What is Plastic Extrusion: Types & Applications

Plastic is the most common material around us. Various processes, including plastic extrusion, are used to manufacture plastic components.

This guide below has details of what is plastic extrusion, the different processes involved, the materials used, as well as its pros and cons. So let's read.

What is Plastic Extrusion?

Plastic extrusion is a process used to manufacture components made using thermoplastic in mass quantity. The thermoplastics are melted and left in molds to take the desired shapes. An extruder is then used to remove the melted plastic from the die and attain the desired shape.

There are various parts of the extruder, which are as follows:

Hopper: This extruder part has plastic as pellets, powder, or granules.

Feed Throat: It links the barrel and hopper to channel the plastic from the hopper towards the barrel during the process.

Breaker Plate: A breaker plate maintains pressure and works like a filter to help prevent other materials from entering the barrel.

Barrel: It uses heat to melt the plastic; it has a rotating screw that applies the required pressure, which helps in directing the plastic to the feed pipe.

Feed pipe: It is used to transport molten plastic from barrel to die.

Die: Die allows the molten plastic to take shape and achieve the required geometry.

Cooling System: Cooling systems help to facilitate the cooling of plastic and allow it to solidify quickly.

Pros of Plastic Extrusion

The process of plastic extrusion has various advantages, some of which are as follows:

• The process offers ease in that when the extrusion takes place, and the component is yet to cool down, the shape of the hot plastic can be changed. Hence, the manufacturers can enhance the quality of the final component.
• When compared to other processes of manufacturing plastic components, the process of plastic extrusion is quite affordable because it doesn't need tooling.
• Plastic extrusion is a highly flexible method offering plastic profiles and shapes, provided that the cross-section is constant.

Cons of Plastic Extrusion

Along with the advantages, there are some downsides to the plastic extrusion process, and these are as follows:

• When removed from the plastic extruder, the hot plastic may expand and cause a difference in dimensions from the required product.
• This process of plastic extrusion is limited in terms of the product types manufactured, as some designs require investments in different extrusion equipment.

How Does Plastic Extrusion Work?

There are four steps involved in the process of plastic extrusion, and these are as follows:

Addition of Additives

Plastic extrusion starts by adding additives to the plastic used in the processes. These additives can be UV inhibitors or colorants.

Melting Plastic

The second stage is where the plastic is melted by being fed into the hopper. It moves to the feed throat and to the barrel where a high temperature helps plastic to melt. The rotating screw in the barrel allows the plastic to stay in the molten state.

Mold Formation

When the molten material is pushed towards the end of the barrel, it passes through screens at the end. The molten material is allowed to pass through the die, which helps achieve the desired component.

Cooling

When the molten plastic has passed through the die, it is left to cool using water showers or cooling rolls. The process of cooling ensures that the shape remains the same as the extruded one.

Different Types of Plastic Extrusion

There are different types of plastic extrusion processes which are used, and some of these are discussed below:

Tubing Extrusion

The tubing extrusion process carries out general plastic extrusion. It is suitable for items that have a tube-like structure with a hollow shape, like pipes and tubes. It is also suitable for manufacturing tubes and drinking straws for use in the medical industry.

In order to have the hollow shape, a pin or mandrel is added to the die, which creates these holes through the pressure laid on the molten plastic.

Blow Film Extrusion

The blow film extrusion process is suitable for manufacturing shopping bags. It has an upright cylinder with a circular opening. The molten plastic is pulled up with the help of nip rolls from the die during the process. The nip rollers are positioned at a height based on the required cooling.

There is an air exit in the center of the die, which helps to blow the air and create a bubble. It expands the cross-section of the plastic. The bubble is then flattened with the help of nip rolls, and a double-layered film is produced.

Sheet Film Extrusion

The process of sheet film extrusion is a rolling and pulling process. In the process, the rolling helps to attain the required shape and even supports cooling. The surface features of the sheet are also determined through rolling.

Over Jacket Extrusion

Over jacket extrusion helps manufacture insulation wires. The tooling used in this extrusion process, which helps in coating the wires, is jacketing and pressure.

