Analysis of Injection Molding Machine Filling Speed Setting: Professional Practices of Foray

Category: Events

Release time:2025-10-28

In the injection molding process, the setting of filling speed directly affects the product's surface quality, dimensional accuracy, and production efficiency. As a key player in the injection molding industry, Foray has accumulated extensive valuable experience in setting the filling speed of injection molding machines through its production practices.

The importance of filling speed

The close relationship between injection speed and product quality makes it a critical parameter in injection molding. By determining the start, middle, and end segments of the filling speed and achieving a smooth transition from one setpoint to another, a stable melt surface speed can be ensured, producing the desired molecular orientation and minimizing internal stress.

Foray has accumulated extensive experience in setting segmented filling speeds. In production practice, technicians have found that the rational setting of filling speed not only affects the product's appearance but also directly relates to its mechanical properties and dimensional stability. The first injection is performed at a low speed to displace the cold slug, after which the second-stage injection speed is increased to fill the mold cavity, reducing the time for the plastic to flow from the gate to the end. This maintains the plastic's viscosity at a minimum during filling and delays solidification. However, achieving the correct switchover point for holding pressure is challenging during high-speed injection, necessitating the use of multi-stage deceleration to effectively control and master the switchover point. For thicker sections near the gate, excessively high injection speeds can cause turbulent flow, leading to cold material retention in the channels and resulting in flow marks. Therefore, a slow-speed, low-pressure injection should be used to push away the cold slug, allowing subsequent plastic to flow in smoothly. Gradually reducing the pressure during the holding phase can minimize residual stress in the molded product.

Foray emphasizes that mold geometry is a key factor in determining filling speed. Thin-walled sections require the highest injection speeds, while thick-walled parts need a slow-fast-slow speed profile to avoid defects. To ensure part quality meets standards, injection speed settings should maintain a constant melt front velocity. Since melt flow velocity affects molecular alignment and surface condition in the part, the speed should be reduced when the melt front reaches intersecting structural areas. For complex molds with radial flow paths, it is essential to ensure a balanced increase in melt throughput. Long flow paths must be filled quickly to reduce cooling of the melt front.

Filling Speed and the Resolution of Common Quality Issues

Meanwhile, by adjusting the filling speed, Foray has successfully resolved many common product quality issues.

Adjusting the injection speed can help eliminate defects caused by slowed flow at the gate. When the melt passes through the nozzle and runner to reach the gate, the surface of the melt front may have already cooled and solidified, or the melt may stagnate due to the sudden narrowing of the runner until sufficient pressure is built up to push the melt through the gate. This can result in a pressure spike at the gate, leading to surface defects.

Therefore, we control the injection speed at the final stage to avoid or reduce defects such as flash, burn marks, and trapped air. Reducing the speed at the end of the filling stage prevents over-packing the cavity, avoiding flash and minimizing residual stress. Trapped air caused by poor venting at the end of the mold flow path or filling issues can also be resolved by reducing the venting speed, particularly during the final stage of injection.

Conclusion

In the practice of Foray, most injection molding defects can be resolved by adjusting the injection speed. Therefore, the key to optimizing the injection molding process lies in the rational setting of injection speed and its segmentation. Precise speed control is crucial for enhancing product quality and serves as a critical technical approach for Foray to maintain its competitive edge in the market. Through scientific speed settings and meticulous segmented control, the company has not only improved the aesthetic quality of its products but also significantly enhanced their mechanical properties and dimensional stability, delivering higher-quality injection-molded products to customers.

Looking ahead, with the continuous advancement of injection molding technology, Foray will further deepen its research on filling speed settings, consistently striving to improve product quality and production efficiency.

Keywords: Analysis of Injection Molding Machine Filling Speed Setting: Professional Practices of Foray