JP4159297B2 - Spot welding system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spot welding system that performs a friction stir spot spot welding (friction stir spot welding) by superimposing a plurality of materials to be joined , and in particular, a long plate material (a material to be joined) having a curved portion. about the spot joining system for joining.
[0002]
[Prior art]
Conventionally, when manufacturing a long plate material having a curved portion, a method of manufacturing a welded configuration by placing a metal plate on a surface plate having a curved portion corresponding to the curved portion. And as described in JP-A-3-75279. A method for performing friction stir spot welding by superposing a plurality of thin flat plates is already known as disclosed in JP-A-2001-314982.
[0003]
Further, as shown in FIG. 12, the horizontal frame portion of the portal frame 102 that moves the butting portion K ′ of the two works K (materials to be joined) placed on the flat bed 101 in the longitudinal direction X. Also known is a friction stir welding by a joining head 105 mounted on 102a, wherein the joining head 105 is provided so as to be movable in a lateral direction Y and movable up and down in a vertical direction Z via a movable member 104. It has been. As described above, a technique for joining the butt portions of the materials to be joined placed on a flat bed by a friction stir method is described in, for example, Japanese Patent Application Laid-Open No. 2000-135577.
[0004]
The recently developed spot welding method by friction stirrer does not require a lot of electric power and has no advantage of generating consumables. Also, the arrangement of joints is free and can be joined close to each other. However, since the indentation or the like does not remain in the joint and can be used as an exterior plate, its use has recently been promising.
[0005]
[Problems to be solved by the invention]
Therefore, it is desired to develop a spot welding system capable of automatically and continuously spot-bonding a plurality of superposed materials (metal plates) when spot-bonding by a friction stir method.
[0006]
The object of the present invention is to employ a friction stir method spot joining method that does not require a large amount of power and does not generate consumables when spot joining is performed by overlapping a plurality of materials to be joined. And it is providing the spot joining system which can be joined automatically.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is a spot joining system for spot joining by overlapping a plurality of materials to be joined, the surface plate on which the materials to be joined are placed, and the surface plate A gate-type frame disposed so as to straddle, a spot bonding head that is attached to the gate-type frame and that frictionally stir spot-bonds the material to be bonded placed on the surface plate, and the material to be bonded is predetermined. Moving means for moving in the feed direction, and a mounting table for guiding the material to be joined on both the inlet side and the outlet side of the surface plate.
[0008]
According to the invention of claim 1 having the above-described configuration, the material to be joined is placed on the surface plate and moved by the moving means in a predetermined feeding direction (a direction from the inlet side to the outlet side of the surface plate). By the spot welding head mounted on the portal frame, the friction stir spot welding can be stably performed. Therefore, automation of friction stir spot welding is realized.
[0009]
According to a second aspect of the present invention, the material to be joined is a plate material having a curved portion, and the surface plate and the mounting table have a curved support portion corresponding to the curved portion of the material to be joined. Features.
[0010]
According to invention of Claim 2 which has said structure, the friction stir spot joining can be carried out for the board | plate materials (to-be-joined material) which have a curved-surface part in at least one part. Accordingly, it is possible to stably perform friction stir spot welding on a plate material such as an exterior material that is curved at least partially.
[0011]
According to a third aspect of the present invention, the spot bonding head is configured to be traversable and tiltable in a direction perpendicular to the feeding direction of the materials to be bonded, and to be vertically movable, and the portal frame is It is movable in the feed direction of the material to be joined.
[0012]
According to invention of Claim 3 which has said structure, while being able to move a to-be-joined material by a moving means, a portal frame | frame is moved, and spot joining head itself is made to move the said to-be-joined material (longitudinal). Direction) . Therefore, it is not limited to the movement range of the portal frame, and spot joining is possible from a material to be joined having a short length to a material to be joined having a long length regardless of the length of the material to be joined.
[0013]
According to a fourth aspect of the present invention, the moving means grips an end portion of a material to be joined placed on the surface plate or a placing table and performs a feeding operation at a predetermined pitch.
[0014]
According to invention of Claim 4 which has said structure, when moving a to-be-joined material or carrying out spot joining, the edge part of to-be-joined material can be hold | gripped firmly. Furthermore, since feeding at a predetermined pitch becomes possible, spot bonding can be performed with high accuracy at predetermined pitch intervals at predetermined positions.
