• 한국기계가공학회지
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• 제15권4호
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• pp.93-100
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• 2016

The laser surface treatment of magnesium alloy was studied. $ZrO_2$ was used as sintering ceramics, and its corrosion resistance was verified. Appropriate laser parameters were proposed for homogeneous solidification of the sintered layer. The chemical compositions of the sintered layer were analyzed with laser-induced breakdown spectroscopy. $Na_2SO_4$ was used for a corrosion test, and the resistance of the sintered sample was confirmed. The microstructures of the sintered parts were also examined. The solidified grains on the top sintered surface were observed; however, reasonable fusion was obtained at the interface between the baseline and the ceramics. Laser surface treatment using $ZrO_2$ on magnesium alloy showed an improvement in corrosion resistance.

• 한국정밀공학회지
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• 제26권8호
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• pp.29-34
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• 2009

• 한국재료학회지
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• 제14권4호
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• pp.300-306
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• 2004

A laser welding has been made between sintered tip of Fe-Co-W and low carbon steel shank for the diamond saw blade. The welding characteristics and formation of defect has been investigated carefully for the weld fusion zone in different welding condition. Full penetration has been observed for the whole range of heat input investigated in the present work. Bead width and under-fill have been increased with the increase of heat input. With increasing of heat input small cavities were decreased while large cavities were increased. The ratio of total cavity area to the entire weld bead area was not changed significantly with change of heat input. Most of cavities were found near the tip, and supposed to be formed from the pore in the tip.

• 한국기계가공학회지
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• 제21권7호
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• pp.1-9
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• 2022

Peeling and dimensional deformation that occur during a manufacturing process are accompanied by an increase in the manufacturing cost and production time caused by manufacturing defects. In order to solve this problem, it is essential to predict risk factors at the design stage through computational analysis of the additive manufacturing process and to control shape distortion due to residual stress. In this study, the dimensional characteristics were improved by applying the distortion compensation design through computational analysis to minimize the distortion occurring in the DMLS(Direct Metal Laser Sintering) method of the metal additive manufacturing process.

• 한국레이저가공학회지
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• 제7권3호
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• pp.25-36
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• 2004

This study was performed to clarification of the formation of weld discontinuities in the dissimilar laser fusion zone. Welding parameters were beam power of 1300, 1430, 1560, and 1700 W and travel speed of 1, 1.3, and 1.7 m/min. Most cavities in the fusion zone were observed near the tip. Cavities in the fusion zone observed to be formed and grown from pores in the tip. More cavities were formed as the beam position moves to the tip side. Small cavities were decreased but large cavities were increased when the energy input increased. W content in the fusion zone was increased with heat input and as the beam position close to the tip. In the fusion zone, W content in the dendrite boundary was increased with heat input. Considering the propagation path and fracture morphology, cracks were solidification cracking, and were initiated and propagated along the dendrite boundaries. The formation of cracks might be related with the W rich ${\mu}$ phase which was formed in the grain boundaries and dendrite boundaries.

• 한국정밀공학회지
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• 제23권4호
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• pp.183-190
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• 2006

Digital 3D Real Object Duplication System (RODS) consists of 3D Scanner and Solid Freeform Fabrication System (SFFS). It is a device to make three-dimensional objects directly from the drawing or the scanning data. In this research, we developed an office type SFFS based on Three Dimensional Printing Process and an industrial SFFS using Dual Laser. An office type SFFS applied sliding mode control with sliding perturbation observer (SMCSPO) algorithm for control of this system. And we measured process variables about droplet diameter measurement and powder bed formation etc. through experiments. In case of industrial type SFFS, in order to develop more elaborate and speedy system for large objects than existing SLS process, this study applies a new Selective Dual-Laser Sintering (SDLS) process and 3-axis Dynamic Focusing Scanner for scanning large area instead of the existing f lens. In this process, the temperature has a great influence on sintering of the polymer. Also the laser parameters are considered like that laser beam power, scan speed, and scan spacing. Now, this study is in progress to evaluate the effect of experimental parameters on the sintering process.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2016년도 추계학술대회 논문집
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• pp.134-134
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• 2016

