CN113084331A - Friction stir welding equipment and using method - Google Patents

Abstract

A friction stir welding device and a using method thereof are characterized in that the friction stir welding device comprises a lifting mechanism, a side arm, a first moving mechanism, a workpiece placing table, a workpiece placing mechanism and a second moving mechanism; the supporting part comprises a side arm and a lifting mechanism, the side part of the side arm is provided with the lifting mechanism, and the bottom of the lifting mechanism is provided with a stirring head through a fixed chuck; the workpiece placing mechanism comprises a clamping mechanism, a vacuum chuck, a workpiece placing table, a first screw rod, a second screw rod, a base, a servo motor and a vacuum pump; according to the invention, the workpiece can be sucked tightly and pre-positioned through the vacuum chuck, and then the corner cylinder is used for compressing and limiting, so that the fixing effect of the workpiece can be effectively improved through a double-limiting mode, the welding precision of the workpiece is ensured, and the corresponding corner cylinder is selected for clamping, so that the clamp has a wider and more flexible application range.

Description

Friction stir welding equipment and using method

Technical Field

The invention relates to a welding technology, in particular to a friction stir welding technology, and specifically relates to friction stir welding equipment and a use method thereof.

Background

Friction stir welding is characterized in that a welded material is partially plasticized by heat generated by friction between a stirring head rotating at a high speed and a workpiece, and when the stirring head moves forwards along a welding interface, the plasticized material flows from the front part to the rear part of the stirring head under the action of the rotating friction force of the stirring head and forms a compact solid-phase welding seam under the extrusion of the stirring head.

The welding equipment at present is when placing the work piece, and the processing bench is arranged in earlier with the work piece, then adjusts the position of each anchor clamps and carry out spacingly to the work piece, and only single centre gripping mode is spacing for the spacing effect of work piece is not good, probably shifts in the welding, influences the welding precision, and the structure of centre gripping is relatively fixed, can't be suitable for the work piece of different shapes.

Disclosure of Invention

The invention aims to design a friction stir welding device with good clamping limiting effect and accurate welding line aiming at the problems of difficult clamping and low efficiency caused by the lack of corresponding complete equipment in the existing friction stir welding, and simultaneously provides the friction stir welding device with convenient use.

One of the technical schemes of the invention is as follows:

a friction stir welding apparatus characterized by: comprises a supporting part and a workpiece placing mechanism 8; the supporting part comprises a side arm 2 and a lifting mechanism 1, the lifting mechanism 1 is installed on the side part of the side arm 2, a fixed chuck 5 is installed on the lifting mechanism 1, and a stirring head 51, a first laser 6 and a second laser 7 are installed on the fixed chuck 5; the lifting mechanism 1 comprises a first slide rail 11 and a first slide block 12, the first slide rail 11 is mounted on the side part of the side arm 2, and the first slide block 12 is slidably mounted on the first slide rail 11; the fixed chuck 5 is arranged on the first slide rail 11, and the first slide rail 11 is driven to move up and down through a servo motor and a screw nut structure; the workpiece placing mechanism 8 comprises a clamping mechanism 81, a vacuum chuck 82, a workpiece placing table 83, a first screw 84, a second screw 85, a base 86, a servo motor 87 and a vacuum pump 88, wherein the first screw 84 is rotatably connected inside the base 86, and the first screw 84 is meshed with the second screw 85; the second screw 85 is connected with a servo motor 87, the top end of the first screw 84 is fixed with a workpiece placing table 83, and a vacuum pump 88 is arranged in the workpiece placing table 83; the vacuum pump 88 is connected with the vacuum chuck 82, and the vacuum chuck 82 is arranged at the top of the workpiece placing table 83; a plurality of clamping mechanisms 81 are distributed on the outer side of the vacuum chuck 82; the clamping mechanism 81 comprises a pressing head 811, a mounting block 812 and an angle cylinder 813, wherein the angle cylinder 813 is vertically fixed on the top surface of the workpiece placing table 83, and the mounting block 812 is arranged at the top end of the angle cylinder 813; a pressing head 811 is fixed to the bottom of one end of the mounting block 812; the workpiece placing mechanism 8 is positioned at the lower part of the stirring head 51; the lower side part of the side arm 2 is provided with a first moving mechanism 3 and a second moving mechanism 9 which drive the workpiece placing mechanism 8 to move longitudinally and transversely in a horizontal plane, the first moving mechanism 3 comprises a second slide rail 31, a second slide block 32 and a fixed block 33, the fixed block 33 is fixed at the lower side part of the side arm 2, and the top of the fixed block 33 is provided with the second slide rail 31; the second slide rail 31 is connected with a second slide block 32 in a sliding manner, a second moving mechanism 9 is arranged at the top of the second slide block 32, the second moving mechanism 9 comprises a third slide rail 91 and a third slide block 92, the third slide rail 91 is fixed at the top of the second slide block 32, the third slide rail 91 is connected with the third slide block 92 in a sliding manner, and the workpiece placing mechanism 8 is installed on the third slide block 92; the second slider 32 and the third slider 92 are driven by respective servo motors and lead screw-nut mechanisms.

