Experimental investigations into transient roughness reduction in ball-end magneto-rheological finishing process

Ball-end magneto-rheological finishing (BEMRF) process is a variant of magneto-rheological finishing (MRF) which is capable of finishing magnetic as well as nonmagnetic materials to finish surfaces up to the order of nanometers. The development of this process has been fairly recent and the literature has focused on quantifying and analyzing the effects of finishing on different materials with it. This research work presents a time-based roughness reduction study of BEMRF process to find out the behavior of machining parameters in finishing over lengthy time intervals. EN31 steel has been chosen as the work material for this study. Firstly, a machining parameter optimization is carried out for finishing of EN31 steel with BEMRF process. A detailed time-based experimental study is then carried out to find the effect of time on finishing with BEMRF process. The time-based study revealed a transient roughness reduction phenomenon in which a particular set of machining parameters was capable of reducing the surface roughness only up to a limited roughness value. The study concluded a database for finishing of EN31 steel with BEMRF process which can be used for optimum time-based finishing with BEMRF process.     

Nanofinishing of FDM-fabricated components using ball end magnetorheological finishing process

Fused deposition modeling (FDM) is among the extensively used and the most economical additive manufacturing processes. Currently, the surface finish obtained for FDM additive manufactured parts are not at par with the current industrial application. To overcome the limitation of high surface roughness of 3D printed parts, a novel finishing technique has been proposed which includes primary and secondary finishing processes. While facing and lapping has been used as primary finishing technique, the secondary finishing involves the use of ball end magnetorheological finishing (BEMRF) process. BEMRF process is an unconventional finishing process which utilizes an advanced approach to impart finish on magnetic as well as non-magnetic materials that may be flat or freeform in shape. This article presents the experimental and analytical study to finish a polylactic acid (PLA) workpiece material manufactured by FDM process and finished using the BEMRF technique. The surface roughness of the FDM component has been reduced from initial surface roughness Ra = 20 µm to final value of Ra = 81 nm by combined primary and secondary finishing processes. The effect of magnetorheological polishing (MRP) fluid’s composition and finishing time is discussed and is followed by optimization of MRP fluid for maximum percentage reduction in surface roughness.     

Improved magnetorheological honing process for nanofinishing of variable cylindrical internal surfaces

Improved magnetorheological honing process is developed for nanofinishing of variable cylindrical internal surfaces with better surface integrity. In the present work, finishing performance of existing magnetorheological honing process is enhanced. The present improved process consists magnetorheological honing tool having curved permanent magnet end surfaces. When magnetic field is analyzed using Ansoft Maxwell, the improved magnetorheological honing process results in uniform and higher magnitude of magnetic flux density over its magnetic tool curved end surfaces as compared to the tool having magnetic flat end surfaces. Therefore, an improved magnetorheological honing process has been developed with tool having curved permanent magnet end surfaces. During experimentation, surface roughness values Ra, Rq, and Rz get decreased by 76.28%, 76.67%, and 75.20%, respectively, with improved magnetorheological honing tool having curved end magnetic surfaces, while 47.97%, 46.24%, and 47.08% decreased with tool having flat end magnetic surfaces in same 60 minutes of finishing time. This results in enhancement of finishing performance of the present improved magnetorheological honing process in terms of reduced finishing time and ability to produce good surface integrity. Hence, the present improved magnetorheological honing process performance with tool having curved end magnetic surfaces is found as comparatively better than the finishing tool having flat end permanent magnetic surfaces.     

A trend toward abrasive nano finishing of plane surfaces with magnetic field energy

