• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.8-9
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• 2018

3D printing has the unique advantage of the ability to customize freeform product even in small quantity. However, we need to select and apply the only necessary parts of it because of the high cost of the manufacturing technology. It is of critical importance in irregular-shaped curtain walls to ensure precision of construction as well as quality fo finish. Complex shape that have structural members at varying angles can have nodes of different shapes making it unfeasible to construct using a general node connection detail. Therefore, this study aims to utilize smart node system using 3D printing as a solution to complex irregular-shaped curtain wall design.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.10
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• pp.817-829
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• 2014

One of the main issues in tissue engineering has been the development of a three-dimensional (3D) structure, which is a temporary template that provides the structural support and microenvironment necessary for cell growth and differentiation into the target tissue. In tissue engineering, various biomaterials and their processing techniques have been applied for the fabrication of 3D structures. In particular, 3D printing technology enables the fabrication of a complex inner/outer architecture using a computer-aided design and manufacturing (CAD/CAM) system, and it has been widely applied to the fabrication of 3D structures for tissue engineering. Novel cell/organ printing techniques based on 3D printing have also been developed for the fabrication of a biomimetic structure with various cells and biomaterials. This paper presents a comprehensive review of the functional scaffold and cell-printed structures based on 3D printing technology and the application of this technology to various kinds of tissues regeneration.

• Journal of the Korean Society of Radiology
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• v.10 no.8
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• pp.571-576
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• 2016

3D printing has recently been used in various fields. Among various applications, 3D face data must be generated for 3D face printing. A laser scanner is used to acquire 3D face data, but there is a restriction that a person should not move during scanning. In this paper, we propose a 3D face modeling method based on a single image and a face transformation system to use the generated 3D face for virtual cosmetic surgery. We have defined facial feature points from the 3D face database for 3D face data generation. After extracting feature points from a single face image, 3D face of the input face image is generated corresponding to the 3D face feature points defined from the 3D face database. After 3D face modeling, 3D face modification part is applied for use such as virtual cosmetic surgery.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.1
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• pp.65-71
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• 2016

In recent years, 3D printing has received increasing attention due to releases of low-cost 3D printers based on open-source platform. 3D printing is expected to reduce the barrier to entry in the traditional manufacturing processes by increasing flexibility and creating an advantage to manufacture customized products at low costs. In this study, a unique eyeglass frame was designed to have a snake shape, which has an asymmetric geometry unlike traditional frames. The eyeglass frame was designed in a customized manner by reflecting dimensional characteristics of a customer's face. Finite element analysis was performed to investigate the structural safety of the 3D printed frames during the assembly process. The analysis also considered the effect of anisotropic material properties as determined by tensile tests. The eyeglass frame was then printed using the customized sizes and the best building process. The eyeglass frame was successfully assembled with lenses and without structural failure during its assembly procedure.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.11
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• pp.3-10
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• 2018

Cladding that finishes the exterior of a building could enhance the value of the building, and shape control is an important factor. With the recent development of 3D printing, cementitious claddings were printed by 3D printer in China, U.S.A and elsewhere. On the other hand, the structural safety of the exterior panel should be examined, as casualties occur when the exterior panel fails due to typhoon or impact. Cement-based cladding is reinforced by wire mesh to improve safety. Introducing 3D printing composite system with polymer and cement, makes it possible to produce claddings fast and accurate. Prior to the development of 3D printing cementitious cladding, the major parameters influencing the optimal shape were identified based on structural performance. The wind load, joint, and bond behavior between polymer and cement were considered. Polymer laminate shape, order, and thickness were variables, and finite element analysis was performed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.470-476
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• 2019

The braking force for a train is generally provided by compressed air. The pressure valve system that is used to apply appropriate braking forces to trains has a complex flow circuit. It is possible to make a channel shape that can increase the flow efficiency by 3D printing. There are restrictions on the flow shape design when using general machining. Therefore, in this study, the compressed air flow was analyzed in a pressure valve system by comparing flow paths made with conventional manufacturing methods and 3D printing. An analysis was done to examine the curvature magnitude of the flow path, the diameter of the flow path, the magnitude of the inlet and reservoir pressure, and the initial temperature of the compressed air when the flow direction changes. The minimization of pressure loss and the uniformity of the flow characteristics influenced the braking efficiency. The curvilinear flow path made through 3D printing was advantageous for improving the braking efficiency compared to the rectangular shape manufactured by general machining.

