Selective melting beam shaping and residual stress regulation cooperation method and system

Abstract

The invention discloses a selective melting beam shaping and residual stress regulation cooperation method and system, and belongs to the technical field of selective melting additive manufacturing. The method comprises the steps that slicing data of a to-be-formed part are obtained, and characteristic parameters of all areas are analyzed; light beam spot parameters are adjusted in real time through a dynamic light beam shaping module based on the characteristic parameters; in the forming process, stress associated data of a molten pool and a heat affected zone are collected through a multi-dimensional stress monitoring module; the cooperative control unit analyzes the data based on a preset correlation model and judges stress abnormity; if yes, light spot parameter adjustment and stress regulation and control operation are synchronously controlled; and subsequent forming parameters are corrected through a closed-loop algorithm. The system comprises corresponding function modules and a process database. According to the method, light beam shaping and residual stress regulation are coordinated, the residual stress of parts is effectively reduced, deformation and cracking are reduced, the forming precision and the production efficiency are both considered, the process stability is improved, and the adaptation range of materials and complex structures is widened.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of selective laser melting additive manufacturing technology, in particular to a selective laser melting light beam shaping and residual stress regulation and control method and system. BACKGROUND

[0002] Selective laser melting additive manufacturing technology (SLM) as one of the core technologies in the field of additive manufacturing, with its characteristics of directly forming complex hollow, thin-walled, special-shaped and other difficult-to-machine structures, and high density and excellent mechanical properties of parts, has been widely used in aerospace, medical implants, high-end equipment core components and other high-end manufacturing fields. At present, the industry continues to optimize the SLM process: in the light beam application layer, the existing technology can realize the basic adjustment of spot size and shape through optical components to adapt to the melting requirements of different materials; in the residual stress control layer, general methods such as overall substrate preheating and post-forming heat treatment have been formed, and the two types of technologies play a role in improving the forming precision and improving the stress state, and promote the SLM technology to gradually move towards industrialized mass production.

[0003] However, the existing SLM technology has not formed a systematic coordination mechanism for light beam shaping and residual stress regulation, resulting in obvious bottlenecks in process optimization. The specific technical problems are as follows: first, light beam shaping and residual stress regulation are independent of each other, light beam parameters are mostly based on regional type preset fixed values, and cannot be dynamically adjusted in combination with real-time stress state in the forming process, while residual stress regulation is mostly "offline" post-processing or "one-size-fits-all" overall preheating, which lacks synchronization with the light beam forming process, and is difficult to alleviate local (such as regional connection and support combination) stress concentration; second, the application depth of slice data is insufficient, and only basic layering and path planning can be completed, and the characteristic parameters (such as regional type and material thickness) in different regions of the slice cannot be accurately analyzed, and thus personalized basis for light beam parameter adjustment cannot be provided; third, the forming process lacks closed-loop control of "monitoring-analysis-adjustment", although some temperature or deformation data can be collected, there is a lack of stress abnormality comprehensive judgment based on correlation model, and the subsequent light beam parameters and stress regulation strategies cannot be corrected in real time according to the regulation effect, ultimately leading to problems such as excessive residual stress and deformation cracking of parts, and difficulty in balancing forming precision and production efficiency. SUMMARY

[0004] The purpose of the present application is to overcome one or more of the deficiencies of the prior art and provide a selective laser melting light beam shaping and residual stress regulation and control method and system.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] A selective laser melting light beam shaping and residual stress regulation and control method, comprising the following steps:

[0007] S1. acquiring slice data of a part to be formed, and analyzing characteristic parameters of each region in the slice data;

[0008] S2. adjusting, by a dynamic beam shaping module, a light spot parameter of a light beam in real time based on the characteristic parameters;

[0009] S3. in a selective melting forming process, collecting, by a multi-dimensional stress monitoring module, stress correlation data of a molten pool and a heat affected zone in real time;

[0010] S4. transmitting the stress correlation data to a cooperative control unit, and analyzing, by the cooperative control unit based on a preset correlation model, the stress correlation data to determine whether there is stress abnormality in a current forming region;

[0011] S5. if there is stress abnormality, the cooperative control unit generates a cooperative control instruction to synchronously control the dynamic beam shaping module to adjust the light spot parameter and control a partition cooperative control module to perform a stress control operation, so as to realize cooperation of light beam shaping and residual stress control.

[0012] S6. based on the adjusted parameters and feedback data, the cooperative control unit corrects subsequent forming parameters through a closed-loop control algorithm to complete closed-loop cooperative control of “monitoring-analysis-adjustment”.

[0013] Further, in the step S1, the characteristic parameters include region types, including a contour region, a filling region and a transition region, and material thicknesses of corresponding regions.

[0014] Further, in the step S2, the light spot parameters include a light spot shape, an energy density distribution and a light spot size; when the dynamic beam shaping module adjusts the light spot shape, the contour region corresponds to output of a flat-top light spot, the filling region corresponds to output of a Gaussian light spot, and the transition region corresponds to output of a gradient light spot.

[0015] Further, the shape transition of the gradient light spot is controlled by a light spot edge energy decay rate, and the light spot edge energy decay rate is adjusted linearly with the material thickness of the transition region.

[0016] Further, in the step S3, the stress correlation data includes temperature data, part deformation data and local residual stress data; the multi-dimensional stress monitoring module collects the temperature data by an infrared thermal imager, collects the deformation data by a laser displacement sensor, and collects the local residual stress data by an ultrasonic stress detector.

