Quality Evaluation And Application Of Flexible-punch Micro-ultrasonic Sheet-metal Forming

With the rapid development of the product towards micromation, the demand for micro parts is also increasing rapidly. In the field of micro-stamping, traditional mechanical methods are more difficult to the smaller size due to the difficulties such as micro mold processing, punch and die for medium, new technology of micro-stamping machining such as the laser and electromagnetic forming has still some problems to be solved at present. It is an effective way to look for a new micro-molding method that develops the micro sheet metal parts, and further reduces the size of the part.The research group proposed a new micro-stamping method in 2011 – “ultrasonic micro forming methods of flexible punch in the metal sheet”. Based on the previous work of the research group, the paper further studies the application of this method in a variety of micro-stamping process, as well as process improvement and other issues. Experiments and research results show that this method could be used for micro embossing, micro deep drawing, and has wider adaptability. At the same time, the small parts forming ability and the unique advantages of the method also forebode the high research value and good prospects. The main work of the paper includes:(1) Improving the forming experiment platform to further, preparing single mold required for the experiment. The original experiment platform conducts appropriate improvements to conform to the various needs of this thesis. Meanwhile, exploring different micro mold manufacturing method, preparing for a variety of different shaped micro-mold experiments required.(2) Forming sheet metal heat treatment and mechanical testing. Explore suitable heat treatment process parameters, prepare the blank with different grain sizes, thickness grain size ratio, access to basic parameters of the mechanical properties of thin dough by stretching experiments. Experimental results show that as the grain size reduces, the corresponding thickness grain size ratio increases, and the material yield strength, tensile strength, elongation increase; The yield strength and tensile strength of the material after heat treatment decreases, elongation rate increases, more conducive to stamping.(3) Micro-embossing experiments. Study these two key parameters ultrasonic vibration time and dwell time, which have a significant impact on the quality of parts forming, and replication capacity of the mold fine structure by the method. The results show that when ultrasonic vibration time is 0.5s and dwell time is 1.5s, micro structure parts with the size between 200-800μm using the method, its shape replication is up to 98%. The tiny uneven structure of the mold surface size smaller than 50μm, its shape replication is close to 84%. This indicates that it has a strong shape replication ability when the method is applied to the imprint process. Through a lot of experiments, obtain a set of optimal parameters. Meanwhile, some defects and causes of the existing parts, also conducts a preliminary analysis.(4) Micro-bulging experiments. Study influence of parameters on the forming such as power, ram pressure, ultrasonic vibration time and material thickness. The results show that, within a certain range, with power, ram pressure, ultrasonic vibration time increase, the parts forming becomes better; the thinner the thickness of the material, the stronger the ability to replicate.(5) Micro deep drawing experiments. Experiments research the feasibility and the existing problems of the method applied in the micro deep drawing process, and putting forward the improved scheme for problems.