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Optimization of Conformal Cooling Channels with Array of Baffles for Plastic Injection Mold
박홍석,Xuan-Phuong Dang 한국정밀공학회 2010 International Journal of Precision Engineering and Vol. No.
Cooling system has an important role in the injection molding process in terms of not only productivity and quality, but also mold-making cost. In this paper, a conformal cooling channel with an array of baffles is proposed for obtaining uniform cooling over the entire free-form surface of molded parts. A new algorithm for calculating temperature distribution through molding thickness, mold surface temperature and cooling time was presented. The relation among cooling channels’ configuration, process parameters, mold material, molding thickness and temperature distribution in the mold for a given polymer is expressed by a system of approximate equations. This relation was established by the design of experiment and response surface methodology based on an adequate physical-mathematical model, finite difference method and numerical simulation. By applying this approximate mathematical relation, the optimization process for obtaining target mold temperature, uniform temperature distribution and minimizing the cooling time becomes more effective. Two case studies were carried out to test and validate the proposed method. The results show that present approach improves the cooling performance and facilitates the mold design process in comparison to the trial-and-error simulation-based method.
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반추동물의 고농후사료급여(高濃厚飼料) 문제점과 Buffer 제의 사용효과
박홍석 한국영양사료학회 1983 韓國營養飼料學會誌 Vol.7 No.1
반추동물은 反芻胃 醱酵를 통하여 대부분의 사료를 消化하고 揮發性 底級脂肪酸(VFA)의 형태로 에너지를 吸水 利用한다. 반추위 醱酵는 수없이 많은 微生物에 依해 이루어지며, 多量의 농후사료를 급여하면 반추위 pH가 底下되어 여러가지 문제가 생긴다. 반추동물은 침 (Saliva)을 分泌하여 그 속에 함유된 NaHCO₃또는 Na₂HPO₄와 같은 buffer 제와 生成되는 VFA에 의해 pH를 유지한다. 농후사료 급여 比重이 너무 높아 침의 분비가 적을 때 buffer제를 飼料에 첨가하여 낮아지는 pH를 修正하고 기타 문제점을 解決하려는 많은 努力이 진행되어 왔다. Buffer제의 添加는 반추위 pH를 높여주고 젖산, 특히 lactic afidosis의 원인이 되는 D-lactate의 生成을 감소시키는 效果가 있다. 젖소와 肥肉牛에 있어서 buffer제 添加에 의한 VFA의 生成形態에는 차이가 있어서, 젖소의 경우는 buffer제의 첨가로 초산 또는 뷰틸산의 生成을 높여주는가 하면, 비육우에 있어서는 반대로 프로피온산을 증가시키고 초산 生成을 감소시키는 것으로 여러 실험결과는 나타났다. 이런 現像은 젖소의 乳脂率을 높여주고 비육우의 增體效率을 높여 준다는 意味에서 바람직한 方向의 改善이다. 그러나 젖소와 비육우에 있어 buffer계에 의한 VFA生成에 差異가 나는 원인은 確實하지가 않다. Buffer제의 使用이 실제 生産性에 效果를 나타내는지의 與否는 buffer제의 種類와 使用水準, 농후사료의 구성이나 급여 수준에 따라 달라지는 것 같다. 이제까지 진행되어온 많은 實驗結果로 미루어 볼때 buffer제의 첨가는 반추동물의 젖산중독(lactic acidosis), 젖소의 肥滿症(fat cow syndrom), 비육우의 농후사료 過食(grain ergogement) 등을 예방하는데 도움을 준다. 그러나 效率的인 buffer제의 使用을 위하여 앞으로의 硏究努力이 좀더 필요하다 하겠다.
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Energy-Efficient Optimization of Forging Process Considering the Manufacturing History
박홍석,Trung-Thanh Nguyen,Xuan-Phuong Dang 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.3 No.2
Increasing the energy efficiency of manufacturing processes is one of the many ways to reduce manufacturing cost and to resolve environmental issues. This paper systematically investigates the manufacturing process of an automotive crankshaft via a numerical simulation approach towards energy savings. The aim of this work is to propose potential solutions for improving the energy efficiency of the forging process chain in which energetically relevant parameters are optimized variables. The process chain is holistically optimized because the manufacturing history among the different processing steps is considered. We developed a discrete-event simulation based method to facilitate the holistic optimization of the forging process chain with regards to energy efficiency. To elucidate the weaknesses of the current process chain, manufacturing data were examined. Subsequently, a discrete-event simulation (DES) model was used in conjunction with design of experiments (DOE) in order to determine significant parameters as well as optimization scenarios. Finally, energy consumption optimizations were realized based on a consideration of the parameter adjustments. The research results show that the energy efficiency of the forging process chain could be improved by approximately 10% compared to the current state. Therefore, this work contributes to make the manufacturing crankshaft become greener and more efficient.
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DESIGN OF CONFORMAL COOLING CHANNELS FOR AN AUTOMOTIVE PART
박홍석,N. H. PHAM 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.1
The cooling system plays a crucial role in determining the bproductivity and quality of an injection molding process. With the current growth of Solid Freeform Fabrication (SFF) techniques, mold designers have been striving for not only improvement in cooling system performance but also for a method to do so automatically. In this paper, a method is proposed for developing a conformal cooling system that facilitates uniform cooling over the entire mold surface with minimum cycle time. Based on the temperature distribution after the filling stage, the mold surface is split into zones which will be cooled by optimized subconformal channels obtained from the optimization process. The optimization process in which the objective function is stated as minimization of the cooling time with boundaries ensuring a realistic design will optimize the cooling system layout in terms of cooling channel size and location. Finally, all subcooling channels are combined to generate the entire conformal cooling system for the injection mold. The cooling system plays a crucial role in determining the bproductivity and quality of an injection molding process. With the current growth of Solid Freeform Fabrication (SFF) techniques, mold designers have been striving for not only improvement in cooling system performance but also for a method to do so automatically. In this paper, a method is proposed for developing a conformal cooling system that facilitates uniform cooling over the entire mold surface with minimum cycle time. Based on the temperature distribution after the filling stage, the mold surface is split into zones which will be cooled by optimized subconformal channels obtained from the optimization process. The optimization process in which the objective function is stated as minimization of the cooling time with boundaries ensuring a realistic design will optimize the cooling system layout in terms of cooling channel size and location. Finally, all subcooling channels are combined to generate the entire conformal cooling system for the injection mold.
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