Laser Cutting

The focused beam of a laser makes it well suited for the energy transfer necessary to cut metal by melting or burning the material along a cut line. Assist gas such as nitrogen or carbon dioxide is used in conjunction with laser cutting to prepare newly cut surfaces for painting or corrosion resistance. An example of the gas assist laser technique is CO2 laser cutting, and it is considered the most powerful wave laser. A laser cutter is often controlled through a precision program combination of CNC and CAD computer systems. CNC systems use CAD designs to input all the necessary machining details into a computer program that then fully directs the laser cutting process, requiring a minimal staff to simply oversee the production and make sure the machines are well maintained. Lasers that are used for cutting may also be used to create patterns and holes in other laser machining and laser micromachining services such as laser drilling and laser welding. Other common laser marking processes include laser etching and laser engraving. Many manufacturers of laser cut products are able to offer custom laser cutting, which is used when the design is too complex or intricate to cut by hand.

Many manufacturing industries, particularly in microtechnology and electronics, depend on laser cutting's microscopic tolerances and precision accuracy to fabricate small, intricate parts. Medical devices use laser cutting to drill catheter holes, hypo-tubes, gas flow orifices and filtering devices, all of which must be perfect since lives depend on them being so. Laser cutting is also used in many manufacturing industries to fabricate precision parts, nozzles, solar cells, gaskets and circuit boards for aerospace and automotive markets. Cell phone parts, computer microchips, transducers and many types of military and communication devices are made with precision laser cut parts. While laser cutters cannot cut through thick metals or create three dimensional shapes in metal plates like water jet cutters can, laser cutters offer tolerances more precise than any other cutting method, with lower edge distortion than most. Many systems we depend upon on a daily basis, such as water piping and refrigeration systems require parts mass manufactured by laser cutting tools.

Using lasers to cut and machine metal has distinct advantages over conventional cutting processes such as thermal machining, mechanical machining, arc welding, EDM and flame cutting. 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, roll-off or edge factor, leaving very little burring on part edges. Laser cutters have higher accuracy rates over any other metal cutting method, with smaller slicing widths and slightly higher precision tolerances than even water jet cutting. Laser cutting is faster than conventional tool-making techniques and has a quicker turnaround for parts regardless of complexity because design changes can be easily accommodated. The use of CNC machining allows for fewer technicians and ensures safety, unlike arc welding, which can be dangerous for the welder and requires individual workers for each piece. Many different kinds of laser cutting services are available, all of which make highly efficient use of materials, creating little waste.

Laser cutting does have a few disadvantages, most of which involve the drawbacks of hot cutting. The material being cut gets very hot, so in narrow areas thermal expansion and warping may be a problem. Distortion and oxidation can be caused by oxygen, which is sometimes used as an assist gas, because it puts stress into the cut edge of some materials; this is typically a problem in dense hole patterns. Lasers also require large amounts of energy, making them more costly to run. Lasers are not very effective on metals such as aluminum and copper alloys due to their ability to reflect light as well as absorb and conduct heat, nor can laser cutting be used on crystal, glass or any other non-metals. Lasers, even low-powered ones, are potentially hazardous to a person's eyesight. The laser beam can focus on an extremely small spot on the retina, causing permanent burn damage in seconds. Infrared and ultraviolet lasers are even more dangerous because the "blink reflex" protects the eyes only if the light can be seen. Although laser cutting and laser cutting services do not offer quite as much cost efficiency as cold water jet cutting, nor do they offer the completely bur-free finished edging of water jet cutting processes, laser cutting is capable of creating tighter accuracies on a smaller scale than any other type of metal cutting process.

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Laser Cutting Types

• CNC laser cutting is a process that uses an intense laser beam to cut part shapes out of sheet material. The parts remain flat because the heat distortion is minimal.
  
• CO₂ laser cutting is a process that uses carbon dioxide as the main lasing medium. CO₂ lasers use a mixture of gases-such as helium and nitrogen, with CO₂ being the most predominant-to create a cut quality similar to that of milled edges of mild steels and can operate in continuous wave (CW) or pulses.
  
• Custom laser cutting is always done with CNC machining programs that are custom programed to design unique designs exactly like the buyer desires.
• Evaporative laser cutting is the process of ablating target materials, typically low vaporization temperature and low thermal conduction materials, through direct vaporization.
  
• Excimer laser cutting is a process that uses the noble gas compounds for lasing. Excimer lasers generate light in ultraviolet to near-ultraviolet spectra.
  
