Powder bed solid phase additive manufacturing system and method based on multi-level constraint mechanism

Abstract

This invention discloses a powder bed solid-state additive manufacturing system and method based on a multi-level constraint mechanism. First, a first-level macroscopic constraint is established through boundary constraints, limiting the powder spreading space and restricting powder peripheral displacement. Then, an in-situ pre-printed frame structure forms a second-level boundary constraint. Next, forming along an interlaced path, a third-level unit constraint is constructed using the mutual support force between the formed segments and powder units, dividing the area to be filled into discrete units. Finally, using the formed path as a rigid mold wall, a fourth-level filling constraint is formed for thermoplastic flow, promoting the coordinated fusion of each unit and the frame. This method, through precise control of physical entity constraints and in-situ pre-formed block mold walls, combined with spatial lattice design to construct a dynamic local constraint system, effectively suppresses material overflow and flash phenomena during solid-state additive manufacturing, breaking through the forming bottleneck of large components and significantly improving the component's density, comprehensive mechanical properties, dimensional accuracy, and forming efficiency.

Description

Technical Field

[0001] This invention relates to the field of powder bed stirring friction additive manufacturing technology, and more specifically to a powder bed solid phase additive manufacturing system and method based on a multi-level constraint mechanism. Background Technology

[0002] Additive manufacturing technology, based on different material forming mechanisms, is mainly divided into melt additive manufacturing, characterized by melting and solidification, and solid-state additive manufacturing, characterized by thermoplastic forming. Traditional laser melting additive manufacturing uses a high-energy beam to rapidly melt and solidify raw materials. While offering high flexibility, the intense phase transformation process easily leads to physical defects in the formed parts, such as grain coarsening, porosity, and thermal cracking. In contrast, powder bed solid-state additive manufacturing utilizes the frictional heat generated by the high-speed rotation of a stirring tool to achieve a thermoplastic state in the powder. Under pressure, solid-state bonding is achieved, resulting in significantly finer grains. Furthermore, the pre-laid powder bed design effectively eliminates the material blockage problem common in traditional solid-state processes, demonstrating enormous application potential in the manufacturing of aluminum alloy components.

[0003] However, existing powder bed solid-state additive manufacturing processes face significant challenges when scaling up to large structural components with dimensions of at least 300 mm × 300 mm.

[0004] First, during the powder layup stage, the physical angle between the scraper and the mold wall at a fixed height makes it difficult to even out the powder near the edge. The resulting large pores cause the powder to disperse outward during printing, leading to material shortages. Second, metal powders have significant dispersion. In large components lacking direct mold wall constraints, powder at the edge of the stirring tool is flung away by centrifugal force during high-speed rotation. This results in insufficient thermoplastic fluid in the central area to fill the entire shoulder, causing dimensional deviations in the deposited layer or internal porosity. Furthermore, flash is also a key factor restricting forming quality. The forward side of the stirring tool carries a large amount of material forward and overflows from the shoulder. In large-scale printing, due to the lack of lateral pressure support, this plastic overflow not only causes material loss but also disrupts the stability of the forming process.

[0005] In summary, existing technologies in the powder bed solid-phase additive manufacturing of large components urgently need to address technical issues such as uneven powder distribution at the boundary due to the lack of effective lateral constraints, powder bed stress dispersion and instability, and flash caused by the overflow of thermoplastic fluid, in order to achieve high density, high geometric accuracy, and excellent mechanical properties in the forming of large-sized components. Summary of the Invention

[0006] The purpose of this invention is to provide a powder bed solid-phase additive manufacturing system and method based on a multi-level constraint mechanism. The system constructs a first-level macroscopic constraint through precise control of the boundary constraint device, while the pre-formed block mold wall inside the powder bed serves as a second-level boundary constraint. Combined with spatial lattice design, the forming area is divided into restricted independent units, and dynamic local third-level and fourth-level constraints are constructed by utilizing the mutual support between the solid skeleton and the powder units, thus breaking through the forming bottleneck of large components.

[0007] According to a first aspect of the present invention, a powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism is provided, comprising the following steps:

[0008] S1. Establish boundary constraints around the printing area to limit the spatial height of a single layer of powder and lay the powder. Use the boundary constraints to restrict the macroscopic displacement of the powder to the outer periphery of the printing area, forming a first-level macroscopic constraint for the powder bed.

[0009] S2. Using a powder bed solid-phase additive manufacturing tool, a frame structure is pre-printed within the printing area, and the frame structure forms a secondary boundary constraint on the area to be filled inside it.

[0010] S3. Within the area enclosed by the frame structure, the powder bed solid-phase additive tool is controlled to form along an interlaced path; wherein, during the forming process, the formed path segments and adjacent powder units are used to generate mutual support forces on the current forming path, thereby forming a three-level unit constraint for lateral limiting of the interlaced path, and dividing the area to be filled into multiple discrete powder units.

[0011] S4. Using the formed path segment as a lateral rigid mold wall, a four-level filling constraint is formed for the thermoplastic flow of powder units. Solid-phase additive filling is performed on each powder unit, so that the frame structure, intersecting paths and each powder unit are fused together under the synergistic effect of multi-level constraints to complete single-layer thermoplastic forming.

[0012] S5. Repeat steps S1 to S4 until the component is formed.

[0013] As an optional implementation, in step S1, the boundary constraint is provided by a multi-level lifting constraint frame, and the spatial height of the single-layer powder spreading is limited by adjusting the height of the constraint frame so that the vertical distance between the top surface of the constraint frame and the current surface to be formed is equal to the preset single-layer printing thickness.

[0014] As an optional implementation, in step S2, the frame structure is a closed dot matrix skeleton generated according to the outline of the printed component.

[0015] As an optional implementation, in step S3, the intersecting paths are mutually orthogonal grid-like paths, and the intersecting paths divide the internal powder into square or rectangular block units.

[0016] As an optional implementation, in the staggered paths, the spacing between two adjacent paths is 1.6 to 1.8 times the diameter of the working end face of the powder bed solid-phase additive manufacturing tool.

[0017] As an optional implementation, in step S4, when the powder unit is being filled with solid additive manufacturing, the forward side of the powder bed solid additive manufacturing tool is controlled to move toward the formed path segment, using the formed path segment to prevent the overflow of thermoplastic fluid, thereby suppressing flash generation and guiding the fluid to fill the tool shoulder gap.

[0018] As an optional implementation, in step S4, when the powder unit is filled and shaped by the powder bed solid additive tool, the thermoplastic shearing action generated by rotational friction causes the edge of the powder unit to undergo interfacial remelting and microstructure penetration with the adjacent frame structure or intersecting path, forming a metallurgical bond.

[0019] As an optional implementation, in step S1, the powder is spread evenly using a powder spreading device, and the working end face of the scraper of the powder spreading device is brought close to the top surface of the boundary constraint and scraped across it. The powder gap is reduced by the scraping action, and the powder is brought into close contact with the inner wall surface of the boundary constraint.

[0020] As an optional implementation, before the powder is laid in step S1, a substrate preheating step is also included: controlling the powder bed solid additive tool to perform no-load reciprocating friction on the substrate surface, using frictional heat to make the substrate reach a preset temperature suitable for powder bonding, and increasing the roughness of the substrate surface.

