小口径非球面小球头接触式抛光及磁流变抛光组合加工

目的 为了提高非球面光学模具的表面质量和加工效率。方法 分析当前非球面超精密抛光方式及其特点,针对小口径非球面光学模具,提出一种小球头接触式抛光及磁流变抛光的组合加工方法,对小球头进行设计,并抛光碳化钨圆片,对比小球头接触式抛光及轴向、径向、水平方向磁极的永磁体球头的磁流变抛光的加工性能。分别对编号为1^#、2^#、3^#等3个相同轮廓形状的碳化钨非球面模具进行单一方式抛光试验和组合加工试验。结果 通过对小球头抛光碳化钨圆片的加工性能进行分析发现,接触式抛光小球头的去除率为926.5 nm/h,表面粗糙度达到4.396 1 nm;轴向、径向、水平方向磁极的永磁体小球头磁流变抛光的去除率分别为391.7、344.3、353.7 nm/h,表面粗糙度分别为1.425 2、1.877 6、1.887 5 nm。对采用组合加工方法抛光碳化钨非球面的有效性进行验证时发现,非球面1^#在单一接触式抛光60 min后表面粗糙度从8.786 6 nm降至3.693 2 nm;非球面2^#在单一磁流变抛光60 min后表面粗糙度从8.212 1 nm降至1.674 5 nm;非球面3^#在组合抛光方法下先进行15 min接触式抛光,再进行15 min磁流变抛光,表面粗糙度从8.597 2 nm降至1.269 4 nm,面形精度由175.2 nm提高到138.4 nm。结论 组合加工方法可以弥补单一抛光方法的缺陷,并能有效地提高工件的面形精度。与单一接触式抛光方法相比,组合加工方法获得的表面质量更好,抛光后表面粗糙度为1.269 4 nm,远小于单一接触式抛光下的3.693 2 nm;与单一磁流变抛光方法相比,组合加工方法更高效,将样件抛光到同等级别粗糙度所需时间从60 min减少至30 min。     

偏置量对固结磨料小工具头抛光面形收敛效率的影响

目的 解决自由曲面磨抛面形收敛困难的问题,提高抛光小工具头的抛光效率.方法 提出一种偏置式固结磨料小工具头,基于固结磨料小工具头的结构特征参数,建立抛光小工具头的去除函数理论模型,并进行仿真分析,应用定点抛光法建立抛光小工具头去除函数实验模型,并验证抛光小工具头理论去除函数合理性,基于CCOS技术原理建立工件表面定量去除模型,通过虚拟加工实验探索偏置量对固结磨料小工具头抛光钛合金后的面形收敛效率的影响.结果 归一化理论去除函数曲线与实验曲线吻合度较高,定点抛光去除函数仿真模型能够很好地预测定点抛光斑的去除轮廓形状.抛光小工具头抛光钛合金的面形误差随偏置量增加,呈现先减小、后增大的趋势,无偏置的抛光小工具头抛光后,面形数据均方根(RMS)收敛效率为54.56％,波峰值与谷峰值之差(PV)的收敛效率为60.21％,当抛光小工具头偏置量为1.5 mm时,抛光后的RMS收敛效率达到最高,为73.83％,PV收敛效率为69.68％.结论 固结磨料小工具头去除函数理论模型可指导确定性材料去除,偏置量为1.5 mm时的抛光小工具头具有最强的修正误差能力,可以显著提高固结磨料小工具头抛光工艺的面形收敛效率.     

Loose abrasive blasting as an alternative to slurry polishing of optical fibre end faces

A novel method of polishing the end face of an optical fibre by blasting it with loose dry abrasive grit travelling at high speeds is presented. The method, called loose abrasive blasting (LAB), is specifically designed to improve the surface quality of micro-lenses ground at the tips of optical fibres. Thus, the method described is suitable for polishing non-flat surfaces. Blasting is carried out by immersing the fibre tip in a stream of high kinetic energy abrasive grit. The surface finish attainable using LAB is compared with that of cleaved, ground and slurry polished fibre end faces. Optical microscopy photographs are presented as a qualitative comparison. The surface roughnesses are measured using atomic force microscopy (AFM). For cleaved fibres, the surface roughness improved by a factor of 2 and 6 for slurry polished and dry diamond blasted fibres, respectively.     

