Some plastic parts are swollen or bubbling on the back of the metal insert or in a particularly thick part after the mold is demolded. This is because the plastic that is not completely cooled and hardened releases gas expansion under the action of the puncturing. .
solution:
1. Effective cooling. Reduce the mold temperature, extend the mold opening time, and reduce the drying and processing temperature of the material.
2. Reduce the filling speed, reduce the forming cycle and reduce the flow resistance.
3. Improve pressure and time.
4. Improve the condition that the wall of the workpiece is too thick or the thickness changes greatly.
Analysis of the Causes of the Shock Pattern of Injection Molding Products
A rigid plastic part such as PS forms a dense corrugation on the surface near the gate, centered on the gate, sometimes called a shock pattern.
The reason is that when the melt viscosity is too large and the mold is filled in a stagnant form, the front end material quickly condenses and shrinks as soon as it contacts the surface of the cavity, and the subsequent melt expands the contracted cold material to continue the process. 4. The alternating flow causes the surface to form a surface striate during the advancement.
Solution:
(1) Increase the barrel temperature, especially the nozzle temperature, and also increase the mold temperature.
(2) Increase the injection pressure and speed to make it quickly fill the model cavity.
(3) Improve the flow path, gate size, and prevent excessive resistance.
(4) The mold exhaust should be good, and a large enough cold well should be set.
(5) Do not design the parts too thin.