[0015]
The invention of claim 5 is a spot joining system for spot joining by overlapping a plurality of materials to be joined having curved portions, and having a curved support portion corresponding to the curved portion of the materials to be joined. A surface plate on which the material to be joined is placed, a gate-type frame disposed so as to straddle the surface plate, and a material to be joined mounted on the surface plate and rubbed against the material to be joined An entrance side of the surface plate having a spot joining head for stirring spot joining, a moving means for moving the joined material in a predetermined feeding direction, and a curved support portion corresponding to the curved portion of the joined material And a mounting table for guiding the material to be joined on both sides on the outlet side, and the spot joining head is traversable and tiltable in a direction orthogonal to the feeding direction of the material to be joined, and is vertically moved up and down. While freely configured Wherein the gate-shaped frame is fixed in position.
[0016]
According to the invention of claim 5 having the above-described configuration, it is possible to move the material to be joined on the mounting table by the moving means even when the portal frame is fixed at a fixed position. Spot bonding can also be performed on the bonding material.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the spot bonding system of the present invention will be described with reference to FIGS.
[0023]
1 is a perspective view showing the entire spot bonding system of the present invention, FIG. 2 is a plan view showing the whole system, FIG. 3 is a side view thereof, and FIG. 4 is a front view thereof. 5 is an enlarged perspective view showing the moving means, FIG. 6 is an enlarged side view of the spot bonding head, and FIG. 7 is an enlarged front view of the spot bonding head. FIGS. 8A and 8B show an embodiment of the thrust amount control device for the spot bonding head, where FIG. 8A is a side view showing the main part, and FIG. 8B is a block diagram showing the flow of control. FIGS. 9A and 9B show another embodiment of the spot welding head thrust amount control device. FIG. 9A is a side view showing the main part, and FIG. 9B is a block diagram showing the flow of control.
[0024]
First, the spot bonding system will be described with reference to FIGS. The spot welding system of the present invention has a portal frame 1 on which a friction stir spot welding head 2 is mounted, and the portal frame 1 is provided on a rail 3 so as to be movable in the horizontal direction (X direction in FIG. 1). It has been. Then, the spot joining head 2 is moved by the movement of the portal frame 1, so that a predetermined position of the material to be joined placed on the surface plate 6 is spot joined. In this example, two materials to be joined, that is, a superposition of the upper plate material P1 and the lower plate material P2 are spot-joined, but a superposition of three or more plate materials is spot-joined. You can also.
[0025]
The spot joining head 2 is provided so as to be traversable in the lateral direction (Y direction in FIG. 1) with respect to the portal frame 1 and to be movable up and down in the vertical direction (Z direction in FIG. 1).
[0026]
Therefore, if the length of the material to be joined is short enough to be placed on the surface plate 6, all necessary portions can be obtained by moving the portal frame 1 in the X direction (see FIG. 1). It is possible to perform spot bonding. However, when the length of the material to be joined is longer than the surface plate 6, it is impossible to perform spot joining to all necessary locations by simply moving the portal frame 1, and therefore the material to be joined itself is also moved in the X direction. There is a need. Therefore, in this example, the mounting tables 4 and 5 are provided on the inlet side and the outlet side of the surface plate 6, respectively, and the moving means 7 for moving the material to be bonded mounted on the mounting tables 4 and 5 is provided. is doing.
[0027]
The plate materials P1 and P2 (materials to be joined) placed on the entrance-side placement table 4 and the surface plate 6 are gripped by the moving means 7 and fed by a predetermined pitch. The spot joining head 2 that has moved to the joining position with respect to the material to be joined that has stopped at a predetermined position is lowered, performs friction stir spot joining, and the spot joining head 2 is raised after the joining is completed. Thereafter, pitch feed of the materials to be joined or movement of the spot joining head 2 is executed, and the next friction stir spot joining is performed. By repeating this operation, friction stir spot welding is performed at all required positions in the longitudinal direction of the materials to be joined.
