Rotary Shears
Analysis of the Application of Rotary Shears in the Steel Coil Cutting Industry and Formulas for Calculating Key Design Parameters
Thanks to their core advantages of high-speed dynamic shearing and precise length cutting, Rotary shears have become essential equipment in the steel sheet cutting industry and are widely used for the cut-to-length processing of hot-rolled sheets, cold-rolled sheets, galvanized sheets, and other types of steel plates. They serve as a crucial link between upstream processes such as rolling, pickling and galvanizing, and downstream finished product processing, directly determining the dimensional accuracy, cross-sectional quality and production line efficiency of the finished steel plates. The following section examines industry application scenarios and core value propositions, whilst addressing the specific requirements of steel plate shearing. It systematically outlines the core design parameters and calculation formulas for Rotary shear mechanisms, providing precise support for technical design and optimization within the industry.
Core Applications of Rotary Shear in the steel sheet cutting industry and used for the cut-to-length processing
Rotary shears must accommodate the processing requirements of steel plates of varying thicknesses, materials and specifications, covering the entire range of shearing scenarios from standard plates to special-purpose steel plates. Their core applications are concentrated in the following areas
Continuous shearing of hot-rolled sheet: Designed to match high-speed continuous production lines The continuous production nature of hot-rolled sheet (thickness 1.2–6 mm, running speed up to 80–100 m/min) requires Rotary shears to perform cut-to-length shearing whilst the steel plate is moving at high speed, without interrupting the production line's rhythm. The Rotary shear must form a speed closed-loop with the cut-to-length feeding mechanism to achieve absolute synchronization between the shear blade and the steel plate at the moment of shearing, thereby preventing plate stretching or cross-sectional skew caused by speed discrepancies. In production lines for hot-rolled sheet metal used in household appliances and automotive components, the Rotary shear mechanism must accommodate flexible switching between different fixed-length settings (1–12 m) to ensure the continuous operational efficiency of the production line and minimize downtime losses
Precision shearing of cold-rolled steel, galvanized steel and stainless steel: meeting stringent surface quality requirements
Cold-rolled steel, galvanized steel (thickness 0.3–6 mm) and stainless steel require extremely high standards of surface flatness and cross-sectional finish, and are widely used in high-end applications such as household appliance panels and automotive body panels. Rotary shear machines must control the blade gap and shearing force during high-speed cutting to prevent issues such as burrs, scratches, zinc coating peeling, roller marks and surface damage, whilst ensuring cutting accuracy of ≤±0.5 mm. For example, in automotive and home applicant galvanized sheet Cut to length lines, Rotary shears must adapt to galvanized sheets of varying strengths. By precisely controlling shearing parameters, they ensure that the cut steel sheets can be used directly for stamping and forming without the need for secondary trimming.
Customized Shearing of Special Steel Sheets: Meeting the Demands of Irregular Shapes and High-Strength Materials Specialty steel sheets such as high-strength steel, wear-resistant steel and stainless-steel present significantly greater shearing challenges due to their high hardness and toughness. Rotary shear machines must be specifically optimized in terms of blade holder strength and shearing force reserve to accommodate the shearing characteristics of different materials. For instance, high-strength steel requires an increase in shearing force of over 30%, whilst stainless steel necessitates optimizations of blade material and cooling systems to prevent blade sticking and chipping during the shearing process. In production lines for special steel plates used in the energy and automotive sectors, Rotary shear mechanisms must deliver customized shearing to meet the demands of irregular shapes, fixed dimensions and frequent specification changes-such as trapezoidal, diamond-shaped and corrugated plates-thereby ensuring both the processing quality and efficiency of these special steel plates.
Core Design Parameters and Calculation Formulas for Rotary Shear (Suitable for Steel Plate Shearing Applications)
The design of a Rotary shear lies in balancing high-speed operation, precise synchronization and shearing stability. Its key parameters must be calculated based on core variables such as steel plate thickness, width, operating speed and material strength. The following outlines the calculation formulas for core design parameters and analyses of their applicable scenarios
Shear Force Calculation: The Core Basis for Ensuring Shearing Capacity Shear force is critical for selecting the Rotary shear mechanism's power system. It must be calculated based on the steel plate's material strength, thickness, width and shearing method (parallel shearing, oblique blade shearing) to ensure the cutting blades can completely sever the steel plate, thereby preventing material jamming and overload.
