Perimeter guarding of robot cells

There are implications for safety not just when a robot is installed, but each time it is reprogrammed, and perimeter guarding should be assessed and reconsidered on each occasion to ensure it is meeting the safety requirements. Should the guarding need adjustment, the advantages of modular perimeter guarding systems come to the fore.

So says Jeremy Procter, a member of standards committees ISO/TC 199/WG 6 (Safety distances and ergonomic aspects) and BSI MCE/3 (Safeguarding of machinery), and managing director of Procter Machine Guarding, who outlines the requirements for perimeter guarding of robot cells in this article.

Industrial robots are increasingly being adopted for automated manufacturing applications beyond the traditional automotive sector. Once programmed, a robot will perform the same task consistently and reliably, but safeguards have to be in place to protect personnel in the vicinity from coming into contact with the robot, end-of-arm tooling or payload.

Furthermore, account has to be taken of the unpredictability of personnel and the chance that something might go wrong with the robot, controller, process or materials, resulting in unexpected movements or other hazards.

Robots offer the advantage that they can be programmed to repeat a particular task with great accuracy, and a further benefit is that they can be reprogrammed to perform a different task, whether that is a variation of the original task or a completely new task elsewhere within the factory. Whenever a robot is reprogrammed, the perimeter guarding must be reconsidered to check that it still providing adequate robot safety.

Generally modular perimeter guarding systems come in two types: steel and aluminium. Procter Machine Guarding is in the unusual position of offering both types, so can give an unbiased opinion on which would be best for a particular application. In some cases aluminium is preferred for its light weight, clean and ‘high tech’ aesthetics, and the fact that guarding can be constructed, modified or extended with no need for welding or painting. In other cases, steel is preferred for its rugged construction and ‘heavy duty’ appearance that is more appropriate in, for example, the metals processing industries.

Modular aluminium perimeter guarding

Since 2014 Procter Machine Guarding has been working in partnership with Bosch Rexroth to specify, design and install the EcoSafe modular aluminium perimeter guarding system. Depending on the customer and the project, Procter can provide any level of service required; this might entail the supply of EcoSafe posts, panels, gates and fittings that have been part-assembled to a customer’s design, or a fully project managed service including a site survey, design, specification, assembly and installation of EcoSafe perimeter guarding.

EcoSafe frame heights can be specified from 250mm to 2000mm and the extruded aluminium posts are either 45x45mm or 45x90mm. Panel frames are assembled from 30x30mm aluminium extrusions, with the most common infill being galvanised steel 12AWG (2mm) triple crimp wire, though the specially designed slots in the extrusion can alternatively accept panels up to 5.8mm or 7.6mm thick (depending on the type selected), or 2-4mm or 4-5mm if the optional spring clamps are used.

Horizontal or vertical rails can be added to the panels for increased strength and stiffness, with these being 30x45mm to allow the infill to be inserted from both sides.

The Bosch Rexroth EcoSafe perimeter guarding range includes a wide choice of standard components and accessories for creating hinged or sliding doors, attaching interlocks or installing glazing panels, for example. There are also specially designed brackets that enable frames to be installed very quickly within the support posts and, importantly, removed rapidly when access is required for maintenance.

Modular steel perimeter guarding for robot cells

For robot perimeter guarding projects requiring steel posts and panels, Procter Machine Guarding usually recommends Satech Strong, a heavier-duty modular perimeter guarding system. However, for projects where small, lightweight robots are used, the Satech Basic modular perimeter guarding is very cost-effective.

Satech Strong perimeter guarding features uprights manufactured from 60x60x2mm rolled hollow section steel, together with panels in which the frame is fabricated from either 20x20mm or 30x30mm steel with 3mm welded wire mesh infill on a 22x100mm grid. Patented fast assembly clamps enable the guards to be assembled quickly and easily – and disassembled again if access is required for maintenance.

Whereas the Basic perimeter guarding series uses separate posts and base plates, the Strong perimeter guarding series benefits from steel bases that are welded to the post for additional strength, and pre-punched with four mounting holes for fixing to the floor.