[0028]
The entrance side mounting table 4 and the outlet side mounting table 5 are each provided with a moving means 7 for gripping and moving the material to be joined, and the materials to be joined are moved by the cooperation of both. The moving means 7 does not necessarily need to be provided on the inlet side mounting table 4 and the outlet side mounting table 5, and moves the material to be bonded on the surface plate 6 to perform spot bonding over the entire length thereof. If possible, it may be provided only for one of the mounting tables 4 and 5.
[0029]
The moving means 7 will be described with reference to FIGS. The material to be joined is placed on the entrance side placing table 4 and the moving means 7 is set. The materials to be joined are obtained by superposing the upper plate material P1 and the lower plate material P2, and both are plate materials having curved portions.
[0030]
The entrance-side mounting table 4 has a curved portion corresponding to the curved portion of the material to be joined, and a large number of rolling wheels 41 that are rolling spheres are embedded on the upper surface. It is set as the structure provided with the conveyance function which was provided and was able to move the to-be-joined material (plate material P1, P2) freely.
[0031]
When gripping and transporting each end of the material to be joined, the moving means 7 shown in FIG. 5 (a) is effective, and the screw is rotated by rotating the ball screw 75 mounted in the moving guide 71. Block 74 can be moved linearly. By moving the gripping portion 73 and the arm portion 72 integrally formed with the screw block 74 linearly, the workpiece is moved in the horizontal direction. Reference numeral 76 denotes a guide guide for guiding the arm portion 72 that moves linearly. The guide guide 76 includes a large number of rolling bearings, but may be other methods that can move (convey) with low friction.
[0032]
The grip portion 73 has a U-shaped cross section and is configured to be fixed with a set screw after the upper plate member P1 and the lower plate member P2 are mounted, but is elastically fixed using a spring. It is good also as a structure and it is good also as an air chuck system.
[0033]
The moving means 7 that grips and moves each end of the material to be joined is configured to perform accurate pitch feeding.
[0034]
The moving means 7A shown in FIG. 5 (b) grips and moves the end portion of the intermediate portion of the material to be joined. A moving guide 71 is disposed on both sides of the machine base, and the moving guide 71 is interposed between the moving guides 71. The connecting arm portion 72 a can be moved horizontally via the screw block 74. The screw block 74 moves linearly with the rotation of the ball screw 75. A vertical member 73b and a gripping member 73a are integrally provided at a predetermined position of the connecting arm portion 72a, and are configured to grip and send the rear end of the material to be joined.
[0035]
If the moving means 7A is employed, it can be gripped at any position on the rear end of the material to be joined, and a place to be gripped can be selected by a combination of the upper plate member P1 and the lower plate member P2. However, depending on the size of the gripping member 73a, it is necessary to secure a traveling space in which the gripping means 73a moves. In that case, a step is provided on the upper surface of the mounting table 4 so that the gripping means 73a can travel, or the mounting table may be divided into two mounting tables 4a and 4b to provide a moving space. Which of the moving means 7 or the moving means 7A is employed depends on the shape or combination of the upper plate material P1 and the lower plate material P2 of the material to be joined.
[0036]
The spot bonding head 2 will be described with reference to FIGS. A bracket 25a is mounted on the portal frame 1 so as to be able to traverse in a direction perpendicular to the feed direction of the material to be joined. The linear guide 23d, the guide member 23c, and the attachment are attached to the bracket 25a via a pivot shaft 24g. A plate 25b is provided. The mounting plate 25b is integrally provided with a rotary tool 21 that is a spot welding tool, a motor 22a that rotates the rotary tool 21, and an air cylinder 23a that moves in the vertical direction. While being pressed against the material to be joined. The bracket 25a is also provided with a servo motor 24a. The driving force of the servo motor 24a is transmitted to the worm 24e via the pulley 24b, the transmission belt 24c, and the pulley 24d, and is used to rotate the worm wheel 24f. Since the linear guide 23d, the guide member 23c, and the mounting plate 25b are integrally provided on the pivot shaft 24g of the worm wheel 24f, the spot joining head 2 is rotated by the rotation of the servo motor 24a. Therefore, the spot welding head 2 can maintain a state in which the head is swung by a predetermined angle with respect to the vertical direction by the servo motor 24a, and spot bonding can be performed at a predetermined angle with respect to the vertical direction.
