• Design & Manufacturing
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• 제2권4호
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• pp.37-43
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• 2008

Supplementary features in injection molded products, which are boss, rib and snap fit, are mainly located in the products. These features might make molding flow improper in injection processing and consequently give rise to some of molding troubles such as short shot and hesitation. The sink mark on boss parts is generated by the volumetric shrinkage that is caused by both the molding thickness and the closed boss height. The volumetric shrinkage is affected by packing pressure and its amount tends to decrease by increasing the packing pressure. The packing pressure can therefore increase flow rate to a boss part and causes the sink mark depth to increase. As the molding thickness and the closed boss height in the boss part can increase the part volume, these may yield bad solidifying and also extend the molding cycle. In this paper, both the injection molding test and the flow analysis were carried out to investigate the effect of sink marks generated in the boss part of injection molded products.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1354-1357
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• 2003

Mold Analysis is crucial factors in the design of injection molding process. Since the qualify of products depends on filing, shrinkage and etc, the procedure of prediction through analysis in the design of injection molding process is needed. In many cases, this kind of analysis makes it possible to predict pressure pattern which determines the condition of injection molding process. Crystallinity is the factor that determines the shrinkage of products. The studies showed the factors that had been related to the degree of crystallinity, which were mostly Weight Reduction, mold temperature and melt temperature. Therefore, the objective of this study is to see the differences of the degree of crystallinity depending on the positions of foamed plastics. The procedure of this study is as the following. First, Simulate the pressure gradient in mold cavity that can produces specimen by using Moldflow. Secondly, produce specimen and measure the degree or crystallinity of each part of specimen by using XRD. Lastly, identify the sensitivity of conventional plastic and foamed plastic on pressure gradient by comparing the simulation and the results of measurement.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.864-869
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• 2004

It is net easy to predict the shrinkage rate of a plastic injection mold in its design process. The shrinkage rate should be considered as one of the important performances to produce the reliable products. The shrinkage rate can be determined by suing the CAE tools in the design produces. However, since the analysis can take minutes to hours, the high computational costs of performing the analysis limit their use in design optimization. In this study, the surrogate models based on the DACE is used in lien of the original models, facilitating design optimization.

• Design & Manufacturing
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• 제6권1호
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• pp.5-11
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• 2012

The sink mark on boss parts is generated by the volumetric shrinkage that is caused by both the molding thickness and the boss wall thickness. The volumetric shrinkage is caused by packing pressure and its amount tends to decrease by increasing the packing pressure. The packing pressure can therefore increase the flow rate to a boss part and causes the depth of sink mark to increase. As the molding thickness and the boss wall thickness in the boss part can increase the part volume, these may yield bad solidifying and also extend the molding cycle. In this paper, both the injection molding test and the flow analysis were carried out to investigate the effect of sink mark that was generated in the boss wall thickness of injection molded products. The sink mark could also be caused by thickness ratio of boss part. For a given thickness ratio of boss, several molding process parameters such as packing pressure, packing time and melt temperature, affecting to generation of the sink mark were discussed.

• Journal of Ginseng Research
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• 제18권1호
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• pp.60-65
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• 1994

Fresh ginseng of same grade was stored under the 4$\pm$1$^{\circ}C$ and 87~92% RH for 10 weeks. During the storage, an aliquot amount of the ginseng was drawn, freeze dried and chemical constituents and physicochemical parameters were measured. After 10 weeks of storage drying rate and shrinkage of ginseng were 1520% and 9.04%, respectively, mold growth was seen at week 5 and observed for 51.2% of the ginseng week 10. Amylase activity level was elevated at the early stage of storage and decreased to 5% of initial value at week 5. At week 5, the elevated amylase activity was inconcomitant with the appearance of the mold growth. Crude protein contents were increased and decreased, respectively 5 week post storage. No significant changes in crude fat, crude fiber, ash, total sugar, n-butanol extract and ginsenoside were observed. The content of water-extractable substance showed maximum at week 7 to 8. The value of pH was slightly elevated and reducing sugar was increased during the storage. Key words Ginseng storage, physicochemical properties, drying rate, shrinkage, amylase activity.

