Roundness measurement of spherical artifacts at arbitrary latitude

This technical note examines an approach to measuring the roundness of spherical artifacts at arbitrary latitude. A roundness measurement includes the combined contributions from the artifact’ form error and the spindle’ error motion. We show that it is possible to separate the spindle error from artifact form error at any inclination with respect to the axis of rotation if the axial and radial error motion is independently measured using an error separation technique such as Donaldson reversal. Comparison of the predicted and measured results shows agreement to less than a nanometer.     

Research on global form deviations for spiral bevel gear based on latticed measurement

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超声振动切削超薄壁精密零件的圆度误差试验研究

试验研究了超声振动车削直径为47.75mm壁厚为0.8-1.5mm的照相机导向筒超薄壁精密零件的圆度形成规律及切削参数对圆度误差的影响。研究表明:超声车削精密超薄壁零件,圆度误差最小是普通精密切削的1/3。     

Genetic approach for automatic detection of form deviations of geometrical features for effective measurement strategy

Shortening the planning times and reducing manufacturing costs are strategic specifications, to which the entire product developing process must subordinate itself. The consequent use of available metrological processes and components can ensure the long-term stability of production processes. With a worker-oriented integral effort, the process chain from the CAD system to an integrated inspection planning to the feature-based measuring on form tester and coordinate measuring machines can form a quality loop. Automatic production of a complete feature list directly from the CAD system and the uniform inspection planning under specification of feature-oriented measurement strategies creates the premise for standardized methodologies and international comparability of results of measurement.

The non-comparability of measurement results is often the cause of a lack of trust between customer and supplier, unnecessary discussion and sometimes even litigation. Coordinate measurement offers the operator numerous opportunities for influencing the result of measurement in almost any way. This especially concerns the specifications for performing and evaluating the measurement by considering the form deviation of the real workpiece prospective for the manufacturing process. A measurement strategy is defined which ensures the undershooting of a target uncertainty [Koordinatenmesstechnik, Carl Hanser, München, 1999; Werkergerechte und prozesskettenorientierte Messtechnik, in: Koordinatenmesstechnik, VDI-Verlag, Düsseldorf, 2001, p. 37].

This work presents a method to detect form deviations of standard geometrical features (line, circle, plane, cylinder, cone and sphere) of a manufactured part using genetic algorithm. Deviations of a geometrical element are detected in terms of the combination of several basic deviation types (waviness, random deviation, offset, peak, etc.) with their parameter values. Genetic algorithm arrives at the optimal values of these basic deviation types which reproduce the profile very close to the measured one. This information can be stored in knowledge-based system and the shape of the part can be reproduced to adopt a suitable measurement strategy. An interactive software assistance with graphical view is developed to effectively handle the detection procedure. Effectiveness of the detection software is illustrated with a synthetic and a measured profile of the crank shaft.     

两点法在曲轴圆度误差测量中的应用

采用误差分离技术,将经典三点法演化为两点法,对曲轴轴颈圆度误差进行实时在位精确测量。实现曲轴轴颈圆度误差和工件主轴回转运动误差的有效分离,去除了工件主轴回转运动误差对圆度误差的影响,对系统的测量精度及测量误差做了详细分析。     

Uncertainty analysis of positional deviations of CNC machine tools

The assessment of the measurement uncertainty is an indispensable task in all calibration procedures. By international accord, the evaluation is to be done in accordance with the ISO Guide to the Expression of Uncertainty in Measurement (GUM). To calibrate the positional deviations of computer numerically controlled (CNC) machine tools, calibration laboratories will usually follow the guidelines in ISO 230-2 International Standard. However, that standard does not address uncertainty. In this paper, we present an uncertainty evaluation scheme that is firmly grounded in the GUM, and can therefore be of use as a guide to develop appropriate uncertainty calculations in this and similar types of calibrations.     

Determining the theoretical method error during an on-machine roundness measurement

The analysis of the theoretical method error was conducted for on-machine measurements of roundness profiles based on the assessment of radial variations. The derived mathematical relationships were represented graphically. The absolute and relative theoretical method errors were determined for the assumed initial conditions. Planned further research activities are given.     

