Laser beam machining

Last updated October 28, 2023

Laser beam machining (LBM) is a form of machining that uses heat directed from a laser beam. This process uses thermal energy to remove material from metallic or nonmetallic surfaces. The high frequency of monochromatic light will fall on the surface, thus heating, melting and vaporizing the material due to the impinge of photons (see Coulomb explosion).^[1] Laser beam machining is best suited for brittle materials with low conductivity, but can be used on most materials.^[2]

Laser beam machining can be done on glass without melting the surface. With photosensitive glass, the laser alters the chemical structure of the glass allowing it to be selectively etched. The glass is also referred to as photomachinable glass. The advantage of photomachinable glass is that it can produce precisely vertical walls and the native glass is suitable for many biological applications such as substrates for genetic analysis.

Types of lasers

There are many different types of lasers including gas, solid states lasers, and excimer.^[3]

Some of the most commonly used gases consist of; He-Ne, Ar, and Carbon dioxide laser.

Solid-state lasers are designed by doping a rare element into various host materials. Unlike in gas lasers, solid state lasers are pumped optically by flash lamps or arc lamps. Ruby is one of the frequently used host materials in this type of laser.^[3] A ruby laser is a type of the solid state laser whose laser medium is a synthetic ruby crystal. The synthetic ruby rod is optically pumped using a xenon flashtube before it is used as an active laser medium.^[4]

YAG is an abbreviation for yttrium aluminum garnet which are crystals that are used for solid-state lasers while Nd:YAG refers to neodymium-doped yttrium aluminum garnet crystals that are used in the solid-state lasers as the laser mediate.

YAG lasers emit a wavelength of light waves with high energy. Nd:glass is neodymium–doped gain media made of either silicate or phosphate materials that are used in fiber laser.

Cutting depth

The cutting depth of a laser is directly proportional to the quotient obtained by dividing the power of the laser beam by the product of the cutting velocity and the diameter of the laser beam spot.

t\propto {\frac {P}{vd}},

where t is the depth of cut, P is the laser beam power, v is the cutting velocity, and d is the laser beam spot diameter.^[5]

The depth of the cut is also influenced by the workpiece material. The material's reflectivity, density, specific heat, and melting point temperature all contribute to the lasers ability to cut the workpiece.

The following table^[6] shows the ability of different lasers to cut different materials:

material	wavelength (micrometer) CO2 laser: 10.6	wavelength (micrometer) Nd:YAG laser: 1.06
ceramics	well	poorly
plywood	very well	fairly well
polycarbonate	well	fairly well
polyethylene	very well	fairly well
Perspex	very well	fairly well
Titanium	well	well
Gold	not possible	well
Copper	poorly	well
Aluminium	well	well
stainless steel		very well
construction steel		very well

Applications

Lasers can be used for welding, cladding, marking, surface treatment, drilling, and cutting among other manufacturing processes. It is used in the automobile, shipbuilding, aerospace, steel, electronics, and medical industries for precision machining of complex parts.

Laser welding is advantageous in that it can weld at speeds of up to 100 mm/s as well as the ability to weld dissimilar metals. Laser cladding is used to coat cheap or weak parts with a harder material in order to improve the surface quality. Drilling and cutting with lasers is advantageous in that there is little to no wear on the cutting tool as there is no contact to cause damage.

Milling with a laser is a three dimensional process that requires two lasers, but drastically cuts costs of machining parts.^[2]^[7] Lasers can be used to change the surface properties of a workpiece.

The appliance of laser beam machining varies depending on the industry. In light manufacturing the machine is used to engrave and to drill other metals. In the electronic industry laser beam machining is used for wire stripping and skiving of circuits. In the medical industry it is used for cosmetic surgery and hair removal.^[2]

Advantages

Since the rays of a laser beam are monochromatic and parallel (i.e. zero etendue) it can be focused to a small diameter and can produce as much as 100 MW of power for a square millimeter of area.
Laser beam machining has the ability to engrave or cut nearly all materials, where traditional cutting methods may fall short.
There are several types of lasers, and each have different uses.
The cost of maintaining lasers is moderately low due to the low rate of wear and tear, as there is no physical contact between the tool and the workpiece.^[3]
The machining provided by laser beams is high precision, and most of these processes do not require additional finishing.^[3]
Laser beams can be paired with gases to help the cutting process be more efficient, help minimize oxidization of surfaces, and/or keep the workpiece surface free from melted or vaporized material.

Disadvantages

The initial cost of acquiring a laser beam is moderately high. There are many accessories that aid in the machining process, and as most of these accessories are as important as the laser beam itself the startup cost of machining is raised further.^[3]
Handling and maintaining the machining requires highly trained individuals. Operating the laser beam is comparatively technical, and services from an expert may be required.^[3]
Laser beams are not designed to produce mass metal processes.
Laser beam machining consumes a lot of energy.
Deep cuts are difficult with workpieces with high melting points and usually cause a taper.

Related Research Articles

<span class="mw-page-title-main">Laser construction</span>

A laser is constructed from three principal parts:

Welding is a fabrication process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to cool, causing fusion. Welding is distinct from lower temperature techniques such as brazing and soldering, which do not melt the base metal.

Metalworking is the process of shaping and reshaping metals to create useful objects, parts, assemblies, and large scale structures. As a term it covers a wide and diverse range of processes, skills, and tools for producing objects on every scale: from huge ships, buildings, and bridges down to precise engine parts and delicate jewelry.

