Study on cylindrical magnetic abrasive finishing using unbonded magnetic abrasives

The process principle and the finishing characteristics of unbonded magnetic abrasive within cylindrical magnetic abrasive finishing are described in this study. The unbonded magnetic abrasive is a mechanical mixture of SiC abrasive and ferromagnetic particles with a SAE30 lubricant. Iron grit and steel grit, for which three various particle sizes were prepared for both, were used as ferromagnetic particles, each of them being mixed with 1.2 and 5.5 μm SiC abrasive, respectively. Also, the finishing characteristics on surface roughness and material removal as well as their mechanisms were investigated. Experimental results indicate that steel grit is more suitable for magnetic abrasive finishing because of its superior hardness and the polyhedron shape. The variations of material characteristics on the work surface both before and after finishing were also investigated. Si content was increased obviously, however its corrosion resistibility decreased on a surface that was finished via steel grit mixed with SiC abrasive.     

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.     

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.     

Contents

The attempts of researchers to obtain accurate and high-quality surfaces have led to the invention of new methods of finishing. Magnetic abrasive finishing (MAF) is a relatively new type in which magnetic field is used to control the abrasive tools. Surfaces of moulds, for instance, are among those which require very high-surface smoothness. Usually, this type of part has freeform surfaces. In this study, the effect of magnetic abrasive process parameters on finishing freeform surfaces of aluminium parts has been examined. This method was achieved through a combination of the magnetic abrasive process and computer numerical control. The use of a simple hemisphere to be joined on the flat area of the magnet as well as spark machining for forming a sphere at the end of a magnet were performed during experimentation. Gap, rotational speed of the machining head, amount of abrasive powder and feed rate were among the parameters that were tested in experiments. The design of experiments is based on the response surface methodology. Significant parameters and the regression equations governing the process were also determined. The impact of intensity of the magnetic field was obtained using MAXWELL finite element software. In the MAF process, magnetic abrasives play the role of cutting tools. However, the magnetic abrasives are not easily available as these are produced by special techniques such as sintering method, adhesive based, plasma based or gel based. This study presents the basic polishing characteristics of the magnetic abrasives produced by the mechanical alloying process. After the mechanical alloying process fine magnetic abrasives are obtained, in which the abrasive particles adhere to the base metal matrix without any bonding material. In this study, investigation was performed only on the convex area of workpiece. Optimum parameters are gap size of 0.5?mm, feed rate of 10?mm?min^?1 rotational speed of 2100?rev?min^?1 and powder amount of 1.75?g. To help understand the effectiveness of the MAF process, scanning electron microscopy and atomic force microscopy of the machined surfaces have been carried out.     

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.     

基于PSO-ELM的316L不锈钢细长管磁粒研磨内表面粗糙度预测模型

针对316L不锈钢细长管磁粒研磨加工过程中,最佳工艺参数难以选择,以及加工后对工件内表面粗糙度（Ra）的预测问题,将影响磁粒研磨316L不锈钢细长管内表面粗糙度的四个工艺参数作为输入值,内表面粗糙度作为输出值,构建粒子群（PSO）优化极限学习机（ELM）模型来预测316L不锈钢细长管内表面粗糙度,利用PSO对工艺参数进行全局寻优,获得最佳工艺参数组合,最后通过试验与预测结果进行对比。构建的PSO-ELM表面粗糙度预测模型拟合优度R2为0.984 8,绝对误差（MAE）为0.013 4,均方根误差（RMSE）为0.021 4。得到的最佳工艺参数组合为：主轴转速2 389.011r/min,进给速度3.167 mm/s,磨料粒径216.185μm,加工时间35.856 min,预测Ra为0.178μm。对工艺参数进行调整,试验得到的Ra为0.182μm,与预测值相比误差为2.24%。基于PSO-ELM方法构建316L不锈钢细长管内表面粗糙度预测模型,实现对工件内表面粗糙度的精确预测,应用粒子群方法得到最佳工艺参数组合,提高了磁粒研磨316L不锈钢细长管的加工效率。     

Design and development of the magnetorheological abrasive flow finishing (MRAFF) process

A new precision finishing process for complex internal geometries using smart magnetorheological polishing fluid is developed. Magnetorheological abrasive flow finishing (MRAFF) process provides better control over rheological properties of abrasive laden magnetorheological finishing medium. Magnetorheological (MR) polishing fluid comprises of carbonyl iron powder and silicon carbide abrasives dispersed in the viscoplastic base of grease and mineral oil; it exhibits change in rheological behaviour in presence of external magnetic field. This smart behaviour of MR-polishing fluid is utilized to precisely control the finishing forces, hence final surface finish. A hydraulically powered experimental setup is designed to study the process characteristics and performance. The setup consists of two MR-polishing fluid cylinders, two hydraulic actuators, electromagnet, fixture and supporting frame. Experiments were conducted on stainless steel workpieces at different magnetic field strength to observe its effect on final surface finish. No measurable change in surface roughness is observed after finishing at zero magnetic field. However, for the same number of cycles the roughness reduces gradually with the increase of magnetic field. This validates the role of rheological behaviour of magnetorheological polishing fluid in performing finishing action.     

