Closed-loop control friction solid-phase additive manufacturing method and system for gradient material accurate forming

Abstract

The invention provides a gradient material accurate forming-oriented closed-loop control friction solid-phase additive manufacturing method and system. The invention discloses a closed-loop control friction solid-phase additive manufacturing method for gradient material accurate forming. The method comprises the following steps that S1, a metal substrate is prepared, and a reference digital twin model is loaded; s2, depositing a first metal layer by adopting a friction solid-phase additive process; s3, at a preset interval of completing one-layer deposition or multi-layer deposition, the current actually-measured forming surface of the workpiece is scanned to obtain three-dimensional point cloud data of the workpiece; s4, generating a three-dimensional shape deviation graph containing positive and negative deviation values of each coordinate point; s5, generating a compensatory manufacturing scheme for depositing a next layer; s6, the friction solid-phase additive manufacturing equipment is driven to execute a compensatory manufacturing scheme to deposit a next layer; and S7, the steps S3-S6 are repeatedly executed. According to the method, the component precision of the gradient material component can be maintained while morphology compensation is carried out.

Description

Technical Field

[0001] The present invention relates to a friction solid-phase additive manufacturing method and system, and in particular to a closed-loop controlled friction solid-phase additive manufacturing method and system for precise forming of gradient materials, belonging to the technical field of metal additive manufacturing. Background Art

[0002] Friction solid-phase additive manufacturing (FSAM) uses intense frictional heat generation and mechanical stirring to build up metal materials layer by layer in a plastic state below their melting point. By avoiding the melting and solidification of the metal, this technology effectively suppresses metallurgical defects such as cracks, pores, and high residual stresses common in traditional melt additive manufacturing. It exhibits unique advantages in the fabrication of dissimilar metals and gradient material components.

[0003] However, most existing friction solid-phase additive manufacturing processes use open-loop control, meaning the entire manufacturing process is strictly executed according to preset process parameters such as rotational speed, forward speed, and axial force. This open-loop control method cannot cope with the complex and dynamically changing physical fields during the manufacturing process. Friction solid-phase additive manufacturing is essentially a violent thermal-mechanical coupling process. The deposition of each layer will produce complex thermal cycles and stress evolution in the formed part, resulting in unpredictable thermally induced deformation of the workpiece and non-uniform accumulation of materials. This deformation and accumulation error accumulates layer by layer, ultimately resulting in significant deviations between the actual formed part and the theoretical three-dimensional model in terms of key dimensions and surface morphology.

[0004] This problem is particularly prominent in the manufacture of components made of gradient materials. Because the material composition of different locations within a component continuously changes, its thermophysical properties, such as thermal conductivity and thermal expansion coefficient, also vary accordingly, making the prediction and control of thermal deformation extremely difficult. Ultimately, high-performance gradient material components manufactured through open-loop control often require extensive subsequent CNC machining to correct their morphology and dimensions. This not only significantly increases manufacturing costs and cycle time, but can even lead to direct scrapping due to insufficient machining allowances or excessive deformation. Summary of the Invention

[0005] Based on the above background, the purpose of the present invention is to provide a closed-loop controlled friction solid phase additive manufacturing method and system for precise forming of gradient materials, so as to solve the problem of cumulative morphological errors caused by the thermal-mechanical coupling effect in the friction solid phase additive manufacturing process, maintain the composition accuracy of gradient material components while performing morphological compensation, and significantly improve the dimensional accuracy and forming quality of the final components.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials is disclosed. The method is used to be performed in a friction solid phase additive manufacturing system having friction solid phase additive manufacturing equipment, a non-contact three-dimensional optical scanner, and a central control unit. The method includes the following steps:

[0008] S1. Prepare a metal substrate and load a reference digital twin model containing the target part's three-dimensional geometric information, a preset process parameter window, and an interlayer material composition gradient distribution scheme into the central control unit;

[0009] S2. Depositing a first metal layer on the metal substrate using a friction solid phase additive process according to preset parameters in the reference digital twin model;

[0010] S3. During a predetermined interval between the completion of one layer of deposition or multiple layers of deposition, driving the non-contact three-dimensional optical scanner to scan the currently measured forming surface of the workpiece to obtain three-dimensional point cloud data thereof;

