• Title/Summary/Keyword: injection compression molding

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The Behavior of Shrinkage on PMMA in Injection Molding Compression Molding (사출압축성형시 PMMA 재료의 성형수축거동)

  • Choi, Y.S.;Han, S.R.;Jeong, Y.D.
    • Journal of Power System Engineering
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    • v.9 no.4
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    • pp.83-89
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    • 2005
  • Molding shrinkage is one of the problems to be solved in conventional injection molding. Despite many trying-out has been to solve it, intrinsic cause of shrinkage such as orientation and thermal exchange between melt and mold has not been solved yet. For reducing shrinkage and residual stress on molding, injection compression molding process was invented. In this study, experiments about effects of injection compression molding's parameters on shrinkage of PMMA molding were conducted and compared with conventional injection molding's shrinkage. Before the injection compression molding experiment, molding shrinkage rate was predicted by analyzing pvT diagram and was compared with the results of experiment. The shrinkage rate of injection compression molding was lower than convention injection molding's one which was different from the predicted shrinkage. The reason was observed that the experimental mold was not a proper type for injection compression, flowing backward of melt into nozzle and unreasonable mechanism of injection molding machine.

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A Study on the Molding Characteristics of Injection Compression Molding Through Computer Simulation (컴퓨터 해석을 통한 사출압축성형의 성형특성에 관한 연구)

  • Chun, Y.H.;An, H.G.;Lyu, M.Y.
    • Elastomers and Composites
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    • v.47 no.4
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    • pp.341-346
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    • 2012
  • Injection molding is one of the widely used polymer processing operations. It is being used for not only conventional injection molding but gas injection molding, water injection molding, and injection compression molding. Injection compression molding involves injection and compression operation, and it gives uniform physical property and high dimensional quality of product. In this study, injection compression characteristics for various product shapes have been investigated by computer simulation. Product containing side wall showed not much effective in injection compression molding since wall thickness direction was perpendicular to the compression direction. Uniform and low shrinkage was observed in injection compression molding comparing conventional injection molding. Subsequently injection compression molding can be used for molding precise product. Optimal injection compression molding condition was obtained using design of experiment for plastic lens and the results were compared with conventional injection molding.

The Behavior of Shrinkage on PMMA in Injection Compression Molding (사출압축성형시 PMMA 재료의 성형수축거동)

  • Choi Y.S.;Kang C.M.;Jeong Y.D.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.589-592
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    • 2005
  • Molding shrinkage s variation is one of the problems to be solved in conventional injection molding. Despite many trying-out has been to solve these, intrinsic causes of shrinkage such as orientation and thermal exchange between melt and mold has yet not solved. For reducing shrinkage and residual stress on molding, injection compression molding process was invented. In this study, experiments about effect of injection compression molding's parameters on shrinkage of molding were conducted with PMMA and compared with conventional injection molding's shrinkage. Before the injection compression molding experiment, molding shrinkage rate was predicted by analyzing pvT graph and was compared with the results of experiment. The shrinkage rate of injection compression molding was lower than convention injection molding' one but was different from the predicted shrinkage. The reason was observed that experiment mold as not positive type, flowing backward of melt into nozzle and unreasonable mechanism of injection molding machine.

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The Effect of Various Molding Methods for Precision Optical Products Using Birefringence Analysis (정밀 광학부품의 복굴절 분석을 통한 각종 성형법의 영향에 관한 연구)

  • Min, I.K.;Cho, S.W.;Yoon, K.H.
    • Transactions of Materials Processing
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    • v.22 no.1
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    • pp.48-53
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    • 2013
  • As the adoption of injection molding technology increases, injected-molded optical products require higher dimensional accuracy and optical stability than ever before. In the present study, four kinds of molding methods, i.e., conventional injection molding (CIM), injection/compression molding (ICM), rapid heat and cooling the mold(RHCM) and rapid injection/compression molding (RICM) were selected in order to investigate the optical anisotropy of a 7 inch Light Guide Plate(LGP) by examining the gap-wise distribution of birefringence and the extinction angle. The results indicate that the compression process can decrease flow-induced birefringence over the whole region and that rapid heating can decrease the birefringence level better than conventional molding. In addition, for the combination of compression and rapid heating a reversal flow was detected from the distribution of the extinction angle near the gate.

Finite Element Analysis of Injection/Compression Molding Process (사출압축성형 공정에 대한 유한요소 해석)

  • 이호상
    • Transactions of Materials Processing
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    • v.13 no.2
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    • pp.180-187
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    • 2004
  • A computer code was developed to simulate the filling stage of the injection/compression molding process by a finite element method. The constitutive equation used here was the compressible Leonov model. The PVT relationship was assumed to follow the Tait equation. The flow-induced birefringence was related to the calculated flow stresses through the linear stress-optical law. Simulations of a disk part under different process conditions including the variation of compression stroke and compression speed were carried out to understand their effects on birefringence variation. The simulated results were also compared with those by conventional injection molding.

