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Mould problems solution

What are the problems that always appear on injection molds?

Nov. 10, 2021

Dark spots on the product

Black spots mainly appear at the gate of the injection mold, just like dark spots. This is especially true when producing products with high viscosity and low flow materials such as PC, PMMas or ABS. When the cold surface layer resin is taken away by the central flowing resin, this obvious deficiency may occur on the product surface.

It is generally believed that this deficiency often occurs in the filling and holding pressure stages.

Even if the injection rate of the melt into the mold is constant, its flow rate will change. When entering the gate area, the melt flow rate is high, but when entering the cavity, the melt flow rate begins to decrease. The change in flow velocity at the front of the melt flow leads to insufficient surface.

Reducing the injection speed is one way to solve this problem. In order to reduce the speed of the melt flow front at the gate, the injection can be divided into several steps, and the injection speed can be gradually increased to obtain a uniform melt flow rate throughout the filling stage.

Temperature is also a cause of dark spots on the material. It is necessary to increase the temperature and screw back pressure to reduce the incidence of this phenomenon. The low temperature of the mold can also easily make the surface of the object insufficient, so increasing the temperature can also solve the problem of the surface of the injection mold.

Low melt temperature is another important reason for dark spots in product companies. Increasing the temperature of the barrel and the back pressure of the screw can effectively reduce the probability that this social phenomenon has occurred.

In addition, the temperature of the mold is too low to affect the surface defects, so increasing the mold temperature is another feasible way to overcome the surface defects of the product.

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