Residual wall thickness of water‐powered projectile‐assisted injection molding pipes

Abstract

Water‐powered projectile‐assisted injection molding (W‐PAIM) is an innovative molding process for the production of hollow shaped polymer parts. The W‐PAIM utilizes high pressure water as a power to drive a solid projectile to displace the molten polymer core to form the hollow space. The residual wall thickness (RWT) and its distribution are the important quality criteria. The experimental and numerical investigations were conducted. Experimental specimens showed that the RWT of a W‐PAIM pipe was much thinner than that of a water‐assisted injection molding pipe. The cross‐section size of the projectile defined the basic penetration section size. The software FLUENT was used to obtain the instantaneous distributions of the flow field, which revealed the forming mechanism of the RWT. The experiments indicated that the processing parameters, such as melt temperature, melt injection pressure, mold temperature, and water injection delay time had obvious effects on the RWT, while the water pressure had little effect on it. The RWT of curved pipes was thin at the inner concave side while thick at the outer convex side. The RWTs at the bend portion are influenced by the deflection angle and bending radius, which is due to the pressure difference between the two sides. POLYM. ENG. SCI., 59:295–303, 2019. © 2018 Society of Plastics Engineers

Prediction of process parameters of water‐assisted injection molding based on inverse radial basis function neural network

“…Short shot is used for the molding method, which means first mold is partly filled with polymer melt, and then water is injected to push the melt to fill the mold fully. Based on the main processing parameters influencing residual wall thickness, [ 15 ] in this study the selected processing parameters are short shot size A s , melt temperature T me , water pressure P w , delay time t d , and mold temperature T mo . Value ranges are indicated in Table 4.…”

Numerical and experimental investigations on the mechanism of flow‐induced fiber orientation in short‐shot water‐assisted injection‐molded short‐glass‐fiber‐reinforced polypropylene

“…Injection delay time refers to the time from the completion of melt injection to the beginning of water injection, which has a significant influence on the water penetration behavior. 12,15,39 Therefore, water injection delay time was investigated in terms of its effect on the fiber orientation at the selected positions. Figure 17 shows the SEM micrographs of cryo-fractured surfaces molded under different water injection delay times (0, 3, 5 s), other processing parameters were the basic ones listed in Table 1.…”

Shrinkage and Warpage Mechanism of Overflow Water-Assisted Injection Molding Short Fiber-Reinforced Polymers

“…e impact of the short fiber-reinforced polymer WAIM technology on the quality of the final molding products includes many parameters, such as process parameters, material parameters, and structural parameters. In this study, according to the results of the research group, [36,37] after the high-pressure water penetrated the melt, the influence of water injection pressure, water injection delay time, melt temperature, mold temperature, and fiber mass content on the shrinkage of products was studied, which each factor was at 4 levels in the orthogonal experiment.…”