| GAIM (Gas-Assisted Injection Molding) is a new technique of moldingplastics. It uses the high pressure N2 to push the filling melt and make the gaspacking. Then it forces the gas channel inside the plastic part forming a hollowcross-section, eliminates the shrinkage-trace on plastics surface. The strengthenlids forming in the gas channel enhance the strength of plastic parts. It supplies aspecial molding method for the uneven thickness plastic part molding. Especially,it opens a new molding area for reducing the weight of automobile parts and theelectronic appliance parts. It is innovated in 21 Century Ninety Time and wasknown as technology revolution of ushering the era in the plastic industry. GAIMhas been extensively researching and practicing overseas while it's a juveniletechnique in use interiorly. GAIM was developed and innovated constantly basedon Conventional Injection Molding and Foaming Molding. With the developmentof automobile industry and electronic appliance trade, light-duty, environmentalprotected and household trend is that for worldwide automobile industry.Reducing cost, increasing production and efficiency, shortening research anddevelopment cycle of new product is the most important task to our nationalautomobile industry. GAIM plays an important role in the process. The moldingproblem involved in complicated plastics, thin plastics, high strength plastics andexact plastics has caught engineer's and scholar's attention. The followings arestudied in this paper.1. Studying polymer rheologic theory of GAIMIn this paper it studies the viscosity model and constitutive equations that incommon use in analyzing polymer melt rheology, analyzes the P-V-T stateequations describing polymer processing and cooling. It studies motion equationsof Hele-shaw flow often used in GAIM. Putting forward boundary condition ofdifferent processing phase. Analyzing applicability and limitation in using thedifferent viscosity models.2. Studying the gas-liquid two-phase flow theoryStudy on the present status of gas-liquid two-phase flow and boundarycondition of gas penetrating through melt. Diffusion of jet fluid characters afterpressure gas penetrating through melt is analyzed by experiment and theory inGAIM technology. Gas-jet is to be divided four zone: a) Gas-jet shock zone; b)Gas-jet buffer; c) Uniform gas penetrating zone; d) Gas quadric penetrating zone.In near zone of gas sprue the surging of gas is much intensive, emerging complexflow status and diffusion feature. And after a certain distance away from the gassprue they become even. The bubble becomes slender due to the secondarypenetration. The result is provided with significant guidance to technologicimplode and mould design of GAIM.3. Gas channel structure and the theory study on melt thickness beingpenetrated by the gas.Gas channel design is a critical factor for GAIM technology and it is specificfor GAIM part. It belongs to the structure design of GAIM part. The design andchoice of the gas channel structure must be combined with part. Parts with ratherlarge cross-section for gas penetrated are suitable for GAIM, while those withnarrow cross-section are not. Also parts with thick wall are suitable for GAIM.Gas penetrating polymer melt along gas channel is studied by experiment, inwhich it studies the round cross-section gas channel and gains the equation ofthickness of skin melt. The experiment result shows that the theory value matcheswith the experiment value.4. Based on Moldflow software, the Jetta Front Bumper is analyzed inConventional injection molding and Gas-assisted injection molding. The influenceof melt temperature, injection time, especially the location and the number of thegate are studied in Conventional injection molding; the influence of melt shot size,gas pressure and melt/gas delay time besides the above parameters are alsoresearched in Gas-assisted injection molding. By simulating analysis of JettaFront Bumper, achieving optimizing processing parameters, establishing molding...
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