During the injection molding process, many defects can occur, including bubbles, shrinkage marks, black spots, and so on. When there are injection molding defects, we should analyze the possible causes of these defects and improve the injection molding product based on these points. Next, we will analyze the causes and solutions of the black spot defect.

1. Excessive empty space in the material barrel can cause a portion of the molten material to remain in the material barrel, resulting in overheating and differentiation of these molten materials, resulting in black spots during the injection molding process. In response to this phenomenon, the temperature of the material barrel can be lowered first to investigate whether the problem can be eliminated. Or check whether there are dead corners in the barrel, nozzle, and mold.

2. Assume that the injection molding machine injection speed is too fast, the injection pressure is too high, and the relative movement speed between the melt and the cavity wall is too high during mold filling, which is prone to conflict and overheating, leading to the formation of black spots in the melt differentiation. In this regard, the injection speed and injection pressure can be appropriately reduced.

Due to poor exhaust from the material barrel and injection mold, the residual gas in the molten material will be burned due to thermal contraction, resulting in black spots on the surface of the plastic part. We can adjust the exhaust structure of the material barrel and injection mold.