A Study on the Molding Technology for the Preform of Blow Molding Through Compression Molding (압축성형을 통한 블로우 성형품용 프리폼 성형기술 연구)

  • Choi, S.H.;Min, H.K.;Lyu, M.Y.
    • Transactions of Materials Processing
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    • v.16 no.1
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    • pp.3-8
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    • 2007
  • Novel compression molding system for preform has been developed in this study. The preforms for injection blow molding and injection stretch blow molding are being manufactured by injection molding. However it contains gate mark that affects the bottom crack in the PET bottle. The compression molded preform does not contain gate mark, thus the appearance quality of bottle has been increased and the residual stress near gate(bottom of the bottle) has been reduced. The thickness distributions, haze, and transmittance are well accepted for the preform. Also, flow characteristics of the resin between a core and cavity could be analyzed through computer simulation.

Injection/compression molding for micro pattern (미세패턴 성형을 위한 사출 압축 성형 공정 기술)

  • Yoo Y.E.;Kim T.H.;Kim C.W.;Je T.J.;Choi D.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.100-104
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    • 2005
  • The injection molding is very effective process for various plastic products due to its high productivity. It is also good fur precise products like optical parts. Various thermoplastic materials are also available with this injection molding process. In recent, however, as the overall size of the product increases and micro or nano scale of patterns are applied to the products, we now have some problems such as low fidelity of the replication of the pattern, high molding pressure, or warpage from the in-mold stress. Injection/compression molding is studied to overcome those problems in molding large thin plate with micro pattern array on its surface. An injection compression mold is designed to 3 pieces mold for side gate. We install 4 pressure transducers and 9 thermocouples to measure the melt pressure and surface temperature in the cavity during the process. As a result, the maximum molding pressure for injection compression molding is reduced to 1/3 compared to injection molding and the uniformity of the pressure in the cavity is enhanced by about 15%.

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A study on carbon composite fabrication using injection/compression molding and insert-over molding (사출/압축 공정과 인서트 오버몰딩을 이용한 탄소복합소재 성형에 대한 연구)

  • Jeong, Eui-Chul;Yoon, Kyung-hwan;Hong, Seok-Kwan;Lee, Sang-Yong;Lee, Sung-Hee
    • Journal of the Korea Society of Die & Mold Engineering
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    • v.14 no.4
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    • pp.11-16
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    • 2020
  • In this study, forming of carbon composite parts was performed using an injection/compression molding process. An impregnation of matrix is determined by ability of wet and flow rate between the matrix and reinforcement. The flow rate of matrix passing through the reinforcements is a function of permeability of reinforcement, a viscosity of matrix and pressure gradient on molding, and the viscosity of the matrix depends on the mold temperature, molding pressure and shear strain of matrix. Therefore, compression molding experiment was conducted using a heating mold in order to confirm the possibility of matrix impregnation. The impregnation of the matrix through the porosities between the woven yarns was confirmed by the cross-sectional SEM image of compression molded parts. An injection molding process was also performed at a short cycle time, high molding pressure and low mold temperature than those of compression experiment conditions. Deterioration of impregnation on the surface of molded parts were caused by these injection conditions and it could be the reason of decreasing the maximum tensile strength. In order to improve impregnation of matrix on the surface, injection/compression molding and insert-over molding were applied. As a result of applying injection/compression molding and insert-over molding, it was shown that the improvement of impregnation on the surface and the maximum tensile strength was increased about 2.8 times than the virgin matrix.

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Modeling of the filling process during resin injection/compression molding

  • Chang, Chih-Yuan
    • Advanced Composite Materials
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    • v.16 no.3
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    • pp.207-221
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    • 2007
  • The filling process of resin injection/compression molding (I/CM) can be divided into injection and compression phases. During the resin injection the mold is kept only partially closed and thus a gap is present between the reinforcements and the upper mold. The gap results in preferential flow path. After the gap is filled with the resin, the compression action initiates and forces the resin to penetrate into the fiber preform. In the present study, the resin flow in the gap is simplified by using the Stokes approximation, while Darcy's law is used to calculate the flow field in the fiber mats. Results show that most of the injected resins enter into the gap during the injection phase. The resin injection time is extremely short so the duration of the filling process is determined by the final closing action of the mold cavity. Compared with resin transfer molding (RTM), I/CM process can reduce the mold filling time or injection pressure significantly.

Numerical Study on The Injection-Compression Molding Characteristic of High Viscosity Plastic Fluids (고점도 유동장이 사출-압축 성형에 미치는 영향)

  • Park, Gyun-Myoung;Kim, Chung-Kyun
    • Tribology and Lubricants
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    • v.18 no.5
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    • pp.345-350
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    • 2002
  • Recently, as the development of manufacturing technique on SMC(sheet molding compound), various numerical and experimental approaches to injection and compression molding have been investigated. Injection and compression molding, however, has so various cases with complicated boundary condition that it is difficult to analyze mold characteristics precisely. In addition, since a slight change in process variables can significantly change the resulting mold thickness, a proper design is important to compression molding process. Therefore, in this study, the effects of various parameters on compression molding process have been investigated using FEM(finite element method) to formulate the melt front advancement during the mold filling process. To verify the results of present analysis, they are compared with those of reference. The results show a strong effect of initial charge volume, injection time and pressure as a result of variations in the rectangular charge shape.