What are the burning of injection molding products?
In the process of injection molding, injection molding products are due to high temperature. This is easy to cause plastic parts to burnt. Today we will take stock of what factors will cause injection molding products to burnt.
1. Follower rupture causes burning problems
The melt is injected into the type cavity under high temperature, high speed, and high pressure. In this case, it is very easy to cause rupture. Horizontal breaks appear on the surface of the melt, and the broken area is roughly mixed with plastic surface layer to form paste. The phenomenon of burning also appeared.
The essence of the melting rupture is due to the elastic behavior of the high polymer melt. When the melt flows in the tube, the melt near the barrel is frurated by the tube wall, the stress is large, the molten flow speed is compared Small, once the melt is injected from the nozzle, the stress of the tube wall disappears, and the melt flow rate of the middle part of the tube is extremely high. The melt at the tube wall is carried by the melt at the center. Relatively continuous, the flow speed of the internal and external melts will be re -arranged to tend to the average speed.
Second, the size of the injection speed will produce burnt
During the injection process of the melt, the injection speed of the injection molding has a great impact on the appearance of the plastic part. When the flowing material is slowly injected, the molten flowing state is layer flow; when the injection speed rises to a certain value, the flow state gradually gradually gradually gradually gradually gradually gradually gradually gradually becomes gradually gradually gradually gradually. Turn into a turbulent flow. Under normal circumstances, the surface of the plastic parts formed by layer flow is relatively bright and flat. The plastic parts formed under the condition of the flow not only have plaques on the surface, but also the internal pores are prone to generate. Therefore, the injection speed should not be too high, and the flow material should be controlled in a stratified state.
Third, the temperature of the melt is too high
The temperature of the melt is too high, which can easily cause the melt decomposition and coking, resulting in a spots on the surface of the plastic parts. Generally, the screw rotation of the injection molding machine should be less than 90r/min, and the back pressure is less than 2MPa. Essence If the rotation time when the screw is returned is too long during the molding process, excessive friction heat can be generated, the screw speed can be appropriately increased, the molding cycle is extended, the back pressure of the screw is increased, the temperature of the charging section of the tube is increased, and the raw materials with poor lubrication are used. Methods overcome.
Fourth, mold failure
If the mold exhaust holes are blocked by the anticipide precipitated by the mold and the raw materials, the mold exhaust settings are not enough or the position is incorrect, and the charging speed is too fast. Essence In this regard, the obstruction should be removed, the molding power is reduced, and the exhaust of the mold should be removed. The determination of the form and location of the mold port is also very important. When designing, it should fully consider the molten flow state and the exhaust performance of the mold.