SINAMICS S120 1FT6132 Encoder Exchange: Drive-CLiQ vs EnDat M24

Problem Definition: 1FT6132 Encoder Variant Mismatch

The 1FT6132 is a member of the Siemens SIMOTICS S 1FT6 family of brushless permanent-magnet synchronous servomotors. It is offered in two mechanically identical variants that differ only in the encoder interface electronics. The -4FA1 MLFB suffix designates a motor whose absolute encoder is terminated inside the motor junction box as a DRIVE-CLiQ signal pair; the -4EA1 suffix designates the same motor whose absolute encoder is terminated in an M24 18-pin flange connector using the Heidenhain EnDat 2.1/2.2 protocol. The two motors share the same stator, winding, bearings, and tapered encoder shaft; only the encoder electronics and the connector at the rear of the motor differ.

On the SINAMICS S120 Book Size platform, the -4FA1 variant connects directly to a DRIVE-CLiQ port on the Motor Module or on a hub. The -4EA1 variant cannot connect directly to a DRIVE-CLiQ port because EnDat M24 uses a 17-pin (or 18-pin) M24 connector with 5 V power and differential EnDat clock/data, not the 8-pin DRIVE-CLiQ RJ45-style interface. The -4EA1 motor requires a Sensor Module - SMC20 (cabinet-mounted) or SME20 (external-mounted) - which translates the EnDat stream into the SINAMICS encoder channel format and re-injects it on the DRIVE-CLiQ network.

When a -4FA1 unit fails in service and the only spare available is a -4EA1 unit, the field question is whether the encoder can be transferred from one motor to the other so that the original motor continues to operate on the existing SINAMICS S120 topology. The mechanical, electrical, parameter, and firmware implications of such a transfer are documented below, together with the supported engineering options when a direct encoder swap is not viable.

1FT6132 Family and Encoder Options

The 1FT6132 belongs to the 132 mm shaft-height segment of the 1FT6 family, with a 192 mm IEC flange and a 6-length (longer) stack. The MLFB structure common to both the -4FA1 and -4EA1 motors is given in the table below. Option code definitions can be revised across catalog editions; verify the option code for the specific motor against the rating plate and the Siemens Product Configurator at siemens.com/Configurator.

The trailing F or E option code in the MLFB defines the encoder interface. The F variant is a Siemens-format DRIVE-CLiQ encoder with 24 V supply and a Siemens electronic rating plate; the E variant is a Heidenhain EnDat M24 encoder with 5 V supply and a Heidenhain catalog number. The two encoders are mechanically interchangeable on the motor but electrically, electronically, and parametrically distinct.

Mechanical Compatibility of the Encoder Mounting

The 1FT6 family uses a tapered (1:10) encoder shaft of standard dimensions across the entire 1FT6 catalog. Both the F (DRIVE-CLiQ) and E (EnDat) option code encoders mount on the same taper and are clamped with the same central screw. The encoder housing O-ring seal and the motor-side mounting flange are identical.

Three mechanical limits apply when a field swap is considered:

1. Encoder housing diameter and length are identical between the two variants, so no interference occurs in the motor housing.
2. Encoder central screw: use the Siemens-specified torque value from the 1FT6 installation guide (typically around 5 Nm for the central clamping screw; verify against the 1FT6 Commissioning Guide for the exact value). Do not reuse a screw that has been removed and reinstalled more times than the catalog allows; check the encoder installation manual for the screw-reuse count.
3. Cable entry and routing: the E variant routes a heavier M24 cable to the SMC20; the F variant uses a 6FX8002 DRIVE-CLiQ cable with a much smaller bend radius. Cable bend radius and EMC separation from the motor power cable must be respected in either configuration.

Electrical Interface: DRIVE-CLiQ vs EnDat M24

The two encoders are electrically incompatible at the connector level. The relevant differences are summarized below.

A -4EA1 motor cannot be plugged directly into a SINAMICS S120 DRIVE-CLiQ port. It must first connect to an SMC20 or SME20 Sensor Module, which converts the EnDat stream into the SINAMICS encoder channel format. The 5 V supply on the EnDat cable is critical: the cable resistance between SMC20 and the encoder must be checked against the Heidenhain EnDat specification to ensure that the supply at the encoder terminals remains within ±5 % of nominal. Long motor-to-cabinet distances require a 5 V sense return or an encoder with extended supply range; verify with the Heidenhain EnDat 2.1/2.2 manual and the SMC20 manual.

