A servo indexing table is a rotary indexing table with a servo motor driving for programmable motion. Indexing tables are designed for repetitively positioning of workpieces for further machining processes with precision, such as drilling and milling. A servo motor, incorporated with a servo drive, is responsible for the motion control. Servo indexing tables are also known as servo rotary indexers. They are versatile devices that are utilized in manufacturing, inspection, and assembly tasks.
The most distinct difference between servo indexing tables and other types of rotary tables is the use of servo motors and rotary indexing. A servo motor receives the command signal and drives the indexing table rotating to the exact points with high accuracy. The angles and the indexed position can be set freely depending on the exact needs.
Generally, the command signal conveys the target velocity or represents a preferred torque or position. After receiving the signal from the control system, the servo drive along with the encoder can amplify the signal and convey electric current to the servo motor. The servo motor drives the indexing table to perform motion proportional to the signal. The drive keeps adjusting for high-precision motion control.
The essential parts of servo indexing tables include the parts feeder, the stationary head, the indexing tables, the work carriers, and the servo motors. The indexing table and the servo motor are of the most primary components.
The servo indexing table consists of the bearing, the index plate, the feed pawl, the accessory pin, and the center stud. The standard index plate can be set to index 90 degrees (4 index), 60 degrees (6 index), 45 degrees (8 index), 30 degrees (12 index), or 15 degrees (24 index). A standard index plate has 24 teeth. There are baffles to prevent engaging improper teeth when indexing the degrees of lower than 15 is required.
The center stud has the top plate and index plate rigidly pinned to it supported by the top bearing of the servo indexing table. There is a feed pawl to which the hardened pawl stops against a pin to prevent forward rotary motions. Since the working parts of the table are completely enclosed, the accessory pin is required to actuate a valve or micro-switch for secondary operations when the table is at the new indexed position.
The servo motor receives amplified signals from the servo drive and runs the rotary indexers. A sensor connects to a servo motor, indicating the status of the motor, and reports back to the servo drive. Ideally, the servo motor rotates at a velocity that is immensely close to the velocity signal received by the drive from the control system. Deviations may take place during the process. As the drive detects the status of the motor, it compares the status with the command signal so that the drive can regulate and correct the deviation by changing the voltage, frequency, and pulse width to the motor.
To achieve the desired performance, parameters including stiffness (also called proportional gain), damping (derivative gain), and feedback gain can be corrected by the servo drive. Performance tuning refers to the process of adjusting these parameters. Most servo motor models require a mating drive of a particular model to function, while there are also drives that are compatible with multiple motor models.
Manipulators utilize servo rotary indexers in many applications especially for manufacturing, inspection, and assembly tasks. The optimal design is greatly suitable for bottling, assembly, testing, and machining including welding, grinding, drilling and milling. For repetitive and successive machining and assembly tasks, the servo indexing table usually takes individual pieces around in operation or moves a high volume of small pieces around stations.
A servo rotary indexer is just one component of the system when setting a custom manufacturing or machining system. The entire scope of the production is essential when choosing the indexers. Servo indexing tables provide high precision positioning with no backlash or wobbling. The incorporation of the servo drive and servo motor not only enables the table to index with precision but also allows the status meets the command signal to ensure a permanent outstanding sequential performance.
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