Whether they are used for new projects or for upgrading existing plant, safety light curtains are an excellent way of enhancing productivity without compromising safety. Provided there is no requirement for a physical barrier, safety light curtains save valuable time in comparison with conventional access gates with safety switches. While safety light curtains in themselves can deliver benefits to end users and integrators alike, there is even more to be gained when light curtains are linked to a safety fieldbus such as SafetyBUS p.
Pilz offers a comprehensive range of Type 2 and Type 4 safety light curtains, with a SafetyBUS p interface available on the Type 4 models. All of the Type 2 and Type 4 optoelectronic safety devices meet the requirements of EN 61496-1: 1997 (Safety of machinery - Electrosensitive protective equipment. Part 1: General requirements and tests) and prEN 61496-2: 1997 (Safety of machinery - Electrosensitive protective equipment. Part 2: Particular requirements for equipment using active optoelectronic protective devices). Models are available with resolutions of 14, 30 and >40mm for sensing breaches of the barrier by finger, hand or body.
The SafetyBUS p versions present integrators and users with a number of advantages, such as the ease with which they can communicate with fieldbus - and hence the safety-related control system - via a single M12 connector. Furthermore, a second M12 port enables the direct connection of additional I/O in the form of two emergency stop inputs, one test/start input, two muting sensors and a muting lamp (with their status communicated via SafetyBUS p). This eliminates the need for any cabinet installation and associated wiring. Note also that the light curtain draws its power directly from an active junction, which means that it is not necessary to install a separate 24V DC supply. For applications where several light curtains are daisychained together, Pilz has a software utility for checking that the proposed distance between the light curtains will not cause an unacceptable voltage drop in the cables.
Safety light curtains normally require the installer to configure the blanking, muting and other settings by means of a series of switches, but this procedure is not required when using a device connected to a SafetyBUS p network. Instead the light curtain is programmed via the Pilz PSS WIN-PRO software suite. Not only does this help to avoid errors, but it also ensures that subsequent replacements - perhaps due to physical damage to the light curtain - are quicker because the light curtain configuration can be downloaded automatically from the safety controller via the SafetyBUS p fieldbus.
With SafetyBUS p, the light curtain diagnostics are also vastly improved. Users can readily access information that is normally unavailable remotely from light curtains, such as the operational mode, status and errors relating to alignment, emitting, muting and emergency stops. This diagnostic data is a major benefit compared with alternative light curtains, resulting in simplified system maintenance and increased plant availability.