[0017] Further, in the step S4, the preset correlation model is a "temperature gradient-deformation amount-residual stress" correlation model; when the stress anomaly is determined by the cooperative control unit, the allowable deformation amount threshold of the current region is calculated first, and then the actual deformation amount is compared with the threshold, and if the actual deformation amount exceeds the threshold, the stress anomaly is determined.

[0018] Further, in the step S5, the stress regulation operation of the partition cooperative regulation module includes local induction heating and pulse laser impact; if the current region is the support and substrate combination position, the pulse laser impact is started synchronously, and the impact times are positively correlated with the residual stress value of the current region.

[0019] Further, in the step S6, the closed-loop control algorithm dynamically corrects the light beam output power and the local preheating temperature based on the parameter matching relationship of different materials and part structures in the process database, and the process database can be iteratively updated based on the forming data.

[0020] A melting light beam shaping and residual stress regulation cooperative system comprises a dynamic light beam shaping module, a multi-dimensional stress monitoring module, a partition cooperative regulation module, a cooperative control unit and a process database.

[0021] Further, the multi-dimensional stress monitoring module comprises a temperature monitoring submodule, a deformation monitoring submodule and a stress monitoring submodule; the partition cooperative regulation module comprises a heating submodule and a pulse impact submodule; the cooperative control unit is provided with a preset correlation model and a closed-loop control algorithm, and the regulation parameters can be optimized based on the process database.

[0022] The beneficial effects of the present application are as follows:

[0023] (1) Through the cooperation of dynamic light beam shaping and multi-dimensional stress regulation, the residual stress of the part is effectively reduced, and the deformation and cracking problems in the forming process are reduced.

[0024] (2) By adapting different light spot parameters for different regions without additional post-processing, the part forming precision and production efficiency are improved.

[0025] (3) Through multi-dimensional monitoring, closed-loop control and process library iteration, the process stability is improved, and the material and complex structure adaptation range is widened. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A selective melting light beam shaping and residual stress regulation synergistic method is provided for the embodiment. DETAILED DESCRIPTION

[0027] The technical solutions of the present application will be described clearly and completely below in conjunction with the embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort fall within the scope of the present application.

[0028] Embodiment 1

[0029] A selective melting light beam shaping and residual stress regulation synergistic method is provided, comprising the following steps:

[0030] S1. Obtain slice data of a part to be formed, and analyze characteristic parameters of each region in the slice data;

[0031] S2. Based on the characteristic parameters, adjust the spot parameters of the light beam in real time through a dynamic light beam shaping module;

[0032] S3. In the selective melting forming process, collect stress-related data of the molten pool and the heat-affected zone in real time through a multi-dimensional stress monitoring module;

[0033] S4. Transmit the stress-related data to a synergistic control unit, which analyzes the stress-related data based on a preset correlation model, and determines whether there is stress abnormality in the current forming region;

[0034] S5. If there is stress abnormality, the synergistic control unit generates a synergistic regulation instruction, synchronously controls the dynamic light beam shaping module to adjust the spot parameters, and controls a partition synergistic regulation module to perform stress regulation operations, so as to realize the synergy of light beam shaping and residual stress regulation;

[0035] S6. The synergistic control unit corrects the subsequent forming parameters through a closed-loop control algorithm based on the adjusted parameters and feedback data, to complete the closed-loop synergistic control of “monitoring-analysis-adjustment”.

[0036] In the step S1, the characteristic parameters include the region type, including the contour region, the filling region and the transition region, and the material thickness of the corresponding region.

[0037] In the step S2, the spot parameters include the spot shape, the energy density distribution and the spot size; when the dynamic light beam shaping module adjusts the spot shape, the contour region corresponds to outputting a flat-top spot, the filling region corresponds to outputting a Gaussian spot, and the transition region corresponds to outputting a gradient spot.

[0038] The shape transition of the gradient light spot is controlled by a light spot edge energy decay rate, which is linearly adjusted with the material thickness of the transition zone.

[0039] In the step S3, the stress-related data includes temperature data, part deformation data and local residual stress data; the multi-dimensional stress monitoring module collects temperature data by an infrared thermal imager, collects deformation data by a laser displacement sensor, and collects local residual stress data by an ultrasonic stress detector.

[0040] In the step S4, the preset correlation model is a "temperature gradient-deformation-residual stress" correlation model; when the cooperative control unit judges that the stress is abnormal, it first calculates the allowable deformation threshold of the current region, then compares the actual deformation with the threshold, and if the threshold is exceeded, it is determined that the stress is abnormal.

[0041] In the step S5, the stress regulation operation of the partition cooperative regulation module includes local induction heating and pulse laser impact; if the current region is the support and substrate combination, the pulse laser impact is started synchronously, and the impact frequency is positively correlated with the residual stress value of the current region.

[0042] In the step S6, the closed-loop control algorithm dynamically corrects the light beam output power and the local preheating temperature based on the parameter matching relationship of different materials and part structures in the process database, and the process database can be iteratively updated by forming data.

[0043] A selective melting light beam shaping and residual stress regulation cooperative system, comprising: a dynamic light beam shaping module for adjusting the light spot parameters of the light beam in real time according to the regional characteristics of the part slice; a multi-dimensional stress monitoring module for collecting stress-related data of the molten pool and the heat-affected zone; a partition cooperative regulation module for performing stress regulation operation on the stress abnormal region; a cooperative control unit connected with the dynamic light beam shaping module, the multi-dimensional stress monitoring module and the partition cooperative regulation module for receiving stress-related data, analyzing stress abnormal state, generating cooperative regulation instructions, and realizing closed-loop control; a process database connected with the cooperative control unit for storing process parameter correlation data to provide data support for cooperative control.

