（9） Moisturestrreams Injection Molding Process Defect Handling Manual (65 types)

Apparent water marks are long silver threads on the surface of the product, with the opening direction of the water marks along the material flow direction. In places where the product is not fully filled, the fluid front end is very rough.
Physical causes
Some plastics such as PA, ABS, PMMA, SAN, and PBT are easy to absorb water. If plastic storage conditions are not good, moisture can enter particles or adhere to the surface. When particles melt, moisture will be converted into steam to form bubbles. During injection, these bubbles will be exposed to the surface of the fluid front, burst, and produce irregular lines
The causes and improvement measures related to processing parameters are shown in the following table:
1. The residual moisture in the particles is too high. Check the storage conditions of the particles, shorten the time of the particles in the hopper, and provide sufficient pre drying for the material