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A Guide to Robot Cell Perimeter Guarding

18/03/2015

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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, outlines the requirements for perimeter guarding of robot cells.

Industrial robots are increasingly being adopted for automated manufacturing applications beyond the traditional automotive sector where they are now well established. 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, the 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.

Robot Machine Guards

It is vital that perimeter guarding for robot cells is adequate and the correct guarding is selected for any given application

Physical perimeter guards are the norm for ensuring robot safety, though light guards, laser area scanners and pressure-sensitive mats can be appropriate for use at entry/exit points for materials and personnel. Other types of guarding that are occasionally adopted include a camera-based system and roller shutter doors. This latter option can be particularly useful where optoelectronic devices or safety mats are unsuitable, perhaps because floor space is limited (guards have to be spaced adequately from the hazard, as specified in BS EN ISO 13855:2010, the successor to BS EN 999) or because optoelectronic guards and safety mats cannot provide protection from hazards such as weld flash or spatter. Procter Machine Guarding offers the Talos High-Speed Roller Door, which is available in a range of sizes and specifications, including optional viewing panels.

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 guarding must be reconsidered to check that it still providing adequate robot safety. Should the guarding need adjustment, the advantages of modular perimeter guarding systems quickly become apparent.

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 lightweight, clean and ‘high tech’ aesthetics, and the fact that guards 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 steel perimeter guarding for robot cells
For robot guarding projects requiring steel posts and panels, Procter Machine Safety 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 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 series uses separate posts and base plates, the Strong 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 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. 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 series.

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

If customers have prepared their own layout designs, Procter can quote against these on either a supply-only or supply-and-install basis. Where required, guard 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 guards 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.

To inquire about aluminium and steel modular perimeter guarding for robot cells, please go to the Contact Us page, or visit the Perimeter Guarding section of the website to see further details and download brochures.

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