Laser Cutting: Advantages & Inconvenients

Laser cutters are high-energy, focused laser beams that cut sheets of steel, wood, plastic, and other materials into two-dimensional parts in the manufacturing and hobbyist arenas. "Laser" is a commonly used term for "Light Amplification by Stimulated Emission of Radiation," which explains the physical science necessary to generate laser light. It is a widely adopted technology suited for the mass production of precise two-dimensional parts.

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The laser-cutting process utilizes a computer-generated program called a G-code, a set of machine-readable instructions instructing the machine where to move the laser-cutting head. Once the program is loaded, the material may require additional preparation before loading material onto the cutting bed. Once the material is loaded, a small, high-energy light beam is initiated and focused on one spot to heat the material and initiate the cutting process. As the material heats, the laser is directed to cut multiple parts using a series of mirrors and lenses. The intense heat melts and often vaporizes material as it is directed across the bed while cutting parts from the material sheet. Parts are removed and may be further processed.

Laser cutters are used in a range of applications, including engraving, laser welding, tube cutting, and sheet metal and plate cutting. There are several different types of lasers and methods used for Laser Cutting. These include the following:

Types of Laser Cutting:

• CO2 Lasers &#; This laser utilizes carbon dioxide (CO2), Helium (HE), and Nitrogen (N) to optimize the cutting process; Nitrogen help to amplify the energy while Helium helps to dissipate the remaining energy after the cut. These lasers are often used with metals plate but struggle with materials that have high reflectivity and thermal absorption.
• Fiber Lasers &#; Flexible fiber optic cables carry photons to produce the beam with the assistance of rare earth elements such as erbium, neodymium, thulium, or yttrium. Each element produces different wavelengths for varying applications. These lasers are best suited for cutting reflective materials like brass or gold and, due to the flexibility of the fiber cable, can be mounted to robotic arms. 
• Nd:YAG lasers &#; This powerful, high-density laser is often used for marking and etching. This laser utilizes a neodymium (Nd) doped yttrium aluminum garnet crystal (Y3Al5O12) which aids the photon acceleration to create a high-intensity beam. Nd:YVO lasers operate similarly with improved power stability, reduced heat, and greater laser intensity. 

Laser cutters are used to cut a wide range of materials. The most commonly cut materials are listed as follows:

• Acrylic &#; This transparent, rigid material is also known as polymethyl methacrylate or PMMA.
• Aluminum &#; A reflective material, fiber lasers cut most types of aluminum.
• Brass &#; Best cut with a fiber laser.
• Cork &#; Cork can be easily laser-cut or engraved.
• Felt &#; A fabric that cuts easily, especially if 95%+ wool. 
• Hardboard &#; Easy to cut but releases fumes from adhesives.
• Leather &#; This material is easily cut or engraved, often for personalized items
• Stainless Steel (SS) &#; Fiber lasers are best suited for SS.
• Steel &#; This includes mild steel and carbon steel. High-power lasers can cut up to 20&#;25 mm plate thickness. 
• Wood &#; Low-power lasers are used for the different types of wood.
• Other materials include:

Laser classification

(1)C02 laser: Wavelength of C02 laser is 9~12um(typical wavelength is 10.6um). Due to its high efficiency, good beam quality, wide power range (tens of thousands of watts), continuous pulse and other advantages, it has become the most important and most widely used gas laser.Mainly used in material processing, scientific research, national defense testing and other aspects.Common forms are: sealed longitudinal electrically excited CARBON dioxide laser, TEA carbon dioxide laser, axial fast current high power carbon dioxide laser, cross current high power carbon dioxide laser.

(2) A semiconductor diode laser is a device excited by a certain amount of semiconductor material.Its working principle is that through certain incentives, the band gap of the semiconductor materials (conduction band and valence band), or a band of semiconductor materials and impurities (acceptor or donor) level, realize the balance of the vector population inversion, when in a state of population inversion of a large number of electrons and holes, radiation when the stimulated emission of radiation.The wavelength of light varies with the band gap.

