Research On Milling Temperature Measuring Tool Embedded With Thin Film Thermocouple

Cutting area temperature is one of the most important research fields in metal cutting,and it is an important parameter that affects tool life and quality of machined parts.Because the position of the tool tip-work piece thermal contact area changes rapidly with the spindle rotation during the milling process,the traditional temperature measurement method is limited by the conditions of large volume,slow response speed,and difficult arrangement of the sensor,it is difficult to realize real-time measurement of the temperature in the milling area,resulting in real-time measurement.Face the above technical problems,this paper develops a milling temperature measuring tool embedded with thin film thermocouple.The main research contents are as follows:The thin film thermocouple temperature sensor was prepared by DC pulsed magnetron sputtering.SiO2 insulating film,NiCr and NiSi thermoelectric film and SiO2 protective film were deposited on the flank of the blade.The SiO2 insulating film was prepared by the fractional deposition method,which could obtain better insulation in a smaller thickness.The resistance value of SiO2 insulating film with thickness of 2.7?m can reach 2.05 × 107?.The boundary between the NiCr and NiSi thermoelectric films prepared by photolithography is clear and regular,without edge diffraction,and the two thermoelectric films overlap to form a good contact temperature measuring hot junction,and the thin film thermocouple circuit conducts well.The prepared thin film thermocouple sensor was characterized by SEM and TEM.It was proved that the surface of each layer was dense and uniform,and the layers of the film in the cross-section structure were in good contact and the element distribution was accurate.The static and dynamic characteristics of the film thermocouple embedded in the milling temperature measuring tool are studied.The results show that the thin film thermocouple Seebeck coefficient is 34.14?V/? in the temperature range of 30?120?,and the maximum nonlinear error is 0.05%,and the dynamic response time is 0.132ms.The wear equivalent test of the thin film thermocouple was designed.The research proves that the static and dynamic characteristics of the film thermocouple following the wear of the tool are basically unchanged,which proves the accuracy of the experimental data of the milling temperature test of the film thermocouple temperature measuring sensor.The thermal conduction model of thin film thermocouples was studied based on the micron-nanoscale heat transfer theory.The thermal insulation properties of SiO2 insulating films and the influence of film-to-blade thermal resistance on the thermal conduction model were considered,making improvements and equivalent studies.The two-dimensional steady-state heat transfer model of the blade-film was established by finite element simulation software,the blade-film temperature field distribution cloud map was obtained by numerical simulation.The 6061 aluminum alloy milling temperature test experiment system based on embedded thin film thermocouple temperature measuring tool was built.The CCD response surface experimental scheme based on milling speed,axial cutting depth and feed rate was designed.The milling temperature and cutting parameters were established based on the test results.The second-order prediction model under interaction proves that the return model is reliable and provides reliable theoretical and experimental data basis for the monitoring and prediction process of the milling area temperature.