Causes of glow lines in the gate area of injection molded products

In the design of the point gate in the vertical direction of the part, a radiation system consisting of different color depths and luster, called glow lines, appears on the surface of the part during injection molding with the gate as the center. There are three kinds of manifestations, namely dark lines on a dark base, dark lines on a dark base, and dense and white dark lines around the gate.



Most of these defects appear in the injection of polystyrene and modified polystyrene mixture, related to the following factors: the two materials in the rheology, coloring and other aspects of the difference between the pouring system of the stratosphere and turbulent layer flow rate and the difference in the heat condition; plastic due to thermal decomposition and generate scorched wire; plastic into the mold when the gaseous material interference.

Solution measures.

(1) When using mixed plastic, mix the plastic well, and the size of the plastic particles should be the same and uniform.

(2) plastic and coloring agent to be mixed evenly, if necessary, to add appropriate dispersant, with mechanical mixing.

(3) Plasticization should be complete, and the plasticizing performance of the machine should be good.

(4) Reduce the injection pressure and speed, shorten the injection and holding time, while increasing the mold temperature and raising the injection nozzle temperature, while reducing the temperature of the front furnace.

(5) to prevent the degradation of plastic and cause increased viscosity of the melt and coking material: such as attention to the screw and barrel wear and tear and the existence of dead space, or heating system out of control, improper processing operations caused by long-term heating and decomposition of the plastic. This can be done by polishing the inner surface of the front end of the screw and barrel.

(6) Improve the gate design, such as enlarging the gate diameter, changing the gate position, changing the gate to rounded transition, trying to local heating of the gate, add cold material well at the runner end.