High torque co rotating twin screw extruder

Types of high torque co rotating twin screw extruders

A high-torque co-rotating twin-screw extruder consists of two parallel intermeshing screw elements that are driven by a high-torque motor. The motor provides enough force to turn the screws, pushing and processing the material. The screws work together to increase the force and mix the material efficiently. This type of extruder is designed for effective material processing by providing a strong and thorough motor drive system.

High-torque co-rotating twin-screw extruders are further categorized based on their specific geometrical configurations.

• Full Flighted Screws:

  Full-flighted screws have a uniform flight all around the screw. It has an unbroken thread that runs the length of the flight. This type of screw is used in high-torque co-rotating twin-screw extruders to convey bulk solid materials. The full flight of the thread pushes bulk solid materials down its length. Because of this, full-flighted screws are also often referred to as conveying screws.

• Hollow Flighted Screws:

  Hollow-flighted screws have a flight that consists of a thread with a gap in the thread. The gaps in the threads offer openings for fluids to pass through. This feature allows hollow-flighted screws to have a significant mixing effect. Besides, the opening in this type of screw allows for heating or cooling of the material. Thus, hollow-flighted screws are commonly used in twin-screw extruders for processing materials that require both mixing and temperature adjustment.

• Elements with nipped lands:

  These screw components have narrowed land areas that increase shear forces for mixing materials. They often have a gap for dewatering or venting, which is useful in extrusion operations. Also, the elements can have either a groove or a raised ball, depending on the desired mixing action. Specifically, the raised spheres promote coiling and circular flow within the barrel. Conversely, grooves encourage radial movement from the perimeter to the center. Either method significantly increases the melting and mixing of the materials being extruded.

• Coronan elements:

  Coronas resemble threads in shape, but the rise of the thread is much less than that of normal threads. Coronam elements create a vast open space when the screws rotate. The open space allows free movement of the material, which results in excellent material melting and mixing.

• Intermeshing screws:

  Often found in high-torque co-rotating twin-screw extruders, intermeshing screws are screw designs where the two screws are fitted in such a way that they partially penetrate each other. The design allows for better conveying and mixing of materials, improving melt uniformity. Moreover, the close interaction between the screws promotes efficient thermal transfer, which is essential for materials that are sensitive to heat.

The aforementioned are just a few of the many different screw configurations that can be used in high-torque co-rotating twin-screw extruders. Each screw design has its unique features and specific applications. It is also important to note that variations in screw design can affect material processing, including mixing, conveying, and shearing.

Specifications and maintenance of high torque co-rotating twin screw extruder

Specifications

• Intermeshing control: The rotation of the screws can vary between 2:1 and 3:1, fully intermeshing, or non-uniform, depending on the type of material processed and the desired final product.
• Temperature control: The barrel temperature control system can maintain a temperature up to about 400°F, though some materials, like PVC, can reach around 464°F. Other tricks for controlling the material temperature are water cooling jackets on the outside or air cooling on the inside.
• Torque capacity and motors: For materials with more significant feeding rates and higher viscosities, more enormous feeding rates (up to 8000 kg/h) and more extended, more massive motors with higher torque (up to 90 Nm/kg) or gearboxes are used. For instance, a motor with 80 torque and 18,500 N.m of power may be used for more giant motors, whereas another may have 11,000 N.m of power, more for standard use.
• Diameter: The diameter size ranges between 18-72 mm. In general, larger screw diameters have a longer pitch and at lower speeds. Bigger screws have more extended flights and work at lower speeds. Flights are the areas that carry the material.
• Length-to-diameter ratio: Usually, L/D (Length-to-diameter ratio) varies from 20 to 50. A more extended ratio implies that there is more mixing, and more pressure is built up before the material is extruded.
• Feeding system: It can take up to 28 kg of material per min or 7000 kg per unit time. There are three main molds: circular, which is mostly used for pipe extrusion, flat, used for sheet/matrix extrusion, and strand commonly for pelletizing.

