Cutting Mild Steel – Air or Oxygen?	Marking Polyethylene Bottles	Cutting Closed Cell Foam

Cutting Mild Steel – Air or Oxygen?

The Firestar f400 laser with integrated RF continues to build its reputation as the laser of choice in sub-kilowatt metal cutting applications. With a beam quality (M²) value of < 1.2 and a mode quality of TEM00 at 95% purity, the f400’s near-perfect beam outshines the competition.

This application involved cutting 1.0 mm (0.040”) thick mild steel using 400 watts of power. One of our primary goals during this cutting trial was to determine the trade-offs between cut speed and edge quality when using various assist gases. Generally, an oxygen assist is used when cutting metals because oxygen reacts exothermically with the steel adding energy to the cut process (much like an oxygen-acetylene cutting torch) and increasing cut speeds.

Photo 1 shows the resulting edge quality when using 400 watts and an oxygen assist of 5.5 bars (80 PSI). At these settings, we achieved cut speeds of 7.62 meters per minute (300 inches/min). A bottom view of the steel sheet shows a slight amount of underside dross on the cut edge.

Photo 2 shows the result of our second test setup using breathing grade air instead of oxygen for the assist gas. At a power level of 400 watts and an assist pressure of 5.5 bars (80 PSI)—the same settings as before—we achieved cut speeds of only 1.27 meters per minute (50 inches/min). A bottom view of the cut edge shows a large amount of underside dross and a much larger heat affected zone (HAZ) due to the inefficiency of the air assist.

Air or oxygen? Based on gas prices per Standard Cubic Foot (SCF), ultra-pure oxygen (> 99.996%) is 5.5 times more expensive than breathing grade air, however the resulting cut speeds are six times faster with vastly improved edge quality and a virtually non-existent HAZ.

Photo 1: A sheet of 0.040” thick mild steel cut
with 400 watts. Using 80 PSI of ultra-pure oxygen
(> 99.996%) assist, we achieved excellent edge quality at cut speeds of 300 inches per minute.

We created this contrasting mark on
polyethylene bottles using 10 W of power
in a cycle time of 0.62 seconds per bottle.

Cutting Closed Cell Foam

Closed cell foam is lightweight, durable, and moisture-resistant—making it an ideal material in the construction industry as joint filler or as building insulation. Its resilience means it is a smart choice for creating the custom inserts used in equipment cases to protect instruments from shock and its buoyancy is useful in the manufacture of flotation devices.

Our application test focused on cutting various thicknesses of closed cell foam including a laminated piece with an overall thickness of 33.3 mm (1.3125”). Our cutting setup was powered by a Firestar f201 (200 W) laser where the beam is directed through X-Y flying optics into an industrial cutting head.

We used 200 watts of power at a speed of
40 inches per minute to cut this block of
1.3125” thick closed cell foam with 40 PSI
of clean, dry air assist.