In new developed parts, roughness has become an effective parameter and influences the performance of the entire system. Manufacturing of parts with fine surface finish have been a target for many advanced industries. Sometimes, it is difficult to reach highly polished surface quality by conventional methods. One of the newly introduced methods for obtaining fine finished surfaces is nano‐scale finishing with abrasive particles in magnetic fields. It is a relatively new finishing process that can be used to produce efficiently shiny surface quality for certain parts [1]. In this process, the cutting movement is provided by the magnetic field energy of permanent or electric poles. Magnetic abrasive particles (MAPs) are used to remove chips, and polish the work‐piece surface [2, 3]. The work‐piece is in the shape of a flat plane. An apparatus has been designed and made for machining the upper face of the plane. Nd‐Fe‐B magnets are used to establish the magnetic field. An NC machine is applied to create the rotational movement of MAPs in the horizontal plane and maintain the vertical position accurately. Various experiments have been designed to specify the machining characteristics of the MAF process. In these experiments different effective conditions are determined. Permanent magnets with 1.2 T magnetic flux density are used as magnetic poles. Homogeneous mechanical mixture of abrasive powder (Silicon Carbide) and ferromagnetic iron particles are used as the MAPs. The experimental setup was designed for finishing the aluminium alloy AA–6061. Test results indicated that the finishing parameters affect the material removal rate (MRR) and surface roughness.     

Study of Magnetic Abrasive Finishing for AISI321 Stainless Steel

In recent years, magnetic abrasive finishing (MAF) has become a reliable unconventional technology among researchers in industries due to need for the surface roughness reduction in metals. In this study, experiments based on influential parameters in the MAF process including rotational speed, working gap, and abrasive particle size were designed and conducted in the full factorial method in order to achieve the optimum parameters in finishing of steel AISI 321. A combination of silicon carbide (SiC), iron (Fe), and oil (SAE40) was utilized as magnetic abrasive tool. Prior to the experiments, the surface of the workpiece was abraded to the lowest value of roughness in order to obtain accurate results through the procedure. In general, the results indicate that the parameters of working gap, rotational speed, and abrasive particle size influence the surface roughness from the most to the least, respectively. Indeed, the minimum surface roughness is obtained through working gap of 1 mm, workpiece rotational speed of 500 rpm, and abrasive particle size of 100 mesh, with 50% improvement compared with initial surface roughness. Finally, the more involved parameters deviate from optimum values, the worse results are obtained compared with optimum acquired consequences.     

A novel magnetorheological honing process for nano-finishing of variable cylindrical internal surfaces

A novel magnetorheological honing process is designed and developed for nano-finishing of cylindrical internal surfaces with the help of permanent magnets. The radial movement of magnetic tool surface is adjusted as per the internal diameter of different cylindrical components and make it fixed before start of finishing so that it can maintain constant working gap while perform finishing. The present developed magnetic tool surface always constitutes higher magnetic field than the inner surface of ferromagnetic or non-ferromagnetic cylindrical workpiece. This is an important requirement to finish the internal surface of ferromagnetic or non-ferromagnetic cylindrical components because it ensures MR polishing fluid cannot stick on the workpiece surface while performing the finishing. Hence, present developed process is useful for finishing of ferromagnetic cylindrical molds, dies, hydraulic actuators, etc. for its better functional applications after the conventional honing or grinding process. The internal surface roughness of cylindrical ferromagnetic workpiece is dropped to 90?nm from its initial value of 360?nm in 100 minutes of finishing. Further scanning electron microscopy has also been done to understand the surface characteristics of finished workpiece. The results revealed that the developed magnetorheological honing process is capable to perform nano-finishing of internal surface of the ferromagnetic cylindrical components.     

Polishing of paramagnetic materials using atomized magnetic abrasive powder

This paper reports on the polishing of paramagnetic materials in the magnetic abrasive finishing (MAF) process by using atomized-type magnetic abrasive powder (MAP). After atomization process, a spherical MAP with captured Al₂O₃ hard particles was obtained. The MAF process was experimented on two plane workpieces with different hardnesses. An orthogonal array containing five factors with three levels was applied in the experiment. Based on analysis results, the model of surface roughness was obtained, and the rotational speed of the MAPs played the most dominant role in the surface quality of both finished experimental materials. By comparing the value of the finished surface roughness at different process parameters, the influence of single process parameter on processing quality was analyzed. Furthermore, the minimum surface roughness of both materials was obtained at the best combination of process parameters. Finally, the experiment of the material removal and the produced surface morphology was examined in order to understand the finishing characteristics of the atomized MAPs during the MAF process.     

