基于半球形测头的自由曲面截形测量方法

提出的半球形测头测量自由曲面任意截形方法避开了用球形测头测量曲面的复杂过程和由此产生的三维测头半径补偿的数学模型及大量运算，消除了在三维曲面截形测量时由于被测曲面的扭曲对测头所造成的干涉，可使曲面测量直接转化为曲线测量，从而大大简化了测量和数据处理过程。     

三坐标机测量形面特征参数补偿方法探讨

三坐标机测量形面特征参数过程中,往往要求测头在某一给定的位置上进行测量.当测头运动方向受到被测形面几何形状的阻挡时,其实际到达的位置偏离于程序给定的位置.这种情况下,测量的结果需要通过补偿进行修正.介绍了两种补偿此测量误差的方法测头半径补偿法、公差带控制法,并分析了这两种补偿方法的特点和适用场合.     

止端螺纹环规测量中一个值得注意的问题

螺纹环规的中径尺寸大多在万能测长仪上借助侧规进行比较测量,也有在三座标万工显上利用“⊥”型测头直接测量。但这些仪器上的测头往往较少,如万能测长仪只配0.8、1.35、1.8、2.3和3.175五种测头,这些测头显然不是恰当直径。通常,使用中的螺纹环规不作也不便于测量牙形半角。但由于使用中牙形侧面磨损不均匀(参看图2),牙形半角的误差将会加大,尤其是牙形被截短的止端螺纹环规往往会引起较大的中径测量误差。以φ0.8钢球与止端环规牙形的接触为例见图1。     

坐标测量机对凸轮曲线的测量与拟合及其评价

坐标测量机测量凸轮时,确定工件坐标系是一大难题。文中提出一种方法,可以从凸轮任意位置开始检测。仅测量一次凸轮轮廓,所有的测量数据均用于建立被测凸轮的工件坐标系,并可使测量误差、形位误差对凸轮工件坐标系建立的影响降低至最小程度。此外还提出了一种修正开关式球测头半径的计量学方法。     

用球形和倒锥测头测线性螺旋面齿形的测量误差分析与处理

一、测量误差的产生在 PWF—250滚刀检查仪或“万工显”上测蜗杆或滚刀齿形时,现行的测量方法,是使测头中心在包含蜗杆螺旋面直母线,且与蜗杆轴线平行(包括重合)的平面(它称为测量平面)内运动(图1),所以,若螺旋面是完全正确的,而且要无测量误差的话,则当测头沿直母线方向移动时其中心的轨迹应为一平行干直母线的直线。也就是说要求测头在直线运动过程中所形成的柱面能与螺旋面的直母线相切,     

大升角ZI造型滚刀刃口齿形测量方法研究

多头、大螺旋升角渐开线造型(ZI)滚刀进行刃口齿形测量时存在干涉,从ZI造型滚刀刃口齿形测量特点出发,分析轴截面截形和基圆切平面截形之间的位置关系,给出干涉产生的原因,推导干涉判定条件。针对原测量算法缺陷,提出刃口齿形T向测量算法,通过变换测量截面,算法限定测头的测量深度,有效解决大升角ZI造型滚刀刃口齿形测量的干涉问题。经算法整合,滚刀测量软件可实现刃口齿形测量干涉的预判,实现测量策略自适应选择。实际测试证明:刃口齿形T向测量算法能够顺利完成大升角渐开线造型滚刀刃口齿形的测量,与原测量算法比较,测量结果正确。     

基于模糊神经网络的接触式测头动态误差补偿

测头动态误差严重制约高精度坐标测量机发展,为此,提出基于模糊神经网络的测头动态误差补偿方法以提高测量精度.首先利用三坐标测量机测量标准球和标准环规得到训练样本和测试样本,然后分别使用训练样本和测试样本对接触式测头动态误差进行建模和补偿,最后与BP神经网络模型和静态误差模型进行比较试验.结果表明,经模糊神经网络模型补偿后误差从4.6μm减小至1.3μm,精度提升70%以上;模糊神经网络对测头动态误差具有更好的补偿效果和稳定性.证明模糊神经网络模型能够有效提高测头的动态测量精度.     

