1. Improper control of process conditions. If large inj […]
1. Improper control of process conditions.
If large injection molding machine specification, the screw rotation speed is too high, the injection pressure is too great, the injection pressure maintaining time is too long, can form excessive filling, makes the molding shrinkage rate is smaller than expected and demoulding it difficult.
In addition, the nozzle temperature is too low, and the cooling time is too short and the injection is broken, which can cause the deform. Therefore, beyond a sticky mold and mold release bad failure, should be appropriate to reduce the injection pressure, injection time, reduce the cylinder and the melting temperature, longer cooling time, and prevent the liquid to flow, etc.
2. Improper use of release agent.
The purpose of the use of the mold is to reduce the adhesion between the surface of the plastic parts and the surface of the mold cavity, to prevent the two from sticking to each other, so as to shorten the molding cycle and improve the surface quality of the plastic parts. However, due to the release agent demoulding effect is influenced by chemical action, are also affected by the physical conditions, and molding materials and processing conditions are different, selected the best variety and dosage of release agent must according to the specific circumstances to determine.
When the injection pressure is too large, the shrinkage rate is smaller than expected, and it becomes difficult to remove the mold. If the injection pressure is reduced, the injection time is reduced, the melting material and mold temperature are reduced, it becomes easy to remove the mold. In this case, it is more effective to reduce the friction between the plastic and the mold. It is also effective to improve the light treatment, cancel the side wall, grind and increase the top lever. When forming deeper parts, it is more helpful to blow the compressed air into the mold and the parts (refer to the "cracking, crack, microcrack, and whitening").
4. Make pieces stick to the mold.
In order to avoid this situation, the mould should be installed correctly. The reason for the large demoulding resistance is due to the low finish or the convex concave of the side wall. At this time, should be on the side of the dynamic mold to set the z-type pull rod to pull the production. In the mold design, it is necessary to fully consider this phenomenon. It is also effective to set the temperature difference on both sides.