The vacuum chuck 82 protrudes from the top center of the workpiece placing table 83, and the vacuum chuck 82 has a rectangular structure.

The first moving mechanism 3 and the second moving mechanism 9 are distributed in a cross shape.

The first laser 6 and the second laser 7 are respectively installed on two sides of the fixed chuck 5, and the installation heights of the first laser 6 and the second laser 7 are the same.

The first laser 6, the second laser 7 and the control host 9a form a welding seam control system; each scanning line has not less than 500 measuring points to ensure the measuring precision and the identification accuracy of the welding seam characteristics; the first laser 6 and the second laser 7 are adopted in the height direction, the lasers have three-dimensional measurement capability, can measure and calculate deviation of a spatial three-dimensional object in real time, are connected with the control host machine 9a, and simultaneously, the control host machine 9a is in direct communication with the numerical control PLC, so that position errors in the welding process are always compensated; in the aspect of repeated positioning accuracy of the laser, the height direction is 0.5 mu m, the xz plane is 5 mu m, the distance between each data point is 20 mu m, the sampling frequency is 50-200 Hz and can be adjusted, matching is carried out according to the actual processing speed, the distance between the laser and a workpiece is 75 +/-10 mm, the used laser is a blue laser, and the shell protection grade is IP 67.

The vacuum degree of the vacuum chuck 82 is not lower than-75 kPa, the suction force per unit square centimeter is not less than 1kg, a boss with the length of 1cm multiplied by 1cm and a groove with the width of 3mm are arranged on the upper surface of the vacuum chuck 82 and used for laying sealing strips, and the laying of the sealing strips needs to avoid the hollow area of the workpiece, is consistent with the outer contour of the workpiece and retracts inwards by not less than 5 mm.

The number of the corner cylinders 813 is 6, and the corner cylinders are distributed in a rectangular shape, wherein 4 of the corner cylinders are symmetrically arranged at two long sides of the rectangular shape in pairs, and the other two corner cylinders are symmetrically arranged at two short sides of the rectangular shape; the corner cylinder 813 has a 90-degree rotation pressing function, a single cylinder has a pressing force of more than 40kg and can automatically rotate by 90 degrees to avoid a workpiece, a piston body of the cylinder is provided with a magnetic ring, a cylinder body is provided with a magnetic switch installation groove for installing a magnetic switch and detecting the real-time state of the corner cylinder 813, and meanwhile, the electromagnetic switch of the corner cylinder 813 is controlled by the control host 9a in real time.

The second technical scheme of the invention is as follows:

a welding method based on friction stir welding equipment is characterized in that:

the host sends a start;

the host sends a command to start searching for the weld joint, and at the moment, the movement mechanism needs to move in the x, y or z direction, and in order to prevent accidents, the movement mechanism needs to be limited;

the host sends a found welding line, the moving mechanism starts to move in the z direction at the moment, the z-direction position is positioned at the same time, and the moving mechanism needs to adjust the x-direction position and the y-direction position in real time according to the data in the x direction and the y direction;

the host sends the completion of the pre-scanning, at the moment, the movement mechanism stops moving in the z direction, and the movement mechanism waits for the completion of the adjustment of the x-direction position and the y-direction position according to the data in the x direction and the y direction;

after the position adjustment in the x direction and the y direction is finished, the stirring head rotates, the moving mechanism starts to move in the z direction, and the moving mechanism adjusts the position in the x direction and the y direction in real time according to the data in the x direction and the y direction;

when the host computer cannot search the welding seam or reaches the set welding length, the host computer sends reset;

and after the slave computer receives the reset command, stopping welding, moving the motion mechanism to the initial position and resetting all data.

