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and the target temperature. Using the curve in Fig. 8(b), the output ratio is converted into the temperature. 4.2 Example of Output Waves. Figure 9 shows an example of the output wave from the dynamometer and the pyrometer in up milling. The interrupted cutting force and the temperature are detected simultaneously, and the cutting force and cutting temperature arrive 4.3 Temperature History in Up Milling and Down Milling. Figures 10 and 11 show the measured wave forms for resultant (b) down milling cutting force and the tool temperature in up and down milling, The tool temperature also increases as cutting progresses, since the contact length between the rake face and the chip and the heat flux into the cutting tool increase. The temperature reaches a maximum at the end of cutting and then decreases gradually. The temperature variation corresponds well to the calculated results in Sec. 3.2. In down milling, however, since the instantaneous undeformed chip thickness is greatest at the beginning of the cutting, the cutting force is also greatest. Unlike the case in up milling, the tool temperature increases immediately at the beginning of the cutting. The temperature reaches a maximum during cutting and begins to Fig. 10 Cutting force and tool temperature in up milling (z=0.1 mm): (a) cutting force and (b) temperature decrease during the cutting period. The temperature variation in down milling also corresponds well to the calculated results in Sec. 3.2. 4.4 Temperature Variation at Different Depths in the Tool Insert. Figures 12 and 13 show the calculated and measured temperature variations at different depths in the tool insert in up milling and down milling, respectively. The distance between the rake face and the bottom of the hole is varied from 0.1 mm t0 0.5 mm at intervals of 0.1 mm. The figure shows that with increasing depth from the rake face, the tool temperature decreases and a time lag occurs in the temperature history. In up milling, the measured peak temperature is 4800 C at a depth of 0.1 mm and 200 0 C The measured temperature tends to be lower than the calculated temperature as the depth from the rake face becomes large. This is partly because the model in analysis postulates a l/8 infinite body and does not consider a small hole in the tool insert. However, the tendency of the temperature variation in the cutting and noncutting cycles in both up and down milling agrees well with the calculated results. 4.5 Temperature Gradient Toward Inner Direction of Tool Insert. Figures 14 and 15 show the variation in the temperature gradient toward the inner direction of the tool insert in up and down milling, respectively. The gradient is obtained by reading the wave form of the temperature. In each figure, (a) shows the variation during the cutting period, and (b) shows the variation during the noncutting period. In addition, th is the elapsed time after the beginning of the cutting period, and te is the elapsed time after the beginning of the noncutting period. The solid lines show the calculated gradient. In up milling, at the beginning of cutting, In down milling, the temperature gradient in the depth direction increases rapidly at the beginning of the cutting, in contrast with up milling. However, in the latter half of the cutting period, th=6-10 ms, the surface temperature is almost constant, and the increase in temperature gradient becomes small. It can be estimated that the thermal impact caused by cyclical variation in temperature gradient during cooling is smaller in down milling than in
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up milling. 5 Conclusions In this study, a new technique in radiation temperature measurement using two optical fibers is applied to investigate the temperature variation at different depths in a tool insert during the cutting and noncutting cycles in end milling. The main conclusions are as follows: Fig. 14 Variation in temperature gradient toward inner direction of tool insert in up milling (th: elapsed time after beginning of cutting period and elapsed time after beginning of noncutting period): (a) cutting period and (b) noncutting period(1)A pyrometer using two optical fibers and a fiber coupler enables measurement of the temperature variation in the tool insert throughout the cutting and noncutting cycles in end milling. (2)Temperature analysis using a Green's function was applied to the end milling process and explains well the temperature variation beneath the rake face in up milling and down milling.(3)In up milling, the temperature increases gradually during the cutting period and reaches the maximum value just after the cutting. During the noncutting period, the temperature decreases gradually. In down milling, the temperature increases immediately after the cutting starts, it reaches a maximum and then begins to decrease during the cutting period. The rate of temperature increase in down milling is higher than that in up milling. These results suggest that the thermal impact to the cutting tool during heating is larger in down milling than in up milling, whereas that during cooling is larger in up milling than in down milling. Acknowledgment References [1] Chakraverti, G., Pandey, P. C., and Mehta, N. K., 1984, "Analysis of Tool Temperature Fluctuation in Interrupted Cutting," Precis. Eng., 6(2), pp. 99105. [2] Palmai, Z., 1987, "Cutting Temperature in Intermittent Cutting," Int. J. Mach. Tools Manuf., 27(2), pp. 261-274. [3] Stephenson, D. A., and Ali, A., 1992, "Tool Temperatures in Interrupted Metal Cutting," ASME J. Eng. Ind., 114, pp. 127-136. [4] Radulescu, R., and Kapoor, S. G., 1994, "An Analytical Model for Prediction of Tool Temperature Fields During Continuous and Inrerrupted Cutting," ASME J. Eng. Ind., 116, pp. 135-143. [5] Jen, T. C., Eapen, S., and Gutierrez, G., 2003, "Nonlinear Numerical Analysis in Transient Cutting Tool Temperatures," ASME J. Manuf. Sci. Eng., 125, pp. 48-56. [6] Wang, K. K., Wu, S. M., and Iwata, K., 1968, "Temperature Responses and Experimental Errors for Multitooth Milling Cutters," ASME J. Eng. Ind., 90, pp. 353-359. [7] McFeron, D. E., and Chao, B. T., 1958, "Transient Interface Temperatures in Plain Peripheral Milling," Trans. ASME, 80, pp. 321-329. [8] Schmidt, A. 0., 1953, "Workpiece and Surface Temperatures in Milling," Trans. ASME, 75, pp. 883-890. [9] Ueda, T., Hosokawa, A., Oda, K., and Yamada, K., 2001, "Temperature on Flank Face of Cutting Tool in High Speed Milling," CIRP Ann., 50(1), pp. 37-40.
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