[0011] S4, registering and digitally comparing the three-dimensional point cloud data obtained in step S3 with the corresponding theoretical forming surface in the reference digital twin model to generate a three-dimensional topography deviation map containing positive and negative deviation values ​​of each coordinate point;

[0012] S5. Generating a compensatory manufacturing plan for depositing a next layer based on the three-dimensional topography deviation map, the compensatory manufacturing plan comprising a corrected tool path and dynamically modulated process parameters associated with each point on the path;

[0013] S6. driving the friction solid phase additive manufacturing apparatus to execute a compensatory manufacturing scheme to deposit a next layer, wherein at least one of a tool rotation speed, a forward speed, an axial forging force, or a material feed rate of the friction solid phase additive manufacturing apparatus is changed in real time according to a dynamically modulated process parameter based on the real-time position of the apparatus on the path, so as to locally and actively compensate for the topography deviation of the previous layer;

[0014] S7. Repeat steps S3-S6 until the entire gradient material component is manufactured.

[0015] Preferably, in step S3, while driving the non-contact three-dimensional optical scanner, the non-contact infrared thermal imager is also driven to synchronously scan the measured forming surface to obtain its surface temperature distribution map; in step S4, the three-dimensional morphology deviation map and the surface temperature distribution map are fused to generate a thermal-morphology coupling deviation map; in step S5, when generating the compensatory manufacturing plan, the coordinated compensation of morphology deviation and heat accumulation deviation is considered at the same time.

[0016] This step expands the control dimension from simple geometric morphology to thermal physics, and can further deal with problems of uneven material properties or secondary deformation caused by local overheating or overcooling.

[0017] Preferably, in step S5, the coordinated compensation of the morphology deviation and the heat accumulation deviation is achieved by a weighted multi-objective optimization algorithm, and the expression of the weighted multi-objective optimization algorithm is:

[0018] J=W E ×∑(E i ) 2 +W T ×∑(T i -T t ) 2 ;

[0019] Where J is the total cost function to be minimized, E i To compensate for the predicted residual morphology deviation of the i-th sampling point in the region, T i is the predicted peak temperature of the i-th sampling point in the compensation area, T t W is the upper limit of target process temperature in compensation region. E is the shape deviation weight, W T is the thermal accumulation deviation weight, and satisfies W E +W T =1.

[0020] Preferably, in step S5, the logic for generating the compensatory manufacturing solution includes:

[0021] For a negative deviation area detected in the three-dimensional topography deviation map, instructing the friction solid phase additive manufacturing device to reduce the forward speed and / or increase the material feed rate when depositing the next layer passing through the negative deviation area, so as to achieve excess deposition of material to fill the negative deviation area;

[0022] For the positive deviation area detected in the three-dimensional morphology deviation map, the friction solid phase additive manufacturing equipment is instructed to reduce the axial forging force and / or reduce the material feed rate when depositing the next layer passing through the positive deviation area, so as to achieve under-deposition of material for flattening.

[0023] Preferably, in step S5, the dynamically modulated process parameters are calculated by a volume conservation compensation algorithm, and the volume conservation compensation algorithm includes the following steps:

[0024] Calculating the material surplus or deficit volume of the target compensation area by performing surface integral of the deviation value within the target compensation area according to the three-dimensional topography deviation map;

[0025] Solving an optimization problem with a least square sum of residual deviations between the compensated surface and the theoretical surface as an objective function to determine the distribution of the forward speed or material feed rate in the target compensation area as a continuous function when the next layer passes through the target compensation area, so that the volume of the newly deposited material offsets the surplus or deficit volume of the material;

[0026] The expression of volume conservation compensation algorithm is:

[0027] ΔV=∫∫AE(x,y)dA;

[0028] Where A is the target compensation area, ΔV is the material surplus or loss volume of the target compensation area, and E(x, y) is the height deviation value at the coordinate point (x, y) in the three-dimensional topography deviation map.

[0029] The algorithm realizes regional volume compensation, avoids the introduction of new surface defects due to local drastic compensation, and ensures smooth transition of the compensation area.

[0030] Preferably, in step S5, when generating a compensatory manufacturing scheme for depositing the next layer, a pre-trained prediction model is used to predict the residual deviation or thermally induced secondary deformation that may be generated in the next layer after performing standard compensation based on the three-dimensional morphology deviation map data of the current layer and historical layers, and the compensatory manufacturing scheme is feed-forward corrected to offset the predicted deviation.