[0021] According to a second aspect of the present invention, a powder bed solid-state additive manufacturing system with boundary constraints is provided, comprising:

[0022] A base, on which a worktable is provided, and a boundary constraint device is provided on the outer periphery of the worktable;

[0023] The boundary constraint device includes a multi-level constraint frame, each level of which is an axially through hollow frame and nested with each other. The multi-level constraint frames together enclose a formed cavity located above the worktable.

[0024] A powder feeding device is located above the worktable and is used to provide a preset amount of powder material to the forming area.

[0025] A powder spreading device, disposed above the forming cavity, is used to spread the powder provided by the powder feeding device evenly into the forming cavity to form a powder bed; and

[0026] The printing apparatus includes a powder bed solid-phase additive manufacturing tool that can extend into the forming cavity, the powder bed solid-phase additive manufacturing tool being used to perform solid-phase processing on the powder bed to achieve material layer stacking.

[0027] As an optional implementation, the constraint frame includes a baseline constraint level, an intermediate nested level, and an end constraint level, wherein the intermediate nested level and the end constraint level can be independently adjusted up and down in a direction perpendicular to the surface of the worktable.

[0028] As an optional implementation, the reference constraint hierarchy includes a first-level constraint frame, which includes a first-level outer frame and a first-level inner frame disposed therein, with a first annular assembly gap formed between the first-level outer frame and the first-level inner frame.

[0029] The intermediate nested level includes a second-level constraint frame, which includes a second-level outer frame and a second-level inner frame disposed inside it. A second annular assembly gap is formed between the second-level outer frame and the second-level inner frame, and the second-level constraint frame is fitted inside the first annular assembly gap.

[0030] The end constraint level includes a third-level constraint frame, which is fitted within the second annular assembly gap.

[0031] As an optional implementation, interlocking limiting flange structures are provided between the first-level constraint frame, the second-level constraint frame, and the third-level constraint frame.

[0032] The first outer frame and the first inner frame are respectively provided with a first outer limiting flange and a first inner limiting flange that extend relative to each other on the inner side of their top ends.

[0033] The second outer frame and the second inner frame are respectively provided with a second outer limiting lower flange and a second inner limiting lower flange extending in opposite directions on the bottom outer side. The second outer limiting lower flange is located below the first outer limiting flange, and the second inner limiting lower flange is located below the first inner limiting flange.

[0034] The top inner sides of the second-level outer frame and the second-level inner frame are respectively provided with a second outer limiting upper flange and a second inner limiting upper flange that extend relatively.

[0035] The bottom outer side of the third-level constraint frame is provided with a third outer limiting flange and a third inner limiting flange extending in opposite directions, and the third outer limiting flange and the third inner limiting flange are both located below the corresponding second outer limiting upper flange and the second inner limiting upper flange.

[0036] As an optional implementation, the outer wall of the second-level outer frame and the inner wall of the first-level outer frame are slidably fitted together by a linear guide component, and the inner wall of the second-level inner frame and the outer wall of the first-level inner frame are slidably fitted together by a linear guide component; the outer wall of the third-level constraint frame and the inner wall of the second-level outer frame are slidably fitted together by a linear guide component, and the inner wall of the third-level constraint frame and the outer wall of the second-level inner frame are slidably fitted together by a linear guide component.

[0037] As an optional implementation, the linear guide assembly includes a guide rail disposed vertically on the side wall of the constraint frame, and a slider disposed on the corresponding limiting flange and slidingly matched with the guide rail.

[0038] As an optional implementation, the constraint box further includes a linear drive component for driving the movement of the constraint box, the linear drive component including a first lead screw component and a second lead screw component;

[0039] The first lead screw assembly is symmetrically arranged at the top corner of the third-level constraint frame, and is used to directly drive the third-level constraint frame to rise and fall.

[0040] At least two sets of second lead screw assemblies are symmetrically arranged in the second annular assembly gap. The second lead screw assembly is connected to the second-level constraint frame through a load transfer block to drive the second-level constraint frame to rise and fall. The third-level constraint frame is provided with clearance holes for the second lead screw assembly to pass through.

[0041] As an optional implementation, the top surface of the workbench is provided with a stepped protrusion, the workbench passes through the first-level inner frame, and the protrusion overlaps the flange at the top of the first-level inner frame; the outer periphery of the protrusion is in contact with the inner wall of the second-level inner frame.

[0042] As can be seen from the above technical solutions of the present invention, the powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism proposed in this invention systematically solves the problems of forming quality and mechanical properties in the solid-state additive manufacturing of large components through a multi-level progressive constraint mechanism.

[0043] First, by finely controlling the powder spreading height through boundary constraints, the physical angle between the scraper and the mold is eliminated, which significantly reduces the powder porosity and suppresses powder dispersion, thus solving the problem of insufficient material at the edge from the source.

[0044] Secondly, the pre-printed frame structure is used to establish geometric boundaries, providing a rigid envelope and stress support for large components, effectively avoiding forming instability without mold support;

[0045] Based on this, dynamic partition constraints are constructed through spatial lattice, breaking down large areas into smaller parts. The pre-formed skeleton is used as a dynamic mold wall to provide lateral pressure, and the precise positioning of the stirring tool's forward side during filling completely suppresses flash defects, ensuring the continuous stability of the thermoplasticization process.

[0046] In addition, by utilizing the differences in forming timing and path direction, a progressive heterogeneous structure with grain phase differences is constructed inside the component, which significantly improves crack propagation resistance and enhances the static strength and fatigue life of the component.

[0047] Ultimately, this invention ingeniously achieves mutual constraint between the solid skeleton and the flexible powder, eliminating the dependence on large rigid molds and providing an efficient industrial solution for solid-phase additive manufacturing of large and complex components such as high-performance aluminum alloys. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the structure of a powder bed solid-phase additive manufacturing system based on a multi-level constraint mechanism, as exemplified by the present invention. Figure 2 This is a schematic diagram of the phase distribution of the boundary constraint device according to an example of the present invention.

[0049] Figure 3 This is an exploded view of the phase distribution of the boundary constraint device according to an example of the present invention.

[0050] Figure 4 This is a schematic diagram of the boundary constraint device according to an example of the present invention.

[0051] Figure 5 This is a cross-sectional view of the phase distribution of the boundary constraint device according to an example of the present invention.

[0052] Figure 6 This is a partial schematic diagram of the connection structure of the boundary constraint device according to an example of the present invention.

[0053] Figure 7 This is a schematic diagram of the phase distribution of the lifting drive component according to an example of the present invention.

[0054] Figure 8 This is a partial cross-sectional view of the phase distribution of the lifting drive component according to an example of the present invention.

[0055] Figure 9 This is a process flow diagram of the powder bed solid-phase additive manufacturing method based on a multi-level constraint mechanism according to the present invention.

[0056] Figure 10 This is a schematic diagram showing the orientation of the forward and backward sides of the powder bed solid additive manufacturing tool according to an example of the present invention.

[0057] Figure 11 This is a schematic diagram of the printing process of the frame structure of the present invention.

[0058] Figure 12 This is a schematic diagram of the printing process of interlaced paths in an example of the present invention.

