Servo motors are very specialist and high precision motors. Repairs to them require a specialist set of skills in electronic, electrical and mechanical repair along with specialised test facilities. At Fletcher Moorland we have been developing and progressing our servo motor repair department for the past 25 years. We have managed this by combining the skills from each of our core business activities to develop a specialist servo motor repair department.
To ensure a successful servo motor repair, you need to be proficient in all areas of electro-mechanical repair and electronic repair. Consider what can go wrong with a servo motor. On the electro-mechanical side there are the bearings, windings, shaft, keyway, housings, etc. but on the electronic side there can be all types of specially aligned feedback systems, printed circuit boards, memory devices etc. They are more than just motors with a few additions.
An understanding of how servo systems and feedback devices work is essential. Servo motors come in a variety of forms, from AC & DC, but more importantly what type of feedback system is incorporated in each type? These can be one or a combination of the following, incremental encoders, absolute encoders, geared encoders, resolvers, electronic tachogenerators, optical or hall-effect commutation sensors. Each type of which, requires different alignment and test equipment for each manufacturer. The data from these can be in a variety of forms, from single outputs to serial and parallel data communications in binary, hexadecimal or gray code. This data needs to be checked and verified. In a number of cases the feedback data is in a specialised communication form specific to the OEM. For a number of these systems, we have built specialist equipment just to read the data. This is even before a repair is started!

Even the mechanical repair needs to be carried out with specialist equipment. Rotors should never be removed from a servo motor by hand. Dragging a rotor over the magnets will cause damage.
Alignment of feedback devices is critical, we have built our own equipment, some of which was built in conjunction with OEM’s to align, resolvers, encoders, commutation sensors etc to the manufacturers specific motor types.
The most important aspect of a servo motor repair is the ability to fully test and verify the operation. Being able to run the motor is the absolute minimum for testing. Servo motors will not run on a standard 3 phase supply. One method of testing is to have the associated PSU and servo drive coupled to the motor. This is then linked to a specially built motion controller to communicate to the drive and then run the motor to simulate the conditions that would be seen on a CNC or robot. We use this method of testing for Siemens, Bosch, NUM, Indramat, Control Techniques, Vickers, Reliance, Allen Bradley, Baldor, Lenze, ABB and various other manufacturers’ motors.
Certain servo motors require more complex methods of testing, i.e. Fanuc, Kawasaki, Yaskawa, Sanyo Denki and Nachi as the motor communicates directly with a machine controller and not the drive. We have developed and engineered various facilities to meet the demanding test requirements for these motors.
Finally, to test and verify a servo motor it needs to be run against a dynamic load. We use our own designed and built dynamic load rig. We have the capability to run a servo motor through a motion controller, against a changing load similar to the conditions that would be encountered on site. This test is critical as the motor reaches its operating temperature where its operating performance can be monitored.
Do we know it all? No, we don’t. New and more complex servo motors are coming to the market every year. Our R&D engineers are looking to the future. No servo motor repair company can afford to stand still and not to be continually developing their repair capabilities. We have recently added to our already vast testing facility by designing and developing a touch screen interface controller to automate our testing facility. We have also bought and redesigned the ‘Mitchell’ TI3000 and TI5000EX servo motor repair and test equipment. These off the shelf items are good in verifying the repair of a servo motor however our R&D team have redesigned them to give current monitoring of each phase and have more than doubled the load range of the existing test.
Servo motors are complicated; and we are servo motor repair specialists. Major OEM’s put their confidence in us to repair and service their servo motors. Some on a recognised basis and some on a confidential basis.

We are now repairing thousands of servo motors. Whoever you choose to use for your servo motor repairs, demand the results of the final run and load test so you are sure it will work.

If you want any further information on servo motor repair or you wish to see our facility in action, just call us and arrange a visit.