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Research Papers

# Temperature Variation in the Cutting Tool in End Milling

[+] Author and Article Information
Masahiko Sato

Department of Mechanical and Aerospace Engineering, Tottori University, 4-101 Koyamacho-minami, Tottoti-shi, Tottori 680-8552, Japansato@mech.tottori-u.ac.jp

Naoki Tamura, Hisataka Tanaka

Department of Mechanical and Aerospace Engineering, Tottori University, 4-101 Koyamacho-minami, Tottoti-shi, Tottori 680-8552, Japan

J. Manuf. Sci. Eng 133(2), 021005 (Mar 11, 2011) (7 pages) doi:10.1115/1.4003615 History: Received March 04, 2010; Revised January 21, 2011; Published March 11, 2011; Online March 11, 2011

## Abstract

This paper describes the cyclic temperature variation beneath the rake face of a cutting tool in end milling. A newly developed infrared radiation pyrometer equipped with two optical fibers is used to measure the temperature. A small hole is drilled in the tool insert from the underside to near the rake face, and an optical fiber is inserted in the hole. One of the optical fibers runs through the inside of the machine tool spindle and connects to the other optical fiber at the end of the spindle. Infrared rays radiating from the bottom of the hole in the tool insert during machining are accepted and transmitted to the pyrometer by the two optical fibers. For a theoretical analysis of the temperature in end milling, a cutting tool is modeled as a semi-infinite rectangular corner, and a Green’s function approach is used. Variation in tool-chip contact length in end milling is considered in the analysis. Experimentally, titanium alloy Ti–6Al–4V is machined in up and down milling with a tungsten carbide tool insert at a cutting speed of 214 m/min. In up milling, the temperature beneath the rake face increases gradually during the cutting period and reaches a maximum just after the cutting. In contrast, in down milling, the temperature increases immediately after cutting starts; it reaches a maximum and then begins to decrease during cutting. This suggests 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. Temperature variation is measured at different depths from the rake face. With increasing depth from the rake face, the temperature decreases and a time lag occurs in the temperature history. At 0.6 mm from the major cutting edge, the temperature gradient toward the inner direction of the tool insert is about $300°C/0.5 mm$. The calculated and experimental results agree well.

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## Figures

Figure 1

Experimental setup

Figure 2

Detail of tool insert: (a) location of the hole inserting optical fiber and (b) cross-sectional view of the blind hole

Figure 3

Frequency characteristics of amplifier

Figure 4

Tool insert model

Figure 5

Variation of heat source area: (a) up milling and (b) down milling

Figure 6

Variation in tool-chip contact length: (a) up milling and (b) down milling

Figure 7

Calculated temperature history (z=0.1 mm): (a) up milling and (b) down milling

Figure 8

Calibration curve of pyrometer: (a) relationship between the output voltage of pyrometers and the target temperature, and (b) relationship between the output ratio of pyrometers and the target temperature

Figure 9

Typical output waves of dynamometer and pyrometers

Figure 10

Cutting force and tool temperature in up milling (z=0.1 mm): (a) cutting force and (b) temperature

Figure 11

Cutting force and tool temperature in down milling (z=0.1 mm): (a) cutting force and (b) temperature

Figure 12

Calculated and measured temperature in up milling: (a) calculated temperature and (b) measured temperature

Figure 13

Calculated and measured temperature in down milling: (a) calculated temperature and (b) measured temperature

Figure 14

Variation in temperature gradient toward inner direction of tool insert in up milling (th: elapsed time after beginning of cutting period and tc: elapsed time after beginning of noncutting period): (a) cutting period and (b) noncutting period

Figure 15

Variation in temperature gradient toward inner direction of tool insert in down milling (th: elapsed time after beginning of cutting period and tc: elapsed time after beginning of noncutting period): (a) cutting period and (b) noncutting period

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