Friction stir additive manufacturing device and method for double-shaft synchronous operation

Abstract

The invention discloses a double-shaft synchronous operation stirring friction additive manufacturing device which comprises two stirring heads, and the arrangement direction of the two stirring heads is perpendicular to the moving direction of the stirring friction additive manufacturing device. A shaft shoulder of the stirring shaft is in a star shape and is provided with protruding parts which protrude outwards in the radial direction and are evenly arranged at intervals in a radial shape, and the protruding parts are internally provided with material distribution cavities which are sunken upwards and communicated with discharging holes in the stirring head. A groove area is formed between every two adjacent protruding parts, the protruding part of each stirring head is inserted into the groove area of the other stirring head, the lower end faces of the shaft shoulders of the two stirring shafts are coplanar, and stirring needles protruding downwards are arranged on the lower end faces of the shaft shoulders. The invention further discloses a friction stir additive manufacturing method. A single heat sink layer wider than a single stirring head can be formed at a time through the two stirring heads, and due to the fact that the protruding parts of the two stirring heads are arranged in a staggered mode, plasticized materials in the two stirring heads can be fused with each other, and the product quality is guaranteed.

Description

Technical Field

[0001] The present invention relates to a friction stir additive manufacturing device for biaxial synchronous operation and a friction stir additive manufacturing method using the friction stir additive manufacturing device. Background Art

[0002] Friction stir additive manufacturing is a new type of solid-phase additive manufacturing method, which can achieve high-performance additive manufacturing of materials such as aluminum alloy, magnesium alloy, copper alloy or titanium alloy. At present, the additive method mainly focuses on single-pass multi-layer additive components. When manufacturing large-size products, a multi-layer and multi-pass additive method needs to be adopted, resulting in low production efficiency. Summary of the Invention

[0003] To solve the problem in the prior art that when manufacturing large-size products by friction stir additive manufacturing, a multi-layer and multi-pass additive method needs to be adopted, resulting in low production efficiency, the present application first proposes a friction stir additive manufacturing device for biaxial synchronous operation, which includes a base and two stirring heads rotatably installed on the base; when the friction stir additive manufacturing device operates, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device;

[0004] Each stirring head includes a stirring shaft extending in the vertical direction and a material feeding hole formed in the stirring shaft. The lower end of the stirring shaft is formed as a shoulder, and a stirring pin protruding downward is provided on the lower end surface of the shoulder; the shoulder is star-shaped, and the shoulder has protruding portions protruding radially outward and evenly spaced in a radial pattern. A cloth cavity is formed by upward depression in the protruding portion. The cloth cavity is open downward, and the cloth cavity communicates with the material feeding hole; the material feeding hole is a regular polygon, and the bar has an outer peripheral surface with the same shape as the inner peripheral surface of the material feeding hole;

[0005] The space between two adjacent protruding portions of the same stirring head forms a groove area, and the protruding portions of each stirring head are inserted into the groove areas of the other stirring head; the radially outer edges of the cloth cavities of the same stirring head are located on a virtual circle, and the virtual circles corresponding to the two stirring heads partially intersect; the virtual circle corresponding to each stirring head is coaxially arranged with the stirring shaft of the stirring head;

[0006] Corresponding to each stirring head, a pressing mechanism is installed on the base, and the pressing mechanism is used to push the bar located in the material feeding hole downward; a driving motor for driving the stirring head to rotate is also installed on the base, and the driving motor is a servo motor; the lower end surfaces of the two shoulders are coplanar.

[0007] In this application, when the friction stir additive manufacturing device is working, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device during operation, so that the two stirring heads move side by side synchronously along the set direction, and a single-layer heat sink layer wider than that of a single stirring head can be formed at one time. According to the different sizes of the groove areas of the two stirring heads, the single-layer heat sink layer formed in this application is 1.7 - 1.9 times that of the existing single-layer heat sink. When the friction stir additive manufacturing device in this application is working, the bar stock in the feeding hole is thermoplastified by friction and forms plasticized material. The plasticized material flows radially along the stirring head in the cloth cavity and fills the entire cloth cavity. When the two stirring heads rotate synchronously, since the protruding parts of the two stirring heads are arranged in an interlaced manner, the plasticized materials in the two stirring heads can be fused with each other, so that the heat sink layers formed by the two stirring heads can be seamlessly fused together, ensuring the product quality.

