Gradient porous structure with excellent mechanical property and functionality and LPBF self-adaptive input manufacturing method thereof

Abstract

The invention relates to a porous structure manufactured through laser powder bed melting additive manufacturing, in particular to a gradient porous structure with excellent mechanical property and functionality and an LPBF self-adaptive input manufacturing method of the gradient porous structure. According to the method, basic geometric parameters and gradient characteristics of the gradient porous structure are defined by utilizing Grasshopper parameterization design software. A gradient porous structure with excellent mechanical properties and functionality is generated through a grasshopper plug-in of software, and smooth transition from a solid state to a porous state is achieved. An LPBF technology is adopted and combined with an angle partitioning strategy, the gradient porous structure is melted layer by layer, the gradient porous structure is partitioned according to the strut suspension angle on the basis of optimizing process parameters, the optimized process parameters are applied to a model of the partitioned region, and the gradient porous structure is obtained. Scanning of each layer of the overhanging supporting columns at different angles is in appropriate laser parameter input, and the problems of deformation and high porosity caused by heat accumulation in the LPBF process are effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of laser powder bed fusion additive manufacturing, and in particular to a gradient porous structure having excellent mechanical properties and functionality and a LPBF adaptive input manufacturing method thereof. Background Art

[0002] Porous structures are widely used in precision parts, aerospace, and medical implants due to their lightweight, good thermal insulation, high wave absorption and shock absorption, and good bone integration. However, with the increase of porosity, the mechanical properties of porous structures will decrease, especially when the structural design is unreasonable, it will cause greater stress concentration, leading to premature fracture failure. In order to solve this problem, macroscopic gradient changes of porous structures are designed and introduced into the preparation, in which the meaning of gradient involves changes in pore shape, porosity, and size. Gradient structures usually have mechanical deformation behaviors different from uniform structures and can meet the functional requirements of porous structures in different application scenarios.

[0003] The high-precision preparation of gradient porous structures can be achieved through the Laser Powder Bed Fusion (LPBF) 3D printing method, but the preparation of fine porous structures is still a problem in 3D printing. During the rapid melting and cooling process, complex porous structures will produce large thermal stresses. The rapid change of the cross-section of the connecting nodes during the manufacturing process will cause the molten pool to be unstable, resulting in spattering during the melting process, and then generating pores with a large amount of pores. When the pillars of the porous structure are suspended, the step effect causes the heat flow direction to change, the thermal stress distribution is uneven, and warping and deformation, increased powder sticking, often lead to poor forming quality. Solutions to the above problems are urgently needed.

[0004] At present, the methods for solving angle overhang structures mainly focus on the optimization of laser parameters and scanning strategies. Patent CN114565745A adaptively allocates laser power, scanning speed and scanning path through the scanning path area planning method of the overhang feature. This optimized process parameter allocation helps to improve the overall quality and performance of the parts. However, the problem of whether the overhang range is too large depends on the setting of the critical value θ, which is not conducive to the use of the same parameter. The laser power and scanning speed used in patent CN109513050 B are selected by the process according to the porosity of each layer. This adjustment is to control the energy input and cooling rate during the melting process, so as to accurately control the pore structure and material properties of each layer. Patent CN117620179A optimizes the process parameters, which can significantly reduce the thermal conductivity of metal porous insulation parts, improve their air permeability and thermal insulation performance, and maintain the strength of the structure. However, the optimization of process parameters applied to the entire porous structure or a porous structure of a certain height will still cause serious powder sticking problems for some pillars with too low overhang angles. In addition, there are many pores and severe powder adhesion at the nodes of the porous structure. Summary of the invention

[0005] The purpose of the present invention is to avoid the shortcomings of the prior art and provide an LPBF adaptive input manufacturing method for a gradient porous structure with excellent mechanical properties and functionality. The LPBF forming method of the gradient porous structure adopts a parametric design method to obtain a gradient porous structure with excellent mechanical properties and functionality, and then the gradient porous structure with excellent mechanical properties and functionality is prepared by LPBF additive manufacturing technology. The obtained gradient porous structure with excellent mechanical properties and functionality can better simulate the mechanical properties of natural bones and provide excellent biomechanical adaptability.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] Provided is a method for manufacturing an LPBF adaptive input of a gradient porous structure having excellent mechanical properties and functionality, comprising the following steps:

[0008] Step 1, parametric digital design: parametric modeling is performed using the Grasshopper plug-in provided by the Rhino software. The component library function of Grasshopper is used to define a radial gradient distribution algorithm to construct an initial Voronoi gradient porous structure. The gradient porous structure is composed of a plurality of pillars to obtain a gradient porous structure model. The radius of the gradient porous structure is 5 mm, the length is 10 mm, and the thickness of each pillar is 0.2 mm.

[0009] Step 2, model angle region division: the obtained Voronoi gradient porous structure is divided according to the angle of the pillar, with the Z direction perpendicular to the center of the cylinder as the central axis and the XY plane as the bottom surface. The obtained gradient porous structure model is divided into pillars of different angles. Starting from the bottom surface, the angles between the center of different pillars and the bottom surface are different. The obtained gradient porous structure model is divided into six regional models of 0-15°, 15-30°, 30-45°, 45-60°, 60-75°, and 75-90°;

[0010] Step 3: Model repair and support addition: Import the obtained six area models into the magic software for triangular patch repair, and add bottom surface support to the bottom area model to meet the requirements of LPBF technology;

[0011] Step 4: Slicing: Use professional slicing software to slice the 3D model of the required formed parts;

[0012] Step 5: Parametric design of gradient porous structure

[0013] Formed rod design: Use the Grasshopper plug-in to set the rod diameter range for each area, and set hanging rods at different angles within the rod diameter range;

[0014] Parameter verification: Through full-factor experimental iterative optimization, the optimal forming range of overhanging rods at different angles is determined;

[0015] Step 6: Application of different angle hanging rod forming parameters to gradient porous structure

[0016] Forming of each regional model of the gradient porous structure: Select the laser parameters within the optimal forming range after optimizing the overhanging rods at different angles and apply them to different regional models of the entire gradient porous structure model to ensure that the forming parameters of the six regional models meet the design requirements;

[0017] Step 7: LPBF technology preparation

[0018] Model import: Import the partition model obtained in step 3 into the LPBF machine;

[0019] Parameter application: Select the laser parameters of the different regional models obtained in step 6 and input them into the LPBF machine for printing to obtain a gradient porous structure.

[0020] In some embodiments, in the design of the formed rod, an arched base is first simulated, and six areas are divided on the arched base according to the curvature, each area corresponds to a rod diameter inclination range in an area, and the rod diameter inclination with the best performance is selected in each area.

[0021] In some embodiments, the arcuate base is in a quarter ring configuration.

[0022] In some embodiments, after step seven, the gradient porous structure is post-processed, and the post-processing includes removing the bottom support or ultrasonic cleaning with alcohol.

[0023] In some embodiments, the post-treated gradient porous structure is subjected to performance testing and analysis, including:

[0024] Morphological observation: the obtained finished product is subjected to CT scanning, the data is reconstructed to obtain a solid model, and the solid model is compared with the gradient porous structure model in step 1 to print the size difference;

[0025] Mechanical properties test: The prepared gradient porous structure was subjected to a mechanical properties test.

[0026] In some embodiments, the post-processed gradient porous structure is subjected to forming parameter evaluation and adjustment, including:

[0027] Effectiveness evaluation: The feasibility of forming parameters is evaluated based on the difference in forming size of the gradient porous structure, the amount of powder adhering to the surface, or the internal defects of the model;

[0028] Process adjustment: The porosity, pore size and rod diameter are adjusted in the design and preparation process to obtain a gradient porous structure with excellent mechanical properties and functionality.

[0029] Also provided is a gradient porous structure having both excellent mechanical properties and functionality, which is obtained by the above-mentioned manufacturing method.

[0030] The beneficial effects of the LPBF adaptive input manufacturing method of the gradient porous structure with excellent mechanical properties and functionality of the present invention are as follows:

[0031] (1) The present invention provides an LPBF adaptive input manufacturing method for a gradient porous structure having both excellent mechanical properties and functionality. The method enhances the structural stability and durability of the gradient porous structure by precisely controlling the structural parameters of the forming rod and adopting the partition forming technology, which is conducive to long-term stable use.

