A tri-axial friction stir additive manufacturing apparatus and method of friction stir additive deposition

Abstract

The application discloses a triaxial friction stir additive manufacturing device, which comprises two deposition stirrers and a homogenizing stirrer, the arrangement direction of the two deposition stirrers is perpendicular to the moving direction of the triaxial friction stir additive manufacturing device, and the homogenizing stirrer is located on the downstream side of the two deposition stirrers; the deposition shoulder of the deposition stirrer is provided with a protruding part protruding outward in the radial direction, the protruding part is provided with a material distribution cavity concave upward, and the material distribution cavity is communicated with a discharging hole in the deposition stirrer; a groove area is formed between two adjacent protruding parts, and the protruding part of each deposition stirrer is inserted into the groove area of the other deposition stirrer; and the lower end surface of the homogenizing shoulder of the homogenizing stirrer is provided with a homogenizing stir pin protruding downward. The application also discloses a friction stir additive deposition method. The application utilizes the two deposition stirrers to form a wider single-layer heat sink layer at one time, and utilizes the homogenizing stirrer to stir the middle area of the single-layer heat sink layer again, so that the uniformity of the middle area is improved.

Description

Technical Field

[0001] This invention relates to a triaxial stirring friction additive manufacturing apparatus and a stirring friction additive deposition method using the triaxial stirring friction additive manufacturing apparatus. Background Technology

[0002] Friction stir additive manufacturing is a novel solid-state additive manufacturing method that enables high-performance additive manufacturing of materials such as aluminum alloys, magnesium alloys, copper alloys, and titanium alloys. Currently, additive manufacturing methods mainly focus on single-pass, multi-layer additive components. When manufacturing large-size products, multi-layer, multi-pass additive manufacturing methods are required, resulting in lower production efficiency. Summary of the Invention

[0003] To address the issue of low production efficiency caused by the need for multi-layer, multi-pass additive manufacturing when using friction stir additive manufacturing for large-size products in existing technologies, this application first proposes a triaxial friction stir additive manufacturing apparatus, which includes a base and two deposition stirring heads and a homogenizing stirring head rotatably mounted on the base. The virtual line connecting the central axes of the two deposition stirring heads is called the central connecting line segment, which extends along the direction of the first axis. Another axis is perpendicular to the central axis of the homogenizing stirring head and extends along the direction of the second axis. The midpoint of the central connecting line is located on the second axis. Both the first axis and the second axis extend horizontally and are perpendicular to each other.

[0004] When the triaxial friction stir additive manufacturing apparatus is in operation, the extension direction of the central connecting line segment is perpendicular to the moving direction of the triaxial friction stir additive manufacturing apparatus, and the homogenizing stirring head is located downstream of the two deposition stirring heads.

[0005] Each deposition stirring head includes a deposition stirring shaft extending vertically and a feed hole formed within the deposition stirring shaft. The lower end of the deposition stirring shaft is formed as a deposition shoulder, and a first stirring pin protruding downward is provided on the lower end face of the deposition shoulder. The deposition shoulder is star-shaped and has radially outwardly protruding protrusions that are evenly spaced. Within each protrusion is an upwardly recessed feeding cavity, which is open downward and communicates with the feed hole. The feed 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 feed hole.

[0006] The space between two adjacent protrusions of the same deposition stirring head is formed as a groove area, and the protrusion of each deposition stirring head is inserted into the groove area of ​​another deposition stirring head; the radial outer edge of the material distribution chamber of the same deposition stirring head is located on a virtual circle, and the virtual circles corresponding to the two deposition stirring heads intersect; the virtual circle corresponding to each deposition stirring head is coaxially arranged with the deposition stirring axis of the deposition stirring head.

[0007] For each deposition stirring head, a pressing mechanism is installed on the base to push the bar stock located in the feeding hole downwards; a deposition motor for driving the deposition stirring head to rotate is also installed on the base, and the deposition motor is a servo motor.

[0008] The homogenizing stirring head includes a homogenizing stirring shaft extending vertically and a homogenizing shoulder formed at the lower end of the homogenizing stirring shaft. A homogenizing stirring needle protruding downward is provided on the lower end face of the homogenizing shoulder. A homogenizing motor for driving the homogenizing stirring head to rotate is also mounted on the base. The homogenizing motor is a servo motor. The lower end faces of the two deposition shoulders are coplanar with the lower end faces of the homogenizing shoulders.

[0009] The outer diameter of the homogenizing shoulder is 0.8-1.2 times the intersection length of the two virtual circles, and the intersection length of the two virtual circles is DS, where D is the diameter of the virtual circle and S is the distance between the central axes of the two deposition stirring heads.

[0010] In this application, during operation of the triaxial stirring friction additive manufacturing apparatus, the arrangement direction of the two deposition stirring heads is perpendicular to the movement direction of the apparatus, allowing the two deposition stirring heads to move synchronously side-by-side along a set direction. This enables the formation of a single-layer heat sink layer that is wider than that formed by a single stirring head. Depending on the size of the groove area of ​​the two deposition stirring heads, the single-layer heat sink layer formed in this application is 1.7-1.9 times larger than that of existing single-layer heat sink layers. During operation of the triaxial stirring friction additive manufacturing apparatus in this application, the bar stock in the feeding hole is plasticized by frictional heat, forming a plasticized material. This plasticized material flows radially along the deposition stirring head within the feeding chamber and fills the entire chamber. When the two deposition stirring heads rotate synchronously, the staggered arrangement of their protrusions allows the plasticized material within the two deposition stirring heads to fuse together, ensuring that the heat sink layers formed by the two deposition stirring heads are seamlessly integrated and guaranteeing product quality.

