Key Engineering Materials Vol. 625

Abstract: Roundness and spindle error motion measurements are two fundamental issues in the geometrical measuring techniques. Most of the fixture with rotating cylindrical shaft, cylinder defined by the minimum circumscribed axis, can be obtained the minimum circumscribed rotation surface high-precision axis. Generally, a more accurate measurement points, can result in a more accurate cylindrical shaft, but the longer the time of the calculation time. In this paper, the drawing method can handle a large number of measurement data to avoid lengthy and complicated calculations, and can quickly obtain the minimum circumscribed cylindrical axis precise location, deviation and cylindrical radius and tolerance. This article is the use of the minimum circumscribed cylinder theoretical approach with computer drawing ways. Comparison is relatively quick and easy. The actual display of the results, which can be easily, obtained the position, skew and deviation of the spindle. This paper will be established a cylindrical outer edge quality assessment model and provided a basis for the cylindrical outer edge quality assessment. This paper for seeking the axis of cylindrical shank is based on minimum circumscribed cylindrical theory with computer drawing method and instances for verification. The computer drawing method can be determined spindle eccentric angle and the distance of deviation, to provide a reliable model for the evaluation of rotary spindle, the mode established by the paper at the same time applicable to any other rotating spindle error evaluation.

Abstract: The magnetostrictive position sensor (MPS), which can be used to detect the absolute position of motion objects in a coordinate system, is widely used in industry. It is especially applicable to the conditions of greasy dirt, oil and water. As an important disadvantage for MPS, the measurement blind area (BA) occurs due to the induced electromotive force (EMF) oscillation when the magnetic field of excitation pulse passes the receiving coil. A new structure with two coils is proposed in this paper. Two signals can be obtained by each coil, respectively, and the BA will be improved by different operations between two signals. Finally, the validity of this approach has been proved by experiments.

Abstract: Laser scanners have become very popular means of point clouds acquisition and 3D reconstruction. However, the accuracy specifications given by laser scanner producers in their publications and pamphlets are not consistent. Experience shows that sometimes these should not be trusted. Therefore, how to reasonably evaluate and quantify main technical parameters of the instruments is particularly important. It is very necessary to investigate in calibration devices and methods that are suitable for laser scanners. The 80m indoor ranging facility of the National Institute of Metrology (NIM) at Beijing, China, is equipped with an interferometer comparator, precise air flotation rail systems and environmental parameter automatical compensation system. The facility is a closed loop feedback control system and can provide a high-precision reference distance value with different intervals. A expanded standard uncertainty (k=2) of U(L_s) is superior to 0.5μm+0.5×10^-6L. This paper describes the calibration principle and procedure, including mounting white standard spheres with surfaces of diffuse reflection at the mobile platform as non-contact targets, scanning and measuring the white spheres , fitting the coordinates of the sphere centers and calculating the relative distance among sphere centers. As an example, this paper also presents analysis and evaluation on the measurement uncertainty of ranging accuracy.

Abstract: In this paper, cutting force and its power spectrum analysis at different tool wear levels are explored. A dynamic model is established to simulate the measured cutting force compositions, and a series of cutting experiments have been conducted to investigate the cutting force evolution with the tool wear progress. Research results reveal that in the time domain, the cutting force in UPRM is characterized as a force pulse follows by a damped vibration signals, the vibration can be modeled by a second order impulse response of the measurement system. While in the frequency domain, it is found that the power spectrum density at the natural frequency of dynamometer increases with the progress of tool wear, which therefore can be utilized to monitor diamond tool wear in UPRM.

Abstract: Measurement uncertainty has important economic consequences for calibration and inspection activities and is often taken as an indication of the quality of a test laboratory. Smaller uncertainty values are generally of higher value. In industry decision rules employed in accepting and rejecting products are based on the measurement uncertainty budget of the related characteristics of the products. Conformity assessment based on the product specification and the measurement evaluation is an important part of the industrial quality assurance of manufactured products and for the stability of production processes. The aim of this paper is to describe the relationship between the conformance zone and the acceptance zone and to address the problem of determining acceptance limits that define the boundaries of the acceptance zone.

