Visualization of the flow history contours at the cross‐section of a weld‐line in an injected molded part

Abstract

This article presents visualization of flow history contours at the cross-section of an injection molded part along the weld-line originated by an obstacle pin in a plate-shaped cavity. The visualized flow history contours unveiled the interface of the two adjacent flows through which the penetration of one flow front to the other at the interface was observed. The penetration which was the most at the core of the part behind the obstacle pin was inferred to be originated from an eccentricity in the position of the obstacle pin. Applying image processing techniques, a sequence of the variation in the shape of the interface along the weld-line was extracted from which the amount of penetration at different distances behind the obstacle was measured. Experimental results revealed an oscillation in the direction of the penetration along the weld-line at the core of the part. A scanning electron microscope micrography was also applied to characterize the V-notch along the weld-line at the surface of the molded part. V-notch characterization was used to investigate the possible correlation between the internal and external behaviors of the molten plastic during weld-line formation by which an obstruction affected zone at the weld-line area behind the obstacle pin was distinguished.

Effect of supercritical nitrogen content on the weld lines and mechanical properties of microcellular injection molded double gate PP/Al parts

“…When PP/Al/scN 2 melt was injected from the double gate, the face-to-face encounter of the melt in the two flow directions leads to an obvious cold weld line on the specimen surface. 4 The width of the weld line on the surface of the solid and foamed samples was accurately measured, and the statistical experimental results were shown in Figure 6. The average weld line width of the solid sample was 30.41 μm.…”

“…Injection molding has been widely expanded and applied to numerous industries due to its ability to produce high‐quality, complex parts with excellent dimensional accuracy, and repeatability at a relatively low cost per part, such as automotive, electronics, aerospace, medical devices, and consumer products 1–3 . As a kind of surface defect that cannot be ignored, the formation of weld lines in plastic products occurs during the injection molding process 4 . When the molten polymer is injected into the mold cavity, it flows through channels and gates to fill the various parts of the mold.…”

“…defect that cannot be ignored, the formation of weld lines in plastic products occurs during the injection molding process. 4 When the molten polymer is injected into the mold cavity, it flows through channels and gates to fill the various parts of the mold. When multiple flow fronts converge at a junction, they can create an area of turbulence and mixing, 5 which can result in a visible weld line.…”

Optimization and application of temperature field in rapid heat cycling molding

“…As for the RHCM，the melt merge angle of selected points at L3 weld lines W1-W3 (fig. 10(a)) is larger (75°-90°) than that of CIM (60°-80°), which means better welding strength [27]. Since melt temperature is an important factor for weld line strength, we also compared the changes of melt temperature variation with time during filling (fig.…”

Theoretical and visual study of bubble dynamics in foam injection molding

“…1. The setup was found to be a very effective visualization system for injection molding process [15][16][17][18]. The system consists of four major units: (i) a 70-ton injection-molding machine, (ii) a visual mold equipped with a transparent glass window, (iii) a CO 2 gas injection apparatus, and (iv) a visualization set up includ-ing a high-speed camera, light sources, and a data acquisition system.…”