[0044] The multi-dimensional stress monitoring module includes a temperature monitoring sub-module, a deformation monitoring sub-module and a stress monitoring sub-module; the partition cooperative regulation module includes a heating sub-module and a pulse impact sub-module; the cooperative control unit has a preset correlation model and a closed-loop control algorithm, which can optimize the regulation parameters based on the process database.

[0045] Example 2

[0046] The embodiment provides a selective melting light beam shaping and residual stress regulation cooperative method, and the specific implementation steps are as follows:

[0047] Step S1: acquiring slice data of a part to be formed and analyzing characteristic parameters:

[0048] The core of step S1 is to complete the conversion of the part to be formed from a three-dimensional model to slice data, and accurately extract key characteristic parameters of each region in the slice, so as to provide basic data support for subsequent light beam shaping and stress regulation, and specifically includes the following sub-steps:

[0049] S1.1 acquiring slice data of the part to be formed:

[0050] Through a professional additive manufacturing slicing process, the three-dimensional model of the part to be formed is subjected to layer-by-layer slicing processing. In the slicing process, according to the overall structural complexity of the part, the forming precision requirement and the material characteristics, a reasonable slice layer thickness (the layer thickness parameter is set based on the melting characteristics of the material and the forming efficiency requirement) is determined, and a slice data file containing the contour, internal structure and forming path planning basic information of each slice layer is generated. The slice data file needs to be recognized by the subsequent cooperative control unit, and can support the region division and parameter analysis operation.

[0051] S1.2 analyzing the region type parameters in the slice data:

[0052] The generated slice data is subjected to region division and type identification, and each slice layer is divided into three core regions of contour region, filling region and transition region. Among them, the contour region is defined as the region where the outer boundary, inner hole boundary and key fitting surface of the part are located, which directly determines the dimensional accuracy and surface quality of the part; the filling region is defined as the region inside the part which is not a key bearing and needs to be filled by cladding material, and the forming efficiency of this region has a greater impact on the overall production cycle; the transition region is defined as the connection region between the contour region and the filling region, and between different material thickness regions, which is prone to stress concentration due to energy distribution mutation and needs to be paid attention to. In the region division process, the cooperative control unit will automatically identify the boundary range of each region in combination with the structure and function information (such as bearing parts and fitting parts) of the three-dimensional model of the part, to ensure the accuracy and rationality of the region division.

[0053] S1.3 analyzing the material thickness parameters in the slice data:

[0054] For each divided region, the material thickness parameter of the corresponding region is parsed from the slice data. The parsing of the material thickness parameter needs to be combined with the slice layer thickness and the three-dimensional structure of the part model: for a planar region, the material thickness is the size of the region in the direction perpendicular to the slice layer; for a curved surface region, the material thickness is the average size of the region in the forming direction; for a thin-walled or hollow structure region, the material thickness is the minimum wall thickness size of the region. The parsed material thickness parameter will be used as an important basis for subsequent spot parameter adjustment and stress regulation operations, for example, thick-walled regions need to adapt to higher energy input to ensure sufficient cladding, and thin-walled regions need to control energy input to avoid overheating deformation.

[0055] Step S2: adjusting the spot parameters of the light beam based on the characteristic parameters:

[0056] Step S2 uses the region type, material thickness and other characteristic parameters parsed in step S1 as a basis to adjust the spot parameters of the light beam in real time through a dynamic light beam shaping module, so that the spot characteristics are accurately matched with the forming requirements of different regions, which specifically includes the following sub-steps:

[0057] S2.1 determines the adjustment dimension of the spot parameters:

[0058] The adjustment dimension of the spot parameters includes three core parameters: spot shape, energy density distribution and spot size. Among them, the spot shape needs to be selected according to the region type (such as flat spot, Gaussian spot, gradient spot), the energy density distribution needs to be adapted to the cladding requirements of the region (such as high uniformity distribution, gradient distribution), and the spot size needs to be determined in combination with the material thickness and the forming efficiency (such as small size spot to ensure accuracy, large size spot to improve efficiency). The dynamic light beam shaping module can realize the coordinated adjustment of the three types of parameters through internal optical regulation components (such as deformable mirrors, digital micromirror arrays), and the adjustment process can respond to the instructions of the coordinated control unit in real time.

[0059] S2.2 calculates the spot energy density and adjusts:

[0060] According to the region type and the material thickness, the required spot energy density of the current region is calculated by formula (1) to ensure that the energy input matches the region forming requirements:

[0061] E=(P×k1) / S;

[0062] In formula (1):

[0063] E is the spot energy density, with a unit of W / mm², representing the energy input intensity of the light beam per unit area, which directly affects the temperature of the molten pool and the cladding quality;

[0064] P is the output power of the light beam, with a unit of W, which is the basic energy parameter of the dynamic light beam shaping module and can be adjusted according to the energy density requirements;

[0065] k1 is a spot shaping coefficient, the value range is 0.6-1.2, which is determined according to the region type (k1 value is 0.6-0.8 in the contour area to reduce the energy density to avoid the thermal influence area being too large; k1 value is 1.0-1.2 in the filling area to improve the energy density to ensure the cladding efficiency; k1 value is 0.8-1.0 in the transition area to realize the smooth transition of the energy density);

[0066] S is the effective action area of the spot, the unit is mm², which is directly related to the spot size, the larger the spot size, the larger the effective action area.

[0067] After the target energy density E is calculated, the cooperative control unit sends instructions to the dynamic beam shaping module to adjust the beam output power P or the effective action area S of the spot, so that the actual spot energy density reaches the calculated value. For example, for the contour area, if the initial beam output power is fixed, the effective action area S of the spot can be reduced and the value of k1 can be reduced to realize the output of a low-energy-density flat-top spot, thereby ensuring the forming precision of the contour area.

