Simulation And Experimental Study Of Flow Field Particles In Short Arc Milling

Short arc milling is under the action of a certain proportion of gas and liquid pressure.In the process of EDM,the working medium in the discharge gap between the workpiece and the tool will be broken down to form a discharge channel,which will produce obvious arc effect in the channel.The high temperature generated by the arc will transfer to the workpiece surface along with the channel,under the impact of the mixed medium of water and gas.It is a kind of non-contact special processing that the melted part is solidified into particles and separated from the matrix to achieve the function of removing the workpiece.In the process of machining,the movement and distribution of the eroded particles in the machining gap will affect the material removal rate,electrode loss rate and other important factors.If the erosion is not removed in time,the particle accumulation will increase the electrode loss,reduce the surface processing quality,seriously short circuit,and burn down the machine control system.Therefore,it is of great significance to study the particle erosion not only for convection field,but also for further revealing the processing mechanism.First of all,through a series of comparative experiments,it is concluded that tungsten copper and graphite materials are better than copper materials in the integrity of the work piece;the electrode rotation has a significant current change amplitude relative to the static of the electrode,that is,the heat generated by the arc in unit time is higher,which is conducive to the material erosion and separation under the effect of axial force;according to the discharge theory analysis,the arc plasma in different polarity States The external forces on the body are different.Combined with the experiment,it is proved that the integrity of the tool and the removal rate of the material are more in line with the actual needs when the positive polarity processing is used.At the same time,the gas-liquid mixed medium is more conducive to transforming the pressure ionic state to form the arc channel under the voltage breakdown,which provides the experimental basis for the subsequent processing.Secondly,by using the commonly used simulation software FLUENT,a two-dimensional model is established,which is consistent with the actual situation.The flow field characteristics of machining depth,electrode diameter,inner hole diameter and workpiece material are studied.The distribution of pressure field,velocity field and particle concentration in the flow field of machining gap is analyzed,and the influence of each factor on the gap flow field,machining efficiency and electrode loss is discussed.A series of comparative experiments were carried out to study and verify each factor,machining efficiency and electrode loss.Finally,the electrode fixture in the short arc milling machine tool is modified,and the particle collecting device is designed.The particle shape produced under the factors of polarity effect,tool characteristics,electrode speed,voltage,duty cycle and frequency is explored through experiments.The microstructure and surface chemical composition of the collected particles are observed by scanning electron microscope,and the short arc machining material is revealed.According to the characteristics of material removal,the influence rules of different parameters on particle diameter are calculated by MATLAB,and the removal mechanism of short arc material is revealed from the point of view of particle.