Fabrication Of Micro Punching Mold By Micro-EDM

The trend of product miniaturization increases the demand for micro parts, which also requires the development of efficient micro-manufacturing technologies. Micro punching is such a promising process due to high production rates, low cost, good quality and superior mechanical properties of the formed parts. The challenge in application of micro punching process comes from the fabrication and accurate alignment of micro punching tools. Micro-EDM is capable of machining a variety of complex three-dimensional (3D) micro-cavities in any electrically conductive materials. Besides, this technology can be implemented on-line to realize the concept of on-the-machine tool fabrication. All of those above make micro-EDM become an ideal process for manufacturing micro punching mold.A novel process of producing micro punching mold by micro-EDM was proposed in this paper. An experimental platform was set up for studying this process, and its control system was developed based on LabVIEW software. Micro die and reverse electrode were prepared by micro-EDM milling. The micro punch was prepared by reverse-EDM. To improve the machining efficiency, ultrasonic vibration was applied to machining fluid to help the removal of debris. The total process was implemented on-line to avoid clamping error. The machining gap of reverse-EDM was confirmed by trial machining experiment, in which a micro punch with square shape and small area was machined. Compared with reverse-EDM, the movement of the electrode in micro-EDM milling is more complex. According to the different shapes and design sizes of micro die and reverse electrode, trial machining experiments were designed respectively to confirm the machining gaps. Based on the values, micro punching molds with square shape and complex shape were produced successfully.Machining results of micro punching molds were analyzed in this paper. The taper of machined feature is due to the electrode wear and secondary discharge during micro-EDM. The random machining errors in Y direction are caused by the thermal deformation during a long machining time. The structure of the experimental equipment in this direction is similar to a cantilever. According to the causes of the machining errors, the mold feature sizes were divided into two categories and measures were proposed to control the machining accuracy. On the basis, the machining quality can be improved by control the machining error range and change the design size of the mold.Based on the micro punching mold with square shape, the mold assembly process was researched in this paper. The alignment of micro punch and micro die can be realized by the coordinate transformation. According to the analysis, the method which is based on detection in electrical contact method can be influenced by many factors, such as process fillet, machining taper of micro punch, machining accuracy of micro mold and debris. This paper provides a foundation for the further research of micro punching.