Electric heating – Metal heating – By arc
Patent
1996-08-09
1999-07-20
Mills, Gregory L.
Electric heating
Metal heating
By arc
2191218, 21912185, B23K 2610
Patent
active
059252715
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Filed of the Invention
The invention relates to a device and a process in which this device can be used, for laser beam shaping, particularly in laser beam machining of work pieces. The term laser beam machining is understood to mean not only laser beam surface hardening, in particular transformation hardening, but also other laser beam surface machining processes, such as alloying, remelting, cladding, stripping, welding, cutting, and others. The invention can be used in the treatment of metallic, non-metallic, and/or ceramic work piece surfaces in a solid or liquid state.
2. Description of Background Information
It is known that in laser machining, a particular importance is attached to both the quality of the "raw beam" and the beam shaping with which the "raw laser beam" is "shaped" for the desired use, since as a result, the process, quality, quantity, and efficiency have a decisive influence in surface machining. Hence the demand on the one hand, for an optimum "raw laser beam quality" and on the other hand, for focussing or beam-shaping elements (transmission and reflection optics, in particular metal optics) that are adaptable--i.e. that correspond to the "raw beam quality" and the stated machining goal. A decrease of the "raw beam quality" is generally connected with the availability of higher power lasers (>5 kW). Among other things, this means that the power density distribution over the raw beam cross section is uneven, i.e. nonhomogeneous, and means that the beam diameters as a whole increase in size, which means that the optical components and the container diameters for the beam transmitting segments must be enlarged and much more in addition. The availability of beam-shaping elements for larger beam diameters is very limited because of price, optics manufacturing, and power compatibility and at the same time, requires additional measures, e.g. cooling etc., in technical application.
Starting from these disadvantages, the attempt has been made to shape and deflect the laser beam by means of static or dynamic beam-shaping elements or a combination of the two.
All versions of the static beam shaper have the advantage of being suited for higher laser powers, but they are generally blamed for the disadvantages of insufficient power peak compensation and poor flexibility, i.e. can only be used for one operating point (spot measurement). The spot of a static beam shaper, with its shortcomings that have already been discussed, is calculated and produced for precisely defined raw beam parameters, e.g. diameter, divergence, mode image configuration, angle from beam axis to beam shaper axis, deflection angle, among other things. With practical operations, it is determined that all of these parameters are subject to changes of short or long duration. Thus for example, in operations with a number of work stations, by means of different length beam paths alone, deviations from the defined beam parameters occur (illumination of the mirror surface of the static beam shaper) or by means of laser operating state changes because of service life (changing of the decoupling disk; soiling of the internal laser mirror). In laser material machining, these changes cause qualitative differences in the work piece, which finally have a negative influence on the work result so that the aim is to counteract these changes by means of costly additional measures, e.g. installation of telescopes, adaptive optical elements, coupled with sensory mechanisms and regulation, etc. A certain power peak compensation takes place with dynamic beam shapers, e.g. scanner mirrors. These have the shortcoming, though, that in general, they can be used only in a laser power range of up to a maximum of 5 kW, where the geometric distribution of the beam intensity in the spot (power peaks, beam nonhomogeneities, etc.) are evened out (homogenized) on the work piece surface. The power excesses (nonhomogeneities) dictated by principle at the turnaround points of the scanner mirror, e.g. on the right and left ed
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English Language Abstract of JP 61-292,122.
Gnann Rudiger Arnold
Morgenthal Lothar
Pollack Dieter
Arnold Karl H.
Fraunhofer-Gesellschaft zur Forderung der ange-wandten Forschung
Mills Gregory L.
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