| Compared with conventional metal cutting tools,the geometric structure and cutting mechanism of micro-cutting tools are quite different.High-speed steel,cemented carbide(including coating),ceramics,CBN,and diamond are the mainstream conventional metal cutting tool materials,while most of the micro-cutting tools are made of high-speed steel and cemented carbide,and ceramic materials are rarely used to make micro-cutting tools.Ceramics,as one of the candidates for tool materials,has high hardness,good wear resistance,and heat resistance.It can also meet the requirements of micro-cutting in theory,especially for difficult-to-machine materials.To solve the problems of insufficient wear resistance of cemented carbide micro-end mill,and coating peeling off,and insufficient edge sharpness of the coated micro-end mills,the cermet with comprehensive mechanical properties between cemented carbide and cubic boron nitride is used to manufacture micro-end mill,and the research on the material,design,and manufacture and cutting performance of micro-end mills are carried out.The general research idea is:taking the difficult-to-machine material TC4 titanium alloy as the workpiece,from the perspective of tool material preparation and mechanical properties,optimize the preparation of the cermet to suitable for making micro-end mill,and evaluate the mechanical properties and behavior of the cermet;From the perspective of tool structure design and manufacture,design the spatial geometry of the cermet micro-end mills with the diameter between 0.3 mm and 1.0 mm,and conduct structural manufacture research;From the cutting load point of view,demonstrate cermet material can meet the cutting performance requirements of the micro-end mill;From the application point of view,research on the cutting performance of the cermet micro-end mills in micro-milling of TC4 titanium alloy.This research can expand and enrich the types of micro-tools,provide tool support and tool guarantee for the manufacturing of microstructures of difficult-to-machine materials,and has good academic research and engineering application value.The specific research work is as follows:Based on the research on the preparation of tool materials by the predecessors of our research group,given the characteristics of micro milling and the requirements for the material and structure of the micro-end mill,TC4 titanium alloy is selected as the cutting object,research the optimization and performance evaluation of the cermet.The results showed that when the sintering temperature was 1475℃,the microstructure of the cermet was the most uniform and fine,and its flexural strength,Vickers hardness,and fracture toughness have reached the optimal value;In the temperature range that the tool should bear under micro-milling conditions,the high-temperature flexure strength of the cermet shows an increasing trend,the high-temperature hardness,and high-temperature fracture toughness shows a decreasing trend,and the ability of the cermet to resist crack growth at high temperatures has been improved.Research the space geometry design and manufacturing process of the cermet micro-end mill.Considering the mechanical properties of the cermet and micro-machining characteristics,research the spatial geometry structure suitable for the cermet micro-end mill,and design spatial geometric structures,such as the double taper neck structure,tool tip protection structure,and tool tip shape;Research the thermo-mechanical coupling simulation model of milling TC4 titanium alloy with the cermet micro-end mill,optimizing the helix angle,peripheral radial rake angle and relief angle of the cermet micro-end mill;Based on the tool grinding software of Helitronic Tool Studio,virtual grinding of the spatial geometry of the cermet micro-end mill,formulating the manufacturing process plan and parameters for grinding the cermet micro-end mill,establish the mathematical model of grinding force when grinding the spiral groove of the cermet micro-end mill.The results show that the effectiveness of the simulation model of milling TC4 titanium alloy is verified by micro-milling experiments;When grinding the spiral groove of the cermet micro-end mill with a diameter of 0.3 mm,the maximum tensile stress acting on the cutting part of the cermet micro-end mill is less than 231.8 MPa,which is smaller than that of the tensile strength of the cermet.According to the first strength theory,the structure of the cutting part does not break under the action of the bending moment.The cermet micro-end mills with a diameter between 0.3 mm and 1.0 mm have been successfully manufactured.From the cutting load point of view,demonstrate cermet material can meet the cutting performance requirements of the micro-end mill.Research the model of stress on the cutting edge and milling force of the cermet micro-end mill.The results show that the correctness of the model is verified by micro-milling experiments,and it is demonstrated that the maximum normal contact stress on the cutting edge of the cermet micro-end mill is less than the compressive strength of the cermet.Therefore,the cermet micro-end mill can bear the stress on the cutting edge without damageFrom the application point of view,research the cutting performance of the cermet micro-end mill in the micro-milling of TC4 titanium alloy.Explore the wear,damage mechanism,and machining quality of the cermet micro-end mills with a diameter between 0.3 mm and 1.0 mm.The results show that the four types of cermet micro-end mills with different diameters all have good cutting performance.The main damage forms of the cermet micro-end mills with a diameter of 0.3 mm,0.5mm,and 0.8 mm were wear,and the main wear mechanism is adhesion wear,and the main form of wear is flank wear;The main damage form of the cermet micro-end mills with a diameter of 1.0 mm is breakage.Compared with coated and uncoated cemented carbide micro-end mills,the machining efficiency of the cermet micro-end mills is increased,and a smaller burr width and surface roughness can be obtained. |
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