Plastic product injection molding processing inlet

1. Excessive viscosity of plastic

When the viscosity of the molten material is too high, it quickly condenses upon contact with the surface of the Mold cavity. The flowing molten material forces the condensed material to continue flowing, resulting in stripes. The reason for the formation of stripes is mostly due to improper mold temperature. It can be eliminated by changing the forming conditions, i.e. increasing the melt temperature and mold temperature. Increase the injection pressure and speed to quickly fill the model cavity. Improve the size of the runner and gate to prevent excessive resistance. The mold exhaust should be good and a sufficiently large cold well should be set up. Do not design the parts too thin.

2. Uneven temperature of molten material

The molten material stuck at the nozzle head of the injection machine should be removed together with the formed part during demolding. If there are residual parts or cold materials cooled by the main runner and runner, they are injected into the mold cavity and also generate ripples. Injecting hot molten material at the beginning can eliminate ripples. Attention should be paid to polishing the injection machine nozzle, increasing the nozzle temperature, and designing sufficiently large cold material cavities on the mold to also eliminate ripples.



3. Improper mold temperature

If the mold temperature is too low, the molten material in the low-temperature area immediately condenses, resulting in ripples. Although increasing the mold temperature can eliminate this defect, it will inevitably extend the molding cycle.

In the design of a point gate perpendicular to the direction of the workpiece, a radiation system consisting of different color depths and glosses appears on the surface of the workpiece during Injection Molding, called a ray of light. There are generally three manifestations, namely dark lines on a dark background, dark lines on a dark background, and dense white lines around the gate. This type of defect mostly occurs during the injection of polystyrene and modified polystyrene mixtures, and is related to the following factors: there are differences in rheological and coloring properties between the two materials, as well as differences in flow rates and heating conditions between the laminar and turbulent layers of the pouring system; Plastic generates burnt filaments due to thermal decomposition; The interference of gaseous substances during plastic injection molding.


Solution: (1) When using mixed plastic, it is necessary to mix the plastic well, and the particle size of the plastic should be the same and uniform.

(2) Plastic and colorants should be mixed evenly, and appropriate dispersants should be added if necessary, and mixed mechanically.

(3) The plasticization should be complete, and the plasticization performance of the machine should be good.

(4) Reduce injection pressure and speed, shorten injection and holding time, increase mold temperature, increase nozzle temperature, and reduce front furnace temperature.