Although robotic welders are one of the most expensive pieces of equipment on a plant floor, welder manufacturers may not provide the safeguarding needed for compliance with Occupational Safety & Health Administration (OSHA) regulations and American National Standards Institute (ANSI) standards. This represents a challenge as well as a danger for any manufacturer deploying robotic welders.
ANSI, in particular, is the author of industry-specific safety standards as to how robotic welders are required to be safeguarded. ANSI/RIA R15.06-2012 is now harmonized with the International ISO 10218-1 & 2 standard for robot manufacturers and robotic system integrators. In addition, the American Welding Society (AWS) has created more than 350 standards for welding practices and procedures and safety standards for welding robot systems.
Compared with other robotic systems that have been in place in U.S. manufacturing since the 1960s, robotic welding is a relatively newer technology, having been introduced in the mid-1980s. Today, however, it is estimated that more than half of the robots in North American manufacturing are used in welding. Robotic arc welding alone now commands about 20% of all industrial robotic applications. Despite this surge in use, some robotic welder manufacturers continue to not include basic safeguarding devices as part of a new equipment package, nor are they required to do so in the United States. This places safeguarding responsibilities, as well as the legal liability should an accident occur because of the absence of safeguards, squarely on the shoulders of the end user.
The term “safeguarding” simply refers to protective measures for employees who operate or come into contact with dangerous moving machines in a manufacturing setting. Safeguarding devices will detect or prevent accidental or intentional access to a potential hazard. Safeguarding devices operate automatically to protect workers from hazards found at the point of machine operation, power transmission, and other places moving parts are found.
While the total number of workers injured each year has decreased significantly since 1970, when the Occupational Safety and Health Act was passed that first required safeguarding, experts say the rate of fatal and non-fatal worker injuries is still far too high. In 1970, there were about 38 worker deaths a day, compared to 13 a day in 2014.
Machine guarding violations are one of the top 10 industrial-environment violations cited by OSHA, ranking No. 8 in 2016. Unguarded hazardous machinery is a major source of amputations and other traumatic injuries. According to OSHA, nearly 5,000 workers in metal fabricating plants suffer nonfatal injuries annually in the United States. Besides being dangerous, a lack of machine safeguarding can be expensive. OSHA recently fined a steel tubing manufacturer $139,800 and placed it in OSHA’s Severe Violator Enforcement Program for repeat and serious machine guarding violations found at its Ohio facility. In another instance, OSHA assigned a Jacksonville, FL, manufacturer $697,700 in penalties in connection with the death of a 32-year-old machine helper.
Robotics professionals are quick to point out that while industrial accidents involving robots do happen, they are infrequent. But again, they do happen – typically during nonroutine operating conditions, such as programming, maintenance, testing, setup, or adjustment. Way back in 1979, the first recorded death by robot happened in a car factory where a worker collecting parts from a storage facility was hit and killed by a robotic arm. Fast-forward to June 2015, when a worker in a German Volkswagen factory was crushed to death when setting up an industrial robot. A month later, a similar type accident involving a robot occurred in India. Accident statistics maintained by OSHA identify 27 fatalities associated with robots from 1984 to 2013, while the total number of workplace fatalities in the United States in 2013 alone was 4,585.
In short, industrial accidents involving robotics are rare but are increasing as robots’ use proliferates across all manufacturing sectors. Also, the ability of a robot to move and act independently through advanced software and vision systems raises important safety questions, especially with the emerging trend of “co-bots” manufacturers are starting to install to work alongside workers on the production line.
Safeguarding robotic welders
An effective risk-reduction strategy for the deployment of robotic welders includes a customized combination of electrically interlocked perimeter guards, safety light curtains, safety laser scanners, and pressure-sensitive safety mats. Additional safety devices such as automatic weld screens and high-volume ventilation systems can also minimize exposure to hazards in the welding environment.
Perimeter guards are designed to keep machine operators and other plant employees safely away from the robotic welding cell. The guards are positioned around a robot work envelope and incorporate gates equipped with interlocks so that all automatic operations of the robot and associated machinery will stop when any gate is opened. Robotic welders tend to do the same thing again and again, and cannot generally tell what it is they are working with. That’s why factories establish “danger” or “kill” zones with perimeter guards that people have to stay out of while the robot is operating. OSHA will issue citations for robotic welding cells that are unguarded or improperly guarded for not meeting 29 CFR 1910.212, also known as the “general duty clause.”
A laser scanner is a reliable, cost-effective safeguard installed around robotic welders. These are fully programmable devices, utilizing an infrared laser to scan its surroundings and measure distances. It can be set up to scan on a horizontal or vertical plane. Should a person or object come into contact with the infrared beam, hazardous machine motion stops.
A light curtain system is another common safeguard used with robotic welding equipment. Often it’s used where an operator requires frequent access to a hazard and the hazardous machine motion can be stopped relatively quickly. Most systems include a transmitter that emits infrared light to the receiver. The transmitter and receiver can be installed top to bottom (vertical protection field) or side to side (horizontal protection field). Should an object or the operator interrupt an infrared beam, it generates a stop signal to the machine control. The light screen sensing field can be desensitized to ignore some objects but respond to other objects of a defined size, or muted for temporary suspension to allow material feeding.
Pressure-sensitive safety mats are yet another option for safeguarding robotic welding equipment. While they can be used around the perimeter of machines, more commonly they’re used as a secondary safety device located inside of perimeter guarding systems. When someone stands on the mat, the metal plates make contact and hazardous machine motion stops. They must not be used as primary safeguarding except when all other means are not applicable. Also, when installing mats, ensure they’re located so an operator or other employee, when stepping onto the mat, cannot reach into the point-of-operation hazard prior to the machine’s hazardous motion coming to a stop.
Along with these measures, it is critical to remember the human variable. If a specific safeguard prevents the operator from running the welder the way he or she wants to, the operator may look to defeat safeguarding without understanding the ramifications of doing so. Providing training to know how to intervene if a production problem arises is extremely important to keep workers safe.