The invention has the beneficial effects that:

according to the invention, the workpiece can be sucked and pre-positioned through the vacuum chuck, and then the corner cylinder is used for compressing and limiting, so that the fixing effect of the workpiece can be effectively improved through a double-limiting mode, the welding precision of the workpiece is ensured, and the corresponding corner cylinder is selected for clamping according to the shape of the workpiece, so that the clamp has a wider application range and is more flexible.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

FIG. 1 shows an overall structural schematic of an embodiment of the present invention;

FIG. 2 is a schematic cross-sectional view of a workpiece placement mechanism according to an embodiment of the invention;

FIG. 3 is a perspective view of a workpiece placement mechanism according to an embodiment of the invention;

FIG. 4 is a schematic top view of a workpiece placement mechanism according to an embodiment of the invention;

FIG. 5 shows a schematic overall side view of an embodiment of the invention;

fig. 6 shows a schematic diagram of a workpiece placement mechanism, a stirring head, a first laser, and a second laser distribution structure according to an embodiment of the invention.

In the figure: 1. the device comprises a lifting mechanism, 11, a first slide rail, 12, a first slide block, 2, a side arm, 3, a first moving mechanism, 31, a second slide rail, 32, a second slide block, 33, a fixed block, 4, a workpiece placing table, 5, a fixed chuck, 51, a stirring head, 6, a first laser, 7, a second laser, 8, a workpiece placing mechanism, 81, a clamp, 811, a pressure head, 812, a mounting block, 813, an angle cylinder, 82, a vacuum chuck, 83, a workpiece placing table, 84, a first screw, 85, a second screw, 86, a base, 87, a servo motor, 88, a vacuum pump, 9, a second moving mechanism, 91, a third slide rail, 92, a third slide block, 9a and a control host.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The first embodiment.

As shown in fig. 1-6.

A friction stir welding apparatus includes a support portion and a work placing mechanism 8, as shown in FIG. 1; the supporting part comprises a side arm 2 and a lifting mechanism 1, the lifting mechanism 1 is arranged on the side part of the side arm 2, and a stirring head 51 is arranged at the bottom of the lifting mechanism 1 through a fixed chuck 5; the bottom of the side arm 2 is fixed with a workpiece placing table 83, and the side part of the side arm 2 is vertically fixed with a lifting mechanism 1; specifically, the lifting mechanism 1 includes a first slide rail 11 and a first slide block 12, the first slide rail 11 is mounted on the side portion of the side arm 2, and the first slide block 12 is slidably connected to the first slide rail 11; a fixed chuck 5 is fixed on the side part of the first slide rail 11; the stirring head 51 can be driven to move up and down by the lifting mechanism 1. The workpiece placing mechanism 8 comprises a clamping mechanism 81, a vacuum chuck 82, a workpiece placing table 83, a first screw 84, a second screw 85, a base 86, a servo motor 87 and a vacuum pump 88; a first screw 84 is rotatably connected inside the base 86, and the first screw 84 is engaged with a second screw 85; the end part of the second screw rod 85 is connected with a servo motor 87; a workpiece placing table 83 is fixed at the top end of the first screw 84, and a vacuum pump 88 is installed inside the workpiece placing table 83; the vacuum pump 88 is connected with the vacuum chuck 82, and the vacuum chuck 82 is arranged on the top of the workpiece placing table 83; a plurality of clamping mechanisms 81 are distributed on the outer side of the vacuum chuck 82; the clamping mechanism 81 comprises a pressing head 811, a mounting block 812 and an angle cylinder 813, wherein the angle cylinder 813 is vertically fixed on the top surface of the workpiece placing table 83, and the mounting block 812 is arranged at the top end of the angle cylinder 813; a pressing head 811 is fixed to the bottom of one end of the mounting block 812; the workpiece placing mechanism 8 is specifically positioned at the bottom of the stirring head 51, the vacuum chuck 82 protrudes outwards from the center of the top of the workpiece placing table 83, and the vacuum chuck 82 is of a rectangular structure; the workpiece placing mechanism 8 can rotate to move up and down, so that the workpiece is pressed tightly, and the workpiece can be pre-positioned through the sucking disc. A first moving mechanism 3 is arranged on the side part of the side arm 2, the first moving mechanism 3 comprises a second slide rail 31, a second slide block 32 and a fixed block 33, the fixed block 33 is fixed on the side part of the side arm 2, and the second slide rail 31 is arranged at the top of the fixed block 33; the second slide rail 31 is connected with a second slide block 32 in a sliding manner; the top of the second slide block 32 is provided with a second moving mechanism 9, the second moving mechanism 9 comprises a third slide rail 91 and a third slide block 92, the top of the second slide block 32 is fixed with the third slide rail 91, and the third slide rail 91 is slidably connected with the third slide block 92; the first moving mechanism 3 and the second moving mechanism 9 are distributed in a cross shape, and the workpiece placing mechanism 8 is fixed on the top surface of the third sliding block 92; the first moving mechanism 3 and the second moving mechanism 9 can drive the workpiece to move horizontally and vertically. A first laser 6 and a second laser 7 are respectively arranged on two sides of the fixed chuck 5, and the first laser 6 and the second laser 7 are the same in height; the first laser 6 and the second laser 7 can scan the welding seam, and the welding precision is ensured. As shown in fig. 1, the first laser 6, the second laser 7 and the control host 9a form a weld seam control system; each scanning line has not less than 500 measuring points to ensure the measuring precision and the identification accuracy of the welding seam characteristics; the first laser 6 and the second laser 7 are adopted in the height direction, the lasers have three-dimensional measurement capability, can measure and calculate deviation of a spatial three-dimensional object in real time, are connected with the control host machine 9a, and meanwhile, the control host machine 9a can be directly communicated with the numerical control PLC to always compensate position errors in the welding process; in the aspect of repeated positioning accuracy of the laser, the height direction is 0.5 mu m, the xz plane is 5 mu m, the distance between each data point is 20 mu m, the sampling frequency is 50-200 Hz and can be adjusted, matching is carried out according to the actual processing speed, the distance between the laser and a workpiece is 75 +/-10 mm, the used laser is a blue laser and has higher accuracy, and the protection grade of a shell is IP 67; in consideration of the problem of actual welding, the cross of a plurality of welding seams does not occur, the problem is avoided as much as possible, a process database is added in the setting of software, and the software automatically carries out comparison, classification, identification and selection according to the characteristic form.

