Laser additive manufacturing light spot energy control method and system based on multiple parameter sets

Abstract

The invention discloses a laser additive manufacturing light spot energy control method and system based on multiple parameter sets. The method comprises the following steps that (1) characteristic parameters describing light spots are defined; 2) considering laser divergence to obtain a quantitative relation between a pose parameter set and energy density distribution and between an energy parameter set and energy density distribution, and constructing a body heat source model; and (3) a multi-parameter set closed-loop control process including parameter optimization and simulation calculation is implemented, and the influence of different combined light spot shapes and energy distribution formed by different parameter regulation and control in multi-laser coaxial wire feeding additive manufacturing on a molten pool and a deposition layer is studied. The method is based on accurate theoretical modeling and parametric description of the shape and energy distribution of a complex combined light spot formed by multiple laser beams, light beam divergence is considered in the period, and flexible control over the shape, size and distribution characteristics of the combined light spot is achieved through multi-parameter regulation and control over full-degree-of-freedom pose parameters and energy parameters.

Description

Technical Field

[0001] This invention relates to the field of multi-laser beam additive manufacturing technology, and in particular to a method and control system for controlling the shape, size and characteristic distribution of laser spot during multi-laser wire feeding additive manufacturing by constructing a multi-parameter system, establishing a physical model and adjusting related parameters. Background Technology

[0002] Energy input is a crucial aspect of laser additive manufacturing, determining the continuity, cross-sectional shape, and surface quality of the deposited layer's melt path. The combined spot of multiple laser beams on the forming surface is a primary focus of energy input; therefore, precise control over the spot's shape and energy distribution is of paramount importance.

[0003] Emerging multi-laser filament additive manufacturing involves more complex energy inputs compared to single-laser systems. It not only involves the superposition of energy from multiple laser beams acting on the substrate and filament, but also requires consideration of heat source variations caused by laser placement and tilted irradiation in actual production. Current technologies have several shortcomings in spot control. Many existing patents and related research are limited to adjusting the spot or energy distribution through simple laser power adjustment or fixed optical devices, offering limited spot control. Numerical simulations using traditional single-laser heat source models fail to adequately consider the divergence characteristics during beam propagation, resulting in insufficient accuracy in predicting the actual processing and making it difficult to accurately describe and simulate the actual spot energy distribution. No parameter-based spot control method has yet been found that considers the changes in heat source energy field caused by multi-laser placement and tilted irradiation in actual production, as well as the divergence characteristics during beam propagation. Furthermore, some methods focus only on a single function of the equipment, lacking system integration and failing to achieve an integrated process from parameter setting and model calculation verification to process optimization. These shortcomings limit the process optimization of laser additive manufacturing based on spot control.

[0004] Patent No. 202311536605.8 discloses a multi-laser mapping synthesis method and system with non-uniform energy distribution; Patent No. 202410572462.4 discloses an additive manufacturing method based on the coupling of a heat source and a planned path with non-uniform energy distribution; Patent No. 202410256997.0 discloses a laser additive printing head and printing method with reflective laser; Patent No. 202411832484.6 discloses a laser pulse energy control method and system for surface treatment; and Patent No. CN202410369086.9 discloses a semiconductor laser homogenization spot shaping system and its shaping method. However, the above-mentioned existing patents either only focus on the energy distribution obtained by two-dimensional mathematical decomposition and synthesis of power, or focus on improving the internal hardware structure of the laser and the design of the optical system to achieve spot shaping. Therefore, there is a lack of accurate theoretical modeling, parameterization, and control methods for the shape and energy distribution of complex combined light spots formed by multiple laser beams; the control parameters are limited to additive dynamic parameters such as scanning speed, wire feeding speed, and laser power, and the beam propagation and divergence characteristics are not considered. Summary of the Invention

[0005] To overcome the aforementioned problems, this invention discloses a laser additive manufacturing spot energy control method and system based on a multi-parameter set. Specifically, it coordinates and controls the laser energy input by controlling the laser pose and laser energy parameters, thereby regulating the combined spot shape, size, and characteristic distribution of the forming surface and solving for the energy. Compared to single-variable control of laser power achieved through two-dimensional static mathematical mapping and energy distribution control achieved through laser internal structure design, this method enables precise control of spot energy and prediction of the energy field under full degrees of freedom of laser head pose during multi-laser wire feeding additive manufacturing.

