Friction stir additive manufacturing device adopting wires and with back pressure support

Abstract

The invention provides a friction stir additive manufacturing device adopting wires and having a back pressure support function. The friction stir additive manufacturing device comprises an additive part, a supporting part, a driving part and a pressing part. The material adding part comprises a static shaft shoulder and a stirring shaft which are inserted together; the supporting part comprises a thrust ball bearing installed on the static shaft shoulder, a bearing structure detachably installed on the thrust ball bearing and a back pressure supporting structure installed on the bearing structure. The driving part comprises a hollow shaft torque motor and a driving shaft, and the driving shaft rotates along with a hollow shaft of the hollow shaft torque motor and axially moves; the pressing part comprises an end plate fixed to the top of the hollow shaft and an electric cylinder installed on the end plate, and the electric cylinder is used for driving the stirring shaft to move in the axial direction. According to the friction stir additive manufacturing device, the bearing mechanism and the backpressure supporting structure can be detached from the additive part together, so that the friction stir additive manufacturing device performs conventional workpiece machining, and after the bearing mechanism and the backpressure supporting structure are installed, the workpiece needing backpressure supporting can be subjected to additive machining, so that collapse of a corresponding area is avoided.

Description

Technical Field

[0001] This invention belongs to the field of friction stir additive manufacturing, and specifically relates to a friction stir additive manufacturing device with back pressure support using filament. Background Technology

[0002] When a friction stir additive manufacturing apparatus using filament as raw material is in operation, the substrate of the workpiece is placed on the worktable. During the additive manufacturing process, the stirring needle presses against the substrate under a certain pressure and penetrates into the substrate. When performing multi-layer additive manufacturing, the stirring needle penetrates into the topmost additive layer. Therefore, a back pressure reaction force is required throughout the additive manufacturing process to balance the downward pressure of the stirring needle. In existing additive manufacturing processes, the worktable acts as a back pressure support device and provides a back pressure reaction force to balance the downward pressure of the stirring needle. As a result, the shape of the workpiece is relatively regular, mainly flat or ring-shaped. When the shape of the workpiece becomes more complex, it is necessary to first make a regular flat or ring-shaped workpiece and then perform cutting to carry out a subtractive manufacturing operation, which leads to a decrease in work efficiency.

[0003] When the bottom of the workpiece has a recessed structure, the area corresponding to this recessed structure cannot independently withstand the downward pressure of the stirring pin, causing the area to collapse and affecting the smooth progress of the additive manufacturing process. Therefore, it is necessary to configure matching support components. Since different workpieces require different support components, a large number of support components are needed, which severely restricts the application of the friction stir additive manufacturing method.

[0004] In addition, existing friction stir additive manufacturing equipment usually requires the stationary shoulder and the stirring shaft to be connected separately to the non-rotating part and the rotating shaft rotor of the machining equipment used for additive manufacturing. Due to the diverse structures of friction stir additive manufacturing, it cannot be directly configured onto the corresponding machining equipment. It is necessary to set up corresponding connecting fixtures according to different machining equipment. Some machining equipment even requires major modifications, which leads to an increase in the cost of friction stir additive manufacturing. Summary of the Invention

[0005] To at least partially solve the aforementioned problems in the prior art, this application proposes a friction stir additive manufacturing apparatus with back pressure support using filament, comprising an additive part, a support part, a drive part, and a pressing part; the additive part includes a stationary shoulder and a stirring shaft, the stationary shoulder having an inner cavity, the stirring shaft including a helical rod, a drive shaft connected to the upper end of the helical rod, and a stirring needle formed at the lower end of the helical rod, the helical rod being inserted into the inner cavity of the stationary shoulder, forming a helical channel between the helical rod and the stationary shoulder, and a filament feeding hole communicating with the helical channel being opened on the stationary shoulder;

[0006] The support unit includes a thrust ball bearing, a load-bearing structure, and a back pressure support structure. The seat ring of the thrust ball bearing is fixed on the stationary shaft shoulder. The load-bearing structure is detachably mounted on the shaft ring of the thrust ball bearing. The back pressure support structure is mounted on the load-bearing structure and is located below the stirring shaft. The load-bearing structure includes two opposing rods that extend vertically. The upper ends of the rods are detachably mounted on the shaft ring of the thrust ball bearing. The back pressure support structure includes a support shaft and a support roller. The two ends of the support shaft are slidably mounted on a rod and can reciprocate vertically. The support roller is rotatably sleeved on the support shaft.

