Technical Informations

How to solve the bubble phenomenon in injection molding?

Injection molding is a common process for plastic molding. The advantages of injection molding are fast production speed, high efficiency, automation of operation, variety of colors, shapes from simple to complex, size from large to small, and accurate product size. The product is easy to be upgraded and can be made into complex shapes, and the injection molding is suitable for molding processing such as mass production and complex shape products.

There are many kinds of plastic materials used in the injection molding process, and the types and forms of mold design are also varied. In addition, the operator's familiarity with the specific injection molding machine and the operational skills between the workers, the differences in practical experience are also different. At the same time, the objective environment (such as ambient temperature, humidity, air cleanliness) will also vary with the seasons. These objective and subjective conditions together determine the defects of injection molded products. For example, how to solve the bubble phenomenon in injection molding?

According to the occurrence of bubbles, the countermeasures are as follows:

When the finished product has a large wall thickness, the outer and outer surfaces are cooled faster than the middle portion. Therefore, as the cooling progresses, the plastic resin in the middle portion is shortened and the outer surface is enlarged, so that the middle portion is insufficiently filled. This condition is called a vacuum bubble. The main treatment methods are:

a. According to the wall thickness, determine the reasonable gate, sprue scale. Usually the gate height should be 50% to 60% of the finished wall thickness.

b. Stop at the gate sealing, leaving a certain amount of compensation for the injection material.

C. The injection time should be slightly longer than the gate sealing time.

d. Decrease the injection speed and improve the injection pressure.

e. Select materials with high melt viscosity grades.

Because of the formation of bubbles due to the occurrence of volatile gases, the main methods of treatment are:

a. Fully pre-dry.

b. Decrease the resin temperature to avoid decomposition gas.

Bubbles formed by poor fluidity can be treated by improving the temperature of the resin and the mold and improving the injection speed.

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