Electric heating – Metal heating – By arc
Patent
1989-12-21
1994-12-13
Albritton, C. L.
Electric heating
Metal heating
By arc
21912162, 21912172, 21912183, B23K 2614
Patent
active
053731352
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a process for treating workpieces by means of laser radiation, particularly for the cutting, hole burning and removal of material with respect to metallic workpieces, in which the treated site of the workpiece is monitored by means of a radiation detector which contributes to reducing the intensity of the laser radiation when an upper limit value is reached and to increasing it when a lower limit value is reached.
STATE OF THE ART
A process of the initially mentioned type is known in the case of a treatment method in which laser-induced plasma is used. The respective upper limit value is that laser intensity at which a laser-induced detonation wave is generated. The lower limit value is that laser intensity which is at least required for the production of a surface plasma. The known radiation detector monitors the plasma radiation or other physical quantities originating from the plasma so that, by using the measuring results, the laser intensity can be controlled by a suitable modulation in the sense of maintaining the plasma formation while avoiding an undesirable detonation wave.
REPRESENTATION OF THE INVENTION
In contrast, the invention is based on the object of improving a process of the initially mentioned type in such a manner that it may also be used when the work takes place without plasma, particularly during hole burning, cutting and removing of material.
This object is achieved in that, by means of the radiation detector, the heat radiation emanating from its treatment site is measured, by which a higher temperature is monitored as the upper limit value of a predetermined temperature range and a lower temperature is monitored as the lower limit value of this temperature range, and that the laser radiation is switched off when an upper limit value is reached, and is switched on again when a lower limit value is reached.
First, it is important for the invention that heat radiation emanating from the treatment site is used as the measurable variable for a controlled process. The heat radiation is a function of the temperature, that is, at specific temperatures, heat or light is generated of a very specific wave length. When heat radiation of this wave length occurs with a specific intensity, it may be assumed that the treatment site has a very specific temperature characterized by the wave length and its intensity. At this temperature, a specific treatment result exists for a specific workpiece geometry, for example, a specific still acceptable cut quality. This higher temperature determining the upper limit value is in each case determined empirically, according to supplied information, such as the discussed workpiece geometry, the cut quality, the cutting speed, the material, or the like. Also the lower limit value of a predetermined temperature range can be defined correspondingly as the lower temperature by a heat radiation of a very specific wavelength and intensity.
In addition, it is important for the process according to the invention, particularly for its easy implementation, that the reduction or the increase of the intensity of the laser radiation can be achieved by a simple switching-on and switching-off, thus by measures which practically require no expenditures with respect to circuits. Advantageously, the workpiece is treated with a continuous laser radiation. A laser operation of this type is particularly advantageous for the simple switching-off and switching-on of the laser radiation when the limit values are reached.
The above-discussed temperature range is predetermined in such a manner that the upper limit value, in the case of metallic workpieces, is between the evaporating temperature and the melting temperature, and that the lower limit value, in the case of a melting treatment, is approximately equal to the melting temperature and for the treatment with reactive cutting gas, is in the range of the ignition temperature.
In a further development of the invention, the process is carried out in such a manner that the advancing of
REFERENCES:
patent: 4825035 (1989-04-01), Moriyasu et al.
patent: 5041714 (1991-08-01), Funk
patent: 5196672 (1993-03-01), Matsuyama et al.
Abels Peter
Beyer Eckhard
Harzinger Gerd
Petring Dirk
Albritton C. L.
Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung
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