How to select a suitable hollow rotary actuator?

1.Basic introduction of hollow rotary actuator

A hollow rotary actuator is a specialized type of rotary actuator that features a central opening or hollow shaft, allowing for the passage of wiring, piping, or other components through the center of the rotating component. This design simplifies the integration of the actuator into equipment by reducing the complexity of routing cables and tubes. They are used in a wide range of applications, including robotics, automation, testing equipment, and more. 

2.Working principle of hollow rotary actuator

1.Energy Input: The actuator receives energy, usually electrical, hydraulic, or pneumatic, to initiate motion. 

2.Torque Generation: This energy is converted into rotational torque by the motor.

3.Speed Reduction & Torque Amplification: A gear reducer (often a harmonic drive) slows down the motor's speed but increases the output torque.

4.Hollow Shaft Rotation: The reduced and amplified torque is then used to rotate the hollow shaft.

5.Position Feedback & Control: Encoders, sensors, and feedback systems monitor the actuator's position and speed, ensuring precise control and repeatability.

6.Integration: The actuator is then integrated into a larger system, such as a robot joint or a positioning table, to perform specific tasks.      

3.Main advantages of hollow rotary actuator

1.Simplified Wiring and Piping:The hollow center allows for the passage of cables, pneumatic lines, and even optical fibers through the actuator.This eliminates the need for external routing, reducing clutter and potential interference.Equipment can be designed with a smaller footprint due to the reduced need for space around the actuator for wiring and piping. 

2.Reduced Assembly Time and Parts Count:The hollow flange design allows for direct mounting of loads, eliminating the need for couplings or other connecting parts. This reduces the number of components, simplifying assembly and reducing the potential for errors. Reduced parts count also translates to lower costs and less maintenance. 

3.Enhanced Precision and Stability:By eliminating the need for external couplings and transmission mechanisms, hollow rotary actuators minimize the impact of component rigidity and assembly errors on accuracy.This leads to more precise and repeatable positioning. 

4.Compact and Lightweight Design:The integrated design, with the motor and hollow output table, results in a more compact unit compared to traditional designs using separate components.This is especially beneficial in applications where space is limited. 

5.Increased Flexibility and Design Options:The hollow center provides flexibility in how the actuator is integrated into the overall system. For example, equipment tables or arms can be mounted directly onto the hollow output table, simplifying the design and reducing the need for custom mounting solutions. 

6.Improved Rigidity and Load Capacity:Some hollow rotary actuators, like the DGII series from Oriental Motor, utilize cross-roller bearings for high rigidity and load capacity.This allows for handling of heavier loads and withstanding higher moment loads.    

4.Selection tips for hollow rotary actuators

1.Load and speed evaluation: The maximum load capacity of the platform and the required speed range must be clearly defined. Load calculations must include static and dynamic loads to ensure platform stability; the speed must match the working requirements of the equipment. Too low speed may lead to insufficient efficiency, and too high speed may affect accuracy. ‌

2.Accuracy and rigidity requirements: Determine the accuracy requirements (micrometer level or angle level) according to the application scenario (such as processing, measurement, etc.), and give priority to high-rigidity design to reduce deformation. It should be noted that the larger the model, the greater the allowable inertia moment load, but the smaller the displacement. ‌

3.Installation and space adaptation: It is necessary to select horizontal, vertical or side installation methods in combination with the equipment layout, and reserve maintenance space. The hollow design facilitates pipeline layout, but it must match the internal space requirements.

4.Safety factor and verification: When calculating, a safety factor of more than 1.5 times should be reserved, and parameters such as bearing friction and backlash should be verified. After selection, an operation test should be carried out to ensure that the direction and speed are stable and reliable.

5.Drive matching and maintenance: Match the motor power and control method (such as stepper/servo), and choose low-maintenance products to reduce downtime. The status of key components such as bearings and gear sets should be checked regularly.