Automatic model generation method for rib plate structure of SLM forming shape control process

Abstract

The invention discloses an automatic model generation method for an SLM forming shape control process rib plate structure. The automatic model generation method comprises the steps that a datum curve of a rib plate to be generated is marked; parameters of the rib plate are set; based on the reference curve, a rib plate body model is generated in combination with set rib plate parameters; parameters of the separation holes are set; based on the reference curve, a sphere model is generated in combination with set separation hole parameters; according to the rib plate body model and the sphere model, Boolean subtraction is carried out, and a final rib plate model with separation holes is obtained. According to the method, one-button type generation of the rib plate type process structure can be achieved, the modeling duration of the rib plate type process structure is greatly shortened, multiple types of selectable rib plate type process structure generation modes can be provided, flexible selection can be achieved according to product structure characteristics and forming requirements, and parameters are controllable and adjustable; a series of problems of an existing modeling method based on boundary representation in SLM forming process structure design are solved.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing technology, and in particular relates to an automatic model generation method for rib structure in SLM forming control process. Background Technology

[0002] In recent years, metal additive manufacturing technology has developed rapidly and has been widely used in many fields, especially in the aerospace industry where its functional integration and lightweight structure characteristics have become increasingly prominent. However, as the size of additively manufactured parts continues to increase and their structures become more complex, problems such as deformation, warping, or cracking caused by the accumulation of local thermal stress during the printing process are becoming increasingly prominent. To suppress these defects, it is usually necessary to introduce removable process structures to assist in forming during the manufacturing process, ensuring the smooth progress of the forming process.

[0003] Currently, most process structures can be generated with a high degree of automation using commercial software (such as Materialise Magics). However, the automated generation function of such software for ribbed process structure models is limited. Firstly, the generated types are relatively simple and singular, unable to support the generation of complex, multi-type ribs. Secondly, designability is insufficient, with few adjustable parameters, and errors or deviations from expectations are prone to occur during model generation. Therefore, ribbed process structures still require manual design using traditional solid 3D modeling software (such as Creo and UG) based on boundary representation (B-rep). This process consumes a significant amount of time for tasks such as locating baseline curves and repeatedly inputting similar parameters. Furthermore, limitations imposed by existing modeling software algorithms and the complex heterogeneous surfaces of existing topological products easily lead to problems such as the inability to select contour curves for heterogeneous surfaces and the inability to array separation holes along special curves. This results in an exceptionally complex design and modeling process for ribbed process structures, becoming one of the key factors restricting the forming quality and efficiency of large-size, complex structural parts. Therefore, it is urgent to optimize existing modeling methods for process ribs to improve the reliability and economy of additive manufacturing. Summary of the Invention

[0004] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide an automatic model generation method for stiffener structures in SLM forming control process, which aims to solve a series of problems existing in the existing boundary representation (B-rep) based modeling method in SLM forming process structure design.

[0005] To address the aforementioned technical problems, this invention discloses an automatic model generation method for stiffener structures in SLM forming control processes, comprising: Mark the reference curve for the stiffener to be generated; Set the stiffener parameters; Based on the baseline curve and the set stiffener parameters, a stiffener body model is generated. Set the parameters of the separation orifice; Based on the baseline curve and the set separation hole parameters, a sphere model is generated; Based on the rib plate body model and the sphere model, Boolean subtraction is performed to obtain the final rib plate model with separation holes.

[0006] In the above-mentioned automatic model generation method for stiffener structure in SLM forming control process, the reference curve of the stiffener to be generated is marked, including: identifying the contour curve of the product and marking it as the reference curve of the stiffener to be generated; or, creating a curve that fits the product surface on the product surface and marking it as the reference curve of the stiffener to be generated.

[0007] In the above-mentioned automatic model generation method for rib structure in SLM forming control process, the rib parameters are set, including: defining the generation direction or closed curve of the opening area of ​​the rib to be generated according to the type of rib to be generated; and setting the thickness a, secondary reinforcement thickness b, cross rib reinforcement threshold c, and embedding depth d of the rib to be generated.

[0008] In the above-mentioned automatic model generation method for rib structure in SLM forming control process, the types of ribs to be generated include: vertical side conformal ribs, bottom edge support ribs, and window edge support ribs. Among them, vertical side conformal ribs refer to a type of rib that extends outward from the side of the product to support the shape control; bottom edge support ribs refer to a type of rib that grows layer by layer from the substrate and is finally connected to the product for support and forming; window edge support ribs refer to a type of rib that closes the opening model inside the product to prevent it from warping and deforming.

