Servo Motor FAQs
Expert insights into servo motors, encoder alignment, preventive maintenance, and more.
Maintenance and Repair
How do I diagnose why my servo motor isn’t working?
When a servo motor stops working, the first step is to determine whether the problem lies in the motor itself, the feedback device, the drive, or the motor/drive wiring. Visual inspection, electrical testing, and feedback verification help isolate the issue quickly.Additional Resources:
- The Quick Reference Guide to Servo Motor Maintenance and Repair
- 8 Tips for Troubleshooting Servo Motor Problems
What are the common servo issues?
The most common servo motor issues include feedback device failures, winding shorts or opens, insulation breakdown, brake malfunctions, motor bearing wear, cable damage, and overheating.Additional Resources:
- The Quick Reference Guide to Servo Motor Maintenance and Repair
Is the issue electrical or mechanical?
Servo motor issues can be electrical, mechanical, or a combination of both. Our tester and procedures help rule out all of the complicated electrical possibilities.Additional Resources:
- The Quick Reference Guide to Servo Motor Maintenance and Repair
- Diagnosing Servo Motor Issues: Electrical or Mechanical?
What tools do I need on site?
To diagnose a servo motor on site, you would need wrenches and screwdrivers with a variety of bits or adapters, the Mitchell Electronics TI-5000JX, TI-5260-PSP, and possibly a spare 24VDC supply for unlocking a brake.Additional Resources:
- How You Can Perform Servo Motor Repairs In-House
- 7 Requirements for an In-House Servo Motor Repair Environment
- Advantages of a Servo Motor Tester that Can Read Multiple Serial Protocols
- The Quick Reference Guide to Servo Motor Maintenance and Repair
Should I fix in-house or send out for repair?
With proper training and tools, servo motor repairs are generally simple and straightforward. Whether you perform servo motor repairs in-house or outsource them to the experts, there are steps that could be taken to make the process as quick and cost-effective as possible.Additional Resources:
- The Quick Reference Guide to Servo Motor Maintenance and Repair
- 5 Mistakes to Avoid with Servo Motor Maintenance and Repair
- Common Problems When Attempting Servo Motor Repairs Without the Proper Tools
- How You Can Perform Servo Motor Repairs In-House
What tests do I need to run?
You should run servo motor tests that confirm the feedback device is working and aligned correctly, that the motor lockups are balanced along with the winding resistances, and that the brake (if present) operates correctly.Attempting to identify other issues with the machine in general could include swapping out servo motors, drive components, and/or cabling to try to identify the issue.
Additional Resources:
- The Quick Reference Guide to Servo Motor Maintenance and Repair
- VIDEO SERIES: 9-Step Guide to Servo Motor Testing
How much does it cost to send a servo out for repair?
Service could cost anywhere from several hundred to several thousand dollars depending on the issues. Then you must factor in physically shipping the motor to the repair shop.How often should I perform maintenance on my servo motors?
You can track motor usage in the drive and have the motor serviced when wearable parts like bearings are at their rated usage limits. You might have preventative maintenance schedules that are more regular or scheduled with routine machine maintenance. You can make sure to always have a spare motor in working condition.Additional Resources:
- The Quick Reference Guide to Servo Motor Maintenance and Repair
- The Manufacturer’s Preventive Maintenance Checklist
- VIDEO: Why Manufacturers Need to Prioritize Servo Encoder Testing
Technical Issues
How do I align the encoder?
Encoder alignment depends on the motor manufacturer and feedback technology being used. Many encoders require precise mechanical positioning relative to the motor shaft, while others must also be electronically aligned.Using the proper alignment procedure and dedicated test equipment helps ensure the encoder is installed and calibrated correctly before the motor is returned to service.
Additional Resources:
- Encoder Alignment Made Simple
- VIDEO: How to Align an Encoder with TI-5000EX
- VIDEO: Testing the Encoder on a Servomotor
How do I decrypt encoder memory?
