• 대한치과보철학회지
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• 제37권5호
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• pp.640-650
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• 1999

As an optimal quality of the restorations, there should be a least amount of seating discrepancy between the casting and abutment teeth. However, high viscosity of the cementing medium and its resulting thickness may prevent complete seating of the restoration. The use of die spacing material provides adequate internal relief for the cementing medium. The purpose of this study is to compare the thickness of three commonly used die spacing materials. Materials and Methods: Stone plates were fabricated and divided into 12 sections to be painted with die spacers. Tru-Fit, Whip-Mix and Belle do St. Claire die spacer which are commonly used in dental practice were tested in this study. Each die spacers were painted layer by layer according to the manufacturer's recommendation. The average thickness of each die spacers were measured with light microscope(${\times}100$) and compared between them. Results and Conclusions. A silver-colored Tru-Fit die spacer has the lowest value of thickness without statistical significance comparing with a gold-colored Tru-Fit die spacer and a gray layer of Whip-Mix die spacer has the highest value of thickness without any statistical significance comparing with Belle de St. Claire die spacer. Three and four layers of Tru-Fit die spacer and two layers of Whip-Mix and Belle de St. Claire die spacers seem to be in the acceptable range of thickness of 25 to $45{\mu}m$ for optimal seating of the restorations. The standard experimental design and method should be fur thor evaluated for more consistent and objective results.

• 한국산학기술학회논문지
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• 제9권2호
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• pp.281-285
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• 2008

냉간단조금형(Cold Forging Die)의 다이블록(Dieblock)을 제작하는 방법 중의 하나로, 다이블록 제작용 재료를 면가공 하여 다이블록 상면(上面)을 마스터펀치(Master Punch)인 호브(Hob)로 압입(Indentation) 시켜 절삭가공((Cutting Work)이 아닌 다이호빙(Die Hobbing) 방법으로 임프레션(Impression)을 성형하여 제작하고 있다. 이 방법에 의하여 다이블록의 재료를 합금공구강(Alloy Tool Steel)인 SKD11을 사용하여 제작하고, 스테인리스판(Stainless Sheet Metal)을 제품 재료로 하여 냉간단조가공(Cold Forging Work)을 수행하였더니 6,000 스트로크(Stroke)에서 금형수명(Die Life)을 다 하고 파손되었다. 본 논문에서는 다이블록 재료를 고속도공구강(High Speed Tool Steel)인 SKH51로 교체 제작하고, 탄소강(Carbon Steel)인 S45C를 제품 재료로 하여 냉간단조가공을 수행하였더니 21,000 스트로크에서 금형수명을 다하고 파손되어 종래의 방법과 비교 검토하였을 때 350%의 금형수명 연장 효과를 얻게 되었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 춘계학술대회 논문집
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• pp.135-138
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• 2004

Since the upsetting type is superior to an extrusion type to get the dimensional accuracy of cold forged spur gear, the upsetting type process far spur gear cold forging has been studied. FE analysis of upsetting type process fur spur gear cold forging was performed to investigate about flow pattern of workpiece and die stress. To analyze the elastic characteristics of die, both rigid and elastic material model were used during loading stage. Under-filled defects were detected In lower portions of spur gear forged by upsetting type in experimental. When the elastic material model for die was used, the under-filled defects could be predicted. On the other hand, if the material model of die was rigid, the defects could not been presented because the die deflection was not considered.

• 대한기계학회논문집
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• 제17권12호
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• pp.2970-2981
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• 1993

In hot closed-die forging the load increases rapidly near the final stage. Preforming operation is important to both the sound final forging and die-service life. In this study, the material flows during preforming and final forging are investigated. The physical modeling with Plasticine as a model material showed clear flow patterns. The forging process were numerically simulated by the finite element method with the isothermal and the non-isothermal models. The flow patten of the isothermal simulation showed good agreements with the experiments. Temperature changes and pressure distributions on the die surfaces during one cycle of the forging process were obtained from the non-isothermal simulation. High pressure and temperature were developed at certain areas of the die surfaces. It was concluded that those areas usually coincide with each other and should be distributed by the preforming operations to enhance the die life.

