Extrusion Control for Plastics Processing
Resin or other raw thermoplastic material is fed into the barrel of an extruder by gravity from a hopper on top. The resin delivered to the hopper might have liquid colorants, UV inhibitors, or pellets of additives. The method is quite similar to plastic injection molding, except that it is often continuous. In contrast to injection molding, which involves pumping a fluid resin through a die, the completed product is pulled out. This enables a wider range of profiles to be produced in continuous lengths, sometimes with additional reinforcing.
The plastic resin is pushed into the barrel, and a spinning screw heats the resin to a melting point that is right for it. The material contacts the Screw Chillers as it reaches the feed throat at the back of the barrel. Most of the time, the barrel is heated in stages, from the back (where the resin goes in) to the front (where the pellets come out), using three or more different PID-controlled heat zones. So, the plastic resin can slowly melt as it moves through the barrel. This reduces the risk of overheating, which could cause the polymer to break down.
When the resin comes out of the barrel through the screw at the front, it goes through a strong screen to get rid of any unwanted particles. The pressure at this location may surpass 5000 psi. Hence screens are often reinforced with a breaker plate (34 MPa).
The resin must first break through the breaker plate to get inside the die. The profile or shape of the finished product is determined by the die, which must be made so that the molten plastic flows smoothly and evenly from a cylindrical profile to the product’s profile shape. As long as the profile is continuous, almost any form can be created. If the flow isn’t even at this stage, the product will have strains in places where you don’t want them. Warping due to stress due to cooling is possible.
The four sections of a conventional extruder are as follows:
To the Zone of Feeding
There is a fixed altitude at which planes may fly in this region. The flight depth is the measurement from the screw’s minor diameter at the bottom of the flight to its major diameter at the top of the flight.
Compression or Transitional Zone
This is the region where the flight depth begins to drop. A thermoplastic substance undergoes politicization as a result of compression.
There is a return to a constant flight depth in this region. A specialized mixing device may be used to guarantee the substance is thoroughly melted and thoroughly combined.
Zone of Metering
In this region, the flight depth is stable but lower than in the mixing region. The pressure in this area also helps push the molten metal through the die that shapes it. Visit For More Information About :- Follow Me