The ripple effect of high-speed laser cutting
Leadership Summit panelists discuss broad view of part flow, from cutting and bending to the shipping dock
With solid-state laser technology upping throughput in fabricating shops, managing flow from cutting to bending to downstream processes has never been more important. A panel discussion at The FABRICATOR’s Leadership Summit provides some insight into the right combination of modern machine tools and software that can help fabricators stay on top of this production challenge.
The laser has evolved to become the heartbeat of precision sheet metal fabrication, and in recent years it has gotten a lot faster. Fiber and disk lasers cut through thin sheet at unprecedented speeds, while at the same time CO2 lasers have progressed also to churn out more parts while consuming less power and laser gas.
The industry is going through a bit of a renaissance within the laser cutting work envelope. After years of steadily increasing speeds and powers, new laser technologies are challenging perceptions. Now fiber and disk lasers have progressed to the point where productive plate cutting with them isn’t a far-out concept. More than ever, fabricators have a menu of highly efficient and reliable cutting options.
The renaissance has dramatic implications outside the laser cutting work envelope—from order entry and scheduling to programming, material loading, parts identification, offloading, transporting, bending, and welding—and a panel of equipment experts drove home this point at The FABRICATOR’s Leadership Summit held in Austin, Texas, earlier this year. All these technologies create a seamless cutting-forming continuum, and working in concert, they can deliver formed parts to downstream joining and assembly at just the right time, reducing the time it takes for raw stock to be transformed into things of value, ready for shipment.
“The laser industry is in a tremendous state of change right now, and it looks like all for the better.” So said Jason Hillenbrand, national laser product manager for Amada America, Buena Park, Calif.
It’s estimated that about 20 percent of cutting lasers sold in 2013 were of the solid-state variety, though most expect the solid-state market to grow significantly in the years to come. Part of what has made fiber and disk laser technology so effective is its power density. A focused 4-kW CO2 laser beam produces 65 million to 75 million watts per square inch. A focused 2-kW fiber laser beam, which generally produces a kerf width about half that of CO2 (depending on the application and optics arrangement), produces about 100 million watts per square inch.
“That point of extreme power density allows us to vaporize material much more quickly,” Hillenbrand said, “and allows us to move the cutting head at a much higher rate of speed. That makes it ideal for high-speed cutting of thin material.”
What has kept the solid-state laser less productive in thicker material has been in part its beam parameter product, or BPP, which conventionally has been between 2.0 and 2.5, ideal for cutting thin material. The BPP value has hinged in large part on a solid-state laser’s delivery fiber.
For years laser manufacturers have known that a larger-diameter delivery fiber would increase the BPP value and, hence, the laser’s cutting efficacy in thicker plate. But as Hillenbrand explained, “The problem has been that you can’t have two different delivery fibers on one machine. This is where the hang-up has been.”
Manufacturers have tackled this challenge using different lens arrangements and, most recently, proprietary methods to cut both thick and thin material using the same delivery fiber. These have led to some of the latest advances on display at last year’s FABTECH® show in Chicago, where several solid-state laser cutting machines from different manufacturers cut thin sheet and then switched to thick plate—and all parts emerged with a clean edge.
At the same time CO2 lasers, by now a mature technology, have progressed to become more cost-effective than ever, and this includes lower power consumption, assist gas, and laser gas usage. During his presentation, Mike Pellecchia, Midwest regional manager at Mitsubishi Laser, Wood Dale, Ill., showed a slide of a small gas cylinder. “This T-sized bottle could last you six months,” he said. “A bottle of gas with a mix of, say, 28 percent helium might cost $160. So you can see the cost of laser gas has come down to a minimum.”
Some CO2 lasers have cyclonic cleaning systems that remove particulates from the laser gas, extending the life of laser optics. Overall maintenance cycles have been extended as well. “There are CO2 lasers on the market that you will not open up for at least 6,000 hours,” he said.
To drive home a broader point, Pellecchia quizzed the audience on cutting efficiencies. In one application, a CO2 laser cut 0.060-in.-thick carbon steel with a nitrogen assist gas running at 475 IPM, while a fiber laser cut at 875 IPM. That’s a no-brainer, of course—the fiber laser wins. For another application involving thick material, a CO2 laser cut at 65 IPM, while a solid-state laser cut at 30 IPM. In this case, the CO2 laser wins.
But how about a 0.040-in.-thick stainless application? One 5-kW fiber machine cut the material at an impressive 34 inches per second (IPS), but another machine cut it at a mind-blowing 60 IPS. So what was this incredibly fast mystery machine? Pellecchia flipped the slide to reveal not a laser, but a hydraulic shear.
Cutting isn’t a race to the fastest IPM. The cutting speed itself is just a piece of the puzzle. Most important, the rest of the puzzle pieces need to be shaped just right to take advantage of the fast cutting technologies reshaping the metal fabrication landscape.
It’s a marvel to watch a modern laser slice through a nest in no time flat, but it doesn’t make a company more money unless it helps the fabrication shop ship more products in less time, and that won’t happen if you have constant bottlenecks before or after the laser.
As Al Bohlen, vice president and general manager at Elgin, Ill.-based Mazak Optonics Corp., put it, “If we’re cutting parts significantly faster, we want flow.”
Material handling towers have been around for years, but modern systems allow users to, say, interrupt a schedule for a hot order. If the machine is running 30 sheets for one job, a technician can interrupt that with a single-sheet order, then resume the larger batch.
On top of this, automation cells can be designed to handle the full range of applications. “We now have fabricators asking us about putting both a CO2 and a fiber laser in the same laser automation cell,” Bohlen said, “so they can benefit from both technologies.”