The welding working process comprises the following steps: the welding seam tracking sensor is used as a host, and the movement mechanism is used as a slave; the laser line surface of the welding seam tracking sensor is on the xoy plane, the welding seam is vertical to the z axis, and the welding direction is the positive direction of the z axis; the host sends a start; the host computer sends and begins to search for the weld joint, the movement mechanism needs to act in the x or y direction at this moment (in order to prevent the accident from happening, the movement mechanism continues to limit); the host sends a found welding line, the moving mechanism starts to move in the z direction at the moment, height information in the z direction is searched at the same time, and the moving mechanism needs to adjust the positions in the x direction and the y direction in real time according to data in the x direction and the y direction; the host sends the completion of the pre-scanning, at the moment, the movement mechanism stops moving in the z direction, and the movement mechanism waits for the completion of the adjustment of the x-direction position and the y-direction position according to the data in the x direction and the y direction; after the position adjustment in the x direction and the y direction is finished, the stirring head rotates, the moving mechanism starts to move in the z direction, and the moving mechanism adjusts the position in the x direction and the y direction in real time according to the data in the x direction and the y direction; when the host computer cannot search the welding seam or reaches the set welding length, the host computer sends reset; and after the slave computer receives the reset command, stopping welding, moving the motion mechanism to the initial position and resetting all data.

The welding seam position tracking process comprises the following steps: the welding seam position tracking process comprises the following steps: 1. the motion mechanism enables the welding gun to trigger a scanning starting signal at the midpoint (approximate position) of a certain edge of the welding frame, the industrial personal computer triggers the laser profile sensor to start scanning after receiving the scanning starting signal, and the scanning software analyzes the scanned profile in real time and extracts welding spot data; when the welding frame finishes the first preposed distance, the scanning software triggers a welding starting signal to the PLC to start welding; the movement of an x-direction motor, a z-direction motor, a y-direction motor and a rotating motor is adjusted in real time through the data of the front distance section and the data of each motor in the welding process; and when the scanning software cannot detect the welding point, the scanning software finishes sending the data of the preposed distance section and triggers a scanning finishing signal, and the PLC stops welding after receiving the scanning finishing signal and finishes welding.

