Ultrasonic assisted magnetic abrasive finishing of hardened AISI 52100 steel using unbonded SiC abrasives

Ultrasonic assisted magnetic abrasive finishing (UAMAF) integrates the use of ultrasonic vibrations and magnetic abrasive finishing (MAF) process to finish surfaces to nanometer order in a relatively short time. The present study emphasizes on the fabrication of UAMAF setup. Using this experimental setup, experimental studies have been carried out with respect to five important process parameters namely supply voltage, abrasive mesh number, rotation of magnet, abrasive weight percentage, and pulse on time (T_on) of ultrasonic vibrations selected based on literature available in the area of MAF process and ultrasonic generator controls. Percentage change in surface roughness (?Ra) for AISI 52100 steel workpiece has been considered as response and unbonded SiC abrasives are used in the work. The experimental results showed that the UAMAF process has better finishing potential as compared to those obtainable by using MAF process for similar processing conditions. The surface roughness value obtained by UAMAF was as low as 22 nm within 80 s on hardened AISI 52100 steel workpiece using unbonded SiC abrasives. Scanning electron microscopy and atomic force microscopy studies were carried out to feel the surface texture produced and to identify finishing mechanism.     

Surface finishing of cobalt chromium alloy femoral knee components

This paper describes the modification of surface roughness and lay of cobalt chromium alloy femoral knee components by magnetic abrasive finishing (MAF), including clarification of the MAF surface-processing mechanisms. The MAF process creates characteristic surfaces by micro-cutting of abrasive pressed by magnetic particles that nearly conform to the surface, removing large asperities and creating microasperities compared to hand-buffed surfaces. The process enables smoothing the surface on the nanometer scale with critical control of surface lay (e.g., crosshatch angle), altering the contact angle of water by a combination of kinematic behavior of magnetic particles over the freeform condyle surface.     

模具曲面光整加工中数字化磁力研磨技术

本文针对模具制造过程中模具表面的自动化研磨光整加工的问题，介绍了一种数字化磁力研磨技术。简述了其原理，详细论述了数字化研磨三维加工模型的获得、工艺参数的选择、数字化研磨轨迹的生成方法以及专用和改装的数字化磁力研磨设备等关键技术，证实利用数字化磁力研磨可以对模具曲面进行有效地自动化光整加工。     

磁粒研磨加工技术的研究进展

磁粒研磨加工是一种应用广泛且高效的表面加工技术,具有加工质量高、适用范围广、柔性加工、自锐性好、易于实现自动化等优点,能够有效去除工件表面的划痕、积碳、毛刺和卷边等缺陷.首先,综述了磁粒研磨加工技术的发展与研究,包括磁粒研磨加工技术的提出与发展、数学模型分析和加工参数产生的影响,其中着重论述了加工过程中单颗磨粒的力学模...     

Simulation for the prediction of surface roughness in magnetic abrasive flow finishing (MAFF)

The final machining (or finishing) of precision parts with high level of surface finish and close tolerance is making the application of magnetic abrasive finishing technology increasingly important. Magnetic abrasive flow finishing (MAFF) is a new abrasive finishing process combining the features of abrasive flow finishing (AFF) and magnetic abrasive finishing (MAF). MAFF provides a high level of surface finish and close tolerances for wide range of industrial application. This paper focuses on the modeling and simulation for the prediction of surface roughness on the workpiece surface finished by MAFF process. A finite element model is developed to find the magnetic potential distribution in the magnetic abrasive brush formed during finishing action and then it is used to evaluate machining pressure, surface finish and material removal. The simulation results are compared with the experimental results available in the literature. The simulated workpiece surface roughness shows features similar in nature to the experimental results.     