[0068] S2.3 Adjust the shape of the spot to adapt to the region type:

[0069] According to the different region types, the dynamic beam shaping module adjusts the shape of the spot: for the contour area, a flat-top spot is output, the energy density of which is uniformly distributed within the spot range, which can reduce the over-melting or burr of the edge of the contour area caused by energy concentration, and reduce the range of the thermal influence area, thereby ensuring the precision of the part size; for the filling area, a Gaussian spot is output, the energy density of which decays from the center to the edge, which can ensure sufficient cladding in the central area while reducing the excessive fusion of the edge area with the already formed part, thereby improving the forming efficiency and internal quality of the filling area; for the transition area, a gradient spot is output, the shape of which gradually transitions from the flat-top of the contour area to the Gaussian of the filling area, thereby avoiding uneven energy distribution caused by sudden changes in the shape of the spot.

[0070] S2.4 Control the shape transition process of the gradient spot:

[0071] For the gradient spot of the transition area, the shape is smoothly transitioned by adjusting the edge energy decay rate of the spot, and the edge energy decay rate of the spot is linearly adjusted with the material thickness of the transition area. Specifically, when the material thickness of the transition area changes from thick to thin, the edge energy decay rate of the spot linearly increases from low to high. The edge energy decay rate of the thick wall side is low, which is close to the decay characteristics of the Gaussian spot of the filling area, to ensure sufficient energy input to clad the thick wall material; the edge energy decay rate of the thin wall side is high, which is close to the decay characteristics of the flat-top spot of the contour area, to avoid overheating and deformation of the thin wall material. By linearly adjusting the edge energy decay rate, the energy distribution of the transition area is continuously changed, which effectively eliminates the stress concentration hidden danger at the region junction.

[0072] Step S3: Collect stress correlation data of the molten pool and heat-affected zone:

[0073] Step S3 involves collecting various data related to residual stress in real time through a multi-dimensional stress monitoring module during the selected area melting and forming process. This provides data support for subsequent stress anomaly judgment and coordinated control. Specifically, it includes the following sub-steps:

[0074] S3.1 Determine the acquisition type of stress correlation data:

[0075] The stress-related data is clearly defined to include three core categories: temperature data, part deformation data, and local residual stress data. Temperature data reflects the temperature distribution and gradient of the molten pool and heat-affected zone, and is a direct factor leading to thermal stress. Part deformation data reflects the real-time morphological changes of the part during forming, and is an external manifestation of residual stress release. Local residual stress data directly characterizes the internal stress state of the part and is a key basis for determining whether the stress exceeds the limit. All three types of data must be collected simultaneously to form a complete stress state assessment dataset.

[0076] S3.2 Collect temperature data of the molten pool and heat-affected zone:

[0077] The temperature monitoring submodule (such as an infrared thermal imager) within the multi-dimensional stress monitoring module collects real-time temperature data of the molten pool's central region and the edge of the heat-affected zone (HAZ), denoted as T1 (real-time temperature of the molten pool's central region, in °C) and T2 (real-time temperature of the HAZ's edge, in °C), respectively. During data acquisition, the temperature monitoring submodule must synchronize with the dynamic beam shaping module's trajectory to ensure accurate capture of the temperature distribution in the corresponding area each time the beam spot is applied. For example, when the beam spot moves to the contour region, the temperature monitoring submodule focuses on the molten pool and adjacent HAZ in the contour region; when the beam spot moves to the filling region, it focuses on the molten pool and the HAZ connecting to the transition region in the filling region. The collected temperature data must be transmitted to the collaborative control unit in real-time for subsequent temperature gradient calculations.

[0078] S3.3 Collect deformation data of the part:

[0079] The deformation monitoring submodule (such as a laser displacement sensor) in the multidimensional stress monitoring module collects the part deformation data of the current forming area in real time, denoted as ΔL (the actual deformation of the current monitoring area, in mm). The position of the deformation monitoring submodule needs to be selected at the characteristic position of the part, including the side wall of the thin-walled area, the end surface of the load-bearing area, the junction of the transition area, and other parts prone to deformation. During the collection process, the deformation monitoring submodule sets an initial reference position (the position of the area before forming), and calculates the deformation data by comparing the deviation between the real-time position and the reference position. For example, for the thin-walled area, the deformation monitoring submodule continuously monitors the deflection change of the thin-walled area, and if the deflection exceeds a certain range, it prompts that there may be stress concentration in the area.

[0080] S3.4 Collecting local residual stress data of the part:

[0081] The stress monitoring submodule (such as an ultrasonic stress detector) in the multidimensional stress monitoring module collects the local residual stress data of the current forming area. The collection timing is divided into online collection and offline collection: online collection is to pause the forming process after forming a certain number of layers, and then detect the local residual stress of the formed area; offline collection is to detect the overall residual stress of the key area after the entire part is formed. During the collection process, the stress monitoring submodule adjusts the detection parameters according to the type of the area, for example, for the contour area and other key precision areas, a higher detection resolution is used; for the filling area and other non-key areas, a higher detection efficiency is used. The collected local residual stress data needs to be stored in association with the temperature data and the deformation data to form a multidimensional stress database.

