Injection molding plastic parts appear gap reason analysis and solution

Injection molding is one of the important processes of plastic products, and the gap is one of the common problems. The gap will lead to the strength and beauty of products are affected, but also affect the quality of products and market competitiveness.

First, injection molding plastic parts gap cause analysis

1. Improper material selection: the thermal expansion coefficient of different materials is different. If the thermal expansion coefficient of the selected material is inconsistent with the thermal expansion coefficient of the product, it will lead to the generation of voids.

2. Unreasonable mold design: Unreasonable mold design is also an important reason for the gap. If the mold runner design is not reasonable, it will lead to incorrect gate location, resulting in the generation of voids.

3. Improper processing technology: improper processing technology is also an important reason for the gap. If the temperature control in the process is not accurate, or the cooling time is not enough, it will lead to inconsistent shrinkage of the product, resulting in the generation of voids.

Two, injection molding plastic parts gap solution

1. Optimize the selection of materials: the selection of materials with the same thermal expansion coefficient can avoid the generation of voids. With the assistance of the material supplier, the corresponding material selection and testing can be carried out to ensure that the selected material is suitable for the thermal expansion coefficient of the product.

2. Adjust the mold structure: Through reasonable design of the mold structure, the incorrect position of the gate can be avoided, so as to avoid the generation of gaps. The mold structure can be adjusted and optimized with the assistance of the mold designer to ensure that the gate position is correct so as to avoid the generation of voids. For example: the gate cross section is too small to increase the gate cross section, shorten the runner; The nozzle hole is too small to increase the nozzle hole; Gate opening in thin wall area, gate opening in thick wall area, etc.

3. Improve the processing technology: By improving the processing technology, the shrinkage of products can be avoided, so as to avoid the generation of voids. The corresponding adjustment and optimization can be carried out on the production line, such as: the holding pressure is too low to increase the holding pressure; The holding time is too short to improve the holding time; Too low die wall temperature increases die wall temperature; The melt temperature is too high to reduce the melt temperature.

Injection molding plastic parts of the gap performance for the product internal gap performance as a circular or elongated bubble form. Only transparent products can be seen from the outside of the space inside; Opaque products cannot be detected from the outside. Voids tend to occur in articles with relatively thick walls and are at their thickest.