Research On Improving Surface Quality And Machining Recision Of PTFE Workpiece

In this thesis,PTFE material is used as the object of study,because of the weak rigidity and high elasticity of the material,it is difficult to process the precision workpiece.This thesis uses lathe machining,from the tool material,tool geometry Angle,cutting paRameters and methods to improve the rigidity of the material to conduct a comprehensive and systematic study,so that the surface roughness and machining accuRacy of the workpiece can be improved,the main research contents of this thesis are as follows:Firstly,the effects of material and tool cha Racteristics on surface roughness and machining accuRacy were analyzed.Develop the PCD turning tool geometry angle single factor rotation experimental prog Ram and build the experimental platform.According to the experimental results,the influences of tool Rake Angle,back Angle and tool tip arc Radius on cutting force,cutting tempe Rature and surface roughness and the causes of formation are analyzed.The effect of cutting force and cutting tempe Rature on the machining accuRacy and surface quality of the workpiece was concluded.The influence of cutting force and cutting tempe Rature on machining accuRacy and surface quality is obtained.The optimized geometric angle of PCD tool is 25 ° Rake angle,15 ° Rake angle and 0.6 mm tool tip Radius.Then,the optimized PCD turning tool is used to carry out the cutting paRameter experiment of PTFE workpiece.The orthogonal experiment method of three factors and four levels is adopted.According to the experimental results,the influence of cutting paRameters on three research objectives: cutting force,cutting tempe Rature and surface roughness is analyzed by using Range method.It is found that the back feed has little influence on the machining accuRacy,while the cutting speed and feed have great influence on the machining accuRacy.Secondly,the RBF Radial basis function neu Ral network prediction model is established by Isight software combined with the cutting experimental results,and the cutting paRameters are optimized by NSGA-? genetic algorithm according to the prediction model.Finally,three groups of optimal paRameters are Randomly selected for experimental verification.The results show that the error of prediction value obtained by Isight software is basically less than 10%,which meets the error requirements.The results show that the accuRacy and surface quality of PTFE workpiece processed by the Pareto paRameter set can meet the requirements,which can provide reliable guidance for the actual processing.Finally,the rigidity of polytet Rafluoroethylene is improved by liquid nitrogen freezing.The experimental results show that the surface hardness of the workpiece is increased by 1.68 times,the surface roughness after processing reaches Ra = 0.339 ? m,and the roundness of the workpiece is also improved.According to the experimental results,the correction formula of cutting error under liquid nitrogen condition is fitted.The experimental results show that the rigidity of PTFE is improved after liquid nitrogen freezing,and the machining avoidance phenomenon is reduced in precision turning,so that the workpiece precision and surface quality are improved.The research content of this thesis improves the performance evaluation system of PCD tool turning polytet Rafluoroethylene material,and provides a reliable reference for improving the machining precision and surface quality of PTFE workpiece.The turning method under liquid nitrogen freezing condition provides a new research idea and theoretical reference for the precision turning of other weak steel materials.