[0059] Figure 13 This is a schematic diagram of the printing process of solid-phase additive filling of powder units according to an example of the present invention.

[0060] Figure 14 This is a schematic diagram showing the structure and dimensions of the printed component in an embodiment of the present invention; wherein, Figure 14 Part 'a' in the diagram is a 3D view of the printed component; Figure 14 Part b in the diagram is the front view of the printed component; Figure 14 Part c in the figure is the left view of the printed component.

[0061] Reference numerals: 100, base; 110, worktable; 111, boss; 120, boundary constraint device; 121, constraint frame;

[0062] 121A, First-level constraint frame; 121A-1, First-level outer frame; 121A-11, First outer limiting flange; 121A-2, First-level inner frame; 121A-21, First inner limiting flange;

[0063] 121B, Second-level constraint frame; 121B-1, Second-level outer frame; 121B-11, Second outer lower flange; 121B-12, Second outer upper flange; 121B-2, Second-level inner frame; 121B-21, Second inner lower flange; 121B-22, Second inner upper flange;

[0064] 121C, third-level constraint frame; 121C-1, third outer limiting flange; 121C-2, third inner limiting flange;

[0065] 122. Guide rail; 123. Slider; 124. First lead screw assembly; 125. Second lead screw assembly;

[0066] 200. Powder feeding device; 300. Powder spreading device; 310. Scraper; 400. Printing device. Detailed Implementation

[0067] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0068] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0069] Powder bed solid additive manufacturing system with boundary constraints

[0070] Combination Figures 1-8 As shown, the exemplary powder bed solid additive manufacturing system with boundary constraints of the present invention includes a base 100, a powder feeding device 200, a powder spreading device 300, and a printing device 400.

[0071] The base 100, which serves as the mounting base for the printing platform, is horizontally installed on the ground. The base 100 has a connecting part that engages with the connecting part on the first end face of the worktable 110, thereby fixing the worktable 110 on the base 100.

[0072] Boundary constraint device

[0073] [Structure of boundary constraint device]

[0074] like Figures 2-3 As shown, the workbench 110 is provided with a boundary constraint device 120 on its outer periphery, which is used to limit the spatial height of a single layer of powder by physical boundary, thereby providing an initial first-level macroscopic constraint for the powder bed.

[0075] In one example, the boundary constraint device 120 includes multiple nested constraint frames 121, each of which is a hollow frame structure with a central axis through it, used to enclose and form a vertically through-type placement cavity inside.

[0076] In another specific example, the multi-level constraint box 121 includes a base constraint level, an intermediate nested level, and an end constraint box from the outside to the inside; wherein, the intermediate nested level can be set to N levels (N is an integer greater than or equal to 1) according to actual process requirements, so as to realize progressive constraint on the boundary of the forming area; the constraint boxes at each level maintain a precise fit, and the intermediate nested level and the end constraint box can be independently adjusted up and down in a direction perpendicular to the surface of the worktable 110.

[0077] In one of the preferred examples, such as Figures 4-5 As shown, the multilevel constraint box 121 is a three-level constraint box, including a first-level constraint box 121A, a second-level constraint box 121B, and a third-level constraint box 121C;

[0078] The first-level constraint frame 121A, which serves as the reference level for the entire device, includes a first-level outer frame 121A-1 and a first-level inner frame 121A-2 located inside it. A preset distance is maintained between the inner wall of the first-level outer frame 121A-1 and the outer wall of the first-level inner frame 121A-2, thereby forming an annular assembly gap between their perimeter walls.

[0079] The second-level constraint frame 121B, which is an intermediate nested layer, includes a second-level outer frame 121B-1 and a second-level inner frame 121B-2 located inside it. The second-level constraint frame 121B is entirely fitted into the annular assembly gap formed by the first-level constraint frame 121A.

[0080] The outer wall of the second-level outer frame 121B-1 is slidably fitted with the inner wall of the first-level outer frame 121A-1, and the inner wall of the second-level inner frame 121B-2 is slidably fitted with the outer wall of the first-level inner frame 121A-2; in addition, there is also an annular gap between the inner wall of the second-level outer frame 121B-1 and the outer wall of the second-level inner frame 121B-2.

[0081] The third-level constraint frame 121C, which is the end constraint level, is located in the annular gap between the second-level outer frame 121B-1 and the second-level inner frame 121B-2. The outer wall of the third-level constraint frame 121C is slidably connected to the inner wall of the second-level outer frame 121B-1, and its inner wall is slidably connected to the outer wall of the second-level inner frame 121B-2.

[0082] Through sliding contact, both the second-level constraint frame 121B and the third-level constraint frame 121C can move independently up and down relative to the worktable 110 in the vertical direction.

[0083] The height of each constraint frame is no greater than the height of the workbench 110; preferably, the height of each constraint frame is equal to the height of the workbench 110. This equal height design not only ensures that each constraint frame can be completely contained within the envelope space formed by the first-level constraint frame 121A in the initial state, but also ensures that the boundary constraint device can provide the most effective powder containment height under the maximum lifting stroke.

[0084] like Figure 5 As shown, in some examples, the top inner sides of the first-level outer frame 121A-1 and the first-level inner frame 121A-2 are respectively provided with a first outer limiting flange 121A-11 and a first inner limiting flange 121A-21 that extend relative to each other;

[0085] The bottom outer ends of the second-level outer frame 121B-1 and the second-level inner frame 121B-2 are respectively provided with a second outer limiting lower flange 121B-11 and a second inner limiting lower flange 121B-21 extending in opposite directions; the second outer limiting lower flange 121B-11 is located below the first outer limiting flange 121A-11, and the second inner limiting lower flange 121B-21 is located below the first inner limiting flange 121A-21; through this hook-and-loop engagement, the maximum upward movement of the second-level constraint frame 121B is limited, and the lateral contact between the flanges is used to limit its translation in the X and Y axis directions and its rotation around the Z axis;

[0086] The top inner sides of the second-level outer frame 121B-1 and the second-level inner frame 121B-2 are respectively provided with a second outer limiting upper flange 121B-12 and a second inner limiting upper flange 121B-22 that extend in opposite directions; the bottom outer side of the third-level constraint frame 121C is respectively provided with a third outer limiting flange 121C-1 and a third inner limiting flange 121C-2 that extend in opposite directions, and the third outer limiting flange 121C-1 and the third inner limiting flange 121C-2 are respectively perpendicularly interlocked with the corresponding second-level limiting upper flanges (121B-12, 121B-22).

[0087] Through the aforementioned multi-level staggered flange structure, a stable axial sliding pair is formed between the constraint frames at each level, ensuring that each frame retains only a single degree of freedom of movement in the vertical direction (axial direction).

[0088] In some examples, the multi-level constraint box 121 achieves precise sliding fit between the constraint boxes at each level through a linear guide component. Taking the aforementioned three-level constraint box as an example, the specific structure is as follows:

[0089] {Guided mate between first-level and second-level constraint frames}

[0090] like Figure 6 As shown, at least one set of vertical guide rails 122 are respectively provided on the inner walls of the first outer frame 121A-1 and the first inner frame 121A-2. The guide rails 122 are matched with the sliders 123 provided on the second outer limiting lower flange 121B-11 and the second inner limiting lower flange 121B-21.

