Laser cutting

Introduction

The production of laser cutting machines began thirty years ago The first ever ‘gas-assisted’ laser cuts were done in 1967.. The progress was very fast
and at present time every year over 3000 laser cutting machines are installed in the world.Today, laser cutting is used extensively for producing profiled flat plate and sheet, for diverse applications in the engineering industry sectors.

Laser cutting is one of the largest applications of lasers in metal working industry. It is based on vaporize the material in a very small area by focused laser beam. Process characteristics are: uses a high energy beam of coherent light; beam is focused on an small spot on the work piece by a lens; focused beam melts, vaporizes, or combusts material; molten material is ejected out from the melt area by pressurized gas jet. Laser cutting is the high speed cutting with a narrow kerf width that results in superior and enhanced quality, higher accuracy and greater flexibility.

By combining the laser beam and the machine providing motion, in addition to the applied numerically controlled system, it is possible to provide for a continual sheet cutting along the
predetermined contour. The laser beam can cut very hard or abrasive materials. Cutting with lasers is a very cost effective process with low operating and maintenance costs and
maximum flexibility.Metals, ceramics, polymers and natural materials such as wood and rubber can all be cut using CO2 lasers.

Working

The machine utilizes an intense beam of focused laser light to cut the part. Material under the beam experiences a rapid rise in temp. and is vaporized. Laser cuts with a minimum of distortion, no mechanical cutting forces.Gas is blown into the cut to clear away molten metals, or other materials in the cutting zone. In some cases, the gas jet can be chosen to react chemically with the workpiece to produce heat and accelerate the cutting speed

1. A high intensity beam of infrared light is generated by a laser.
2. This beam is focused onto the surface of the workpiece by means of a lens.
3. The focused beam heats the material and establishes a very localised melt (generally smaller than 0.5mm diameter) throughout the depth of the sheet.
4. The molten material is ejected from the area by a pressurised gas jet acting coaxially with the laser beam as shown in fig 1. (N.B. With certain materials this gas jet can accelerate the cutting process by doing chemical as well as physical work. For example, Carbon or mild steels are generally cut in a jet of pure oxygen. The oxidation process initiated by the laser heating generates it’s own heat and this greatly adds to the efficiency of the process.)
5. This localised area of material removal is moved across the surface of the sheet thus generating a cut. Movement is achieved by manipulation of the focused laser spot (by CNC mirrors) or by mechanically moving the sheet on a CNC X-Y table. ‘Hybrid’ systems are also available where the material is moved in one axis and the laser spot moved in the other.

Advantages

•Excellent control of the laser beam with a stable motion system achieves an extreme edge quality. Laser-cut parts have a condition of nearly zero edge deformation, or roll-off