Research On Removal Stability Of Atmospheric Pressure Plasma Processing And The Figuring Of Axicon Optics

Atmospheric pressure plasma processing(APPP)is an efficient and low-cost deterministic machining method,which can achieve the nondestructive machining of precision optical elements with high precision.However,its removal stability seriously restricts the further improvement of machining accuracy.To solve this problem,this paper uses modeling and simulation methods to deeply explore the working characteristics of plasma,and further studies the factors that affect the removal stability of APPP.On the basis of the above research,a preliminary experimental study on the figuring of axicon optics by APPP is carried out.Firstly,according to the composition of RF plasma generating system,the corresponding impedance matching network model is established.Based on the principle of maximizing the output power of the RF power supply,the optimal impedance matching point of the matching network is derived.The simulation model of plasma impedance characteristics is established and the influence of machining distance and power variation on plasma equivalent impedance is studied.Considering that the essence of APPP is chemical etching,the simulation model of particle concentration distribution in discharge area is established.The results show that the concentration distribution of different active particles on the workpiece surface is Gaussian.Then,the factors that affect the removal stability of APPP are studied experimentally.The experimental results show that the power fluctuation mainly affects the removal depth,but has little influence on the full width at half maximum(FWHM).The influence of electrode material and coating thickness on removal stability is compared,and the electrode with better removal stability is selected.The influence of the position of the ground electrode on the removal stability is studied.It is found that the mean value of the removal depth of different positions is significantly different.Through analysis and experimental verification,it is proved that the extra inductive load caused by the irregular grounding of ground electrode is the cause of the above phenomenon.At last,the figuring experiment of the axicon optics by APPP is carried out,and the reason of error is analyzed.According to the previous research results,the simulation and prediction model of the surface removal function of the axicon optics is established,and the surface shape error introduced by the gaussian removal function assumption is analyzed.A dwell time solution model for the axicon optics is established by using the linear equation,and the regularization factor and additional removal quantity are introduced to optimize the solution of the model,which effectively reduces the proportion of negative values in the dwell time solution and the residual surface shape error.