• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 금형가공 심포지엄
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• pp.180-186
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• 2002

The simulated die-casting process in which the traditional plaster casting process is combined with Rapid Prototyping technology is being used to produce Al, Mg, and Zn die-casting prototypes. Unlike in the die-casting process, molten metal in the conventional plaster casting process is fed via a gravity pour into a mold and the mold does not cool as quickly as a die-casting mold. The plaster castings have much larger and grosser grain structure as compared as the die-castings and the thin walls of the plaster mold cavity may not be completely fillet Because of lower mechanical properties induced by the large grain structure and incomplete Idling, the conventional plaster casting process is not suitable for the trial die-casting Process. In this work, an enhanced trial die-casting process has been developed in which molten metal in the plaster mold cavity is vibrated and pressurized simultaneously. Patterns for the casting are made by Rapid Prototyping technologies and then plaster molds, which have runner system, are made using these patterns. Imparted pressurized vibration to molten metal has made grain structure of castings much finer and improved fluidity of the molten metal enough to obtain complete filling at thin walls which can not be filled in the conventional plaster casting process.

• 한국정밀공학회지
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• 제18권7호
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• pp.167-173
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• 2001

The simulated die-casting process in which the traditional plaster casting process is combined with Rapid Prototyping technology is being used to produce AI, Mg, and Zn die-casting prototypes. Unlike in the die-casting process, molten metal in the conventional plaster casting process is fed via a gravity pour into a mold and the mold does not cool as quickly as a die-casting mold. The plaster castings have much larger and grosser grain structure as compared with the normal die-castings and the thin walls of the plaster mold cavity may not be completely filled. Because of lower mechanical properties induced by the large grain structure and incomplete filling, the conventional plaster casting process is not suitable for the trial die-casting process to obtain quality prototypes. In this work, an enhanced trial die-casting process has been developed in which molten metal in the plaster mold cavity is vibrated and pressurized simultaneously. Patterns for the casting are made by Rapid Prototyping technologies and then plaster molds, which have a runner system, are made using these patterns. Pressurized vibration to imparted molten metal has made grain structure of castings much finer and improved fluidity of the molten enough to obtain complete filling at thin walls which may not be filled in the conventional plaster casting process..

• 한국세라믹학회지
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• 제28권12호
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• pp.1019-1025
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• 1991

The effect of dissolved Ca ion from plaster mold during slip casting on the microstructure and fracture toughness of high-purity sintered alumina were investigated. When the alumina slip containing 1000 ppm MgO was casted on a calcined alumina mold, the sintered compact had a homogeneous microstructure with equiaxed grains. However, when the same slip was casted on a plaster mold, the sintered compact consisted of the mixture of equiaxed and elongated grains. This inhomogeneous microstructure was also observed in the sintered alumina doped with 100o ppm MgO and 100 ppm CaO whose compact was prepared on the calcined alumina mold indicating that the inhomogeneity was caused by CaO. It was found that the specimen containing both MgO and CaO had higher fracture toughness than that containing MgO only. The enhanced fracture toughness by CaO is probably due to the crack deflection along the boundaries of the elongated grains.

• International Journal of Precision Engineering and Manufacturing
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• 제2권1호
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• pp.56-61
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• 2001

This work is concerned with the development of a new plaster die casting process the combines pressurization and vibration for the prototyping of die-castings, and also with a plaster die-casting machine that has a structure quite similar to that of an ordinary die casting machine. The machine utilized an air cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the LOM process to prepare a plaster mold. In the process, a plunger int he developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine produced a prototype of an end clutch cover with a remarkable improvement in mechanical properties.

• 한국주조공학회지
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• 제4권4호
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• pp.5-13
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• 1984

This paper is presented for showing the effect of cooling rate on dendrite arm spacing, correlated with the chilling power of molding materials (conventional plaster, foamed plaster, silica sand) and section thickness, and also showing relationship between dendrite arm spacing and mechanical properties for an aluminum - 8.6 percent silicon - 3.6 percent copper alloy. Local solidification time $(t_f)$ and secondary dendrite arm spacing (d) could be varied widely in accordance with the molding materials and casting thickness, and the following relationship is obtained: $d=9.4t_f\;^{0.31}$ A good correlation between dendrite arm spacing and mechanical properties such as ultimate tensile strength, yield strength, hardness was found, that is, mechanical properties decreased in a linear manner with increase in log of secondary dendrite arm spacing. Ultimate tensile strength in conventional plaster mold casting decreased by 15 percent comparing with the sand casting, where as in foamed plaster mold casting, it decreased by 30 percent comparing with the sand casting. From those results, it has been verified that DAS might be the most representative parameter for predicting mechanical properties varing with the different cooling condition.

• 한국주조공학회지
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• 제21권4호
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• pp.253-259
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• 2001

There are many methods to produce metal foams, which can be classified into three groups according to the state of the starting metal i.e. liquid or powder or solid. Three types of defects such as cell closing, cell deformation or breakdown and cell misrun are thought to be occurred when we make the open cell aluminum foams by precision casting. Filling ability of the mold slurry between preform is related with cell closing, mold collapsibility is related with cell deformation or breakdown, mold temperature and pouring pressure are related with cell misrun. These factors can be evaluated by measuring slurry fluidity, burnout strength and permeability of the mold. Properties of the plaster mold were evaluated to find optimum mold conditions for high quality open cell aluminum foam in this study. Permeability was almost zero independent of burnout conditions, however, crack initiation was found on the surface of all specimens one or two minutes after taking out from the furnace. Crack has grown and disappeared with time. This crack may facilitate the mold filling when molten metal is poured, because of the improved mold permeability. It was considered that crack initiation and disappearance was closely related with temperature difference between the surface and inner part. Knocking-out the mold is a difficult problem due to the small cell size, because continuous mesh structure of the metal foam is not strong. It is not easy to remove molding material after pouring. We can expect that water quenching can facilitate the knocking-out the mold after solidification without damaging cell structures. Collapsed particles after water quenching became bigger with the increase in time.

