| Cemented carbide is a kind of superhard material,which is widely used in mechanical manufacturing,especially in aerospace,biomedical instruments,die manufacturing and other fields.Due to its extremely high strength and hardness,mechanical grinding of its material surface will cause damage to grinding wheel,and a large amount of heat generated during grinding process will lead to grinding burns and changes in metallographic structure of workpiece,affect the performance of cemented carbide.EDM technology relies on pulse spark discharge between tool and workpiece electrodes to remove workpiece materials,although it is not limited by material strength and hardness,its processing efficiency is low and the surface quality after processing is poor,not conducive to efficient and high-quality processing of cemented carbide materials.In this study,a method of ultrasonic assisted EDM grinding is proposed,which is to introduce ultrasonic vibration and electrode rotating motion on the basis of EDM to strengthen the medium circulation in the discharge area,improve the processing efficiency and improve the surface quality of the workpiece.Therefore,it is of great significance to develop an ultrasonic EDG device.The research contents are as follows:(1)The overall design of the ultrasonic EDM grinding device,including the design of the electronic control system and device structure.According to the design scheme of the device structure,the main components involved in the transmission system and power system of the device are selected and checked,and the ultrasonic horn and the whole device are structurally designed,drawing the three-dimensional model of the device and introducing the assembly relationship,complete the development of the device.(2)Developed a set of EDM electronic control system,which consists of two parts:pulse power supply and gap control system.Based on the design requirement of pulse power supply,three processing states,coarse,semi-precise and fine,are designed by using controllable RC pulse power supply,and the performance of these three processing states is experimented.Based on the design requirements of the gap control system,the design method of the full hardware circuit is used to detect the gap state in real time and quickly,and is controlled by the single chip microcomputer,drive the stepper motor feed and retreat according to the detection result of the gap state,the automatic control of clearance state is realized.(3)The processing experiment of cemented carbide was carried out by using the developed ultrasonic EDG processing device.The influence of different electrode materials on the electrode loss is explored in order to find a kind of high efficiency and low loss electrode material for a long time grinding experiment.At the same time,the influence of current and electrode speed on surface roughness and material removal rate of cemented carbide workpiece is studied.The results show that with the increase of current,the material removal rate increases,and the surface roughness value increases.With the increase of electrode speed,the material removal rate increases,but the surface roughness value decreases.The results of comparative experiments under different working conditions show that ultrasonic EDG can significantly improve the processing efficiency and surface quality of the workpiece.The device developed in this paper has the characteristics of small size,low cost,high processing efficiency,adjustable pulse energy and good processing stability,it can provide support for the following research on surface removal of cemented carbide materials. |
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