In the point gate design in the vertical part direction, a radiation system composed of different color depths and lusters, which is centered on the gate, is called a ray line. There are three general manifestations, namely dark dark lines, dark lines at the bottom and dark lines around the gate.
Most of these defects occur when injecting polystyrene and modified polystyrene mixtures, which are related to the following factors: the two materials differ in rheology, coloration, etc., and the flow system stratosphere and turbulent layer flow rate and There are differences in heat conditions; plastics are burnt due to thermal decomposition; the interference of gaseous substances when plastics enter the mold.
(1) When using mixed plastic, mix the plastic, and the particle size of the plastic should be the same and uniform.
(2) The plastic and the colorant should be mixed evenly, and if necessary, a suitable dispersing agent should be added and mechanically mixed.
(3) The 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, increase the mold temperature, increase the temperature of the nozzle, and reduce the temperature of the front furnace.
(5) Melts and coking substances that prevent the degradation of plastics and increase the viscosity: If there is a dead angle at the screw and barrel, or if the heating system is out of control, improper processing will cause the plastic to decompose for a long time. It is possible to pass the polishing screw and the inner surface of the front end of the barrel.
(6) Improve the gate design, such as enlargement of the gate diameter, change the gate position, change the gate to a rounded transition, try to locally heat the gate, and add a cold well at the runner end.