[0009] In the above-mentioned automatic model generation method for stiffener structure in SLM forming control process, the generation direction or closed curve of the opening area of ​​the stiffener to be generated is defined according to the type of stiffener to be generated. This includes: if the stiffener to be generated is a vertical side conformal stiffener or a bottom edge support stiffener, the generation direction of the stiffener to be generated is defined; if the stiffener to be generated is a window edge support stiffener, the closed curve of the opening area is marked.

[0010] In the above-mentioned automatic model generation method for stiffener structures in SLM forming control process, the thickness a, secondary reinforcement thickness b, cross stiffener reinforcement threshold c, and embedding depth d of the stiffener to be generated are set according to the following principles: 0.6mm≤a≤1.0mm, and a≤A 2a≤b≤5a c=H / a 3D≤d≤10D, and d≤A Where A represents the skin thickness, H represents the height of the stiffener to be generated, and D represents the printing layer thickness.

[0011] In the above-mentioned automatic model generation method for rib structure in SLM forming control process, the rib body model is generated based on the reference curve and the set rib parameters. This includes: performing vector calculations based on the spatial coordinates of the differential point of the reference curve, combined with the defined generation direction or the closed curve of the opening area, and the set values ​​of a, b, c, and d, to obtain the coordinates of each endpoint of the rib body's outer frame, and inputting each endpoint coordinate into the model generation software, filling the triangular facets to form the rib body model.

[0012] In the above-mentioned automatic model generation method for rib structure of SLM forming control process, the separation hole parameters are set, including: setting the hole diameter e, hole spacing f, and distance g between the separation hole and the product; wherein, 1mm≤e≤3mm, 2e≤f≤4e, and 0.8e≤g≤1.2e.

[0013] In the above-mentioned automatic model generation method for rib structure in SLM forming control process, a spherical model is generated based on the reference curve and the set separation hole parameters. This includes: calculating the offset of each differential point on the reference curve according to the set values ​​of e, f, and g to obtain the separation hole distribution curve; performing array distribution calculation based on the starting point of the separation hole distribution curve to obtain the position information of the separation hole positions; and filling the array to form a spherical model according to the separation hole distribution curve and the calculated position information of the separation hole positions.

[0014] The above-mentioned automatic model generation method for stiffener structure in SLM forming control process also includes: fine-tuning the position of the two sphere models at the beginning and end according to the actual situation.

[0015] The present invention has the following advantages: (1) This invention discloses an automatic model generation method for ribbed structures in SLM forming control process, which can realize one-click generation of ribbed process structures and greatly reduce the modeling time of ribbed process structures.

[0016] (2) This invention discloses an automatic model generation method for rib structure in SLM forming control process, which can provide multiple selectable rib process structure generation modes, which can be flexibly selected according to product structure characteristics and forming requirements, and the parameters are controllable and adjustable.

[0017] (3) This invention discloses an automatic model generation method for stiffener structure in SLM forming control process. The stiffener generation has high stability and can avoid the problem of separation hole not being effectively generated under B-rep modeling algorithm. Attached Figure Description

[0018] Figure 1 This is a flowchart of an automatic model generation method for stiffener structures in SLM forming control process according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a vertical side conformal stiffener plate in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of a bottom edge support rib plate in an embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a window edge support rib in an embodiment of the present invention; Figure 5 This is a schematic diagram illustrating the automatic generation process of a process stiffener model in an embodiment of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments disclosed in the present invention will be described in further detail below with reference to the accompanying drawings.

[0020] Rib-type process structures consist of a rib body and an array of separation holes. The rib body provides overall support strength, while the separation holes separate the product from the rib body, clearly defining the boundary between the two, weakening the connection strength between the product and the rib body, and facilitating later disassembly. For rib-type process structures, this invention proposes an automatic model generation method for rib structures in SLM forming control processes, which can automatically generate various types of rib models, such as straight-side conformal ribs, bottom edge support ribs, and window edge support ribs.

[0021] Reference Figure 1 In this embodiment, the automatic model generation method for rib structure in SLM forming control process includes: S1 marks the reference curve for the stiffener to be generated.

[0022] In this embodiment, the product's contour curve can be directly used as the reference curve: the product's contour curve is identified and marked as the reference curve for the stiffener to be generated. Alternatively, a curve that fits the product surface can be created and marked as the reference curve for the stiffener to be generated.

[0023] S2 sets the stiffener parameters.

[0024] In this embodiment, the setting of the stiffener parameters mainly includes two aspects: 21) Define the generation direction or closed curve of the opening region of the stiffener to be generated according to the type of stiffener to be generated.

