There are many types of rotary tables in the market, such as the stepper motor rotary table, all of which essentially work positioning devices widely used in metalworking applications. It allows work to be cut or drilled at identical intervals around a fixed axis (normally horizontal or vertical). Some of the key advantages of a rotary table include the repeatability, short time of indexing, flexible indexing positions, as well as the tolerability of exceptionally high axial and radial torques during rotation and stopping.
Systems based on rotary table are generally very durable, and will not require a repair until a longer period of time. Depending on the applications, the rotary table may be complemented with an internal or external clamp. In this article, we’ll specifically address the stepper motor rotary table.
Following the above, a stepper motor rotary table is basically a motorized rotary table driven by a step motor instead of a servo motor. Stepper motor rotary tables are available in many different table diameters, size apertures, mounting options and motor choices, and are a great solution for many industrial automation applications.
Stepper motor rotary tables are mostly used alongside industrial robots, fiber optics and photonics, vision systems, machine tools, assembly, semiconductor equipment, medical component laser machining, electronic manufacturing and other high performance motion control applications.
Rotary tables are frequently coupled with servo motors. Now you may be wondering why and when a stepper motor would be preferred over a servo driven rotary table. In the rest of this article, we are going to touch base on the basics of what it means for something to be driven by a stepper motor, and how it is different from a servo motor.
A step motor is designed with windings in the stator and magnets connected to the rotor. As the name implies, a stepper motor is based on a motion increment mechanism referred to as “steps”. These steps are typically indicated in degrees. When installed on a rotary table, the stepper motor and the stepper drive rotate in pre-set angles proportional to the stepper pulses. A typical rotary table equipped with stepper motor can achieve 200 steps for every revolution, which is equivalent to approximately 1.8 degrees per full step.
That said, the stepper system of a rotary table consists of two complementary components: the stepper motor and stepper drive. The stepper drive works alongside the step motor to enable rotations of rotary table in pre-defined angles. Some common types of stepper drive include:
● Microstep Drivers: This type of stepper driver powers the step motor winding to generate torque. The step motor coupled with the driver is positioned at smaller increments among full steps, offering higher resolution with less torque. Although this system does not guarantee accuracy, the motor does run with relatively less noise. This driver is typically used when the motor’s resolution needs to be increased.
● Drivers with Oscillators: An oscillator is utilized to generate pulses to power a stepper motor at a pre-defined speed. They can generally be retrofitted onto the hardware construction of a microstepper drive.
● Full or Half Step Drivers: This type of stepper drivers, as the name already suggests, enable both full step mode and half step mode, which run at 1.8 degree per full step and 0.9 degree per full step, respectively.
Choosing the right motor for your rotary table is important to ensure good productivity and efficiency of your motion control application. And choosing between a stepper motor and a servo motor is certainly not an easy task as you have to take many factors into consideration such as the cost, efficiency, torque, speed, circuitry and so on.
With that said, the main difference between a stepper motor and a servo motor lies in the total pole count. Servo motors have a low pole count which amounts to about 4 to 12, whereas stepper motors have relatively higher pole count, ranging between 50 and 100. The pole count is directly associated with the motion increment of the motor, and the difference in these pole counts indicate that stepper motors move incrementally in a closed loop system with consistent pulse. Servo motors on the other hand need an encoder to adjust pulses to control positions.
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