JP3290977B2 - Abnormal stop control method in friction stir welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormal stop control method in friction stir welding, and when a welding tool is damaged during friction stir welding, the welding tool is instantaneously detected and the operation is stopped.
An object of the present invention is to shorten the length of a defective joint caused by tool breakage as much as possible so that the jointed joint can be repaired quickly.

[0002]

2. Description of the Related Art Friction stir welding is used as a method of joining aluminum metal plates. However, the length of a joint such as an aluminum mold used for a floor plate or a side plate of a railway vehicle is extremely long. On the other hand, the friction stir welding of the plate material P is performed in a state where the plate material P is butted on the support plate 4 as shown in FIGS. Is cut off at the lower end surface by about 0.1 mm (L in FIG. 2). The joining tool T is a hard metal member, and the relatively thin pin 1 protruding from the tip thereof rotates at high speed while receiving strong resistance in the forward direction. Destruction is inevitable. If the tool T is fractured in the middle of joining, only the surface of the joining portion is left in the main body 2 of the tool T without joining.
Will be cut off at the shoulders 3 of the body . When joining middle bonding tool is fatigue fracture, the portion where the tool T is advanced after it is damaged because not joined, it is necessary to join the parts again. On the other hand, since the joining length until one tool undergoes fatigue failure is predicted, the tool is replaced within the predicted range to prevent the tool from fatigue failure during welding, but the fatigue strength is reduced. Limits vary from tool to tool and can still break before reaching the expected bond length. If the tool breaks during welding, the operator senses a change in the drive motor sound, etc., and immediately stops the operation.
Nevertheless, since the tool moves forward by that time, it is inevitable that the defective joining part will be a certain length, and the friction stir welding operation will be automated, and one friction stir welding machine will be monitored by one worker In some cases, this becomes even more remarkable, and it takes a lot of man-hours to repair the defective joint.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem associated with the breakage of a friction stir welding tool as much as possible. An object of the present invention is to devise an abnormal stop control method so that a defective joint generated due to fatigue fracture of a tool is reduced as much as possible.

[0004]

Means taken to solve the problem The means taken to solve the above problem is to detect breakage of the friction stir welding tool.
Abnormality stop control method of stopping the driving, the current value of the rotational driving motor of the FSW tool is compared with a reference value, when the current value becomes less than 80% of the reference value, the rotation
By stopping the drive motor and forward drive motor at the same time,
There, the other solutions, the current value of the forward drive motor of the FSW tool with a reference value, the current value of the reference value 80
%, The forward drive motor and the rotary drive motor
Data at the same time.

[0005]

The size of the friction stir welding tool is appropriately selected depending on the thickness of the tool to be welded, and the load on the rotary drive motor is substantially constant depending on the size of the tool, but the gap between the welding lines is small.
If there is a variation between them, the load fluctuates. in this case
Since the load fluctuates within a range of approximately ± 10%, when the load becomes 80% or less of the reference current value (average drive current value in a normal state), it is determined that the junction is abnormal. If the pin of the welding tool is fatigue-ruptured during welding, it immediately drops to 80% or less. By stopping the operation when the pin becomes 80% or less, the operation can be surely performed simultaneously with the fatigue failure of the tool. Stopped. The current of the forward drive motor during the bonding is a substantially constant 2.3A, because the fluctuation range of the current in the normal joint is less than ± 10% even by the larger, the reference current value 80 % Or less is considered to be a bonding abnormality. If the pin of the welding tool is fatigue-ruptured during welding, it immediately drops to 80% or less of the reference current value.
By stopping the operation when it becomes less than%, the operation is surely stopped at the same time as the fatigue fracture of the tool. The reference current value may be set in advance according to the thickness of the plate to be joined, or may be the latest average current value during operation (for example, the average value in the last 1 second). In addition, since the current values of the rotary motor and the forward drive motor at the time of joining start are small, the stop signal is generated under the AND condition that the current value has decreased from high to low and that the measured data is 80% or less of the reference value. Is generated, the “80 of the reference value” is obtained during bonding.
The operation can be stopped only when the value falls below%. In addition, since the reduction rate of the drive current value when the tool is broken due to fatigue is more remarkable than the case due to other factors, instead of setting the reference current value and comparing this with the measurement data, It is also possible to calculate a reduction rate of the current value and issue a stop signal when the reduction rate is greater than the set reduction rate.

