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2026-05-05
When the dual-axis drive saves real money, when it doesn't, and how to tell the difference before you spec the panel.
Both drives sit inside the same Sigma-7 family, run the same SigmaWin+ software, and carry the same SIL3 safety rating. The split is simple on paper — one drive runs one motor, the other runs two — but anyone who has actually laid out a panel for a multi-axis machine knows the choice has a longer tail than that.
The S in SGD7S means single-axis: one amplifier, one motor. The W stands for "double" — two motors driven from one housing. Both work with the same Sigma-7 motor families (SGM7J, SGM7A, SGM7P, SGM7G), and the commissioning workflow in SigmaWin+ is essentially the same for either drive.
The dual-axis design isn't just a marketing feature. Yaskawa's own product description for the SGD7W EtherCAT puts it directly: dual-axis capability "decreases system costs, cuts components counts and conserves panel space." That last point is the one most engineers feel first. Half the connectors on the front face. Less DIN rail. One bus connection feeding two axes instead of two separate runs.
Is the SGD7W just two SGD7S units glued into one box?
That's a useful intuition, but not quite right. Each axis on the SGD7W has its own power output stage, its own encoder feedback input, and its own dynamic brake circuit. From the controller's perspective, the two axes look fully independent — you can run one in position mode and the other in torque mode at the same time if the application calls for it.
What gets shared inside the housing: the network communication interface (one EtherCAT or MECHATROLINK-III port serves both axes), the main DC bus, the cooling fan, and the digital I/O block. That sharing is what produces the panel-space saving — and also what caps the per-axis power range lower than the SGD7S. A single housing can only dissipate so much heat before the design starts compromising reliability.
Specs drawn from Yaskawa's Sigma-7 SERVOPACK product pages and the official SGD7S/SGD7W selection manual.
The model number convention is consistent across both drives. After the SGD7S- or SGD7W- prefix, the next three digits encode the rated current — and that current corresponds to a specific motor capacity. The pairings below come straight from Yaskawa's standard combination tables.
| SGD7S Model | Motor Capacity | Voltage | SGD7W Model | Per-Axis Capacity |
|---|---|---|---|---|
| SGD7S-R70A | 50 W | 200 V single/3-phase | SGD7W-1R6A | 200 W |
| SGD7S-R90A | 100 W | 200 V single/3-phase | SGD7W-2R8A | 400 W |
| SGD7S-1R6A | 200 W | 200 V single/3-phase | SGD7W-5R5A | 750 W |
| SGD7S-2R8A | 400 W | 200 V single/3-phase | SGD7W-7R6A | 1.0 kW |
| SGD7S-5R5A | 750 W | 200 V single/3-phase | SGD7W-2R6D | 750 W (400 V class) |
| SGD7S-7R6A | 1.0 kW | 200 V 3-phase | — | — |
| SGD7S-120A | 1.5 kW | 200 V 3-phase | — | (SGD7W tops out at 1.5 kW per axis) |
| SGD7S-180A | 2.0 kW | 200 V 3-phase | — | — |
| SGD7S-200A | 3.0 kW | 200 V 3-phase | — | — |
| SGD7S-330A | 5.0 kW | 200 V 3-phase | — | — |
| SGD7S-470A | 6.0 kW | 200 V 3-phase | — | — |
| SGD7S-550A | 7.5 kW | 200 V 3-phase | — | — |
| SGD7S-590A | 11 kW | 200 V 3-phase | — | — |
| SGD7S-780A | 15 kW | 200 V 3-phase | — | — |
Model-to-capacity mapping per Yaskawa's Sigma-7 SERVOPACK product manual and standard motor combination charts. The 14th digit of the part number encodes hardware options like dynamic brake and encoder type — verify with SigmaSelect before ordering.
If any axis on your machine exceeds 1.5 kW, the SGD7W is off the table for that one — you'll need an SGD7S regardless of what the other axes look like.
The SGD7S has the broader catalogue. Yaskawa offers it with MECHATROLINK-III, EtherCAT (including a variant with FSoE for safety over EtherCAT), Analog/Pulse for legacy controllers, and integrated Sigma-7Siec and MP2600iec versions for stand-alone motion control without a separate PLC. The SGD7W is offered in MECHATROLINK-III and EtherCAT only — the two networks that handle multi-axis synchronization properly.
That distinction matters more than it sounds. If you're standardizing on EtherCAT for a new line, both drives slot in cleanly. But if your existing system uses analog command signals from an older motion controller — for example, a CNC with ±10 V outputs — the SGD7S Analog variant is your only option in the Sigma-7 lineup.
Quite a lot. The Sigma-7 platform was a step up from Sigma-V, and the core control technology is identical between SGD7S and SGD7W. The features in the table below are shared — picking one drive over the other doesn't change what the control loop can do per axis.
| Feature | What it means in practice |
|---|---|
| 3.1 kHz speed loop bandwidth | Industry-leading response. Settling time on positioning moves is noticeably shorter than Sigma-V or competing drives in the same class. |
| Tuningless mode | Out-of-the-box stable control without manual gain adjustment. Works well for standard rigid loads. Saves real hours during commissioning. |
| Auto-tuning with inertia adaptation | Maintains tuning accuracy across inertia changes up to 30:1. The same parameters work whether the axis is loaded or unloaded. |
| 24-bit absolute encoder | Over 16 million counts per revolution. Eliminates power-up homing and gives smooth low-speed performance. |
| Vibration suppression | Active filters compensate for machine resonance, friction, and torque ripple. Especially valuable on belt-driven or geared loads. |
| IEC 61508 SIL3 safety | Safe Torque Off and other safety functions certified to SIL3 / PLe — no external safety relays for STO. |
| Backward compatibility | Sigma-7 motors work with Sigma-V drives and vice versa for migration. Most users replace the drive first, motors later. |
Unit price isn't the right comparison. What you're actually buying when you choose the SGD7W is panel real estate, wiring time, and commissioning simplicity. To break it down:
Panel width. Two SGD7S units side-by-side typically take 30–50 mm more horizontal space than one SGD7W. On a busy multi-axis panel, that adds up — sometimes enough to drop down to a smaller cabinet size.