[0006] The technical solution of the present invention is as follows:

[0007] A method for controlling the laser spot and solving the energy in multi-laser wire feeding additive manufacturing based on a multi-parameter set includes the following steps:

[0008] 1) Define the characteristic parameters describing the light spot: Establish a composite parameter system including the pose parameter set, the light spot characteristic parameter set, and the energy parameter set, and construct the mathematical relationship between the pose parameter set and the light spot characteristic parameter set, i.e., the light spot characteristic model;

[0009] 2) Considering the laser divergence characteristics, the quantitative relationship between the pose parameter set, energy parameter set and energy density distribution is obtained respectively, and a volume heat source model is constructed;

[0010] 3) Implement a multi-parameter set closed-loop control process that includes parameter optimization and simulation calculation, and study the influence of different combinations of laser spot shapes and energy distributions formed by different parameter adjustments on the molten pool and deposition layer in multi-laser coaxial wire feeding additive manufacturing.

[0011] Furthermore, in step 1), when establishing the parameter set, the beam cross-section at the laser mirror is regarded as a circle, the center of the circle is the laser pose reference point, the normal of the center is the straight line where the beam propagation direction is located, the pose reference points of each laser beam are distributed in a ring around the origin of the coordinate system, the forming surface is the upper surface of the deposition substrate at z = Z1, and the reference point of the filament that is fed vertically downward along the Z axis and acts on the substrate is (0,0,Z1).

[0012] Furthermore, the characteristic parameters (set of characteristic parameters of the combined light spot) describing the size and distribution of the combined light spot at the forming surface include the angle between the normal of the center of the i-th laser beam and the z-direction of that point, i.e., the angle θ between the circular surface and the XY plane. zi Distribution radius R Si Distribution angle The angle β between the line containing the major axis and the line connecting the center of the ellipse and (0,0,Z1) (take the acute angle, with counterclockwise as positive, called the rotation angle). i Beam waist radius w 0i .

[0013] Furthermore, the pose parameter set includes the radius R of the i-th laser array. Li and distribution angle θ i The angle α by which the normal to the center of the beam rotates about the reference point in the X and Y directions. xi and α yi The energy parameter set includes the power P of the i-th laser beam. 0i λ, the wavelength of the light beam i Focal length f i .

[0014] Wherein, the major axis of the ellipse of the i-th laser beam spot is 2a i and short axis 2b i The relationship with the feature parameters is as follows With the distribution radius R of each single light spot Si Rotation angle β i Taking the case where they are all equal, β i When β is 0, the combined light spot is petal-shaped. i When the values ​​are not zero, the combined light spot is cyclone-shaped, and the relationship between the light spot characteristic parameters and the pose parameter set is as follows:

[0015]

[0016] Furthermore, in step 2), the Rayleigh formula is rewritten and the super-Gaussian distribution formula is rewritten based on a multi-parameter set to fit the single-beam laser additive energy distribution of the forming surface as follows:

[0017] x and y are the x and y coordinates in the defined absolute coordinate system, s1 and t1, s2 and t2 are the offset factors of the beam center x and y respectively, q1 and q2 are the rotation factors of the beam x and y, and k is the order of the super-Gaussian distribution.

[0018] Furthermore, in step 2), according to Beer-Lambert's law, the energy density distribution decreases from the forming surface with increasing laser penetration depth. The volume heat source model is as follows: Where R is the surface reflectivity of the substrate, n is the number of lasers or laser beams, and γ is the absorption coefficient of the material (m). -1 ), s i For the optical path length (when z>Z1) derived from the pose parameter set, s i If we consider the temperature variation of R and γ in different materials during the additive manufacturing process, we can replace R and γ with R(T) and γ(T), such as considering a segmented model of phase transition.

[0019] Furthermore, the closed-loop control process in step 3) is based on the quantitative relationship between the pose parameter set and the spot feature parameter set. By directly controlling the pose parameter set and related parameters of the energy parameter set, the shape, size and distribution of the combined spot on the substrate forming surface (upper surface) and the energy distribution are controlled, and the corresponding volume heat source model is obtained. This model is then applied to the simulation calculation to verify and correct the volume heat source model, and the effects of different combined spot patterns and corresponding energy distributions on the molten pool and the deposition layer are compared.

