• Polymer(Korea)
• /
• v.32 no.6
• /
• pp.501-508
• /
• 2008

Small injection molded articles such as lens and mobile product parts are usually molded in multi-cavity mold. The problem occurring in multi-cavity molding is flow unbalance among the cavities. The flow unbalance affects the dimensions and physical properties of molded articles. First of all, the origin of flow unbalance is geometrical unbalance of the delivery system. However, even the geometry of the delivery system is well balanced, cavity unbalance occurs. This comes from the temperature distributions in the cross-section of runner. Temperature distribution depends upon injection speed because heat generation near runner wall is high at high injection speed. Among the operational conditions, injection speed is the most significant process variable affecting the filling unbalances in multi-cavity injection molding. In this study, experimental study of flow unbalance has been conducted for various injection speeds and materials. Also, the filling unbalances were compared with CAE results. The dimensions and weights of multi-cavity molded parts were examined. The results showed that the filling unbalances vary according to the injection speeds and resins. Subsequently, the unbalanced filling and pressure distribution in the multi-cavity affect the dimensions and physical states of molded parts.

• Proceedings of the KAIS Fall Conference
• /
• 2009.12a
• /
• pp.678-681
• /
• 2009

사출성형은 열가소성수지의 가공법으로써 정밀도나 고품질의 제품을 효과적으로 생산하는데 널리 이용되며 플라스틱은 현재 광범위하게 사용되고 있는 공업재료 중의 하나이다. 과거에는 플라스틱을 일회용품 및 외장재로 사용하였다. 그러나 산업기술이 발전하며 플라스틱은 금속을 대체 할 수 있는 재료로서 사용할 수 있다는 인식의 변화로 점차 기계요소용 재료로 사용되고 있으며 기계요소용 재료로 사용됨에 따라 플라스틱 제품이 정밀한 부품으로 사용되기 위해서는 금형의 가공뿐만 아니라 사출성형 시 용융수지가 금형의 각 캐비티에 균형적으로 충전되는것이 요구된다. 이러한 요구조건을 만족하기 위해서는 각 캐비티의 가공치수는 매우 높은 정밀도를 유지해야 하며, 각 캐비티에서의 충전과 냉각도 동일한 상태를 유지해야 한다. 충전 불균형은 성형품의 품질에 큰 저해 요인으로서 플라스틱 제품의 치수성, 밀도, 외관품질, 강도 등에 불균일한 결과를 가져오는 요인으로 지적되고 있다. 실제로 충전 불균형은 충전 단계에서 런너 내에서 발생하는 불균일한 전단분포에 기인하여 발생되므로 점도변화에 영향을 주는 수지의 물성, 런너의 배열과 같은 외부 요인과 사출압력, 사출속도, 수지온도, 금형온도와 같은 성형공정 조건에 의한 요인에 의한 충전 불균형의 양상이 달라지게 된다. 본 연구는 다수 캐비티 금형에서 충전 불균형 현상에 대한 원인을 검토하고 실제로 사출성형을 실시하기 전 사출성형해석 소프트웨어를 이용하여 시뮬레이션을 하여 다수 캐비티에 대한 충전 패턴을 미리 예측하여 보았다.

• Proceedings of the KAIS Fall Conference
• /
• 2010.05b
• /
• pp.1245-1248
• /
• 2010

플라스틱은 가공이 용이하기 때문에 우리 생활에 널리 이용되고 있다. 과거에는 단순히 제품의 외장제로 이용되었지만 산업이 발달함에 따라 금속을 대체 할 정도로 사용 범위가 증가하고 있다. 또한 사용량이 증가함에 따라 제품의 생산량을 증가시키기 위해선 다수 캐비티의 금형 사용이 필수적으로 되었다. 다수 캐비티 사출성형에서 각 캐비티 간 제품의 품질 및 물성을 향상시키기 위해선 각 캐비티로 충전되는 수지가 균형을 이루어야 한다. 하지만 기하학적으로 균형을 갖추고 있는 러너를 설계하여도 실제 사출성형에서는 불균형 충전이 일어나게 된다. 이러한 불균형 충전은 미국의 Beaumont에 의해서 처음 규명된 뒤 충전불균형 현상을 해결하기 위해 많은 연구가 진행되었다. 본 논문에서는 다수 캐비티 사출성형에서 균형충전을 위한 러너시스템을 제안하였다. 이 러너시스템은 온도가 불균일한 수지의 흐름을 혼합함으로써 수지의 흐름을 균일하게 하여 균형충전을 이루도록 하였다. 또한 사출성형해석프로그램인 Moldflow를 이용한 유동해석을 통해 그 효과를 나타내 보았다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.10a
• /
• pp.72-75
• /
• 2003

Almost all injection molds have multi-cavity runner system for productivity and are designed with geometrically balanced runner system in order to minimize filling imbalance between cavity to cavity during processing. However, filling imbalances have been observed though geometrically balanced runner lay-out are used. Generally, these filling imbalances are due to thermal unbalance, viscosity, characteristic of polymers and so on. These kinds of filling imbalances has already been reported by Beaumont[1] since 1997. In this study, we presented filling imbalaces in balanced runner that has unnary branch type lay-out through experimental tests. As a result of experiments, we could present the processing conditions for the balanced filling in geometrically balanced runner that has unnary branch type lay-out

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.4
• /
• pp.1581-1588
• /
• 2011

In this study, flow characteristics in a multi-cavity injection molding process were investigated. One of main problems occurred in the multi-cavity molding is a flow imbalance among cavities since it affects physical properties and quality of products. Charge imbalance is caused by the uneven shear stress. Therefore, changes in viscosity affect the physical properties of resin and injection conditions differ in the filling imbalance phenomenon. Through, this study focus on experimental studies of flow imbalance for PC and PP resin occurring in a balanced delivery system. Experimental results were compared with CAE results. By experimental and CAE analysis, main cause for the flow imbalance is temperature distribution in cross section of runner. New runner system with a simple change of runner shape was suggested to avoid the flow imbalance. A series of simulation to confirm feasibility of Volume Runner's effects was conducted using injection molding CAE.