[0031] This step further introduces feedforward control to deal with the inertial accumulation and hysteresis effects of errors in an active and predictive manner.

[0032] Preferably, the prediction model is a long short-term memory network model, the input of the prediction model is a time series data set consisting of three-dimensional morphological deviation maps of the current layer and multiple historical layers in the past, and the output of the prediction model is the predicted residual deviation map of the next layer without applying feedforward correction.

[0033] The friction solid phase additive manufacturing process has a long-term memory effect, and the structure of the long short-term memory network model is particularly suitable for dealing with such time series dependency problems.

[0034] Preferably, in step S6, when overdeposition or underdeposition of material is performed at point (x, y), for the gradient material composed of two materials M1 and M2, their respective independent material feed rates f1 and f2 are determined by a real-time component fidelity algorithm, and the real-time component fidelity algorithm includes the following set of constraint equations:

[0035] f1+f2=ft;

[0036] ∫(f1)dt / (∫(f1)dt+∫(f2)dt)=Ct;

[0037] Where ft is the total material feed rate for morphology correction determined by the compensatory manufacturing scheme, Ct is the target composition concentration of material M1 defined by the reference digital twin model at point (x, y), f1 is the feed rate of material M1, f2 is the feed rate of material M2, and ∫()dt is the cumulative feed amount from the beginning of the component to the current moment.

[0038] The present invention further provides a manufacturing system using the closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials, the system comprising:

[0039] A friction solid phase additive manufacturing device comprising a friction head for performing rotational and forward motions and a corresponding drive unit;

[0040] Non-contact 3D optical scanner;

[0041] a central control unit electrically connected to the friction solid phase additive manufacturing device and the non-contact three-dimensional optical scanner via a communication bus;

[0042] Wherein, the central control unit is configured as follows:

[0043] Receive and store a reference digital twin model containing geometric information, process parameters, and material gradient distribution;

[0044] During the inter-layer manufacturing interval, controlling the non-contact three-dimensional optical scanner to scan the surface of the workpiece to obtain measured three-dimensional data;

[0045] Comparing the measured three-dimensional data with the reference digital twin model to generate a three-dimensional shape deviation map;

[0046] Based on the three-dimensional topography deviation map, calculating and generating a compensatory manufacturing solution including a modified tool path and dynamically modulated process parameters; and,

[0047] The friction solid phase additive manufacturing device is controlled to perform deposition of the next layer according to the compensatory manufacturing plan.

[0048] Preferably, the system further comprises a non-contact infrared thermal imager, and the central control unit is further configured to:

[0049] The data of the non-contact three-dimensional optical scanner and the non-contact infrared thermal imager are integrated to perform thermal-morphological coupling deviation analysis and coordinated compensation.

[0050] Compared with the prior art, the present invention has the following advantages:

[0051] The present invention provides a closed-loop controlled friction solid-phase additive manufacturing method for precise forming of gradient materials. It uses a closed-loop control strategy of layer-by-layer detection and layer-by-layer compensation to effectively suppress the layer-by-layer accumulation of morphology errors caused by thermal deformation and non-uniform material stacking. By fusing multi-source sensing information such as three-dimensional morphology and surface temperature and adopting a weighted multi-objective optimization algorithm, it can make a trade-off between dimensional accuracy and thermal damage suppression, and achieve coordinated optimization control of component geometric morphology and internal performance. For gradient material components, a real-time composition fidelity algorithm is used to compensate for the morphology while dynamically solving the independent feed rates of multiple material sources to ensure that the final chemical composition of the compensation area remains highly consistent with the theoretical design value. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0053] Figure 1 This is a flow chart of a closed-loop controlled friction solid-phase additive manufacturing method for precise forming of gradient materials according to the present invention. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be further described in detail below through specific embodiments and in conjunction with the accompanying drawings. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any form of modification and / or change made to the present invention will fall within the scope of protection of the present invention.

[0055] In the present invention, unless otherwise specified, all parts and percentages are by weight. The equipment and raw materials used are commercially available or commonly used in the art. The methods in the following embodiments, unless otherwise specified, are conventional methods in the art. The components or equipment in the following embodiments, unless otherwise specified, are all universal standard parts or components known to those skilled in the art. Their structures and principles are known to those skilled in the art through technical manuals or routine experimental methods.