[0008] Further, to reduce the manufacturing cost of the equipment, the structures of the two stirring heads are the same, and the diameters of the virtual circles corresponding to the two stirring heads are the same. The diameter of the virtual circle is 3 - 8 mm larger than the distance between the central axes of the two stirring heads. Since the structures of the two stirring heads are the same, a single type of bar stock can meet the needs of the two stirring heads, and at the same time, the corresponding accessories of the two stirring heads can also be interchanged, reducing the maintenance cost of the equipment.

[0009] Further, to enable the stirring head to distribute the material evenly during operation and lay the plasticized material evenly, the radially inner ends of two adjacent cloth cavities of the same stirring head are interconnected.

[0010] Further, for each stirring head, a driving motor is provided. The driving motor is a hollow shaft torque motor. The hollow shaft torque motor includes a stator, a rotor rotatably lined inside the stator, and a hollow shaft fixed on the rotor. The hollow shaft of the hollow shaft torque motor is rotatably installed on the outer wall of the stirring head through a transition bearing, and the stator of the hollow shaft torque motor is fixed on the base;

[0011] A limiting mechanism is also installed on the hollow shaft of each hollow shaft torque motor. The limiting mechanism includes at least one limiting rod. The limiting rod is movably installed on the hollow shaft. There is a limiting hole corresponding to the limiting rod on the stirring head. The limiting rod can reciprocate radially along the stirring head and insert into the corresponding limiting hole or withdraw from the limiting hole;

[0012] When the limiting rod is inserted into the limiting hole, the hollow shaft can drive the corresponding stirring head to rotate synchronously; when the limiting rod withdraws from the limiting hole, the hollow shaft and the corresponding stirring head can rotate relatively; when the limiting rod on the hollow shaft of one of the hollow shaft torque motors is inserted into the corresponding limiting hole, the limiting rod on the hollow shaft of the other hollow shaft torque motor withdraws from the corresponding limiting hole;

[0013] A gear is fixed on the outer walls of both stirring heads. The gears on the two stirring heads are meshed with each other, and the transmission ratio of the gears on the two stirring heads is 1:1.

[0014] In this application, two driving motors are provided, corresponding to the two stirring heads respectively. When one of the driving motors drives the corresponding stirring head to rotate, it can drive the other stirring head to rotate synchronously through the gears. To avoid the generation of reverse current when the other driving motor rotates passively, which may cause impact and damage to the driving motor and the corresponding accessories, a limiting mechanism is provided. When working, the hollow shaft of one of the driving motors is connected to the corresponding stirring head through the limiting mechanism, and the connection between the hollow shaft of the other driving motor and the corresponding stirring head is disconnected, thereby avoiding the generation of reverse current due to the rotation of the hollow shaft of the other driving motor and ensuring the safe use of the driving motor. In addition, after setting two driving motors, the continuous production can be ensured. The two driving motors can be used as backup units for each other, forming a redundant design. During the production process, when one of the driving motors fails and cannot work normally, the other driving motor can be started to continue the production of the product, reducing production costs.

[0015] Specifically, to ensure the installation stability of the hollow shaft, the hollow shaft of the hollow shaft torque motor is rotatably installed on the outer wall of the stirring head through two transition bearings arranged at intervals up and down. The lower transition bearing is a slewing bearing, and the upper transition bearing is a deep groove ball bearing. Among the two transition bearings, the slewing bearing is used to support the weight of the entire hollow shaft torque motor, and the deep groove ball bearing is to prevent the hollow shaft from tilting when only the slewing bearing is used.

[0016] Specifically, to facilitate the operation of the limiting rod, for each limiting rod, an adjustment hole extending radially along the stirring head is provided on the corresponding hollow shaft. The adjustment hole is an internal thread hole and is a through hole, and the limiting rod is screwed into the corresponding adjustment hole.

[0017] Furthermore, to facilitate continuous feeding, a feeding mechanism is provided for each stirring head. Each feeding mechanism includes a support plate and a raw material container rotatably arranged on the support plate. The support plate is detachably installed on the base and is located above the stirring head. The raw material container has a rotating shaft and a plurality of raw material through holes arranged around the rotating shaft. Each raw material through hole can only accommodate one bar stock in the radial direction. A feeding hole communicating with the blanking hole is provided on the support plate. When the raw material container rotates, each raw material through hole can sequentially communicate with the feeding hole, and the bar stock in the raw material through hole can enter the blanking hole of the corresponding stirring head through the feeding hole.

[0018] Specifically, the blank holding mechanism is a piston cylinder. A piston cylinder is provided corresponding to each stirring head. The cylinder barrel of the piston cylinder is fixed on the base, and the piston rod of the piston cylinder extends downward and can freely extend into the blanking hole to squeeze the bar stock downward. The piston cylinder can specifically be a hydraulic piston cylinder or an electric piston cylinder.

