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Lasers are an efficient and effective tool for cutting metal and are widely used in the metal fabrication and manufacturing industries. They are most effective, however, when combined with CNC machining. Laser cutting works by focusing a high-powered laser onto the surface of the metal, usually focused through an optical system. The material is then removed by being burnt, vaporized, or blown away as a jet of gas, leaving a precisely cut edge and a high quality surface finish. Industrial lasers are used to cut pipes and tubes as well as flat sheet material. How Lasers Work A laser beam is generated by stimulating a lasing material with electrical discharges contained within a closed container. This generates a beam of light that is then reflected within the machine by using a partial mirror until it achieves enough energy to escape as a beam of single coloured coherent light. This beam of light is then directed through fiber optics and/or mirrors and focused on the metal to be cut. The cutting section of the beam is very fine, usually less them 0.32mm in diameter. Advantages Of Using CNC Machining Lasers The advantages of using lasers to cut metal rather mechanical cutting processes include: - It is easier to keep the work-piece in place - mechanical cutting applies various forces that mean the piece has to be solidly clamped to keep it steady. - Reduced contamination - as there is no swarf, cooling fluid or external blade that can wear and leave deposits, it is a much cleaner process. - Better precision - physical blades wear and this can affect the line of their cut. Lasers are no affected this way and the cutting point does not vary. - Reduced chance of warping - as there is no drag of a blade through the material, and the hot cutting point is very localised, deformation from mechanical forces is avoided. - Intricate cuts are also achievable - mechanical blades are limited in their ability to change direction. - Lasers are more accurate and use less energy than plasma cutters. When combined with the control offered by CNC machining, lasers can cut complex shapes and designs quickly and accurately. This makes them ideal for many metal fabrication tasks such as cutting profiles and internal structures for machinery. Types of Lasers There are three main types of lasers used for metal-cutting: CO 2 Laser - Suitable for cutting, boring and engraving. Neodymium (Nd) Lasers and neodymium yttrium-aluminium-garnet (Nd-YAG) lasers. These are both identical in style and differ only in the jobs they are used for. Nd lasers are ideal for boring and when high energy but low repetition are required. The Nd-YAG laser is better for applications when very high power is needed and for boring and engraving. All the types of laser are used for welding. CO 2 lasers are used in many industrial cutting processes and the materials they are used for cutting include mild steel, aluminium, stainless steel and titanium. The lasers themselves generate a high degree of heat and need cooling. Depending on the size and configuration of the system, the waste heat generated during operation may be transferred by a coolant or directly to air. Water is often used as a coolant, usually circulated through a chiller or heat transfer arrangement. There are also two other types of laser, although these are less common in metal fabrication . Laser Microjet - this is a laser that is guided by a water-jet. The laser beam is pulsed into a low-pressure water jet that is used to guide the laser beam, as if it were an optical fiber. The light beam is guided by internal reflection within the water jet. The advantage of this system is that the water also cools and removes the material being cut. Other advantages of this wet system are higher dicing speeds and omnidirectional cutting. Fiber Lasers - this is a solid state laser that uses a solid gain medium, rather than a gas or a liquid. The system is arranged so that a seed laser beam is amplified inside the glass fiber.
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