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。     

磁流变抛光光学表面加工面形控制技术研究

磁流变抛光是一种新型超精密光学表面加工方法。由于其抛光过程可控,磁流变抛光过程可以有效去除表面及亚表面破坏层,提高表面质量,修正元器件表面面形误差。抛光过程容易实现计算机数控,通过数控过程的合理设计,磁流变抛光过程可以有效地对球面及非球表面进行抛光加工。研究了实现面形修正的驻留时间算法,并对光学球面器件进行了试验加工,抛光后其表面面形误差2点峰谷值从0.17μm降低到0.07μm。     

电火花线切割型腔模具的磁流变抛光方法

电火花线切割贯通形型腔模具的内腔形状复杂,一般抛光方法很难达到高精度的要求。在型腔模具的加工过程中,切割的内型与型腔模具相符合,如能利用内型抛光型腔,会极大地降低成本。针对这一问题,提出了一种新的型腔模具磁流变抛光方法,并对其磁场分布进行了分析。该方法利用加工型腔模具时切割下来的内型,与柱状磁铁连接,在其表面产生磁场,对浸在磁流变抛光液中的型腔模具进行往复循环抛光。这种方法不需单独制作与型腔形状吻合的永久磁铁抛光磨具,节省了成本,提高了效率。     

轴对称非球面轨迹包络磨削中砂轮对刀误差分析

硬脆材料的轴对称非球面光学零件所具有的回转曲面,既需要达到很低的表面粗糙度值又要有很高的几何形状精度,采用轨迹包络磨削加工是达到其精度要求的重要工艺方法。轨迹包络磨削过程中,砂轮的对刀误差是影响轴对称非球面形状精度的关键因素之一。通过建立砂轮的对刀误差数学模型,推导出轨迹包络磨削轴对称回转非球面过程中出现对刀误差时的磨削轨迹曲线方程,并分析了x方向存在、y方向存在、x和y方向同时存在对刀误差对轴对称回转非球面的曲面形状精度的影响。分析结果表明:砂轮的对刀误差将影响轴对称回转非球面的母线的形状和位置。     

旋转磁场下非球面工件的磁性混合流体抛光

针对非球面光学元件的结构特点及其表面质量要求,在磁性混合流体抛光基础上,设计并制作以径向充磁永磁体为旋转磁场源的半球头抛光头。首先,通过Ansoft Maxwell磁场仿真,分析对比不同形状、不同尺寸磁体和偏心距下各磁体周围磁场的分布状况,选定直径为10.0 mm、高度为5.0 mm、偏心距为2.5 mm、径向充磁的圆柱形磁体。其次,通过观测并比较不同组成、配方和供应量的磁性混合流体在抛光头上的行为,确定磁性混合流体抛光液成分。最后,采用制备的磁性混合流体抛光液及自制的抛光头对非球面PMMA工件进行抛光试验。经过15 min抛光后,PMMA工件表面质量明显改善,其面型精度R_q由0.703 μm下降到2.433 nm,表面粗糙度R_a由0.545 μm下降到1.786 nm,说明研制的抛光头能实现非球面工件的纳米级抛光。      

磁流变抛光技术的研究进展

磁流变抛光技术具有加工面形精度高、表面粗糙度小、加工过程易于控制、表面损伤小、加工过程中不产生新的损伤等优秀特点,因此多应用于加工要求高的精密和超精密领域,最常应用于光学加工方面。综述了磁流变抛光技术材料去除数学模型的建立进展,论证了该模型的正确性,总结出该基本模型具有通用性,模型能够适用于平面和凸球面等形面加工中,此外,对实现计算机控制抛光过程的准确性具有指导意义。概述了磁流变抛光工艺实验进展,总结磁流变抛光影响抛光效果的主要因素是磁场强度和磁场发生装置,在优化工艺参数组合下能够达到纳米级表面,能够消除亚表面损伤,还能够用以加工各种复杂形面等。就目前磁流变抛光技术的发展新方向作以总结,包括集群磁流变抛光技术、组合磁流变抛光技术以及磁流变-超声复合抛光技术,介绍这几种加工方法的工作原理以及能够达到的实验效果。最后对现阶段磁流变抛光技术中存在的问题做出总结,并针对各个问题提出相对应的思考和展望。     

