A dynamic gantry-type shell friction stir welding equipment with automatic positioning, detection and clamping

Abstract

The present invention provides a dynamic gantry-type shell stir friction welding device with automatic positioning, detection and clamping, comprising a base, a workbench, a gantry, a longitudinal displacement mechanism, a first lateral displacement mechanism, a first vertical displacement mechanism, a welding mechanism, a clamping and fixing mechanism, and a controller. The gantry column of the present invention is provided with a device capable of realizing workpiece flipping, clamping and lifting functions, so as to realize the function of clamping the shell to be processed and moving it to the workbench, and flipping the shell to be processed to realize multi-faceted processing. The present invention increases the number of independently completed work steps, reduces the use of other machines, reduces production costs, and reduces the area occupied by workstations. The present invention achieves welding area positioning and detection by replacing a three-coordinate measuring head with the welding mechanism through precise control of the displacement of the welding mechanism stirring head, combines the multi-purpose capability of one axis, and installs an industrial camera on the welding mechanism to monitor the surface processing quality of the workpiece from above, making monitoring more intuitive so that the controller can control the welding mechanism to achieve better welding quality, thereby greatly improving welding efficiency.

Description

Technical Field

[0001] The invention belongs to the field of friction stir welding equipment, and relates to a friction welding equipment with automatic positioning and detection quality, and in particular to a dynamic gantry shell friction stir welding equipment with automatic positioning, detection and clamping. Background Art

[0002] With the rapid development of the manufacturing industry, the demand for joining technologies is increasing. As a key joining method, welding is also subject to higher demands in terms of quality and efficiency. Compared to other welding methods, friction stir welding (FSW) utilizes solid-phase welding, offering advantages such as environmental friendliness, low cost, and high weld strength. Since its introduction, various optimization research and design efforts have been conducted both domestically and internationally, and the technology is developing towards high quality, high efficiency, high precision, and multifunctionality. Currently, FSW requires the coordination of other equipment (such as robotic arms) for gripping and flipping, which can easily lead to errors when multiple equipment are used at the same station. Clamping and positioning typically use fixed fixtures, which offer limited flexibility, limited adaptability to workpiece shapes, and inability to guarantee accurate tilting and lifting during clamping. Monitoring cameras are often located to the side, away from the spindle, preventing a clear view of the surface finish from above. Positioning and inspection typically require separate stations, increasing loading and unloading times and compromising accuracy, which is time-consuming and labor-intensive. With the advent of Industry 4.0, there is an urgent need for multifunctional FSW equipment that can serve multiple purposes, reduce costs, and improve efficiency by eliminating the need for additional equipment. Summary of the Invention

[0003] In order to solve the above technical problems, the present invention provides a dynamic gantry-type shell friction stir welding device with automatic positioning, detection and clamping, comprising a base, a workbench, a gantry, a longitudinal displacement mechanism, a first transverse displacement mechanism, a first vertical displacement mechanism, a welding mechanism, a clamping and fixing mechanism and a controller; the workbench is arranged on the base; longitudinal displacement mechanisms are respectively provided on both sides of the base, and the lower ends of the columns on both sides of the gantry are respectively connected to the longitudinal displacement connecting plates of the longitudinal displacement mechanisms; the first transverse displacement mechanism is arranged on the crossbeam at the upper part of the gantry, and the first vertical displacement mechanism is connected to the transverse displacement connecting frame of the first transverse displacement mechanism; the welding mechanism is arranged at the lower end of the first vertical displacement mechanism;

[0004] The lower parts of the uprights on both sides of the gantry are respectively provided with a flip clamping mechanism, and the flip clamping mechanism includes a second vertical displacement mechanism, a sliding connecting frame, a second lateral displacement mechanism, a clamping head, a clamping head rotating shaft, a clamping head connecting seat, and a clamping head driving motor; the second vertical displacement mechanism is arranged at the lower part of the gantry column, and the sliding connecting frame is slidably connected to the second vertical displacement mechanism; the second lateral displacement mechanism is arranged on the upper part of the sliding connecting frame, and the clamping head connecting seat is slidably connected to the second lateral displacement mechanism; the clamping head is arranged at the front end of the clamping head rotating shaft, and the clamping head rotating shaft is pivotally connected to the clamping head connecting seat through a bearing seat; the clamping head driving motor is arranged above the clamping head connecting seat, and the output shaft of the clamping head driving motor and the clamping head rotating shaft are engaged with the gear to drive the clamping head rotating shaft to rotate; the flip clamping mechanisms on both sides of the gantry are arranged relatively;

[0005] The welding mechanism includes a spindle motor, a camera drive motor and an industrial camera. The spindle motor is located at the lower end of the welding mechanism, and the output end of the spindle motor is connected to a three-coordinate measuring head or a stirring head. The camera drive motor is located on the side of the spindle motor, and the industrial camera is connected to the output shaft of the camera drive motor.

[0006] The clamping and fixing mechanisms are arranged on both lateral sides of the workbench;

[0007] The controller is arranged on the base and is respectively connected to the longitudinal displacement mechanism, the first lateral displacement mechanism, the first vertical displacement mechanism, the spindle motor in the welding mechanism, the camera drive motor and the industrial camera, the clamping and fixing mechanism, and the second vertical displacement mechanism, the second lateral displacement mechanism, and the clamping head drive motor in the flip clamping mechanism, and collects and outputs control signals.

[0008] The longitudinal displacement mechanism includes a longitudinal slide rail, a longitudinal drive motor, a longitudinal displacement connecting plate, a grating scale and a grating scale guide rail; the longitudinal slide rail is arranged longitudinally along the base, the longitudinal drive motor is arranged at one end, the output shaft is connected to the longitudinal lead screw, the longitudinal lead screw is parallel to the longitudinal slide rail, and the other end of the longitudinal lead screw is connected to the base through a bearing seat; the longitudinal displacement connecting plate is slidably connected to the longitudinal slide rail through a slider; a longitudinal lead screw nut is provided at the bottom of the longitudinal displacement connecting plate, and the longitudinal lead screw and the longitudinal lead screw nut are connected and cooperated to form a lead screw pair; the grating scale guide rail is arranged parallel to the longitudinal slide rail, the grating scale is fixed to the lower part of the longitudinal displacement connecting plate through the grating scale connecting plate, and one end is connected to the grating scale guide rail;

