Safe Torque Off has crossed a critical threshold. With Kendrion's new FIO Drive Control STO, machine builders no longer need a separate safety module to achieve SIL 3 / PL e protection on a compact servo axis. The announcement lands as the EU Machinery Regulation (2023/1230) heads toward its January 20, 2027 application date, forcing functional safety, cybersecurity and digital documentation into the same CE-marking conversation. For integrators racing to shrink panels and compliance time, embedding Safe Torque Off directly into a 25 mm EtherCAT drive is no longer a feature — it is an architectural decision.
Analyst Insight: The race to decentralize machine architectures is colliding with stricter functional-safety mandates. Drives that carry certified safety internally remove external relays, reduce wiring and shrink certification effort — turning the servo drive into a first-class safety component rather than a peripheral risk.
Why Safe Torque Off Is Moving Inside the Drive
Kendrion describes the FIO Drive Control STO as the first time it has integrated a SIL 3 / PL e-certified Safe Torque Off function into its modular FIO drive family. The module delivers a dual-channel STO directly on board, so builders can trigger a safe torque shutdown without adding a dedicated STO module.
The market logic is straightforward. Compact, decentralized architectures — small robotics, handling systems, AGVs, and medical or laboratory equipment — demand reliable stopping without bulky safety hardware. Space is the bottleneck, and restart time is the hidden cost.
What the FIO Drive Control STO Delivers
The device is a 4-quadrant servo drive for stepper and BLDC motors, measuring just 25 × 120 × 90 mm and mounted on a DIN rail. In a safety trigger, output power is cut within a few milliseconds across two independent channels, in line with the drive safety functions defined by IEC 61800-5-2.
Crucially, EtherCAT communication and logic power stay live, preserving position and communication status. Once the safety circuit is released, the drive restarts immediately — no reboot, no rehoming — slashing downtime after a safety stop.
Key Specifications at a Glance
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Product: Kendrion (Kuhnke) FIO Drive Control STO
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Safety function: Safe Torque Off (STO), dual-channel, SIL 3 / PL e certified
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Drive type: 4-quadrant servo drive for stepper and BLDC motors
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Fieldbus: EtherCAT (DS402 device profile)
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Dimensions: 25 × 120 × 90 mm, DIN rail mount
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Supply: 24 V DC logic; IP20 protection class
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Shutdown behaviour: Output power cut within milliseconds; EtherCAT and logic power remain active
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Restart: Immediate, without reboot or rehoming
Market Trend: Analysts increasingly view built-in SIL 3 / PL e safety as a differentiator rather than a checkbox. When safety is certified inside the drive, machine builders can compress engineering, reduce component count and simplify PLC-based safety architectures — an advantage that compounds across multi-axis systems.
Where Integrated Safety Pays Off First
Kendrion positions the module for applications where installation space and restart time are decisive. Small-scale robotics, handling systems and automated guided vehicles stand out, alongside medical and laboratory equipment where dependable stopping is non-negotiable.
In each case, the value is cumulative: fewer safety relays, shorter wiring runs, smaller cabinets and less engineering overhead per axis.
Functional Safety: The Bigger Picture
Safe Torque Off is a hardware-based function that prevents a drive from generating the energy needed to produce torque in the motor. Under IEC 61800-5-2, it sits among a family of standardized drive safety functions that also include Safe Stop 1 (SS1) and Safely-Limited Speed (SLS).
Certification to SIL 3 or PL e means a drive's internal safety circuitry is fully redundant and deterministic — the assurance level machine builders increasingly expect by default as the EU Machinery Regulation tightens from 2027.
SPS 2026: The Launch Stage
The FIO Drive Control STO will make its public debut at SPS 2026, the smart production solutions fair in Nuremberg from November 24 to 26, 2026. The show remains Europe's leading platform for electric automation, drawing roughly 1,200 exhibitors and 50,000 trade visitors across 15 halls.
Announcing ahead of the event signals where Kendrion sees differentiation: not in raw torque, but in the marriage of safety and compactness.
Analyst Insight: Watch how competitors respond at SPS 2026. If integrated STO at SIL 3 / PL e becomes standard across the compact drive segment, the pressure shifts to software, diagnostics and lifecycle documentation — areas the EU Machinery Regulation explicitly targets.
FAQ
What does Safe Torque Off actually do?
STO severs the electrical pulses to a drive's power semiconductors, preventing the motor from generating torque. The drive remains powered and connected to the network.
Why does SIL 3 / PL e matter?
These are the highest commonly required integrity levels for machinery safety. Achieving them internally means the drive can be trusted as a safety subsystem without external relays in many architectures.
Does the drive lose position after an STO trigger?
No. EtherCAT communication and logic power stay active, so position and communication status are retained and the drive can restart without rehoming.
Which motors does it support?
Stepper and brushless DC (BLDC) motors, in a compact 25 mm-wide DIN-rail module.
The Bottom Line
Kendrion's FIO Drive Control STO is a measured but telling move. It packages certified Safe Torque Off into a drive narrow enough to fit tight panels, then keeps the axis ready to run the instant safety clears. As regulatory deadlines and space constraints converge, that combination of safety and speed may prove more valuable than any single specification on the datasheet.
