坦化加工试验研究

为了提高光电晶片集群磁流变平坦化加工效果,提出集群磁流变变间隙动压平坦化加工方法,探究各工艺参数对加工效果的影响规律。以蓝宝石晶片为研究对象开展了集群磁流变变间隙动压平坦化加工和集群磁流变抛光对比试验,通过检测加工表面粗糙度、材料去除率,观测加工表面形貌、集群磁流变抛光垫中磁链串受动态挤压前后形态变化,研究挤压幅值、工件盘转速、挤压频率以及最小加工间隙等工艺参数对加工效果的影响规律。试验结果表明：集群磁流变平坦化加工在施加工件轴向微幅低频振动后,集群磁流变抛光垫中形成的磁链串更粗壮,不但使其沿工件的径向流动实现磨粒动态更新、促使加工界面内有效磨粒数增多,而且在工件与抛光盘之间的加工间隙产生动态抛光压力、使磨粒与加工表面划擦过程柔和微量化,形成了提高材料去除效率、降低加工表面粗糙度的机制。对于2英寸蓝宝石晶电（1英寸=2.54 cm）集群磁流变变间隙动压平坦化加工与集群磁流变抛光加工效果相比,材料去除率提高19.5%,表面粗糙度降低了42.96%,在挤压振动频率1 Hz、最小加工间隙1 mm、挤压幅值0.5 mm、工件盘转速500 r/min的工艺参数下进行抛光可获得表面粗糙度为Ra0.45 nm的超光滑表面,材料去除率达到3.28 nm/min。证明了集群磁流变变间隙动压平坦化加工方法可行有效。     

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.     

Study on improving the trajectory to elevate the surface quality of plane magnetic abrasive finishing

This paper aims to improve the surface integrity and surface homogeneity with various trajectories by a newly self-designed experiment device. In the experiments, three kinds of polishing trajectories were studied with attached revolution motion to magnetic abrasive brush (MAB) based on conventional magnetic abrasive finishing (MAF) process. The surface roughness, the cross-sectional shape, and the 3D micro-morphology were chosen as the response variables to explore the feasibility and benefits of the proposed improving polishing method. The results show that the plane homogeneity and surface quality improved in varying degrees after improving the polishing trajectory. In addition, combining MAF theory to analyze related reasons, the trajectory expression of the magnetic abrasive particles (MAPs) was established and was simulated by Graph software. The theoretical analysis is consistent with the experimental results which indicated that analysis of polishing trajectory can be used to predict polishing results. Thus, it is feasible to plan polishing trajectory reasonable according to workpiece profile and surface quality requirements.     

Surface roughness modeling in chemically etched polishing of Si (100) using double disk magnetic abrasive finishing

Abstract

The present paper focuses on proposing a new method for determining the surface roughness of chemically etched polishing of Si (100) using double disk magnetic abrasive finishing (DDMAF). Based on chemical etching in KOH solution Vicker’s hardness of Si (100) at different concentration of KOH was determined in context to chemical etching phenomenon. A mathematical relationship was established to relate Vicker’s hardness of Si (100) as a function of the concentration of KOH. The penetration depth of abrasive particle into Si (100) workpiece was determined considering viz; the normal force acting on the abrasive particle under the influence of magnetic flux density and Vicker’s hardness of etched Si (100). The other modeling variables such as wear constant, penetration area of the abrasive particle into Si (100) workpiece which is dependent on the penetration depth of abrasive particle was modified in terms of magnetic flux density and concentration of KOH. The process parameters such as working gap, abrasive mesh number and the rotational speed of the primary magnet were also considered in modeling the surface roughness. The results of surface roughness obtained by the model were also experimentally validated. The theoretical and experimental findings agreed well with each other.     

