On-line Dimension Measurement Method Of Large High-Temperature Forging

Large scale hot forgings are the rough casts which are frequently used to make huge technological manufactures, and widely applied in some strategic industries which include electric power, shipbuilding, petroleum and chemicals, metallurgy, aerobatics, aerospace and so on. This kind of technology has an important role in Chinese manufacturing industry. As the large-scale forgings are molded under the high temperature, the online measurement and precision control for the dimension and error on form and position has been an unresolved problem for a long period. The precise measurement and feedback of hot forging dimension has a significantly theoretic and economic value to guide the production techniques, and to enhance the utilization efficiency and its manufacturing productivity of large-scale hot forging materials. After sufficiently summarizing and analyzing the domestic and overseas measurement method and technology about the large hot forging dimension, the vision coordinate measurement technique based on laser tracker is presented in this dissertation, and it is highly possible to improve the measuring speed and precision for the large-scale hot forgings.The key points and innovative works of this dissertation are listed as follows:1. The system combining laser tracker with vision coordinate measurement technique is applied in the on-line measurement process of large-scale hot forgings. This method can be used to conquer the problems generated by the adverse circumstances, high temperature on the surface, blind points of vision measurement and large dimension during the on-line dimension measurement processes of large-scale hot forgings. The on-line measurement accuracy of hot forgings is possible to be greatly increased by applying this method.2. The basic structures of measurement systems are presented and the specific measuring processes are described. The the measurement model based on laser tracker is presented, and the system models are optimized through the gradient decreasing method.3. Influences of heat conduction, heat convection and heat radiation on the measurement environment and the measurement instrument are analyzed and computed. According to the requirements of measurement system for the measured circumstances, the key components of measurement systems and the basic structure of light pen are designed.4. The experiments about the influence of heat radiation on the surface temperature of measuring components, the performance of anti-heat radiation materials and the effect of inhomogeneous temperature field on the laser beam are carried out. The experimental results have verified the validity of transient analysis of temperature field around hot forgings. The impacts of temperature on the air refractive index and the length measure with interferometry are computed, and the computing results are contrasted with the experimental ones. These results have demonstrated the technological feasibility of our measuring schemes. In addition, through a plethora of simulation experiments, the factors of impacting the measuring accuracy are analyzed and established, and the related measuring experiments are performed in the laboratory. The simulation and experimental results have both confirmed that this new measuring method can satisfy the on-line measurement requirements of large-scale hot forgings.5. Based on this newly designed measurement systems, we can adopt different detecting heads to measure different forging diameters, and propose that the detecting heads use the spherical ordinate and utilize the accurate positioning of spherical measuring point , and then we can take us of the radius compensating techniques to effectively reduce the numerically computing errors.