A dual-axis synchronous friction stir additive manufacturing apparatus and method

Abstract

This application discloses a dual-axis synchronous friction stir additive manufacturing apparatus, comprising two stirring heads arranged perpendicular to the moving direction of the apparatus. The shoulders of the stirring shafts are star-shaped and have radially outwardly protruding, evenly spaced protrusions. Each protrusion has an upwardly recessed feeding chamber that connects to the material feeding hole inside the stirring head. A groove is formed between two adjacent protrusions, and the protrusion of each stirring head is inserted into the groove of the other stirring head. The lower end faces of the shoulders of the two stirring shafts are coplanar, and downwardly protruding stirring needles are provided on the lower end faces of the shoulders. This application also discloses a friction stir additive manufacturing method. This application utilizes two stirring heads to form a wider single-layer heat sink layer in a single operation compared to a single stirring head. Because the protrusions of the two stirring heads are staggered, the plasticized materials inside the two stirring heads can fuse together, ensuring product quality.

Description

Technical Field

[0001] This invention relates to a dual-axis synchronous friction stir additive manufacturing apparatus and a friction stir additive manufacturing method using the same 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 producing large-size products using friction stir additive manufacturing, this application first proposes a dual-axis synchronous friction stir additive manufacturing apparatus, which includes a base and two stirring heads rotatably mounted on the base; when the friction stir additive manufacturing apparatus is in operation, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing apparatus.

[0004] Each stirring head includes a stirring shaft extending vertically and a feeding hole formed within the stirring shaft. The lower end of the stirring shaft is formed as a shoulder, and a downwardly protruding stirring needle is provided on the lower end face of the shoulder. The shoulder is star-shaped and has radially outwardly protruding parts that are evenly spaced in a radial pattern. Within each protruding part is an upwardly recessed cloth cavity, which is open downwards and communicates with the feeding hole. The feeding 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 feeding hole.

[0005] The space between two adjacent protrusions of the same stirring head is formed as 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 cloth chamber of the same stirring head is located on a virtual circle, and the virtual circles 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.

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

[0007] In this application, during operation of the friction stir additive manufacturing apparatus, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the apparatus, allowing the two 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 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 friction stir 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 stirring head within the feeding chamber and fills the entire feeding chamber. When the two stirring heads rotate synchronously, the staggered arrangement of the protrusions of the two stirring heads allows the plasticized materials within the two stirring heads to fuse together, ensuring that the heat sink layers formed by the two stirring heads are seamlessly integrated and guaranteeing product quality.

[0008] Furthermore, to reduce manufacturing costs, the two agitator heads have identical structures, and the diameters of the virtual circles corresponding to the two agitator 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 agitator heads. Because the two agitator heads have identical structures, a single type of bar stock can meet the needs of both agitator heads, and the corresponding accessories of the two agitator heads can also be interchanged, reducing equipment maintenance costs.

[0009] Furthermore, in order to ensure that the 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 mixing head are connected to each other.

[0010] Furthermore, each stirring head is equipped with a drive motor, which 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 stirring head via 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, which is movably installed on the hollow shaft. The stirring head has a limiting hole corresponding to the limiting rod. The limiting rod can reciprocate along the radial direction of the stirring head and insert into or out of the corresponding 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 is withdrawn from the limiting hole, the hollow shaft and the corresponding 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.

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

[0014] This application incorporates two drive motors, each corresponding to one of the two stirring heads. When one drive motor rotates its corresponding stirring head, it synchronously drives the other stirring head via gears. To prevent back current from being generated when the other drive motor rotates passively, which could impact and damage the drive motor and its accessories, a limiting mechanism is provided. During operation, the hollow shaft of one drive motor is connected to the corresponding stirring head via this limiting mechanism, while the connection between the hollow shaft of the other drive motor and its corresponding stirring head is disconnected. This prevents back current from being generated by the rotation of the hollow shaft of the other drive motor, ensuring its safe operation. Furthermore, the use of two drive motors ensures continuous production. The two drive motors can serve as backups for each other, forming a redundant design. During production, if one drive motor malfunctions, the other drive motor can be started to continue production, reducing production costs and lowering overall production expenses.

[0015] 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 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.

[0016] Specifically, to facilitate the operation of the limiting rods, an adjustment hole extending radially along the 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.

