Haochen Hot Runner tells you that when the valve needle cannot be pushed to the bottom, there will be a material head on the surface of the product. The reasons for this are

1、 When the injection temperature of the product is reached, the length of the valve needle after thermal expansion cannot reach the surface of the mold cavity.

2、 Is the front end of the valve needle smaller than the size of the mold gate.

3、 The concentricity and roundness of the valve needle and valve needle sleeve are not enough to get stuck

4、 The concentricity of the cylinder, splitter plate, hot nozzle, and gate is not sufficient.