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| Place of Origin | Germany |
| Brand Name | SIEMENS |
| Certification | CE ROHS |
| Model Number | 6SN1118-0AD11-0AA1 |
The Siemens 6SN1118-0AD11-0AA1 is the single-axis, standard-interface analog closed-loop control card for the SIMODRIVE 611-A drive system — the analog-interface generation of Siemens' SIMODRIVE 611 servo drive platform that was the backbone of SINUMERIK CNC-equipped machine tools through the 1990s and 2000s. The card plugs into the control board slot of a SIMODRIVE 611 power module and provides the complete current and velocity regulation loops for one feed axis driven by a 1FT5 synchronous servo motor.
The SIMODRIVE 611-A "analog" designation refers to the command interface between the CNC control and the drive: the velocity setpoint arrives from the CNC (typically SINUMERIK 840D, 810D, or older series) as an analog ±10V signal.
The 6SN1118-0AD11-0AA1 reads this analog reference, compares it to the motor's speed feedback from the encoder, and regulates the output current to the motor windings to minimise the velocity error. This closed-loop architecture — with current and velocity loops executing at very high sample rates — produces the following accuracy and bandwidth that CNC contour milling and turning require.
The "standard interface" in the part number suffix (-0AD11) distinguishes this variant from the enhanced-interface version (-0AA11).
The standard interface provides the essential drive functions: velocity control, current control, enable/inhibit signals, and motor encoder feedback. The enhanced interface version adds additional signal capabilities — a more complete set of status and alarm outputs — but for the core closed-loop servo function both variants are equivalent.
This card is 1FT5 specific.
The 1FT5 is Siemens' analog-era synchronous servo motor family, used extensively in German and European CNC machines manufactured through the late 1990s and early 2000s.
The control card's current regulation parameters, encoder interface, and commutation logic are tuned for 1FT5 motor characteristics. It is not compatible with the later 1FT6, 1FK6, or 1FK7 motor families, which require different control cards (SIMODRIVE 611 Universal or digital variants).
| Parameter | Value |
|---|---|
| Series | SIMODRIVE 611-A |
| Axes | 1 (single-axis) |
| Motor Compatibility | 1FT5 synchronous servo motors |
| Drive Type | Feed drive (FD) |
| Interface | Standard (analog ±10V setpoint) |
| Design | Plug-in card (611 power module) |
| Control | Closed-loop velocity + current |
| Weight | ~0.4 kg |
| Discontinued | 09/30/2020 |
| Successor | 6SN1118-0NH01-0AA0 (1FT6/1FK7 only) |
The SIMODRIVE 611-A system separates the power conversion hardware (the power module) from the axis control intelligence (the control card). A 611 power module provides the inverter power stage — converting the DC bus voltage from the SIMODRIVE supply module into the three-phase AC output that drives the motor — but contains no axis control logic on its own.
The control card (such as the 6SN1118-0AD11-0AA1) plugs into the front slot of the power module and provides all closed-loop functions: encoder signal processing, current regulation, velocity regulation, and the analog interface to the CNC.
This plug-in architecture has a practical maintenance advantage: a failed control card can be replaced without replacing the power module, and vice versa.
If the power transistors in the power module have failed (often a consequence of a motor short circuit or sustained overload), the control card is typically undamaged and can be reused in a replacement power module.
If the control card has failed (more common in older units where electrolytic capacitors on the card have deteriorated), the power module is unaffected.
The 1FT5 compatibility constraint is not merely a communication protocol difference — it runs deeper. The 6SN1118-0AD11-0AA1 control card's firmware contains motor-specific parameter sets for the 1FT5 family: pole pair numbers, stator resistance and inductance values for current regulation tuning, and encoder pulse counts for the built-in encoder simulation interface.
Connecting a 1FT6 or 1FK7 motor with different parameter values would result in unstable current regulation, potentially destructive oscillation, or failure to achieve correct commutation.
When a machine running 1FT5 motors needs a servo drive upgrade path, the migration to a current-generation SIMODRIVE 611 Universal or SINAMICS S120 drive system typically requires simultaneous replacement of both the drives and the motors.
