• 사물인터넷융복합논문지
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• 제8권2호
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• pp.55-59
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• 2022

최근 4차 산업혁명으로 인하여, 고객 제품형 제품 설계 및 새로운 서비스 개발을 위하여 IoT 기술이 주목받고 있다. 최근 적층제조 기술은 IoT 센서를 직접 제작하거나, 센서를 포함한 기기를 만드는 분야에 다양하게 활용되고 있다. IoT 기기를 적층제조를 활용하여 제작시, 적층제조 고유의 설계 장점을 활용하기 위해 다양한 부품들을 병합하는 설계 방법론이 큰 관심을 받고 있다. 부품병합을 통해 조립 공정을 단축하고, 부품 경량화 등의 장점을 이룰 수 있기 때문이다. 따라서, 본 연구에서는 적층제조를 활용한 부품병합을 지원하기 위한 설계 방법론을 개발하였다. 이를 통해 제품의 기능 및 제품 내 부품의 기능과 물리적 연결성을 분석한 제품 아키텍쳐를 생성하고, 인접한 기능들 및 부품을 Girvan Newman 알고리즘을 활용하여, 최종 부품병합 후보군을 선정하도록 지원한다. 제안한 설계 방법론을 검증하고자 사례연구를 통해 적층제조로 출력된 전기 자전거의 부품병합과정을 분석하였다.

• 한국기계가공학회지
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• 제17권2호
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• pp.47-53
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• 2018

Nowadays, additive manufacturing (AM) technology is a promising process to fabricate complex shaped devices applied in medical and dental services. Among the AM processes, a DLP (digital light processing) type 3D printing process has some advantages, such as high precision, relatively low cost, etc. In this work, we propose a simple method to fabricate precise dental models using a DLP 3D printer. After 3D printing, a part is commonly post-cured using secondary UV-curing equipment for complete polymerization. However, some shrinkage occurs during the post-curing process, so we adaptively control the UV-exposure time on each layer for over- or under-curing to change the local shape-size of a part in the DLP process. From the results, the shrinkage amounts in the post-curing process vary due to the UV-dose in 3D printing. We believe that the proposed method can be utilized to fabricate dental models precisely, even with a change of the 3D CAD model.

• 한국기계가공학회지
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• 제14권4호
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• pp.134-139
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• 2015

PolyJet technology is an additive manufacturing (AM) technology commonly used for modeling, prototyping, and production applications. It is one of the techniques used for 3D printing. The PolyJet technique is a process that joins materials to fabricate a product from 3D CAD data in a layer-by-layer manner. The orientation of a layer can affect the mechanical properties of the product manufactured by the PolyJet technique because of its anisotropy. In this paper, tensile and shearing tests of specimens were developed with the PolyJet technique in order to study the mechanical properties according to the orientation of a layer. The mechanical properties of the specimens were determined on the basis of true stress-strain curves from tensile and shearing tests. In addition, the tensile and shearing tests were simulated under the same conditions as those of experiment, and the experiment and simulated results were compared. Through this study, the fracture criteria could be established.

• 한국분말재료학회지
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• 제26권4호
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• pp.319-326
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• 2019

Additive manufacturing (AM) is a highly innovative method for joining dissimilar materials for industrial applications. In the present work, AM of STS630 and Ti-6Al-4V powder alloys on medium entropy alloys (MEAs) NiCrCo and NiCrCoMn is studied. The STS630 and Ti64 powders are deposited on the MEAs. Joint delamination and cracks are observed after the deposition of Ti64 on the MEAs, whereas the deposition of STS630 on the MEAs is successful, without any cracks and joint delamination. The microstructure around the fusion zone interface is characterized by scanning electron microscopy and X-ray diffraction. Intermetallic compounds are formed at the interfacial regions of MEA-Ti64 samples. In addition, Vicker's hardness value increased dramatically at the joint interface between MEAs and Ti-6Al-4V compared to that between MEAs and STS630. This result is attributed to the brittle nature of the joint, which can lead to a decrease in the joint strength.