Formula for parallel-blade shearing force
Applicable to the shearing of medium- and heavy-gauge plates and hot-rolled sheets using parallel blades, where the shearing blades are parallel to the direction of travel of the steel plate and the shearing force is evenly distributed across the entire cross-section:
F=0.8×σb×A
Parameter descriptions:
F: Required shearing force (N);
σb: Tensile strength of the steel plate (MPa); for example, 400–500 MPa for Q235 steel plate and 500–600 MPa for Q345 steel plate;
A: Cross-sectional area of the shear section (mm2), A=b×h;
b: Width of the steel plate (mm);
h: Steel plate thickness (mm);
0.8: Shear force correction factor, accounting for the effects of shear blade wear, shear clearance and plastic deformation of the steel plate, to ensure a safety margin is incorporated into the design.
Formula for parallel-blade shearing force
Applicable to the shearing of medium- and heavy-gauge plates and hot-rolled sheets using parallel blades, where the shearing blades are parallel to the direction of travel of the steel plate and the shearing force is evenly distributed across the entire cross-section:
F=0.8×σb×A
Parameter descriptions:
F: Required shearing force (N);
σb: Tensile strength of the steel plate (MPa); for example, 400–500 MPa for Q235 steel plate and 500–600 MPa for Q345 steel plate;
A: Cross-sectional area of the shear section (mm2), A=b×h;
b: Width of the steel plate (mm);
h: Steel plate thickness (mm);
0.8: Shear force correction factor, accounting for the effects of shear blade wear, shear clearance and plastic deformation of the steel plate, to ensure a safety margin is incorporated into the design.
Formula for Shear Force in Bevel blades Shearing
Applicable to the bevel blades shearing of thin plates and cold-rolled sheets, where the shear blade is set at a certain angle (typically 1–5°) to the direction of travel of the steel plate. The shear force is applied gradually, reducing peak loads and minimizing impact on the equipment:
F=0.6×σb×b×h×sinα
• Parameter descriptions:
◎ Shear blade inclination angle (°); 1–3° for thin sheets and 3–5° for thick sheets. A larger angle results in a lower peak shear force, but slightly reduces the flatness of the cut surface;
◎ 0.6: Correction factor for oblique-blade shearing; as the shear force is distributed, this factor is lower than that for parallel-blade shearing.
Correction formula accounting for shearing speed
When the steel plate running speed is high (＞60 m/min), the inertial forces of the steel plate and the dynamic loads during the shearing process must be taken into account to correct the shearing force:
F (dynamic)=F × (1+0.1×10v)
• Parameter description:
◎ v: Steel plate running speed (m/min);
◎ 0.1×(v/10): Dynamic load correction factor; the higher the speed, the greater the dynamic impact, and the correction factor increases accordingly to ensure the power system meets the requirements of high-speed shearing.
Synchronous Blade Speed Calculation: The Core Prerequisite for Shearing Accuracy
The fundamental requirement of a flying shear is that the blade tip speed must exactly match the strip speed. Any speed difference can cause material stretching, angled shear faces, or length deviations. Therefore, calculating the synchronous speed is decisive for shearing precision.
vblade=vstripvblade=vstrip
Parameter Description:
vbladevblade: Linear speed at the blade tip (m/min)
vstripvstrip: Strip travel speed (m/min)
Core Principle:
At the moment of cutting, the linear speeds of the blade and the strip must be perfectly equal to ensure that the shear plane is perpendicular to the direction of strip travel. This prevents angled cuts and burrs while ensuring accurate cut-to-length dimensions.
Derived Calculation:
Relationship Between Blade Rotational Speed and Synchronous Radius
Given the rotational radius of the blade RR (mm), the blade rotational speed nn (r/min) is calculated as:
n=vstripπ×R×10−3n=π×R×10−3vstrip
Parameter Description:
RR is the distance from the blade rotation center to the blade tip. During design, this distance must be determined based on the mechanism type (e.g., crank type, rocker type) to ensure compatibility between rotational speed and structural strength.
Cut Length and Shear Cycle Calculation: Key to Matching Production Line Rhythm
The cut length is a critical specification for finished strip products. The shear cycle must be synchronized with the strip speed and the required cut length to ensure continuous production and prevent material buildup or tension issues.
Cut Length Formula
L=vstrip×tL=vstrip×t
Parameter Description
LL: Cut length of the strip (m)
tt: Shear cycle time (min), i.e., the time interval between two cuts
Core Principle
The cut length is determined by both the strip speed and the shear cycle. During design, the shear cycle must be derived inversely from the target cut length to ensure that the mechanism rhythm aligns with production line requirements.
Shear Cycle Formula
t=60nsheart=nshear60
Parameter Description
nshearnshear: Number of cuts per minute (cuts/min), i.e., the shearing frequency
Derived Calculation
Matching Shearing Frequency with Cut Length
If the required cut length is LL and the strip speed is vstripvstrip, the shearing frequency must satisfy:
nshear=vstripLnshear=Lvstrip
Example
For a strip speed of 80 m/min and a cut length of 4 m, the shearing frequency is 20 cuts/min. This means 20 cuts must be completed per minute to continuously cut the strip to the specified 4-meter length.
