Transient Thermal And Analytical Model Of The Cutting Zone During Screw Whirlwind Milling Process

Screws are widely used in high-grade CNC machine tools and the other automation equipment as the high efficiency and precision transmission parts.However,the traditional turning,grinding and the other screw processing methods can not satisfy the efficient production and ecological development.Compared with the traditional screw processing methods,screw whirlwind milling process has the characteristics of higher material removal rate and better environmental protection.And there are significant differences between screw whirlwind milling process and the other cutting processes.And the differences are mainly behaved in the cutting heat source,heat conduction,heat distribution and the mode of thermal load.Therefore,the study of the tool,the work-piece and the chip temperature distribution with different cutting conditions during screw whirlwind milling process is important.And the analysis of temperature distribution in the cutting zone has important theoretical significance and practical application value for controlling the thermal shock during crew whirlwind milling process,improving the surface integrity of work-piece and predicting the usage condition of tool in order to prolong its service life.According to the characteristic of screw whirlwind milling process,this paper analyzes the tool,the work-piece and the chip transient temperature based on the time-varying heat source in the cutting zone.And the main works are as follows.First of all,the geometric characteristics of un-deformed chip are analyzed from the aspects of the un-deformed chip thickness,the un-deformed chip width and the un-deformed chip area according to the forming process of screw whirlwind milling.And then,combined with the heat source area in the cutting process,the characteristics of transient temperature are analyzed.On the above basis,the framework of transient temperature model in the cutting zone is developed.Secondly,based on the analysis of temperature characteristics of screw whirlwind milling,the time-varying heat source characteristics of screw whirlwind milling in the cutting zone are modeled.And the time-varying heat source characteristics model including the time-varying heat source characteristics model in the shear zone,the frictional heat source characteristics model in the tool-chip contact zone and the boundary equation of the frictional heat source.The time-varying heat source characteristics model in the shear zone is used to analyze the size of time-varying heat source in the shear zone,which including the model of the un-deformed chip thickness,the un-deformed chip width and the un-deformed chip area in the process of screw whirlwind milling.The frictional heat source characteristics model in the tool-chip contact zone is used to determine the size of the frictional heat source,which including the model of the contact width of tool-chip,the contact length of tool-chip and the contact area of tool-chip.And the boundary equation of the frictional heat source is used to determine the boundary of frictional heat source in the process of screw whirlwind milling.Thirdly,according to the model of time-varying heat source characteristics of screw whirlwind milling,the time-varying model of heat release intensity of tool,workpiece and chip in the cutting zone are modeled.And combined with the heat transfer theory of metal cutting,the temperature models are developed for analyzing the transient temperature in the cutting zone.And the temperature models mainly include transient temperature model of workpiece,transient temperature model of chip and transient temperature model of tool.Finally,several experiments are conducted and the comparison of experimental and analytical values demonstrate the effectiveness of the proposed method.And the model of the paper revealed the effect of un-deformed chip geometry,cutting velocity and heat release intensity on the dynamic changes of the temperature in the cutting zone.