JP2005014093A - Profile control device in friction stir joining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To devise a profile control device so that a joining tool may track a central part of a gap of joining lines irrespective of the shape of the gap in the joining lines and the size of width of the gap in the joining lines, in order to avoid occurrence of poor joining for a joint joined by friction stir as much as possible. <P>SOLUTION: The profile control device for friction stir joining joins aluminum plates by tracking the joining lines with a joining tool, while controlling the XYZ direction and position of the joining tool with a servomotor. Moreover, this device is equipped with a CCD camera being placed ahead of the joining tool in the direction of advancement in the friction stir joining device and taking a picture of the joining lines being joined, and is provided with markings parallel to joining end surfaces being prepared on the upper surfaces of joining ends of the aluminum plates. And image processing is applied to a picture taken with the CCD camera using an image processing device, and the amount of deviation between the position of the marking in the image and the imaged base line is calculated with an operation means, being transmitted to a servo amplifier, and the servomotor is controlled by feedback so that the joining tool may track the central part of the joining line. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a copying control apparatus in friction stir welding, and causes a friction stir welding tool to accurately track the center of the gap of the joint line of the joint, and causes a joining failure due to deviation from the center of the joint line gap of the welding tool. Can be reliably prevented.

Friction stir welding is used for joining aluminum plates, but the length of joints such as aluminum molds used for floor boards and side boards of Shinkansen vehicles and conventional limited express vehicles is extremely long.
On the other hand, the friction stir welding of the plate material P is performed in a state where the aluminum plate P is abutted on the support plate 4 as shown in FIGS. 1 and 2, and the abutting surface and the upper surface of the joining portion are the pins 1 of the tool T and It is heated and softened by frictional heat with the shoulder 3 of the tool body 2, and the butted surfaces are joined. The joining tool T is a hard metal member, and a relatively thin pin 1 protruding from the tip of the joining tool T rotates at a high speed while receiving a strong resistance in the forward direction.
Since an aluminum plate such as a double skin mold is molded, the longer the aluminum plate, the lower the linearity, and when this is abutted, a gap is formed in the joining line. For this reason, the friction stir welding is performed by pressing the plates P, P abutted on the support plate 4 in the lateral direction with a vise or the like so as to make the gap between the joining lines as small as possible.
Further, the position of the head H of the friction stir welding apparatus is controlled in each axial direction of the XYZ coordinate axes, and the welding tool T is controlled so as to track the joining line. Deviation from the center is inevitable in practice, and the magnitude of this deviation is one of the major factors that cause poor bonding.

On the other hand, regarding a joint by friction stir welding, if there is a poorly joined part, this part becomes a weak point, and a crack is generated from this part, and this crack may grow and cause joint damage. For this reason, a repair operation is performed in which the joint full length is subjected to inspections such as ultrasonic flaw detection and visual inspection to identify a defective joint and repair it.
There is not one factor that causes joint failure due to friction stir welding, but there is no doubt that one of the factors is the deviation of the welding tool from the center of the joint line. The influence of the deviation on the joining quality is increased, and air is entrained by the stirring action of the pin 1 of the joining tool T, so that it is often the case that poor joining due to internal defects occurs. For example, the fact that a fine cavity in the longitudinal direction (usually referred to as “tunnel”; see FIG. 3) is formed inside the joint J is a typical joint defect.
The joint length is inspected to identify a joint failure portion, and the joint failure portion is repaired. However, it takes time to identify the joint failure, and the reliability of the inspection result for failure portion identification is not necessarily 100%.
Therefore, in order to avoid the occurrence of joint failure as much as possible, the joining tool can accurately track the center of the joint line gap regardless of the shape of the joint line gap and the width of the joint line gap. It is desirable to make it.
Japanese Patent Laid-Open No. 2000-135575 Patent No. 3258307

  Therefore, the present invention aims to avoid as much as possible the occurrence of poor bonding in the friction stir welding joint. Therefore, the joining tool can be used regardless of the shape of the gap of the joining line and the width of the gap of the joining line. An object of the present invention is to devise the copying control device so as to track the center of the gap of the joining line.

The means taken in order to solve the above-mentioned problems is premised on a copying control device in friction stir welding in which the joining line is traced with the joining tool and the aluminum plate is joined while the position of the joining tool is controlled by a servo motor. The following (a), (b) and (c) are included.
(A) providing a CCD camera ahead of the welding tool of the friction stir welding apparatus in the direction of travel and photographing the joining line to be joined by the CCD camera;
(B) On the upper surface of the joining edge of the aluminum plate, a marking parallel to the joining end face is provided, and the image captured by the CCD camera is image-processed by an image processing device, and the image of the position of the marking in the image is displayed. The amount of deviation from the reference line is calculated by the calculation means,
(C) The servo motor is feedback controlled so that the displacement amount is transmitted to the servo amplifier and the joining tool tracks the center of the joining line.

[Action]
When the above images captured by a CCD camera are image-processed by an image processing device such as an image processing board, an image processing sensor, a video capture board, or an image processing program, the workpiece is an aluminum plate, but the joint is parallel to the joint end face. The marking on the upper surface of the edge is clear in the image. When the lateral position control is performed so that the marking in the video coincides with the reference line on the image, the position where the friction stir welding tool is shifted from the marking by a predetermined distance in the lateral direction is accurately tracked. The friction stir tool tracks the center portion of the joining line by adjusting the predetermined deviation amount to the interval from the marking to the center of the joining line. The gap between the joining lines is extremely small. And the variation in the gap width of the joining line in the friction stir welding of the aluminum plate is very small (because it is pressed strongly from the lateral direction to become a minute gap, so the variation in the gap width is also small), and the marking is at the center of the gap Therefore, the friction stir welding tool will track the center of the gap of the joint line almost accurately by tracking the above marking regardless of whether the joint line is curved or straight. .

