Studium symbiózy geometrické a pracovní přesnosti frézovacích center

Abstract

The dissertation dealt with the study of the symbiosis of geometric and working precision of milling centers. In the beginning of the thesis, the issue of precision machining, the quality of machine tools and their accuracy within the framework of various influences were explained. In the overview of current issues, the works of authors who have already dealt with the mentioned issues were presented. In the theoretical part, the work focused on the types of precision of machine tools. The concepts of geometric and working accuracy of machines, their parameters and possible measurement methods were explained here. In the next part, the work dealt with modern measuring devices and their use. In the experimental part of the thesis, the scheme of the progress of the individual goals of the dissertation and their timeline is presented. The milling center DMU 50, which is located in the premises of the laboratories of the University of Mining and Technology of the Ostrava University, was used for the experiments. The necessary equipment and material for the implementation of the work was provided by the Faculty of Mechanical Engineering. Renishaw's Ballbar QC20-W measuring device was used to measure the geometric accuracy of the machine tool. This device can wirelessly measure the parameters of the machine tool even in the horizon of several time periods for their eventual comparison. Its parameters and measurement procedure are described in the work. Part of the Ballbar program are the evaluation graphs that were described and used in the next steps of the experiment. Before the actual measurement with the Ballbar system, a control measurement was performed to detect inaccuracies and defects on the spindle of the milling center. The second control measurement was to determine the repeatability and compensation of the position setting. These two control measurements did not reveal significant problems that would affect further measurements. After that, the measurement itself was started with the Ballbar system within a period of 3 years to determine the accuracy of the machine tool as a function of time. The measurement took place for all three planes of the machine (xy, yz, zx). This data was processed into graphs and tables for a better clarity of the entire issue. The last measurement labeled B11(xy, yz, zx) was analyzed in more detail, as it was used for further analysis of possible symbiosis. To determine the working accuracy of the machine tool, control samples marked V(xy, yz, zx) were designed. These samples were produced on the DMU 50 milling center in six pieces for each plane. Sample production took place immediately after the last measurement with the Ballbar system for the most accurate possible comparison of both methods. After manufacturing the control samples, they were measured on a Wenzel LH 65 three-coordinate measuring machine. The samples were clamped and measured in the same way as they were made in the machine tool, including the exact position relative to the axes. This measure ensured that the same values were obtained for both measurement methods. From the six samples of each plane, one was always selected for further analysis of the possible symbiosis of both accuracy measurement methods. In conclusion, it can be said that symbiosis between working and geometric accuracy of machining centers is possible. In conclusion, there are several recommendations for further research in this area.