Numerical Simulation Investigation Of Short-Shot Water-Assisted Injection Molding For Tube

Water-assisted molding was developed basedon the gas-assisted molding technology, because of different packing media, compared to gas-assisted molding, water-assisted molding had many advantages, The main method of water-assisted injection molding were short–shot method and overflow method. The main application object was the tube parts. Currently, short shot water-assisted injection molding process method extreme lack of theoretical research, In this paper, we investigated the short water-assisted injection molding process method for numerical simulation in order to grasp the molding process and the quality factor, regularity and mechanism. Factors can be divided into two blocks,one was physical parameters of materials, another was molding process parameters.Water-assisted injection molding process parameters including: Melt injection volume, melt injection temperature, water temperature, water injection delay and so on. These parameters affect melt cooling, crystalline, material distribution and parts quality. Optimized and control these parameters have an important value on the success of water-assisted injection molding technology.In this paper, the main research as follow:1. According to the water-assisted injection molding filling process characteristic, and the theory of polymer, fluid dynamic, etc, after a reasonable assumption on the boundary conditions, we established the theoretical model which described the flow of water-assisted injection molding process of filling the two-dimensional and three-dimensional, purely viscous, transient, non-isothermal.2. Based on the finite volume method to solve the flow model. QUICK format was used to Discrete flow pressure field, velocity field, temperature field.3. Based on the VOF method, water assisted injection molding edge mobile interface to track, to achieve the water assisted injection mold filling process of numerical simulation.4. Using the Fluent software, combined with the actual working conditions, we studied physical parameters of materials and process parameters on the impact of water assisted injection molding, and revealed the mechanism of its effects.5. This paper also analyzed and compared the influence of the merits under the same water-assisted injection molding of short shot method and overflow method.6. Finally, through behavior, molding pressure, molding time and the cooling effect of the four aspects, water-assisted injection molding and gas-assisted injection molding were compared.In this paper, the main results as follow:1. With the melt injection temperature, the water velocity, water injection temperature, water injection delay time increased, the radial penetration distance of water increased, the axial depth of penetration decreased.2. With the increasing the melt consistency coefficient, power law index,amount of melt injection, the water penetration distance decreased and the radial penetration distance had little change.3. With the consistency coefficient, power law index, melt injection volume, injection speed, injection time delay increased, the inlet pressure also increased.4. With the increasing of melt injection temperature and water injection temperature, the pressure droped at inlet.5. Compared overflow and short shot method, Axial water penetration increased, the radial penetration distance reduced. Overflow forming need more pressure.6. The filling and cooling time of water-assisted injection molding is only 50% of gas-assisted molding and at the time to release the products, no temperature difference.