Updated: Jan 9
Robotic welding provides manufacturers with several competitive advantages. Most importantly, it makes them more productive while generating more consistent, higher quality welds and reducing waste. Robots also empower manufacturers to address the current shortage of skilled welders to recruit. In addition, by taking the human element out of the welding process, robots eliminate operator dangers such as electric shock, exposure to gases and toxic fumes, and flash burns to the eye’s cornea. Ironically, new dangers have replaced the old ones, which is why it is critical for manufacturers to follow best safety practices when implementing a robotic welding program to avoid accidents.
Robotics professionals are quick to point out that while industrial accidents involving robots do happen they are infrequent. But again, they do happen. Accidents typically during non-routine operating conditions, such as programming, maintenance, testing, setup, or adjustment, when the employee is temporarily within the working envelop. 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 one-ton robotic arm. Fast forward to June 2015, when a German Volkswagen factory employee was crushed to death when setting up an industrial robot. A month later, a similar type accident involving a robot occurred in India.
The first step in developing a robotic welding safety strategy is to conduct a risk assessment that takes into account the severity of potential injury, frequency of exposure to a hazard, and the probability of injury. A risk evaluation is then performed to determine whether additional safety measures are needed to reduce the risk.
Typically, an effective safeguarding system for robotic welders is a combination of electrically interlocked perimeter guards, safety light curtains, safety laser scanners and pressure sensitive safety mats. Automatic weld curtains and high-volume ventilation systems can also minimise exposure to hazards in the welding environment. Torch length and robot reach must to be factored in when designing the system. Here is a review of suggested equipment:
Perimeter guards are designed to keep machine operators and other plant employees safely away from the robotic welding cell other than when they must enter for loading and unloading work-pieces or maintaining the welding equipment, robot and other machinery. Perimeter 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 if a worker is in vicinity. That's why factories establish "danger" or "kill" zones with perimeter guards that people have to stay out of while the robot is operating.
A laser scanner is a reliable, cost-effective safeguard installed around robotic welders. These are fully programmable devices, utilising 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, including where an operator requires frequent access to a cell 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 desensitised 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. Pressure sensitive safety mats are not be used as primary safeguarding except when all other means are not applicable.
Along with these measures, it is critical to remember the human variable. For instance, if a safeguard prevents the operator from loading and unloading parts from the cell, they may remove it without understanding the dire ramifications. More times than not, the problem is poor design. Improperly designed safety equipment frustrates workers and leads to a false sense of security, ultimately creating accidents.
Welding has always been a dangerous job, and there is no doubt that robots are making it safer by performing dangerous, repetitive tasks. But given the fact that tens of thousands of robots are now working in a close, collaborative manner with employees and often do not have the sensory ability to detect if those employees are in their vicinity, safety needs to be kept top-of-mind. A simple programming error or hardware malfunction can lead to a powerful robotic arm unexpectedly moving large distances at a high rate of speed. Safeguarding employees against these hazards is required to comply with stringent regulations. That same safeguarding equipment also provides an opportunity to make a positive impact on the bottom line since the cost of a robot-related injury goes far beyond hospital and medical costs.
(extract from ISHN News 8th April 2019)