涡轮叶片当量测具设计及误差分析

介绍了涡轮叶片喉道当量的测量方法,并基于UG设计了一种用于叶片加工过程中当量测量的测具。分析了复杂曲面采用点定位时的定位误差,介绍了误差修正方法,并采用该方法对所设计测具的定位及测量误差进行了分析和修正。     

同步规划测量式叶片免形状精密测头系统

针对叶片测量测头灵活性差、无法兼顾精度和效率的问题,提出了一种免形状、高精度测头系统技术方案。首先基于"同步规划测量"思想,研发了新型免形状光学测头系统,然后分析了系统的工作原理、理论模型和关键技术,最后进行了实验研究,验证了方案的可行性和测头系统的精度水平。研究结果表明,该测头系统在无需输入叶片理论模型数据和姿态精调的情况下,自动进行路径规划并同步完成叶片型面数据的采集。测点数据的采集全部在传感器基准距离附近完成,从而有效地限制了倾角误差,综合测量精度控制在10μm以内。该测头系统具有算法简单、高精度、免形状等特点,在叶片类空间自由曲面测量领域具有较好的应用前景。     

燕尾形导轨L尺寸的测量

全国联合设计的新系列摇臂钻床均采用了图1所示的燕尾形导轨。目前,这种形式的导轨广泛地应用在机械制造中。 根据这种燕尾形导轨各部分的尺寸,我们设计了一种测量工具,可用来测量燕尾形导轨的L尺寸。该测量工具采用了比较法进行测量。经过几年的验证,使用性能良好,结构紧凑合理,测量结果准确可靠,从而结束了多年来使用样板进行测量的落后方法。 测量工具如图2所示。该测量工具V型转动测量砧的A面与活动测杆的中心线平行,并可在一个平面内任意转动。因此,该测量工具可以放在最合适的位置,使v型转动测量砧工作面、活动测杆工作面与燕尾形导…     

叶片型面的三坐标测量数据处理及误差分析与补偿

三坐标测量机进行接触式测量时,一般采用球形测头。在测量过程中,测量机采集的是测头中心的坐标值,在测量常规几何要素（如平面、球、圆柱等）时,测量软件可以根据被测量要素的数学模型自动进行测头半径的补偿。但在测量叶片等没有预设数学模型的零件时,测量软件无法自动进行测头半径补偿。叶片具有复杂的空间几何形状,一般包括榫头和叶身两部分。叶身的形状复杂,没有任何数学模型,通常采用截面法来描述,即用多个平行的理想平面与叶身相截,每个截面又根据需要取一定数量的点,通过截面位置和截面内点的位置来描述整个叶片的形状。因此对叶片型面的测量就是要获得这些点的位置数据。叶片各个截面的形状不同,并存在叶身空间的扭曲和倾斜,因此叶片型面的测量尤其是半径补偿技术的应用具有特殊性,     

叶片型面及其模具型面的数控加工

<正> 汽轮机和燃气轮机的叶片及其模具型面是由一组等距或不等距的平行截面型线组成的空间扭曲面,每一型线是用一组离散的节点座标表示。以前型面的加工是用手工依靠每一型面样板打磨抛光而成,不但劳动量大、精度差,而且不能保证各截面之间型面的光顺,影响了叶片的质量。     

轴型叶片通用组合测具研制

轴型叶片通用组合测具研制项目,设计了一种对不同型号产品通用、上下工序通用、大幅缩短生产周期的测具。通用组合测具在新型号叶片上可以直接使用,实现了新品试制工装制造零投入,解决了生产瓶颈,达到了按时交付、提前交付的目标。     

整体叶盘叶片型面检测用检具设计

介绍了整体叶盘的结构以及整体叶盘叶片型面的样板检测方法 ,并结合某一试验用整体叶盘 ,给出了测量检具的具体设计步骤     

叶片型面及其模具型面的数控加工

汽轮机和燃气轮机的叶片及其模具型面是由一组等距或不等距的平行截面型线组成的空间扭曲面,每一型线是用一组离散的节点座标表示。以前型面的加工是用手工依靠每一型面样板打磨抛光而成,不但劳动量大、精度差,而且不能保证各截面之间型面的光顺,影响了叶片的质量。随着计算机应用和数控加工技术的发展,我们采用了一套数学方法编制程序在计算机上实现了型面数控加工的自动编程,并     

叶轮机械叶片的计算机辅助设计

本文讨论了基于叶轮机械三元流动通用理论的叶型设计及优化过程,改进了叶型积迭和叶片加工用平面样板曲线的计算方法,发展了绘制叶片和叶轮的各种平面投影、空间轴测投影及消除被遮盖的隐藏线的计算机绘图方法,并已获得实际应用。本文给出了典型的实例。     

叶片截面浮动测具

介绍叶片截面浮动测具的结构设计和使用方法。用以检测精锻叶片截面型线和内背弧型线的错位。测具使用方便、快速可靠,能满足叶片精锻工艺要求。     

Limits of topographic measurement by the scanning tunnelling and atomic force microscopes

Parameters describing the topographic character of a surface (height, surface wavelength, slope and curvature) can be derived from equivalent sinusoidal profiles. The response of a surface-measuring instrument may be modelled in terms of instrument parameters such as stylus radius, and scanning range and resolution. The performance of the instrument may then be mapped as a zone in amplitude-wavelength (AW) space to show the sinusoidal profiles it is capable of measuring. In a first-order analysis the STM and AFM are considered as equivalent to contact-stylus instruments with a notional stylus radius equal to the tip radius plus the gap. Comparisons between different instruments and types of instrument are readily made by mapping in AW space. The error arising from convolution of the sinusoidal profile with that of the finite tip may be quantified and plotted as contours in AW space.     

