November 9, 2016

Lightweight construction with lasers


Lightweight materials stretch conventional tools to their limits. Processing high-strength steel, titanium and composite fiber materials is easier for lasers—especially where parts are difficult to access.

Lasers are omnipresent in industrial manufacturing. They drill, cut, weld, hone, turn, score, inscribe, structure, perforate, and polish metals, plastics, glass, ceramics, paper, wood and many other materials. Lasers show their strengths where conventional tools wear out, mechanical processes are too slow or inaccurate and where sensitive materials have to be handled carefully.

Lightweight construction is one of these areas. To reduce the energy consumption of aircraft, automobiles and machinery and to enable fast, precise maneuvering with less power, lightweight construction engineers minimize the moving masses. But to ensure that safety and reliability are not adversely affected, high-strength steel, titanium, and fiber-reinforced plastics strengthen the highly loaded, filigree structures. Ceramic materials offer a lever to reduce weight. All the named materials pose problems for conventional tools. As long as lightweight construction was used in manufacturing processes, these were not too obvious. In the meantime, however, demand from high-volume markets is growing. Efficient, reproducible production processes are needed.

Laser systems enablers of industrialized lightweight construction

With fiber-reinforced materials the problem is that glass or carbon fibers absorb the energy used to drill, mill, and cut, which causes the duromers and elastomers that are embedded in them to melt. Cold processing with high energy picosecond pulses from UV lasers prevent this. In contrast, the aim when welding and repairing the composites is to remove the resin layer without damaging the thin fibers. These can be loaded only longitudinally, but break easily with transverse loads. Where mechanical cutting, drilling, and milling processes cannot be used, CO2 and fiber-guided diode lasers in the near-infrared range of 800 to 860 nm can be a remedy.

Apart from careful mechanical and thermal handling, lasers also offer wear-free processing. Tools are blunt within a few hours when used to cut, drill and mill carbon components. When composites with different thicknesses are being processed, the tools have to be changed. However, lasers can be adjusted during the process. In addition, unlike bulky tools, focused light can be guided into tight spaces and along complex contours. This allows industry to fully exploit the benefits of forming reinforced plastics.

Wide range of uses for lasers in lightweight construction

The automotive and aircraft industries see the future in hybrid lightweight construction, in which fiber-reinforced plastics are used alongside aluminum, titanium, and high-strength steel. Lasers ensure that the joints in this material mix hold. Short pulse lasers roughen metals specifically before they are joined. Laser technology ensures precisely dosed energy input in the joint zone to minimize heat absorption of the fibers.

As with tough composites, lasers are also in demand for processing hard metals and ceramics. Conventional tools are soon blunt when used on high-strength steels. They are completely unable to make complex 3D cutouts. 3-D laser cutting machines are the only solution—and are also extremely flexible. They cut changing contours and recesses without time-consuming tooling. The controllability of lasers is especially useful for handling hard metals. If the laser fluence is too high, they tend to form bubbles. If it is too low, spikes form. With flexible pulse duration in burst modus, both can be prevented with minimized process duration. But there are more uses for lasers in lightweight construction. Whether the work involves removing layers from high-strength tailored blanks before welding, laser cutting of titanium or aluminum or precise cutting, inscribing, or drilling of ceramics without microcracks—or solutions for lightweight construction, lasers are the answer.