So you think you’ve got what it takes to rebuild your broken DC servo motor. Just a rotor with a couple of bearings, right? Wrong. There are many factors to consider before disassembling your own DC servo motor.
Your servo motor does not have the power it once had. You are starting to encounter current and torque alarms on your machine. You check the couplings, bearings, maybe even swap drives. Nothing seems wrong and the problem is probably in the motor.
Your servo drive pops an error code. You write down the error code and look it up in the manual—it corresponds to a “resolver overspeed” alarm. Next to that is written “check the feedback cables” as a probable solution. You replace the cable and get the same alarm.
The problem: Your motor has failed and you need to remove it from your machine. You have disconnected all the electrical, disconnected the coupling, cursed the engineer who designed the machine, and are now ready to remove the motor. There is just one obstacle left however, the motor weighs way more than you can lift by hand.
Hearing servo sounds like knocking, or your servo motor has a strong vibration? You send it somewhere for repair and you are told that the bearing fit is no good. You get a quote to change the bearings and repair the bearing fit. Problem solved, you say… Then your servo is returned and fails again. What is so difficult about fixing a bearing fit?
Your servo suffers from intermittent failure, feedback loss, runs choppy, or trips out on some sort of encoder error. Could electrical noise be the culprit?
DC servo motors very often come in for repair because their brushes have worn out. This seems like a straight forward problem with an easy solution; install new brushes! And while this could be true, premature brush wear can be a sign of larger problems with your servo motor. There are a few points you can check to narrow down the cause of your premature brush wear.
Servotech repairs thousands of servo motors a year, and occasionally we receive repair orders with simple issues that the customer likely could have addressed themselves.
We get a lot of customers who call us and say, “I have a Fanuc A06B Motor, can you fix that?” The answer is “Yes!” But did you know that ALL Fanuc servo motors, no matter what size or purpose, have a part number that starts with A06B?
