In modern continuous production lines, steel products often need to be cut while still moving at high speed. This is where the flying shear becomes essential. It allows steel bars, strips, or other rolled products to be cut without stopping the rolling process, maintaining production efficiency and product quality.
What Is a Flying Shear?
A flying shear is a cutting machine designed to shear moving rolled products transversely while they are still in motion. Because the cutting tool moves together with the material during the shearing moment, the machine can perform cutting without interrupting the continuous process.
Flying shears are widely used in continuous rolling mills, but they are also common in other continuous processing lines such as continuous galvanizing lines, tinning lines, and slitting or finishing lines. Their typical functions include:
- Cutting rolled products into fixed lengths
- Cropping the head or tailof the material
- Supporting continuous downstream processing
In high-speed production lines, the performance of the flying shear can even become one of the factors that limits the maximum rolling speed. For this reason, flying shear technology has continuously evolved along with the development of modern rolling mills.
Types of Flying Shears
Flying shears can be classified in several ways depending on their function and mechanical design.
By application:
- Crop Flying Shear– used to remove the head or tail of rolled products
- Fixed-Length Flying Shear– used to cut products into specified lengths
By working principle or structural design:
Common types include:
- Disc Flying Shear
- Drum Flying Shear
- Crank Rotary Lever Flying Shear
- Pendulum Flying Shear
Different designs are selected according to rolling speed, product size, required cutting accuracy, and the overall layout of the production line.
Main Components of a Flying Shear
A typical flying shear system consists of several key subsystems:
- Drive mechanism– provides power and motion to the shear
- Shearing mechanism– performs the actual cutting operation
- Cutting length adjustment system– controls the target product length
- Blade side-clearance adjustment mechanism– ensures proper cutting conditions
Depending on the application, additional auxiliary devices may also be installed, such as:
- Pinch rolls for material feeding
- Straightening devices
- Crop collection or scrap handling equipment
These components help ensure stable operation and improve cutting quality.
Basic Requirements for Flying Shears
The most important feature of a flying shear is its ability to cut material while it is moving. To achieve reliable performance, several basic requirements must be met.
1. Synchronization between the blade and the moving material
During the cutting moment, the shear blade must move in the same direction as the rolled product. The instantaneous velocity of the blade in the rolling direction should be approximately equal to the material speed:
- Ideally: blade speed ≈ material speed
- In practice: blade speed is typically 1–3% higher
If the blade speed is lower than the material speed, the blade will resist the movement of the product, which can cause bending or even entanglement with the blade.
If the blade speed is too high, excessive tensile stress may be generated in the material, reducing cut quality and increasing mechanical impact loads on the machine.
2. Ability to cut different product lengths
A flying shear should be capable of producing multiple fixed lengths on the same machine, depending on product specifications and customer requirements. At the same time, both length accuracy and cutting surface quality must meet relevant technical standards.
3. Compatibility with mill productivity
The shear must operate reliably at speeds that match the production capacity of the rolling mill or processing line, ensuring it does not become a bottleneck in the system.
Operating Modes of Flying Shears
Flying shears generally operate in one of two working modes.
Start-Stop (Intermittent) Mode
In this mode, the shear starts, performs one cut, and then stops at a specific position. The next cut requires the machine to start again.
This working method allows flexible length control and is commonly used in:
- Crop shears
- Lines where the required product length is relatively long
- Lower-speed rolling operations
Continuous Mode
In high-speed rolling lines where products are shorter and cutting frequency is high, the continuous operating mode is often used.
In this mode, the shear shaft and blades rotate continuously, and each cutting action is controlled through synchronization techniques such as:
- Adjusting the shear shaft speed
- Controlling the idle cutting coefficient
- Coordinating with line speed
Continuous operation is particularly suitable for high-speed rolling mills and modern automated production lines.
