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About Lasers 7KH 3KRWRQLF 6SHFWUXP DQG /DVHU /LQHV4SHFWUXP³:DYHOHQJWKV7KH 9LVLEOH 6What Is A Laser?LASER is an acronym standing for Light Amplification by Stimulated Emission ofRadiation. All lasers are comprised of a few basic components that work together toproduce light that is1.Monochromatic (consisting of only one color/wavelength)2.Directional (does not spread out as much as ordinary light. If the laser beam issent through a special telescope called a collimator, it will spread out even less)3.Coherent (all light waves in phase, they start at the same moment and are thesame size)4.BrightThe light from a laser is intensified in such a way as to provide a beam that can beused to cut, drill, engrave, mark and weld. Rofin-Baasel provides systems for materialprocessing applications such as marking, welding and cutting.The basic components of a laser are:The atoms in the Active Medium (solid-state crystal, liquid or gas) absorb theenergy emitted by the Excitation Mechanism (typically a Krypton Arc-Lamp, DiodeArray, or Electrode Set) and are excited, or pumped , to a higher-than-normalenergy level. Once the majority of the atoms of the Active Medium have beenexcited to a higher energy level, a condition know as Population Inversion occurswithin the laser. The atoms are unstable in this condition and shortly return to theiroriginal energy levels, releasing their stored energy in the form of a light wave(Photon).A portion of the light released as the atoms return to stable orbits is released in adirection perpendicular to the mirrors at the end of the resonator. These Photons ofenergy reflect back and forth from the mirrors through the Active Medium, and arefurther amplified by the laser to form a coherent beam of light. Once the energy withinthe laser system achieves a certain level, then a portion of that light is transmittedthrough the partially transmissive reflector resulting in a beam. Measuring the LightThere are many different types of lasers for a wide variety of purposes, each havingan output beam different from other types. This is what determines the applicationof each particular laser type.Some lasers produce a CW beam ( Continuous Wave ), or a beam which is oncontinuously. Others give only a short pulse of light.The Pulsed laser produces energy measured in a unit called joules. One joule is theamount of light energy produced by a one-watt light bulb when it is on for onesecond. The industry has seen pulsed lasers producing energy bursts from a fewthousandths of a joule to over 100 joules. In addition to energy, the speed withwhich a laser delivers its energy is very important. If a pulsed laser produced onejoule of energy in a burst that lasted 100 seconds, only 1 joule/100 sec or 1/100 of awatt of power would reach the target. But if the same laser delivered one joule ofenergy in 1/1000 second, then1 joule1/1000 secor 1000 watts of power are delivered. A one-joule ruby laser producing a light pulselasting for 1/1000 second will drill a clean hole in a razor blade.If the pulse were even shorter, for example 1/1,000,000 second, but the energy wasstill one joule, the power produced would be1 joule1/1,000,000 secsor 1,000,000 watts.Another important measurement of a laser bean is its power density , a measure-ment of the concentration of the laser energy (something is concentrated when it isheld together tightly).Think of one watt of power spread over a large area versus one watt concentratedinto a spot the size of the head of a pin. Power density is measured in watts persquare centimeter, written: watts/cm².Lasers for Cutting and WeldingCarbon dioxide lasers are high-powered, and the fact that they can be either pulsed orcontinuous wave makes them very useful in industry. The beam is invisible, but can bevery intense.The laser melts and cuts metal in the same way a torch does; by applying heat. Thedifference is that the laser applies the heat much faster and is concentrated. Themetal melts and then vaporizes and is blown out of the area before the heat can becarried away. Laser cutting produces clean cuts and does not weaken the metal liketorch cutting.The Triagon Series of high-power industrial CO2 lasers are available in a widerange of powers from 1kW 12kW. The 9kW 12kW higher power range Triagonlasers can cut mild steel to 30mm thickness and weld thinner materials (<15mm) atthe highest speeds.For tasks such as thin sheet cutting or cutting complex geometries even from a steeltube (dia 1.5 1.8 mm, and wall thickness of <100µm), Rofin-Sinar Inc. of Plymouth,MI, offers the StarCut line of Pulsed Nd:Y AG lasers featuring optimized resonatordesign for cutting widths as fine as 25µm unmatched accuracy.The laser is very good for welding small parts that must be done very accurately.Most laser metal cutters and welders are controlled with a computer and can makesmall welds in tiny parts that cannot be done with other welders. The StarWeld line ofspot- and seam-welders can even weld different metals and metal combinations in closeproximity to other delicate materials highly useful in the jewelry or dental industries. Lasers for Marking and EngravingIn