A neuro-fuzzy approach to generating mold/die polishing sequences

A neuro-fuzzy approach to generating polishing sequences is presented. The measured initial surface roughness of the EDMed mold or die and the desired final polished surface roughness are the major inputs fed to the system. After receiving this input, the system consults its database for the polishing efficiency curves of the abrasive stone grain sizes available to it. With the outputs of this system being optimized for minimum polishing time, there is a selected sequence of grain sizes from among an available set, with each grain size used for each polishing step. There was a series of initial polishing experiments which were conducted for the different available grain sizes and workpiece roughness at different pressures and RPM's, with a change in roughness measured for polishing duration. From this, the database is constructed for designing the fuzzy logic rules. For constructing the exact membership function of the fuzzy interface, the neuro-fuzzy technique is combined with learning ability of neural network and the inferring ability of fuzzy logic system. Finally, while considering the stone-changing time, the actual experimental results from suggested polishing sequences are compared with the predicted value in order to establish the proposed approach.     

Non-abrasive polishing of glass

Supersmooth surfaces are often needed in high- and new-technology products. The traditional polishing method to obtain supersmooth surfaces is abrasive polishing. In this paper, a new kind of polishing method, non-abrasive polishing (NAP), is presented. The polishing wheel of NAP is made of ice that is frozen deionized water, so there is no abrasive in the polishing wheel. Compared with traditional polishing methods, NAP can obtain Ångström-order surface roughness values free from microscratches and subsurface cracks. Based on adhesion theory, the material removal mechanism of NAP is presented in the paper. The paper also analyzes the polishing equipment and processing technique of NAP. The best surface roughness, R_a=0.48 nm, of K9 glass is obtained using NAP. According to the relationship between surface roughness and adhesion, the surface roughness fluctuation phenomenon is explained in the paper. The surface roughness fluctuation phenomenon is expected to be avoided by measuring the fractal dimension of the polished surface.     

单晶碳化硅的电磁场励磁大抛光模磁流变抛光

目的 研发一种高精高效单晶碳化硅表面抛光技术。方法 采用电磁场励磁的大抛光模磁流变抛光方法加工单晶碳化硅,利用自制的电磁铁励磁装置与磁流变抛光装置,进行单因素实验,研究电流强度、工作间隙和抛光时间等工艺参数对单晶碳化硅磁流变抛光加工性能的影响,并检测加工面粗糙度及其变化率来分析抛光效果。结果 在工作间隙1.4 mm、电流强度12 A的工艺参数下,加工面粗糙度值随着加工时间的增加而降低,抛光60 min后,加工面粗糙度值Ra达到0.9 nm,变化率达到98.3%。加工面粗糙度值随通电电流的增大而减小,随着工作间隙的增大而增大。在工作间隙为1.0 mm、通电电流为16 A、加工时间为40 min的优化参数下抛光单晶碳化硅,可获得表面粗糙度Ra为0.6 nm的超光滑表面。结论 应用电磁场励磁的大抛光模盘式磁流变抛光方法加工单晶碳化硅材料,能够获得亚纳米级表面粗糙度。     

Surface treatments of CdGeAs_2 single crystals

The performances of second harmonic generation(SHG)and optical parametric oscillator(OPO)in CdGeAs_2 crystal are strongly influenced by surface quality.In this paper,the surfaces of samples were treated by mechanical polishing(MP),chemical polishing(CP),chemical-mechanical polishing(CMP)and CP following CMP closely(CMP + CP).Then,the surface state was characterized by optical microscopy(OM),scanning electron microscopy(SEM),atomic force microscopy(AFM)and X-ray photoelectron spectroscopy(XPS).AFM measurements show that an ultra-smooth surface is achieved after CMP+ CP treatment and the roughness value is 0.98 nm.Meanwhile,the roughness of the surfaces treated by MP,CP and CMP are 4.53,2.83 and 1.38 nm,respectively.By XRD rocking curves,the diffraction peak which belongs to the wafer treated by CMP+CP is the highest in intensity and best symmetrical in shape.XPS analysis indicates that Ge~(4+) proportions of GeO_2 in total Ge content of CdGeAs_2 wafers' surface after MP,CP,CMP and CMP + CP treatment are 27.6%,42.8%,6.1% and 30.3%,respectively.     

