Papers by Keyword: Profile Measurement

Abstract: The dimensions of a workpiece have been measured during the milling process using a 3D laser inspection system. Re-clamping of the work piece has been avoided but a short interruption of the milling process took place. All three dimensions of the part have been measured, height and width using a profile scanning devise based on the laser triangulation method and the length using also the displacement features of the machine tool. Gauge blocks with the reference dimension of 4, 8, 10, 14, 18 and 23 mm have been used for the verification of the measurements. The measured values for the height deviate from the real value between 0 to 19 μm. The deviations of the length lie between 0 and 33 μm. The deviations of the width are higher and they lie between 0 and 150 μm, because of the scanning steps of the devise. The measurement of the width could be improved using a second scanner perpendicular to the first one in order to achieve an overall part inspection with deviations lower than 33 μm.

Abstract: Recently, manufacturing process simulation using finite element (FE) model become important. Therefore, validation of the finite element model is crucial. This study will present validation of 2D finite element simulation of cold heading at room temperature. Validation of the simulation model is carried out by comparing the resulted bulge profile of the cold upsetting specimen to the profile of the specimen, which is obtained from an optical 3D surface measurement technique namely Infinite Focus Alicona system. Based on the result, both profiles show a very good agreement.

Abstract: For tFor t For tFor the imaging advantages of aspheric optical component, it has been widely used in the aviation, aerospace, defense and civilian high-technology. Aspherical surface shape test is a key factor restricted aspheric processing and a complex sophisticated testing techniques. The well known measurement methods are faulty. Each method has advantages and disadvantages; many methods cannot be used for online testing. In this paper，the geometric principle of a swing-arm profilometer as a novel method to measure aspherics is introduced．The deviation between the actual and the ideal of aspherical surface shape is confirmed by the high-precision measurement for the vertical height with a specific path on the aspherical optical surfaces. By adjusting the location of measuring devices to maintain the distance of rotation center to the center of workpiece equal to the length of swing-arm,we can achieve the measurement for the workpiece of different machining tool. The measurement system mainly consists of the lifting and landing system of the high-precision axis,the high-precision level turntable rotary table, the high rigidity measuring arm and the high precision measurement sensors. And the follow-up data processing puts forward a number of error correction models at the same time. The advantages of the measurement method are that the measurement sports is only a simple turning motion .It will be helpful to reduce measurement errors and improve the efficiency of measurement.

Abstract: The main objective of this study is to assess the quality of the cold forging hole by focusing the roundness of the hole. In this study, a cold forging process of blind hole of Aluminum Alloy AA6061 experimental rig was developed. In the experiment, two major design parameters i.e. the depth of embossing and diameter of the punch were studied and their influence to the roundness was measured based on the profile obtained from the surface measurement technique. The results will be validated using commercial roundtest machine.

Abstract: The underlying data form of a wafer is a matrix of length (or height) measurements. In the presence of noise, evaluation parameters are normally biased. The expectation value such as peak-to-valley and GBIR (global backside ideal range) is systematically larger than the “true” value. Correction and compensation need a large population of measurements to analytically estimate both bias and the uncertainty. In this study, approach to obtain the true value is to extract a “true” profile by filtering noise from the measured data. In previous paper, the digital filter with wavelet transformation (WT) is proposed and efficiency to remove the noise, however, the method is introduced the pseudo-Gibbs effect. Then, we propose the digital filter with new algorithm of total variation (TV). In this paper, the new algorithm of TV is proposed and the digital filter by new TV indicate that data is filtered without the pseudo-Gibbs effect. The digital filters by WT and new TV are applied on the sample data of actual measurement system to investigate their performance of noise reduction.

Abstract: The paper analyses the compensation error which is caused by the probe radius of shape measurement instrument with the theory of envelope, and the model of the probe center is established. After having coordinates of envelope point corresponding to data point, actual curve equation has been obtained by using non-uniform B-spline curve. Finally, the effect is simulated and analysed by Matlab, and the result shows that the method of data processing has high precision.

Abstract: In the semiconductor industry, high resolution and high accuracy measurement is needed for the geometric evaluation of Si wafers. The flatness parameters are important to evaluate the wafer profile and are required to be the same level as the design rule of IC, and the tolerance for flatness is very tight. According to SEMI (Semiconductor Equipment and Materials International) standards, the required wafer flatness will be 22 nanometres by the year 2016. However, to obtain a higher resolution for sensors, the uncertainty becomes very large compared to the resolution and influences the measured data when the noise is increased. High resolution instruments always incorporate a certain degree of noise. In the presence of noise, form parameters are normally biased. Correction and compensation need a large population of measurements to analytically estimate both bias and uncertainty. The estimation is still far from perfect because of the nature of noise. Another approach is to extract a true profile by filtering noise from the measured data. For the purpose of noise reduction, low-pass filters by Gaussian smoothing and Fourier transform are often used. The noise is normally considered to be a component of small deviation (amplitude) with high frequency which also takes a normal distribution around zero. However these conventional filters can remove the noise in the spatial frequency domain only. So, it is essential to design a filter capable of removing the noise both in the spatial frequency domain and the amplitude component. Thus, we have designed and developed new type of digital filter for denoising. We introduce two new digital filters. One is wavelet transform capable of denoising in the spatial frequency domain and amplitude component, and the other is total variation that can be applied to discontinuous signals without introducing artificial Gibbs Effects.

Abstract: A multiple probes scanning system comprised of two displacement sensors and one angle sensor is studied for ultra-precise profile measurement. The least squares method is applied to reconstruct the measured profile with uncertainty estimation. The parameters that influence the uncertainty associated with the measured profile are investigated. In order to obtain the optimized uncertainty, the determination of the relative parameters has been discussed in two cases. The first one is that how to select suitable sensors when intervals between two displacement sensors are known. The second one is that how to select suitable intervals between two displacement sensors when the specifications of the sensors are known. The processes of the selection in two cases are illustrated respectively according to the actual situations of the measurement.

Abstract: Large aspheric mirrors with diameter over 300 millimeters with high surface accuracy are wildly used in many areas such as astronomical telescopes. Interferometers are widely used in profile measurement of optical flat and sphere. However, standard reference aspheric surface which is necessary for this method is difficult to make. Scanning defletometry based on ESAD (Extended Shear Angle Difference) is used to measure ultra-precise large near-flat and slight curved optical surface with the accuracy of sub-nanometer. However, it is not possible for it to measure aspheric surface because of the limitation of the measuring range of autocollimators. We proposed a new measuring method to scan the surface of a large aspheric optical surface using autocollimator with rotatable optical devices fixed on linear motion stage. To eliminate the influence of the pitching error of the scanning stage, we use two mirrors reflecting laser comes from autocollimator, which have the same effect with a pentaprism used in ESAD. To enlarge the measuring range of the autocollimator, we use a rotatable mirror to fit the changes of the slope of the mirror surface under measurement. The error analysis of the method is done. Measurement of an optical flat mirror and a sphere mirror with diameter of 50 mm and biggest slope of 6000 arc-second are done. The rotatable optical devices that we designed are proved effective on eliminating the pitching error of the moving stage.

Abstract: The uncertainty estimation of coordinate and profile measurement is essential for accurate measurement and establishment of traceability. We proposed an uncertainty propagation method to estimate the uncertainty of coordinate and profile measurement. In this article, the multi sensor algorithm with uncertainty estimation method is described for the profile measurement. Additionally, two examples of multi sensor method are introduced. According to the simulation results of assessing uncertainty and the experimental results, the validity of the method was confirmed.