The effect of different thermal treatments on the sub-50 nm copper nanoparticles is examined in the aspects of chemical, electrical and surface morphology. The copper nanoparticles are chemically synthesized and fabricated for paste-type solution. Simple bar coating method is practiced as a deposition process to form copper thin film on a typical slide glass. Deposited copper thin films are annealed by two different routes: general tube furnace with 99.99 % Ar atmosphere and selective laser sintering process. The thermal behavior of the different thermal-treated copper thin films is compared by SEM, XRD, FT-IR and XPS analysis. In this study, the laser sintering process ensures low annealing temperature, fast working speed and ambient-accessible route. Moreover, the laser-sintered copper thin film shows good electrical property and enhanced chemical stability than conventional thermal annealing process. Consequently, the proposed laser sintering process can be compatible with plastic substrate for flexible applications.

• 대한치과보철학회지
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• 제56권2호
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• pp.173-178
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• 2018

직접식 금속 레이저 소결 방식 시스템은 기공 오차 및 주조 결함 없이 제작 비용 및 제조 시간 단축을 장점으로 전악 임플란트 지지 고정성 보철물 제작에 유용하다. 본 증례에서는 직접식 금속 레이저 소결 방식과 치과용 캐드캠으로 제작된 단일구조 지르코니아 크라운을 사용하여 무치악 상악에서 임플란트 지지 고정성 치과 보철물의 성공적인 결과를 보고하고 임상적 의의를 평가하였다. 51세의 건강한 중년 여성이 상악 전 치아의 동요도를 주소로 서울대학교 치과병원에 내원하였다. 모든 상악 치아 발치 후 직접식 금속 레이저 소결 기술 및 캐드캠 단일구조 지르코니아 크라운을 사용하여 코발트-크롬 프레임을 포함하는 임플란트 지지 고정성 치과 보철물을 제작하였다. 최종 수복물 장착 6개월 후, 기계적 및 생물학적 합병증은 발견되지 않았고 보철물은 기능 및 심미적으로 만족스러운 결과를 보였다. 직접식 금속 레이저 소결 시스템을 이용하여 추가적인 기공 작업 없이 임플란트 지지 고정성 보철물을 제작하여 제조 시간을 단축하고 신뢰할 수 있는 정확도와 적합성을 얻었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.183-183
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• 2011

리튬 이온 배터리의 cathode 및 electrolyte 재료로 사용되는 LiCoO2을 sputtering이나 pulsed laser deposition을 이용하여 박막으로 증착하기 위해서는 target이 필요하다. Target은 원료 분말을 가압 성형한 후 고온에서 소결하여 제조된다. LiCoO2 target 제조과정에서 고밀도를 얻기 힘들고 Li 성분의 증발이 일어난다. 또한 Li2O 분말은 흡습성이 매우 크다. 본 연구에서는 시간과 온도를 조절하여 최적화된 소결 과정을 통해 target의 밀도가 이론밀도와 근사한 값을 갖도록 하고, LiCoO2 또는 Co3O4 분말에 각각 흡습성이 낮은 Li2CO3 분말을 첨가하여 Li 성분을 조절하였다. Li과 Co의 조성비가 1:1-2:1인 고밀도의 LiCoO2 target을 제조하여 박막 증착 후 Li과 Co의 조성비가 1:1이 되도록 하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.1299-1302
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• 2004

A real object duplication system (RODS), including three dimensional (3D) scanner and solid freeform fabrication system (SFFS), is a device to make three-dimensional objects directly from the drawing or photo data. A Selective Multi-Laser Sintering (SMLS) process designed in this paper is by which computer images received using 3D scanner are built up from polymer powder on building room of large size using dual laser at industrial type SFF system. Using the process can rapidly produce real object duplication components of industrial type such as cylinder, engine block, chassis of automobile, etc. In this paper, the industrial type SFF system using SMLS process is manufactured and the system is satisfied with high precision and high speed processing technique. To research characteristics of each part for theindustrial type SFF system, a structure and thermal analysis and test of each part is carried out. Also, to achievement of high performance for industrial type SFF system, design and fabrication for the structure, heater, nitrogen supply, laser and control part are carried out.