[0056] The following detailed description of the embodiments of the present invention is made in conjunction with the accompanying drawings. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present invention. However, one or more embodiments may be implemented by those skilled in the art without these specific details.

[0057] An embodiment of the present invention discloses a closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials. The method is performed in a friction solid phase additive manufacturing system having friction solid phase additive manufacturing equipment, a non-contact three-dimensional optical scanner, and a central control unit. The method includes the following steps:

[0058] S1. Prepare a metal substrate and load a reference digital twin model containing the target part's 3D geometry information, preset process parameter windows, and interlayer material composition gradient distribution scheme into the central control unit.

[0059] S2. Depositing the first metal layer on the metal substrate using a tribo-solid-phase additive manufacturing process according to the preset parameters in the reference digital twin model.

[0060] S3. During a predetermined interval between the completion of one layer of deposition or multiple layers of deposition, a non-contact three-dimensional optical scanner is driven to scan the currently measured forming surface of the workpiece to obtain three-dimensional point cloud data thereof;

[0061] S4, registering and digitally comparing the three-dimensional point cloud data obtained in step S3 with the corresponding theoretical forming surface in the reference digital twin model to generate a three-dimensional topography deviation map containing the positive and negative deviation values ​​of each coordinate point;

[0062] S5. generating a compensatory manufacturing plan for depositing a next layer based on the three-dimensional topography deviation map, the compensatory manufacturing plan including a corrected tool path and dynamically modulated process parameters associated with positions of various points on the path;

[0063] S6. driving the friction solid phase additive manufacturing apparatus to execute a compensatory manufacturing scheme to deposit a next layer, wherein at least one of a tool rotation speed, a forward speed, an axial forging force, or a material feed rate of the friction solid phase additive manufacturing apparatus is changed in real time according to a dynamically modulated process parameter based on the real-time position of the friction solid phase additive manufacturing apparatus on the path, so as to locally and actively compensate for the morphology deviation of the previous layer;

[0064] S7. Repeat steps S3-S6 until the entire gradient material component is manufactured.

[0065] The following will refer to Figure 1 , the specific implementation steps of the method of the present invention are described in detail.

[0066] Step S1: Model loading and system initialization

[0067] A reference digital twin model containing complete manufacturing information is loaded into the central control unit. The model is a multi-dimensional information collection, which specifically includes:

[0068] Geometric information: The complex structure of the target part, such as the three-dimensional shape and internal flow channel, represented in the form of high-precision meshes or voxels.

[0069] Material distribution information: A 3D spatial map that precisely defines the target material composition for each voxel (x, y, z) within the part. For example, for a gradient component composed of aluminum (M1) and magnesium (M2), the map would specify that the composition at point (x1, y1, z1) should be 90% M1 + 10% M2, while at point (x2, y2, z2) it should be 30% M1 + 70% M2.

[0070] Process parameter window: A database based on materials science and empirical data that recommends reasonable initial process parameter ranges for different material composition combinations, including but not limited to tool speed, forward speed, axial forging force, etc.

[0071] Step S2: First layer deposition

[0072] Based on the information in the digital twin model, the central control unit controls the friction solid phase additive manufacturing equipment to deposit the first layer or the first few layers on the cleaned and clamped metal substrate.

[0073] Step S3: Online measurement between layers

[0074] Once the preset number of layers is deposited, the mixing head automatically retracts to a safe position. The central control unit then drives the in-line measurement unit to directly above the workpiece, scanning the measured surface just deposited. The preset number of layers is typically one, but can be multiple for larger components.

[0075] Three-dimensional topography scanning is achieved by scanning the surface with a preset resolution using a line laser profiler or structured light scanner, quickly acquiring three-dimensional point cloud data consisting of millions of points.

[0076] Synchronous thermal field scanning is achieved by using a non-contact infrared thermal imager working in sync with a 3D scanner to capture the temperature distribution on the workpiece surface. Because frictional solid-phase additive manufacturing involves a highly coupled thermomechanical process, topographical deviations are often directly related to localized excessive heat accumulation. Obtaining this temperature distribution provides critical physical field information for subsequent analysis and coordinated compensation.

[0077] Step S4: Multiphysics Deviation Analysis and Quantification

[0078] This step is automatically completed by software algorithms within the central control unit.

