JPH0679786B2 - Welding control method and apparatus - Google Patents

Description

The present invention relates to a welding control method and control device for an automatic welding machine in which a welding gun is sequentially moved by a robot to a plurality of welding point positions of a workpiece to perform welding. Regarding

(Prior Art) Conventionally, in this kind of automatic welding machine, the robot is operated according to teaching data to move the welding gun to each spot position, and at each spot position, the welding gun is closed to remove the gap between the electrode tips at the tip of the gun arm. The work is sandwiched between the two and is energized in this state to weld the work, and after all welding positions are completed, the welding gun is returned to the standby position, the welded work is discharged, and the next work is set to the fixed position. After that, the welding gun is moved from the standby position to repeat the above-mentioned work welding work.

(Problems to be solved by the invention) By the way, when a work is forgotten to be set or a setting error such as a position shift occurs, when the welding gun is moved to the welding point position according to the teaching data and closed, the electrode tips are moved to each other. There is a case of hitting without hitting or pinching a part of the work other than the hitting point.In the past, even if such an abnormality occurred, the power is still supplied and the problem such as damage to the gun or punching of the work may occur. There was a problem that would arise.

The present invention focuses on such a problem, accurately determines the presence or absence of the above abnormality, prevents the occurrence of defects such as damage to the gun and punching of the work, and further detects the missing electrode tip. Its purpose is to

(Means for Solving the Problem) In order to achieve the above object, the invention of claim 1 is a welding control method for an automatic welding machine, which performs welding by sequentially moving a welding gun to a plurality of spot positions on a work by a robot. Before welding the first welding point of the workpiece, the welding gun is idled, the opening of the gun arm at this time is stored as a reference opening, and the opening corresponding to the thickness of the workpiece is made for each welding point. Angle setting value is set, the opening of the gun arm is detected when the welding gun is closed at each dot position, and the deviation between this detection opening and the reference opening is calculated. And the presence or absence of abnormality is determined by comparing with, and when the detected opening is lower than the reference opening, an abnormal signal indicating the disconnection of the electrode tip is output. To do.

The invention according to claim 2 provides a welding control device suitable for carrying out the invention according to claim 1, wherein the opening detection means for detecting the opening of the gun arm of the welding gun, and the idle gun when the welding gun is idle. First storage means for storing the opening degree detected by the detection means, second storage means for storing an opening degree set value corresponding to the thickness of the work set for each of the hitting point positions, and each hitting point position When the welding gun is closed at 1, the opening degree detected by the detecting means and the opening degree stored in the first storage means are compared with each other, and the deviation means calculates the deviation between the opening degree and the second opening. The first storage means is provided with a determination means for comparing the opening setting value stored in the storage means to determine whether or not there is an abnormality, and the opening detected when the welding gun is closed at each spot position. When the opening is lower than the one stored in the Characterized in that a means for outputting a signal.

(Operation) The reference opening is the opening of the gun arm during blank driving, that is, when the electrode tips hit each other and the distance between the tips becomes zero, and is detected when the welding gun is closed at each hit point position. The deviation between the detected opening and the reference opening accurately represents the opening between the chips when the gun is closed. Therefore, if the electrode tip sandwiches the hitting point of the work, the opening set value corresponding to this hitting point becomes equal to the deviation, and the presence or absence of abnormality can be accurately determined by comparing the two.

In addition, the electrode tip may be welded to the work and come off from the gun arm when the gun is opened. In this case, the detection opening becomes lower than the reference opening when the welding gun is closed at the next hitting point. In this case, if an abnormal signal indicating that the electrode tip is missing is output, it is possible to take appropriate measures against the missing tip.

(Embodiment) Referring to FIG. 1, (1) shows an X-shaped welding gun having a pair of gun arms (3) and (3) opened and closed by a pressure cylinder (2). The welding gun (1) is sequentially moved to a plurality of hitting points of the work W, the gun arms (3) and (3) are closed at each hitting point, and the work W is sandwiched between the electrode tips (4) and (4) at the tip thereof. Pressurize with
Both electrode tips (4) (4) by welding transformer (5)
The work W is spot-welded by energizing the space.

