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TECHNICAL PAPERS

Dynamic Analysis of a Mesoscale Machine Tool

[+] Author and Article Information
Sang Won Lee1

S. M. Wu Manufacturing Research Center, University of Michigan, Ann Arbor, MI 48109sangwonl@umich.edu

Rhett Mayor

 Powerix Technologies, Ann Arbor, MI 48105

Jun Ni

S. M. Wu Manufacturing Research Center, University of Michigan, Ann Arbor, MI 48109

1

To whom correspondence should be addressed.

J. Manuf. Sci. Eng. 128(1), 194-203 (Jun 21, 2005) (10 pages) doi:10.1115/1.2123007 History: Received November 11, 2004; Revised June 21, 2005

Miniaturized machine tools, referred to as mesoscale machine tools (mMTs) henceforth, have been proposed as a way to manufacture micro/mesoscale mechanical components. A thorough study of the dynamic behavior of the mMT is required for the successful development of its machine structure. This paper demonstrates the development of an mMT, the performance evaluation of its mesoscale milling process, and the characterization of its dynamic behavior. The mMT is developed by using an air turbine spindle and three piezoelectric linear stages, and its volumetric size is 150×70×140mm. A series of micro/mesoscale milling experiments are conducted, and the performances in the developed mMT testbed are evaluated. The dynamic characteristics of the mMT can be different from those of conventional machine tools because the mMT is a miniaturized structure and comprises different machine components. Therefore, the effect of the miniaturization of a structure on the change of its dynamic behavior, called scaling law of the structural dynamics, is studied numerically and experimentally. The dynamic characteristics of the developed mMT that are estimated from the scaling law of the structural dynamics are much different from those obtained from an experimental modal analysis, and the flexible joints of the developed mMT are mainly responsible for this significant difference. Therefore, the joint dynamics of the mMT are studied by introducing an equivalent lumped parameter model, thus enabling simple identification of the joint dynamics and the effective modification of its critical joints to enhance a machining performance.

Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 2

Microscopic photos of the milled slot; tool diameter ϕ=635μm

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Figure 3

Schematic and SEM photo of micro endmill (ϕ=508μm)

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Figure 4

Impulse excitation and acceleration measurement points of the mMT testbed

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Figure 5

Inertance FRFs of the mMT testbed

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Figure 6

SEM photos of milled slots

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Figure 7

Surface roughnesses (Ra) of milled slots versus cutting frequencies

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Figure 8

Photo of the conventional vertical milling machine and map for experimental modal analysis

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Figure 9

FE mesh model of the conventional vertical milling machine structure

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Figure 10

Measured receptance FRFs of the conventional vertical milling machine

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Figure 11

Mode shapes of the conventional vertical milling machine; experimental results

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Figure 12

Mode shapes of the conventional vertical milling machine; FE analysis results

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Figure 13

Measured receptance FRFs of the mMT testbed

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Figure 14

Photo of the coupled structure of the mMT testbed

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Figure 15

5-DOF lumped parameter model of the coupled system

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Figure 16

Measured and estimated receptance FRFs of the base-plate substructure

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Figure 17

Measured and estimated receptance FRFs of the XY stage unit with free boundary condition

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Figure 18

Measured and estimated receptance FRFs of the base plate–XY stage substructure

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Figure 19

Measured and estimated receptance FRFs of the adapter with free boundary condition

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Figure 20

Measured and estimated receptance FRFs (G41) of the entire coupled structure–Case 1: Four-screw bolting

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Figure 21

Measured and estimated receptance FRFs (G41) of the entire coupled structure–Case 2: Two-screw bolting

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