An injection molding machine is comprised of four main components: the base, the hopper, the barrel, and the clamping unit. There are also smaller components such as the nozzle, ejector pins, split mold, clamping unit, injection unit and hydraulic unit.
The base holds all the other parts and the electronics needed to run the machine. The electronics on the device have to control a range of heaters, hydraulics, sensors, and injection pressure.
Below please find the components of injection molding and how they work:
1. Hopper
The hopper is the component where the plastic material is poured before the injection molding process can begin. The hopper usually contains a dryer unit to keep moisture away from the plastic material. It may also have small magnets to prevent any harmful metallic particles from entering the machine. Next, the plastic material is poured into the following major component from the hopper, called the barrel.
2. Barrel
The barrel, or the material tube and barrel, heats the plastic material into a molten state to let plastic flow through the barrel. The screw inside injects the plastic into molds or cavities in the clamping unit. Therefore, the temperature in the barrel needs to be adequately regulated to maintain the appropriate temperature for different types of plastic material. The function of the cylinder is to transport, compact, melt, agitate and press the plastic before it reaches the injection mold.
3. Screw Motion or Reciprocating Screw
Reciprocating screws were created in the mid-1950s, and by 1960 they quickly began to replace the older systems. The advantage of the reciprocating screw design is that it helps manage the temperature of the molten plastic.
The screw moves plastic through the barrel. First, as the pellets are fed from the hopper into the barrel, the screw is rotated, driving the material forward while more pellets are added. Second, the flights provide a continuous mixing action that distributes heat evenly throughout the mass. This mixing also helps to purge the mechanism of different materials and any colors left behind from an earlier production runs on the same injection molding machine.
The reciprocating screw is responsible for providing most heat to the thermoforming plastic. This is because the diameter of the screw decreases as it approaches the tip. As a result, plastic pellets are pulled along by the flights, compressed into a tighter space, and cut by turning flights. This action creates friction that mixes the pellets uniformly and heats them to the proper temperature.