Nd:YAG (neodymium-doped yttrium aluminum garnet; Nd:Y₃Al₅O₁₂) is a crystal that is used as a lasing medium for solid-state lasers. The dopant, triply ionized neodymium, Nd(III), typically replaces a small fraction (1%) of the yttrium ions in the host crystal structure of the yttrium aluminum garnet (YAG), since the two ions are of similar size. It is the neodymium ion which provides the lasing activity in the crystal, in the same fashion as red chromium ion in ruby lasers.

<span class="mw-page-title-main">Laser cutting</span> Technology that uses a laser to cut materials

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 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, leaving an edge with a high-quality surface finish.

<span class="mw-page-title-main">Laser engraving</span> Engraving objects using lasers

Laser engraving is the practice of using lasers to engrave an object. Laser marking, on the other hand, is a broader category of methods to leave marks on an object, which in some cases, also includes color change due to chemical/molecular alteration, charring, foaming, melting, ablation, and more. The technique does not involve the use of inks, nor does it involve tool bits which contact the engraving surface and wear out, giving it an advantage over alternative engraving or marking technologies where inks or bit heads have to be replaced regularly.

A diode-pumped solid-state laser (DPSSL) is a solid-state laser made by pumping a solid gain medium, for example, a ruby or a neodymium-doped YAG crystal, with a laser diode.

Many ceramic materials, both glassy and crystalline, have found use as optically transparent materials in various forms from bulk solid-state components to high surface area forms such as thin films, coatings, and fibers. Such devices have found widespread use for various applications in the electro-optical field including: optical fibers for guided lightwave transmission, optical switches, laser amplifiers and lenses, hosts for solid-state lasers and optical window materials for gas lasers, and infrared (IR) heat seeking devices for missile guidance systems and IR night vision.

Laser beam welding (LBW) is a welding technique used to join pieces of metal or thermoplastics through the use of a laser. The beam provides a concentrated heat source, allowing for narrow, deep welds and high welding rates. The process is frequently used in high volume and precision requiring applications using automation, as in the automotive and aeronautics industries. It is based on keyhole or penetration mode welding.

Yttrium aluminium garnet (YAG, Y₃Al₅O₁₂) is a synthetic crystalline material of the garnet group. It is a cubic yttrium aluminium oxide phase, with other examples being YAlO₃ (YAP) in a hexagonal or an orthorhombic, perovskite-like form, and the monoclinic Y₄Al₂O₉ (YAM).

Neodymium-doped yttrium orthovanadate (Nd:YVO₄) is a crystalline material formed by adding neodymium ions to yttrium orthovanadate. It is commonly used as an active laser medium for diode-pumped solid-state lasers. It comes as a transparent blue-tinted material. It is birefringent, therefore rods made of it are usually rectangular.

Laser-hybrid welding is a type of welding process that combines the principles of laser beam welding and arc welding.

A solid-state laser is a laser that uses a gain medium that is a solid, rather than a liquid as in dye lasers or a gas as in gas lasers. Semiconductor-based lasers are also in the solid state, but are generally considered as a separate class from solid-state lasers, called laser diodes.

This is a list of acronyms and other initialisms used in laser physics and laser applications.

Neodymium-doped yttrium lithium fluoride (Nd:YLF) is a lasing medium for arc lamp-pumped and diode-pumped solid-state lasers. The YLF crystal (LiYF₄) is naturally birefringent, and commonly used laser transitions occur at 1047 nm and 1053 nm.

A dopant is a small amount of a substance added to a material to alter its physical properties, such as electrical or optical properties. The amount of dopant is typically very low compared to the material being doped.

Laser drilling is the process of creating thru-holes, referred to as “popped” holes or “percussion drilled” holes, by repeatedly pulsing focused laser energy on a material. The diameter of these holes can be as small as 0.002”. If larger holes are required, the laser is moved around the circumference of the “popped” hole until the desired diameter is created.

Fusion welding is a generic term for welding processes that rely on melting to join materials of similar compositions and melting points. Due to the high-temperature phase transitions inherent to these processes, a heat-affected zone is created in the material.

Lightwave Electronics Corporation was a developer and manufacturer of diode-pumped solid-state lasers, and was a significant contributor to the creation and maturation of this technology. Lightwave Electronics was a technology-focused company, with diverse markets, including science and micromachining. Inventors employed by Lightwave Electronics received 51 US patents, and Lightwave Electronics products were referenced by non-affiliated inventors in 91 US patents.

References

↑ "Ruby laser treatment. DermNet NZ". www.dermnetnz.org. Retrieved 2016-03-01.
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1 2 3 4 5 6 "Laser Beam Machining". www.mechnol.com. 10 February 2016. Archived from the original on 6 March 2016. Retrieved 2016-02-17.
↑ "Solid Medium Lasers". hyperphysics.phy-astr.gsu.edu. Retrieved 2016-03-01.
↑ Kalpakjian; Schmid (2008). Manufacturing Processes for Engineering Materials (5 ed.). Prentice Hall. ISBN 9780132272711.
↑ J. Berkmanns, M. Faerber (June 18, 2008). Laser cutting. LASERLINE Technical.
↑ Meijer, Johan (June 2004). "Laser beam machining (LBM), state of the art and new opportunities". Journal of Materials Processing Technology. 149 (1–3): 2–17. doi:10.1016/j.jmatprotec.2004.02.003.