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Special Section: Micromanufacturing

Microendmill Dynamics Including the Actual Fluted Geometry and Setup Errors—Part II: Model Validation and Application

[+] Author and Article Information
Sinan Filiz

Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213

O. Burak Ozdoganlar1

Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213ozdoganlar@cmu.edu

This is only true when considering a limited range of frequencies, since more peaks associated with higher modes occur at smaller diameters and aspect ratios.

1

Corresponding author.

J. Manuf. Sci. Eng 130(3), 031120 (Jun 13, 2008) (13 pages) doi:10.1115/1.2936379 History: Received December 17, 2007; Revised February 25, 2008; Published June 13, 2008

This paper presents a study to validate the microendmill dynamics model derived in Part I. A laser Doppler vibrometer system that is coupled with a microscope is used to measure the natural frequencies and mode shapes of nonrotating microendmills with different geometries. Free-free boundary conditions are obtained by suspending the microendmills using elastic bands. The dynamic excitation is delivered through miniature piezoelectric elements attached to the microendmill shanks. In each case, the model is compared to experimental results and solid-element finite-element (FE) models. To evaluate the model in the presence of rotational effects, the model is compared to an FE model. In most cases, the model was seen to capture the dynamic behavior of microendmills accurately. The validated model is used to investigate the effects of microendmill geometry, and radial and tilt runouts on the modal behavior of microendmills. Furthermore, possible geometric simplifications to fluted region are evaluated based on the accuracy of the predicted natural frequencies of the microendmills.

Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 12

Normalized mode shapes and damped and undamped rotating-tool-frame natural frequencies for a 15deg taper angle tool rotating with 2kHz(120,000krpm). The dashed lines indicate the boundaries between the sections.

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Figure 13

Change in the natural frequencies for (a)–(c) varying tip section diameter, (d)–(f) varying tip section aspect ratio, (g)–(i) varying taper angle, and (j)–(l) varying helix angle. The first natural frequencies within the pair is plotted with solid lines and the second natural frequency within the pair is plotted with dashed lines.

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Figure 1

Experimental setup for free-free boundary conditions

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Figure 2

(a) An FE model of the four-fluted microendmill; (b) a zoomed view of the tip section; (c) the FE model with the piezoelectric element; (d) the FE model with the elastic bands

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Figure 3

Experimental FRF amplitude (solid line) and predicted natural frequencies (dashed line) for (a) B1 and (b) B2

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Figure 4

Experimentally obtained operating deflection shapes (triangles) and predicted mode shapes (solid lines) for B1. (a) First mode, (b) second mode, (c) third mode, and (d) fourth mode. Tool sections are indicated with dashed lines, and the x-axis of the plots represents the distance along the tool axis.

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Figure 5

Experimentally obtained operating deflection shapes (triangles) and predicted mode shapes (solid lines) for B2. (a) First mode, (b) second mode, (c) third mode, and (d) fourth mode.

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Figure 6

SEM images of (a) and (b) four-fluted F1, (c) and (d) four-fluted F2, (e) and (f) four-fluted F3, and (g) and (h) three-fluted H1 microendmills

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Figure 7

Experimental frequency response (solid line), predictions from the model (dashed lines), and predictions of FE simulations (dashed-dotted lines) of the resonance peak locations for (a) F1, (b) F2, (c) F3, and (d) H1

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Figure 8

Experimentally obtained operating deflection shapes (triangles) and predicted mode shapes (solid lines) for F3. (a) First mode, (b) second mode, (c) third mode, and (d) fourth mode

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Figure 9

SEM images of the (a) and (d) T1, (b) and (e) T2, and (c) and (f) T3

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Figure 10

Experimental frequency response (solid line), predictions from the model (dashed lines), and predictions of FE simulations (dashed-dotted lines) of the resonance peak locations for (a) T1, (b) T2, and (c) T3

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Figure 11

Experimentally obtained operating deflection shapes (triangles) and predicted mode shapes (solid lines) for T3. (a) Mode 1-1, (b) Mode 1-2, (c) Mode 2-1, (d) Mode 2-2, (e) Mode 3-1, (f) Mode 3-2, (g) Mode 4-1, and (h) Mode 4-2. Tool sections are indicated with dashed lines.

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Figure 14

Dynamic tool-tip runout for (a) varying spindle-axis offset, (b) varying tool-tilt angle, (c) varying tool plane angle, (d) varying spindle-axis offset with Ω=2.5kHzμm, ϕ=0deg, (e) varying α with Ω=2.5kHzμm, ϕ=0deg, and (f) varying ϕ with Ω=2.5kHzμm (—, e=2.5μm and α=0; ---, e=5μm and α=0; ⋯, e=2.5μm and α=0.025deg; -⋅-⋅-, e=5μm and α=0.025deg; -⋅⋅-⋅⋅-, e=2.5μm and α=0.05deg; --⋅--⋅--, e=5μm and α=0.05deg)

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Figure 15

Cross sections of (a) a two fluted microendmill and (b) a four-fluted microendmill for the simplified geometry analysis

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Figure 16

Percent error for the first four modes of (a) two-fluted tools with varying diameter, (b) two-fluted tools with varying aspect ratio, (c) four-fluted tools with varying diameter, and (d) four-fluted tools with varying aspect ratio. First natural frequency (—), second natural frequency (---), third-natural frequency (-⋅-⋅-), and fourth natural frequency (⋯).

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