Why do injection molded parts produce air bubbles and vacuum bubbles?

Injection molded parts are prone to air bubbles and vacuum bubbles during processing, which may be due to the following reasons

The reasons case injection molded parts produce air bubbles and vacuum bubbles

Improper control of molding conditions

Many process parameters have a direct impact on the generation of air bubbles and vacuum bubbles. Injection pressure is too low, injection speed is too fast, injection time and cycle is too short. Add too much or too little material, insufficient pressure, uneven cooling or insufficient cooling. As well as material temperature and mold temperature control is not appropriate. All will cause air bubbles in the molded part.

Especially when injecting at high speed, the gas in the mold can not discharge in time, resulting in too much residual gas in the melt. In this regard, the injection speed should reduce appropriately. อย่างไรก็ตาม, if the speed is reduc too much and the injection pressure is too low, it will be difficult to exhaust the gas in the melt. Bubbles as well as dents and under-injection will easily occur. ดังนั้น, special care should be taken when adjusting the injection speed and pressure.

Mold Defects

If the gate position of the mold is incorrect or the gate cross-section is too small, the main flow channel and manifold are long and narrow, there is a dead space for gas storage in the flow channel or the mold is poorly ventilated, it will cause air bubbles or vacuum.
ดังนั้น, should first determine whether the mold defects produce air bubbles and vacuum bubble the main reason. Then, adjust the structural parameters of the mold for the specific situation, especially the location of the gate should be set in the thick wall of the molded part.

Raw materials do not meet the use requirements

If the moisture or volatile matter content in the molding raw material exceeds the standard. The material particles are too small or uneven in size. Too much air is in the material supply process. The shrinkage of the raw material is too large. The melt index of the melt is too big or too small. Too much recycled material content. Will affect the molded parts to produce air bubbles and vacuum bubbles.
In this regard, should be used to pre-dry the raw material, sieve out the fine material, replace the resin, reduce the amount of recycled materials and other methods to be resolved.