圆弧逼近加工椭圆曲线轮廓宏程序的编制

以椭圆曲线轮廓的加工为例,分析了逼近圆弧半径的选取方法,编制了圆弧逼近加工椭圆曲线轮廓的用户宏程序。结果表明,相同条件下,圆弧逼近加工可获得更高的精度和表面质量。     

双圆弧逼近任意曲线的处理方法

本文叙述的是双圆弧、精度可控的逼近平面任意曲线的程序设计方法。详细介绍了双圆弧逼近任意曲线的步骤和取点切线斜率、误差计算、Ｇ指令自动判定的处理方法。     

基于MATLAB单双圆弧混合逼近曲线的算法及实现

讨论了单圆弧和双圆弧逼近的特点,结合两者的优点,用优化三点圆弧以允差逼近曲线和单双圆弧混合逼近的算法,理论上使得曲线有拐点和极值点时整个逼近圆弧的光滑连接,并保证了圆弧逼近的段数达到最少。基于Matlab采用比例法、一维搜索和优化相结合的方法进行程序的编翩求解节点,算法简单,可靠,程序运行快速高效。为数控加工复杂的曲线和CAD系统提供了参考。     

数控机床加工曲线轮廓的一种方法

目前用数控机床加工曲线的方法很多。我们研制了用最小二乘法在微机上对曲线进行分段圆弧逼近的BASIC程序,所得逼近圆弧与传统方法相比,具有精度高(对曲线误差≤1μm),各段圆弧连接光滑,所得逼近圆弧段最少等优点。现简介如下。     

参数方程曲线的最优逼近算法及实现

讨论了参数方程以单圆弧和双圆弧混合逼近的优点,用优化三点圆弧以允差逼近曲线和单双圆弧混合逼近的算法,使得曲线有拐点和极值点时整个逼近圆弧的光滑连接。讨论了参数方程分段点的性质,保证了分段点判断的可靠性。在曲率极值点处采用圆弧延长法,进一步减少了圆弧逼近的段数。对称图形采用对称算法,提高了图形的对称性,大大提高了程序的速度。基于Matlab采用优化的方法进行程序的编制求解节点。为CAD系统和数控加工复杂的曲线提供了参考。     

平面点列的一致逼近及容差平滑圆弧拟合及其应用

本文用最小二乘法一致逼近及容差平滑分段圆弧拟合平面点列。该方法具有操作实施简便易行,拟合圆弧具有双重一致逼近及在连接点容差平滑可控,误差不大于给定值时,拟合圆弧段数最少等特点,可直接用于数控加工、绘图等工程作业。     

对列表函数曲线的数学处理方法

在数控加工中,经常遇到由列表函数描述的如凸轮、样板、模具等非规则曲线的零件加工。要达到零件精度要求,保证其光滑、凸凹性,其关键是建立可靠有效的逼近方法,编制出相应的计算程序,通过计算机算出其相应的坐标点,再编成数控加工程序来实现。根据现代数控机床均具有直线、圆弧插补功能的特点和实际经验,采用二次曲线——圆弧对其进行逼近,非常有效。现介绍一种高精度逼近方法——双圆弧相切法。     

用连续圆弧逼近非圆曲线的方法

在数控机床上加工非圆曲线时,采用连续圆弧逼近法比用多段直线逼近法有几个优点:1)所有相邻圆弧在连接点处相切,从而成为连续圆弧,光滑无棱;而用直线逼近时,在连结点出现一个棱角;2)圆弧逼近较直线逼近程序段数少,从而可减少穿孔制带工作量,缩短纸带长度3)斜率和曲率半径也很接近于所逼近的曲线,而直线法的曲率半径则为无穷.大,相差甚远;4)计算出连续圆弧后,加上刀具半径R,可以很容易地形成一条新的与之等距的连续圆弧。这就是数控机床上刀具中心的运动轨迹。 连续圆弧法的计算过程(图1): 由原始曲线y—F(。)的始点/开始,在曲线上取B,C,D…     

用圆弧逼近方法处理列表曲线轮廓

讨论了列表曲线轮廓的数据处理方法。介绍了三点作圆圆弧逼近、重叠三点作圆法、带切线条件的圆弧逼近等逼近列表曲线的方法，为数控编程提供了必要的理论依据。     

数控车床加工曲线形零件的实用方法

用数控车床加工曲线形零件,如加工液压中心架的定位面曲线(图1a)。由于一般数控机床只有直线和圆弧插补功能,加工曲线时会产生很大困难。特别是函数关系复杂的曲线形状更是如此,因此用直线或圆弧近似代替曲线就成为加工的关键。 通常,加工时逼近曲线的计算是依靠数控机床本身的计算功能实现的,如图1b、c。方法是每计算一步,机床就执行一步。其中,图1b表示用直线逼近曲线;图1c为在曲线上找三点,用过该三点的圆弧来逼近曲线,另外还有一些其它方法。但在数控机床上直接采用以上方法有很多缺陷。如用直线逼近时难以保证其曲线光滑;每一段圆弧或…     

Experimental Investigation on Electrical Discharge Drilling of Ti-6Al-4V Alloy

This article describes the experimental investigation related to creation of holes in aerospace titanium alloy workpiece using static electrode machining and electrical discharge drilling (EDD) process. Special attachment for holding and rotating the tool electrode was developed and installed on electrical discharge machining (EDM) machine by replacing the original conventional tool holder provided on die sinking EDM. The effect of input parameters such as gap current, pulse on-time, duty factor and RPM of tool electrode on output parameters for average hole circularity (C_a) and average surface roughness (R_a) have been studied. It is observed that the effect of rotating electrode machining has considerable influence on the output parameters over stationary electrode machining. The micro-graphs and photographs of few selected samples were taken by SEM and metallurgical microscope, which also commensurate with the findings of the study.     

