Analysis of the influence of the geometric shape of automotive plastic injection molding parts on injection molding fluidity and filling

1. The influence of geometric shape on fluidity

Runner design: planner of flow path
The runner design of automotive plastic injection molding parts is one of the cores of injection mold design. It directly determines the flow path and speed of the melt after it enters the mold cavity from the injection molding machine nozzle. Reasonable runner design is like an efficient transportation network, which can ensure that the melt flows evenly and quickly in the mold cavity, reduce flow resistance, and improve filling efficiency. On the contrary, unreasonable runner design may cause poor melt flow, eddy currents and stagnation, which in turn affects the uniformity and integrity of injection molding parts.

The geometry of the mold, especially the width, depth and shape of the runner, is a key factor affecting the melt flow resistance. A wide and shallow runner design can reduce the friction between the melt and the mold wall, reduce flow resistance, and make the melt flow more smoothly. On the contrary, a narrow and deep runner design will increase the difficulty of melt flow, which may not only cause the melt temperature to drop too quickly and affect fluidity, but also cause degradation due to excessive shear force, affecting material properties.

In addition, the branch structure of the runner also needs to be carefully designed to avoid uneven flow of the melt at the branch, causing problems such as insufficient or excessive filling in some parts. Reasonable runner branch angles, quantity and position can ensure that the melt is evenly distributed to all corners of the mold to achieve efficient and balanced filling.

2. The influence of geometry on filling efficiency
The geometry of the injection molded part not only affects the fluidity of the melt, but also directly determines the filling efficiency. Complex geometric shapes, such as deep cavities, thin walls, and multi-rib structures, place higher requirements on the filling of the melt. The deep cavity structure requires the melt to have sufficient flow length and the ability to maintain high temperature to avoid premature solidification; the thin-walled structure requires the melt to have a high flow rate and good filling properties to ensure fast and complete filling of the mold cavity.

In order to improve the filling efficiency, designers need to comprehensively consider the geometric characteristics of the injection molded parts, adopt advanced processes such as hot runner technology and multi-point pouring, and adjust the injection molding parameters (such as injection speed, pressure, temperature, etc.) to match specific geometric shape requirements. At the same time, pre-analyzing the flow state of the melt through simulation software and optimizing the mold design are also important means to improve filling efficiency.

3. The influence of geometric shape on the quality of final injection molded parts
The geometric shape of injection molded parts not only affects the fluidity and filling properties during the injection molding process, but also directly determines the quality and performance of the final product. Unreasonable geometric design may lead to defects such as weld marks, shrinkage holes, bubbles, warping, etc., which seriously affect the strength and appearance of injection molded parts. Therefore, the limitations of the injection molding process should be fully considered in the design stage, and reasonable geometric shape design, such as setting weld wells, optimizing wall thickness distribution, and adopting rounded corner transitions, can reduce defects and improve product quality.