Papers by Keyword: Straightness

Abstract: The straightness is an important indicator in measuring the quality of shaft parts. Laser peening straightening (LPS) is a new mechanical method to straight the shaft through inducing residual compressive stress into the shaft surface. Compared with the traditional method, the process of laser peening correction is high efficiency and can be controlled precisely. In the present work, the mechanism of laser peening straightening for shaft straightness is revealed and a three-dimensional finite model is developed to investigate the effects of laser parameters for shaft straightness correction. The results show that the peak pressure and pulse duration should be more than 4 GPa and 8 ns when laser peening straightening is used to correct the shaft straightness. The straightening amount increases with laser power density, laser pulse duration, multiple laser peening. The maximum correction amount for shaft straightness with LPS is no more than 0.01mm.

Abstract: A novel Micro Electro Mechanical System (MEMS) measurement device for straightness measurement with a three point method has been proposed. This device integrates three cantilever displacement sensors with a narrow pitch on a silicon chip. The authors determine appropriates shape, dimensions of the cantilever, and a fabrication process. According to simulation results, a triangular cantilever with altitude 12 mm long, base 4mm long, and 0.25 mm thickness was adopted to realize the target measuring range of 100 μm. Near the end of each cantilever, a square frustum probe 250 μm high which was fabricated by anisotropic wet etching was placed. Near the base of cantilevers, four piezo resistance gauges were formed; two are active gauges for measuring stress arise from a displacement at the probe and the others are dummy gauges for temperature compensation. Wiring and contact terminals were fabricated on the base substrate and the total size of the device is 20 mm × 32 mm. The fabrication process of this device was designed and result of a trial production was reported.

Abstract: In the field of surface profile measurement, many software datums were proposed. When a measured surface profile is large, the number of sampling point becomes large. As the result, the influence of the random error becomes large. To decrease the error propagation, the concept of the division of the length datum is applied to the integration method for surface profile measurement. Analytical results and simulation show when integration method is used as the software datum for surface profile measurement, combination of the large scale integration method and short scale integration method is useful to decrease the error propagation.

Abstract: Cylindrical parts with a protrusion are expected to be used in the components of consumer electronics and automotive products. The machining efficiency of these parts is very low, making them difficult to be mass-produced. The aim of our present work is to develop a highly accurate and highly efficient grinding process for a cylindrical surface with a protrusion. This paper describes the results of experiments using a straight cup-shaped grinding wheel. The following conclusions can be drawn. (1) To prevent uneven wear of the grinding wheel, an oscillation operation is necessary during the grinding process. (2) By employing the straight cup-shaped grinding wheel, the grinding process is realized with the aim of achieving the following: high machining accuracy, roundness below 3 μm, straightness below 2 μm, and surface roughness below 2 μmRzjis.

Abstract: In this study, it is discussed how the cutting conditions for drilling deep holes in austenite stainless steel affect the machining accuracy of the hole straightness and the cutting temperature rise. As a result, it is possible to reduce the thrust force and make the machining time short by the combination of the step-feed amount and the feed rate. By changing the drill in incremental step from short drill length to long drill length, the straightness was improved. It was also found that the temperature rise of the drill was around 10 K regardless of the cutting speed when the small step-feed amount of 10 μm was given.

Abstract: The objective of this research is to examine the relation between the straightness and the cutting force ratio during the CNC turning process. The cutting force is monitored and obtained by installing the dynamometer on the turret of CNC turning machine. The relation between the cutting force ratio and the straightness is investigated under the various cutting conditions, which are the cutting speed, the feed rate, the depth of cut, the tool nose radius and the rake angle. The experimentally obtained results showed that the straightness can be improved with an increase in cutting speed, tool nose radius and rake angle. The relation between the dynamic cutting force and straightness profile can be proved by checking the frequency of the cutting force in frequency domain with the use of the Fast Fourier Transform (FFT), which is the same as the straightness profile. Hence, the cutting force ratio can be used to predict the straightness during the cutting regardless of the cutting conditions. The cutting force ratio is proposed to predict the straightness during turning process by employing the exponential function for the sake of straightness. The multiple regression analysis has been utilized to calculate the regression coefficients of the in-process prediction of straightness model by using the least square method at 95% confident level. It has been proved by the cutting tests that the in-process straightness can be predicted during the cutting within ±10% measured straightness with the high accuracy of 91.85%.

Abstract: This paper describes influence of the cutting conditions on the hole shape accuracy in deep-hole machining of stainless steel with small-diameter drill. The drilling tests were carried out by changing the step feed, the rotational speed and the feed rate in order to investigate the relationship between the straightness of the hole and the cutting conditions. As a result, it was found that the thrust force decreased with a decrease in the step feed amount and accordingly the straightness was improved. By changing the drill in incremental step from short drill length to long drill length, the straightness was improved.

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: In the straightness profile measurement of a mechanical workpiece, hardware datums have been the traditional standard. However, when the straightness profile is measured using a scanning displacement sensor set on an X-stage as the hardware datums, output of a displacement sensor includes the signal of straightness profile and the sensor’s parasitic motion, i.e. straightness error motion. Then, error separation techniques of the straightness profile from parasitic motions have been developed. For example, two-point method uses two displacement sensors and separates the sensor’s straightness error motion from the straightness profile. However, the conventional two-point method cannot measure a large-scale workpiece because the large sampling number causes random error amplification. In this article, the influence of the random error of generalized two-point method is shown. As the result of the theoretical analysis and numerical analysis, random error propagation decrease when sampling number increase. Further, experimental results obtained by generalized two-point method with large sampling number are analyzed using Wavelet transform and influence of error of the generalized two-point method is discussed in the space-spatial frequency domain.

Abstract: Aiming at the low efficiency and precision of nowadays domestic auto-straightening machine of shafts, a new kind of shafts straightness detection system is researched and developed. The supporting part of the measuring mechanism adopts the mechanical structure of auto-going-down of straightening points supporting pedestal. The whole convolute measuring system fixes on the machine tool orbit sliding table, whose movement can change the position for the straightening point and make positioning faster and more accurate. In addition, this detection system bases on applications math and builds math model by Fourier transform which can separate the elliptical error signal, straightness error signal and impulse error signal and then gained ideal straightness error of shafts.