[0011] The homogenizing stirring head re-stirs the middle area of ​​the single-layer heat sink, i.e., performs a re-stirring, to improve the uniformity of the middle area, thereby improving the uniformity of the overall quality of the single-layer heat sink.

[0012] Furthermore, to reduce the manufacturing cost of the equipment, the two deposition stirring heads have the same structure, and the diameter of the virtual circle corresponding to the two deposition stirring heads is the same. The diameter of the virtual circle is 3-8 mm larger than the distance between the central axes of the two deposition stirring heads.

[0013] Since the two sedimentation stirring heads have the same structure, a single type of bar stock can meet the needs of both sedimentation stirring heads, and the corresponding accessories of the two sedimentation stirring heads can also be interchanged, reducing the maintenance cost of the equipment.

[0014] Furthermore, in order to ensure that the deposition mixing head can distribute the material evenly during operation and that the plasticizer is laid out uniformly, the radial inner ends of two adjacent material distribution chambers of the same deposition mixing head are connected to each other.

[0015] Furthermore, a deposition motor is provided for each deposition stirring head. The deposition motor is a hollow shaft torque motor. The hollow shaft torque motor includes a stator, a mover rotatably lined 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 deposition stirring head via a transition bearing. The stator of the hollow shaft torque motor is fixed on the base.

[0016] 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, which is movably installed on the hollow shaft. The sedimentation stirring head has a limiting hole corresponding to the limiting rod. The limiting rod can reciprocate along the radial direction of the sedimentation stirring head and insert into or withdraw from the corresponding limiting hole.

[0017] When the limiting rod is inserted into the limiting hole, the hollow shaft can drive the corresponding sedimentation stirring head to rotate synchronously; when the limiting rod is withdrawn from the limiting hole, the hollow shaft and the corresponding sedimentation stirring head can rotate relative to each other; when the limiting rod on the hollow shaft of one hollow shaft torque motor 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;

[0018] A gear is fixed on the outer wall of each of the two sedimentation stirring heads. The gears on the two sedimentation stirring heads mesh with each other, and the transmission ratio of the gears on the two sedimentation stirring heads is 1:1.

[0019] This application incorporates two deposition motors, each corresponding to a deposition stirring head. When one deposition motor drives its corresponding stirring head to rotate, it can synchronously drive the other stirring head via gears. To prevent back current from being generated when the other deposition motor is passively rotating, which could impact and damage the deposition motor and its accessories, a limiting mechanism is provided. During operation, the hollow shaft of one deposition motor is connected to its corresponding stirring head via this limiting mechanism, while the connection between the hollow shaft of the other deposition motor and its corresponding stirring head is disconnected. This prevents back current from being generated by the rotation of the other deposition motor's hollow shaft, ensuring the safe operation of the deposition motors. Furthermore, the use of two deposition motors ensures continuous production. The two motors can serve as backups for each other, forming a redundant design. During production, if one deposition motor malfunctions and cannot operate normally, the other deposition motor can be started to continue production, reducing production costs and lowering overall production expenses.

[0020] Specifically, to ensure the installation stability of the hollow shaft, the hollow shaft of the hollow shaft torque motor is rotatably mounted on the outer wall of the sedimentation stirring head via two intermediate transition bearings. The lower transition bearing is a slewing bearing, and the upper transition bearing is a deep groove ball bearing. Of the two transition bearings, the slewing bearing supports the weight of the entire hollow shaft torque motor, while the deep groove ball bearing prevents the hollow shaft from tilting when the slewing bearing is used alone.

[0021] Specifically, to facilitate the operation of the limiting rods, an adjustment hole extending radially along the sedimentation stirring head is provided on the corresponding hollow shaft for each limiting rod. The adjustment hole is an internally threaded hole and a through hole, and the limiting rod is screwed into the corresponding adjustment hole.

[0022] Furthermore, to facilitate continuous feeding, a feeding mechanism is provided for each sedimentation stirring head. Each feeding mechanism includes a support plate and a raw material container rotatably mounted on the support plate. The support plate is detachably mounted on the base and located above the sedimentation stirring head. The raw material container has a rotating shaft and several raw material through holes arranged around the rotating shaft. Each raw material through hole can only accommodate one rod in the radial direction. A feed hole is provided on the support plate that connects to the discharge hole. When the raw material container rotates, each raw material through hole can sequentially connect to the feed hole, and the rod in the raw material through hole can enter the discharge hole of the corresponding sedimentation stirring head through the feed hole.

[0023] Specifically, the pressing mechanism is a piston cylinder, with one piston cylinder corresponding to each sedimentation stirring head. The cylinder barrel is fixed on the base, and the piston rod extends downward and can freely enter the feeding hole to press the bar stock downward. The piston cylinder can be a hydraulic piston cylinder or an electric piston cylinder.

