Where Plasma Makes the Cut

A descendant of the gas tungsten arc welding (GTAW) process developed in World War II to join light metals such as aluminum in aircraft 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 interviewed Dirk Ott, vice president of mechanized plasma systems for Thermal Dynamics Automation (www.thermal-dynamics.com). He provides expertise on how plasma cutting compares to laser cutting in cost and other areas, why an integrated, single-source system makes sense, and how fabricators can leverage the advantages of the technologies together.

Versus Laser Cutting: Weigh Cost And Performance

Plasma cutting systems provide time and cost advantages in certain applications. Precision work, such as cutting holes, requires precise coordination between system components.

Any comparison between the processes must consider economics, as laser cutting systems have an initial cost at least double that of plasma cutting 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.

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, intricate parts on thicker material,” he says, “they become a pain to separate…they get stuck.”

Stainless steel and aluminum represent other areas where plasma cutting provides an effective alternative to its laser counterpart on thicker sheet and plate.

“Plasma provides almost identical cut quality to laser for aluminum and stainless steel if intricate cutting details aren’t required, “ Ott says, “and at a lower cost due to high gas consumption required for lasers to cut these materials.”

Elements of this integrated plasma system include the power source, torch, torch height control, automatic gas control and CNC with operator interface.

“Laser cutting machines undergo higher acceleration than plasma cutting...to as high as 4 g,” says Ott. “That translates to greater machine-maintenance requirements. Motors must be changed more often, for example.”

Also, laser components tend to be more delicate, translating to damage from wear and tear or from material hits or drops.