[0019] This application can be connected to the fixed part of machining equipment such as a friction stir welding machine, a CNC milling machine, and a CNC machining center through the base, and use the machining equipment to move the friction stir additive manufacturing device. Of course, a dedicated moving device can also be set up to move the friction stir additive manufacturing device.

[0020] Secondly, to enable the above-mentioned friction stir additive manufacturing device to complete production smoothly, this application also discloses a friction stir additive manufacturing method, which is carried out using the friction stir additive manufacturing device described in any one of the above. The friction stir additive manufacturing method includes the following steps:

[0021] (1) Feed the bar stock into the blanking holes of the two stirring heads and make the lower end surface of the bar stock flush with the lower end surface of the shoulder.

[0022] (2) Place the shoulder on the surface of the area to be additively manufactured on the base material, start the driving motor, and the two stirring heads rotate synchronously, so that the shoulder contacts the upper surface of the base material, and the stirring pins penetrate into the base material for friction preheating for 10 - 25 seconds.

[0023] (3) Start the blank holding mechanism, and the bar stock in the blanking hole moves downward, generating a upsetting force between the bar stock and the area to be additively manufactured on the base material. At the same time, withdraw the stirring head upward by 0.2 - 2.0 mm, and move the friction stir additive manufacturing device along the set path. The bar stock undergoes thermoplasticization under the action of friction and flows out of the blanking hole. Keep the stirring head rotating, and the thermoplasticized bar stock is deposited on the base material and forms an additively manufactured surface under the flattening action of the shoulder, realizing the cladding of a single-layer heat sink layer in the area to be additively manufactured and forming an additively manufactured layer; the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device.

[0024] After thermoplasticization, the bar stock becomes plasticized material and fills the cloth cavities of the two shoulders. The plasticized materials in the two cloth cavities are fused with each other and synchronously deposited on the base material.

[0025] When the top end surface of the bar stock in the blanking hole drops to be flush with the upper surface of the support plate, align the next bar stock with the feed hole, and the blank holding mechanism continues to squeeze the bar stock downward.

[0026] (4) Repeat the cladding of the single-layer heat sink layer in the area to be additively manufactured until the required additive height is reached.

[0027] In this manufacturing method, when the friction stir additive manufacturing device is working, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device during operation, so that the two stirring heads move side by side synchronously along the set direction, and a single-layer heat sink layer wider than that of a single stirring head can be formed at one time. During the production process, the bar stock is frictionally thermoplastified in the blanking hole to form plasticized material, which flows radially along the stirring head in the cloth cavity and fills the entire cloth cavity. When the two stirring heads rotate synchronously, since the protruding parts of the two stirring heads are arranged in an interlaced manner, the plasticized materials in the two stirring heads can be fused with each other, so that the heat sink layers formed by the two stirring heads can be seamlessly fused together, ensuring the product quality. Brief Description of the Drawings

[0028] Figure 1 is a schematic structural diagram of an embodiment of the present application.

[0029] Figure 2 is Figure 1 the view in the direction of A-A in

[0030] Figure 3 is Figure 2 the bottom view of

[0031] Figure 4 is a schematic structural diagram of the first stirring head and corresponding accessories.

[0032] Figure 5 is Figure 4 the view in the direction of B-B in Detailed Description of the Embodiment

[0033] Embodiment 1

[0034] First, the structure of the friction stir additive manufacturing device with double-axis synchronous operation will be described below. Please refer to Figures 1-5 , the friction stir additive manufacturing device includes a base 500 and two stirring heads rotatably mounted on the base. The two stirring heads are respectively a first stirring head 201 and a second stirring head 202; when the friction stir additive manufacturing device operates, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device. In the drawings, the direction of the first arrow X indicates the arrangement direction of the two stirring heads, and the direction of the second arrow Y indicates the moving direction of the friction stir additive manufacturing device during operation, that is, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device during operation.

[0035] In this embodiment, the structures of the two stirring heads are the same. Taking the first stirring head 201 as an example, the structure of the two stirring heads will be described below. The first stirring head 201 includes a stirring shaft 21 extending in the vertical direction and a blanking hole 22 formed in the stirring shaft 21. The lower end of the stirring shaft 21 is formed as a shoulder 25, and the lower end surfaces of the two shoulders are coplanar.

