• 한국자동차공학회논문집
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• 제25권1호
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• pp.35-41
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• 2017

The use of engineering plastics in automotive components is increasing with the trend towards improving the car strength and reducing weight. Among the different choices of materials, engineering plastic emerged as the necessary material for achieving lower costs, reduced weight and improved production efficiency. To produce the automotive parts, it is important to predict defect and validation of injection molding prior to design. Injection molding analysis and structural analysis are widely applied as a part of the design process when developing automotive parts. Injection molding analysis, in particular, involves a highly complicated mechanism that requires deep knowledge of polymer properties as well as an analytic approach different from that used for a general isotropic material when the molded material is used as a structural material. This is because the parts made of polymer have pre-stress factors such as intrinsic deformation and residual stress. The most important factors for injection molded plastic products are injection molding condition and cavity design, taking into account ease of molding, mass production and application. Despite optimal injection molding conditions and cavity design, however, glass fiber orientation is critically linked to strength reduction. The application of injection molding and structural coupled analysis provides a low-cost solution for product molding and structural validation, all prior to the actual molding. The purpose of this study involves the validation, pre-study, and solution of defect in injection-molded polymer automotive parts using the simulation software for injection molding and structural coupled analysis. Finally, this thesis provides validation of an injection molding and structural coupled analytic mechanism that can demonstrate the effect of glass fiber orientation on mechanical strength. Design improvement ideas for the injection molded product of PPS (Poly Phenylene Sulfide)+40% glass fiber are also suggested.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1348-1356
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• 2002

The present work concerns the optimal design for injection molding processes by using the design of experiments (DOE) and numerical analysis. The DOE approaches is planned to be able to consider two-way interaction, and have been applied progressively for both mold design and process design. Numerical analyses have been carried out as a design of experiments for mold parameters such as runner specifications and cooling channel configurations. In order to determine optimal process parameters, experiments have been performed for various process conditions with the DOE scheduling. As a result, the quality and productivity of the product have been improved, and the proposed approach can be successfully reflected on the industrial injection molding process of precision electronics parts.

• 한국기계가공학회지
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• 제19권8호
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• pp.50-55
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• 2020

This study investigates the injection molding of a plastic rack gear and focuses on deflections in the part. The causes of deflections were found and resolved through a trade-off study by injection molding analysis. Based on a warpage analysis, the fiber orientation was found to be a dominant factor in the occurrence of deflections. Changes in the part design and various injection conditions were analyzed for their effects in reducing deflections. Based on the trade-off study, a new part bottom design, injection time, and melt temperature were recommended. A trial injection was done for the new plastic rack gear, and measurements showed that its flatness surpassed that of the original part and met the specified requirement. The short injection time, low melt temperature, and symmetric similar configuration of the part contributed to the reduction in deflections. Therefore, optimized gate design and injection conditions as well as a new part design were validated through injection molding analysis in this study.

• 한국기계가공학회지
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• 제14권1호
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• pp.44-50
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• 2015

This paper presents a heuristic process-optimization procedure for minimizing warpage in injection-molded parts based on the dynamic robust design methodology. The injection molding process is known to have intrinsic variations of its process conditions due to various factors, including incomplete process control facilities. The aim of the robust design methodology advocated by Taguchi is to determine the optimum design variables in a system which is robust to variations in uncontrollable factors. The proposed procedure can determine the optimal robust conditions of injection molding processes at a minimum cost through a trade-off strategy between the degree of warpage and the packing time.

• Design & Manufacturing
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• 제7권1호
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• pp.1-6
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• 2013

The injection molding process is a predominant method for producing plastic parts. In order to maximize productivity and molding quality in a injection mold, it is important that each cavity in a multi-cavity injection mold is identical. This requires that cavity dimensions should be identical and delivery system of melt to each cavity have to be the same. Despite the geometrically balanced layout in multi-cavity injection mold more than 4 cavities, it has been observed that the filling in each cavity results in imbalances. Most of cases, this phenomenon of filling imbalances have a bad effect on dimension accuracy, warpage, molding appearance and strength of molding parts. In this study, experiment were conducted to investigate the effect of filling imbalances on the molding quality(surface gloss, shrinkage, tensile strength) in the multy-cavity injection mold.

• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.89-94
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• 2008

The injection molding process is a predominant method for producing plastic parts. In order to maximize productivity and molding quality in a injection mold, it is important that each cavity in a multi-cavity injection mold is identical. This requires that cavity dimensions should be identical and delivery system of melt to each cavity have to be the same. Despite the geometrically balanced layout in multi-cavity injection mold more than 4 cavities, it has been observed that the filling in each cavity results in imbalances. Most of cases, this phenomenon of filling imbalances have a bad effect on dimension accuracy, warpage, molding appearance and strength of molding parts. In this study, experiment were conducted to investigate the effect of filling imbalances on the molding quality(surface gloss, shrinkage, tensile strength) in the multy-cavity injection mold.

• 한국산학기술학회논문지
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• 제11권1호
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• pp.1-6
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• 2010

본 연구에서는 성형해석 및 실험적 방법을 통하여 페트 용기의 두께 편차를 최소화하기 위한 프리폼 최적화 설계를 수행하였다. 사출성형과정을 정확하게 묘사하기 위하여 3차원 모델을 이용하여 충진, 보압 및 냉각해석을 통하여 최적의 프리폼 설계변수를 설정하였으며, 이 결과를 이용하여 블로우 성형해석을 수행하였다. 성형해석결과를 평가하기 위한 사출성형 및 블로우 성형실험을 수행하였으며, 실험결과와 해석결과는 정성적으로 일치하는 것을 확인하였다. 이러한 실험결과 데이타를 설계에 반영함으로서 최적의 프리폼 형상을 얻을 수가 있었다.

• 소성∙가공
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• 제20권1호
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• pp.11-16
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• 2011

Recently, according to the rapid development of display, many display applications, such as, cellular phone, navigation, monitor and LCD TV have been changed from CRT type to LCD type. BLU(Back Light Unit) is one of main parts in LCD unit and generally, it consists of a light source, a reflective sheet, a LGP(Light Guide Plate), a diffuser sheet, and two prism sheets. The most important component of BLU is a light guide plate, which diffuses the input light to the TFT-LCD module uniformly. The LGP is usually made by injection molding process, and it has numerous optical micro patterns on the surface. In the present study the micro-patterned stamper which has cylindrical shape was fabricated by using the UV-LiGA process. And the replication characteristics have been compared among three different kinds of injection molding process; general injection molding, injection/compression molding and RHCM(Rapid Heating and Cooling Molding). Average replication ratios of CIM and ICM were 19.1% and 64.6%, respectively. On the other hand, the average replication ratio of RHCM process showed the higher value of 98.4% among these. It show that maintaining the mold surface above $T_g$ could increase the replication ratio of micro patterns substantially.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.778-784
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• 2001

Injection molding is a very important industrial process for the manufacturing of plastics objects. During an injection molding process of composites, the fiber-matrix separation and fiber orientation are caused by the flow of molten polymer/fiber mixture. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation orientation and injection molding conditions. So far, there is no research on the measurement of fiber orientation using image processing. In this study, the effects of fiber content ratio and molding condition on the fiber orientation-angle distributions are studied experimentally. Using the image processing method, the fiber orientation distribution of weld-line parts in injection-molded products is assessed. And the effects of fiber content and injection molding conditions on the fiber orientation functions are also discussed.

• 한국기계가공학회지
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• 제14권4호
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• pp.92-99
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• 2015

The deformation of injection molding is seriously affected by injection molding conditions, such as melt and mold temperature and injection and holding pressure. In these conditions, the mold temperature is controlled by flowing coolant, which can be classified by the Reynolds number in the mold-cooling channel. In this study, the deformation of the automotive side molding according to the variation of the Reynolds number in the coolant was simulated by Moldflow. In the results, as the Reynolds number was increased, the mold cooling was also increased. However, when the Reynolds number exceeded a certain range, the mold cooling was not increased further. In addition to the Moldflow verification, the mold cooling by the coolant was simulated by CFX. The CFX results confirmed that the Reynolds number significantly influenced the mold cooling. The coolant, which has a high Reynolds number value, quickly cooled the mold. However, the coolant, which has a low Reynolds number value, such as 0 points, hardly cooled the mold. In an injection molding experiment, as the Reynolds number was high, the deformation of the moldings was reduced. The declining tendency of the deformation was similar to the Moldflow results.