The Great Debate: Plasma Cutter or Oxyfuel Torch?

Whether you should put your trust in a flame or an arc depends on what you do.

Plasma or oxyfuel? The answer to which tool is better for your cutting needs depends on a number of factors - alloy, thickness, location, variety of work, power resources, cost, etc. This article first introduces each process, and then sheds some light on what tool will work better for you. It is written from the basis of handheld units and for professionals who use such equipment.

 

 

Plasma Arc Cutting

Plasma - the fourth state of matter - is an ionized gas that conducts electricity. Plasma is created by adding energy to an electrically neutral gas. In this case, the gas is compressed air and the energy is electricity. By adding electricity through an electrode (hafnium), the gas becomes imbalanced and conducts electricity. The more electrical energy added, the hotter the plasma arc becomes. Plasma arc cutting machines control this powerful energy by constricting the arc and forcing it through a concentrated area (the nozzle). By increasing air pressure and intensifying the arc with higher voltages, the arc becomes hotter and more capable of blasting through thicker metals and blowing away the cuttings, with minimal cleanup required.

Plasma Arc Cutting Basics. With a power source, plasma torch, compressed air, electrical power, and a supply of tips and electrodes, plasma arc cutting machines can rapidly and precisely cut through, gouge, or pierce any electrically conductive metal without preheating and with a minimal heat-affected zone. Plasma can cut metals such as aluminum, stainless steel, brass, and copper in excess of 1 in. thick, in addition to expanded and stacked metals. Oxyfuel Cutting

With oxyfuel cutting, an oxygen/fuel gas flame preheats the steel to its ignition temperature. A high-power oxygen jet is then directed at the metal creating a chemical reaction between the oxygen and the metal to form iron oxide, also known as slag. The high-power oxygen jet removes the slag from the kerf. Cut quality, preheating times, and thicknesses can be influenced by the type of fuel gas used. Oxyfuel cutting is used for ferrous (iron-containing), mild and low-alloy steels in thicknesses up to 24 in.

Oxyfuel Cutting Basics

With a fuel tank, oxygen tank, and a torch, you can cut steel anywhere - except for nonferrous metals such as aluminum and stainless steel. Oxyfuel cutting allows metalworkers to cut extremely thick metals with ease, and a variety of torch options allow users to braze, solder, fusion weld, gouge, preheat, and bend metals as needed.

Conclusion: Take Your Pick

This article is intended to give a comprehensive overview of plasma arc cutting and oxyfuel cutting and the inherent benefits of each as they relate to factors most important to professionals in the metalworking industry. The discussion of alloys and thicknesses may have made the choice easy for you, but you may still have some questions. Experience is the best resource in choosing between a plasma arc and an oxyfuel system - we encourage you to contact manufacturers, local distributors, or others in your field to find out what works best in your niche of the metalworking world. We simply can't cover every situation or challenge you might come across, but we hope we have pointed you in the right direction.


Table 1 (Compares the features and capabilities of the two cutting systems)

 
PLASMA ARC CUTTING
OXY/FUEL CUTTING
Metals
Plasma cuts any electrically-conductive metal (steel, aluminum, copper, stainless steel, etc.) from very thin (<3/8 in.) up to 2 inches.
Oxy/fuel cuts ferrous (iron-containing) steels up to 24 in. thick. Metals such as aluminum and stainless steel cannot be cut with Oxy/fuel due to the formation of an oxide that prevents oxidation from fully occurring.
Industries
Common in metal fabrication, construction, agriculture, maintenance, automotive repair, metal art, sculpting, home hobby and DIY applications.
Agricultural, fabrication, construction, maintenance repair, mining, automotive, hobbyists, DIY applications.
Preheating
Not required
Required
Productivity
Plasma cutting works exceptionally well on thinner materials (<1/2 in.), depending on the output of the power source. It can also cut stacked material and works well on expanded metals. Prep time is minimal with no preheating requirements. Produces a small and precise kerf (cut) width. Features a small heat-affected zone that prevents warping and damage. Cleanup is rarely needed as dross is cleanly blown away.
Oxy/fuel is capable of efficiently cutting metals up to 24 in. thick. It is not dependent on a primary power source. Fuel gas and tip design options enhance performance.
Portability
Portability varies based on technology, size of power source and size of air tanks (if not using a built-in air compressor). Many units can work efficiently in the field off of engine-driven generators and a variety of primary power sources thanks to primary power management technologies offered in some plasma cutters.
Highly portable and is not dependent on a primary power source or compressed air – capable of cutting anywhere with gas tanks and torches.
Versatility
Stack cutting, beveling, shape cutting, gouging and piercing of metals is possible with plasma cutters.
With a combination torch, oxy/fuel systems can be used for heating, brazing, soldering welding, gouging, riser cutting and bending metals
Safety Concerns (Operated properly, each tool is safe and effective. Improper use can lead to the following problems.)
Electrocution; fires started by sparks; cutting in and around combustible materials; damage to protective clothing, skin and tissue if used improperly. Always wear appropriate clothing.
Flashbacks; fires started by sparks, cutting in and around combustible materials, damage to protective clothing, skin and tissue if used improperly. Always wear appropriate clothing.


Article courtesy of Miller Electric Manufacturing Company and Smith Equipment.