Machining Accuracy Evaluation And Process Optimization Of The Original Mold Of An Optical Functional Film With A Triangular Pyramidal Texture

With the increasing maturity of ultra-precision machining technology,the preparation of functional textured surfaces has become a research hotspot in the field of precision machining.The texture on the surfaces of the original mold can be copied to the thin film to form the optical functional textured film in a large area and at low cost by electroforming and imprinting technology.The processing error of the original mold will be directly copied on the working mold during precision electroforming,which will affect the manufacturing accuracy of the optical functional textured film.Therefore,the processing accuracy of the original mold has become the main factor restricting the improvement of the optical performance of the optical functional textured film.This thesis analyzes the problem that restricts the processing accuracy of the original mold of an optical functional texture film with a triangular pyramidal texture,and proposes an optimization scheme for the cutting process to improve the chip morphology.Firstly,the formation mechanism of the Poisson burr at the cut-in end and the positive and negative exit burr at the cut-out end was explored.According to the characteristics of the original mold for planing the triangular pyramidal texture by the forming method,the influence of the change of the cross-sectional area of the cutting layer on the edge burrs was theoretically analyzed.According to the distribution characteristics of edge burr,the ratio of effective optical function area was proposed as an evaluation index of original mold for machining accuracy.Secondly,the chip morphology and the maximum stress distribution were established through the cutting simulation of the original mold with the triangular pyramidal texture.The corresponding relationship formed by the edge burr,the trajectory method and the single-edge method processing schemes were proposed and the cutting process parameters were optimized;Finally,the optimization results of the 3D cutting simulation process parameters were applied to the cutting experiment of the original mold.The dimensional accuracy,shape accuracy,and surface roughness of the original mold under different processing schemes were detected,and the effective optical function area ratio of the original mold was calculated according to the size of the edge burr,so as to obtain the optimal processing scheme.The results indicate that the Poisson burr is mainly distributed on the cut-in edge,the positive exit burr is mainly distributed at the bottom of a texture unit,and the negative exit burr is mainly distributed at the middle of the cut-out edge.The forming method always has the problem of chip interference.The chip formation is characterized by a raised layered structure in the middle,and the size of the edge exit burr on the inclined side of the chip is larger.The proposed trajectory method and single-edge method can not only reduce the chip thickness but also improve the chip interference phenomenon.The simulation and optimization of the cutting process parameters show that the cutting speed has a little effect on the edge burr size.However,with the increase of cutting depth,the edge burr size of the three machining schemes shows a trend of decreasing first and then increasing.And the edge burr size of the trajectory method and single-edge method is always smaller than that of the forming method.When the original mold with the triangular pyramidal texture is cut by single-edge method,the ratio of effective optical functional area K_s is 10.1%higher than that compared with the original mold cut by forming method.The minimum average value of the surface roughness Ra of the triangular pyramid side surface cut by the single-edge method is 12.64nm.The proposed ratio of the effective optical functional area provides an evaluation index for the processing accuracy of the original mold of an optical functional film with a triangular pyramidal texture,and can indirectly reflect the optical properties of the optical functional film with a triangular pyramidal texture.The proposed single-edge processing strategy can solve the problem of edge burr caused by chip interference and provides an important theoretical basis and engineering application guidance for the preparation of high-precision original mold with an optical functional texture.