• Journal of Computational Design and Engineering
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• v.2 no.1
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• pp.47-54
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• 2015

In recent years, 3D printers have become popular as a means of outputting geometries designed on CAD or 3D graphics systems. However, the complex user interfaces of standard 3D software can make it difficult for ordinary consumers to design their own objects. Furthermore, models designed on 3D graphics software often have geometrical problems that make them impossible to output on a 3D printer. We propose a novel AR (augmented reality) 3D modeling system with an air-spray like interface. We also propose a new data structure (octet voxel) for representing designed models in such a way that the model is guaranteed to be a complete solid. The target shape is based on a regular polyhedron, and the octet voxel representation is suitable for designing geometrical objects having the same symmetries as the base regular polyhedron. Finally, we conducted a user test and confirmed that users can intuitively design their own ornaments in a short time with a simple user interface.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.80-85
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• 2021

In the fourth industrial revolution, the demand for metal three-dimensional (3D) printing technology is rapidly increasing. Metal 3D printing is an efficient method for manufacturing products because the method reduces material waste compared to subtractive manufacturing. In addition, products with complex shapes, such as turbine blades, can be easily produced using metal 3D printing because the method offers a high degree of freedom. However, due to the long production time of metal 3D printing, mass production is impossible, and post-processing is necessary due to its low precision. Therefore, it is necessary to develop a new hybrid process that can efficiently process metals and to develop a metal 3D-printing-based hybrid processing system technology to secure high processing precision and manufacture complex shapes. In this study, the structural stability of a metal 3D printer based hybrid machining center was analyzed through structural analysis before its development. In addition, we proposed a design modification that can reduce the weight and increase the stiffness of the hybrid machining center by performing shape lightning based on the structural analysis results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.491-497
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• 2017

In recent years, 3D printing has received increasing attention due to its potential for direct fabrication beyond the traditional rapid prototyping. 3D printing has the advantage of being able to manufacture complicated shapes that were thought impossible to produce by traditional manufacturing processes. This advantage has driven applications of 3D printing to direct manufacturing of functional parts, such as lightweight structures and component integration. In this study, a porous shell structure is designed for the purpose of weight reduction and ventilation. Finite element (FE) analyses are performed to compare the effective stiffness of the porous structure with the conventional solid structure. Structural reinforcements are also considered in order to make up the stiffness reduction due to the porosity, and the relevant FE analyses are performed to investigate the effect of the reinforcement design on the bending stiffness. The optimized reinforced structure is then proposed through response surface analysis.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.3
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• pp.10-21
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• 2021

Recently, the demand for atypical structures with functions and sculptural beauty is increasing in the construction industry. Existing mold-based structure production methods have many advantages, but building complex atypical structures represents limitations due to the cost and technical characteristics. Production methods using molding are suitable for mass production systems, but production cost, construction period, construction cost, and environmental pollution can occur in small quantity batch production. The recent trend in the construction industry calls for new construction methods of customized small quantity batch production methods that can produce various types of sophisticated structures. In addition to the economic effects of developing related technologies of 3D Concrete Printers (3DCP), it can enhance national image through the image of future technology, the international status of the construction civil engineering industry, self-reliance, and technology export. Until now, 3DCP technology has been carried out in producing and utilizing residential houses, structures, etc., on land or manufacturing on land and installing them underwater. The final purpose of this research project is to produce marine structures by directly printing various marine structures underwater with 3DCP equipment. Compared to current underwater structure construction techniques, constructing structures directly underwater using 3DCP equipment has the following advantages: 1) cost reduction effects: 2) reduction of construct time, 3) ease of manufacturing amorphous underwater structures, 4) disaster prevention effects. The core element technology of the 3DCP equipment is to extrude the transferred composite materials at a constant quantitative speed and control the printing flow of the materials smoothly while printing the output. In this study, the extruding module of the 3DCP equipment operates underwater while developing an extruding module that can control the printing flow of the material while extruding it at a constant quantitative speed and minimizing the external force that can occur during underwater printing. The research on the development of 3DCP equipment for printing concrete structures underwater and the preliminary experiment of printing concrete structures using high viscosity low-flow concrete composite materials is explained.