| Under extreme working conditions of aerospace,titanium alloys,superalloys and other difficult-to-process advanced materials generally have the characteristics of high toughness,high viscosity and poor heat transfer,especially the poor use of composite materials for water-based/oil-based cutting fluids,resulting in conventional cooling methods can not achieve the required cooling efficiency and surface morphology quality,so it is necessary to find an effective new cooling processing technology and device.Ultra-low temperature machining technology refers to a green processing method that uses strong cooling media such as liquid nitrogen in machining,which has the advantages of no/low pollution,strong cooling capacity,high processing efficiency,long tool life,and good surface integrity of parts.In this paper,an integral liquid nitrogen internal cooled tool holder device is developed to ensure the stability and tightness of the tool holder rotation at high speed while cooling drilling and milling at ultra-low temperature.According to the performance requirements of the internally cooled tool holder,the finite element simulation analysis method is used to optimize the design of the integral internal cooling tool holder structure.The main contents are as follows:(1)Rationalize the structure and assembly feasibility of the integral tool holder,analyze the advantages of the integral tool holder,and design the internal sealing device to further improve the sealing strength of the tool holder.(2)Based on Abaqus for the cutting simulation of liquid nitrogen internal cooling tool holder,the influence of cutting on the workpiece at different temperatures was compared horizontally to verify the advantages of ultra-low temperature cutting.(3)Based on the design of the internal cooling structure of the tool holder,analyze the heat source of each part of the tool holder,use Ansys simulation software to build a fluid-solid thermal coupling simulation model,ignore the friction of the dynamic and static contact surface,compare the temperature field change of the tool holder under different materials,and seek a reliable material for the production of the tool holder.(4)According to the knowledge of statics and the simulation principle of Ansys,the design idea of tool holder stiffness is proposed,and parametric simulation results are obtained,and the best stiffness design of tool holder is obtained by comparing the deformation and stress at different levels of the same factors and combining with actual working conditions.(5)Based on the design requirements of the tool holder nozzle,Fluent is used to change the angle,distance and speed of the tool holder liquid nitrogen nozzle and the cutting edge to spray on the surface of the TC4 titanium alloy sheet to obtain the temperature,stress and displacement changes of the thin plate parts,and optimize the design of the tool holder liquid nitrogen nozzle.The research results show that the combined sealing device is selected for the sealing between the support shell and the body of the tool holder of the integral internal cooling tool shank drilling and milling device,that is,the combination of U-shaped elastic sealing ring and labyrinth seal,and then combined with the advantages of integral structure design,the tool holder sealing device is jointly realized.The larger the taper of the shank,the stronger the rigidity,and it can be designed with a 5° cone angle to improve the cutting rigidity of the tool holder;The angle between the nozzle of the tool handle and the vertical direction is 45° for the optimal injection angle structure design,the smaller the distance between the nozzle and the blade,the better the spraying effect,and the 10 mm nozzle distance is selected,and the large flow rate in the spray speed design has a good improvement in the cooling efficiency;The tool holder material can choose 316 stainless steel,40 Cr and other low thermal conductivity and high strength materials;The external support shell design material is epoxy resin polymer material or FRP material,which can well suppress the heat conduction inside the tool holder. |
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