[0009] The first transverse displacement mechanism includes a first transverse slide rail, a first transverse drive motor, a first transverse lead screw, a transverse displacement connecting frame, and a first transverse lead screw nut. The first transverse slide rail is arranged on the crossbeam on the upper part of the gantry, the first transverse drive motor is arranged at one end of the crossbeam, the output shaft is connected to the first transverse lead screw, the first transverse lead screw is arranged parallel to the first transverse slide rail, and the other end of the first transverse lead screw is connected to the crossbeam of the gantry through a bearing seat; the transverse displacement connecting frame is slidably connected to the first transverse slide rail through a slider; a first transverse lead screw nut is provided at the bottom of the transverse displacement connecting frame, and the first transverse lead screw and the first transverse lead screw nut are connected and cooperated to form a screw pair;

[0010] The first vertical displacement mechanism includes a fixed frame, a first vertical slide rail, a first vertical drive motor, a first vertical lead screw, and a first vertical lead screw nut. The fixed frame is fixed to the side of the lateral displacement connecting frame; the upper end of the first vertical slide rail is connected to the first vertical drive motor, and the lower end is connected to the welding mechanism; the fixed frame is slidably connected to the first vertical slide rail through a slider; the first vertical lead screw nut is fixed in the fixed frame, the output shaft of the first vertical drive motor is connected to the upper end of the first vertical lead screw, and the lower end of the first vertical lead screw passes through the first vertical lead screw nut and is connected to the welding mechanism;

[0011] The longitudinal drive motor, the first transverse drive motor and the first vertical drive motor are respectively connected to the controller and controlled by the controller. The longitudinal displacement mechanism, the first transverse displacement mechanism and the first vertical displacement mechanism are all provided with an accordion cover for dust prevention.

[0012] The second vertical displacement mechanism includes a second vertical slide rail, a second vertical driving motor, a second vertical lead screw, and a second vertical lead screw nut. The second vertical slide rail is provided on both sides of the sliding connecting frame and is fixedly connected to the column of the gantry; the sliding connecting frame is slidably connected to the second vertical slide rail through a slider; the second vertical driving motor is provided on one side of the sliding connecting frame and is fixedly connected to the column of the gantry; the output shaft of the second vertical drive motor is connected to the second vertical lead screw, and the other end of the second vertical lead screw is connected to the sliding connecting frame through a bearing seat; the second vertical lead screw nut is provided on one side of the sliding connecting frame, and the second vertical lead screw and the second vertical lead screw nut are connected and cooperated to form a lead screw pair;

[0013] The second transverse displacement mechanism includes a second transverse slide rail, a second transverse drive motor, a second transverse lead screw, and a second transverse lead screw nut. The second transverse slide rail is arranged at the top of the sliding connection frame, and the clamping head connection seat is slidably connected to the second transverse slide rail through a slider; the second transverse drive motor is fixed to the outer end of the top of the sliding connection frame, the output shaft of the second transverse drive motor is connected to the second transverse lead screw, and the other end of the second transverse lead screw is connected to the sliding connection frame through a bearing seat; the second transverse lead screw nut is arranged at the bottom of the clamping head connection seat, and the second transverse lead screw and the second transverse lead screw nut are connected and cooperated to form a screw pair;

[0014] The second vertical drive motor and the second horizontal drive motor are respectively connected to the controller and controlled by the controller.

[0015] The clamping head is a boss-type clamping head, and a contoured groove is provided on the surface.

[0016] The clamping and fixing mechanism includes a fixed bracket, which is respectively arranged on the two lateral sides of the workbench. The fixed bracket is respectively provided with a lever cylinder, and the lever cylinders on both sides are arranged opposite to each other; a fixed block is also provided on the fixed bracket on one side, and a clamping cylinder is provided on the fixed bracket on the other side, and a movable block is provided at the output end of the clamping cylinder; the lever cylinder and the clamping cylinder are respectively connected to the controller and controlled by the controller.

[0017] A tool holder is provided at the rear of the workbench, and a tool handle clamping plate is provided at the upper end of the tool holder. When the tool handle clamping plate is not raised, the tool holder supports the tool handle clamping plate from the bottom. The tool holder is fixedly connected to a vertical electric push rod, and the top of the electric push rod is fixedly connected to the tail end of the tool handle clamping plate; several tool handle clamping parts are provided at the front of the tool handle clamping plate for clamping a spare stirring head or a three-coordinate measuring head.

[0018] Working principle and control method of the present invention

[0019] The longitudinal displacement mechanism drives the gantry to move forward longitudinally to reach the shell workpiece to be processed. In the flip clamping mechanism at the lower part of the columns on both sides of the gantry, the sliding connecting frame is first driven to the specified height by the second vertical displacement mechanism, and then driven by the second horizontal displacement mechanism to make the clamping head connecting seats on both sides move toward each other, so that the clamping heads on both sides clamp the two sides of the shell workpiece to be processed; the second vertical displacement mechanism makes the sliding connecting frame rise to the specified height; finally, the longitudinal displacement mechanism drives the gantry to move backward longitudinally, so that the shell workpiece to be processed reaches above the workbench.

[0020] When performing stir friction welding, the clamping head is driven by the clamping head driving motor to rotate the shell workpiece to be processed to a suitable angle; the second vertical displacement mechanism causes the sliding connecting frame to drop to a specified height, and the shell workpiece to be processed falls on the workbench; the clamping cylinder on one side of the clamping and fixing mechanism pushes the movable stopper to move to the other side, and works together with the fixed stopper on the other side to clamp the shell workpiece to be processed; the lever cylinders on both sides rotate the lever cylinder clamping arms to clamp the shell workpiece to be processed on the workbench.

