Causes and Solutions for Vibration Marks in Injection Molding Products

 

Due to the different materials used in each product, defective products frequently occur during injection molding. For example, vibration marks often appear on rigid plastic products. What are the causes? Are there any good solutions?

 

Causes of Vibration Marks in Injection Molding Products

 

On the surface of rigid plastic parts such as PS near the gate, dense ripples form around the gate, sometimes called vibration marks. The cause is that when the melt viscosity is too high and it fills the mold in a stagnant flow manner, the material at the front quickly cools and shrinks upon contact with the cavity surface, while the subsequent melt expands out of the already shrunk cold material and continues to advance. This constant alternation causes surface vibration marks to form as the material flows forward.

 

 

Solutions for Vibration Marks in Injection Molding Products:

 

(1) Increase the barrel temperature, especially the nozzle temperature, and also increase the mold temperature.

 

(2) Increase the injection pressure and speed to quickly fill the mold cavity.

 

(3) Improve the runner and gate dimensions to prevent excessive resistance.

 

(4) The mold should have good venting and a sufficiently large cold slug well.

 

(5) The part should not be designed to be too thin.