[0020] A laser additive manufacturing spot energy control system based on a multi-parameter set includes: a parameter input module, a model calculation engine, and a closed-loop verification platform;

[0021] The parameter input module is used to configure the pose parameter set, spot feature parameter set, and energy parameter set.

[0022] The model computation engine and closed-loop verification platform are used to build and verify spot feature models and volume heat source models.

[0023] The beneficial effects of this invention are as follows: Based on the accurate theoretical modeling and parameterized description of the shape and energy distribution of complex combined light spots formed by multiple laser beams, while considering beam divergence, the shape, size, and distribution characteristics of the combined light spots can be flexibly controlled through multi-parameter adjustment of pose parameters and energy parameters with full degrees of freedom. Furthermore, the corresponding energy fields of combined light spots on different forming surfaces under Gaussian / near-flat-top distribution modes in the substrate can be solved. The solved energy fields are used as energy input for simulation, and the number of trial and error is reduced through the mathematical mapping of parameters-energy field-forming quality. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the multi-laser beam pose and coordinate system of the present invention;

[0025] Figure 2 This is a schematic diagram of the single laser beam spot characteristic parameters and pose parameters of the present invention;

[0026] Figure 3 This is a top view schematic diagram of the combined light spot shape and corresponding characteristic parameters in this invention;

[0027] Figure 4 This is a diagram showing the heat source outline and energy distribution of the combined light spot on the shaped surface of the present invention.

[0028] Figure 5 This is a schematic diagram of the propagation and divergence of a single laser beam according to the present invention;

[0029] Figure 6 This is a flowchart of the multi-parameter set closed-loop control of the present invention;

[0030] Figure 7 This is a schematic diagram of the simulation results of the molten pool morphology on different combinations of light spots and corresponding energy distributions according to the present invention;

[0031] Figure 8 This is a schematic diagram illustrating the simulation results of the overall morphology and cross-sectional shape of the sediment layer under different combinations of light spots and corresponding energy distributions according to the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] A method for laser additive manufacturing spot control and energy calculation based on a multi-parameter set is described below:

[0034] 1) Define characteristic parameters describing the laser spot, establish a composite parameter system including a pose parameter set, a spot characteristic parameter set, and an energy parameter set, and construct the mathematical relationship between the pose parameter set and the spot characteristic parameters; the beam cross-section at the laser mirror is considered circular, the center of the circle is the laser pose reference point, and the normal to the center is the straight line containing the beam propagation direction. The pose reference points of each laser beam are distributed in a ring around the origin of the coordinate system. The forming surface is the upper surface of the deposition substrate at z = Z1. The reference point acting on the substrate along the Z-axis vertically downwards is (0,0,Z1). The poses and coordinate systems of multiple laser beams are as follows: Figure 1 As shown; the characteristic parameters describing the size and distribution of the combined light spot at the forming surface include the angle between the normal of the i-th beam center and the z-direction at that point, i.e., the angle θ between the circular surface and the XY plane. zi Distribution radius R Si Distribution angle The angle β between the line containing the major axis and the line connecting the center of the ellipse and (0,0,Z1) (take the acute angle, with counterclockwise as positive, called the rotation angle). i Beam waist radius w0i The pose parameter set includes the radius R of each laser array. Li and distribution angle θ i The angle α by which the normal to the center of the beam rotates about the reference point in the X and Y directions. xi and α yi The energy parameter set includes the power P of each laser beam. 0i λ, the wavelength of the light beam i Focal length f i Taking a laser beam as an example, the characteristic parameters and pose parameters of the laser spot are shown in the following diagram. Figure 2 The major axis of the single-spot ellipse is 2a i and short axis 2b i The relationship with the feature parameters is as follows 2b i =2w0, with the distribution radius R of each single spot of the six laser beams. Si Rotation angle β i Taking the case where they are all equal, β i When β is 0, the combined light spot is petal-shaped. i When the light spot is not zero, the combined light spot is cyclone-shaped. Figure 3 As shown, the relationship between the light spot feature parameters and the pose parameter set is as follows:

[0035]

