Engineering News

Lasers expand the machine-tool envelope

Newton, MA -Lasers may never supplant drilling, milling, and grinding for the mass of industrial production, but make no mistake-they're changing the definition of what machine tools do.

  • Higher-performance assemblies

  • Lower-cost tooling

  • Greater design flexibility

Advances in laser machining technology include higher power, higher precision beams, a shift to fiber-optic-transmissible wavelengths, and the promise of machined micromachines.

Although laser machine tools still represent a small portion of the entire machine tool market, their share is increasing, according to Charles Carter, vice president of the Association for Manufacturing Technology. "It reflects their growth in cost effectiveness in delivering power to a workpiece, as well as their flexibility in precision cutting and welding of thin materials," he says.

Industry sources say that these advances will mean more options for designers, including:

Easier integration of composite materials

  • Smaller heat-affected zones around holes and joints

  • More-rigid structures through continuous, one-sided welds as opposed to spot-welded construction

  • Lower-cost cutting of sheet-metal shapes without creation of punches and dies

Laser machining progress can be seen in the rapid development of neodymium: yttrium aluminum garnet (Nd:YAG) lasers. Compared to more widely used CO 2 lasers, these solid-state devices are more easily cooled and offer more robust design. In addition, their shorter wavelength can be transmitted through fiber-optic cables instead of the precision waveguides needed for longer-wavelength sources.

At 3,000W, the HLP 3000 from Hobart Lasers & Ad-vanced Systems, Troy, OH, claims to be the most powerful continuous-wave Nd:YAG laser available. "That power translates into greater cutting and welding speed-up to 180 inches per minute," explains company President Harrison Hobart. The lamp-pumped system delivers its 1.06-aem beam through a 600-aem-core-diameter fiber-optic cable up to 150m long, and permits multiplexing of a single laser generator among several machining workstations.

Because it's not pulsed, the laser permits continuous weld lines between parts during assembly operations. Moreover, those welds can be performed from a single side of the assembly. These two features, coupled with the multi-axis flexibility of robotic laser welders, will permit automobile designers to eliminate many of the frame holes now necessary for access to resistance spot welders and create better welds at the same time, says Hobart. The result: higher fatigue life and stiffer car bodies.

Solid-state lasers. The promise of completely solid-state Nd:YAG lasers prompted the federal government to enter into a technology-reinvestment project with a consortium of 16 companies to accelerate the laser's development. Pumped by diodes, not flashlamps, such systems offer improved reliability and even higher speeds.

According to Len Marabella, program manager for consortium-leader TRW, Inc., Redondo Beach, CA, the Precision Laser Machining project focuses on developing two new capabilities. One, a 2.5-kW average, 25-MW peak-power pulsed laser, will cut and drill metals and composites more quickly and accurately than currently possible. The second, a 6-kW average long-pulse model, will specialize in welding and heat-treating applications.

With beta-site testing expected in 1996, Marabella reports progress has been rapid. The new machines should offer clear advantages to designers, he says.

"Greater speed and accuracy reduces the heat-affected zone around the laser-processing site,

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