固着磨料研磨抛物面的建模与实验研究

针对抛物面零件的加工难题,采用固着磨料来研磨抛物面零件是一种新方法。根据抛物面受力下的力学分析,总结出了抛物面研磨时的受力状态以及相对研磨速度的变化,基于Preston方程总结出的磨具保形磨损理论,推导出磨具上丸片的分布规律。根据算例设计出了满足要求的磨具系统,磨具的研磨实验表明,面型最大误差为0.085 7 mm,面型精度能满足大部分零件的精度要求。     

一种新型非球面高效研磨方法的研究

针对目前非球面加工的难题，提出了一种利用弯曲成形法制作磨具来实现非球面高效研磨的新方法。阐述了弯曲成形法高效研磨的原理，建立了磨具弯曲成形的数学模型，分析了磨具成形的等距线误差。实验结果表明：采用弯曲成形法制作的磨具成形精度较高，面形精度达到微米级；采用该方法研磨非球面零件是可行的，能满足中等精度的非球面零件研磨加工要求；效率高、成本低，有很好的开发和应用前景。     

薄型非球面弹性变形面形复制加工技术研究

提出一种新型非球面加工技术——弹性变形面形复制加工技术,该技术综合利用光学玻璃材料的线弹性特性以及面形复制加工机理,将复杂的非球面加工转变为简易的平面加工,适合加工薄型大曲率半径非球面。阐述弹性变形面形复制加工技术的基本机理,随后以直径为40 mm、顶点曲率半径为2 500 mm的抛物面作为目标面形,通过有限元仿真确定使工件与靠模紧密贴合所需的工件最小去除厚度,建立加工过程的材料去除模型,并由此确定加工时间。在所搭建的弹性变形面形复制加工系统上进行加工试验,试验结果证明所建立材料去除模型有效。最终工件加工面形精度为PV 0.62 μm。对加工面形精度影响因素进行分析,并提出改进工件加工面形精度的措施。     

等前角剐齿刀设计计算方法

针对目前剐齿加工生产中加工工件表面质量差,左右齿面加工精度不一致的问题,提出了一种等前角剐齿刀的设计计算方法。根据待加工工件齿面的几何特征和剐齿加工的运动关系,基于曲面共轭原理,求取工件齿面共轭面;选择球面作为初始前刀面,以无理论刃形误差为目标,采用齿面共轭面与初始前刀面的交线作为切削刃;根据切削前角一致性原则对初始前刀面进行再设计,沿切削刃构造前刀面;通过模拟刃磨,求取一系列无理论刃形误差的切削刃,依次构造后刀面,最终获得完整的具有相等切削前角的剐齿刀具;通过计算实例验证该设计计算方法的可行性和有效性。     

三弧段等距型面设计参数计算研究

针对某型大功率高速水力测功器主轴三弧段等距型面曲线点样本集（测点）,提出一种简单的参数计算方法。通过该方法得到了三弧段等距型面曲线偏心量、等距值等设计参数,再通过极坐标方程得到三弧段等距型面拟合曲线理论坐标点。经与实际测点对比,三弧段等距型面拟合曲线理论坐标点与实际测点基本吻合,两者极径差值随角度在-0.09～0.02mm范围内变化,呈先增、后减、再增的变化趋势,曲线近似呈周期性变化;在160°～180°范围内,三弧段等距型面拟合曲线理论坐标点与实际测点极径差值随角度增加而增大,原因可能是某型高速水力测功器主轴三弧段等距型面在180°位置附近受力变形或者加工偏差过大;三弧段等距型面拟合曲线理论坐标点极径相对误差基本控制在0.09%以内,变化趋势与理论坐标点、实际测点极径差值曲线变化趋势基本一致,误差满足工程需要,从而验证了参数计算方法的准确性,所得到的参数可以作为某型高速水力测功器三弧段等距型面曲线的设计参数。     