[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 mounted on the support plate. The support plate is detachably mounted on the base and located above the 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 bar 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 bar in the raw material through hole can enter the discharge hole of the corresponding stirring head through the feed hole.

[0018] Specifically, the pressing mechanism is a piston cylinder, with one piston cylinder corresponding to each 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.

[0019] 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.

[0020] Secondly, to ensure the smooth completion of production by the aforementioned friction stir additive manufacturing apparatus, this application also discloses a friction stir additive manufacturing method, which employs the friction stir additive manufacturing apparatus described in any of the above claims. This friction stir additive manufacturing method includes the following steps:

[0021] (1) Feed the bar stock into the feeding holes of the two mixing heads and make the lower end face of the bar stock flush with the lower end face of the shaft shoulder.

[0022] (2) Place the shoulder on the surface of the substrate to be added, start the drive motor, and the two stirring heads rotate synchronously so that the shoulder contacts the upper surface of the substrate and the stirring needle is inserted into the substrate for frictional preheating for 10-25 seconds.

[0023] (3) Start the pressing mechanism, the bar in the feeding hole moves downward, so that the bar and the area to be added to the substrate are generated by the forging force. At the same time, the stirring head is pulled back 0.2-2.0mm, and the friction stirring additive manufacturing device moves along the set path. The bar is thermoplasticized under the action of friction and flows out from the feeding hole. The stirring head is kept rotating. The bar is thermoplasticized and deposited on the substrate. Under the flattening action of the shoulder, an additive forming surface is formed, realizing the deposition of a single heat sink layer in the area to be added, forming the added manufacturing layer; the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stirring additive manufacturing device.

[0024] After the bar stock is thermoplasticized, it forms a plastic material that fills the fabric cavities of the two shoulders. The plastic materials in the two fabric cavities are fused together and deposited synchronously on the substrate.

[0025] 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.

[0026] (4) Repeat the stacking of single-layer heat sink in the area to be added until the required additive height is achieved.

[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, so that the two stirring heads move side by side synchronously along the set direction, which can form a single-layer heat sink layer that is wider than that of a single stirring head in one go. During the production process, after the bar stock is frictionally thermoplasticized in the feeding hole, it forms a plasticized material, which flows radially along the stirring head in the feeding cavity and fills the entire feeding cavity. When the two stirring heads rotate synchronously, the protrusions of the two stirring heads are staggered, which allows the plasticized material in the two stirring heads to fuse together, so that the heat sink layers formed by the two stirring heads can be seamlessly fused together, ensuring product quality. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of an embodiment of this application.

[0029] Figure 2 yes Figure 1 A view from the center AA direction.

[0030] Figure 3 yes Figure 2 A bottom view.

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

[0032] Figure 5 yes Figure 4 A view from the center (BB direction). Detailed Implementation

[0033] Example 1

[0034] The following section first describes the structure of the dual-axis synchronous friction stir additive manufacturing apparatus. Please refer to [link to relevant documentation]. Figures 1-5 The friction stir additive manufacturing apparatus includes a base 500 and two stirring heads rotatably mounted on the base, namely a first stirring head 201 and a second stirring head 202. When the friction stir additive manufacturing apparatus is in operation, the arrangement direction of the two stirring heads is perpendicular to the movement direction of the friction stir additive manufacturing apparatus. In the accompanying drawings, the first arrow X indicates the arrangement direction of the two stirring heads, and the second arrow Y indicates the movement direction of the friction stir additive manufacturing apparatus during operation; that is, the arrangement direction of the two stirring heads is perpendicular to the movement direction of the friction stir additive manufacturing apparatus during operation.

[0035] In this embodiment, the two stirring heads have the same structure. The structure of the two stirring heads will be described below using the first stirring head 201 as an example. The first stirring head 201 includes a stirring shaft 21 extending in a vertical direction and a feeding 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 and has radially outwardly protruding portions 251 evenly spaced. Within each protrusion is an upwardly recessed fabric 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 fabric 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 fabric cavities of the same stirring head are interconnected. A downwardly protruding stirring pin 27 is provided on the lower end face of the shoulder.

[0037] The space between two adjacent protrusions of the first stirring head forms a groove region 254, and the protrusion of each stirring head is inserted into the groove region of the other stirring head. The radially outer edge 2521 of the cloth chamber 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 axis of the first stirring head, and the virtual circle corresponding to the second stirring head is coaxially arranged with the stirring axis of the second stirring head. The virtual circles corresponding to the two stirring heads partially intersect.