固结磨料研磨K9玻璃亚表面损伤层深度测量方法研究

光学工件研磨后亚表面损伤层深度是确定其抛光加工余量的重要依据。采用三种典型的光学材料亚表面损伤层深度测量方法(BOE分步腐蚀法、BOE差动腐蚀法、磁流变抛光斑点法),测量比较了固结磨料研抛垫(FAP)研磨后K9玻璃的亚表面损伤层厚度;建立了亚表面损伤模型,分析比较测量误差产生的原因。结果表明:在实验条件下,BOE分步腐蚀法测量精度优于其他两种方法;BOE分步腐蚀法、磁流变抛光斑点法、BOE差动腐蚀法的测量精度分别约为0.1nm、17nm、200nm;亚表面损伤层总深度与其裂纹深度之间存在对数关系。     

磁流变效应微磨头抛光特性研究

为研究磁流变效应微磨头对玻璃等硬脆材料的抛光性能、考察Fe3O4基电磁流变液的抛光特性,在对微磨头基体的锥台端部的磁感应强度进行仿真分析的基础上,利用Fe3O4基磁流变液添加平均粒度7μm的金刚石微粉对玻璃材料进行了抛光加工实验。实验研究了磁流变效应微磨头抛光玻璃工件时加工间隙、磁感应强度对材料去除的影响,考察了工件表面抛光截面的形状特征。结果显示磁流变效应微磨头定点抛光的加工痕迹呈近似“U”形,工件表面的材料去除主要取决于微磨头与工件表面的研磨压力和磨粒的自我更新能力,材料去除量随着电磁感应器励磁电压的增大而呈线性增大,而随加工间隙的增大呈线性减小。     

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。     

氮化硅陶瓷滚子的油基磁流变抛光液研究

针对氮化硅陶瓷滚子磁流变抛光的工艺技术,提出了所用油基磁流变抛光液的基本要求,确定了该磁流变抛光液的各组分及其最佳体积比,并研究了配制方法;利用陶瓷滚子抛光试验机研究了磁流变抛光液不同抛光磨料、不同粒径对氮化硅陶瓷滚子抛光质量和抛光效率的影响规律。结果表明:配制的磁流变抛光液具有良好的稳定性,能够满足氮化硅陶瓷滚子的抛光要求;抛光效果随着抛光磨料及其粒度大小的不同而不同,其中以氧化铝为磨料的磁流变抛光液对陶瓷滚子抛光的表面粗糙度值最小,以金刚石微粉M1.5/3为磨料的磁流变抛光液对陶瓷滚子抛光的材料去除率最高。     

Ultraprecision finishing of micro-aspheric surface by ultrasonic two-axis vibration assisted polishing

Micro-glass lenses for digital cameras and blue laser DVD pick-up devices are generally molded by using micro-aspheric ceramic molds made of tungsten carbides. These molds are finished by micro-polishing using loose abrasives after grinding. Improvement to the accuracy of the molds is necessary, and high numerical aperture (NA) optics with steep angles are required. In order to finish the molds of high NA, an ultrasonic two-axis vibration assisted polishing machine with piezo-electric actuators was proposed and developed. Some micro-aspheric molds made of binderless tungsten carbide were polished, and surface roughness of 8 nm Rz was obtained.     

Ultra-precision finishing of micro-aspheric mold using a magnetostrictive vibrating polisher

Demands of micro-aspheric glass lenses are increasing in optical devices such as digital cameras and blu-ray players. In this paper, a novel vibration-assisted polishing machine using a magnetostrictive vibrating polisher is proposed and developed to improve the efficiency, surface roughness and stability of finishing. The magnetostrictive vibrating polisher can generate a radius of 30 μm circular vibrating motion at frequency 9.2 kHz. From the polishing experiments, a smooth removal function was obtained. The form accuracy was improved to less than 100 nm P–V and the surface roughness was reduced to 3.3 nm Rz (0.4 nm Ra).     

A study of the effects of process parameters for injection molding on surface quality of optical lenses

The purpose of this study is to determine the effects of process parameters on optical quality of lenses during injection molding. The quality characteristics chosen are light transmission, surface waviness and surface finish. The Taguchi method is used to perform screening experiments to identify the important significant process parameters affecting quality of lenses. Through empirical and theoretical analysis, the most significant process parameters affecting surface waviness is the melt temperature, followed by mold temperature, injection pressure and packing pressure. On the other hand, injection molding process parameters are found to have little effect on light transmission and surface finish of lenses. Regression approach is then implemented based on surface waviness data from full factorial experiments to formulate the regression models. Three different regression methods are used, namely, linear, exponential and nonlinear regression. Verification experiments are executed to examine the accuracy of the regression model for predicting quality characteristics of lenses. The result showed the highest accuracy prediction of surface waviness was from a nonlinear regression model. An error of only 4.24% suggested the existence of a correlation among injection molding process parameters.     

