Analysis of the causes of swelling, bulging, and shock lines of injection molded products

Some plastic parts are swollen or blistered on the back of the metal insert or in particularly thick parts soon after molding and demolding. This is because the plastic is not completely cooled and hardened under the action of internal pressure penalty release gas expansion caused.



Solution measures.

1. Effective cooling. Lower the mold temperature, extend the mold opening time and lower the drying and processing temperature of the material.

2. Reduce the mold filling speed, reduce the molding cycle, and reduce the flow resistance.

3. Increase the pressure and time of holding pressure.

4. Improve the condition that the wall of the part is too thick or the thickness varies greatly.

Analysis of the causes of the vibration pattern of injection molded products

PS and other rigid plastic parts form dense ripples on the surface near the gate, sometimes called shock lines.

The reason is that when the melt viscosity is too large and the mold is filled in the form of stagnant flow, the material at the front end quickly condenses and shrinks when it touches the surface of the cavity, while the molten material later expands the cold material that has shrunk and continues to move forward.

Solution.

(1) improve the barrel temperature, especially the injection nozzle temperature, but also to improve the mold temperature.

(2) Increase the injection pressure and speed, so that it can quickly fill the cavity.

(3) Improve the flow channel and gate size to prevent excessive resistance.

(4)The mold exhaust should be good, and a large enough cold material well should be set.

(5) The parts should not be designed too thin.