[0024] Furthermore, to ensure successful re-mixing of the middle region of the single-layer heat sink, the lower end face of the homogenizing shoulder is closed, and the homogenizing stirring needle is threaded onto the homogenizing shoulder. During re-mixing, the homogenizing shoulder presses against the surface of the single-layer heat sink, and the homogenizing stirring needle is inserted into the single-layer heat sink to re-mix it. Because the lower end face of the homogenizing shoulder is closed, the material after secondary mixing can be leveled.

[0025] This application can be connected to the fixed part of machining equipment such as friction stir welding machine, CNC milling machine, and CNC machining center via a base, and the friction stir additive manufacturing device can be moved by the machining equipment. Of course, a special moving device can also be set up to move the friction stir additive manufacturing device.

[0026] Secondly, to ensure the smooth completion of production by the aforementioned triaxial friction stir additive manufacturing apparatus, this application also discloses a friction stir additive deposition method, which employs the triaxial friction stir additive manufacturing apparatus described in any of the above claims. This friction stir additive deposition method includes the following steps:

[0027] (1) Feed the bar stock into the feed holes of the two deposition mixing heads and make the lower end face of the bar stock flush with the lower end face of the deposition shoulder.

[0028] (2) Place the deposition shoulder on the surface of the substrate to be added, start the deposition motor, and rotate the two deposition stirring heads synchronously so that the deposition shoulder contacts the upper surface of the substrate and the first stirring needle is inserted into the substrate for frictional preheating for 10-25 seconds.

[0029] (3) Start the pressing mechanism, the bar in the feeding hole moves downward, so that the bar and the substrate to be added are generated with a forging force. At the same time, the deposition stirring head is pulled back 0.2-2.0mm, and the triaxial stirring friction additive manufacturing device moves along the set path. The bar is thermoplasticized under friction and flows out from the feeding hole. The rotation of the deposition stirring head is maintained. The bar is thermoplasticized and deposited on the substrate. Under the flattening action of the deposition shoulder, an additive forming surface is formed, realizing the deposition of a single-layer heat sink layer in the area to be added, forming an additive manufacturing layer; the arrangement direction of the two deposition stirring heads is perpendicular to the moving direction of the triaxial stirring friction additive manufacturing device.

[0030] After the bar stock is thermoplasticized, it forms a plastic material that fills the fabric cavities of the two deposition shoulders. The plastic materials in the two fabric cavities are fused together and deposited synchronously on the substrate.

[0031] When the top surface of the bar in the feed hole descends to be flush with the upper surface of the support plate, the next bar is aligned with the feed hole, and the pressing mechanism continues to press the bar downward.

[0032] The deposition motor is started synchronously, so that the homogenizing stirring needle is inserted into the single-layer heat sink and the homogenizing shoulder is pressed against the forming surface of the single-layer heat sink to re-stir the middle area of ​​the single-layer heat sink; the length of the homogenizing stirring needle extending downward from the lower end face of the homogenizing shoulder is 1.1-1.2 times the thickness of the single-layer heat sink.

[0033] (4) Repeat the stacking of single-layer heat sink in the area to be added until the required additive height is achieved.

[0034] In this deposition method, during operation of the triaxial stirring friction additive manufacturing apparatus, the arrangement direction of the two deposition stirring heads is perpendicular to the moving direction of the apparatus. This allows the two deposition stirring heads to move synchronously side-by-side along a set direction, enabling the formation of a single-layer heat sink layer that is wider than that formed by a single stirring head. During production, the bar stock undergoes frictional thermoplasticization within the feeding hole, forming a plasticized material that flows radially along the deposition stirring head within the feeding chamber, filling the entire chamber. When the two deposition stirring heads rotate synchronously, the staggered arrangement of their protrusions allows the plasticized material within both heads to fuse together, ensuring a seamless fusion of the heat sink layers formed by the two stirring heads and guaranteeing product quality. The homogenizing stirring head further stirs the middle region of the single-layer heat sink layer, i.e., performs a re-mixing, improving the uniformity of the middle region and thus enhancing the overall uniformity of the single-layer heat sink layer's internal quality. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of an embodiment of this application.

[0036] Figure 2 yes Figure 1 A view from the center AA direction.

[0037] Figure 3 yes Figure 2 A bottom view.

[0038] Figure 4 This is a schematic diagram of the structure of the first sedimentation stirring head and its corresponding accessories.

[0039] Figure 5 yes Figure 4 A view from the center (BB direction).

[0040] Figure 6 yes Figure 1 Rear view.

[0041] Figure 7 This is a structural diagram of the homogenizing mixing head and related accessories. Detailed Implementation

[0042] Example 1

[0043] The structure of the triaxial stirring friction additive manufacturing apparatus is described below. Please refer to [link / reference]. Figures 1-7 The triaxial friction stir additive manufacturing apparatus includes a base 500 and two deposition stirring heads and a homogenizing stirring head rotatably mounted on the base. The two deposition stirring heads are a first deposition stirring head 201 and a second deposition stirring head 202, respectively.

