Flexible Punch Ultrasonic Micro Stamping Technology In Sheet-metal Forming

Flexible punch micro ultrasonic sheet-metal forming is a new technologic method in manufacturing micro sheet metal parts. In this method, plastic powders in a stock bin are crushed and rubbed under high- frequency vibration and excitation of an ultrasonic head, then fused into a viscous fluid medium under high temperature and formed a flexible punch, through which the main pressure of the ultrasonic head is transmitted to the thin metal blank, which is extruded into the die cavity, forming the thin metal sheet.This method using plastic powder formed flexible punch under the action of ultrasonic wave, instead of the traditional rigid punch in experiment, which is hard processing and difficulity to accurate alignment. At the same time, it comprehensive the advantages of viscous medium forming and ultrasonic forming. Used as a viscous medium in the forming process, molten plastics can improve the deformation uniformity of the sheet, delay material necking, and increase the forming ability. Additionally, molten plastics were used as a flexible punch to transmit a part of the ultrasonic vibration to the thin sheet metal and die. This provided the advantages of ultrasonic forming, such as decreasing the friction between the blank and die, and reducing the flow stress of the blank. These unique advantages enable the method has high research value and application prospects.This dissertation discussed the influence of process parameters of the Micro-USF for micro-part's replication capacity, and studied some problems in sheet- metal micro bulging and micro deep drawing process. The main work of this dissertation includes:(1) Improving the forming experimental platform, studing the influence of the experiment conditions and process parameters to the forming ability of the micro parts, analysising process parameters of the experimental platform and determin ing the optimal time parameters. Experimental studies have shown that, according to the temperature test of plastic powders during the time of ultrasonic loading and unloading, it can determine the optimal time parameter. When the ultrasonic amplitude is 32.7?m, setting the ultrasonic action time on 0.5s and pressure duration time on 1.5s, the flexible punch molding quality is the best, so it is a set of optimal parameter.(2) The influence of process parameters on the forming of parts by micro bulging experiment. In this paper, we use of different thickness by annealing of T2 copper sheet for forming materials to study the influence of process parameters on sample forming ability, which including the main pressure of the ultrasonic head, ultrasonic action time and pressure duration time. Experimental studies have shown that, when ultrasonic action time is less than 0.5s, the pressure duration time is less than 1.5s and the pressure below 0.3MPa, with the increase of these three parameters, the parts becomes better. For the only a few hundreds micrometers of the channel, The replication capacity of samples can reach up 98%, showing the strong forming ability in micro bulging process. Additional, the phenomenon of sample rupture in the process of micro bulging experiment are analysed. After improvement, the sample can be easily formed.(3) Micro deep drawing experiment. This dissertation using two kinds of micro drawing dies, the box sides of 2mm and cup diameter of 500?m, studing the experiment of the micro deep drawing process in micro-USF method. In the process of the experiment, the preparation of the blank, the deviation and breaking of sample are analyzed, and the improved scheme of these problems are put forward.