[0007] The drive unit includes a hollow shaft torque motor, which includes a first stator, a first mover rotatably mounted inside the first stator, and a hollow shaft fixedly connected to the first mover. The first stator is fixedly mounted on a stationary shoulder, and the drive shaft is slidably connected to the hollow shaft. The drive shaft is limited to rotating only with the hollow shaft and moving along the axial direction of the hollow shaft, but not rotating relative to the hollow shaft. The hollow shaft can drive the stirring shaft to rotate via the drive shaft.

[0008] The pressing part includes an end plate and an electric cylinder. The end plate is fixed to the top of the hollow shaft. One of the cylinder barrel and the piston rod of the electric cylinder is fixedly mounted on the end plate, and the other of the cylinder barrel and the piston rod is fixedly mounted on the drive shaft. The end plate and the drive shaft are spaced apart in the vertical direction. The electric cylinder can drive the stirring shaft to reciprocate axially relative to the hollow shaft.

[0009] When the electric cylinder drives the stirring shaft to move upward relative to the hollow shaft along the axial direction, the stirring needle can be completely accommodated in the inner cavity of the stationary shaft shoulder. When the electric cylinder drives the stirring shaft to move downward relative to the hollow shaft along the axial direction, the lower end face of the screw rod can be coplanar with the lower end face of the stationary shaft shoulder, or the lower end face of the screw rod can extend downward beyond the lower end face of the stationary shaft shoulder.

[0010] In this application, the supporting structure is detachably mounted on the shaft ring, allowing the supporting mechanism and other components mounted on the supporting structure to be removed from the additive manufacturing unit. This enables the friction stir additive manufacturing apparatus of this application to perform conventional workpiece processing. After installing the supporting structure and its connected components, additive manufacturing can be performed on workpieces requiring back pressure support to prevent collapse in the corresponding areas. By adjusting the position of the support shaft on the hanger, the distance between the support roller and the stationary shoulder can be adjusted to accommodate substrates of different thicknesses and different additive thicknesses. After processing one additive layer, the position of the support roller on the hanger is adjusted, and the additive manufacturing unit is simultaneously lifted upwards until the distance between the stationary shoulder and the uppermost additive layer reaches the thickness of one additive layer. The support roller is then supported on the lower surface of the substrate, and the formation of the next additive layer continues. This process is repeated until the entire component is produced. The additive layer is also called a deposited layer.

[0011] When it is necessary to adjust the orientation of the support relative to the additive manufacturing part, the entire support can be rotated around the central axis of the stationary shoulder by rotating the shaft ring. This adjusts the orientation of the support relative to the additive manufacturing part, so that during the production process, there is no need to adjust the orientation of the additive manufacturing part. The direction of movement of the entire friction stir additive manufacturing device can be changed while maintaining the orientation of the additive manufacturing part.

[0012] This application also includes a driving unit and a pressing unit. The driving unit drives the stirring shaft to rotate, and the pressing unit adjusts the height of the stirring shaft relative to the stationary shoulder, thus completing the work of the stirring needle penetrating the substrate or the existing additive layer. Therefore, this application only requires mounting the stationary shoulder on a movable device or a moving part of a device to perform additive manufacturing; alternatively, the stationary shoulder can be mounted on a stationary device, while the substrate is fixed on a moving device, and the additive manufacturing process is completed by moving the substrate.

[0013] Furthermore, to facilitate the adjustment of the back pressure support structure's position on the hanger rod, thereby adjusting the distance between the support shaft and the stationary shoulder to accommodate substrates of different thicknesses and enable the formation of multiple additive layers, a stepless adjustment mechanism is provided below the back pressure support structure. This stepless adjustment mechanism includes a lead screw, a mandrel, and a tapered roller. The two ends of the lead screw are rotatably mounted on a hanger rod, and the lead screw includes a first threaded section and a second threaded section. The helical directions of the threads on the first threaded section and the second threaded section are opposite, and a mandrel is meshed on the first threaded section and the second threaded section, respectively. A tapered roller is rotatably mounted on each mandrel, with the small end of each tapered roller facing the other tapered roller. The tapered roller can rotate freely relative to its mandrel. The support roller includes a straight cylindrical section and tapered sections located at both ends of the straight cylindrical section. The large end of each tapered section faces the other tapered section, and each tapered roller is supported on a tapered section.

[0014] A limiting mechanism is provided on the suspension rod to restrict the rotation of the mandrel around its own central axis. When the lead screw rotates, it can drive the mandrel to move in opposite directions along the axial direction, but the mandrel cannot rotate relative to its own central axis. When the mandrel drives the tapered roller to reciprocate along the axial direction, it can drive the back pressure support structure to reciprocate along the vertical direction. Preferably, the tapered roller is rotatably mounted on the mandrel via bearings.

