BOxygen and nitrogen, two standard
assist gases used in laser cutting, create
two different reactions at the laser head.
Oxygen produces an exothermic reaction, and the laser burns the metal.
Nitrogen fosters a melting process, and
the laser heats the metal without a
chemical reaction, with the nitrogen gas
pushing the molten puddle through the
kerf. During air cutting, the combination of the laser energy being forced
through a tight focal point and the presence of compressed air creates a plasma
ball at the surface of the material,
which then cuts the metal.
Air cutting revisited
More research reveals more can be done using shop air in laser cutting
By Erin Chasse and
ged about the capabilities and limitations of compressed-air cutting.
Editor’s Note: This is an update of “A breath
of fresh air” that appeared in The FABRICATOR®, August 2006, p. 42.
Last summer industry reports
about the initial study results
on the benefits of laser cutting parts using compressed
air instead of oxygen or nitrogen as an
assist gas were made public. Cutting
with compressed shop air showed considerable benefits, including a significant cost savings and speed increases
over nitrogen and oxygen assist cutting. As with any emerging technology, additional research has been conducted and new findings have emer-
The FABRICATOR article in August
advised fabricators to use the compressed-air cutting technique for parts
that would be coated, bent on a press
brake, or not otherwise visible when
the manufactured product was complete. Recent findings make it possible
to expand this recommendation to
more material types and thicknesses,
including parts on which the edge
quality is visible. Compressed-air cutting is now possible on 0.074-inch
steel and thinner, 0.120-in. stainless
steel and thinner, and 0.25-in. aluminum and thinner.
Additionally, compressed air can
be used as an assist gas with thicker
material. The maximum thickness has
increased for aluminum to 0.50 in.
thick. Previously cutting 0.180-in.
stainless steel and carbon steel with
compressed air required a laser cutting
machine with a 6,000-W resonator.
Now it can be cut reliably using 4,000-
W and higher laser resonators.
New research has also taught us
that different laser resonator styles perform differently in each material and
thickness. For example, a diffusion-cooled resonator creates very good edge
quality on materials 0.080 in. and thinner, while a 4,000-W, fast-axial-flow
resonator cuts well on 0.135-in. material. Meanwhile, 5,000- and 6,000-W,
fast-axial-flow resonators using compressed air cut 0.250-in. aluminum
with the same edge quality and speed
as nitrogen-assisted cutting.
In the August article, the compressed-air pressure figures presented
were limited to standard shop air pressures. Since the article was published,
laser technology specialists have successfully tested the capabilities of cutting with higher pressures and conducted analyses that make it possible
to justify the financial investment
necessary to upgrade laser machine
compressors to cut thicker material.
For example, increasing pressure
enables users of 4,000-W machines to
cut 0.375-in. to 0.5-in. aluminum.
Using higher than typical shop air
pressures ( 105 pounds per square inch)
may mean a small investment for some
users, while other users already will be
capable of these pressures.
Technical advances are continually made to laser cutting machines and
the techniques that enhance them.
Fabricators should be on the lookout
for more examples of operational
improvements in laser cutting sheet
metal and plate. ■
Erin Chasse is the sales engineer for laser cutting machines, and Mickey Lawson is an
applications engineer at TRUMPF Inc., 111
Hyde Road, Farmington, CT 06032, 860-
Visit www.thefabricator.com; enter the
article number (digits only) in the home
page search box:
• “A breath of fresh air: Laser cutting
technique offers a new alternative” 1416
• “Optimizing CO2 laser use: Part I” 1245
• “Optimizing CO2 laser use: Part II” 1284
The FABRICATOR | An FMA Publication
www.thefabricator.com | March 2007