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Laser-cutting,Using Light to Shape Matter.SOLUTIONS with Effective, Practical Advice
It enables shaping of a great variety of materials including metals of all kinds. From inexpensive steels to special alloys, but also plastics, paper, wood, leather, rubber and more. As a process it is enjoying exceptional and rapid expansion. It is adopted by many industrial manufacturing activities due to its unique advantages. Among them: economy, productivity, part precision and quality, material utilization and production flexibility. Furthermore, as no contact is made while cutting, the process leaves no marks or contamination of the material. High quality cuts are obtained with no extra finishing operations. The Laser is essentially a beam of monochromatic coherent light. Lenses or mirrors concentrate it into a very small spot of highly intensified energy.
High concentrated energy is capable of melting or vaporizing most materials. Pressurized coaxial additional gas flow, through the nozzle tip, blows away molten and vaporized material. In fusion cutting inert nitrogen removes the molten drops. In oxidation cutting active oxygen reacts with the metals, adding heat exothermically. Compared to other methods, the benefits of laser beam as a cutting tool are:
The parameters that determine the applicability of the process to different materials and that establish the cutting quality are:
Pulsed lasers are preferred for precise cutting of thin metals and continuous wave (CW) are used for Laser-cutting widely ranging material thickness. The operator sets the peak power of the pulse, the pulsing frequency (number of pulses per second) and the pulse duty (percentage of pulse on-time per pulse period) (Pulse period = on-time + off-time). Continuous wave output is equivalent to 100% duty. A pulsed laser outputs short time powerful bursts of energy, useful for piercing the material to start a cut in the interior of a sheet or plate. Typically, the diameter of a focused process laser beam is about 0.20 mm, concentrating 1000 to 4000 watts of energy at the focal spot. This is enough to melt or vaporize most common materials. Aluminum and copper are highly reflective materials. To improve their ability to be cut by laser they should be covered with a light absorbing layer colored black. In the past gas lasers based on Carbon Dioxide (CO2) were used exclusively for elevated powers, which was achieved with limited efficiency. Newer solid state (crystal) lasers compete now with them even at relatively high power levels. The optical fiber lasers with computer controlled pulses facilitate Laser-cutting of intricate features in thin material like cardiovascular stents and silicon wafers for solar panels. The pulsed mode results in minimal recast layer and Heat Affected Zone, very critical to special applications. The widely varying depth of field and the small spot sizes produce small kerfs and straight walls even in thick metals. High power multimode lasers permit Laser-cutting of automotive body parts, of holes for riveting in alloys of aluminum and titanium for aerospace applications, and of thick plates for the shipbuilding industry. Laser-cutting machines are integrated into large computer controlled systems that implement design files on workpieces. Laser-cutting machines move either the cutting head or the metal or both. For maximum speed and efficiency, high performance precision systems, using ball screws and linear motors, move the low inertia parts including optical fibers and cutting head, while heavy materials are kept stationary on pallets. In Laser-cutting at high speed, the minimum radius for internal corners is about 0.75 mm (0.030 in). The minimum hole size can be as low as 20% of the stock thickness, depending on thickness. Nesting parts to be cut within the given surface and cutting along common lines, as well as stacking sheets, allow considerable economies to be realized. Job shops can provide the advantages of this processing to interested parties. A short note on Laser-cutting appears in our page on Cutting Torch. Almost eighty references to the Laser subject as treated in our website and in the periodic publications Practical Welding Letter, can be found by running a Google search in any of our website pages. More than seventy articles on Laser-cutting can be found at A short article on Underwater Laser Cutting was published (11) in issue 96 of Practical Welding Letter for August 2011. An Article on Underwater Laser Cutting for Nuclear Decommissioning was published (7) in Issue 138 of Practical Welding Letter for February 2015.
An Article on Traceability in Automated Cutting was published (2) in Issue 146 of Practical Welding Letter for October 2015. An Article on A new way to measure Laser Power was published (7) in Issue 152 of Practical Welding Letter for April 2016.
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