Modular Safety Controller

The Flexi Soft safety controller from SICK offers a range of main modules, expansion modules, motion control modules, and gateways that can be used to create a customized solution for your safety application.

Aw 26278 Flexi Soft

If there’s one truism in industrial control applications, it’s that one size surely does not fit all. Even if you arrive at an approach that works perfectly today, it likely won't be long before you encounter the need for a small change somewhere in the system that will necessitate a different approach. As a result, control system modularity has become more of requirement for modern automation than just a desirable option.

To address this issue, SICK offers the Flexi Soft safety controller. The Flexi Soft concept offers a range of main modules, expansion modules, motion control modules, and gateways that can be used to create a customized, efficient solution for safety applications.

Flexi Soft contains all the components needed by modern safety systems, such as:

  • Main control modules, available with or without safe networking;
  • Expansion modules for standard and safety applications;
  • Gateways into all common bus systems; and
  • Motion control modules

The controller can grow module-by-module as a given task evolves via its ability:

  • to integrate up to two gateways and twelve expansion modules;
  • connect for as many as 256 safety sensors via Flexi Loop; and
  • network up to 32 safety controllers.

In terms of application, the Flexi Soft safety controller is an ideal choice for safeguarding against hazardous points in presses and laser cutting systems used in machine building applications. It is also an efficient tool for the packaging industry, which uses machines with a large number of doors and flaps that require protective measures. In these kinds of applications, Flexi Soft keeps the amount of wiring used to a minimum by allowing you to network overlapping safety functions in modular machines and integrate them into the standardized system controllers. Plus, the license-free Flexi Soft Designer configuration software offers intuitive programming, rapid commissioning, and continuous monitoring. The entire configuration can be documented in multiple languages with just one click.


The main modules of the Flexi Soft safety controller can handle connections of up to 12 Flexi Soft expansion modules and up to two Flexi Soft gateways. The main module offerings are:

  • CPU0, which performs basic controller functions and includes an RS-232 programming interface;
  • CPU1, which offer the CPU0 functions plus an interface for handling the advanced functions of SICK safety sensors;
  • CPU2: offers CPU1 functions plus backup function automatic configuration recovery;
  • CPU3: offers CPU2 functions plus USB programming and Flexi Line interface;

Available I/O modules for Flexi Soft include:

  • XTDI input extension with eight safety inputs and eight test pulse outputs;
  • XTIO input/output extension with eight safety inputs and four safety outputs (per SIL3);
  • XTDS input/output extension with eight safety inputs, four standard outputs, two switchable outputs or test pulse outputs; and
  • STIO input/output extension with six inputs, six outputs, and two switchable inputs or outputs.

Gateway modules for Flexi Soft offer Active Heartbeat or Passive Polling modes and display diagnostic information in a text format. The gateway diagnostics interface with all common networks, including PROFINET IO, PROFIBUS-DP, EtherCAT, CANopen, Modbus TCP, Ethernet (TCP/IP), DeviceNet;


Beyond the numerous custom configurability options enabled with the Flexi Soft modular controller system, other measurable benefits include:

  • Prevention of redundant inputs and outputs;
  • Less downtime due to gateways for all common fieldbus systems;
  • Diagnostic interfaces on the main module and configuration memory for quick commission, faster troubleshooting and reduced downtime;
  • Fast and easy configuration enabled with wiring diagrams and documentation in the FlexiSoft Designer; and
  • Predefined TUV-certified software function blocks for common applications.

Watch the video below highlighting the Flexi Soft modular safety controller system.

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