A History of Laser Cutting

When you hear the word &#;laser,&#; what do you think of? For many people, lasers bring to mind images of Star Wars lightsabers and sci-fi movies. While lasers often feature in popular culture, many industries use laser technology as part of their manufacturing processes to cut and engrave materials. In fact, you&#;ve almost certainly encountered a product made using laser cutters.

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Although laser cutting seems like modern technology, the history of laser cutting may surprise you. The first lasers had their roots in Einstein&#;s theoretical work and followed a fascinating path before becoming the higher power lasers used in many industries today. Let&#;s trace the history of laser cutting from Einstein through to the first working laser and beyond to the modern day.

What Is Laser Cutting?

Laser cutting is a technique used to cut or engrave hard materials by burning, melting or vaporizing. The process has multiple industrial applications across various industries and can be used to drill holes or cut shapes in metal and other materials on a production line. Laser cutting is also used as an artistic technique to engrave decorative designs on surfaces.The primary advantage of laser cutting technology is its accuracy, and the high power beam is concentrated through a laser cutting nozzle for pinpoint accuracy. Modern laser cutting generally uses CAD technology, allowing artists and engineers to create intricate designs with an industrial laser.

How Does Laser Cutting Work?

A laser works by energizing the atoms in a solid, liquid or gas medium. This requires an energy pump, which could be an electrical current or even a second laser. As the atoms in the medium absorb energy, they start emitting light. This light is concentrated by placing a mirror at each end of the medium, creating an optical cavity.Laser cutting works by focusing a laser beam onto sheet metal or another hard material. Mirrors, lenses and compressed gases such as carbon dioxide allow technicians to adjust the laser beam focus through a laser cutting nozzle.The narrow beam then melts or burns away the material, and the technician can then move to the next area by moving the cutting materials or laser head. CAD technology allows the laser head to move across the cutting sheet metal or other material automatically.

What Are the Types of Laser Cutters?

Laser cutters are defined by their laser medium. A solid state laser uses a material such as ruby or glass to create a focused laser beam. Gas laser cutting uses a gas (usually CO2), and a liquid laser requires a liquid medium. The most common types of laser cutting are:

1. Gas laser cutting:

   The gas laser cutting process is often known as CO2 laser cutting. A CO2 laser cutter fires a laser beam through a CO2 mixture. This technique is generally used for cutting nonmetal materials like wood.

2. Crystal laser cutting:

   Crystal laser cutters can cut and engrave various materials, including metal and nonmetal surfaces. However, they aren&#;t especially durable and are expensive to build and run.

3. Fiber laser cutting:

   A fiber laser cutter is the most recently invented laser machine. Such a machine uses a medium made of optical fibers and is less expensive to make than gas or crystal laser cutters. Another advantage of fiber lasers is their higher power output. This economical cutting tool is suitable for various metal and nonmetal materials.

Who Invented Laser Cutting?

The history of laser cutting began back in when Albert Einstein came up with the theory of &#;stimulated emission of radiation,&#; the principle behind the modern laser. He theorized that electrons could emit photons when they absorbed enough energy to move up an energy level within an atom.In , a scientist called Gordon Gould expanded on Einstein&#;s theory. He suggested that the stimulated emission of radiation could be used to amplify light. His theory was dubbed Light Amplification by Stimulated Emission of Radiation &#; or LASER for short.Jump forward a year to , when Theodore Maiman created the first-ever working laser in a California laboratory. He used synthetic ruby to generate a deep red beam, although many of his contemporaries couldn&#;t see a use for his ruby laser. In fact, the technology was described as &#;a solution looking for a problem&#; and was met with skepticism and even suspicion by the public. However, many members of the scientific community saw the potential in Maiman&#;s invention, including scientists at Bell Labs in New Jersey.It wasn&#;t until that a scientist at Bell Labs finally developed thermal cutting techniques using lasers. Kumar Patel invented a gas laser cutting process using a carbon dioxide mixture and found it to be a quicker and more cost-effective improvement on ruby laser cutting. His colleague at Bell Labs, J.E. Geusic, invented the crystal laser process later that year. The invention captured the popular imagination, and it was featured in a famous scene in the film Goldfinger, during which the titular villain attempted to cut James Bond in two with a laser beam.

