Design And Analysis Of The Internally Cooled Smart Turning Tool And Experimental Study

Due to no coolant contamination and special cooling effect for the internallycooled tool, an internally cooled smart turning tool is proposed so as to meet therequirement of the efficient cutting of difficult-to-machine materials with no coolantcontamination to the working environment and workpieces. The main idea is tobuild micro cooling channels within the tool and located close to the cutting tip,forming a closed-loop of the internal cooling circuitry. The cooling lubricantcontamination will be avoided and the cutting temperature be reduced when coolingfluid circulates flowing through the closed channel. The cutting temperature at thetool tip can be estimated by measuring the cooling fluid’s temperatures at the inletand outlet of the cooling structure. In this thesis, the key enabling technology fordesign of an internally cooled smart cutting tool were theoretical analysed includingits design theory and methods, thermal characteristics, tool wear prediction andcontrol. Experimental cutting trials are carried out to further evaluate and validatethe method and concept of applying the smart cutting tool system.Internal cooling structure with optimal design is the foundation of efficientcooling, which is the premise of the energy-resource efficient machining. Based onthe analysis of cooling effect, and the relationship between coolant temperatures riseand the cutting temperature was proposed, in light of the mechanical and thermalrequirements of the cutting tool, and the general design principles of the internallycooled cutting tool. Taking a specific internal cooling structure, for example, itsgeometric parameters of the micro cooling structure are obtained by using combinedFEA and CFD simulations. The optimal internally cooled cutting tools are machinedby CNC Machining. The comparison of the mechanical and thermal propertiesbetween the ordinary turning tool and internally cooled turning tool was carried outthrough the indepth analysis. The results show that their mechanical properties aremore or less the same. The cooling fluid can effectively reduce the cuttingtemperature, which is depended on the flow rate and decreases rapidly as theincreasing the flow rate within a certain range. Furthermore, the cooling fluid doesnot have significant effect after exceeding the critical flow rate. The effects of thetool-chip contact surface area and heat flow rate, cooling fluid inlet velocity andtemperature are analysed.The analytical model of the relationship between cutting temperature and inletand outlet temperatures is the basis of online measurement of cutting temperature.The temperature distribution on the tool surfaces was fitted using exponentialfunction and the equivalent surface heat transfer coefficients were obtained based on the numerical modeling. Analytical thermal model of the tool is established usingthe lumped parameter method based on the principle of heat transfer. Theoreticalanalysis and numerical simulation results are in good agreement, the influence ofinlet velocity, tool-chip interface area on cutting temperature, outlet temperature andtheir relationships are discussed, and the cutting temperature computationalalgorithm is fitted using the least-squares method. The selection of the optimal inletvelocity, the error source and countermeasures during cutting process are discussed.Tool wear monitoring and control is a prerequisite to ensure machining qualityand safety in automated precision machining processes. The intrinsic modellingrelationship between the tool wear and cutting temperature is established using theexperimental results published at Annals of the CIRP by other researchers.Therefore, the tool wear can be controled to some extent by adaptive control of thecutting temperature by adjusting the cooling liquid flow and cutting parameters inreal time. The influence of tool wear on the thermal characteristics of the internallycooled tool is theoretical analysed. Simulations were undertaken to investigate theinfluence of flank wear on the tool cutting temperature, outlet temperature, and thecutting temperature prediction model was thus obtained with taking account of thetool wear effect. The tool wear prediction model was establised by using the outlettemperature rise. The tool wear control method based on the critical cuttingtemperature constraints is proposed. The tool wear control method based on thecritical cutting temperature constraints is proposed. A PID controller is designed tocontrol the cutting temperature, and its validity is demenstrated by the simulatedanalysis and cutting experiment.In order to validate the cutting temperature prediction model and study thecutting performance, cutting trials on aluminum alloy6061-T6and titanium alloyTi6Al4V under different cutting conditions are carried out by using the internallycooled turning tool and ordinary tool. The cutting trails demonstrate that theinnovative tooling design concept can effectively reduce the tool temperature whilesensing the cutting temperature at tool tip, which can reduce cutting temperature,prolong the tool life and enhance the workpiece surface quality.