[0015] Due to gravity, the tapered sections at both ends of the support roller press against the corresponding tapered rollers. When the screw is turned, when the two mandrels drive the tapered rollers to move towards each other, they push the support roller upwards. When the two mandrels drive the tapered rollers to move away from each other, the tapered rollers tend to move away from the support rollers. The support rollers, under the influence of gravity, move downwards to rest on the tapered rollers. This allows for smooth adjustment of the distance between the support rollers and the stationary shoulder. Because both the tapered sections of the tapered rollers and the support rollers are tapered, the height of the support rollers can be continuously and smoothly adjusted, forming stepless adjustment. This, in turn, allows for stepless adjustment of the distance between the support rollers and the stationary shoulder, accommodating the formation of additive layers of different thicknesses.

[0016] Specifically, the limiting mechanism includes a guide rod and a sliding member. Both ends of the guide rod are mounted on a suspension rod. For each mandrel, a sliding member is provided. One end of the sliding member is slidably mounted on the guide rod and can slide along the axial direction of the guide rod, while the other end is fixed to the corresponding mandrel. By utilizing the limiting effect of the sliding member, rotation of the mandrel around its central axis is prevented, while the reciprocating movement of the mandrel along the axial direction is not affected, ensuring the stepless adjustment mechanism can adjust the distance between the support roller and the stationary shoulder.

[0017] Furthermore, to improve control flexibility, a drive motor is mounted on a boom, and the output shaft of this drive motor is connected to the lead screw. In actual production, this drive motor can also be integrated into an automatic control system to improve control over the lead screw rotation.

[0018] Specifically, to facilitate disassembly of the support unit, a pressure ring is fixed on the shaft ring. The upper end of the lifting rod passes freely from bottom to top through the lifting rod hole on the pressure ring and is then screwed with a lifting rod nut to connect the lifting rod to the pressure ring. When the workpiece being processed is annular, it is impossible to directly insert the workpiece substrate between the stirring shaft and the back pressure support structure, and it is also impossible to remove the friction stirring additive manufacturing device from the workpiece after processing. In this case, it is only necessary to unscrew the lifting rod nut from the lifting rod to separate the entire support unit from the additive manufacturing unit, and then insert the substrate between the support unit and the additive manufacturing unit, or remove the workpiece and then install the lifting rod on the pressure ring via the lifting rod nut.

[0019] Furthermore, to facilitate control of the rotation of the support unit relative to the additive manufacturing unit, a steering mechanism is also included. This steering mechanism comprises a ring gear and a steering motor. The ring gear is fixedly mounted on the upper surface of the pressure ring, and the steering motor is mounted on the stationary shoulder. The gear on the output shaft of the steering motor meshes with the ring gear. When it is necessary to adjust the direction of the support unit relative to the additive manufacturing unit, the steering motor can be used to drive the pressure ring to rotate relative to the shoulder, thereby adjusting the direction of the support unit relative to the additive manufacturing unit. This allows the entire friction stir additive manufacturing apparatus to change its direction of movement while maintaining the orientation of the additive manufacturing unit during production, without needing to adjust the orientation of the additive manufacturing unit.

[0020] Furthermore, to ensure stable operation of the equipment, the stationary shoulder, stirring shaft, thrust ball bearing, and ring gear are coaxially arranged.

[0021] Furthermore, to prevent the power cord of the electric cylinder from tangling when it rotates with the hollow shaft, a conductive slip ring is also included. This conductive slip ring includes a second stator and a second mover rotatably disposed inside the second stator. The second stator is fixedly mounted on the first stator or the shoulder of the stationary shaft. The power cord of the electric cylinder is connected to the second mover.

[0022] Furthermore, to facilitate the installation of the friction stir additive manufacturing apparatus, a mounting portion is provided on the stationary shoulder. This mounting portion is used to connect the stationary shoulder to the non-rotating part of the machining equipment. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of an embodiment of this application.

[0024] Figure 2 for Figure 1 Enlarged view of section A.

[0025] Figure 3 for Figure 2 A view from the center (BB direction). Detailed Implementation

[0026] See Figures 1-3 A friction stir additive manufacturing apparatus with back pressure support using filament includes an additive section, a support section, a drive section, and a pressing section 90. The additive section includes a stationary shoulder 18 and a stirring shaft 20. The stationary shoulder 18 is cylindrical, having an inner cavity, and is coaxially arranged with the stirring shaft 20. The upper end of the stationary shoulder extends radially outward to form a flange 19, which serves as a mounting part for connecting the stationary shoulder to a non-rotating part of a machining equipment. A mounting hole 191 is provided on the flange 19.