Which Was the First Group to Use a Laser Cutter?

The first group to use laser cutting was the Western Engineering Research Center in Buffalo, New York, in . The group wanted to find a more efficient way to manufacture electrical wires. At the time, manufacturers used diamond dies to extrude metal wire, and the die holes were expensive, difficult and time-consuming to drill.The Western Engineering Research Center pioneered the use of focused laser beam cutting to drill the holes more quickly. This was a crucial moment in the history of laser cutting and paved the way for other companies to explore potential uses for laser technology. Much of the group&#;s work concentrated on finding out more about the safety of laser beams and their potential effects on human health.

A History of Laser Cutting Uses

Shortly after the Western Engineering Research Center started using laser cutting technology as a drilling technique, scientists developed the gas laser cutting method using carbon dioxide. This development made laser cutting technology more versatile. The development of lasers capable of cutting through metals such as mild steel was particularly crucial to the technology&#;s widespread adoption.In , the Boeing company became the first company to use gas laser cutting commercially. Three of its employees co-wrote a paper exploring the concept of using a carbon dioxide laser to cut titanium, Hastelloy and ceramic. This paper led to the development of multi-beam laser cutting, and Boeing started using laser beams as an efficient cutting process on its production lines. Western Electric started mass-producing cutting machines that were widely used in the aerospace industry during the s.The use of gas laser cutting became widespread during the s. It&#;s thought that roughly 20,000 industrial laser cutters were in use during this period, with a collective value of about $7.5 billion. In fact, laser cutting techniques revolutionized production industries to such an extent that Professor Bill Steen said their invention hailed the beginning of a new industrial revolution.In , we reached another pivotal moment in the history of laser cutting. Until this point, laser cutting was two-dimensional. Prima Industrie of Collegno, Italy, invented a 3D laser cutting technique that significantly expanded the potential applications of laser cutting technology.

Laser Technology Today

Laser cutting has come a long way since the Boeing company produced laser-drilled dies in the late 60s. Nowadays, laser power is widely used in various industries, particularly in car manufacture. Advances in laser cutting technology mean that the technique can be used on thicker and more varied materials, from metal to ceramic and even paper. Fiber and CO2 laser cutting methods allow manufacturers to cut materials significantly faster than previous techniques, enabling them to scale up production while cutting down on labor hours.Simply look around your home and you&#;ll almost certainly find a product cut or engraved using lasers. Many industries use lasers to engrave logos or text onto products, such as the letters on your computer&#;s keyboard.

What&#;s Next?

It&#;s not the end of the road for technological developments in laser cutting. Engineers and scientists continue to innovate, and this is likely to lead to the development of even more powerful laser cutting machines to increase thickness capacity, cutting speeds and precision. Advances in automation will allow production lines to operate unmanned 24 hours a day and enable safer working environments for technicians working with laser cutting machines.

Talk to the Laser Cutting Machine Experts

Laser cutting is a fascinating technology with an interesting and often surprising history. To get the most out of this precise and efficient technology, you need the correct equipment.Thunder Laser USA is one of America&#;s premier manufacturers of powerful and high-quality CO2 laser cutting machines. Whether you need a machine for etching, engraving or cutting, Thunder Laser USA can help you find the right product for your unique requirements. Get in touch with the expert customer service team to discuss your needs and explore how the right laser cutting machines could benefit your business.

Technology that uses a laser to cut materials

Diagram of a laser cutter

Laser cutting process on a sheet of steel CAD (top) and stainless steel laser-cut part (bottom)

Laser cutting is a technology that uses a laser to vaporize materials, resulting in a cut edge. While typically used for industrial manufacturing applications, it is now used by schools, small businesses, architecture, and hobbyists. Laser cutting works by directing the output of a high-power laser most commonly through optics. The laser optics and CNC (computer numerical control) are used to direct the laser beam to the material. A commercial laser for cutting materials uses a motion control system to follow a CNC or G-code of the pattern to be cut onto the material. The focused laser beam is directed at the material, which then either melts, burns, vaporizes away, or is blown away by a jet of gas,[1] leaving an edge with a high-quality surface finish.[2]

