It is a snake-shaped squirt flow formed upon the melt’s entering the cavity with thick walls and large section with excessively high injection rate. Such snake-shaped squirt flow can stay at the surface of plastic parts, whereby influencing the appearance quality, and meanwhile, minute welding mark may

form at the snake-shaped folding; moreover, it can also result in poor exhausting and reduce the quality of plastic parts. The ejection is mainly due to overhigh screw rate as well as improper position and type of gate.

The treatment measures include optimizing the position, form and dimension of gate to enlarge contact between melt at the gate and the surface wall of cavity and to reduce melt shearing rate and shearing stress; reducing injection rate of screw to avoid overhigh rate when the melt is injected into mold cavity. Lapping gate, tab gate and fan gate can be adopted to achieve such purpose.