Electric heating – Metal heating – By arc
Patent
1991-04-15
1993-08-03
Shaw, Clifford C.
Electric heating
Metal heating
By arc
21913771, B23K 9095
Patent
active
052331580
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to arc welding, and more particularly, to a control method capable of effecting satisfactory arc welding by automatically controlling arc welding current and voltage.
2. Description of the Related Art
In order to adjust arc welding current and voltage for satisfactory arc welding, trial welding is conventionally conducted by driving a welding machine with a tentatively set a power supply output and an electrode feeding speed. If the welding current and voltage measured during the trail welding are outside their respective allowable ranges, the trail welding is executed again after resetting the power supply output and the electrode feeding speed. Thus, according to the conventional method, the power supply output and the electrode feeding speed must be adjusted by the method of trial and error so that the welding current and voltage fall within their allowable ranges, while repeating the trail welding. Thus, the adjustment of the welding current and voltage requires labor.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a control method capable of effecting satisfactory arc welding by automatically controlling arc welding current and voltage.
In order to achieve the above object, a welding current and voltage control method according to the present invention comprises the steps of: (a) detecting values of arc welding current and voltage; (b) calculating an error between the detected value of the arc welding current and a target value and an error between the detected value of the arc welding voltage and a target value; (c) calculating a correction amount of an electrode feeding speed of an arc welding machine in accordance with the calculated error of the arc welding current; and (d) calculating a correction amount of a power supply output of the arc welding machine in accordance with the respective calculated errors of the arc welding current and voltage.
According to the present invention, as described above, the respective correction amounts of the electrode feeding speed and the power supply output of the arc welding machine are calculated in accordance with the errors between the respective detected values and target values of the welding current and the power supply output can be corrected automatically to compensate the welding current and voltage errors, whereby the welding current and voltage can be automatically adjusted. Thus, there is no need of trail welding for the adjustment of the welding current and voltage, and the arc welding can always be effected satisfactorily.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph illustrating, by way of example, the welding current-welding voltage characteristic of an arc welding machine;
FIG. 2 is a graph illustrating, by way of example, the welding current-electrode feeding speed characteristic of the arc welding machine;
FIG. 3 is a schematic block diagram showing an arc welding robot for embodying an arc welding current and voltage feedback control method according to one embodiment of the present invention; and
FIG. 4 is a flow chart showing a welding current and voltage feedback control process executed by means of the welding robot of FIG. 3.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIG. 1, a welding voltage V of a typical arc welding machine drops straight and drastically as a welding current I increases in a first welding current region where the welding current I takes a small value. In a second (normal) welding current region where the welding current I takes a value greater than the value in the first welding current region, the welding voltage V drops straight in a rate of change lower than the rate of change in the first welding current region as the welding current I increases. The greater the power supply output of the welding machine, the higher the welding voltage. In FIG. 1, symbols U1 and U2 (>U1) designate values of the power supply output. Thus, the welding voltage V can be expressed as a function
REFERENCES:
patent: 3538376 (1970-11-01), Parker
patent: 4441009 (1984-04-01), Toohey
patent: 4521672 (1985-06-01), Fronius
patent: 4851639 (1989-07-01), Sugitani et al.
Karakama Tatsuo
Kobayashi Eiichi
Fanuc Ltd.
Shaw Clifford C.
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