SINAMICS S120 Topology with DRIVE-CLiQ

The SINAMICS S120 Book Size drive system uses a DRIVE-CLiQ ring or star topology. The Control Unit CU320-2 has six DRIVE-CLiQ ports (X100-X105) on its front panel, and each Motor Module Book Size has two DRIVE-CLiQ ports (X200, X201) on its front panel. The encoder is normally connected to the Motor Module X200 port of the drive that controls the motor.

A direct DRIVE-CLiQ encoder (F variant) is a single-cable, single-port solution. An EnDat encoder (E variant) is a two-cable solution: a power/signal cable from the motor M24 connector to the SMC20, and a DRIVE-CLiQ cable from the SMC20 to the Motor Module or to a DMC20 hub in the topology. The SMC20 occupies one DRIVE-CLiQ address on the network and must be considered in the topology when calculating the maximum number of nodes per Control Unit.

CU320-2 supports a maximum of 8 drive objects (depending on firmware) and 24 DRIVE-CLiQ nodes; the Sensor Module consumes one slot in the topology. The DO list and topology should be checked after adding the SMC20 to confirm that the system stays within its limits. The Hub Module DMC20 is required when more than six axis drives are connected and the topology is converted to a star, or when an encoder must connect to a port that is not on a Motor Module - the latter is the typical SMC20 installation.

Parameter Mapping: Replacing a DRIVE-CLiQ Encoder with an SMC20 + EnDat

When the encoder channel is moved from a direct DRIVE-CLiQ connection to an SMC20 + EnDat, the drive object parameters must be updated so that the SINAMICS reads the encoder data through the Sensor Module channel. The relevant parameters are summarized below.

The key parameter change is p0430[0], which routes the encoder evaluation to the Sensor Module drive object. After changing p0430, copy RAM to ROM and power-cycle the Control Unit to clear the parameter consistency check.

Encoder Exchange Procedure

The procedure below covers the case where a -4EA1 (EnDat M24) motor is to be used in a system that was configured for a -4FA1 (DRIVE-CLiQ) motor. The reverse case is symmetric.

1. Lock and tag out the drive system; verify zero energy at the Motor Module DC link before any mechanical work. Wait 5 minutes after isolation for the DC link capacitors to discharge to safe voltage per the SINAMICS S120 manual.
2. Document the existing configuration: motor MLFB, encoder type, electronic rating plate contents (drive p0100...p0199 and r0200...r0206), and the encoder evaluation parameters. Save the active drive project from STARTER or Startdrive as a backup, and export the parameter list to a CSV file. Note the DRIVE-CLiQ port on the Motor Module (typically X200) and label the cable.
3. Disconnect the DRIVE-CLiQ cable from the original motor at the motor side. Cap the connector to prevent contamination.
4. Install the SMC20 in the cabinet. Mount on a DIN rail or on a flat surface in accordance with the SMC20 manual. Observe the EMC mounting guidelines: bond the SMC20 body to the cabinet backplane with a low-impedance bond (paint-free contact surface, short bonding strap).
5. Lay a Heidenhain or Siemens extension cable from the motor M24 connector to the SMC20. Terminate the shield on the SMC20 end with a 360° EMC gland; terminate the motor end on the connector shell. Verify the 5 V supply at the encoder end with a multimeter after power-up.
6. Lay a DRIVE-CLiQ cable (6FX8002-2DCxx-xxxx) from the SMC20 to the Motor Module X200 port or to a DMC20 port. The cable is now on the DRIVE-CLiQ network and the SMC20 will be auto-detected on the next topology identification.
7. Power up the Control Unit and the Motor Module. Open STARTER or Startdrive and call "Topology → Identify" (STARTER) or "Topology → Read in" (Startdrive). Confirm that the new SMC20 appears in the topology and that the Motor Module sees the EnDat encoder through the Sensor Module channel.
8. Configure encoder parameters on the drive object: set p0430[0] to the index of the SMC20 drive object, set p0437[0] as needed for diagnostics, and set p0140 if the SMC20 is on a separate drive object. p0140 is automatically set when the topology is identified.
9. Run automatic configuration and check that the electronic rating plate data is read from the EnDat encoder. Verify that p0420[0], p0421[0], and p0423[0] show the correct resolution.
10. Save the project to ROM and to the drive. Power-cycle the Control Unit. After the power-cycle, the SINAMICS will read the EnDat encoder data through the SMC20 and the Motor Module will treat it as encoder 1.
11. Run encoder commissioning: commutating-angle test (p1990 = 1) and, if required, a pole-position identification. The 1FT6 motor has a calibrated absolute encoder, so the commutation angle is read from the encoder and a test run is verification only; however, run p1990 to confirm.
12. Run a low-speed reference motion at e.g. 50 rpm and confirm with the STARTER/Startdrive trace tool that the actual speed (r0063) and the position actual value (r0481) track the setpoint.
13. Run a controlled stop and a high-speed test motion within the system speed limits. Verify that no fault F3x, F4x, or F2xxx appears in the fault buffer.