[0091] Meanwhile, vertical guide rails are also provided on the outer walls of the second-level outer frame 121B-1 and the second-level inner frame 121B-2 to slide with the sliders on the first outer limiting flange 121A-11 and the first inner limiting flange 121A-21.

[0092] This design, which guides the inner and outer walls synchronously, ensures that the second-level constraint frame 121B has extremely high axial stability during the lifting process.

[0093] {Guided mate between level 2 and level 3 constraint frames}

[0094] Similarly, vertical guide rails are provided on the inner walls of the second-level outer frame 121B-1 and the second-level inner frame 121B-2, which cooperate with the corresponding sliders provided on the third outer limiting flange 121C-1 and the third inner limiting flange 121C-2.

[0095] Vertical guide rails are provided on the outer walls of both sides of the third-level constraint frame 121C, which slide in cooperation with the sliders on the second outer limit upper flange 121B-12 and the second inner limit upper flange 121B-22.

[0096] Based on the above dual guiding mechanism, the second-level constraint frame 121B and the third-level constraint frame 121C respectively constitute independent sliding pairs. Under the action of the driving mechanism, each level of constraint frame can overcome frictional resistance and perform high-precision independent reciprocating motion relative to the worktable 11 in the vertical direction, thereby realizing real-time dynamic adjustment of the powder spreading height.

[0097] like Figures 7-8 As shown, in some examples, the lifting power source for each level of constraint box is provided by a linear drive component. Taking the aforementioned three-level constraint box as an example, the specific structure is as follows:

[0098] The third-level constraint frame 121C is symmetrically provided with first lead screw assemblies 124 at its four apex corners. By driving the first lead screw assemblies 124, the third-level constraint frame 121C can be directly driven to perform vertical lifting and lowering movements.

[0099] The third-level constraint frame 121C and the second-level constraint frame 121B can form a stroke linkage relationship through the aforementioned flange structure: when the third-level constraint frame 121C moves upward to its upper limit of stroke, the limiting flange at its bottom and the limiting flange at the top of the second-level constraint frame 121B will mechanically interfere and abut, thereby driving the second-level constraint frame 121B to move upward synchronously through traction, so as to realize the height coordination adjustment of the multi-level boundaries.

[0100] At least two sets of second lead screw assemblies 125 are symmetrically arranged in the annular gap between the second-level outer frame 121B-1 and the second-level inner frame 121B-2. The second lead screw assemblies 125 are symmetrically arranged with the central axis of the second-level inner frame 121B-2 as the center of symmetry. This symmetrical layout can ensure the uniform distribution of driving force in the circumferential direction and effectively avoid the phenomenon of constraint frame skewing or jamming caused by driving force imbalance during the forming process of large-size components.

[0101] Each second lead screw assembly 125 is equipped with a corresponding load transfer block. When the second lead screw assembly 125 is started for driving, the load transfer block simultaneously generates displacement coupling with the structural positions (such as corresponding limiting flanges or reinforcing ribs) of the second-level outer frame 121B-1 and the second-level inner frame 121B-2.

[0102] Through the transmission action of the second lead screw assembly 125 and the load transmission block, the height of the second-stage outer frame 121B-1 and the second-stage inner frame 121B-2 in the vertical direction is synchronously raised and lowered.

[0103] Understandably, the third-level constraint frame 121C is provided with clearance holes corresponding to the position of the second lead screw assembly 125, so that the second lead screw assembly 125 can pass through the third-level constraint frame 121C and maintain a radial clearance with it; through this clearance structure, it is ensured that the second lead screw assembly 125 will not mechanically interfere with the third-level constraint frame 121C when driving the second-level constraint frame 121B to rise and fall.

[0104] like Figure 3 As shown, in some examples, the top surface of the worktable 110 is provided with a stepped boss 111 structure. When the worktable 110 is assembled with the boundary constraint device, the lower half of the worktable 110 passes through and fits into the first-level inner frame 121A-2, and the boss 111 structure on its top surface overlaps and is supported on the first inner limiting flange 121A-21, thereby realizing the axial positioning of the worktable 110 within the boundary constraint device; and

[0105] The outer periphery of the boss 111 is closely fitted to the outer wall of the second-level inner frame 121B-2. This multi-level nested fitting design not only enhances the radial stability of the worktable 110, but also effectively prevents powder from leaking into the assembly position through the gap during the forming process.

[0106] Understandably, the worktable 110, boundary constraint device 120, first lead screw assembly 124, and second lead screw assembly 125 are all directly or indirectly fixedly connected to the base 100 through fasteners, which effectively suppresses mechanical vibration caused by high-frequency motion during the printing process, thereby ensuring the stability of the forming process and the dimensional accuracy of the components.

[0107] The second-level constraint box 121B, serving as an intermediate nested layer, is not limited to a single-layer structure. Depending on the actual requirements of the dimensions and powder spreading accuracy of the component to be formed, the intermediate nested layer can be configured as a multi-level nested architecture; for example…

[0108] It should be understood that if the intermediate nesting level needs to be a multi-level nested architecture, taking the aforementioned three-level constraint frame as an example, between the first-level constraint frame 121A and the third-level constraint frame 121C, several sets of intermediate sub-modules with functions and structures equivalent to the second-level constraint frame 121B are sequentially nested radially. Each set of intermediate sub-modules forms a progressive linkage and constraint relationship through the aforementioned limiting flange, guide rail and lead screw assembly. This expandable nested structure enables the device to flexibly adapt to the manufacturing of large components with different spans, significantly improving the process versatility of the equipment.

[0109] Understandably, the material of the boundary constraint device is selected based on the thermo-coupling environment during solid-state additive manufacturing; in some preferred examples, the boundary constraint device is made of high-strength metallic materials, such as steel (e.g., tool steel, stainless steel, or heat-resistant alloy steel).

[0110] How to use boundary constraint devices

[0111] Taking the aforementioned three-level constraint frame as an example, the operating logic of the boundary constraint device in the powder bed solid-state additive manufacturing process is as follows:

[0112] First stage: First, the second lead screw assembly 125 is started. Driven by the second lead screw assembly, the second-level constraint frame 121B rises relative to the base and the worktable 110. At this time, the second-level inner frame 121B-2 first covers and fits the outer periphery of the stepped boss of the worktable 110, thereby building the first macro boundary constraint for the area to be formed, in order to accommodate the powder layer initially laid.

[0113] Second stage: As the number of printing layers increases, when the second-level constraint frame 121B moves upward to its preset upper limit of travel, the first lead screw assembly 124 is activated. The first lead screw assembly 124 drives the third-level constraint frame 121C to continue to extend upward relative to the second-level constraint frame 121B, so as to achieve dynamic compensation for the higher-level forming space.

[0114] In each powder-laying cycle, precise stepping control of the first lead screw assembly 124 and the second lead screw assembly 125 ensures that the top surface of the constraint frame currently in operation is always flush with the current printing layer (powder bed surface). Because the constraint frames at each level maintain a tight sliding fit with each other and between the inner frame and the worktable, the path of powder leakage to the outer periphery can be effectively blocked when the next layer of powder-laying operation is performed, thereby eliminating powder leakage and ensuring the consistency and density of the single-layer powder-laying thickness.