[0006]

Next, an embodiment will be described with reference to the drawings. In this embodiment, an aluminum plate having a thickness of 4.5 mm is joined, and the diameter of the pin 1 of the joining tool is 5 mm.
The joining is performed at a rotation speed of 1750 rpm and a forward speed of 600 mm / min. Average current value of the rotary drive motor _{M 1} during the friction stir welding length 8m in this embodiment is 11.4 A, the maximum current value 12.0A, minimum current value is 11.0A, while average current value of the forward drive motor _{M 2} is 2.3A, the maximum current value 2.33A, the minimum current value is 2.28A (friction stir welding apparatus is different,
These specific current values are different). Rotary drive motor M
₁ is transmitted from the sensor 10 to the CPU 12, and the current measurement data of the forward drive motor M ₂ is transmitted from the sensor 11 to the CPU 12. In this embodiment, a reference current value of 11.4 A for the rotary drive motor and a reference current value of 2.3 A for the forward drive motor are set in the reference memory 13. The CPU 12 repeatedly calls the measurement data of the sensors 10 and 11 at 0.5 second intervals,
Compared with the reference value, when the one is below 80% of the reference value, issues a stop signal to the controller 14, is programmed to stop the rotation drive motor M ₁ and the forward drive motor M ₂ at the same time I have. As a result of performing a test on the two joining tools, the first one was broken at a joining length of 5 m, and the rotating drive current at that time decreased to 9.1 A, and the current value of the forward drive motor decreased to 1.8 A. Also, 2
The first one broke at a joint length of 4.5 m, at which time the rotational drive current dropped to 9.0 A, and the current value of the forward drive motor dropped to 1.6 A. In any case, the current value is equal to the reference value × 0.8 A (80% of the average current value) at the same time when the welding tool is damaged.
%) Or less, and the forward operation of the friction stir welding machine stops within 0.5 seconds after the current value falls below the reference value.
The advance distance of the welding tool during this time is 5 mm or less. Therefore, the forward motion is stopped almost simultaneously with the fatigue failure of the tool pin.
It stops almost equivalent to the radius of the main body of the tool.

[0007]

As described above, according to the present invention, among various changes such as a change in sound and a change in vibration caused by the fatigue fracture of a welding tool, the current value of the rotary drive motor and the forward drive motor of the tool is reduced. Detects the fatigue failure of the joining tool by the change in the value, and when the value becomes 80% or less of the reference value compared with the reference value, the rotary drive motor and the forward drive motor are immediately stopped, so almost no damage to the pin At the same time, the operation is stopped, and the occurrence of defective joints due to the continued rotation and advancement of the tool after the pin is broken can be completely and reliably prevented. In addition, compared to the case where the bonding operation is stopped by detecting a change in sound or a change in vibration, the detection means and the control system can be simplified since the change in the drive current is detected. it can. In addition, the driving current is theoretically almost constant depending on the thickness of the plate to be joined or the size of the joining tool. However, differences in joining conditions (changes in the gap between the joining surfaces, changes in the pressing force of the tool, etc.) ) Causes the drive current to fluctuate slightly. However, by using the average value as the reference value and 80% of the threshold value as the threshold value, it is possible to reliably detect the fatigue failure of the welding tool without considering the steady-state fluctuation of the average driving current due to the difference in welding conditions. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view of a friction stir welding apparatus.

FIG. 2 is a sectional view taken along line YY of FIG.

FIG. 3 is a schematic diagram of the embodiment.

[Explanation of symbols]

P: Aluminum plate T: Friction stir welding tool 1: Friction stir welding tool pin 2: Friction stir welding tool body 3: Friction stir welding tool shoulder 10: Rotational drive current sensor 11: Forward drive current sensor 12 : CPU 13: Reference memory 14: Controller M ₁ : Rotary drive motor M ₂ : Forward drive motor

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B23K 20/12

Claims (2)

(57) [Claims] The present invention relates to a friction stir welding tool, which detects a breakage of the tool.
A abnormal stop control method for stopping the movement, the current value of the rotational driving motor of the FSW tool is compared with a reference value, when the current value becomes less than 80% of the reference value, the rotary drive motor
Stir welding that simultaneously stops the motor and the forward drive motor
Abnormal stop control method. 2. An abnormal stop control method for detecting breakage of a friction stir welding tool and stopping the drive thereof, wherein the current value of a forward drive motor of the friction stir welding tool is compared with a reference value, and the current value is set to a reference value. When the value falls below 80% of the value, the forward drive mode
Stir welding that simultaneously stops the motor and the rotary drive motor
Abnormal stop control method.