[0027] The stirring shaft 20 includes, from bottom to top, a spiral rod 24, a drive shaft 23 connected to the upper end of the spiral rod, and a stirring needle 27 formed at the lower end of the spiral rod 24. Specifically, the spiral rod 24 includes a vertically downward extending rod body 241 and spiral blades 242 formed on the outer circumferential surface of the rod body. The stirring needle 27 is formed on the lower surface of the rod body. The lower end face of the rod body forms the stirring shaft end face 251. The spiral rod 24 is inserted into the inner cavity of the stationary shaft shoulder, forming a spiral channel 243 between the spiral rod and the stationary shaft shoulder. A wire feeding hole 181 communicating with the spiral channel is provided on the stationary shaft shoulder.

[0028] The support includes a thrust ball bearing 41, a load-bearing structure 40, and a back pressure support structure 50. A support ring 42 is fitted onto the stationary shoulder 18 and is bolted to the outer wall of the stationary shoulder. The thrust ball bearing 41 includes a housing ring 411, a shaft ring 412 located above the housing ring, and balls located between the housing ring and the shaft ring. The shaft ring is rotatably supported on the housing ring by the balls, and the housing ring 411 of the thrust ball bearing 41 is fixed to the upper side of the support ring 42.

[0029] The load-bearing structure 40 includes two opposing hanger rods 44 and a pressure ring 43. The pressure ring is fitted onto the stationary shaft shoulder and presses against the upper surface of the shaft ring 412 of the thrust ball bearing 41. Both hanger rods are mounted on the pressure ring. The hanger rods extend vertically and have a support flange 441 at their upper part. An external threaded section is provided on the hanger rod above the support flange. The external threaded section passes through the hanger rod hole 431 of the pressure ring 43 from bottom to top and is screwed with a hanger rod nut 442, thus suspending the hanger rod on the pressure ring 43 and detachably mounting the upper end of the hanger rod onto the shaft ring.

[0030] To ensure a stable connection with the thrust ball bearing 41, a lower groove is provided on the upper side of the support ring 42, and the seat ring 411 is tightly held in the lower groove. An upper groove is provided on the lower side of the pressure ring 43, and the shaft ring 412 is tightly held in the upper groove.

[0031] A back pressure support structure 50 is mounted on the bearing structure 40 and is located below the stirring shaft. The back pressure support structure 50 includes a support shaft 51 and a support roller 52. Both ends of the support shaft are connected to a suspension rod, and the support roller is rotatably mounted on the support shaft. Specifically, in this embodiment, to allow the support roller to rotate flexibly on the support shaft, both ends of the support roller are rotatably mounted on the support shaft via an angular contact bearing A53. A shoulder A is formed at both ends of the inner cavity of the support roller, and a locking nut A54 is screwed onto both ends of the support shaft. The locking nut A presses against the inner ring of the angular contact bearing A, and the outer ring of the angular contact bearing A presses against the shoulder step surface 523 of the shoulder A, allowing the support roller 52 to rotate freely and be held on the support shaft 51. The mounting method of the angular contact bearing A uses existing mature technology and will not be described in detail. It is understood that in another embodiment, the angular contact bearing A can be omitted, and the support roller 52 can be directly rotatably mounted on the support shaft.

[0032] To enable the back pressure support structure 50 to be adjusted according to the thickness of different workpieces and different thickness areas of the same workpiece, so as to maintain the contact between the support roller and the lower surface of the workpiece and provide support for the workpiece, a groove 443 is provided on each hanger rod. The groove 443 extends vertically and passes through the opposite sides of the hanger rod along the axial direction of the support shaft. The two ends of the support shaft are respectively formed as support ends 511, and each support end is inserted into the groove of a hanger rod. To prevent the support shaft from moving along its axial direction, an anti-movement nut 512 is screwed on each support end 511. The anti-movement nut is located on the outside of the hanger rod. The groove 443 allows the two ends of the support shaft to be slidably mounted on a hanger rod and to move back and forth in the vertical direction.

[0033] It is understood that, in another embodiment, a slide rail can be installed on the inner side of the boom, and corresponding sliders can be installed at both ends of the support shaft so that the sliders are held in place on the slide rail.