[0021] The first lateral displacement mechanism and the first vertical displacement mechanism move together to move the welding mechanism to the area to be welded. The three-coordinate measuring head of the welding mechanism measures the perpendicularity and weld parameters between the surface of the shell workpiece to be processed and the welding mechanism. After the inspection, the welding mechanism moves to the tool holder to replace the stirring head and proceed with welding. After the three-coordinate measuring head measures the parameters, the controller adjusts the deviation angle based on the collected data so that the deviation angle between the surface of the shell workpiece to be processed and the welding mechanism relative to the standard perpendicularity is less than ±5". The welding mechanism is automatically moved to the welding starting point. The movement satisfies the following relationship:

[0022] The welding mechanism includes translation and tilting. x, y, and z are the displacements of the welding mechanism along the X, Y, and Z axes, and α, β, and γ are the tilt angles of the welding mechanism along the X, Y, and Z axes:

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] j→i homogeneous coordinate transformation matrix:

[0031]

[0032] in The welding mechanism tilt angle transformation matrix along the X axis;

[0033] The welding mechanism tilt angle transformation matrix along the Y axis;

[0034] The welding mechanism tilt angle transformation matrix along the Z axis;

[0035] Displacement transformation matrix of welding mechanism along Z axis;

[0036] Displacement transformation matrix of welding mechanism along Y axis;

[0037] Displacement transformation matrix of welding mechanism along X axis;

[0038] When the shell workpiece to be processed needs to be flipped and welded, the clamping heads on both sides are used to clamp the shell workpiece to be processed, and the shell workpiece to be processed is rotated under the drive of the clamping head driving motor; while rotating, it is welded by the welding mechanism.

[0039] It realizes "one axis for multiple uses" automatic positioning, detects various parameters of the welding area and then welds, which improves the welding quality. The industrial camera (CCD) on the side of the welding mechanism is used for real-time monitoring.

[0040] Furthermore, the present invention determines the desired field of view (FOV) and working distance (WD), and then calculates the focal length (f) of the industrial camera lens based on these two requirements and the known target surface size, and selects the industrial camera and lens. The calculation method is as follows:

[0041]

[0042]

[0043]

[0044]

[0045] Where H represents the horizontal width of the CCD target surface, and V represents the vertical height of the CCD target surface.

[0046] Furthermore, when the stirring head of the present invention is working, the shaft shoulder and the stirring needle are optimal when the welding temperature is about 80% of the melting point of the base material;

[0047] The total heat input for friction stir welding of the present invention is as follows:

[0048] Friction between the shaft shoulder and the base material generates heat:

[0049] The friction between the stirring needle and the base material generates heat:

[0050] The friction between the end face of the stirring needle and the base material generates heat:

[0051] Total heat input of friction stir welding: Q = Q1 + Q2 + Q3;

[0052] therefore

[0053] Among them, R1 is the shoulder radius; R2 is the root radius of the mixing head; R3 is the end radius of the mixing head; σ v is the yield strength of aluminum alloy; τ v is the yield shear stress; n is the stirring head speed; α is the cone angle; β is the shoulder concave angle;

[0054] When the length of the stirring needle at the end of the stirring head is 70% to 80% of the thickness of the weldment, the forming quality is best; the function of the stirring head shoulder is to limit the overflow of plastic metal from the forming area and generate a certain amount of heat input at the same time; if the shoulder size is too large, the heat input will increase, which will cause the size of the heat-affected zone to increase and the weldment to be easily deformed; if the shoulder size is too small, it is necessary to increase the rotation speed or reduce the welding speed to ensure the heat input, so the forming efficiency is low. In the present invention, the best effect is achieved when the ratio of the stirring head shoulder diameter to the stirring needle diameter is 3:1.

[0055] The motion trajectory of friction stir welding is a straight line, with the starting and ending positions being P1 and P2 respectively. The actual position of the stirring head after compensation is P, and k is the error compensation coefficient:

[0056] P=P1+k(P2-P1)k∈[0,1]

[0057] The corrected starting and ending positions are P 1c 、P 2c :

[0058] P c =P 1c +k(P 2c -P 1c )k∈[0,1]

[0059] P c =P d -E(P d )

[0060] Among them, P c is the actual position of the stirring head after the correction and introduction of the compensation amount, P d is the desired stirring head position, E(P d ) is the three-dimensional position error;

[0061]

[0062] Among them, T yx is the verticality error between X and Y axes, T zx is the verticality error between ZX axes, is the X-axis displacement error, is the Y-axis displacement error, is the Z-axis displacement error, E is the cumulative error;

[0063]

[0064]

[0065] The displacement and rotation angle errors in three directions are approximately expressed as:

[0066]

[0067] Where i represents the XYZ coordinate axis; the subscript xyz represents movement along the XYZ axis or rotation around the XYZ axis; δ represents the angle of rotation; and △ represents the displacement.

[0068] Beneficial effects of the present invention:

[0069] Compared with the prior art, the gantry column of the present invention is equipped with a device that can realize the function of flipping, clamping and lifting the workpiece. It has a compact structure and can clamp the shell to be processed and move it to the workbench. The shell to be processed can be flipped to realize multi-faceted processing. At the same time, the clamping head is provided with a contoured groove, which is clamped to the preset protrusions at the center of the two sides of the workpiece to be processed to ensure uniform force. The positioning is accurate and the coaxiality is guaranteed during flipping and lifting. The present invention can independently complete more work steps, reduce the use of other machines, production costs and workstation area occupied. The present invention accurately controls the displacement of the welding mechanism stirring head, combines the multi-purpose capability of one axis, replaces the three-coordinate measuring head of the welding mechanism to realize welding area positioning and detection, and installs an industrial camera on the welding mechanism to monitor the surface processing quality of the workpiece from above. The monitoring is more intuitive, so that the controller can control the welding mechanism to achieve better welding quality, greatly improving the efficiency of welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0071] Figure 2 This is a schematic structural diagram of the longitudinal displacement mechanism of the present invention;

[0072] Figure 3 This is a schematic structural diagram of the first lateral displacement mechanism of the present invention;

[0073] Figure 4 This is a schematic structural diagram of the first vertical displacement mechanism of the present invention;

[0074] Figure 5 This is a schematic structural diagram of the clamping and fixing mechanism of the present invention;

[0075] Figure 6 This is a schematic structural diagram of the flip clamping mechanism of the present invention;

[0076] Figure 7 This is a schematic diagram of the tool holder structure of the present invention;

[0077] 1. Base 2. Workbench 3. Gantry;

[0078] 4. Longitudinal displacement mechanism 401, longitudinal slide rail 402, longitudinal drive motor 403, longitudinal displacement connecting plate 404, grating scale 405, grating scale guide rail 406, longitudinal lead screw 407, longitudinal lead screw nut;

[0079] 5. First lateral displacement mechanism 501, first lateral slide rail 502, first lateral drive motor 503, first lateral lead screw 504, and lateral displacement connecting frame;

[0080] 6. First vertical displacement mechanism 601, fixing frame 602, first vertical slide rail 603, first vertical drive motor 604, first vertical lead screw 605, first vertical lead screw nut;

