• Transactions of Materials Processing
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• v.22 no.6
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• pp.334-339
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• 2013

Direct Laser Melting is a prototyping process whereby a 3-D part is built layer wise by melting the metal powder with laser scanning. This process is strongly influenced by the shielding gas and the laser operating parameters such as laser power, scan rate, layering thickness, and rescanning. The shielding gas is especially important in affecting the microstructure and mechanical properties. In the current study, fabrication experiments were conducted in order to analyze the effect of shielding gas on the forming characteristics of direct laser melting. Cylindrical parts were produced from a Fe-Ni-Cr powder with a 200W fiber laser. Surface quality, porosity and hardness as a function of the layering thickness and shield gas were evaluated. By decreasing the layering thickness, the surface quality improved and porosity decreased. The selection of which shield gas, Ar or $N_2$, to obtain better surface quality, lower porosity, and higher hardness was examined. The formability and mechanical properties with a $N_2$ atmosphere are better than those parts formed under an Ar atmosphere.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.340-343
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• 2000

ITO(Indium Tin Oxide) films for transparent electrodes of FPD(Flat Panel Display) were patterned in atmosphere using laser. A pulse type(repetition rate of 10 Hz) Q-switched Nd:YAG laser which can generate the fundamental wavelength at 1064 nm or its harmonics(532, 266 nm) was used for Patterning of the ITO film. In case of using the second harmonic(532 nm) of Nd:YAG laser, the ITO film(thickness of 20 nm) was removed clearly with a laser fluence of 5.2 J/$\textrm{cm}^2$ and a beam scan speed of 200${\mu}{\textrm}{m}$/s. But the glass substrate was damaged when the laser fluence was over 5.2 J/$\textrm{cm}^2$. We discussed the etching mechanism of the ITO film using Nd:YAG laser with observation of the etching characteristics including a depths and widths of ITO films as a function of laser fluence using SEM(Scanning Electron Microscopy) and surface profiler($\alpha$-step 500).

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.6
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• pp.505-510
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• 2016

This paper presents a searching method of corresponding points robust to rotational error for scan-matching used for SLAM(Simultaneous Localization and Mapping) in mobile robot. A differential driving mechanism is one of the most popular type for mobile robot. For driving curved path, this type controls the velocities of each two wheels independently. This case increases a wheel slip of the mobile robot more than the case of straight path driving. And this is the reason of a drifting problem. To handle this problem and improves the performance of scan-matching, this paper proposes a searching method of corresponding points using extraction of a closest point based on rotational radius of the mobile robot. To verify the proposed method, the experiment was conducted using LRF(Laser Range Finder). Then the proposed method is compared with an existing method, which is an existing method based on euclidian closest point. The result of our study reflects that the proposed method can improve the performance of searching corresponding points.

• Journal of Industrial Technology
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• v.28 no.A
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• pp.163-166
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• 2008

In this paper, the swept source optical coherence tomography system has realized using a free-space interferometer based on a beam splitter. Personal computer has completed the control for tunable wavelength laser digitally and the B-scan motor as well. From each experiment for an onion and a salmon egg, we confirmed that the in vivo epidermal cross-sectional images for them can be obtained appropriately.

• Journal of the Korean Geophysical Society
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• v.8 no.3
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• pp.153-157
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• 2005

A discussion of a method has been used with success in terrain modelling to estimate the height at any point on the land surface from irregularly distributed samples. The special requirements of terrain modelling are discussed as well as a detailed description of the algorithm and an example of its application.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.118-123
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• 2011

Manufacturing of the bipolar plate of a direct methanol fuel cell (DMFC) by direct laser melting technology (DLM) was attempted. The DLM technology is highly influenced by process parameters such as laser power, scan rate and layering height. Therefore, an analysis of the DLM technology was performed under various conditions. The bipolar plates were fabricated using the DLM process with 316L stainless steel (STS 316L) plates and powder. Powder melting trials at various energy density were performed in order to select a feasible melting range for a given laser power. The melting line height increases and eventually saturates when the energy density increases, but decreases when the laser power increases at a given energy density. For the estimation of the potential performance of the bipolar plate, the surface roughness and contact resistance of the DLM layer were also analyzed. The changes of line height and thickness are useful information to report when manufacturing bipolar plate of fuel cell through the DLM process.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.4
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• pp.261-268
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• 1999

Laser-induced thermochemical etching has been recognized as a new powerful method for processing a variety of materials, including metals, semiconductors, ceramics, insulators and polymers. This study presents characteristics of direct etching for Si substrate using focused argon ion laser beam in aqueous KOH and $CCl_2F_2$ gas. In order to determine process conditions, we first theoretically investigated the temperature characteristics induced by a CW laser beam with a gaussian intensity distribution on a silicon surface. Major process parameters are laser beam power, beam scan speed and reaction material. We have achieved a very high etch rate up to $434.7\mum/sec$ and a high aspect ratio of about 6. Potential applications of this laser beam etching include prototyping of micro-structures of MEMS(micro electro mechanical systems), repair of devices, and isolation of opto-electric devices.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1389-1393
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• 2007

Selective Laser Sintering (SLS) is currently recognized as a leading process in the new field of solid freeform fabrication (SFF). It is used to fabricate in a short time any 3 dimensional shapes by layer-by-layer sintering of polymer, ceramic or metal powder. To develop this SFF system, it needs effective laser scanning path, temperature and z-axis control for lamination. Therefore, in this study, through the application of control algorithm for sintering process have performed, temperature evaluation for sintering process has performed and the manufacturing sample using SLS process.

• Electrical & Electronic Materials
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• v.9 no.3
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• pp.240-245
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• 1996

Non-ozone layer destructive Chlorofluorocarbon(CFC) altematives(CHCIF$_{2}$ and $C_{2}$H$_{2}$F$_{4}$) have been initially used for laser-induced thenrmochemical etching of GaAs. High etching rate up to 188.mu.m/sec and an aspect ratio of 2.7 have been achieved by a single scan of laser beam, respectively. The etching rate at constant ambient gas pressure was found to saturate for beam power. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron microscopy(AES). Etched profile, depth and width were observed by scanning electron microscope(SEM).

• Proceedings of the KSRS Conference
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• v.1
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• pp.504-507
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• 2006

Airborn Lidar technology has been applied to diverse applications with the advantages of accurate 3D information. Further, Lidar intensity, backscattered signal power, can provid us additional information regarding target's characteristics. Lidar intensity varies by the target reflectance, moisture condition, range, and viewing geometry. This study purposes to generate normalized airborne LiDAR intensity image considering those influential factors such as reflectance, range and geometric/topographic factors (scan angle, ground height, aspect, slope, local incidence angle: LIA). Laser points from one flight line were extracted to simplify the geometric conditions. Laser intensities of sample plots, selected by using a set of reference data and ground survey, werethen statistically analyzed with independent variables. Target reflectance, range between sensor and target, and surface slope were main factors to influence the laser intensity. Intensity of laser points was initially normalized by removing range effect only. However, microsite topographic factor, such as slope angle, was not normalized due to difficulty of automatic calculation.