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Research Papers

Automated Part Centering With Impulse Actuation

[+] Author and Article Information
S. J. Furst, T. A. Dow, K. Garrard, A. Sohn

Department of Mechanical and Aerospace Engineering, North Carolina State University, Campus Box 7910, Raleigh, NC 27695–7910

J. Manuf. Sci. Eng 132(1), 011007 (Jan 07, 2010) (9 pages) doi:10.1115/1.4000681 History: Received December 17, 2008; Revised October 27, 2009; Published January 07, 2010; Online January 07, 2010

Centering a part on a spindle for precision machining is a tedious, time-consuming task. Currently, a skilled operator must measure the run-out of a part using a displacement gauge, then tap the part into place using a plastic or rubber hammer. This paper describes a method to automatically center a part on a vacuum chuck with initial run-out as large as 2.5 mm. The method involves measuring the magnitude and direction of the radial run-out and then actuating the part until the part and spindle centerlines are within 5μm of each other. The run-out can be measured with either a touch probe mounted to a machine axis or an electronic gauge. The part is tapped into place with a linear actuator driven by a voice coil motor. This paper includes an analysis of run-out measurement uncertainty as well as the design, performance modeling, and testing of the alignment actuator. This actuator was employed for part realignment and successfully positioned a hemispherical part with an initial run-out of 1–2.5 mm to within 5μm of the spindle centerline. This capability shows that the run-out of a part manually placed on flat vacuum chuck can be automatically corrected.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Touch Points and best fit sinusoid for run-out measurement

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Figure 2

Chosen touch points and randomly generated radial errors

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Figure 3

Hemishell centerpoint location uncertainty

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Figure 4

Influence of centerpoint measurement uncertainty

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Figure 5

Standard model of friction force as a function of velocity

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Figure 6

Elastic asperities at the friction interface (22)

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Figure 7

Idealized force profiles

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Figure 8

Variation in force with stroke in a VCM (24)

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Figure 9

Model of assembled tapping actuator

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Figure 10

Exploded view of VCM actuator

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Figure 11

Variation in impact stroke y with applied force

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Figure 12

Initial kinetic energy required to produce a peak impact force

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Figure 13

Force and stress during simulated collisions

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Figure 14

Test setup for voice coil motor actuator

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Figure 15

Voltage input for VCM actuator at 1 Hz

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Figure 16

Typical velocity profile of the translating core

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Figure 17

Peak impact force variation

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Figure 18

Deviation of repeated taps at a gain of 0.6

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Figure 19

Setup for part actuation test

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Figure 20

Displacement of hemishell part due to taps at applied random angles

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Figure 21

Displacement of part due to successive taps at gain of 0.6

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Figure 22

Displacement of part due to successive taps at gain of 0.7

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Figure 23

Displacement of part due to successive taps at gain of 1.0

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Figure 24

Path of part during various centering operations

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