Electric heating – Metal heating – By arc
Patent
1992-04-02
1994-12-20
Albritton, C. L.
Electric heating
Metal heating
By arc
21912167, B23K 2600
Patent
active
053748034
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a laser cutting process in which workpieces such as steel plates are cut off by means of laser beam.
BACKGROUND TECHNIQUE OF THE INVENTION
Heretofore, when cutting off a workpiece, such as a steel plate, by making use of a laser processing machine, O.sub.2 gas having a pressure of 0.5 to 6 kg/cm.sup.2 has been used as an assist gas under such a condition as focusing a laser beam onto an upper surface of the workpiece. On the other hand, when cutting off a workpiece, such as a thin plate having the thickness of less than 1 mm, air has been used also as an assist gas, because a little dross is attached to the workpiece.
O.sub.2 gas can be used as an assist gas without causing any problem when a workpiece is made of soft steel. However, when cutting a workpiece made of material having a high viscosity in its melted state such as, for example, stainless steel, aluminum, and so forth, if the gas is used, it does not become possible to obtain a fine cut surface, because dross generated upon cutting the workpiece is attached to the cut surface.
In order to improve the above mentioned inexpediency, a pressure of assist gas may be raised so as to blow off the dross. However, if the pressure of assist gas is raised, there has been a disadvantage in that a volume of assist gas increases with the result that a costs increase.
On the other hand, when using air as an assist gas, dross tends to attach to a cut surface of a workpiece, because a degree of oxidization of the dross is low as compared with the case in which O.sub.2 gas is used as an assist gas. As a result, it does not become possible to obtain a fine cut surface of the workpiece to be cut. Therefore, there has been such an inexpediency as being necessary to require many working steps as an aftertreatment such as, for example, an application of machining on the cut surface of the workpiece.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-described circumstances, and has for its aim to provide a laser cutting process in which a fine cut surface without attaching any dross thereto can be easily obtained.
In order to attain the above-mentioned aim, according to a first feature of the present invention, there is provided a laser cutting process which comprises the steps of: applying a piercing to a workpiece by irradiating a laser beam toward a focus adjusted onto an upper surface of the workpiece under such a condition as using air having a relatively low pressure; ejecting air having a high pressure toward a cutting portion of the workpiece from a nozzle main body for emitting the laser beam mounted on a laser processing machine under the condition such that the laser beam is irradiated from the nozzle main body toward a focus adjusted onto a rear surface of the workpiece or in the proximity thereof; and cutting the workpiece while blowing off dross generated upon the cutting operation by means of the ejected high pressure air.
In the above feature, a high pressure type air compressor which can supply air having a pressure of 8 to 15 Kg/cm.sup.2 is used as a supply source of high pressure air. In addition, according to a second feature of the present invention, there is provided a laser cutting process as set forth in the above-described first feature, the laser cutting process being characterized in that, after applying the piercing, a feed speed of the nozzle main body along the cutting direction of the workpiece is varied gradually such as, for example, at three stages, in turn, of 10%, 20% and 40% of a preset value of speed.
According to the present invention having the foregoing features, since the laser cutting process is adapted such that the focus of the laser beam is adjusted onto the rear surface of the workpiece or in the proximity thereof and that the workpiece is cut by means of laser beam while ejecting air having a high pressure of 8 to 15 kg/cm.sup.2 from the nozzle main body for emitting the laser beam, it becomes possible to cut the workpiece ef
REFERENCES:
patent: 3629546 (1971-12-01), Fray
patent: 3965328 (1976-06-01), Locke
patent: 4987286 (1991-01-01), Allen
International Search Report, Dec. 18, 1989, PCT/JP89/01050.
International Preliminary Examination Report.
Albritton C. L.
Kabushiki Kaisha Komatsu Seisakusho
Kananen Ronald P.
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