1. Improper control of molding conditionsMany process parameters have a direct impact on the generation of bubbles and vacuum bubbles. Setting the injection pressure is too low, the injection speed is too fast, the injection time and cycle are too short, the amount of material added is too much or too little, the pressure is insufficient, the cooling is uneven or insufficient, and the material temperature and mold temperature are not properly controlled. Air bubbles are generated in the part. Especially during high-speed injection, the gas in the mold is too late to be discharged, resulting in too much gas remaining in the melt. For this, the injection speed should be appropriately reduced. If the speed drops too much and the injection pressure is small, it is difficult to exhaust the gas in the melt, and it is easy to produce bubbles, dents and undershot. Therefore, you should be especially careful when adjusting the injection speed and pressure. In addition, by adjusting the injection and holding pressure time, improving the cooling conditions, controlling the amount of feed and other methods to avoid the generation of bubbles and vacuum bubbles. If the cooling condition of the plastic part is poor, the plastic part can be put into hot water and slowly cooled immediately after demoulding, so that the cooling rate of the inner and outer parts tends to be the same. When controlling the mold temperature and the melt temperature, pay attention to the temperature not too high, otherwise it will cause the melt to decompose and generate a lot of gas or excessive shrinkage, forming bubbles or shrinkage holes; if the temperature is too low, it will cause the filling and compaction Insufficient, voids are easily generated inside the plastic parts, forming bubbles. In general, the melt temperature should be controlled slightly lower, and the mold temperature should be controlled slightly higher. Under such process conditions, it is not easy to produce a large amount of gas, and it is not easy to produce shrinkage holes. When controlling the temperature of the barrel, the temperature of the feeding section should not be too high, otherwise it will cause backflow and return of the material and cause bubbles.
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