• 실천공학교육논문지
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• 제10권2호
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• pp.89-94
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• 2018

사출 성형에서 금형 온도는 성형품의 품질에 큰 영향을 준다. 어느 정도의 온도가 적정한가는 성형 재료, 성형품에서 요구되는 품질에 의해서 결정되고 중요한 것은 그 온도가 안정적이어야 한다. 먼저 그 수지에 적합한 금형 온도 조건 범위 내에서 성형품이 요구하는 품질에 맞는 금형 온도를 설정해야 한다. 즉, 성형품의 표면 광택, 성형 사이클의 단축, 변형 방지, 수축 및 수지 흐름의 용이성 등의 중요성에 의해서 금형 온도는 변화한다. 실질적인 금형 기술 향상을 위해서 사출 금형을 설계하고 제작하는 산업체에서 적용할 수 있는 온도 제어에 대한 애로 기술 과정의 훈련 모형을 제시하고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집C
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• pp.621-626
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• 2001

Microcellular foaming process was developed at MIT in 1980's to save a quantity of raw materials and improve mechanical properties. There are many process variables in appling microcellular foaming process to the conventional injection molding process. Of all process variables, part dimension control and shrinkage are the most influential on the post molded dimension. The post molding dimensional change of thermoplastic resins is important to tool designers for predicting the specific difference of molded part vs. actual mold cavity. Generally, articles injection molded are smaller in size than the cavity; hence, the term shrinkage factor is used to define the allowance a designer specifies. It is important to consider the factors that influence molded part dimension. According to ASTM Designation: D 955, shrinkage from mold dimensions of molded plastics was measured. In injection molding, the difference between the dimensions of the mold and of the molded article produced therein from a given material may vary according to the design and operation of the mold. In this paper, shrinkage data of molded plastic parts was obtained. It can be an important information for designing optimum mold system in a microcellular foaming injection molding process.

• Design & Manufacturing
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• 제13권4호
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• pp.34-39
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• 2019

In this paper, in order to improve the formability and quality of the injection molded parts in the molds for molding the motorcycle rear cowl injection molded parts with different volumes at the same time, the flow of the molded parts is changed through the injection molding CAE analysis by changing the gate position, runner size and position. It is to find the optimum gate position, the diameter of the runner and the position where the balance is equal. The molded article formed by the optimization resulted in the uniformity of the molten resin at the same time at the corner of the product, thereby maintaining the flow balance favorable for mass production at lower injection pressure.

• 폴리머
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• 제35권1호
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• pp.1-6
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• 2011

사출성형은 고온의 수지를 고압으로 금형에 충전하고 냉각하여 제품을 만드는 공정으로 큰 온도차이와 고압에 의해 성형품에 잔류응력이 형성된다. 이러한 잔류응력은 시간이 지남에 따라 이완되면서 제품에 변형을 일으켜 형상 품질을 저하시킨다. 본 연구에서는 광탄성 장치를 이용하여 투명한 사출성형품의 잔류응력을 측정하는 방법을 연구하였다. 빛은 전자파처럼 진행하는데 편광필름을 통과하면 하나의 파장만이 진행하게 된다. 그 파장이 시편을 통과하면서 시편에 존재하는 잔류응력 때문에 복굴절이 형성되고 두 번째 편광필름을 통과하면서 다양한 색의 패턴을 보이게 된다. 이 색의 패턴을 이용하여 사출성형으로 제작된 사각평판의 잔류응력을 정량적으로 측정하였다. 또한 컴퓨터 해석을 통해 사출성형품의 광학적 특성을 예측하였으며 실험과 비교하였다.

• Design & Manufacturing
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• 제12권3호
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• pp.55-59
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• 2018

In a multi-cavity mold having a runner layout of a fish bone structure, problems of unbalanced filling between cavities occur constantly. Unbalanced charging lowers the dimensional accuracy of a molded article and causes deformation after molding. To solve this problem, the gate size connected to each cavity is adjusted using the BGV (Balanced Gate Value) equation. In this paper, in order to solve the filling imbalance problem of the runner layout mold of fish bone structure through injection molding analysis study, we compared the charging imbalance phenomenon before and after improvement after adjusting the gate size by applying BGV equation. From the results of the molding analysis, the shrinkage ratio before and after the improvement of the molded article was improved by only about 0.08%. Based on these results, it was confirmed that the charging imbalance problem was not significantly improved even when the BGV equation was applied.

