Experimental Study On Rotary Ultrasonic Machining Using Grinding Tools

Since hard and brittle materials which have low-ductility and high hardness, such as silicon, diamond, ceramic, optical glass, cemented carbide and hardened steels, have lots of excellent properties, they have been widely used in aerospace, aviation, automobile, metallurgy and machining industries. However, this type of materials are also difficult to be machined if using conventional machining method. As one of the cost-effective machining methods, rotary ultrasonic machining (RUM) is a hybrid machining process that combines the material removal mechanisms of diamond grinding and ultrasonic machining (USM). Its development makes it more easily to carry out the machining on these materials.The targets of this paper are studying the mechanism of rotary ultrasonic machining, the characteristics of cemented carbide by rotary ultrasonic machining, and adding the function of rotary ultrasonic machining to a conventional drilling (milling) machine. The contents of this paper are:(1) Quantities of experiments were conducted to investigate the characteristics of RUM. According to the feed direction and the part of the cutting tool contacted with the workpiece, three different machining types are classified as drilling, side grinding and face grinding. By analyzing the kinematics of diamond grits of the cutter, it is found that the reasons for the cutting force difference between with and without ultrasonic vibration are not same for the three machining processes.(2) In this study, four kinds of diamond tools were used for the grinding experiments on cemented carbide YG8, both with and without ultrasonic vibration. By using the white light interferometer and the microscope which has a large depth of focus, surface qualities of the workpiece were analysed. The experimental results show that: for diamond tools with big grain size, the surface roughness of the workpieces machined with rotary ultrasonic vibration are worse than these without rotary ultrasonic vibration. While the roughness differences between the workpieces machined with and without rotary ultrasonic vibration are not obvious if the grain size is small. Furthermore, compared with conventional diamond machining, it will be easier for rotary ultrasonic grinding to prevent the growth of cracks.(3)In order to accelerate the development of rotary ultrasonic machining in our country and solve the problems encountered during the machining process of hard and brittle materials, a rotary ultrasonic machining device is developed. By using this device, a conventional machining tool can be used to realize the function of rotary ultrasonic machining.