Study On Chip Removal And Cooling Mechanism Of Pulsed Cutting Fluid In MQL Deep-hole Drilling

The MQL Deep hole drilling technology with precision,high efficiency,low cost,and environment-friendly is the urgent need for deep hole parts processing in today’s aerospace,new energy equipment manufacturing and high-tech industries.A large number of research results show that the introduction of MQL technology in the traditional drilling process not only improves the production environment and reduces production costs,but also significantly improves the lubrication and cooling effects of the tools and workpieces.However,due to the high compressibility of the high-pressure gas/liquid mist and low viscosity,it is very easy to cause the unsmooth removal of iron scraps and the non-uniformity of the cutting heat diffusion in the long and closed chip removal space.As a result,bit breaks or broken teeth of the drill bit are generated,causing damage and thermal deformation on the surface of the workpiece hole.Therefore,how to control the chip removal status and the cutting zone temperature in real time under the normal operating conditions of the machining process,and then drill the desired deep hole to form the predetermined requirements becomes a hot and key issue in the MQL Deep hole drilling technology research.For this reason,this paper proposed a regulatable pulsed chip removal mechanism,which provided theoretical and technical support for the real-time control of the chip removal status and temperature in cutting zone during the MQL Deep hole drilling process,and had important theoretical and practical engineering application values.Based on the physical conditions that the actual deep-hole cutting fluid should meet,considering the multiple factors such as supply pressure of cutting fluid,pressure loss and friction force along the stroke,a mathematical model of chip resistance in actual machining was constructed.Based on the analysis and calculation of the unsteady turbulent force of the cutting fluid,the instantaneous fluid pressure velocity characteristics of the coolant were obtained,and the influence of the amplitude and frequency of the fluid.force of the pulse cutting fluid on the chip removal effect were investigated.Based on the mechanism of tool-workpiecc cutting area and pulsed cutting fluid,a fluid-solid coupling model for dynamic cutting process of deep-hole lean drilling tool was built.Based on this,combined with the Navier-Stokes convection heat transfer equation,the dynamic evolution regular pattern of the flow field velocity distribution of the cutting fluid in a full pulse excitation period was obtained,and the mechanism of the influence of the amplitude and frequency of the fluid force of the pulsed cutting fluid on the temperature distribution and cooling efficiency of the cutting zone is ascertained.Considering the effect of pulse flow velocity on the enhanced heat exchange in the cutting zone temperature,the dynamic cutting heat of deep hole drilling is equivalent to the heat conduction problem with moving heat source.At the same time,the convective heat transfer coefficient between tools and the cutting fluid was solved and made it consistent with each other’s accuracy.Based on this,the influence of the amplitude and frequency of the pulsed cutting fluid on the convective heat transfer coefficient between the cutting fluid and the cutting tool was obtained.