[0032] (2) The present invention discloses an LPBF adaptive input manufacturing method for a gradient porous structure having both excellent mechanical properties and functionality. The method utilizes LPBF printing technology to achieve high-precision manufacturing of complex geometric structures, while improving production efficiency, effectively eliminating material waste, and reducing costs. Furthermore, the method can avoid using inappropriate energy density in different overhanging areas under a single laser parameter, and utilize the structural characteristics of angle partitioning to adaptively allocate appropriate laser process parameters, thereby avoiding local heat accumulation and thermal deformation, thereby ensuring the forming quality of the overhanging structure of the part, and effectively solving the problems of deformation and large number of pores caused by heat accumulation during the LPBF process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a gradient porous structure in a specific embodiment.

[0034] Figure 2 It is the angular area division of the gradient porous structure in a specific implementation manner.

[0035] Figure 3 It is the size data of a single-pass molten pool in a specific implementation manner.

[0036] Figure 4 Detailed description of the invention The figures are formed rod models at different angles in a specific implementation manner.

[0037] Figure 5 It is the range of processing parameters for different overhang angle areas in a specific implementation manner.

[0038] Figure 6 is a histogram of the internal pore size distribution in a specific embodiment. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0040] The terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The singular forms of "a", "the" and "the" used in the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0041] It should be understood that although the terms "first", "second", "third", etc. may be used to describe various information in the present invention, such information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of the present invention, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0042] Example

[0043] This embodiment discloses a LPBF adaptive input manufacturing method of a gradient porous structure with excellent mechanical properties and functionality, comprising the following steps:

[0044] Step 1. Parametric digital design: The morphology of the Voronoi structure is similar to the porous structure of natural bones and can be used to form irregular pore-shaped scaffolds with different porosities. Compared with uniform porous structures and irregular porous structures, the gradient porous structure is a porous structure with a spatial variation mechanism. It can adjust the layout of the structure by changing its own load and boundary conditions according to different situations, thereby obtaining better performance. Therefore, this patent designs a Voronoi gradient porous structure with excellent mechanical properties and functionality for use in LPBF technology. First, parametric design is required. The grasshopper plug-in that comes with the Rhino software is used for parametric modeling. The component library function of Grasshopper is used to define the radial gradient distribution algorithm to construct the initial Voronoi gradient porous structure. The radius of the gradient porous structure is 5mm, the length is 10mm, and the thickness of each pillar is 0.2mm. See Figure 1 .

[0045] Step 2: Model angle region division: The obtained Voronoi gradient porous structure is divided according to the angle of the pillar overhang, with the Z direction perpendicular to the center of the cylinder as the central axis and the XY plane as the bottom surface. The obtained model is divided into pillars of different angles. Starting from the bottom surface, the angles between the center of different pillars and the bottom surface are different. The obtained model is divided into six regional models of 0-15°, 15-30°, 30-45°, 45-60°, 60-75°, and 75-90°, see Figure 2 ;

[0046] Step 3: Model repair and support addition: Import the obtained six area models into the magic software for triangular patch repair, and add bottom surface support to the bottom area model to meet the requirements of LPBF technology;

[0047] Step 4: Slicing: Use professional slicing software to slice the 3D model of the required formed parts;

[0048] Step 5: Parameter design: Set the laser scanning planning path information file for each area model, including laser power, scanning speed, scanning spacing, etc., and import it into the machine after success;

[0049] Specific parameter selection for partitioning: Starting from a single pass, the single pass forming process window under different parameter combinations is studied to obtain the single pass molten pool width and depth (see Figure 3), select laser parameters within different angle ranges according to the depth of the single-pass molten pool. The molten depth cannot be too large, otherwise the molten pool will easily sink under low-angle forming. Under high angles, a better combination of outer contour parameters can be selected to achieve the edge-drawing effect. A certain combination of laser parameters (see Table 1, where the scanning spacing is 0.7 times the molten width commonly used in the literature) is applied to the printing of the forming rod (see Figure 4 ) to obtain the processing parameter range for different overhang angle areas (see Figure 5 ), and then select the appropriate laser parameter combination from each angle range to apply to the six angle division areas to form a gradient porous structure with relatively good quality. The outer contour uniformly selects a better laser parameter combination of 30W-200mm / s.

