Laser fundamentals

The light generated by a laser is in phase, highly collimated and generally of a single wavelength. This allows it to be easily focused in atmosphere to a spot with a diameter in the order of 10 to 1000µm, giving very high power densities at the workpiece. This light can be generated using a wide variety of industrial laser sources. The most common laser sources used for industrial applications are CO 2 , direct diode, Nd:YAG and Yb disk and Yb fibre lasers.

The choice of laser for a given industrial application is governed by a number of considerations, such as:

  • the amount of power required for the application and that available from the laser.
  • the complexity of the component and flexibility of the light delivery system.
  • the wavelength of the laser light affecting both it's transmission to, and interaction with, the processing medium.
  • capital cost and proven reliability against proposed production benefits.
  • beam quality. A measure of the capability of a laser system to produce a minimum focused spot size.

The laser group at TWI offers an informed and impartial service in providing advice in the correct choice and qualification of lasers for materials processing applications.

Benefits of lasers for materials processing

Lasers can produce light capable of being focused to achieve power densities in the order of 104 W/mm 2 , which produces enough concentrated power to vaporise most engineering materials. In metals this creates a stable vapour keyhole surrounded by molten parent material which can be moved and used for welding or cutting.

It is the ability of the laser light to be precisely controlled which gives it such a wide range of material processing applications. The intense and precisely delivered energy concentration can be used to produce welds, cuts, material excavations and modified surfaces in most engineering materials with very little heat input. Whichever the application, lasers have:

  • Suitability for cutting, drilling, welding, marking, cladding, heat treating, surfacing.
  • Ease of automation.
  • Low heat input, resulting in little distortion.
  • High processing speeds.
  • Ability to cut and weld.
  • No contact with the workpiece (laser light can travel through air and vacuum).
  • Suitability for many materials, including metals and plastics.
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