• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.608-611
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• 2003

In this paper, laser direct micromaching is developed to fabricate micro patterns using UV laser ( λ$_3$= 355 nm). Experimentally, laser beam paths mainly influences the surface shape quality. Thus. we proposed laser beam path generator by extracting shape data in a blueprint worked through CAD modeler and using genetic algorithm that considers the characteristics of laser beam. The results show that various shapes of micro patterns could be manufactured using proposed method in this paper.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.26-31
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• 2008

A precision four-degree-of-freedom measurement system has been developed for simultaneous measurement of four motion errors of a linear stage, which include straightness and angular errors, The system employs a retro-reflector to detect the straightness errors and a plane mirror to detect the angular errors. A common-path compensation method for laser beam drift is put forward, and the experimental results show that the influences of beam drift on four motion errors can be reduced simultaneously. In comparison with the API 5D laser measuring system, the accuracy for straightness measurement is about ${\pm}1.5{\mu}m$ within the measuring range of ${\pm}650{\mu}m$, and the accuracy for pitch and yaw measurements is about ${\pm}1.5$ arc-seconds within the range of ${\pm}600$ arc-seconds.

• Transactions of Materials Processing
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• v.13 no.3
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• pp.216-224
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• 2004

In this study, we have developed a new UV$({\lambda}=355nm)$ laser micromachining technology by direct ablation method without masks. This technology allows that 3D micro parts can be fabricated rapidly and efficiently with a low price. And it has a benefit of reducing fabricating process simply. Due to micro parts' fabrication, such technologies need the control of XYZ stages with high precision, the design of optical devices to maintain micron spot sizes of laser beam and the control technology of laser focus. The developed laser manufacturing process for laser micromachining is that, after extracting coordinates of shape data from CAD model data, a beam path considering manufacturing features of laser beam is created by using genetic algorithm. This generated manufacturing process is sent to stage controller. In order to improve the surface quality of micro parts, we have carried out experiments on iteration manufacturing and beam step-over by using a minimum focus size. Moreover, we have fabricated a micro-channel through the developed laser micromachining technology and verified it through the results.

• Korean Journal of Optics and Photonics
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• v.28 no.4
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• pp.153-157
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• 2017

An infrared camera and laser common-path optical system is applied to DIRCM (directional infrared countermeasures), to increase boresighting accuracy and decrease weight. Thermal effects of a laser beam in a common-path optical system are analyzed and evaluated, to predict any degradation in image quality. A laser beam with high energy density is absorbed by and heats the optical components, and then the surface temperature of the optical components increases. The heated optical components of the common-path optical system decrease system transmittance, which can degrade image quality. For analysis, the assumed simulation condition is that the laser is incident for 10 seconds on the mirror (aluminum, silica glass, silicon) and lens (sapphire, zinc selenide, silicon, germanium) materials, and the surface temperature distribution of each material is calculated. The wavelength of the laser beam is $4{\mu}m$ and its output power is 3 W. According to the results of the calculations, the surface temperature of silica glass for the mirror material and sapphire for the lens material is higher than for other materials; the main reason for the temperature increase is the absorption coefficient and thermal conductivity of the material. Consequently, materials for the optical components with high thermal conductivity and low absorption coefficient can reduce the image-quality degradation due to laser-beam thermal effects in an infrared camera and laser common-path optical system.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.8
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• pp.721-728
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• 2014

In this paper, it is proposed a method of optimizing path parameters for large-area laser processing. On-the-fly system is necessary for large-area laser processing of uniform quality. It is developed a MOTF(Marking On-The-Fly) board for synchronizing the stage and scanner. And it is introduced the change of the error due to the change of parameters and algorithm for large-area laser processing. This algorithm automatically generates stage path and a velocity profile using acceleration and deceleration parameters. Since this method doesn't use a G-code, even if without expert knowledge, it has an advantage that can be accessed easily. Angle of one of the square of $350{\times}350mm$ was changed from $50^{\circ}$ to $80^{\circ}$ and analyzed the error corresponding to the value of Ta. It is calculated the value of Ta of the best with a precision of 20um through measurement of accuracy according to the Ta of each angle near the edge.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.141-147
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• 2003