Magnetorheological nanofinishing of BK7 glass for lens manufacturing

BK7 is a high-quality crown glass which is used where additional benefits such as temperature sensitive applications of fused silica glass are not required. Due to very low inclusion content with extremely low bubbles, BK7 glass can find its application in lens manufacturing. The present work focuses on nanofinishing of the BK7 glass specimen for ratifying its utility in practical application. A programmable logic controlled 3-axis motions are fed to the magnetorheological (MR) rotating tool for finishing the glass specimen. MR polishing fluid used for nanofinishing consists of deionized water, magnetic iron particles, and cerium oxide powder. Under the influence of magnetic field, the stiffened MR polishing fluid is assisted in reducing the surface roughness of glass up to nanolevel range. Optical properties such as transmittance, absorbance, and reflectance of finished BK7 glass are analyzed and found suitable for lens manufacturing. Results of higher surface quality with excellent finishing are obtained by the present MR finishing process. After 90?min of finishing, the surface roughness values R_a and R_q are reduced to 17 and 27?nm from the initial values of 41 and 57?nm, respectively. To study the surface morphology, scanning electron microscopy is performed on BK7 glass.     

Optimization of process parameters affecting surface roughness in magnetic abrasive finishing process

Development in manufacturing technology enhances the mechanical behavior of machined parts and improves the surface finish with high precision, which conveys the progressive importance of magnetic abrasive finishing (MAF) process. In current research work, magnetic abrasive particles were used as finishing tools during the MAF process. However, these magnetic abrasives are fabricated by special techniques, i.e., the adhesive bonding-based method, the sintering method, the plasma-based method and so on. The present study explores the basic finishing characteristics of the magnetic abrasive produced by the sintering process. After the sintering process, improved quality of magnetic abrasives was obtained, where the abrasive particle sticks on the base metal matrix. The abrasive particle used is alumina powder and the magnetic particle is iron powder. Experiments were performed on Stainless Steel 202 to inspect the sound effects of several process parameters such as rotational speed, electromagnet voltage, machining gap and abrasive particle size on machining performance. Apart from that, surface roughness was also measured, which revealed the influence of the abrasive particle on the machined surface in terms of surface finish. It is observed from this study that appropriate size of magnetic abrasive particle optimizes the surface finish.     

Experimental investigations into sintering of magnetic abrasive powder for ultrasonic assisted magnetic abrasive finishing process

The importance of magnetic abrasive powder (MAP) in finishing the surface of work materials as a flexible cutting tool in the presence of a magnetic field during the ultrasonic assisted magnetic abrasive finishing (UAMAF) process is quite evident. A sufficiently intense magnetic field provides the desired magnetic force to the iron particles. This holds nonmagnetic abrasive particles firmly and thus makes flexible chains. However, at higher rotational speeds of the magnet due to the requirement of high centripetal force, the chains start flying away from the finishing zone. In the present work, to overcome this deficiency, bonded MAPs were developed using the sintering technique. The effect of various process parameters on the magnetic property (magnetization) of sintered MAPs was investigated. Design of experiments (DoE) was planned as per the L₈ orthogonal array of the Taguchi method, and magnetizations along with M-H curves for all eight different MAPs were measured. Subsequently, analysis of experimental data was carried out using various techniques to optimize the process parameters. It was observed that sintering temperature affects magnetization the most. Scanned microscopy (SEM) and X-ray diffraction (XRD) analysis were also carried out to investigate bonding strength in sintered MAP.     

Ultrasonic Assisted Electrical Discharge Machining of Ti–6Al–4V Alloy

In this research, an attempt was made to investigate the influence of copper tool vibration with ultrasonic frequency on output parameters in the electrical discharge machining of Ti–6Al–4V. The selected input parameters for the experiment comprise of ultrasonic vibrations of tool, current and pulse duration and the outputs are tool wear ratio (TWR), material removal rate (MRR), and stability of machining process and surface integrity of a workpiece, including surface roughness, thickness of recast layer, and formation of micro cracks. Scanning electron microscope and X-Ray diffraction were employed to examine the surface integrity of the workpiece. The results revealed that tool vibration with ultrasonic frequency enhances MRR via increasing normal discharges and decreasing arc discharges and open circuit pulses. Also, by using ultrasonic vibrations in finishing regimes, the density of cracks and TWR decrease while in roughing regimes, the thickness of recast layer, density of cracks, and TWR increase.     

