Some plastic parts, after molding and demoulding, soon appear swelling or bubbling on the back of the metal insert or in the particularly thick part. This is caused by the expansion of the gas released by the internal pressure of the plastic that has not been completely cooled and hardened.

Solution:

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

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

3. Increase the holding pressure and time.

4. Improve the condition that the wall of the parts is too thick or the thickness changes greatly.

Analysis of the cause of the seismic marks of injection molded products

PS and other rigid plastic parts on the surface near the gate, the formation of dense ripples centered on the gate, sometimes called the seismic marks.

The reason is that when the melt viscosity is too large and the mold is filled in the form of stagnation, the front end of the material will soon condense and shrink as soon as it touches the surface of the cavity, and the later molten material will expand the cold material that has shrunk and continue to advance. The continuous alternations of the material flow in the forward formation of the surface of the seismic marks.

Solution:

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

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

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

(4) Mold exhaust should be good, to set a large enough cold feed well.

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

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