• Gas laser cutting is a process in which gas is used as the activating agent.
  
• Nitrogen cutting or inert gas cutting provides cut edges covered with melted and resolidified metal comprised of the same metal mixture of the material. Thus it has the same resistance to corrosion and is useful for food processing facilities, chemical plants and sign production.
  
• Laser cutters perform all the services and all of the processes that cut metal or other materials with lasers to create precision products.
• Laser drilling is the process of creating a hole in material with a laser beam.
  
• Laser engraving uses lasers to etch into a surface.
• Laser etching is the process of marking the material without cutting all the way through using reduced power.
  
• Laser machining is the removal of material brought about by laser material interaction. Laser machining is a term that includes laser drilling, laser cutting, laser grooving, laser marking or laser scribing.
  
• Laser marking is a process in which material is indelibly marked at very fast speeds (milliseconds per character). Laser marking is flexible, programmable and environmentally clean.
  
• Laser metal cutting involves lasers cutting the most common material used to produce machining products: metal.
• Laser micromachining is a process used to create extreme detail and to cut very precise components that require close tolerances.
  
• Laser welding is the process of using a laser beam to connect two or more pieces of metal together by melting the areas to be joined and allowing them to resolidify.
  
• Liquid laser cutting is the process in which large organic dye molecules are used as the active lasing medium.
  
• Melt shearing, also known as "fusion," is the laser cutting process that creates a melt, which a gas jet blows out of the melt zone, typically with air. The resultant cut edge is of high quality but is covered with microscopic ripples.
  
• Moving optics laser cutting is a process in which mirrors are used to reflect the laser beam to the cutting head while the work piece material remains fixed.
  
• Multi-axis laser cutting is a kind of laser cutting utilizing multiple axes instead of one. The advantage of multi-axis laser cutting is the capability of cutting three-dimensional shapes, while the disadvantages are the higher expense over flat bed cutting, longer set up times and increased safety hazards.
  
• Oxygen assist cutting is a process in which the oxygen does the actual cutting, and the laser beam maintains the reaction.
  
• Pulsed laser cutting is a cutting process that uses single or train pulses, as opposed to continuous wave lasers. These pulses supply greater power at shorter intervals.
  
• Semiconductor laser cutting is a process utilizing semiconductor materials as the active medium.
  
• Solid state laser cutting is a process in which the active medium of the laser (typically not semiconductor lasers) is in a solid state.

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Laser Cutting Terms

Ablation - The elimination of material with an industrial laser by evaporation, vaporization or melting.
 
Alloy Steels - A steel alloy containing a primary iron component minus any other metals necessary to make stainless steel.
 
Articulated Arm - A device consisting of a series of hollow tubes and mirrors that supplies the beam in a CO₂ laser.
 
Assist Gas - A gas used to facilitate the cutting process and to blow melted material through the cut area. Oxygen is usually utilized for cutting ferrous metals, and any inert gas produces oxide-free cut edges.
 
Attenuation - The decrease in radiation power or energy as the beam is passing through a scattering or absorbing medium.
 
Beam - A group of rays that may be convergent, divergent or parallel.
 
Beam Diameter - The diameter of a circular beam at a particular point in which the intensity lowers to a fraction of its maximum value.
 
Beam Divergence - The spread of the beam angle, expressed in milliradians. One radian equals 3.4 minutes of arc or nearly 1 mil.
 
Computer Numerical Control (CNC) - A computer that controls the machine's movement. CNC controls motion tables or position the work piece beneath the focused laser beam. (http://www.iqsdirectory.com/cnc-machining/)
 
Coated Steels - Carbon or mild steel made with coatings like zinc plating, mill scale, paint, rust or identification marks. Reduced cutting speeds and more dross on the bottom of the cutting edge are the result.
 
Collimation - The capability of a laser beam not to spread significantly (low divergence) with distance.
 
Collimator - An optical device consisting of two lenses separated by the sum of their focal length that is used to provide a desired beam diameter to meet beam delivery specifications.
 
Continuous Wave (CW) - The continuous-emission mode of a laser, as opposed to the pulsed operation mode.
 
Copper/Copper Alloys - Metals that exhibit an extreme reflectivity to laser light and have high thermal conductivities. These two characteristics lower the cutting speeds and the highest thickness of material that can be cut.
 
Crystal - A solid crystalline material with a regular array of atoms utilized as laser sources.
 
Cut Initiation - Also called "piercing," it is the use of the laser in the pulsed mode for hole drilling with air or oxygen as the assist gas.
 
