16.07.2025 by Viktor Siebert
Yaskawa SGMAH-02A1A21D AC Servo Motor in DMU 70 by DMG Mori
A tooling manufacturer contacted us regarding a malfunction of a Yaskawa servo motor, model SGMAH-02A1A21D, installed in a DMU70 machine from Deckel Maho, DMG Mori. The associated Yaskawa drive unit SGDH-02AE-OY displayed alarm A.84, a typical indicator of an encoder issue.
Diagnosis of the UTSAH-B16EC-E Encoder
The motor was equipped with a UTSAH-B16EC-E encoder, which we tested in our diagnostic system. The test confirmed an encoder fault. We proceeded with our standard repair process, which includes complete disassembly, sandblasting, thorough cleaning, drying, and replacement of all critical components.
Professional Overhaul with Repainting
The motor was fitted with new seals and ball bearings. A new encoder was installed and precisely programmed to the motor. It was then repainted and tested in our in-house testing facility under load, with varying speeds and direction changes. We followed our checklist step by step, and photos and videos of the final test were recorded.
Advance Warning Regarding the Drive
When we shipped the motor, we included an important note: in similar past cases, the drive unit had also been damaged. It is often difficult to determine whether the encoder or the drive was the original cause of the failure. Based on our experience, the root cause is usually in the motor, which subsequently damages the drive’s encoder control circuit.
Immediate Complaint After Installation
The customer reinstalled the motor without first testing the drive. As a result, alarm A.84 appeared again immediately. He contacted us and complained about the repair. Our sales manager took over the case, promptly sent a proof video along with the full checklist, and advised the customer again to test the drive before installation.
Examination of Both Units
The customer then sent both the motor and the drive to us. Upon arrival, both units were promptly inspected. Our diagnosis confirmed the suspected issue: the encoder had already caused damage to the drive’s control board. The drive had been compromised by the faulty encoder prior to our repair.
Repair of the SGDH-02AE-OY Servopack
We carried out a standard overhaul of the drive as well. Our technicians follow a precise checklist and replace all known weak points. This includes the sensitive encoder control circuit. After successful repair and testing, both units were returned to the customer.
Successful Outcome and Positive Feedback
Since then, the machine has been running without issues. The customer expressed his gratitude for our professional and transparent approach. He noted that no one else had been able to assist him with this type of complex fault. He also criticized some component resellers who make big promises but have no technical expertise or real solutions.
Information about the mentioned Servopack and Servomotor:
More information about our Yaskawa repairs can be found here.
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Device Data (Technical Specifications)
| Specification | Value |
|---|
| Model | SGMAH-02A1A21D |
| Rated Power | 200 W |
| Voltage | 200 V AC |
| Rated Current | 2.1 A |
| Rated Torque | 0.637 Nm |
| Rated Speed | 3000 rpm |
| Insulation Class | Class B |
| Encoder | UTSAH-B16EC-E (17-bit absolute) |
| Protection Class | Standard (not IP67) |
| Weight | Approx. 1.1 – 1.4 kg (depending on version) |
| Bearings | Ball bearings |
| Mounting Type | Flange mounting |
Environment and Compatibility
- Application Area: Industrial machinery, CNC machining centers, e.g. DMG Mori DMU70
- Compatible With: Yaskawa SGDH-02AE-OY Servopack (200V)
- Ambient Operating Temperature: 0 °C to 40 °C
- Humidity: 20–80% RH (non-condensing)
- Mounting Orientation: Horizontal or vertical
- Vibration Resistance: Max. 0.5 G
- Cabling: Must be routed separately from power cables; encoder cable max. 20 meters
Functional Description
The SGMAH-02A1A21D is a compact AC servo motor with sinusoidal commutation and a 3-phase drive. It is equipped with a high-resolution absolute encoder (UTSAH-B16EC-E) and offers precise positioning, speed regulation, and torque control. Position feedback is transmitted to the Yaskawa SGDH-series Servopack. The system supports position, speed, and torque control modes. This motor is ideal for high-precision, low-to-medium power automation applications.
Alarm Codes and Troubleshooting
| Alarm Code | Name | Description | Solution |
|---|
| A.84 | Encoder Data Error | Invalid or corrupted encoder data | Check encoder cable, restart, replace encoder if necessary |
| A.83 | Encoder Battery Error | Battery voltage below 2.7 V | Replace battery, reset system |
| A.81 | Encoder Backup Error | Power loss on absolute encoder, position data lost | Reinitialize encoder setup, check battery supply |
| A.82 | Encoder Checksum Error | Internal encoder memory checksum failed | Replace encoder |
| A.C9 | Encoder Communication Error | No communication between encoder and drive | Check cable layout, grounding, shielding |
| A.03 | Main Circuit Encoder Error | Power supply or encoder initialization failure | Check power supply, replace Servopack if needed |
Motor Components
| Component | Description |
|---|
| Encoder | UTSAH-B16EC-E, 17-bit, absolute |
| Output Shaft | Smooth, with optional keyway |
| Frame / Flange | Die-cast aluminum housing |
| Bearings | Sealed ball bearings |
| Seals | Oil-resistant seals (depending on version) |
| Housing | Black-coated aluminum body |
| Cable Connection | Fixed cable or connector (depending on version) |