曲轴类零件轴向尺寸检测的新方法

本文介绍了一种利用微处理器的单测头，数字化的曲轴类复杂零件轴向尺寸的检测装置，分析了单测头测量时测头直径的影响与补偿方法。     

坐标测量机进行曲面测量的方法和不确定度分析

坐标测量机在使用测头进行测量时，从控制系统传送到坐标测量机软件中的测针球中心点的坐标，这个值距离我们所需要的测针与工件的接触点相差一个测头半径，要想得到这个接触点的坐标就需要用软件来进行处理，也就是“测头半径补偿”。在测量机软件进行测头半径补偿时，对不同的元素有不同的方法。在测量圆时，软件首先使用球心点计算出一个圆，然后判断是内圆还是外圆，如果是内圆就在圆直径上加上测针球的直径（校正后的等效直径），反之就减去球直径。球、圆柱、椭圆、圆锥等都采用了这种算法。平面则是首先用球心点计算出平面，然后沿法向矢量相反的方向减一个测球半径。点元素的补偿方法比较特殊，如果软件单纯沿法向矢量进行半径补偿，当测点的方向没有沿工件表面的法向，就会出现余弦误差，所以在测量软件中将点元素的半径补偿强制为沿坐标轴方向，如果没有零件坐标系，就沿机器坐标系轴向补偿。在测量前的测头校正时，每一个测头只进行5次校正测量，在沿这5个位置的方向接近测量时，测量软件只能用坐标系进行矢量补偿。     

曲轴类零件轴向尺寸检测的新方法

本文介绍了一种利用微处理器的单测头、数字化的曲轴类复杂零件轴向尺寸的检测装置，分析了单测头测量时测头直径的影响与补偿方法，介绍了装置的机械结构，微处理器检测的硬、软件系统。该装置测量不确定度和重复性都在0.01mm以内。     

基于部分补偿干涉的非球面顶点曲率半径加工误差测量

测量非球面顶点曲率半径加工误差对预估成像系统质量和计算机辅助装校有重要意义。传统的部分补偿干涉系统只能测量非球面面形误差,即被测非球面与标称非球面之间的不规则偏差。通过分析系统剩余波前特定像差项随被测面位置的变化关系,基于部分补偿干涉原理,提出了一种非球面顶点曲率半径加工误差测量方法,测得非球面顶点曲率半径加工误差。仿真实验结果表明,所提出的误差测量方法具有可行性,其原理相对测量精度不低于0.003%。     

A radius compensation method of barrel tool based on macro variables in five-axis flank machining of sculptured surfaces

Barrel tool radius compensation is very important to improve the five-axis CNC machining precision and efficiency of sculptured surfaces. By combining macro variables and math function of CNC controller, a radius compensation method of barrel tool based on macro variables in five-axis flank machining of sculptured surfaces was presented. The basic principle of barrel tool radius compensation in five-axis flank machining was firstly investigated. For a specific five-axis CNC machine tool with dual rotary tables, a relationship equation between compensated cutter location (CL) data and machine control (MC) data could be derived. A post-processor with the function of five-axis barrel tool radius compensation was then developed by using the C++ language, which could generate the NC programme with macro variables of barrel tool radius compensation. Finally, the NC programme was obtained automatically by the developed post-processor for the aero-engine blade surface machining. The machining process was simulated on the software VERICUT, and machining experiments were also conducted on the five-axis machine tool. Both the simulation and experimental results showed that the proposed method could perform the function of barrel tool radius compensation in the NC programme for five-axis flank machining.     

四点测球法在球坑自动检测中的应用

本首先介绍了四点测球法的基本原理和理论最优方案,然后针对本课题中球坑测量的要求,提出两种不同方案进行讨论、比较。最后按照确定的方案给出了实施方案和结果,解决了在线自动检测球坑半径值的难题。     

Evaluations of the BGA Solder Ball Shape by Using Energy Method

Presented herein are the evaluation results of the BGA solder ball shape using energy method, two types of solder, viz. Sn37Pb and Sn80Pb, are selected .The geometry of the solder bump is firstly estimated using free computer software, the Surface Evolver, an interactive program which is an energy-based approach for the study of liquid droplet surfaces shaped by surface tension and other energies. The solder bump is then numerically constructed in a finite element model that simulates a BGA package. The influences of both upper and bottom solder pad radii, the surface tension on the balls, and the external load axially applied to the reflow solders on the stand-off height and the contact angle for both solder materials are investigated. The results show that for both solder materials, the stand-off height remains at a height under some pad radius. The height decreases as both upper and bottom pad radii increase. On the other hand, the contact angle presents a nearly inverse trend with respect to the pad radii. The study of the effect of surface tension reveals that at a constant pad radius, the solder ball stand-off height increases with surface tension; however, the trend becomes saturated eventually. The contact angle decreases as the surface tension becomes large. The trend also tends to be saturated. The results of the effects of axially applied load on the stand-off height and the contact angle show that as the applied load is increased so is the contact angle; nevertheless, the stand-off height becomes shorter.     

