Development And Research Of A CNC Micro-milling Machine Tool System

The applications of micro-cutting processing technology to the machining of 3D precision micro components evoked the great technological revolution in the field of micro-manufacturing. Differed from the MEMS and ultraprecision machining processing, it is a novel effective way using traditional machining method to manufacture micro- and meso-scale components with efficiently and high precisely. The ultraprecision machine tool is fundamental equipment to fufill micro-cutting technology. At present, it is at the initial stage of the domestic study on the special micro-cutting equipments. It is deficient in comprehensive research from system project to performance evaluation on the development of micro-cutting machine tools. Furthmore, although many practical systems have been developed abroad, most of them are trial and keep technical secret to our country. In this dissertation, the key technologies for constructing a miniature CNC micro-milling machine tool are studied deeply and its main technical performance effectting the machining precision of the parts are evaluated systemically. The main creative achievements are as follows:1) A 3-axis linked miniature CNC milling machine tool system was successfully constructed for manufacturing of micro procucts. The machine has a base size of 300 mm×400 mm×500 mm and the size of XYZ workspace is 50mm×50mm×20mm. With a full closed loop numerical control system of 0.05μm resolution installed in feed axis, it bears the capability of submicro scale machining. The machine tool is equipped with available high speed air spindle, precision stages uphold by cross roller-bearings with each axis, PMLM(Permanent Magnet Linear Motor)and IPC-based multi-axis motion controller. Under the techniques of optimized path interpolation and error compensation, it performed the micro machining of components including the micro straight slots, micro concentric circle slots, thin walls, micro grars and micro sphere shapes. Test results indicate that the milling machine tool implements the capability of machining meso-scale 3D components of high-aspect-ratio.2) Combining the multi-body system theory and homogeneous transformation matrices, the analysis of volumetric errors was made on the built machine tool mechanical body. The synthetic volumetric error model of the machine tool was presented. Then the volumetric error parameters of machine tool were obtained by means of measurement and were compensated using synthesis dynamic compensation methodology.3) A method of robust parameter analysis based on loss model to the machine tool optimization of structural design was proposed. It provides a mathematical base of the machine tool structural optimization design. And using it, the minimization of the machine tool design errors was obtained.4) The direct drived characteristic of micro-feeding platform was studied. And the single axis servo control performance of the machine tool was analyzed based on the established mathematical model of linear actuator. A satisfying control strategy was proposed based on PI position controlling algorithm combining the speed and accelerated speed feedback controller and notch filter. Furthmore, based on analyzing the multi-axis contour error of machine tool, a cross-coupled controller which fits for the linear motor drived micro feeding platform was presented in the dissertation.5) The micro milling performance of the machine tool system was studied according to the analyzing of the micro milling mechanism based on the minimum cutting thickness theory. A series of experiments have been conducted in order to verify the proposed theory and characterize the key factors affecting surface roughness. Moveover, a lot of milling tests of micro parts on the machine tool proved its capability.