[0050]

[0051] The embodiment selected

[0052] #1: 0-15°, 60W-1000mm / s-49μm; 15-30°, 60W-1200mm / s-43μm; 30-45°, 60W-800mm / s-51μm ; 45-60°, 90W-1000mm / s-56μm; 60-75°, 90W-1200mm / s-52μm; 75-90°, 90W-800mm / s-60μm.

[0053] #2: 0-15°, 60W-800mm / s-51μm; 15-30°, 60W-800mm / s-51μm; 30-45°, 60W-800mm / s-51μm ; 45-60°, 60W-800mm / s-51μm; 60-75°, 60W-800mm / s-51μm; 75-90°, 60W-800mm / s-51μm.

[0054] #3: 0-15°, 90W-800mm / s-60μm; 15-30°, 90W-800mm / s-60μm; 30-45°, 90W-800mm / s-60μm ; 45-60°, 90W-800mm / s-60μm; 60-75°, 90W-800mm / s-60μm; 75-90°, 90W-800mm / s-60μm.

[0055] Step 6. Material loading: Load the selected metal powder onto the printer's workbench, flatten it, and adjust the scraper so that the metal powder can be evenly spread on the forming cylinder to create the first layer of printing;

[0056] Step 7, deoxidation stage: the forming chamber of the SLM equipment is evacuated or filled with inert gases such as nitrogen and argon to form an atmosphere environment for the protective forming process;

[0057] Step 8, Printing process: The working cylinder brings the substrate and parts down to a certain height (about 30 to 50μm), and the powder feeding cylinder rises relatively to a certain distance and the powder spreading roller spreads the metal powder in advance. Then the next forming work cycle is carried out.

[0058] Step 9. Cooling: After printing, the parts need to be cooled.

[0059] Step 10. Post-processing: Some parts may require additional post-processing steps, such as support removal, alcohol ultrasonic cleaning, heat treatment, machining, polishing, etc., to achieve the final appearance and performance requirements; the obtained parts were observed under a surface optical microscope, and it was found that there was not much difference in appearance between the partitioned and non-partitioned forming effects, which further illustrates the process stability of the LPBF technology.

[0060] Step 11: Quality control: Perform quality control tests and perform micro-CT scanning on the obtained parts to ensure that the parts meet the design requirements. Obtain the internal pore size distribution histogram (see Figure 6 ), further illustrating the feasibility of partitioning.

[0061] Depend on Figure 6 It can be seen that the number of internal defects of #1 obtained by partition printing is significantly less than that of the overall printing #2 and #3. It can be seen that partition printing of gradient porous structures can effectively reduce product defects.

[0062] The present embodiment discloses an LPBF adaptive input manufacturing method for a gradient porous structure with excellent mechanical properties and functionality. The method uses Grasshopper parametric design software to define the basic geometric parameters and gradient characteristics of the gradient porous structure, including pore size, porosity and size. The gradient porous structure with excellent mechanical properties and functionality is generated by the grasshopper plug-in provided by the software, achieving a smooth transition from solid to porous. During the preparation process, LPBF technology is used in combination with an angle partitioning strategy to melt the gradient porous structure layer by layer. This partitioning preparation method can partition the gradient porous structure with excellent mechanical properties and functionality according to the pillar overhang angle on the basis of optimizing the process parameters, and apply the optimized process parameters to the model of the divided area, so that each layer of the pillars overhanging at different angles are scanned in a suitable laser parameter input to achieve a gradient porous structure with better forming effect, reduced powder sticking and reduced defects, and effectively solve the deformation and high porosity problems caused by heat accumulation during the LPBF process.

[0063] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0064] In the description of the present application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present application; the directional words "inside and outside" refer to the inside and outside relative to the contours of each component itself.

