INTRODUCTION
The technology is more advanced machining. It is evident from the start many types of high-tech machines that have emerged and developed in the world. One example is the Laser Beam Machining (LBM) which we discuss in this paper.
LBM uses a monochromatic beam of high-power so that the tool can be used on almost any type of material. In everyday life, LBM is used as a tool to cut or perforate materials with high accuracy.
In the production process, although it has a high strength and a good degree of accuracy, LBM technology is still rarely used. This is because in the execution of this instrument needed professional expertise and operational costs are quite expensive. Even so, it is not wrong for us to learn this technology, given that this technology will grow and bring a meaningful contribution in the future machining.
1. meaning
LASER BEAM Machining (LBM) is a cutting method, in which the workpiece is melted and evaporated by a strong monochromatic laser beam. When the rays of the work piece, producing heat and vaporize things trickle down to the hard work though.
LBM can be used for welding and cutting metals / nonmetals. In addition, the LBM can also be used for brazing (piteously), soldering, drilling, and make a sign (marking).
Figure 1 The letter "E" are Made with LBM
2. Basic principles of Laser Establishment
The word "laser" is an acronym for "light amplification by stimulated emission of radiation". Can be formed due to the absorption of laser energy by the quantum material / medium of the laser light source that causes an atomic electrons jump to a higher energy level (orbit farther from the nucleus). These electrons will then fall into the orbit of his home as he spontaneously emits energy that has been absorbed before. Energy form of radiation that has a wavelength equal to the energy penstimulasinya and in phase with it.
Figure 2 Electron in orbit
3. Types of Laser
3.1 Gas Laser
CO2 laser is one of the most common gas lasers. To shape the medium we use a gas mixture of helium (He), nitrogen (N2), and CO2 in a tube. Bereksitasi N2 molecules will absorb the energy caused by the release of electrons from the electrodes so that the CO2 molecules pound CO2 molecules were excited and emit radiation, while He took the electron gas CO2 level to the outermost orbit.
In Figure 3 Excitation of CO2 Lasers
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CO2 lasers can operate properly when the waves it produces are made continuously or often referred to as Continuous Wave Carbon Dioxide (CWCO2).
This type provides high power output and continuous conversion efficiencies greater than 13% (most likely in the top 20%), and low power density. In addition, this type of surgery also requires a relatively short time making it the most promising methods in the production process.
3.1.1 He and Ne
This type of laser system pumped by electric discharge between two elektroda.Sistemnya consists of one or more types of gas. The gas atoms undergo collisions with electrons so as to obtain additional discharge energy to bereksitasi. Perlaseran recent developments in the gas medium can be replaced with a metal vapor, but it will lead to the development of other types of lasers. Metal vapor laser types will be discussed separately. Gas laser capable of emitting radiation with wavelengths ranging from the ultra violet to infra-red. Nitrogen laser using N2 gas is one of the most important of this type of laser, the laser wavelength is in the area of ??ultra violet (3371 A ?). While the carbon dioxide laser is a gas laser that emits powerful laser in the infrared region (10600 A ?). Laser gas laser heliumneon popular course, widely used as laboratory equipment and prices in the market sawalayan readers. The resulting laser is in the visible red spectrum (6328 A ?).
Under normal circumstances helium atoms are essentially energy levels 1S0, because their outer electron configuration is 1 s2. At the time of discharge electron helium atom grind it bereksitasi to get the energy to a higher energy level as 1S0 and 1s2s 3S1 of electron configuration. Once helium atoms excited to the levels that he can no longer return to baseline levels, something that is forbidden by the selection rules of radiation. A coincidence that several energy levels of neon atoms have nearly equal to the energy levels of the helium atom. As a result of energy transfer between the two types of atoms was very terbolehjadi through collisions. Can be seen in Figure 5
that were pounded by a neon atom helium atom will be excited to the level 1S0 1P1, 3P0, 3P1, 3P2 of the 2p55s electron configuration. After the helium atoms collide going right back to the basic energy level. Therefore, the selection rules allow transitions from energy levels to ten levels of energy that 2p53p configuration, the neon atom can be triggered to emit laser. Terms of population inversion by itself has been fulfilled, because the thermal equilibrium levels in the Ne atom 2p53p very rare population.
Figure 4. Energy level diagram of He and Ne
The resulting laser intensity will have the clearest in the wavelength 6328 A ? earlier. Actually, He-Ne laser beam is strongest is in the 11523 A ? (near infrared) caused by the transition of one of the 4 levels in the atomic Ne 2p54s, who happened to be adjacent to the energy level 3S1atom He, to one of the 10 energy levels in 2p53p. This laser system gas tubular cylindrical with a length of one meter and a diameter of 17 mm. Both ends of the tube is closed by two parallel reflective mirror, called mirror Fabry - Perot,
so that the gas tube also functions as a resonant cavity optisnya. Two electrodes mounted near the ends and connected to a high voltage source to cause the discharge tube. He and Ne pressure in the tube is about 1 torr and 0.1 torr, in other words He atom is approximately 10 times more than the Ne atom. He chopped the more it is able to maintain continuous population inversion, so that the resulting laser also is continuous, not intermittent as
such as the ruby laser pulse. The continuous nature of an advantage than the gas laser ruby laser. Continuous laser is very useful for the transmission of speech communication, music or television pictures. He-Ne laser efficiency is also low, only about 1 percent, the laser output is only of order milliwatts. While the CO2 laser can generate several kilowatts of power continuous laser with higher efficiency.
Figure 5. Gas Laser System
3.2 Laser Solid
Materials used an electric nonkonduktor material that was given power by the vibrating beam flux using direct current power and stack capacitors.
Ruby 3.2.1
Ruby crystals composed of aluminum oxide (corundum) which contains about 0.1% khromik oxide. Laser rods can be single crystals of synthetic ruby 1 cm diameter and 10 cm long.
Neodymium 3.2.2
A neodymium glass (Nd: Glass) containing 2-6% neodymium and made ??the rods similar to the ruby rod. Neodymium glass is two or three times as efficient as ruby and less sensitive to temperature changes. Nd: Glass produces violet light with a wavelength of 351 nm.
In addition, there is a mixture of neodymium titrium-aluminum-garnet (Nd: YAG). Nd: YAG can produce accurate holes 12 mm deep in under 10 seconds and a hole 25 mm in 40 seconds. Nd: YAG produces a green light with a wavelength of 532 nm.
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