SIEMENS 6ES7351-1AH02-0AE0

What is 6ES7351-1AH02-0AE0 and where is it used?

The SIEMENS 6ES7351-1AH02-0AE0 is a SIMATIC S7-300 FM 351 positioning assembly for rapid/creep-speed drives. It is designed to reliably perform positioning tasks in traditional automation environments, for example on linear axes, rotary axes, simple handling units, feed drives, feeding systems or movable machine axes. The assembly features two independent channels, allowing one linear or rotary axis to be controlled per channel. For feedback, each channel supports either an incremental encoder or an SSI absolute encoder. This makes the module particularly attractive for existing systems where robust PLC technology with clearly manageable positioning logic is required.

Overview of the key technical data and what it means

The assembly operates with a 24 V DC supply voltage within a permissible range of 20.4 to 28.8 V. The maximum current consumption is 350 mA, with an additional requirement of up to 150 mA via the backplane bus. Each channel provides 8 digital inputs and 8 digital outputs for typical positioning functions such as reference cam signals, start/stop, rapid traverse, creep speed, and clockwise/counter-clockwise rotation. Supported feedback devices include symmetrical and asymmetrical incremental encoders, SSI absolute encoders, and 2-wire sensors. For SSI applications, 13-bit or 25-bit telegram lengths, Gray code, and clock frequencies of up to 1.5 MHz are relevant. For maintenance personnel and purchasers, these specifications indicate which sensor technology, wiring arrangements and power supplies are compatible with the existing system without requiring additional hardware.

Product status, life cycle status and obsolescence

Siemens lists the 6ES7351-1AH02-0AE0 in the Industry Mall as a spare part. The specified Product Lifecycle Status PM410 indicates product discontinuation, effective from 01/10/2025. For operators of older S7-300 systems, this is a clear signal that long-term availability must be actively managed through repair, function-tested replacement units or strategic stockholding. A direct replacement officially designated by the manufacturer as a 1:1 successor could not be verified in the Siemens product sources reviewed. Instead, Siemens refers in its migration guide to S7-1500 technology solutions such as TM Count 2x24V or TM PosInput 2 in combination with CPU functions. This represents a migration option, but not a plug-in replacement for the FM 351.

Available EICHLER services and when they are relevant

For this assembly, EICHLER offers Repair, Exchange, Used assemblies and New assemblies. Repair is particularly suitable when the existing system still meets operational requirements, the mechanical peripherals are to remain unchanged, and a retrofit would currently introduce more risk than benefit. For repairs, EICHLER provides technical cleaning, preventive maintenance, comprehensive functional testing and a minimum 24-month warranty. This is especially important for obsolete or discontinued FM assemblies, as the objective is not only to replace a component but also to maintain the functionality of the existing axis and encoder environment. For purchasing and production departments, this provides a reliable option for reducing breakdown times and extending the economical operation of legacy systems.

What is the 6ES7351-1AH02-0AE0 used for in practice?

The assembly is used for positioning tasks with rapid traverse and creep speed, wherever axes are moved using robust PLC-based positioning logic rather than a complex servo control system. Typical applications include linear positioning systems, rotary positioning systems, feed axes, feeding systems, and legacy machines based on the S7-300 architecture. The key advantage lies in its seamless integration into existing systems and the clear separation between the PLC, the positioning logic, and the connected drive system.

Which encoders can I connect to the FM 351?

The FM 351 supports symmetrical incremental encoders, asymmetrical incremental encoders, SSI absolute encoders, and 2-wire sensors. For SSI encoders, parameters such as 13-bit or 25-bit telegram lengths, Gray code, and suitable clock frequencies are relevant. For users, this means that encoder selection must match the assembly not only mechanically but also electrically and in terms of parameterisation. Especially in retrofit or spare parts projects, it is important to verify that the existing encoder type, signal levels, cable length, and telegram parameters are compatible with the FM 351.

Is 6ES7351-1AH02-0AE0 still available or has it already been discontinued?

Siemens classifies the assembly as a spare part and specifies the lifecycle status PM410 – Product cancellation, effective from 01/10/2025, in the Industry Mall. This clearly places the module within the scope of obsolescence management. For operators, this does not automatically mean the immediate end of serviceability, but procurement becomes a planning issue. Anyone operating a critical machine with an FM 351 should secure repair options, a spare parts strategy, and, where appropriate, strategic stockholding at an early stage.

Is there a direct Siemens successor for the FM 351?

A direct 1:1 successor to the FM 351 could not be verified in the Siemens product sources reviewed. Instead, Siemens outlines migration paths to the S7-1500 platform in its official migration guide, for example through TM Count 2x24V or TM PosInput 2 combined with software functions within the CPU. This is an important consideration for decision-makers: there is a defined migration path, but there is no simple plug-and-play replacement module that can replace the FM 351 without engineering effort.

Can I commission the FM 351 with STEP 7 Professional or in TIA Portal?

Yes. Siemens provides an official support document that explicitly describes an example project for STEP 7 Professional V11 and TIA Portal V11 or later. For maintenance and engineering teams, this is important because existing FM 351 applications can be documented and reproducibly migrated into modern engineering environments. Nevertheless, the FM 351 remains a legacy assembly from the S7-300 platform, making correct hardware parameterisation, suitable HSP/support package versions, and the proper integration of the supplied example blocks essential.

When is repair more sensible than replacement or migration?

Repair is particularly economical when the mechanical components, wiring, encoders, and PLC environment of the existing system are intended to remain unchanged, and a migration to new technology would introduce additional downtime. On the EICHLER website, repair is described as including technical cleaning, preventive maintenance, functional testing, and a minimum 24-month warranty. For a discontinued FM assembly, this can be the most practical solution for avoiding downtime, reducing procurement risks, and continuing to operate the existing machine without immediate re-engineering.