Papers by Keyword: On-Machine Measurement (OMM)

Abstract: The current requirements for an efficient dimensional inspection of manufactured parts have lead to development of different in process and on-machine measurement (OMM) techniques. Touch trigger probes (TTP) are the most common technologies utilized, inspired on contact probes used on coordinate measuring machines (CMMs). The on-machine accuracy of TTPs depends upon precision of the tool-machine control as well as upon the procedure for TTP presetting. Taking this into account, a different OMM technique is considered in this work, which consists on a laser micrometer (LM) that is commonly used for in-process measurement of continuous products. The behaviour of TTP and LM is analysed and discussed in terms of repeatability and reproducibility. Results obtained by both techniques are compared each other by measuring a cylindrical workpiece and by checking the results with those obtained on a CMM.

Abstract: On-machine measurement and statistical analysis of wheel topography are important for real-time monitoring the wheel condition during grinding and predicting the performance of grinding process. In this paper, the surface topographies of grinding wheel in the different stages of the grinding of fused silica and BK7weremeasured with a white light interferometer, which was set on the surface grinder. Height parameters of 3D surface roughness were proposed to evaluate the wheel wear. Wheel wear mechanisms were essentially determined by analyzing the different material removal modes of optical glasses. Grinding of BK7 mainly causes severe attritious wear of grains, while grinding fused silica, self-sharpening effect makes grinding sustain for a long time.

Abstract: At present, on-machine measurement has received extensive attention due to high efficiency and automatic quality control. In this paper, two applications of on-machine vision measurement of metal parts were introduced. With regard to geometric measurement of small square part, four sides and angle were measured. The procedure of camera calibration, image processing and geometric representation was expounded. For medium square part, four overlapped images were captured by controlling the worktable movement. Size and shape measurement were achieved after image mosaicing. Two application results proved that this kind of on-machine visual measurement is efficient and practical.

Abstract: In this paper, an on-machine profile measuring system for aspheric ground surface was presented, which involved data processing with improved two-dimensional weighted mean filtering and free form surface fitting. To verify the reliability of this system, a calibration experiment was done by comparing the measuring results of Ф320mm mirror between the WYKO 24 inch interferometer and the on-machine measuring system. The experiment results show that the on-machine measurement is effective and it can provide foundation for compensation machining. By comparing the measurement experiment results of the Keyence LC2430 with the WYKO interferometer, it is demonstrated that the deviation of PV is better than 0.23μm and the deviation of RMS better than 0.08μm.

Abstract: The causes of machining errors are very complicated and apt to mutual influence in aspheric grinding, so it is difficult to improve machining accuracy by control one cause. To compensate the machining error of large aspheric grinding, an error-compensation technique using on-machine profile measurement system in three axes grinding machine are presented. To verify the effectiveness of the compensation machining and the reliability of the measurement system, experiments on high-precision grinding machine were performed. Moreover, the compensation machining with the on-machine measurement substantially decreases the machining errors and improve machining accuracy by more than 45%, compared with the non-compensation machining.

Abstract: A novel movable monocular stereo vision measurement system was designed considering the application objectives and on-machine measurement situation. The physical model and mathematical model for measurement accuracy was established. The appropriate structure parameters scope was obtained after simulation analysis. Finally, an application example of the measurement system is introduced.

Abstract: It is necessary to develop an on-machine measurement system of cutting tools with high precision and high efficiency on the NC machining, so that it can decrease non-production time and improve machining efficiency. A system for high precision measurement of rotating tools on the basis of image processing is described in this paper. Images are acquired from a digital camera and transmitted into a computer. The working profile of rotating tools and geometrical parameters are extracted accurately through image processing technology. Depending on theoretical analysis and experiments, this system can be widely applied to tool offset and NC programming based on working profile of the tools.

Abstract: The On-machine measurement is usually based on the data of points. When data come from the CNC machine tools, the information they carry may be invalid. Therefore, it is unsuitable to compensate the errors by rotating and translating all data. In this paper, a practical algorithm is proposed to compensate the errors. Firstly, the valid data are picked out and sorted according to their normal vectors. By using the least square method, an error reference frame is constructed. Then the relation between the compensation values and coordinates of the theoretical points is derived. Finally, an example of aircraft structural parts is presented to validate the design.

Abstract: One of the most important challenging problems in modern mechanical manufacture industry is how to reload the repaired tool properly to the numerical machine. An innovation method is put forward considering the above mentioned problem. It takes account of raster sensors due to the characteristics of high accuracy, wide scope of dynamic measurement, non-contact measurement and flexible to automation and numeralization. A measurement system is constructed based on the principle of raster sensors. One operating example of raster provides quite precise results, which would be one of the solutions to the key problem of reloading machine tool.

Abstract: A non-contact on-machine measurement system has been developed since various precise machines are getting lighter and smaller; therefore, processing with nano-precision is demanded recently. This system makes possible to measure with high precision without any damages and it is unnecessary for workpieces to attach or detach from a machine tool. Moreover, this system achieves on-machine form error compensation with high precision. On the other hand, the details of the system performances are still unknown. This study focuses on evaluating the performances by the comparison of the results that measured by this system and an existing measurement instrument under various conditions. As a result, this system shows an equivalent capability of measurement with high precision as the existing measurement instrument.