Fundamental Research On Machine Tool, Cutting Tool And Cutting Mechanism For Micro-Milling

The academy and industrial field at home and abroad pay more attention to micro-milling technology because of its comprehensive advantages such as relatively better economy, the capability to fabricate complex three-dimensional shapes with variety of materials, etc. However, micro-milling is a new technology, currently the study of micro-milling machine tool is far from adequate, the micro milling cutter, the mechanism of micro-milling, micro-milling processing technique and other studies are also at the exploratory stage. Therefore, financed by the national Eleventh Five-Year Plan in advance to support aviation research funds (NO. 61901090302) and the National Natural Science Foundation of China (NO. 50775114), this dissertation focuses on micro-milling machine tool design and build, micro-milling cutter structural design and manufacturing, the size effect in micro-milling process, as well as micro-milling process optimization in the milling of miniaturized parts. The key research carried out in order to guide the milling process at the micro/meso scale, and lays the theoretical foundation for business applications of micro manufacturing technology. The main content in this paper may be summarized as follows:(1)A 3-axis micro-milling machine tool is developed and the CNC system of the parallel dual-CPU based IPC and Windows operating system is constructed. The developed micro-milling machine tool provides application platform and research object for further research of miniaturized machine tools and micro-milling theory. A mathematical model of servo parameters adjustment is established by considering the different characteristics of the linear motor driven platform under the position, velocity and torque control modes, and its precision movement control technology under high acceleration and deceleration is mainly studied. The test results of machined straight groove, thin-walled parts and the Archimedes spiral further validate the good processing performance of developed micro-milling machine tool.(2)A finite element model of micro-milling cutter is established according to micro-milling process characteristics, and the structural mechanics of micro-milling cutter is analyzed by loading on the surface. The modal, load distribution and the stress and distortion characteristics of micro-milling cutter is studied systematically. On this basis, the geometry of micro-milling cutter whose diameter is below 0.5mm is intensively research. The results indicate that the stiffness and strength of traditional spiral groove cutter is very low, which is easy to bend and break in milling process. However, the micro-milling cutter with triangular pyramid and other simplified geometric structure can get a higher stiffness and strength, and is more beneficial to the fabrication of micro-milling cutter and improvement of tool life.(3)A special micro energy pulse generator with the minimum pulse width of 125ns for machining micro-milling cutter is developed based on key technologies and theories of micro-EDM and the analysis of realization way. The crawling question in small displacement servo feed of servo system is solved by selecting the appropriate servo control strategy. At the same time, the special electrode and device are designed integrated with the characteristics of the micro-EDM. The manufacture precision of micro-milling cutter is improved by shaping its cutting edge on-line in the developed micro-milling machine tool.(4)A coupled thermo-mechanical model with cutting edge radius considered is used to simulate the process of two-dimensional orthogonal machining using commercial finite element software ABAQUS for the size effect in micro-milling process. The actual micro cutting process is studied by simulation model. The cutting temperature factors in size effect and the influence of the rounded cutting edge on size effect is studied deeply. Moreover, the intrinsic mechanism why the rounded cutting edge causes size effect has been sufficiently clarified.(5)In order to optimize the machining parameters to improve the processing efficiency and processing accuracy of micro-milling, the impact law of the spindle speed, axial cutting depth, feed per tooth, cutting edge radius and other parameters on cutting force, surface roughness and micro-burr is studied by milling characteristics experiments with typical micro three dimensional parts.