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Lasers on the Cutting Edge

Bruce Morey
By Bruce Morey Senior Technical Editor, SME Media

In the last seven to eight years, solid-state lasers have come to dominate laser welding and cutting,” said Tom Bailey, product specialist for Trumpf Inc. (Farmington, CT). While Trumpf still produces CO2 lasers, for most applications solid-state lasers literally outshine them. They are two to five times faster, simpler to integrate into a machine tool, and less expensive to both purchase and operate. “The hourly cost to an operator using a solid-state laser is an order of magnitude less,” he said.

Welding with green laser light is ideal for copper. Here, the Trumpf TruDisk 421 generates laser light at 515 nanometers, showing the versatility of solid-state lasers such as disk lasers.

Solid-state lasers come in a variety of forms. What differentiates them is the shape of the resonator, the device that is pumped with a source light that produces the laser beam. “Trumpf produces a variety of solid-state lasers, including fiber, disk, rod, and direct-diode lasers,” he said. Solid crystals made of ytterbium-aluminum-garnet, or YAG, are coated with a special light absorber, according to Bailey. They are then formed into long thin strands for fiber lasers, rods of about ½–1″ (12.7–25.4 mm) in diameter or disks about the size of nickel coin. Direct-diode lasers are a little different, made of a semiconductor material. Each has its advantages, with the disk laser especially useful in high-power applications because the disk shape is easier to cool at higher power over long periods, according to Bailey. Direct-diode semiconductor lasers are the most efficient and simple to make, but beam quality of direct diodes in terms of focus and spot size is not—yet—at the same level as other solid-state devices.

In a word, solid-state lasers are simple. Simple to operate, simple to integrate. It is why fiber lasers are dominating, especially in cutting. What manufacturers are doing now is creatively integrating them even more seamlessly into production as they move into new applications for laser processing.

New Applications

Besides being simpler to operate, solid-state lasers produce light in a different wavelength, near-infrared (about 1 µm) compared to the far-infrared (about 10 µm) of the CO2 lasers. Aluminum, copper, brass, and steel absorb near-infrared better, making it easier to cut them with solid-state lasers. Trumpf announced new systems for a variety of applications, including high-speed laser deposition welding, fusing metal powder for 3D printing, and copper welding with green-light laser. “These lasers are now penetrating into general manufacturing, like refrigerators,” said Bailey. Cheaper batteries powering electric vehicles and stabilizing the power grid will, in part, be enabled by laser welding of electrodes.

BLM Group USA provides a single machine for bending, forming and cutting of tubes, with the majority of such systems using versatile fiber laser solid-state systems.

In fact, the speed of the laser may no longer be the bottleneck in manufacturing. “Solid-state lasers are outpacing the ability of material handling to feed the material,” he said. Look for companies like Trumpf to emphasize new offerings in systems built around lasers emphasizing automation and speed of handling.

For Mark Barry, vice president of sales and marketing for Prima Power Laserdyne LLC (Champlin MN), the new generation of solid-state lasers, especially fiber lasers, offers vast improvements in productivity over the older “conventional” CO2 and Nd:YAG lasers. “Laserdyne has a customer who improved a cutting and drilling operation from 54 hours to 15 by upgrading to one of our systems that features a fiber laser and uses advanced processing techniques,” he said.

A key feature of fiber lasers is the level of control over the parameters an engineer can employ. Changes in frequency of pulse, power level and duration of pulse are instantaneous, according to Barry, compared to the time lags evident with older CO2 and Nd:YAG lasers. “By controlling the fiber laser in real time, we can produce welding effects we could not do before,” he said. Case in point—all of today’s pacemakers are welded with lasers. “Now we have the ability to use our SmartTechnique feature and create weld seams without blemishes and dips inherent with a laser lacking such control. Previously, manufacturers would see dimples in the weld seam and feel compelled to inspect more than they needed to just because it was so visual,” he explained. The same goes for drilling and cutting. Changing the laser parameters within the space of a drilling cycle can reduce ejected debris and allow fine control over the kerf.