[0082] S3.5 Calculating the temperature gradient of the molten pool and the heat-affected zone:

[0083] The cooperative control unit calculates the temperature gradient G of the molten pool and the heat-affected zone by formula (2) according to the collected temperature data (T1, T2) and the distance parameter (d) obtained by analyzing the slice data, to evaluate the risk of thermal stress generation in the area:

[0084] G = |T1-T2| / d;

[0085] In formula (2):

[0086] G is the temperature gradient, in ℃ / mm, representing the temperature change rate of the molten pool center and the edge of the heat-affected zone, the larger the temperature gradient, the higher the possibility of thermal stress generation;

[0087] T1 is the real-time temperature of the molten pool center area, in ℃, collected by the infrared thermal imager, reflecting the melting state of the molten pool;

[0088] T2 is the real-time temperature of the edge of the heat-affected zone, in ℃, collected by the infrared thermal imager, reflecting the cooling state of the heat-affected zone;

[0089] d is the straight-line distance between the center area of the molten pool and the edge of the heat-affected zone, in mm, obtained by analyzing the slice data (according to the coordinate positions of the molten pool area and the heat-affected zone in the slice, the shortest straight-line distance between the two is calculated).

[0090] After calculating the temperature gradient G, the cooperative control unit compares it with the temperature gradient reference value corresponding to the material stored in the process database. If G is significantly higher than the reference value, it is preliminarily judged that there is a risk of excessive thermal stress in this area, which needs to be further confirmed in combination with subsequent deformation data and residual stress data.

[0091] Step S4: analyze stress-related data and judge stress abnormalities:

[0092] Step S4 transmits the stress-related data collected in step S3 to the cooperative control unit, analyzes the data based on the preset correlation model, and judges whether there is a stress abnormality in the current forming area. Specifically, the following sub-steps are included:

[0093] S4.1 calls the preset "temperature gradient-deformation-residual stress" correlation model:

[0094] The cooperative control unit has a preset "temperature gradient-deformation-residual stress" correlation model. This model is built based on the forming data of different materials and different part structures stored in the process database. For example, for titanium alloy materials, the model includes the corresponding relationship between deformation and residual stress under different temperature gradients; for high-temperature alloy materials, the model includes the influence of temperature gradient on residual stress under different wall thicknesses. When analyzing data, the cooperative control unit first calls the appropriate correlation model parameters from the process database according to the material type and structural characteristics of the part to be formed, ensuring the accuracy of model analysis.

[0095] S4.2 Calculate the allowable deformation threshold of the current area:

[0096] To determine whether the part deformation is within a reasonable range, the cooperative control unit calculates the allowable deformation threshold ΔLmax of the current monitoring area by formula (3). This threshold is the maximum deformation that the part can withstand under the current forming conditions. If it exceeds this threshold, it is judged as excessive deformation, which may be accompanied by residual stress abnormalities:

[0097] ΔLmax = α × L × ΔTallow;

[0098] In formula (3):

[0099] ΔLmax is the allowable deformation threshold, in mm, representing the maximum deformation that the part can withstand in the current area, which is a key indicator for judging whether the deformation is excessive;

[0100] a is the linear expansion coefficient of the material used for the part to be formed, in units of °C-1, called from the process database (the linear expansion coefficients of different materials are different, for example, there is a significant difference between the linear expansion coefficients of titanium alloy and aluminum alloy);

[0101] L is the characteristic length of the current monitoring area, in units of mm, obtained by analyzing the slice data (such as the wall thickness of thin-walled parts, the span of load-bearing parts, the connection length of transition zones, etc., the longer the characteristic length, the larger the deformation generally);

[0102] ATallow is the maximum temperature fluctuation value allowed for the current area, in units of °C, determined according to the material type (different materials have different high-temperature deformation resistance capabilities).

[0103] After calculating ΔLmax, the cooperative control unit stores it as the deformation judgment reference for the current area, which is used for subsequent comparison with the actual deformation ΔL.

[0104] S4.3 Comprehensive judgment of whether the current area has stress abnormalities:

[0105] The cooperative control unit combines the three types of stress-related data and the calculated temperature gradient G and the allowable deformation threshold ΔLmax to make a multi-dimensional stress abnormality judgment:

[0106] 1. Deformation comparison: Compare the actual deformation ΔL with the allowable deformation threshold ΔLmax. If ΔL > ΔLmax, it is directly determined that the area has stress abnormalities and cooperative regulation needs to be started. If ΔL ≤ ΔLmax, it enters the subsequent judgment link.

[0107] 2. Temperature gradient comparison: Compare the calculated temperature gradient G with the temperature gradient safety value corresponding to the material in the process database. If G exceeds the safety value, even if ΔL ≤ ΔLmax, it is determined that there is a potential stress abnormality in the area (because a large temperature gradient easily leads to stress accumulation in the subsequent forming process), and warning regulation needs to be started. If G does not exceed the safety value, it enters the residual stress comparison link.

[0108] 3. Residual stress comparison: Compare the collected local residual stress data with the residual stress safety threshold corresponding to the material in the process database. If the local residual stress exceeds the safety threshold, it is determined that the area has stress abnormalities. If it does not exceed, it is determined that the stress state of the current area is normal and cooperative regulation does not need to be started.

[0109] Through the above three-level judgment, the cooperative control unit can comprehensively and accurately identify the stress state of the current forming area, avoiding misjudgment or omission caused by single data judgment.

[0110] Step S5: Generate cooperative regulation instructions and perform stress regulation operations:

[0111] Step S5, after the collaborative control unit determines that there is a stress anomaly, generates a collaborative control command that includes beam spot parameter adjustment and stress control operations to achieve the coordination of beam shaping and residual stress control. Specifically, it includes the following sub-steps:

[0112] S5.1 Adjust the spot parameters to alleviate stress anomalies:

[0113] The collaborative control unit sends beam spot parameter adjustment commands to the dynamic beam shaping module based on the type of stress anomaly (such as excessive deformation, excessive temperature gradient, or excessive residual stress).