[0036] 2) Considering laser divergence, determine the quantitative relationship between the pose parameter set, energy parameter set, and energy density distribution, and construct a volume heat source model; the laser beam radius w during propagation... i It is not a constant value, but varies with the propagation distance and is related to the focal length f. i w 0i A schematic diagram of single laser beam propagation and divergence is shown below. Figure 4 As shown, the Rayleigh formula can be rewritten in the coordinate system of step 1) to obtain... Where λ i f is the laser wavelength. i This is the focal length; assuming the laser emitter only has focusing or refraction functions and no other beam shaping system, the super-Gaussian distribution formula is rewritten based on a multi-parameter set to fit the single-beam laser additive energy distribution of the shaped surface as follows: x and y are the x and y coordinates in the defined absolute coordinate system; s1 and t1, s2 and t2 are the offset factors of the beam center in x and y, respectively; q1 and q2 are the rotation factors of the beam in x and y; and k is the order of the super-Gaussian distribution. According to Beer-Lambert's law, the energy density distribution decreases with increasing laser penetration depth from the forming surface. Taking a six-laser-beam model as an example, the volumetric heat source model interacting with the material is as follows: Where R is the surface reflectivity of the substrate, n is the number of lasers or laser beams, and γ is the absorption coefficient of the material (m). -1 ), s i For the optical path length (when z>Z1) derived from the pose parameter set, s i (0), considering the temperature changes of R and γ for different materials during additive manufacturing, R and γ can be replaced with R(T) and γ(T). Taking the petal-shaped and cyclone-shaped combined spot of a six-laser beam forming surface as an example, the corresponding volume heat source contour and energy distribution are shown in the figure. Figure 5 As shown.

[0037] 3) Implement a multi-parameter set closed-loop control process that includes parameter optimization and simulation calculations to study the impact of different combinations of laser spot shapes and energy distributions formed by different parameter adjustments on the molten pool and deposition layer in multi-laser coaxial wire feeding additive manufacturing; the closed-loop control process is illustrated in the diagram below. Figure 6 As shown, based on the quantization relationship between the pose parameter set and the spot feature parameter set obtained in steps 1) and 2), the shape, size, distribution, and energy distribution of the combined spot on the substrate forming surface (upper surface) are controlled by directly controlling the relevant parameters of the pose parameter set and energy parameter set, and the corresponding volume heat source model in step 2) is obtained. The obtained volume heat source model is applied to the simulation calculation and the volume heat source model is corrected. Based on the spot feature model and the volume heat source model, the shape, size, distribution, and energy distribution of the combined spot are controlled to make the heat source energy heat and melt the additive manufacturing material according to the desired distribution, forming the molten pool and deposition layer corresponding to the desired combined spot. The influence of different combined spots and corresponding energy distributions on the morphology and fluidity of the molten pool, the morphology and mechanical properties of the deposition layer are compared, and the relevant laws are sorted out to guide the implementation of closed-loop process control optimization. Taking the desired combined spot types as petal shape and cyclone shape as examples, the simulation results of molten pool and deposition layer with different morphologies are as follows. Figure 7 and Figure 8 As shown. Taking sedimentary layers as an example, it can be seen that the cyclone-shaped combined spot increases the average width of the sedimentary layer compared to the petal-shaped one, but reduces the uniformity of the layer height. Therefore, by directly controlling the α of the pose parameter set... xi and α yi Adjusting the β of the light spot i This improves the uniformity of layer height while ensuring a certain width of the sedimentary layer.

[0038] The embodiments described in this specification are merely examples of implementations of the inventive concept. The scope of protection of this invention should not be considered as limited to the specific forms stated in the embodiments. The scope of protection of this invention also extends to equivalent technical means that can be conceived by those skilled in the art based on the inventive concept.

Claims

1. A method for controlling the spot energy in laser additive manufacturing based on a multi-parameter set, characterized in that, Includes the following steps: 1) Define the characteristic parameters describing the light spot: Establish a composite parameter system including the pose parameter set, the light spot characteristic parameter set, and the energy parameter set; Construct the mathematical relationship between the pose parameter set and the light spot characteristic parameter set, i.e., the light spot characteristic model; 2) Considering the laser divergence characteristics, the quantitative relationship between the pose parameter set, energy parameter set and energy density distribution is obtained respectively, and a volume heat source model is constructed; 3) Implement a multi-parameter set closed-loop control process that includes parameter optimization and simulation calculation, and study the influence of different combinations of laser spot shapes and energy distributions formed by different parameter adjustments on the molten pool and deposition layer in multi-laser coaxial wire feeding additive manufacturing.

