Sequential valve gating molding

Sequential valve gating molding

What is Sequential Valve Gate Molding (SVG)?

Sequential Valve Gating (SVG) molding is a specialized technique used in multi-cavity injection molding. It employs a system where each gate has an individual valve controlled by a timing system. This allows molders to control the filling sequence of each cavity independently, ensuring optimized part quality and reducing or eliminating defects, especially for large or complex parts.

Sequential valve gating enables the precise regulation of the opening and closing of separate gates within a mold. This enables different sections of a molded item to be filled with plastic at various intervals, leading to a more accurate management of material flow.

By utilizing this technique, it is possible to minimize warping, eradicate knit lines, and enhance the aesthetic appeal of the final product.

1. Process

As with traditional injection molding, the process begins with closing the mold.

Molten plastic is injected into the mold. However, instead of simultaneously filling every cavity, the sequential valve gating system controls the opening and closing of individual gates, determining the order and the rate at which each cavity is filled.

Once the desired amount of material has been injected into a cavity, the associated gate valve is closed, stopping the flow of the material.

The process repeats for each cavity in a predetermined sequence until all cavities are filled.

After all cavities are filled, the plastic cools and solidifies.

Once cooled, the finished parts are ejected from the mold.

2. Advantages

By controlling the flow and pack of molten plastic into individual cavities, internal stresses in the parts are minimized. This leads to reduced warpage and distortion in the final parts.

The sequential filling helps in reducing flow marks, knit lines, or other surface defects, resulting in a better-quality surface finish.

SVG can lead to faster cycle times, especially for larger or complex parts, as it can optimize the filling process to ensure rapid yet defect-free molding.

Precise control over the injection process can result in less overpacking and reduced flash, leading to material savings.

With the controlled filling of each cavity, there’s a higher likelihood of producing consistent parts in multi-cavity molds.

3. Applications

For parts with large surface areas or complex geometries, SVG can help in ensuring uniform filling and reducing defects.

Many automotive parts, like bumpers or dashboards, can benefit from SVG due to their size and the need for a high-quality finish.

In molds with many cavities producing the same or similar parts, SVG can help ensure each part is of consistent quality.

4. Challenges

The SVG system adds complexity to the molding machine, which might require specialized training for operators.

Installing an SVG system involves additional costs for the equipment and control systems.


In summary, Sequential Valve Gating Molding is a specialized technique that provides molders with precise control over the injection process, ensuring high-quality parts with reduced defects. While it adds complexity and costs to the molding setup, the benefits in terms of part quality, consistency, and potential material savings can outweigh the drawbacks in many applications.

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