general, laser marking and engraving systems fall into three basic categories: dotmatrix marking systems, focused-spot stroke marking systems and stencil (mask)marking systems. Rofin-Baasel can provide focused-spot stroke marking systems anddot matrix marking systems (the RS-Marker® PowerLine and the StarMark® line oflamp- or diode-pumped Nd:Y AG and CO2 laser systems).How does the laser mark a part?A laser creates an image on an object by either vaporizing or melting the material(leaving a engraved mark), locally annealing the surface to produce a dark mark (asin the case of many steels, titanium and the like), or through a thermal-chemicalreaction between the beam and the part surface as in the case of a number of ser marks are permanent in most cases and withstand many post-processing applica-tions very well.What is a Focused-Spot Stroke Marker?Two laser types (active medium) are typically used in stroke marking systems, depend-ing on the marking application. The first of these is a Neodymium Doped, YttriumAluminum Garnet (Nd:Y AG) laser which produces near infrared light at a wavelength of 1.06 microns, or a Waveguide CO 2 gas laser that emits light at a wavelength of 10.6microns.The pumping of the Nd:Y AG laser can be accomplished in one of two ways, either through the incorporation of a Krypton Arc-lamp or through utilization of light-emitting diodes. Applications requiring more than a few watts of power ordinarily utilize the flash-lamp method of excitation. CO 2 lasers utilize DC power or RF energy to excite the gas medium.Stroke Markers utilize a pair of microprocessor-controlled mirrors to steer the beam emitted by the laser to form alphanumeric characters, logos or patterns. The laser writes with light just as you would write with a pencil, forming characters one stroke at a time. One mirror controls the X-axis while the second mirrorcontrols the Y -axis.The size of the mark field is deter-mined by the focusing lens that is incorporated into the system. There are basically two types of focusing lenses: pre-scan and post-scan. A pre-scan based system places a simple thin lens prior to the scanning mirrors. This is the least expensive method of focusing the laser beam but will typically produce more distortion in the mark than a post-scan system.Remember, a stroke marking system draws characters just as you would with a pencil and paper. To mark the letter L , the beam would firstThe most common laser marking systems use a flat-field lens and distortion correction software in this arrangementposition itself at the upper left corner of the character, then once in place the beam would be steered downward, stop and then finish the character to the right. The piece being marked in most cases needs to be stationary, just as the piece of paper is station-ary when you write a letter.How fast does a stroke-marking system mark?Stroke marking systems use high-speed scanners, electronics and marking algo-rithms to draw characters as fast as 300 or more per second. Practically speaking, though, most materials being marked cannot absorb the beams energy at that rate. Marking of metals, then, is usually accomplished at 10-50 characters per second, and nonmetallic or treated surfaces may mark as high as 150 characters per second. How large a mark area can be generated?Without using an X-Y table to move the part or the lens, the largest mark area that can be achieved using a flat-field lens is nearly 15 in diameter. Some companies offer areas larger than this, but the beam quality from these systems is not always high quality.Rofin-Baasel standard marking areas for the StarMark lines are:Lens Name Mark Field Working Distance Typical Spot Size 100 mm90mm (3.54 )101mm (4 ).076mm (0.003 ) 160 mm150mm (5.91 )185mm (7.3 ).10mm (0.004 ) 254 mm230mm (9.06 )295mm (11.6 ).12mm (0.005 ) 330 mm300mm (11.81 )356mm (14 ).15mm (0.006 ) 420 mm380mm (14.96 )508mm (20 ).20mm (0.008 )The precision flat-field lenses used by the RS-Marker PowerLine laser markers produce a square mark field. Available lens sizes are:Lens Name Mark Field Working Distance Typical Spot Size f10060x60 mm (2.4x2.4 )109mm (4.3 )076mm (0.003 )f160120x120mm (4.7x4.7 )198mm (7.8 ).10mm (0.004 )f240160x160mm (6.3x6.3 )329mm (12.9 ).12mm (0.005 )f254180x180mm (7.1x7.1 )345mm (13.6 ).12mm (0.005 )f300240x240mm (9.5x9.5 )408mm (16.0 ).15mm (0.006 )f420300x300mm (11.8x11.8 ).20mm (0.008 )How is information entered into the Laser System?Our CAN BUS based StarMark® systems offer a MicroSoft Windows operating system featuring CAN technology. The StarMark systems use a proprietary Laser-CAD graphical interface design tool for mark layout designs, and feature direct links to databases via Windows ODBC engine, and interfacing to PLC and com-puter-controlled systems. The RS-Marker PowerLine systems use a unique single PC -type proprietary software package, VisualLaserMarker (VLM). Text, logos or graphics can be created with the drag and drop functions or imported from already existing files to the work sheet which represents the mark field. An open interface architecture based on ActiveX® technology is provided for integration into customized production equipment.。