• 한국유변학회:학술대회논문집
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• 한국유변학회 2006년도 춘계 학술발표회 논문집
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• pp.81-84
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• 2006

Slot coating process, in continuous and patch modes, has been applied for the many precise coating products, e.g., flat panel displays and second batteries. However, manufacturing uniform coating products is not a trivial task at high-speed operations because various flow instabilities or defects such as leaking, bubbles, ribbing, and rivulets are frequently observed in this process. It is no wonder, therefore, that many efforts to understand the various aspects of dynamics and coating windows of this process have been made both in academia and industry. In this study, as the first topic, flow dynamics within the coating bead in slot coating process has been investigated using the one-dimensional viscocapillary model by lubrication approximation and two-dimensional model by Flow-3D software. Especially, operability windows in both 1D and 2D cases with various slot die lip designs have been successfully portrayed. Also, effects of process conditions like viscosity and coating gap size on slot coating window have been analyzed. Also, some experiments to find minimum coating thickness and coating windows have been conducted using slot die coater implemented with flow visualization device, corroborating the numerical results. As the second topic, flow dynamics of both Newtonian and Non-Newtonian fluids in patch or pattern slot coating process, which is employed in manufacturing IT products such as secondary batteries, has been investigated for the purpose of optimal process designs. As a matter of fact, the flow control in this system is more difficult than in continuous case because od its transient or time-dependent nature. The internal die and die lip designs for patterned uniform coating products have been obtained by controlling flow behaviors of coating liquids issuing from slot. Numerical simulations have been performed using Fluent and Flow-3D packages. Flow behavior and pressure distribution inside the slot die has been compared with various die internal shapes and geometries. In the coating bead region, efforts to reduce irregular coating defects in head and tail parts of one patterned coating unit have been tried by changing die lip shapes. It has been concluded that optimal die internal design gas been developed, guaranteeing uniform velocity distribution of both Newtonian and shear thinning fluids at the die exit. And also optimal die lip design has been established, providing the longer uniform coating layer thickness within one coating unit.

• Current Optics and Photonics
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• 제3권1호
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• pp.16-21
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• 2019

We present a broad-bandwidth comb-spacing-swept source (CSWS) based on a differential polarization delay line (DPDL) for interferometric three-dimensional (3D) imaging. The comb spacing of the CSWS is repeatedly swept by the tunable DPDL in the multiwavelength source to provide depth-scanning optical coherence tomography (OCT). As the polarization differential delay of the DPDL is tuned from 5 to 15 ps, the comb spacing along the wavelength continuously varies from 1.6 to 0.53 nm, respectively. The wavelength range of various semiconductor optical amplifiers and the cavity feedback ratio of the tunable fiber coupler are experimentally selected to obtain optimal conditions for a broader 3-dB bandwidth of the multiwavelength spectrum and thus provide a higher axial resolution of $35{\mu}m$ in interferometric OCT imaging. The proposed CSWS-OCT has a simple imaging interferometer configuration without reference-path scanning and a simple imaging process without the complex Fourier transform. 3D surface images of a via-hole structure on a printed circuit board and the top surface of a coin were acquired.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.3-10
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• 2008

Micro-electrical discharge machining (micro-EDM) is an effective method for machining all types of conductive materials regardless of hardness. Since micro-EDM is an electro-thermal process, the energy supplied by the pulse generator is an important factor in determining the effectiveness of the process. In this study, an investigation was conducted on the micro-EDM of tungsten carbide (WC) to compare the performance of transistor and resistance/capacitance (RC) pulse generators in obtaining the best quality micro-hole. The performance was measured by the machining time, material removal rate, relative tool wear ratio, surface quality, and dimensional accuracy. The RC generator was more suited for minimizing the pulse energy, which is a requirement for fabricating micro-parts. The smaller-sized debris formed by the low-discharge energy of RC micro-EDM could be easily flushed away from the machined zone, resulting in a surface free of burrs and resolidified molten metal. The RC generator also required much less time to obtain the same quality micro-hole in WC. Therefore, RC generators are better suited for fabricating micro-structures, producing good surface quality and better dimensional accuracy than the transistor generators, despite their higher relative tool wear ratio.

• 한국분말재료학회지
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• 제25권6호
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• pp.475-481
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• 2018

Selective laser melting (SLM), a type of additive manufacturing (AM) technology, leads a global manufacturing trend by enabling the design of geometrically complex products with topology optimization for optimized performance. Using this method, three-dimensional (3D) computer-aided design (CAD) data components can be built up directly in a layer-by-layer fashion using a high-energy laser beam for the selective melting and rapid solidification of thin layers of metallic powders. Although there are considerable expectations that this novel process will overcome many traditional manufacturing process limits, some issues still exist in applying the SLM process to diverse metallic materials, particularly regarding the formation of porosity. This is a major processing-induced phenomenon, and frequently observed in almost all SLM-processed metallic components. In this study, we investigate the mechanical anisotropy of SLM-produced 316L stainless steel based on microstructural factors and highly-oriented porosity. Tensile tests are performed to investigate the microstructure and porosity effects on mechanical anisotropy in terms of both strength and ductility.