[0081] 7. Welding mechanism 701, spindle motor 702, camera drive motor 703, industrial camera 704, three-coordinate measuring head 705, stirring head;

[0082] 8. Clamping and fixing mechanism 801, fixing bracket 802, lever cylinder 803, fixed stopper 804, pressing cylinder 805, movable stopper

[0083] 9. Controller 10. Flip clamping mechanism;

[0084] 11. Second vertical displacement mechanism 1101, second vertical slide rail 1102, second vertical drive motor;

[0085] 12. Sliding connecting frame;

[0086] 13. Second lateral displacement mechanism 1301, second lateral slide rail 1302, second lateral drive motor 1303, second lateral lead screw;

[0087] 14. Clamping head 1401, contoured groove;

[0088] 15. Clamping head rotating shaft 16. Clamping head connecting seat 17. Clamping head driving motor;

[0089] 18. Tool holder 1801, tool handle clamping and dragging plate 1802, electric push rod 1803, tool handle clamping and dragging part. DETAILED DESCRIPTION

[0090] See Figure 1-7 As shown:

[0091] The present invention provides a dynamic gantry-type shell friction stir welding device with automatic positioning, detection and clamping, which includes a base 1, a workbench 2, a gantry 3, a longitudinal displacement mechanism 4, a first lateral displacement mechanism 5, a first vertical displacement mechanism 6, a welding mechanism 7, a clamping and fixing mechanism 8 and a controller 9; the base 1 is an I-shaped cast steel integrally formed base, and the workbench 2 is arranged in the middle of the crossbeam of the base 1; longitudinal displacement mechanisms 4 are respectively provided on both sides of the base 1, and the lower ends of the columns on both sides of the gantry 3 are respectively connected to the longitudinal displacement connecting plates 403 of the longitudinal displacement mechanism 4; the first lateral displacement mechanism 5 is arranged on the crossbeam at the upper part of the gantry 3, and the first vertical displacement mechanism 6 is connected to the lateral displacement connecting frame 504 of the first lateral displacement mechanism 5; the welding mechanism 7 is arranged at the lower end of the first vertical displacement mechanism 6;

[0092] The lower part of the columns on both sides of the gantry 3 is respectively provided with a flip clamping mechanism 10, and the flip clamping mechanism 10 includes a second vertical displacement mechanism 11, a sliding connecting frame 12, a second lateral displacement mechanism 13, a clamping head 14, a clamping head rotating shaft 15, a clamping head connecting seat 16, and a clamping head driving motor 17; the second vertical displacement mechanism 11 is provided at the lower part of the gantry 3 column, the sliding connecting frame 12 is slidably connected to the second vertical displacement mechanism 11; the second lateral displacement mechanism 13 is provided on the sliding connecting frame 12, the clamping head connecting seat 16 is slidably connected to the second lateral displacement mechanism 13; the clamping head 14 is provided at the front end of the clamping head rotating shaft 15, and the rear end of the clamping head rotating shaft 15 is pivotally connected to the clamping head connecting seat 16 through a bearing seat; the clamping head 14 extends out of the gantry 3; the clamping head driving motor 17 is provided above the clamping head connecting seat 16, and the output shaft of the clamping head driving motor 17 is engaged with the clamping head rotating shaft 15 through gears to drive the clamping head rotating shaft 15 to rotate; the flip clamping mechanisms 10 on both sides of the gantry 3 are arranged opposite to each other;

[0093] The welding mechanism 7 includes a spindle motor 701, a camera drive motor 702 and an industrial camera 703. The spindle motor 701 is provided at the lower end of the welding mechanism 7, and the output end of the spindle motor 701 is connected to a three-coordinate measuring head 704 or a stirring head 705; the camera drive motor 702 is provided on the side of the spindle motor 701, and the industrial camera 703 is connected to the output shaft of the camera drive motor 702;

[0094] The clamping and fixing mechanism 8 is provided on both lateral sides of the workbench 2;

[0095] The controller 9 is arranged on the base 1. The controller 9 includes modules such as a data collector, a data processor, a PLC controller, a display, and buttons, all of which are existing equipment for realizing functions such as data acquisition, processing, output of control signals, and human-computer interaction; the controller 9 is respectively connected to the longitudinal displacement mechanism 4, the first lateral displacement mechanism 5, the first vertical displacement mechanism 6, the spindle motor 701 in the welding mechanism 7, the camera drive motor 702 and the industrial camera 703, the clamping and fixing mechanism 8, and the second vertical displacement mechanism 11, the second lateral displacement mechanism 13, and the clamping head drive motor 17 in the flipping and clamping mechanism 10, and collects and outputs control signals.

[0096] The longitudinal displacement mechanism 4 includes a longitudinal slide rail 401, a longitudinal drive motor 402, a longitudinal displacement connecting plate 403, a grating ruler 404 and a grating ruler guide rail 405; the longitudinal slide rail 401 is longitudinally arranged along both sides of the base 1, the longitudinal drive motor 402 is arranged at one end, the output shaft is connected to the longitudinal lead screw 406, the longitudinal lead screw 406 is parallel to the longitudinal slide rail 401, and the other end of the longitudinal lead screw 406 is connected to the base 1 through a bearing seat; the longitudinal displacement connecting plate 403 is slidably connected to the longitudinal slide rail 401 through a slider; the bottom of the longitudinal displacement connecting plate 403 is provided with a longitudinal lead screw nut 406 7. The longitudinal lead screw 406 is connected and cooperated with the longitudinal lead screw nut 407 to form a lead screw pair. The longitudinal drive motor 402 drives the longitudinal lead screw 406 to rotate in the forward or reverse direction, which is converted by the longitudinal lead screw nut 407 into a forward and backward longitudinal translation movement of the longitudinal displacement connecting plate 403, thereby driving the overall forward and backward longitudinal translation movement of the gantry 3; the grating scale guide rail 405 is arranged parallel to the longitudinal slide rail 401, and the grating scale 404 is fixed to the lower part of the longitudinal displacement connecting plate 403 through the grating scale connecting plate, with one end connected to the grating scale guide rail 405 for measuring the precise displacement distance of the longitudinal displacement connecting plate 403;