Posts are offered in five nominal heights from 1120mm to 2640mm, and panels in four heights from 960 to 1900mm and seven widths from 200mm to 1500mm. Components are finished in a tough polyester powder coat; posts and panels can be supplied in RAL 9005 black, RAL 1021 yellow, RAL 7035 grey or custom colours, though the most common combination is yellow posts and black panels for good visibility of the guarding and the process beyond.

Satech Basic perimeter guarding uses uprights manufactured from 40x40x2mm rolled hollow section steel, together with panels in which the frame is fabricated from 20x20mm steel with 3mm welded wire mesh infill on a 22x100mm grid. The posts are supported on base plates formed from steel plate with three or four pre-punched holes for securing the guarding to the floor. Posts are offered in five nominal heights from 1120mm to 2640mm and are height-adjustable to accommodate for uneven floors.

Perimeter guarding panels are available in four heights from 960 to 1900mm and seven widths from 200mm to 1500mm. Customers can choose either screwed assembly or the Satech patented fast assembly clamps for joining panels and posts. Colour choices are the same as for the Strong perimeter guarding series.

A further perimeter guarding option is panels with clear polycarbonate or sheet steel infills, the latter of which can be equipped with viewing windows if required. There is an extensive choice of Satech perimeter guarding access gates, ranging from single- and double-leaf hinged gates, tracked or cantilevered sliding gates, and rise-and-fall gates. These can all have interlocks pre-installed, ready for connecting to the robot cell’s safety-related control system.

Compliance and standards

When Procter takes responsibility for the specification and design of steel or aluminium modular perimeter guarding, the guards comply with EC and HSE requirements and are CE marked or issued with a Declaration of Conformity as appropriate on completion. Standards that are complied with include the following:

• BS EN ISO 12100:2010 Safety of machinery. General principles for design. Risk assessment and risk reduction
• BS EN 953:1997+A1:2009 Safety of machinery. Guards. General requirements for the design and construction of fixed and movable guards
• Note that BS EN 953 will shortly be superseded by BS EN ISO 14120 Safety of machinery. Guards. General requirements for the design, construction and selection of fixed and movable guards
• BS EN ISO 13855:2010 Safety of machinery. Positioning of safeguards with respect to the approach speeds of parts of the human body
• BS EN ISO 13857:2008 Safety of machinery. Safety distances to prevent hazard zones being reached by upper and lower limbs
• BS EN 349:1993+A1:2008 Safety of machinery. Minimum gaps to avoid crushing of parts of the human body
• BS EN ISO 10218-2:2011 Robots and robotic devices. Safety requirements for industrial robots. Robot systems and integration
• BS EN ISO 11161:2007+A1:2010 Safety of machinery. Integrated manufacturing systems. Basic requirements
• Although HSG43 Industrial Robot Safety is no longer published by the HSE (Health and Safety Executive), this publication contains valuable guidance.

Whether customers specify aluminium or steel modular perimeter guarding for their robot cells, Procter Machine Guarding can also supply and install interlocks, safety light barriers and pressure-sensitive safety mats. Importantly, the company can design, manufacture and install bespoke perimeter guarding for infilling any areas where standard modular perimeter guarding is unsuitable, such as around infeed or outfeed conveyors, or where the guarding abuts other machinery.

This can be done in such a way that the bespoke elements blend visually with the standard modular perimeter guarding components used elsewhere. In addition, extra protection can be installed where forklift trucks operate, to safeguard against damage to the perimeter guarding and safety devices that could result in costly downtime.

If customers have prepared their own perimeter guarding layout designs, Procter can quote against these on either a supply-only or supply-and-install basis. Where required, perimeter guarding switches can be installed in preparation for connecting to a safety-related control system, which saves time for the customer or system integrator.

In the event that a robot is redeployed at a later date, customers can reconfigure the EcoSafe or Satech modular perimeter guarding themselves, or Procter Machine Guarding can undertake the work, including the supply and installation of any additional standard elements or bespoke infill panels, thereby ensuring that robot safety is maintained.

Visit the Procter Machine Guarding website for more information on perimeter guarding.

See all stories for Procter Machine Guarding