Cutting Bed Size - A characteristic that determines the size of the material to be cut. Bed sizes are commonly 4' X 8' and some are as big as 5' X 10'.
 
Cut Width - A measurement that is dependent on the properties of the material cut, the lens focal length and the type of gas in the laser. The width of a cut from a laser will usually be between 0.1 and 0.4 mm.
 
Cycle Time - The amount of time required for the completion of the laser process.
 
Depth Of Field (DOF) - The operating span of the focused laser beam calculated as a function of the focal length of the lens, the wavelength and the diameter of the unfocused beam. A shorter focal length gives a smaller depth of field.
 
Drift - Undesirable variations of either amplitude or frequency of laser output.
 
Dross - Solidified melt on the lower edge of the laser cut. Higher amounts of dross result from surface rust, poor quality steel and incorrect process parameters but can be reduced by increasing the oxygen pressure and pulsed laser cutting.
 
Duty Cycle - The actual length of time that the laser beam is cutting, drilling, welding or heat-treating, as compared to the cycle time.
 
Enclosed Laser Device - A laser or laser system closed off to prevent hazardous optical radiation from escaping the enclosure.
 
Feed Rate - The rate at which the cutting head moves.
 
Focal Point - The position of maximum energy concentration of a focused laser beam. Focal point is determined by measuring where the laser beam has the least diameter and the refracted light rays of a lens conjoin.
 
Gas Jet Assist - A coaxial assist gas utilized to attain extreme power levels required for cutting particular metals, usually nitrogen, oxygen and argon.
 
Gas Jet - A device that blows gas into the cutting zone to clear away molten metals or other materials. At times, the gas reacts chemically with the work piece to create heat and increase the cutting speed.
 
Heat Affected Zone (HAZ) - A small area next to the cut zone that undergoes changes in material properties as a result of heat conducted into the work piece as it is cut.
 
Hologram - An interference phenomena captured on a plate or film that can contain large amounts of information and from which 3D images can be constructed.
 
Kerf - The slit, notch or groove produced by a laser cutter or the width of such a cut. The kerf is reliant on the work piece thickness, the properties of the material, the lens focal length and the kind of cutting gas in the laser.
 
Laser Cutting Grade Steels - Kinds of steels particularly manufactured for laser cutting applications. These steels maintain the strength of standard materials, but with reduced amounts of impurities like sulphur and silicon, and can be cut to a greater highest thickness at faster speeds.
 
Laser Resonator - Also called "laser cavity," it consists of the optical mirrors, pumping system and active medium. Laser resonators can be stable or unstable based on whether the oscillating beam converges into the cavity or spreads out from the cavity
 
Laser Product - A legal phrase indicating a laser or laser system or any other product that integrates or is intended to integrate a laser or laser system.
 
Lens - An optic that is either refractive or reflective and affects the convergence of rays of light at a point. The depth of focus and power density of a lens can change with differences in laser beam diameters.
 
Melting Point - The temperature at which a material melts. Materials having high melting points must be cut more slowly with a laser, since more energy is needed to melt them.
 
Mode Locking - A method that creates very short laser pulses by making the phase differences of many modes or frequencies in the laser cavity fixed (locked).
 
Neodymium Solid-State Glass (Nd:Glass) Lasers - Lasers that provide high-power, short pulses for particular industrial applications.
 
Neodymium:Yttrium-Aluminum Garnet Solid-State Lasers (Nd:YAG Lasers) - Lasers that are like Nd:glass lasers in that they are both pumped by flashlamp and beam transmissions through fiber optics, but the ND:YAG laser light can achieve finer detail work. It is also better than the CO₂ laser on highly reflective material.
 
Nozzle - A component of the gas jet in laser cutting that constricts the assist gas and directs it to a columnar flow.
 
Power Density - Laser output per unit area, expressed in watts per square centimeter (W/cm²).
 
Pulse - A single, irregular burst of a laser, in contrast to a continuous beam. True pulses attain greater peak powers than what a continuous wave output can do.
 
Pulse Frequency - The speed at which pulses are produced, expressed in pulses per second.
 
Reflectivity - The degree to which a material reflects laser light. Extremely reflective material such as aluminum and copper alloys are harder to cut, necessitating lowered work speeds.
 
Substrate - A sheet of base material that may or may not have an interconnection pattern.
 
Ultrashort Pulsed Laser - Laser whose pulse duration time is below one nanosecond.
 
Vaporization - The conversion of a solid or liquid into a vapor. Lasers vaporize the metal or material they are cutting.