Robotic Work Cells: Selecting the Height & Width of Your Fencing

Robot safety fencing exists to keep people out of this space, prevent objects from flying out of the robot cell, and, in some cases, to help block intense welding arcs and spatter. Robotic fencing must be designed based on the unique hazards found in the workplace’s risk assessment. Sizing, including height and width, is just one design-based factor manufacturers have to consider. The sizing will vary based on the environment, but there are safety regulations that fencing must comply with.

Understanding Safety Regulations

Multiple regulations cover robot safety and the use of robot safety fencing. Those with a particular emphasis on fence height and mesh size are:

• ANSI/RIA R15.06: A U.S. standard maintained by the Association for Advancing Automation that covers requirements for manufacturing, installing, and safeguarding industrial robots, and performing risk assessments. The standard also includes calculations for maximum reach envelope.
• ISO 10218-2: The international standard covering the safety of industrial robot cells, and includes minimum separation distances based on maximum reach.
• OSHA 29 CFR 1910.212: The U.S. standard for machine guarding and safety.
• ISO 13857: An international standard that specifies safety distances to prevent hazard zones being reached by upper and lower limbs.

Questions to Ask When Sizing Your Fencing

Beyond safety regulations, these are the questions you should be asking when designing your fencing:

What’s the Maximum Reach Envelope?

Start here when selecting the size of your robotic fencing. The maximum reach is the greatest distance the robot arm can extend from its mounting location and must include any tooling mounted at the end of the arm. It is not sufficient to rely solely on manufacturer data on robot capabilities.

What Is the Full Height of the Robot (Including End-of-Arm Tooling)?

Fencing around a robot must be tall enough that no one can reach into the work envelope. For most applications, the default is around 2,000 mm (79”), but taller fencing may be required in certain situations, including:

• When the robot is mounted on a pedestal or otherwise elevated.
• When elevated walkways pass near the robot cell.
• When equipment that could be stood on is placed adjacent to the cell.

How Far Does the Robot Travel After Triggering a Stop Signal?

If a gate is opened or a light curtain is activated, a safety-rated controller signals the robot to stop moving. It takes a finite amount of time for the signal to reach the robot controller, and then once power is cut, momentum can allow for some additional movement.

Given that the robot can travel at 2 m/s or more, the EOAT will continue moving for some distance before coming to rest, and this must be taken into account when designing a fencing system for a robotic cell.

Does the Robot Work on Tasks That Could Result in Flying Objects or Debris?

Some operations, such as grinding and welding, can create flying debris, and others have the risk of the robotic gripper unexpectedly releasing an object. In both cases, the fencing must be a) high enough to prevent debris from flying over the fencing, and b) solid to prevent materials from passing through the fencing panels.

Will Anything Need to Pass Through or Under the Fence?

Many robotic cells use conveyors to deliver and remove products, and these often pass through or under the fence panels. Simply mounting panels high enough for conveyors to run underneath is not acceptable. ISO 10218-2, for instance, covers lower limb access restrictions.

Where a panel is raised locally or an opening is created for a conveyor, the entry point must be guarded to prevent human intrusion into the work envelope.

Will You Need to Use an Overhead Crane?

If a cell is served by an overhead crane, the fence height must allow access while still providing protection. Consideration should also be given to the risk that the load may not be raised high enough to clear the panels. Cutouts protected by light curtains could be a solution.

Do You Need to Monitor the Inside of the Cell?

The latest generation of robot safety standards details situations that require monitoring of human workers inside the cell. Mesh fence panels provide good visibility, but it may also be useful to incorporate cameras to provide a better view.

Where fence panels are opaque, other monitoring systems, such as cameras, must be installed.

Where Are HMIs Installed?

HMI position determines where operators, maintenance technicians, and engineers will stand while working on the robotic system. They will need good visibility of the robot, but should not be put in a position that encourages reaching through or leaning over the fence.

Another way of looking at this is that fence dimensions at the HMI location must be such that it’s not possible to enter or reach into the hazardous area.

Why Performing a Risk Assessment Is the Best First Step

A risk assessment is a structured approach to identifying the potential hazards around a robot cell and developing mitigating actions. Carrying out a risk assessment before designing robot guarding will ensure the final system protects against all anticipated risks.

Assessments should also be performed when processes or heavy machinery are changed, as this introduces new risks.

Get Advice From a Professional

Once a risk assessment has been performed, ROBO FENCE® can help you design effective safety fencing and provide guidance on appropriate guarding systems based on industry regulations and the unique hazards associated with your plant or facility.

All robotic safety systems are manufactured in-house by our partner, Square Group, LLC, and engineered to meet the specific needs of your application and to integrate seamlessly into your environment. Contact us today to request a project consultation.