Tandem arc welding device

A tandem arc welding device in which the welding conditions and a program describing contents of operation are treated as independent to each other. It handles the welding conditions altogether simply as those parameters for the fore-going welding and those parameters for the hind-going welding. By so doing, a program can be produced without taking which of the two welders will become fore-going into consideration. Furthermore, a program and welding conditions thus provided offer superior re-usability and reproducibility to the tandem arc welding.

TECHNICAL FIELD

The present invention relates to a tandem arc welding device which performs certain specific operation patterns in accordance with a certain specific operation program for welding an object of welding at certain specific welding conditions.

BACKGROUND ART

In the industry manufacturing various kinds of structural members by making use of welding, efforts are being made to improve operation efficiency by increasing the speed of welding or introducing a high-deposition welding process. In order to further improve the efficiency, some welding firms have introduced an integrated welding torch which can supply two weld wires, or such a welding method which uses a single-electrode welding torch for two pieces disposed in proximity to each other. They are referred to as the tandem arc welding.

A tandem arc welding system performs a certain specific action at a certain specific speed and controls the welding process to accomplish a welding operation. An operation program is provided on an assumption that the two electrodes, including the weld wires which are supplied penetrating through respective electrodes, are disposed substantially on welding line in a certain welding section, in front and the rear orientation.

Now, a tandem arc welding device is described in its outline formation and operation, referring toFIG. 1.FIG. 1shows the outline structure of a tandem arc welding device having an integrated 2-electrode welding torch. Integrated 2-electrode welding torch50is attached on a welding robot manipulator or the like working gear, not shown, and travels on the surface of welding object60along a certain specific welding line. A device for putting a robot manipulator, etc. into action is coupled with control unit20. Control unit20is connected with two welders,30and40. Respective welders30and40are provided with a weld wire feeder, not shown, for feeding a weld wire, not shown, to welding torch60; namely, the torch is supplied with two weld wires. Within welding torch50, each of the two weld wires is delivered penetrating through an electrode tip, not shown. The electrode tips are connected with output terminals of welder30and welder40via power cable31and power cable42, respectively. Electric powers from welder30and welder40are supplied to respective weld wires. Welding object60is connected to the ground terminals of welder30and welder40by way of grounding cable32and grounding cable41. The arcs between the weld wires and welding object60constitute circuits for the welding currents.

Control unit20houses an operation program and welding conditions, and controls a welding robot manipulator, etc. by transferring from time to time the instructions and parameters to welder30and welder40via control line33and control line43in accordance with the operation program. Welder30and welder40control their own weld wire feeders so that the weld wires are supplied for certain specified quantities corresponding to the parameters instructed by control unit20. In this way, a tandem arc welding device implements a certain specific welding operation on welding object60at a certain specified place.

Now in the following, description is made on how a tandem arc welding is implemented, with reference toFIG. 2.FIG. 2illustrates a scene where a tandem arc welding is being carried out with an integrated 2-electrode welding torch (ref.FIG. 1), in the direction from the right to the left. The terminologies here, “fore-going” means that which is proceeding ahead along a welding line, while “hind-going” means that which is going in chase of the “fore-going”.

Reference is made toFIG. 2, there are two electrode tips, fore-going electrode tip51and hind-going electrode tip52, disposed at a certain specific electrode-to-electrode distance within the inside of nozzle58of integrated 2-electrode welding torch50. Fore-going electrode tip51is supplied with fore-going weld wire53, while hind-going electrode tip52is supplied with hind-going weld wire54.

Fore-going weld wire53obtains electric power from a welding power supply source for fore-going electrode, not shown, via fore-going electrode tip51, and generates fore-going arc55between fore-going wire53and welding object60. The heat of arcing melts fore-going wire53and welding object60to supply molten pool61with the molten metals. At the same time, hind-going weld wire54obtains electric power from a welding power supply source for hind going electrode, not shown, via hind-going electrode tip52, and generates hind-going arc56between hind-going wire54and welding object60. The heat of arcing melts hind-going wire54and welding object60to supply molten pool61with molten metals. Fore-going wire53and hind-going wire54are delivered continuously while integrated 2-electrode welding torch50travels at a certain specific speed. Molten metal pool61moves forward and weld bead62is formed behind it; thus, a welding operation takes place. Fore-going electrode tip51(or hind-going electrode tip52) and fore-going weld wire53(or hind-going weld wire54) are referred to as the electrode, altogether.