Network nodes. Each SGD7S takes one EtherCAT or MECHATROLINK-III node. The SGD7W takes one node for two axes. On a 16-axis machine that's 8 fewer nodes to address, configure, and diagnose during a fault.
Power wiring. One main bus connection and one ground per SGD7W instead of two. Multiply by axis count and the saved conduit fill and termination labour become meaningful.
Heat dissipation. One fan, one heatsink. Thermal management of one SGD7W is more efficient than two equivalent SGD7S units running side-by-side.
List prices vary by region and configuration, but as a rough benchmark from US distributor pricing: an SGD7W-2R6D30B (dual-axis, 750 W per axis, 400 V class, MECHATROLINK-III) lists around US$2,849. Two equivalent SGD7S units at the same per-axis rating typically run 1.4× to 1.6× the SGD7W price — and that's before accounting for the extra cabling, panel space, and node licenses on the controller side.
| Application | Recommended Drive | Reasoning |
|---|---|---|
| Single-axis indexing table | SGD7S | Only one motor; no benefit from dual-axis amp |
| X-Y gantry pick-and-place (similar payload) | SGD7W | Two axes, similar power, both run continuously — textbook fit |
| SCARA robot (4 axes, varied power) | Mix | SGD7W for the lighter wrist axes, SGD7S for the larger base/shoulder |
| Rotary table on a CNC (single high-power axis) | SGD7S | Likely above 1.5 kW; outside SGD7W range |
| PCB drilling head (X-Y stage) | SGD7W | Both axes in 200–750 W range; panel space critical |
| Multi-station packaging machine (8 axes) | SGD7W × 4 | Halves the amplifier count; reduces network address space |
| Press feeder (servo press + indexer) | Mix | Press axis often >3 kW (SGD7S); indexer in SGD7W range |
| Semiconductor wafer handling robot | SGD7W | Multiple low-to-medium power axes; clean room panel space at premium |
| Web tension control on a coater | SGD7S | Single tension axis, often higher power; analog command integration easier |
| Delta robot (3 parallel arms) | SGD7W + SGD7S | Two arms paired in SGD7W, third on SGD7S — or three SGD7S if power exceeds dual range |
Not really. They share the network interface, the commissioning software, and the parameter structure. From the controller's perspective, an SGD7W presents itself as two slave nodes with sequential addresses — so you can interleave SGD7S and SGD7W on the same EtherCAT or MECHATROLINK-III network without anything special.
What does need attention: documentation and spare parts. If you have ten machines in a plant and three of them use a mix while seven use only SGD7S, the spares inventory has to cover both, and your maintenance team has to know the wiring difference. Some end users prefer to standardize on one or the other for that reason — even when the dual-axis would technically save money on a given build.
Five questions, in this order. Don't skip ahead — each step closes off options for the next.
| Model Number | Type | Description |
|---|---|---|
| SGD7S-R70A30A | Single-axis | 50 W, 200 V class, MECHATROLINK-III, 0.66 A continuous |
| SGD7S-1R6A20A | Single-axis | 200 W, 200 V class, EtherCAT, 24-bit absolute encoder support |
| SGD7S-2R8A20A | Single-axis | 400 W, 200 V class, EtherCAT, 2.8 A rated |
| SGD7S-7R6A00A | Single-axis | 1.0 kW, 200 V class, MECHATROLINK-III |
| SGD7S-180A00A | Single-axis | 2.0 kW, 200 V 3-phase, MECHATROLINK-III |
| SGD7S-330A00A | Single-axis | 5.0 kW, 200 V 3-phase |
| SGD7S-780A00A | Single-axis | 15 kW, 200 V 3-phase — top of the SGD7S range |
| SGD7W-1R6A20A | Dual-axis | 200 W per axis, 200 V class, EtherCAT |
| SGD7W-2R8A20A | Dual-axis | 400 W per axis, 200 V class, EtherCAT |
| SGD7W-5R5A20A | Dual-axis | 750 W per axis, 200 V class, EtherCAT |
| SGD7W-7R6A20A | Dual-axis | 1.0 kW per axis, 200 V class, EtherCAT |
| SGD7W-2R6D30B | Dual-axis | 750 W per axis, 400 V class, MECHATROLINK-III |
Article numbers per Yaskawa Sigma-7 SERVOPACK catalogues and selection manuals. The 14th digit of the model code denotes hardware options (dynamic brake, encoder type) and varies independently — confirm against the SigmaSelect configurator before placing the order.
The choice between SGD7S and SGD7W comes down to two things: the per-axis power requirement, and how many axes you have in the comparable power band. Anything above 1.5 kW per axis is automatically SGD7S territory. Below that, if axes pair up naturally by power and duty, the SGD7W is usually the better economic choice once you factor in panel space and wiring labour. If your axes are scattered across the machine with no natural pairing, sticking with SGD7S keeps the build simpler.
The motion performance — bandwidth, settling time, accuracy — is identical between the two. You're not trading off control quality. The trade is footprint and component count against the inventory simplicity of a single drive type.
If you're sizing a specific machine and want a sanity check, send us the axis list with motor power and the controller you're using. We supply genuine Yaskawa Sigma-7 SERVOPACKs (both SGD7S and SGD7W) along with the matching SGM7 servo motors, with full Yaskawa documentation and lead-time information.
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