History

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In , the first production laser cutting machine was used to drill holes in diamond dies. This machine was made by the Western Electric Engineering Research Center.[3] In , the British pioneered laser-assisted oxygen jet cutting for metals.[4] In the early s, this technology was put into production to cut titanium for aerospace applications. At the same time, CO2 lasers were adapted to cut non-metals, such as textiles, because, at the time, CO2 lasers were not powerful enough to overcome the thermal conductivity of metals.[5]

Process

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Industrial laser cutting of steel with cutting instructions programmed through the CNC interface

The laser beam is generally focused using a high-quality lens on the work zone. The quality of the beam has a direct impact on the focused spot size. The narrowest part of the focused beam is generally less than 0. inches (0.32 mm) in diameter. Depending upon the material thickness, kerf widths as small as 0.004 inches (0.10 mm) are possible.[6] In order to be able to start cutting from somewhere other than the edge, a pierce is done before every cut. Piercing usually involves a high-power pulsed laser beam which slowly makes a hole in the material, taking around 5&#;15 seconds for 0.5-inch-thick (13 mm) stainless steel, for example.

The parallel rays of coherent light from the laser source often fall in the range between 0.06&#;0.08 inches (1.5&#;2.0 mm) in diameter. This beam is normally focused and intensified by a lens or a mirror to a very small spot of about 0.001 inches (0.025 mm) to create a very intense laser beam. In order to achieve the smoothest possible finish during contour cutting, the direction of the beam polarization must be rotated as it goes around the periphery of a contoured workpiece. For sheet metal cutting, the focal length is usually 1.5&#;3 inches (38&#;76 mm).[7][8]

Advantages of laser cutting over mechanical cutting include easier work holding and reduced contamination of workpiece (since there is no cutting edge which can become contaminated by the material or contaminate the material). Precision may be better since the laser beam does not wear during the process. There is also a reduced chance of warping the material that is being cut, as laser systems have a small heat-affected zone.[9] Some materials are also very difficult or impossible to cut by more traditional means.[10]

Laser cutting for metals has the advantage over plasma cutting of being more precise[11] and using less energy when cutting sheet metal; however, most industrial lasers cannot cut through the greater metal thickness that plasma can. Newer laser machines operating at higher power ( watts, as contrasted with early laser cutting machines' -watt ratings) are approaching plasma machines in their ability to cut through thick materials, but the capital cost of such machines is much higher than that of plasma cutting machines capable of cutting thick materials like steel plate.[12]

Types

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 watt CO2 laser cutter

There are three main types of lasers used in laser cutting. The CO2 laser is suited for cutting, boring, and engraving. The neodymium (Nd) and neodymium yttrium-aluminium-garnet (Nd:YAG) lasers are identical in style and differ only in the application. Nd is used for boring and where high energy but low repetition are required. The Nd:YAG laser is used where very high power is needed and for boring and engraving. Both CO2 and Nd/Nd:YAG lasers can be used for welding.[13]

CO2 lasers are commonly "pumped" by passing a current through the gas mix (DC-excited) or using radio frequency energy (RF-excited). The RF method is newer and has become more popular. Since DC designs require electrodes inside the cavity, they can encounter electrode erosion and plating of electrode material on glassware and optics. Since RF resonators have external electrodes they are not prone to those problems. CO2 lasers are used for the industrial cutting of many materials including titanium, stainless steel, mild steel, aluminium, plastic, wood, engineered wood, wax, fabrics, and paper. YAG lasers are primarily used for cutting and scribing metals and ceramics.

In addition to the power source, the type of gas flow can affect performance as well. Common variants of CO2 lasers include fast axial flow, slow axial flow, transverse flow, and slab. In a fast axial flow resonator, the mixture of carbon dioxide, helium, and nitrogen is circulated at high velocity by a turbine or blower. Transverse flow lasers circulate the gas mix at a lower velocity, requiring a simpler blower. Slab or diffusion-cooled resonators have a static gas field that requires no pressurization or glassware, leading to savings on replacement turbines and glassware.

The laser generator and external optics (including the focus lens) require cooling. Depending on system size and configuration, waste heat may be transferred by a coolant or directly to air. Water is a commonly used coolant, usually circulated through a chiller or heat transfer system.