A new magnetorheological finishing process for ferromagnetic cylindrical honed surfaces

In today’s industries, the internal surface finishing of cylindrical objects is highly demanded to improve their functional performance in various engineering applications. During the traditional honing operation, the finishing forces produced by abrasives on the workpiece surface are not easily controllable and also produce various surface defects. Therefore, to further improve the surface integrity of the traditionally cylindrical honed surface made of ferromagnetic or non-ferromagnetic materials, a new magnetorheological (MR) finishing process has been used with a controlled magnetic field. The experimentation is performed on the honed surface made of gray cast iron, which is generally used as a cylinder liner. The percentage change in surface roughness values, i.e., Ra, Rq and Rz, reduced by 77.44%, 70.16% and 72.16%, respectively, with better improvement in surface after 90 minutes of finishing. The experimental results demonstrated the effectiveness of present process for improving the functional applications of ferromagnetic cylindrical honed surface after removing the various surface defects such as deeper grooves, honing grooves with shaper edges, torn and folded metals, and cavities or holes. The applications of new MR finishing process can also be useful in the internal finishing of injection barrel of a molding machine, cylindrical molds and dies, hydraulic cylinder, etc.     

Development of magnetorheological finishing process for external cylindrical surfaces

The recent increase in demand for functional and technological requirements of the component results in the development of complex geometrical shapes and that too with close tolerances and fine surface quality. To fulfill the needs for finishing the external cylindrical surfaces such as groove, taper, step surfaces, and threads, an advanced finishing process based on magnetorheological (MR) fluid has been developed. The developed process can finish the external cylindrical surfaces with controlled magnetic field as likely similar to turning operation. Fine finishing of external cylindrical surfaces is a significant requirement in many functional applications. The wide applications of this present process can be valuable in automotive, machine tool production, valves manufacturing, and aerospace. A modified new MR finishing tool with flat and curved tip surface has been made to perform finishing on external cylindrical surfaces. The present cylindrical finished workpiece is useful in macaroni manufacturing machine. The surface roughness values Ra, Rq, and Rz are reduced to 54.41%, 51.65%, and 40% with flat tool tip surface and 80.88%, 81.32%, and 82.5% with curved tool tip surface in 90 min of finishing time. The overall results reported that the present process with curved tool tip surface is comparatively more useful in finishing the external cylindrical surfaces.     

航空钛合金板胶接表面粗糙度的超声测量

采用一种新的超声频谱法快速测量航空钛合金板经喷砂预处理后的胶接表面粗糙度,并引入表面面积均方根粗糙度系数Sr来表征材料表面三维微观形貌．以航空Ti-6Al—4V钛合金胶接板为测量试样,超声换能器接收测试试样表面的反射回波,并计算得到AR参数谱．以反射脉冲AR参数谱和声波镜面反射理论为基础,建立了有关脉冲波声反射系数和表面均方根粗糙度系数Sr的数学模型．利用表面粗糙度系数理论模型．数值计算反射回波的理论频谱曲线,并与实测反射回波AR谱进行拟合．利用最小值搜索算法,处于最佳拟合时的表面粗糙度系数Sr即为试样胶接表面的测量结果．实验表明,超声反射频谱法测量结果与轮廓仪测量结果符合得很好,该测量方法在材料或零部件表面粗糙度在线测量中具有广泛的应用前景．     

Surface roughness evaluation via ultrasonic scanning

Despite extensive applications of ultrasonic waves to various nondestructive testing and evaluation of materials, scattering of focused ultrasonic waves due to surface roughness has not been fully investigated. This paper presents an analytical and experimental evaluation of surface roughness measurement using focused ultrasonic beams. The characteristics of focused ultrasonic waves are analyzed by using the impulse response method with a sine-modulated Gaussian pulse as source. First, the beam profile in the focal plane of the focused ultrasonic transducer is analyzed both numerically and experimentally. Second, peak amplitude distribution and reflected waveforms from a flat surface with various incident angles are analytically generated and compared with experimental results. Then, the peak amplitudes of the ultrasonic waves reflected from cusped surfaces which are easily found among machined surfaces are analyzed and compared with experimental data for the first time. The analysis shows good agreement between analytical and experimental results. The excellent correlation between the measurements using a profilometer and the proposed ultrasonic system demonstrates a good potential for surface roughness measurement by ultrasonic sensing.     