• 대한기계학회논문집A
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• 제35권8호
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• pp.855-861
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• 2011

본 연구에서는 극박 압연 이론과 6 단 압연기 수식 모델을 이용하여 압연 후 판 형상 예측에 대하여 제안하였다. 폭 방향에서 롤 사이의 접촉 압력과 판과 워크롤 사이의 압연하중은 6 단 압연기의 형상학적 구조와 경계조건을 이용한 수식모델을 통하여 계산된다. 그리고 압연 방향의 압연하중 분포는 Fleck 의 극박 압연 이론을 이용하여 계산하였다. 워크롤의 3 차원 탄성 변형량은 폭 과 압연방향의 압력분포에 의하여 계산된다. 이때, 3 차원 판 형상은 워크롤의 탄성변형에 의하여 얻어진다. 또한 3 차원 판 형상은 극박 압연 실험과 유한요소해석을 통하여 검증하였다.

• 대한치과기공학회지
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• 제34권3호
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• pp.213-220
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• 2012

Purpose: The aim of this study was to determine the repeatability and reproducibility of two dental scanners. Methods: The master die and the stone replicas(Kavo, Germany) were digitized in touch-probe scanner(Incise, Renishaw, UK), white light scanner(Identica, Medit, Korea) to create 3-dimensional surface-models. The number of points in the point clouds from each reading were calculated and used as the CAD reference model(CRM). Discrepancies between the points in the 3-dimensional surface models and the corresponding CRM were measured by a matching-software(Power-Inspect R2, Delcam Plc, UK). The t-student test for one samples were used for statistical analysis. Results: The reproducibility of both scanner was within $3{\mu}m$, based on mean value. The mean value between measurements made directly on the touch probe scanner digital models and those made on the white light scanner digital models was $2.20-2.90{\mu}m$, and was statistically significant(P<0.05). Conclusion: With respect to adequate data acquisition, the reproducibility of dental scanner differs. Three-dimensional analysis can be applied to differential quality analysis of the manufacturing process as well as to evaluation of different analysis methods.

• 농업과학연구
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• 제22권1호
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• pp.11-23
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• 1995

The CAD/CAM system for the manufacturing automation is the newest technology in mechanical engineering area and becomes the important research subject nowadays. Most of all hardwares and softwares for the CAD/CAM system used in the our manufacturing companies such as automobile company are developed by the foreign country and the purchasing price of them is very expensive but their applicability to a certain area is very limited. This study was conducted to develope a CAD/CAM system for the design and the automatic manufacturing of the iron pattern shaped with 3 - dimensional free curved surface, and to test its applicability to the design and the manufacturing of the rotary blade. The results obtained from the study are as follow; 1. The CAD system which can process graphic procedures from the free curved surface shaped data was developed with personal computer. 2. The CAM main program was developed. This main program could produce CL data from CAD data file by checking the tool interference according to the cutting mode. 3. The sub. program which can simulate the tool trace from the CL data was developed. 4. The post processor for the Deckel FP2NC NC milling machine from CL data file was developed and the sub program could transmit NC program through modem to NC milling machine was developed. 5. The developed CAM system seemed to be applicable to any other system. Because the measuring results of the cross sectional thickness of the plastic model from the manufacturing iron pattern by the system showed that this system could properly check the tool interference. 6. In took 75~90 hours to manufacture two iron patterns of rotary blade. For the sake of convenience in applying to the other systems, this system was developed in BASIC and FORTRAN computer language and minimum portion of machine language as possible.

• 대한기계학회논문집A
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• 제34권7호
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• pp.929-933
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• 2010

3 차원 패키징을 위해 열가압 공정으로 제조된 Cu-Cu 접합 계면의 접합 특성을 평가하기 위해 4 점 굽힘 실험을 수행하였다. Cu가 코팅된 Si 웨이퍼 2 장을 $350^{\circ}C$에서 1 시간 동안 15kN 의 하중으로 접합시킨 후, 동일한 온도에서 1 시간동안 어닐닝을 수행하였다. 접합된 웨이퍼를 $30\;mm\;{\times}\;3\;mm$ 크기로 잘라 시험편을 준비하였다. 시험편의 중심에 깊이 $400\;{\mu}m$의 노치를 가공하였다. 시험기에 광학계를 부착하여 노치에서의 크랙 발생과 계면에서의 크랙 진전을 관찰하였다. 일정한 테스트 속도로 실험을 수행하여, 이에 상응하는 하중을 측정하였다. Cu-Cu 접합 계면 에너지는 $10.36\;J/m^2$ 으로 측정되었으며, 파괴된 계면을 분석하였다. 표면 분석 결과, $SiO_2$와 Ti의 계면에서 파괴가 일어났음을 확인하였다.

• 한국정밀공학회지
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• 제34권2호
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• pp.89-94
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• 2017

Micro-screws can be defined by their outer diameter of generally less than 1 mm. They are manufactured by head forging and thread rolling processes. In this study, the thread rolling process was numerically analyzed for a micro-screw with a diameter and pitch of 0.8 and 0.2 mm, respectively. Through finite element (FE) analysis, the effects of two design parameters (die gap and chamfer height) on the dimensional accuracy were investigated. Three combinations of chamfer heights were chosen first and the corresponding die gap candidates selected by geometric calculation. FE analyses were performed for each combination and their results indicated that the concave chamfer height should be less than 0.3 mm, while a 10 ?m difference in the die gap might cause degeneration in dimensional accuracy. These results conclude that ultra-high accuracy is required in die fabrication and assemblies to ensure dimensional accuracy in micro-screw manufacturing.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.566-569
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• 2002

Rapid Prototyping is a prototyping technology that produces complicated parts directly form three dimensional CAD data with high efficiency, and has been extensively applied to various manufacturing processes. The aim of this research is to apply a 3D printer part as wax pattern in the investment casting process. The difference between conventional pattern wax and 3D printer wax is compared by experiments. The direct casting method is developed for ceramic-shell investment casting.