Electric heating – Metal heating – By arc
Patent
1991-04-25
1993-01-26
Albritton, C. L.
Electric heating
Metal heating
By arc
21912167, 21912182, 21912184, B23K 2600, B23K 2614
Patent
active
051824345
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a laser beam machining method of processing a machining path having an acute angle by a laser beam, and more particularly, to a laser beam machining method of efficiently effecting an automatic cutting work even at an acute-angle processing portion which is susceptible to an influence of heat.
2. Background Art
In cutting work using a laser beam, the laser beam is applied to a portion of a material to be cut, and at the same time, an assist gas is blown onto that portion from a nozzle tip. When cutting a metallic material, oxygen is generally used as the assist gas so that an oxidative reaction is used in conjunction with the heat-energy processing by the laser beam, and local heat processing work is collected. When processing an acute-angle portion, however, the traveling speed of a machining table is substantially lowered, and thus the heat input in the stock per unit time is increased. Immediately after the arrival of the laser beam at the turn, in particular, the acute-angle vertex portion is melted by local heat previously produced in the stock due to heat conduction before the cutting work, and for the same reason, a considerable reduction in cut surface roughness occurs in the region near the vertex portion.
The method used to cope with this problem varies in accordance with whether the resulting product is on the side of an acute or narrower angle or on the side of a greater angle.
If the product is on the acute-angle side (inside the cutting path), a loop processing method is used. In this method, the cutting work is continued until the turn of the acute angle is cleared, the machining is continued, forming a circular arc of a suitable size or a straight line to return to the turn, and an advance for the originally intended machining is restarted. This method enables a substantial reduction of the machining speed at the acute angle, which is attributable to the correlation between the force of inertia of the machining table and a servomotor, to be lessened. If the size of the loop is increased, then the vertex of the acute angle will be cooled.
If the product is on the obtuse-angle side (outside the cutting path), on the other hand, a method is used such that the machining conditions are changed before the turn is reached, to thereby attempt to minimize the heat input, and the same operation is performed while the machining is advanced for a suitable distance from the turn.
If the product is on the acute-angle side, however, it is necessary to create a program for the path of machining at the loop processing portion, in addition to the path of the originally intended machining, and thus the size of the loop must be changed in accordance with the thickness of the material to be machined and the size of the acute angle. Moreover, since an unwanted machining is added, the material will be unduly consumed.
Furthermore, if the product is on the obtuse-angle side it is very difficult to set the machining conditions. Namely, know-how based on experience and perception is required to determine the position at which the machining conditions should be changed or the position at which the machining conditions should be restored to the original conditions, during the progress of the machining operation. Moreover, since the heat input is restricted during the machining, the operation is limited to an extent such that the cutting work becomes impossible. Also, since many changes are made in the machining conditions of this method, a complicated machining program is required, and thus a problem arises in the use thereof.
DISCLOSURE OF THE INVENTION
The present invention has been contrived in consideration of these circumstances, and an object thereof is to provide a laser beam machining method of automatically effecting an acute-angle machining without the need for a complicated machining program or the machining of unnecessary portions.
To solve the above problems, according to the present invention, there is provided a laser beam machining met
REFERENCES:
patent: 4870560 (1989-09-01), Seki et al.
patent: 4914599 (1990-04-01), Seki et al.
Albritton C. L.
Fanuc Ltd.
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