LASER CUTTING: THE MODERN MARVEL
Many of you may have heard about applications or gadgets related to LASER(Light Amplification by Stimulated Emission of Radiation) in movies and news or maybe on the Discovery and National Geographic channels, where they explain what LASER is and how it is helping in our day-to-day operations. You must have seen how a sniper aims for a perfect shot using a LASER beam. LASERs are very useful in cutting diamonds or hard to cut metals. It is also used in the medical treatment of a person and military purposes.
Currently, the USA is working on a technology with the help of which they are confident of inventing a cloaking technique. The technology will be able to make any object invisible to human eyes using LASER beams. The cloaking techniques are thoroughly explained and visualized in movies like Avengers or in Marvel’s Agents of S.H.I.E.L.D. Though many of us think that it’s hypothetical but in real life, we are too close to developing such things that will change the concept of war.
What is Laser Cutting?
In scientific terms, we can say that a LASER is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation where the emission generally covers an extremely limited range of visible, infrared, or ultraviolet wavelengths. From 1916 to 1960 small but effective developments took place in the concept of LASER, wherein 1916 it’s concept was introduce by Albert Einstein, and by the end of 1960, it was finally made open for public use.
One of the most important advantages of using a LASER is Laser Cutting. The Lasers are used for cutting metal plates, stainless steel, aluminum plates, or diamonds. In 1965, the first production of a Laser Cutting machine was used to drill holes in diamonds that were made by Western Electric Engineering Research Center. By the end of 1967, the British made LASER-Assisted oxygen jet used for cutting metals also at the same time CO2 LASERs were made but they were not powerful to overcome the thermal conductivity of metals.
Types of Laser Cutting
There are three main types of LASERs used for Laser Cutting i.e. Gas LASER, Crystal LASER, and Fiber LASER. All of these types have different properties that are developed over the years.
Gas Laser Cutting is also known as CO2 Laser Cutting, which completely uses carbon dioxide as its main mixture. It was first invented in 1964 but at that time it was not powerful to cut metals having higher thermal conductivity. Since then, it has not only evolved but now it can cut metals having higher thermal conductivity too. It was a wavelength of 10.6 micrometers and is used in medical and industrial settings.
Crystal Laser Cutting is a process that uses LASERs made from Nd: YAG (Neodymium-doped Yttrium Aluminum Garnet) and Nd: YVO (Neodymium-doped Yttrium Ortho-vanadate). These crystals are part of the solid-state group, and the crystals allow for extremely high powered cutting. The main and biggest advantage of using Crystal Laser Cutting over Gas Laser Cutting is that it can cut both metals as well as non-metals. It uses a wavelength of 1.064 micrometers and used for military purposes. One of the biggest disadvantages of Crystal Laser Cutting is its price as its kit is too costly.
The next type of Laser Cutting technique is Fiber Laser Cutting which is the most advance and is mostly used by all industries. It has several similarities to the crystal process that optical fiber also belongs to the solid-state group, and it also has a wavelength of 1.064 micrometers. One of the biggest advantages of using Fiber Laser Cutting is its service life which is longer than any other type. Also, it requires very little maintenance and its parts are easily available.
How Laser Cutting Works?
The beam is a column of very high-intensity light, of one wavelength, or color. In the case of a typical CO2 LASER, that wavelength is within the Infra-Red part of the spectrum, so it’s invisible to the human eye. The beam is merely about 3/4 of an inch in diameter because it travels from the LASER resonator, which creates the beam through the machine’s beam path. Then it is bounced in several directions by a variety of mirrors, or “beam benders” before it’s finally focused onto the plate, due to which the whole energy is concentrated at one point. Now the focused beam goes through the bore of a nozzle right before it hits the plate. Mostly it’s the gas like oxygen or nitrogen which flows through the nozzle bore.
Focusing the beam is often done by a special lens, or by a curved mirror, and this takes place within the laser cutting head. To achieve this, the beam must be precisely focused so that the form of the main target spot and therefore the density of the energy therein at the spot are perfectly round, consistent, and centered in the nozzle. By focusing the massive beam right down to one pinpoint, the warmth density at that spot is extreme due to which sufficient energy to achieve thermal conductivity of metal is achieved. You may think of it as an experiment wherein by using a magnifying glass, you directed the energy from the sun rays onto a leaf and started a fire. Now imagine about focusing 6k watts of energy into a single spot, and think how hot that spot will get.
The high power density leads to rapid heating, melting, and partial or complete vaporizing of the fabric. When cutting Low-Carbon Steel, the warmth of the beam is enough to start a typical “oxy-fuel” burning process, and therefore the Laser Cutting gas is going to be pure Oxygen, just like an oxy-fuel torch. When cutting Chrome Steel or Aluminum, the beam simply melts the fabric, and Nitrogen is employed to blow the molten metal out of the kerf.
On a CNC Laser Cutter, the laser cutting head is moved over the metal plate within the shape of the specified part, thus cutting the part out of the plate. A capacitive height system maintains an accurate distance between the top of the nozzle and therefore the plate that’s being cut. This distance is important because it determines where the focal point is relative to the surface of the plate. Cut quality can be affected by raising or lowering the focal point from just above the surface of the plate, at the surface, or just below the surface.
