Rearch On Geometric Design And Grinding Technology Of Micro-mill For Moulds Of Micro Lens Arrays

Micro lens arrays are widely used in aviation,aerospace and optics manufacturing industry for their unique optical properties,but it is difficult to achieve high efficiency and low cost process of the micro lens array with large area small size.Precision molding technology can effectively improve the manufacturing efficiency of the micro lens array.The forming quality of micro lens arrays depends largely on the geometric accuracy and surface quality of the moulds,therefore,the precision fabrication of the moulds of micro lens array is the key to manufacture the micro lens arrays with high quality.micro milling technology is an effective method to realize high efficiency and high precision process of the moulds of micro lens arrays with complex geomety for its unique advantages.The high-precision,high-quality and high-consistency requirements of the moulds of micro lens array with large area small size need micro mills with longer tool life and better milling performance,which bring more challenges to tool design and manufacture.In this paper,according to the machining features of the moulds of micro lens array,based on the micro milling mechanism and the tool design theory,the research on geometric design and grinding technology of micro mill for moulds of micro lens arrays is developed,the main research contents are as follows:1.The geometric characteristics of the ball part of the micro ball end mill with S shape are analyzed and the cutting edge curve,rake face and clearance face are optimized and modeled mathematically.The design principle of micro ball end mill for moulds of micro lens arrays is put forward,according to the machining characteristics of micro lens arrays.Two kinds of new micro ball end mills,micro ball end mill with straight edge and micro ball end mill with conical flank,are proposed and the mathematical models of the two new micro ball end mills are established using the differential geometry theory.Finally,the tool angles of the new micro ball end mills are deduced.2.Based on the kinematic principle of the six-axis CNC grinding machine,the transformation matrix between tool coordinate system and machine coordinate system is deduced.The grinding models of rake and clearance face are established,based on the equation of the helix with constant lead and interference condition.The overcut problem of the cutting edge when the rake face is ground using the cylindrical grinding wheel is studied and the influence factors and distribution law of the maximum overcut value are analyzed.The grinding apporach of the two new micro ball end mills are proposed and the trajectory of each axis of the machine tool is derived.The grinding model or grinding methods are verified by the grinding experiment and measurement of micro ball end mill.3.The effects of rake angle and relief angle on chip deformation,milling force and milling temperature were studied based on the finite element milling simulation.The effects on the milling force,tool wear and machining quality of the micro lens array of the relief angle are studied through the micro milling experiment on H13 hardened steel,and the conclusion can be obtained:the micro ball end mill with the relief angle 20~?is more suitable for machining micro lens arrays on H13 hardened steel.The milling performances of the three kinds micro ball end mills in micro milling process are analyzed contrastively,and the results show that the designed micro ball end mill with conical flank has smaller milling force and better machining quality.