[0036] The shoulder 25 is star-shaped. The shoulder 25 has protrusions 251 that protrude radially outward and are evenly spaced radially. A cloth cavity 252 is formed by being recessed upward within the protrusions. The cloth cavity is open downward. The cloth cavity 252 communicates with the blanking hole 22, enabling the bar stock in the blanking hole to flow into each cloth cavity after being plasticized. The blanking hole is a regular polygon, and the bar stock has an outer peripheral surface with the same shape as the inner peripheral surface of the blanking hole. In this embodiment, the inner peripheral surface of the blanking hole and the outer peripheral surface of the bar stock are regular hexagons with the same shape. The radially inner ends of two adjacent cloth cavities of the same stirring head communicate with each other. A stirring needle 27 that protrudes downward is provided on the lower end surface of the shoulder.

[0037] The space between two adjacent protrusions of the first stirring head forms a groove area 254, and the protrusions of each stirring head are inserted into the groove areas of the other stirring head. The radially outer edge 2521 of the cloth cavity 252 of the first stirring head is located on a virtual circle 253. The virtual circle corresponding to the first stirring head is coaxially arranged with the stirring shaft of the first stirring head, and the virtual circle corresponding to the second stirring head is coaxially arranged with the stirring shaft of the second stirring head. The virtual circles corresponding to the two stirring heads partially intersect.

[0038] In this embodiment, the diameters D of the virtual circles corresponding to the two stirring heads are the same. The diameter D of the virtual circle is 5 mm larger than the distance S between the central axes of the two stirring heads. That is, in the direction of the connection line between the centers of the two dotted circles, the two virtual circles intersect by 5 mm. It can be understood that in other embodiments, the diameter D of the virtual circle can also be 3 mm, 6 mm, or 8 mm larger than the distance S between the central axes of the two stirring heads, or other distances between 3 - 8 mm.

[0039] A driving motor for driving the stirring head to rotate is also installed on the base. Corresponding to each stirring head, a driving motor is provided. The driving motor is a servo motor. In this embodiment, the driving motor specifically uses a hollow shaft torque motor. For ease of description, the hollow shaft torque motor corresponding to the first stirring head is called the first hollow shaft torque motor 101, and the hollow shaft torque motor corresponding to the second stirring head is called the second hollow shaft torque motor 102. The structures, sizes, powers, and installation methods of the two hollow shaft torque motors are the same. The installation method of the hollow shaft torque motor will be described below taking the installation method of the first hollow shaft torque motor 101 as an example.

[0040] The first hollow shaft torque motor 101 includes a stator 11, a rotor 13 rotatably disposed inside the stator, and a hollow shaft 14 fixed to the rotor 13. A winding 12 is provided inside the stator 11. The hollow shaft 14 of the first hollow shaft torque motor 101 is rotatably mounted on the outer wall of the stirring shaft 21 of the first stirring head through a transition bearing. In this embodiment, the hollow shaft 14 of the first hollow shaft torque motor 101 is rotatably mounted on the outer wall of the stirring shaft 21 of the first stirring head through two transition bearings arranged at intervals up and down. The two transition bearings are a slewing bearing 33 and a deep groove ball bearing 34 respectively, and the slewing bearing 33 is located below the deep groove ball bearing 34. The outer ring A332 of the slewing bearing 33 is located outside its inner ring A331. A lower support ring 26 is provided on the outer wall at the lower end of the stirring shaft 21. The inner ring A331 is fixed to the upper side of the lower support ring 26 by bolts, and the outer ring A332 is fixed to the lower end of the hollow shaft 14 by bolts.

[0041] On the outer peripheral surface at the upper end of the stirring shaft 21, there is a first step surface 212 facing upward. On the upper part of the inner peripheral surface of the hollow shaft 14, there is an upper support ring 131 protruding radially inward. The inner and outer rings of the deep groove ball bearing 34 are respectively supported on the upper surfaces of the first step surface 212 and the upper support ring 131. The hollow shaft 14 is mainly mounted on the stirring shaft by the slewing bearing 33. The deep groove ball bearing 34 is only used to ensure the coaxiality of the hollow shaft and the stirring shaft and prevent the hollow shaft from shaking. Since the deep groove ball bearing 34 only bears radial force and does not bear axial force, when installing the deep groove ball bearing 34, it is only necessary to tightly sleeve the inner ring of the deep groove ball bearing on the stirring shaft and tightly line the outer ring of the deep groove ball bearing on the inner peripheral surface of the hollow shaft.

