Developments in sawing, waterjet cutting
March 10, 2011
Lasers have been in use for industrial purposes for decades, and their capabilities continue to develop. Many machines these days can cut sheet and tubular sections, and fabricators are finding that the laser’s programmability really broadens their capabilities.
Editor's Note: This is the second installment in a two-part series. Part I covers developments in saws and waterjet machines. Part II deals with lasers and plasma cutting machines.
For metal fabricators that deal with sheet and plate, cutting is a matter of using heat, abrasive action, or a shearing force to make a cut through a single thickness of material. Tube and pipe fabricators have a few more challenges. They have to cut through two walls separated by a void; too much pressure deforms the workpiece; for some processes, the workpiece is stationary and for others it has to rotate; and if the shape to be cut is round, it generally doesn't stack well. That said, many equipment manufacturers specialize in providing cutting equipment for tube and pipe, and several have rolled out new machines in the past year or so.
Watts Specialties recently released model QC 81, a plasma cutter that handles pipe from 1 in. to 6 in. diameter.
"It's primarily a coupon cutter," said Lars Anderson, the machine's designer. "Until now fabricators were cutting them on a band saw or a plasma machine like the Watts W-60, but the QC 81 has automatic beveling, so it will bevel each end of the coupon."
A key capability of the new machine is eliminating guesswork in setting the focal point.
"The users can set the focal point to the ID of the pipe so they can cut an accurate length with bevels on each end," Anderson said. "This allows them to process pipe much faster than they would have been able to in the past." A laser indicator shows fabricators where to make the cut.
"The laser line tells the operator where to make the cut, based on the position of the focal point of the torch," Anderson said. "It allows the operator to cut the pipe to the length he wants to have."
The unit has three standard angles—90, 37½, and 30 degrees—selected by inserting a pin into a corresponding hole.
Anderson added that as the unit's head rotates around the pipe, it tracks the pipe's surface to prevent a collision.
"There's a floating axis on the head. It tracks the pipe using a spring-loaded roller ball that contacts the pipe. If the head were at a fixed height, and the pipe's weld seam projected so far that it came into contact with the head, the head might pause or stop altogether. The roller ball raises the torch so this doesn't happen. Likewise, it allows the torch to track the pipe's shape, which isn't necessarily perfectly round." Anderson mentioned that because the pipe is stationary, it doesn't move laterally (walk), which can result in a spiral cut.
Anderson noted that the machine also is suitable for low-volume production; adding a linear measurement device allows the operator to make cuts to a consistent length.
Laser cutting machines used to come in two varieties: equipped with a bed for sheet metal or chucks for tubes, pipes, and profiles. These days many manufacturers offer machines with both a bed and chucks.
In 2010 Mazak introduced the SuperTurbo-X Mark III RTC laser system, which accepts flat material up to 5 ft. by 10 ft. and round pipe up to 14.76 in. in diameter. An extended Z axis, 16.14 in., adds to its versatility, as does a tapping head. It is available with either a 2,500- or 4,000-W resonator, for a maximum cutting capacity of 0.87 in. or 1 in. in mild steel, respectively.
Likewise, BLM Group USA's LT Combo handles tubular shapes and sheet metal. The standard tube loader/unloader handles lengths up to 20 ft.; the standard pallet changer accommodates sheet material up to 5 ft. by 10 ft. Laser sources are available from 2 kW to 4.5 kW.
AltaMAR, which makes several tube-only models, found a niche for a combination machine that has a small-format bed. The company's model LT2024 has a 24- by 24-in. platform for cutting flat components and handles tubular shapes up to 2 in. square and 12 ft. long.
Prima Power North America Inc., which focuses on the flat segment of the fabrication industry, makes an attachment for sheet and plate fabricators that allows them to add tube and pipe to their laser cutting capabilities.
A typical success story concerns one of the company's customers involved in manufacturing the stanchions used to secure computers in police cars and emergency vehicles. After purchasing the rotary axis and doing some experimenting, the fabricator realized that his capabilities went far beyond manufacturing the same old stanchions he became able to offer his customers substantial design flexibility for new designs or improvements to existing tubular products.
