Materials-processing scientists gather at ICALEO

Nov. 1, 2000
DEARBORN, MI—The home of the Big Three automakers (Detroit) was a fitting location for this year's International Congress on Applications of Lasers & Electro-Optics (ICALEO), Oct. 2 to 5, which profiled a large selection of automotive-related laser R&D efforts.

CONFERENCE REPORT

DEARBORN, MI—The home of the Big Three automakers (Detroit) was a fitting location for this year's International Congress on Applications of Lasers & Electro-Optics (ICALEO), Oct. 2 to 5, which profiled a large selection of automotive-related laser R&D efforts. It's no wonder. According to plenary speaker Lawrence Burns, vice president of R&D and planning at General Motors Corp. (Detroit), world wide, less than 20% of the general populace own an automobile. The potential remains for automakers to reap healthy profits for several years to come—as long as they can successfully tap global markets. One requirement, adds Burns, is the capability to efficiently produce higher volumes of low-cost, reliable vehicles with a maximum sticker price near the $8000 mark.

Overall, ICALEO attendance was tracking about 10% to 15% higher than last year's event, with preliminary estimates calling for 500 attendees. Not all were automotive engineers. In addition to automotive technical sessions, conference attendees had the option to attend sessions on laser material processing and microfabrication. The common thread among all sessions, however, was the use of lasers to provide efficient solutions to common manufacturing problems.

Consider the body-in-white (the major structural framework of an automobile). Paul Denney and Jian Xie of the Edison Welding Institute (EWI; Columbus, OH) discussed a dual-laser-beam process for welding galvanized steel (material zinc coated for corrosion protection). Since the production volume of such parts is high, laser welding of coated sheets in the lap condition (one sheet overlaps the other slightly) has been a major research effort for the automotive industry for some time. The problem is that any zinc between the sheets of material can lead to pores or blowholes in the lap-weld area, conditions that could be eliminated if vapors boiled off during processing had an escape route.

The EWI scientists split the beam of a 6-kW CO2 laser into two beams of equal-power located in tandem (one in front of the other). This approach was found to alter the weld pool dynamics, which improved surface quality of galvanized steel. The process also successfully reduced porosity and blowholes during welding of aluminum.

In the microfabrication sessions, femtosecond laser ablation was a common research topic. Engineers at Clark-MXR Inc. (Dexter, MI), for example, compared the benefits of machining the refractory metal rhenium with both 180-fs and 8-ns pulses. A 0.004-in.-thick sample was machined with a micromachining workstation by a 775-nm laser and an f/50 focusing system. Laser energy was the same for both femtosecond and nanosecond pulses, and in each case, the lens was moved along the z-axis to obtain the minimum throughput time required during percussion drilling. Femtosecond pulsies produced a 400-µm trepanned hole with good cut quality in just 5 s. Nanosecond pulses could not punch through the material even after 2 min. of exposure. Only when the scientists doubled the laser pulse energy, were they able to drill the rhenium with nanosecond pulses (75 min).

Lest one assume that femtosecond pulses always outperform nanosecond pulses during microfabrication, another conference presenter cautioned that the success depends on the processing conditions and the work material. He then presented test results that demonstrated better hole quality with nanosecond pulses—and that type of dissension is what continues to make ICALEO a successful forum for laser researchers and end users alike.

Paula Noaker Powell

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