[0097] The first transverse displacement mechanism 5 includes a first transverse slide rail 501, a first transverse drive motor 502, a first transverse lead screw 503, a transverse displacement connecting frame 504, and a first transverse lead screw nut. The first transverse slide rail 501 is arranged on the crossbeam at the upper part of the gantry 3 and is arranged along the direction of the crossbeam; the first transverse drive motor 502 is arranged at one end of the crossbeam, and the output shaft is connected to the first transverse lead screw 503. The first transverse lead screw 503 is arranged parallel to the first transverse slide rail 501, and the other end of the first transverse lead screw 503 is connected to the first transverse slide rail 501. One end is connected to the gantry 3 crossbeam through a bearing seat; the lateral displacement connecting frame 504 is slidably connected to the first transverse slide rail 501 through a slider; a first transverse lead screw nut is provided at the bottom of the lateral displacement connecting frame 504, and the first transverse lead screw 503 is connected and cooperated with the first transverse lead screw nut to form a lead screw pair. The first transverse drive motor 502 drives the first transverse lead screw 503 to rotate in the forward or reverse direction, which is converted by the first transverse lead screw nut into a left and right transverse translation motion of the lateral displacement connecting frame 504 on the gantry 3 crossbeam;

[0098] The first vertical displacement mechanism 6 includes a fixing frame 601, a first vertical slide rail 602, a first vertical drive motor 603, a first vertical lead screw 604, and a first vertical lead screw nut 605. The fixing frame 601 is fixed to the side of the horizontal displacement connecting frame 504; the upper end of the first vertical slide rail 602 is connected to the first vertical drive motor 603, and the lower end passes through the fixing frame 601 and is connected to the welding mechanism 7; the fixing frame 601 is slidably connected to the first vertical slide rail 602 through a slider; the first vertical slide rail 602 is connected to the first vertical drive motor 603 through a slider; A vertical lead screw nut 605 is fixed in the fixing frame 601. The output shaft of the first vertical drive motor 603 is connected to the upper end of the first vertical lead screw 604. The lower end of the first vertical lead screw 604 passes through the first vertical lead screw nut 605 and is connected to the welding mechanism 7. The first vertical drive motor 603 drives the first vertical lead screw 604 to rotate in the forward or reverse direction, which is converted by the first vertical lead screw nut 605 into the synchronous up and down movement of the first vertical drive motor 603 and the welding mechanism 7.

[0099] The longitudinal drive motor 402, the first transverse drive motor 502 and the first vertical drive motor 603 are respectively connected to the controller 9 and controlled by the controller 9. The longitudinal drive motor 402, the first transverse drive motor 502 and the first vertical drive motor 603 are all provided with an accordion cover for dust prevention.

[0100] The second vertical displacement mechanism 11 includes a second vertical slide rail 1101, a second vertical drive motor 1102, a second vertical lead screw, and a second vertical lead screw nut. The second vertical slide rail 1101 is at least four, and two are arranged in a group on both sides of the sliding connection frame 12, and are fixedly connected to the inner wall of the column of the gantry 3; the sliding connection frame 12 is slidably connected to the second vertical slide rail 1101 through a slider; the second vertical drive motor 1102 is arranged on one side of the sliding connection frame 12, and is fixedly connected to the inner wall of the column of the gantry 3 The column is fixedly connected; the output shaft of the second vertical drive motor 1102 is connected to the second vertical lead screw, and the other end of the second vertical lead screw is connected to the sliding connection frame 12 through a bearing seat; the second vertical lead screw nut is provided on one side of the sliding connection frame 12, and the second vertical lead screw and the second vertical lead screw nut are connected and cooperated to form a lead screw pair, and the second vertical drive motor 1102 drives the second vertical lead screw to rotate in the forward or reverse direction, which is converted by the second vertical lead screw nut into an up and down displacement movement of the sliding connection frame 12;

[0101] The second lateral displacement mechanism 13 includes a second lateral slide rail 1301, a second lateral drive motor 1302, a second lateral lead screw 1303, and a second lateral lead screw nut. The second lateral slide rail 1301 is arranged at the top of the sliding connection frame 12, and the clamping head connecting seat 16 is slidably connected to the second lateral slide rail 1301 through a slider; the second lateral drive motor 1302 is fixed to the outer end of the top of the sliding connection frame 12, and the output shaft of the second lateral drive motor 1302 is connected to the second lateral lead screw 1303, and the other end of the second lateral lead screw 1303 is connected to the sliding The dynamic connecting frame 12 is connected through the bearing seat; the second transverse lead screw nut is arranged at the bottom of the clamping head connecting seat 16, and the second transverse lead screw 1303 is connected and cooperated with the second transverse lead screw nut to form a lead screw pair, and the second transverse drive motor 1302 drives the second transverse lead screw 1303 to rotate in the forward or reverse direction, which is converted by the second transverse lead screw nut into the left and right transverse translation movement of the clamping head connecting seat 16; the flipping clamping mechanism 10 on both sides of the gantry 3 moves synchronously and symmetrically, that is, the clamping head connecting seats 16 on both sides move toward each other or in opposite directions under the drive of the second transverse displacement mechanism 13.

[0102] The second vertical drive motor 1102 and the second horizontal drive motor 1302 are respectively connected to the controller 9 and controlled by the controller 9 .

[0103] The clamping head 14 is a boss-type clamping head 14 with contoured grooves 1401 on its surface, which are symmetrically distributed on the clamping head 14 to improve coaxiality and reduce pressure, and are clamped onto the preset protrusions at the center of both sides of the workpiece to be processed, making the clamping more secure.

[0104] The clamping and fixing mechanism 8 includes a fixed bracket 801, which is respectively arranged on both sides of the workbench 2. Each fixed bracket 801 is provided with at least two lever cylinders 802, and the lever cylinder 802 is an ordinary air-compressed pipe-type lever cylinder. The lever cylinders 802 on the fixed brackets 801 on both sides are arranged opposite to each other; a fixed stopper 803 is also provided on the fixed bracket 801 on one side, and a clamping cylinder 804 is provided on the fixed bracket 801 on the other side, and a movable stopper 805 is provided at the output end of the clamping cylinder 804; the movable stopper 805 is arranged opposite to the fixed stopper 803, and the output end of the clamping cylinder 804 pushes the movable stopper 805 to extend and retract; the lever cylinder 802 and the clamping cylinder 804 are respectively connected to the controller 9 and controlled by the controller 9.