定位误差的矩阵法计算

<正> 现在的工件加工精度要求越来越高,由于加工件用作定位基准的表面总有一定形状和尺寸的误差,所以在一般定位过程中不可避免地会造成误差,即定位误差中的基准位置误差。过去常常对定位误差计算法只是计算平面内产生的误差。随着加工精度的提高,越来越显示了定位误差计算的重要性和必要性。工件在空间的六个自由度,用矩阵法表达更好,矩阵法可以计算工件空间任意点的误差。它还可用计算机求解,便于确定工件最佳定位方案。矩阵法计算公式:     

摆线齿轮砂带磨削

摆线齿轮是一种对称等分柱面,其径向截形为短幅外摆线等距曲线。目前,加工摆线齿轮最常用的方法是盘状砂轮磨削法,如图1所示。属于点成(?),工件旋转一圈只能磨出一条(?)。为了磨出整个齿面,工件需旋转很多圈,生产效率低。若用线成形法,则生产率会大大提高。线成形法是点成形法当砂轮半径趋于无限大时的特例,即切削工具由回转     

基于等距曲面的弧面凸轮单侧面数控加工刀位优化算法

针对弧面凸轮廓面的多轴数控加工,在分析现有各种加工工艺方法,尤其是分析单侧面加工方法存在的不足的基础上,围绕减小加工得到的实际廓面与理论设计廓面的极差,提出一种以刀轴轨迹面与凸轮廓面等距曲面的极差最小为优化目标的弧面凸轮单侧面数控加工刀位数据计算的优化算法。所建立的刀位优化算法综合了不可展直纹面侧铣加工的两点偏置算法和三点偏置算法的优点。通过实例对各种单侧面刀轨规划算法进行加工误差综合对比分析,结果表明所建立的刀位计算优化算法正确有效,可显著减小编程误差,为进一步提高弧面凸轮单侧面加工精度和完善加工工艺奠定了扎实的理论基础。     

基于改进遗传算法的等距型面轮廓参数及误差计算

等距型面轮廓曲线为非圆曲线,其参数测量和误差计算都比较困难,目前尚无统一的评价标准。本文根据圆的测量方法,采用最小包容区域法和改进的遗传算法来计算等距型面的轮廓参数及其误差,提高了等距型面轮廓曲线的测量精度,为等距型面的精确测量提供了一种新的计算方法。     

无理论刃形误差直齿插齿刀设计

为了提高插齿加工精度,提出一种无理论刃形误差插齿刀具设计方法。基于曲面共轭原理,根据待加工齿面和插齿加工运动特点,建立齿面共轭面的数学模型。前刀面选择球面形式,应用割线法求得共轭面和前刀面的交线,进而建立切削刃的数学模型。从刀具重新刃磨后仍能满足无理论刃形误差要求的角度出发,求取多条切削刃,利用所求得切削刃曲线构造后刀面,建立后刀面数学模型。插齿加工实验表明,采用无理论刃形误差直齿插齿刀加工工件,刀具重磨前后加工精度有较好的一致性,从而证明了该设计方法的正确性和可行性。       

Investigation and optimization of the internal cylindrical surface lapping process of 440c steel

