Safety over networks: Where connectivity meets productivity

23 November 2020

Dr Martin Kidman discusses the issues relating to machine safety in an era of greater machine connectivity.

As Industry 4.0 machine connectivity grows, so does the potential to make automated production and material handling processes more flexible and responsive. Manufacturing and logistics environments still requires interaction between humans and machines, but the physical barriers between them are being gradually removed, creating more dynamic ways of working. 

Machines need no longer be rooted to the spot, separated from each other and from humans. Autonomous vehicles automatically change their paths to avoid obstacles, production areas are frequently reconfigured, machine settings and tooling must be changed rapidly to accommodate product variation.   

These modern, dynamic production environments are founded on bi-directional communications networks between machine controllers and a range of devices.  Connecting machines over networks has brought many advantages by dramatically reducing wiring and increasing plant autonomy. Bi-directional communication also offers the opportunity for diagnostic insights and other simultaneous data exchanges, right from the heart of machines.

The safety challenge
But how do you ensure this more responsive and interconnected world remains safe for the humans working in it and how can the safety of the machines and the wider systems they are part of be kept inherently safe?

The possibility to transfer safe (as opposed to ‘non-safe’) data over networks has only really been possible since the turn of the 21st century when the IEC 61784-3 standard was published. It covers functional safety fieldbuses and gives the rules and profile definitions of adding a safe data layer on top of existing fieldbus protocols. 

A key advantage of implementing a safe network is that wiring is dramatically simplified by communicating over same fieldbus system. Traditionally, a safety system has needed many individually-wired connections with added, in-built redundancy.  With complete safety information about different devices at their fingertips, designers can also configure and reconfigure complex safety systems without the need to redraw wiring diagrams every time. 

Safety device manufacturers have introduced their own proprietary safety protocols.  SICK’s EFI (Enhanced Function Interface), for example, enables fail-safe communication using the “Black Channel” approach allowing the transmission of both failsafe and standard data on the same bus system. Using EFI, safe communication has a very low probability of dangerous failure and does not normally reduce a system’s integrity, enabling performance levels of up to PLe (EN ISO 13849) and safety integrity levels of up to SIL3 (IEC 62061) to be maintained.

The EFI interface was initially a linear bus system enabling communication between four SICK devices.  Then, the release of the innovative SICK Flexi Soft EFI-pro Gateway enabled open and safe integration via EtherNet/IP CIP Safety and allowed connection to devices like the SICK microScan3 safety laser scanner as well as to third-party robot controllers -, remote I/O modules and safety PLCs. 

Connecting a safety laser scanner to a safety controller over EFI Pro enables designers to access all safe data over one cable to create adaptive, scalable modular safety. Field switching, adding multiple scanners or connecting to EtherNet/IP-enabled robots, encoders and other devices, no longer requires multiple cables and programming tools.

The system enables safe human and robot collaboration with minimal effort.  Especially where speed and distance are issues, it offers intelligent and responsive safeguarding for situation-dependent robot protection. 

With Safe EFI-Pro, Automated Guided Vehicles (AGVs) and carts can work more quickly, intelligently and safely. The SICK microScan3 EFI Pro safety laser scanner offers storage of 128 Individual fields and simultaneous field evaluation of up to eight protective fields, with up to a 9m range. Simultaneous protective monitoring of multiple fields means less need for switching between monitoring cases, so dynamic protective fields can be shorter, and therefore more responsive and efficient. The safe contour detection field supports applications such as safe AGV docking and protecting workers at narrow access points as well as providing signals for self-muting. 

Dr Martin Kidman is a safety specialist at SICK UK.

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