Analysis Of Characteristics For The Complete Set Of High-Precision CNC

Based on the demand of engineering practice, the research for machine characteristics of precision machining center is of great significance. This article relied on the topics of "High-precision CNC machine tools and basic manufacturing equipment" which is one of the major projects of national science and technology. From theory, simulation and testing, we analyses the static and dynamic characteristics of the machining center MDH65. The purpose is to improve the performance of vibration resistance for the whole set of high-precision CNC.This article regarded tool-machine-work piece as a flexible system. By introducing the relative vibration principle, the concept of the relative dynamic stiffness for the complete set of machine is proposed. It systematically exposed the principles, methods, test systems and test process of the machine relative dynamic stiffness test for the complete machine. The results showed that the method is effective, and certified it is a new way for the dynamic characteristics study of the complete set of machine. The main work of this paper can be summarized as follows:1. The relative vibration displacement between the cutting force and tool when complete set of machine elastic system is exciting is analyzed. Based on the relative vibration displacement between the tool and the workpiece, put forward the concept of relative dynamic stiffness, presents its mathematical expression, clarify its physical meaning and provides a theoretical basis for the performance evaluation of the relative excitation test and the whole machine tool vibration resistance.2.For the finite element analysis being more accurate, collecting the data in the spot with the experimental method, using the identification method of response data modal, the contact stiffness and damping ratio of the contact surface have been obtained, which provides necessary parameters for simulation analysis.3.Replacing the combination surface with spring damper element, undertook the analysis of static stiffness and the stiffness weak links were found; Get the natural frequency, damping ratio and the corresponding vibration modes through the modal analysis; Obtain the machine displacement response under the dynamic cutting force by harmonic response analysis; Combining the dynamic cutting force and displacement response curve, we obtained the simulation dynamic stiffness of the end surface of the spindle and work surface. Under the guide of the relative theory of vibration, we also obtained simulation relative dynamic stiffness of the whole set of machine. By analyzing and comparing, we discovered that column, spindle and spindle box of vibration have a large impact on the overall.4. According to the concept of the dynamic stiffness, based on the real-time processing, put forward a relative dynamic stiffness test method for machine tool self-excited vibration; build the overall relative dynamic stiffness test system; we did the experiments in the drilling condition, and the dynamic flexibility curve is obtained. The consistence of simulation and test results shows validity and accuracy of the relative dynamic stiffness test method, and which made further assurance that the column is the weak link.5. To improve dynamic capability of parts of the machine tool and reduce or eliminate the interference source from inside and outside, put forward vibration suppression scheme. On suppressing vibration of the processing center for relative dynamic stiffness test, dynamic characteristics of the machine are improved obviously which proved the effectiveness of the vibration suppressing effectiveness.