Abstract
Recently, water-assisted injection molding was employed in the automobile industry to manufacture three-dimensional hollow tube-type products with functionalities. However, process optimization is difficult in the case of water-assisted injection molding because of the various rheological interactions between the injected water and the polymer. In this study, the boiling phenomenon that occurs because of the high melt temperature when injecting water and the molding characteristics of the hollow section during the water-assisted injection process were analyzed by a water-assisted injection molding analysis. In addition, the changes in the residual wall thickness accompanying changes in the process conditions were compared with the analysis results by considering water-assisted injection molding based on gas-assisted injection molding. Furthermore, by comparing the cooling characteristics and inner wall surface qualities corresponding to the formation of the hollow section by gas and water injections, a water-assisted injection molding technique was proposed for manufacturing hollow products with functionality.
Highlights
Gas-assisted injection molding (GAIM) is the major injection molding technique used to reduce the thickness of thickwalled products [1, 2]
Water has an excellent effect in terms of enhancing the productivity by reducing the cooling time by 30–40%; this is because water has an excellent cooling characteristic, with its thermal conductivity and heat capacity being 40 and 4 times, respectively, those of a gas. It has an advantage over GAIM in that the hollow products with functionality obtained by water-assisted injection molding (WAIM) have a thin and fine interior surface and the residual wall thickness is regular unlike in the case of GAIM products [4, 5]
A GAIM-based WAIM system has been developed to molding of three-dimensional hollow products
Summary
Gas-assisted injection molding (GAIM) is the major injection molding technique used to reduce the thickness of thickwalled products [1, 2]. Water has an excellent effect in terms of enhancing the productivity by reducing the cooling time by 30–40%; this is because water has an excellent cooling characteristic, with its thermal conductivity and heat capacity being 40 and 4 times, respectively, those of a gas It has an advantage over GAIM in that the hollow products with functionality obtained by WAIM have a thin and fine interior surface and the residual wall thickness is regular unlike in the case of GAIM products [4, 5]. Most of researches were conducted by experiments for process conditions are extremely difficult This is because the hollow shape formed by water injection is sensitive to changes in the viscosity of the polymer, product shape, and molding process. The cooling characteristics and interior surface qualities of GAIM and WAIM products were compared to analyze the effectiveness of WAIM in molding hollows with functionality
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