A Complete Plastic Extrusion Process Guide for U.S. Industrial Manufacturers

EXPLORING THE PLASTIC EXTRUSION PROCESS AND DISCOVERING THE HISTORY, PURPOSE, AND ADVANTAGES OF PLASTIC EXTRUDERS

Plastic products are ubiquitous throughout modern society with the material’s intrinsic characteristics of affordability, lightweight nature, and impressive strength. Plastic extrusion leverages these attributes to transform raw materials into products serving diverse industries, from construction to consumer goods.

Plastic extrusion is a fundamental process in the U.S. industrial manufacturing sector, crucial for shaping various plastic products integral to daily life. The plastic extrusion process involves heating and pressurizing granular plastic material through plastic extrusion machines, more commonly known as extruders, to create continuous profiles, showcasing the efficiency and versatility of plastic fabrication. Alongside plastic injection molding, plastic extrusion is critical to high-volume production, particularly for crafting endless profiles like pipes, tubes, and door profiles.

The plastic manufacturing process originated over a century ago, with plastic extrusion applications continually evolving to meet the diverse needs of various sectors. The enduring appeal of plastic extrusion lies in its ability to deliver precise results with minimal complexity, making it a preferred choice for numerous industrial manufacturing projects. However, like any manufacturing process, plastic extrusion has limitations, including challenges such as material waste, energy consumption, and design complexity, necessitating careful consideration and optimization.

What is Plastic Extrusion?

Plastic extrusion is a manufacturing process essential for creating various plastic objects with fixed cross-sectional profiles. This process utilizes specialized equipment, including a rotating screw and a heated barrel, to melt and shape polymer materials enriched with desired additives. The raw material, usually in the form of granulates, is fed into a hopper and then conveyed through the barrel by the rotating screw. As the plastic progresses through the barrel, it undergoes compression, heating, and mixing, facilitated by the screw’s design and gradually increasing temperature zones controlled by proportional–integral–derivative (PID) controllers.

Compressive force and shear friction generate additional heat, ensuring thorough mixing and homogenizing of the plastic melt. The molten plastic material is then passed through a screen pack, supported by a breaker plate, to filter contaminants and remove any rotational memory of the material. The filtered melt is then forced through a die, which imparts the final profile and shape to the extruded product. Upon exiting the extruder, the newly formed extrudate goes through a cooling process, which varies depending on the product’s specific profile and shape.

Tracing the History of Plastic Extrusion

Plastic extrusion dates back to the 18th and 19th centuries, marked by notable inventions and advancements that have shaped the industry into what it is today.

Early Innovations in Extrusion

The origins of extrusion can be traced back to the 18th century when Joseph Bramah invented the manual piston extruder to produce seamless lead pipes. Bramah’s invention laid the foundation for subsequent developments in extrusion technology. In the early 19th century, John Smeaton and Richard Brooman made significant contributions, with Smeaton patenting a twin-screw extrusion machine and Brooman modifying an extrusion machine to coat copper wires with Gutta Percha.

The Evolution of Plastic Extrusion

The modern plastic extrusion industry gained momentum in the 20th century, with advancements such as the first successful thermoplastic extrusion process performed by Paul Troester and his wife Ashley Gershoff in 1935. This breakthrough was followed by Roberto Colombo of Italy’s newly designed twin-screw extruders, further enhancing the efficiency and precision of plastic extrusion processes.

The Various Plastic Extrusion Processes

Plastic extrusion encompasses various processes tailored to meet the demands of shaping plastic materials. Understanding the purpose of each extrusion process is crucial for selecting the most appropriate method.

Tubing Extrusion

Tubing extrusion produces long tubes, pipes, and similar items. This plastic extrusion process involves the application of positive internal pressure to handle hollow parts efficiently. The material passes through the die, where air pressure may also be applied, before being pulled into a cooling tank for water cooling.

Blow Film Extrusion

Blow film extrusion is a standard plastic extrusion process for creating plastic films. The material is cooled before leaving the die, resulting in a semi-solid tube that is subsequently blown to expand to the desired size and film thickness. This plastic extrusion process is limited to thinner plastic films, with thicker sheets requiring alternative methods.

Sheet Film Extrusion

Sheet film extrusion is similar to blow film extrusion but is for thicker workpieces that cannot be blown. The material goes through a pulling and rolling process to achieve the desired shape and thickness. Cooling and permanent solidification are facilitated during the rolling process, making it suitable for producing ice cream boxes and juice cartons.

Over Jacket Extrusion

Over jacket extrusion is ideal for applications such as wire coating, where a plastic cover is applied to materials. This plastic extrusion process involves pulling the material through the die with pressure or jacketing tooling, depending on the desired level of adhesion between the plastic and the material.

Understanding the Types of Plastic Extruders

Investing in a plastic extruder requires careful consideration of various factors, including the type of extruder best suited for production needs. Two primary options available in the market are single-screw extruders and twin-screw extruders. Both types of extruders offer distinct advantages and capabilities that can significantly impact production speed, mixing capability, and operational flexibility.