Mainstream Acceptance

The Laserdyne 606D from Prima Power Laserdyne features two independent workstations in a single enclosure. In this picture workspace dividers are removed for clarity.

Barry points out that customer acceptance of fiber lasers may be a bigger factor than the technology itself. It is enabling the next step in laser cutting and welding system development—making the machines adaptable for multiple processes and creating space efficient machines. “We just completed and are now selling a new workstation with two independent working areas,” said Barry. The Laserdyne 606D Dual Workstation is a multiaxis laser system, with two separate lasers, motion systems, and motion controllers. The new 606D consists of four main components: two six-axis motion systems, an integral Class 1 enclosure with dual automated doors, two S94P laser process controls for motion and laser coordination, and two fiber lasers.

“The big advantage is floor space utilization with this system,” he said. “One thing we are continuing to hear today that was only occasionally commented on is that engineers are conscious of how big laser systems can be, and how much floor space they take. They want to use them in cell manufacturing, so the size of the total system has to shrink even though the working cube needs to remain the same or even grow a little larger.”

Another important application where fiber lasers are dominating is trimming advanced high-strength steel, or AHSS, a new trend in automotive lightweighting. It is hot forming and quench in the die that need trimming. “There is no practical way to trim this hard, boron steel without a laser and it has become an important worldwide market for Prima Power and others,” he said. The company’s latest system, the Laser Next 2130, is designed for trimming hot-stamped automotive door rings with high quality and short cycle times.

The use of lasers by the BLM Group USA (Novi, MI) illustrates how cutting with light has become mainstream, and why the switch to solid-state is so important. “The BLM Group is primarily a machine tool builder that uses lasers as part of what it does,” said Andrew Dodd, North American sales director for the company. He states they were one of the first companies to incorporate solid-state fiber lasers, purchasing them from third-party vendors and integrating them into the company’s tube-cutting machinery. Now most machines use fiber-laser sources rather than CO2.

“For our customers, fiber lasers meant lower operating costs [compared to CO2]; for us it meant easier integration,” he said. “Fiber lasers come in a maintenance-free box with a flexible cable coming out the end. They are simple to integrate and usually run very reliably.” Most new BLM machines are fiber, with CO2 lasers sold only for special conditions, according to Dodd. “Sometimes only because that is what the customer is familiar with,” he stated.

Laser cutting typically requires an assist gas. Oxygen is often used to provide an exothermic process but adds heat and oxidation to the cut surface. BLM Group now regularly uses nitrogen as an inert assist gas to get a clean cut. “The use of high-pressure nitrogen might be considered an expense. However, we have done numerous studies in thin materials to show that the faster cutting speeds more than make up for the increased nitrogen assist gas,” he said.

The company provides tube bending, wire bending, and endforming machines as well as tube, sheet, and five-axis laser cutting systems. Solid-state lasers mean delivering the beam over a flexible fiber-optic cable, greatly enhancing the delivery options and allowing for more freedom in space. “Our newest offering is the LC5 machine that can cut both flat sheets and tubes,” he said. “Our five-axis laser cuts tubes that have already been bent, putting the holes in accurately and repeatedly.” The ease of fiber laser delivery was especially useful in designing the LT Free five-axis tube cutter.

Dodd agreed that the challenge today is how fast and efficient a machine can move the axes and place material for cutting, not how fast the laser can cut. That is why a key technology the company offers with its machines is its Artube CAD/CAM software for designing and programming tubular parts. It imports a CAD model of the part and lets operators program off-line how to bend and cut the part most efficiently.

Improving the Old, for Now

Bystronic’s proprietary fiber cutting head with automatic focus position and focal length adjustment is designed specifically for fiber-laser cutting.

