SIEMENS 1FK7042-5AF71-1EH0 Servo Motor – SIMOTICS S-1FK7

SIEMENS 1FK7042-5AF71-1EH0: Frame-42 Permanent-Magnet Servo Motor for Multi-Axis Motion Control

The 1FK7042-5AF71-1EH0 belongs to the SIMOTICS S-1FK7 compact servo series — a product line engineered by Siemens AG specifically for high-dynamic, closed-loop positioning tasks within SINAMICS S120 drive architectures. The frame size 42 designation indicates a 42 mm stator stack diameter, placing this unit in the lower end of the 1FK7 power range while retaining the full electromagnetic and mechanical design standards of the broader SIMOTICS S platform.

The order code breaks down as follows: 1FK7 = SIMOTICS S compact servo family; 042 = frame size 42; 5 = rated speed class 3000 rpm; AF = shaft height and winding variant; 71 = shaft extension with feather key groove, IP64 sealing; 1 = natural convection cooling (IC410); E = incremental encoder (TTL, 2048 ppr); H = no holding brake; 0 = standard vibration class A. Each position in the order code carries a deterministic hardware implication — there is no ambiguity in the physical configuration delivered.

This motor is designed to operate as a native axis within the SINAMICS S120 booksize or chassis topology. The incremental TTL encoder output feeds directly into the Motor Module’s onboard encoder interface or an external SMC20 Sensor Module Cabinet-Mounted unit, enabling position and speed feedback loops with a cycle time of 125 µs at the drive level. The absence of a holding brake (H suffix) reduces rotating inertia and eliminates brake wear as a maintenance variable — appropriate for horizontal-axis or gravity-compensated applications where power-off position hold is not a safety requirement.

The permanent-magnet synchronous rotor construction delivers a continuous stall torque of approximately 1.18 Nm with a peak torque capability near 3.5 Nm, yielding a peak-to-continuous ratio of approximately 3:1. This ratio supports aggressive acceleration ramps without thermal saturation during short-duty cycles. The Class F winding insulation (155°C thermal limit) combined with natural convection cooling (IC410) allows sustained rated operation at ambient temperatures up to 40°C without auxiliary cooling infrastructure, reducing installation complexity in compact machine cabinets.

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Technical Parameters

Hardware Logical Analysis

Rotor Inertia and Dynamic Response: The 42 mm frame size yields a rotor moment of inertia in the range of 0.07–0.10 kg·cm², which is low enough to achieve mechanical time constants below 5 ms under rated load. This characteristic is critical for applications requiring high bandwidth position loops — the servo drive can execute velocity reversals within a single interpolation cycle (typically 1 ms in SINAMICS S120 servo control mode) without overshoot accumulation across multiple axes.

Incremental Encoder Signal Integrity: The TTL incremental encoder outputs differential A/B/Z signals at 2048 ppr, providing 8192 counts per revolution in quadrature decoding mode. The differential line driver architecture (RS-422 compatible) provides common-mode noise rejection exceeding 7 V, which is essential in cabinet environments where PWM switching transients from adjacent Motor Modules generate conducted and radiated EMI in the 2–20 MHz band. The encoder cable shield must be terminated at both the motor connector and the drive’s PE rail to maintain signal integrity at cable lengths up to 50 m.

Winding Thermal Model: SINAMICS S120 implements a software-based motor thermal model (I²t monitoring) that tracks winding temperature in real time without requiring a physical temperature sensor in this configuration. The model uses measured motor current, ambient temperature input, and the motor’s thermal time constant (typically 15–25 minutes for frame-42 units) to predict winding temperature and issue pre-fault warnings before the 155°C Class F limit is approached. This eliminates nuisance trips while protecting the winding from thermal degradation.

EMC Design: The motor housing is constructed from die-cast aluminum alloy with a continuous conductive path from the flange to the encoder connector shell. This provides a low-impedance ground reference for the encoder shield and suppresses capacitively coupled noise from the stator winding to the encoder electronics. The motor power cable must use a shielded, symmetrically twisted four-conductor design (U/V/W/PE) with the shield bonded to the drive’s motor cable shield clamp — not the PE terminal — to avoid ground loop currents that degrade encoder signal quality.