• The Journal of Advanced Prosthodontics
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• 제10권5호
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• pp.347-353
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• 2018

PURPOSE. The purpose of this study was to evaluate the marginal discrepancy of heat-pressed ceramic veneers manufactured using a CAD/CAM system. MATERIALS AND METHODS. The ceramic veneers for the abutment of a maxillary left central incisor were designed using a CAD/CAM software program. Ten veneers using a microstereolithography apparatus (AM group), ten veneers using a five-axis milling machine (SM group), and ten veneers using a traditional free-hand wax technique (TW group) were prepared according to the respective manufacturing method. The ceramic veneers were also fabricated using a heat-press technique, and a silicone replica was used to measure their marginal discrepancy. The marginal discrepancies were measured using a digital microscope (${\times}160$ magnification). The data were analyzed using a nonparametric Kruskal-Wallis H test. Finally, post-hoc comparisons were conducted using Bonferroni-corrected Mann-Whitney U tests (${\alpha}=.05$). RESULTS. The $mean{\pm}SD$ of the total marginal discrepancy was $99.68{\pm}28.01{\mu}m$ for the AM group, $76.60{\pm}28.76{\mu}m$ for the SM group, and $83.08{\pm}39.74{\mu}m$ for the TW group. There were significant differences in the total marginal discrepancies of the ceramic veneers (P<.05). CONCLUSION. The SM group showed a better fit than the AM and TW groups. However, all values were within the clinical tolerance. Therefore, CAD/CAM manufacturing methods can replace the traditional free-hand wax technique.

• 대한의용생체공학회:의공학회지
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• 제41권1호
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• pp.14-21
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• 2020

Recently, porous additive manufactured(AM) cages have been introduced to provide more desirable stiffness and may be beneficial to bone ingrowth. They are designed to attempt to reduce the subsidence problem of traditional titanium cage and to get osseointegrative property that PEEK doesn't have. This study was performed to evaluate the mechanical performance of newly developed lumbar porous AM cages. Three types of mechanical tests were performed in accordance with the ASTM standards: Static compression, compression-shear, and subsidence tests. The porous AM cages with 60% porosity showed similar device stiffness and strength as the various products submitted to FDA 510(k), and their wider contact area improved the subsidence test results by about 50%. In conclusion, the porous AM cages developed in this study were considered mechanically safe and could be an alternative to solid PEEK cages.

• 대한방사선기술학회지:방사선기술과학
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• 제41권1호
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• pp.53-60
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• 2018

The purpose of this study was investigating the effect of 3D printing technology that changes the speed of sound (SOS) and the broadband ultrasound attenuation (BUA) by controlling the density of the media phantom. We used 3D printers which called additive manufacturing (AM) by using material with polylactic acid (PLA). The inside of the medium phantom was filled crossly with 100%, 90%, 80%, 70%, 60%, and 50% of the material. The ultrasonic instrument measured the SOS and the BUA using a 0.55 MHz ultrasound output in opposing mode with a pair of transducers. As a result, the density of the medium phantoms with the SOS showed very high correlation (r = 0.944), but the SOS showed very low correlation (r = 0.500). It is expecting that the manufacturing and measurement method of the medium phantom using 3D printing technology will be used as basic data for ultrasonic bone mineral density.

• 한국분말재료학회지
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• 제30권3호
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• pp.223-232
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• 2023

Metal additive manufacturing (AM) has transformed conventional manufacturing processes by offering unprecedented opportunities for design innovation, reduced lead times, and cost-effective production. Aluminum alloy, a material used in metal 3D printing, is a representative lightweight structural material known for its high specific strength and corrosion resistance. Consequently, there is an increasing demand for 3D printed aluminum alloy components across industries, including aerospace, transportation, and consumer goods. To meet this demand, research on alloys and process conditions that satisfy the specific requirement of each industry is necessary. However, 3D printing processes exhibit different behaviors of alloy elements owing to rapid thermal dynamics, making it challenging to predict the microstructure and properties. In this study, we gathered published data on the relationship between alloy composition, processing conditions, and properties. Furthermore, we conducted a sensitivity analysis on the effects of the process variables on the density and hardness of aluminum alloys used in additive manufacturing.

• 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.

• Composites Research
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• 제34권4호
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• pp.212-225
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• 2021

금속 기지재 복합재료들(MMCs, Metal matrix composites)은 우수한 기계적 물성(강성, 강도, 마모 저항성, 경도 등)과 뛰어난 특성(열전도, 전기전도도, 부식 저항 등)으로 다양한 산업군에 활용되고 있다. 적층제조 기술이 발달함에 따라 복잡한 형상을 시간과 비용을 절약하여 제조할 수 있다는 이점으로, 적층 제조한 MMCs에 관한 연구가 활발하게 이루어지고 있다. 하지만 MMCs를 적층 제조할 경우, 다양한 원인들에 의해 여러 문제들이 발생할 수 있다. 따라서 본 연구에서는 다양한 MMCs의 특징들을 소개하고, 위의 문제들이 발생하는 원인을 고찰하여 소재와 Powder bed fusion (PBF) 공정 설계 관점에서 해결책을 제시하고자 한다. 본 논문은 향후 PBF 방식으로 적층 제조한 MMCs를 개발할 때 설계 및 제조 가이드라인을 제시하여 줄 수 있을 것이다.