[0115] Combination Figure 1 As shown, the powder feeding device 200 is used to provide a preset amount of powder material to the forming area;

[0116] In some examples, the powder feeding device 200 can be a commercially available automated powder feeding device, the specific structure of which will not be described in detail.

[0117] The powder spreading device 300 is used to spread the powder provided by the powder feeding device 200 into the forming space defined by the boundary constraint device 120;

[0118] In some examples, the powder spreading device 300 includes a scraper 310, which reciprocates along the horizontal direction (X / Y axis) under the drive of a drive mechanism to form a powder layer of uniform thickness and smooth surface to be formed.

[0119] The printing apparatus 400 includes a powder bed solid-phase additive tool for achieving layered stacking of powder materials through solid-phase bonding technology.

[0120] In some examples, powder bed solid additive manufacturing tools include a stirring friction device, such as a stirring head and a rotary drive spindle.

[0121] During the printing process, the friction stirrer extends into the powder bed under pressure, using the frictional heat generated by the rotation of the stirring head to bring the powder into a plastic state, and in conjunction with the mechanical stirring force, achieves solid bonding between the powder and the formed substrate.

[0122] Powder Bed Solid-State Additive Manufacturing Method Based on Multi-Level Constraint Mechanism

[0123] Combination Figure 9 As shown, using the aforementioned powder bed solid-state additive manufacturing system, the powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism in this invention example includes the following steps:

[0124] S1. Establish boundary constraints around the printing area to limit the spatial height of a single layer of powder and lay the powder. Use boundary constraints to restrict the macroscopic displacement of the powder to the outer periphery of the printing area, forming a first-level macroscopic constraint for the powder bed.

[0125] The first-level macro-constraint constructed by boundary constraints allows for precise control of the powder spreading height of each layer, eliminating the physical angle between the traditional fixed-height mold and the scraper. This enables the powder in the corners to be spread evenly and compactly, which significantly reduces the porosity of the powder bed and enhances the mutual friction between powders. This suppresses the tendency of powder to disperse towards the edge during the printing process from the source, effectively solving the problem of material shortage at the edge of the deposition layer.

[0126] S2. Using a powder bed solid-phase additive manufacturing tool, a frame structure is pre-printed within the printing area to form a secondary boundary constraint on the area to be filled inside the frame structure.

[0127] By constructing a secondary boundary constraint using a pre-printed frame structure, a rigid profile of the component to be formed is established within the powder bed. This frame structure not only limits the maximum spatial range of thermoplastic metal flow but also provides a stable force support for subsequent more refined zoning constraints. This solves the problem of forming instability and dimensional deviations that easily occur in the edge areas of large components when there is a lack of external mold wall support.

[0128] S3. Within the area enclosed by the frame structure, the powder bed solid-phase additive tool is controlled to form along an interlaced path. During the forming process, the formed path segments and adjacent powder units are used to generate mutual support forces on the current forming path, thereby forming a three-level unit constraint for lateral limiting of the interlaced path, and dividing the area to be filled into multiple discrete powder units, which is called a spatial lattice structure.

[0129] S4. Using the formed path segment as a lateral rigid mold wall, a four-level filling constraint is formed for the thermoplastic flow of powder units. Solid-phase additive filling is performed on each powder unit, so that the frame structure, intersecting paths and each powder unit are fused together under the synergistic effect of multi-level constraints to complete single-layer thermoplastic forming.

[0130] The three-level unit constraint and four-level filling constraint constructed by the spatial lattice path divide the large-area printing area into several restricted independent blocks. The formed lattice skeleton, as a dynamic mold wall, not only provides sufficient lateral support pressure for subsequent powder filling, ensuring uniform powder distribution and full plasticization under the shoulder, but also physically blocks the plasticization overflow of the material forward by moving the forward side of the stirring tool toward the skeleton boundary, significantly suppressing flash defects.

[0131] S5. Repeat steps S1 to S4 until the component is formed.

[0132] By utilizing the time difference and path direction differences between the frame structure, staggered paths, and solid filling, a progressive heterogeneous structure with significant grain phase differences is formed inside the component. This microstructure inhomogeneity means that when cracks propagate to the interfaces of different functional layers, they must overcome greater phase shift resistance. Macroscopically, this manifests as a significant increase in crack tortuosity, effectively hindering crack propagation and thus greatly improving the static strength and fatigue life of large structural components.

[0133] In some embodiments, in step S1, the boundary constraint is provided by a multi-level lifting constraint frame, and the spatial height of the single-layer powder spreading is limited by adjusting the height of the constraint frame so that the vertical distance between the top surface of the constraint frame and the current surface to be formed is equal to the preset single-layer printing thickness.

[0134] In some embodiments, in step S2, the frame structure is a closed lattice skeleton generated according to the outline of the printed component.

[0135] In some embodiments, in step S3, the intersecting paths are mutually orthogonal grid-like paths, which divide the internal powder into square or rectangular block units.

[0136] In some embodiments, in the staggered paths, the spacing between two adjacent paths is 1.6 to 1.8 times the diameter of the working end face of the powder bed solid additive manufacturing tool.

[0137] In some embodiments, in step S4, when solid-phase additive filling of the powder unit, the forward side of the powder bed solid-phase additive tool is controlled to move toward the formed path segment, using the formed path segment to prevent the overflow of thermoplastic fluid, thereby suppressing flash generation and guiding the fluid to fill the tool shoulder gap.

[0138] Understandable, such as Figure 10 As shown, the forward side of the powder bed solid-phase additive manufacturing tool refers to the side where the rotation direction of the friction stir tool is in the same direction as the travel direction, and the backward side refers to the side where the rotation direction of the friction stir tool is in the opposite direction to the travel direction.

[0139] In some embodiments, during step S4, when the powder unit is filled and shaped by the powder bed solid additive tool, the thermoplastic shearing action generated by rotational friction causes the edge of the powder unit to undergo interfacial remelting and microstructure penetration with the adjacent frame structure or intersecting path, forming a metallurgical bond.

[0140] In some embodiments, in step S1, the powder is spread evenly using a powder spreading device, and the working end face of the scraper of the powder spreading device is brought close to the top surface of the boundary constraint to slide across, thereby reducing the powder gap through the scraping action and making the powder in close contact with the inner wall surface of the boundary constraint.

[0141] In some embodiments, before the powder is laid in step S1, a substrate preheating step is also included: controlling the powder bed solid additive tool to perform no-load reciprocating friction on the substrate surface, using frictional heat to bring the substrate to a preset temperature suitable for powder bonding, and increasing the roughness of the substrate surface.

[0142] Below, in conjunction with Figures 1-13 As shown, taking the printing of a T-shaped part as an example, we adopt a powder bed solid-state additive manufacturing system and a three-level constraint frame. The stirring friction device of the powder bed solid-state additive manufacturing tool is specifically a stirring head. The powder bed solid-state additive manufacturing method based on the multi-level constraint mechanism specifically includes the following steps:

[0143] Step 1: Initial positioning and benchmark location of the boundary constraint device

[0144] The control system drives the first lead screw assembly 124 and the second lead screw assembly 125 to place the second-level constraint frame 121B and the third-level constraint frame 121C in the initial retracted position (i.e., retracted inside the first-level constraint frame 121A).