AN EXPERIMENTAL ANALYSIS OF MAGNETIC ABRASIVES FINISHING OF PLANE SURFACES

Magnetic abrasive finishing (MAF) uses magnetic force of very low magnitude applied on ferromagnetic abrasive particles to obtain very high level surface finish. The process has been investigated extensively in the finishing of cylindrical surfaces. This paper reports an experimental work on the analysis of surface roughness and material removal using response surface method in the MAF of plane surfaces. The surface finish was found to improve significantly with an increase in the grain size, relative size of abrasive particles vis-à-vis the iron particles, feed rate and current. The optimum parameter levels which gave better surface finish and the higher material removal were also obtained from this experimentation.     

Effect of fluid composition on nanofinishing of single-crystal silicon by magnetic field-assisted finishing process

Magnetic field-assisted finishing is a deterministic process particularly used for finishing optical materials. The main component of this process is magnetorheological fluid which consists of magnetic particles, abrasive particles, carrier fluid such as water or oil, and some additives to impart stability. Under the influence of magnetic field (generated by either permanent magnet or electromagnet), magnetic particles form chain-like structure and support many abrasive particles to perform finishing of workpiece surface. Selection of abrasive and carrier fluid in this process is one of the major concerns which play vital role on finishing mechanism and surface quality. In the present experimental investigation, aluminum oxide and cerium oxide are chosen as abrasives while deionized water and paraffin oil are selected as carrier fluids. A set of experiments are carried out to study chemical interactions of abrasive and carrier fluid on the silicon surface. A rheological study is carried out to study behavior of magnetorheological fluid fluids under magnetic field.     

Enhanced magnetic abrasive finishing of Ti–6Al–4V using shear thickening fluids additives

The available magnetic field assisted finishing process is considered as the critical stage for improvement of workpiece surface quality. This paper aims to investigate the key quality performance of an enhanced magnetic abrasive finishing in achieving nanolevel finish on Ti–6Al–4V workpieces with initial micrometer surface roughness values. The finishing media, combining the intelligent shear thickening fluids (STFs), carbonyl iron particles and SiC particles, is developed. Finishing experiments for Ti–6Al–4V workpieces are conducted using an established platform, aiming to investigate the effects of varying STFs concentration, working gap, feed rate and spindle rotational speed. It is observed from the experimental results that the developed finishing media is effective for surface finishing comparing to the finishing media without STFs. The surface roughness of 54 nm was achieved from the initial value of 1.17 μm, which improved by over 95%, under the experimental conditions of 0.8 mm working gap, 15000 mm/min feed rate, 900 rpm spindle rotational speed and 15 wt% STFs. Surface observations showed that a smooth surface without obvious scratches was obtained.     

Design and fabrication of a novel polishing tool for finishing freeform surfaces in magnetic field assisted finishing (MFAF) process

Surface finish is a critical requirement for different applications in industries and research areas. Freeform surfaces are widely used in medical, aerospace, and automobile sectors. Magnetic field assisted finishing process can be used very efficiently to finish freeform surfaces. In this process, magnetorheological fluid is used as the polishing medium and permanent magnet is used to control its rheological properties to generate finishing force during polishing. To avail sufficient magnetic field in the finishing zone, it is necessary to design an optimum polishing tool. In the present study, a specially designed polishing tool is designed using a finite element based software package (Ansys Maxwell^®) based on Maxwell equations. At first, dimension of the permanent magnet is determined for designing optimum tool geometry. After that, dimension and configuration of the magnet fixture are optimized. A special type of metal named mu-metal which is a nickel-iron based alloy is selected for magnet fixture due to its magnetic-field shielding property. Mu-metal directs the magnetic flux lines in such a way that in the finishing zone the magnetic flux can be concentrated on the workpiece surface required for finishing. Also, the Mu-metal magnet fixture shields the magnetic field from outside environment so that MR fluid as well as any surrounding magnetic materials do not stick to the polishing tool. Experiments are carried out to validate the Maxwell simulation results to compare the magnetic flux distribution on the workpiece surface which shows good agreement between them. Also, finishing of flat titanium workpieces are carried out and it is found that the novel polishing tool has the capability to finish the workpieces in the nanometer range.