[0034] To facilitate the adjustment of the height of the back pressure support structure 50, thereby adjusting the distance between the support roller 52 and the stationary shoulder to accommodate processing areas of different workpiece thicknesses or substrates of different thicknesses, this embodiment also provides a stepless adjustment mechanism 60, which is located below the back pressure support structure.

[0035] The continuously variable adjustment mechanism 60 specifically includes a lead screw 61, a spindle 63, and a tapered roller 64. The two ends of the lead screw are each formed as an optical shaft 613, which are rotatably mounted on a suspension rod. The lead screw includes a first threaded section 611 and a second threaded section 612, with opposite helical directions. A spindle 63 meshes with each of the first and second threaded sections. A tapered roller 64 is rotatably mounted on each spindle 63, and the tapered roller can rotate freely relative to its corresponding spindle. The tapered roller is conical, with the small end of each tapered roller facing the other tapered roller. In this embodiment, the optical shaft is directly rotatably mounted in a corresponding shaft hole on the suspension rod. It can be understood that in another embodiment, the optical shaft can be mounted in the corresponding shaft hole via a bearing.

[0036] In this embodiment, each tapered roller is rotatably mounted on its corresponding mandrel via two angular contact bearings B65 and locked in place by lock nuts B66. The mounting method of the angular contact bearings B uses existing mature technology and will not be described in detail. It is understood that in another embodiment, the angular contact bearings B can be omitted, and the tapered roller can be directly rotatably fitted onto the mandrel.

[0037] The support roller 52 includes a straight cylindrical section 521 and tapered sections 522 located at both ends of the straight cylindrical section 521. The tapered sections are tapered, and the large end of each tapered section faces the other tapered section. Each tapered roller is supported on a tapered section.

[0038] During operation, the straight section 521 of the support roller 52 is supported on the lower surface of the workpiece 80, and each conical roller 64 is supported on a conical section 522. For clarity, in the attached drawings, there is a distance between the straight section 521 of the support roller 52 and the workpiece 80, and a distance between the conical roller 64 and the conical section 522.

[0039] To facilitate the driving of the lead screw, a drive motor 62 is installed on a boom, and the output shaft of the drive motor is connected to the lead screw.

[0040] To prevent the mandrel from rotating with the lead screw during its rotation, a limiting mechanism 70 is provided on the suspension rod. This limiting mechanism restricts the mandrel from rotating around its own central axis and is located below the continuously variable adjustment mechanism. The limiting mechanism 70 includes a guide rod 71 and a sliding member 72. Both ends of the guide rod are fixed to the suspension rod by a connecting bolt 73. A sliding member 72 is provided for each mandrel. Each sliding member 72 includes a sliding rod 722 and a connecting screw 723. A collar 721 is welded to one end of the sliding rod 722. This collar 721 freely fits onto the guide rod and can slide freely along the axial direction of the guide rod. The connecting screw 723 secures the other end of the sliding rod 722 to the end face of the corresponding mandrel 63.

[0041] Under the constraint of the limiting mechanism, when the lead screw rotates, it can drive the mandrel to move towards or away from each other in the axial direction, and the mandrel cannot rotate relative to its own central axis; when the mandrel drives the conical roller to move back and forth in the axial direction, it can drive the back pressure support structure to move back and forth in the vertical direction.

[0042] To facilitate rotation of the back pressure support structure and enable the additive manufacturing unit to change its direction of travel while maintaining its orientation, a steering mechanism is also provided in this embodiment. This steering mechanism includes an annular gear ring 46 and a steering motor 47. The annular gear ring 46 is fixedly mounted on the upper surface of the pressure ring 43, and the steering motor 47 is mounted on the outer wall of the stationary shoulder. A gear 48 on the output shaft of the steering motor meshes with the annular gear ring. The annular gear ring, thrust ball bearing, stirring shaft, and stationary shoulder are coaxially arranged.

[0043] In this application, both the drive motor 62 and the directional motor 47 are servo motors for precise control.

[0044] The drive unit includes a hollow shaft torque motor 10, which includes a first stator 110, a first mover 13 rotatably mounted inside the first stator, and a hollow shaft 14 fixedly connected to the first mover. The central axis 101 of the hollow shaft torque motor 10 extends vertically. In this embodiment, the first stator 110 specifically includes a housing 11, an upper end cover 15, and a lower end cover 16. The housing 11 is cylindrical and extends vertically, and a winding 12 is provided on the inner side of the housing. The structure of the hollow shaft torque motor can be achieved using existing mature technology and will not be described in detail here.