The SMC20 firmware is part of the SINAMICS S120 firmware bundle; no separate firmware update is required. The DRIVE-CLiQ version on the SMC20 should match the version required by the SINAMICS firmware; mismatched versions can result in F01360 (DRIVE-CLiQ component version mismatch) during topology identification. The 1FT6 family is supported by SINAMICS S120 firmware V4.4 and later, and STARTER V4.x or Startdrive V15 in TIA Portal is the commissioning tool. The Siemens Industry Online Support portal is the source for the current firmware bundles and the S120 commissioning manual.

Drive-CLiQ Cable, Connector, and Topology Constraints

A 6FX8002-2DCxx-xxxx prefab DRIVE-CLiQ cable is required between the SMC20 and the Motor Module or hub. The cable is a Cat5e-equivalent, 8-core, shielded, with an RJ45-style industrial plug on each end. Available lengths are 0.5 m, 1 m, 2 m, 3 m, 5 m, 8 m, 10 m, 12 m, 15 m, 20 m, 25 m, 30 m, 40 m, 50 m, 75 m, and 100 m. The minimum bend radius is 75 mm in fixed routing and 125 mm in flexible routing. The cable transmits DRIVE-CLiQ at 100 Mbit/s and the 24 V supply for downstream devices. The total length of all DRIVE-CLiQ cables in a CU320-2 ring is limited to 350 m.

For the EnDat M24 cable between the motor and the SMC20, the Siemens M24 extension cable (e.g. 6FX8002-2EAxx-xxxx for EnDat 2.1/2.2) is recommended. The cable has a 17-pin M24 connector on the motor end and a 17-pin M24 connector on the cabinet end (or a D-sub connector that adapts to the SMC20). For long cable runs, confirm the 5 V drop on the power pair using the cable resistance table in the Heidenhain EnDat specification; the typical 5 V supply is regulated inside the SMC20.

The DMC20 (DRIVE-CLiQ Hub Module Cabinet-Mounted 20) is required when the topology has more than six axis drives on a single CU320-2 or when the SMC20 is mounted far from the Motor Module. The DMC20 has 6 DRIVE-CLiQ ports and is used in a star layout. When inserting an SMC20 into an existing ring, the topology must be re-identified.

Fault Codes and Diagnostics

When the encoder is reconnected through the SMC20, the SINAMICS may report one or more of the faults below. The fault number prefix F3x is for encoder faults; the 3 in 3x indicates the encoder number. A 1FT6 motor has encoder 1 on the drive object, so the fault prefix is F31xxx. The actual fault text is on the drive parameter description in STARTER or Startdrive.

Multiturn encoders with 22+12-bit resolution report F31002 if the multiturn data is invalid, often after a power cycle if the encoder battery is missing on battery-buffered multiturn units. Most 1FT6 DRIVE-CLiQ encoders do not use a battery buffer, but Heidenhain EnDat encoders in the E variant may use a buffer for multiturn data. Confirm the encoder order code and the requirement for a buffer battery against the Heidenhain data sheet.

Why the Original Approach of Mechanical Encoder Transfer Fails in Practice

The original question - "Can I exchange the encoder and connection from the new motor with the components from the original" - is mechanically straightforward, but for several reasons it is not a supported field solution:

1. Calibration of commutation offset. The Heidenhain absolute encoder is calibrated to the rotor during motor manufacture. The commutation offset, the position of the absolute singleturn zero, and (for multiturn) the multiturn reference are stored in the encoder EEPROM and replicated in the Siemens electronic rating plate of the F-variant motor. If the encoder is moved to a different rotor, the offset is no longer correct. Re-calibration requires a Siemens commissioning fixture or a p1990 / p1980 procedure with a pole-position identification. The p1990 procedure is generally not used on 1FT6 because the encoder-motor pairing is guaranteed at the factory.
2. Siemens electronic rating plate on the F variant. The DRIVE-CLiQ encoder on the -4FA1 motor carries a Siemens-format electronic rating plate that is read on first commissioning. If the encoder from one motor is swapped to another, the electronic rating plate now reports the wrong motor data and the SINAMICS S120 protection limits, Kp/Ki values, and motor equivalent circuit data are no longer correct. The drive could operate but with degraded performance and a loss of safety margin.
3. Heidenhain catalog number. The E-variant encoder has a Heidenhain catalog number (e.g. ECN 113 or ECN 1325) and an EnDat 2.1 or 2.2 protocol. The F-variant encoder has a Siemens catalog number (e.g. 6FX2001-5xxx) and a Siemens-specific DRIVE-CLiQ interface. The two encoders are not drop-in replacements for each other; they have different connector types, different supply voltages, and different protocols.
4. Thermal and EMC certification. The 1FT6 family is delivered as a certified motor + encoder pair. Swapping the encoder in the field voids the safety and EMC certification of the motor.

In short, transferring the encoder from one motor to another is mechanically possible but electrically, parametrically, and contractually not supported. The supported approach is to keep the new motor as a complete assembly (encoder + motor) and adapt the rest of the system to match, as described in the section below.

Supported Engineering Alternatives

Given that the in-service motor and the spare motor are physically identical but electrically different at the encoder interface, three supported options exist.

Option 1: Order a Replacement -4FA1 Motor

Order a new 1FT6132-6SC71-4FA1 motor from Siemens with the matching MLFB. The electronic rating plate is pre-loaded with the correct motor data, and the new motor drops into the existing DRIVE-CLiQ topology. This is the recommended path when downtime must be minimized and a long-term spare is required. Contact the local Siemens Industry partner or use the Siemens ASP&A portal to confirm the MLFB and the lead time.

Option 2: Add an SMC20 to the Existing -4EA1 Motor

The -4EA1 motor can be used in a -4FA1 system if an SMC20 (or SME20, SMC30 with EnDat mode, or SMC40 with SSI/EnDat) is added. This is described in the encoder exchange procedure above. The trade-off is a more complex topology and the need for a parameter re-mapping. The topology limit of 24 DRIVE-CLiQ nodes per CU320-2 and the DO limit of 8 per CU320-2 must be respected.

Option 3: Convert the In-Service Drive Configuration

If the drive allows the encoder to be reassigned to encoder 2 (or another free encoder interface), the -4EA1 motor can be used directly. The drive would be configured with p0430[0] for the new SMC20, p0400 set to EnDat 22-bit, and the closed-loop control re-commissioned. This is the cleanest engineering approach when the spare stock is permanent and the machine must continue to operate with the available -4EA1 motor.

Verification and Acceptance Test

After the change, the following verification steps confirm that the system is operating correctly:

1. Confirm no fault is active in the SINAMICS fault buffer. The fault buffer should be cleared with p3981 = 0 → 1, then 0, after the new commissioning is complete.
2. Read the encoder actual position in r0481 and the speed actual in r0063; verify that both track the setpoint values r0062 and r0060 in trace mode.
3. Confirm the encoder type in p0400, the catalog number in p0420, the multiturn resolution in p0421, and the singleturn resolution in p0423.
4. Run p1990 = 1 (pole-position test) and observe the result. A 1FT6 motor with a calibrated EnDat encoder should not require a re-calibration; the test should pass without an error.
5. Run a controlled acceleration and deceleration at 50 %, 75 %, and 100 % of the rated motor speed. Monitor the Motor Module DC link current in r0027 and the motor torque in r0080. The current should not exceed the motor rated current on the rating plate.
6. Run a continuous duty cycle representative of the production duty. Monitor the fault buffer for 24 h to confirm no latent encoder warning reappears.
7. Save the project to the engineering server and to the drive's CompactFlash card (for SINAMICS S120 with a CU320-2 CF card) so that the configuration is preserved on the next power-up.

Confirm the current catalog numbers against the Siemens Product Configurator and the Siemens Industry Online Support portal at the time of order. The SINAMICS S120 Commissioning Manual, the 1FT6 Commissioning Guide, the SMC20 manual, and the Heidenhain EnDat 2.2 Specification (Heidenhain document 297 517-xx) are the primary references for this engineering work.

Frequently Asked Questions