Study the characteristics of magnetic finishing with gel abrasive

Given the flexible polishing effect in magnetic abrasive finishing (MAF), the precise and mirrorlike surface can be obtained during this process. However, the abrasives are easily flown away from the working area regardless of what abrasives are used in MAF; this situation will reduce the polished efficiency and induce the pollution problem in the environment. Besides, the abrasives cannot recycle after the finishing process. Therefore, a novel abrasive medium, using the silicone gel to mix the ferromagnetic particles and abrasive, was developed to enhance the disadvantages in MAF. Magnetic finishing with gel abrasive (MFGA) was utilized in this study to polish the cylindrical rod of mold steel; furthermore, this cylindrical rod was fixed in a horizontal chuck that could rotate and vibrate in the axial direction. This study focused on the finishing efficiencies and the surface roughness of the workpieces after MFGA. Moreover, recycling times of gel abrasive were also the main effects that need to be approved. The results demonstrated that surface roughness of the cylinder part was reduced to 0.1 μm Ra from an initial value of 0.677 μm Ra within 10 min, and surface roughness could decrease to 0.038 μm Ra after 30 min in MFGA. Surface roughness reduction in MFGA was 3 times of surface roughness reduction in MAF using the unbonded magnetic abrasive as medium. Roughness improvement rate still remained at a high level of 90% when the same abrasive medium (35 g) was used 15 times to finish 15 workpieces; therefore, this result proved that the gel abrasive had excellent ability for recycling.     

CBN磁性磨料磁力研磨TC4钛合金工艺参数优化

为提高磁力研磨TC4钛合金的研磨效果,采用了一种新型CBN磁性磨料,通过正交试验法对磁力研磨TC4钛合金试验中各工艺参数进行优化,并通过试验评价新型CBN磁性磨料的结合强度和研磨能力。结果表明:优化工艺参数为:进给速度1mm/min、主轴转速1500r/min、加工间隙1mm和磨料填充量2.5g。在采用CBN磁性磨料和最优工艺参数组合下,钛合金工件经过30min研磨表面粗糙度从0.330μm下降到0.098μm,表面质量明显提高。研磨60min后磁性磨料未出现磨料脱落和破碎现象,磨料结合十分牢固。     

Analysis of forces on the freeform surface in magnetorheological fluid based finishing process

The magnetorheological (MR) fluid based finishing process is a deterministic process for finishing of flat, curved and freeform surfaces. In case of finishing, the knowledge of forces acting on the curved workpiece surface in different conditions improves the understanding of the process. An experimental investigation is carried out to measure the forces on the freeform surface in real time. The effects of the process parameters such as angle of curvature of the workpiece, rotational speed of the tool and feed rate on normal, tangential and axial forces, are studied. The normal force is found to be more dominant compared to other forces. A theoretical model of normal force and tangential force acting on the workpiece is also proposed to improve the understanding of the workpiece–abrasive particles interaction in the MR fluid based finishing process. A comparison of theoretical and experimental results is carried out to validate the proposed models, which show that the trends are in good agreement.     

Investigation of the finishing characteristics in an internal tube finishing process by magnetic abrasive finishing combined with electrolysis

In this research, the finishing characteristics in a tube's internal finishing process using the method of magnetic abrasive finishing (MAF) combined with electrolysis has been studied. Electrolysis produces an aluminium oxide film that accelerates the removal of the initial hairline morphology on the surface. Subsequently, the film is removed with MAF. This process significantly minimises the surface roughness in a reduced time. The way the finishing conditions, such as the pole–pipe gap, iron particle size and abrasiveness combinations, and processing time affected the surface morphology in the MAF machining process has been particularly examined. The surface roughness was measured and images of the finished surfaces were recorded to study the morphology changes. Prolonged electrolysis finishing was seen to deepen the oxidation film and pits, which adversely affects the surface. This evidence suggests that the pit residuals contribute to higher surface roughness values.     

Modelling and optimisation of magnetic abrasive finishing process based on a non-orthogonal array with ANN-GA approach

ABSTRACT

Magnetic abrasive finishing (MAF) is an advanced precise finishing method that achieves micro-level to nano-level surface roughness. In industries, MAF is highly recommended where zero or negligible post-process surface defects are an obligatory requirement. In the same context, process optimisation is essential for making it commercially viable. This study presents an artificial neural network and genetic algorithm (ANN-GA), a robust modelling and optimisation tool (applicable to any sort of data set orthogonal array design or non-orthogonal array design) that is applied to scrutinise and improve the performance of the magnetic abrasive finishing of stainless steel SS302. In addition, the results from ANN-GA modelling and optimisation have been compared with conclusions drawn from conventionally used Taguchi-ANOVA analysis. An L₂₇ non-orthogonal array design has been opted for as per machining set-up restriction. Abrasive size, voltage, machining gap, and rotational speed were the design variables considered in the present research work. It was found that the parametric design used in this study provides a straightforward, methodical, and proficient method of modelling and optimisation of change of surface roughness or finishing behaviour during the MAF process. Modelling and optimisation done with ANN-GA show a maximum value of (ΔR _a)_max equal to 0.256?µm, which is 7% better than the result obtained from Taguchi-ANOVA analysis.     