异形柱面数控车铣组合加工成形机理研究

文中从三面圆弧型截面的结构特征分析入手，采用凸轮机构运动原理，对其车铣组合加工过程的成形规律进行动态分析，从而建立了三面形非圆截面数控车铣加工轨迹控制模型，并由相对运动原理，论证了所建模型的正确性。建模方法简单直观，是解决复杂型面组合加工建摸的有效途径。     

数控机床进给速度对圆度的影响测试与分析

对球杆仪的测试应用及研究现状进行了阐述,并介绍了球杆仪的测试原理。针对某型立式加工中心的X-Y平面进行了圆度误差测试,圆度测试在500 mm/min,1 000 mm/min,3 000 mm/min的进给速度下进行。给出了不同进给速度下的圆度图和圆度误差数据,得到了伺服轴的进给速度越大,圆度误差越大的结论。对球杆仪测试的圆度误差进行了误差分离,得到了不同进给速度下的误差数据及排序,并对各项误差的原因及影响进行了分析。     

基于离散点截形螺旋面加工原理研究

提出了基于离散点的圆柱螺旋面成形刀具计算方法，分别建立了已知螺旋面工件截形离散点数据计算成形刀具廓型的数学模型及已知刀具截形离散点数据计算由其加工的螺旋面工件的数学模型。利用累积三次参数样条法计算螺旋面工件截形及成形刀具廓型各离散点的倾斜角。分析了成形刀具的计算误差，对成形刀具数据型值点以累积三次参数样条进行插值，用双圆弧样条拟合的方法进行光顺处理。实例证明，两模型是正确性的、可行的，能够满足离散点条件下螺旋面高效率、高精度的加工要求。     

21世纪先进的活塞加工技术

通过对活塞加工技术的深入剖析,阐述了活蓉加工的工艺特点,提出了21世纪活塞外圆、销轧等关键部位的最新的加工技术.     

基于圆度误差的磁力轴承动态特性研究

主动磁力轴承系统的位移反馈是基于传感器检测的非接触圆表面,将导致表面圆度误差引入到位移反馈信号中.从圆度误差的机理分析出发,推导了误差与干扰电流的数学关系,仿真分析了圆度误差对磁力轴承动态特性的影响.研究结果表明:圆度误差对高频率的转子影响较大,该影响可通过修正控制参数来减小.这一结论对磁力轴承的加工制造和控制有一定的指导意义.     

NURBS曲面插值参数化及其在数控加工中的应用

对NURBS曲面插值以及曲面数控加工NC代码生成的基本算法进行研究,提出了在自由端点边界条件下的控制点反求算法,引入插值参数和曲面形状修改参数,利用MATLAB三维空间图形处理工具显示各参数变化对曲面插值及曲面形状的影响,研究曲面参数化在刀位轨迹生成中的应用.以某曲面零件为数控加工仿真对象,模拟其在虚拟环境下的切削过程,利用VC++和OpenGL,编程实现重构算法并完成曲面加工轨迹仿真,通过实例验证了该曲面造型方法及数控代码生成方法的正确性.     

Development of a novel ultrasonic unit for grinding of ceramic matrix composites

Ceramic matrix composites (CMCs) are promising materials for many high-technology engineering applications in harsh and severe environments due to their superior properties. However, in spite of all advantages, the employment of CMCs has been impeded by their high machining and finishing costs. Many of recently developed CMCs are very difficult to machine with the conventional machining technology, and improvement of the existing machining process is required and crucial. To overcome the existing technological constraints in the grinding of CMCs, a special designed block sonotrode was invented (and was registered for patent). The realization of ultrasonic-assisted machining on conventional machine tools can be carried out with much less effort by means of the new invented system. The invented block sonotrode is a specially designed perforated plate and demonstrates a multi-resonant frequency behavior. Experimental results illustrate the high performance of the presented method. A significant reduction in grinding forces and surface roughness and an increase in G-ratio have been achieved.     

Ultra-precision nano-structure fabrication by amplitude control sculpturing method in elliptical vibration cutting

This paper studies the nano-structure fabrication on hardened steel by means of elliptical vibration cutting equipped with the ultra-precision amplitude control sculpturing method. Machining performance of the amplitude control sculpturing method is investigated, and the limitation in nano-scale machining is explored. In this proposed method, machinable part geometry is essentially restricted by vibration conditions and tool geometry. In addition, a considerable error between the amplitude command and the envelope of the tool trajectory is generated when the slope of the machining part geometry becomes steep. To overcome this error, a compensation method for the amplitude control command is proposed. In order to clarify the machining performance of the proposed technology, a series of analytical and experimental investigations are conducted. Furthermore, by applying the proposed command compensation method, nano-structures with a large ratio of structure height to wave length are machined accurately. The proposed sculpturing method is subsequently applied to the machining of nano-textured grooves and a three-dimensional grid surface, which verifies the feasibility of the proposed amplitude control sculpturing method.     

AN INVESTIGATION INTO DIMENSIONAL ACCURACY AND SURFACE FINISH ACHIEVABLE IN DRY TURNING

This paper presents experimental and analytical results of an investigation into dimensional accuracy and surface finish achievable in dry turning. The Taguchi method and Pareto ANOVA analysis are used to determine the effects of the major controllable machining parameters, viz. cutting speed, feed rate and depth of cut, on three key quality characteristics, viz. diameter error, surface roughness and circularity, and subsequently to find their optimum combination. The work and tool materials selected are alloy steel AISI 4340 and enriched cobalt-coated carbide, respectively. The results indicate that while the surface roughness can be optimized through proper selection of feed rate, optimization of diameter error and circularity is difficult due to complex interactions between the input parameters.