This paper represents an absolute positioning system using a light navigation path for mobile robot. The absolute positioning system is composed of the projector unit which generates a laser beam using laser diode and mobile robot with the optical detector which has some optical sensors. The projector unit is fixed over the navigating plane of mobile robot to generate the light navigation path, and the optical detector located upper part of mobile robot detects the generated laser beam from the projector. The navigation of mobile robot is controlled by the micro-processor which compares the detected present position from the detector with the previously programmed navigation path. And experimental results show that our sensor system can be used for the absolute positioning system of the mobile robot.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.583-588
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• 2002

The purpose of the study is to evaluate fracture toughness on the Laser and the electron beam welded joints of high tensile steels (HT500, HT550, HT650) by using 3-point bend CTOD and Charpy impact test. WM (weld metal) CTOD tests have been carried out using two kinds of CTOD specimen, the Laser beam welding (108mm length, and 24mm width, and 12mm thickness) and the electron beam welding (l71mm length, and 38mm width, and 19mm thickness). WM Charpy impact specimen is a standard V-notch type, and the temperature of the experiment is changed from -45 to 20 degree of centigrade. FE-analysis is also performed in order to investigate the effect of stress-strain fields on fracture characteristics. Results of the standard V-notch Charpy test are influenced by strength mis-match effect and the absorbed energy vE depends on crack path, and The transition temperature of Laser beam welded joints is more higher than that of electron beam welded joints. Results of the 3-point bend test give low critical CTOD and the crack path is in the weld metal of al specimens. These results indicate fracture toughness characteristics of the welded joints and transition temperature of HT500 are similar both a Laser beam welded joint and an electron beam welded joint. But the fracture toughness and the transition temperature of the electron beam welded joints of HT550 and HT650 are higher than those o the Laser beam welded joints.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.4
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• pp.428-433
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• 2015

A non-symmetric laser beam was used for cutting a thin glass substrate and its effect was investigated. In laser cutting of brittle materials, controlling crack initiation on the surface is crucial; however, it is difficult to ensure that crack propagation occurs according to a designed laser path. A lot of deviation in crack propagation, especially at the edge of the substrate, is usually observed. A non-symmetric laser beam generates a non-uniform energy distribution, which enhances directional crack propagation. A 20-W pulsed YAG laser was used for cutting a thin glass substrate. Parametric analysis was carried out and the crack control of the non-symmetric laser beam was improved. A theoretical model was presented and the limitations of the proposed process were also discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1295-1298
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• 2004

Selective Laser Sintering(SLS) method is one of Rapid Prototyping(RP) technologies. It is used to fabricate desirable part to sinter powder and stack the fabricated layer. To develop this SLS machine, it needs effective scanning path and the development of scanning device. This paper shows how to make fast scanning path with respect to scan spacing, laser beam size and scanning direction from 2-dimensional sliced file generated in commercial CAD/CAM software. Also, we develop the scanning device and its control algorithm to precisely follow the generated scanning path. Scanning path affects precision and total machining time of the final fabricated part. Sintering occurs using infrared laser which has high thermal energy. As a result, shrinkage and curling of the fabricated part occurs according to thermal distribution. Therefore, fast scanning path generation is needed to eliminate the factors of quality deterioration. It highly affects machining efficiency and prevents shrinkage and curling by relatively lessening the thermal distribution of the surface of sintering layer. To generate this fast scanning path, adaptive path generation is needed with respect to the shape of each layer, and not simply x, y scanning, but the scanning of arbitrary direction must be enabled. This paper addresses path generation method to focus on fast scanning, and development of scanning system and control algorithm to precisely follow generated path.

• Laser Solutions
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• v.5 no.3
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• pp.15-20
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• 2002

The principal obstacle to selection of a laser processing method in production is its relatively high equipment cost and the natural unwillingness of production supervision to try something new until it is thoroughly proven. The major objective of this work is focused on the combined features of gas tungsten arc and a low-power cold laser beam. In this work, the laser beam from a 7 watts carbon monoxide laser was combined with electrical discharges from a short-pulsed capacitive discharge GTA welding power supply. When the low power CO laser beam passes through a special composition shielding gas, the CO molecules in the gas absorbs the radiation, and ionizes through a process blown as non-equilibrium, vibration-vibration pumping. The resulting laser-induced plasma(LIP) was positioned between various configurations of electrodes. The high-voltage impulse applied to the electrodes forced rapid electrical breakdown between the electrodes. Electrical discharges between tungsten electrodes and aluminum sheet specimens followed the ionized path provided by LIP. The result was well-focused melted spots.