2. The laser additive manufacturing spot energy control method based on a multi-parameter set according to claim 1, characterized in that, The pose parameter set includes: the radius R of the i-th laser array. Li and distribution angle θ i Z1 is the z-axis coordinate of the upper surface of the additive substrate, i.e., the forming surface; α is the angle α by which the normal to the center of the i-th laser beam rotates about the X and Y directions with the reference point as the base point. xi and α yi .

3. The laser additive manufacturing spot energy control method based on a multi-parameter set according to claim 1, characterized in that, The set of light spot characteristic parameters includes: the angle θ between the center normal of the i-th laser beam and the Z-axis. zi Distribution radius R Si and distribution angle Light spot ellipse rotation angle β i Beam waist radius w 0i .

4. The laser additive manufacturing spot energy control method based on a multi-parameter set according to claim 1, characterized in that, The energy parameter set includes: the power P of the i-th laser beam. 0i Wavelength λ i Focal length f i .

5. The laser additive manufacturing spot energy control method based on a multi-parameter set according to claim 2, characterized in that, The major axis 2a of the ellipse of the i-th laser beam i and short axis 2b i The relationship with the feature parameters is as follows: 2b i =2w 0i .

6. The laser additive manufacturing spot energy control method based on a multi-parameter set according to claim 1, characterized in that, The mathematical relationship between the pose parameter set and the spot feature parameter set is as follows:

7. The laser additive manufacturing spot energy control method based on a multi-parameter set according to claim 1, characterized in that, The method for establishing the volume heat source model includes the following steps: 1) Calculate beam divergence characteristics by rewriting the Rayleigh formula based on a multi-parameter set; Rewriting Rayleigh's formula in the coordinate system of step 1) yields: Where λ i f is the laser wavelength. i It is the focal length, and z is the z-coordinate in the defined absolute coordinate system; 2) Fitting the energy distribution of a single laser beam based on the super-Gaussian distribution formula and a multi-parameter set; Assuming the laser emitter only has focusing or refraction functions and no other beam shaping system, the energy distribution of a single laser additive process on the forming surface is fitted by rewriting the super-Gaussian distribution formula based on a multi-parameter set as follows: x and y are the x and y coordinates in the defined absolute coordinate system, s1 and t1, s2 and t2 are the offset factors of the beam center x and y respectively, q1 and q2 are the rotation factors of the beam x and y, k is the order of the super-Gaussian distribution, and Z1 is the z coordinate of the upper surface of the additive substrate. 3) Calculate the energy decay characteristics with depth based on the Beer-Lambert law; According to Beer-Lambert's law, the surface energy distribution decreases with increasing laser depth starting from the forming surface. s i For the optical path length derived from the pose parameter set, when z > Z1, s i =0; I Si This represents the energy distribution of a single laser additive process on the forming surface. The expression for the bulk heat source model of multiple laser beams acting on a substrate is obtained as follows: Where R is the surface reflectivity of the substrate, n is the number of lasers or laser beams, γ is the absorption coefficient of the material, and A zi s is the attenuation factor after laser light strikes the material. i The optical path length is derived from the pose parameter set.

8. The laser additive manufacturing spot energy control method based on a multi-parameter set according to claim 1, characterized in that, Step 3) specifically involves: controlling the shape, size, and distribution of the combined light spot on the forming surface by directly controlling the pose parameters; applying the obtained heat source model to the simulation calculation and correcting the heat source model; and comparing and analyzing the effects of different combined light spots and corresponding energy distributions on the molten pool and the deposition layer.

9. A control system for implementing the control method according to any one of claims 1-8, characterized in that, include: Parameter input module, model calculation engine, and closed-loop verification platform; The parameter input module is used to configure the pose parameter set, spot feature parameter set, and energy parameter set. The model computation engine and closed-loop verification platform are used to build and verify spot feature models and volume heat source models.

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