JPH0245953B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a MIG blaze welding method, and more particularly to a MIG blaze welding method for relatively large workpieces that need to be precisely welded, such as roof panels and side panels of automobiles. When welding, the MIG BLAZE uses a position detection sensor to detect the optimal welding location even if there is some positional deviation between the workpieces, and starts the welding process by guiding the tip of the welding torch to that location. Regarding welding methods.

MIG blaze welding is a process in which a consumable electrode with a relatively low melting point is continuously fed at a constant speed into a shielding gas atmosphere ejected through a nozzle, and the electrode is melted to weld two parts together. It is widely used, especially in automated production lines. For example, on an automobile production line, roof panels and side panels are welded together using a MIG blaze welding machine built into a robot.

However, when roof panels and side panels are press-molded, there are often variations in product accuracy due to assembly errors or the like.
Conventionally, the following method has been used when attempting to perform the process on a workpiece having such size errors. That is, a positioning hole is drilled in each workpiece to be welded, and the relative positional relationship between the welding robot and the workpiece is determined based on this hole, and welding is performed.

Welding is performed by performing so-called weaving by alternately swinging the tip of the welding torch laterally with respect to the welding progress direction at the welding site of the workpiece placed for welding.

In advance, jigs are prepared for each workpiece, and the workpieces are regulated under the positioning action of these jigs to absorb dimensional errors of the workpieces and perform welding.

However, the commonly adopted welding methods described above expose the following drawbacks. That is, the number of machining steps increases in order to drill a hole for positioning the workpiece. Moreover, depending on the welding location, it may be impossible to drill a hole in the workpiece, and as a result, it becomes difficult to position the workpiece itself, making it difficult to perform precise welding. On the other hand, due to continuous welding, the amount of heat input to the workpiece increases significantly, and the welded area may sag. For this reason, new processing is required to correct the distortion of the sagging portion of the work. Furthermore, in weaving, the amount of weld build-up is large, so the surface of the workpiece must be finished after welding, and the number of man-hours required for this finishing process is so large that it cannot be ignored. Furthermore, the jig for regulating the position of the workpiece becomes large and expensive, and depending on the type of workpiece, it is difficult to place the jig at the desired position. This exposes the inconvenience that positioning cannot be performed.

The present invention has been made in order to overcome the various inconveniences and shortcomings described above, and the present invention has been made by installing a sensor for detecting the position of the workpiece in close proximity to the tip of the welding torch of a MIG blaze welding machine, and detecting the position of the workpiece by this sensor. An object of the present invention is to provide a MIG blaze welding method in which the tip of a welding torch is moved based on a deviation signal of a welding part of a workpiece, and MIG blaze welding is performed on the workpiece at an optimal position.

In order to achieve the above object, the present invention sets a workpiece at a predetermined position during welding, makes a groove region defined by two members constituting the workpiece face the position detection sensor, and Based on the position information of the workpiece, if the deviation of the workpiece exceeds a specified value, an abnormality alarm is issued, and if the deviation of the workpiece is within the specified value, the welding torch is activated. The present invention is characterized in that an optimal movement trajectory is selected from among a plurality of pre-stored movement trajectories, and welding is performed on the groove portion along the movement trajectory.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the MIG blaze welding method according to the present invention will be described in detail with reference to the accompanying drawings, in relation to an apparatus for carrying out the method.

In FIG. 1, reference numeral 10 indicates a pedestal;
A MIG blaze welding machine 12 consisting of, for example, a five-axis robot is movably suspended and held on the pedestal 10. Since the MIG blaze welding machine 12 is a known one, a detailed explanation thereof will be omitted. A photovoltaic type optical sensor 18 that receives reflected light from the light source 16 is also fixedly installed (see FIG. 2).

On the other hand, a floor holder 20 is disposed below the welding machine 12 to receive a workpiece W sent out from a transport system (not shown), that is, an automobile body. Therefore, it is displaced in the vertical direction, and the workpiece W placed thereon is directed toward the welding machine 12 and moved forward and backward.

Next, a control system for the optical sensor 18 and welding machine 12 arranged as described above will be explained with reference to FIG. 3.

The output side of the optical sensor 18 is connected to an A/D converter 22, and the output side of the A/D converter 22 is connected to a central processing unit 24, which essentially consists of a microcomputer. The output side of the central processing unit 24 is connected to the controller 26 of the welding machine 12, and performs a displacement operation of the welding torch 14 via a rotational motion source (not shown).

The central processing unit 24 includes a CPU 28,
Storing the processing procedure applied to the CPU 28
The ROM 30 energizes the welding machine 12 and stores necessary data such as the trajectory of the welding torch 14.
RAM 32, input port 3 connected to the CPU 28 and receiving the output signal from the A/D converter 22
4. It includes an output port 36 for controlling the welding machine 12 by giving an output signal from the CPU 28 to the welding machine controller 26.

Therefore, welding machine 12 having the above configuration
The operation when performing MIG blaze welding using the control system will be explained below based on the broach chart of FIG.

First, move the floor cradle 2 from the transport system (not shown).
Workpiece W is fed to zero. According to the present applicant's confirmation, there is currently a maximum positioning error of about ±2.5 mm for the workpiece W on the floor pedestal 20. Therefore, it is sufficient for the output signal of the optical sensor 18 according to the present invention to control the displacement of the welding machine 12 within this range.

