Extruder to pellet plastic: the plastic recycling machine and how it works

Plastic recycling has already become a global issue as the demand for products are on the increase. Today, manufacturers are charged with ensuring that old plastics are reused to cut down on the input of these materials into our ecosystem.

However, one of the most determining processes when it comes to the transformation of plastic material is the extrusion stage. This allows you to manufacture objects with a wide variety of shapes, colors and characteristics. In the extrusion machine, the polymer is melted inside a sleeve and screw. This depends on the polymer, the temperatures and types of screws vary.

In this article we will detail all the necessary information about this fundamental machine in the chain of a recycling plant.

What is a plastic recycling machine?

This extruder machine that is in charge of the extrusion of polymers through the action of pressing, melting, molding, pressing and pushing the materials. The result is a new mold that will have the desired shape according to the shape and design of the spindle used in the plastic recycling machine.

The extruder allows to obtain the mold quickly and continuously, speeding up the industrial recycling process and making the most of the raw material.

Operation of a plastics extruder

In the extruder machine the raw material that is in the form of granules, previously crushed, passes through a funnel (hopper) that constantly supplies the cylinder or "barrel" that has a high temperature. Inside there is a spindle that pushes the material along the cylinder generating pressure and raising the temperature to allow the melting and modeling of the raw material.

Types of extrusion machines

The spindle is the piece in charge of pushing the material through the cylinder, pressing it to shape it until the desired object is achieved. Spindles are a type of large diameter and length screw of different shapes or designs, capable of shaping thermoplastic material when it reaches high temperatures.

There are two types of extruder or plastic recycling machines according to the number of screws.

1. The most common machines have a single spindle (Mono Spindle). This is to build pressure in the molten polymer to enhance extrusion from the die.

2. Twin screw or multi screw extruders used for mixing and compounding or reacting polymeric materials. The flexibility of this machinery allows it to be adapted for specific compounds since the spindles can be counter-rotating or co-rotating.

Pellets manufacturing process

The pellets are cylindrical in shape with right angle edges and have a good degree of uniformity. Resin manufacturers and composite producers can process the widest range of materials in these systems, everything from unreinforced polyolefins to filled engineering resins up to 90% by weight.

In this process, once the extrusion has elapsed, the grain is cut even when the plastic has not solidified. Once the soft plastic material is cut and still in a fluid state, it is immediately solidified with cold water, thereby avoiding the generation of dust, obtaining a regular grain and facilitating its packaging and transport. To change the grain size, the extrusion volume and cutting speed are automatically adjusted or by changing the number of cutters according to the extruder output.