Engineering Notes by Oriental Motor

Flexible Configurations For Hollow Rotary Actuators

[fa icon="calendar"] Originally posted on May 21, 2020 11:30:00 AM
Last updated on May 21, 2020 / by Johann Tang

Johann Tang

Hollow rotary actuators are useful in motor applications such as rotary index tables where the electrical cables or piping can fit through the center hollow bore of the actuator.  Furthermore, mechanical parts, such as belt and pulleys, are eliminated by the hollow ring gear to minimize footprint.

Here's a video of an articulated robotic arm assembly being rotated by the hollow rotary actuator.


Product Design & Benefits


Hollow rotary actuator internal structure


The DGII (DG2) Series hollow rotary actuator uses an AZ Series absolute stepper motor to drive a hollow output table attached to a hollow ring gear.  The hollow bore diameter can be as big as 100 mm to fit necessary cabling and/or piping.  The cross-roller bearings can support a high amount of thrust, radial and moment loads for its size while ensuring accuracy and durability.  The built-in battery-less mechanical absolute encoder eliminates external home and limit sensors.  2 reduction ratio options are offered at 18:1 and 36:1 to eliminate additional belt and pulleys. 

DG2 Series hollow rotary actuator eliminates mechanical parts

Flexible Configurations

Multiple configurations offer more flexibility in installation of these hollow rotary actuators.  Two examples are shown below.


Horizontal mount type and vertical mount type hollow rotary actuators


Vertical Motor Mount Type

Hollow rotary actuator - vertical motor mount

The original design of the DG and DG2 Series hollow rotary actuators only offered a vertical mount type as shown above (on the right side).  The motor's pinion shaft faces upward.

Although this was ideal for customers who were looking for a lower height profile hollow rotary actuator, extra work was necessary to cut a hole in the mounting plate or table for the motor to fit through.  Who wants to do extra work?


Horizontal Motor Mount Type

Hollow rotary actuator - horizontal motor mount

Recently, a newer horizontal motor mount type hollow rotary actuator was released.  With the motor's pinion shaft now facing sideways, a motor clearance hole is no longer necessary. 

There are two configurations for cable outlet direction: left or right.


Horizontal motor mount type hollow rotary actuator cable output directions


3rd Option: Vertical Motor Mount Type with Installation Pedestal

With an installation pedestal (additional accessory) machining of a motor clearance hole in the installation plate is eliminated.  However, the height profile is increased.

Pedestal Pedestal with hollow rotary actuator


Pedestal, pedestal with DG2 hollow rotary actuator


The horizontal motor mount type is ideal for users who want the easiest and cost-effective mounting configuration.  The height profile is reduced to 73 mm.

The vertical motor mount type is ideal for users who want the lowest height profile (35.5 mm) from the installation plate.  However, a hole needs to be cut in the plate for the motor.

The vertical motor mount type can also be used with an installation pedestal, which eliminates the need to cut a hole in the plate.  However, the height profile increases to 107.5 mm.

Flexible configurations of hollow rotary actuators

For more information about the DGII (DG2) Series hollow rotary actuators, including lineup, features, accessories and downloads, please click below.

DGII (DG2) Series Lineup

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Topics: Stepper Motors, Robotics, Absolute Positioning, Alphastep Hybrid Control, Linear & Rotary Actuators, Gearheads, Rotary/Index Tables

Johann Tang

Written by Johann Tang

Johann Tang is a Product Specialist at Oriental Motor USA Corp. Before joining the marketing team, he spent 15 years in sales, technical application support, and training of various types of fractional horsepower electric motors, gear motors, actuators, drivers, and controllers. If you have any questions, please feel free to use the live chat window, 1-800-GO-VEXTA (1-800-468-3982), or, to reach our product support team. Johann can be reached via LinkedIn. Sorry, comments have been turned off.

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