Magnetic abrasive finishing of cutting tools for machining of titanium alloys

Uncoated carbide tool surfaces are conditioned using magnetic abrasive finishing (MAF) to improve the tool wear characteristics by reducing friction between the tool and chip. The configuration of the magnetic particle chains that drive the abrasives plays an important role in surface finishing with minimal damage to the tool cutting edges. Roughnesses of less than 25 nm Ra on the flank and nose and less than 50 nm Ra on the rake can be achieved. In turning of Ti–6Al–4V alloy rods (at 100 m/min cutting speed), MAF-processed tools exhibited tool lives of up to twice as long as unprocessed tools.     

Study on the inner surface finishing of tubing by magnetic abrasive finishing

With the development of industry manufacturing technology, fine surface finish is in high demand in a wide spectrum of industrial applications. Presently, it is required that the parts used in manufacturing semiconductors, atomic energy parts, medical instruments and aerospace components have a very precise surface roughness. Amongst them, vacuum tubes, wave guides and sanitary tubes are difficult to polish by conventional finishing methods such as lapping, because of their shapes. The surface roughness of these tubes affects the performance of the entire system, but the finishing technology for these tubes is very scant in manufacturing fields. This project was proposed by a Shanghai Far East pharmaceutial and mechanical factory. They stated that the roughness of the inner surface must be less than 0.3 μm Ra after finishing. An internal magnetic abrasive finishing (MAF) process is proposed for producing highly finished inner surfaces of tubes used in this study. The process principle and the finishing characteristics of unbounded magnetic abrasive within internal tubing finishing are described first. MAF setup was designed for finishing three kinds of materials tubing, such as Ly12 aluminum alloy, 316L stainless steel and H62 brass. Experimental results indicated that finishing parameters such as polishing speed, magnetic abrasive supply, abrasive material, magnetic abrasive manufacturing process and grain size have critical effects on the material removal rate (MRR). How the inner surface micro shape changes course during finishing of an aluminous tube is demonstrated.     

磁力研磨光整加工技术的实验研究

对影响磁力研磨光整加工技术的各种因素进行了实验研究 ,得到了各种因素的影响规律及存在的最佳值 ,对该技术在模具型腔精加工的应用具有重要的意义。     

Magnetic field assisted abrasive based micro-/nano-finishing

Micro-/nano-machining (abbreviated as MNM) processes are classified mainly in two classes: traditional and advanced. Majority of the traditional MNM processes are embedded abrasive or fixed geometry cutting tool type processes. Conversely, majority of the advanced MNM processes are loose flowing abrasive based processes in which abrasive orientation and its geometry at the time of interaction with the workpiece is not fixed. There are some MNM processes which do not come under the abrasive based MNM category, for example, laser beam machining, electron beam machining, ion beam machining, and proton beam machining. This paper gives a comprehensive overview of various flowing abrasive based MNM processes only. It also proposes a generalized mechanism of material removal for these processes. The MNM processes discussed in this paper include: Abrasive Flow Finishing (AFF), Magnetic Abrasive Finishing (MAF), Magnetorheological Finishing, Magnetorheological Abrasive Flow Finishing, Elastic Emission Machining (EEM) and Magnetic Float Polishing. EEM results in surface finish of the order of sub-nanometer level by using the nanometer size abrasive particles with the precisely controlled forces. Except two (AFF and EEM), all other processes mentioned above use a medium whose properties can be controlled externally with the help of magnetic field. This permits to control the forces acting on an abrasive particle hence the amount of material removed is also controlled. This class of processes is capable to produce surface roughness value of 8 nm or lower. Using better force control and still finer abrasive particles, some of these processes may result in the sub-nanometer surface roughness value on the finished part. Understanding the mechanism of material removal and rotation of the abrasives in these processes will help in rationalization of some of the experimental observations which otherwise seem to be contradicting with the established theories. It also explains why a magnet used in MAF should have a slot in it even though the area under the slot has “non-machining” zone. It elaborates based on the experimental observations why to use pulse D.C. power supply in MAF in place of smooth D.C. power supply.     

