Bosch Rexroth MSK Servo Motors, repairing and aligning the encoder.



I’ll start with a bit of history here as I’ve been in the servo motor repair industry for over 25 years. Back then we saw pretty basic servo motors, many were resolver fed, a lot with incremental encoders and some more complex Yaskawa motors with absolute encoders. We had to reverse engineer the systems to be able to carry out a repair and there were only a few OEM types that we saw. I’m sure many of you in the repair industry will remember using an oscilloscope and turning the resolver stator to align with the correct motor phase to re-align the feedback, it was pretty much like that.

Fast forward 25 years and to see how far we’ve developed in the servo motor repair field it’s pretty amazing. A great deal is made about feedback alignment and whilst that is pretty important, you should still remember that a servo motor is still an electric motor, ok it has permanent magnets on the rotor but it has a wound stator, bearings and shaft that require expert knowledge to inspect and repair as needed. Feedback systems have changed and developed vastly over the last 10 years. It’s no longer a case of ‘physically aligning’ certain feedback systems.

Take the Bosch Rexroth MSK series of servo motor for example. This is one servo motor who uses a programmable Sick/Stegmann encoder. Just removing and replacing the encoder is not adequate for this type of servo.

I mentioned that it uses a programmable encoder, the data in this encoder is critical for the operation. In the case of the servo motor in the photograph above we found the encoder bearings were worn, so, as part of the repair process we need to replace it. Just to replace the encoder and send back to the customer would mean we have an unhappy customer as the motor would not work on his machine (Incidentally we have found that the repair trade gets a bad name because this is often the case, the manufacturer then gets involved saying that third party repairs are unreliable). We have invested in equipment to be able to download the encoder data, verify it, and upload to a new encoder. You may be surprised to know the data in the encoder includes the motor model and serial number, motor current and voltage data, speed data, not just the alignment data. Without this important programming equipment; repairs to this type of servo motor are just not possible.

To ensure our repairs meet the OEM nameplate specifications we carry out a full load test where the motor is run to full power, the brake holding torque is checked and a full vibration analysis is carried out on the motor. We ensure that all servo motors, not just the Bosch Rexroth ones are sent out of our workshops as good as when they were new. We also back this up with an OEM equivalent warranty of 12 months too.

We have many customers in the food and drink sector, processing and packaging industries who send us their Bosch Rexroth servo motors because we have proven our capability and offer a reliable and cost reduced alternative to the OEM. What’s more is our service is available 24 hours a day, every day of the week from our 24 hour manned workshops.

We now see hundreds of different motor types, all these types require different techniques and procedures to not only repair; but along and test fully.

Here’s another motor type we see regularly, a Siemens 1Ft6044 servo motor, why not watch the entire repair process on a video we filmed recently – Siemens Servo Repair



Fletcher Moorland Ltd.
Elenora Street

T: 01782 411021