[0045] An upper flange 111 and a lower flange 112 are respectively provided at the upper and lower ends of the outer casing. The upper flange 111 is located above the lower flange 112. The upper end cover has a first flange corresponding to the upper flange. A first bolt fixes the first flange to the upper flange. The lower end cover has a second flange corresponding to the lower flange. A second bolt fixes the second flange to the lower flange, so that the upper end cover and the lower end cover can be detachably installed at the top and bottom of the outer casing, respectively.

[0046] The upper and lower ends of the housing are rotatably connected to the hollow shaft 14 via the upper angular contact bearing 31 and the lower angular contact bearing 32, respectively. The upper angular contact bearing 31 and the lower angular contact bearing 32 enable the housing to provide axial force to the stirring shaft 20 via the hollow shaft 14, so that the stirring needle 27 can be pressed into the workpiece.

[0047] In this embodiment, an upper flange 113 is provided on the upper part of the outer peripheral surface of the hollow shaft 14, and the upper end cover has an inwardly protruding abutting flange 153. The lower surface of the abutting flange 153 is a downward-facing stepped surface. The upper flange abuts against the lower side of the inner ring of the upper angular contact bearing, and the abutting flange 153 abuts against the upper side of the outer ring of the upper angular contact bearing via its lower surface, so that the upper end cover 15 abuts against the hollow shaft 14 via the upper angular contact bearing 31.

[0048] A stepped portion 114 is provided at the lower end of the hollow shaft 14. The stepped portion is formed by a radial inward indentation from the outer circumferential surface of the hollow shaft, and the stepped portion has a downward-facing stepped surface. The inner side of the lower end cover has an upward-facing abutting surface 164, which is also an upward-facing stepped surface. The stepped portion 114 presses against the upper side of the inner ring of the lower angular contact bearing, and the abutting surface 164 presses against the lower side of the outer ring of the lower angular contact bearing, so that the lower end cover 16 abuts against the hollow shaft 14 via the lower angular contact bearing 32.

[0049] In this embodiment, the lower end cover 16 is integrally formed on the upper side of the flange flange 19, thereby connecting the first stator 110 to the flange flange 19, so that the first stator is indirectly mounted on the stationary shoulder via the flange flange.

[0050] The drive shaft 23 is slidably connected to the hollow shaft. The drive shaft 23 is limited to rotating with the hollow shaft and moving axially along the hollow shaft, but cannot rotate relative to the hollow shaft. The hollow shaft can drive the stirring shaft to rotate via the drive shaft. Thus, the entire stirring shaft 20 is limited to rotating with the hollow shaft and moving axially along the hollow shaft, but cannot rotate relative to the hollow shaft.

[0051] In this embodiment, the drive shaft is connected to the hollow shaft by a flat key 17. A first keyway 171 extending axially is formed on the inner circumferential surface of the hollow shaft, and a second keyway 172 is formed on the outer circumferential surface of the drive shaft. The flat key 17 is inserted into the first and second keyways, connecting the drive shaft and the hollow shaft circumferentially, so that the hollow shaft can drive the drive shaft to rotate, thereby driving the entire stirring shaft to rotate. The first keyway extends axially through the upper and lower end faces of the hollow shaft, and the second keyway extends axially upward through the upper end face of the drive shaft, so that the stirring shaft can move axially relative to the hollow shaft under the action of the pressing part. In this embodiment, three flat keys are provided, which are evenly spaced around the drive shaft. For the sake of simplicity, only one flat key is shown in the figure. It can be understood that in another embodiment, a spline can be used instead of a flat key.

[0052] The pressing part 90 includes an end plate 91 and an electric cylinder 92. The top surface of the drive shaft is lower than the top surface of the hollow shaft, so that the top surface of the drive shaft is accommodated in the inner cavity of the hollow shaft. The end plate is fixedly mounted on the top surface of the hollow shaft with bolts. The cylinder barrel 921 of the electric cylinder 92 is fixedly mounted on the upper surface of the end plate. The piston rod 922 of the electric cylinder 92 passes freely downward through the end plate hole 911 on the end plate and is connected to the drive shaft 23. An external thread is provided on the outer circumferential surface of the end of the piston rod 922, and the piston rod is screwed onto the top of the drive shaft 23 through the external thread. It can be understood that in another embodiment, the cylinder barrel 921 can also be fixed on the drive shaft and the piston rod can be fixed on the end plate. In this embodiment, the electric cylinder is specifically an AC servo electric cylinder.