[0042] The upper end cover 111 and the lower end cover 112 are respectively installed at the upper and lower ends of the stator by bolts, and the upper end cover is rotatably connected to the outer wall of the hollow shaft through an upper angular contact bearing 31, and the lower end cover is rotatably connected to the outer wall of the hollow shaft through a lower angular contact bearing 32. The connection methods of the upper angular contact bearing 31 with the upper end cover and the hollow shaft, and the lower angular contact bearing 32 with the lower end cover and the hollow shaft are all mature existing technologies and will not be elaborated here.

[0043] In this embodiment, the base 500 includes an upper flat plate 501 and a lower flat plate 502 arranged at intervals in the vertical direction, and the upper flat plate is installed above the lower flat plate through a support column 503. To make the structure compact, the lower end cover 112 is directly welded to the lower flat plate, thereby mounting the two hollow shaft torque motors on the base. It can be understood that in other embodiments, a special mounting seat can also be provided on the hollow shaft torque motor, and then the hollow shaft torque motor can be mounted on the base through the mounting seat.

[0044] A limiting mechanism is also installed on the hollow shaft of each hollow shaft torque motor. The limiting mechanism corresponding to the first hollow shaft torque motor is called the first limiting mechanism, and the limiting mechanism corresponding to the second hollow shaft torque motor is called the second limiting mechanism.

[0045] The structures of the two limiting mechanisms are the same. Taking the first limiting mechanism as an example, the first limiting mechanism includes three limiting rods 17 evenly spaced around the first stirring head. Each limiting rod 17 extends radially along the first stirring head. Corresponding to each limiting rod, a limiting hole 211 is formed in the stirring shaft of the first stirring head. The limiting hole 211 is a blind hole and radially penetrates the outer peripheral surface of the stirring shaft. Corresponding to each limiting rod, an adjusting hole 141 extending radially along the first stirring head is formed in the hollow shaft 14 of the first hollow shaft torque motor. The adjusting hole is an internally threaded hole in the shape of a through hole, and the limiting rod is screwed into the corresponding adjusting hole. The second limiting mechanism is the same as the first limiting mechanism.

[0046] By screwing the limiting rod, the limiting rod can move reciprocally in the radial direction of the corresponding stirring head, and the limiting rod can be inserted into the corresponding limiting hole or withdrawn from the limiting hole. When the limiting rod is inserted into the limiting hole, the hollow shaft is connected to the corresponding stirring head as a whole, and the hollow shaft of the hollow shaft torque motor can drive the corresponding stirring head to rotate synchronously; when the limiting rod is withdrawn from the limiting hole, the connection between the hollow shaft and the corresponding stirring head is disconnected, and the hollow shaft of the hollow shaft torque motor and the corresponding stirring head can rotate relative to each other. When the limiting rod on the hollow shaft of one of the hollow shaft torque motors is inserted into the corresponding limiting hole, the limiting rod on the hollow shaft of the other hollow shaft torque motor is withdrawn from the corresponding limiting hole.

[0047] Thus, when the hollow shaft of one of the hollow shaft torque motors drives the corresponding stirring head to rotate synchronously, the other stirring head can be driven to rotate by the following gears. Since the other stirring head is in a disconnected state from the hollow shaft of the corresponding hollow shaft torque motor, the other stirring head and the hollow shaft of the corresponding hollow shaft torque motor can be kept stationary, so as to avoid the generation of back current in the hollow shaft torque motor corresponding to the other stirring head and reduce the safety or service life of the hollow shaft torque motor.

[0048] In Figure 1In it, the limiting rod 17 of the first limiting mechanism is inserted into the corresponding limiting hole 211 on the first stirring head 201. The hollow shaft 14 of the first hollow shaft torque motor is connected to the first stirring head 201 as a whole through the limiting rod of the first limiting mechanism, so that the hollow shaft 14 of the first hollow shaft torque motor can drive the first stirring head 201 to rotate synchronously. The limiting rod 17 of the second limiting mechanism withdraws from the corresponding limiting hole 211 on the second stirring head 202, and the connection between the hollow shaft 14 of the second hollow shaft torque motor and the second stirring head 202 is disconnected, so that the hollow shaft 14 of the second hollow shaft torque motor can rotate relative to the second stirring head 202.

[0049] It can be understood that when the limiting rod 17 of the second limiting mechanism is inserted into the corresponding limiting hole 211 on the second stirring head 202, the hollow shaft 14 of the second hollow shaft torque motor is connected to the second stirring head 202 as a whole through the limiting rod of the second limiting mechanism, so that the hollow shaft 14 of the second hollow shaft torque motor can drive the second stirring head 202 to rotate synchronously. At this time, the limiting rod 17 of the first limiting mechanism withdraws from the corresponding limiting hole 211 on the first stirring head 201, and the connection between the hollow shaft 14 of the first hollow shaft torque motor and the first stirring head 201 is disconnected, so that the hollow shaft 14 of the first hollow shaft torque motor can rotate relative to the first stirring head 201.

