Research On Key Technology Of Online Measurement System Of Large Forgings

Large forgings are the key components of various heavy equipments and productions, which have the characteristics of large dimensions, high technology, single-piece production etc. When forging, the operators usually need to online measure their dimensions so that they can control the forging dimensions. This may reduce material waste and energy consumption, and improve the productivity. But current measurement techniques can not satisfy the requirement of the industry since they have manual operation, low precision, less data and slow speed. So it has a great scientific and practical significance to research the online measurement technology of large forgings.To solve the inadequacy of measurement technology for large forgings, this dissertation was supported by the national973program, the principle of online measurement for large forgings was researched, and a technological solution based on laser radar was presented. In this technology, a parallel scanning system was used to carry a pulsed time-of-flight (TOF) laser distance measurement sensor, and this can obtain key dimensions of large forgings. To this end, the detailed research was developed as following:1. The technology limits and qualifications were researched and a scanning technique based on laser radar was selected as the technology solution for large forgings. The pulsed TOF laser distance measurement sensor is the core one which can obtain the distance of a red-hot large forging at a long range and a large scope. It dispels the influences of high temperature, radiant light, large dimensions and so on. A2-degree-of-freedom (2-dof) parallel spherical scanning device was designed and the two motors were both at the base, which had many advantages such as high stiffness, low inertia, high presion.2. Input torque of the scanning system was derived and the sources that give the torque fluctuation were obtained. The balancing conditions were achieved by shaking force balancing and could be used to guide the design of the scanning system. Then dynamical performance increased, e. g., shaking forces were eliminated, maximum torque was reduced, and input torque curve became smoothing. These were proved by the simulations and experimentations.3. The influence approaches of the temperature on the dimension measurement were analyzed and the index of refraction of the air in the forging field was obtained. According to the index of refraction, influence equations of large hot forging to the distance measurement of the TOF were proposed. Then a model of measurement errors was presented and the errors of dimensions measurement were simulated by it. The simulation can guide the subsequent measurement and data processing.4. A calibration of image navigation system was modeled and performed according to the corresponding relationship of the image navigation and scanning system. Then a calibration model of the scanning system was presented, which didn’t depend on other measurement tools. The simulation and experiments confirmed the model.5. The large forgings were classified to the classes of cuboids, circular cylinder and sphere and the data processing models were built respectively. The least-square methods were designed and the iterative computations were avoid during data processing for online measurement. The subsequent experiments confirmed the motheds.6. A prototype of the dimension measurement system of large forgings was developed by means of the foregoing results. The experimentations in laboratory and forging plant confirmed the technology. It shows that the technology can apply into the forging industry successfully.