In the modern industrial system, efficient mixing, conveying and processing of materials are the core links that determine product quality, production efficiency and energy utilization. Especially in the fields of plastic modification, polymer material synthesis, fine chemicals, food processing and pharmaceuticals, the complexity of material handling places strict requirements on equipment performance. Flat Twin Screw technology has become an indispensable key equipment in these fields with its unique structural design and excellent performance.

Background of Flat Twin Screw

Flat Twin Screw technology originated in the 1950s and was originally used for plastic extrusion molding. With the advancement of material science and processing technology, its application areas have gradually expanded to high-value-added fields such as highly filled composite materials, reactive extrusion, and food processing. Compared with single-screw extruders, Flat Twin Screw realizes the decoupling and optimization of material conveying, mixing, plasticizing, and reaction processes through the synergistic effect of twin screws, and shows advantages in processing high-viscosity, heat-sensitive, and easily degradable materials.

Working principle of Flat Twin Screw

The working principle of Flat Twin Screw is based on the rotational motion of the screw and the flow of materials in the screw groove. When the screw rotates, the material is pushed by the screw thread to move along the screw axis. Due to the gap between the screws and the special design of the screw thread, the material will be subjected to shear force, extrusion force and friction force during the movement, achieving mixing, conveying and processing.

In the conveying section, the screw thread design enables the material to be smoothly conveyed from the feed port to the processing area. As the material enters the compression section, the screw groove volume gradually decreases, the material is compressed and plasticized, the temperature and pressure gradually increase, and the viscosity and fluidity of the material change. In the mixing section, the screw thread design becomes more complex, and the material is subjected to strong shear and stirring in the screw groove to achieve full mixing and uniform distribution.

Basic structure and design of Flat Twin Screw

Flat Twin Screw consists of a pair of precision-machined parallel screws and a pair of mutually perpendicular hollow shafts. The surface of the screw is specially designed with a complex thread structure to control the flow and mixing of the material. The design of the hollow shaft reduces the weight of the equipment and also improves the rigidity and stability of the screw, ensuring reliability and durability during high-load operation. The screw thread structure usually includes a conveying section, a compression section and a mixing section. The conveying section is responsible for conveying the material from the feed port to the processing area, the compression section compresses and plasticizes the material through the gradually decreasing screw groove volume, and the mixing section achieves full mixing and uniform distribution of the material through complex screw thread design.

1. Geometric characteristics of parallel twin screw system

Screw configuration: Flat Twin Screw adopts a combination of building block screw elements, including conveying section, compression section, mixing section and special function section. The thread depth, pitch and helix angle of each section can be designed independently to adapt to different material characteristics.
Axial clearance control: The clearance between screws is usually controlled at 0.1-0.5mm, which not only ensures self-cleaning, but also avoids excessive shearing and material degradation.
Hollow shaft design: The interior of the screw adopts a hollow structure, and precise temperature control is achieved through circulating medium.

2. Meshing principle and self-cleaning mechanism

The meshing mode of the twin screw is divided into full meshing and partial meshing. The full meshing design forms a forced material conveying channel through the close cooperation between the screw ridge top and the screw groove of the other screw, which significantly improves the mixing efficiency. Its self-cleaning property comes from the periodic scraping of the other screw groove when the screw rotates, preventing material retention and degradation.

3. Modular design concept

Modern Flat Twin Screw widely adopts modular design, and the screw elements are connected by splines, which can be quickly replaced to adapt to different process requirements.

Efficient mixing mechanism of Flat Twin Screw

1. Shear mixing:

The rotation of the screw causes the material to be subjected to strong shear force in the screw groove, and the relative movement and friction between the material molecules make the material fully mixed. Shear mixing can break the agglomeration and agglomeration of the material and improve the dispersion and uniformity of the material.

2. Convection mixing:

The screw thread design makes the material form a complex flow path in the screw groove, and the material constantly changes direction and speed during the flow process to achieve convection mixing. Convection mixing can promote mutual diffusion and penetration between materials and improve the mixing effect of materials.

3. Diffusion mixing:

In Flat Twin Screw, the diffusion effect between material molecules also plays an important mixing role. The rotation of the screw and the special design of the thread form a high shear and high turbulence environment in the screw groove, which accelerates the diffusion speed between material molecules and improves the mixing effect.

Efficient conveying mechanism of Flat Twin Screw

1. Continuous conveying:

Flat Twin Screw realizes continuous conveying of materials through the rotation of the screw. The material moves axially in the screw groove. The conveying process is stable and reliable, which can meet the needs of continuous production.

2. Quantitative conveying:

The thread design of Flat Twin Screw enables the volume and flow of materials in the screw groove to be precisely controlled, which can achieve quantitative conveying of materials and ensure the stability and consistency of the production process.

3. High-pressure conveying:

In Flat Twin Screw, the material is compressed and plasticized in the compression section, and the temperature and pressure gradually increase. The thread design of the screw enables the material to be smoothly conveyed under high pressure, which is suitable for conveying high-viscosity and high-density materials.

Efficient processing mechanism of Flat Twin Screw

1. Plasticizing processing:

In Flat Twin Screw, the material is compressed and plasticized in the compression section, the temperature and pressure gradually increase, the viscosity and fluidity of the material change, and the material is plasticized. Plasticizing processing can effectively improve the processing performance of the material, improve the processing quality and production efficiency of the material.

2. Reaction processing:

In Flat Twin Screw, the material is subjected to strong shearing and stirring in the mixing section, the interaction and reaction speed between the material molecules are accelerated, and the reaction processing of the material is realized. Reaction processing can effectively promote the chemical reaction between materials and improve the reaction effect and product quality of the material.