[0038] In this embodiment, the diameter D of the virtual circles corresponding to the two stirring heads is the same. The diameter D of the virtual circle is 5mm larger than the distance S between the central axes of the two stirring heads. That is, the two virtual circles intersect by 5mm 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 3mm, 6mm or 8mm larger than the distance S between the central axes of the two stirring heads, or other distances between 3-8mm.

[0039] A drive motor for rotating the stirring head is also installed on the base. Each stirring head has a corresponding drive motor, which is a servo motor. In this embodiment, the drive motor is specifically a hollow shaft torque motor. For ease of description, the hollow shaft torque motor corresponding to the first stirring head is referred to as the first hollow shaft torque motor 101, and the hollow shaft torque motor corresponding to the second 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.

[0040] 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 stirring shaft 21 of the first 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 stirring shaft 21 of the first 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 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.

[0041] A first stepped surface 212 facing upwards is provided on the outer circumferential surface of the upper end of the 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 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 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.

[0042] 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.

[0043] In this embodiment, the base 500 includes an upper plate 501 and a lower plate 502 spaced apart vertically, 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 hollow shaft torque motors on the base. It is understood that in other embodiments, a dedicated mounting bracket can be provided on the hollow shaft torque motor, and then the hollow shaft torque motor can be mounted on the base via the mounting bracket.

[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 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 stirring head. Each limiting rod 17 extends radially along the first stirring head. Corresponding to each limiting rod, a limiting hole 211 is formed on the stirring shaft of the first stirring head. The limiting hole 211 is a blind hole that penetrates radially through the outer circumference of the stirring shaft. Corresponding to each limiting rod, an adjusting hole 141 extending radially along the first 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.

[0046] Twisting the limiting rod allows it to reciprocate radially along the corresponding stirring head, inserting into or retracting from the corresponding limiting hole. When the limiting rod is inserted into the limiting hole, the hollow shaft and the corresponding stirring head are connected as one unit, enabling the hollow shaft of the hollow shaft torque motor to drive the corresponding stirring head to rotate synchronously. When the limiting rod is retracted from the limiting hole, the connection between the hollow shaft and the corresponding stirring head is broken, allowing the hollow shaft of the hollow shaft torque motor and the corresponding 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.

[0047] Therefore, when the hollow shaft of one of the hollow shaft torque motors drives the corresponding stirring head to rotate synchronously, it can drive the other stirring head to rotate through the gears described below. Since the other stirring head is disconnected 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 to avoid generating back current in the hollow shaft torque motor corresponding to the other stirring head, which would reduce the safety or service life of the hollow shaft torque motor.

[0048] exist Figure 1In 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.

[0049] 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.

[0050] A gear is fixed to the outer wall of each of the two 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 on the upper end of the stirring shaft of the first stirring head, and the second gear 82 is fixedly installed on the upper end of the stirring shaft of the second 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 on the top of the stirring shaft. The gears are supported on the second step surface, and a key 214 is inserted between the stirring shaft and the gears.

[0051] To improve the efficiency of adding bar stock, in this embodiment, a feeding mechanism 60 is provided for each stirring 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 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 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 bar stock in the raw material through hole can enter the discharge hole of the corresponding stirring head through the feed hole. A loading hole 55 for placing bar stock 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 bar stock to 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 plate and are detachably mounted on the base using bolts.

[0053] To facilitate the rotation of the raw material container 61, in this embodiment, a top plate 51 is provided above the support plate 52. This top plate is supported on the support plate by columns 53, forming a frame structure 50 together with the support plate. Two feeding motors 65 are installed on each top plate, each corresponding to a raw material container 61. The drive shaft of each feeding motor is connected to the rotating shaft of its corresponding raw material container 61 to drive the container to rotate.

[0054] For each 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 base material 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 other embodiments, an electric piston cylinder is used to replace the hydraulic piston cylinder.

[0055] In this embodiment, two drive motors are provided, which serve as backups for each other. When a working drive motor fails and cannot operate, the hollow shaft of the drive motor can be disconnected 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, thus avoiding waste of the workpiece.

[0056] 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.

[0057] Example 2

[0058] This embodiment describes a friction stir additive manufacturing method. This embodiment uses the friction stir additive manufacturing apparatus from Embodiment 1. The friction stir additive manufacturing method includes the following steps:

[0059] (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 stirring head, connecting the first 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 stirring head, disconnecting the second stirring head from the hollow shaft on the second hollow shaft torque motor.