As shown in figures 2 and 3, the workpiece fixture is combined by a clamping mechanism 81 and a vacuum chuck 82, the vacuum chuck 82 and a vacuum pump 88 form a negative vacuum fixture, the vacuum degree is not lower than-75 kPa, the suction force per unit square centimeter is 1kg, the upper surface of the vacuum chuck 82 is provided with a boss with the length of 1cm multiplied by 1cm and a groove with the width of 3mm for laying sealing strips, the laying of the sealing strips is to avoid the hollow area of the workpiece and is consistent with the outer contour of the workpiece as much as possible and is preferably retracted inwards by 5mm, the vacuum pump 88 is a high-power vacuum generation retainer, and when the vacuum degree is lower than-65 KPa, the use is stopped to check the problem of pipeline air leakage.

As shown in fig. 4, the corner cylinders 813 are provided with 6 in total and are distributed in a rectangular shape, wherein 4 cylinders are symmetrically arranged two by two at two long sides of the rectangular shape, and the other two cylinders are symmetrically arranged at two short sides of the rectangular shape; the corner cylinder 813 has a 90-degree rotating pressing function, the cylinder has 40kg of pressing force singly and can rotate 90 degrees automatically to avoid a workpiece, a piston body of the cylinder is provided with a magnetic ring, a cylinder body is provided with a magnetic switch mounting groove for mounting a magnetic switch, the real-time state of the corner cylinder 813 is detected, and meanwhile, the electromagnetic switch of the corner cylinder 813 is controlled by the control host 9a in real time to control starting and stopping.

As shown in fig. 2 and 3, a base 86 is placed on the xy plane, the base 86 can drive the whole fixture and the workpiece to rotate freely by 360 degrees to adapt to the problem of a process inclination angle, wherein a servo motor 87 is used as power, and the precision is high; because the base 86 is used as a technological requirement, the laying problem of the clamp and the pipeline is considered, in order to prevent the winding of the lead and the pneumatic pipeline in the rotation process, a 24-circuit 2-circuit pneumatic slip ring is arranged, the slip ring is divided into an upper part and a lower part which are respectively provided with a 24-circuit 2A lead and a 2-circuit 8mm air pipe connector, the upper part and the lower part can rotate relatively, the conduction of the pipeline is not influenced, and the damage of the pipeline is avoided.

Example two.

A welding method based on friction stir welding equipment comprises the following steps:

the host computer sends and begins;

secondly, the host sends a start of searching for the welding seam, at the moment, the movement mechanism needs to move in the x, y or z direction, and in order to prevent accidents, the movement mechanism needs to be limited;

the host sends a found welding seam, the moving mechanism starts to move in the z direction at the moment, the z-direction position is positioned at the same time, and the moving mechanism adjusts the x-direction position and the y-direction position in real time according to the data in the x direction and the y direction;

the host sends the pre-scanning completion, at this time, the movement mechanism stops moving in the z direction, and the movement mechanism waits for completing the position of the x direction and the y direction according to the data adjustment of the x direction and the y direction;

after the position adjustment in the x direction and the y direction is finished, the stirring head rotates, the moving mechanism starts to move in the z direction, and the moving mechanism adjusts the position in the x direction and the position in the y direction in real time according to the data in the x direction and the y direction;

when the host cannot search the welding seam or reaches the set welding length, the host sends reset;

and seventhly, after the slave computer receives the reset command, stopping welding, moving the motion mechanism to the initial position and resetting all data.

The working principle of the invention is as follows:

in the using process, a workpiece is placed at the top of the vacuum chuck 82, and then the vacuum pump 88 pumps out air at the position of the vacuum chuck 82, so that the position of the vacuum chuck 82 is in a negative vacuum state, and the workpiece is tightly sucked;

according to the size and shape of a workpiece, a corresponding working cylinder can be selected, cylinder parameters are preset, then the corner cylinder 813 receives an instruction sent by the control host machine 9a to act, the corner cylinder 813 receiving the instruction works simultaneously to press and limit the workpiece area at the bottom of the corner cylinder 813, the corner cylinder 813 rotates 90 degrees to the top of the workpiece, then the corner cylinder 813 drives the mounting block 812 to move downwards, the workpiece can be stopped when the pressing heads 811 are tightly attached to the surfaces of the workpiece, and at the moment, the pressing and limiting of the workpiece can be realized through the pressing heads 811; at this time, the welding preparation can be made;