[0044] The virtual line connecting the central axes of the two sedimentation stirring heads is called the central line segment 258. For clarity, this central line segment 258 is represented by a double-dotted line. This central line segment 258 extends along the first axis. An axial line 701 is perpendicular to the central axis of the homogenizing stirring head and extends along the second axis. The midpoint 259 of the central line segment lies on this axial line. Both the first and second axes extend horizontally and are perpendicular to each other. In the attached diagram, the first arrow X indicates the direction of the first axis, and the second arrow Y indicates the direction of the second axis. For clarity, the midpoint 259 of the central line segment is represented by a small circle.

[0045] When the triaxial friction stir additive manufacturing apparatus is in operation, the extension direction of the center connecting segment 258 is perpendicular to the moving direction of the triaxial friction stir additive manufacturing apparatus, and the homogenizing stirring head is located downstream of the two deposition stirring heads.

[0046] In this embodiment, the two deposition stirring heads have the same structure. The structure of the two deposition stirring heads will be described below using the first deposition stirring head 201 as an example. The first deposition stirring head 201 includes a deposition stirring shaft 21 extending in a vertical direction and a feed hole 22 formed in the deposition stirring shaft 21. The lower end of the deposition stirring shaft 21 is formed as a deposition shoulder 25.

[0047] The deposition shoulder 25 is star-shaped and has radially protruding, evenly spaced protrusions 251. Within each protrusion is an upwardly recessed feeding cavity 252, which is open downwards and connects to the feed hole 22, allowing the bar stock in the feed hole to flow into each feeding cavity after plasticization. The feed hole is a regular polygon, and the bar stock has an outer circumferential surface with the same shape as the inner circumferential surface of the feed hole. In this embodiment, the inner circumferential surface of the feed hole and the outer circumferential surface of the bar stock are both regular hexagons. The radially inner ends of two adjacent feeding cavities of the same deposition stirring head are interconnected. A downwardly protruding first stirring pin 27 is provided on the lower end face of the deposition shoulder.

[0048] The space between two adjacent protrusions of the first deposition stirring head forms a groove region 254, and the protrusion of each deposition stirring head is inserted into the groove region of the other deposition stirring head. The radially outer edge 2521 of the feeding chamber 252 of the first deposition stirring head is located on a virtual circle 253. The virtual circle corresponding to the first deposition stirring head is coaxially arranged with the deposition stirring axis of the first deposition stirring head, and the virtual circle corresponding to the second deposition stirring head is coaxially arranged with the stirring axis of the second deposition stirring head. The virtual circles corresponding to the two deposition stirring heads partially intersect.

[0049] In this embodiment, the diameter D of the virtual circles corresponding to the two deposition stirring heads is the same. The diameter D of the virtual circle is 5 mm larger than the distance S between the central axes of the two deposition stirring heads. That is, the two virtual circles intersect by 5 mm in the direction of the line connecting the centers of the two dashed circles. 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 deposition stirring heads, or other distances between 3 and 8 mm.

[0050] A deposition motor for driving the deposition stirring head to rotate is also installed on the base. One deposition motor is provided for each deposition stirring head. The deposition motor is a servo motor. In this embodiment, the deposition motor is specifically a hollow shaft torque motor. For ease of description, the hollow shaft torque motor corresponding to the first deposition stirring head is referred to as the first hollow shaft torque motor 101, and the hollow shaft torque motor corresponding to the second deposition stirring head is referred to as the second hollow shaft torque motor 102. The two hollow shaft torque motors have the same structure, size, power, and installation method. The following description uses the installation method of the first hollow shaft torque motor 101 as an example to illustrate the installation method of the hollow shaft torque motor.

[0051] The first hollow shaft torque motor 101 includes a stator 11, a mover 13 rotatably mounted inside the stator, and a hollow shaft 14 fixed on the mover 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 deposition stirring shaft 21 of the first deposition stirring head via transition bearings. In this embodiment, the hollow shaft 14 of the first hollow shaft torque motor 101 is rotatably mounted on the outer wall of the deposition stirring shaft 21 of the first deposition stirring head via two transition bearings spaced apart vertically. The two transition bearings are a slewing bearing 33 and a deep groove ball bearing 34, respectively, wherein 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 the inner ring A331. A lower support ring 26 is provided on the outer wall of the lower end of the sedimentation stirring shaft 21. The inner ring A331 is fixed to the upper side of the lower support ring 26 with bolts, and the outer ring A332 is fixed to the lower end of the hollow shaft 14 with bolts.

[0052] A first stepped surface 212 facing upwards is provided on the outer circumferential surface of the upper end of the sedimentation stirring shaft 21. An upper support ring 131 protruding radially inwards is provided on the upper part of the inner circumferential surface of the hollow shaft 14. The inner and outer rings of the deep groove ball bearing 34 are respectively supported on the upper surfaces of the first stepped surface 212 and the upper support ring 131. The hollow shaft 14 is mainly mounted on the sedimentation 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 sedimentation stirring shaft and to prevent the hollow shaft from shaking. Since the deep groove ball bearing 34 only bears radial force and not axial force, when installing the deep groove ball bearing 34, it is only necessary to ensure that the inner ring of the deep groove ball bearing is tightly fitted on the stirring shaft and that the outer ring of the deep groove ball bearing is tightly lined on the inner circumferential surface of the hollow shaft.