[0050] A gear is fixed on the outer wall of each of the two stirring heads. The two gears are respectively called the first gear 81 and the second gear 82. The first gear 81 is fixedly installed at the upper end of the stirring shaft of the first stirring head, and the second gear 82 is fixedly installed at the upper end of the stirring shaft of the second stirring head. The two gears mesh with each other, and the transmission ratio of the two gears is 1:1. To facilitate fixing the gears, a second step surface 213 facing upward is provided at the top of the stirring shaft. The gear is supported on the second step surface, and a key 214 is inserted between the stirring shaft and the gear.

[0051] To improve the feeding efficiency of the bar stock, in this embodiment, a feeding mechanism 60 is provided corresponding to each stirring head. Each feeding mechanism 60 includes a support plate 52 and a raw material container 61 rotatably provided on the support plate 52. The support plate is located above the stirring head. Each raw material container has a rotating shaft and ten raw material through holes 62 arranged around the rotating shaft. Each raw material through hole can only accommodate one bar stock in the radial direction. A feeding hole 54 communicating with the blanking hole is provided on the support plate. When the raw material container rotates, each raw material through hole can sequentially communicate with the feeding hole, and the bar stock in the raw material through hole can enter the blanking hole of the corresponding stirring head through the feeding hole. A loading hole 55 for placing the bar stock into the raw material through hole is provided on the top plate 51. One loading hole is provided corresponding to each raw material container 61. By rotating the raw material container, each raw material through hole can be located directly below the corresponding loading hole, so that the bar stock can be inserted into the raw material through hole through the loading hole.

[0052] In this embodiment, the support plates of the two feeding mechanisms are combined into a single integral plate and are detachably mounted on the base using bolts.

[0053] To facilitate driving the raw material container 61 to rotate, in this embodiment, a top plate 51 is provided above the support plate 52. The top plate is supported on the support plate by columns 53, such that the support plate, the top plate, and the columns together form a frame structure 50. Two feeding motors 65 are mounted on the top plate. Each feeding motor corresponds to a raw material container 61, and the drive shaft of the feeding motor is connected to the rotating shaft of the corresponding raw material container 61 to drive the raw material container to rotate.

[0054] Corresponding to each stirring head, a pressing mechanism is mounted on the top plate. In this embodiment, both pressing mechanisms employ hydraulic piston cylinders 120. The cylinder barrels of the hydraulic piston cylinders are fixed to the upper side of the top plate, and the piston rods of the hydraulic piston cylinders can freely pass downward through the top plate and extend into the raw material through-hole 62 of the raw material container 61 to push the bar stock inserted in the feeding hole downward, causing a upsetting force between the bar stock and the base material. That is, the hydraulic piston cylinders are indirectly mounted on the base via the frame structure 50. It can be understood that in other embodiments, electric piston cylinders can also be used to replace the hydraulic piston cylinders.

[0055] In this embodiment, two drive motors are provided, and the two drive motors are backup units for each other. When the working drive motor fails and cannot operate, the hollow shaft of the drive motor can be disengaged from the corresponding stirring shaft, and the hollow shaft of the other drive motor can be connected to the corresponding stirring shaft to continue working, avoiding waste of workpieces.

[0056] This embodiment can be connected to the fixed part of machining equipment such as a friction stir welding machine, a CNC milling machine, and a CNC machining center via the base, and the machining equipment is used to move the friction stir additive manufacturing device. Of course, a dedicated moving device can also be provided to move the friction stir additive manufacturing device.

[0057] Embodiment 2

[0058] This embodiment describes the friction stir additive manufacturing method. This embodiment is carried out using the friction stir additive manufacturing device in Embodiment 1. The friction stir additive manufacturing method includes the following steps:

[0059] (1) Turn the limit rod on the first hollow shaft torque motor so that the limit rod is inserted into the limit hole on the first stirring head, connecting the first stirring head to the hollow shaft on the first hollow shaft torque motor. Turn the limit rod on the second hollow shaft torque motor so that the limit rod withdraws from the limit hole on the second stirring head, disconnecting the second stirring head from the hollow shaft on the second hollow shaft torque motor.

[0060] Feed the bar stock into the blanking holes of the two stirring heads through the feed hole, and make the lower end surface of the bar stock flush with the lower end surface of the shaft shoulder.