Single-Screw Extruders

Single-screw extruders are characterized by their simple design, featuring a single rotating screw within the barrel. These extruders are well-suited for applications requiring straightforward profiles, such as pipes and sheets. While single-screw extruders effectively perform their intended tasks, they are relatively slower in operation and may not offer optimal mixing capabilities. Additionally, their suitability for complex shapes is limited compared to twin-screw extruders.

Twin Screw Extruders

Twin-screw extruders feature parallel screws within the barrel, offering enhanced stability and performance. Depending on applications, the twin screws can rotate in the same direction or in different directions. This design characteristic enables twin-screw extruders to deliver superior exhaust performance, increased speed, and improved mixing capabilities compared to single-screw extruders. The versatility of twin-screw extruders makes them suitable for various applications requiring complex shapes and precise mixing.

Material Options for Plastic Extrusion

Choosing the right material is crucial for achieving desired results in plastic extrusion projects, as different materials offer unique properties and applications. A variety of materials are available for extruders to produce a diverse range of products for cars, computers, refrigerators, televisions, and more.

ABS (Acrylonitrile Butadiene Styrene)

ABS is prized for its toughness, waterproof surface, and glossy appearance, making it suitable for diverse applications requiring durability and aesthetics.

Acrylic

With excellent light transmission and weather-ability, acrylic is often used as a versatile alternative to glass, offering strength, clarity, and the ability to undergo tinting, diffusion, and frosting.

PVC (Polyvinyl Chloride)

PVC is a widely used plastic polymer in both rigid and flexible forms. Rigid PVC offers impact resistance and UV stability, making it ideal for applications like pipes and custom plastic profiles. Flexible PVC, on the other hand, provides versatility and tear resistance at a lower cost.

CPVC (Chlorinated Polyvinyl Chloride)

CPVC offers a high balance of stiffness, high-temperature performance, and impact resistance, making it suitable for flame performance and durability applications.

Polypropylene

Known for its stability over various temperatures, mineral-filled polypropylene is ideal for thermal resistance and durability applications.

Polycarbonate

Polycarbonate offers a good balance of stiffness, abrasion resistance, impact resistance, and temperature performance, making it suitable for various applications.

Styrene

Styrene balances toughness, colorability, strength, and stiffness, making it suitable for applications where these properties are crucial.

TPA (Thermoplastic Alloy)

TPA is ideal for weatherstrips, gaskets, and other items requiring compression set, low-temperature stability, and elongation.

Polyethylene

Polyethylene balances strength, colorability, and low-temperature performance, making it suitable for various applications.

TPV (Thermoplastic Vulcanizate)

TPV offers excellent tear resistance, weather-ability, low-temperature flexibility, and tensile strength, making it suitable for diverse applications.

The Advantages and Disadvantages of Plastic Extrusion

Plastic extrusion offers several advantages, including the ability to manufacture products in high volume, efficiently and continuously. The process enables the production of a diverse range of plastic objects, from pipes and tubes to door profiles, with precise control over their dimensions and properties.

Additionally, the versatility of plastic extrusion makes it suitable for various industrial applications where continuous profiles are required. However, plastic extrusion presents challenges like any industrial manufacturing process, such as careful temperature control to ensure product quality and energy consumption.

Energy-Efficient Solutions for Plastic Extrusion Processes

The energy consumption of plastic extrusion primarily stems from driving the extrusion screw and heating, with shear heating along the barrel generating much of the required heat. Efficient operation involves selecting appropriate equipment and optimizing speed and temperature control. Retrofitting with servo motors and incorporating smart technology can enhance efficiency, while upgrades to the extruder drive alone can yield significant energy savings.

Extruding is an energy-intensive process, so optimizing the time it needs to run is the most effective method of reducing the electrical requirement. Behavioral strategies about machine scheduling will reduce machine idle time. On average, about 10 percent of industrial injection molding machines’ energy consumption is used for non-productive loads. The next most effective energy solution is mitigating the heat losses of the barrels so that much of the heat generated is being used to heat the product rather than the area around the facility.

Energy-efficient consultants focus on optimizing each production step and ancillary systems like cooling towers and compressed air, with considerations during the design phase leading to rapid payback on additional costs. Minimizing energy demand and optimizing supply for utilities such as cooling water and compressed air contribute to energy efficiency in plastic extrusion processes.

Contact APenergy, the Energy Efficiency Experts of Plastic Extrusion, Today

APenergy has over 35 years of experience working with industrial plastics manufacturers to identify areas of inefficiency and make data-driven decisions to reduce energy consumption and costs. By utilizing utility incentives and rebate programs for plastic extruders, including insulation jackets, VSDs, VFDs, and other practical energy-saving solutions, APenergy guides manufacturers toward energy efficiency.

The APenergy team helps companies set energy-saving goals through our incentive management service, track progress, and achieve favorable ROIs. Our expert team is ready to assist companies with energy-efficient solutions. For more information, contact the APenergy team, the leading energy efficiency consultants, at 740-862-4112 or message us.