[0053] The upper end cover 111 and the lower end cover 112 are respectively bolted to the upper and lower ends of the stator. The upper end cover is rotatably connected to the outer wall of the hollow shaft via the upper angular contact bearing 31, and the lower end cover is rotatably connected to the outer wall of the hollow shaft via the lower angular contact bearing 32. The connection methods of the upper angular contact bearing 31 to the upper end cover and the hollow shaft, and the connection methods of the lower angular contact bearing 32 to the lower end cover and the hollow shaft, all adopt existing mature technologies and will not be described in detail.

[0054] In this embodiment, the base 500 includes an upper plate 501 and a lower plate 502 spaced apart in a vertical direction, wherein the upper plate is mounted above the lower plate via a support column 503. For a compact structure, the lower end cover 112 is directly welded to the lower plate, thereby mounting the two deposition motors on the base. It is understood that in other embodiments, a dedicated mounting bracket can be provided on the deposition motor, and then the deposition motor can be mounted on the base via the mounting bracket.

[0055] 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.

[0056] The two limiting mechanisms have the same structure. The following description uses the first limiting mechanism as an example. The first limiting mechanism includes three limiting rods 17 evenly spaced around the first deposition stirring head. Each limiting rod 17 extends radially along the first deposition stirring head. Corresponding to each limiting rod, a limiting hole 211 is formed on the deposition stirring shaft of the first deposition stirring head. The limiting hole 211 is a blind hole that penetrates radially through the outer circumference of the deposition stirring shaft. Corresponding to each limiting rod, an adjusting hole 141 extending radially along the first deposition stirring head is formed on the hollow shaft 14 of the first hollow shaft torque motor. This adjusting hole is a through-hole with internal threads, and the limiting rod is screwed into the corresponding adjusting hole. The second limiting mechanism is the same as the first limiting mechanism.

[0057] Twisting the limiting rod allows it to reciprocate radially along the corresponding sedimentation stirring head, inserting or retracting it into or out of the corresponding limiting hole. When the limiting rod is inserted into the limiting hole, the hollow shaft is connected to the corresponding sedimentation stirring head, enabling the hollow shaft of the hollow shaft torque motor to drive the corresponding sedimentation stirring head to rotate synchronously. When the limiting rod is retracted from the limiting hole, the connection between the hollow shaft and the corresponding sedimentation stirring head is broken, allowing the hollow shaft of the hollow shaft torque motor and the corresponding sedimentation stirring head to rotate relative to each other. When the limiting rod on the hollow shaft of one hollow shaft torque motor is inserted into the corresponding limiting hole, the limiting rod on the hollow shaft of the other hollow shaft torque motor is retracted from the corresponding limiting hole.

[0058] Therefore, when the hollow shaft of one of the hollow shaft torque motors drives the corresponding sedimentation stirring head to rotate synchronously, it can drive the other sedimentation stirring head to rotate through the gears described below. Since the other sedimentation stirring head is disconnected from the hollow shaft of the corresponding hollow shaft torque motor, the other sedimentation stirring head and the hollow shaft of the corresponding hollow shaft torque motor can be kept stationary to avoid the back current generated by the hollow shaft torque motor corresponding to the other sedimentation stirring head, which would reduce the safety or service life of the hollow shaft torque motor.

[0059] exist Figure 1 In the process, 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 via 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 is withdrawn 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.

[0060] It is 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 exits 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.

[0061] A gear is fixed to the outer wall of each of the two deposition stirring heads. The two gears are referred to as the first gear 81 and the second gear 82, respectively. The first gear 81 is fixedly installed at the upper end of the deposition stirring shaft of the first deposition stirring head, and the second gear 82 is fixedly installed at the upper end of the deposition stirring shaft of the second deposition stirring head. The two gears mesh together, and the transmission ratio between the two gears is 1:1. To facilitate the fixing of the gears, a second step surface 213 facing upward is provided at the top of the deposition stirring shaft. The gears are supported on the second step surface, and a key 214 is inserted between the deposition stirring shaft and the gears.

[0062] To improve the efficiency of adding rods, in this embodiment, a feeding mechanism 60 is provided for each deposition mixing head. Each feeding mechanism 60 includes a support plate 52 and a raw material container 61 rotatably mounted on the support plate 52, with the support plate located above the deposition mixing 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 rod in the radial direction. A feed hole 54 is provided on the support plate, connecting to the discharge hole. When the raw material container rotates, each raw material through hole can sequentially connect to the feed hole, and the rod in the raw material through hole can enter the discharge hole of the corresponding deposition mixing head through the feed hole. A loading hole 55 for placing rods into the raw material through holes is provided on the top plate 51. A loading hole is provided for each raw material container 61. Rotating the raw material container can make each raw material through hole directly below the corresponding loading hole, allowing the rod to be inserted into the raw material through hole through the loading hole.

[0063] In this embodiment, the support plates of the two feeding mechanisms are combined into a single plate and are detachably mounted on the base using bolts.

[0064] To facilitate the rotation of the raw material container 61, 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, so that the support plate, the top plate, and the columns together form a frame structure 50. Two feeding motors 65 are installed on the top plate, each feeding motor corresponding to one raw material container 61. 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.

