Laser drilling

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Laser drilling is a non- cutting machining process in which so much energy is locally introduced into the workpiece by means of laser radiation that the material is melted and partially evaporated. The ionized vapor (more precisely plasma ) is thrown away by the different pressure between the environment and the location of the drilling . A melting of the material at the edge of the hole is not desirable.

Procedure

Single pulse drilling

The laser radiation is switched on for a short period of time and pierces the material with a pulse . The disadvantage is the low maximum penetrable material thickness of about 2 mm and the high pulse energy required. When using flash-lamp-pumped solid - state laser radiation, the reproducibility is limited by the low pulse-to-pulse stability. With fiber laser radiation, the reproducibility is significantly greater.

Percussion drilling

The laser radiation hits the workpiece in several successive pulses at the same point and melts and vaporizes some of the material. The melted material is driven out of the bore by the evaporating parts. This means that much deeper bores are possible than with the single pulse method (approx. 30 mm). The advantages are the higher drilling depths, which can also be inclined towards the surface, the higher geometric quality with regard to the conicity of the drilling and the possibility of machining extremely hard materials. The longer process time is a disadvantage.

Trepanning

First, as with percussion drilling, a through hole is created. The hole is expanded to the required diameter by means of a relative movement between the laser radiation and the workpiece. The advantages of trepanning are smaller enamel layers on the bore wall. The possible creation of rear wall damage to the workpiece is disadvantageous, since the laser radiation passes through the bore during the relative movement.

Helical drilling

Helical drilling works like percussion drilling, only the radiation also rotates. This leads to a spiral removal of the material. The process is particularly suitable for very precise bores in terms of diameter and roundness in thin materials up to approx. 2 mm. Positive or negative taper are also possible using this method.

Advantages over conventional methods

  • Contactless processing without applying force to the component
  • Thanks to its small optics, laser radiation can be used for drilling in hard-to-reach places (e.g. fuel nozzles )
  • minimal heat load and no coolant required
  • easy to automate
  • flexible
  • Production of the smallest bores from approx. 40 µm, which are hardly or not at all feasible with mechanical processes

Disadvantages compared to conventional methods

  • mostly more expensive than conventional methods
  • compared to conventional methods, the energy consumption is enormous, i. H. the efficiency is extremely poor

Examples

See also

literature

  • Friedrich Dausinger: Laser beam tool . Energy coupling and process effectiveness. Vieweg + Teubner, Stuttgart 1995, ISBN 3-519-06217-8 ( Lasers in material processing ), (Also: Stuttgart, Univ., Habil.-Schr.).
  • Friedrich Dausinger, Friedemann Lichtner, Holger Lubatschowski (Eds.): Femtosecond Technology for Technical and Medical Applications. Springer, Berlin et al. 2004, ISBN 3-540-20114-9 ( Topics in applied Physics 96).

Web links