Investigation on the surface formation mechanism in micro milling of cemented carbide

Cemented carbide is widely applied in optical glass molding process due to its excellent properties. The surface quality of cemented carbide mold is directly related with the glass element quality, mold life and production cost. In this paper, micro milling experiments were conducted on cemented carbide to investigate the surface formation mechanism. The surface morphology characteristics of different material removal modes were compared. Both the surface formation mechanism and damage behavior during micro milling process were analyzed in detail. The machining parameters selection strategy was suggested to obtain the high material removal rate and smooth surface quality. The surface quality was found to be less affected by the machining parameters when cemented carbide is removed with ductile mode than brittle mode.     

保护渣碱度对薄板坯结晶器平均热流量的影响

在钢的连铸过程中,钢水在结晶器内的凝固对铸坯的产量和质量均有很大影响,几乎所有的铸坯表面缺陷均形成于结晶器内。近年来,随着连铸拉速的增加及对铸坯表面质量要求的提高,有关结晶器冷却、传热对钢水的初始凝固及表面纵裂纹影响的研究成为连铸科学研究的重点。结晶器壁热流不均是纵裂纹产生的有利环境,保护渣控制传热为常用的措施。薄板坯浇铸时由于拉速高,为获得表面无缺陷铸坯,对保护渣控制传热的要求更高,同时也需协调保护渣的润滑功能。通过生产试验,研究比较3种碱度保护渣（CaO/SiO2分别为1.06、1.26和1.48）对薄板坯结晶器平均热流量的影响,发现与低碱度保护渣相比,使用高碱度保护渣时,结晶器热流量最低,有利于实现弱冷却,形成均匀凝固坯壳,在一定拉速条件下浇铸裂纹敏感钢种时有助于获得良好表面质量的铸坯。     

扬声器外壳的四侧抽芯注射模设计

扬声器外壳表面质量要求高,结构复杂.塑件模具主要通过CAD软件进行设计,采用点浇口转潜伏式浇口的形式、1模2腔、4侧抽芯机构,塑件采用延时顶出方法来满足产品质量要求,有效提高模具设计准确性与合理性.     

Fabrication of optical freeform molds using slow tool servo with wheel normal grinding

Precision molding is recognized as the most appropriate technology for the mass production of glass freeform optics. However, difficulty arises when fabricating freeform molds with sub-micron form accuracy and nanometre-scale surface finish. A novel wheel normal grinding approach with fillet-end grinding wheel based on slow tool servo is proposed to ensure that the wheel errors are not transferred to mold surface and, thus, that the required machining accuracy is achieved. The wheel path generation strategy and the corresponding wheel truing method are presented. A toric tungsten carbide mold is ground to experimentally verify the validity of the proposed method.     

Polishing of Structured Molds

High precision molds for the replication of structured optical elements like Fresnel lenses or prism arrays are generated by diamond machining or precision grinding. In some cases surface quality of the replicated components is not sufficient to meet the increasing demands concerning surface roughness and form accuracy for optical applications. Subsequent polishing of the structures may therefore be necessary. Within this work structured molds were finished by a newly developed abrasive polishing process, by laser polishing, and by abrasive flow machining. This paper focuses on the material removal mechanisms and achievable surface quality in abrasive polishing. Surface quality is compared to that achieved by laser polishing and abrasive flow machining.     

连接夹注射模设计

针对连接夹塑件的结构特点,设计了塑料连接夹注射模。根据塑件特点和生产效率,合理确定了分型面位置、型腔数量及排列方式、侧抽芯机构形式。模具采取单侧错位抽芯结构,不仅简化了模具结构,还提高了生产效率和塑件的外观质量。     

旋转变压器电刷组件塑压模设计与工艺

通过对微特电机上旋转变压器的电刷组件的分析,介绍了一种带电刷丝塑料件的模具设计,提出了模具中主要零件的设计与加工方法。经生产加工验证,该模具结构合理,塑件脱模顺利,表面质量好,尺寸精度高。