[0065] For each deposition stirring head, a pressing mechanism is installed on the top plate. In this embodiment, both pressing mechanisms use hydraulic piston cylinders 120. The cylinder barrel of the hydraulic piston cylinder is fixed to the upper side of the top plate, and the piston rod of the hydraulic piston cylinder can freely pass downward through the top plate and extend into the raw material through hole 62 of the raw material container 61, pushing the bar inserted in the feeding hole downward, so that the bar and the substrate generate a forging force. That is, the hydraulic piston cylinder is indirectly mounted on the base through the frame structure 50. It can be understood that in another embodiment, an electric piston cylinder can also be used instead of a hydraulic piston cylinder.

[0066] In this embodiment, two deposition motors are provided, which serve as backups for each other. When a working deposition motor malfunctions and cannot operate, the hollow shaft of the deposition motor can be disconnected from the corresponding deposition stirring shaft, and the hollow shaft of the other deposition motor can be connected to the corresponding deposition stirring shaft to continue working, thus avoiding waste of the workpiece.

[0067] Please see Figure 5 and Figure 6 The homogenizing stirring head 70 includes a homogenizing stirring shaft 71 extending vertically and a homogenizing shoulder 75 disposed at the lower end of the homogenizing stirring head. A downwardly protruding homogenizing stirring pin 76 is disposed on the lower end surface of the homogenizing shoulder 75. In this embodiment, the homogenizing stirring shaft 71 is a solid shaft, making the lower end surface of the homogenizing stirring shaft closed. The homogenizing stirring pin is bolted to the bottom of the homogenizing shoulder to facilitate adjustment of the extension length of the homogenizing stirring pin. For clarity, Figure 5 In the original design, the feeding mechanism 60 and the hydraulic piston cylinder 120 were removed, and only the partial structure of the two sedimentation stirring heads was retained.

[0068] The outer diameter of the homogenizing shoulder is 0.8-1.2 times the intersection length of the two virtual circles, and the intersection length of the two virtual circles is DS, where D is the diameter of the virtual circle and S is the distance between the central axes of the two deposition stirring heads. Specifically, in this embodiment, the outer diameter of the homogenizing shoulder is 1 time the intersection length of the two virtual circles.

[0069] The homogenizing motor 40 is mounted on the base. The homogenizing motor is a servo motor used to drive the homogenizing stirring head to rotate. The homogenizing motor 40 includes a stator A41, a mover A43 rotatably lined inside the stator A41, and a hollow shaft A44 fixed on the mover A43. A winding A42 is provided inside the stator A41.

[0070] A flange 72 protruding radially outward is provided at the upper end of the homogenizing stirring shaft. The hollow shaft A44 is sleeved on the homogenizing stirring shaft from bottom to top and abuts against the flange 72. The locking bolt 73 passes through the flange and is screwed onto the top of the hollow shaft A44 to fix the hollow shaft A44 on the homogenizing stirring shaft. A key A74 is provided between the hollow shaft A and the homogenizing stirring shaft to improve the connection strength between the two.

[0071] The upper end cover A411 and the lower end cover A412 are respectively bolted to the upper and lower ends of the stator A. The upper end cover A is rotatably connected to the outer wall of the hollow shaft A via the upper angular contact bearing A414, and the lower end cover A is rotatably connected to the outer wall of the hollow shaft A via the lower angular contact bearing A413. The connection methods of the upper angular contact bearing A414 to the upper end cover A and the hollow shaft A, and the connection methods of the lower angular contact bearing A413 to the lower end cover A and the hollow shaft A, all adopt existing mature technologies and will not be described in detail. In this embodiment, the stator 41 is directly welded to the base 500. It can be understood that in other embodiments, the stator A can also be mounted on the base using bolts, thereby mounting the entire homogenizing motor on the base. The lower end faces of the two deposition shoulders are coplanar with the lower end face of the homogenizing shoulder.

[0072] In this embodiment, to achieve a compact structure, the lower end cover A412 is directly welded to the lower plate, thereby mounting the two homogenizing motors on the base. It is understood that in other embodiments, a dedicated mounting bracket can be provided on the homogenizing motor, and then the homogenizing motor can be mounted on the base via the mounting bracket.

[0073] This embodiment can be connected to the fixed part of machining equipment such as friction stir welding machine, CNC milling machine, and CNC machining center via a base, and the friction stir additive manufacturing device can be moved using the machining equipment. Of course, a special moving device can also be set up to move the friction stir additive manufacturing device.

[0074] Example 2

[0075] This embodiment describes the friction stir additive deposition method. This embodiment uses the triaxial friction stir additive manufacturing apparatus from Embodiment 1. The friction stir additive deposition method includes the following steps:

[0076] (1) Tighten the limiting rod on the first hollow shaft torque motor so that the limiting rod is inserted into the limiting hole on the first sedimentation stirring head, connecting the first sedimentation stirring head to the hollow shaft on the first hollow shaft torque motor. Tighten the limiting rod on the second hollow shaft torque motor so that the limiting rod is removed from the limiting hole on the second sedimentation stirring head, disconnecting the second stirring head from the hollow shaft on the second hollow shaft torque motor.

