Electric heating – Metal heating – By arc
Patent
1991-08-08
1993-12-21
Albritton, C. L.
Electric heating
Metal heating
By arc
21912163, 21912167, B23K 2602
Patent
active
052723127
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a method for quality assurance when processing materials with laser energy, and preferably laser beam welding or cutting. In such processing, the ultraviolet light arising in the plasma cloud during the material processing operation is detected by a detector in a wavelength of approx. 200 nm up to approx. 450 nm to control the laser beam coupling in the workpiece as well as the check for specified limits of other process parameters such as laser output power, beam defocussing, beam quality, feeding of shielding gas and working gas as well as workpiece structure, cleaning status of the workpiece surface, and welding gap width. Such a quality assurance method is known from DVS-report No. 113 on the conference "ECLAT '88", p. 58-59. Known devices use a light sensitive detector consisting of a silicon photodiode, which has an enhanced UV-light sensitivity, and an optical filter, which is transparent only for the particular UV-light wavelengths. The filter is located between the welding pool (4) and the detector. The received UV-signal is turned into an electric signal by the detector, and is fed to a processing unit. With such a device, it is possible during a laser material processing, to detect changes of the various parameters and identify them as possible material processing faults.
This known device has the disadvantage, in that it is not possible to detect and indicate a processing fault during a laser welding process, when two or more parameters with contrary effects on the welding plasma have changed at the same time. Furthermore, if a high detection sensitivity is adjusted, such a device indicates too many faults, being in fact the result of a laser welding process parameter disturbance but not the result of welding failures.
As background of this invention also the use of a photodiode for monitoring a laser drilling process was considered. This well known monitoring method is shown in: JP-DS "Pat. abstr. of Japan", 1987, Vol. 11/No. 166, M-593, Kokai No.: 61-296980.
SUMMARY OF THE INVENTION
The object of the present invention is therefore to provide a device and method wherein quality control of the well, being produced by laser energy, is effected during the welding process itself, independent of changes of one or several processing parameters which may cause a welding fault.
In this invention, the apparatus has the advantage, that the quantity of the liquid material which is thrown out of the welding pool (4) due to the energy feed and consequently due to the vapor pressure in the "key-hole", is electro-optically detected at a predetermined wavelength of 800 nm up to preferably 1300 nm by at least one photodiode and transformed into an electrical signal which is led to a processing unit. The apparatus and method allows the user to determine the dimension of the hollows having arisen in the workpiece. The welding faults can be detected and can be identified as processing faults with the aid of the processing unit as defined herein.
A fundamental advantage of the method is found in the fact that unambiguous monitoring of real welding faults is possible. This is based on the fact that the dimension of the drops which are thrown out of the welding pool is equivalent to the dimension of the pores and hollows being let in the weld. The apparatus of the invention has the advantage that the method according to the invention can practically be used. With this apparatus, even deep-seated pores arising in the weld during a laser welding process can be detected without destruction. This shows an additional advantage of the apparatus due to the detection of the workpiece position relative to the laser processing head during the laser operating process, the position of the detected welding faults in the workpiece can reliably be found after the operation for further analyzing purposes or for a workpiece post processing.
The position detection can be realized e.g. for a rotary-symmetrical workpiece with an incremental or absolute rotary angle encoder whose ro
REFERENCES:
patent: 4939336 (1990-07-01), Meyer et al.
patent: 5059761 (1991-10-01), Koegl et al.
patent: 5067086 (1991-11-01), Yamazaki et al.
patent: 5155329 (1992-10-01), Terada et al.
patent: 5164565 (1992-11-01), Addiego et al.
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