Simulations of gas penetration in thin plates designed with a semicircular gas channel during gas-assisted injection molding

Chen, Shia Chung; Cheng, Nien-Tien; Hsu, K. S.

doi:10.1016/0020-7403(95)00051-8

Cited by 37 publications

(9 citation statements)

References 3 publications

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“…The advantages of the GAIM process include reduction in cycle time, part weight, shrinkage, warpage, injection pressure and clamping force, apart from improvement of the surface finish and elimination of sink marks [4][5][6] . Up to now, many studies focusing on the mathematic simulation [7][8][9][10][11][12][13][14] and experimental verification [15][16][17][18][19][20][21][22] of the process have been done during the past decade, while few publications concerning the relationship between the processing conditions and the mechanical properties of GAIM part can be found.…”

Section: Introductionmentioning

confidence: 99%

Gas-assisted Injection Molded Polypropylene/Glass Fiber Composite: Foaming Structure and Tensile Strength

Zheng

Shen

et al. 2009

Polymer-Plastics Technology and Engineering

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Tensile strength of isotactic polypropylene (iPP)/glass fiber (GF) composites and neat iPP molded respectively by gas-assisted injection molding (GAIM) was examined. For comparison, tensile strength of the counterparts, which were molded by conventional injection molding (CIM) under the same processing conditions but without gas penetration, was also examined. Tensile strength of the CIM parts steadily increases with the increase of the GF content. For neat iPP molded by GAIM, as the gas pressure increases the tensile strength increases. However, for the iPP/GF composites, the tensile strength generally decreases when the gas pressure increases. And, at a given content of GF, tensile strength of the parts molded by GAIM is unexpectedly lower than that of the counterparts molded by CIM. At a given gas pressure, the higher the fiber content, the lower the tensile strength. In addition, scanning electron microscope (SEM) results show that foaming structure should be responsible for the poor tensile strength of the composites molded by GAIM. The poor adhesion between the glass fibers and the matrix and the unique properties of the gas used in GAIM process are the substantial factors in the formation of foaming structure.

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Section: Introductionmentioning

confidence: 99%

Gas-assisted Injection Molded Polypropylene/Glass Fiber Composite: Foaming Structure and Tensile Strength

Zheng

Shen

et al. 2009

Polymer-Plastics Technology and Engineering

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“…While for parts presenting thick sections such approach is clearly inappropriate, even for thin parts a mid-plane approach may be rough, as the gas penetration is a three-dimensional (3D) phenomenon. Chen et al [1] used a particle-tracking algorithm for computing both gas and melt front advancements. Their methodology is based on models describing the coating melt thickness existing between the solidiÿed material and the gas=melt interface, as a function of processing parameters, material properties and ow geometry.…”

Section: Introductionmentioning

confidence: 99%

“…As for the traditional injection moulding, the numerical simulations of gas-assisted injection are mostly based on the thin wall, Hele-Shaw approximation [1][2][3]. While for parts presenting thick sections such approach is clearly inappropriate, even for thin parts a mid-plane approach may be rough, as the gas penetration is a three-dimensional (3D) phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Three‐dimensional finite element solution of gas‐assisted injection moulding

Ilinca

Hétu

2001

Numerical Meth Engineering

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SUMMARYThis paper presents a ÿnite element algorithm for solving gas-assisted injection moulding problems. The ÿlling material is considered incompressible and has temperature and shear rate dependent viscosity. The solution of the three-dimensional (3D) equations modelling the momentum, mass and energy conservation is coupled with two front-tracking equations, which are solved for the polymer=air and gas=polymer interfaces. The performances of the proposed procedure are quantiÿed by solving the gas-assisted injection problem on a thin plate with a ow channel. Solutions are shown for di erent polymer=gas ratios injected. The e ect of the melt temperature, gas pressure and gas injection delay, on the solution behaviour is also investigated. The approach is then applied to a thick 3D part. Published in

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“…Gas penetration in the postfilling stage is noted as ''secondary gas penetration''. Compared with conventional injection molding (CIM), GAIM can substantially reduce operating expenses by reducing material costs, lowering injection pressure and clamping force requirements, and reducing cycle times for thick-walled parts [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. In addition, some of the molding problems encountered in CIM of large parts such as sink marks, residual stresses, distortion, and warpage may also be greatly reduced using GAIM.…”

Section: Introductionmentioning

confidence: 99%

“…Generally speaking, only when the design and processing parameters are well understood, can the gas-assisted injection molding process obtain its advantage. Due to the complexity of gas channel design and processing control, computer simulation [3,7,8] is expected to become an important and a required tool to assist in part design, mold design and process evaluation in recent years. However, fundamental studies concerning the effects of gas channel design and molding conditions on gas penetration [5][6][7][8], molding window [9][10][11] as well as part properties [12][13][14][15][16][17][18][19][20][21][22][23][24] are still required to develop quantitative design/molding guidelines to assist in the application of GAIM.…”

Section: Introductionmentioning

confidence: 99%

Study of the Bending Properties in Gas-assisted Injection Molded Fiber-reinforced Nylon Parts

Chien

Cheng

Chen

2004

Journal of Reinforced Plastics and Composites

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Glass fiber-reinforced Nylon plate parts designed with gas channels having five different types of cross section but with the same section were gas-assisted injection molded (GAIM). Effects of glass fiber content and geometrical factors introduced by various section shapes and the associated dimensions of gas channels on bending properties of GAIM parts were investigated via a bending test. Test results were also compared with those of conventional injection molded parts. Based on the measured results, it is found that gas-assisted injection molded parts show better bending properties including flexural strength, absorbed energy and bending stiffness than conventional injection molded parts. Alternatively, bending performance of GAIM parts increases when the content of glass fiber is increased. However, the fiber content of 15% has pretty good efficiency of bending performance. Meanwhile, for five gas channel designs, both gas channel designs attached with top rib (shapes D and E) show the higher bending stiffness and maximum bending load, correspondingly. So, generally speaking, these two gas channel designs provide the best enhancement in bending performance, however, parts with semicircular and rectangular gas channel designs (shapes A and B) can absorb more bending energy than the other designs. Alternatively, the flexural strength shows only slight influence from gas channel design, the deviation from average values less than 10%. The present study provides part designers with a design guideline for choosing the most effective gas channel design and fiber content to achieve a specific objective of part structural performance.

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Simulations of gas penetration in thin plates designed with a semicircular gas channel during gas-assisted injection molding

Cited by 37 publications

References 3 publications

Gas-assisted Injection Molded Polypropylene/Glass Fiber Composite: Foaming Structure and Tensile Strength

Gas-assisted Injection Molded Polypropylene/Glass Fiber Composite: Foaming Structure and Tensile Strength

Three‐dimensional finite element solution of gas‐assisted injection moulding

Study of the Bending Properties in Gas-assisted Injection Molded Fiber-reinforced Nylon Parts

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