• 한국주조공학회지
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• 제42권1호
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• pp.3-11
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• 2022

본 연구에서는 전산모사를 활용하여 오스테나이트계 내열강인 HR3C 합금의 수축 결함 파라미터를 확보하고, 건전부 85% 이상의 잉곳 몰드 설계 및 제작을 진행하였다. 잉곳 몰드 설계 단계에서 전산모사를 활용하여 최적의 잉곳 몰드를 설계 및 제작하였으며, 제작한 잉곳 몰드를 통해 시험조업을 수행하였다. 시험조업 후, 절단 및 비파괴 검사를 통해 결함 양상을 분석하여 수축 결함 파라미터와 잉곳 몰드 설계를 검증하였다. 검증 결과를 기반으로 HR3C 합금의 수축 결함 파라미터 (Niyama 인자, 급탕효율인자, 열간 균열 인자 등)를 확보하였으며, 확보한 파라미터를 통해 건전부 85% 이상의 잉곳 몰드 설계 방안을 확보하였다.

• 소성∙가공
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• 제6권6호
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• pp.489-499
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• 1997

The injection molding process is analyzed to get the information on the mold design parameters and the optimum process conditions for automotive plastic front fender. The gate position, runner size and cooling channel are determined by the estimation of the flow balance, packing time, uniform cooling and shrinkage and warpage in the injection molding analyses. The procedure can be used in the mold design in the early stage when developing plastic parts.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.136-142
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• 1999

The injection molded part shrinks in the process of solidification by the amount of the coefficient of linear thermal expansion multiplied by the temperature difference between the coefficient of linear thermal expansion multiplied by the temperature difference between the room temperature and the temperature at which the solid structure is formed in the mold And it is called warpage for this type of deformation that shrinkage are not uniform throughout the injection molded part. To predict warpage phenomena in the articles the results obtained theoretically from the change of mold temperature fiber content of composites have been compared with exsperimental results.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 춘계 학술논문 발표대회
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• pp.9-10
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• 2017

In case of the concrete is poured into the HPC(Hollow Precast Concrete) column, the shrinkage condition of the HPC surface and the infilled concrete may be different, causing an interfacial space and deteriorating the integration performance. In this study, manufacturing HPC column mold and and the drying shrinkage properties with the charging concrete were examined. As a result, case of the shrinkage reducing agent showed the best drying shrinkage reduction effect. In the case of the expansive agent, the length change was lower than that of plain, but the difference from the shrinkage reducing agent was large, so it is considered that mixing condition of expansion mixing condition should be improved.

• 한국세라믹학회지
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• 제36권1호
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• pp.89-96
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• 1999

석고몰드의 단점을 극복할 수 있는 다공질 알루미나 몰드의 제조저건을 확립하였다. 다공질 알루미나 몰드의 제조를 위해 활성탄의 질량비에 따라 조성비를 달리하여 첨가한 후, ESA와 유동특성 등을 조하삼으로써 안정된 이상 슬러리를 제조하였으며, 이를 석고몰드에 캐스팅하여 얻은 원통형 알루미나 몰드를 사용하여 활성탄의 양과 소결온도에 따른 수축율 변화와 마모에 대한 저항성을 측정하였다. 다공질 알루미나 몰드의 소결에서는 비수축 소결구인 표면확산에 의해 입자간 넥 강도의 증진을 통한 몰드의 강도 증진을 도모하는 것이 바람직하며, 이를 위해 1,00$0^{\circ}C$이하에서 유지시간의 변화에 따른 열역학적 방법, 1,00$0^{\circ}C$이상의 온도에서 알루미나의 수축을 억제하면서 빠른 승온속도를 열처리온도에 따른 동역학적 방법과 이 두가지 방법을 혼합하는 방법 등으로 구분하여 다동질 알루미나 몰드의 소결조건을 분석하였다. 위 방법들에 대한 다공질 알루미나 몰드의 캐스팅 특성을 분석한 결과, 복합 소결법이 최적임을 알수 있었다. 제조된 다공질 알루미나 몰드의 비교적 높은 강도를 보였으며, 석고몰드레 비해 빠른 건조시간, 산, 염기에 대한 내식성 및 캐스팅 특성이 우수하였다.