Microtopographic analysis of turned surfaces by model-based scatterometry

Turned surface profiles can be divided into a periodic and a random component. The periodic component is a function of the tool shape and the feed rate. The random component is caused by machine vibrations. To monitor the turning process, the periodic component is the essential global microtopographic feature which reacts sensitively to tool wear and tool scars. A measuring method evaluating the periodic component of turned surfaces is developed based upon the model-based scatterometry. Using an optimized scattering geometry, the model-based scatterometry leads to an intensified mapping of the microtopographic surface features in the angular distribution of scattered light. The profile parameters measured with the introduced scattering technique agree well with the values obtained by stylus measurements. Hence, in the range of precision engineering (R_a≤1.5 μm) the mean profile of the dominant periodic component can be measured optically without scanning and without resorting to comparator standards.     

Periodic Gaussian filter according to ISO 16610-21 for closed profiles

It is well known that the Gaussian filter according to ISO 16610, part 21 has nice metrological properties but also has some restrictions. The evaluable measuring length of open profiles is shortened by so-called filter running-in and running-out lengths which are a factor of the width of the Gaussian weighting function. ISO 16610-21 suggests a simplistic transfer of filtering of open profiles to filtering of closed profiles (e.g. roundness measurements). And this leads, due to the running-in and running-out lengths, to an unnecessary restriction. Because in case of a closed profile, it has to be taken into consideration that the profile can be extended infinitely and thus any measuring length of an equivalent open profile can be reproduced. Hence, as this paper shows, the measuring length for closed profiles can be arbitrary for any given width of the Gaussian weighting function.     

蜗轮齿形误差测量中的测头半径补偿

建立了坐标法测量蜗轮齿形的误差模型 ,重点分析了蜗轮齿形测量中的测头三维补偿方法 ,并进行了补偿精度分析 ,认为该方法特别适用于非渐开线蜗轮齿形的测量。     

一种基于最小条件的线轮廓度误差评定方法

提出一种模拟实际量具测量过程的方法来评定线轮廓度误差。该方法遵循国家标准中对形状公差的最小条件要求,通过分析测量点与对应包络边界的位置关系,将测量点集视为刚体,计算边界收缩至最小区域的过程中刚体与边界可能出现的相对运动,最终使所有测点位于最小包容区域内。结果表明：所提方法的评定过程相对于常用优化算法的大范围搜索更有全局性与单一性,可有效避免出现由算法缺陷导致搜索结果陷入局部解的情况。该方法适用于线轮廓度误差的评定。     

一种用于快速检测双曲螺杆成型刀具的方法研究

利用基于数控技术和光栅测量原理的双曲螺杆成型刀具廓形测量装置,获得被测刀具的轮廓点坐标,基于最高点重合法和微量平移法计算被测刀具的轮廓误差,据此判定刀具是否合格.通过对某型号双曲螺杆刀具廓形进行实际检测,验证了该方法是可行的和实用的.     

Measurement of nose radius wear in turning tools from a single 2D image using machine vision

Flank and crater wear in cutting tools have been extensively studied in the past using direct and indirect methods. In finish and hard turning, however, nose radius wear plays a greater role in determining the surface quality of the finished product. This is due to the direct interaction between the tool nose area and the workpiece during machining. Nose radius wear can be measured from the 2D profiles of the tool before and after machining using a vision method. This approach, however, requires two images of cutting tools to be recorded and precisely aligned before subtraction. This work proposes a new method of measuring nose wear area from a single 2D image of the worn tool. The nose profile is extracted in the Cartesian coordinates and converted to a polar-radius plot. From the plot, the nose wear area is determined by simple subtraction.     

Generation of Tool Paths for Machining Free-Form Pockets with Islands Using Distance Maps

In this paper, we present a new procedure for generating tool paths using discrete distance maps, especially for dealing with free-form shaped pockets with multiple islands. In this procedure, a discrete distance map is computed by shading a right circular cone having the height of a given offset distance, while moving its apex along the boundary curve segments. Using the discrete distance maps, the proposed algorithm effectively extracts the characteristic points or the valid self-intersection points of offset curve segments. For an offset distance, one or more offset profiles are constructed without the topological problems by offsetting the boundary curve segments within the parameter values specified by these chararteristic points, and connecting them into closed profiles using the topological information contained in the distance map. The gouging-free tool path is constructed by connecting these offset profiles, starting from the innermost offset profile. In the proposed method, we do not need any artificial bridges for a pocket with multiple islands to merge the pocket profile and the island profiles into a single boundary profile.     

面轮廓度触摸法检具设计

针对汽车发动机零件进气歧管的结构特点,分析了被测要素的检测方法,介绍了面轮廓度触摸法检具的结构及设计。对于同等精度要求的批量零件的检测,该检具检测方法简单实用,在保证检测精度的同时可提高检测效率。     

Tool vibration and its influence on surface roughness in turning

The frequency content of tool vibration and the surface profile in turning under normal cutting conditions was studied by measuring the frequency spectra of tool vibration and the surface profile. The predominant frequencies of tool vibration and the surface profile in the circumferential direction were found to be the same. The cutting speed, workpiece rigidity and the method of fixing the workpiece were found to influence the surface roughness and tool vibration.