The development goals in the project planning of safety devices include the seamless integration of safety functions into the process, transparency with regard to the operating status, minimized installation effort and high connectivity. The relocation of many safety functions from hardware to software and the use of electronic safety switching devices and safety controllers create the prerequisites for achieving these goals.

Individual instead of from the catalog

If the specific requirements of an application go beyond the 'mainstream' (but not only then), customer-specific adaptation of the safety functions helps to optimize the interaction between machine safety and the process. In this respect, Schmersal has established a solution path with individual software modules for both programmable safety controllers and parameterizable small safety controllers, as these can be delivered ex works with customer-specific software.

Such customer-specific safety solutions are developed and planned by a project team at Schmersal in the 'Systems and Solutions' business unit. Here are some practical examples.

Compact controller replaces 13 relay modules

The Protect PSC1 programmable safety controllers form the basis of many safety solutions - with customer-specific software on request.

© Schmersal

A company that manufactures food processing machines and was developing a new machine series consulted Schmersal with the aim of optimizing and consolidating the selection of safety 'hardware' for monitoring several safety doors and flaps on a cutting system. The challenge was to standardize the 13 different types of safety evaluations that were installed in various product series of the machine manufacturer. This was triggered by a mix of availability requirements, increased safety standards and discontinuations on the part of the manufacturers.

In collaboration with Schmersal, the functions of these 13 safety modules were combined in one device: the compact safety controller 'Protect Select', or more precisely, the OEM version with customer-specific software modules. This means that a single version of the compact control unit can now be used in all product series - without limiting the functionalities. As part of the project, the safety parameters were determined and all machine safety requirements were taken into account. Among other things, the machine user now has improved diagnostic options in the event of faults and irregularities.

Customized standstill monitoring

A manufacturer of bread slicing machines for supermarkets was looking for a solution for monitoring and integrating the safety devices standstill monitoring of the cutting device, guard locking, sensor monitoring of the guard and emergency stop. In competition with several suppliers, Schmersal was also able to prevail here with the concept of the 'Protect Select' compact safety control system in an OEM version. The concept with customer-specific software takes into account all the individual requirements of the machine manufacturer. The control system can be used universally for several series, enables comprehensive diagnostic functions and offers considerable cost benefits compared to conventional standstill monitoring.

Installation of safety switching devices

There are also advantages in the installation and integration of safety switching devices in the field if the safety technology is customized, as the third example shows: A manufacturer of packaging machines monitors the safety doors of a machine series with solenoid interlocks (AZM 300), safety sensors (RSS 260) as well as control devices and emergency stop, among other things. Schmersal's Application Engineering department suggested connecting these (safety) switching devices via a 'Safety Fieldbox'. It enables the connection of up to eight safety switching devices of different types in the field. Both the safety-related and operational signals are collected and connected to higher-level controllers via Profinet/Profisafe. In the future, users will also have access to versions with Ethernet/IP, CIP Safety and Ethercat FSoE connections. This means that machine manufacturers benefit from simplified installation and users benefit from fast diagnostics in the event of a fault.

Ways out of the material shortage

A new task for the 'Systems and Solutions' team has only arisen in recent months. The reason for this is the continuing shortage of electronic components. At Schmersal, this means that the latest generations of electronic safety switching devices in particular have at times not been and cannot be produced in the quantities required by the market.

The task is therefore to find alternative solutions that require as few changes as possible from the machine manufacturer's point of view and offer full functionality from the user's point of view. With a little engineering effort and a precise analysis of the requirements, this can be easily accomplished - especially as some identical switches with a different operating principle are available. An example: The magnetic safety sensor BNS16 and the electromechanical safety switch AZ16 are available as alternatives (without microcontroller) to the safety sensors of type RSS16 with safe RFID technology (and microcontroller). In individual cases, however, safety calculations must be carried out to determine which solution is actually suitable - only to find out, unfortunately, that not all the necessary properties can be implemented 1:1.

Tobias Thiesmann is System and Solution Manager at the Schmersal Group in Wuppertal.

© Schmersal

An example from consulting practice: For one and the same application (cycle time 1000 s = 12,672 actuations per year, three devices in series), a maximum performance level (PL) e and a high diagnostic coverage (DC) were determined for the RSS260 RFID safety sensor. Performance level d and a low DC were determined for the AZ16 electromechanical safety switch. PL c and no DC were calculated for the BNS260. The reasons for this are wear (which does not occur with RFID-based safety sensors), fault masking and a lack of self-monitoring functions (for short-circuits or cross-circuits or similar). In addition, the series connection has a negative effect on the performance level. However, the designer can make use of the option to transfer certain functions (e.g. self-monitoring for short-circuits and cross-circuits) to the evaluation, for example to the safety relay module.

As the examples show, early collaboration with safety system experts can bring benefits when designing new machine series or optimizing existing ones. This applies when the use of customer-specific (safety) software is being considered.