Page 188 - High Power Laser Handbook

156 Diode Lasers High-Power Diode Laser Arrays 157

an example of plastic welding a remote car key, which was one of the
first diode laser welding applications in industry.
The advantage of the diode laser, in comparison with conven-
tional solid-state lasers, is its shorter wavelength and “top hat” beam
profile without intensity peaks. This avoids local overheating that
might damage the welded components.

Local and Selective Heat Treating
A unique advantage of the diode laser hardening process over con-
ventional heat treating processes is that it is possible to adjust its spot
to the contour requiring hardening and, therefore, to achieve
extremely high throughput. Its easy mode of operation allows the
diode laser to be integrated easily into production processes and, if
desired, to be used with an industrial robot (Fig. 6.24).
Compared with other lasers used for hardening, diode lasers
have the added advantage of a shorter emission wavelength that is
better absorbed by metals, as well as superior process stability. In
addition, diode lasers do not require special absorption layers that
can prevent temperature control by a pyrometer and that also may
result in surface contamination.
Laser Brazing
In addition to requiring high strength and a small heat-affected zone,
particularly high demands are made on the appearance of the weld
seam in the case of visible seams. Laser brazing is an ideal approach
for such situations. As an example, in the automotive industry, laser
brazing is used to join the external visible parts of vehicles, such as
the trunk lid, roof seams, doors, or C pillars (Fig. 6.25). Diode lasers
are now considered proven technology for providing high levels of
reliability and process stability for many applications that require
three-shift production, such as the automotive industry.

Figure 6.24 Laser hardening of tools and springs. (Courtesy of LaserLine)