A new porous block sonotrode for ultrasonic assisted micro plastic forming

The micro plastic forming process (MPFP) was a developing method widely used for the fabrication of miniature metallic parts. A hybrid MPFP assisted by ultrasonic vibration could be helpful to reducing forming load and improve product quality. In the ultrasonic assisted MPFP, the ultrasonic vibration was usually superimposed on the forming punch but seldom on the workpiece although the ultrasonic vibration of the workpiece could improve the micro-formability of material more effectively. This phenomenon was partly due to the weight and random shape of the workpiece. To realize the ultrasonic vibration of the workpiece in MPFP, a new type of porous block sonotrode was developed in this study. The sonotrode could convert the ultrasonic vibration from longitudinal direction to normal direction and get uniform amplitude on the central square radiant surface. It could also excite the micro workpiece or mold with resonant vibration along the normal direction and was insensitive to the fluctuation of structure and weight of micro workpiece. The simulated analysis and experiment results show that the porous block sonotrode can excite micro workpiece with ultrasonic resonant vibration, reduce the average extrusion force over 15 % and increase the extrusion height over 85 %.