Experimental study on the penetration interfaces of pipes with different cross‐sections in overflow water‐assisted coinjection molding

Abstract

The residual wall thicknesses (RWT) of the skin and the inner layers are important quality indicators of water-assisted coinjection molding (WACIM) parts. The influences of the shape of the cavity cross section and the processing parameters, including the water pressure, water delay time, inner melt temperature, and inner melt flow rate, on the penetration of the inner melt and water were explored via experiments. The results showed that the shape of the penetration section of the inner melt was closer to the cavity section with round corners, while that of the water ended up being round. Both the penetration ratios of the inner melt and the water increased proportionally with increasing circle ratio. Both the minimum values of the total RWT and the inner melt RWT increased with increasing circle ratio. Both the maximum values of the total RWT and the inner melt RWT increased with increasing Max_D, which is the maximum distance between the inscribed circle center and the wall. Both the penetration ratios of the inner melt and the water increased with increasing water pressure, decreased with increasing water delay time, and increased with increasing inner melt flow rate and increasing inner melt temperature.

Overview of the Experimental Trends in Water‐Assisted Injection Molding

“…Part geometry, especially for the part with curved section and sudden dimensional transition, has an important effect on the water penetration length and residual wall thickness. The influences of the cavity cross‐section shape (i.e., part geometry) and the processing parameters on the water penetration behavior were explored by Kuang et al For the circular pipe, the residual wall thickness was rather even, but for the noncircular pipes, the maximum residual wall thickness always occurred at the wall (the farthest from the center of the cross‐section), as shown in Figure . Huang and Deng investigated the influences of short‐shot size, melt temperature, water injection delay time, and water pressure on the water penetration length and residual wall thickness of WAIM curved polypropylene (PP) pipe.…”

Optimization of Residual Wall Thickness Uniformity in Short-Fiber-Reinforced Composites Water-Assisted Injection Molding Using Response Surface Methodology and Artificial Neural Network-Genetic Algorithm

“…Overflow water-assisted injection molding (OWAIM) is a promising method for producing functional plastic parts with hollow sections and thin residual wall thickness (RWT) [1][2][3]. e process of OWAIM includes two steps.…”

Nondestructive measurement of layer thickness in water‐assisted coinjection‐molded product by ultrasonic technology

“…Water‐assisted coinjection molding (WACIM) is an innovative polymer injection‐molding technology, which is used to produce hollow products with multilayer walls . Comparable to water‐assisted injection molding (WAIM) and coinjection molding (CIM), WACIM has advantages of reduction of amount of polymer used, weight reduction, performance improvement, and greater freedom of product design . Recently, WACIM technology has been widely used for automotive components, household items, and furniture parts, highlighting a bright future for WACIM with regard to market prospects .…”

“…Comparable to water‐assisted injection molding (WAIM) and coinjection molding (CIM), WACIM has advantages of reduction of amount of polymer used, weight reduction, performance improvement, and greater freedom of product design . Recently, WACIM technology has been widely used for automotive components, household items, and furniture parts, highlighting a bright future for WACIM with regard to market prospects . In WACIM, the thickness of the layer walls significantly affects the mechanical properties of molded products and is an important factor in judging the quality of the products .…”

“…employed a computational fluid dynamics method to simulate the WACIM process, and they found that layer thickness was affected by injection delay time, temperature, and injection velocity. They also investigated the influence of cross‐sectional shape and processing parameters on layer thickness . Yang et al .…”