[0025] The types of stiffeners to be generated include, but are not limited to: vertical side conformal stiffeners, bottom edge support stiffeners, and window edge support stiffeners. Among these, vertical side conformal stiffeners refer to stiffeners that extend outwards from the sides of the product to support and control its shape, such as... Figure 2 As shown. Bottom edge support ribs refer to a type of rib that grows layer by layer from the substrate and is ultimately connected to the product to provide support and shape, such as... Figure 3 As shown. Window edge support ribs refer to a type of rib used to close open areas within a product, preventing warping and deformation, such as... Figure 4 As shown.

[0026] If the stiffener to be generated is a vertical side conformal stiffener or a bottom edge support stiffener, then the generation direction of the stiffener to be generated needs to be defined: generally, it is generated along the negative Z-axis (i.e., perpendicular to the substrate); if there are special requirements (such as needing to avoid the lower product body), the generation direction can also be specified by yourself.

[0027] If the rib to be generated is a window edge support rib, then only the closed curve of the opening area needs to be marked, and the growth direction does not need to be specified.

[0028] 22) Set the thickness a, secondary reinforcement thickness b, cross reinforcement threshold c, and embedding depth d of the stiffener to be generated.

[0029] Generally, the thickness 'a' needs to be set by considering the forming material, product characteristics, and removal method. For example, for aluminum alloy products with thin-walled skin dot matrix structures, the stiffeners can be removed manually by fitter. The value of thickness 'a' usually follows the following principle: 0.6mm≤a≤1.0mm, and a≤A, where A represents the skin thickness. That is, the thickness 'a' can be taken in the range of 0.6mm to 1.0mm, but it cannot exceed the skin thickness.

[0030] Secondary reinforcement refers to the thickening of the stiffening plate at the lower end of the separation hole for structures with large deformation stress. The thickness at this position is the secondary reinforcement thickness b, which usually needs to meet the condition 2a≤b≤5a.

[0031] The cross-rib reinforcement threshold *c* is the ratio of the rib plate's height to its thickness, i.e., *c* = *H* / *a*. When *c* is too large, such as greater than 200*a*, it is usually necessary to add cross-ribs to reinforce the rib plate to prevent it from deforming and becoming unstable. To ensure a complete fit between the rib plate and the product interface, the embedding depth *d* of the rib plate must typically satisfy: 3D ≤ *d* ≤ 10D, and *d* ≤ *A*, where *D* represents the printing layer thickness. That is, the embedding depth *d* can be within the range of 3Dmm to 10D, but it cannot exceed the skin thickness.

[0032] S3 generates the stiffener body model based on the baseline curve and the set stiffener parameters.

[0033] In this embodiment, STL patch modeling technology can be used. By differentiating complex curved surfaces to form small triangular patches, a vector algorithm based on the triangular patches is used to automatically generate the rib plate body model, breaking through the algorithm limitations of existing boundary representation (B-rep) modeling software. Specifically: based on the spatial coordinates of the differential points forming the reference curve, combined with the defined generation direction or the closed curve of the opening region, and the set values ​​of a, b, c, and d, vector calculations are performed to obtain the coordinates of each endpoint of the rib plate body outline frame. The obtained coordinates of each endpoint of the rib plate body outline frame are then input into model generation software (such as commercial software like Materialise Magics), and the rib plate body model is formed after filling the triangular patches.

[0034] S4, set the parameters of the separation hole.

[0035] In this embodiment, the setting of the separation hole parameters mainly includes setting the hole diameter e, hole spacing f, and distance g between the separation hole and the product. Typically, the hole diameter e, hole spacing f, and distance g between the separation hole and the product need to be set considering material strength and rib thickness to facilitate subsequent separation of the rib from the product by the fitter and grinding away any remaining rib residue. Preferably, the values ​​of e, f, and g can be set according to the following principles: 1mm ≤ e ≤ 3mm, 2e ≤ f ≤ 4e, 0.8e ≤ g ≤ 1.2e.

[0036] S5 generates a sphere model based on the baseline curve and the set separation hole parameters.

[0037] In this embodiment, the offset of each differential point on the reference curve can be calculated according to the set values ​​of e, f, and g to obtain the separation hole distribution curve; the array distribution calculation is performed with the starting point of the separation hole distribution curve as the reference to obtain the position information of the separation hole position; and the array distribution sphere model is filled and formed according to the separation hole distribution curve and the calculated position information of the separation hole position.