A new lapping method is proposed for internal cylindrical surfaces finishing. Regression analysis and artificial neural network (ANN) were used for modeling this lapping process and predicting the effects of parameters of rotational speed of the lapping tool (ω), the length of the lapping tool (L) and difference in external diameter of the lapping tool and internal diameter of the workpiece (D) on the material removal rate (MRR), out-of-cylindricity (C) and surface roughness (Ra) of the lapped holes. Comparison of the results of the regression and ANN models with the values obtained from the experiments indicates that the MRR, Ra and C are more accurately predicted using ANN models. MRR, Ra and C of the lapped holes have been optimized using genetic algorithm (GA) and particle swarm optimization (PSO) algorithm. The results show that the highest MRR, which is equal to 2029 μg/min, has been achieved at ω of 400 rpm, D of 0.1 mm and L of 45 mm. The lowest Ra of the lapped hole is 64 nm which has been obtained at ω of 100 rpm, D of 0.1 mm and L of 20.82 mm. The minimum C of the lapped hole is 3 μm, which was obtained at ω of 212 rpm, D of 0.1 mm and L of 28.3 mm. The most important problem in the lapping process is the low MRR which causes increased cost and production time. Therefore, in the lapping process, the selection of conditions, that in addition to the production of pieces with geometric accuracy and surface roughness needing a high MRR, is very important. In this study, MRR, Ra and cylindricity of the lapped holes was optimized using multi-objective PSO (MOPSO) algorithm and non-dominated sorting genetic algorithm II (NSGA II), and the Pareto optimal solutions were obtained. Comparison of the results obtained from NSGA II and MOPSO shows that both of these algorithms can achieve optimal Pareto front with the same accuracy, but the time required to reach the MOPSO algorithm to the optimal Pareto front is 25 % less than the NSGA II.

     

基于“S”形加工样件的复合数控机床几何误差逆向追踪

基于对"S"形加工样件的复合机床误差影响溯源的研究,提出一种辨识影响加工缺陷最大的误差参数的方法。该方法将"S"形样件加工缺陷与复合数控机床成形运动综合考虑,采用三次B样条曲面对"S"形样件加工缺陷进行数学表征,并逆向推导出了"S"形样件加工缺陷处对应的刀具中心的实际位置,求解出了实际加工曲面到机床刀具的映射关系。同时利用多体系统误差分析理论建立了复合机床加工缺陷生成模型,并从机床角度求解出了缺陷处误差的表达方程。接着在"S"形样件缺陷产生的位置处,根据误差参数的敏感度及其实测值计算各项误差参数对加工缺陷的贡献并进行排序,确定对加工缺陷影响较大的5项误差参数。试验结果表明:该5项误差参数和全部误差参数同时作用下各点的误差进行差值比较,发现差值最大不超过±1.5μm,因此ε_(yC_1)、δ_z(B)、ε(C_1)、ε_x(C_1)、ε_(x_1C_1)是对加工缺陷影响较大的5项误差参数。     

A swing arm method for profile measurement of large optical concave surfaces in the lapping process

Generally, optical components are fabricated by grinding, lapping, and polishing. Usually, these processes take a long time to obtain high surface quality. Therefore, in the case of large optical components, on-machine inspection (OMI) is essential, because the workpiece is fragile and difficult to set up for fabricating and measuring. This paper describes a swing arm method for measuring the surface profile of large optical concave mirrors. The measuring accuracy and uncertainty for the method are studied. Experimental results show that this method is especially useful in the lapping process, where an accuracy of 3–5 μm is obtained. Inspection data is also provided to correct the residual figuring error in lapping or polishing processes .     

砂轮约束磨粒喷射加工外圆表面创成机理及三维形貌

磨粒喷射精密光整加工是重要零件在磨削后进行去除表面缺陷层、降低粗糙度和波纹度为目的光整加工新工艺。试验在MB1332A外圆磨床上完成,加工试样为表面粗糙度0.6 m左右的45钢。加工表面形貌和微观几何参数分别用扫描电子显微镜和Micromesvre2表面轮廓仪测量。应用自相关函数对磨削加工表面和光整加工表面进行分析,并研究材料去除机理和微观表面形貌的创成机理。在楔形区游离磨粒获得能量对工件进行抛磨、滑擦、和微切削是材料去除机理的核心因素,磨料流体侧向挤出是均化和降低表面波纹度的主要因素。试验结果表明,试样表面从连续的方向一致的沟槽被随机不连续的微坑所代替,表面粗糙度明显得到改善。随着加工循环的增加,工件表面的粗糙度值由0.6 m下降到0.2 m左右。此外,光整加工可以获得各向同性网纹交错的表面,表面轮廓的支撑长度率提高,对工件的耐磨性有利。     