[0037]
The joining head 2 is configured to be movable up and down in the vertical direction together with the mounting plate 25b by the expansion and contraction of the piston rod 23b of the air cylinder 23a disposed on the upper part of the linear guide 23d.
[0038]
The joining head 2 includes a motor 22a at an upper portion, and a rotary tool 21 is rotatably supported at a lower end portion by a bearing 22c. The rotary tool 21 is connected to the lower end of the rotary shaft 22b of the motor 22a so as to be integrally rotatable. The rotary tool 21 has a central pin 21b protruding from the center of the tip of the tool body 21a, and is formed of a metal material that is harder and more rigid than the material to be joined.
[0039]
By controlling the air cylinder 23a and controlling the amount of movement of the piston rod 23b, the amount of protrusion of the rotary tool 21 with respect to the material to be joined may be controlled, but in order to control the amount of protrusion more precisely, FIG. As shown in FIGS. 8 (a) and 8 (b), a control device 80 using a servo motor 81 and a load cell 83 may be employed instead of the air cylinder 23a.
[0040]
The servo motor 81 moves the bonding head 2 downward. The joining head 2 is slidably attached to the L-shaped bracket 82 in the vertical direction, and a load cell 83 is interposed between the bracket 82 and the joining head 2. Then, the reaction force from the tip rotary tool 21 is measured by the load cell 83 during the joining operation, and the reaction force value set in advance by the controller 84 and a comparator (not shown) as shown in FIG. 8B. In comparison, the rotation amount of the servo motor 81 is controlled via the CPU 85. The controller 84 can arbitrarily set an optimal pressing force of the rotary tool 21. Reference numeral 81a in the figure denotes a screw shaft, and reference numeral 81b denotes a nut.
[0041]
FIG. 9 shows another embodiment of the thrust amount control device for the rotary tool 21. In this example, a control device 80 ′ that measures and controls the amount of protrusion of the rotary tool 21 with respect to the material to be joined by the distance sensor 86 is provided. Further, a presser roller 87 is attached in advance of the distance sensor 86 so that the overlapped materials to be joined do not float. Therefore, the distance sensor 86 is attached to the rotary tool 21, the distance between the rotary tool 21 and the material to be joined is measured, compared with the distance set in advance by the controller 88 using a comparator, and the deviation is detected by the CPU 89 by the servo motor 81. To control. Distance information such as a measured value by the distance sensor 86 is fed back to the CPU 89.
[0042]
Next, the spot bonding operation will be described in more detail with reference to FIGS. The portal frame 1 has a horizontal frame portion 11 and a vertical frame portion 12, and a traveling portion 13 having wheels 14 on the front and rear is disposed. Rails 3 are laid parallel to the longitudinal direction on floors B on both sides of the surface plate 6. As the wheel 14 rolls on the rail 3, the portal frame 1 travels (moves horizontally) in the longitudinal direction. The traveling unit 13 includes a traveling drive motor 13a and a brake 13b.
[0043]
Guide rails 16 and 17 are laid in the horizontal direction on the upper surface of the horizontal frame portion 11, the guide base 25 is along the guide rails 16 and 17, and the ball screw shaft 18 is vertically below both sides of the horizontal frame portion 11. It extends over the frame portion 12. A nut portion 18c is screwed onto the ball screw shaft 18, and the nut portion 18c is moved at a predetermined angle in both forward and reverse directions via an endless belt 18b by a servo motor 18a mounted on each guide base 25. It is configured to rotate and stop. The guide base 25 is moved laterally to an arbitrary position by rotating a nut portion 18c screwed to the ball screw shaft 18 in a predetermined direction by a servo motor 18a.
[0044]
Then, by rotating the worm 24e clockwise and counterclockwise by the servomotor 24a, the worm wheel 24f meshing with the worm 24e rotates integrally with the pivot shaft 24g, and the joining head 2 mounted on the mounting plate 25b pivots. It turns around the central axis of the support shaft 24g and is set at an angle corresponding to the joint located on the curved surface of the material to be joined. FIG. 7 shows that the joining head 2 is tilted about the pivot shaft 24g as a rotation center.
[0045]
The spot welding head 2 shown in FIG. 4 is movable in the lateral direction (Y direction) by each servo motor 18a, and is driven via a screw shaft 15a and a nut 15b by a servo motor 15 installed at the upper end of the guide base 25. Thus, it can freely move up and down (Z direction). Further, the joining head 2 is configured to be tiltable by a servo motor 24a and to be vertically moved by an air cylinder 23a or a servo motor 81.