Inertia Torque Calculation: Key to Ensuring Equipment Stability
During high-speed operation of a flying shear, the inertia torque generated by rotating components such as the blade holder and blades causes structural vibration, which can compromise shearing accuracy. Calculating and controlling the inertia torque is essential for stable operation.
M=J×αM=J×α
Parameter Description:
MM: Inertia torque (N·m)
JJ: Moment of inertia of rotating components (kg·m²). This depends on the mass distribution of the blade holder and other components, calculated as J=∑miri2J=∑miri2, where mimi is the mass of each component and riri is its distance from the rotation center.
αα: Angular acceleration (rad/s²), which relates to the acceleration or deceleration time of the blade, calculated as α=Δω/Δtα=Δω/Δt, where ΔωΔω is the change in angular velocity and ΔtΔt is the acceleration or deceleration time.
Optimization Strategies:
Reduce the inertia torque-and thus vibration-by optimizing mass distribution (e.g., concentrating mass closer to the rotation center), shortening acceleration or deceleration times, and refining the motion profile.
Blade Gap Calculation: Key to Achieving Quality Shear Surfaces
The blade gap directly affects the quality of the sheared surface and the formation of burrs. Excessive gaps cause burrs, while insufficient gaps accelerate blade wear. The optimal gap must be calculated based on strip thickness and material.
δ=k×hδ=k×h
Parameter Description
δδ: Blade gap (mm)
hh: Strip thickness (mm)
kk: Gap coefficient, which depends on material type and thickness. Typical values are as follows:
For mild steel and low-alloy steel: k=0.03k=0.03 to 0.050.05 (upper values for greater thickness)
For high-strength steel and stainless steel: k=0.05k=0.05 to 0.080.08 (larger gaps needed for harder materials)
For thin sheets (h≤2h≤2 mm): k=0.02k=0.02 to 0.030.03 (tighter gaps for improved surface quality)
Core Requirement
The blade gap must be adjustable to accommodate variations in actual strip thickness. A gap adjustment mechanism should be incorporated into the design to suit different material specifications.
Shearing Work Calculation: Supplementary Basis for Drive System Selection
Shearing work, the product of shearing force and cutting stroke, represents the energy consumed during the cutting process. It serves as a critical reference for selecting the drive system (electric motor, hydraulic system) to ensure sufficient energy capacity for the shearing action.
W=F×sW=F×s
Parameter Description
WW: Shearing work (J)
FF: Shearing force (N)
ss: Cutting stroke (mm), i.e., the distance the blade travels from initial contact with the strip to complete separation. For parallel blade shearing, ss is approximately equal to the strip thickness hh; for inclined blade shearing, ss is larger.
Derived Application
The drive system's power must meet the work requirements per unit time. The motor power PP (kW) can be calculated as:
P=W×nshear60×ηP=60×ηW×nshear
Where ηη is the transmission efficiency (0.85–0.9 for gear drives; 0.8–0.85 for belt drives). This formula ensures the motor power matches both the shearing frequency and the work per cycle, avoiding undersizing or oversizing.
Integrating Parameters into the Steel Plate Shearing Application Context
The above formulas do not operate in isolation; they must be applied collaboratively within the specific context of steel plate shearing to form a complete design framework
The application of flying shears in steel plate cutting relies on a systematic integration of precise parameter calculation and real-world operational conditions. By applying the formulas described above, manufacturers can achieve full-process precision-from structural design to performance optimization-ensuring efficient, accurate, and stable operation of steel plate shearing lines. With 16 years of deep expertise in steel plate shearing equipment, Shanghai Huoyu Industrial Co., Ltd. continuously evolves its product development to meet modern industry requirements, supporting the sector's transition from basic functionality to advanced operational excellence.
Input Requirements
Define the steel plate thickness hh, width bb, material tensile strength σbσb, strip speed vstripvstrip, and target cut length LL.
01
Core Parameter Calculation
Start by calculating the shearing force FF, then determine the blade gap δδ using the gap formula. Confirm synchronous speed using vblade=vstripvblade=vstrip, followed by calculating the blade rotational speed nn.
02
Rhythm Matching
Using the cut length and shearing frequency formulas, determine the number of cuts per minute nshearnshear and the corresponding shear cycle tt to ensure alignment with production line rhythm.
03
Stability Verification
Compute the inertia torque MM and optimize blade holder mass distribution to minimize vibration. Use the shearing work formula to verify drive system power, ensuring adequate energy reserves.
04
Dynamic Adjustment
For high-speed shearing applications, apply dynamic load correction factors to adjust shearing force and drive system parameters to accommodate dynamic cutting conditions.
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