during processing, the servo motor 87 drives the second screw rod 85 to rotate, so as to drive the first screw rod 84 to rotate, and the first screw rod 84 drives the workpiece placing table 83 to rotate, so as to drive the workpiece to rotate to a position to be processed; then the third slide block 92 slides along the third slide rail 91, the second slide block 32 slides along the second slide rail 31 to realize the adjustment of the horizontal direction and the longitudinal direction of the workpiece, the first slide block 12 moves along the first slide rail 11 to realize the up-and-down movement of the stirring head 51 for welding, and the lifting mechanism 1, the first moving mechanism 3 and the second moving mechanism 9 are mutually matched to realize the automatic welding of all the positions of the workpiece;

first laser instrument 6 and second laser instrument 7 possess and have three-dimensional measuring ability, can carry out real-time measurement and calculation deviation to the three-dimensional object in space, are connected with the industrial computer, but control host 9a and numerical control PLC direct communication simultaneously compensate the position error among the welding process all the time, guarantee that the welding seam is more accurate.

The electrical components are all externally connected with a matching circuit:

the lasers are all laser profile sensors, and adopt LM6-0018 model manufactured by Shanghai lunar step electronics technology Limited, and the supporting circuit thereof can be provided by manufacturers.

The control host adopts TSNC-S3MB model produced by Tianjin Thiessen numerical control, and the matching circuit can be provided by manufacturers.

The vacuum pump is a vacuum generation retainer, and is D180-110 model manufactured by Dongguan power suction cup manufacturing company Limited, and a matching circuit of the vacuum pump can be provided by a manufacturer.

The corner cylinder is of the type MKB25 × 30L manufactured by jeardson ltd, and its supporting circuit can be provided by the manufacturer.

The magnetic switch is of a CS1-U type manufactured by Jenned Limited, and a supporting circuit of the magnetic switch can be provided by manufacturers.

The servo motor is 80SFM-E04030 produced by Tianjin Thiessen numerical control, and a matching circuit thereof can be provided by a manufacturer.

Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

The present invention is not concerned with parts which are the same as or can be implemented using prior art techniques.

Claims (8)

1. A friction stir welding apparatus characterized by: comprises a supporting part and a workpiece placing mechanism (8); the supporting part comprises a side arm (2) and a lifting mechanism (1), the lifting mechanism (1) is installed on the side part of the side arm (2), a fixed chuck (5) is installed on the lifting mechanism (1), and a stirring head (51), a first laser (6) and a second laser (7) are installed on the fixed chuck (5); the lifting mechanism (1) comprises a first sliding rail (11) and a first sliding block (12), the first sliding rail (11) is mounted on the side portion of the side arm (2), and the first sliding block (12) is mounted on the first sliding rail (11) in a sliding mode; the fixed chuck (5) is arranged on the first slide rail (11), and the first slide rail (11) is driven to move up and down through a servo motor and a screw nut structure; the workpiece placing mechanism (8) comprises a clamping mechanism (81), a vacuum chuck (82), a workpiece placing table (83), a first screw (84), a second screw (85), a base (86), a servo motor (87) and a vacuum pump (88), wherein the first screw (84) is rotatably connected inside the base (86), and the first screw (84) is meshed with the second screw (85); the second screw rod (85) is connected with a servo motor (87), the top end of the first screw rod (84) is fixed with a workpiece placing table (83), and a vacuum pump (88) is installed inside the workpiece placing table (83); the vacuum pump (88) is connected with the vacuum sucker (82), and the vacuum sucker (82) is installed at the top of the workpiece placing table (83); a plurality of clamping mechanisms (81) are distributed on the outer side of the vacuum chuck (82); the clamping mechanism (81) comprises a pressure head (811), a mounting block (812) and a corner cylinder (813), the corner cylinder (813) is vertically fixed on the top surface of the workpiece placing table (83), and the top end of the corner cylinder (813) is provided with the mounting block (812); a pressing head (811) is fixed at the bottom of one end of the mounting block (812); the workpiece placing mechanism (8) is positioned at the lower part of the stirring head (51); a first moving mechanism (3) and a second moving mechanism (9) which drive the workpiece placing mechanism (8) to move longitudinally and transversely in a horizontal plane are arranged at the lower side part of the side arm (2), the first moving mechanism (3) comprises a second slide rail (31), a second slide block (32) and a fixed block (33), the fixed block (33) is fixed at the lower side part of the side arm (2), and the second slide rail (31) is arranged at the top of the fixed block (33); the second slide rail (31) is connected with a second slide block (32) in a sliding manner, a second moving mechanism (9) is arranged at the top of the second slide block (32), the second moving mechanism (9) comprises a third slide rail (91) and a third slide block (92), the third slide rail (91) is fixed at the top of the second slide block (32), the third slide rail (91) is connected with the third slide block (92) in a sliding manner, and the workpiece placing mechanism (8) is installed on the third slide block (92); the second slider (32) and the third slider (92) are driven by respective servo motors and lead screw and nut mechanisms.