"The flexibility has allowed him to change his whole business," said Michael Millette, laser products manager for Prima Finn-Power North America Inc. "Instead of machining them, he cuts them with lasers, and it has allowed him to get a lot more creative. He has been able to change his business, expand his business, and get more flexible with his designs. It's wide open for him when he's trying to do any new geometry."
Millette mentioned that the capabilities of a rotary axis reflect those of the laser cutting machine.
"When you put it on a 2-D machine, the cutting head is always perpendicular to the centerline of the tube," he said. "You have no tilt axis. When you put it on a 3-D machine, you have full 5-axis capabilities, so you can do just about any shape you can imagine on a tube.
"This sort of attachment is ideal for most job shops because it opens up an entirely new market segment for them," he said.
Likewise, TRUMPF offers the RotoLas, a tube cutting device which is an option for the TruLaser 3030 2-D machine. It is able to handle tube and pipe up to 14.5 in. dia. One customer found that his investment in the rotary axis attachment is paying off in three distinct ways. First, he has created a niche in laser-cutting large-diameter applications. Second, the laser combines several operations, such as cutting and chamfering, on one machine. Third, the additional capabilities are strengthening customer relationships.
Laser machine manufacturers also are offering more choices in maximum cutting diameter. Mazak Optonics Corp. recently supplemented its FabriGear series with its 220 model. It handles round tube and pipe up to 8.66 in. diameter, so it fits into a niche between the FabriGear 150, designed for rounds up to 6 in. in diameter, and the FabriGear 300, which fabricates rounds up to 11.8 in.
TRUMPF's TrueLaser Tube 5000 handles diameters up to 6 in., and its TruLaser Tube 7000 comes in two versions. The standard model goes up to 8 in. dia.; the second model handles workpieces up to 10 in. dia. The company has found that fabricators have been moving toward larger-diameter machines.
"Every 7000 ordered in the last year was ordered with the option," said Product Manager Stefan Schreiber.
A laser machine with a big jump in maximum diameter can introduce fabricators to new niches in the fabricating market, as BLM recently found out. The company introduced its JUMBO machine, which comes in two versions, a small one for diameters up to 14 in. and a large one for tube up to 20 in.
"For tubes this large, fabricators usually mark the tube with a template, then cut it with a hand-held torch," said Laser Tube Product Manager Jeff Arendas. "A laser provides much higher accuracy, but also much more design flexibility. It allows designers to create new joints and intersections, such as hook-and-slot or insertion joints. All the parts slip together, the features are precisely located, and assemblies come together faster," he said.
Although laser-cut parts are well-suited to architectural applications, Arendas noted that most building codes deal with beams and girders, but not tubular components. However, this isn't a roadblock.
"Diligence on the part of the designer is key in getting a print approved," he said.
Architecture isn't the only industry that uses such large diameters. Arendas mentioned that OEMs involved in agricultural machinery, oilfield com-ponents, pipelines, conveyor systems, and shipbuilding fabricate large-diameter tube.
Arendas explained that some laser machine characteristics—such as cutting versatility and accuracy—are appealing to many fabricators, regardless of what they manufacture.
"Part designers can incorporate features such as a tab on one part and a slot on a mating part," Arendas said (see Figure 1). "They fit together, so there's no need for a fixture, and part fit-up is so accurate that welding time can be reduced by up to 25 percent," he said.
Fabricators that do quite a bit of low-volume, high-mix work find that a laser's ability to change over rapidly is critical to productivity. For shops working with 20-in.-dia., 60-ft.-long tubes, a bigger motivator is that a laser reduces material handling, Arendas said.
"Such a tube might have to make several stops as it works its way through a shop—first at a mill, then a burn table, and so on," Arendas said. "With a laser, they can do all the operations in one location."
Lasers are even making inroads into some metalworking applications that formerly were stamped.