[0105] A tool holder 18 is provided at the rear of the workbench 2, and a tool handle clamping plate 1801 is provided at the upper end of the tool holder 18. When the tool handle clamping plate 1801 is not raised, the tool holder 18 supports the tool handle clamping plate 1801 from the bottom. A vertical electric push rod 1802 is provided on the tool holder 18 and is fixedly connected to it. The top of the electric push rod 1802 is fixedly connected to the tail end of the tool handle clamping plate 1801, and the electric push rod 1802 is used to lift the tool handle clamping plate 1801; several tool handle clamping parts 1803 are provided at the front of the tool handle clamping plate 1801, which are used to clamp a spare stirring head 705 or a three-coordinate measuring head 704; this facilitates the spindle motor 701 of the welding mechanism 7 to replace the three-coordinate measuring head 704 or the stirring head 705.

[0106] Working principle and control method of the present invention

[0107] The longitudinal displacement mechanism 4 drives the gantry 3 to move forward longitudinally to reach the shell workpiece to be processed. In the flip clamping mechanism 10 at the lower part of the columns on both sides of the gantry 3, the sliding connecting frame 12 is first driven to the specified height by the second vertical displacement mechanism 11, and then driven by the second horizontal displacement mechanism 13 to make the clamping head connecting seats 16 on both sides move toward each other, so that the clamping heads 14 on both sides clamp the two sides of the shell workpiece to be processed; the second vertical displacement mechanism 11 makes the sliding connecting frame 12 rise to the specified height; finally, the longitudinal displacement mechanism 4 drives the gantry 3 to move backward longitudinally, so that the shell workpiece to be processed reaches above the workbench 2.

[0108] When performing stir friction welding, the clamping head 14 is driven by the clamping head drive motor 17 to rotate the shell workpiece to be processed to a suitable angle; the second vertical displacement mechanism 11 causes the sliding connecting frame 12 to drop to a specified height, and the shell workpiece to be processed falls on the workbench 2; the clamping cylinder 804 on one side of the clamping and fixing mechanism 8 pushes the movable stopper 805 to move to the other side, and works together with the fixed stopper 803 on the other side to clamp the shell workpiece to be processed; the lever cylinder 802 of the fixed brackets 801 on both sides rotates the lever cylinder clamping arm to clamp the shell workpiece to be processed on the workbench 2.

[0109] The first lateral displacement mechanism 5 and the first vertical displacement mechanism 6 move together to move the welding mechanism 7 to the area to be welded. The three-coordinate measuring head 704 of the welding mechanism 7 measures the perpendicularity and weld parameters between the surface of the shell workpiece to be processed and the welding mechanism 7. After the inspection, the welding mechanism 7 moves to the tool holder 18 to replace the stirring head 705 and proceed with the welding process. After the three-coordinate measuring head 704 measures the parameters, the controller 9 adjusts the deviation angle based on the collected data so that the deviation angle between the surface of the shell workpiece to be processed and the welding mechanism 7 relative to the standard perpendicular is less than ±5″. The welding mechanism 7 is automatically moved to the welding starting point. The movement satisfies the following relationship:

[0110] The welding mechanism includes translation and tilting. x, y, and z are the displacements of the welding mechanism along the X, Y, and Z axes, and α, β, and γ are the tilt angles of the welding mechanism along the X, Y, and Z axes:

[0111]

[0112]

[0113]

[0114]

[0115]

[0116]

[0117]

[0118] j→i homogeneous coordinate transformation matrix:

[0119]

[0120] in The welding mechanism tilt angle transformation matrix along the X axis;

[0121] The welding mechanism tilt angle transformation matrix along the Y axis;

[0122] The welding mechanism tilt angle transformation matrix along the Z axis;

[0123] Displacement transformation matrix of welding mechanism along Z axis;

[0124] Displacement transformation matrix of welding mechanism along Y axis;

[0125] Displacement transformation matrix of welding mechanism along X axis;

[0126] When the shell workpiece to be processed needs to be flipped and welded, the clamping heads 14 on both sides are used to clamp the shell workpiece to be processed, and the clamping head driving motor 17 is driven to rotate the shell workpiece to be processed; while rotating, it is welded by the welding mechanism 7.

[0127] The system realizes "one axis for multiple uses" automatic positioning, detects various parameters of the welding area and then welds, thus improving the welding quality. The industrial camera 703 (CCD) on the side of the welding mechanism 7 is used for real-time monitoring.

[0128] Furthermore, the present invention determines the desired field of view (FOV) and working distance (WD), and then calculates the focal length (f) of the industrial camera 703 lens based on these two requirements and the known target surface size, and selects the industrial camera 703 and lens. The calculation method is as follows:

[0129]

[0130]

[0131]

[0132]

[0133] Where H represents the horizontal width of the CCD target surface, and V represents the vertical height of the CCD target surface.

[0134] Furthermore, when the stirring head 705 of the present invention is working, the shaft shoulder and the stirring needle are optimal when the welding temperature is about 80% of the melting point of the base material;

[0135] The total heat input for friction stir welding of the present invention is as follows:

[0136] Friction between the shaft shoulder and the base material generates heat:

[0137] The friction between the stirring needle and the base material generates heat:

[0138] The friction between the end face of the stirring needle and the base material generates heat:

[0139] Total heat input of friction stir welding: Q = Q1 + Q2 + Q3;

[0140] therefore

[0141] Wherein, R1 is the shoulder radius; R2 is the root radius of the stirring head 705; R3 is the end radius of the stirring head 705; σ v is the yield strength of aluminum alloy; τ vis the yield shear stress; n is the stirring head 705 speed; α is the cone angle; β is the shoulder concave angle;

[0142] When the length of the stirring needle at the end of the stirring head 705 is 70% to 80% of the thickness of the weldment, the forming quality is best; the function of the shoulder of the stirring head 705 is to limit the overflow of plastic metal from the forming area and generate a certain amount of heat input at the same time; if the shoulder size is too large, the heat input will increase, which will cause the size of the heat-affected zone to increase and the weldment to be easily deformed; if the shoulder size is too small, it is necessary to increase the rotation speed or reduce the welding speed to ensure the heat input, so the forming efficiency is low. In the present invention, the best effect is achieved when the ratio of the shoulder diameter of the stirring head 705 to the stirring needle diameter is 3:1.

