Electric heating – Metal heating – By arc
Patent
1986-09-30
1987-06-02
Albritton, C. L.
Electric heating
Metal heating
By arc
219 12NQ, 219121LW, B23K 2602
Patent
active
046706380
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method and to a device for displacing the impact point of a laser beam on a part.
Industrial applications of laser beams are becoming more and more numerous and diverse, with laser beams being used, in particular, for cutting, marking, welding parts, surface treatments, etc.
In general, the laser beam is directed onto a mirror which directs it to a focusing lens interposed between the mirror and the part to be treated. The impact point of the laser beam on the part is displaced along a predetermined trajectory either by displacing the mirror/focusing-lens assembly relative to the part, or else by displacing the part and its support relative to the mirror/lens assembly.
In either case, the masses that need to be displaced are relatively large and have inertia which greatly limits the acceleration and the speed at which the laser beam may be displaced relative to the part, particularly when the trajectory of the impact point includes regions of small radius of curvature. Such slowing down gives rise to the risk of the part being burned, and also wastes time, thereby making the use of a laser beam less competitive relative to conventional cutting or marking devices.
The object of the invention is a method and a device for displacing a laser beam, which method and device do not suffer from these drawbacks and which allow the impact point of a laser beam to be displaced over a part with accelerations that are much higher than those that could be obtained previously, in particular when the trajectory of the impact point includes regions of very small radius of curvature.
Another object of the invention is a method and a device enabling a laser beam to be displaced along a predetermined trajectory with a very much higher degree of accuracy than could be obtained previously.
The method in accordance with the invention which consists in directing a laser beam onto a mirror for deflecting it onto a part, and in displacing the mirror support or the part support relative to the other support with predetermined motion corresponding substantially to the desired trajectory for the beam impact point on the part is characterized in that it consists in superposing on said motion a small amplitude motion of the mirror relative to its support, in mounting the mirror rotatable about axes which cross at its center, and in determining the small amplitude motion by rotating the mirror about said axes.
Preferably, the mirror is suspended from its center by magnetic attraction and without friction by means of a cushion of air, and its rotary motion about the above-specified axes is controlled by varying current flowing through coils which are placed in a fixed magnetic field and which are fixed on the mirror at points situated on the above-specified rotary axes.
The invention also provides a device for displacing the impact point of a laser beam on a part, the device comprising a mirror onto which the laser beam is directed together with means for displacing the mirror support or the part support relative to the other support with motion corresponding substantially to the trajectory desired for the laser beam impact point on the part, characterized in that the mirror is rotatably mounted relative to its support about two perpendicular rotary axes passing through its center, and in that means are provided for displacing the mirror about said two axes with small amplitude motion which is superposed on the above-specified motion of the mirror support or the part support relative to the other support.
The invention thus provides for an average trajectory of a laser beam impact point on a part to be determined, with said average trajectory not including portions of very small radius of curvature, and for superposing on said average trajectory a small amplitude curve of the laser beam impact point on the part in order to obtain exactly the desired trajectory for the laser beam impact point. This small amplitude displacement is obtained by rotating the reflecting mirror whose mass is very small and whose moment
REFERENCES:
patent: 3225206 (1965-12-01), Strong et al.
patent: 4429210 (1984-01-01), Sudo et al.
Albritton C. L.
Bertin & Cie
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