Hollow bore motors are a special class of electric motor that have hollow shafts and are also known as hollow shaft and/or through shaft motors. The center portion of the motor is a hole completely through the center axis of the motor which allows various items such as cables, hoses, piping or even lasers to pass through without obstruction. A servo hollow bore motor has all the performance and benefits of classic shaft style servo motors but are mechanically different with the hollow bore.
Hollow Bore / Direct Drive / Frameless Motors
Direct Drive Motor
A direct drive motor is one that directly drives a load without using any speed reduction mechanism such as a belt or reduction gears. Eliminating a speed reducing mechanism enables high speed, excellent response time and eliminates mechanical nonlinearities introduced by gear boxes. Hollow bore motors are often used in rotary positioning applications as a direct drive motor.
A frameless motor consists of a stator and rotor assembly with permanent magnets as found in any brushless motor, but frameless motors do not include a shaft, bearings or end bells. Typically, this type of motor is a hollow bore style and allows for integration into a mechanical system. This type of motor is very analogous to bearing style encoder versus a kit style encoder mechanical design.
Feedback encoders used with hollow bore motors must also have a through bore design as not to introduce obstructions limiting “pass through” attributes of the hollow bore motor design. Posital’s new CCD series of Large Hollow Bore Multiturn Absolute kit encoders are ideal for hollow bore motors.