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Choose the Right Coupling for Your Servo System

Download: The entire Flexible Antivibration Coupling product line.

The latest servomotor technologies are found in a wide variety of industries such as medical, automation, robotics, and semiconductor. As demands for higher speed and precision continue, coupling technology must advance to ensure optimum servo system performance.

Considerations When Picking Couplings for Servo Applications:

  • Flexibility - Misalignment Capability
  • Coupling Size
  • Torsional Stiffness
  • Damping Capabilities
  • Zero Backlash

considerations when picking couplings for servo applications

Flexible couplings were specifically designed to solve the problems created by lateral, angular, and axial misalignment in drive systems. Flexible couplings fasten to machine drive shafts in order to transmit torque while accommodating misalignment. Couplings used for a servo system require zero-backlash, flexibility, and torsional rigidity.

In servo applications couplings usually connect high-precision and high-speed drives to sensitive loads. Couplings must have high-torsional stiffness, zero backlash, and misalignment capability, while holding transmitted rpm. A recent improvement in servomotors has increased their speed response frequency, but vibration or hunting occurrences arise when increased gain is present, especially where disc or bellows couplings are used.

Coupling Types

To resolve hunting and maintain peak performance in a servo system a coupling has been developed that provides vibration damping while maintaining torsional rigidity. The Antivibration Flexible Coupling series has a unique construction. Aluminum hubs are molded with vibration reducing rubber (FKM). The resulting rubber lined finger-like structure allows for optimal torsional rigidity and damping.

Structure of Antivibration Flexible Coupling

This unique coupling design provides the solution to higher speed frequencies by absorbing the resulting vibrations while maintaining a high level of accuracy. When compared to disk type couplings the antivibration rubber type repeatedly suppressed hunting and improved servomotor gain while reducing stabilization time. Integrated damping in couplings can dramatically reduce stabilization time resulting in increased machine-axis speed and general productivity.

Coupling Damping Performance Comparision

Improvements in coupling design address vibration occurrences in servo systems. Other benefits are accurate position repeatability, quiet operation, and more compact component size due to high-torque capability.

Stabilization Time, Change in Stabilization Time Due to Gain, and Industry Changes in Servomotor Speed Response Frequency

1. Purpose Testing was conducted to see the relationship between a coupling's Static Torsional Stiffness and positioning repeatability on an actuator.

2. Testing Equipment:

Testing Equipment

3. Method

Testing methodology adheres to JIS B 6192 protocols and the testing equipment used the Anti-vibration type, Disk type and Jaw type couplings where the accuracy of stop position accuracy was measured 7 times.                                                         
The gap of Max. and Min. values was calculated and respective values were compared (See Test results).          
The origin of position is set at both the center and edge for the max range liner stroke. Max value as testing parameter was written in ± with its half value as below:

4. Testing Conditions:
Testing Conditions

5. Testing Result:
Testing Result

6. Conclusion

Static Torsional Stiffness does not gravely impact positioning repeatability on actuators. Sub-micron value variations referenced above are likely due to the precision performance of the actuator.

7. Rubber Durability

Rubber is used as a component to impart damping properties and data on the durability has been accumulated since the advent of anti-vibration couplings in 2007. The graphs below show that even after 100 million drive tests, there is no drop in performance due to rubber deterioration.

Rubber Durability