In a tandem arc welding, the fore-going electrode and the hind-going electrode have, respectively, their own specific roles. For example; inFIG. 2, the molten metals in molten pool61formed by fore-going arc55which is generated by fore-going wire53tends to flow backward under the influence of arcing power of fore-going arc55. Meanwhile, the arcing power of hind-going arc56which is generated by hind-going wire54pushes it back. Molten pool61stands on a balance between the two powers. Besides the above-described, each of the electrodes plays specific role of its own for the weld penetration and the shaping of weld bead62. Thus, the two electrodes are not playing the same functions. So, welder30and welder40need to be provided with different parameters of welding conditions in carrying out a welding.

Arrow mark59inFIG. 2indicates, for example, a welding operation conducted in the forward direction, viz. a welding proceeding from the right to the left. On the other hand, if a welding is made along the reverse direction, the direction is opposite to that indicated by arrow mark59, or the direction from the left to the right inFIG. 2. Since parameters to be sent to fore-going welder30(or welder40) are different from those to be sent to hind-going welder40(or welder30), the welding condition parameters for welder30and those for welder40have to be exchanged when making a welding the reverse direction. Therefore, when controlling the welding conditions in a conventional tandem arc welding device, the program is required to include a certain procedure for specifying which of the two will be the fore-going. As a practical example, there can be four modes: namely, a tandem welding mode which uses both of welders30and40, with one of which specified as fore-going electrode; that which uses the other welder as the fore-going; and a single welding mode which uses only one of the welders30and40alone. In providing an operation program for a tandem arc welding, there has been a generally-used technique of specifying the modes. Such conventional technique used for tandem arc welding is disclosed in, for example, Patent Document 1 described later.

As described in the above, the conventional tandem arc welding devices has a restriction that the welding conditions need to be provided considering which of electrodes50aor50bwill be the fore-going, and the operation program has to include such descriptions in it. This means that both the operation program for welding object60and the welding conditions described in there are dependent on a reality which one of the electrodes is the fore-going. Therefore, program making staff have always keep in mind which of the electrodes is going ahead of the other. Furthermore, this has another inconvenience that re-use of an operation program and welding conditions contained in there for other welding object60is limited.

DISCLOSURE OF THE INVENTION

A tandem arc welding device having two electrodes and operating on an operation program for welding a welding object, which welding device includes a welding conditions holding unit for holding those parameters of welding conditions containing an indication about an electric current and an indication about a voltage to be sent to a welder of fore-going electrode, among the two electrodes, proceeding ahead of the other on a welding direction, and those parameters of welding conditions containing an indication about an electric current and an indication about a voltage to be sent to a welder of hind-going electrode, among the two electrodes, proceeding behind the other electrode on the welding direction altogether in a state isolated from the operation program; a welding conditions editing unit for editing data items constituting the welding conditions; an electrode decision unit for deciding fore-going electrode based on fore-going electrode information which indicates as to which one of the two electrodes described in the operation program will be the fore-going; and a welder control unit which designates one of the two welders as welder of fore-going electrode while the other welder as welder of hind-going electrode, based on decision of the electrode decision unit, and sends the parameters for fore-going welding and the parameters for hind-going welding in the welding conditions of the welders, respectively.

REFERENCE MARKS IN THE DRAWINGS

100Welding Conditions Holding Unit

110Table of Welding Conditions

111Table of Welding Conditions

112Table of Welding Conditions

120Welding Condition Parameters for the Fore-going

130Welding Condition Parameters for the Hind-going

150Fore-going Electrode Information

160Information for Designating Table of Welding Conditions

200Welding Conditions Editing Unit

300Electrode Decision Unit

400Welder Control Unit

500Welding Conditions Decision Unit

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention offers a tandem arc welding device, in which the conditions of tandem arc welding and the operation program describing contents of the operation are provided to be independent to each other and the welding conditions are handled altogether simply as those parameters needed for foregoing welding and those for hind-going welding. By so doing, a program can be provided without considering which of the two will be used as welder of fore-going electrode. Furthermore, a program and welding conditions thus provided have superior re-usability and reproducibility.

Exemplary embodiments of the present invention are described below, referring toFIG. 1throughFIG. 7.

