Brand New Sigma-7 Rotary AC Servo Motor YASKAWA SGM7A-01A6A21 High Performance for Industrial Controlling

The Yaskawa SGM7A-01A6A21 is a compact Sigma-7 (SGM7A) brushless rotary AC servomotor intended for high-responsiveness, low-inertia motion in small axes. In plain terms: it’s the kind of motor you choose when the machine needs fast acceleration, clean settling, and repeatable positioning—without wasting space or turning the panel into a space heater.

This specific model sits in the 100 W / 200 V class, pairing a 24-bit high-resolution encoder with a batteryless absolute feedback design for precise control and simpler maintenance. Yaskawa also highlights Sigma-7 rotary servomotors as low inertia, high speed units with high efficiency and low heat generation, and notes that the series supports downsizing by up to 20% while staying flange compatible with Sigma-5—useful for upgrades and retrofits where mechanical interfaces are already fixed.

Why this variant matters: “straight shaft without key”

A subtle but important differentiator of SGM7A-01A6A21 is its shaft end: straight without key. Compared with keyed shafts, a smooth shaft is typically paired with clamping-style couplings, shrink discs, or zero-backlash hub couplers. The practical advantages are:

• Cleaner torsional behavior (less keyway-related play and fewer micro-impacts under reversal, if the coupling is properly sized).

• Simplified alignment for compact mechanisms, especially on light axes where every millimeter counts.

• Good repeatability in fast indexing when the mechanical connection is designed as a friction clamp.

The tradeoff is that installation quality matters: correct clamping torque, correct hub fit, and sensible safety margins for peak torque events. For machines with frequent impacts, aggressive emergency stops, or high shock loading, you’d confirm the coupling’s torque rating and the shaft/hub interface details with extra care.

Performance profile: small motor, serious dynamics

On paper, the SGM7A-01A6A21 is rated for:

• Rated output: 0.1 kW

• Rated torque: 0.318 N·m

• Instantaneous maximum torque: 1.11 N·m

• Rated speed: 3000 min⁻¹

• Maximum speed: 6000 min⁻¹

That combination is a sweet spot for compact automation: fast acceleration, short high-torque bursts for indexing, and enough top speed to keep linear axes moving briskly through belt ratios or screw pitches without forcing a gearbox into the design.

Just as important for tuning is the motor moment of inertia, listed as 0.0352 × 10⁻⁴ kg·m². Low motor inertia generally helps when the load itself is light and you want rapid speed changes without sluggishness. Yaskawa also states an allowable load moment of inertia of 40×, indicating that the motor/drive system is intended to handle a meaningful range of reflected inertia (though good engineering still prefers staying comfortably inside extreme ratios when possible).

Feedback and commissioning: 24-bit, batteryless absolute

The motor is specified with a 24-bit encoder and batteryless absolute encoder type. In production environments, that typically supports three practical goals:

1. High positional granularity for smooth low-speed motion and accurate contouring (especially noticeable in inspection, dispensing, and precision indexing).

2. More predictable recovery behavior after power interruptions (absolute position reduces dependence on repeated homing cycles in many machine designs).

3. Lower maintenance overhead compared with battery-backed encoder schemes.

If you’re standardizing a machine family, batteryless absolute feedback is often a quiet cost-saver because it removes a small but recurring failure mode: the forgotten battery.

Mechanical envelope: designed for tight packaging

For integration work, this model’s published dimensions are straightforward and compact:

• Size (H × W × D): 54.7 × 40 × 101.5 mm

• Flange dimension (LC): 40 mm

• Flange diameter (LA): 46 mm

• Shaft diameter / length: 8 mm / 25 mm

• Weight: 0.5 kg

On moving axes (small Z slides, light gantries, compact rotary stations), that low mass is not a footnote—it directly reduces required acceleration torque and helps keep the system responsive.

Model-code logic: what “A21” is telling you

Yaskawa’s Sigma-7 servomotor product manual describes how the model number encodes key choices such as serial encoder type, shaft end, and options (e.g., holding brake). For the SGM7A family, the important takeaway is: the model code is not cosmetic. It maps to mechanical and feedback differences that affect cabling, couplings, and sometimes commissioning assumptions. In the same manual section, Yaskawa distinguishes shaft end variants (including straight without key vs straight with key and tap) and encoder categories (including 24-bit batteryless absolute).

So if you are replacing a motor in the field, matching “SGM7A-01A6A21” exactly is meaningful: it reduces the chance of discovering (too late) that your coupling or shaft interface doesn’t match, or that your feedback expectations changed.

Typical application fits

Given its power class, shaft style, and encoder configuration, the SGM7A-01A6A21 is commonly well suited to:

• Pick-and-place sub-axes and light rotary modules (fast acceleration, quick settle)

• Small belt or screw-driven linear stages in packaging and assembly

• Lab automation and inspection tooling where smooth low-speed motion matters

• Labeling, feeding, indexing, and cutoff synchronization on compact machines

• Retrofits from Sigma-5 flange-compatible builds where you want better dynamics without redesigning brackets

Integration checklist (practical, not glamorous)

Before locking the design, you typically validate:

• Drive/SERVOPACK compatibility with Sigma-7 rotary servomotors and the selected feedback type (absolute vs incremental, batteryless absolute behavior).

• Coupling selection suitable for a smooth shaft (clamp torque capacity, hub fit, alignment tolerance).

• Duty cycle and thermal environment, even if the series emphasizes efficiency and low heat.

• Mechanical resonance management (stiffness, belt compliance, screw whip, or mounting plate flex), because high-performance servos will happily expose weak mechanics.

None of this is exciting. All of it prevents commissioning week from becoming a troubleshooting festival.

Key Specifications Table (SGM7A-01A6A21)