[0077] The bar stock is fed into the discharge holes of the two deposition mixing heads through the feed hole, and the lower end face of the bar stock is flush with the lower end face of the deposition shoulder.

[0078] (2) Place the deposition shoulder on the surface of the substrate to be added, start the deposition stirring head, and make the two deposition stirring heads rotate synchronously. The deposition shoulder contacts the upper surface of the substrate, and the first stirring needle is inserted into the substrate for friction preheating for 15 seconds.

[0079] (3) Start the hydraulic piston cylinder as the pressing mechanism, so that the piston rod of the hydraulic piston cylinder extends downward and squeezes the bar down, so that the bar in the feeding hole moves downward and generates a forging force between the bar and the substrate to be added. At the same time, the deposition stirring head is pulled back 1.2mm and the triaxial stirring friction additive manufacturing device moves along the set path. The bar undergoes thermoplasticization under friction and flows out from the feeding hole. Keep the rotation of the deposition stirring head, and the bar is thermoplasticized and deposited on the substrate. Under the flattening action of the deposition shoulder, an additive forming surface is formed, realizing the stacking of a single-layer heat sink layer in the area to be added, forming an additive manufacturing layer; the arrangement direction of the two deposition stirring heads is perpendicular to the moving direction of the triaxial stirring friction additive manufacturing device.

[0080] After the bar stock is thermoplasticized, it forms a plasticized material that fills the cloth cavity of the two deposition shoulders. During the rotation of the two deposition agitators, the protrusions of the two deposition agitators intersect each other, causing the plasticized material in the two cloth cavities to fuse together and be deposited synchronously on the substrate. This results in a wider single-pass single-layer heat sink layer than a single agitator, thereby improving work efficiency.

[0081] When the top surface of the bar stock in the feed hole descends to be flush with the upper surface of the support plate, the piston rod of the hydraulic piston cylinder is lifted upward, so that the lower end of the piston rod faces upward and exceeds the top surface of the raw material cavity. The raw material container is rotated so that the next bar stock is aligned with the feed hole and abuts against the bar stock in the feed 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.

[0082] The deposition motor is started synchronously, so that the homogenizing stirring needle is inserted into the single-layer heat sink and the homogenizing shoulder is pressed against the forming surface of the single-layer heat sink to re-stir the middle area of ​​the single-layer heat sink; the length H of the homogenizing stirring needle extending downward from the lower end face of the homogenizing shoulder is 1.1 times the thickness of the single-layer heat sink.

[0083] (4) Repeat the stacking of single-layer heat sinks in the area to be added until the required additive height is achieved. During the repeated stacking of single-layer heat sinks, the bar stock generates an upsetting force between itself and the surface of the already added layer, and undergoes frictional thermoplastic deposition.

Claims

1. A triaxial stirring friction additive manufacturing apparatus, characterized in that, It includes a base and two deposition stirring heads and a homogenizing stirring head rotatably mounted on the base. The virtual line connecting the central axes of the two deposition stirring heads is called the central line segment. The central line segment extends along the direction of the first axis. An axial line is perpendicular to the central axis of the homogenizing stirring head and extends along the direction of the second axis. The midpoint of the central line segment is located on the axial line. The first axis and the second axis both extend horizontally and are perpendicular to each other. When the triaxial friction stir additive manufacturing apparatus is in operation, the extension direction of the central connecting line segment is perpendicular to the moving direction of the triaxial friction stir additive manufacturing apparatus, and the homogenizing stirring head is located downstream of the two deposition stirring heads. Each deposition stirring head includes a deposition stirring shaft extending vertically and a feed hole formed within the deposition stirring shaft. The lower end of the deposition stirring shaft is formed as a deposition shoulder, and a first stirring pin protruding downward is provided on the lower end face of the deposition shoulder. The deposition shoulder is star-shaped and has radially outwardly protruding protrusions that are evenly spaced. Within each protrusion is an upwardly recessed feeding cavity, which is open downward and communicates with the feed hole. The feed 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 feed hole. The space between two adjacent protrusions of the same deposition stirring head is formed as a groove area, and the protrusion of each deposition stirring head is inserted into the groove area of ​​another deposition stirring head; the radial outer edge of the material distribution chamber of the same deposition stirring head is located on a virtual circle, and the virtual circles corresponding to the two deposition stirring heads intersect; the virtual circle corresponding to each deposition stirring head is coaxially arranged with the deposition stirring axis of the deposition stirring head. For each deposition stirring head, a pressing mechanism is installed on the base to push the bar stock located in the feeding hole downwards; a deposition motor for driving the deposition stirring head to rotate is also installed on the base, and the deposition motor is a servo motor. The homogenizing stirring head includes a homogenizing stirring shaft extending vertically and a homogenizing shoulder formed at the lower end of the homogenizing stirring shaft. A homogenizing stirring needle protruding downward is provided on the lower end face of the homogenizing shoulder. A homogenizing motor for driving the homogenizing stirring head to rotate is also mounted on the base. The homogenizing motor is a servo motor. The lower end faces of the two deposition shoulders are coplanar with the lower end faces of the homogenizing shoulders.

