Abstract
The gas-assisted injection molding (GAIM) process is so complicated that increasing reliance has been placed on CAE (Computer Aided Engineering) as a tool for both mold designers and process engineers. In this paper, a 3D theoretical model and numerical scheme is presented to simulate the GAIM process, in which an equal-order velocity-pressure formulation method is employed to eliminate the pressure oscillation. In addition, the whole flow field including the gas and melt regions is calculated using a uniform momentum equation with the viscosity of gas raised to a certain order of magnitude, and a 3D control volume scheme is employed to track the flow front of the melt and gas. Finally, the validity of the model has been tested through case studies and experimental verification.
Highlights
Gas-assisted injection molding (GAIM) is one of the important and innovative molding processes and considered to be a revolution in terms of injection molding technology [1, 2]. is new process came into practice as ripe technology in the 1990s, and has been spread widely due to its outstanding advantages
Compared with conventional injection molding (CIM), GAIM offers a considerable number of advantages, such as reduced part weight, injection pressure, clamp force, shrinkage, warpage, and residual stress
In gas-assisted injection molding, the mold cavity is partially, about 70–90% of the mold cavity, filled with the polymer melt, and the gas with high pressure will be injected into the melt immediately or after some delay time. ree distinct regions can be indentified during the gas-assisted injection molding filling stage: the solidified melt layer close to the mold wall, the deforming viscous melt, and the penetration gas. e three regions are confined by the melt and gas fronts
Summary
Gas-assisted injection molding (GAIM) is one of the important and innovative molding processes and considered to be a revolution in terms of injection molding technology [1, 2]. is new process came into practice as ripe technology in the 1990s, and has been spread widely due to its outstanding advantages. E models based on Hele-Shaw are simple and have less time cost, but they are used mainly for the analysis of shell structure parts without 3D features As for these molded parts with the more complex three-dimensional geometries and uniform thickness walls often encountered in gasassisted injection molding, the velocity and the changes of parameters in the gapwise direction are considerable and cannot be neglected. A 3D finite element model is presented to deal with the melt filling, in which an equal-order velocitypressure formulation method [11] for 3D flow field is employed to eliminate the pressure oscillation. E software based on this 3D model has been developed and can calculate the pressure field, velocity field, temperature field, and gas penetration in the injection process without pressure oscillation. A 3D control volume scheme is employed to track the flow front of the melt and gas. e software based on this 3D model has been developed and can calculate the pressure field, velocity field, temperature field, and gas penetration in the injection process without pressure oscillation. e validity of the model has been tested through case studies and experimental verification
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