Abstract: A bran-new style coordinate measuring system with 3-PUU parallel mechanism and its advantages was proposed which could realize 3D measurement with only one linear grating and two precision guides. Firstly, measuring space with a 0.05mm error of structure parameter as target was explored based on 6 bars direct kinematics model, workspace and error model, and then the principle of maximum measuring space was presented to elaborate the relationship between measuring space and length of bar. Then in order to enlarge the scale of measuring space of Coordinate Measuring Machine (CMM), improve the measuring accuracy and flexibility of CMM, the key dimensions and positional parameters of CMM were optimization designed according to the direct kinematics model and the principle of maximum measuring space. Finally the deformation of key components was processed by Finite Element Method (FEM) according to the motion characteristics and parameters of the new CMM prototype, so that the affect of deformation to measuring accuracy can be controlled and decreased. Results are shown that the measuring space of CMM is 1100mm in x axis, 535mm in y axis, 426mm in z axis; deformation of beam is the main reason to influence the measuring accuracy and should be offset after calibration.

Abstract: In this paper, a non-contact coordinate measuring machine with laser displacement sensor, which consists of three translational axes, is designed and built independently. In order to obtain the measuring precision, it needs to calibrate the coordinate measuring machine. Learning from the calibration method of contact coordinate measuring machine, a detection method is proposed for calibrating the precision of the non-contact coordinate measuring machine. Based on the homogeneous coordinate transformation theory, the error model of coordinate measuring machine is built under the condition that the positioning errors, angular errors, straightness errors and perpendicularity errors are taken into comprehensive consideration. The final error expressions of three axes can be calculated in the use of error model and homogeneous coordinate transformation theory. The final values of the errors are acquired through the analysis of the error curves, which can be obtained by using the laser interferometer system. The method proposed in this paper is using the two-dimensional ball plate to measure the errors. By locating three different positions of the ball plate in the space and using automatic centering procedure to measure the center position which is previously calibrated, the final errors of three axes can be detected directly. By comparing the two results, it testifies that the two-dimensional ball plate detection method is reasonable. Comparing with the laser interferometer method, the two-dimensional ball plate detection method reduces the workload of adjusting the optical path and the time of measuring errors, which has the vital significance in calibrating the precision of non-contact coordinate measuring machine.

Abstract: Two-axes stages (XY stage) are used for precise machining and precise positioning. The XY stage should have the resolution of nanometer in the nanotechonology. In order to determine that the XY stage has enough small resolution, it is necessary to evaluate the positioning accuracy. The shape of stage axes affects measurement result. Therefore, it is necessary to know the shape of the axes. This paper describes the method how to evaluate the straightness of the stage to measure the behavior of the stage. The behavior of the stage is measured by laser interferometer, which measures the displacement. The reflection mirrors are set up on the stage, which reflects the laser. The result of measurement by the laser interferometer includes both of the shape of the reflection mirrors and the shape of the axes. In the case of nanometer positioning, the shape of the reflection mirrors affects measurement result, as the profile error of reflection mirrors are as small as motion error. We theoretically and experimentally inspect whether both errors can be separated from the displacement. In this simulation, the shape of axes and the shape of the reflection mirrors are generated randomly. The shape of axes and the shape of reflection mirrors are estimated by non-linear least-squares method. The estimated shape of axes and shape of reflection mirrors are compared with the ideal shape of them. After simulation, similar method is applied to the actual stage and laser interferometer. The result of simulation and measurement are shown.

Abstract: Self-A (Self-calibratable Angle device) rotary encoder can detect some kinds of angle error, not only its encoder scale error, but also the encoder attachment error (e.g. eccentricity error). When rotary table with built-in Self-A encoder rotates only one revolution, inner Self-A rotary encoder can calibrate the own angle error with a high accuracy. However, in the case of the Self-A using the encoder of 36,000 graduation scales, since the angular interval of the calibrated main scales corresponds to 36", it is insufficient for high resolution angular indexing control with high accuracy. Generally, the angle error of electric interpolation signal is estimated to be 1 % of main scale resolution that corresponds to about 0.36" for 36,000 scales encoder. Accordingly, even if Self-A had the ability which can calibrate in the accuracy 0.1", when it was controlling the rotary table using an electric interpolation signal, its total accuracy worsened to about 0.36". For improvement in precise angular-position control, we developed Self-A rotary table which can calibrate the angle signal at high resolution including electric interpolation signals. In this paper, we introduce the performance of the new high resolution Self-A encoder table. It keeps high accuracy and good repeatability in the 360° whole range as well as in the short range of ±1,000".