[0143] Furthermore, the friction stir welding motion trajectory is a straight line, with the starting and ending positions being P1 and P2 respectively. The actual position of the stirring head after compensation is P, and k is the error compensation coefficient:

[0144] P=P1+k(P2-P1)k∈[0,1]

[0145] The corrected starting and ending positions are P 1c 、P 2c :

[0146] P c =P 1c +k(P 2c -P 1c )k∈[0,1]

[0147] P c =P d -E(P d )

[0148] Among them, P c is the actual position of the stirring head 705 after the correction and introduction of the compensation amount, P d is the desired stirring head 705 position, E(P d ) is the three-dimensional position error;

[0149]

[0150] Among them, T yx is the verticality error between X and Y axes, T zx is the verticality error between ZX axes, is the X-axis displacement error, is the Y-axis displacement error, is the Z-axis displacement error, E is the cumulative error;

[0151]

[0152]

[0153] The displacement and rotation angle errors in three directions are approximately expressed as:

[0154]

[0155] Where i represents the XYZ coordinate axis; the subscript xyz represents movement along the XYZ axis or rotation around the XYZ axis; δ represents the angle of rotation; and △ represents the displacement.

Claims

1. A dynamic gantry-type shell friction stir welding device with automatic positioning, detection and clamping, characterized by: The machine comprises a base, a workbench, a gantry, a longitudinal displacement mechanism, a first transverse displacement mechanism, a first vertical displacement mechanism, a welding mechanism, a clamping and fixing mechanism, and a controller; the workbench is provided on the base; longitudinal displacement mechanisms are respectively provided on both sides of the base, and the lower ends of the columns on both sides of the gantry are respectively connected to the longitudinal displacement connecting plates of the longitudinal displacement mechanisms; the first transverse displacement mechanism is provided on the crossbeam at the upper part of the gantry, and the first vertical displacement mechanism is connected to the transverse displacement connecting frame of the first transverse displacement mechanism; the welding mechanism is provided at the lower end of the first vertical displacement mechanism; The lower parts of the columns on both sides of the gantry are respectively provided with a flip clamping mechanism, and the flip clamping mechanism includes a second vertical displacement mechanism, a sliding connecting frame, a second lateral displacement mechanism, a clamping head, a clamping head rotating shaft, a clamping head connecting seat, and a clamping head driving motor; the second vertical displacement mechanism is arranged at the lower part of the gantry column, the sliding connecting frame is slidably connected to the second vertical displacement mechanism; the second lateral displacement mechanism is arranged on the upper part of the sliding connecting frame, and the clamping head connecting seat is slidably connected to the second lateral displacement mechanism; the clamping head is arranged at the front end of the clamping head rotating shaft, and the clamping head rotating shaft is pivotally connected to the clamping head connecting seat through a bearing seat; the clamping head driving motor is arranged above the clamping head connecting seat, and the output shaft of the clamping head driving motor and the clamping head rotating shaft are engaged with the gear to drive the clamping head rotating shaft to rotate; the flip clamping mechanisms on both sides of the gantry are arranged relatively; the clamping head is a boss-type clamping head, and the surface is provided with a contoured groove; The welding mechanism includes a spindle motor, a camera drive motor and an industrial camera. The spindle motor is located at the lower end of the welding mechanism, and the output end of the spindle motor is connected to a three-coordinate measuring head or a stirring head. The camera drive motor is located on the side of the spindle motor, and the industrial camera is connected to the output shaft of the camera drive motor. The industrial camera performs real-time monitoring. The clamping and fixing mechanisms are arranged on both lateral sides of the workbench; The controller is provided on the base and is respectively connected to the longitudinal displacement mechanism, the first lateral displacement mechanism, the first vertical displacement mechanism, the spindle motor in the welding mechanism, the camera drive motor and the industrial camera, the clamping and fixing mechanism, and the second vertical displacement mechanism, the second lateral displacement mechanism, and the clamping head drive motor in the flip clamping mechanism, and collects and outputs control signals; The first lateral displacement mechanism and the first vertical displacement mechanism move together to move the welding mechanism to the area to be welded. The three-coordinate measuring head of the welding mechanism measures the perpendicularity and weld parameters between the surface of the shell workpiece to be processed and the welding mechanism. After the inspection, the welding mechanism moves to the tool holder to replace the stirring head and proceed with welding. After the three-coordinate measuring head measures the parameters, the controller adjusts the deviation angle based on the collected data so that the deviation angle between the surface of the shell workpiece to be processed and the welding mechanism relative to the standard perpendicularity is less than ±5". The welding mechanism is automatically moved to the welding starting point. The movement satisfies the following relationship: The welding mechanism includes translation and tilting. x, y, and z are the displacements of the welding mechanism along the X, Y, and Z axes. The tilt angle of the welding mechanism along the X, Y, and Z axes: ， ， ， ， ， ， ， Homogeneous coordinate transformation matrix: ， ； ； ； ； ； ； When the shell workpiece to be processed needs to be turned over for welding, the shell workpiece to be processed is clamped by the clamping heads on both sides, and the shell workpiece to be processed is rotated under the drive of the clamping head driving motor; while rotating, it is welded by the welding mechanism; The motion trajectory of friction stir welding is a straight line, with the starting and ending positions being P1 and P2 respectively. The actual position of the stirring head after compensation is P, and k is the error compensation coefficient: ， The corrected starting and ending positions are : ， ， in, The actual position of the stirring head after the correction and introduction of the compensation amount, is the desired stirring head position, is the three-dimensional position error; ， in, is the verticality error between XY axes; is the verticality error between Z and X axes; is the X-axis displacement error; is the Y-axis displacement error; is the Z-axis displacement error; is the cumulative error; ， ， The displacement and rotation angle errors in three directions are expressed as: ， in, represents the XYZ coordinate axis; the subscript xyz represents movement along the XYZ axis or rotation around the XYZ axis; δ represents the angle of rotation; △ represents the displacement.

