Laminated Fitting Forming Of 3D Metal Micro-structure And Its Application

With the development and application of MEMS, micro-parts have been widely used in microelectronics, precision machinery, biological, medical and aerospace fields. However, it is difficult to use ordinary processing method to fabricate micro-parts due to their tiny size, weight very light. With the research in this field, it appeared a series of micro-machining technologies to fabricate the micro-parts and the main technologies include: LIGA/UV-LIGA, micro-EDM, micro-ECM, femtosecond two photon photopolymerization and femtosecond laser processing technology. These technologies have done good work on the fabrication of micro-parts. However, it is difficulty for these technologies to fabricate 3D micro-structure with a complex structure.Based this reason, A laminated fitting forming process of 3D metal micro-structure mold is proposed. The process is based on the laminated object manufacturing(LOM) and micro-double-staged laminated object manufacturing(micro-DLOM). The multi-layer metal foil 2D micro-structures can fit the preliminarily laminated 3D micro-molds. Based on the mentioned principle, the 3D metal micro-structure with a complex structure and unrestricted ratio of depth to width can be fabricated. This paper proposes the use of ultrasonic bulge-forming process to fabricate metal micro-bulging parts. This approach involves the ultrasonic plasticization of powder in a laminated die cavity and the subsequent formation of a molten resin bulge. A micro ultrasonic-powder-molding method(micro-UPM) is used to fabricate the micro-plastic parts.Under the support of National Natural Science Foundation of China(No.51175348、51375315、51405306), a fabrication process and application of 3D laminated micro-mold was studied in detail. The fabrication of 3D micro-mold, micro-bulging parts and micro plastic parts proved that it is a feasible and progressive technology. The details of the investigation are described in the following points:(1) To describe the change of the temperature field when femtosecond laser ablated metal films, Two Temperature Model(TTM) is solved by Crank- Nicolson method, thus one-dimensional temperature field is numerically simulated during the interaction between femtosecond laser and metal films. Through the analysis of numerical simulation results, a saturated power density and a saturated time are found during the interaction between material electrons and femtosecond laser photons. Factors which will influence the electronic- lattice energy couple time are also analysed and it is found that the laser energy density and electronic- lattice energy couple coefficient are the main factors to influence the electronic- lattice energy couple time.The other ends of the Cu foils to be processed should be bent upward and blocked with a stopper. The other ends of the Cu foils being processed should be fixed by a magnet holder. The processed Cu foils should be bent downward and blocked with a stopper. The innovation structure is conducive to remove waste when the 2D micro-structure is cutting for fabricating the 3D micro mold. The metal foil bending deformation is analyzed.(3) Based on the above metal foil bending structure, a combined forming process of a 3D micro-mold based on femtosecond laser cutting and micro electric resistance slip welding is improved. Firstly, 10μm thickness 0Cr18Ni9 stainless steel foils are cut by femtosecond laser to get 2D microstructure under 120 m W femtosecond laser power, 50μm/s cutting speed and 0.75μm cutting compensation quantity. Then, the foils are welded by micro electric resistance slip welding together to get the 3D microstructure under 0.21 V welding voltage, 0.2MPa welding pressure, 100 ms squeeze time, 10 ms welding time, and 160 numbers of slip welding. Experimental results show that the forming process could be a useful method to fabricate the micro-molds with good size accuracy and surface quality.(4) The fabrication of a 3D micro-mold based on WEDM and thermal diffusion welding is also proposed. The wire-cutting experiment is made to focus on studying the impact rule of wire cutting discharge voltage, discharge current and pulse width on wire cutting quality. The experiment is applied to research the impact rule of the thermal diffusion time and pressure in thermal diffusion welding. Through above research, the better technological parameters of cutting and welding are obtained to fabricate micro-mold with good surface quality, size accuracy and the overall mechanical properties.(5) This paper proposes the use of ultrasonic bulge-forming process to fabricate T2 copper foil microstructures. This approach involves the ultrasonic plasticization of powder in a laminated die cavity and the subsequent formation of a molten resin bulge. The experiment is made to focus on studying the impact rule of ultrasonic power, ultrasonic pressure and ultrasonic work time on the micro bulging-parts quality. Through above research, the better technological parameters of ultrasonic welding are obtained to fabricate micro-mold micro bulging part. The structure and dimensions of the micro bulging parts manufactured by the ultrasonic bulge-forming technique are mainly determined by the concave micro-cavity. Therefore, the proposed technique can be used for fabricating micro bulging parts with smaller size and complex structures. Moreover, this method avoids the incorrect location of the concave-convex dies, which is common in traditional techniques. Based on the previous 3D metal micro-cavity, the micro-plastic parts are fabricated to use the method of micro-UPM. The plasticizing mechanism of polymer melt under ultrasonic vibration in a die cavity is studied.