[0053] The end plate and the drive shaft are spaced apart in the vertical direction, meaning there is a distance between the lower surface of the end plate and the upper surface of the drive shaft, allowing the electric cylinder to drive the stirring shaft to reciprocate axially relative to the hollow shaft. The distance between the end plate and the drive shaft satisfies the following conditions: when the electric cylinder drives the stirring shaft to move axially upward relative to the hollow shaft, the stirring needle can be completely accommodated in the inner cavity of the stationary shaft shoulder; when the electric cylinder drives the stirring shaft to move axially downward relative to the hollow shaft, the lower end face of the stirring needle extends downward beyond the lower end face of the stationary shaft shoulder, enabling additive manufacturing. In this embodiment, the axial movement distance of the drive shaft relative to the hollow shaft is three times the height of the stirring needle, providing sufficient space for the axial movement of the drive shaft relative to the hollow shaft.

[0054] To prevent the power cord of the electric cylinder from tangling when it rotates with the hollow shaft, this embodiment also includes a conductive slip ring 93. The conductive slip ring 93 includes a second stator 931 and a second mover 932. The second mover is rotatably mounted inside the second stator via a first angular contact bearing 935 and a second angular contact bearing 936. The conductive slip ring 93 can be manufactured using current technology and will not be described in detail. The second stator is bolted to the upper surface of the upper end cover 15 of the first stator, and the power cord of the electric cylinder is connected to the second mover 932.

[0055] In the embodiment, the friction stir additive manufacturing apparatus performs additive manufacturing operations according to the following steps:

[0056] (1) First, the substrate 81 is inserted between the stirring shaft and the back pressure support structure 50. Then, the drive motor 62 drives the lead screw to rotate, so that the two mandrels 63 drive the corresponding conical rollers 64 to move axially. The height of the back pressure support structure 50 is adjusted so that the support roller 52 is supported on the lower surface of the upward concave area of ​​the substrate, providing support for the downward pressure of the stirring needle and preventing the concave area from sinking downward under the pressure of the stirring needle. Then, the hollow shaft torque motor is started so that its mover drives the stirring shaft to rotate. The electric cylinder is started simultaneously to push the stirring shaft downward so that the stirring needle is inserted into the substrate and reaches the set depth. The electric cylinder is then paused. The filament enters the spiral channel through the filament feeding hole 181. Then, under the push of the spiral conveying rod, the filament is squeezed, plasticized and flows downward. Finally, it is discharged from the spiral channel and stirred and welded with the surface layer of the substrate. The lower end face 183 of the stationary shaft shoulder 18 smooths the surface after additive manufacturing, forming the first additive layer 82.

[0057] (2) Start the electric cylinder, lift the stirring shaft upward, so that the stirring needle retracts into the inner cavity of the stationary shoulder, and then use the drive motor to drive the screw to rotate, so that the two spindles 63 drive the corresponding conical rollers 64 to move axially, and simultaneously lift the stationary shoulder upward, so that the distance between the lower end face of the stationary shoulder and the first additive layer reaches the thickness of one additive layer, and then pause the upward lifting of the stationary shoulder.

[0058] (3) Restart the hollow shaft torque motor so that its mover drives the stirring shaft to rotate. Simultaneously start the electric cylinder and push the stirring shaft downward so that the stirring needle penetrates into the substrate and reaches the set depth. Then pause the electric cylinder. The filament enters the spiral channel through the filament feeding hole 181. Then, under the push of the spiral conveying rod, the filament is squeezed, plasticized and flows downward. Finally, it is discharged from the spiral channel and stirred and welded with the surface of the first additive layer. The lower end face 183 of the stationary shaft shoulder 18 smooths the surface after additive layering to form the second additive layer.

[0059] (4) Repeat steps (2) and (3) to continue forming the additive layer 82 until the production of workpiece 80 is completed.

[0060] When the substrate is ring-shaped, before installing the substrate, first unscrew the hanger nut from the hanger, then insert the substrate between the additive manufacturing section and the support section, insert the hanger into the hanger hole, and screw the hanger nut onto the hanger. Install the hanger on the pressure ring. After the workpiece production is completed, first unscrew the hanger nut from the hanger, then remove the workpiece, then insert the hanger into the hanger hole, screw the hanger nut onto the hanger, and install the hanger on the pressure ring, ready for use.