纳米磨料硬度对超光滑表面抛光粗糙度的影响

通过均相沉淀法制备了纳米CeO2和Al2O3粉体,研究了在相同抛光条件下纳米CeO2、Al2O3和SiO2磨料对硅片的抛光效果,用原子力显微镜观察了抛光表面的微观形貌并测量其表面粗糙度.结果表明:纳米CeO2磨料抛光后表面具有更低的表面粗糙度,在5 靘5 靘范围内表面粗糙度Ra值为0.240 nm,而且表面的微观起伏更趋向于平缓;考虑了纳米磨料在抛光条件下所发生的自身变形,其变形量相当于一部分抵消了纳米磨料嵌入基体材料的切削深度,而这个切削深度最终决定了抛光表面的粗糙度;分析指出这个变形量与纳米磨料的硬度成反比,硬度低的纳米磨料由于自身变形量大,导致切削深度小,抛光后表面的粗糙度值低.解释了在相同的抛光条件下不同硬度的纳米磨料具有不同的抛光表面粗糙度的原因.     

Problems in High Current Density Nickel and Chromium Deposition

Five optical methods are discussed here by which the surface finish of polished or electrodeposited metal surfaces may be studied. Four are dealt with briefly because they have been adequately described in the literature. The fifth is believed to be new in its application to metal finishing. Preliminary results obtained for polished brass surfaces and for various electrodeposited metal coatings are discussed.

The presence of an oxide film has a marked influence on the optical behaviour of a metal surface. The properties of such a film may be learnt from the methods here outlined. Of particular practical interest is the anodic oxide film, familiar long since as a surface finish for aluminium and of current interest as a possible protection for other metals. The methods described are of general application. Illustrations are provided of the results obtained on anodised tantalum surfaces.     

Influence of the microstructure and laser shock processing (LSP) on the corrosion behaviour of the AA2050-T8 aluminium alloy

The corrosion behaviour of AA2050-T8 was studied after polishing and after laser shock processing (LSP) treatment using the electrochemical microcell technique and the SVET. After polishing, pitting at constituent particles and intergranular corrosion were observed. By contrast, no intergranular corrosion developed after LSP. Microcell measurements revealed that LSP increases the pitting potential. SVET measurements revealed that local anodic currents are systematically lower on LSP-treated surfaces than on polished ones. The current density on the LSP-treated surface remains constant around 50 μA cm⁻² up to 123 min after immersion, while on the polished surface it reaches 200 μA cm⁻².     

An XPS study of the surfaces on Fe-Cr,Fe-Co and Fe-Ni alloys after mechanical polishing

Using an XPS technique, the composition and thickness of the surface film and the composition of the underlying alloy surface on Fe-Cr, Fe-Co and Fe-Ni alloys were studied after polishing with silicon carbide paper in trichloro-ethylene and cyclohexane. The compositions of the underlying alloy surface after polishing were almost the same as those of the bulk alloys but the film compositions depended on the alloying addition and environment during polishing. The cationic fractions in the surface films on the Fc-Cr alloys polished in both solvents were almost the same as the corresponding atomic fractions of the bulk alloys. In contrast, iron ions were apt to be concentrated in the surface films on the Fe-Co and Fe-Ni alloys, and the weights of nickel ions were different in the surface films on the Fe-Ni alloys polished in different solvents. Chloride ions were found in the surface films due to the reaction of the metal surface with trichloro-ethylene. The amount of chloride ions was particularly large in the surface films on the Fe-Ni alloys. Heating the alloy specimens under the vacuum of the spectrometer resulted in almost complete reduction of the surface films on the Fe-Co and Fe-Ni alloys, and in the change in the compositions of all alloy surfaces.     