Sculptured surface reconstruction from CMM measurement data by a software iterative approach

The reverse engineering approach is being widely applied in designing and manufacturing of sculptured surfaces. The first step in the reverse engineering process is collection of data lying on the surface. When using a coordinate measuring machine (CMM) with a touch trigger probe for digitizing data points, the probe radius must be compensated according to normal vectors. Previous works were addressed on the iterative measurement procedure to reduce the error caused by the compensation. The major problem of iterative methods is time consumption in digitization. This paper proposes a new architecture based on look-up table that keeps the estimated normal vectors of the measurement data to refine the data points digitized by CMM. The digitized data are first fitted into several NURBS curves by interpolation. The skinning method is then applied to interpolate these curves. Thus a smooth NURBS surface can be constructed and more accurate normal vectors of the measurement points can be obtained to compensate for the probe radius. By using this software iterative technique, we need only one digitization procedure. Therefore, much time can be saved and the efficiency of reverse engineering can be improved.     

球面渐开线齿形的螺旋锥齿轮NURBS设计

 为避免传统设计和加工的近似球面渐开线齿形螺旋锥齿轮存在的缺陷,提出了一种新型螺旋锥齿轮设计方案．从齿面精确组成和形状特征出发,将球面渐开线理论应用于齿面基本曲线的方程表达式求导中,实现了齿面曲线的分段参数化．然后,对组成齿面的各区域分别求取齿面离散点数据,并采用三次均匀B样条曲面方法进行初步的拟合与拼接．为了进一步提高齿面精度,借助NURBS方法对拼接后的齿面进行了统一的NURBS精确拟合,并给出了齿面统一参数化的优化方法．最后的算例表明了相关方法的精确性和可行性,为螺旋锥齿轮的数字化设计与NURBS加工提供了新的思路与途径．     

卧式行星球磨机最佳参数的数值模拟

采用颗粒离散元法模拟得到卧式行星磨磨筒内钢球平均接触力大小以及随填球率、钢球直径、磨筒半径和公转半径的变化规律,并与实验结果进行了比较分析。结果表明:行星磨的粉磨速率可以由平均接触力大小来确定,粉磨速率的对数是平均接触力线性函数,斜率为0.087。磨筒填球率的增加,导致钢球的平均接触力减小;随着钢球直径、磨筒半径、公转半径的增大,平均接触力呈线性增长,斜率分别为2.5,0.14,0.03,其中钢球直径对平均接触力的影响最大。     

螺纹综合测量机的扫描原理与误差分析

检测圆柱螺纹主要方法有螺纹综合测量机的轮廓扫描法和测长机的三针法、量球法,两种检测方法的测量结果存在一些差异。通过论述螺纹综合测量机检测圆柱螺纹的结构原理,构建轮廓扫描几何模型,设计针尖半径补偿算法,并对检测方法的误差影响因素进行了分析。经分析,所提出的螺纹综合测量机的轮廓扫描法具有测量精度高、速度快、参数全面、检测过程自动化,受人为因素干扰小的特点,是螺纹综合参数测量的最好方法。     

An improved dynamic model for angular contact ball bearings under constant preload

High-speed spindles are typically installed with angular contact ball bearings. This research has established a dynamic model for angular contact ball bearings under constant preload. By analyzing the constant preload mechanism, and the gyroscopic and centripetal forces, a dynamic non-linear model for angular contact ball bearings was proposed using Hertz contact theory. The model was solved by numerical iteration to obtain the dynamic parameters of an angular contact ball bearing which included: the dynamic normal contact force and contact angle, the maximum compressive stress and axial displacement, the contact pattern, stiffnesses, etc. To validate the model, a test device was designed which was equipped with a constant preloaded bearing group. By measuring the relative displacement of the bearings’ inner and outer rings under different conditions, the accuracy of the model was proved. This modeling method provided a theoretical basis for calculating bearing thermal characteristics, fatigue life, and an optimized radius of curvature of the bearing ring channel.