[0079] The spatial registration uses the iterative closest point (ICP) algorithm to perform high-precision spatial alignment of the measured point cloud data with real-world coordinates obtained in step S3 with the corresponding theoretical level in the digital twin model to eliminate systematic errors caused by installation or positioning.

[0080] Deviation calculation and visualization is achieved by calculating the normal distance E(x,y) from each measured point cloud data point to the theoretical surface, thereby generating a colored 3D topography deviation map. In this map, red areas represent protrusions that are higher than the theoretical surface, and blue areas represent pits that are lower than the theoretical surface.

[0081] Data fusion is achieved by fusing the topography deviation map with the simultaneously acquired temperature distribution map at the pixel or region level. This generates a coupled thermal-topography deviation map. For example, it can visually reveal that a dark blue pit region corresponds to a dark red high-temperature area, providing data support for the control system to determine that the pit is caused by local overheating leading to material softening and collapse.

[0082] Step S5: Generation of compensatory manufacturing solutions

[0083] Based on the deviation map, the central control unit generates a compensatory manufacturing plan for the next layer through a series of advanced algorithms.

[0084] Simple feedback control approaches, such as a strategy of filling as many pits as possible, are ineffective and even harmful in complex friction solid-phase additive manufacturing processes. This is because process parameters are strongly coupled. For example, reducing speed to increase deposition also dramatically increases heat input, and errors are both lagging and cumulative. Therefore, this application employs a multi-level, multi-model intelligent decision-making algorithm.

[0085] A simple point-to-point compensation approach involves adding 0.1mm to the path of the next layer if point A is 0.1mm lower. This can cause dramatic parameter jumps at the edges of the compensation area, introducing new stress concentrations and surface defects. Therefore, this application uses a volume conservation compensation algorithm to calculate dynamically modulated process parameters.

[0086] The volume conservation compensation algorithm includes the following steps:

[0087] According to the three-dimensional morphology deviation map, the material surplus and deficit volume of the target compensation area is calculated by performing surface integral on the deviation value in the target compensation area.

[0088] Solving an optimization problem with a least square sum of residual deviations between the compensated surface and the theoretical surface as an objective function to determine the distribution of the forward speed or material feed rate in the target compensation area as a continuous function when the next layer passes through the target compensation area, so that the volume of the newly deposited material offsets the surplus or deficit volume of the material;

[0089] The expression of volume conservation compensation algorithm is:

[0090] ΔV=∫∫AE(x,y)dA;

[0091] Where A is the target compensation area, ΔV is the material surplus or loss volume of the target compensation area, and E(x, y) is the height deviation value at the coordinate point (x, y) in the three-dimensional topography deviation map.

[0092] The algorithm first accurately calculates the material surplus or deficit volume ΔV that needs to be compensated by performing a surface integral of the deviation value E(x,y) over the entire pit or bump area A. It then transforms the compensation problem into an optimization problem: finding a parameter function that varies continuously over area A so that when the next layer passes through this area, the volume of newly deposited material is exactly equal to ΔV and smoothly transitions with the surrounding area.

[0093] When processing the thermal-morphological coupling deviation map, correcting the morphology may aggravate heat accumulation, while suppressing heat accumulation may make the pitting more serious. Therefore, this application uses a weighted multi-objective optimization algorithm to achieve synergistic compensation for morphological deviation and thermal accumulation deviation. The expression of the weighted multi-objective optimization algorithm is:

[0094] J=W E ×∑(E i ) 2 +W T ×∑(T i -T t ) 2 ;

[0095] Where J is the total cost function to be minimized, E i To compensate for the predicted residual morphology deviation of the i-th sampling point in the region, T i is the predicted peak temperature of the i-th sampling point in the compensation area, T t W is the upper limit of target process temperature in compensation region. E is the shape deviation weight, W T is the thermal accumulation deviation weight, and satisfies W E +W T =1.

[0096] The algorithm makes intelligent trade-offs by minimizing a total cost function J, which is a weighted sum of the topographic deviation cost and the thermal deviation cost. E and W T According to the specific working conditions, for example, when manufacturing the final forming surface with extremely high dimensional accuracy requirements, W can be set E =0.8 and W T =0.2, giving priority to ensuring the morphology; when manufacturing thin-walled structures that are prone to thermal cracks, W can be set E =0.3 and W T =0.7, giving priority to thermal stability. The algorithm searches for a set of process parameter combinations that minimize the total cost function J through iterative calculation, thereby achieving the best balance between the two conflicting objectives.

