lower in these applications than the
consumption of compressed air or
nitrogen, thus reducing costs.
Regardless of material type and
thickness, the laser cutting operation begins with a piercing process
that governs the overall cut quality.
In other words, if the pierce is clean,
the stage has been set for a clean
cut. However, if the pierce is poor or
incomplete, the part may have poor
cut quality and, in some cases, be
set aside for rework.
Naeem said Prima Power Laserdyne’s cutting tests using a 20-kW
Naeem said that the application of the SmartPierce process, which used compressed air for piercing and oxygen for cutting, optimized the piercing process.
The high-powered QCW fiber laser was used as the power source. (SmartPierce
is a technique that involves pulse-by-pulse changes in any or all of peak power,
pulse width, and pulse frequency, Naeem explained. Direct control of the laser
with the Laserdyne control provides this capability.)
When SmartPierce was used, the cycle time to provide consistent pierces in
7.5-mm steel plate using compressed air was reduced to just 0.4 seconds.
Of course, a;er compressed air is used for piercing, a purge of the nozzle is
needed to switch to the low-pressure oxygen flow for laser cutting. A minimum
dwell time of 2 seconds was required to purge the assist gas delivery lines for
consistent cutting. With modification to the assist gas hardware, the changeover dwell time between the two assist gases was reduced to 0.7 seconds. While
this may not seem like a major time savings, the total time savings is quite significant and can add up to hours per day when multiplied by hundreds of cut
features required in multiple automotive components.
To achieve the stated goals by minimizing changeover time between the two
assist gases (compressed air and oxygen), the equipment manufacturer developed and tested extensively its new Dual Gas Delivery Cutting Nozzle (see
Figure 2). The nozzle is designed to deliver both coaxial and directional noncoaxial assist gas for piercing thick steel sections followed by fast laser cutting
of the material. The directional noncoaxial gas acts as an assist gas for piercing
and simultaneously protects the laser optics and nozzle assembly during piercing. The coaxial gas is used for the cutting process. When both gases are used,
piercing is accomplished quickly and cleanly through the thick sections, and the
need to purge gases when transitioning from piercing to cutting is eliminated.
Prima Power Laserdyne’s dual gas process uses compressed air for piercing
and oxygen for cutting to provide consistent cut quality.
“Major QCW laser enhancements in process speed
and quality have been made recently in both aerospace
and medical device manufacturing. These are now
being adopted in other industries, particularly in the
—Dr. Mohammed Naeem, Prima Power Laserdyne
Vander Wert said the final innovation in this new laser process was to create
a routine for mapping selected surfaces of the actual 3-D blank to adjust for its
imperfect shape before piercing and cutting the various features. This mapping
process was required to meet the feature location tolerances for the part.
SmartSense is a laser-based, noncontact measurement tool that operates
coaxial with the cutting laser beam. It collects and analyzes measurement data
from the surface. The mapping results are used to adjust the planes of processing to reflect the real part location and shape to achieve laser processed feature
precision. This technique provides the proper location of holes and other cut features within the component despite a less-than-perfect shape of the blank.
Editor-in-Chief Dan Davis can be reached at email@example.com.
Prima Power Laserdyne, 763-433-3700, firstname.lastname@example.org, www.primapower.com