Flexible Shaft Couplings

What is Flexible Shaft Coupling?

A flexible shaft coupling is a mechanical component used to connect two rotating shafts while compensating for slight misalignment, vibration, and shaft movement. Unlike rigid couplings, flexible coupling types can handle angular, axial, and parallel misalignment, making them ideal for servo motors, encoders, gearboxes, and other rotating machinery. They are crucial in applications where high precision, damping, and torque transmission are required.

Types of Flexible Coupling

There are several types of coupling designed for different load conditions and alignment requirements. Common flexible coupling types include:

• Oldham Coupling: Known for its ability to handle lateral misalignment. The oldham coupling mechanism uses three disks—two connected to shafts and a flexible plastic central disk—to absorb shaft misalignment. Commonly used in automation and positioning systems.
• Jaw Coupling: A popular motor coupling type that consists of two metal hubs and an elastomer insert (the jaw coupling spider). It offers vibration damping and is available in many jaw coupling types for general industrial use.
• Bellows Coupling: High torsional stiffness and zero backlash make it ideal as a servo coupling or encoder coupling. The metal bellows flex to accommodate misalignment without sacrificing accuracy.
• Disc Coupling / Flexible Disc Coupling: Delivers excellent torque transmission and durability. Often used in precision motion control systems requiring minimal backlash and high torsional rigidity.
• Slit Couplings: Made from a single piece of material with slits, which allows for flexibility and reduces the likelihood of backlash. and the lightweight design contributes to low inertia, which is beneficial in high-speed applications.

Coupling Materials

Selecting the right coupling material ensures optimal performance and longevity. Common options include:

• Aluminium Coupling / Aluminum Alloy: Lightweight and corrosion-resistant, suitable for compact setups and moderate torque.
• Stainless Steel Coupling: Corrosion-resistant and strong—ideal for harsh environments or cleanroom applications.
• Steel: Offers high strength for demanding load conditions.
• Plastic: Used for low-torque, lightweight applications.
• Alloy Materials: Provide a good balance of strength and flexibility.

Each shaft coupling material impacts torque, weight, corrosion resistance, and price—so always check specifications to match your application.

Applications of Flexible Shaft Couplings

Flexible couplings are found in various mechanical and automation systems, including:

• Motor Shaft Coupling: For connecting motors to driven equipment.
• Servo Motor Coupling: Enables precision in servo-driven systems.
• Encoder Coupling: Minimizes backlash in motion feedback systems.
• Motor Gearbox Coupling: Ensures proper torque transfer in gear-motor assemblies.
• Bearing Coupling: Maintains shaft alignment between supported components.

From small-scale electronics to heavy-duty industrial setups, the right flexible coupling helps maintain system integrity and operational stability.

How to Select the Best Coupling

Choosing the best coupling involves more than just matching shaft diameters. Consider the following:

• Torque Requirements: Use a suitable torque coupling that meets load conditions.
• Misalignment Tolerance: Select based on expected angular, parallel, or axial misalignment.
• Speed & Backlash: Critical in servo coupling and encoder coupling applications.
• Environmental Conditions: Heat, moisture, and chemical exposure may influence the choice of stainless coupling, plastic coupling, or rubber coupling types.
• Coupling Size and Length: Ensure compactness without compromising torque.
• Vibration Damping: Use damping coupling or spider coupling to reduce system shock.