Plasma cutting is a clean and efficient way of cutting metals in a smooth and rapid operation. A plasma cutter works by superheating gas, which releases electrons from nuclei and causing them to move rapidly. The energy created by collisions between these fast-moving electrons enables plasma’s cutting power.
Plasma discharges at 30,000 degrees F. By focusing plasma with a cutting tool, machinists in the automotive and fabricating industries can cut thick metals rapidly, as the plasma beam liquefies metal. The plasma beam is controlled by an electrical current on an arc, which directs the beam and provides a surrounding cloud of shielding gas, which controls the frequency and intensity of the beam. Because of this electric arc, plasma is only capable of cutting electrically conductive metals, like stainless steel, aluminum and mild steel.
Plasma cutters are growing increasingly efficient and affordable, as manufacturers develop methods of simplifying their machines and make customizable tooling.
Industrial plasma cutters have advanced in ways one might expect: reduction in part complexity, greater digital-control capability and trending toward both smaller, portable systems and larger units capable of bigger machining operations. More generally, plasma has also shown improved “cut quality, consumable life and versatility” while growing more reliable and cost effective, according to plasma cutter manufacturer Hypertherm, in Hanover, N.H.
A machinist observes a CNC plasma torch while it cuts prototype parts. Credit: Aaron Muszalski
But plasma has advanced in other ways. Several decades ago, plasma was primarily used for cutting thin metals, as the torch was incapable of accurately cutting materials beyond a token thickness. However, plasma remains a functional choice for thin materials, as it avoids overheating and thus warping metals better than other cutting methods. These days, plasma is also capable of cutting metals up to 1.75 inches thick. “We still use oxyfuel when cutting our thickest stuff, but for the vast majority of jobs, plasma is faster and gives us better cuts,” Brian Balon, project manager at Kalkaska, Mich.-based industrial environmental services company Northern A-1, told Hypertherm, for the manufacturer’s plasma-cutting education series.
One example streamlines the process. ESAB Welding & Cutting, in Florence, S.C., has introduced SmartCycle Technology to integrated plasma cutters. The SmartCycle process combines various aspects of the plasma cutter, such as the CNC, gantry, plasma system, torch height control and programming software, into one integrated unit. This combination foregoes unnecessary tool motion and counter-purpose programming that can add considerable time to any plasma cutting operation.
ESAB’s Vision T5 CNC, Smart Voltage Height Control and m3 Plasma systems are integrated through Columbus III software to enable digital cross-check of necessary operations. By digitally comparing operation needs, the program can determine the fastest and most efficient cutting method, tool movement and arc height and energy requirements, leading to operations that double productivity.
Another method of speeding plasma operations is the reduction of cut-to-cut cycles. Hypertherm’s Integrated Plasma Cutting Solutions technique relies on digital controls to self-monitor and optimize torch movement. A suite of controls operates under Hypertherm’s ProNest 2010 software, communicating torch location, table motion and gas preflow information in a bundle. The software than calculates how best to optimize movement by, for instance, bypassing torch retract movements in order to progress cut to cut. By reducing the multiple retraction movements in a single operation, the process can be sped up considerably.
Plasma cutting requires considerable energy supplies, although these needs are shrinking. Longevity Global Inc. has introduced MOSFET and IGBT technology to control plasma energy use. These machines help control the way plasma cutters use circuits by managing circuit gateways, protecting the plasma from high-voltage current flow overexposure.
