Study On Removal Characteristics Of Difficult Machining Materials With Bonnet Polishing By Robot-assisted

Tungsten carbide,titanium alloy and other materials,are widely used in molds,cutting tools,aeroengine blades and other occasions,because of their unique and excellent physical and chemical properties.However,they both belong to difficult to machine materials due to the hard texture of tungsten carbide and the high strength and toughness of titanium alloy.The bonnet polishing technology is a polishing method that uses the spherical cap bonnet as a polishing tool,the bonnet realizes the efficient removal of workpieces according to a certain precession mode.At present,the bonnet polishing has been well applied to the precision polishing of BK7,fused quartz and other optical glasses,as well as silicon carbide and other superhard materials,and has shown good processing flexibility and versatility.In order to make full use of the characteristics of high-efficiency and precision polishing of bonnet,and systematically study the processing characteristics of bonnet for difficult to machine materials such as tungsten carbide and titanium alloy,this paper takes industrial robots as the main body,builds a robot-assisted bonnet polishing system.Taking tungsten carbide and titanium alloy materials as machining objects,corresponding polishing experiments are carried out to verify the feasibility and reliability of bonnet polishing for such difficult machining materials,and put forward reasonable processing parameters and process flow.The main research contents of this paper include:(1)Based on the principle of bonnet polishing,a robot bonnet polishing system platform was built by ABB IRB4600 six-axis industrial robot and adopted the joint processing method of "sixaxis industrial robot + bonnet polishing tool".Pure rubber bonnet and semi-rigid bonnet were developed respectively to facilitate the polishing process planning and experiment of titanium alloy and tungsten carbide materials,according to the needs of flexible polishing and highefficiency polishing.(2)Taking the semi-rigid bonnet as an example,the removal function modeling and process parameters of bonnet polishing were studied.Based on Preston equation,the velocity distribution model and contact stress distribution model of semi-rigid bonnet polishing were established.Using the experimental method,the Preston equation coefficients are solved to realize the static removal function modeling,and then the two-dimensional convolution model of bonnet polishing is solved.The single factor experiment method was used to study the effects of the material removal efficiency and surface roughness by different process parameters,such as dwell time,precession angle,reduction pressure,spindle speed,bonnet pressure.(3)Study on removal characteristics of tungsten carbide by bonnet polishing.Complete the experimental preparation for tungsten carbide bonnet polishing,and carry out the bonnet polishing experiments of two different tungsten carbide materials(WC-8Co with binder and binderless WC-0Co)by using the characteristics of efficient removal of semi-rigid bonnet,such as the analysis of removal efficiency under different parameters,the analysis of surface roughness of polishing spots,the surface integrity experiment after uniform polishing,etc.Through the analysis of surface morphology and surface material composition before and after polishing,Thus,the process characteristics of tungsten carbide material polished by bonnet are systematically obtained.(4)Study on removal characteristics of titanium alloy(Ti6Al4V)by bonnet polishing.According to the characteristics of high strength,high toughness and easy scratching of titanium alloy,the combination of "semi-rigid bonnet + flexible pure rubber bonnet" was used to carry out the removal characteristics and surface integrity experiments of titanium alloy.Similarly,polishing s were finished of the preparation of titanium alloy,and carry out material removal characteristic experiment,uniformity polishing and other experiments.The experimental results show that the titanium alloy Ti6Al4 V can be pre-polished by semi-rigid bonnet and fine polished by pure rubber bonnet,so as to ensure the polishing efficiency and polished surface quality.In addition,the feasibility of bonnet polishing titanium alloy was further proved through the detection and analysis of the polished surface,chemical reaction and phase transformation.