混合型磁性磨料在磁力研磨加工中的应用

介绍了一种新型的磁性磨料 ,并对该磨料的加工性能进行了实验研究 ,得到了该磨料的最佳配比。这对磁力研磨技术的生产化 ,以及该技术在模具精加工中的应用具有重要的意义     

钛合金管内表面的电化学磁力研磨复合光整试验

针对热挤压成型对钛合金管的内表面会产生微裂纹、褶皱、毛刺等表面缺陷的问题,提出了一种高效率的电化学磁力研磨复合光整加工方法。设计了电化学磁力研磨复合光整加工的实验装置,分别与纯磁力研磨加工和纯电化学加工进行了光整加工试验对比,检测分析了不同工艺加工前后表面的粗糙度、微观形貌、摩擦磨损行为、表面残余应力和能量谱。结果表明:在相同的加工时间内,与单纯电化学加工和磁力研磨加工相比,电化学磁力研磨复合光整加工的表面粗糙度Ra可达到0.2μm,材料去除量和加工效率显著提高;表面显微形貌要明显优于其他两种加工方式;且加工后表面很好地维持了原有材料的化学成分和表面性质;能够使表面由拉应力转变为约–200 MPa的压应力状态,从而获得更好的表面应力状态。     

Shape adaptive grinding of CVD silicon carbide

Because of the direct relationship between removal rate and surface roughness in conventional grinding, ultra-precision finishing of hard coatings produced by chemical vapour deposition (CVD) usually involves several process steps with fixed and loose abrasives. In this paper, an innovative shape adaptive grinding (SAG) tool is introduced that allows finishing of CVD silicon carbide with roughness below 0.4 nm Ra and high removal rates up-to 100 mm³/min. The SAG tool elastically complies with freeform surfaces, while rigidity at small scales allows grinding to occur. Since material removal is time dependent, this process can improve form error iteratively through feed moderation.     

磁力研磨工艺对整体叶盘表面完整性的影响

针对铣削加工对整体叶盘零件表面完整性控制不能满足使用要求的难题,利用磁力研磨所特有的柔性、自适应性、可控性等优点,研发了一种基于机器人的自由曲面磁力研磨装置,对整体叶盘零件进行加工试验。试验结果表明:经过磁力研磨后零件的表面粗糙度数值大幅度降低;铣削加工残留下来的加工纹理基本去除;原始表面上的微裂纹减弱或彻底消除;近表层原始显微组织中的变质层被部分去除;残余应力也明显减小。由此表明磁力研磨加工工艺能够提高整体叶盘的表面完整性,从而可以提高零件的疲劳强度和使用寿命。     

PVA基粘弹性磁性磨具的实验研究及加工参数优化

目的检验新研制的PVA基粘弹性磁性磨具的表面光整加工性能,掌握配比参数、加工条件等因素对加工效果的影响规律,并对加工参数进行优化以达到最佳加工效果。方法以6061铝合金管外圆表面为光整加工实验对象,通过先导实验首先确定出影响加工效果的主要因素及其参数范围,而后基于响应曲面法实验,对主轴转速、两相质量比、磨粒尺寸及加工时长等因素与工件表面粗糙度下降率(%?Ra)之间的关系进行了探究分析。结果最后通过对实验结果进行方差分析,建立了PVA基粘弹性磁性磨具加工铝合金管外表面的%?Ra预测模型,并对影响参数进行了优化设计,得到在最佳实验条件下(加工时间46 min、两相质量比1.45、主轴转速635r/min、磨粒尺寸65目),工件表面粗糙度下降率为92.5%,最低表面粗糙度为59 nm,显著改善了加工效果。结论作为一种新型光整加工介质PVA基粘弹性磁性磨具,其具有良好的自适应性及流动性,能达到较好的光整加工效果。影响%?Ra的单因素显著性从强到弱依次为:加工时长、主轴转速、磨粒尺寸、两相质量比。交互作用显著的因子为两相质量比+主轴转速、加工时长+主轴转速、两相质量比+磨粒尺寸。在主轴转速、加工时长取高水平,两相质量比取中等水平,磨粒尺寸取低或高水平时,能得到较好的表面加工效果。     

模具数字化磁力研磨加工中研磨运动轨迹的研究

介绍了模具制造过程中,模具表面数字化磁力研磨加工的原理和特点,分析了曲面磁力研磨加工轨迹对研磨质量的影响,提出了相应的解决办法。