Plastic is a material used for innumerable purposes in our day-to-day life today. They come in various colors, shapes, textures, sizes, and thicknesses.
Plastic extrusion is a renowned method for large-scale production. It is mainly used for producing continuous structures.
If you want to know more about this method, this guide is your best source of information! Learn about the process of plastic extrusion, the different types of extrusions available, and their advantages and uses. It will help you decide which method is ideal for your requirements.
About Plastic Extrusion
Plastic extrusion is the process of melting hard plastic into liquid form and using it to form the desired structures in an uninterrupted process. Additives can also be used to enhance the properties of plastic.
It is a large-scale manufacturing method done using a plastic extruder. Let’s look at its main components to understand how it functions better.
- Hopper: the component from which thermoplastic granules are inserted and stored.
- Feed Throat: The passage that transfers granules to the barrel.
- Barrel: The component with different heating chambers where the plastic is melted and mixed well.
- Screw: The mechanism inside the barrel gradually pushes the plastic from one end to the other.
- Die: The part that molds the melted plastic into the required shape and size.
- Cooling system: the mechanism that cools and solidifies the plastic in its new form.
How Does It Work?
For extrusion, plastic pellets, powder, or granules are inserted into the barrel from a hopper. These beads of solid plastic melt quicker than blocks and fasten the process. The screw(s) in the barrel powered by a motor is responsible for pushing the plastic to the other end of the barrel.
The pressure and heat exerted by its constant rotation enable this task. As plastic moves through the barrel, the thread of the screw reduces, compressing the plastic.
The heat zones in the barrel, together with the heat and pressure exerted by the rotation of the screw, melt the plastic uniformly. Then, liquid plastic is filtered to remove contaminants and pushed through the die to form the desired shape.
The die is the main component responsible for providing the shape to the plastic material, and depending on what you are manufacturing, the die used here can differ. The cooling method can also vary based on the type of extrusion.
The Evolution of Plastic Extrusion
The duo Paul Troester and Ashley Gershoff founded Germany’s first plastic extruder in 1935. Plastic extrusion has revolutionized the large-scale manufacturing sector, and these machines have evolved to be more efficient at uniformly melting and mixing plastic.
They are also compatible with more varieties of thermoplastics than they were in the past, offering manufacturers more choices.
Moreover, plastic extrusion has improved to a great extent such that thermoplastics are melted and reformed effectively without losing the material’s mechanical properties. The additives and colorants can also make it better.
Different Types of Plastic Extrusion Processes
Also known as the extruded tubing process, this method manufactures tubes, pipes, straws, and other hollow structures. The process is similar to the standard procedure but requires different molds to achieve the hole(s).
During the die stage, a pin or mandrel is inserted into the die, and positive pressure is exerted on the internal side of the part. The complexity of the process depends on the number of holes and the type of material used.
If the part includes multiple holes, you have to insert more pins in the middle of the die.
Blown Film Extrusion
Blown film extrusion is for manufacturing polymer films used for different packaging purposes. Usually, a circle die is used for this purpose, and the air is injected into the center of the die to inflate the plastic into a thin tube.
Then, the polymer is pulled upwards by nip rollers while compressed air expands the film further. We can achieve the desired film thickness and width at this stage. The bubble of the film is flattened and then used for further processing depending on its functionality.
Sheet/ film extrusion is a method used for manufacturing sheets and films that require more thickness than products attained through blown film extrusion.
These processes are similar, but the sheet film extrusion achieves shape, texture, and consistency via a pulling and rolling mechanism.
The molten plastic goes through a flat die to form a flat sheet or film. Then, it is cooled by the action of cool rolls pulling the sheet to achieve the required thickness and solidify it. The rolls also provide texture to the sheet.
Applications of films or sheets manufactured this way include ice cream tubs, yogurt cups, plastic pots, and juice cartons.
Also known as over-coating, over-jacket extrusion covers a substrate with a plastic layer. The substrate goes through the die, which is overcoated with a thermoplastic layer. Over-jacket extrusion involves the selection of two methods; pressure tooling and jacketing tooling.
If the plastic layer should be bonded well with the substrate, pressure tooling is the ideal choice. In this case, we exert high pressure or stronger adhesion. If bonding is not a requirement, jacket tooling is suitable.
There are different types of polymers that we can use for over-jacket extrusion. Popular applications include insulation for wires and cables.
What Are the Different Types of Plastic Extruders?
Single Screw Extruder
In this extruder, only one screw is used for the extruding and mixing processes. The plastic goes into the barrel from one end, passing through the screw to the other end. The screw pushes the plastic through the die utilizing high pressure.
