Cutting

Cutting with gases dates back to the late 1800's, but has only really grown since the beginning of this century, as the transportation of cylinders and bulk gases became possible. Well known cutting methods are:

• Autogenous Cutting
• Laser Cutting
• Plasma Cutting

Autogenous cutting is performed using a flame of fuel gas and oxygen which first heats the material to the ignition temperature for the steel. When this temperature has been reached, the cutting oxygen is opened and the material starts to burn. The oxygen beam blows the combustion products out of the cut. The burner is moved at an even speed, and material is burnt off in a narrow column. The oxygen beam has a circular cross-section and can therefore cut in all directions with a good result.

The method depends on the material igniting in oxygen at a temperature lower than its melting point. The ease which with the material can be cut is affected by the state of the surface and the material's chemical composition. Suitable burn gases for cutting are Mapp, acetylene or propane. Oxygen is also used. The burn gases give somewhat different temperature distribution and total heat. This means that the choice of burn gas depends on the type of work to be done. Choice of the correct combination of equipment and gas is crucial for attaining the best result, both technically and financially. Acetylene and Mapp are used as cutting gases for cutting metals.

Laser cutting is cutting with light beams of uniform wavelength. The process is not dependent on the ignition temperature of the material as in autogenous cutting, or on the electricity conducting properties as in plasma cutting. Laser cutting can therefore be used with few limitations on all metals, and on other materials and timber goods. Most laser cutters are so-called CO₂ lasers which use a mixture of nitrogen, CO₂ and helium to produce the laser light. We have developed our own serie of cutting gases and laser gases with the product name LAZER. The laser gas is a mixture of gases or pure gases such as Lazer helium, Lazer CO₂ and Lazer nitrogen. The cutting gases are normally Lazer oxygen P or Lazer nitrogen P.

Plasma cutting is a method based on melting the material. The material must be able to conduct electricity. Electricity is used to heat the material, and the melt is blown out of the cut with the plasma gas beam. This makes plasma cutting independent of the limitations which apply to autogenous cutting. The method can therefore be used on most metals. The plasma cutting process uses a plasma gas and a secondary gas/shielding gas. The method is used in a water bath to avoid smoke/light from the process, or in the air with an exhaust opening for smoke.

The choice of gas for the process depends on the material/thickness to be cut, whether the process is carried out under water or in the air, and the requirement to the quality of the cut on the cut surface. The correct choice of gas can mean that subsequent treatment of the cut parts can be avoided. Typical plasma gases are oxygen, nitrogen, argon and possibly hydrogen as an addition to N₂ and Ar. N₂ or CO₂ can be alternatives for compressed air.