(3)YAG laser: It can be divided into :ND-YAG crystal, CE-ND-YAG crystal, YB-YAG crystal, Ho-YAG crystal, er-YAG crystal.

1.Nd-yag laser: solid state laser, nm, Nd- YAG laser crystal with the best comprehensive performance.The maximum output power of continuous laser is W, which is widely used in military, industrial, medical and other industries.If continuous operation is adopted, the multi-mode output of 400W can be obtained by using the first order oscillation.If the laser output is at the 100-watt level, a single lamp can be used

2.Ce-n-yag laser: Ce-Nd-YAG crystal is formed by adding Ce ions on the basis of ND-AG crystal.Ce ion · Can produce good photon energy absorption in the ultraviolet spectrum region, and the energy is transferred to Nd ion in the way of non-radiation transition, thus improving the spectral utilization.Therefore, the efficiency is high, the threshold is low, the repetition frequency characteristic is good.

3.Yb-yag laser :Yb3+ doped into yAG matrix is a kind of laser crystal, which can produce 1.03um near-infrared laser.It and ND-YAG belong to the same matrix, but because of doping different, its growth process is also different.

4.Ho-yag laser: It can produce nm and nm lasers which are safe for human eyes.It is mainly suitable for optical communication, radar and medical applications.Ho-yag laser has strict requirements on cooling and drying, but water cooling is controlled below 10&#;.The drying plant shall be free from steam.In the safe band range of human eyes, the possibility of accidental injury to human body, especially eyes, is greatly reduced due to the large water absorption capacity and extremely shallow penetration.

5.Er-yag laser: output wavelength is 2.9um and can be absorbed by water. It is mainly used in medicine.Because the crystal mainly absorbs visible and ULTRAVIOLET light, the material of the light cavity reflector is mostly aluminum and silver, which has a high reflectivity.At present, the maximum output power of the E-YAG laser is up to 3 watts, and the maximum pulse output is up to 51.It is the solid-state laser with the longest wavelength, highest output power and highest efficiency in the world.The absorption of nm by human body is 10 times that of nm, so laser surgery and vascular surgery have great application potential.

Advantages and disadvantages of laser

Advantages:

(1) Heat absorption can be reduced to the minimum amount required

(2) Single channel welding parameters of 32mm plate thickness have been verified, which can reduce the time needed for welding of thick plate and even save the use of solder metal;

(3) There is no need to use the electrode, and there is no need to worry about contamination or damage of the electrode.And since it is not a contact welding process, wear and deformation of the machine can be reduced to a minimum;

(4) Laser beam is easy to be focused, aligned and guided by optical instruments.It can be placed at an appropriate distance between the artifact and the bootstrap tool or between the artifact.Due to the above space limitations, other welding rules cannot be formulated;

(5) Workpiece can be placed in an enclosed space

(6) Laser beam can be focused on a very small area, and small parts with close spacing can be welded;

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(7) Wide range of weldable materials, which can be used for bonding various heterogeneous materials;

Easy automatic high speed welding, digital or computer control

(9) When welding thin material or thin diameter wire, unlike arc welding, it is easy to have trouble of remelting;

(10) It is not affected by the magnetic field, and can accurately align the positive welding parts;

(11) Two metals with different physical properties (e.g. different resistances) can be welded;

(12) No vacuum or X-ray protection is required;

(13) Adopt perforated welding, the depth/width ratio of welding pass can reach 10:1;

(14) Device can be switched to transmit the laser beam to multiple workstations.

Disadvantages:

(1)Welding position should be very accurate and within the focus range of the laser beam;

(2) When the welding part needs to use the clamp, it must ensure that the final position of the welding part is in alignment with the welding spot impacted by the laser beam;

(3) Laser welding is not suitable for production line;

(4) Laser will change the weldability of materials with high reflectivity and high thermal conductivity, such as aluminum, copper and their alloys;

(5) In the process of medium and high energy laser beam welding, plasma controller is required to drive away the ionized gas around the weld pool to ensure the reappearance of weld;

(6) Energy conversion efficiency is too low, usually less than 10%;

(7)Weld solidifies rapidly, and there may be problems of porosity and embrittlement;

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