[0114] 1. If the excessive deformation is caused by local overheating (manifested as ΔL>ΔLmax and T1 is significantly higher), the dynamic beam shaping module is instructed to reduce the beam energy density E in that area (by reducing the beam output power P or expanding the effective area S of the beam), and at the same time adjust the beam shape to a more uniform flat-top beam to reduce local energy concentration.

[0115] 2. If the stress anomaly is caused by an excessive temperature gradient (manifested as G exceeding the safe value), the dynamic beam shaping module is instructed to expand the spot size, increase the effective area S of the spot, make the energy distribution more dispersed, and reduce the temperature gradient G.

[0116] 3. If the stress anomaly occurs in the transition zone (manifested as excessive residual stress at the junction of regions), the dynamic beam shaping module is instructed to further optimize the edge energy attenuation rate of the gradient spot, so that the energy distribution in the transition zone is smoother and stress concentration caused by sudden energy changes is avoided.

[0117] After the beam spot parameters are adjusted, the dynamic beam shaping module needs to feed back the adjusted parameters (such as the adjusted P, S, E) to the collaborative control unit in real time for subsequent closed-loop control.

[0118] S5.2 Initiates localized induction heating for stress regulation:

[0119] For areas with excessive temperature gradients or excessive residual stress, the collaborative control unit instructs the heating sub-module (such as the local induction heating component) in the partition collaborative control module to start local preheating operation. The local preheating temperature Tpre is corrected by formula (4) to ensure that the preheating temperature is adapted to the current stress state and to avoid overheating or underheating.

[0120] Tpre = T0 + β × (G - G0);

[0121] In formula (4):

[0122] Tpre is the corrected local preheating temperature, in °C, which represents the target preheating temperature that the local induction heating module needs to achieve.

[0123] T0 is the initial preheating reference temperature of the material, in units of ℃, called from the process database (the initial preheating reference temperature of different materials is different to adapt to its heat sensitivity);

[0124] β is the temperature correction coefficient, the value range is 0.8-1.5, determined according to the stress concentration degree of the region (the value of β in the stress concentration region is 1.2-1.5, in order to improve the preheating temperature and enhance the stress release effect; the value of β in the non-concentration region is 0.8-1.0, in order to avoid excessive preheating affecting the forming efficiency);

[0125] G is the current calculated temperature gradient, in units of ℃ / mm, reflecting the thermal stress state of the current region;

[0126] G0 is the temperature gradient reference value, in units of ℃ / mm, called from the process database (it is the average value of the temperature gradient of the material under normal forming conditions, used to judge the deviation degree of the current temperature gradient).

[0127] The local induction heating module preheats the current stress abnormal region according to the corrected preheating temperature Tpre, reduces the temperature difference between the molten pool and the heat-affected zone by increasing the temperature of the heat-affected zone, thereby reducing the generation of thermal stress. During the preheating process, the temperature monitoring submodule needs to monitor the temperature of the preheating region in real time to ensure that the actual preheating temperature is consistent with Tpre.

[0128] S5.3 Start pulse laser impact for stress control:

[0129] For the regions prone to high residual stress (such as the joint between the support and the substrate, the joint between the thick wall and the thin wall, etc.), which are characterized by a significant over-standard local residual stress, the pulse impact submodule (such as the pulse laser impact assembly) in the partitioned collaborative control module is instructed by the collaborative control unit to start the pulse laser impact operation. The principle of pulse laser impact is that the shock wave generated by pulse laser acts on the surface of the part, causing plastic deformation of the local material, thereby releasing the internal residual stress.

[0130] The impact times of the pulse laser impact module are positively related to the residual stress value of the current region: the collaborative control unit calculates the difference between the residual stress value and the safety threshold according to the local residual stress data collected by the ultrasonic stress detector. The greater the difference, the more the impact times; the smaller the difference, the fewer the impact times. During the impact process, the deformation monitoring submodule needs to monitor the deformation amount change of the part in real time. If the deformation amount abnormally increases, it will be fed back to the collaborative control unit in time to adjust the impact parameters (such as reducing the impact intensity and reducing the impact times).

[0131] S5.4 Synchronize coordination of spot adjustment and stress control operation:

[0132] In the execution of spot parameter adjustment, local induction heating and pulsed laser shock operation, the cooperative control unit needs to realize the synchronous coordination of the three types of operations:

[0133] 1. Time synchronization: spot parameter adjustment and local induction heating need to be started at the same time to ensure that the preheating effect is synchronized with the spot energy input, avoiding the increase of stress caused by the fact that the preheating is not in place when the spot energy is input;

[0134] 2. Parameter coordination: if the spot energy density E is reduced, the local preheating temperature Tpre is also reduced synchronously (by adjusting the value of β in formula 4), to avoid excessive heating caused by the reduction of energy input but the preheating temperature being too high;

[0135] 3. Feedback synchronization: the real-time data of the three types of operations (such as the adjusted spot parameters, the actual preheating temperature and the number of shocks) need to be transmitted synchronously to the cooperative control unit to ensure that the cooperative control unit can master the regulation and control effect in real time and provide basis for subsequent closed-loop correction.