[0097] The friction solid phase additive process has significant inertia and memory effects, that is, the defects generated in a certain layer will have an impact that will be reflected in the next few layers with a lag and accumulation. Simply looking at the hysteresis feedback control of the previous layer cannot eradicate this systematic deviation. Therefore, when generating a compensatory manufacturing scheme for depositing the next layer, the present application uses a pre-trained prediction model based on the three-dimensional morphology deviation map data of the current layer and historical layers to predict the residual deviation or thermally induced secondary deformation that may be generated in the next layer after performing standard compensation, and performs feedforward correction on the compensatory manufacturing scheme to offset the predicted deviation. The prediction model is a long short-term memory network model. The input of the prediction model is a time series data set composed of the three-dimensional morphology deviation map of the current layer and multiple historical layers in the past. The output of the prediction model is the predicted residual deviation map of the next layer without applying feedforward correction.

[0098] During the training phase, the predictive model learns from a large amount of historical manufacturing data to understand the inherent patterns between one deviation map sequence and the residual deviation of the next layer. In actual manufacturing, the trained model receives the actual deviation map sequence of the past several layers as input and outputs a predicted residual deviation map. This predicted map represents the deviation that is likely to occur in the next layer even after standard compensation is applied. The central control unit uses the negative value of this predicted deviation map as a feedforward correction and adds it to the compensation solution generated by the algorithm.

[0099] Step S6: Performing compensatory deposition

[0100] The central control unit compiles the resulting compensatory manufacturing plan into machine-executable code, driving the equipment to deposit the next layer.

[0101] When the algorithm of step S5 decides to increase the total material feed rate f to fill a pit, t When the increase is 20%, how to allocate this 20% increment to the feed rate f1 of the M1 material and the feed rate f2 of the M2 material is the core problem in the manufacture of gradient materials. If both f1 and f2 are simply increased by 20%, the material composition ratio in the compensation area will remain unchanged, but its cumulative composition will deviate from the theoretical design value due to the over-deposition here. Therefore, when the present application performs over-deposition or under-deposition of materials at point (x, y), for the gradient material composed of two materials M1 and M2, their respective independent material feed rates f1 and f2 are determined by the real-time composition fidelity algorithm. The real-time composition fidelity algorithm includes the following set of constraint equations:

[0102] f1+f2=ft;

[0103] ∫(f1)dt / (∫(f1)dt+∫(f2)dt)=Ct;

[0104] Where ft is the total material feed rate for morphology correction determined by the compensatory manufacturing scheme, Ct is the target composition concentration of material M1 defined by the reference digital twin model at point (x, y), f1 is the feed rate of material M1, f2 is the feed rate of material M2, and ∫()dt is the cumulative feed amount from the beginning of the component to the current moment.

[0105] The control goal of this algorithm is to maintain the fidelity of the cumulative component concentration. In each control cycle, it solves a set of equations containing two core constraints in real time:

[0106] Instantaneous flow constraint (f1+f2=ft): This constraint ensures the effectiveness of the morphology correction, that is, the instantaneous total flow of the two materials must be equal to the value calculated by the morphology compensation algorithm.

[0107] Cumulative composition constraint (∫(f1)dt / (∫(f1)dt+∫(f2)dt)=Ct): This constraint requires that the ratio of the total deposition of M1 material to the total deposition of the two materials from the start of manufacturing to the current moment must be strictly equal to the theoretical composition concentration Ct of material M1 defined by the digital twin model at that point.

[0108] By solving these two equations simultaneously in real time, the algorithm can dynamically and nonlinearly adjust f1 and f2.

[0109] Step S7: Iteration loop

[0110] Repeat steps S3-S6 until the entire gradient material component is manufactured.

