• Title/Summary/Keyword: Elliptical Vibration Cutting(EVC)

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Kinematical Analysis and Vibrational Characteristics of Orthogonal 2-dimensional Vibration Assisted Cutting Device (직교형 2차원 진동절삭기의 기구학적 해석 및 진동 특성 고찰)

  • Loh, Byoung-Gook;Kim, Gi-Dae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.9
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    • pp.903-909
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    • 2012
  • In elliptical vibration cutting(EVC) where the cutting tool traces a micro-scale 2-dimensional elliptical trajectory, the kinematical and vibrational characteristics of the EVC device greatly affect cutting performance. In this study, kinematical and vibrational characteristics of an EVC device constructed with two orthogonally-arranged stacked piezoelectric actuators were investigated both analytically and experimentally. The step voltage was applied to the orthogonal EVC device and the associated displacements of the cutting tool were measured to assess kinematical characteristics of the orthogonal EVC device. To investigate the vibrational characteristic of the orthogonal EVC, sinusoidal voltage was applied to the EVC device and the resulting displacements were measured. It was found from experiments that coupling of displacements in the thrust and cutting directions and the tilt of the major axis of the elliptical trajectory exists. In addition, as the excitation frequency is in vicinity of resonant frequencies the distortion in the shape of the elliptical trajectory becomes greater and change in the rotation direction occurs. To correct the shape distortion of the elliptical trajectory, the shape correcting procedure developed for the parallel EVC device was applied for the orthogonal EVC device and it was shown that the shape correcting method successfully corrects distortion.

Development of Ultra-precision Ultrasonic Surface Machining Device Using Cyclic Elliptical Cutting Motion of a Couple of Piezoelectric Material (압전소자의 미세회전운동을 이용한 초정밀 초음파 표면가공기 개발)

  • Kim, Gi-Dae;Loh, Byung-Gook;Kim, Jeong-Su
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.5 no.3
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    • pp.29-35
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    • 2006
  • Various types of elliptical motions are generated by PZT mechanism which is composed of two parallel piezoelectric actuators. Elliptical vibration cutting(EVC) is obtained by attaching single crystal diamond cutting tool to the mechanism, and V-grooving for Brass and Aluminum is carried out by applying the EVC. It is experimentally observed that the cutting force in the process of the EVC reduces compared to the ordinary non-vibration cutting, which is due to the decrease of undeformed chip thickness and frictional force between the tool and chip. Ultrasonic elliptical vibration cutting(UEVC) suppresses burr formation and decreases cutting force still more, so UEVC makes it possible to enhance the shape accuracy of machined surface.

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Compensating the Elliptical Trajectory of Elliptical Vibration Cutting Device (타원궤적 진동절삭기의 타원궤적 보정)

  • Loh, Byoung-Gook;Kim, Gi-Dae
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.7
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    • pp.789-795
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    • 2011
  • In elliptical vibration cutting (EVC), cutting performance is largely affected by the shape of an elliptical path of the cutting tool. In this study, two parallel piezoelectric actuators were used to make an elliptical vibration cutting device. When harmonic voltages of $90^{\circ}$ out-of-phase are supplied to the EVC device, creation of an ideal elliptical trajectory whose major and minor axes are parallel to the cutting and thrust directions is anticipated from a kinematic analysis of the EVC device, however, the paths we experimentally observed showed significant distortions in its shape ranging from skew to excessive elongation of the major axis of the ellipse. To compensate distortions, an analytical model describing the elliptical path of the cutting tool was developed and verified with experimental results, and based on the analytical model, the distorted elliptical paths created at 100 Hz, 1 kHz, and 16 kHz were corrected for skew and elongation.

Micro Ultrasonic Elliptical Vibration Cutting (I) The Generation of a Elliptical Vibration Cutting Motion for Micro Ultrasonic Machining (미세 초음파 타원궤적 진동절삭 (I) 미세 초음파 가공을 위한 타원 절삭경로 생성)

  • Loh Byung-Gook;Kim Gi Dae
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.12 s.177
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    • pp.190-197
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    • 2005
  • For precise micro-grooving and surface machining, a mechanism for creating elliptical vibration cutting (EVC) motion is proposed which uses two parallel piezoelectric actuators. And based on its kinematical analysis, variations of EVC path are investigated as a function of dimensional changes in the mechanism, phase difference and amplitude of excitation sinusoidal voltages. Using the proposed PZT mechanism, various types of two dimensional EVC paths including one dimensional vibration cutting path along the cutting direction and thrust direction can be easily obtained by changing the phase lag, the amplitude of the piezoelectric actuators, and the dimension of the mechanism.

Characteristics of Rotational Vibration of Cutting Edge in Elliptical Vibration Cutting by Modulation of Excitation Frequency (타원궤적 절삭기의 가진주파수에 따른 절삭 날 회전 진동 특성)

  • Loh, Byoung-Gook;Kim, Gi-Dae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.3
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    • pp.258-263
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    • 2011
  • The direction of the cutting tool plays a critical role in elliptical vibration cutting(EVC) where the cutting tool cuts workpiece in a trochoidal motion. In this study, EVC cutting device was developed using two parallel piezoelectric materials and it was observed that the rotation direction of the tool reverses as the EVC device undergoes resonance at which either flexural(cutting direction) or longitudinal( thrust direction) mode shapes occurs. To analytically explain reversal of the rotation direction, kinematic motion analysis of the tool was modified to incorporate amplification of the vibration amplitude and phase introduced by resonance. It successfully demonstrated, through Matlab simulation, reversal of the rotation direction of the cutting tool as the excitation frequency increases beyond resonance frequencies at which either flexural or longitudinal vibration occurs.

