Partial-Ductile Grinding and Reduced Polishing for Ophthalmic Glass Molds

Plastic lenses are manufactured by the classical replication technique where two glass molds are assembled in a jacket and liquid plastic is injected into it. The glass molds are fabricated conventionally by fracture mode grinding, followed by lapping, and Finally polishing. This paper presents an alternative fabrication process using partial-ductile grinding, followed by a short polishing in an industrial polishing machine. The partial-ductile surfaces were generated on a laboratory ultra-precision machine using Fine grit resinoid-bond diamond wheel and they were compared to the glass molds prepared by industry. The results showed that (i) as much as 100% ductile streaks (fully ductile grinding) can be obtained in the ultra-precision ground surface and (ii) a net saving of 55 seconds polishing time if only 60% of ductile streaks on the glass mold surface was used prior to polishing.     

磨具弯曲成形法非球面研磨的研磨模型

磨具弯曲成形法是加工光学非球面零件的新方法,是线接触研磨过程.给出了弯曲成形法研磨的原理,基于Preston方程,限定磨具弯曲成形法特定研磨条件,分析了加工面上的任意一点的压力函数和相对速度函数,推导了磨具弯曲成形法研磨材料去除量函数表达式,推导了研磨作用时间函数.该研磨模型为磨具弯曲成形法研磨实践提供了理论依据.     

单晶金刚石机械研磨与化学机械抛光工艺

单晶金刚石在工业、国防等领域的应用日益广泛,对其加工表面质量的要求不断提高,使用常温低压的化学机械抛光可实现金刚石的超光滑低损伤表面加工.通过理论分析及实验研究得出,使用硅酸盐玻璃材质研磨盘进行研磨加工,可以将金刚石表面粗糙度Ra降至15~25 nm,且无明显机械划痕;在2 MPa压力及室温环境下进行单晶金刚石化学机械抛光实验,优选出Fenton试剂酸性水基抛光液,使用该抛光液抛光单晶金刚石可获得粗糙度Ra值4 nm以下的光滑表面.     

Grinding of Toroidal and Cylindrical Surfaces on SiC Using Diamond Grinding Wheels

This paper presents the methods and experimental results for grinding toroidal and cylindrical surfaces made of silicon carbide using diamond grinding wheels and an inexpensive CNC machining center. The mirrors were successfully obtained by automatic grinding operations with good shape accuracy, mirror surface finish, and low roughness heights. The time consumed in the process is very short. Industrial manufacture of lenses usually involves three operations — grinding without dressing, lapping, and polishing. In the laboratory studies, however, mirrors and lenses have been manufactured only with grinding process, because of 100% ductile-mode material removal in grinding with dressing. These processes were individually evaluated for surface roughness and surface integrity using surface roughness testers and a scanning electron microscope.     

小口径非球面的超精密车削和抛光组合加工

针对目前小口径非球面零件在超精密加工中存在的加工效率和加工精度等问题,分析了现今小口径非球面超精密加工方法及其特点,提出了一种超精密金刚石车削和斜轴磁流变抛光超精密组合加工方法．其中小口径非球面斜轴磁流变抛光方法的特点是抛光主轴采用倾斜安装,并且抛光头由外部旋转抛光体和内部励磁装置两部分构成．通过开发新型的小口径非球面超精密复合加工装备,对小口径单晶硅非球面进行了超精密组合加工实验．实验结果表明工件的表面粗糙度R。由车削后的9．1nm下降到抛光后的3．2mm,证明了该组合加工工艺是提高小口径非球面加工效率和精度的一种有效加工方法．     

硼硅酸盐浮法玻璃的抛光温度

浮法工艺的优点之一是可以获得极佳的玻璃表面质量,硼硅酸盐浮法玻璃是近年来的研究热点。本文采用原子力显微镜（AFM）研究了温度和时间对硼硅酸盐玻璃浮法成形过程中抛光阶段的影响。研究结果表明：高温抛光过程中时间不是限制玻璃表面抛光质量的决定因素,温度是决定抛光质量的关键。硼硅酸盐浮法玻璃在大于1250℃以上的温度可以快速达到良好的抛光效果。     

助磨剂对泡沫玻璃配合料粉磨效率的影响

采用干法粉磨工艺,选取丙三醇、硅酸钠、三异丙醇胺、三乙醇胺、木质素磺酸钠5种助磨剂,研究助磨剂对泡沫玻璃配合料粉磨的影响;改变助磨剂掺量,以粉体粒度评价助磨剂对配合料粉磨效率影响。结果表明:随着助磨剂掺量的增大,粉磨效率提高,但是粉磨效率存在一个极值,该极值与助磨剂的种类和用量相关;泡沫玻璃配合料的最佳助磨剂为三乙醇胺,最佳掺量(质量分数)为0.04%,粉磨后平均粒径为13μm,比未用助磨剂的配合料平均粒径减小43%。     