[0145] The lower half of the workbench 110 is fitted into the first-level inner frame 121A-2, and the stepped boss on its top surface abuts against the first inner limiting flange 121A-21, thus completing the axial positioning of the starting plane.

[0146] Step Two: Primary Macroeconomic Constraints

[0147] A substrate of the same size as the worktable is fixed on the worktable. The second lead screw assembly 125 is driven to make the second-level constraint frame 121B rise upward. The second-level inner frame 121B-2 is attached to the outer periphery of the boss of the worktable 110, and also to the outer periphery of the substrate, forming a first forming space with a preset depth above it.

[0148] The powder feeding device 200 supplies powder, and the scraper 310 of the powder spreading device 300 moves laterally to spread the powder evenly on the substrate, ensuring that the surface of the powder layer is flush with the top surface of the second-level inner frame 121B-2. The rigid sidewalls of the second-level inner frame 121B-2 provide a first-level macroscopic constraint on the powder bed as a whole.

[0149] Step 3: Second-level boundary constraints

[0150] The stirring head of the printing device 400 moves downward and performs preliminary printing along the geometric outer contour path of the component to be printed. The frictional heat generated by the high-speed rotation of the stirring head plasticizes the powder and fuses it with the solid phase of the substrate, thus constructing a closed frame structure in situ inside the powder bed. Figure 11 As shown in A), this framework structure serves as a secondary boundary constraint, achieving initial envelopment and stabilization of the powder in the core area to be formed.

[0151] Step 4: Third-level element constraints

[0152] Within the area enclosed by the frame structure, the stirring head is controlled to print intermittently along mutually orthogonal longitudinal and transverse paths, that is, multiple lines are printed in a single pass according to a preset transverse interval (e.g., Figure 12 As shown in B), then print multiple lines in a single pass according to the preset vertical interval (e.g., Figure 12 As shown in C), the printed area is divided into several independent powder-to-fill blocks by the formed path segment. Figure 12 The marker O in the diagram uses the pre-formed path segments and powder blocks to form a three-level element constraint for the lateral support force generated in the area to be printed.

[0153] Step 5: Utilizing the pre-formed path segment as a lateral rigid mold wall, a four-level filling constraint is created for the thermoplastic flow of the powder blocks. The stirring head then performs solid-phase additive filling on each powder unit (e.g., Figure 13 As shown in the figure, the lattice framework, intersecting paths and powder blocks undergo plastic flow and are completely fused into a whole under the synergistic effect of multi-level constraints, thus completing the single-layer full densification forming.

[0154] Step Six: After each layer of printing is completed, the second lead screw assembly 125 drives the second-level constraint frame 121B to step up one layer thickness, and the scraper 310 spreads powder again. Steps Three to Five are repeated until the second-level constraint frame 121B moves to its upper limit of travel.

[0155] Step 7: When the second-level constraint frame reaches its travel limit, start the first lead screw assembly 124 to drive the third-level constraint frame 121C to rise relative to the second-level constraint frame 121B. Continue to repeat steps 2 to 5, and repeat until the solid-state additive manufacturing of the entire T-shaped part is completed.

[0156] In another example of the present invention, a large aluminum alloy component prepared by the aforementioned powder bed solid-phase additive manufacturing method based on a multi-level constraint mechanism is also provided.

[0157] This invention ingeniously combines a solid skeleton with flexible powder for mutual constraint. Through a multi-level progressive constraint mechanism, it breaks away from the dependence of traditional processes on large, rigid molds. This combination of an adjustable frame and spatial lattice design overcomes the technical challenges of poor thermoplastic stability and uneven distribution of mechanical properties in the printing of large components, providing a reliable solution for the high-performance and high-precision manufacturing of large and complex components made of lightweight alloys such as aluminum alloys.

[0158] To facilitate better understanding, the present invention will be further illustrated below with several specific examples, but the preparation process is not limited to these examples, and the content of the present invention is not limited to these examples.

[0159] Unless otherwise specified, the following embodiments are all conventional methods.

[0160] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0161] Equipment specifications:

[0162] Worktable: The lower part of the worktable measures 500 mm × 500 mm × 300 mm (length × width × height), and the boss of the worktable measures 550 mm × 550 mm × 50 mm (length × width × height).

[0163] Boundary constraint device: The inner cavity dimensions of the first-level inner frame 121A-2 are 500 mm × 500 mm × 300 mm (length × width × height), and the inner cavity dimensions of the first-level outer frame 121A-1 are 700 mm × 700 mm × 300 mm (length × width × height); the wall thickness of each constraint frame is 30 mm.

[0164] The inner cavity dimensions of the second-level inner frame 121B-2 are 550 mm × 550 mm × 300 mm (length × width × height), and the inner cavity dimensions of the second-level outer frame 121B-1 are 650 mm × 650 mm × 300 mm (length × width × height); the wall thickness of each constraint frame is 30 mm.

[0165] The inner dimensions of the third-level constraint frame 121C are 600 mm × 600 mm × 300 mm (length × width × height); the wall thickness of the constraint frame is 80 mm, and it is designed for hollow assembly.

[0166] The length of each limiting flange is 20 mm.

[0167] Before printing begins, the control system drives the first lead screw assembly 124 and the second lead screw assembly 125 to place the second-level constraint frame 121B and the third-level constraint frame 121C in the initial retracted position (i.e., retracted inside the first-level constraint frame 121A); and determines that the lower half of the worktable 110 is fitted into the first-level inner frame 121A-2, with the stepped boss on its top surface abutting against the first inner limiting flange 121A-21, thus completing the axial positioning of the starting plane.

[0168] The powder bed solid additive manufacturing tool is specifically a stirring head with a shoulder diameter of 30 mm.

[0169] The printed component is a T-shaped component, with structural dimensions as follows: Figure 14 As shown.

[0170] Example 1

[0171] Raw materials: 6061 aluminum alloy substrate with dimensions of 550 mm × 550 mm and a thickness of 20 mm, and powder particle size of 43 μm ± 18 μm.

[0172] (1) Polish the substrate and remove the surface oil stains with alcohol to avoid affecting the additive manufacturing process. Fix the substrate on the worktable, drive the second lead screw assembly 125 to raise the second-level constraint frame 121B by 20 mm, fix the substrate through the constraint frame, turn on the motor, put the working end face of the stirring head close to the substrate, set the process parameters, the stirring head rotation speed is 300 rpm, the travel speed is 50 mm / min, and the empty knife travels back and forth on the substrate 3 times to preheat the substrate.

[0173] (2) Continue to drive the second lead screw assembly 125 to raise the second-level constraint frame 121B by 1 mm, forming a first forming space with a preset depth above the substrate;

[0174] The powder feeding device 200 supplies powder, and the scraper 310 of the powder spreading device 300 moves laterally to spread the powder evenly on the substrate, ensuring that the surface of the powder layer is flush with the top surface of the second-level inner frame 121B-2.

