The YASKAWA SGM7A-20A6A21 is an industrial AC servo motor in YASKAWA’s Sigma-7 motion platform, developed for automation systems that require controlled torque, accurate speed regulation, and repeatable positioning under high-cycle operation. In real factories, motion components are judged by how they behave when the machine is pushed: frequent accelerations, sudden decelerations, changing loads, and long operating hours. A servo motor used in these conditions must do more than rotate—it must behave predictably in a closed-loop control system, maintaining stable motion even when the mechanical environment is imperfect.
A modern servo axis is a coordinated system composed of the motor, the servo drive, feedback handling, and the motion controller. The controller defines the trajectory, the drive regulates current to create torque, and the feedback loop continually corrects error. This feedback-driven correction is the core reason servo systems are used in automation: they provide precise movement and strong disturbance rejection, not just continuous rotation. For applications such as indexing, synchronized conveying, automated assembly, and packaging, that correction translates into stable throughput and consistent product quality.
The SGM7A-20A6A21 is often selected when an axis requires robust dynamic performance and sufficient margin for demanding motion profiles. Many production machines operate with short move distances, high acceleration ramps, and frequent start-stop cycles. These conditions produce repeated peaks in torque demand and require the servo motor to respond quickly without introducing mechanical shock or oscillation. If the motor is undersized, the axis may overheat, trip on overload, or show inconsistent motion as the system reaches its limits. If the motor is properly sized with adequate margin, the axis can hold stable behavior, reducing vibration, lowering stress on couplings and bearings, and improving overall reliability.
Servo performance is also strongly influenced by the machine design around it. Load inertia, mechanical stiffness, belt compliance, gearbox backlash, and resonance modes can dominate the behavior of an axis. Even a high-quality servo motor cannot compensate for poor alignment or unstable mechanics without consequences. In well-designed systems, however, a Sigma-7 servo motor helps achieve smooth transitions between acceleration, constant velocity, deceleration, and holding—exactly the behavior that keeps automated processes consistent.
From a maintenance and operations perspective, the Sigma-7 ecosystem is widely used and therefore practical to standardize. Plants that run multiple servo-driven machines often prefer to keep consistent families of motors and drives because it reduces the number of spare parts needed and makes troubleshooting faster. A familiar platform also shortens commissioning time when new machines are installed or when existing lines are upgraded. The model identification SGM7A-20A6A21 provides clear traceability for procurement and service teams, which is critical when downtime is expensive and incorrect substitutions can lead to compatibility problems or unstable tuning.
In the sections below, the information is organized in a structured and search-friendly format. It avoids icons and focuses on clear language, practical value, and integration guidance, with tables that can be quickly scanned by engineers, maintenance teams, or purchasing staff.
Product Identification Table
| Item | Details |
|---|---|
| Manufacturer | YASKAWA |
| Motion Platform | Sigma-7 |
| Motor Series | SGM7A |
| Model | SGM7A-20A6A21 |
| Product Type | Industrial AC Servo Motor |
| System Role | Torque source in a closed-loop motion control system |
| Typical Pairing | Compatible Sigma-7 servo drives and motion controllers |
| Common Use Areas | Packaging, assembly automation, indexing, material handling, general machinery |
What This Servo Motor Is Designed to Do
The role of the SGM7A-20A6A21 is to provide controllable torque that can be regulated precisely by the servo drive. In many automation systems, the motor must repeatedly perform three tasks:
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Accelerate the load quickly without losing control stability
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Stop precisely and settle fast so the next process step can begin
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Hold position under disturbance such as changing load force, friction, or external vibration
These tasks require a motor that supports stable closed-loop control behavior. When a servo axis is stable, it improves accuracy and reduces mechanical stress. When it is unstable, problems appear as oscillation, overshoot, inconsistent timing, and increased wear on mechanical components.
Performance Concept Table (System-Level)
| Motion Requirement | Why It Matters in Industry | System Outcome When Done Well |
|---|---|---|
| Controlled acceleration | Prevents shock, reduces slip and misalignment | Higher throughput with fewer mechanical issues |
| Fast settling after moves | Shortens cycle time without sacrificing accuracy | More units produced per hour |
| Stable holding control | Maintains position during process steps | Better quality and repeatability |
| Disturbance rejection | Handles load variation and friction changes | Less tuning drift and fewer rejects |
Typical Applications for SGM7A-20A6A21
Packaging and labeling equipment
Packaging lines often require high-speed indexing and precise timing. The servo motor must coordinate with sensors, feeders, cutters, or seal stations. Stable speed regulation helps maintain registration, while smooth stopping reduces mechanical shock and improves process consistency.