[0111] An embodiment of the present invention further discloses a manufacturing system using the closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials, the system comprising:

[0112] A friction solid phase additive manufacturing device comprising a friction head for performing rotational and forward motions and a corresponding drive unit;

[0113] Non-contact 3D optical scanner;

[0114] a central control unit electrically connected to the friction solid phase additive manufacturing device and the non-contact three-dimensional optical scanner via a communication bus;

[0115] The central control unit is configured as follows:

[0116] Receive and store a reference digital twin model containing geometric information, process parameters, and material gradient distribution;

[0117] During the inter-layer manufacturing interval, controlling the non-contact three-dimensional optical scanner to scan the surface of the workpiece to obtain measured three-dimensional data;

[0118] Comparing the measured three-dimensional data with the reference digital twin model to generate a three-dimensional topography deviation map;

[0119] Based on the 3D topography deviation map, a compensatory manufacturing solution is generated by calculation, including a modified tool path and dynamically modulated process parameters; and,

[0120] The friction solid phase additive manufacturing device is controlled to perform deposition of the next layer according to a compensatory manufacturing plan.

[0121] In addition, the system includes a non-contact infrared thermal imaging camera, and the central control unit is configured to:

[0122] The data from a non-contact three-dimensional optical scanner and a non-contact infrared thermal imager are integrated to perform thermal-morphological coupling deviation analysis and collaborative compensation using the closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials.

[0123] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from the principles of the present invention, and such improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A closed-loop controlled friction solid-phase additive manufacturing method for precise forming of gradient materials, characterized by: The method is used to be performed in a friction solid phase additive manufacturing system having a friction solid phase additive manufacturing device, a non-contact three-dimensional optical scanner, and a central control unit, and the method includes the following steps: S1. Prepare a metal substrate and load a reference digital twin model containing the target part's three-dimensional geometric information, a preset process parameter window, and an interlayer material composition gradient distribution scheme into the central control unit; S2. Depositing a first metal layer on the metal substrate using a friction solid phase additive process according to preset parameters in the reference digital twin model; S3. During a predetermined interval between the completion of one layer of deposition or multiple layers of deposition, driving the non-contact three-dimensional optical scanner to scan the currently measured forming surface of the workpiece to obtain three-dimensional point cloud data thereof; S4, registering and digitally comparing the three-dimensional point cloud data obtained in step S3 with the corresponding theoretical forming surface in the reference digital twin model to generate a three-dimensional topography deviation map containing positive and negative deviation values ​​of each coordinate point; S5. Generating a compensatory manufacturing plan for depositing a next layer based on the three-dimensional topography deviation map, the compensatory manufacturing plan comprising a corrected tool path and dynamically modulated process parameters associated with each point on the path; S6. driving the friction solid phase additive manufacturing apparatus to execute a compensatory manufacturing scheme to deposit a next layer, wherein at least one of a tool rotation speed, a forward speed, an axial forging force, or a material feed rate of the friction solid phase additive manufacturing apparatus is changed in real time according to a dynamically modulated process parameter based on the real-time position of the apparatus on the path, so as to locally and actively compensate for the topography deviation of the previous layer; S7. Repeat steps S3-S6 until the entire gradient material component is manufactured.

2. The closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials according to claim 1, characterized in that: In step S3, while driving the non-contact three-dimensional optical scanner, the non-contact infrared thermal imager is also driven to synchronously scan the measured forming surface to obtain its surface temperature distribution map; in step S4, the three-dimensional morphology deviation map and the surface temperature distribution map are fused to generate a thermal-morphology coupling deviation map; in step S5, when generating the compensatory manufacturing plan, the coordinated compensation of morphology deviation and heat accumulation deviation is simultaneously considered.

3. The closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials according to claim 1, characterized in that: In step S5, the coordinated compensation of the morphology deviation and the heat accumulation deviation is achieved by a weighted multi-objective optimization algorithm. The expression of the weighted multi-objective optimization algorithm is: J=W E ×∑(E i ) 2 +W T ×∑(T i -T t ) 2 ; Where J is the total cost function to be minimized, E i To compensate for the predicted residual morphology deviation of the i-th sampling point in the region, T i is the predicted peak temperature of the i-th sampling point in the compensation area, T t W is the upper limit of target process temperature in compensation area. E is the shape deviation weight, W T is the thermal accumulation deviation weight, and satisfies W E +W T =1.

