The Research On The Liquid Nitrogen Through-tool Tool Holder In Cryogenic Machining

Cryogenic machining is an effective approach to improve the machining performance of difficult-to-machine materials.It has been proved to have the advantages of suppressing tool wear,improving processing efficiency,improving the surface quality of workpieces and environmental protection.Among various cryogenic cooling methods,through-tool cooling has become a development trend of cryogenic cooling because of its good cooling effect and minimal waste.Therefore,the development of related equipment has become the key to the further development of cryogenic machining technology.As the most widely used cooling agent for cryogenic machining,liquid nitrogen has the characteristics of low boiling point and easy gasification,which puts forward higher requirements for the heat insulation and sealing ability of related equipment.In this paper,the development of the liquid nitrogen through-tool tool holder is studied,exploratively on the structure design and the simulation method of multifield coupling.The structure of the tool holder was designed with high-speed rotary shaft dynamic sealing and heat insulation of liquid nitrogen,the strength and stiffness of the tool holder was checked by finite element method,and the liquid nitrogen through-tool function was realized on the machine without through-tool cooling function.By analyzing the energy flow process inside the tool holder,and the energy flow between the tool holder and the external environment under the working condition,the steady temperature field model was established.Based on the Palmgren bearing frictional heat generation model,the heat generation of the heat source in the handle was calculated.Based on heat transfer,thermal convection and thermal radiation,the influence factors of the temperature field of the tool holder were analyzed,and the reasonable thermal boundary conditions were provided for the finite element simulation of the tool holder.The finite element analysis software ANSYS Workbench was used to analyze the steadystate temperature field and deformation field under the working conditions of the tool holder.A thermal fluid-solid coupling multi-field finite element simulation model was established for the tool holder.By analyzing the temperature field and deformation field without thermal insulation conditions and different insulation layer thicknesses,the thermal insulation structure design and thermal insulation effect were checked.The heat insulation performance and the cutting ability of the tool holder were proved by experiments.Based on the taguchi experimental method,the advantages of the through-tool cryogenic machining and the working performance of the tool holder were verified.This article has developed a tool holder device for liquid nitrogen through-tool cryogenic machining.This equipment can realize the cryogenic through-tool cooling for drilling and milling processing function of difficult-to-machine materials on ordinary machine tools.