Time to Re-Examine Robotic Arc-Welding Safety

October 27, 2023

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Anyone walking the aisles of FABTECH 2023 rightfully would conclude that collaborative robots (cobots) are a hot commodity for welding applications. The allure of cobots comes from their ease of use (little to no programming knowledge required), fast deployment (make parts the same day your cobot arrives) and ability to improve productivity. Additionally, pre-engineered welding cells also have become very attractive, particularly as artificial-intelligence (AI)-driven systems promise to reduce programming complexity, which long has been a hurdle for fabricators in high-mix, low- to medium-volume applications.

In essence, the democratization of welding automation has arrived. In the next few years, thousands of small- and medium-sized businesses (SMBs) will become first-time automation users. Driven by increased reshoring opportunities in the face of labor and supply-chain challenges, application of automation technology is forecast to expand at a compound annual growth rate exceeding 10 percent, with welding robots representing a large part of these applications.

However, SMBs would be wise to proceed with caution when implementing robotic/cobotic welding cells, by first familiarizing themselves with the standards related to robotic welding. These standards, created by the American Welding Society (AWS), cover safety, system components, risk assessment, personnel, training and system testing.

For a deep dive into the standards and some critical perspective on robotic-welding safety, we turn to Vernon Mangold Jr., principal consultant at Kaysafety, Dayton, OH. Mangold, past-chairman of the AWS D16 Committee on Robotic and Automatic Welding, contributed to AWS D16.1, Specification for Robotic Arc Welding Safety, and is the principal author of AWS D16.3, Risk Assessment Guide for Robotic Arc Welding.

Q: Please explain your philosophy when it comes to welding safety.

Mangold: There is no acceptable injury. My grandmother said that there is no substitute for high morals when you’re talking about safety. She reminded me that every severe accident that happens in a manufacturing plant is in some respects avoidable, but you must have a desire to remove the hazard. Our highest priority must be safety, not the cost-per-second of cycle time.

Q: What are the biggest hazards associated with automated welding?

Mangold: The key issue is not validating the entire application, which encompasses hardware integrated with the software to make a manufacturing system. Everyone worries about robot-arm collisions, but they don’t happen as often as surmised. Most incidents result from failures of everything surrounding the robot. People become fixated with the robot and miss obvious hazards, such as the movement of large weldments, pinch points and controls integration. Moreover, welding may be just one step for any number of automated processes, such as painting, grinding and parts handling. Each one of these has its own idiosyncrasies that may be innocuous on the surface but which could lead to potential injuries. Finally, we can’t forget all of the more typical welding-safety hazards, such as exposure to ultraviolet light, heat and sparks.

Q: You say that there’s no room for safety complacency. Please expand on that.

Mangold: Previous safe operation is not a substitute for engineering reasoning. Anytime a metal former makes a change to robotic hardware or control structure it should perform a risk assessment. When investigating an accident, I first check for changes, then ask if the process has been validated. If the answer is “yes,” I then ask, “What failed?” And if “no,” I then ask, “Why not?”

Q: How should metal formers know what safeguards to employ?

Mangold: I recommend a structured risk-assessment process that describes the application, itemizes the equipment, lists potential personnel-safety hazards, analyzes the risks of each hazard, selects mitigation tools, verifies the mitigation and documents the necessary steps. For guidance on how to develop such a process, readers can turn to AWS D16.3, Risk Assessment Guide for Robotic Arc Welding, which walks through the elements of the process, provides terms and definitions, offers guidance for safeguarding, and even includes a sample risk-assessment form.

Q: Are there any tricks of the risk-assessment trade?

Mangold: There is no substitute for going through the formal process. After that, I engage in “what-if” scenarios. Another technique I use: stripping an automated-welding setup of all of its safeguards and then building a risk assessment backward based on the safety requirements of the processes. I then add safeguards and produce a parallel report to determine the cost of those safeguards and evaluate their effectiveness. I employ this process during system inception as well as after making any changes.

Q: What strikes you about the rise of cobots for automating the welding process?

Mangold: I’ve spent my entire career working to make robots quicker, more resilient and accurate, and able to carry higher payloads. Cobots reverse all of those advances so that humans can work alongside. However, just because a metal former can install a cobot and be up and running in hours doesn’t mean that it can avoid due diligence for safe operation, and that can take days or weeks.

Q: Does the AWS D16.3 standard cover cobots?

Mangold: Yes, Table 1 of section 5.5.1 of the standard describes three robotic operating subclassifications based on the robot’s payload, rotational torque of any auxiliary equipment, and the velocity of the robot or any other moving equipment in the system. Cobots are classified as “low-energy robots.”

Q: Have you investigated any safety incidents with cobots?

Mangold: Yes, two of them, and neither were welding-related or fatal. One case involved a maintenance worker in an adjacent cell and the other involved someone performing maintenance on the cobot system. In both cases the cobot arms did not strike anyone; however, the ancillary, integrated machinery caused the accidents, and that is perhaps the hardest thing to convey to young or inexperienced technicians. Planning these cells requires consideration of the entire automation environment.

Q: In a nutshell, how can metal formers improve cobot safety?

Mangold: We tend to blame the operator, but what we really must do is remove incentives for unsafe activities. For example, a hot part by its nature will prevent people from grabbing it, but the only other incentive that an operator would have for grabbing a hot part is trying to beat the clock to win the cycle-time war. Metal formers seeking to be good corporate citizens take safety seriously. They employ a risk-assessment process as part of their standard manufacturing-analysis tools, and engineer systems to remove hazards. MF

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