• 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.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.195-201
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• 2002

This paper deals with the precision grinding for aspherical surface of optical parts. A parallel grinding method using the spherical wheel was suggested as a new grinding method. In this method, the wheel axis is positioned at a $\pi$/4 from the Z-axis in the direction of the X-axis. An advantage of this grinding method is that the wheel used in grinding achieves its maximum area, reducing wheel wear and improving the accuracy of the ground mirror surface. In addition, a truing by the CG (curve generating) method was proposed. After truing, the shape of spherical wheel transcribed on the carbon is measured by the Form-Talysurf-120L. The error of the form in the spherical wheel which is the value ${\Delta}x$ and $R{^2}{_y}$ inferred from the measured profile data is compensated by the re-truing. Finally, in the aspherical grinding experiment, the WC of the molding die was examined by the parallel grinding method using the resin bonded diamond wheel with a grain size of ＃3000. A form accuracy of 0.16${\mu}m$ P-V and a surface roughness of 0.0067${\mu}m$ Ra have been resulted.

• Korean Journal of Metals and Materials
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• v.49 no.9
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• pp.726-731
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• 2011

The present work shows how the flexural displacement-induced fracture strength of silicon devices, whose back surfaces have wafer grinding-induced scratch marks, depends on the crystallographic orientation. Experimental results indicate that silicon devices with scratch marks parallel to their lateral direction (i.e. reference axis in this work) are very susceptible to flexural fracture, as compared to devices with marks which deviated from the direction. The 3-point bending test shows that the fracture strength of silicon devices having marks which are oriented away from the reference axis is 2.6 times higher than that of devices with marks parallel to the axis. It was particularly interesting to see that silicon devices with identical preferred marks even reveal different fracture strengths, depending on whether the marks are involved in specific crystal planes such as {111} or {011}, called cleavage planes. This work demonstrates that silicon devices with the reference axis-aligned scratch marks not existing on such cleavage planes can have higher fracture strength approximately 20% higher than those existing on the planes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2237-2244
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• 2002

This research develops a low-cost and high accuracy kinematic calibration method based on the following principles: 1) the platform locations are accurately measured by a constrained movement to inspect a calibration target; 2) the constrained movement is chosen to guarantee the parameter observability; 3) the mechanical fixture to constrain the movement and the sensor to check the constrained movement are implemented by low-cost and high-accuracy devices; 4) the calibration is easily done at an industrial environment. The kinematic parameters calibrated with respect to a single plane aren't influenced due to the misalignment of the plane. A parameter observability is successfully obtained even through one planar constraint, which guarantees that all kinematic parameters are estimated by minimizing the cost function.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1991.10a
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• pp.116-123
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• 1991

사각 patch로써 곡면을 표현하는 일반적인 CAD/CAM시스템에서 NC가공을 위한 가공데이타를 생성할 때에는 보통 두가지 가공방법을 사용한다. 그 하나는 isoparametric가공이며 다른 하나는 cartesian가공이다. 금형부에서 사용하는 CAD/CAM시스템인 catia에서도 위의 두가지 NC가공방식을 모두 사용할 수 있다. 그런데 isoparametric가공의 경우, 공구간섭처리를 위한 곡면모델의 수정에 많은 시간이 소요되며, NC프로그래머의 실수로 인한 가공불량 발생의 가능성도 크고 황삭가공에도 매우 불편하다. 이러한 문제는 cartesian가공방법으로 해결이 가능하며, catia의 경우 parallel plane machining기능이다. 그러나 이 기능을 catia에서 통상적인 방법으로 modeling된 곡면에 적용할 경우에 그 신뢰성이 매우 낮다. 따라서 금형부에서는 그 방식은 cartesian으로 하되 신뢰성이 높은 NC가공 S/W를 개발하게 되었다. 이는 catia시스템에서 modeling된 곡면으로부터 NC 가공데이타를 생성하는 S/W로서 VS Fortran으로 작성되었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.537-538
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• 2006

Split and recombine type reaction module was made by electrical discharge machining. The reaction module has special features to well mix the two reactants which have high flow ratio or high concentrations difference. It could be achieved by deviding one flow equally by two and inserting second flow in between. The mixing performance was measured by a parallel competing reaction with iodide-iodate system. The result shows that the developed three inlets micromixer has better mixing efficiency than comercialized Y type micromixer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.647-655
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• 2003

This paper studies the observability of calibration system with a constraint movement by a constraint operator. The calibration system with the constraint movement need only simple sensing device to check whether the constraint movements are completed within an established range. However, it yields the concern about the poor parameter observability due to the constraint movements. This paper uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of a observation matrix. The number of identifiable parameters are examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a parallel typed machining center and the calibration results are presented. These results verify that the calibration system with low-cost indicators and simple planar table is accurate as well as reliable.

• Smart Structures and Systems
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• v.21 no.2
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• pp.151-161
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• 2018

A new type of cascade sandwiched piezoelectric ultrasonic transducer is presented and studied. The cascade transducer is composed of two traditional longitudinally sandwiched piezoelectric transducers, which are connected together in series mechanically and in parallel electrically. Based on the analytical method, the electromechanical equivalent circuit of the cascade transducer is derived and the resonance/anti-resonance frequency equations are obtained. The impedance characteristics and the vibrational modes of the transducer are analyzed. By means of numerical method, the dependency of the resonance/anti-resonance frequency and the effective electromechanical coupling coefficient on the geometrical dimensions of the cascade transducer are studied and some interesting conclusions are obtained. Two prototypes of the cascade transducers are designed and made; the resonance/anti-resonance frequency is measured. It is shown that the analytical resonance/anti-resonance frequencies are in good agreement with the experimental results. It is expected that this kind of cascade transducer can be used in large power and high intensity ultrasonic applications, such as ultrasonic liquid processing, ultrasonic metal machining and ultrasonic welding and soldering.

• 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.

• IE interfaces
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• v.12 no.2
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• pp.166-173
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• 1999

In this paper, a load balancing problem among operators is considered, when one or more identical machines can be assigned to an operator. The operations of a job are separated into three categories : machine-controlled elements, operator-controlled elements and machine/operator-controlled elements. Machining or forming operations are included into the first category. The second category includes inspection and moving to another machine, and the last category includes setup and loading/unloading operation. The objective is to balance the workloads among operators under the constraints of available machine-time and operator-time. A hierarchical heuristic solution procedure is suggested for allocating jobs to each machine and allocating machines to each operator. The performance of the algorithm is evaluated with various data set.