[0175] (3) Adjust the working end face of the stirring head to a position 1 mm away from the substrate, set the process parameters, the stirring head rotation speed is 900 rpm, the travel speed is 36 mm / min, the layer height is 1 mm, the stirring head first prints along the geometric outer contour path of the T-shaped structure, and builds a closed frame structure in situ inside the powder bed.

[0176] Then, print single passes every 50 mm horizontally, and then print single passes every 50 mm vertically to form a spatial lattice structure. Each powder region in the spatial lattice structure is called a block.

[0177] Finally, move the stirring head to the block position, with the forward side (upper end) of the stirring head close to the forming path segment, and print each block separately.

[0178] (4) Repeat steps (2) and (3) in sequence. During this process, if the second-level constraint box 121B moves to its upper limit of travel, the first lead screw assembly 124 is started to drive the third-level constraint box 121C until the last layer is printed to obtain the required component.

[0179] Example 2

[0180] Raw materials: 7075 aluminum alloy substrate with dimensions of 550 mm × 550 mm and a thickness of 20 mm, and powder particle size of 43 μm ± 18 μm.

[0181] (1) Polish the substrate and remove the surface oil stains with alcohol to avoid affecting the additive manufacturing process. Fix the substrate on the worktable, drive the second lead screw assembly 125 to raise the second-level constraint frame 121B by 20 mm, fix the substrate through the constraint frame, turn on the motor, put the working end face of the stirring head close to the substrate, set the process parameters, the stirring head rotation speed is 200 rpm, the travel speed is 100 mm / min, and the empty knife travels back and forth on the substrate 3 times to preheat the substrate.

[0182] (2) Continue to drive the second lead screw assembly 125 to raise the second-level constraint frame 121B by 1 mm, forming a first forming space with a preset depth above the substrate;

[0183] The powder feeding device 200 supplies powder, and the scraper 310 of the powder spreading device 300 moves laterally to spread the powder evenly on the substrate, ensuring that the surface of the powder layer is flush with the top surface of the second-level inner frame 121B-2.

[0184] (3) Adjust the working end face of the stirring head to a position 1 mm away from the substrate, set the process parameters, the stirring head rotation speed is 300 rpm, the travel speed is 40 mm / min, the layer height is 1 mm, the stirring head first prints along the geometric outer contour path of the T-shaped structure, and builds a closed frame structure in situ inside the powder bed;

[0185] Then, print single passes every 50 mm horizontally, and then print single passes every 50 mm vertically to form a spatial lattice structure. Each powder region in the spatial lattice structure is called a block.

[0186] Finally, move the stirring head to the block position, with the forward side (upper end) of the stirring head close to the forming path segment, and print each block separately.

[0187] (4) Repeat steps (2) and (3) in sequence. During this process, if the second-level constraint box 121B moves to its upper limit of travel, the first lead screw assembly 124 is started to drive the third-level constraint box 121C until the last layer is printed to obtain the required component.

[0188] Mechanical property testing

[0189] Tensile tests, hardness tests, and microstructure observations were performed on the samples of Examples 1 and 2 (the sample of Comparative Example 1 was a 6061 aluminum alloy component obtained by water quenching after rolling a billet from an ingot provided by Nanjing Zhongke Yucheng Laser Technology Co., Ltd., and holding it at 520℃ for 50 min; the sample of Comparative Example 2 was a 7075 aluminum alloy component obtained by water quenching after rolling a billet from an ingot provided by Nanjing Zhongke Yucheng Laser Technology Co., Ltd., and holding it at 470℃ for 60 min; the component dimensions were the same as those of the Examples). The results are shown in the table below.

[0190] sample Hardness (HV) Tensile strength (MPa) Yield strength (MPa) Example 1 49 167 83 Example 2 73 343 137 Comparative Example 1 60 184 92 Comparative Example 2 82 362 151

[0191] Based on the test results above, it can be seen that the aluminum alloy components prepared using the method of the present invention have virtually no flash or overflow at the edge of the forming zone. This proves that the multi-level constraint mechanism effectively suppresses material overflow during the stirring friction process, significantly improves the near-net-shape forming accuracy of the components, and greatly reduces the allowance for subsequent subtractive processing.

[0192] Meanwhile, the test results show that the microhardness, tensile strength and yield strength of the aluminum alloy components prepared by the method of the present invention are very close to the level of the same material after solution treatment. The excellent strength index indicates that under the high pressure environment generated by multi-level constraints, the powder particles have undergone sufficient thermoplastic flow, realizing high-quality solid metallurgical bonding, and the formed structure is dense. No traditional welding defects such as pores, lack of fusion or inclusions were found inside.

[0193] Furthermore, since the paths of the spatial lattice structure are non-parallel in space, there are significant differences in the grain orientation between adjacent deposition layers, which can be used to improve the overall mechanical properties of the component by utilizing the crack propagation mechanism.

[0194] Therefore, this invention, through the synergistic cooperation of solid constraint frames and in-situ process constraints, not only solves the problems of overflow and powder leakage in solid-state additive manufacturing and achieves near-net-shape forming without flash; but also improves the proportion of large-angle grain boundaries through staggered path planning and significantly enhances the comprehensive mechanical properties of components by utilizing crack propagation mechanisms; experiments have shown that the components prepared by this method have achieved technical indicators comparable to heat-treated forgings and have extremely high industrial application value.

[0195] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A powder bed solid-phase additive manufacturing method based on a multi-level constraint mechanism, characterized in that, Includes the following steps: S1. Establish boundary constraints around the printing area to limit the spatial height of a single layer of powder and lay the powder. Use the boundary constraints to restrict the macroscopic displacement of the powder to the outer periphery of the printing area, forming a first-level macroscopic constraint for the powder bed. S2. Using a powder bed solid-phase additive manufacturing tool, a frame structure is pre-printed within the printing area, and the frame structure forms a secondary boundary constraint on the area to be filled inside it. S3. Within the area enclosed by the frame structure, the powder bed solid-phase additive tool is controlled to form along an interlaced path; wherein, during the forming process, the formed path segments and adjacent powder units are used to generate mutual support forces on the current forming path, thereby forming a three-level unit constraint for lateral limiting of the interlaced path, and dividing the area to be filled into multiple discrete powder units. S4. Using the formed path segment as a lateral rigid mold wall, a four-level filling constraint is formed for the thermoplastic flow of powder units. Solid-phase additive filling is performed on each powder unit, so that the frame structure, intersecting paths and each powder unit are fused together under the synergistic effect of multi-level constraints to complete single-layer thermoplastic forming. S5. Repeat steps S1 to S4 until the component is formed.

2. The powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism according to claim 1, characterized in that, In step S1, the boundary constraint is provided by a multi-level lifting constraint frame. The spatial height of the single-layer powder spreading is limited by adjusting the height of the constraint frame so that the vertical distance between the top surface of the constraint frame and the current surface to be formed is equal to the preset single-layer printing thickness.

3. The powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism according to claim 1, characterized in that, In step S2, the frame structure is a closed dot matrix skeleton generated according to the outline of the printed component.

4. The powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism according to claim 1, characterized in that, In step S3, the intersecting paths are mutually orthogonal grid-like paths, which divide the internal powder into square or rectangular block units.