All this may allow parts to be cut in a cell at an unprecedented rate, but what if parts are lost in the mix? Dynamic nesting—inserting disparate parts making up an entire assembly or multiple assemblies on one sheet—complicates matters even more. Such nesting promotes efficient part flow, allowing all parts of a subassembly to reach the welding area faster and greatly reducing WIP. But with so many different parts moving so quickly, parts get lost. How can a fabricator maintain the flow?
Bohlen showed some remedies, one being a labeling function on the cutting system itself. Before cutting, the system prints labels onto parts. That label can have a number, bar code, or anything else to help workers identify the part. “When the nest is cut and delivered downstream, parts are already prelabeled,” he said. “The automatic delivery of material, unloading of the nest, and loading of the new sheet—this is all occurring while the labeler is preparing the next sheet for the next run.”
Onward to Forming
Once cut parts emerge, automation can remove and sort parts. Automation ranges from suction-based part-removal mechanisms to pick-and-place robots that remove and stack parts.
When it comes to fiber and disk laser cutting, kerf width also plays a role. In newly developed systems the kerf width is becoming programmable. “But when you perform a standard cut with a solid-state laser, you will have a thinner kerf,” said Jim Rogowski, managing director of machine and power tool sales at TRUMPF Inc., Farmington, Conn.
As one example, on a solid-state laser cutting 0.040- to 0.250-in.-thick mild steels, speed increases on average by 106 percent, but the kerf width also decreases by up to 80 percent. “It often becomes difficult to get those parts out of the nest, even on thin gauge,” he said. This in turn makes reliable parts-removal automation even more valuable.
A shop must carefully manage its WIP to avoid downstream bottlenecks. Rogowski talked of automated cart systems that help workers move heavy material with their fingertips. He also showed a system in which cut parts emerge on a conveyor to a compact rail system, which carries those cuts parts directly to the adjacent bending cell. Parts are also nested and offloaded with bending ergonomics in mind. When the parts arrive in the bending area, the forming technician doesn’t need to flip parts awkwardly. He simply turns around, grasps the part, slides it against the backgauge, and begins the bend sequence.
Of course, this flow can be interrupted by long setup times in bending, and here is where automatic tool change as well as flexible robotics come into play. Some modern brakes come with the ability to automatically change tools between jobs, effectively automating the changeover process.
Rogowski also showed a flexible robotic cell capable of automatic tool changes and fast bending—faster, in fact, than a human is capable of. Moreover, the entire brake was designed with the robot in mind, having a window in the middle of the press brake bed for the robot to reach behind the tooling set, to speed handling.
“Fabricators need to look at innovative ways to move material through the shop, and they need to bend their parts faster,” Rogowski said. “The ability to cut faster can cause a lot of WIP and wait times at your press brakes.”
Software and Programming
Such efficiencies upstream make reducing downtime at the brake even more important, and a lot of it can be reduced with offline programming. “Offline brake programming is a major way of preventing bottlenecks at the press brake,” said Frank Arteaga, head of product marketing for Bystronic Inc., Elgin, Ill. “It’s a major portion of what we’ve seen takes a lot of time with setup.”
It also makes sense from an asset utilization standpoint. As Arteaga explained, “A setup person may install tooling, and then he needs to do the programming on the computer control—and now he’s basically using a $200,000 press brake as a PC.”
In an ideal situation, software becomes the mortar that helps tie the bricks of metal fabrication machinery together—from bending back to cutting and, before that, nesting, scheduling, order entry—all linked to a companywide enterprise resource planning (ERP) system.
Because it takes available brake tooling dimensions into account, software can unfold the solid model with the exact bend deductions, not ones developed from a table. This reduces or eliminates necessary adjustments at the brake itself. When the operator downloads the bend program to the press brake, he can see a simulation of the bend sequence and, if necessary, quickly alter it to suit his work preferences. But otherwise, the program arrives at the brake complete and ready to go.
Besides programming, software handles machine monitoring, providing information regarding overall equipment effectiveness (OEE), machine availability, and uptime information. “There’s bidirectional information flow going back and forth from the machines to the software,” Arteaga said. “You’re able to maintain real-time information as to what’s going on at the machines, how long they’ve been operating, and how efficient they are. You can also start to do measurements. For instance, because you know exactly when a machine is cutting and bending parts, you know how long it takes for those parts to go from cutting to bending, to see how many parts are contained within the WIP.”
Implemented to its fullest extent, software now can automate to some extent many front-office tasks, including scheduling. “The ERP communicates with an automated job management software, which then nests the orders based on material type, thickness, and due-date criteria. The nests are then routed to a particular machine on the floor, based on their capabilities and preset criteria [like sheet utilization levels],” Arteaga said. “From the ERP down to the machine level, the entire process can be fully automated.”
Myriad technologies working together promote consistent flow through the shop, and all aim to reduce the overall manufacturing cycle. New laser cutting technologies have raised the efficiency bar for the remainder of the shop, both upstream and downstream.
WIP doesn’t make payroll; finished jobs do. The less time it takes for parts to make their way through the shop, the more work a fabricator can take on, and the more money it can make. And that, of course, is the name of the game.
On his final slide, Rogowski showed a video of a scanning laser system cutting thin gauge—with a cycle time measured in milliseconds. Blink once, and you’d miss it. “Femtosecond and picosecond lasers exist already,” he said. “This is coming, so the question is, How are we going to keep pace with this next step in laser cutting?”
The FABRICATOR is North America's leading magazine for the metal forming and fabricating industry. The magazine delivers the news, technical articles, and case histories that enable fabricators to do their jobs more efficiently. The FABRICATOR has served the industry since 1971.