A laser microjet is a water-jet-guided laser in which a pulsed laser beam is coupled into a low-pressure water jet. This is used to perform laser cutting functions while using the water jet to guide the laser beam, much like an optical fiber, through total internal reflection. The advantages of this are that the water also removes debris and cools the material. Additional advantages over traditional "dry" laser cutting are high dicing speeds, parallel kerf, and omnidirectional cutting.[14]

Fiber lasers are a type of solid-state laser that is rapidly growing within the metal cutting industry. Unlike CO2, Fiber technology utilizes a solid gain medium, as opposed to a gas or liquid. The &#;seed laser&#; produces the laser beam and is then amplified within a glass fiber. With a wavelength of only nanometers fiber lasers produce an extremely small spot size (up to 100 times smaller compared to the CO2) making it ideal for cutting reflective metal material. This is one of the main advantages of Fiber compared to CO2.

Fibre laser cutter benefits include:

• Rapid processing times.
• Reduced energy consumption & bills &#; due to greater efficiency.
• Greater reliability and performance - no optics to adjust or align and no lamps to replace.
• Minimal maintenance.
• The ability to process highly reflective materials such as copper and brass.
• Higher productivity - lower operational costs offer a greater return on your investment.

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Methods

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There are many different methods of cutting using lasers, with different types used to cut different materials. Some of the methods are vaporization, melt and blow, melt blow and burn, thermal stress cracking, scribing, cold cutting, and burning stabilized laser cutting.

Vaporization cutting

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In vaporization cutting, the focused beam heats the surface of the material to a flashpoint and generates a keyhole. The keyhole leads to a sudden increase in absorptivity quickly deepening the hole. As the hole deepens and the material boils, vapor generated erodes the molten walls blowing ejection out and further enlarging the hole. Nonmelting materials such as wood, carbon, and thermoset plastics are usually cut by this method.

Melt and blow

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Melt and blow or fusion cutting uses high-pressure gas to blow molten material from the cutting area, greatly decreasing the power requirement. First, the material is heated to melting point then a gas jet blows the molten material out of the kerf avoiding the need to raise the temperature of the material any further. Materials cut with this process are usually metals.

Thermal stress cracking

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Brittle materials are particularly sensitive to thermal fracture, a feature exploited in thermal stress cracking. A beam is focused on the surface causing localized heating and thermal expansion. This results in a crack that can then be guided by moving the beam. The crack can be moved in order of m/s. It is usually used in the cutting of glass.

Stealth dicing of silicon wafers

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The separation of microelectronic chips as prepared in semiconductor device fabrication from silicon wafers may be performed by the so-called stealth dicing process, which operates with a pulsed Nd:YAG laser, the wavelength of which ( nm) is well adapted to the electronic band gap of silicon (1.11 eV or  nm).

Reactive cutting

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Reactive cutting is also called "burning stabilized laser gas cutting" and "flame cutting". Reactive cutting is like oxygen torch cutting but with a laser beam as the ignition source. Mostly used for cutting carbon steel in thicknesses over 1 mm. This process can be used to cut very thick steel plates with relatively little laser power.

Tolerances and surface finish

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Laser cutters have a positioning accuracy of 10 micrometers and repeatability of 5 micrometers.[citation needed]

Standard roughness Rz increases with the sheet thickness, but decreases with laser power and cutting speed. When cutting low carbon steel with laser power of 800 W, standard roughness Rz is 10 μm for sheet thickness of 1 mm, 20 μm for 3 mm, and 25 μm for 6 mm.

R z = 12.528 &#; S 0.542 P 0.528 &#; V 0.322 {\displaystyle Rz={\frac {12.528\cdot S^{0.542}}{P^{0.528}\cdot V^{0.322}}}}

Where: S = {\displaystyle S=} steel sheet thickness in mm; P = {\displaystyle P=} laser power in kW (some new laser cutters have laser power of 4 kW); V = {\displaystyle V=} cutting speed in meters per minute.[16]

This process is capable of holding quite close tolerances, often to within 0.001 inch (0.025 mm). Part geometry and the mechanical soundness of the machine have much to do with tolerance capabilities. The typical surface finish resulting from laser beam cutting may range from 125 to 250 micro-inches (0.003 mm to 0.006 mm).[13]

Machine configurations

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Dual-pallet flying optics laser Flying optics laser head

There are generally three different configurations of industrial laser cutting machines: moving material, hybrid, and flying optics systems. These refer to the way that the laser beam is moved over the material to be cut or processed. For all of these, the axes of motion are typically designated X and Y axis. If the cutting head may be controlled, it is designated as the Z-axis.