Maintenance

• Cleaning: Regular cleaning of the barrel, screws, and other parts of the extruder is vital to preventing material contamination and ensuring product quality. Thorough cleaning should be performed after each production batch or at fixed intervals according to the manufacturer's recommendations.
• Lubrication: Proper lubrication of moving parts, such as bearings and transmission components, can reduce wear and operating resistance, ensuring smooth operation. Selected lubricants should be suitable for twin-screw extruders and comply with relevant safety standards.
• Wear and tear inspection: Regular inspection of the twin-screw extruder is required to check for signs of wear and damage to critical components, such as screws, barrels, gears, etc. If there is wear or damage, the parts should be repaired or replaced promptly to avoid affecting the machine's performance and stability.
• Temperature and pressure calibration: Regular calibration of temperature and pressure control parameters to ensure the correct functioning of these twin-screw extruder parameters. This helps maintain the stability of the extrusion process and product quality.
• Electrical system maintenance: Keep the electrical portions of the equipment, such as controllers and connectors, to avoid issues with electrical contact and circuit function.
• Follow the manufacturer's guidance: Each model of twin-screw extruder may have its specific maintenance requirements and recommendations. It is essential to follow the manufacturer's directions to ensure proper maintenance and care.

Scenarios of high torque co-rotating twin screw extruder

The high torque co-rotating twin screw extruder has several applications in different industries.

• Food industry: The high torque co-rotating twin screw extruder is used to process a variety of pet foods, such as snacks, food tubes, etc. The extruder can also be used to make textured soy protein, puffed food, starch, etc. The high temperature, high pressure and shearing force generated in the extrusion process can improve the digestion and absorption of animals for food.
• Chemical industry: In the chemical industry, a high torque co-rotating twin screw extruder is often used to melt blend and modify engineering plastics, PVC, rubber, etc., to achieve objectives, such as improving strength, increasing impact resistance, making surface glossy, enhancing the flame-retardant grade, etc. For example, the modifier for ABS plastic is synthesized by a high-torque twin-screw rubber granule extruder with a specific formula. Not only can the productivity be improved, but also the processing quality can be guaranteed.
• Medical industry: In the medical industry, the machine can be used to make capsule lines, etc. It can do well to the mixture of medicines by molecular binding and can improve the release of drugs, thereby enhancing the therapeutic effort of drugs.
• Wood industry: In the wood industry, the machine can be used to process wood-plastic composite materials, wood pulp fibers, etc. The material is fully mixed and melted by the high shear force generated by the twin screw extrusion, which can well combine wood fibers and plastic, thus improving the mechanical properties and durability of the composite materials.
• Other industries: High torque co-rotating twin screw extruders can also be used in other industries, such as the automotive industry, construction industry, and electronic industry, to process a variety of materials.

How to choose high torque co rotating twin screw extruder

High torque twin screw extruders can be used in various applications. They can be chosen based on the following parameters.

• Production capacity

  The main goal when selecting a high-torque extruder is to achieve the desired output. Assess the required production volume and consult with a high-torque screw manufacturer to determine the appropriate size and configuration that can meet capacity without compromising quality.

• Material compatibility

  High-torque twin-screw extruders are versatile and can process different types of materials, such as polymers, elastomers, thermoplastics, PVC, PET, and wood plastic. Each material has unique characteristics and processing requirements, so it is important to ensure that the selected extruder is compatible with the intended material.

• Processes required

  High-torque twin-screw extrusion can carry out various processes, including melting, mixing, reaction, polymerization, granulation, and compounding. The screws' design and configuration may vary depending on the specific process. Therefore, it is important to select an extruder capable of handling the required process efficiently and effectively.

• Operating environment

  High-torque twin-screw extruders can have different degrees of protection against environmental factors. For example, in wet or corrosive environments, extruders with moisture-resistant and anti-corrosion properties should be selected to ensure equipment longevity and reliable operation.

• Energy-efficiency

  High torque twin screw extrusion requires considerable energy input, especially for high-capacity production. Choosing a high-energy efficient motor can significantly reduce energy consumption and operating costs.

High Torque Co-Rotating Twin Screw Extruder Q & A

Q: What are high torque twin screw extruders used for?

A: High torque co-rotating twin screw extruders are often connected to a motor that generates more than normal torque, improving the machine’s ability to process high-viscosity materials. They are commonly used in the chemical, food, and plastic industries.

Q: What is the difference between a twin-screw extruder and a single-screw extruder?

A: A single-screw extruder has a single screw that conveys and heats the material through external heaters. The high-torque twin-screw extruder contains two parallel intermeshing screws that rotate together, allowing for better mixing and melting of materials.

Q: Do twin-screw extruders have advantages over single screws?

A: Yes, the high torque twin-screw extruder offers greater flexibility in processing various materials, better melting and mixing efficiency, improved material conveying, and better mechanical properties to the end products.

Q: Can high-torque twin-screw extruders be used for devolatilization?

A: Yes, they can efficiently remove volatiles from the melt while maintaining excellent material conveying and thermal distribution.