[0065] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0066] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of this application.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for manufacturing LPBF adaptive input of a gradient porous structure with excellent mechanical properties and functionality, comprising the following steps: Step 1, parametric digital design: parametric modeling is performed using the Grasshopper plug-in provided by the Rhino software. The component library function of Grasshopper is used to define a radial gradient distribution algorithm to construct an initial Voronoi gradient porous structure. The gradient porous structure is composed of a plurality of pillars to obtain a gradient porous structure model. The radius of the gradient porous structure is 5 mm, the length is 10 mm, and the thickness of each pillar is 0.2 mm. Step 2, model angle region division: the obtained Voronoi gradient porous structure is divided according to the angle of the pillar, with the Z direction perpendicular to the center of the cylinder as the central axis and the XY plane as the bottom surface. The obtained gradient porous structure model is divided into pillars of different angles. Starting from the bottom surface, the angles between the center of different pillars and the bottom surface are different. The obtained gradient porous structure model is divided into six regional models of 0-15°, 15-30°, 30-45°, 45-60°, 60-75°, and 75-90°; Step 3: Model repair and support addition: Import the obtained six area models into the magic software for triangular patch repair, and add bottom surface support to the bottom area model to meet the requirements of LPBF technology; Step 4: Slicing: Use professional slicing software to slice the 3D model of the required formed parts; Step 5: Parametric design of gradient porous structure Formed rod design: Use the Grasshopper plug-in to set the rod diameter range for each area, and set hanging rods at different angles within the rod diameter range; Parameter verification: Through full-factor experimental iterative optimization, the optimal forming range of overhanging rods at different angles is determined; Step 6: Application of different angle hanging rod forming parameters to gradient porous structure Forming of each regional model of the gradient porous structure: Select the laser parameters within the optimal forming range after optimizing the overhanging rods at different angles and apply them to different regional models of the entire gradient porous structure model to ensure that the forming parameters of the six regional models meet the design requirements; Step 7: LPBF technology preparation Model import: Import the partition model obtained in step 3 into the LPBF machine; Parameter application: Select the laser parameters of the different regional models obtained in step 6 and input them into the LPBF machine for printing to obtain a gradient porous structure.

2. The LPBF adaptive input manufacturing method of a gradient porous structure with excellent mechanical properties and functionality according to claim 1, characterized in that: In the design of the formed rod, an arch base is first simulated, and six areas are divided on the arch base according to the curvature. Each area corresponds to a rod diameter inclination range in an area, and the rod diameter inclination with the best performance is selected in each area.

3. The LPBF adaptive input manufacturing method of a gradient porous structure with excellent mechanical properties and functionality according to claim 2, characterized in that: The arched base is in a quarter ring configuration.

4. The LPBF adaptive input manufacturing method of a gradient porous structure with excellent mechanical properties and functionality according to claim 1, characterized in that: After step seven, the gradient porous structure is post-processed, and the post-processing includes removing the bottom support or ultrasonic cleaning with alcohol.

5. The LPBF adaptive input manufacturing method of a gradient porous structure with excellent mechanical properties and functionality according to claim 4, characterized in that: The performance of the post-processed gradient porous structure was tested and analyzed. include, Morphological observation: the obtained finished product is subjected to CT scanning, the data is reconstructed to obtain a solid model, and the solid model is compared with the gradient porous structure model in step 1 to print the size difference; Mechanical properties test: The prepared gradient porous structure was subjected to a mechanical properties test.

6. The LPBF adaptive input manufacturing method of a gradient porous structure with excellent mechanical properties and functionality according to claim 5, characterized in that: Evaluation and adjustment of forming parameters for post-processed gradient porous structures, including Effectiveness evaluation: The feasibility of forming parameters is evaluated based on the difference in forming size of the gradient porous structure, the amount of powder adhering to the surface, or the internal defects of the model; Process adjustment: The porosity, pore size and rod diameter are adjusted in the design and preparation process to obtain a gradient porous structure with excellent mechanical properties and functionality.

7. A gradient porous structure with excellent mechanical properties and functionality, characterized in that: It is produced by the production method according to any one of claims 1 to 6.

Images