Bearing and Mechanical Endurance: The output shaft is supported by precision angular contact bearings preloaded to eliminate axial play. Rated radial load at the shaft end is typically 80–120 N at rated speed, with bearing MTBF exceeding 30,000 hours under rated conditions. The feather key groove (DIN 6885 Form A) accommodates standard coupling hubs without requiring custom machining, reducing mechanical integration time.

System Integration Benefits

• DRIVE-CLiQ Electronic Nameplate: The motor stores its complete parameter dataset (rated torque, inertia, encoder resolution, thermal model coefficients) in an onboard EEPROM accessible via the DRIVE-CLiQ protocol. SINAMICS S120 reads this data automatically during commissioning, eliminating manual parameter entry and the associated risk of configuration errors across multi-axis systems.
• 125 µs Servo Control Cycle: SINAMICS S120 in servo control mode executes current, speed, and position control loops at 125 µs, 125 µs, and 250 µs respectively. The 1FK7042’s low rotor inertia allows the speed controller bandwidth to reach 800–1200 Hz, enabling tight contouring accuracy in multi-axis interpolation tasks.
• STO Safety Function (IEC 62061 SIL 2 / ISO 13849 PLd): Safe Torque Off is implemented directly in the SINAMICS S120 Motor Module without external safety relays. STO response time is <10 ms, meeting Category 3 stop requirements for collaborative robot cells and guarded machine zones.
• Startdrive Integration (TIA Portal): Full parameterization, trace recording, and fault diagnostics are available within TIA Portal V16+ via the Startdrive engineering tool. Drive and motor data are stored in the TIA project, enabling version-controlled configuration management across machine variants.
• PROFINET IRT Synchronization: When the SINAMICS S120 CU320-2 PN is synchronized via PROFINET IRT (Isochronous Real-Time), all axes share a common clock reference with jitter <1 µs. This enables electronic gearing and cam synchronization between the 1FK7042 axis and other servo axes without mechanical coupling.
• Diagnostic Transparency: The SINAMICS S120 drive continuously monitors motor current harmonics, encoder signal quality (A/B amplitude ratio, Z pulse width), and thermal model state. Fault codes are propagated to the SIMATIC S7 PLC via PROFINET diagnostics alarms, enabling predictive maintenance workflows without additional sensor hardware.
• Scalable Multi-Axis Architecture: The 1FK7042 shares the same SINAMICS S120 DC bus with larger 1FK7 or 1FT7 motors. Regenerative energy from decelerating axes is redistributed across the DC bus to accelerating axes, reducing peak demand on the Active Line Module and lowering energy consumption by 15–30% in cyclic motion profiles.
• Compact Cabinet Footprint: The frame-42 motor body and the corresponding SINAMICS S120 Single Motor Module (6SL3120-1TE13-0Axx) occupy minimal panel space. The motor’s natural convection cooling eliminates the need for forced-air cooling ducts or heat exchangers, simplifying cabinet thermal management in space-constrained installations.

Quality Assurance & Global Logistics

Every 1FK7042-5AF71-1EH0 unit dispatched from our Xiamen warehouse undergoes a structured pre-shipment verification protocol: insulation resistance measurement (≥100 MΩ at 500 VDC between winding and housing), no-load run test at rated speed to confirm encoder signal integrity and bearing noise signature, and visual inspection of the SIEMENS holographic authenticity label and factory test certificate. Serial numbers are cross-referenced against SIEMENS Industry Online Support (support.industry.siemens.com) to confirm genuine origin and production date.

Packaging follows SIEMENS OEM standards: anti-static foam insert, moisture-barrier bag with desiccant, and original cardboard carton with factory seal intact. Export documentation includes commercial invoice, packing list, and certificate of origin (China). HS Code 8501.52 applies for customs classification in most jurisdictions. EAR99 classification — no export license required for standard destinations.

Logistics options from Xiamen, China: DHL Express (3–5 business days to EU/US), FedEx International Priority (3–5 days), UPS Worldwide Expedited (4–6 days), and sea freight LCL for volume orders (18–25 days to major ports). Tracking numbers are issued within 24 hours of payment clearance. Insurance coverage is included for shipments exceeding USD 500 in declared value.

Warranty terms: 12 months from shipment date. DOA (Dead on Arrival) units are replaced within 7 business days upon receipt of photographic evidence and return authorization. Warranty covers manufacturing defects and encoder failure under rated operating conditions. Physical damage, incorrect wiring, or operation outside rated parameters voids warranty coverage.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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