2. The automatic positioning, detection and clamping dynamic gantry-type shell friction stir welding equipment according to claim 1 is characterized in that: The longitudinal displacement mechanism includes a longitudinal slide rail, a longitudinal drive motor, a longitudinal displacement connecting plate, a grating scale and a grating scale guide rail; the longitudinal slide rail is arranged longitudinally along the base, the longitudinal drive motor is arranged at one end, the output shaft is connected to the longitudinal lead screw, the longitudinal lead screw is parallel to the longitudinal slide rail, and the other end of the longitudinal lead screw is connected to the base through a bearing seat; the longitudinal displacement connecting plate is slidably connected to the longitudinal slide rail through a slider; a longitudinal lead screw nut is provided at the bottom of the longitudinal displacement connecting plate, and the longitudinal lead screw and the longitudinal lead screw nut are connected and cooperated to form a lead screw pair; the grating scale guide rail is arranged parallel to the longitudinal slide rail, the grating scale is fixed to the lower part of the longitudinal displacement connecting plate through the grating scale connecting plate, and one end is connected to the grating scale guide rail; The first transverse displacement mechanism includes a first transverse slide rail, a first transverse drive motor, a first transverse lead screw, a transverse displacement connecting frame, and a first transverse lead screw nut. The first transverse slide rail is arranged on the crossbeam on the upper part of the gantry, the first transverse drive motor is arranged at one end of the crossbeam, the output shaft is connected to the first transverse lead screw, the first transverse lead screw is arranged parallel to the first transverse slide rail, and the other end of the first transverse lead screw is connected to the crossbeam of the gantry through a bearing seat; the transverse displacement connecting frame is slidably connected to the first transverse slide rail through a slider; a first transverse lead screw nut is provided at the bottom of the transverse displacement connecting frame, and the first transverse lead screw and the first transverse lead screw nut are connected and cooperated to form a screw pair; The first vertical displacement mechanism includes a fixed frame, a first vertical slide rail, a first vertical drive motor, a first vertical lead screw, and a first vertical lead screw nut. The fixed frame is fixed to the side of the lateral displacement connecting frame; the upper end of the first vertical slide rail is connected to the first vertical drive motor, and the lower end is connected to the welding mechanism; the fixed frame is slidably connected to the first vertical slide rail through a slider; the first vertical lead screw nut is fixed in the fixed frame, the output shaft of the first vertical drive motor is connected to the upper end of the first vertical lead screw, and the lower end of the first vertical lead screw passes through the first vertical lead screw nut and is connected to the welding mechanism; The longitudinal drive motor, the first transverse drive motor and the first vertical drive motor are respectively connected to the controller and controlled by the controller.

3. The automatic positioning, detection and clamping dynamic gantry-type shell friction stir welding equipment according to claim 1 is characterized in that: The second vertical displacement mechanism includes a second vertical slide rail, a second vertical driving motor, a second vertical lead screw, and a second vertical lead screw nut. The second vertical slide rail is provided on both sides of the sliding connecting frame and is fixedly connected to the column of the gantry; the sliding connecting frame is slidably connected to the second vertical slide rail through a slider; the second vertical driving motor is provided on one side of the sliding connecting frame and is fixedly connected to the column of the gantry; the output shaft of the second vertical drive motor is connected to the second vertical lead screw, and the other end of the second vertical lead screw is connected to the sliding connecting frame through a bearing seat; the second vertical lead screw nut is provided on one side of the sliding connecting frame, and the second vertical lead screw and the second vertical lead screw nut are connected and cooperated to form a lead screw pair; The second transverse displacement mechanism includes a second transverse slide rail, a second transverse drive motor, a second transverse lead screw, and a second transverse lead screw nut. The second transverse slide rail is arranged at the top of the sliding connection frame, and the clamping head connection seat is slidably connected to the second transverse slide rail through a slider; the second transverse drive motor is fixed to the outer end of the top of the sliding connection frame, the output shaft of the second transverse drive motor is connected to the second transverse lead screw, and the other end of the second transverse lead screw is connected to the sliding connection frame through a bearing seat; the second transverse lead screw nut is arranged at the bottom of the clamping head connection seat, and the second transverse lead screw and the second transverse lead screw nut are connected and cooperated to form a screw pair; The second vertical drive motor and the second horizontal drive motor are respectively connected to the controller and controlled by the controller.

4. The automatic positioning, detection and clamping dynamic gantry-type shell friction stir welding equipment according to claim 1, characterized in that: The clamping and fixing mechanism includes a fixed bracket, which is respectively arranged on the two lateral sides of the workbench. The fixed bracket is respectively provided with a lever cylinder, and the lever cylinders on both sides are arranged opposite to each other; a fixed block is also provided on the fixed bracket on one side, and a clamping cylinder is provided on the fixed bracket on the other side, and a movable block is provided at the output end of the clamping cylinder; the lever cylinder and the clamping cylinder are respectively connected to the controller and controlled by the controller.

5. The automatic positioning, detection and clamping dynamic gantry-type shell friction stir welding equipment according to claim 1, characterized in that: A tool holder is provided at the rear of the workbench, and a tool handle clamping plate is provided at the upper end of the tool holder. When the tool handle clamping plate is not raised, the tool holder supports the tool handle clamping plate from the bottom. The tool holder is fixedly connected to a vertical electric push rod, and the top of the electric push rod is fixedly connected to the tail end of the tool handle clamping plate; several tool handle clamping parts are provided at the front of the tool handle clamping plate for clamping a spare stirring head or a three-coordinate measuring head.

6. The automatic positioning, detection and clamping dynamic gantry-type shell friction stir welding equipment according to claim 1, characterized in that: Determine the desired field of view (FOV) and working distance (WD). Calculate the focal length (f) of the industrial camera lens based on these two requirements and the known target surface size. Select the industrial camera and lens. The calculation method is as follows: ， ， ， ， Where H represents the horizontal width of the CCD target surface, and V represents the vertical height of the CCD target surface.

7. The automatic positioning, detection and clamping dynamic gantry-type shell friction stir welding equipment according to claim 1, characterized in that: When the stirring head is working, the shaft shoulder and the stirring needle are optimal when the welding temperature is 80% of the melting point of the base material; The total heat input for friction stir welding is as follows: Friction between the shaft shoulder and the base material generates heat: ; The friction between the stirring needle and the base material generates heat: ; The friction between the end face of the stirring needle and the base material generates heat: ; Total heat input of friction stir welding: Q=Q1+Q2+Q3; therefore ; Among them, R1 is the shoulder radius; R2 is the root radius of the mixing head; R3 is the end radius of the mixing head; is the yield strength of aluminum alloy; is the yield shear stress; n is the stirring head speed; α is the cone angle; β is the shoulder concave angle; When the length of the stirring needle at the end of the stirring head is 70%~80% of the thickness of the weldment, the forming quality is best; the ratio of the shoulder diameter of the stirring head to the stirring needle diameter is 3:1.

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