When the SGMGH-09DCA6F-OY arrived at our facility, the customer’s initial description was quite general. The motor still started but produced loud grinding noises. During the first manual rotation check it immediately became clear that the bearings were severely damaged. The shaft rotated unevenly, with a metallic roughness and noticeably increased resistance. These are classic symptoms of worn or destroyed bearings, something that was later confirmed during disassembly.

Besides the acoustic issue, the initial insulation measurement revealed a serious electrical problem. The values were far below the acceptable range which typically indicates moisture, coolant or conductive particles inside the motor. This suspicion was confirmed after complete disassembly. Coolant had entered the interior. The old shaft seals were hardened and brittle. In combination with the metallic particles released by the worn bearings, a conductive contamination layer had formed inside the motor. This contamination not only reduced insulation resistance but also negatively affected thermal behavior.

The first step was a complete disassembly of the motor. Rotor, stator, bearing carriers, terminal box and encoder were separated and prepared for cleaning. All metal components were cleaned in an ultrasonic bath. The stator was dried in a controlled oven to restore insulation capability and was then tested with high voltage equipment. Fortunately the windings showed no structural damage despite the coolant exposure which simplified the repair process.

The rotor showed visible abrasion marks. These residues were mechanically removed and the shaft was measured with high accuracy to ensure that it had not warped. Since the shaft was still within tolerance, new precision bearings were installed. Both shaft seals were replaced because their failure was one of the root causes of the damage.

The UTSIH-B17CK encoder had not completely failed but required preventive refurbishment. Moisture and oils can impair the internal components of the encoder or cause long term instability. Therefore it was cleaned, inspected and fitted with new sealing components. The final calibration of the encoder was performed after full reassembly.

Reassembly was done with great care, including correct bearing preload, torque settings for all covers and precise alignment of the encoder. The insulation measurement after assembly showed results comparable to a new motor. This allowed us to proceed with the dynamic test.

The motor was tested on our Yaskawa Sigma II test bench using an SGDH-10DE-OY Servopack. During the dynamic test we monitored start current, torque values, temperature behavior and encoder feedback. After a short warm up period the motor ran completely smooth and free from vibrations. The encoder signals were stable and the Servopack operated exactly within the expected control parameters.

The entire repair, from arrival to final inspection, took less than four days. For the customer this repair was significantly faster and more economical than purchasing a replacement unit or undergoing a retrofit, which had previously been suggested to him. With the preventive overhaul of all critical components, the motor is now prepared for many more years of reliable operation.

Information about the mentioned Servopack and Servomotor:

• Yaskawa SGMGH-09DCA6F-OY AC Servo Motor
• Encoder Yaskawa UTSIH-B17CK
• Yaskawa SGDH-10DE-OY Servopack

More information about our Yaskawa repairs can be found here.

📞 Feel free to contact us if you have any questions regarding your Yaskawa drive technology. Our experienced team is always ready to assist you.

Technical Specifications

Operating Environment and Compatible Devices

This motor is commonly installed in vertical and horizontal axes of modern machine tools, including machining centers, portal systems and handling units. When combined with the SGDH-10DE-OY Servopack, the motor reaches its full dynamic performance. Sigma II Servopacks support 17-bit encoders and use internal protection mechanisms to control torque, speed and position with high precision.

Typical industrial environments include:

• Machine tools with high coolant exposure
• Applications with cyclic load changes
• Axes with high accuracy requirements
• Linear and rotary axes with frequent start and stop movements

Functional Description

The SGMGH series is designed for high continuous loads and uses a robust rotor assembly combined with high quality bearings. The UTSIH-B17CK encoder provides precise feedback to the Servopack which uses position, speed and torque signals to perform real time field oriented control. This ensures high accuracy and reduced thermal losses.

The internal insulation protects the winding system from moisture and conductive contamination. Shaft seals prevent coolant from entering the motor. When these seals age or become damaged, leakage can occur and cause insulation failures or bearing wear.

Alarm Messages and Troubleshooting (Extract from SGDH Manual)

Motor Components