• Design & Manufacturing
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• 제11권1호
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• pp.34-38
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• 2017

Deformation frequently occurring in injection molded products is a phenomenon displayed due to uneven shrinkage distribution and orientation of the whole molded product. Shrinkage deformation is a very serious problem because it causes deformation of the molded article and shortens the performance of the product. In this paper, we are focusing on the warpage of keypad in mobile phone. In other words, we focused on minimizing keypad deformation. In the study, the Taguchi method was applied to find the injection molding conditions that minimize the deformation of the keypad. In the case of this keypad, the main factors influencing the shrinkage deformation were predicted as the melting temperature, coolant temperature and cooling time. In addition, the optimum molding conditions were obtained and the shrinkage strain was minimized. Experiments for the Taguchi method and verification of optimal molding conditions were performed using an injection molding analysis program.

• Elastomers and Composites
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• 제52권4호
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• pp.317-325
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• 2017

Molding conditions can be described as factors that determine the quality of a product obtained from injection molding. Many studies have been performed on the injection molding pressure, injection temperature, packing pressure and other molding conditions related to part quality. However, the most accessible factor among the adjustable molding conditions during actual injection is the injection speed. In this study, we simulated the variation of the physical quantity according to injection speed and performed experiments to understand the effect of injection speed on the actual product. A CAE analysis program (Moldflow) was used to simulate and analyze the results using PC and PBT for two models. In order to compare these results with the experimental results, an actual injection molding was performed for each injection speed, and the correlation between simulation and injection molding, especially for the shrinkage of the molded article, was discussed.

• Design & Manufacturing
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• 제15권4호
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• pp.8-13
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• 2021

A plastic roller for opening and closing the safety door of the injection molding machine was molded. The dimensional change of the measurement position of the roller was studied when the cooling time was applied differently among the molding conditions, and when the temperature of the coolant applied for mold cooling was also applied differently. Cooling times of 300 seconds and 400 seconds, hot and low-temperature coolant were applied. When the low-temperature coolant was applied, the measuring point of the roller shrank by 0.03 mm. However, when the high-temperature coolant was applied, the measuring point shrank by 0.3 mm. It was found that the application of low-temperature coolant among coolants was more suitable for the reference dimension of the molded article compared to the application of high-temperature coolant. Among the cooling water applied for the molding of plastic rollers, when high-temperature coolant is applied, the shrinkage rate measured immediately after ejection was smaller than when low-temperature coolant is applied. However, it was found that post shrinkage, which occurs over time, occurs much larger when high-temperature coolant is applied.

• 한국정밀공학회지
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• 제31권1호
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• pp.9-13
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• 2014

The molding process can be divided into five separate steps: plastification, injection, holding, cooling, and finally ejection. In the plastic injection molding, the effect factor such as mold temperature, injection speed, packing pressure and inhomogeneous cooling under packing process affects both the article dimension and physical characteristics. Especially, the packing pressure is the most critical factor to affect molded articles quality among the packing parameters. In this paper, the CAE simulation considering the molding condition is performed to predict the faulty cause which appears in the packing process between cavities of injection molding machine. From the results of CAE simulation, the packing phenomena according to the product form and the gate position was investigated to improve the article quality and minimize the various molding defects. The effect of packing pressure and gate number on the injection molding was discussed.

• 실천공학교육논문지
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• 제8권2호
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• pp.121-128
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• 2016

사출 성형 공정에서 외관 품질 문제는 대부분의 성형품에서 발생한다. 금형의 열역학적 설계 중의 하나는 어떠한 위치에서 캐비티 표면 온도가 되도록 균일하게 상승하는 것으로 수행된다. 실험적인 평가를 바탕으로 최적의 사출 성형 조건에서 성형품의 미려한 외관 품질을 위해서 캐비티 벽 온도와 다듬질 가공된 캐비티 표면이 성형품의 외관 문제를 피할 수 있는 가장 중요한 요소이다. 또한 잘못된 게이트 형식과 위치 선택은 성형품의 품질에 상당한 영향이 있어서, 각 캐비티로 부터 올바른 러너 밸런스를 유지하는 것은 매우 중요하다. 실질적으로 생산 현장에서 이행될 수 있는 사출 성형 품질을 위한 최적의 금형 설계와 실무 금형 기술 능력 향상을 위해서 현장 교육을 위한 실무적인 금형기술 과정의 교육훈련 모델을 제시하였다.