| Heat is one of the important physical phenomena in metal cutting. Most of the energy consumed in cutting is transformed into heat, apart from some is used to produce the new machined surface and lattice distortion. High cutting temperature can not only reduce the tool life, but also influence machining accuracy because it can easily produce thermal deformation of workpiece and the machining process system and because it is able to surface integrity of the workpiece. Therefore, it has important theoretical significance and practical value to research cutting temperature.The most direct method of cutting temperature research is experimental measurement method. Natural thermocouple method is one of the most convenient and the most widely used methods, and its application is almost mature. But it was generally used in turning, and research on the usage of natural thermocouple in milling especially in NC milling has been a rare occurrence. In paper a measuring system of cutting temperature was developed based on natural thermocouple for NC milling using end milling cutters with indexable inserts, and some related experimental research was conducted using the measuring system. The contents of this paper are as follows:1) Developed a measuring system of cutting temperature in milling steels. As for the difficult problem of leading wire from rotating tool when we apply natural thermocouple method in milling, it was found that by means of installing a precise transmission sliding ring on tool holder, small voltage signal could be conducted out from cutting tool which rotates at high-speed. To eliminate the measurement principle error caused by the temperature variation at the cold junction of the natural thermocouple due to the temperature rise of the insert, a standard T-type thermocouple nipped between the back-end of the insert and the tool holder was used to measure the real-time temperature of the cold junction of the natural thermocouple. And on this basis, the calculation principle of cutting temperature was presented. For the convenience of signal acquisition, a three-channel signal conditioner was designed which has Low-pass filtering functions, chich can adapt to different thermocouples with the cold end compensation function, and whosea mplification factor is adjustable.2) The calibration of three kinds of natural thermocouples and three kinds of work-copper thermocouples was conducted. As for the calibration of natural thermocouple which is difficult to be conducted, the Law of Intermediate Materials was applied, a red copper bar was used as the intermediate material and let inserts and workpiece bar clamp the red copper bar to form natural thermocouple, the red copper bar was heated by a furnace for verification use to get the temperature. For purpose of the cooling of the cold end of inserts, tool side was extended by clamping some inserts which contacted one another. The problems of insulation and application of force uniformly could be resolved by using silicone sheets.3) Some experiments of dry cutting of45carbon steel and AISI stainless steel were conducted. Through the analysis of data’s waveform and calculated cutting temperature and the comparison of the cutting temperature with predecessors’ researches, the feasibility of the measurement system was verified.4) Some cutting temperature measurement experiments were conducted when cutting45carbon steel and AISI316, FV520(B) steels without cutting fluid and with cutting fluids of KLC8210, KLC8205and T15. Then the rule of cutting temperature was researched. It was found that cutting temperature rosed very rapidly, it reached its stable value just after a few cutting periods, and that the cutting temperature when using cutting fluids is not always lower than the temperature when dry cutting. |
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