The pressure cylinder (2) is operated by a pneumatic servo circuit (8) including a servo valve (6) controlled by a servo amplifier (6a) and a regulator (7) controlled by a drive amplifier (7a). It consists of a controlled double-acting air cylinder, and detects the pressure of the welding gun (1) from the pressure of one air chamber of the pressure cylinder (2) that is supplied when the gun arm (3) (3) is closed. A pressure sensor (9) is provided, and the rotation angle of the pinion (10b) on the other gun arm (3) that meshes with the rack (10a) that interlocks with one gun arm (3) determines the gun arm (3) (3). An opening sensor (10) for detecting the opening is provided.

In the figure, (11) shows a robot controller and (12) shows a gun controller consisting of a microcomputer. The RAM (12a) of the controller (12) has welding condition data corresponding to each welding position, that is, welding current. And energization time, pressurizing force, opening set value (hereinafter referred to as θ _s ) corresponding to the thickness of the work W at the hitting position, gun arm after welding (3) (3)
The data such as the opening degree of is stored.

The welding gun (1) is controlled according to the program shown in FIG. 2, which will be described below.

When the arrival of the welding gun (1) at the standby position is confirmed by the signal from the robot controller (11) (), the gun controller (12) sends it to the servo amplifier (6a) via the D / A converter (6b). A pressure command signal is input, air is supplied to the pressure cylinder (2), and the gun arm (3)
(3) is closed, and as shown in FIG. 3 (a), the welding gun (1) is idled (). And the gun arm (3) detected by the opening sensor (10) at the time of this idle shot
The opening θ of (3) is input to the gun controller (12) via the A / D converter (10c), and this opening is stored in the RAM (12a) as a reference opening (hereinafter referred to as θ ₀ ). ().

Here, theta ₀ is changed according to the length of the electrode tip (4), theta ₀ by can know the wear degree of the electrode tip (4), where it defines the allowable range for theta _0, theta ₀
Is within the allowable range (), and when the length of the electrode tip (4) is reduced to the usage limit and θ ₀ falls below the lower limit value α, or when the electrode tip (4) is defective. When θ ₀ exceeds the allowable upper limit value β due to insufficient insertion into the gun arm (3) or because it is too long, etc., the tip abnormality alarm is activated () and the electrode tip (4) is replaced manually or automatically. to (), empty-handed again, θ ₀ of the detection memory, θ ₀
I decided to judge.

Then, when θ ₀ is within the allowable range, the gun controller (11) sends a preparation completion signal to the robot controller (11) to start the robot after the work set is completed (), and the welding gun (1) is turned on. When the welding gun (1) moves according to the teaching data of the robot () and the welding gun (1) arrives at each welding point position, welding is performed in the following procedure.

That is, when arrival of the welding gun (1) at the welding point position is confirmed by a signal from the robot controller (11) (), welding condition data corresponding to this welding point position is read out () and the gun controller (12). To servo amplifier (6
The pressure command signal is input to the a) via the D / A converter (6b), and the pressing force setting signal is input to the driver amplifier (7a) via the D / A converter (7b). Air is supplied to the pressure cylinder (2) via (6) and the regulator (7), the welding gun (1) is closed (), and the pressure sensor (9) drives the A / D converter (9a). When it is confirmed by the signal input to the gun controller (12) via the gun controller (12), the gun arm (3) detected by the opening sensor (10) is detected.
The opening θ of (3) is input to the gun controller (12) via the A / D converter (10c) (), and the CPU (12b) calculates the deviation between θ and θ ₀ (hereinafter referred to as Δθ). ().

Here, θ is a value obtained by adding the distance between the electrode tips (4) and (4) to θ ₀ , and therefore Δθ accurately represents the opening degree between the tips regardless of the length of the electrode tip (4). In the case, as shown in FIG. 3 (b), if the electrode tips (4) and (4) sandwich the hitting point position of the work W, Δθ becomes equal to θ _s. When the non-overlapping portion of the work W is sandwiched as shown in FIG. 6C or when blanking occurs as shown in FIG.
_s, and the electrode tip (4) as shown in FIG.
Δθ becomes a negative value when the omission occurs.