液体磁性磨具小孔光整加工材料去除机理及实验

针对小孔内壁光整加工技术的难题,本文提出一种新型精密研磨孔光整加工技术,以磁致相变理论为指导,从微观角度阐述了液体磁性磨具研磨孔光整加工的材料去除机理.采用"双刃圆半径"模型进行单个磨料颗粒切削模型研究,得出小孔光整加工的材料去除率数学表达式.通过实验验证了磨料粒度、入口压力、电流强度等因素对材料去除率以及表面粗糙度的影响,实验结果表明:在合适的范围内,增大磨料颗粒直径、入口压力以及电流强度有利于提高材料的去除率和表面质量.而当磨粒直径、入口压力以及电流强度选取过大时,虽然能获得较高的材料去除率,但是最终获得的表面粗糙度值并不理想.该研究为通孔零件内壁表面精密光整加工提供了有益参考.     

Nano-surface-finishing of permanent mold punch using magnetorheological fluid-based finishing processes

Various plastic products such as bottles’ plastic caps are manufactured through casting using permanent molds. To obtain the smooth surface on plastic caps during manufacturing, the required permanent mold die punch surface should be defect free and its roughness values in nanometer range. Two different magnetorheological (MR) fluid-based finishing processes are used for nano-surface-finishing of die punch. The MR ball end with solid rotating tool core is used to finish the flat surface, and a turning type MR finishing process is used for external circular surface of the present mold die punch. The material of the present permanent mold punch is P20 tool steel with hardness of 431 VHN. The final roughness values of flat and external circular surfaces of the present die punch are obtained as 30?nm and 80?nm from the initial values of 1080?nm and 630?nm in 120?min of finishing. The change in topography of the surface is observed using metallurgical microscope and mirror image test. The reduction in surface roughness at the nanolevel and microscopic improvement on the die punch surface have demonstrated the feasibility of present finishing processes to be useful in industries for manufacturing the smooth surface of bottles’ plastic caps.     

油基磁流变液的开发及抛光性能研究

磁流变抛光技术可用于具有超光滑要求光学元件的超精密制造。在明确磁流变抛光机理的基础上,开发了油基磁流变抛光液,其体积比配方是:33.84%的羰基铁,57.34%的硅油,6%的氧化铈,2.82%的稳定剂。抛光液初始粘度达到0.5Pas,流变性具有较大范围的稳定性能。实验中,利用磁流变液在外磁场作用下形成的强剪切应力对一平面K9玻璃进行了可控抛光,结果证明其具有良好的抛光特性,抛光23分钟后工件表面粗糙度降低到0.6739nm。     

Hartbearbeitung keramischer Werkstoffe,insbesondere mittels Ultraschall-Erosion

Machining of Ceramics, with Particular Reference to Ultrasonic Erosion A study has been made of the effect of several machining techniques, presumably of ultrasonic machining (USM) and electrical discharge machining (EDM) on the performance of various engineering ceramics. The application of EDM is limited to materials with specific electric resistance of less than about 100 Ω cm. Ultrasonic machining can in contrast be used for all ceramics. However, different results are observed for the individual materials, and characteristic dependencies on the fracture toughness of the machined materials are found. Increasing fracture toughness leads to a reduction of the USM-rate, what is accompanied by a lower surface roughness. The wear of the tool considerably increases during USM of less brittle ceramics. Further influences e.g. by the USM-amplitude and the particle size of the boron carbide powder are discussed. In terms of strength measured with bending bars after surface finishing by different methods the potential of USM is manifested.