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

3. The triaxial stirring friction additive manufacturing apparatus according to claim 1, characterized in that... The radial inner ends of two adjacent feeding chambers of the same deposition mixing head are connected to each other.

4. The triaxial stirring friction additive manufacturing apparatus according to claim 1, characterized in that, For each deposition stirring head, a deposition motor is provided. The deposition motor is a hollow shaft torque motor. The hollow shaft torque motor includes a stator, a mover rotatably lined 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 deposition stirring head via a transition bearing. 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. The limiting mechanism includes at least one limiting rod, which is movably installed on the hollow shaft. The sedimentation stirring head has a limiting hole corresponding to the limiting rod. The limiting rod can reciprocate along the radial direction of the sedimentation stirring head and insert into or withdraw from the corresponding limiting hole. When the limiting rod is inserted into the limiting hole, the hollow shaft can drive the corresponding sedimentation stirring head to rotate synchronously; when the limiting rod is withdrawn from the limiting hole, the hollow shaft and the corresponding sedimentation stirring head can rotate relative to each other; when the limiting rod on the hollow shaft of one hollow shaft torque motor 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; A gear is fixed on the outer wall of each of the two sedimentation stirring heads. The gears on the two sedimentation stirring heads mesh with each other, and the transmission ratio of the gears on the two sedimentation stirring heads is 1:

1.

5. The triaxial stirring friction additive manufacturing apparatus 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 sedimentation stirring head via two transition bearings spaced apart at the top and bottom. The lower transition bearing is a slewing bearing, and the upper transition bearing is a deep groove ball bearing.

6. The triaxial stirring friction additive manufacturing apparatus according to claim 4, characterized in that, For each limiting rod, an adjustment hole extending radially along the sedimentation stirring head is opened on the corresponding hollow shaft. The adjustment hole is an internally threaded hole and a through hole. The limiting rod is screwed into the corresponding adjustment hole.

7. The triaxial stirring friction additive manufacturing apparatus according to claim 1, characterized in that, For each sedimentation stirring head, a feeding mechanism is provided. Each feeding mechanism includes a support plate and a raw material container rotatably mounted on the support plate. The support plate is detachably mounted on the base and located above the sedimentation stirring head. The raw material container has a rotating shaft and several raw material through holes arranged around the rotating shaft. Each raw material through hole can only accommodate one rod in the radial direction. A feed hole is opened on the support plate that connects to the discharge hole. When the raw material container rotates, each raw material through hole can sequentially connect to the feed hole, and the rod in the raw material through hole can enter the discharge hole of the corresponding sedimentation stirring head through the feed hole.

8. The triaxial stirring friction additive manufacturing apparatus according to claim 1, characterized in that, The pressing mechanism is a piston cylinder, with one piston cylinder provided for each sedimentation 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 bar material downward.

9. The triaxial stirring friction additive manufacturing apparatus according to claim 1, characterized in that, The lower end face of the homogenizing shoulder is closed, and the homogenizing stirring needle is installed on the homogenizing shoulder by means of threads.

10. A method for frictional additive deposition, characterized in that, The triaxial friction stir additive manufacturing apparatus according to any one of claims 1-9 is used, and the friction stir additive deposition method includes the following steps: (1) Feed the bar stock into the feed holes of the two deposition mixing heads and make the lower end face of the bar stock flush with the lower end face of the deposition shoulder. (2) Place the deposition shoulder on the surface of the substrate to be added, start the deposition motor, and rotate the two deposition stirring heads synchronously so that the deposition shoulder contacts the upper surface of the substrate and the first stirring needle is inserted into the substrate for frictional preheating for 10-25 seconds. (3) Start the pressing mechanism, the bar in the feeding hole moves downward, so that the bar and the substrate to be added are generated with a forging force. At the same time, the deposition stirring head is pulled back 0.2-2.0mm, and the triaxial stirring friction additive manufacturing device moves along the set path. The bar is thermoplasticized under friction and flows out from the feeding hole. The rotation of the deposition stirring head is maintained. The bar is thermoplasticized and deposited on the substrate. Under the flattening action of the deposition shoulder, an additive forming surface is formed, realizing the deposition of a single-layer heat sink layer in the area to be added, forming an additive manufacturing layer; the arrangement direction of the two deposition stirring heads is perpendicular to the moving direction of the triaxial stirring friction additive manufacturing device. After the bar stock is thermoplasticized, it forms a plastic material that fills the fabric cavities of the two deposition shoulders. The plastic materials in the two fabric cavities are fused together and deposited synchronously on the substrate. When the top surface of the bar in the feed hole descends to be flush with the upper surface of the support plate, the next bar is aligned with the feed hole, and the pressing mechanism continues to press the bar downward. The deposition motor is started synchronously, so that the homogenizing stirring needle is inserted into the single-layer heat sink and the homogenizing shoulder is pressed against the forming surface of the single-layer heat sink to re-stir the middle area of ​​the single-layer heat sink; the length of the homogenizing stirring needle extending downward from the lower end face of the homogenizing shoulder is 1.1-1.2 times the thickness of the single-layer heat sink. (4) Repeat the stacking of single-layer heat sink in the area to be added until the required additive height is achieved.

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