As one of the three technological conditions of injection process, the temperature in injection process is directly related to the technological conditions and process of melt, plasticization, fluidity, filling and so on.

 

The temperature of the melt and the product is determined by the mechanism in which it is contacted. In fact, there are three main types of temperature that need to be controlled: the barrel temperature, the nozzle temperature, and the mold temperature. Among them, the temperature of barrel and nozzle affect the plasticization and flow process and properties of the melt. The mold temperature affects the flow and cooling molding process of the melt.

 

 

Barrel Temperature:

The choice of the barrel temperature is related to the characteristics of the plastic, In the continuous forming process, the most suitable barrel temperature should be between the viscous flow temperature (Tf) or the melting point temperature (Tm) and the thermal decomposition temperature Td. Make sure that the melt is heated at all times, so that the flow pattern of the melt will not be decomposed.

 

Increasing the temperature of the cylinder (melt) is beneficial to the transmission of injection pressure into the mold cavity. When the melt temperature is high, the temperature of the material will remain at the viscous flow temperature (or melting point) for a long time, which is beneficial to the orientation of the oriented macromolecules and reduces the shrinkage of the products. With the temperature increase, the decrease of viscosity, injection system pressure decreases, the melt flow in the mold increases, which can improve the forming performance, increase the injection rate, reduce the melting, filling time, shorten the injection cycle, reduce product roughness (improve product surface finish).

 

Generally speaking, from the side of the hopper (back-end) to the nozzle (froe-end), the temperature of the material barrel is gradually raised. As a result, the temperature of the plastic rises steadily, and the purpose of uniform plasticization is achieved. When the moisture content of the raw material is too high, the temperature at the back end can be appropriately increased.

 

Nozzle Temperature:

Injection molding temperature is critical to the quality of the melt after injection. If the temperature is too high, more than the melting point of binder (for powder metallurgy), a lot of plastic will be broken down. Then there is peculiar smell produced, reducing the quality of plastic products. Additionally, products cannot form properly. As a result, the maximum temperature is slightly below the barrel temperature.

 

Die Temperature:

The temperature of the mold affects the properties of the product, the size of the product, the performance and the forming process. Lower die temperatures are generally used.