• Proceedings of the Korean Society of Precision Engineering Conference
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• 1992.10a
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• pp.106-110
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• 1992

컴퓨터에 의한 입체 형상 이용 기술의 발달로 3차원 CAD 데이타 형상의 제품을 2차원 형상의 층으로 연속적으로 적층 하는 입체인쇄(Stereolithography)기술개발이 활발하게 이뤄지고 있어 부품설계와 생산에 혁신을 예고하고 있으며, 이 같은 입체 인쇄 기술 중에서 특히, 특정 주파수의 빛에 의하여 경화되는 광 경화성수지(Photopolymer)에 레이저(Laser)를 주사하면 표면의 미소경화부만 경화되는 성질을 이용하여 소재를 경화시키는 광 조형법리 각광을 받고 있다. 본 논문에서는 광조형법에 의한 모델성형시 레이저빔의 조사에 의하여 야기되는 광경화성 수지의 상변화에 의한 성형물의 수축 및 뒤틀림에 대한 연구를 수행하였다

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.661-662
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• 2011

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.171-179
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• 2004

Micro-stereolithography technology has made it possible to fabricate a freeform 3D microslructure. This technology is based on conventional stereolithography, in which a UV laser beam irradiates the open surface of a UV-curable liquid photopolymer, causing it to solidify. In micro-stereolithography, a laser beam of a few $\mu m$ diameter is used to solidify a very small area of the photopolymer. This is one of the key technological elements, and can be achieved by using a focusing lens. Thus, the solidification phenomena of the liquid photopolymer must be carefully investigated. In this study, the photopolymer solidification phenomena in response to variations in the scanning pitch of a focused laser beam was investigated experimentally. The effect of layer thickness on the solidification width and depth was also examined. These studies were conducted under the conditions of relatively lower laser power and relatively higher scanning speed. Moreover, the photopolymer solidification phenomena for the relatively higher laser power and lower scanning speed was investigated, too. In this case, comparing to the case of lower laser power and higher scanning speed, the photopolymer absorbed large amount of irradiation energy of the laser beam. These results were compared with those obtained from a photopolymer solidification model. From these results, a new laser-scanning scheme was proposed according to the shape of the 3D model. Samples by each method were fabricated successfully.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.1015-1016
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• 2009

• Journal of the Korean Society for Precision Engineering
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• v.23 no.8 s.185
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• pp.33-38
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• 2006

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.525-526
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• 2006

• Polymer(Korea)
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• v.34 no.5
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• pp.469-473
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• 2010

The curing mechanism and characteristics of UV curable acrylate resins were studied using Photo-DSC, FTIR, and Raman spectroscopy. Effects of chemical structures of acrylate, numbers of functional group, and UV intensity on curing kinetics were investigated with Photo-DSC. FTIR and Raman spectroscopy has been used to understand curing mechanisms and reaction conversion. In order to investigate the effect of oxygen on the photo-curing reaction, the curing process was compared between the acrylate and thiol-ene resins. The reaction conversion was found to be less than 80% for acrylate resins. The photo-curing reaction of the acrylate resin could not proceed to the end because of oxygen which acts as a reaction inhibitor while the thiol-ene resin was hardly affected from oxygen during the curing process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.147-148
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• 2006

A research on scaffold fabrication has been progressed in many research groups. However, the mechanical properties of existing biodegradable materials are still not satisfactory. But, PPF (poly (propylene fumarate)) has a good mechanical property in comparison to other biodegradable materials. Nevertheless, the viscosity of the synthesized PPF is too high to fabricate structures using micro-stereolithography. Therefore, the viscosity of the resin was made low by adding the diethyl fumarate and this material could be used in micro-stereolithography apparatus. Then, a photoinitiator was added for photo crosslinking of the DEF/PPF resin. 2.5D and 3D scaffolds were fabricated our system and curing characteristics of the resin were analyzed through the experiment.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1037-1040
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• 2002

In micro-stereolithography technology, fabrication conditions that include laser power, laser scan speed, laser scan pitch, and material property of photopolymer such as penetration depth and critical exposure are considered as major process variables. But the existing scan path generation methods based only on CAD model have not taken them into account, which has resulted in cross-section dimension of low accuracy. Thus, to enhance cross-section dimensional accuracy, the physical resin solidification n phenomena should be reflected in laser scan path generation and stage operating code. In this paper, multi-line experiments based on single line solidification model are performed. And the method for improving cross-section dimensional accuracy is presented, which is to apply the database based on experimental results to laser scan path generation.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.621-626
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• 2012

In this study, the composite coating materials with improved thermal insulation property were prepared by incorporating the hollow micro-spheres with high heat transfer resistance. The UV curable resin system consisting of hexa aliphatic urethane acrylate (UP118), trimethylolpropane triacrylate (TMPTA), 1,6-hexanediol diacrylate (HDDA), and photoinitiator (Irgacure184) was employed as an organic binder. The glass substrates were coated by the prepared composites via bar coating method and cured under UV radiation. The optical transparency, thermal insulation property, adhesion, and surface hardness of the glass coated with composites containing different type of micro-spheres were investigated. The incorporation of micro-spheres with only 20 vol% of content resulted in remarkable improvement in the thermal insulation property of the coated glass. In addition, the transparent coated glass with light transmittance of about 80% could be obtained when silica micro-sphere (SP) was used as a thermal barrier.