• 한국정밀공학회지
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• 제16권5호통권98호
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• pp.98-103
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• 1999

The application field of porous mold is more and more expended. A mixture of alumina and cast iron is used for making porous mold using slip and vacuum casting method in this study. Slip casting is a process that slurry is poured into silicon rubber mold, dried in vacuum oven, debinded and sintered in furnace, In this procedure, slurry is composed of powder, binder, dispersion agent, and water. Vacuum casting is a technique for removing air bubbles existed in the slurry under vacuum condition. Since ceramics has a tendency of over-shrinkage after sintering, cast iron is used to compensate dimensional change. The results shows that sintering temperature has a great effect on characteristics of alumina-cast iron composite sintered parts. Finally ceramic-metal composite sintered mold can be used for aluminum alloy casting of shoe mold using this process.

• International Journal of Automotive Technology
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• 제7권6호
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• pp.741-747
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• 2006

It has been almost impossible to predict the fatigue life in the field of rubber materials by numerical methods. One of the reasons is that there are no obvious fracture criteria and excessively various ways of mixing processes. Tearing energy is considered as a fracture criterion which can be applied to rubber compounds regardless of different types of fillers, relative to other fracture factors. Fatigue life of rubber materials can be approximately predicted based on the assumption that the latent defect caused by contaminants or voids in the matrix, imperfectly dispersed compounding ingredients, mold lubricants and surface flaws always exists. Numerical expression for the prediction of fatigue life was derived from the rate of rough cut growth region and the formulated tearing energy equation. Endurance test data for dumbbell specimens were compared with the predicted fatigue life for verification. Also, fatigue life of industrial rubber components was predicted.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.220-224
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• 2001

Waste tires are a significant problem with the increasing in number of automobiles. Therefore, many researches have been studied on this field. Recycling is the one of the popular method aspect to environmental and economical in the treatment methods of the waste tire, which loads that the reuse of scrap tire rubber has been a challenge in the past. However, it is not easy method to melt down and mold into new products because the in rubber is a cross-linked polymer. Most difficulty in recycling is the recycled product is not economic. Therefore, the goal of this study is to develop the high valuable products for reused waste tires. In this paper, we try to make an economic recycled technology using scrapped waste tires. This technology may applied for manufacturing the end products such as a rubber block and a ballast mat for high-speed train.

• 대한치과의사협회지
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• 제24권7호통권206호
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• pp.633-642
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• 1986

In order to evaluate the effects of various finishing devices (Sof-Lex disc, diamond point, rubber point, fussure bur) on the surface roughness or two composite resins (Restodent, Enamelite 500), 15 specimens for each composite resin were made in the mold. Composite resin was prepared on the mixing pad by manufacturer's direction and filled in the mold cavity. A sheet of matrix is immediately placed on it and hold for 5 minutes to polymerize the resin. Surface finish was done after 10 minutes from the start of mixing. Scanning electron microscopy and surface profilometer were used to evaluate the surface roughness, porositites and striations of dental composite resins. The following results were observed; 1. The best finished surface was formed by celluloid matrix band. 2. Rubber point was excellent polishing device for Restodent. 3. Sof-Lex disc was the device of choice for polishing Enamelite 500. 4. Different polishing methods were effective for different composite resins. 5. SEMs of variously finished surfaces supported the profilometer measurements.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1259-1260
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• 2006

Intensive technological research on the Dry-bag CIP equipment was carried out to improve the dimensional accuracy and the productivity. The rubber mold design technology using FEM simulation during pressing was introduced, in order to achieve higher dimensional preciseness, and criteria for the selection of the In-line type or Off-line type, were established based on the powder flowability index proposed by Carr. Based on these research results, high productivity Off-line Dry-bag CIP equipment, which can realize good dimensional accuracy with high productivity, was developed even for non-granulated powders with poor packing density.

• Korean Chemical Engineering Research
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• 제48권4호
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• pp.490-498
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• 2010

K사의 방진고무 사출성형에 있어서 애로사항인 토크로드부시(torque rod bush)의 캐비티 가장자리(edge) 구간에서의 에어트랩(air-trap) 발생 및 다이내믹 댐퍼(dynamic damper)에 있어서 사출시 미성형(short shot) 발생 등의 문제점을 해결하기 위하여, 상용 CAE 프로그램인 MOLDFLOW(Ver. 5.2)를 이용한 전산모사를 수행하여 적정금형설계를 도출하고 적정작업조건을 구축하였다. 그 결과 방진고무 중에서 토크로드부시의 사출성형에서의 에어트랩 발생 등의 공정문제를 최적 캐비티 가장자리 경사각 및 게이트 수를 조절함으로써 캐비티 가장자리에서의 유동선단(flow-front)의 유동정체를 방지하고 유동을 원활하게 하여 해결하였다. 한편 다이내믹 댐퍼의 사출시 충전(filling) 단계에서의 캐비티 비충전으로 인한 미성형 불량은 에어벤트(air-vent) 구를 에어트랩 발생 빈도가 매우 높은 유동선단 상향류와 하향류의 두 흐름이 만나는 지점에 설치함으로써 미성형 불량을 해결하였다. 또한 게이트 위치를 댐퍼 상단에서 중단으로 변경하거나 게이트 수를 증가시킨 경우에 미성형 불량이 K사의 경우보다 개선되었다.