4. The closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials according to claim 1, characterized in that: In step S5, the logic for generating the compensatory manufacturing solution includes: For a negative deviation area detected in the three-dimensional topography deviation map, instructing the friction solid phase additive manufacturing device to reduce the forward speed and / or increase the material feed rate when depositing the next layer passing through the negative deviation area, so as to achieve excess deposition of material to fill the negative deviation area; For the positive deviation area detected in the three-dimensional morphology deviation map, the friction solid phase additive manufacturing equipment is instructed to reduce the axial forging force and / or reduce the material feed rate when depositing the next layer passing through the positive deviation area, so as to achieve under-deposition of material for flattening.

5. The closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials according to claim 1, characterized in that: In step S5, the dynamically modulated process parameters are calculated using a volume conservation compensation algorithm, which includes the following steps: Calculating the material surplus or deficit volume of the target compensation area by performing surface integral of the deviation value within the target compensation area according to the three-dimensional topography deviation map; Solving an optimization problem with a least square sum of residual deviations between the compensated surface and the theoretical surface as an objective function to determine the distribution of the forward speed or material feed rate in the target compensation area as a continuous function when the next layer passes through the target compensation area, so that the volume of the newly deposited material offsets the surplus or deficit volume of the material; The expression of volume conservation compensation algorithm is: ΔV=∫∫AE(x,y)dA; Where A is the target compensation area, ΔV is the material surplus or loss volume of the target compensation area, and E(x, y) is the height deviation value at the coordinate point (x, y) in the three-dimensional topography deviation map.

6. The closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials according to claim 1, characterized in that: In step S5, when generating a compensatory manufacturing scheme for depositing the next layer, a pre-trained prediction model is used to predict the residual deviation or thermally induced secondary deformation that may be generated in the next layer after performing standard compensation based on the three-dimensional morphology deviation map data of the current layer and historical layers, and the compensatory manufacturing scheme is feedforward corrected to offset the predicted deviation.

7. The closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials according to claim 6, characterized in that: The prediction model is a long short-term memory network model. The input of the prediction model is a time series data set consisting of three-dimensional morphological deviation maps of the current layer and multiple historical layers in the past. The output of the prediction model is the predicted residual deviation map of the next layer without applying feedforward correction.

8. The closed-loop controlled friction solid phase additive manufacturing method for precise forming of gradient materials according to claim 1, characterized in that: In step S6, when overdeposition or underdeposition of material is performed at point (x, y), for the gradient material composed of two materials M1 and M2, the independent material feed rates f1 and f2 are determined by a real-time component fidelity algorithm, which includes the following set of constraint equations: f1+f2=ft; ∫(f1)dt / (∫(f1)dt+∫(f2)dt)=Ct; Where ft is the total material feed rate for morphology correction determined by the compensatory manufacturing scheme, Ct is the target composition concentration of material M1 defined by the reference digital twin model at point (x, y), f1 is the feed rate of material M1, f2 is the feed rate of material M2, and ∫()dt is the cumulative feed amount from the beginning of the component to the current moment.

9. A manufacturing system using the closed-loop controlled friction solid phase additive manufacturing method for precise shaping of gradient materials according to any one of claims 1 to 8, characterized in that: The system includes: A friction solid phase additive manufacturing device comprising a friction head for performing rotational and forward motions and a corresponding drive unit; Non-contact 3D optical scanner; a central control unit electrically connected to the friction solid phase additive manufacturing device and the non-contact three-dimensional optical scanner via a communication bus; Wherein, the central control unit is configured as follows: Receive and store a reference digital twin model containing geometric information, process parameters, and material gradient distribution; During the inter-layer manufacturing interval, controlling the non-contact three-dimensional optical scanner to scan the surface of the workpiece to obtain measured three-dimensional data; Comparing the measured three-dimensional data with the reference digital twin model to generate a three-dimensional topography deviation map; Based on the three-dimensional topography deviation map, calculating and generating a compensatory manufacturing solution including a modified tool path and dynamically modulated process parameters; and, The friction solid phase additive manufacturing device is controlled to perform deposition of the next layer according to the compensatory manufacturing plan.

10. The closed-loop controlled friction solid phase additive manufacturing system for precise forming of gradient materials according to claim 9, characterized in that: The system also includes a non-contact infrared thermal imager, and the central control unit is further configured to: The data of the non-contact three-dimensional optical scanner and the non-contact infrared thermal imager are integrated to perform thermal-morphological coupling deviation analysis and collaborative compensation.

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