The successor part number (6SN1118-0NH01-0AA0) is designed for 1FT6/1FK7 motors and is explicitly not compatible with 1FT5 — the note "NOT COMPATIBLE" appears in Siemens' own product transition documentation.
The standard interface of the 6SN1118-0AD11-0AA1 provides the signals necessary for a CNC to command and monitor the drive axis: the ±10V analog velocity reference input, enable and inhibit signals, ready/fault status outputs, and the motor encoder connection. This is sufficient for all normal machining functions.
The enhanced interface (on the -0AA11 variant) adds additional terminals: additional alarm outputs, the ability to switch between two separate setpoint sources, and some additional monitoring channels. For most standard CNC machine tool axes, the enhanced interface's extra capabilities are not required.
The standard interface represents the vast majority of 611-A installations in the field and is directly replaceable by any other standard-interface 611-A single-axis 1FT5 card without CNC parameter changes.
Q1: Can the 6SN1118-0AD11-0AA1 be replaced with the enhanced-interface version (6SN1118-0AA11-0AA1) in a machine without CNC parameter changes?
Yes. The enhanced-interface card provides all the functions of the standard interface and then some additional terminals. From the CNC's perspective, the velocity command and enable/inhibit wiring connects identically, and the drive software responds the same way.
The additional terminals on the enhanced interface are simply unused in a standard-interface application. No CNC servo parameters need to be changed for this substitution.
The CNC servo parameters (P-gain, integral time, acceleration limits) that were tuned for the original axis remain valid.
Q2: The successor (6SN1118-0NH01-0AA0) is listed as NOT compatible. What does this mean in practice for a machine still running 1FT5 motors?
It means the successor card cannot be substituted for the 6SN1118-0AD11-0AA1 while keeping the original 1FT5 motors. The successor is designed for 1FT6/1FK7 motors with different electrical characteristics and encoder systems.
If a machine has 1FT5 motors and needs servo drive replacement, sourcing a like-for-like 6SN1118-0AD11-0AA1 exchange is the correct approach for drive-only replacement.
A full drive-and-motor upgrade to a current platform requires replacing both the drives and the motors simultaneously, which is a machine retrofit project rather than a straightforward drive replacement.
Q3: What causes the 6SN1118-0AD11-0AA1 to fail in aging machines, and what symptoms appear before failure?
Common failure modes on aging 611-A control cards include: electrolytic capacitor deterioration (manifesting as increased position deviation during operation, intermittent drive faults at varying ambient temperatures, or complete drive-off at power-on); voltage regulator failures on the control supply circuitry (producing random resets or incorrect parameter storage); and EEPROM corruption from age or power supply transients (causing parameter loss or boot failures).
Symptoms preceding complete failure often include intermittent f600/f603 drive alarms, velocity deviations that develop gradually over months, or alarms that appear at higher motor temperatures or heavier loads and clear when the drive cools.
Q4: Can the control card from a 2-axis 611-A module (6SN1118-0BK11-0AA0) be used to replace a failed single-axis card in a pinch?
No. The 2-axis control card for the 611-A (such as 6SN1118-0BK11-0AA0) is a different physical card designed for a 2-axis power module. The two-axis power module has a different slot connector arrangement and different bus connections than the single-axis power module.
The cards are not physically interchangeable between single-axis and two-axis power modules.
Q5: The machine's commissioning data mentions P-values tuned specifically for this axis. Will these parameters still be in the control card after replacement?
Parameters on SIMODRIVE 611-A analog cards are stored in EEPROM on the control card itself. When a failed card is replaced with a new or refurbished unit, the replacement card comes with factory default parameters — the previous tuning values are not transferred.
The axis must be re-commissioned: servo parameters including velocity loop gain, integral time, acceleration pre-control factor, and position control gain must be re-entered from the original commissioning documentation or a backup file.
For machines where no commissioning documentation exists, the parameters must be re-tuned from first principles, which typically requires a Siemens-trained commissioning engineer.
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