[0061] (2) Place the shaft shoulder on the surface of the area to be additive manufactured on the substrate. Start the stirring heads and make the two stirring heads rotate synchronously. The shaft shoulder contacts the upper surface of the substrate, and the stirring needles penetrate into the substrate for friction preheating for 15 seconds.

[0062] (3) Start the hydraulic piston cylinder acting as the material pressing mechanism, make the piston rod of the hydraulic piston cylinder extend downward, squeeze the bar stock downward, make the bar stock in the blanking hole move downward, generate upsetting force between the bar stock and the area to be additive manufactured on the substrate. At the same time, retract the stirring head upward by 1.2 mm, and make the friction stir additive manufacturing device move along the set path. The bar stock undergoes thermoplasticization under the action of friction and flows out of the blanking hole. Keep the stirring head rotating. The thermoplasticized bar stock is deposited on the substrate and forms an additive forming surface under the flattening action of the shaft shoulder, realizing the cladding of a single-layer heat sink layer in the area to be additive manufactured and forming the additive manufactured layer. The arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device.

[0063] After thermoplasticization, the bar stock becomes plasticized material and fills the cloth cavities of the two shaft shoulders. During the rotation of the two stirring heads, due to the intersection of the protruding parts of the two stirring heads, the plasticized materials in the two cloth cavities are fused with each other and synchronously deposited on the substrate, so that a single-pass single-layer heat sink layer wider than that of a single stirring head can be formed, thereby improving the working efficiency.

[0064] When the top end surface of the bar stock in the blanking hole drops to be flush with the upper surface of the support plate, lift the piston rod of the hydraulic piston cylinder upward so that the lower end surface of the piston rod exceeds the top end surface of the raw material cavity upward. Rotate the raw material container to align the next bar stock with the feed hole and abut it against the bar stock in the blanking hole. The piston rod of the hydraulic piston cylinder extends downward and presses against the top of the next bar stock, squeezing the next bar stock downward and continuing the additive manufacturing operation.

[0065] (4) Repeat the cladding of the single-layer heat sink layer in the area to be additive manufactured until the required additive height is reached. When repeating the cladding of the single-layer heat sink layer, upsetting force is generated between the bar stock and the surface of the additive manufactured layer, and friction thermoplasticization deposition occurs.

Claims

1. A dual-axis synchronous friction stir additive manufacturing device, characterized in that: The invention comprises a base and two stirring heads rotatably mounted on the base; when the friction stir additive manufacturing device is in operation, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device; Each stirring head includes a stirring shaft extending in a vertical direction and a feeding hole formed in the stirring shaft, the lower end of the stirring shaft is formed as a shaft shoulder, and a stirring needle protruding downward is arranged on the lower end surface of the shaft shoulder; the shaft shoulder is star-shaped, and has protrusions protruding radially outward and arranged in a radially uniform interval, and a material distribution cavity is formed by being recessed upward in the protrusion, and the material distribution cavity is open downward, and the material distribution cavity is connected to the feeding hole; the feeding hole is a regular polygon, and the rod material has an outer peripheral surface with the same shape as the inner peripheral surface of the feeding hole; The space between two adjacent protrusions of the same stirring head forms a groove area, and the protrusion of each stirring head is inserted into the groove area of ​​the other stirring head; the radial outer edge of the material distribution cavity of the same stirring head is located on a virtual circle, and the virtual circle parts corresponding to the two stirring heads intersect; the virtual circle corresponding to each stirring head is coaxially arranged with the stirring shaft of the stirring head; Corresponding to each stirring head, a pressing mechanism is installed on the base, which is used to push the rod in the feeding hole downward; a driving motor for driving the stirring head to rotate is also installed on the base, and the driving motor is a servo motor; the lower end surfaces of the two shoulders are coplanar.

2. The friction stir additive manufacturing device according to claim 1, characterized in that: The two stirring heads have the same structure, and the diameters of the virtual circles corresponding to the two stirring heads are the same. The diameter of the virtual circle is 3-8 mm larger than the distance between the central axes of the two stirring heads.

3. The friction stir additive manufacturing device according to claim 1, characterized in that The radial inner ends of two adjacent material distribution cavities of the same stirring head are communicated with each other.