[0060] The bar stock is fed into the discharge holes of the two mixing heads through the feed hole, and the lower end face of the bar stock is flush with the lower end face of the shaft shoulder.

[0061] (2) Place the shoulder on the surface of the substrate to be added, start the stirring head, make the two stirring heads rotate synchronously, the shoulder contact the upper surface of the substrate, the stirring needle penetrates into the substrate, and perform friction preheating for 15 seconds.

[0062] (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, pull the stirring head back 1.2mm and move the friction stirring additive manufacturing device along the set path. The bar undergoes thermoplasticization under friction and flows out from the feeding hole. Keep the stirring head rotating, and the bar thermoplasticized and deposited on the substrate. Under the flattening action of the shoulder, an additive forming surface is formed, realizing the deposition of a single heat sink layer in the area to be added, forming an additive manufacturing layer; the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stirring additive manufacturing device.

[0063] After the bar stock is thermoplasticized, it forms a plasticized material that fills the cloth cavity of the two shoulders. During the rotation of the two agitators, the protrusions of the two 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.

[0064] 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.

[0065] (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 dual-axis synchronous friction stir additive manufacturing apparatus, characterized in that, It includes a base and two stirring heads rotatably mounted on the base; when the friction stir additive manufacturing apparatus is in operation, the arrangement direction of the two stirring heads is perpendicular to the moving direction of the friction stir additive manufacturing apparatus; Each stirring head includes a stirring shaft extending vertically and a feeding hole formed within the stirring shaft. The lower end of the stirring shaft is formed as a shoulder, and a downwardly protruding stirring needle is provided on the lower end face of the shoulder. The shoulder is star-shaped and has radially outwardly protruding parts that are evenly spaced in a radial pattern. Within each protruding part is an upwardly recessed cloth cavity, which is open downwards and communicates with the feeding hole. The feeding 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 feeding hole. The space between two adjacent protrusions of the same stirring head is formed as 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 cloth chamber of the same stirring head is located on a virtual circle, and the virtual circles 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. For each stirring head, a pressing mechanism is installed on the base to push the bar material located in the feeding hole downward; a drive motor for driving the stirring head to rotate is also installed on the base, and the drive motor is a servo motor; the lower end faces of the two shoulders are coplanar.

2. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, The two stirring heads have the same structure, and the diameter of the virtual circle corresponding to the two 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 stirring heads.

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

4. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, For each stirring head, a drive motor is provided. The drive 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 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 stirring head has a limiting hole corresponding to the limiting rod. The limiting rod can reciprocate along the radial direction of the stirring head and insert into or out of the corresponding limiting hole. 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 is withdrawn from the limiting hole, the hollow shaft and the corresponding 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 stirring heads. The gears on the two stirring heads mesh with each other, and the transmission ratio of the gears on the two stirring heads is 1:

1.

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

7. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, For each 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 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 bar 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 bar in the raw material through hole can enter the discharge hole of the corresponding stirring head through the feed hole.

8. The friction stir additive manufacturing apparatus according to claim 1, characterized in that, The pressing mechanism is a piston cylinder, with one piston cylinder 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 bar material downward.

9. A method for friction stir additive manufacturing, characterized in that, The friction stir additive manufacturing method, performed using the apparatus described in any one of claims 1-8, comprises the following steps: (1) Feed the bar stock into the feeding holes of the two mixing heads and make the lower end face of the bar stock flush with the lower end face of the shaft shoulder. (2) Place the shoulder on the surface of the substrate to be added, start the drive motor, and the two stirring heads rotate synchronously so that the shoulder contacts the upper surface of the substrate and the 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 area to be added to the substrate generate a forging force. At the same time, the stirring head is pulled back 0.2-2.0mm, and the stirring friction additive manufacturing device moves along the set path. The bar is thermoplasticized under friction and flows out from the feeding hole. Keep the stirring head rotating. The bar is thermoplasticized and deposited on the substrate. Under the flattening action of the shoulder, an additive forming surface is formed, realizing the deposition of a single heat sink layer in the area to be added, forming an additive manufacturing layer. The two stirring heads are arranged perpendicular to the direction of movement of the friction stir additive manufacturing device; After the bar stock is thermoplasticized, it forms a plastic material that fills the fabric cavities of the two 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. (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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