永磁场磁力研磨TC11钛合金的实验研究

目的解决钛合金机械加工后表面质量差的难题。方法采用磁力研磨工艺对TC11钛合金进行了表面光整加工。以表面粗糙度为主要评价指标,研究了磁力研磨工艺参数对钛合金表面质量的影响,并对工艺参数进行了优化。采用优化后的工艺参数对钛合金进行了表面光整加工,研究了磁力研磨工艺对钛合金金相组织的影响。结果当加工间隙为3 mm时,研磨压力适宜,加工后工件表面粗糙度值最小。采用粒径为100目的磨粒使工件表面研磨加工后纹理更细,表面粗糙度值最低。提高主轴转速,工件表面材料去除率增加,当主轴转速为1500 r/min时,加工后工件表面粗糙度值最小。对比工件加工前后的金相组织,加工后试样表面组织晶粒变细,晶界增多,工件表面应力状态由张应力转变为压应力。结论实验确定了较优的工艺参数组合,即:加工间隙为3 mm,磨粒粒径为100目,主轴转速为1500 r/min。采用永磁场磁力研磨工艺,能够大幅降低TC11钛合金表面粗糙度,并使钛合金表面组织得到改善。     

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.     

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。     

Electrolytic magnetic abrasive finishing

Electrolytic magnetic abrasive finishing (EMAF) is a compound finishing process, involving traditional magnetic abrasive finishing (MAF) and an electrolytic process. The aim of including the electrolytic process into the EMAF system is to produce a passive film (or oxide film), which is much easier to remove than the original metal surface during processing. Moreover, in the presence of both electric and magnetic fields, the negatively charged ions move toward the anode surface along a cycloid curve by the action of the Lorentz force. Under appropriate operating conditions, this phenomenon promotes electrolytic effects, resulting in a further increase in finishing efficiency, yielding a superior surface. This study describes the principles of the process, the finishing characteristics of surface roughness and material removal, and the associated mechanisms. Experimental results show that the EMAF process yields quite excellent finishing characteristics, better than those obtained by MAF, especially with a high electrolytic current. The process parameters such as electrolytic current, electrode gap, magnetic flux density, and rate of workpiece revolution must be appropriately fitted to obtain a superior refined surface with high efficiency.     

脉冲电磁场辅助平面磁粒研磨加工试验

目的 在传统的平面磁粒研磨加工中添加脉冲辅助磁场,增大加工区域中磁感应强度和加工时磁感应强度动态变化,丰富磨料粒子在加工时的运动形式,使研磨轨迹复杂化,降低工件表面粗糙度,获得更好的工件表面形貌.方法 通过分析磨料粒子在有无辅助磁场时各自的受力情况,探究辅助磁场对磨料在加工时运动状态的影响,研究脉冲辅助磁场下磨料的运动...     

Mathematical model determination for improvement of surface roughness in magnetic-assisted abrasive polishing of nonferrous AISI316 material

The new magnetic-assisted abrasive polishing process for non-ferrous materials was proposed in order to increase the magnetic flux density which directly influences the contact force between the workpiece and the abrasives.The permanent magnets were installed under the workpiece and their effects were verified by the experiments.The effect of polishing factors on the improvement of surface roughness was evaluated based on the Taguchi experimental method,and the optimal conditions for polishing AISI316 stainless steel were determined.The predicting model for improving surface roughness was developed and the validity of the developed model was tested.The results show that the permanent magnets are very useful in improving the surface roughness in the magnetic-assisted abrasive polishing process.     

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...     

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.     

模具型腔自动化磁力研磨光整加工

介绍了自由磨粒磁力研磨光整加工机理,在3_TPT五自由度并联机床上对模具型腔进行磁力研磨光整加工试验,研究了磁感应强度、研磨间隙、磨料粒度以及研具表面形状对模具型腔进行磁力研磨光整加工的影响及其变化规律。     

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     

聚磁盘形状对磁粒研磨加工管件内表面的影响

目的提高磁粒研磨法加工管件内表面的质量及加工效率,探究磁粒研磨法中不同形状的聚磁盘对管件内表面的影响。方法利用Maxwell软件对轴向开槽聚磁盘与不开槽聚磁盘进行磁场强度模拟和磁感应线模拟,分析不同形状的聚磁盘的磁感应强度变化和磁场强度分布。利用磁粒研磨法对工件内表面进行研磨加工,对研磨之后的工件表面粗糙度进行测量,并对微观形貌进行观察。结果在磁粒研磨工具转速为500 r/min、加工时长为15 min的条件下,聚磁盘为未开槽时,表面粗糙度由原始的0.509μm降至0.127μm,表面粗糙度改善率(%ΔRa)为75.04%;当聚磁盘为轴向开槽时,工件表面粗糙度由原始的0.553μm降至0.097μm,工件的表面粗糙度改善率(%ΔRa)为82.45%。结论在相同的加工条件下,当聚磁盘轴向开槽时,相对于轴向不开槽的聚磁盘,磁粒研磨管件内表面的研磨效果更好,表面粗糙度改善率和研磨效率更高。     

A study on polishing of molds using hydrophilic fixed abrasive pad

The finishing process for die and mold manufacturing is very important because it influences the final quality of the products. injection molds especially need higher quality surface than general purpose dies and molds. Conventional polishing cannot reduce mold surface down to nanometer roughness efficiently because of loading and glazing. This paper focussed on the development of a fixed abrasive pad using the water swelling mechanism of polymer binder network. Self-conditioning was recognized as a long term polishing stabilization tool without any loading or glazing because water makes the fixed abrasives free by the swelling of the pad. Consequently, a stable nanopolishing process has been realized on the injection mold, based on the experimental results with a polished surface roughness of R_a 15.1 nm on D2 die steel (AISI standard).