Robotic polishing of precision molds with uniform material removal control

In this paper, a uniform material removal (UMR) model is proposed for an automatic mold polishing system (AMPS). Free-form surfaces of mold geometry in IGES format are read and regenerated by the AMPS using the NURBS model. The normal vector, the principal curvatures, and the effective contact area are calculated at any point on the surface. The sensitivity of each factor that influences the material removal is determined by Taguchi experiments. The UMR model is based on maintaining constant velocity and contact pressure by controlling the polishing force according to the effective contact area. Three optical molds were polished using two path patterns with and without UMR control for comparison. The experimental results showed that even the conventional constant-force polishing scheme can achieve nearly the same surface roughness; the surface profile error of the mold with UMR control is less than 1/3 of the mold without UMR control. In addition, the actual material removal depth is less than 5.4% of error compared to the predicted value by the UMR model.     

Characteristics of TiNi Shape Memory Foils Fabricated by Double Cathodes Electrochemical Polishing

Ti₅₀Ni₅₀ shape memory foil with 25 μm in thickness and having two smooth surfaces can be fabricated by an electrochemical polishing technique. This technique, using double cathode plates, may shorten the polishing time and alleviate the over-etched pitting effect. The grains on the surface of the hot-rolled sheet are elongated along the rolling direction, and those in the center of the electrochemically polished foil are equal-axial with an average grain size of approximately 8.5 μm. Both transformation temperature and enthalpy of the electrochemically polished foils decrease with the decreasing specimen’s thickness. The fabricated Ti₅₀Ni₅₀ foils possess the advantages of a more uniform chemical composition throughout the specimen, larger grain size, larger foil area, and greater thickness than those of sputtered TiNi thin films and melt-spun TiNi ribbons.     

Ultra-precision grinding of optical glass lenses with La-doped CeO2 slurry

Higher accuracy and more efficient production of large aperture glass lenses is increasingly required for high-resolution imaging devices. These glass lenses are typically manufactured by both ultra-precision grinding and polishing. However, prolonged polishing deteriorates the lens shape accuracy and diminishes productivity. In order to reduce the required amount of polishing or even obtain a polish-free fine surface, chemical action-assisted ultra-precision grinding using La-doped CeO₂ slurry is proposed and its effectiveness is experimentally evaluated. The results show that the proposed grinding method successfully provides a high-quality surface comparable to a polished surface and results in five times higher productively than conventional grinding.     

抛光垫表面微细结构对抛光性能的影响试验

抛光垫是影响抛光加工效率和表面质量的关键因素之一,但影响规律和作用机理尚不清晰。为研究抛光垫表面微细结构对抛光性能的影响规律,制作有、无固结磨料的表面六边形微细结构抛光垫,分别对YG15硬质合金、单晶Si和单晶4H-SiC三种硬度差异较大的工件进行抛光试验。结果表明：各抛光垫对不同硬度工件抛光效果的影响规律一致,随着抛光工件的硬度增大,各抛光垫的材料去除率（MRR）减小,表面粗糙度Ra增大。抛光垫内的固结磨料能将MRR提高5～10倍,但也会导致Ra增大5～20倍。抛光垫表面微细结构会使得抛光过程中有效接触面积Ap和有效磨粒数Ns减小而导致MRR下降,而抛光垫硬度的增加能够部分弥补抛光垫表面微细结构造成的影响,抛光工件硬度越大,弥补效果越好。增加游离磨料能够有效降低抛光后Ra并提高硬度较大工件的MRR（上升约8%）,但对硬度较小工件的MRR有抑制作用（下降约27%）。根据抛光试验结果,建立工件-磨料-抛光垫接触模型,深入分析抛光垫表面微细结构、表面硬度对不同硬度工件抛光MRR和表面质量的作用机理,为不同工件抛光时抛光垫的选择提供了理论基础。     

Surface finishing of biodegradable stents

The surface conditions of stents influence their polymer/drug coatability, rate of degradation, and ultimately their mechanical strength, ability to expand, and service lifetime. This paper describes new polishing tools developed to mechanically polish entire biodegradable magnesium-alloy stents. Use of the new tools removes material from the peaks of the stent surfaces and enables surface smoothing equivalent to electrolytic polishing (EP) but with less material removal, helping extend the stent service life. Static immersion tests using Dulbecco’s modification of Eagle medium solution demonstrated that stents polished using the new tools had a rate of degradation about 40% lower than EP-processed stents.     