Automated assembly stations
Assembly machines benefit from servo axes that settle quickly and hold position reliably. If the axis oscillates after positioning, cycle time increases because the system must wait for stability. A stable servo axis allows faster transitions between motion and process steps.
Indexing tables and rotary mechanisms
Index tables demand repeatable positioning under repetitive cycles. In these applications, the servo motor’s ability to maintain consistent motion behavior is as important as its output capability. Improved control stability reduces overshoot and improves alignment accuracy.
Material handling and transfer axes
Handling systems often experience variable load conditions, such as changing product weight or shifting center of gravity. A servo motor used in these systems must resist disturbances and maintain consistent response to avoid mispicks, collisions, or timing errors.
Application Summary Table
| Application | Typical Motion Pattern | Key Benefit of a Stable Servo Axis |
|---|---|---|
| Packaging / labeling | Short moves, frequent start-stop | Registration control and reduced vibration |
| Automated assembly | Position, hold, repeat | Fast settling and consistent accuracy |
| Index tables | Repeated precise indexing | Reduced overshoot and repeatability |
| Material handling | Variable load movement | Disturbance rejection and reliable timing |
Integration Guidance (Practical Engineering Notes)
Drive compatibility and sizing
Verify that the selected Sigma-7 servo drive supports SGM7A-20A6A21 and that the drive rating matches both peak acceleration needs and continuous operating demand. Incorrect sizing can lead to overheating, frequent alarms, or unstable tuning.
Mechanical design and resonance awareness
Servo behavior is heavily affected by mechanical stiffness and resonance. Long belts, flexible couplings, or lightly supported structures can introduce vibration modes that appear only at certain speeds. A mechanically stable design simplifies tuning and improves motion smoothness.
Cable routing, shielding, and grounding
Servo systems operate with high switching currents and sensitive feedback signals. Proper cable selection, correct shielding termination practices, and disciplined routing help prevent noise-related issues and intermittent faults that are difficult to diagnose.
Thermal environment planning
Ensure adequate cooling and avoid heat stacking near braking resistors or other high-loss components. Thermal stability helps maintain consistent performance and extends component life.
Integration Checklist Table
| Topic | What to Check | Why It Prevents Problems |
|---|---|---|
| Drive pairing | Supported motor type and correct capacity | Avoids mismatch and unstable operation |
| Duty cycle | Peak and continuous load vs. real profile | Reduces overheating and nuisance trips |
| Mechanical stiffness | Couplings, belts, gearbox behavior | Minimizes resonance and improves settling |
| Wiring practice | Shielding, routing, grounding integrity | Prevents noise faults and instability |
| Temperature control | Cabinet airflow and ambient conditions | Supports long-term reliability |
Maintenance and Lifecycle Considerations
To keep a servo axis reliable, focus on the practical failure points:
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Mechanical alignment: Misalignment increases bearing stress and vibration, reducing service life.
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Connector integrity and strain relief: Cable fatigue and loose connectors can cause intermittent alarms and motion instability.
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Parameter control: Maintain backups of drive parameters and tuning settings. Replacement work is faster and safer when configuration is controlled.
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Monitoring for drift: Increased noise, heat, or loss of positioning stability often indicates mechanical wear or load changes. Addressing it early reduces downtime.
Conclusion
The YASKAWA SGM7A-20A6A21 is an industrial Sigma-7 SGM7A-series AC servo motor suited for automation systems that demand stable closed-loop motion, repeatable positioning, and reliable operation under high-cycle conditions. It is commonly applied in packaging, automated assembly, indexing mechanisms, and material handling where motion quality directly affects productivity and product consistency. When paired with a compatible Sigma-7 servo drive and integrated with disciplined mechanical alignment, realistic sizing, and proper electrical installation, it can support smooth motion behavior, reduced vibration, and improved long-term uptime.
