Special Report: Robot safety keeps evolving as technologies advance

Jan. 23, 2017

With trends toward faster speeds, bigger payloads and greater precision, robots have become indispensable to modern plastics plants. Yet those advancements would come to a crashing halt if those robots or the work cells in which they operate did not provide adequate safety features.

"Workplace safety is extremely important," said Carole Franklin, director, standards development at the Robotic Industries Association (RIA), Ann Arbor, Mich. "Any company that is going to make an investment in the top technology for production has a responsibility to invest in the top technology for safety."

From a standards perspective, there is plenty of guidance. The RIA provides support for the industry through the American National Standards Institute (ANSI)/RIA R15.06-2012 safety standard, which covers the proper use of safety features embedded in robots, as well as how to safely integrate robots into work areas. Additional guidance on the RIA standard is provided through technical reports that cover risk-assessment methodology, implementation of safeguarding devices and compliance of the latest version of the standard to older robots.

The RIA standard is based on ISO 10218, which was released by the International Organization for Standardization in 2011. Franklin noted that the ISO Industrial Robot Safety Working Group is working on a supplemental document about safety for end effectors, also known as end-of-arm tooling (EOAT), which she expects to be released during the first half of this year.

Risk assessment from the start

Risk assessment is a must in any installation, said Franklin and several manufacturers interviewed for this story. Franklin noted that risk assessments should identify any task that will be performed throughout the life cycle of the equipment. That includes installation, day-to-day operation and maintenance and repair.

Scott Kendrick, product project manager for Sepro America LLC, Warrendale, Pa., said risks should be assessed at the outset of any project, with periodic updates to accommodate changes. The assessments should take into account the entire operating environment, including nearby cells and traffic in the plant.

Dino A. Caparco, engineering operations manager for Yushin America Inc., Cranston, R.I., said the company evaluates the safety risks of new installations in work cells, and its first line of defense is to design them out.

One of the key issues in work cell design is discouraging the operator from trying to override a safety feature to perform a task. Duane Royce, VP of robots and automation at Wittmann Battenfeld Inc., Torrington, Conn., said making access to a work area difficult is not sufficient. "If you make things difficult for people, they will find a way around it," he said. "Part of a good guarding situation is that you give the operator the tools for them to do their job safely without the need to go around anything."

In Kendrick's view, the biggest risk of injury occurs when humans enter the robot's space when it is operating at high speeds. "There needs to be a clear understanding of the zones in which the robot is operating — zones where people may enter, zones where arms or hands may enter, and possible interference between the robot and other processing equipment or moving equipment, including carts and forklifts," he said. He recommends that sensors supplement guarding and interlocks. Interlocks can be installed on gates or doors, or could involve proximity sensors and light curtains.

One crucial piece of equipment that is unique to each application is the EOAT. It is a very important part of the robot system, and depending on its specifications, could pose significant risk, RIA's Franklin said.

The EOAT design should always give preference to repeatability and safety over cost, and should be included in the risk assessment, said Bob Shingledecker, VP and GM of Absolute Robot Inc., Worcester, Mass. He said it is important to consider the weight of the EOAT and the payload of the robot.

Caparco of Yushin noted that tool changing is a task that poses potential safety risks. When tool changes need to be performed manually, the robot should be set up to have an ergonomic tool-change position. He added that the company also has supplied automatic tool changers so that the same robot can perform several tasks in a work cell. That eliminates direct contact with the human operator, who can simply change the parameters on the control interface for the new job.

Many safety technologies available

 Fortunately, there is no shortage of available safety aids that can be added to a work cell. "We can integrate the [robot] with a whole different array of safety tools," said Michael R. Greenhalgh, director of operations for Yushin. "There are barrier guarding, safety mats, light curtains, beam-scanning-type systems. And the safety circuit that is in our robots is capable of coordinating with all of those [so] a customer can have a barrier guarding and a light curtain built into one cell."

Wittmann Battenfeld's Royce added that just implementing safety devices is not enough — they have to be used correctly. "Without the proper knowledge and foresight, they are going to be applied incorrectly, and you are going to end up buying a relatively expensive piece of safety equipment that is not really protecting," he said.

Shingledecker noted that safety equipment on modern robots is much more reliable than in the past. "Thirty years ago, most interlocks could be defeated," he said. "But now, with dual-channel safety relays and monitored safety equipment, and controllers and safety PLCs and switches, you can't do that," he said.

In addition to guarding and safety devices, better controls on the robot enable safer operation. "The robot and its controls should make it easy to operate the robot safely. That means a robot that is very ergonomic and geared to the specific application requirements," Sepro's Kendrick said.  "The robot and its controls should be designed to make safe operation very efficient at all times, so that operator should never feel the need to override the robot safety features in order to save time. This means simple programming, easy cycle-time optimization, safe and quick production changeover, as well as smart troubleshooting."

According to Greenhalgh, Yushin's technology allows the vacuum setting for EOAT to be set from the company's controller; in the past, the adjustment had to be made manually from a relay on the arm of the robot.

In another example, the company's E-touch II control provides audible guidance for its RC series of robots. The control issues a warning to the operator that the robot is moving to the wait position. In addition, the controller's HMI highlights the robot's movements and speeds.

What about older robots?

Of course, older robots are not equipped with the latest safety features. According to RIA guidelines, older technology should be in compliance with the standard at the time it was new, and remain in compliance until it is modified in some way or is moved to a new work cell, which would require a new risk assessment.

It would be impossible to decommission all the old robots in use in the industry, said Royce of Wittmann Battenfeld. On the other hand, the older the robot, the less integrity it has regarding safety. "So there really has to be a point when you take a hard look at older equipment and say, 'It's not worth the risk to my employees, my company, and it should be replaced.' There are other times where  ... it would be a wise man that [upgraded], improving some of the safety levels," he said.

Operator training, of course, is crucial, especially in an industry that has seen increasing turnover of employees, according to those interviewed. Kendrick  recommends that training should be simple and easy to understand, and should occur frequently, using concrete, everyday examples of safe operation.

Shingledecker recommends at least a yearly safety refresher course for anyone operating robots.

"When we do a robot installation for a customer, we do training of the new users," he said. The company provides a supplemental safety manual with every robot, which highlights issues that customers may not be familiar with. It provides safety information on every part of the robot and work cell, such as gate guards, electrical components and mechanical interlocks, etc.

 "It always comes back to the end user and their understanding," Shingledecker said. "You want to make sure that the people are properly trained, that you don't have somebody do something that they should not be doing."

John DeGaspari, senior correspondent

[email protected]


Absolute Robot Inc., 508-792-4305, www.absoluterobot.com

Robotic Industries Association, 734-994-6088, www.robotics.org

Sepro America LLC, 412-459-0450, www.sepro-america.com

Wittmann Battenfeld Inc., 860-496-9603, www.wittmann-group.com

Yushin America Inc., 401-463-1800, www.yushinamerica.com