- Created: 2017-04-11
Machine integrators offer advice on press brake safety
by Kip Hanson, senior editor
Safety caps on vitamin bottles, safety helmets when riding bicycles, and those darned irritating safety plugs we stick in electrical outlets to protect our kids: For those of us who once rode in our parent’s car without once wearing a safety belt, it might seem the world has gone a little safety crazy.
But not even the most reckless of us would argue over the importance of workplace safety, especially around machinery that can easily nip off a finger or crush a hand. Isn’t it ironic, then, that press brakes are often the last piece of shop floor equipment to receive attention from the company safety director and are even considered “unguardable” by some industry experts?
As far as Tony Caruso, director of U.S. sales and marketing at safety equipment and automation provider ISB, is concerned, there’s no such thing as “safe distance.” He says that even OSHA sometimes looks the other way when it comes to safeguarding press brakes. “The industry is still transitioning to higher safety standards on machine guarding, especially when it comes to sheet metal fabrication.”
Don’t believe him? Dust off your OSHA Directive Number CPL 02-01-025, Guidelines for Point of Operation Guarding of Power Press Brakes document and start reading. You’ll see plenty of vague guidelines about “guarding by safe distance,” worker training programs and an employer’s requirement to “demonstrate that physical barriers and physical devices are not feasible to guard the power press brake point of operation” in the unsaid hopes of adopting less stringent (and less expensive) means of protection.
Really? That’s like telling your teenager to drive safely and always obey traffic laws.
In all fairness, though, press brakes are admittedly difficult to safeguard. An operator’s hands are in constant contact with the workpiece, making the dual palm buttons found on stamping presses and similar equipment awkward or impossible to use.
The part shape is constantly changing, and barriers that performed properly on the first bend will almost certainly be compromised on the last. Because shop people are generally driven to produce high-quality parts quickly, many will employ whatever workaround is needed to meet quota, occasionally to their own detriment.
Caruso is sympathetic to the needs of press brake owners and operators alike and understands their frustrations about some safety systems. He says most of the lasers and light curtains available today allow the operator to program gaps or “holes” in the beam coverage to accommodate the part shape.
However, because that shape changes throughout the bending process, the holes are often much larger than is considered safe. And for those shops faced with low-volume, high-mix production runs, the operator sets up multiple jobs each day. Unless you’re expecting a visit from the safety director or OSHA, stopping to reprogram the light curtain for a handful of parts is an unlikely event.
Winning the battle
“What do they do?” asks Caruso. “They stick electrical tape, duct tape, a piece of cardboard over the front of the unit, whatever’s needed to block the photocell. One of my competitors even sells little screw-on clips with their systems to make it easier to fool the controller. But guess what? Do that and you’ve just bought an expensive ornament for your press brake.”
This is why many shops throw up their hands, Caruso says, pointing to one customer he worked with recently that owns a handful of press brakes, none of which were guarded. “They figured if they couldn’t safeguard them effectively and productively, why bother trying? Then they had an injury. We put a Merlin system on one of their machines, and lo and behold, what they said was not doable is working quite nicely. That’s the battle we fight every day.”
The Merlin light curtain works by teaching the system what to expect. The smart controller is put into learn mode during machine setup. There’s no need for programming, nor switches to turn individual beams on or off.
Instead, the Merlin keeps track of the bending steps by the operator pressing a foot pedal, taking a snapshot in time of the part shape and location. When the first piece is complete, the Merlin is ready for production.
Press brakes are admittedly difficult to safeguard, which is why OSHA rules are sometimes ambiguous on safety standards.
Jack Worrall is president of JM Engineering Inc., a systems integrator in Massachusetts. He says the Merlin is more advanced than competing systems.
“What happens is, once the press brake goes from high to low speed, the light curtain automatically mutes because the controller knows the part's going to be moving through the beams in that area,” Worrall says.
“We have a top signal, a slow-speed signal and a bottom signal, so we're monitoring the press brake in three different positions,” he continues. “Everybody else relies on a limit switch to do that. But you can tie a rubber band around that switch and the light curtain will be permanently turned off. You see it all the time. But there's no cheating the Merlin.”
Nor is it possible to turn off individual beams, as is the case with other systems. Worrall says that this is especially important for operators that will do whatever it takes to get the job done.
“An operator ends up turning off more than is needed, and sometimes they turn everything off,” he explains. “It’s just human nature. That’s why roughly 25 percent of our business comes from replacing other brands of light curtains with Merlins. It’s the same with laser systems.”
OSHA calculates that the human hand moves at 63 in. per sec., so if it takes a tenth of a second for the press brake to stop, a light curtain has to be 6.3 in. back, according to Worrall. “It's just second grade math. But most laser systems shoot a beam a quarter of an inch below the tool and pretend the machine will stop in time when the beam is broken. That's like screwing a couple of yardsticks to the front of my truck and saying it’ll keep me from hitting a deer or pig: it only works if you're going really slow.”
Worrall adds that it doesn’t matter how well-trained the operator is or the type of work they do; there’s always a danger without a light curtain.
“We just completed an installation on a machine where the guy ran the same tool to make the same part for 25 years,” he says. “Then one day, he cut off three fingers. With a Merlin, the machine would've stopped, he would have repositioned the part and gone back to work. He probably wouldn’t have even known it saved him.”
Serious about safety
Nor should the age or type of machine stop you from making it safe. Worrall recently retrofitted a Merlin to a vintage 1970s press brake, the owners of which said “the devil you know is better than the one you don’t” when faced with buying a new machine. He also routinely installs Merlins on older mechanical or hydraulic press brakes, even though the majority of these machines require the installation of additional electronics.
This is an important point, even for new machines: don’t do it yourself. Jim Blount, field service engineer at Blount’s Press Brake Inc. says light curtains and other safety devices are anything but plug and play.
“Proper integration is key,” Blount says. “If somebody is just looking to slap a pair of light curtains on the machine to keep OSHA off their back, they’re playing a very dangerous game. If someone is hurt and there’s a device on the machine, you can expect some serious questions. How did it fail? Was it set up properly? What interface was used, and was it designed correctly? Depending on how bad the person was hurt, it could cost a lot of money fighting it out in court. That’s why we only work with companies that are serious about safety.”
Blount, like Worrall, spends a lot of time developing and building his own interfaces. He says this not only assures safe, reliable installations, but a safety device that works well for the sheet metal application. “If not, the machine and its light curtain are like oil and water, and the operator will find a way to work around it.” He also provides press brake training, both onsite following a safety light installation and through the Fabricators & Manufacturers Association) certification program.
“Machines today are faster and more dangerous than when I worked on the shop floor,” he says. “At the same time, the operators are generally less skilled. In most shops I visit, they don’t know how to hold the parts safely. They don’t understand basic machine functions, or concepts like how much tonnage to use and the operation of the backgauge. That’s when they get hurt.
“It’s not enough for a shop to install a light curtain and pretend everything is good to go,” he says. “Nor should they throw some warm bodies out there and show them how to load parts. Shop management needs to support and encourage operator training, while also giving them reliable, easy-to-use safety devices. That’s why I love what we do – because we provide both of those things.”