Whether mechanical, hydraulic or servo, C-frame (a.k.a. gap-frame) presses have long been the go-to machine for basic metalworking tasks like punching, piercing, forming, marking, insertion and more. They’re compact, so they take up very little floor space, and their open construction makes them versatile, easy to operate and able to handle a wide range of material shapes and sizes.
Unfortunately, these machines can be a challenge to automate, which is a growing concern as more and more shops struggle with chronic labor shortages. The problem isn’t with the press, however, but rather with the means by which parts are presented to the robot.
“On a C-frame press, you typically have an operator sitting there performing a series of fairly tedious but complex material handling steps,” says Will Healy III, global industry leader for welding at collaborative robot (cobot) manufacturer Universal Robots USA Inc. “They reach into a box of randomly placed parts or blanks, grab one without looking, orient it for placement into the die or fixture, hit the palm buttons, take the finished part out, stack it on a table and repeat the process. It’s boring work, but if you stop to think about everything a person has to do in this scenario, it’s also somewhat magical.”
Making magic
Magical perhaps, but not so much that a robot cannot replicate it. A quick look at a difficult welding application or automotive assembly line illustrates robots can do all this and more, except for one thing: the “grab without looking” step in this sequence of operations.
As with CNC lathes and machining centers, machine tending cobots and robots are becoming commonplace. In these applications, and practically all others, the raw material is usually pre-staged in a grid-like template or presented on a conveyor. This predictability makes it quite easy to teach or program the robot where to grab the next workpiece. This is not the case with the next frontier in automation – bin picking – which, until fairly recently, has been difficult, time-consuming and expensive.
“Are there thousands of shops doing C-frame press tending with a cobot today?” Healy muses. “Absolutely not, but I can tell you that I gave a presentation in June at Fabtech Canada that included an entire section on bin picking, how it’s revolutionizing what’s possible with cobots and why shops should consider them as a viable, cost-effective way to address the skilled labor problem.”
Healy notes that he’s not a big fan of buzzwords, but the magic in this equation is a cobot-mounted vision system coupled with real-time, artificial intelligence-like image processing. Together, they make it possible for a robot to replicate the task described earlier – reach into a bin or dunnage container filled with random parts, grab one, orient it and place it into a machine.
He goes on to suggest that properly equipped cobots are an ideal solution for C-frame press tending, especially now that “we have these amazing algorithms that make randomly placed part identification much faster and easier.”
“Setup involves grabbing the arm and putting it where you want it to go,” Healy explains. “This allows you to do changeovers more quickly than with an industrial robot, which must be programmed for each part. It also makes the work more interesting for humans. Anyone who’s tended a press all day knows it’s not a fun job, which makes it an excellent application for robotics.”
Thriving on innovation
Shawn LaMeau is the stamping automation manager with JR Automation in Holland, Mich., a Hitachi Group company. His primary focus is on the automotive market, which means most of his work revolves around tandem stamping presses, destackers and racking systems. That said, the company boasts 2,000,000 sq. ft of automation and engineering space across more than 20 worldwide locations and provides services for a broad array of industrial markets, including aerospace and defense, medical, warehousing and logistics, and even amusement park rides.
Automation is nothing new to automakers and their tier suppliers, and much of LaMeau’s daily activities involve upgrading or adding functionality to existing lines and equipment. In the case of C-frame presses, it’s not unusual to replace PLCs, motors and drives on equipment that was new in the Reagan era.
“The up and down part of it still works great,” he quips, “but either the controls are outdated, they want to add an HMI [human machine interface], or they need to replace the old DeviceNet communications protocol with Ethernet.”
The lion’s share of LaMeau’s efforts is directed at press line automation, however, an area where the main requirement is speed. “People that have never automated a stamping line think it’s just material handling,” he says. “No big deal, right? The challenge with automotive is that everything is so much faster. For example, they might be running 40 parts per hour in the body shop; on a stamping line, I often need to run 20 parts per min. If you don’t size everything properly and do your due diligence on designing the system, you can end up with a lot of premature failures.”
Simulating the design upfront saves a great deal of grief, he explains. So does working closely with multiple robot manufacturers, one of which is Fanuc America. LaMeau points to Fanuc’s M2000iC/100P 6-axis robot as a go-to solution in numerous tandem line applications. For higher throughput applications that have long relied on the speed of traditional “hard automation,” the Fanuc R-900iA/200P w/LPT robot offers the greater speed and flexibility needed for an increasingly dynamic industry.
LaMeau is also seeing increased use of vision systems to augment human workers on the line and help address some of the headaches that come with greater product variability.
“Let’s say you have a stamped part coming down a conveyor to a racking area,” he says. “By putting a vision system on the end, the controller can track the part and decide which robot should pick it up and what rack to place it on. But by shutting a gate and temporarily idling the robots, that same line can also be operated manually, which is a big help when you have products coming down that haven’t yet been automated. As far as I know, no one else has developed a system that can switch hit like that.”
Seeing double
Gilles Renard agrees. As an application engineering team leader at Kawasaki Robotics USA, he says his department has been seeing increased demand for these kinds of material handling applications. “Instead of spending a lot of money on fixturing and conveyors, manufacturers can now set down a bin filled with parts and let their vision-equipped robot figure out how to grab them. It saves a lot of labor.”
Not only have cameras become less expensive over the past decade, but the software controlling them has grown more powerful. Pre-configured routines are available for bin picking as well as features like automated path determination and collision avoidance, so programming is largely a matter of importing the part’s CAD file, pointing out the most likely pick positions, and showing the robot the bin extents and approach points.
“Everything about robotic automation has improved over the past few years,” Renard says. “People have gained more experience, the software and documentation are better, and you no longer need an automation specialist spending months onsite teaching the robot and integrating it into the machine.”
It’s not yet perfect, though. Renard warns that parts do get stuck in the corner of the bin or in an area the robot can’t reach, which requires human intervention. Lighting remains a concern on highly reflective parts, making them hard to spot, although he’s quick to note that newer cameras are much better in this regard. And, in some situations, an interim fixture might be needed so that the robot can set the part down and re-grip it in a more favorable location before placing it in the machine. Even so, a 95 percent automation success rate is far better than the 100 percent manual alternative.
Staying safe
Advanced technology does more than make bin picking possible; it also makes the shop floor safer or at least easier to navigate. As their name suggests, safety laser scanners use laser light to continuously scan a specific area and send a signal if a human, forklift or other unexpected object breaches the pre-programmed safety zone.
When integrated into a robot-tended manufacturing cell, this signal instructs the droid and machine tool to immediately cease operations until the intruder leaves. Some are even equipped with cameras and network capability to make remote monitoring possible.
“For industrial robots, the rule is that nobody should be able to touch it or its payload while in operation,” Renard notes. “Even with cobots, it’s important that the operator cannot come into contact with any sharp edges or pinch points. Hard fencing and, in some cases, a light curtain is often the best way to prevent this, but if you’re bringing bins of parts into and out of the work area every couple of hours, not having to maneuver through a gate is very useful. Because of this, we’re seeing many companies adopt area safety scanners as a more flexible, cost-effective and easy-to-install solution.”