Elliptical Vibration Cutting with Variable Trajectory for Ultra-precision Micro-Machining (초정밀 미세가공을 위한 궤적 변화에 따른 타원 궤적 진동 절삭)

  • Kim, Gi-Dae;Loh, Byoung-Gook
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.11
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    • pp.52-58
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    • 2007
  • A cutting device capable of generating various shapes of the cyclic elliptical trajectory of a cutting tool was proposed and micro v-grooving experiments were performed to investigate the characteristics of elliptical vibration cutting (EVC). The proposed cutting device is comprised of a pair of parallel piezoelectric actuators with which harmonic voltages of varying phase difference and magnitude are supplied, creating various shapes of the elliptical tool path. The attributes of the elliptical locus involving the direction of the axis of an ellipse, the rotational direction and amplitudes of a trajectory were fine-tuned for stable operation of the EVC. The EVC characteristics performed with brass and copper revealed reduction in the cutting resistance and suppression of burr formation, resulting in the enhancement of form accuracy of machined micro-features. While the effect of the EVC increases with the increase of excitation frequency and the amplitude, it is found that a change in the cutting force decreases as the amplitude of an elliptical locus increases.

Machining of Micro Structure using Elliptical Vibration Grooving Machine (타원궤적 진동절삭 가공기를 이용한 미세 형상 가공)

  • Kim, Gi-Dae;Loh, Byoung-Gook
    • Journal of the Korean Society for Precision Engineering
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    • v.25 no.11
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    • pp.45-51
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    • 2008
  • Successive micro-scale V-grooves and a grid of pyramids were machined by elliptical vibration tufting (EVC) to investigate feasibility of using EVC as an alternative method of creating micro-molds to photo-lithography and electroforming, which have been commonly employed. An elliptical vibration grooving machine was developed which consists of two orthogonally-arranged piezoelectric actuators, a diamond cutting tool, and a motorized xyz stage. The micro-scale features were machined on materials of copper, duralumin, nickel, and hastelloy and it was found that EVC significantly reduces cutting resistance and prohibits generation of side burrs and rollover burrs, thus resulting in improving machining qualify of micro-molds in ail experimented workpiece materials.

Kinematical Characteristics of Vibration Assisted Cutting Device Constructed with Parallel Piezoelectric Stacked Actuators (평행한 적층 압전 액추에이터로 구성된 진동절삭기의 기구학적 특성 고찰)

  • Loh, Byoung-Gook;Kim, Gi-Dae
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.12
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    • pp.1185-1191
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    • 2011
  • The kinematic characteristics of cutting device significantly affects cutting performance in 2-dimensional elliptical vibration cutting(EVC) where the cutting tool cuts workpiece, traversing a micro-scale elliptical trajectory in a trochoidal motion. In this study, kinematical characteristics of EVC device constructed with two parallel stacked piezoelectric actuators were analytically modeled and compared with the experimental results. The EVC device was subjected to step and low-frequency(0.1 Hz) sinusoidal inputs to reveal only its kinematical displacement characteristics. Hysteresis in the motion of the device was observed in the thrust direction and distinctive skew of the major axis of the elliptical trajectory of the cutting tool was also noticed. Discrepancy in the voltage-to-displacement characteristics of the piezoelectric actuators was found to largely contribute to the skew of the major axis of the elliptical trajectory of the cutting tool. Analytical kinematical model predicted the cutting direction displacement within 10 % error in magnitude with no phase error, but in estimating the thrust direction displacement, it showed a $27^{\circ}$ of phase-lag compared with the measured displacement with no magnitude error.

Micro Turning on Face using Elliptical Vibration Cutting (타원궤적 진동절삭법을 이용한 미세 면선삭)

  • Kim, Gi-Dae;Loh, Byoung-Gook
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.1
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    • pp.82-88
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    • 2009
  • Ultra-precision turning is highly needed to manufacture molds for precision lens. In this study, micro-turning combined with elliptical vibration cutting (EVC), which is known to enhance micro- machining quality, was investigated by installing a rotary stage into the micro-grooving machine. From machining experiments involving materials of copper, brass, and aluminum and single and poly crystalline diamond tools, it was found that EVC produced thinner and curlier chips and that better surface finish could be achieved, compared with conventional turning, owing to prohibition of formation of burrs and built-up edges. Therefore, we found EVC micro turning could be readily utilized to manufacture precision mold.

Minimization of Pattern Size on Polycarbonate Material in V-grooving (PC 폴리머 재료의 미세 V-홈 절삭가공 시 패턴 크기 최소화)

  • Kim, Gi-Dae
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.5
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    • pp.523-527
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    • 2011
  • Polycarbonate (PC) polymer is an engineering plastic which has large tensile strength and impact resistance and is wildly used as functional parts like micro mold. Direct machining of PC materials produces lots of burrs and rough surface due to large ductility and weak heat resistance and hence it is very difficult to machine PC materials using cutting tool to make micro-parts. In this study, elliptical vibration cutting (EVC) or 2-dimensional vibration cutting was performed to minimize the size of micro V-grooves on PC material. From the experimental results, it was observed that as the cutting depth and pattern size become smaller, the better machining quality was obtained, which is attributed to the positive effect of EVC that is dependent on the ratio of vibration amplitude to cutting depth. As the height of V-groove becomes less than $1.8{\mu}m$, however, the machining quality becomes lower as the pattern size decreases.