[0136] Step S6: correction of subsequent forming parameters through closed-loop control:

[0137] Step S6, after the cooperative control operation in step S5, based on the feedback results of the adjusted spot parameters and the stress-related data, corrects the parameters of the subsequent forming steps through a closed-loop control algorithm, realizes the closed-loop cooperative control of "monitoring-analysis-adjustment", and ensures the stability of the stress state in the subsequent forming process, which includes the following sub-steps:

[0138] S6.1 Collect feedback data after cooperative control:

[0139] After the cooperative control unit performs the cooperative control operation in step S5, it instructs the multi-dimensional stress monitoring module to re-collect the stress-related data of the current area as feedback data:

[0140] 1. Temperature data: re-collect the adjusted molten pool center temperature T1' and the heat affected zone edge temperature T2', and calculate the new temperature gradient G'=|T1'-T2'| / d;

[0141] 2. Deformation data: re-collect the adjusted part deformation ΔL', and compare the difference between ΔL' and the allowable deformation threshold ΔLmax;

[0142] 3. Residual stress data: re-collect the adjusted local residual stress data and judge whether it is below the safety threshold;

[0143] 4. Spot parameter feedback data: the dynamic beam shaping module feeds back the actual spot parameters (such as output power P, effective action area S, energy density E) after adjustment;

[0144] 5. Stress regulation operation feedback data: the partition coordination regulation module feeds back the actual executed preheating temperature Tpre' and the number of pulse laser impacts N'.

[0145] The above feedback data needs to be compared with the data before regulation (such as G, AL, residual stress value) to evaluate the effect of coordination regulation. If the feedback data shows that the stress abnormality is relieved (such as G' < G, AL' < ALmax, and the residual stress value is below the safety threshold), it is determined that the regulation is effective. If the stress abnormality is not relieved, it is determined that the regulation effect is not good, and the parameters need to be further corrected.

[0146] S6.2 Correct the output power of the subsequent light beam:

[0147] For the case that the regulation effect is not good or needs to be further optimized, the coordination control unit corrects the output power P' of the next light beam through a closed-loop control algorithm combined with formula (5), to ensure that the energy input of the subsequent light beam is accurately matched with the current stress state:

[0148] P' = P x [1 - γ x (AL - ALmax) / ALmax];

[0149] In formula (5):

[0150] P' is the corrected light beam output power, with the unit of W, which is the target output power of the light beam in the subsequent forming step;

[0151] P is the current light beam output power, with the unit of W, which is the adjusted light beam output power in step S5;

[0152] γ is the power correction coefficient, with the value range of 0.5-1.0, which is determined according to the thermal conductivity of the material (for high thermal conductivity materials, γ takes the value of 0.5-0.7, because the material dissipates heat quickly, it needs to adjust the power slightly to change the energy input; for low thermal conductivity materials, γ takes the value of 0.8-1.0, because the material dissipates heat slowly, it needs to adjust the power significantly to effectively change the energy input);

[0153] AL is the actual deformation of the current monitoring area, with the unit of mm, which is collected by the laser displacement sensor (i.e. AL' in step S6.1);

[0154] ALmax is the allowable deformation threshold, with the unit of mm, which is calculated by formula (3).

[0155] The correction logic of formula (5) is: if the actual deformation amount ΔL > ΔLmax, (ΔL-ΔLmax) / ΔLmax is positive, the corrected power P' < P, the energy input is reduced by reducing the power to relieve the deformation; if the actual deformation amount ΔL < ΔLmax, (ΔL-ΔLmax) / ΔLmax is negative, the corrected power P' > P, the power is increased to ensure sufficient cladding, while avoiding poor fusion caused by too low power.

[0156] S6.3 Optimizing subsequent forming parameters based on the process database:

[0157] The collaborative control unit stores all the data of this collaborative control (including stress-related data before control, parameter adjustment data during control, and feedback data after control) into the process database, realizing iterative updating of the database. When correcting subsequent forming parameters, the collaborative control unit calls historical forming data of similar materials and similar structural parts from the process database, compares the differences between the current data and the historical data, and optimizes the parameter adjustment strategy:

[0158] 1. If the current part is the first time to form this type of structure, the collaborative control unit sets the initial parameters (such as spot parameters, preheating temperature, and impact times) for subsequent forming based on the control data this time;

[0159] 2. If the current part is batch forming, the collaborative control unit compares the forming data of this time and the previous parts, and if it finds that the stress anomaly in a certain area repeatedly occurs, it optimizes the initial parameters of that area (such as increasing the initial spot energy density of that area or adjusting the initial preheating temperature) to reduce the occurrence of stress anomaly from the source.

[0160] Iterative updating of the process database not only improves the stability of subsequent forming of the current part, but also provides better parameter reference for the forming of subsequent similar parts, realizing continuous optimization of the process.

[0161] S6.4 Perform subsequent forming with corrected parameters:

[0162] The collaborative control unit sends the corrected parameters such as the output power of the light beam P', the effective action area of the spot S', the local preheating temperature Tpre', and the number of pulse laser impacts N' to the dynamic light beam shaping module and the partition collaborative control module respectively, and starts the subsequent forming step. In the subsequent forming process, the multi-dimensional stress monitoring module needs to continuously collect stress-related data, and the collaborative control unit needs to continuously analyze the data and correct the parameters, forming a closed-loop control cycle of "monitoring-analysis-adjustment-re-monitoring-re-analysis-re-adjustment", to ensure that the stress state of the part is always within the safe range during the entire forming process, and finally realize high-quality and low-stress selective laser melting forming.

