| Nuclear fusion energy becomes the ideal energy of human beings because of thecharacteristic of inexhaustible and clean. KDP crystal is an essential element in nuclearfusion device which is used to achieve optical switch and doubling frequency, butmicro-pits, micro-cracks and other defects would be appeared in the surface of KDPcrystal components after the continuous irradiation of the laser. Micro-milling isrecommended as a promising method by the experts at home and abroad because of itscharacteristics of high flexibility. When cut the KDP crystal, it has special requirementsto the geometry parameters of micro ball end mill for the characteristics of the softbrittle property, so this paper would work out the geometry parameters of rake angle,clearance angle and the cutting edge radius for micro ball end mill through simulation;Then introduct the manufacturing process of micro PCD ball end mill; The last, theexperiments are carried out to verify the cutting and repair performance of self-designed and manufactured micro PCD ball end mill.This paper designed two micro PCD ball end mill, micro flat rake plane-type ballend mill and micro rotary symmetry plane-type ball end mill, after considering both themanufacturing processability of micro PCD ball mill and the material properties of KDPcrystal. The3-dimensional finite element models of the self-designed micro PCD ballend mill cutting the KDP crystal were built, and minimum feed speed effect, cuttingforce and the stress distribution of tool and workpiece during the cutting simulationhave been studied. Then work out the best geometry parameters of self-designed micromills by detecting cutting force and the stress distribution of the micro mill andworkpiece in the cutting process of simulation model. The best rake angle, clearanceangle and cutting edge radius for micro rotary symmetry plane-type ball end mill are-45,45and5m respectively, and for flat rake plane-type ball end mill, it’s-35and12respectively. The dynamic performance of self-designed micro mill was analyzed,good dynamic performance has been achieved, and the smaller overhang volume of mill,the larger possible to prevent resonance. Manufacturing the micro rotary symmetryplane-type ball end mill, however, due to the limitation of grinding equipment, the rakeangle of micro ball end can only be less than-70.The influence of cutting parameters on KDP crystal’s cutting result was studiedthrough the simulation, and realize that P-V value of cutting force is increasing as theincrease of feed rate and milling depth, and the decrease of the spindle speed. It canprovide a reference for subsequent experiments, so guided by the results above, themilling experiments of microgrooves were carried out to explore the cutting parameters of KDP crystal material’s ductile cμtting region. Resμlts show that the spindle speed andthe swing angle of spindle have great inflμence on the sμrface qμality of microgrooves,and the larger valμe was preferred; While the feet rate and milling depth have littleinflμence on the sμrface qμality of microgrooves, and the milling depth wasrecommended to select a small valμe, and feet rate was recommended to select amoderate valμe. Self-designed and NS micro ball end mill were used to conductorthogonal experiments of microgrooves, and the preliminarily cutting performance ofself-designed micro ball end mill was verified by comparing the morphology andsurface roughness of machined microgrooves that the Ra value of microgroovesprocessed by self-designed micro ball end mill is smaller than the microgrooves whichwere processed by NS micro ball end mill. The last of the paper, self-designed and NSmicro ball end mill were used to repair the defects in the surface of KDP crystal, the Ravalue of repair outlines processed by self-designed micro ball end mill is larger than therepair outlines processed by NS micro ball end mill, which may be due to the oversizeof rake angle and roundness error of cutter blade. |
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