[0046]
Therefore, first, the servo motor 18a is positioned in the lateral direction, and the servo motor 15 is generally positioned in the vertical direction. Thereafter, the joining head 2 adjusted to the inclination corresponding to the curved portion of the material to be joined by the servo motor 24 a is pushed down by the air cylinder 23 a or the servo motor 81, and the rotary tool 21 attached to the tip of the joining head 2. Is pressed against the material to be joined to cause spot joining.
[0047]
When the spot joining operation is completed at a predetermined position, each joining head 2 is raised by the air cylinder 23a or the servo motor 81 and separated from the materials to be joined. Then, the portal frame 1 is moved to the next spot joining position. Alternatively, the material to be joined on the surface plate is moved in the horizontal direction by the moving means 7. This operation is repeated to perform spot bonding at all predetermined positions in the longitudinal direction of the materials to be bonded.
[0048]
By the way, in general, in friction stir spot welding, the plate thickness of the material to be joined on the entry side (upper side) of the rotary tool (spot welding tool) tends to be thinned by the joining, and the strength of the part tends to decrease. Therefore, in order to eliminate such a decrease in strength, regardless of the shape of the rotary tool, by increasing the thickness of the material to be joined on the entry side of the rotary tool from the beginning, a predetermined plate thickness after joining is obtained. Can be gripped.
[0049]
As shown in FIG. 10, the upper side plate material P1 on the entry side of the rotary tool 21 forms a thick portion P1a having a thicker thickness than the other portions at the joining portion, and does not become thinner than the surrounding plate thickness even after spot joining. It can be constituted as follows. FIG. 11 is an example in which an upper bonded material 92 (structural plate material) is bonded to a lower bonded material 91 (structural plate material), and a bonded portion of the bonded material 92 on the side into which the rotary tool 21 enters. As shown in FIG. 11 (a), the junction 92A may be thickened from the beginning, as shown in FIG. 11 (b), and as shown in FIG. 11 (b), a long strip-shaped thick portion 92B along the junction is formed. May be. Further, as shown in FIG. 11 (c), a cylindrical thick-walled portion 92C may be formed independently at each joint portion.
[0050]
In this way, a structure having a curved surface portion can be continuously manufactured by spot bonding, and a spot bonding system can be obtained that can manufacture low-power, no consumables, and a beautiful product on the outer surface. Vehicle bodies such as automobiles and trains, aircraft exterior materials, and the like can be automatically produced.
[0051]
In the above embodiment, the portal frame and the material to be joined are configured to move in the feeding direction (X direction). However, depending on the purpose, it may be configured to move only one of them. . That is, the means for moving the portal frame or the means for moving the material to be joined can be omitted.
[0052]
【The invention's effect】
According to the first aspect of the present invention, a surface plate on which a plurality of superposed materials to be joined are placed, a gate-type frame disposed so as to straddle the surface plate, and the gate-type frame are attached. Since it is configured to include a spot bonding head, a moving means for moving the material to be bonded in a predetermined feeding direction, and a mounting table for guiding the material to be bonded on both the inlet side and the outlet side of the surface plate, Spot welding can be performed on the surface plate with high accuracy by the spot welding head that is stably supported by the portal frame while the workpiece is moved by the means.
[0053]
According to invention of Claim 2, since the said to-be-joined material is a board | plate material which has a curved-surface-shaped part, and since the said surface plate and mounting base have a curved-surface-shaped part corresponding to the curved-shaped part of a to-be-joined material, it is a curved surface. Plate-shaped portions having spot-shaped portions can be spot-bonded. Accordingly, it is possible to perform friction stir spot welding of a plate material such as an exterior material having a curved portion.
[0054]
According to the invention of claim 3, the spot bonding head is configured to be traversable and tiltable in a direction orthogonal to the feeding direction of the materials to be bonded, and to be vertically movable, and the portal frame is Since the material to be joined is movable in the feeding direction, the material to be joined can be moved by the moving means, and the spot joining head itself can be moved by the movement of the portal frame, and the movement range of the portal frame However, the present invention is not limited to this, and it is possible to perform spot bonding from a short length to a long length of the bonded material.
