18 Industrial Laser Solutions JULY/AUGUST 2017 www.industrial-lasers.com
LASER SYSTEM MINIMIZES
WASTE AND REDUCES COSTS
Remarkable progress has been seen in lightweighting of automotive parts because of expanded use of high-tensile-strength steel and aluminum. However, most of the cost for lightweighted parts is the raw material—especially for press-blanked parts, where a large amount of material is wasted
because of scrap produced during the cutting-out process
from sheets or coil. Also, for press blanking, a die is required
for each part—therefore, die manufacturing, die change, and
die storage are inevitable.
Minimizing waste and die-related cost not only leads to part-cost reduction, but also reduced energy and CO2 produced
during material production—a challenge for the automotive
industry, which uses a large amount of materials. Honda’s
solution was to develop a die-less Intelligent Laser Blanking
System (ILBS) for mass production.
Aim of ILBS
Press blanking with a die is a process that has been widely
used for mass production in the automotive industry. Contrary
to its high productivity, the drawback of using a die is its expensive manufacturing cost and the need for long-term storage
space. Also, material yield rate of the blanked part is not optimal because of the restrictions of tool edge design caused by
By applying laser blanking to automotive sheet metal production, no die is required and press hardening could be avoided,
leading to higher design freedom, lower cost, and higher formability, which are the advantages to conventional press blanking. However, laser blanking is mostly used in low-volume prototyping because of its overwhelmingly slow process speed
compared to press blanking.
Increasing laser blanking process speed is essential to
maximize its advantage over press blanking. Honda utilizes
ILBS for mass production by developing three key technologies: high-speed laser cutting, a high-acceleration H-gantry
system, and a continuous-feed conveying system (FIGURE 1).
High-speed laser cutting
Laser cutting involves melting of the sheet metal by applying
heat and removing molten metal by applying gas. Therefore,
it is important to increase heat energy density and to optimize
assist-gas condition to increase the cutting speed. We have
used a 5k W fiber laser with a spot diameter of 50μm to improve
heat energy density. For the assist gas, we have used nitrogen
instead of compressed air to avoid oxidization on the cut surface for better quality.
First, we demonstrated that a cutting speed of 120m/min
(sheet thickness: 0.6mm) was possible using a high-power laser
with optimized assist gas condition and standoff (nozzle tip to
work distance). Standoff is an important parameter for laser
cutting, as this will have a direct impact on laser focus point
and assist-gas flow rate. When we say “possible to cut,” this
means that the standoff has enough tolerance to resist disturbance during mass production.
In actual cutting, standoff changes because of laser head
vibration and sheet metal waviness result in defocus of the
laser spot, producing a cut problem. We used a lightweight
laser head that weighs one-third less compared to a conventional laser head with same optical performance, allowing us
to reduce inertial force on the gantry to avoid machine vibration during acceleration (FIGURE 2).
Sheet metal waviness is an important factor for the stand-
off. Like a conventional system, the capacitive displacement
sensor on the laser head tip constantly measures the distance
between the sheet metal, which is then fed back to the z-axis
motor of the laser head to stabilize its standoff. We improved
the measurement frequency and the processing speed to correspond to the cutting speed of ILBS, which is much faster than
a conventional system.
By improving heat energy density, stabilizing standoff, and
optimizing assist-gas condition, we have realized a cutting
speed 3X faster than a conventional laser cutting system in
a mass-production environment with disturbances such as