Use case 1:
Use case 2:
16 Industrial Laser Solutions NOVEMBER/DECEMBER 2016 www.industrial-lasers.com
scan head on a smooth trajectory, while all high-speed movements
are executed by the much-faster scan axes. With this method,
laser-on times of 90% or more can be realized. Experience has
shown that a single weld using remote laser welding can be made
in as little as 20% of the time required to make an equivalent weld
using conventional joining methods (e.g., resistance spot welding,
riveting, and fixed-optic laser welding) [ 2].
With suitable controls, on-the-fly welding can be implemented
in a highly productive manner.
State-of-the art systems allow
for full synchronization with the
robot motion, and provide an
optimized motion planning of the
scan head and the robot axes.
Typically, lap welding applica-
tions with a multitude of short
welds distributed throughout a
part have been targeted with
this approach. In the past, this
application was limited to sim-
ple and flat parts like seat backs.
With the advancement of control technology in recent years,
more complex parts (such as
seat structures, cross car beams, and automotive doors) have been
successfully implemented with Blackbird’s 3D on-the-fly welding
solutions. This solution has enabled weld speeds to be maximized
(>10m/min) and jump times to be minimized (<20ms) for complex
3D parts, while still ensuring access at proper inclination angles to
the weld positions through the part tooling.
The ever-present challenge of allowing a path for zinc vaporization when welding galvanized materials must also be addressed.
To ensure a stable process, the zinc gas released during welding
has to be given a way to evacuate from between the sheets. A number of different production-proven approaches can be observed.
Aside from providing designed-in spacing features on the parts
or clamping techniques that create a defined gap between the
sheets, the most common method is dimpling. In this two-step
approach, during a first run, short laser pulses of a few millisec-
onds are applied to create small bumps with a typical height of
0.1–0.2mm on the surface of the lower sheet. These then serve
as spacers towards the upper sheet, which is welded to the lower
sheet in a second step.
More recently, the technique often referred to as “laser screw
welding” or “laser spot welding” has been developed, which aims
to more directly replace resistance spot welding. This technique
combines the typical laser welding advantages of higher processing speeds, single-sided access, and low heat input, along with
being more tolerant of gaps
between sheets and requiring
no pre-weld dimpling for gal-
A few years ago, BMW, in
cooperation with Blackbird,
The production solution consists of remote welding systems and
controls from Blackbird, together with a coaxial camera for seam
tracking. The result was an enhanced scan system with coaxial
illumination and online seam tracking functionality. For the first
time, the system combined the advantages known from on-the-
fly scanner welding with the requirements of position-critical weld
• Robust seam tracking with a typical accuracy of 0.1mm;
• High flexibility through omnidirectional processing;
• Maximum efficiency via minimized repositioning times and
robot movement; and
• Improved weld joint accessibility through long standoff from
the work piece (~0.5m).
FIGURE 2. The BMW production system with coaxial vision.