Cutting Sheet and Plate Metals

by : Billy Kite

Technological advances in the field of manufacturing are what companies use to gain and maintain a cutting edge over their competition. Thirty years ago no one would believe the technologies of James Bond and Star Wars would find their way to the metal fabricator's shop floor; but they have. Two innovative alternatives to burning or oxidizing sheet and plate steel are:

* Laser Cutting of steel
* Plasma Cutting of steel

Laser technology gained much ground in the 1980's through Defense Department research. The Strategic Defense Initiative (SDI) paved the way for today's advanced commercial applications of laser use.

Laser is a word derived from Light Amplification by Stimulated Emission of Radiation. It involves the use of an electronic optical device. In the case of steel, output from the device, the laser beam, targets an area of the sheet or plate. This laser stream receives its direction from a computer, which pinpoints the area requiring the cut.

Cutting steel with a laser-cutting machine offers an accurate clean cut. Many other materials benefit from this process, such as wood, copper and exotic alloys. Sheet and plate steel receive cuts of close tolerance, much faster than traditional cutting methods. Laser cutting machines are capable of cutting steel up to one inch thick. These machines can perform these accurate cuts repeatedly and with high consistency.

With laser cutting, the cut edges of the steel are clean. This leaves a cut edge with a nice surface finish. This type of cutting allows for less warping of steel; as the zone affected by the heat is small. Laser applications mean less physical contact with the sheet or plate steel. This means less wear on the steel being cut and less chance of a poor quality cut.

Another great advantage of laser cutting of steel is that there is no wear on the laser. This is an advantage over mechanical cutting tools, which undergo stress and wear in the cutting process. If proper maintenance is performed on the optical mirrors used to reflect the laser beam to its target, many months of use are possible before they must be replaced; unlike standard tooling.

Plasma cutting machines utilize a different process. A plasma cutter or torch uses inert gas or compressed air. It uses pressurized nitrogen, argon, or oxygen. Today the use of compressed air is more common.

This air propels at high speed from the cutter nozzle. As air rushes through this specially designed nozzle, an electrical arc develops. This air hits the surface of the steel sheet or plate. Some of this air (or gas) turns to plasma: plasma that is very hot and able to melt the steel receiving the cut. Because it moves at high speed, the plasma blows away the molten metal. This blowing away of molten metal is the cutting process in action.

Plasma cutting machines can cut steel of one inch or less. The plasma cutting process can make non-linear or curved and angled cuts. It works faster on thinner steel than the burning or oxy-fuel process. Any conductive material (ability to transmit electricity) can have the plasma cutting method applied.

The introduction of smaller nozzles and thinner plasma electrical arcs are the result of advances in plasma technology. These produce cut edges close to the quality of those produced by laser methods.

The use of laser and plasma cutting machines give manufacturers the ability to make cuts that are more precise. It also gives them the capability of making different types of cuts, all with greater speed. This helps the efficiency of their operations in the competitive business climate of today.

The steel industry continues to be on the cutting edge of steel cutting technology. And lasers and plasma cutters are one of the methods they employ to stay there.