2. The friction stir welding apparatus of claim 1 wherein: the vacuum chuck (82) protrudes outwards from the center of the top of the workpiece placing table (83), and the vacuum chuck (82) is of a rectangular structure.

3. The friction stir welding apparatus of claim 1 wherein: the first moving mechanism (3) and the second moving mechanism (9) are distributed in a cross shape.

4. The friction stir welding apparatus of claim 1 wherein: the first laser (6) and the second laser (7) are respectively installed on two sides of the fixed chuck (5), and the installation heights of the first laser (6) and the second laser (7) are the same.

5. The friction stir welding apparatus of claim 1 wherein: the first laser (6), the second laser (7) and the control host (9 a) form a welding seam control system; each scanning line has not less than 500 measuring points to ensure the measuring precision and the identification accuracy of the welding seam characteristics; a first laser (6) and a second laser (7) are adopted in the height direction, the lasers have three-dimensional measurement capability, can measure and calculate deviation of a spatial three-dimensional object in real time, are connected with a control host (9 a), and simultaneously, the control host (9 a) is in direct communication with a numerical control PLC (programmable logic controller) to always compensate position errors in the welding process; in the aspect of repeated positioning accuracy of the laser, the height direction is 0.5 mu m, the xz plane is 5 mu m, the distance between each data point is 20 mu m, the sampling frequency is 50-200 Hz and can be adjusted, matching is carried out according to the actual processing speed, the distance between the laser and a workpiece is 75 +/-10 mm, the used laser is a blue laser, and the shell protection grade is IP 67.

6. The friction stir welding apparatus of claim 1 wherein: the vacuum degree of the vacuum chuck (82) is not lower than-75 kPa, the suction force per unit square centimeter is not less than 1kg, a boss with the length of 1cm multiplied by 1cm is arranged on the upper surface of the vacuum chuck (82), a groove with the width of 3mm is arranged for laying a sealing strip, the laying of the sealing strip is to avoid the hollow area of the workpiece, is consistent with the outer contour of the workpiece, and is retracted inwards by not less than 5 mm.

7. The friction stir welding apparatus of claim 1 wherein: the corner cylinders (813) are provided with 6 in total and are distributed in a rectangular shape, wherein 4 cylinders are symmetrically arranged at two long sides of the rectangular shape in pairs, and the other two cylinders are symmetrically arranged at two short sides of the rectangular shape; the corner cylinder (813) has a 90-degree rotating and pressing function, the cylinder has a pressing force of more than 40kg singly and can rotate 90 degrees automatically to avoid a workpiece, the cylinder piston body is provided with a magnetic ring, the cylinder body is provided with a magnetic switch mounting groove for mounting a magnetic switch and detecting the real-time state of the corner cylinder (813), and meanwhile, the electromagnetic switch of the corner cylinder (813) is controlled by the control host machine 9a in real time.

8. A welding method based on the friction stir welding apparatus according to claim 1, characterized in that:

the host sends a start;

the host sends a command to start searching for the weld joint, and at the moment, the movement mechanism needs to move in the x, y or z direction, and in order to prevent accidents, the movement mechanism needs to be limited;

the host sends a found welding line, the moving mechanism starts to move in the z direction at the moment, the z-direction position is positioned at the same time, and the moving mechanism needs to adjust the x-direction position and the y-direction position in real time according to the data in the x direction and the y direction;

the host sends the completion of the pre-scanning, at the moment, the movement mechanism stops moving in the z direction, and the movement mechanism waits for the completion of the adjustment of the x-direction position and the y-direction position according to the data in the x direction and the y direction;

after the position adjustment in the x direction and the y direction is finished, the stirring head rotates, the moving mechanism starts to move in the z direction, and the moving mechanism adjusts the position in the x direction and the y direction in real time according to the data in the x direction and the y direction;

when the host computer cannot search the welding seam or reaches the set welding length, the host computer sends reset;

and after the slave computer receives the reset command, stopping welding, moving the motion mechanism to the initial position and resetting all data.

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