Cause analysis of swelling, bubbling and vibration of injection molded products

After molding and demoulding of some plastic parts, swelling or blistering will appear on the back of the metal insert or in the particularly thick part soon. This is because the plastic that has not been completely cooled and hardened releases gas expansion under the action of internal pressure.

Solution:

1. Effective cooling. Reduce the mold temperature, prolong the mold opening time, and reduce the drying and processing temperature of the material.

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

3. Increase the holding pressure and time.

Improve the condition that the wall surface of the workpiece is too thick or the thickness changes greatly.

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

PS and other rigid plastic parts form dense ripples around the gate on the surface near the gate, sometimes referred to as shock marks.

The reason is that when the melt viscosity is too high and the mold is filled in the form of stagnant flow, the material at the front end will condense and contract as soon as it contacts the surface of the cavity, and the later melt will expand and the contracted cold material will continue to move forward. The continuous alternation of the process makes the material flow form surface vibration patterns in the process of moving forward.

resolvent:

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

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

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

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

Do not design the parts too thin.