4. The friction stir additive manufacturing device according to claim 1, characterized in that: Corresponding to each stirring head, a driving motor is provided, and the driving motor is a hollow shaft torque motor, and the hollow shaft torque motor comprises a stator, a mover rotatably arranged inside the stator, and a hollow shaft fixed on the mover, the hollow shaft of the hollow shaft torque motor is rotatably mounted on the outer wall of the stirring head via a transition bearing, and the stator of the hollow shaft torque motor is fixed on the base; A limiting mechanism is also installed on the hollow shaft of each hollow shaft torque motor, and the limiting mechanism includes at least one limiting rod, which is movably installed on the hollow shaft, and a limiting hole corresponding to the limiting rod is provided on the stirring head, and the limiting rod can reciprocate along the radial direction of the stirring head, and the limiting rod can be inserted into the corresponding limiting hole, or withdrawn from the limiting hole; When the limit rod is inserted into the limit hole, the hollow shaft can drive the corresponding stirring head to rotate synchronously; when the limit rod is withdrawn from the limit hole, the hollow shaft and the corresponding stirring head can rotate relative to each other; when the limit rod on the hollow shaft of one hollow shaft torque motor is inserted into the corresponding limit hole, the limit rod on the hollow shaft of the other hollow shaft torque motor is withdrawn from the corresponding limit hole; A gear is fixed on the outer wall of the two stirring heads. The gears on the two stirring heads are meshed with each other, and the transmission ratio of the gears on the two stirring heads is 1:

1.

5. The friction stir additive manufacturing device according to claim 4, characterized in that: The hollow shaft of the hollow shaft torque motor is rotatably mounted on the outer wall of the stirring head via two transition bearings spaced apart from each other, wherein the transition bearing located at the lower side is a slewing bearing, and the transition bearing located at the upper side is a deep groove ball bearing.

6. The friction stir additive manufacturing device according to claim 4, characterized in that: Corresponding to each limiting rod, an adjustment hole extending along the radial direction of the stirring head is provided on the corresponding hollow shaft, the adjustment hole is an internal threaded hole, and the adjustment hole is a through hole, and the limiting rod is screwed into the corresponding adjustment hole.

7. The friction stir additive manufacturing device according to claim 1, characterized in that: Corresponding to each stirring head, a feeding mechanism is provided, and each feeding mechanism includes a support plate and a raw material container rotatably arranged on the support plate, wherein the support plate is detachably mounted on the base and is located above the stirring head, and the raw material container has a rotating shaft and a plurality of raw material through holes arranged around the rotating shaft, each raw material through hole can only accommodate one rod material in the radial direction, and a feeding hole connected to the unloading hole is opened on the support plate. When the raw material container rotates, each raw material through hole can be connected to the feeding hole in turn, and the rod material in the raw material through hole can enter the unloading hole of the corresponding stirring head through the feeding hole.

8. The friction stir additive manufacturing device according to claim 1, characterized in that: The material pressing mechanism is a piston cylinder, and a piston cylinder is provided corresponding to each stirring head. The cylinder barrel of the piston cylinder is fixed on the base, and the piston rod of the piston cylinder extends downward and can freely extend into the feeding hole to press the rod material downward.

9. A friction stir additive manufacturing method, characterized in that: The friction stir additive manufacturing method is carried out using the friction stir additive manufacturing device according to any one of claims 1 to 8, and the friction stir additive manufacturing method comprises the following steps: (1) Feed the rod into the feeding holes of the two mixing heads and make the lower end surface of the rod flush with the lower end surface of the shoulder; (2) placing the shaft shoulder on the surface of the area to be added to the substrate, starting the drive motor, and rotating the two stirring heads synchronously so that the shaft shoulder contacts the upper surface of the substrate, and the stirring needle penetrates into the substrate for friction preheating for 10-25 seconds; (3) The pressing mechanism is started, and the rod in the feed hole moves downward, so that an upsetting force is generated between the rod and the area to be added of the substrate. At the same time, the stirring head is retracted upward by 0.2-2.0 mm, and the stir friction additive manufacturing device is moved along a set path. The rod is thermally plasticized under the action of friction and flows out of the feed hole. The stirring head is kept rotating, and the rod is thermally plasticized and deposited on the substrate. Under the flattening action of the shoulder, an additive forming surface is formed, and a single-layer heat sink layer is stacked in the area to be added to form an additively manufactured layer; The arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing device; After the rod material is thermally plasticized, it becomes plasticized material and fills the material distribution cavities of the two shoulders. The plasticized materials in the two material distribution cavities merge with each other and are deposited on the substrate synchronously. When the top surface of the bar in the feeding hole drops to be flush with the upper surface of the support plate, the next bar is aligned with the feeding hole, and the pressing mechanism continues to press the bar downward; (4) Repeat the stacking of a single layer of heat sink layer in the area to be added until the required addition height is reached.

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