Embodiment
Since it is desirable to form the marking at the time of extrusion molding of the aluminum plate, it is preferable that a rib parallel to the joining end surface is provided on the upper surface of the end edge of the aluminum plate and used as the marking.

As described above, the present invention captures a marking parallel to the joining line of the plates to be joined by a CCD camera, processes this image, and controls the lateral displacement between the joining line and the reference line on the image by the controller ( CPU) calculates and measures, and feedback-controls the servo motor based on this deviation amount, so that the welding tool tracks the substantially center part of the joining line regardless of whether the joining line is linear or not. Therefore, it is possible to reduce as much as possible a bonding failure caused by a lateral shift from the center of the bonding line gap of the bonding tool.
In addition, since the image captured by the CCD camera is subjected to image processing and the amount of deviation between the marker and the reference line on the image is calculated and measured, the amount of deviation is detected by simple calculation processing, and the joining line It is possible to track the center of each of them with a joining tool almost accurately.
Therefore, the friction stir welding can be performed with high quality regardless of the presence or absence of the bending of the joining line and the magnitude of the bending.

Next, an embodiment will be described with reference to FIGS.
In this embodiment, aluminum plates P, P having a thickness of 4.5 mm and a length of 8 m are joined, and the joining tool pin 1 is joined at a diameter of 5 mm, a rotational speed of 1750 rpm, and a forward speed of 600 mm / min. It is. A marking rib 71 is provided on the upper surface at a position about 20 mm away from the edges of the aluminum plates P, P (FIG. 7). The marking rib 71 is a streak-like projection having an inverted V-shaped cross section. Since the streak is a tracking marking, it is preferably as low as possible and as narrow as possible as long as a clear image is projected, and the width of the base is 2 mm to 3 mm and the height is in the range of 2 mm to 3 mm. Further, the apex angle of the cross-sectional triangle is preferably in the range of 30 to 60 degrees. However, the width, height, and apex angle of the base are just guidelines for implementation, and do not have any special technical significance.
A CCD camera 41 is attached in front of the head H of the friction stir welding apparatus in the traveling direction. Although the horizontal distance D between the CCD camera 41 and the welding tool T is 200 mm, the measurement accuracy of the relationship between the welding tool T and the welding line position is not affected even if this distance is not so small.
The head H moves along the joining line 42 where the aluminum plates P and P to be joined are abutted, and the CCD camera 41 captures an image by taking a picture while tracking the marking rib 71. The range of the image captured at this time is as shown in FIG. 6 (binarized image), and the range of about 20 mm in the advancing direction and about 40 mm in the lateral direction (although there is no special technical meaning in these 20 mm and 40 mm). This is an appropriate range that is easy to understand. In this image, the image of the marking rib 71 appears as a clear shadow 71a (FIG. 6).

The image information captured by the CCD camera 41 is sent to the image processing device 51, and image processing (binarization) is performed by the image processing device 51.
An image of the marking image 71 parallel to the edge of the joint line gap 42a is captured (FIG. 6). The position of the edge of the marking image 71a is detected, the distance c between the edge of the marking image 71a and the reference line S on the image (according to the reference line information read from the memory 53) is measured, and based on this distance c. The servo amplifier is controlled to feedback control the servo motor so that the distance c becomes zero.

FIG. 3 is a perspective view of a friction stir welding apparatus. FIG. 2 is a YY sectional view of FIG. 1. FIG. 5 is a perspective view schematically showing a joint failure due to tunneling in a joint in friction stir welding. FIG. 3 is a perspective view of the embodiment. 1 is a block diagram of a joint failure detection system in an embodiment. Is a binarized image of a joint line gap and marking image by a CCD camera. FIG. 3 is a perspective view showing an example of marking.

Explanation of symbols

H: Head of friction stir welding apparatus M: Forward drive motor P: Aluminum plate material a: Amount of deviation of edge of joining line image from reference line b: Amount of deviation from reference line of gap center of joining line c: Reference of marking image Deviation amount from line T: Friction stir welding tool 1: Friction stir welding tool pin 2: Friction stir welding tool body 3: Friction stir welding tool shoulder 41: CCD camera 42: Joining line 42a: Joining line gap 43 : Image processing area 51: Image processing device 52: Controller (CPU)
53: Memory 71: Rib for marking 71a: Marking image

Claims (2)

In the copying control device in the friction stir welding in which the welding tool tracks the welding line and joins the aluminum plate while controlling the XYZ direction position of the welding tool,
A CCD camera is provided ahead of the welding tool of the friction stir welding apparatus in the traveling direction, and the CCD camera is used to photograph the edge of the aluminum plate,
A marking parallel to the joint end surface is provided on the upper surface of the joint edge of the aluminum plate, and the image taken by the CCD camera is processed by an image processing device, and the reference line on the image at the position of the marking in the image The amount of deviation from the
A copying control device in friction stir welding, which feedback-controls a servo motor based on the deviation amount. 2. A copying control apparatus in friction stir welding according to claim 1, wherein a rib is provided on the upper surface of the joint end edge in parallel with the joint end face when the aluminum plate is formed, and the rib serves as the marking.

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