Laser polishing of parts built up by selective laser sintering

In this work, a surface finish method for parts built-up by selective laser sintering (SLS) is presented. One of the main drawbacks of the SLS technique is the high surface roughness of resulting parts. Therefore, parts have to be polished to be valid for operation conditions. Polishing processes are usually based on manual abrasive techniques. However, in the present paper, a surface polishing method based on laser irradiation is presented. The laser beam melts a microscopic layer on the surface, which re-solidifies under shielding gas protective conditions, resulting in a smoother surface.Laser-polishing tests for lines, planar surfaces and inclined planes have been performed, with satisfactory results in all the cases. The experimental tests were carried out on sintered test parts with an initial roughness of 7.5–7.8 μm Ra. The tested material is a commercial alloy denominated LaserForm ST-100^©, composed by sintered stainless steel and infiltrated bronze that it is used mainly for the constitution of injection moulds. Experimental results present final surface roughness below 1.49 μm Ra, which represent an 80.1% reduction of the mean roughness. Finally, a complete analysis of test probes and its metallurgical composition is presented. Considering that the material presents a non-homogeneous structure, the polished surfaces present slightly higher hardness values and are more homogeneous than the initial ones. Thus, polished surfaces do not present any heat affected zone or cracks, which could cause failure during the part operation.     

Influence of the degree of polishing of alloy AA 5083 on its behaviour against localised alkaline corrosion

A study has been conducted of the influence of the surface finish on the behaviour against the corrosion of samples of alloy AA 5083 immersed in aerated solutions of NaCl at 3.5%. Samples polished from 80 to 1200 grit have been tested, utilising as experimental techniques, measurements of weight loss, optical and scanning electron microscopy, linear polarisations and electrochemical noise measurement (ENM).In the conditions studied, the principal corrosion process that takes place is localised alkaline corrosion (LAC). This type of corrosion occurs as a consequence of the alkalinisation of the area surrounding the Al(Mn,Fe,Cr) cathodic precipitates that exist in the alloy.The results obtained indicate that the samples polished to 1200 grit present a greater susceptibility to processes of localised alkaline corrosion than the samples polished to 80 grit. It has been found that the degree of polishing conditions the number of intermetallic particles exposed. Hence the differences of behaviour observed between the sets of results obtained have been interpreted as an effect function of the density of cathodic intermetallic particles exposed on the surface.     

游离和固结金刚石磨料抛光手机面板玻璃的试验研究

选取不同粒径的金刚石微粉,采用游离磨料和固结磨料两种抛光方法加工手机面板玻璃,比较其材料去除率和抛光后工件表面粗糙度。结果表明：在相同的抛光工艺参数下,磨粒粒径在游离磨料抛光中对材料去除率和抛光后表面质量作用显著,而在固结磨料抛光中作用不显著;采用金刚石固结磨料抛光垫抛光能获得表面粗糙度约为Ra1.5 nm的良好表面质量,并在抛光过程中较好地实现了自修整功能。     

An integrated tool for five-axis electrorheological fluid-assisted polishing

A five-axis electrorheological fluid-assisted polishing equipment is presented for the finishing of curved surfaces in this paper. An integrated electrode tool is specially designed to make the abrasive particles in the electrorheological fluid concentrate around the tool end when the electric field is applied and it is suitable to polish not only the conductive material such as tungsten carbide but also the non-conductive material such as optical glass. The polishing experiments for curved surfaces of tungsten carbide and optical glass are conducted to confirm the validity and suitability of the developed five-axis equipment with the designed integrated electrode tool and to reveal the influence of the process parameters on the workpiece surface roughness in electrorheological fluid-assisted polishing.