Heating and melting processes in injection moulding?

  In the injection moulding process, the heating and melting process is the key step in heating solid plastic pellets to their melting point and converting them into a flowable state. The following are the general steps of this process:
Pellet heating: The plastic pellets are loaded into the hopper of the injection moulding machine and then conveyed into the heated barrel by means of a screw system or a plunger. Inside the heated barrel, the screw rotates and pushes the pellets forward while an electric heater or other heating element is used to heat the pellets. The purpose of the heating is to raise the temperature of the pellets so that they reach their melting point.

  Melting process: Once the pellets have been heated to a high enough temperature, they begin to melt into a liquid state. This stage is critical as the injection moulding machine needs to ensure that the pellets are sufficiently molten to form a uniform, continuous stream of plastic when injected into the mould.
Constant Temperature Maintenance: To ensure that the plastic remains in a proper molten state, a period of constant temperature maintenance usually follows the heating process. This helps stabilise the physical properties of the plastic and prevents premature solidification or over-melting.

  Pressure: Once the plastic pellets have reached the proper melting point and temperature, the injection moulding machine applies pressure. By increasing the pressure, the injection moulding machine pushes the molten plastic into the mould, ensuring that all cavities are filled.
Cooling: Once the mould has been filled and formed into the desired product shape, the injection moulding machine stops applying pressure and cools. During the cooling process, the surface or interior of the mould can be cooled by circulating water to help solidify the plastic.
Mould opening and ejection: Once cooling is complete, the mould is opened and the moulded plastic product is ejected from the mould. This process is called mould opening and ejection.

  The control of the entire heating and melting process is very critical as it directly affects the quality and performance of the product. Operators need to adjust the heating temperature, holding time and pressurisation parameters according to the specific plastic type, product design and injection moulding machine model to ensure consistency and quality of the final product.