The Four Common Techniques Used in Plastic Extrusion

Plastic Extrusion

Plastic extrusion methods vary depending on the complexity of the die shape. Four common techniques include tubing extrusion, blown film extrusion, thin film sheet extrusion, and extrusion with an overlying jacket. Tubing extrusion involves inserting a mandrel or pin into the die and applying positive pressure to create hollow parts.

The basic principles of plastic extrusion are consistent across the various techniques. The extrusion plastic process used is determined by the degree of complexity and intricacy of the die shape. Not all kinds are indeed created equal when it comes to handling intricate layouts.

Here are the four most common varieties of this technique used by companies today:

Extrusion of Tubing, 

The plastic extrusion process used in tubing extension is the same up until the die portion. This method works wonderfully with pipes and long tubes, both of which are hollow. The material is also perfect for making medical tubing and drinking straws.

An extrusion operator will insert a mandrel or pin into the die and then apply positive pressure to the internal cavities through the pin to create hollow parts. When producing a die with more than one hole, the maker would typically position many pins in the center. The number of pins required is proportional to the number of openings.

And since the pins’ air pressure comes from a distinct source, the size of each hole may be easily adjusted.

Extrusion of Blown Films

Producing goods like shopping bags with the blown-film extrusion process is commonplace. The primary distinction between blown-film extrusion and regular extrusion is the die, much as it is with the tubing extrusion plastic process.

The blown film extrusion die is a cylinder that stands on end and has a circular hole that can be anything from a few centimeters in diameter to more than three meters in circumference. Nip rollers are used to lift the molten plastic away from the die.

The nip rollers are typically four to twenty meters above the die. The precise height of the nip roll is determined by the amount of cooling required. Additionally, the film’s wall thickness, or gauge, is established by the speed of the nip rollers. The die is cooled by a ring of air that forms as the film rises.

To create a bubble in the middle of the extruded plastic profile, pressurized air is injected via an air outlet in the center of the die. The circular cross-section of the extruded polymers grows as a result, but only by a certain ratio. The blow-up ratio, also known as the diameter-to-size ratio, can be anywhere from a few percent to over two hundred percent.

Finally, the nip rolls assist in flattening the bubble into a double-layered film with a width equal to half the bubble’s circumference. This two-layer film can be spooled, printed on, or sliced into a variety of shapes. Bags and other products can be made by applying heat to the material and then sealing it.

Extrusion of Thin Film Sheets

Creating the desired shape is where this method differs from blow-film extrusion, to which it is conceptually quite similar. The shape is often achieved through a tugging and rolling operation in this form of extrusion. This involves figuring out the sheet’s thickness and surface texture.

The rolling step helps the product cool and solidify permanently into the desired form.

Extrusion with an Overlying Jacket

Insulate cables with ease using this plastic extrusion. The goal is to encase the substance in plastic. Wires can be coated using either pressure or jacketing extrusion plastic tooling.

The choice between the two tooling types for coating wires depends on the level of contact required between the plastic and the wire.

When a strong bond or close contact between the wire and the material is required, pressure tooling is the way to go. If physical contact and closeness aren’t necessary, though, jacketing tooling is the way to go.

The location of the pin in relation to the die is the primary distinction between these two kinds of tools. It is considered jacketing tooling when the pin is fully extended to flush with the die. For pressure tooling, however, the pin’s end remains inside the crosshead. This means that the wire is covered with plastic while it is still molten inside the die. Here, the pressure builds as the wire and the molten plastic both escape the die.

Video 01: Plastic Extrusion: A Complete Guide To Knowing Its Process