Research On Damping Boring Bar With Large Length-diameter Ratio

Manufacturing industry plays an important role in the national economic construction. It fully reflects the national creativity, competitiveness and overall national strength. With the development of China’s economic, production efficiency and machining accuracy of industry need to be put forward to a higher requirement. The development level of machinery manufacturing determines the growing speed of economic development in our country. Therefore, how to accelerate the development of mechanical manufacturing industry is very important. The inside hole processing plays an important role in mechanical manufacturing, and it is important to improve the efficiency and machining accuracy in boring process, so it becomes a significant subject in scientific research field. This paper uses the modern metal cutting theory as the background, and combines with the previous research content to verify by the experiment based on the theoretical research, meanwhile, looks for a kind of new method to improve the machining accuracy of boring bar processing.In general,the machining vibration won’t be apparent when the using boring bar with small length diameter ratio. But when the aspect ratio of boring bar is higher than 4, it is easier to generate the vibration in the mechanical processing. This phenomenon is created by the insufficient stiffness of boring bar, and the vibration trend will gradually become apparent. It will leads to the lower quality in the process. According to previous research results, when the aspect ratio of boring bar is 10, the deformation in machining process is 16 times higher than the deformation when aspect ratio is 4. When the aspect ratio of boring bar increases from 10 to 12, the deformation of boring bar itself will increases 70% in the machining process. So how to restrain the vibration in the machining process has become a very realistic topic.In the process of deep hole and high speed machining, the boring bar be simplified to a slender cantilever beam for its big length to diameter ratio. The machining accuracy of work-piece will be affected when using this boring bar because its long overhanging low-rigidity structure is prone to produce cutting vibration. A hole should be machined in the dynamic damping boring bar part to install shock absorber, which will affect the static stiffness of the boring bar. And the size of the damping piece is restricted by the radial of the boring bar, thus, the damped effect be affected. The shock-absorbing performance of damping boring bar will be limited due to the certain restrictions by application of single damping measures. So, many kinds of vibration reduction measures should be considered to suppress the vibration of the boring bar in cutting process. A damping boring bar with special structure of non-circular cross section and composite construction is designed to reduce the vibration in cutting process. Thus, the processing quality will be improved while the processing efficiency will be guaranteed.In this paper, the research content mainly includes:(1)The basic requirement of damping boring bar and the main vibration damping measures have clear and defined. And, the design scheme of the damping boring bar with compound structure has been given(2)The statics and dynamics model have been established. The mathematical expression of static stiffness, natural frequency, damping coefficient and the forced vibration amplitude have been analyzed and derived.(3)The finite element model of boring bar has been established in the software of ANSYS, and the modal analysis and harmonic response analysis have been carried out to verify the vibration damping performance of the damping boring bar with compound structure.(4)Finally, the parameter optimization, including damping core diameter and of the flat cutting size of the damping boring bar has been conducted to achieve the best damping effect.