5. The powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism according to claim 1 or 4, characterized in that, In the staggered paths, the spacing between two adjacent paths is 1.6 to 1.8 times the diameter of the working end face of the powder bed solid-phase additive manufacturing tool.

6. The powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism according to claim 1, characterized in that, In step S4, when the powder unit is being filled with solid additive manufacturing, the forward side of the powder bed solid additive manufacturing tool is controlled to move toward the formed path segment. The formed path segment is used to prevent the overflow of thermoplastic fluid, thereby suppressing the generation of flash and guiding the fluid to fill the tool shoulder gap.

7. The powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism according to claim 1, characterized in that, In step S4, when the powder unit is filled and shaped by the powder bed solid additive tool, the thermoplastic shearing action generated by the rotational friction causes the edge of the powder unit to undergo interfacial remelting and microstructure penetration with the adjacent frame structure or intersecting path, forming a metallurgical bond.

8. The powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism according to claim 1, characterized in that, In step S1, the powder is spread evenly using a powder spreading device, and the working end face of the scraper of the powder spreading device is brought close to the top surface of the boundary constraint and scraped across it. The powder gap is reduced by the scraping action, and the powder is brought into close contact with the inner wall surface of the boundary constraint.

9. The powder bed solid-state additive manufacturing method based on a multi-level constraint mechanism according to claim 1, characterized in that, Before the powder is laid in step S1, a substrate preheating step is also included: the powder bed solid additive tool is controlled to perform no-load reciprocating friction on the substrate surface, and the friction heat is used to make the substrate reach the preset temperature suitable for powder bonding and increase the roughness of the substrate surface.

10. A powder bed solid-phase additive manufacturing system with boundary constraints, characterized in that, include: A base (100) is provided on which a workbench (110) is provided, and a boundary constraint device (120) is provided on the outer periphery of the workbench (110). The boundary constraint device (120) includes a multi-level constraint frame (121). Each level of constraint frame (121) is an axially penetrating hollow frame and is nested with each other. The multi-level constraint frames (121) together enclose and form a shaped cavity located above the worktable (110). A powder feeding device (200) is disposed above the worktable (110) and is used to provide a preset amount of powder material to the forming area; A powder spreading device (300) is disposed above the forming cavity and is used to spread the powder provided by the powder feeding device (200) into the forming cavity to form a powder bed; as well as The printing apparatus (400) includes a powder bed solid-phase additive manufacturing tool that can extend into the forming cavity, the powder bed solid-phase additive manufacturing tool being used to perform solid-phase processing on the powder bed to achieve material layer stacking.

11. The powder bed solid-state additive manufacturing system with boundary constraints according to claim 10, characterized in that, The constraint frame (121) includes a reference constraint level, an intermediate nested level and an end constraint level. The intermediate nested level and the end constraint level can be independently adjusted in a direction perpendicular to the surface of the worktable (110).

12. The powder bed solid-state additive manufacturing system with boundary constraints according to claim 11, characterized in that, The reference constraint hierarchy includes a first-level constraint frame (121A), which includes a first-level outer frame (121A-1) and a first-level inner frame (121A-2) disposed inside it. A first annular assembly gap is formed between the first-level outer frame (121A-1) and the first-level inner frame (121A-2). The intermediate nested level includes a second-level constraint frame (121B), which includes a second-level outer frame (121B-1) and a second-level inner frame (121B-2) disposed inside it. A second annular assembly gap is formed between the second-level outer frame (121B-1) and the second-level inner frame (121B-2), and the second-level constraint frame (121B) is fitted inside the first annular assembly gap. The end constraint level includes a third-level constraint frame (121C), which is fitted within the second annular assembly gap.

13. The powder bed solid-state additive manufacturing system with boundary constraints according to claim 12, characterized in that, Interlocking limiting flange structures are provided between the first-level constraint frame (121A), the second-level constraint frame (121B), and the third-level constraint frame (121C); The top inner sides of the first-level outer frame (121A-1) and the first-level inner frame (121A-2) are respectively provided with a first outer limiting flange (121A-11) and a first inner limiting flange (121A-21) that extend relative to each other. The bottom outer sides of the second-level outer frame (121B-1) and the second-level inner frame (121B-2) are respectively provided with a second outer limiting lower flange (121B-11) and a second inner limiting lower flange (121B-21) extending in opposite directions. The second outer limiting lower flange (121B-11) is located below the first outer limiting flange (121A-11), and the second inner limiting lower flange (121B-21) is located below the first inner limiting flange (121A-21). The top inner sides of the second-level outer frame (121B-1) and the second-level inner frame (121B-2) are respectively provided with a second outer limiting upper flange (121B-12) and a second inner limiting upper flange (121B-22) that extend relative to each other. The bottom outer side of the third-level constraint frame (121C) is provided with a third outer limiting flange (121C-1) and a third inner limiting flange (121C-2) extending in opposite directions. Furthermore, the third outer limiting flange (121C-1) and the third inner limiting flange (121C-2) are both located below the corresponding second outer limiting upper flange (121B-12) and second inner limiting upper flange (121B-22).

14. The powder bed solid-state additive manufacturing system with boundary constraints according to claim 13, characterized in that, The outer wall of the second-level outer frame (121B-1) and the inner wall of the first-level outer frame (121A-1) are slidably fitted together by a linear guide component. The inner wall of the second-level inner frame (121B-2) and the outer wall of the first-level inner frame (121A-2) are slidably fitted together by a linear guide component. The outer wall of the third-level constraint frame (121C) and the inner wall of the second-level outer frame (121B-1) are slidably fitted together by a linear guide component. The inner wall of the third-level constraint frame (121C) and the outer wall of the second-level inner frame (121B-2) are slidably fitted together by a linear guide component.

15. The powder bed solid-state additive manufacturing system with boundary constraints according to claim 14, characterized in that, The linear guide assembly includes a guide rail (122) disposed vertically on the side wall of the constraint frame, and a slider (123) disposed on the corresponding limiting flange and slidingly matched with the guide rail (122).

16. The powder bed solid-state additive manufacturing system with boundary constraints according to claim 12, characterized in that, The constraint frame (121) also includes a linear drive component for driving the movement of the constraint frame, the linear drive component including a first lead screw component (124) and a second lead screw component (125). The first lead screw assembly (124) is symmetrically arranged at the top corner of the third-level constraint frame (121C) and is used to directly drive the third-level constraint frame (121C) to rise and fall. At least two sets of second lead screw assemblies (125) are symmetrically arranged in the second annular assembly gap. The second lead screw assembly (125) is connected to the second-level constraint frame (121B) through a load transfer block to drive the second-level constraint frame (121B) to rise and fall. The third-level constraint frame (121C) is provided with a clearance hole for the second lead screw assembly (125) to pass through.

17. The powder bed solid-state additive manufacturing system with boundary constraints according to claim 13, characterized in that, The top surface of the workbench (110) is provided with a stepped boss (111). The workbench (110) passes through the first-level inner frame (121A-2), and the boss (111) overlaps the flange at the top of the first-level inner frame (121A-2). The outer periphery of the boss (111) is in contact with the inner wall of the second-level inner frame (121B-2).

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