• 대한치과보철학회지
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• 제45권4호
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• pp.546-554
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• 2007

Statement of problem: Die materials require abrasion resistance, dimensional stability with time, and high surface wettability for adequate material properties. Wear of gypsum materials is a significant problem in the fabrication of accurately fitting cast prosthetic devices. So It has been recommended that the use of die hardener before carving or burnishing of the wax pattern. Purpose: The purpose of this study was to compare the abrasion resistance and surface microhardness(Knoop) with 3 commonly used gypsum die materials(MG Crystal Rock, Super plumstone, GC $FUJIROCK^{(R)}$ EP) with and without the application of 2 die hardeners. Material and methods: Three die materials were evaluated for abrasion resistance and surface microhardness after application of 2 die hardeners(Die hardener and Stone die & plaster hardener). Thirty specimens of each gypsum material were fabricated using an impression of resin die(Pattern resin; GC Corporation, Japan) with 1-mm high ridges, sloped 90 degrees. Gypsum materials were mixed according to manufacturer's recommendations and allowed to set 24 hours before coating. Specimens were arbitrary assigned to 1 of 3 treatment subgroups (n=10/subgroup): no treatment(control), coated with Die hardener, and coated with Stone die & plaster hardener. Abrasion resistance(measured by weight loss) was evaluated using device in 50g mass perpendicular to the ridges. Knoop hardness was determined by loading each specimen face 5 times for 15 seconds with a force of 50g. A scanning electron microscope was used to evaluate the surface of specimens in each treatment subgroup. Conclusions: The obtained results were as follows: 1. 3 types of die stone evaluated in this study did not show significant differences in surface hardness and abrasive resistance(P<.05). 2. In the abrasive resistance test, there were no significant differences between GC $FUJIROCK^{(R)}$ EP and MG Crystal Rock with or without 2 die hardener(P<.05). 3. Super plumstone treated with Stone die & plaster hardener showed increased wear loss(P<.05) 4. Die hardener coatings used in this study decreased the surface hardness of the gypsum material(P<.05).

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 추계학술대회논문집
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• pp.265-268
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• 2003

In the extrusion process, the working material is forced to flow through a die with the desired profile. In general, the width of an extruded section is limited to about an inch less than the diameter of the round billet. But through the lip die, material is spreaded to produce a wider extruded section than the diameter of round billet. In this study, the extrusion process of an aluminum plate using the lip die is investigated. The width of the extruded plate is 450mm that is formed from the round billet with a diameter of 250mm. The flow characteristic through the lip die is considered to produce the wide-extruded plate with a small billet using rigid plastic FE analysis. Based on the result of FE analysis, new designs of lip die are proposed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 제5회 압출 및 인발가공 심포지엄
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• pp.23-32
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• 2002

The torsional forward extrusion is the process that is executed by punch travel and die rotation. The advantages of having the die rotation on this process are that forming load can be reduced and optimal die angle can be increased. This provides a possibility to extrude cold-worded material where a large extrusion force and die angle are required. Also, this process can improve the material properties owing to the high deformation and uniform strain distribution. The forming load and optimal die angle of this process are determined by the upper bound analysis using stream function and the optimization technique. To verify the theoretical result, we have carried out experiments and FE simulations using DEFORM3D.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.115-119
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• 2004

In the extrusion process, the working material is forced to flow through a die with the desired profile. In general, the width of an extruded section is limited to about an inch less than the diameter of the round billet. But through the lip die, material is spreaded to produce a wider extruded section than the diameter of round billet. In this study, the extrusion process of an aluminum plate using the lip die is investigated. The width of the extruded plate is 450mm that is formed from the round billet with a diameter of 250mm. The flow characteristic through the lip die is considered to produce the wide-extruded plate with a small billet using rigid plastic FE analysis. Based on the result of FE analysis, an optimized design of the lip die is then proposed.

• 소성∙가공
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• 제8권3호
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• pp.245-251
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• 1999

In this study, the experimental considerations of the friction factors are presented in a few cases. The friction factors in the cases of, first, the drawing quality material, SPC3C through the non-coated die of base material. GC30, secondly, SPCC through the Cr-coated GC30 die, and lastly. SPCC through the TD heat treated STD11 die, are measured experimentally both for the increasing die temperature and the blank holding forces. The results show no considerable variations of the value of friction coefficients according to the change of both the die temperature and the die treating conditions.

• Design & Manufacturing
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• 제6권2호
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• pp.42-47
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• 2012

The paper deals with an analysis of an extrusion process with a divided material flow in a combined radial - backward extrusion. We have discussed the influences of tool geometry such as punch nose angle, relative gap height, die corner radius on material flow and surface expansion into can and flange region. To analyse the process, numerical simulations by the FEM and experiment by physical modeling using Al alloy as a model material have been performed. Based on the results, the influence of fixed parameters on the distribution of divided material flow and surface expansion are obtained.