Study on the Key Technology of Measuring Large High-Temperature Forging with Optical-Contact Target

The dimension of large open-die forging with high temperature is a dispensable indicator in the production. It is directly related to the quality of the product and post-processing. By summing up both domestic and international measuring methods, a new one is proposed: optical-contact target flexible CMMs. In this system, the most important part which will be designed by ourselves is the optical-contact target. Due to the specificity of the measurement environment, the effect of the temperature field on it must be considered. In the process of designing, some key parts of the optical-contact target must be determined in theoretically and the choice of the material also must be careful and so on. These will be the key poits of availability of measurement system and level of measurement accuracy. Some key technologys are preliminary studied in this paper.The following work has been done in this paper:1. The development situation on online measurement of large open-die forging is summarized, the theoretical basis of our measuring program is expounded, the principle and the mathmetical model of measuring system are introduced.2. The heat transmission between the forging and the measuring environment, and the effects which the high temperature causes on the key parts of measuring rod are analyzed. In response to these, the solving solutions are put forward, including the influence of heat conduction and thermal convection on the temperature field surrounding the forging, and measures to deal with the thermal radiation.3. By comparing the performances of the three kinds of high-temperature structural materials, the more suitable material to the measuring rod is found.4. Geometrical uniformity of the distribution of spherical surface of the contact elements is studied, including selecting the appropriate uniformity index, comparing the uniformity of the three kinds of global discrete grid models and summing up the facts that affect the uniformity. Then, the locations of the optical targets on the measuring rod are researched. 5. A series of experiments are done to verify the feasibility of measuting program, and the accuracy of material-selecting and analytical methods.