Causes and countermeasures of bubbles in injection mould products

Bubbles in injection mold products are very common problems. There are many reasons for bubbles, which should be solved one by one according to different situations. It is mainly caused by the shrinkage of plastic products. Because the cooling speed of the surface is faster than that of the middle, it will lead to the lack of glue in the center of plastic products and the formation of a vacuum. The following small series will be for the different reasons one by one.

1. Improper control of forming conditions causes the generation of bubbles

Reasons: set the injection pressure is too low, the injection speed is too fast, the injection time and cycle is too short, the feeding amount is too much or too little, the pressure retention is insufficient, the cooling is not uniform or insufficient cooling, and the material temperature and mold temperature control is improper, will cause the bubble in the plastic parts.

Countermeasures: The injection speed should be reduced appropriately, and the injection speed and pressure should be adjusted with special caution. In addition, air bubbles and vacuum bubbles can be avoided by adjusting injection and pressure holding time, improving cooling conditions and controlling feeding amount. In general, the temperature of the molten material should be controlled slightly lower, and the temperature of the die should be controlled slightly higher. When controlling the temperature of the cylinder, the temperature of the feeding section should not be too high, otherwise it will produce backflow and return to cause bubbles.

2. The defects of injection mold cause the generation of bubbles

Reason: If the mold gate position is not correct or the gate section is too small, the main flow channel and the shunt channel are long and narrow, there is a dead Angle of gas storage in the flow channel or the mold exhaust is poor, it will cause bubbles or vacuum.

Countermeasures: It is necessary to first determine whether the mold defects produce bubbles and the main causes of vacuum bubbles. Then, according to the specific situation, adjust the structural parameters of the mold, especially the gate position should be set in the thick wall of the plastic parts. The gate section should not be too small, especially when several plastic parts of different shapes are formed at the same time, attention must be paid to the size of the gate in proportion to the weight of the plastic parts. In addition, the slender and narrow flow passage should be shortened and widened to eliminate the dead Angle of gas storage in the flow passage and eliminate the failure of mold exhaust.

3. The injection molding raw materials do not meet the use requirements, resulting in the generation of bubbles

Reason: if the content of water or volatile substances in the molding raw material exceeds the standard, the particle is too small or uneven, resulting in too much air mixed in the feeding process, the shrinkage rate of the raw material is too large, the melt index of the molten material is too large or too small, and the content of the recycled material is too much, which will affect the bubble and vacuum bubble of the plastic parts.

Countermeasures: Predrying raw materials, screening fine materials, replacing resin, reducing the amount of recycled materials and other methods should be used to solve the problem.

In a word, the solution to the vacuum bubble of injection mold products can be improved by reducing the injection speed, increasing the injection pressure, increasing the feed, and using materials with high melting viscosity. The mission of Fanstar is to master the core technology of injection molding production, communicate and analyze the technology before mold production with customers from the production needs of finished products, so that the mold delivery time is short, the service life is long, the rapid mass production and the finished product quality is excellent! Have the need of injection mold welcome to contact us!