Features and Selection of Couplings Commonly Used in Servo Systems

 I. Curved-Jaw Coupling (also known as Spider Coupling)

Core Features: Metal jaw hubs +non-metallic blossom-shaped elastic element (e.g., polyurethane).

The elastic element is non-metallic, providing excellent buffering and vibration-damping capabilities, effectively absorbing shock and vibration.

Torsional stiffness is moderate, allowing slight elastic deformation, which results in some loss of transmission accuracy.

Misalignment Compensation: Excels at compensating for radial and angular misalignment, but has limited axial compensation capability.

Typical Applications: Medium-to-high-speed, small-to-medium power transmissions that require vibration damping and buffering, such as stepper motor drives and general machinery.

Advantages: Moderate cost, good damping, simple installation.

Disadvantages: Lower accuracy than all-metal couplings; the non-metallic elastic element is prone to aging under high temperatures or in oily environments.

 II. Diaphragm Coupling

Core Features: Metal hubs + stainless steel metal diaphragms.

The elastic element is metallic, offering zero backlash, high torsional rigidity, and precise transmission of speed and torque.

Exceptional misalignment compensation: Effectively compensates for axial, radial, and angular misalignment while imposing minimal additional loads on bearings.

Damping capacity: Moderate; while it does provide some absorption, it is not as effective as non-metallic elastic elements.

Typical Applications: High-precision, high-speed, heavy-duty applications, or harsh environments involving high temperatures, oil, or corrosion.

Advantages: High accuracy, maintenance-free, high-temperature resistance, long service life.

Disadvantages: Relatively high cost; damping capacity is inferior to that of curved-jaw couplings.

 III. Helical Beam Coupling (also known as Slit Coupling)

Core Features: Machined from a single piece of metal (aluminum alloy or stainless steel) with helical cuts.

High torsional rigidity, zero backlash (no clearance) for good precision.

Misalignment Compensation: Primarily compensates for angular and axial misalignment; has limited radial (parallel) misalignment compensation capability.

Damping: Very poor; almost no buffering effect, functioning as a rigid connection.

Typical Applications: Low-torque, high-precision positioning applications—commonly used to connect encoders, optical scales, and light-load lead screws.

Advantages: Simple structure, compact size, zero backlash, moderate cost.

Disadvantages: Requires high installation concentricity; cannot handle high torque; no damping.

 IV. Bellows Coupling

Core Features: Metal hubs + thin-walled metal bellows (stainless steel).

The highest torsional stiffness among the four types, delivering exceptional transmission accuracy with zero backlash.

Good misalignment compensation: Compensates for axial, radial, and angular misalignment while maintaining uniform velocity transmission (no speed fluctuations).

Damping: Poor; almost no buffering effect, functioning as a rigid connection.

Typical Applications: Ultra-high-precision motion control systems, such as CNC machine tool spindles, precision positioning stages, and high-resolution encoder connections.

Advantages: Top-tier accuracy, excellent rigidity, fast dynamic response, long life.

Disadvantages: Relatively expensive; cannot handle heavy loads; no damping; the bellows section is relatively fragile.

Quick Selection Guide

If you need shock absorption and damping (e.g., high motor vibration) → Choose a Curved-Jaw Coupling.

If you need high precision in harsh environments (high temperature, oil, chemical exposure) → Choose a Diaphragm Coupling.

If you need light-load, high precision in a compact space (e.g., encoder connection) → Choose a Helical Beam Coupling.

If you need the highest precision and rigidity (e.g., CNC machines, positioning stages) → Choose a Bellows Coupling.