FIG. 3is an illustration used to describe a tandem arc welding device in first embodiment of the present invention from the view point of functions performed by control unit20shown inFIG. 1. Those portions identical to those shown inFIG. 1are designated using the same symbols, and detailed description on which portions are eliminated. InFIG. 3, control unit20is connected with welder30via control line33, and welder40via control line43.

In control unit20, welding conditions holding unit100stores and administrates the welding condition parameters for the fore-going120(hereinafter referred to as parameters for fore-going120) and the welding condition parameters for the hind-going130(parameters for hind-going130), these parameters being bundled together as one set of welding conditions to be stored in welding conditions table110which is a separate existence independent of operation program140. Parameters for fore-going120is a group of parameters which contain those indications about the electric current, voltage, with or without a pulse, and pulse waveform control parameter, etc. to be sent to welder30(or welder40) of electrode50a(or electrode50b) which is proceeding ahead along welding direction. Parameters for hind-going130is a group of parameters containing those indications about the electric current, voltage, with or without a pulse, and pulse waveform control parameter, etc. to be sent to welder40(or welder30) of electrode50b(or electrode50a) which proceeds behind along welding direction. Contents of welding conditions table110kept within welding conditions holding unit100can be edited by welding conditions editing unit200to desired values. Weld wire53(or weld wire54) and electrode tip51(or electrode tip52) altogether are referred to as electrode50a(or electrode50b).

As shown inFIG. 3, operation program140has, as the attribute information, fore-going electrode information150which indicates which of the electrodes50aand50bis positioned at the front on a welding line. Based on fore-going electrode information150, electrode decision unit300decides which of the electrodes50aand50bwill be fore-going electrode.

In an actual automatic operation, electrode decision unit300recognizes, in accordance with fore-going electrode information150, one of the welders30and40as welder of fore-going electrode while the other welder as welder of hind-going electrode. Welder control unit400sends those parameters for fore-going120and for hind-going130which have been held in welding conditions holding unit100to corresponding welders30and40based on the results of recognition at electrode decision unit300. A certain desired tandem arc welding is thus carried out.

If any one of the constituent parameter items for fore-going120and for hind-going130, for example welding current value, is 0, it means that no welding is made by the relevant electrode. By so describing, the welding device can perform a single welding, not only the tandem welding.

As described in the above, a tandem arc welding device in the first embodiment can administrate those welding conditions without any regard to actual relative positioning among electrodes50aand50bas to which will be the fore-going. Furthermore, those parameters needed for carrying out a tandem arc welding can be administered altogether. This enables to administer the welding conditions with superior re-usability and reproducibility.

FIG. 4is an illustration used to describe a tandem arc welding device in second embodiment of the present invention from the view point of functions performed by control unit20shown inFIG. 1. Those portions identical to those shown inFIG. 1are designated using the same symbols, and detailed description on which portions are eliminated. Unlike the first embodiment, no fore-going electrode information150is provided, as attribute information, in operation program140of a tandem arc welding device in the second embodiment. Fore-going electrode information150is described as an order in operation program140in a tandem arc welding device in the second embodiment; based on the description, electrode decision unit300decides which of the electrodes50aand50bwill be the fore-going. The above described is the point of difference from the tandem arc welding device in first embodiment.

As described in the above, a tandem arc welding device in the second embodiment offers an advantage, in addition to that of the first embodiment, that which one of the electrodes will be the fore-going,50aor50b, can be exchanged freely in a program. This provides a higher degree of freedom in the use a tandem arc welding device, and the field of application will become broader to include, for example, a welding robot system.

FIG. 5is an illustration used to describe a tandem arc welding device in third embodiment of the present invention from the view point of functions performed by control unit20shown inFIG. 1. Those portions identical to those shown inFIG. 1are designated using the same symbols, and detailed description on which portions are eliminated. Unlike the first embodiment, no fore-going electrode information150is provided, as attribute information, in operation program140of a tandem arc welding device in third embodiment. In a tandem arc welding device in accordance with third embodiment, electrode decision unit300judges as to which of the electrodes50aand50bis to be the fore-going on the basis of a direction of welding line registered in operation program and a stance of a robot (a holding device) which holds welding torch50. Based on the above, electrode decision unit300decides which of the electrodes,50aor50b, will be the fore-going. The above described is the point of difference from a tandem arc welding device of the first embodiment.