By the way, the work W is an automobile body in this case, and in this embodiment, the welding machine 12 is used to weld the roof panel W ₁ and the side panel W ₂ that constitute the work W. here,
The roof panel W ₁ has its tip bent in a Z-shape, while the side panel W ₂ has its tip bent in an L-shape. Therefore, when the two tips are aligned, a bevel will be defined as shown in FIG.

In this arrangement, the cylinder device 21 that holds the floor pedestal 20 is driven, and the floor pedestal 20 is raised. As a result, the work W placed on the floor pedestal 20 rises. The presence or absence of the workpiece W and its seating state at a predetermined position are detected by a limit switch (not shown) (STP1). This detection signal causes the welding machine to move, and the welded parts, that is, the welded parts defining the grooves of the roof panel _W1 and the side panel _W2, face the welding torch (STP2).

Therefore, when the energizing signal for the light source 16 is sent,
The light source 16 is turned on and the light source illuminates the upper surface of the roof panel W ₁ in the figure, and on the other hand,
A part of it reaches the bottom part defining the groove of the roof panel _W1 (see 4th light). For this reason,
The light irradiating the top surface of the roof panel _W1 mainly enters the optical sensor 18 as reflected light. That is, depending on the position of the optical sensor 18, it is divided into a part A where the reflected light is strong and a part B where the reflected light is weak.
If either one of B is extracted as an electrical signal, a position control signal for the welding torch 14 can be obtained.

In this case, the method of the present invention extracts the portion A where the reflected light is strong as a position signal. In other words,
The area of the part where the reflected light is strong is determined by the optical sensor 18,
This is sent to the A/D converter 22 as a voltage signal. This signal is then converted into a digital signal by the A/D converter 22 and output from the input port 34 to the CUP
This signal is taken into 28 as an address signal.
In this case, for example, as shown in FIG. 6, the output power of the optical sensor 18 causes the optical sensor 18 to move within ±2.5 mm from the edge defining the groove of the roof panel _W1 .
It is confirmed whether or not it exists directly above within the range of (STP3). If the workpiece W is located at a position deviated by ±2.5mm or more, a position detection abnormality alarm is issued (STP4), a welding machine home position return signal is issued (STP5), and this welding machine Stop (STP6).

On the other hand, the workpiece W is ±2.5mm compared to the setting standard.
, the trajectory of the welding torch 14 is selected. In other words, the CPU 28
The welding torch 14 trajectory data corresponding to the address signal is read from the RAM 32. That is, the five trajectories a to e are selected in advance and stored in the RAM.
(See Figure 7). For example, assume that the address signal selects the trajectory c shown in FIG. 7 as the most appropriate trajectory for the groove (STP7). As a result, a movement signal for the welding torch 14 is sent to the controller 26 via the CPU 28 in order to follow the selected trajectory c, and the arm of the welding machine 12 is displaced (STP8). After this moving operation is completed, the welding machine 12 starts MIG blaze welding (STP9).

When the welding process is completed according to a predetermined program, the welding machine 12 returns to its original position (STP10).
The welding machine 12 is stopped by this return-to-home signal detected via a limit switch or the like (STP11), and the cylinder (not shown) supporting the floor pedestal 20 is lowered to move the workpiece W to the next processing step. will be transported to.

According to the present invention, as described above, it is possible to guide the welding torch to the optimal welding part of the workpiece extremely easily and accurately, and therefore there is no need to perform weaving etc. especially during MIG blaze welding. . Further, since it is not necessary to form a reference hole for positioning the workpiece or to provide a jig or the like, it is possible to achieve the effect of significantly reducing the number of processing steps and processing costs.

Although the present invention has been described above with reference to a preferred embodiment, the present invention is not limited to this embodiment, and similar effects can be achieved by using other position detection sensors instead of optical sensors. Of course, various improvements and changes can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the mutual relationship between the MIG blaze welding machine, a workpiece, and a position detection sensor according to the present invention, FIG. 3
The figure is an explanatory diagram of the control system used to implement the present invention, Figure 4 is an explanatory diagram of the state in which the optical sensor is detecting the position state in the groove part of the workpiece, and Figure 5 is the implementation of the method of the present invention. FIG. 6 is a graph showing the relationship between the output signal of the optical sensor and the welding part of the workpiece, and FIG. 7 is an explanatory diagram showing the trajectory of the welding torch over the workpiece. 10... Frame, 12... Welding machine, 14... Welding torch, 16... Light source, 18... Light sensor, 20
...Floor cradle, 21...Cylinder device, 2
2...A/D converter, 24...Central processing unit, 26...Controller, 28...CPU, 3
0...ROM, 32...RAM, 34...input port, 36...output port.

Claims (1)

[Claims] 1 Set the workpiece in place for welding,
A groove portion defined by two members constituting the workpiece is faced to the position detection sensor, positional information regarding the groove portion of the workpiece is obtained, and the shift of the workpiece is detected based on the positional information of the workpiece. If the deviation of the workpiece exceeds the specified value, an abnormality alarm is issued, and if the deviation of the workpiece is within the specified value, the optimal movement trajectory of the welding torch is selected from among multiple pre-stored movement trajectories, A MIG blaze welding method, characterized in that welding is performed on the groove portion along the movement trajectory.