With the help of the Mitchell Electronics TI-5000JX system, this is possible for various supported motor brands by using the Memory Test function in Athena. In case a motor is not listed under the supported brands, it will be best to contact the support team for further details.Additional Resources:
- VIDEO: Decrypting Memory Data into Human-Readable Format
How do I test actuator motors?
Actuator motors are often just regular rotational servo motors with a ball screw adapter to create linear motion. They can be tested, aligned, and repaired in many of the same ways as regular servo motors.Additional Resources:
- VIDEO: Actuator Motor Testing
Is feedback alignment important?
Yes, proper feedback alignment is critical to servo motor performance. Accurate alignment ensures the drive receives the correct position and commutation information, enabling precise motion control and smooth operation. Misaligned feedback devices can cause commutation errors, positioning inaccuracies, drive faults, excessive current draw, or even prevent the motor from operating altogether.Additional Resources:
- VIDEO: Feedback Alignment is Quick and Easy
- VIDEO: TI-5000JX Document the Feedback Alignment
How do I determine the forward direction of my feedback device?
Looking from the motor shaft end, rotate the motor and watch the feedback angles. The forward direction of the feedback is the direction in which the angles increase (either CW or CCW).Additional Resources:
- VIDEO: Determine the Motor Forward Direction
How do I check motor winding resistance?
1. Take three readings, measuring from U-V (U phase), then V-W (V phase), then W-U (W phase). The resistance readings should all be the same or within 10% of each other.2. Measure the resistance from any of the 3 phases to Ground and make sure there is no continuity.
Attempting to identify other issues with the machine in general could include swapping out servo motors, drive components, and/or cabling to try to identify the issue.
Additional Resources:
- VIDEO: Checking Motor Winding Resistances
How do I determine the Ke rating?
Back-drive the motor at 1,000rpm and record the generated AC voltage (RMS) coming from the windings using line-to-line connections (U-v, V-w, and W-u). This voltage should be nearly equal across all three windings. If not, there may be problems with the motor windings or magnets.An oscilloscope can be used to see the waveform, which, if distorted, could indicate issues with the magnets or windings. The Ke rating can also be used to determine approximately how fast the motor will run on the TI-3000JX system.
Additional Resources:
- VIDEO: Determine the Ke Rating
General Servo Questions
What is a servo encoder? How does it work?
A servo encoder is a feedback device that measures the position, speed, and direction of a servo motor shaft and communicates that information to the servo drive. The drive continuously compares the encoder’s feedback with the commanded motion and makes real-time adjustments to ensure accurate operation.Additional Resources:
- What Is a Servo Motor Encoder?
What are servo motors used for?
Servo motors are used in applications that require precise control of position, speed, and torque. They can be commonly found in CNC machines, Industrial Robots, packaging equipment, material handling systems, and automated assembly lines.Additional Resources:
- What is a Servo Motor Used For? 10 Nontraditional Applications of Servo Motors
What are the different types of servo motors?
The most common include AC induction servo motors, brushed DC servo motors, and permanent magnet brushless servo motors. They can also be categorized by the feedback technology, for example, resolver-based systems or encoders.Brushed vs brushless – what’s the difference?
A brushed motor uses brushes for commutation. A brushed motor can come equipped with an encoder, but the encoder does not need to be aligned with the motor and is only used for speed and direction feedback.A brushless servo motor with a permanent magnet rotor uses a feedback device (encoder, resolver, etc) for commutation. Because of this, the feedback needs to be aligned precisely to the motor.
There are also brushless servo motors with wound rotors that use induction and variable frequency drives to operate. They may or may not have feedback devices, and if they do, they do not require specific alignment.
Additional Resources:
- Brushed Servo Motors vs. Brushless Servo Motors: Which Do I Need?
Have more servo motor questions? Let us know and we'll be happy to answer them!
Or, download the The Quick Reference Guide to Servo Motor Maintenance and Repair ⬇️