• Composites Research
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• 제23권2호
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• pp.31-39
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• 2010

본 논문에서는 모자(Hat)형 보강구조를 가진 복합재 패널을 일체성형(Co-curing), 동시접착(Co-bonding), 이차접착(Secondary bonding)의 세 가지 공법으로 제작하였다. 일체성형은 별도의 접착제 없이 프리프레그 상태의 외피와 보강재를 만들어 함께 성형하는 방법으로 다른 제작 공법에 비해 별도의 조립공정이 불필요한 경제적인 공법이다. 동시접착은 외피와 보강재 중 하나를 먼저 성형하고, 나머지는 프리프레그 상태로 먼저 성형된 구조물과 함께 성형하는 방법이며, 이차접착은 복합재 외피와 보강재를 각각 별도로 제작한 후 이를 접착제를 이용하여 별도로 접착하는 방법이다. 일체성형으로 보강 패널을 제작하는 공정에서는 경화 후 내부 금형의 제거를 용이하게 하기 위한 고무금형을 설계, 제작하였고, 경화 온도로 인해 고무금형에서 발생하는 팽창압력에 대한 유한요소해석을 수행하였다. 제작된 보강 패널은 3-D 측정 장비와 초음파 장비로 치수정밀도 및 내부 결함을 평가하였으며, 직접인장시험(Pull-off test)을 수행하여 기계적 특성을 평가하였다.

• 한국정밀공학회지
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• 제16권6호
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• pp.52-57
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• 1999

Funtional metal prototypes are often required in numerous industrial applications. These components are typically needed in the early stage of a project to determine form, fit and function. Recent R/P(Rapid Prototyping) part are made of soft materials such as plastics, wax, paper, these master models cannot be employed durable test in real harsh working environment. Parts by direct metal rapid tooling method, such as laser sintering, by now are hard to get net shape, pores of the green parts of powder casting method must be infiltrated to get proper strength as tool, and new type of 3D direct tooling system combining fabrication welding arc and cutting process is reported by song etc. But a system which can build directly 3D parts of high performance functional material as metal part would need long period of system development, massive investment and other serious obstacles, such as patent. In this paper, through the rapid tooling process as silicon rubber molding using R/P master model, and fabricate wax pattern in that silicon rubber mold using vacuum casting method, then we tranlsated the wax patterns to numerous metal prototypes by new investment casting process combined conventional investment casting with rapid pototyping & rapid tooling process. with this wax-injection-mold-free investment casting, we developed new investment casting process of fabricating numerous functional metal prototypes from one master model, combined 3-D CAD, R/P and conventional investment casting and tried to expect net shape measuring total dimension shrinkage from R/P part to metal part.

• Elastomers and Composites
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• 제55권2호
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• pp.120-127
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• 2020

In this study, molding shrinkage of PPS resin was investigated. Two types of PPS resins with differing glass fiber and calcium carbonate content were used for this purpose. To observe mold shrinkage, molding conditions based on injection temperature, injection speed, and the position of the cushion were selected. Circular and rectangular specimens were used for the study model. Injection molding simulation was performed to predict the filling pattern and mold shrinkage, and the simulation results were compared with the experimental conclusions. It was observed that the mold shrinkage showed the highest shrinkage (distributed from 0.05% to 0.32%) dependence on the injection temperature, and the lowest shrinkage (distributed from 0.05% to 0.31%) dependence on the injection speed. The role of the position of the cushion in mold shrinkage was difficult to observe. The results of the simulation mostly agreed with the experimental results; however, for some molding conditions, the mold shrinkage in the simulation was overestimated as compared to that in the experiment.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.507-512
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• 2003

A finite element analysis for near-net-shape forming of Al6061 powder was performed under warm pressing. The advantages of warm compaction by rubber isostatic pressing were discussed to obtain parts with better density distributions. To simulate densification and deformed shape of a powder compact during warm pressing, the elastoplastic constitutive equation based on yield function of Shima-Oyane was implemented into a finite element program(ABAQUS). The hyperelastic constitutive equation based on the Ogden strain energy potential was employed to analyze nonlinear elastic response of rubber. Finite element results were compared with experimental data for Al6061 powder compacts under warm pressing.