• 한국정밀공학회지
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• 제32권10호
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• pp.917-923
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• 2015

3D Printing has a great advantage for its capabilities in manufacturing complicated structures in a reasonable manufacturing time, and thus is widely used in various fields. Due to the high cost of the equipment and material, a fairly acceptable equipment, the Projection Stereolithography Apparatus (PSLA), has been developed, using the projection pattern approach for the purpose of quick manufacturing. We evaluated its surface quality, as compared with that of other systems. The result is the development of a high-performance, low-cost 3D Printer and its operating software, using LCD and UV LED. Working materials for an optimal manufacturing are suggested in the research, along with some suggestions of basic approaches for enhancing the accuracy and quality of the manufactured structures.

• 한국정밀공학회지
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• 제27권4호
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• pp.102-108
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• 2010

Projection microstereolithography is a process of fabricating a micro-structure by using dynamic mask such as digital micromirror device(DMD). DMD shapes the beam into cross-sectional image of structure. Photocurable resin is cured by the beam and stacked layer on top of layer. It is difficult to deliver the beam from the DMD to the photocurable resin without any distortions. We assume that the beam exposed to the resin by 1 pixel of DMD has Gaussian distribution, so the shaped beam reflected by the DMD affects its neighboring area. Curing pattern corresponding to a cross-sectional images is predicted by superposition of pixels of Gaussian distribution and it is similar to cured shape.

• 대한기계학회논문집A
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• 제20권10호
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• pp.3068-3078
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• 1996

stereolithography is a process used to rapidly produce polymer components directly from a computer representation of the part. There are several considerations to be made for the efficient use of the process. Especially, the necessity of support structures, which prevent the part from warping, sagging, or parachuting and toppling as the elevator moves up and down in the resin, is one concern. After solidification, the support structures must by removed in the end. Bacause this post-treatment process is often performed manually, the more the support structures, the more it increases the finishing operations. Especially for a complicated part, the removal operations may be difficult, take so much time, and even reduce the accuracy of the product. Thus it is important to efficiently generate the efficient support structure for each part geometry. This paper proposes a procedure to automatically generate the supprot structures focused on accuracy, efficiency, convenience, and generation speed.

• 한국기계가공학회지
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• 제13권2호
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• pp.15-20
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• 2014

The stereolithography(SL) process is a type of fabrication technology which relies on photopolymerization. It has a relatively simple fabrication process and a resolution of several tens of ${\mu}m$. Recently, SL technology has been applied to various areas, such as bioengineering and MEMS devices, due to the development of advanced materials. This technologycan be divided intothe scanning(SSL) and projection (PSL) types. In this paper, in stereolithography, parts are fabricated by curing photopolymeric resins with light. The application of stereolithography can now include fabricated parts. This process, called stereolithography, can fabricate parts by taking into account theirdegrees of geometry complexity. In particular, UV-LED stereolithography can perform quite rapid fabrication in which specific cross-sections are cured upon exposure to light.

• 한국정밀공학회지
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• 제27권3호
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• pp.135-141
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• 2010

Researchers continue to explore possibilities for expanding additive manufacturing (AM) technologies into direct product manufacturing. One limitation is in the materials available for use in AM that can meet the needs of end-use applications. Stereolithography (SL) is an AM technology well known for its precision and high quality surface finish capabilities. SL builds parts by selectively crosslinking or solidifying photo-curable liquid resins, and the resin industry has been continuously developing new resins with improved performance characteristics. This paper introduces a unique SL machine that can fabricate parts out of multiple SL materials. The technology is based on using multiple vats positioned on a rotating vat carousel that contain different photo-curable materials. To change the material during the process, the build platform is raised out of the current vat, a new vat with a different material is rotated under the platform, and the platform is submerged into the new vat so that the new material can be used. This paper introduces a new vat exchange mechanism, cleaning process, recoating process, resin leveling mechanism and process planning technologies for the implementation of multiple material SL. An overview of the system framework is provided and the system integration and control software is described. In addition, several multiple material test parts are designed, fabricated, and described.

• 한국정밀공학회지
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• 제24권8호통권197호
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• pp.138-143
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• 2007

Microstereolithography technology is similar to the conventional stereolithography process and enables to fabricate a complex 3D microstructure. This is divided into scanning and projection type according to aiming at precision and fabrication speed. The scanning MSL fabricates each layer using position control of laser spot on the resin surface, whereas the projection MSL fabricates one layer with one exposure using a mask. In the projection MSL, DMD used to generate dynamic pattern consists of $1024{\times}768$ micromirrors which have $13.68{\mu}m$ per side. The fabrication range and resolution are determined by the field of view of the DMD and the magnification of the projection lens. If using the projection lens with high power, very fine microstructures can be fabricated. In this paper, the projection MSL system adapted to a large surface for array-type fabrication is presented. This system covers the meso range, which is defined as the intermediate range between micro and macro, with a resolution of a few ${\mu}m$. The fabrication of array-type microstructures has been demonstrated to verify the performance of implemented system.

• 한국정밀공학회지
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• 제19권3호
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• pp.152-159
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• 2002

SLA (Stereolithography Apparatus) it a process used to rapidly produce polymer components directly from a computer representation of the part. Though SLA is being recognized as an innovative technology, it still cannot be used to fully practical application since it lacks of dimensional accuracy compared to conventional process. If the shrinkage were perfectly uniform and no distortion took place, excellent part accuracy could still be achieved through and appropriate scaling factor when generating the build file. However, in certain geometries involving intersecting thick and thin sections, nonuniform retrain shrinkage becomes the engine of part distortion. In order to improve the part accuracy of SLA, this paper evaluates how largely each parameter of SLA contributes to the part accuracy and estimates the optimal set of parameter which minimizes the dimension error of the test part, "Slab (100mm$\times$100mm$\times$2mm)"and "scale bar"part. Three control parameters such as critical exposure, generation depth and fill cure depth are used.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.965-969
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• 1995

This paper deals with effective using the IGES file for flexible data exchange among the other CAD/CAM system. If a data exchange between STL file and the neutral IGES file in Stereolithography system is available, a product design becomes more flexible. THere can be many restrictions and difficulties intranslating these data. First, an STL file follows two rules, such as right-hand rule, and vertex-to-vertex rule, thus requires a structural verification. Second, translation should be performed with minmal errors. It becomes very important to translate IGES file of limited kinds of entities fot the purpose of geometric information into STL file with minor data manipulation. The developed system suggests a good approach of translating the sampled B-spline surface of IGES and shows a potential linkage between IGES and STL format file.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 추계학술대회 논문집
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• pp.165-166
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• 2006

• 한국정밀공학회지
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• 제15권3호
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• pp.61-67
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• 1998

Rapid prototyping becomes widely used in design and manufacturing of mechanical and aerospace engineering. Here a drag valve disk consisted of complicate configuration has designed by CAD, and prototyped by a stereolithography apparatus (SLA) to confirm the design configuration. Also the prototyped valve disk was used for checking if it could be applied for casting from the view point of accuracy, cost, and time. The rapid-prototyped disk by SLA was compared with a high-speed machined disk by MAKINO V55, and it is found that the prototyping of the disk by SLA appears more economical, more accurate and faster than by machining with MAKINO V55.