These types of tooling have their uses; if there is a need for adhesion between material and wire, then pressure tooling is opted for. However, if no such adhesion is needed, then jacket tooling is opted for.

The difference between pressure and jacket tooling is the position of the pin. If the pin extends the flush with the die, it is jacketing tooling. When the pin is inside the crosshead, it is pressure tooling.

Material Selection for Plastic Extrusion

Plastic extrusion can be carried out in various materials, and some of these thermoplastics are as follows:

ABS: ABS consists of acrylonitrile and styrene polymerized together, which makes it tough and waterproof. It has a gloss appearance and works at different temperatures.

Acrylic: It is used in diverse industries and has light transmission, clarity, and strength.

PVC: PVC can be opted for different types of applications using plastic extrusion. There are two kinds of PVC: flexible PVC and rigid PVC.

Flexible PVC has high resistance against wear and tear and seamless tensile strength. Rigid PVC is impact-resistant; it even offers UV stability and is used in plastic profiles for windows, doors, and refrigeration.

Mineral-Filled Polypropylene: It is suitable for working over a wide temperature range due to its thermal stability.

Polycarbonate: It offers abrasion resistance, impact resistance, stiffness, and colorability.

Styrene: Styrene is opted for plastic extrusion as it offers strength, stiffness, and toughness.

TPA: It is used to make gaskets and weatherstrips. It offers elongation, an excellent compression set, and low-temperature stability.

Applications of Plastic Extrusion

The process of plastic extrusion is used in a wide range of applications, and some of these are as follows:

Wire Insulation

Plastics offer insulation properties and also are highly flexible. Therefore, when it comes to insulating wires, the process helps to create a durable coating.

Tubes and Pipes

Plastic extrusion is used to manufacture tubes and pipes, and this process is capable of manufacturing pipes using different thermoplastics.

Doors and Windows

Plastic extrusion helps manufacture windows and doors. These are mostly made using PVC, which offers excellent UV resistance.

Shades and Blinds

A plastic extruder, which uses polystyrene thermoplastic, is commonly used to manufacture shades and blinds.

Tips for Designing Products for Plastic Extrusion

To achieve the right and well-designed products using plastic extrusion, some of the tips you must consider are as follows:

• Always ensures that the designs have a uniform cross-section, which helps to optimize the extrusion process.
• Keep the wall thickness uniform so that you can avoid warping and defects in the quality.
• To release the extruded product from dies, the tappers are needed so that the draft angles are incorporated, and release from the die is easier.
• Always consider shrinkage during the process of cooling.

Plastic Extrusion vs. Injection Molding

Plastic extrusion and stampaggio a iniezione are both processes that work with plastics and manufacture plastic components. However, these two processes do differ from one another, and some of these differences are as follows:

• Plastic extrusion is suitable for components with 2D shapes, whereas injection molding is suitable for manufacturing 3D products.
• Plastic extrusion produces components in which the component’s shape is the same as the die. In injection molding, the shape of the component is the same as that of the mold.
• Plastic extrusion produces a consistent cross-section very easily. However, injection molding helps to achieve these cross-sections with intricate dies.
• The components manufactured through injection molding are stronger than the ones manufactured through plastic extrusion.

Your Plastic Manufacturing Partner of Choice - DEK

If you are looking to get the finest quality components of plastics manufactured using the plastic extrusion process, you can consider DEK as your manufacturing partner. We offer high-quality plastic extruded components manufactured with a seamless finish and excellent durability. So, get in touch with us today.

Conclusione

The process of plastic extrusion uses versatile types of plastic and can also be used in various industries. The guide must have given you a clear insight into the process, types, and applications of plastic extrusion.

Domande frequenti

How much does plastic extrusion cost?

The cost of the plastic extrusion may vary based on the design and the type of plastic chosen.

Can plastic extrusion produce sheets?

Yes, sheets can be produced using the process of plastic extrusion.

What are extruders used for?

Extruders help manufacture continuous and long products; these may include tubes, pipes, and coverings for wires.

What are the types of plastic extruders?

The types of plastic extruders are multiple extruders, single screw extruders, and ram extruders.