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Laser cutting

  • Lasers cut by melting the material in the beam path. Materials that are heat treatable will get case hardened at the cut edges. This may be beneficial if the hardened edges are functionally desirable in the finished parts. However, if further machining operations such as threading are required, then hardening is a problem.

    • A hole cut with a laser has an entry diameter larger than the exit diameter, creating a slightly tapered hole.

    • The minimum radius for slot corners is 0.75 mm (0.030 in). Unlike blanking, piercing, and forming, the normal design rules regarding minimum wall thicknesses, minimum hole size (as a percent of stock thickness) do not apply. The minimum hole sizes are related to stock thickness and can be as low as 20% of the stock thickness, with a minimum of 0.25 mm (0.010 in) for upto 1.9 mm (0.075 in). Contrast this with normal piercing operations with the recommended hole size 1.2 times the stock thickness.

    • Burrs are quite small compared to blanking and shearing. They can be almost eliminated when 3D lasers are used and further, eliminate the need for secondary deburring operations.
    • As in blanking and piercing, considerable economies can be obtained by nesting parts, and cutting along common lines. In addition, secondary deburring operations can be reduced or eliminated.

  • Whether laser cutting with CO2 or Nd:YAG lasers, the principles employed are basically the same. The beam from the laser is focused on to the surface of the material being cut by means of a lens.

    The focused laser beam heats the material surface and a very local melt capillary is quickly established throughout the depth of the material. The diameter of this capillary is usually just slightly greater than the diameter of the focused laser beam.

    The great majority of CO2 laser cutting is performed using an assist gas. The significant feature of gas assisted laser cutting is that the molten material is ejected from the base of the capillary by a jet of gas coaxial with the laser beam.

    For some materials this gas can further assist the process by chemical (exothermic) reaction as well as physical work. The cut is generated by either moving the focused laser beam across the surface of the stationary material or by keeping the laser beam stationary and moving the workpiece. Hybrids of these two options are also possible. In this way simple and complex linear cuts or two dimensional parts can be produced. More complex systems are required for three dimensional processing.
    Most laser cutting with CO2 lasers is performed in the power range 1 - 1.5kW.

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