Moving material lasers have a stationary cutting head and move the material under it. This method provides a constant distance from the laser generator to the workpiece and a single point from which to remove cutting effluent. It requires fewer optics but requires moving the workpiece. This style of machine tends to have the fewest beam delivery optics but also tends to be the slowest.

Hybrid lasers provide a table that moves in one axis (usually the X-axis) and moves the head along the shorter (Y) axis. This results in a more constant beam delivery path length than a flying optic machine and may permit a simpler beam delivery system. This can result in reduced power loss in the delivery system and more capacity per watt than flying optics machines.

Flying optics lasers feature a stationary table and a cutting head (with a laser beam) that moves over the workpiece in both of the horizontal dimensions. Flying optics cutters keep the workpiece stationary during processing and often do not require material clamping. The moving mass is constant, so dynamics are not affected by varying the size of the workpiece. Flying optics machines are the fastest type, which is advantageous when cutting thinner workpieces.[17]

Flying optic machines must use some method to take into account the changing beam length from the near field (close to the resonator) cutting to the far field (far away from the resonator) cutting. Common methods for controlling this include collimation, adaptive optics, or the use of a constant beam length axis.

Five and six-axis machines also permit cutting formed workpieces. In addition, there are various methods of orienting the laser beam to a shaped workpiece, maintaining a proper focus distance and nozzle standoff.

Pulsing

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Pulsed lasers which provide a high-power burst of energy for a short period are very effective in some laser cutting processes, particularly for piercing, or when very small holes or very low cutting speeds are required, since if a constant laser beam were used, the heat could reach the point of melting the whole piece being cut.

Most industrial lasers have the ability to pulse or cut CW (continuous wave) under NC (numerical control) program control.

Double pulse lasers use a series of pulse pairs to improve material removal rate and hole quality. Essentially, the first pulse removes material from the surface and the second prevents the ejecta from adhering to the side of the hole or cut.[18]

Power consumption

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The main disadvantage of laser cutting is the high power consumption. Industrial laser efficiency may range from 5% to 45%.[19] The power consumption and efficiency of any particular laser will vary depending on output power and operating parameters. This will depend on the type of laser and how well the laser is matched to the work at hand. The amount of laser cutting power required, known as heat input, for a particular job depends on the material type, thickness, process (reactive/inert) used, and desired cutting rate.

Amount of heat input required for various materials at various thicknesses using a CO2 laser [watts]

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Material Material thickness 0.51 mm 1.0 mm 2.0 mm 3.2 mm 6.4 mm Stainless steel Aluminium Mild steel &#; 400 &#; 500 &#; Titanium 250 210 210 &#; &#; Plywood &#; &#; &#; &#; 650 Boron/epoxy &#; &#; &#; &#;

Production and cutting rates

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The maximum cutting rate (production rate) is limited by a number of factors including laser power, material thickness, process type (reactive or inert), and material properties. Common industrial systems (&#;1 kW) will cut carbon steel metal from 0.51 &#; 13 mm in thickness. For many purposes, a laser can be up to thirty times faster than standard sawing.[21]

Cutting rates using a CO2 laser [cm/second] Workpiece material Material thickness 0.51 mm 1.0 mm 2.0 mm 3.2 mm 6.4 mm 13 mm Stainless steel 42.3 23.28 13.76 7.83 3.4 0.76 Aluminium 33.87 14.82 6.35 4.23 1.69 1.27 Mild steel &#; 8.89 7.83 6.35 4.23 2.1 Titanium 12.7 12.7 4.23 3.4 2.5 1.7 Plywood &#; &#; &#; &#; 7.62 1.9 Boron / epoxy &#; &#; &#; 2.5 2.5 1.1

See also

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References

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Bibliography

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