Claims

1. A friction stir additive manufacturing apparatus with back pressure support using filament, characterized in that, It includes an additive manufacturing section, a support section, a drive section, and a pressing section; the additive manufacturing section includes a stationary shoulder and a stirring shaft. The stationary shoulder has an inner cavity. The stirring shaft includes a spiral rod, a drive shaft connected to the upper end of the spiral rod, and a stirring needle formed at the lower end of the spiral rod. The spiral rod is inserted into the inner cavity of the stationary shoulder, forming a spiral channel between the spiral rod and the stationary shoulder. A wire feeding hole communicating with the spiral channel is provided on the stationary shoulder. The support unit includes a thrust ball bearing, a load-bearing structure, and a back pressure support structure. The seat ring of the thrust ball bearing is fixed on the stationary shaft shoulder. The load-bearing structure is detachably mounted on the shaft ring of the thrust ball bearing. The back pressure support structure is mounted on the load-bearing structure and is located below the stirring shaft. The load-bearing structure includes two opposing rods that extend vertically. The upper ends of the rods are detachably mounted on the shaft ring of the thrust ball bearing. The back pressure support structure includes a support shaft and a support roller. The two ends of the support shaft are slidably mounted on a rod and can reciprocate vertically. The support roller is rotatably sleeved on the support shaft. The drive unit includes a hollow shaft torque motor, which includes a first stator, a first mover rotatably mounted inside the first stator, and a hollow shaft fixedly connected to the first mover. The first stator is fixedly mounted on a stationary shoulder, and the drive shaft is slidably connected to the hollow shaft. The drive shaft is limited to rotating only with the hollow shaft and moving along the axial direction of the hollow shaft, but not rotating relative to the hollow shaft. The hollow shaft can drive the stirring shaft to rotate via the drive shaft. The pressing part includes an end plate and an electric cylinder. The end plate is fixed to the top of the hollow shaft. One of the cylinder barrel and the piston rod of the electric cylinder is fixedly mounted on the end plate, and the other of the cylinder barrel and the piston rod is fixedly mounted on the drive shaft. The end plate and the drive shaft are spaced apart in the vertical direction. The electric cylinder can drive the stirring shaft to reciprocate axially relative to the hollow shaft.

2. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, A stepless adjustment mechanism is provided below the back pressure support structure. The stepless adjustment mechanism includes a lead screw, a mandrel, and a conical roller. The two ends of the lead screw are rotatably mounted on a suspension rod. The lead screw includes a first threaded section and a second threaded section. The helical directions of the threads on the first threaded section and the second threaded section are opposite. A mandrel is meshed on the first threaded section and the second threaded section, respectively. A conical roller is rotatably mounted on each mandrel. The small end of each conical roller faces the other conical roller. The conical roller can rotate freely relative to the mandrel it is on. The support roller includes a straight cylindrical section and conical sections located at both ends of the straight cylindrical section. The large end of each conical section faces the other conical section. Each conical roller is supported on a conical section. A limiting mechanism is provided on the suspension rod to restrict the spindle from rotating around its own central axis. When the lead screw rotates, it can drive the spindle to move towards or away from each other in the axial direction, and the spindle cannot rotate relative to its own central axis. When the spindle drives the conical roller to move back and forth in the axial direction, it can drive the back pressure support structure to move back and forth in the vertical direction.

3. The friction stir additive manufacturing apparatus according to claim 2, characterized in that, The limiting mechanism includes a guide rod and a sliding member. The two ends of the guide rod are respectively mounted on a hanging rod. For each mandrel, a sliding member is provided. One end of the sliding member is slidably mounted on the guide rod and can slide along the axial direction of the guide rod. The other end of the sliding member is fixed on the corresponding mandrel.

4. The friction stir additive manufacturing apparatus according to claim 2, characterized in that, A drive motor is mounted on a boom, and the output shaft of the drive motor is connected to a lead screw.

5. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, A pressure ring is fixed on the shaft ring. The upper end of the lifting rod passes freely from bottom to top through the lifting rod hole on the pressure ring and then a lifting rod nut is screwed on to connect the lifting rod to the pressure ring.

6. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, It also includes a steering mechanism, which comprises a ring gear and a steering motor. The ring gear is fixedly mounted on the upper surface of the pressure ring, and the steering motor is mounted on the stationary shaft shoulder. The gear on the output shaft of the steering motor meshes with the ring gear.

7. The friction stir additive manufacturing apparatus according to claim 7, characterized in that, The stationary shoulder, stirring shaft, thrust ball bearing, and ring gear are coaxially arranged.

8. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, The drive shaft is connected to the hollow shaft using a flat key or spline.

9. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, It also includes a conductive slip ring, which includes a second stator and a second mover rotatably disposed inside the second stator, the second stator being fixedly mounted on the first stator or the stationary shoulder.

10. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, A mounting section is provided on the stationary shaft shoulder.

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