Not Every Rotary Stage is the Same – Types to Look out for
Rotary stages are used in high-performance applications such as electronic manufacturing, laser machining, medical, semiconductor equipment, assembly, machine tools, vision systems, photonics, fiber optics, industrial robots, and other similar applications.
Because of such a wide specter of applications, there are multiple types of rotary stage models, each designed to better fit the application for which it is intended.
Therefore, rotary stages are available with different mounting options, table diameters, and size apertures to provide the best solution for every application. There are four main factors to consider when it comes to rotary stages:
- Runout performance
- The wobble
Based on these parameters, there are two main types of rotary stages:
- Bearing types
- Position control methods
Every rotary stage consists of a moving platform that rotates around a base. The base and platform have to be joined by a bearing to limit the movement of the platform.
This bearing is what restricts platform motion to rotation around one axis. Since a number of unique bearings can be utilized, we will mention two bearing types which are both appropriate for different applications.
When it comes to a plain bearing, it’s nothing more than one surface slowly sliding across another surface. With a minimized side-to-side motion, a base needs to allow the platform to rotate freely in a circular motion.
A plain bearing rotary stage can be adjusted manually and is commonly used only for applications such as coarse positioning in a repeatable manner.
There are two main types of rotary stages that involve a rolling-element bearing:
- Crossed roller
- Ball bearing
Depending on the type of bearings, there’s a number of such rotary stages. Common to the rolling-element bearing is the use of two bearings that are loaded beforehand to ensure that there isn’t any looseness, as this could make the platform rise up from the base.
Position control methods
Depending on position control methods, there are five types of rotary stages:
- Manual direct
- Manual worm drive
- Stepper motor with worm drive
- DC motor and encoder with worm drive
- Linear actuator
These are rotary stages that you can operate by hand. Using manual commands, you can simply turn the platform manually, according to the index marks on the platform. These are used to position the platform at a specific angle. Once the platform is set in a position the user needs, a locking mechanism ensures that it stays fixed.
Manual worm drive
A worm drive allows for more precise position control and there’s a manual control knob that controls the rotation of the worm. The wheel cannot be separated from the platform, which allows for a higher precision when rotating the platform relative to its base.
Stepper motor with worm drive
Stepper motor with worm drive is a bit advanced version of a manual worm drive as a stepper motor helps automate the platform positioning process so that the user doesn’t have to adjust things manually.
A stepper motor works based on a number of preset steps that can be adjusted using the appropriate controller. Such rotary stages are mostly used for those high-performance applications that require constant repetition.
DC motor and encoder with worm drive
Similar to manual worm drive and stepper motor, a DC motor can replace a typical control knob operated by hand, and be used to control the stage position instead. A DC motor comes with an encoder that reports the angular position to the motor controller.
Based on that report, the motor controller moves the stage repeatedly and reliably to set the stage in the desired position.
A linear actuator is used when a high level of precision is required. Since it would be extremely difficult to precisely position a rotary stage in an exact angle, a linear actuator, motorized or manual, may be used.
Since angular positioning needs to be precise and accurate, a linear actuator allows for the rotation of 10–20 degrees.
With all this in mind, it’s safe to say that every application has its rotary stage according to the needs and specifications.
Even with this being so, all the aforementioned types of rotary stages are the most commonly used rotary stages across a wide range of industrial applications. These rotary stage types are based on the specification of the job a rotary stage is intended to do.
There are also rotary stage manufacturers specialized in designing high-precision bearings to offer better design and manufacturing capabilities according to the industry needs.