Therefore, after calculating Δθ, it is first determined whether or not Δθ ≧ 0 (), and when Δθ <0, the tip missing alarm is activated (), and the electrode tip (4) is manually or automatically attached and re-installed. Start (), and when Δθ ≧ 0,
Next, it is determined whether or not | Δθ-θ _s │ ≦ γ (allowable error) (), and when | Δθ-θ _s |> γ, the set miss alarm is activated () and the welding gun (1) is turned on. It was returned to the standby position ().

Then, when | Δθ−θ _s | ≦ γ. The signal from the gun controller (12) activates the transformer drive circuit (13),
Energization is performed for a prescribed time with a prescribed welding current (), and after a lapse of a prescribed hold time from the completion of energization, the gun controller (12) opens the servo amplifier (6a) via the D / A converter (6b) The setting signal is input, the gun arm (6) (6) is opened to the set opening () by the operation of the servo valve (6), and then the welding completion signal is transmitted from the gun controller (12) to the robot controller (11). ,
The robot operates to move the welding gun (1) to the next hitting point position.

Then, when the welding at the final hitting point position is completed, the welding gun (1) is returned to the standby position.

(Effects of the Invention) The present invention has the following effects with the above configuration.

In other words, the opening between the electrode tips can be accurately detected from the deviation between the detected opening of the gun arm and the reference opening when the welding gun is closed at each spot position, and this deviation and the opening corresponding to the workpiece thickness at the spot position can be detected. It is possible to accurately determine whether or not the work is normally sandwiched between the electrode tips by comparing with the temperature setting value, and there is no problem such as damage to the gun or punching of the work due to energization in abnormal conditions such as blank driving. It is possible to prevent the occurrence, and when the electrode chip is removed, it can be detected by distinguishing it from other abnormalities, and it is possible to appropriately deal with the chip removal.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an example of an apparatus used for carrying out the method of the present invention,
FIG. 2 is a flow chart showing a control program for the welding gun, and FIGS. 3 (a) to 3 (d) are explanatory views showing the opening of the gun arm at the time of idle driving, at normal times, and at abnormal times. (1) ... Welding gun, (3) ... Gun arm, (4) ...
… Electrode tip, (10) …… Opening sensor (opening detecting means), (12) …… Gun controller, (12a) …… RAM (first and second storage means) (12b) …… CPU ( Calculation means and discrimination means)

Claims (2)

[Claims] 1. A welding control method for an automatic welding machine, in which a welding gun is sequentially moved to a plurality of welding points of a work by a robot to perform welding, and the welding gun is shot before the welding of the first welding point of the work. Then, the opening of the gun arm at this time is stored as a reference opening, and an opening set value corresponding to the thickness of the work is set for each dot position.
When the welding gun is closed at each dot position, the opening of the gun arm is detected, the deviation between this detected opening and the reference opening is determined, and this deviation is compared with the set value to determine whether there is an abnormality. The welding control method is characterized in that, when the detected opening degree is lower than the reference opening degree, an abnormal signal indicating that the electrode tip is missing is output when the determination is made. 2. An opening degree detecting means for detecting an opening degree of a gun arm of a welding gun, a first storing means for storing an opening degree detected by the detecting means when the welding gun is idled, and each dot position. Second storage means for storing the opening setting value corresponding to the thickness of the work set to the above, and the opening detected by the detecting means when the welding gun is closed at each hitting point and the first opening. A discriminating means for discriminating the presence or absence of abnormality by comparing the deviation stored in the storage means and calculating the deviation thereof with the deviation set value stored in the second storage means. And an abnormality indicating that the electrode tip is missing when the opening detected when the welding gun is closed at each striking position is lower than the opening stored in the first storage means. A welding control device comprising means for outputting a signal.