[0055]
According to the invention of claim 4, since the moving means is a moving means that grips an end portion of the material to be joined placed on the surface plate or the mounting table and performs a feeding operation at a predetermined pitch. When moving or joining, the material to be joined can be firmly held. Moreover, since a predetermined pitch feed is possible, it is possible to correctly perform spot welding at a predetermined position at a predetermined pitch interval.
[0056]
According to the invention of claim 5, the spot joining head is configured to be traversable and tiltable in a direction perpendicular to the feeding direction of the materials to be joined, and to be vertically movable, and the portal frame is Since the fixed structure is adopted, it is possible to move the material to be joined on the surface plate by the moving means even when the portal frame is fixed. Become.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an entire spot joining system according to the present invention.
FIG. 2 is a plan view showing the entirety of a spot bonding system according to the present invention.
FIG. 3 is a side view showing the entire spot bonding system according to the present invention.
FIG. 4 is a front view showing the entire spot bonding system according to the present invention.
FIG. 5 is an enlarged perspective view showing a moving means.
FIG. 6 is an enlarged side view of a spot bonding head.
FIG. 7 is an enlarged front view of a spot bonding head.
FIGS. 8A and 8B show an embodiment of a spot joining head thrust amount control device, where FIG. 8A is a side view showing a main part, and FIG. 8B is a block diagram showing a control flow;
FIGS. 9A and 9B show another embodiment of the spot welding head thrust amount control device, FIG. 9A is a side view showing the main part, and FIG. 9B is a block diagram showing the flow of control. FIGS.
FIG. 10 is an explanatory diagram of an embodiment for maintaining the thickness of a joining portion.
FIGS. 11A, 11B, and 11C are explanatory views of an embodiment in which the thickness is not thinner than the surrounding plate thickness even after spot bonding. FIGS.
FIG. 12 is an overall perspective view of a conventional friction stir welding apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Portal frame 2 Spot joining head 3 Rail 4 Inlet side mounting base 5 Outlet side mounting base 6 Surface plate 7 Moving means 73 Holding member 15 Servo motor 21 Rotating tool 41 Rolling wheel P1 Upper plate | board material (to-be-joined material)
P2 Lower plate material (material to be joined)

Claims (5)

A spot joining system for spot joining by overlapping a plurality of materials to be joined,
A surface plate on which the material to be joined is placed;
A portal frame arranged to straddle the surface plate;
A spot joining head that is attached to the portal frame and that frictionally stir spot-joins the materials to be joined placed on the surface plate;
Moving means for moving the material to be joined in a predetermined feeding direction;
A spot bonding system comprising: a mounting table for guiding the material to be bonded on both the inlet side and the outlet side of the surface plate. The bonded material is a plate material having a curved portion,
The spot bonding system according to claim 1, wherein the surface plate and the mounting table have a curved support portion corresponding to the curved portion of the material to be joined. The spot bonding head is traversable and tiltable in a direction orthogonal to the feeding direction of the materials to be bonded, and is configured to be vertically movable.
The spot joining system according to claim 1, wherein the portal frame is movable in a feeding direction of the material to be joined.   The said moving means grips the edge part of the to-be-joined material mounted in the said surface plate or a mounting base, and performs the feed operation | movement of a predetermined pitch, Any one of Claims 1-3 characterized by the above-mentioned. Spot bonding system. A spot joining system for spot joining by overlapping a plurality of materials to be joined having a curved portion,
A platen having a curved support portion corresponding to the curved portion of the material to be joined, on which the material to be joined is placed,
A portal frame arranged to straddle the surface plate;
A spot joining head that is attached to the portal frame and that performs friction stir spot joining of the workpieces placed on the surface plate;
Moving means for moving the material to be joined in a predetermined feeding direction;
A mounting table that guides the material to be bonded on both the inlet side and the outlet side of the surface plate, having a curved support portion corresponding to the curved portion of the material to be bonded;
The spot joining head is traversable and tiltable in a direction perpendicular to the feeding direction of the materials to be joined, and is configured to be vertically movable, while the portal frame is fixed at a fixed position. A spot bonding system characterized by that.

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