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Proceedings Paper

Industrial aspects of precision machining with copper vapor lasers
Author(s): Martin Hartmann; Juergen Koch; Adolf Lang; Karsten Schutte; Hans Wilhelm Bergmann
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Paper Abstract

The applications of conventional infrared lasers running cw or quasi-sw for drilling, cutting and shaping are limited in the precision achievable due to the long interaction time which leads to heat affected zones. The necessity to use a gas jet to blow the molten material out of the cut kerf will damage fragile workpieces like thin foils. Short laser pulses of sufficient intensity remove the material directly by evaporation and minimize the amount of heat transferred into the solid. Classical infrared laser sources generate a shielding air plasma within some ns at power densities above some 107W/cm2. The optical breakdown threshold value in air can be shifted to higher intensities by using visible light as well as reducing the focal diameter. An alternative way is to shorten the pulse duration to less than 10 ps that a plasma is generated only after the pulse. Thus, the material removal process begins after the deposition of the pulse energy into the material. But such short pulses will generate a pressure wave due to the sudden thermal expansion and can damage or destroy microscopic components. For industrial production the productivity is a further aspect. Hence, a certain mean power is required in order to obtain the desired production rate. Considering the above aspects, copper vapor lasers (CVLs) with ns pulse duration are well suited for precision machining of metals and ceramics. Processing with CVLs is an advantage in that its wavelength is highly absorbed by metallic targets and the probability for the optical breakdown in air is low. CVLs in an oscillator-amplifier-setup incorporate diffraction limited beam quality and high average power. The present paper outlines the potential of the CVL for the industrial use regarding high processing speed and precision. Under these aspects the limiting mechanisms on the material removal process and the necessary processing strategies for scaling up the productivity are shown. The relevant laser parameters for increasing the working speed and the relationship to the achievable precision are given. The design aspects of a copper vapor laser system with high mean output power and repetition rate are outlined. To conclude, several typical machining tasks, e.g. cutting of green foils, drilling of scimmer holes for thermal analysis are presented.

Paper Details

Date Published: 18 August 1997
PDF: 7 pages
Proc. SPIE 3097, Lasers in Material Processing, (18 August 1997); doi: 10.1117/12.281083
Show Author Affiliations
Martin Hartmann, ATZ-EVUS (Germany)
Juergen Koch, Bremer Institut fuer Angewandte Strahlforschung (Germany)
Adolf Lang, ATZ-EVUS (Germany)
Karsten Schutte, ATZ-EVUS (Germany)
Hans Wilhelm Bergmann, ATZ-EVUS (Germany)

Published in SPIE Proceedings Vol. 3097:
Lasers in Material Processing
Leo H. J. F. Beckmann, Editor(s)

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