Representing a location and posture of a robot with homogeneous transformation matrix T6, the elements of T6are consisting of approaching vector a, directional vector o, slope line vector n and placement vector p. Direction from one of the electrodes (electrode50a) towards the other electrode (electrode50b) is represented with directional vector o.

Assuming a vector from place P13registered in operation program140towards place P14as 1=(1x, 1y, 1z), an angle α formed between vector o and vector1is given by the inner product. If, for example, α is smaller than 90 degrees, electrode50bis judged to be the fore-going, if α is exceeding 90 degrees, electrode50ais judged to be the fore-going.

As described in the above, a tandem arc welding device in the third embodiment offers an advantage, in addition to that of the first embodiment, that which one of the electrodes will be the fore-going,50aor50b, can be exchanged freely. Furthermore, which will be the fore-going does not need to be considered in producing a program. This provides a higher degree of freedom in the use a tandem arc welding device, and the field of application will become broader to include, for example, a welding robot system.

FIG. 6is an illustration used to describe a tandem arc welding device in fourth embodiment of the present invention from the view point of functions performed by control unit20shown inFIG. 1. Those portions in fourth embodiment which are identical to those of the first through third embodiments are designated using the same symbols, and detailed description on which portions are eliminated. Unlike the first through third embodiments, number of welding conditions table110is not limited to 1 in a tandem arc welding device in accordance with fourth embodiment. A tandem arc welding device in fourth embodiment is structured so that it can hold a plurality of welding conditions tables; welding conditions table111, welding conditions table112, etc. Operation program140has information for designating welding conditions table160, as attribute information, which specifies a certain specific welding conditions table. Based on information for designating welding conditions table160, welding conditions decision unit500decides which of the welding conditions, among those contained in the plurality of welding conditions tables, are to be used, and welder control unit400makes use of the result of the decision. The above described is the point of difference from the first through third embodiments.

When welder control unit400sends those parameters for fore-going120and parameters for hind-going130included in welding conditions table111, or welding conditions table112, to the corresponding welders30and40, one of suitable methods described in the first through third embodiments may be used.

As described in the above, a tandem arc welding device in fourth embodiment provides a further advantage, besides those advantages described in the first through fourth embodiments, that it can be used for welding at a plurality of joints, not at a single joint alone. Thus a tandem arc welding device will have a broader field of application.

FIG. 7is an illustration used to describe a tandem arc welding device in fifth embodiment of the present invention from the view point of functions performed by control unit20shown inFIG. 1. In a tandem arc welding device in accordance with fifth embodiment, operation program140describes a plurality of information for designating welding conditions table160as an order. Welding conditions decision unit500decides which one of the plurality of welding conditions tables is to be used, and welder control unit400makes use of the result of the decision. The above described is the point of difference from the fourth embodiment.

As described in the above, a tandem arc welding device in the fifth embodiment provides a further advantage, in addition to that of the fourth embodiment, that it can optionally specify in the program if a welding is to be made at a plurality of joints, not only at a single joint alone. Thus a tandem arc welding device will be provided with a broader field of application.

As described in the above first through fifth embodiments, a tandem arc welding device in accordance with the present invention can handle a number of tandem arc welding conditions, isolated from actual operating environments where what matters is which one of the two welders will be the foregoing. Furthermore, each one of the welding conditions can be determined at a certain desired value. Since in an actual automatic welding operation a judgment as to which one of the welders will be fore-going is made automatically by scrutinizing the relevance in the contents of operation program and the welding is controlled accordingly, a program can be produced without taking which one of the welders is of the fore-going electrode into consideration. A program and welding conditions thus provided exhibit superior advantages in the re-usability and reproducibility. This makes it easier to introduce the tandem arc welding, where two welders are driven in complexity, to the actual production floor.

INDUSTRIAL APPLICABILITY

A tandem arc welding device in the present invention treats the tandem arc welding conditions isolated from the program which describes contents of operation, and keeps those welding conditions for fore-going and for hind-going altogether simply as a group of parameters regardless of which one of the two welders will be of the fore-going electrode. By so doing, a program can be produced without taking which of the two welders will become a welder of fore-going electrode into consideration. Thus the welding conditions can be administered with superior re-usability and reproducibility. In this way, the present invention would bring about an advantage to the industry by making it easier to introduce the tandem arc welding, which requires complex control on the two welders, to an ordinary production floor.