Page 28 - MetalForming July 2019

FABRICATION
Where Plasma Makes the Cut
High-precision plasma cutting technology often doesn’t get the attention of its laser and waterjet cutting compatriots, but it has its usage sweet spots.
BY LOUIS A. KREN, SENIOR EDITOR
Adescendant of the gas tungsten arc welding (GTAW ) process developed in World War II to join light metals such as aluminum in air- craft construction, plasma cutting was born when researchers after the war restricted the nozzle opening while looking to improve GTAW.
Today, plasma cutting holds a place where conductive materials must be sliced. But just where is it most effective, and how does it hold up against popular laser and waterjet cutting competitors?
To find out, MetalForming inter- viewed Dirk Ott, vice president of mechanized plasma systems for Ther- mal Dynamics Automation (www.ther- mal-dynamics.com). He provides expertise on how plasma cutting com- pares to laser cutting in cost and other areas, why an integrated, single-source system makes sense, and how fabrica- tors can leverage the advantages of the technologies together.
Versus Laser Cutting:
Weigh Cost And Performance
Though typically employed on inch- es-thick material, “plasma cutting can be very effective in a material thickness range of 2 to 6 mm,” Ott says. “As long as cuts are not overly intricate and detailed, plasma cutting is more cost- effective in this range.”
Any comparison between the processes must consider economics, as laser cutting systems have an initial cost at least double that of plasma cut- ting systems, with the cost difference increasing when adding laser cutter power and speed options, or when specifying a fiber laser. When pricing a 5 by 10-ft. worktable, an investment of roughly $100,000 will deliver a plasma cutting system that handles material to 12 mm thick. Also, keep in mind that plasma cutting offers an option on reflective metals, which, in some cases, adversely affect laser performance.
Plasma cutting systems provide time and cost advantages in certain applications. Precision work, such as cutting holes, requires precise coordination between system components.
As Ott mentions, laser cutting machines offer better overall precision, sometimes as much as three or four times better, depending on material type and thickness. For intricate shapes on thinner materials, laser cutting machines should get the call, he says. That’s due to the miniscule kerf width, or width of the cut material. On thicker materials and plates, the laser cutting speed advantage disappears, and often so does the need for intricately cut, precise shapes. Here, plasma cutting machines represent the cost-effective option. Also, Ott notes, as sheet becomes thicker, and also true for plate, the small kerf inherent in laser cutting proves disadvantageous.
“If a laser cutter produces small,
26 MetalForming/July 2019
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