• 한국세라믹학회지
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• 제30권12호
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• pp.1029-1038
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• 1993

The microstructures of aluminas, included of dissolved CaO as $\alpha$-alumina seeded pseudo-boehmite hydrosol was gelled in plaster mold and doped of MgO as dipping of calcines(120$0^{\circ}C$-2h) into Mg-nitrate solution, were compared to the one of which additives are excluded during the gellation. It was formed the boundary layer of 300~350${\mu}{\textrm}{m}$ distance from surface to the inside, containing of approximately 500ppm CaO by dissolved Ca from plaster mold. As the MgO addition to the boundary layer with dissolved CaO, the microstructure of the layer was uniformed and inhibited the grian growth, compared to one of that additives be excluded specimen and of MgO doped-inside region. This result was considered as abnormal grain growth and effect of flat boundary formation be appeared by effects of dissolved CaO, were decreased by MgO co-doping.

• 정보과학회 논문지
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• 제43권5호
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• pp.516-523
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• 2016

노역분장을 위해서는 석고로 연기자의 얼굴 모형을 만들고, 그 위에 주름을 조소작업한 후 다시 석고로 음각 몰드를 제작하여 얼굴에 붙일 실리콘 피부 패치를 만들게 된다. 이러한 처리 과정은 며칠이 걸리며 연기자나 분장사에게 어려움을 주고 있다. 최근에 3D 프린팅 및 스캐닝 기술이 발전하여, 얼굴을 스캔하여 실물로 제작하는 것이 쉬워지고 있다. 본 논문에서는 석고나 조소작업 없이 노역분장용 실리콘 마스크를 간편하고 효율적으로 제작하기 위해, 얼굴 스캐닝, 인터랙티브 주름 모델링, 몰드 프린팅으로 이루어진 새로운 파이프라인을 제안한다. 고해상도 얼굴 모델에서도 주름을 실시간에 생성하기 위해 노멀맵 기반의 직관적인 스케치 인터페이스를 제시한다. 그리고 최종적인 주름의 기하를 깊이맵을 이용하여 복원하고, 주름진 얼굴의 음각 몰드를 프린팅한다. 또한 완성된 음각 몰드에 실리콘을 부은 뒤 원래의 양각 얼굴을 겹쳐 실리콘 마스크를 제작함으로써, 제안 파이프라인이 기존 방식보다 노역분장용 마스크를 간편하게 제작할 수 있음을 보인다.

• 대한두개안면성형외과학회지
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• 제13권2호
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• pp.125-129
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• 2012

Purpose: Methylmethacrylate is the most commonly used alloplastic material in cranioplasty. However during the polymerization of methylmethacrylate, a significant exothermic reaction takes place. This reaction may result in thermal injury to the brain tissue and other soft tissues. Also it is difficult to make three-dimensional methylmethacrylate implant that is perfectly matched to the defect during the operation time. We report on the molding technique of methylmethacrylate implant using plaster mold and the rapid prototyping model in cranioplasty. Methods: A 44-year-old male was referred to the department for severe frontal hollowness. He was involved in an automobile accident resulting in large frontal bone defect with irregular margin. The preformed patient-specific methylmethacrylate implant was made using plaster mold and the rapid prototyping model before the operative day. The methylmethacrylate implant was placed in the frontal defect and rigidly fixed with miniplates and screws on the operative day. Results: The operation was performed in an hour. In the 6 months follow-up period, there were no complications. Patient was satisfied with the results of cranioplasty. Conclusion: Safe cranioplasty was performed with the preformed patient-specific methylmethacrylate implant using plaster mold and the rapid prototyping model. The result of this method was satisfactory, aesthetically and functionally.

• 한국융합학회논문지
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• 제12권3호
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• pp.141-149
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• 2021

20세기 후반에 등장한 3D 프린터는 21세기에 들어와 4차 산업혁명의 핵심 분야로 자리매김하고 있다. 메이커 운동의 핵심 장비이자 21세기 새로운 가내수공업의 시발점인 3D 프린터는 여전히 낮은 출력 속도와 한정된 필라멘트 재료로 대량생산의 한계를 드러내고 있지만, 최근 도자 공예가들의 3D 프린터 사용은 기하급수적으로 늘고 있다. 하지만 과거 공예사에서 지난하게 반복되어 온 공예의 경전과 새로운 기술과의 불협화음을 타계하는 방법의 일환으로 본 연구는 3D 프린터를 이용하는 '석고 캐스팅' 기법에 주목했다. 이에 세계 도자 공예분야에서 활발히 석고 기법을 개발해 작가만의 디자인에 적용하고 있는 도예가 토니 한센, 위베 반 간스베크, 제이드 크롬프톤, 류희도의 캐스팅 기법을 분석한 후 효과적인 3D 모델링 방법과 3D 프린터를 이용하는 최적의 슬립 캐스팅 방법의 사례를 제시함으로써 3D 프린터와 공예의 융합을 위한 접점을 찾고자 했다.