To a degree, the experience of Hank White bucks the trend for CO2 lasers. “We are seeing fewer sales of CO2 systems, but we still sell quite a few,” he said. He is the national product manager for lasers for MC Machinery Systems Inc. (Elk Grove Village, IL). While agreeing with the many advantages of fiber lasers over CO2 already mentioned—faster cutting speeds, cheaper and simpler operation—he lists reasons for choosing CO2. Perhaps one of those reasons is that Mitsubishi Laser specializes in supplying a low-cost, entry level CO2 cutting SR series machine. “A large percentage of our sales are still CO2,” said White. “Actually, our low-power 2.7-kW CO2 flatbed cutting machine has a lower operating cost than any fiber laser we sell. It cuts up to ¾” [19-mm] mild steel well, though it cuts slower than a fiber laser.”

He also points to the better quality of a cut one can get from a CO2 under certain circumstances. “If you are using nitrogen as an assist gas, which many people do to eliminate the need for a secondary process like oxide and burr removal, then CO2 gives a better cut quality in thicker materials,” he explained. In these cases, depending on the application fiber lasers will usually need a secondary deburring operation because of microburrs that form off the bottom of the cut. While a secondary deburring or polishing operation can fix that, many of his customers want to send the parts straight to paint or weld without a secondary operation. Situations where CO2 with nitrogen provides a cleaner cut include stainless steel kitchen components, aerospace engine components, and agricultural equipment components made of thicker mild steel.

Nevertheless, he noted the majority of his sales are now fiber lasers, and the range of applications where they are meeting or exceeding CO2 performance is growing. “For example, thin gage with higher power fiber lasers is starting to get much cleaner edges, and mild steel using oxygen as an assist gas is pretty much on par in most applications,” he said.

Most new investment and research are going into fiber laser technology, he acknowledged. The company’s newest offering is an entry-level fiber laser cutting machine the company terms SR-F. It features a 3 × 1.5-m footprint with many of the features from its more capable eX-F series. Built on the same platform as its entry-level SR CO2, the company noted it supports higher power and faster cutting speeds. “It is automation-ready for the production floor,” said White.

Improving the Process

One of the key trends that stands out for Frank Arteaga, head of product marketing for Bystronic Inc. (Elgin, IL), is the rate at which solid-state fiber lasers have improved power and performance since their first practical introduction in 2009. “The first fiber lasers for sheetmetal cutting were 1-kW sources, and now we have just introduced a 10-kW fiber laser cutting system in our latest offering—a timeline of only eight years,” he said. By comparison, the industry introduced its first 1-kW CO2 laser in the mid-1980s and it took nearly 25 years before a higher power 6-kW CO2 laser was available.

“The good thing about a fiber laser is that it is two to five times faster than CO2; the bad thing about a fiber laser is that it is two to five times faster,” Arteaga stated. That requires a machine that can keep up in order to fully harness the benefits. That is why Bystronic took special interest in the drive system and internal structure when designing its ByStar fiber laser cutting system. “This is a system designed specifically for fiber laser cutting,” he said, rather than an adapted machine designed for slower CO2 laser cutting systems.
The ByStar fiber laser cutting machine is available with sources ranging from 3 kW up to 10 kW. Bystronic designed a bridge-style machine in a patented triangle design to reduce weight and increase rigidity for faster movements while maintaining accuracy. Linear drive motors in X and Y provide smooth, frictionless motion. The latest option is an integrated rotary axis so that tubes can be cut on the same machine as flat sheets.

The extra speed from the fiber laser can stress a facility like a job shop that is not prepared to handle the increased throughputs. “Everything before and after the fiber laser is affected,” Arteaga said. Because a faster process puts a strain on the front end of the process, programs and raw materials must keep up. “Even after the material is cut, you need to unload, bend, and process the products faster,” he said.

All those processes must be looked at and Bystronic offers its BySoft 7 software to help program cutting and nesting solutions. The Plant Manager module allows the user to take orders from an ERP system and automatically pull them into a queue. Once the orders are gathered, they are segregated by material type, thickness, and due dates. The software will automatically start to build nests based on the effective due dates.

“Plant Manager creates nests even when programmers are not physically present,” said Arteaga. High-speed material automation and bending systems complement Bystronic’s high-speed fiber laser cutting systems

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