Structure Characteristics and Milling Stability Analysis for a Vertical Machine-Tool

• Main Authors: Bo-han Chen, 陳柏翰
• Other Authors: Shen-Yung Lin
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/38c48z

碩士 === 國立虎尾科技大學 === 機械與電腦輔助工程系碩士班 === 101 === Following the rapid growth of 3C industry and its continuous prosperity of products demanding quantities, the processing demands of related components must be particularly on high-speed and efficiency, furthermore, the multi-elements process is returned to employ the machine tool for cutting processing, thus, the demanding quantities of machine tool show a leapfrog growth. The key indexes of machine tools’ functions are high speed, high stiffness and high stability. If the stiffness and the dynamic characteristic of the machine tools’ structural body can be controlled, it will be helpful to reinforce the structural design manufacturing and to avoid the occurrence of structural resonance and vibration. The construction of database of cutting stability may provide the processors the preference basis of process parameters, and it will be helpful to develop the capacity of the machine tools, the promotion of the production rate and increasing the additional values efficiently. Thus, to develop the structural characteristics of machine tools, to construct the database of cutting stability, to predict the suitable combinations of process parameters and to allow users proceed the process under the stable cutting conditions are current topics and striving direction of machine tool manufacturers. The study mainly discusses the structural characteristics of upright processing Vertical center Machine and the stability of cutting in a practical manner. First of all, proceeding the numerical and the experimental model analysis of the processing center machine, discussing the natural structure frequencies of the processing center machine, damping ratios and vibration models. Through the experimental model analysis, obtains five major components and structural characteristics of the whole machine system and correct the numerical simulation analysis model to be equivalent to the actual structure, and takes it as basis for the following design modification of the structure. Then, proceeding the stiffness experiment of cutting tool-drive shaft to obtain the dynamic stiffness and the corresponding frequency of this subsystem, implementing the cutting stability prediction software CutPro, setting up the corresponding milling stability lobe diagram of which compose by process parameters of cutting tool types, workpiece materials and cutting conditions. These will be employed as basis to discuss the dynamic behavior of milling process. According to the stability earlobe chart, determining the milling parameters locate within the stable/unstable boundaries and through the the method of milling experiment, and getting milling parameters of dynamic milling forces, vibration frequency spectrum and Workpiece surface finish of the cutting tools, finishing the cross-determination of the existence of vibration by multi-phase cutting function parameters and verifying the prediction results of software analysis. The result of the model analysis reveals that there are 8 models in the range of axis rotation frequency are induced the structural resonance frequency easily, it must be avoided to use the speed of these vibration exciting frequencies when planning the processing conditions. For the milling stability analysis, the result of cutting force, vibration resonance frequency spectrum and Workpiece surface finis are helpful to determine the existence of vibration, it can be overcome by cross-determination and set up the determination standard of cutting vibration successfully. Efficient prediction of characteristics of milling machine tool can provide the processors the preference basis of process parameters and upgrade the efficiency of milling process effectively.