• Journal of Advanced Marine Engineering and Technology
• /
• v.28 no.6
• /
• pp.931-937
• /
• 2004

Simultaneous filling is a goal in plastic injection mold that has multi cavities. The moldings which have not been filled at the same time have undesired faults such as dimension inaccuracy, residual stress, law mechanical strength, etc. The best way to simultaneous fill is to be injected in a geometrically balanced runner system. In a general processing, however, in balanced runner system mold, filling imbalance would be observed in cavities. These phenomena result from molten polymer's characteristics and circumstances in balanced runner. In this study, the degree of filling imbalance (DFI) was defined for showing rate of filling imbalance in geometrically balanced injection mold that has 8 cavities. Before the main experiment, an injection molding simulation was conducted to know a pattern of filling imbalance with Moldflow software. There were somewhat differences between results of experiment and simulation about the filling imbalance. The reason for the difference was that the software have not concerned about a situation in a real flow channel. It was also investigated how the injection speed affected on filling imbalance in the experiment.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.11a
• /
• pp.175.2-175.2
• /
• 2011

바나듐 3, 4, 5가 이온은 공기 중에서 안정하지만, 바나듐 2가 이온은 쉽게 산화된다. 그러므로 바나듐 2가 이온이 담겨져 있는 음극 탱크가 공기와 접촉하지 않게 하는 것이 중요하다. 충전 중 음극 탱크에 공기가 침투되면, 바나듐 2가 이온은 3가 이온으로 산화되기 때문에 음극과 양극의 전해질에 불균형을 초래한다. 이러한 불균형은 바나듐 레독스 흐름전지 용량저하의 원인이 된다. 본 연구에서는 공기 중 2가 이온 산화에 의한 전해질의 불균형 현상을 쉽게 보여주기 위해, 공기노출과 차단조건에서 충방전 중에 발생한 음극과 양극의 바나듐 이온 상태변화량을 UV-Visible spectrophotometer를 이용해 정량적으로 분석하였다. 분석 결과, 공기노출 조건에서 음극의 충전 시, 충방전 cycle이 진행 될수록 바나듐 2가 이온의 양이 현격히 줄어들었지만, 공기차단 조건에서는 2가 이온의 양이 공기노출 조건보다 훨씬 더 적게 줄어들었다. 즉, 공기차단 조건에서는 바나듐 2가 이온이 3가로 산화되지 않아서 음극의 충전 후 바나듐 3가에서 2가로 전환되는 양이 공기노출 조건보다 더 많은 것을 확인할 수 있었다. 이러한 영향으로 인해, 충방전 10th cycle을 진행해 본 결과, 공기차단 조건에서는 충방전 용량감소가 거의 없었지만 공기노출 조건에서는 현격한 충방전 용량 감소를 보였다.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.9 s.174
• /
• pp.173-178
• /
• 2005

Recently plastic parts are molded for the purpose of mass production in multi-cavity system. Therefore, designer is usually designing mold that has geometrically balanced runner lay-out for filling balance at each cavity. Although, mold is manufactured with geometrically balanced runner lay-out, there are actually filling imbalances in the cavities. These filling imbalances phenomenon are caused by complicated interaction between melt and mold. In this study, based on previous studies for filling imbalances in cold-runner mold, filling imbalances in hot-runner mold were investigated by CAE and injection molding experiments. ABS and PMMA as amorphous polymer, PA as crystalline polymer were used to compare the filling imbalances. There were different results of CAE and experiment. The filling imbalances decreased as injection rate increased without regard to kind of resins and were lower than the one of cold-runner.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.598-601
• /
• 2005

Plastic parts are molded for the purpose of mass production in multi-cavity system. Therefore, designer is usually designing molds that has geometrically balanced runner lay-out for filling balance at each cavities. Although, mold is manufactured with geometrically balanced runner lay-out, there are actually filling imbalances in cavities. These filling imbalances phenomenon are caused by complicated interaction between melt and mold. In this study, based on previous studies for filling imbalances in cold-runner mold, filling imbalances in hot-runner mold were investigated by CAE and injection molding experiments. ABS, PMMA as amorphous polymer and PA, PP as crystalline polymer were used to compare the filling imbalances. The filling imbalances decreased as injection rate increased without regard to kind of resins and were lower than the one of cold-runner.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2005.06a
• /
• pp.706-709
• /
• 2005

Despite geometrical balanced runner system, filling imbalances between cavity to cavity have always been observed in multi-cavity injection mold. These filling imbalances are results from non-symmetrical shear rate distribution within melt as it flows through the runner system. It has been possible to decrease filling imbalance by optimizing processing conditions, but it has not completely eliminated this phenomenon during the injection molding processing. This paper presents a solution of these filling imbalances by using runner core pin which creates a symmetrical shear distribution within runner and the effects on filling imbalance when modifying a shape of runner core pin. As a result of using runner core pin, a remarkable improvement in reducing filling imbalance was confirmed. In addition we investigated how filling imbalances were affected by shape of runner core pin.