弹性模量对弯曲成形法非球面研磨中磨具成形精度的影响

弯曲成形法非球面研磨中弹性模量误差是影响磨具成形精度的关键因素,通过力学和高等数学方法建立了磨具弯曲成形的数学模型,推导出误差公式,分析了弹性模量误差的影响,并给出了算例,表明在选择磨具材料的过程中．要根据工件的精度要求确定材料弹性模量的取值．保证其控制在一定范围内,从而保证磨具的成形精度,进一步提高研磨工件的面形精度。     

弯曲成形法双曲面零件高速研磨的研究

针对双曲面零件的加工难题,提出了采用弯曲成形法实现高速研磨双曲面零件的新方法,阐述了弯曲成形法高速研磨的原理。通过力学和高等数学建立了磨具弯曲成形的数学模型,并推导出磨具的宽度函数表达式。算例分析表明采用此方法可以设计成要求的磨具,通过磨具的弯曲实验验证了采用弯曲成形法实现高速研磨是可行的,面形最大误差为1.0038μm,面形精度能够满足大多数零件的加工精度要求,为进一步的研磨实验提供了理论依据。     

硬脆性材料用柔性磨具研磨的加工表面粗糙度建模

通过分析磨粒与工件表面的作用过程,建立了硬脆性材料柔性磨具加工表面粗糙度的理论预测模型.以橡胶结合剂金刚石研磨盘为柔性磨具、蓝宝石衬底为工件,在不同弹性模量、磨粒浓度、磨粒粒度和研磨压力下开展研磨试验,将不同研磨条件下的表面粗糙度试验值与理论预测值进行比较,发现试验结果与理论模型预测结果的趋势一致,且预测误差为7.71...     

Influence of Cavitation on Unsteady Vortical Flows in a Side Channel Pump

Double-sided lapping is an precision machining method capable of obtaining high-precision surface. However, during the lapping process of thin pure copper substrate, the workpiece will be warped due to the influence of residual stress, including the machining stress and initial residual stress, which will deteriorate the flatness of the workpiece and ultimately affect the performance of components. In this study, finite element method (FEM) was adopted to study the effect of residual stress-related on the deformation of pure copper substrate during double-sided lapping. Considering the initial residual stress of the workpiece, the stress caused by the lapping and their distribution characteristics, a prediction model was proposed for simulating workpiece machining deformation in lapping process by measuring the material removal rate of the upper and lower surfaces of the workpiece under the corresponding parameters. The results showed that the primary cause of the warping deformation of the workpiece in the double-sided lapping is the redistribution of initial residual stress caused by uneven material removal on the both surfaces. The finite element simulation results were in good agreement with the experimental results.     

Experimental study on elastic deformation machining process for aspheric surface glass

Elastic deformation machining is a fabrication method that exploits the elastic deformation properties of materials under stress. Coupled with plane lapping machining process, this new fabrication method is suitable for machining complex aspheric surfaces. Upon completion of the machining process, the workpiece under process will be shaped into a desired surface form. The elastic deformation machining has several advantages over traditional fabrication methods, i.e., high machining compatibility and high fidelity of material property during machining process. The subject of this study is to determine the surface shape of the finished glass workpiece after the lapping process of the elastic deformation machining. The experimental results were compared with theoretical calculations. In the case when the vacuum pressure is 50 kPa, the maximum deviation value between the deformation curves from the theoretical calculation and the experiment results is within 62 μm. In order to improve the precision of form surface, the vacuum pressure is modified from 50 to 42 kPa. This reduction corresponds to a change of workpiece thickness when it is lapped. The results of the change of vacuum pressure show that the form accuracy produced is improved significantly and agrees very well with theoretical calculations. The maximum deviation in this case is 1.6 μm. The study indicates that the experimental plane lapping setup that exploits the material elasticity property can be utilized to fabricate aspheric lenses with axisymmetric surface and low complexity.