"Some companies are making retail display racks on laser machines," said Rick Jackson, vice president of sales for AltaMAR. "Not because a laser is faster than stamping or punching out rectangular slots, but because they can change from one size to another quickly. They don't have to buy a dedicated line to make one product and let that line sit idle between orders. A laser eliminates that, and it eliminates the cost of the tooling, allowing the user to use their investment more or less continuously."
Jackson also cautioned that fabricators need to be aware that tube and pipe aren't always straight and the laser machine needs to accommodate bowed workpieces.
"Our 2410 has a side-sensing laser that senses the side of the tube and determines if the tube is bowed, where it's bowed, and how much it's bowed," Jackson said. "The machine then positions the laser head accordingly so that the laser hits the tube's centerline. Hitting the centerline, or not, makes a big difference," he said.
Pulling It All Together.When shopping for a laser machine, fabricators should understand how all of the machine's capabilities work together—such as positioning speed, rotational speed, and cutting speed—advised TRUMPF's Schreiber. The cutting speed is just one factor, and it isn't necessarily the most critical one. Much of a laser machine's productivity is influenced by the laser head's positioning speed (when it isn't cutting) and its material handling capability. A key capability is the machine's cut-to-cut time, which is the time needed to remove the cut tube from the machine and load the next tube, Schreiber said. For example, the 7000 series has a cut-to-cut time that varies from 22 seconds (for a 21-ft. stick) to 27 seconds (for a 30-ft. stick).
Software also plays an important role. Perhaps more than any machine tool, a laser's versatility is driven by its software. For example, Mazak's software allows its machines to cut common tubular shapes such as round, square, and rectangular; ordinary structural sections such as I beams, H beams, C channel, and angle iron; and user-defined shapes. Furthermore, occasional software upgrades can help boost productivity.
"We made some changes to the software to improve the cycle times," said Mazak Applications Specialist Mark Mercurio, referring to the latest machine in the FabriGear series. "We made some changes to cut paths and nesting to make the machine more efficient," he explained. The new software isn't just for new customers, he added; it's also available to customers with existing machines.
Having two feed systems on one machine also is vital for productivity.
"Our LT2410 has a chain-drag-type system which moves the tube into position, manipulates it, and cuts it up," Jackson said. "It also can feed tubes from a bundle feeder on the back side of the machine. If you were running a large batch of tubes from the bundle feeder and got a hot job of just a few tubes, you could load them from the front of the machine, change the program, and make the new parts. When those are finished, you can go back to the previous program and run tubes from the bundle feeder again."
Jackson also mentioned that fabricators should think economically when considering resonator power. Extra wattage doesn't make the machine cut faster.
"A standard resonator on a machine that cuts tube up to 6 in. diameter is 2 kilowatts," Jackson said. "You could put a 4-kW resonator on that machine, but it really isn't gaining you anything because you don't need all the additional power. You have a second wall that the beam hits. If you don't want the beam to hit the far wall, heat it up, and cause discoloration or oxidation, you have a limit on how much power you can use."
Lasers' Progress. According to Arendas, European tube and pipe fabricators embraced laser capabilities more quickly than their U.S. counterparts did.
"There are about 700 lasers in use in Europe, and about 250 in the U.S., but the tube and pipe markets are nearly the same size," he said.
However, the U.S. market seems to be catching up. According to Millette, laser cutting for tube and pipe is hot right now.
"This is one of the faster-growing segments in the fabrication industry," he said.
Arendas cited another clear trend that lasers continue to make progress in manufacturing: Many parts appear to be designed specifically for a laser.
"You could make a picture frame from four lengths of rectangular tubing, using four welds to assemble it," Arendas said. "That would be the conventional way to do it. With a laser, it's easy to make it from a single length of rectangular tubing. You cut notches in the tubing, remove it from the machine, and make three 90-degree bends by hand and finish it with just one weld.
AltaMAR's Jackson concurred, citing a truck made for the Baja 1000, a grueling competition that runs down the Baja Peninsula. The course is unforgiving and midrace repairs are the norm; the winner is often the sturdiest vehicle, not the fastest one. This particular truck's frame has nodes where six or seven tubes meet (see Figure 2).
We're seeing more designed-for-laser applications like this all the time," Arendas said.