Research On High-intensity Focused Ultrasound-assisted Electrochemical Machining Technology

With the increasing requirements of modern industry for a smaller and more integrated product,the manufacturing industry is faced with a huge challenge and traditional machining methods are no longer able to meet the requirements.Electrochemical machining,with theoretical ion-class machining accuracy,is widely used in aerospace,medical devices and precision moulds for its unique advantages of non-contact,no cutting forces and no wear and tear on tools.However,this technology requires a high rate of electrolyte renewal and removal of electrolytic products in the machining gap.Conventional electrochemical machining techniques often use high speed flushing to renew the electrolyte in the machining area,while high speed flushing in electrochemical micromachining(EMM)can lead to severe electrode shaking.Therefore,the search for a method that can effectively increase the product removal rate in microelectrochemical machining is key to promoting the widespread use of EMM.In this paper,we propose a method of using High Intensity Focused Ultrasound(HIFU)to assist EMM based on the characteristics of microelectrochemical machining in combination with the HIFU technology.The effect of HIFU on bubbles and insoluble products in the electrochemical machining area was investigated in depth and the main work is summarised as follows.(1)The basic principles of electrochemical machining,the basic properties of ultrasound and the various acoustic effects(acoustic flow,acoustic radiation force and acoustic thermal effects,etc.)during the propagation of ultrasound are introduced.The forces on electrolytic products(bubbles,insoluble products)in the standing wave acoustic field are also analysed.At the same time,COMSOL Multiphysics simulation software was used to simulate the acoustic pressure distribution and acoustic thermal effects at the focal point of the HIFU under different conditions.The feasibility of the method for improving the product removal and processing efficiency was demonstrated in principle,providing a theoretical basis for the selection of the HIFU frequency and electrode size in subsequent experiments.(2)In order to reduce the influence of bubbles on the ultrasonic transmission and to provide easy focusing and observation,a vertical upward processing method of the electrode was determined and a processing system was built to meet the requirements.(3)The observation experiment was designed to study the motion of processing products(bubbles,insoluble products)with or without HIFU assistance.The observation results show that the morphology and motion state of the electrolysis products are obviously changed under the action of HIFU.When there is no HIFU,the electrolysis products will seriously accumulate in the machining gap,and the electrolysis products can be removed smoothly under the action of HIFU,which proves that the assistance of HIFU can effectively improve the removal rate of electrolysis products.(4)In order to investigate the effect of high intensity focused ultrasound on the characteristics of microfabrication,experiments were designed for micro-pit,micro-hole and micro-groove machining with/without HIFU assistance.In the micro-pit process experiments without electrode feed,it was found that the application of HIFU significantly enhanced the product removal rate when the product was difficult to be discharged in conventional processing.The application of HIFU to the micro-hole process made the process easier to short-circuit,which is thought to be due to the product collecting in the hole at depths greater than a quarter of a wavelength.The application of HIFU to micro-hole with depths less than a quarter of a wavelength increased the efficiency of the process,as evidenced by the fact that the maximum feed rate for conventional electrochemical machining was only 2.8?m/s,whereas the maximum feed rate for HIFU application was 3.2?m/s.