机器人磨抛工艺参数优化方法研究

为了确保加工质量和加工效率的最优参数组合,进行了机器人砂带磨抛去除参数的优化方法研究.在分析砂带磨抛过程后建立了表面粗糙度和磨抛去除率模型.运用deform软件对工件磨抛过程进行模拟仿真,建立了磨抛去除率和粗糙度回归方程.以加工表面粗糙度和材料磨抛去除率作为目标函数进行双目标优化,并运用NSGA-Ⅱ算法确定了最优参数组合.以仿真数据为基础进行正交试验,对理论和仿真的结果进行了验证.结果表明,采用所确定的最优参数组合进行磨抛加工试验,能够达到预期的磨抛去除率和表面粗糙度要求,表面加工质量良好,所用工艺参数优化方法可行.     

Wetting of Spherical Surfaces by Quantum Fluids

We study adsorption of atoms and fluids on spherical surfaces and present resugts for helium on weak to moderately strong adsorbers such as Cs, Li and Mg. We investigate the growth of a helium film as a function of the number of atoms, by means of a finite range density functional theory. We identify a crossover between nonadsorption and weak adsorption as the sphere radius increases. Path Integral Monte Carlo simulations provide semiquantitative support to these predictions.     

Effects of Cooling and Dressing Methods on Grinding of Glass

Experiments were designed and conducted to evaluate the effects of cooling and dressing methods and five other factors on the grinding of glass. Surface roughness of the ground samples was measured and microscopic studies of the ground glass surfaces were performed. The column effect method and plotting method were applied to analyze and interpret the experimental results. The results showed that the average surface roughness heights of ground glass were improved by 5-36% and 42-52%, respectively, when an improved coolant system and dressing device were employed. The average surface roughness heights decreased by 52-58% and 30-37%, when smaller grit sizes and a resin-bond grinding wheel rather than a metal-bond grinding wheel were used, respectively. In addition, the surface roughness averages decreased by 18-23% and 13-18% when a smaller table-feed rate was used and truing of grinding wheels was performed, respectively. Moreover, compared with the surface roughness heights of the sample that was ground using the existing coolant system and manual dressing method, the surface roughness heights of the sample ground using both the improved coolant system and device-dressing method were improved by 46-70%, because of the positive interaction of these two factors.     

磁流变抛光高精度光学表面中的工艺参数

对磁流变抛光进行高精度光学表面加工中必须考虑和控制的7类参数,即磁流变液黏度、磁场强度、磁流变液流量、抛光轮转速、锻带厚度、切深以及抛光斑点特性进行分析和优化,得出单因素条件下材料的去除量总是同这7类参数的变化存在一定的内在联系．在分析和优化磁流变抛光过程中这些参数的基础上,采用自研的KDMRF-1000机床对一块K4材料口径100mm的平面镜进行了抛光加工实验．经过两次循环大约200min的抛光后．面形误差值由最初的峰谷值（PV）为262nm,均方根值（RMS）为49nm收敛到最终的PV为55nm,RMS为5．7nm实验中面形误差的收敛表明：只要掌握了磁流变抛光过程中的这7种参数的变化规律,就能充分利用磁流变抛光技术,为高精度光学表面的加工提供可靠的保障．     

Fast Coherence Scanning Interferometry for Measuring Smooth,Rough and Spherical Surfaces

Abstract

Coherence scanning interferometry is a useful instrument for measuring the geometry of a wide range of surfaces with high resolution. By introducing two objectives with a high numerical aperture in both arms of a Michelson interferometer it is possible to investigate spherical and aspherical surfaces. In addition to classical interferometry, the method can be applied to smooth, rough or separated surfaces.     

Effect of Polishing Conditions on the Optical Properties of Zinc Selenide Surfaces

The effects of the polish time and the pressure applied to the sample on the quality of polycrystalline ZnSe surfaces prepared by mechanical polishing with fine-particle abrasives on wheels made of pitch–colophony resins are studied. The results indicate that, using 1-m alumina as an abrasive and distilled water as an extender, the fourth surface finish class (RF Standard GOST 11141-84) with deviations from planarity less than half of an interference fringe at a sample diameter of up to 40 mm can be achieved at pressures applied to the sample from 30 to 35 kPa and polish times longer than 225 min. The material removal rate under the optimal polishing conditions is 0.03 m/min.     