频率大范围变换下的电能计量

针对在频率不断变换的情况下对信号功率进行测量的问题,提出了一种可同时测量信号瞬时频率、基波有功功率和视在功率的算法。输入信号为已经滤除了直流和高次谐波的基波分量,通过自适应有限长单位冲击响应(FIR)数字滤波器测量了基波有功功率,通过Prony算法测量了信号的瞬时频率和视在功率,利用改进的最小加权二乘法(WLS)算法提高了功率的精确度。研究结果表明,在频率大量变化的情况下,该算法对信号频率、有功功率以及视在功率的测量的精确度可满足工程应用的需要。     

In-process out-of-roundness measurement probe for turned workpieces

A new in-process and non-contact probe is proposed to measure the diameter and the roundness of turned workpieces. The initial probe discussed in previous publications exhibited diameter measurements with good accuracy (uncertainty 5 μm over 100 mm). This paper discusses the implementation of roundness measurement into the initial probe and its performance. The principle of the roundness measurement is based on the relationship between the displacement and the light intensity. The probe delivers a maximum error of 0.5 μm with an uncertainty of 1 μm for roundness measurement over a range of 100 mm diameter.     

Integration of fiber-optic sensors in measuring machines

In last years, optical metrology due to its capability in miniaturization and sensitivity became the primary solution in measurement of complex geometries and fragile pieces. Here, we propose a promising approach to perform highly accurate distance measurements using low-coherence fiber-optic sensors for quality inspection of nozzle orifices in fuel injection systems. In this effort, we develop an adaptive image processing algorithm in MATLAB and install the necessary hardware on a form tester to accelerate and simplify the aligning process. As a result, the repeatability of measurements is one order of magnitude improved while the standard deviation is almost 60% reduced.     

Optimizing discrete point sample patterns and measurement data analysis on internal cylindrical surfaces with systematic form deviations

Selection of an appropriate sampling strategy and of the correct fitting algorithm are two of the key issues in the practice of modern coordinate metrology. A recent report described the development of new techniques for modeling the form errors of machined part features and illustrated their use in identifying and understanding the relation of form errors to machining process variables. In this report, these mathematical tools are further developed and applied for the determination of optimum, reasonably-sized probing patterns for measurement under time and economic constraints. The focus of the work reported here is on full internal cylindrical surfaces. The technique is, however, of general utility and can be employed with any nominal feature geometry. Its application does, in many cases, produce significant improvements in the uncertainty of derived geometric dimensioning and tolerancing parameters with modest or no increase in measurement time. In contrast to most work on these problems, extensive use is made of process-dependent information in selection of sampling protocol and data analysis method. Since the method begins with an understanding of the form errors introduced into the part by the particular manufacturing regime, at least partial benefit can be seen even when the sample pattern optimization is employed in conjunction with commercial, off-the-shelf CMM control and data analysis software.     

Function-oriented form evaluation of engineering surfaces

Workpieces make contact on their functional boundaries, not on the best fit surfaces. Better quality products can be made by controlling parameters of the production process and evaluating the workpiece based on functional requirements. A new algorithm is proposed in this paper, based on a sound mathematical background, to obtain the functional boundaries that are best represented by enveloping features.     

Uncertainty estimation for multiposition form error metrology

We analyze a general multiposition comparator measurement procedure that leads to partial removal of artifact error for a class of problems including roundness metrology, measurement of radial error motions of precision spindles, and figure error metrology of high-accuracy optical components. Using spindle radial error motion as an explicit example, we present a detailed analysis of a complete test with N orientations of a test ball with respect to the spindle. In particular, we show that (1) all components of the ball roundness error average to zero except those with frequencies of kN cycles/revolution, where k is a positive integer; and (2) the combined standard uncertainty of the measurement is proportional to 1/√N. We then show how a complete set of measurements for an N-position test can be synthesized from only two measurements, and we derive a general expression for the combined standard uncertainty as a function of the number of positions n (2 ≤ n ≤ N) actually measured in an N-position test. This uncertainty can serve as a useful guide to measurement design, involving trade-offs between multiple setup cost and complexity and required levels of angular harmonic resolution and combined standard measurement uncertainty.     