The constant rotation of the screw powers the movement of the material. The screw type and length are selected based on the plastic variety, additives mixed in the process, and other requirements.
Twin Screw Extruder
This extruder consists of a couple of screws and is more effective in mixing than a single-screw extruder. They can be co-rotating or counter-rotating. They also offer large manufacturing capabilities and better control of the extrusion process.
The twin screws transport the melted plastic through the barrel with a figure eight channel. They can handle multiple functions due to the availability of more screw designs.
There are different types of twin screw extruders. The intermeshing extruders consist of two parallel screws that operate together. Non-intermeshing twin screw extruders consist of screws that work separately and don’t interact with each other.
What Are the Benefits of Plastic Extrusion?
As plastic extrusion works by melting and reforming thermoplastics, there’s less wastage of raw materials. If there are plastic leftovers, you can melt them and reuse them for another purpose. It is a sustainable production method and is also environmentally friendly.
Different plastic extrusion methods help you achieve plastic structures in varying shapes, sizes, thicknesses, and hardness.
For example, cling film wraps used for food packaging are thinner and more stretchable than disposable bags. The expected strength can also be achieved during the stretching process in extrusion.
The continued operations and fast processing speed, especially in twin-screw extruders, make plastic extrusion one of today’s cost-effective manufacturing methods. The reusability of the raw materials is another factor that contributes to lowered costs.
Use of Additives and Co-extrusion
Additives can enhance the properties of thermoplastics and improve the end product. The co-extrusion method can also improve the product’s characteristics as both polymers used in the process impart their benefits.
Main Applications of Plastic Extrusion
Pipes and Tubes
The tubing extrusion method is used for achieving a range of tubed structures. Some applications include drainage and irrigation pipes, sewerage pipes, PVC water pipes, fence tubes, deck railings, insulation tubes for wiring purposes, medical tubes, straws, and tube-like components for automotive and aerospace industries.
Plastic tubes are also chemical-resistant; therefore, the potential health hazards are minimal.
As most thermoplastics are excellent insulating materials and are thermally stable, it is used for insulating and jacketing live wires and cables. They provide adequate protection against possible deformation and damage to the wires.
Windows and Doors
Windows, doors, and related fittings are continuous profiles with a fixed cross-section, and these components can easily be done through extrusion.
Moreover, thermoplastic’s durability, longevity, thermal insulation, and UV-resistance properties make them an ideal material for doors and windows.
Blind and Shades
Blinds, shade slats, and base moldings are manufactured through the extrusion method, and they come in metallic-colored, wooden-grain, and many other designs.
As the construction of blinds and shades combine similar parts, they can be produced using this method. Extruded plastic structures are also rigid, stable, and can be made to be UV-resistant.
Applications of plastic films made from extrusion include packaging food, fresh produce, and baked goods that must be kept fresh. Disposable plastic bags, shrink film, stretch film, and juice can liners are also produced this way.
More durable containers like plastic tubs, ice cream containers, and flower pots are also plastic extrusion products.
Kemal: The Best Choice for Quality Plastic Extrusion Services
Kemal is a top company in China offering a wide range of manufacturing solutions, including high-quality plastic extrusion and injection molding. We cater to the manufacturing requirements of leading brands worldwide from different industries.
We are equipped with the latest technology and an efficient team to deliver products that exceed your expectations. We only utilize high-quality raw materials for plastic extrusion and offer a range of thermoplastics for you to choose from.
You can discuss your manufacturing requirements with us or use the instant quotation platform to get an estimate of the cost.
Our high-volume manufacturing capabilities help us exploit economies of scale and offer globally competitive rates for plastic production.
Take a look at all the solutions we offer, and get in touch with us!
Plastic and Aluminum Extrusion: Which is Better?
Choosing between plastic and aluminum extrusion is not easy, and you have to consider the pros and cons of each to select the ideal method for your requirements.
We recommend that you compare the thermal properties, load strength, bacterial resistance, scratch resistance, and other characteristics of the two materials before deciding.
Many prefer it for manufacturing railings, window and door frames, automotive parts, aerospace components, and other sturdy components.
Aluminum is strong, more durable, and long-lasting than plastic in general. But, it has high electric conductivity and is apt for applications where it is essential.
We hope our guide on plastic extrusion helped you understand the process better and determine if it’s the ideal choice for your manufacturing requirements.
Consider the type of product and the material chosen for producing it. In some cases, injection molding can be a better option.
What thermoplastic have you got in mind for your product? Got any questions about its compatibility? Visit Kemal’s website or get in touch with us for more assistance!