The Extruder Gearbox: the Key to Driving Twin Screw Extruder Performance

With the continuous maturation and development of twin-screw extruders, how to select and assess the performance of extruders has always been a concern for users. What kind of twin-screw extruder is with higher performance?

Twin-screw Extruders Characteristics

Generally speaking, high-performance equipment mainly features 3 characteristics:

High quality:

Quality is the most valued aspect by users. The product quality of extruders represents a commitment to customers and is vital for the life and development of a business. Thus, the ability to consistently ensure uniformity across different batches of products is an important indicator for assessing the quality of an extruder.

High efficiency:

Efficiency is a further assessment criterion. On the basis of ensuring quality, maximizing the product yield per unit time is every company’s goal and an essential route for rapid development. High-speed and high-efficiency extruders are one of the main directions in the current extrusion technology development.

High torque:

Torque is the sole standard for measuring all rotational capabilities. A higher torque indicates better equipment performance. The introduction of torque in twin-screw equipment also serves to characterize its performance. Since both screws rotate simultaneously in a twin-screw system, torque is evenly distributed between them. Hence, the concept of specific torque (torque level) was introduced, defined as the equipment’s torque divided by the cubic of the center distance A (cm). A higher specific torque means that the twin-screw can bear greater power, resulting in higher output.

For a twin-screw extruder, its main components are divided into extrusion and transmission parts. The transmission part provides torque for the screws; strong torque output is a guarantee for the efficient operation of the twin-screw extruder. The extrusion part mainly consists of the barrel, screw elements, and the core shaft, where polymer materials complete plasticization, mixing, and extrusion, which is key to ensuring quality. All technological advancements in twin-screw extruders are concentrated in these two parts, forming the hallmark of updates and upgrades for twin-screw extruders.

Granuwel Twin Screw Extruder >>

Compared to other models, a significant feature of twin-screw extruders is the difference in their transmission systems. Twin-screw extruders require power to be evenly distributed to two screws within a confined space, which is the essence of torque distribution technology. Different torque distribution technologies determine the load-bearing capacity of the gearbox and can directly affect the lifespan and performance of the entire machine

Twin Screw Extruder Gearbox Structures

The transmission part (gearbox) has two representative typical structures: the traditional parallel three-shaft transmission structure and the bilateral symmetrical gear transmission structure:

1) The traditional parallel three-shaft transmission structure is a mature twin-screw extruder transmission technology, widely adopted by domestic and international twin-screw extruder gearboxes. It can be divided into standard torque type and high torque type.

Figure 1 Schematic diagram of the parallel three-shaft standard torque principle

Figure 2 Schematic diagram of the parallel three-shaft high torque principle

Figure 1 shows the schematic diagram of the parallel three-shaft standard torque type. Power is transmitted parallel to two output shafts, with output shaft A bearing 50% of the torque; output shaft B also bears 50% of the torque. However, due to the limitation of center distance size, the gear size on shaft B is relatively small, limiting the output torque and making shaft B the weak point in the gearbox, restricting the output torque of this transmission structure.

To increase the torque on shaft B, an improved structure designs two sets of gear transmissions on shaft B (as shown in Figure 2), reducing the torque carried by each set of gears from the original single set’s 50% to 25%, thus doubling the total gear output torque compared to single gear transmission, achieving high torque output.

2) Bilateral symmetrical gear transmission structure

Figure 3 Schematic diagram of the bilateral symmetrical gear transmission structure

Figure 3 shows the schematic diagram of the bilateral symmetrical gear transmission structure. In this structure, output shaft A has sufficient size space, strength, and a large safety factor for rigidity, similar to the previous structure. Output shaft B also faces size limitations due to the center distance restriction. The solution for this structure is to divide the power into upper and lower sets of gears, driving shaft B symmetrically from both directions. This not only halves the load at the meshing points of the upper and lower gears, enhancing the torque load capacity, but also significantly increases the feeding amount, effectively improving production efficiency, and extends service life.

Benefits of Twin Screw Extruder Gearbox

The application of this transmission structure has the following significant implications for the progress of extrusion technology:

1) It provides stable and reliable power for the extrusion system, ensuring reliable power support for stable extrusion；

2) With higher torque output, it enables higher feeding amounts and increases the effective length of the screws, achieving more uniform distribution and dispersion mixing.

Nanjing Granuwel Machinery Co., Ltd. specializes in the research, design, and manufacturing of polymer extruders, focusing on the manufacturing and sales of high-quality extruder equipment. Our independently developed and produced twin-screw gearbox, with the following advantages, has become the preferred choice in the industry:

1. High torque output: By adopting an innovative bilateral symmetrical gear transmission structure, it significantly reduces the load at the meshing points of the upper and lower gears, thereby doubling the feeding amount and greatly enhancing production efficiency.

2. Stable and reliable: It provides continuous and stable power support for the extrusion system, ensuring the continuity and stability of the production process.

3. High efficiency: By increasing torque output, it not only achieves higher feeding amounts but also extends the effective working length of the screws, optimizing material distribution and mixing processes.

4. Long lifespan: Using high-quality materials combined with advanced manufacturing techniques ensures a longer service life for the gearbox.

5. Easy maintenance: The design is simple, facilitating quick disassembly and installation, simplifying routine maintenance and care for users.

6. Energy-saving and environmentally friendly: While pursuing high performance, it focuses on reducing energy consumption and noise, creating a comfortable work environment for users.

In summary, Nanjing Granuwel Machinery Co., Ltd.’s twin-screw gearbox combines numerous advantages such as high performance, stability and reliability, high efficiency, long lifespan, ease of maintenance, and energy conservation and environmental protection, making it your ideal choice.