[0038] Furthermore, the positions of the two sphere models at the beginning and end can be fine-tuned according to the actual situation to avoid the spheres dividing the rib plate boundary and causing suspended formation.

[0039] S6. Based on the rib plate body model and the sphere model, perform Boolean subtraction to obtain the final rib plate model with separation holes.

[0040] Based on the above, combined Figure 5As can be seen, the automated generation process of the process rib model based on the method of the present invention is as follows: On product 1, the reference curve 2 of the rib is marked; Based on the reference curve 2, combined with the set rib parameters, the rib body model 3 is generated; According to the set separation hole parameters, the separation hole distribution curve 4 is obtained, and a sphere model (including: the initial separation hole sphere 5 and the arrayed separation hole sphere 6) is generated; According to the rib body model and the sphere model, Boolean subtraction is performed to obtain the final rib model 7 with separation holes.

[0041] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

[0042] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for automatically generating models of ribbed structures for SLM forming control process, characterized in that, include: Mark the reference curve for the stiffener to be generated; Set the stiffener parameters; Based on the baseline curve and the set stiffener parameters, a stiffener body model is generated. Set the parameters of the separation orifice; Based on the baseline curve and the set separation hole parameters, a sphere model is generated; Based on the rib plate body model and the sphere model, Boolean subtraction is performed to obtain the final rib plate model with separation holes.

2. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 1, characterized in that, Marking the reference curve for the stiffener to be generated includes: identifying the contour curve of the product and marking it as the reference curve for the stiffener to be generated; or, creating a curve on the product surface that fits the product surface and marking it as the reference curve for the stiffener to be generated.

3. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 1, characterized in that, The parameters of the stiffener are set, including: defining the generation direction or the closed curve of the opening area of ​​the stiffener to be generated according to the type of stiffener to be generated; and setting the thickness a, the secondary reinforcement thickness b, the cross stiffener reinforcement threshold c, and the embedding depth d of the stiffener to be generated.

4. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 3, characterized in that, The types of stiffeners to be generated include: vertical side conformal stiffeners, bottom edge support stiffeners, and window edge support stiffeners. Among them, vertical side conformal stiffeners refer to stiffeners that extend outward from the side of the product to support and control its shape; bottom edge support stiffeners refer to stiffeners that grow layer by layer from the substrate and are finally connected to the product to support and shape it; window edge support stiffeners refer to stiffeners that close the openings inside the product to prevent warping and deformation.

5. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 4, characterized in that, Based on the type of stiffener to be generated, define the generation direction or the closed curve of the opening area of ​​the stiffener to be generated, including: if the stiffener to be generated is a vertical side conformal stiffener or a bottom edge support stiffener, then define the generation direction of the stiffener to be generated; if the stiffener to be generated is a window edge support stiffener, then mark the closed curve of the opening area.

6. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 3, characterized in that, The following principles are followed when setting the thickness a, secondary reinforcement thickness b, cross-rib reinforcement threshold c, and embedding depth d of the rib to be generated: 0.6mm≤a≤1.0mm, and a≤A 2a≤b≤5a c=H / a 3D≤d≤10D, and d≤A Where A represents the skin thickness, H represents the height of the stiffener to be generated, and D represents the printing layer thickness.

7. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 3, characterized in that, Based on the reference curve and combined with the set stiffener parameters, a stiffener body model is generated, including: according to the spatial coordinates of the differential point forming the reference curve, combined with the defined generation direction or the closed curve of the opening area, and the set values ​​of a, b, c, and d, vector calculation is performed to obtain the coordinates of each endpoint of the stiffener body's outer frame, and the coordinates of each endpoint are input into the model generation software, and the stiffener body model is formed after filling the triangular facets.

8. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 1, characterized in that, The parameters of the separation hole are set, including the hole diameter e, hole spacing f, and distance g between the separation hole and the product; where 1mm≤e≤3mm, 2e≤f≤4e, and 0.8e≤g≤1.2e.

9. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 8, characterized in that, Based on the reference curve and the set separation hole parameters, a sphere model is generated, including: calculating the offset of each differential point on the reference curve according to the set values ​​of e, f, and g to obtain the separation hole distribution curve; performing array distribution calculation with the starting point of the separation hole distribution curve as the reference to obtain the position information of the separation hole positions; and filling the array distribution sphere model according to the separation hole distribution curve and the calculated position information of the separation hole positions.

10. The method for automatically generating a model of a stiffener structure for SLM forming control process according to claim 1, characterized in that, Also includes: Based on the actual situation, the positions of the two sphere models at the beginning and end were fine-tuned.

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