Injection molding process and temperature control of each process

Injection molding process and temperature control of each process

1. Mold temperature

Some plastic materials require high mold temperature due to high crystallization temperature and slow crystallization speed, and some require higher or lower temperature due to size and deformation control or demoulding requirements, such as PC generally require more than 60 degrees. In order to achieve a good appearance and improve the fluidity of PPS, the mold temperature sometimes needs to be above 160 degrees. Therefore, the mold temperature has an inestimable effect on improving the appearance, deformation, size and rubber mold of the product.

2. Injection pressure

The melt overcomes the resistance required for advancement and directly affects the size, weight and deformation of the product. Different plastic products require different injection pressures. For materials such as PA and PP, increasing the pressure will significantly improve the fluidity. Injection pressure The size determines the density of the product, that is, the appearance of gloss. It has no fixed value, and the more difficult it is to fill the mold, the higher the pressure of the injection part.

3. Barrel temperature

The melt temperature is very important, and the temperature of the shot cylinder used is only a guide. The melt temperature can be measured at the nozzle or using the air jet method. The temperature setting of the injection cylinder depends on the melt temperature, screw speed, back pressure, injection volume and injection molding cycle. If you have no experience in processing a specific grade of plastic, start with the lowest setting.
For ease of control, the shot cylinders are divided into zones, but not all are set to the same temperature. If the operation time is long or operating at high temperature, please set the temperature of the first zone to a lower value, this will prevent the plastic from melting prematurely and shunting. Before the injection molding starts, make sure that the hydraulic oil, hopper seal, mold and injection cylinder are at the correct temperature.

4. Melt temperature

The temperature of the melt plays a major role in the flow properties of the melt. Since the plastic does not have a specific melting point, the so-called melting point is a temperature segment in the molten state. The structure and composition of the plastic molecular chain are different, so the influence on its fluidity is also different. Rigid molecular chains are obviously affected by temperature, such as PC, PPS, etc., but flexible molecular chains such as PA, PP, PE, etc. The fluidity is not obvious by changing the temperature, so the reasonable injection temperature should be adjusted according to different materials .

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