Laser tracker performance quantification for the measurement of involute profile and helix measurements

Standard-conforming measurements for a large involute gear were performed with a manually operated laser tracker system and the corresponding task-specific measurement uncertainties were estimated. Especially, readers using laser trackers for inspecting large involute gears will get information of a taskspecific measurement performance for the first time, which significantly differs from the laser tracker machine specification. To ensure unambiguous and repeatable measurement results, user-friendly auxiliary tools are used, which allows the operator to probe the measurement points according to existing guidelines and standards. Measurements were taken on a robust and highly accurate large involute gear measurement standard of the Physikalisch-Technische Bundesanstalt (PTB) under laboratory conditions. The size of this gear measurement standard complies with those gears used in wind power plants. The external gear materializes a left and a right hand gear as well as a spur gear. The obtained results of profile, helix and surface measurements are presented. These research activities were carried out at the PTB in the department of coordinate metrology.     

三平行传感器式频域法误差分离技术--在线测量圆度误差的新方法

提出了一种能临床测量与分离工件圆度误差和主轴系统回转误差的新方法——三平行传感器式频域法：三个位移传感器呈平行布置，其中一个传感器的测量轴线通过被测对象中心，其优点是测试系统易于安装与调整。给出了该方法的读数方程和权函数表达式以及应用频域法分离求解的途径。提出了避免其谐波抑制的措施。实测结果与经典的三点法的测量结果作了比对，表明该方法简便、正确、有效。     

The min–max problem for evaluating the form error of a circle

There have been many studies to evaluate the form error of a circle. Most of them, such as the optimum methods and limacon model, employed the approximate solution to obtain the desired results. In this paper, three mathematical models depending on the method used to select the exact control points are constructed to evaluate the analytic solution of the minimum circumscribed circle, the maximum inscribed circle and the minimum zone circle by directly resolving the simultaneous linear algebraic equations. These new and simple mathematical methods are verified to be useful for determining the exact solution.     

一种组合台面式多用途铁水罐计量轨道衡

本文介绍了日照钢铁有限公司（以下简称“日照钢铁”）针对炼铁到炼钢的短流程,生产区域紧凑的现状,为优化合理建设,减少投资,通过对轨道衡计量方式的分析、两种罐型兼顾、称重台面设计,选用一种组合式（两台面）的整车计量轨道衡,实现动静两用、铁水罐车混编动态计量。     

Simulated SEM images for resolution measurement

Resolution is a key performance metric, which often defines the quality of a scanning electron microscope (SEM). Traditionally, there is the subjective measurement of the distance between two points on special "resolution" samples and there are several computer-based resolution-calculation methods. These computer-based resolution-calculation methods are much more precise than direct measurement, but none of them can currently be considered an objective way of measuring the resolution. The methods are still under development; therefore, objective testing is necessary. One approach to algorithm testing is to use simulated images. Simulated images are very useful for this purpose because they can be well-defined in all parameters unlike the real SEM images. Simulated images can be generated that closely mimic the gold-on-carbon SEM test sample images that usually consist of bright grains on a dark background. Simulation can account for edge effect, roughness of the substrate, different focusing, drift and vibration, and noise. Shapes, positions, and sizes of the grain structures are random. The simulated images can be then used for testing the resolution-calculation methods, especially for finding how the particular properties of SEM images affect the resultant instrument performance and image resolution. To support this testing, NIST has developed and made available a reference set of simulated SEM images generated using the methods described in this article.     

Recent advances in separation of roughness, waviness and form

Engineering surfaces are comprised of a range of spatial wavelengths. Filtering techniques are commonly adopted to separate the different wavelength components into well-defined bandwidths. Filtering is done prior to numerical characterization and it is also essential for extracting information needed to provide process feedback and establish functional correlation. This paper reviews commonly used filters in surface metrology like the 2RC, Gaussian and several new ones currently under research such as the spline, morphological, wavelets, regression filters and robust regression filters. The need for these new filters and examples illustrating the features of these filters are also presented.