Causes and solutions of shock lines, swelling and bulging in injection molded products

The surface of rigid plastic parts such as PS, etc. near the gate forms dense corrugations centered on the gate, sometimes called shock lines. The reason for this is that when the melt viscosity is too large and the mold is filled in the form of stagnant flow, the front-end material quickly condenses and shrinks when it touches the surface of the cavity, while the later molten material expands the cold material that has shrunk and continues to advance in the process.

Brass Insert Molding for Auto Parts

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.

Analysis of the causes of swelling and bulging 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 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.