January 27, 2009
Knowing the capabilities and drawbacks of laser and waterjet machines is the key in determining which is best for a particular application.
Fabrication has long been a cornerstone of U.S. manufacturing. It plays a central role, providing components and subassemblies to other manufacturing sectors, such as aerospace, appliance, and automotive. Significant advancements in metalworking equipment, materials, and applications have resulted in more options and opportunities for fabricators than ever before. Today's fabricators are looking for more than just speed. They want to have equipment that will add capabilities and flexibility, enabling them to bring in new business.
Dynamic applications in today's hottest industries are using more interesting and unusual materials than before, and many fabricators are being called on to cut more exotic metals and composite materials.
Laser cutting technology is a longtime player in the fabrication world. It uses a high-power laser beam to cut through many types of materials.
Twenty years ago lasers were capable of cutting -inch steel at 1 to 2 inches per minute (IPM). Now they can cut -in. steel at 60 IPM. Automation, increased resonator power, and improvements in controllers have revolutionized the laser industry.
Lasers can quickly and easily switch from one metal to the next with little downtime. Also, laser automation helps fabricators achieve lean manufacturing by increasing output while decreasing or eliminating labor costs.
|Thickness||Waterjet Processing Time||Laser Processing Time|
|0.75 in.||783 sec.||440 sec.|
|0.125 in.||75 sec.||16 sec.|
For this example, waterjet and laser were used to cut a sample part with a linear cut length of 42.5 in. The waterjet had a 0.014-in. orifice and a 0.030-in. nozzle; it consumed 1.2 pounds per minute (PPM) of abrasive. The laser was equipped with a 4,000-W resonator. For the thin sample, the laser used a 2.5-mm nozzle and oxygen at 168 PSI; for the thick one, it had a 3.5-mm
nozzle and oxygen at 210 PSI.
Waterjet cutting is one of today's fastest-growing technologies and is quickly becoming a leading fabrication process. Waterjet cutting uses a high-pressure stream of water with an abrasive such as garnet to make the cut. No heat is generated during waterjet cutting, eliminating the risk of material distortion.
Waterjet cutting is suitable for nearly any material, including glass, ceramic, wood, stone, plastic, and rubber. This versatility can help niche suppliers branch out of small market segments and appeal to a much broader customer base.
Both laser and waterjet machines have a good life expectancy because they don't use dynamic machining forces and they don't make direct contact with the workpiece during the cutting process. So, when both technologies can do the job, how do fabricators determine which process to use? Understanding a few key factors can help them make the choice.
Speed and Thickness. Lasers are well-suited to cutting parts up to 1/2 in., but they can cut metals up to 11/2 in. thick. On the other hand, waterjets can cut material up to 6 in. thick.
Lasers often have a speed advantage over waterjets. For example, on 1-in.-thick carbon steel, a waterjet with a pump that develops 60,000 pounds per square inch (PSI), equipped with a 0.014-in. orifice and a 0.030-in. nozzle, and consuming abrasive at a rate of 1.2 pounds per minute cuts at 2.9 IPM. A laser equipped with a 3,800-W resonator and a 2-mm coaxial nozzle, and using oxygen as the assist gas at 8.4 PSI, can cut more than eight times faster at 24.5 IPM.
Waterjet, however, can cut through significantly thicker metals, and alternative materials, with ease. A sample part was cut with waterjet on these materials: 0.75-in. foam rubber in 45 seconds, 0.375-in. granite in 198 sec., and 0.625-in. glass in 126 sec.
Material. Lasers can process materials other than metals, but this doesn't mean they should. On plastics and rubbers, for example, laser cutting releases byproducts. Waterjet can easily cut these other materials without hazardous chemical releases.
Highly reflective materials such as aluminum and copper also are particularly difficult for lasers to cut. For example, laser's and waterjet's cutting speeds are nearly identical on 0.5-in. aluminum (188 sec. for a laser and 198 sec. for a waterjet), but the edge quality is significantly better with waterjet.
A laser performs best on smooth surfaces; textured surfaces can alter the flow of the assist gas and disrupt the beam's focus. A waterjet, on the other hand, doesn't discriminate when it comes to reflectivity or texture.
Finish. The heat from laser cutting produces a small heat-affected zone (HAZ) near the cut, which could require secondary finishing depending on finish requirements.
Waterjet doesn't create a HAZ. In addition, waterjet cutting delivers a smooth edge finish without jagged edges, slag, or burrs, eliminating the need for secondary finishing processes such as grinding. Also, because it doesn't impart heat, it doesn't distort the parts, which can then be stacked to increase productivity.
Jeff Hahn is national laser product manager and Steve Szczesniak is national waterjet product manager, MC Machinery Systems Inc., 1500 Michael Drive, Wood Dale, IL 60191, 630-616-5920, www.mcmachinery.com.
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