• Journal of Technologic Dentistry
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• v.34 no.2
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• pp.105-111
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• 2012

Purpose: The purpose this study was to evaluate the marginal fitness of metal copings fabricated using rapid prototyping method and to compare the fitness with copings by conventional method. Then clinical availability of fixed dental prostheses (FDPs) fabricated using rapid prototyping method shall be confirmed based on marginal fitness. Methods: Ten same cases of3 unit FDPs epoxy models (abutment teeth 14 and 16) were manufactured. Each of ten epoxy models were scanned by 3shape D-700 scanner to be designed by experienced technician, and photopolymer 3 unit FDPs were fabricated using rapid prototyping methodand fabricated using Lost wax technique (LW) with same models. Marginal fitness of 3 unit FDPs were measured by silicone replica technique. T-test of independent sample for statistical analysis was executed with SPSS 12.0K for Windows. (${\alpha}$=.05) Results: Significantly higher mean (SD) marginal fitness (P<.000) were observed in the RP group $(95.9(18.0){\mu}m$ compared to the conventionally LW group $(80.1(13.8){\mu}m$. Conclusion: Marginal fitness of LW group showed excellent rather than RP group. However marginal fitness of 3 unit FDPs fabricated by RP method did not get out of clinical allowance value range significantly to allow clinical application.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.5
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• pp.772-778
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• 2003

Polystyrene foam is easily melted and vapoured by heat, has a proper quality in the pattern manufacturing and has a low price. The objective of this study is to develop a rapid prototyping method fur polystyrene foam pattern manufacuring to use the eliminative pattern casting (EPC). Applying fur the rapid prototyping concept reversely, the unnecessary part of section is vapored away by heat source of laser beam. In order to examine the applicability between laser beam process and polystyrene foam material, the basic experiments such as hole, line, plane and contour process are carried out. With these results, various three-dimensional shape patterns are made and this rapid prototyping tool for polystyrene foam manufacturing.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.6 no.4
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• pp.8-14
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• 2007

Recently, the variation of industry has been changed faster and faster than before. It is using Rapid Prototyping Method to cope with fast change. This technology used to make a prototype, master pattern of manufactured product by vacuum casting, and so on. But this method has errors by contraction as a necessity. this error has been caused because the shape of prototype is smaller than CAD data. So we must solve the problem about precision of product. Therefore in this study, we will reduce the errors like contraction of material by manufacturing of rapid prototype product. Through these courses, we will enhance a precision of product.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.4
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• pp.226-234
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• 2004

A rapid Prototyping system that laser-cuts and laminates thick layers can fabricate 3D objects promptly with a variety of materials. Building such a system must consider the surface distortions due to both vertical-cut layers and triangular surfaces. We developed a tangential layer-cutting algorithm by rearranging tangential lines such that they reconstruct 3D surfaces more closely and also constitute smoother laser trajectories. An energy function that reflects the surface-closeness with the tangential lines was formulated and then the energy was minimized by a gradient descent method. Since this simple method tends to cause many local minima for complex 3D objects, we tried to solve this problem by adding a simulated annealing process to the proposed method. To view and manipulate 3D objects, we also implemented a 3D visual environment. Under this environment, experiments on various 3D objects showed that our algorithm effectively approximates 3D surfaces and makes laser-trajectory feasibly smooth.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.10
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• pp.46-55
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• 1996

As industrial standard data, the STL format which approximates three dimensional CAD model to triangular facets, is used for RP(Rapid Prototyping) system in recent days. Because most RP system take the only form of two dimensional line segments as an input stream inspite of its imperfectness while converting into STL format, a CAD model is converted into a standard industrial format which is composed of many triangular facets. The error verifying process is composed of four main steps, and these are 1) Remove facets with two or more vertices equal to each other. 2) Fix overlapping error such as more than three facets adjacent to anedge. 3) Fill holes in the mesh by using Delaunay triangulation method. 4) Correct the wrong direction and normal vectors. This paper is concerned with serching the mentioned errors in advance and modifying them.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.483-486
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• 2001

Rapid Prototyping(RP) has been widely applied in designing and developing processes a new product. The functional requirements of a rapid prototyping system are high speed and high accuracy, and they depend on the operating parameters, some of which can be set by users. The accuracy is evaluated by dimensional errors and form errors of manufactured pars. A specially designed specimen with various features has been used for the accuracy evaluation. According to the Taguchi experimental design techniques, and orthogonal array of experiments has been set which has the least number of experimental runs to find the parametric effects. A laser scanner is used to obtain the point data of the parts and Surfacer is used to determine the lengths and angles. The conditions for the FDM manufacturing parametrs have been found.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.83-86
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• 1997

Even as many methods and technologies have been introduced on data generation, parts orientation and layer slicing to acquire the rapid prototyping(RP) parts that have useful surface to satisfy customers' needs such as stylingldesign verification directionlindirect tooling directly from the RP machine, these trials continue to suffer from the surface roughness due to the build characteristics of RP technology. A new postprocess finishing method is suggested in this paper to overcome the surface roughness problem on the surface of the RP parts. To prevent deterioration of dimensional accuracy from the conventional grinding-only, and coating-grinding methods, 4-step surface finishing process is applied. To satisfy the various requirements from the RP oriented industrial f elds, effective procedure, coating material, grmd~ng tools and methods are employed.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.1
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• pp.68-74
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• 2000

The STL file format is an approximation of 3-D model with triangular facets. STL is a standard input file format of Rapid Prototyping(RP) equipment In computer graphics a circle has been approximated with an inscribed polygon which causes an error between the real and approximated circles. In this study an intersecting polygon has been used to approximate the circle and applied to produce more accurate RP part. The newly proposed method shows it's excellence in part accuracy.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.4
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• pp.366-375
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• 2001

Bone shaving for surgical correction is general method in facial asymmetrical patient with fibrous dysplasia. Therefore, decision of bone shaving amount on the preoperative planning is very difficult for improvement of ideal occlusal relationship and harmonious face. Preoperative planning of facial asymmetry with fibrous dysplasia is generally confirmed by the simulation surgery based on evaluation of clinical examination, radiographic analysis and analysis of facial study model. However, the accurate postoperative results can not be predicted by this method. By using the computed tomography based RP(rapid prototyping) model, simulation of facial skeleton can be duplicated and 3-dimensional simmulation surgery can be perfomed. After fabrication of postoperative study model by preoperactive bone shaving, preoperative and postoperactive surgical index was made by omnivaccum and clear acrylic resin. Amount of bone shaving is confirmed by superimposition of surgical index at the operation. We performed the surgical correction of facial asymmetry patients with fibrous dysplasia using surgical index and prototyping model and obtained the favorable results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.11
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• pp.2409-2414
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• 2002

The surfaces of prototypes become rough due to the stair-stepping which is the inevitable phenomenon in the Rapid Prototypes are not used only for the verification of feature. The grinding, coating, or the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. The solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the composition of them is a main operation in post-processing in which lots of costs and long build time are needed. the solution is proposed to increase the efficiency of rapid prototyping by minimizing or removing the regions for post-processing. the factors to cause the surface roughness and their effects are analyzed through the experiments. Software modules are developed to predict the surface roughness of each face in the prototyping with the result. An experimental compensation method is developed to apply the modules to various RP equipments, materials and build styles. The build direction is searched with use of genetic algorithm to maximize the total areas of the surface of which roughness is better than the user-defined value.