单晶金刚石机械研磨结合化学辅助机械抛光组合加工工艺

单晶金刚石因具有最高的硬度和最低的摩擦系数常被用来制备超精密刀具,而表面粗糙度是影响刀具寿命的重要指标.提出采用机械研磨结合化学辅助机械抛光的组合工艺抛光单晶金刚石.实验优化并确定的加工工艺如下:先用5μm和2μm金刚石粉研磨单晶金刚石表面,然后采用化学机械的方法去除机械研磨带来的损伤.用该工艺抛光单晶金刚石,表面粗糙度Ra可达0.8 nm(测量区域70μm×53μm).表面拉曼光谱分析表明化学机械抛光的表面只有1 332 cm-1拉曼峰.     

玻璃纤维增强复合材料的干式磨削加工技术研究

玻璃纤维增强复合材料具有非均质性、各向异性,其可磨削性能与传统金属材料有很大不同。采用两种砂轮对手糊成型高强玻璃纤维增强环氧树脂复合材料层合板进行磨削性能研究,对磨削力和表面粗糙度进行了测量与分析。随着磨削深度的增加,磨削力分力比先增加后减小;随着转速的提高和磨粒尺寸的减小,磨削力分力比减小。玻璃纤维增强复合材料的磨削性能比金属材料差,比陶瓷材料好。     

酸碱处理对磷酸盐激光玻璃表面的侵蚀研究

通过添加重金属钡的酸碱溶液, 在不同外界条件下, 研究了磷酸盐激光玻璃表面结构在酸碱侵蚀过程的反应机理. 结果表明, 酸碱对磷酸盐激光玻璃的侵蚀过程主要包括金属阳离子析出和[PO₄]网络结构破坏等两个重要过程. 金属阳离子的析出主要是非桥氧结构P-O-M(M为K⁺、Ba²⁺、Al³⁺等阳离子)在酸碱作用下生成P-O-H基团, 而[PO₄]网络结构的破坏则是指玻璃网络原有的Q²结构在酸碱的侵蚀下逐渐向Q¹和Q⁰转变. 据此, 推导了磷酸盐激光玻璃在酸碱侵蚀过程中的反应模型.     

On the Lapping Mechanism of Sintered A12O3 Ceramic Surfaces Using Diamonds

In this paper the material removal mechanism during lapping of A1₂O₃ ceramic surfaces is discussed. Powders containing 95% A1₂O₃ were consolidated into green compacts by employing different compaction pressures. The green compacts were subsequently sintered and lapped using synthetic diamonds of different size. The morphology and the chemical composition of the polished surfaces and the lapping debris were examined by Scanning Electron Microscopy (SEM), Energy Dispersive x-ray Analysis (EDAX) and x-ray diffraction (XRD). Based on the experimental observations, the effect of the diamond grit size and of the initial porosity on the surface integrity and the material removal mechanism were investigated. An interpretation is proposed for the nature and the formation of the plastically deformed layer produced on the polished surfaces.     

球形铁基金属玻璃单分散粒子的制备及评价

利用脉冲小孔法在He气氛下制备出了球形粒径可控的[(Fe_0.5Co_0.5)_0.75B_0.2Si_0.05]₉₆Nb₄金属玻璃单分散微粒子, 这些粒子具有粒径均匀和圆球度高等优良特点. 通过XRD、DSC以及TEM对所获得的粒子进行了检测分析, 结果表明随着粒径尺寸的减小, 微粒子的微观结构从混合相逐渐向全金属玻璃相转变, 制备的粒子均为全玻璃相, 临界尺寸小于645 μm. 通过冷却速率的计算, 得到全玻璃相微粒子的临界冷却速率为800~1100 K/s, 该速度与环境气氛的改变无关, 并且该计算值低于同成分的大块金属玻璃合金TTT曲线的测量值.     

Experimental Investigation of Material Removal and Surface Roughness during Optical Glass Polishing

It has been a challenge to finish optical glass surfaces due to their hard and brittle nature. Moreover, tight tolerances of surface figure and finish make polishing a more critical operation. This work reports the results of an experimental study performed for full aperture polishing of BK7 optical glass. Flat samples of borosilicate (BK7) glass are polished using an optical pitch polisher and cerium oxide (CeO₂) slurry. Taguchi's L9 orthogonal array is used for the design of experiments. Abrasive concentration, pressure and overarm speed are considered as variable process parameters. Polishing is performed for duration of 120 minutes for each combination of parameters. Material removal is measured using the precision weighing balance. Surface roughness was measured using a Form Talysurf PGI 120 profiler. Abrasive slurry concentration is observed to be one of the most significant parameters in the optical polishing process. It affects both the material removal rate (MRR) and the surface roughness. Pressure applied at the workpiece–polisher interface affects the MRR, but the variation of pressure is not found to affect the surface roughness significantly. Relative motion at the workpiece–polisher interface is also observed to be significant in defining the final polishing outputs.