[0163] The scheme can effectively reduce the temperature gradient of the molten pool and the heat affected zone and reduce the stress concentration at the junction of the regions by dynamic light spot shaping optimization of energy distribution, combined with local induction heating and synergistic regulation of pulse laser impact. Compared with the traditional single regulation mode, the local residual stress of the part can be targeted to be relieved, the deformation, cracking and other problems caused by stress in the forming process are greatly reduced, and it is especially suitable for materials and complex structure parts sensitive to residual stress. The differentiated light spot parameters are adapted to the characteristics of different regions to ensure the dimensional accuracy of the contour area flat-top light spot, improve the cladding efficiency of the filling area Gaussian light spot, and eliminate the energy mutation hidden danger of the transition area gradient light spot. Without additional post-heat treatment process, the overall production cycle is shortened while ensuring the forming precision of the part, realizing the dual optimization of "precision-efficiency". The combination of multi-dimensional stress monitoring and closed-loop control reduces the influence of human intervention on the process, and the consistency of stress distribution and dimensional accuracy of the parts is significantly improved during batch forming, and the process parameter fluctuation range is reduced. At the same time, the process database can be iteratively updated based on the forming data, and can adapt to different types of materials (such as titanium alloy, high-temperature alloy, etc.) and complex structures (such as thin-walled parts, hollow parts, multi-region transition structures, etc.), widening the application range of the selective melting process. The dynamic updating mechanism of the process database in the scheme can continuously accumulate forming data in different scenarios, and optimize the matching relationship of "light spot parameters-stress regulation parameters". With the increase of data volume, the parameter adjustment accuracy of the synergistic control unit and the stress abnormality prediction ability will continue to improve, realizing the self-iteration and improvement of the process, and providing support for long-term stable production.

[0164] The above only describes the preferred embodiments of the present application, and it should be understood that the present application is not limited to the forms disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified by the above teachings or related art or knowledge within the scope of the concept described herein. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the appended claims of the present application.

Claims

1. A selective melting beam shaping and residual stress regulation synergic method, characterized in that, The method comprises the following steps: S1. Obtain slice data of a part to be formed, and analyze characteristic parameters of each region in the slice data; S2. Based on the characteristic parameters, adjust the spot parameters of the light beam in real time through a dynamic light beam shaping module; S3. In the selective melting forming process, the stress correlation data of the molten pool and the heat affected zone are collected in real time through a multi-dimensional stress monitoring module; S4. The stress correlation data is transmitted to a cooperative control unit, which analyzes the stress correlation data based on a preset correlation model, and judges whether there is stress abnormality in the current forming region; S5. If there is stress abnormality, the cooperative control unit generates a cooperative control instruction to synchronously control the dynamic light beam shaping module to adjust the spot parameters and control the partition cooperative control module to perform stress control operation, so as to realize the cooperation of light beam shaping and residual stress control; S6. Based on the adjusted parameters and feedback data, the cooperative control unit corrects the subsequent forming parameters through a closed-loop control algorithm to complete the closed-loop cooperative control of "monitoring-analysis-adjustment".

2. The method of claim 1, wherein, In the step S1, the characteristic parameters include region types, including contour region, filling region and transition region, and the material thickness of the corresponding region.

3. The method according to claim 1 or 2, characterized in that, In the step S2, the spot parameters include spot shape, energy density distribution and spot size; when the dynamic light beam shaping module adjusts the spot shape, the contour region corresponds to output flat-top spot, the filling region corresponds to output Gaussian spot, and the transition region corresponds to output gradient spot.

4. The method of claim 3, wherein, The shape transition of the gradient spot is controlled by the spot edge energy decay rate, which is linearly adjusted with the material thickness of the transition region.

5. The method of claim 4, wherein, In the step S3, the stress correlation data includes temperature data, part deformation data and local residual stress data; the multi-dimensional stress monitoring module collects temperature data through an infrared thermal imager, collects deformation data through a laser displacement sensor, and collects local residual stress data through an ultrasonic stress detector.

6. The method of claim 5, wherein, In the step S4, the preset correlation model is a "temperature gradient-deformation-residual stress" correlation model; when the cooperative control unit judges the stress abnormality, the allowable deformation threshold of the current region is calculated first, and then the actual deformation is compared with the threshold; if the actual deformation exceeds the threshold, it is determined that there is stress abnormality.

7. The method of claim 6, wherein, In the step S5, the stress control operation of the partition cooperative control module includes local induction heating and pulse laser impact; if the current region is the joint of the support and the base, the pulse laser impact is started synchronously, and the impact times are positively correlated with the residual stress value of the current region.

8. The method of claim 7, wherein, In the step S6, the closed-loop control algorithm dynamically corrects the light beam output power and the local preheating temperature based on the parameter matching relationship of different materials and part structures in a process database, and the process database can be iteratively updated based on the forming data.

9. A selective laser melting beam shaping and residual stress regulation synergic system, characterized in that, It comprises: a dynamic light beam shaping module for adjusting the spot parameters of the light beam in real time according to the region characteristics of the part slice; a multi-dimensional stress monitoring module for collecting stress correlation data of the molten pool and the heat affected zone; The partition cooperative regulation module is used for performing stress regulation operation on the stress abnormal area; the cooperative control unit is respectively connected with the dynamic light beam shaping module, the multi-dimension stress monitoring module and the partition cooperative regulation module in signal connection, is used for receiving stress associated data, analyzing stress abnormal state, generating cooperative regulation instruction and realizing closed loop control; the process database is connected with the cooperative control unit in signal connection, is used for storing process parameter associated data and providing data support for cooperative control.

10. The system of claim 9, wherein, The multi-dimension stress monitoring module comprises a temperature monitoring sub-module, a deformation monitoring sub-module and a stress monitoring sub-module; the partition cooperative regulation module comprises a heating sub-module and a pulse impact sub-module; the cooperative control unit is internally provided with a preset associated model and a closed loop control algorithm, and can optimize regulation parameters based on the process database.

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