| More processing varieties and higher production efficiency are the salient features for flexible production line, machining centers undertake quite a number of critical processing content as the core part of the entire production line. Once problems with the stability of precision of machining center take places, It will directly affect the normal operation of the entire line. Therefore, it is very necessary to carry out structural performance analysis, optimization and analysis of the machining characteristics on the machining center. In fact, not only the producers pay more attention to the ability of stability of precision in the design and production phase, the purchasers value it a lot at the time of acceptance.Based on sub-topic "the stability technology of precision of machining center" from topic national science and technology project-" Xichai flexible production line demonstration project of heavy-duty diesel engine block, cylinder head ", there are two main aspects of work are done combining engineering theory and actual production. Firstly, the analysis of static and dynamic characteristics and structural optimization on the column are carried out as an example (below1,2). Secondly, the machining characteristics of the machine is analyzed (below3,4), including the milling chatter stability domain analysis which is related to the surface quality and stability assessment of machining center for the processing accuracy (size, shape and position). Details of the work are as follows:(1) Finite element analysises of dynamic and static qualities for column are completed, including static analysis, free modal and constrainted modal analysis. Then hammer modal test experiment is conducted aim at the actual column structure, at last the modal test results and computer free mode modal analysis results were compared and analyzed.(2) Structural optimization is done for the column structure. Hyperworks software is used for topology optimization of the column based density method to obtain the conceptual column model. Then ANSYS finite element analysis software is used for size optimization of column model based on response surface method. The results are analyzed and provide a theoretical foundation for improving the column structure.(3) Chatter stability problems of milling process are analyzed for the processing content of process OP100.2in the production line. Hammer modal test is conducted on the milling cutter-spindle system of machining center, the natural frequency, stiffness and damping ratio of the system are obtained. Then milling force simulation experiments are conducted using the Deform software to get the milling force coefficient of the tool. Based on the two results above cutter chatter stability lobe diagram is built to guide the selection and improvement of cutting parameters:spindle speed and depth of cutting, and preventing the occurrence of chatter behavior.(4) Cmk(machine capability index) is used to describe the level of stability of precision quantitatively for machining centers. Trial cut is performed on a set of work piece, accuracy results are obtained by detecting on coordinate measuring machine. Cmk values are obtained by analyzing the two sets of test data and then be analyzed. |
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