Tool Temperature in Titanium Drilling

[+] Author and Article Information
Rui Li, Albert J. Shih

Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109-2125

J. Manuf. Sci. Eng 129(4), 740-749 (Apr 01, 2007) (10 pages) doi:10.1115/1.2738120 History: Received June 01, 2006; Revised April 01, 2007

The spatial and temporal distribution of tool temperature in drilling of commercially pure titanium is studied using the inverse heat transfer method. The chisel and cutting edges of a spiral point drill are treated as a series of elementary cutting tools. Using the oblique cutting analysis of the measured thrust force and torque, the forces and frictional heat generation on elementary cutting tools are calculated. Temperatures measured by thermocouples embedded on the drill flank face are used as the input for the inverse heat transfer analysis to calculate the heat partition factor between the drill and chip. The temperature distribution of the drill is solved by the finite element method and validated by experimental measurements with good agreement. For titanium drilling, the drill temperature is high. At 24.4 m/min and 73.2 m/min drill peripheral cutting speed, the peak temperature of the drill reaches 480°C and 1060°C, respectively, after 12.7 mm depth of drilling with 0.025 mm feed per cutting tooth. The steady increase of drill temperature versus drilling time is investigated.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Experimental setup with workpiece in the spindle and drill in a vertical tool holder

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Figure 2

The spiral point drill and thermocouple locations in the drill flank face: (a) original drill, (b) drills with thermocouples embedded, (c) close-up view of TC1 and TC2, and (d) close-up view of TC3 and TC4

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Figure 3

Solid model of the spiral point drill: (a) side view and (b) top view with seven marked ECTs

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Figure 4

Rake angle, inclination angle, and angle between drill axis and ECT cutting edge

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Figure 5

Mesh for the 3D finite element thermal model: (a) side view and (b) top view

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Figure 6

Oblique cutting model of an ECT

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Figure 7

Thermal conductivity of the WC-Co tool

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Figure 8

Flowchart of the inverse heat transfer solution of drill temperature

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Figure 9

Ti chip at 73.2m∕min peripheral cutting speed (2350rpm rotational speed): (a) the spiral cone followed by the folded long ribbon chip morphology, (b) close-up view of the spiral cone chip at the start of drilling, and (c) chip cross section and chip thickness variation of ECT (C: chip close to the center of drill)

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Figure 10

Chip thickness and shear angle of seven ECTs

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Figure 11

Thrust force and torque versus drilling depth

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Figure 12

Thrust force and torque of seven ECTs

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Figure 13

Comparison of the measured and modeled temperature at four thermocouple locations

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Figure 14

Heat partition factor K at seven ECTs after 1.9mm depth of drilling

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Figure 15

Heat generation rate per unit length qtool′ at seven ECTs after 1.9mm depth of drilling

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Figure 16

Temperature distribution at the drill tip after 12.7mm depth of drilling at peripheral cutting speeds: (a)24.4m∕min, (b)48.8m∕min, and (c)73.2m∕min

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Figure 17

Temperature along the drill chisel and cutting edges after 12.7mm depth of drilling

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Figure 18

Temperature along the drill chisel and cutting edges at 73.2m∕min cutting speed




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