Transition path generation and control method for alternating additive and subtractive composite manufacturing processes
By generating preheating and transition support paths during the alternating process of adding and subtracting materials, the problems of thermal stress and molten pool instability in additive and subtractive composite manufacturing are solved, achieving high-precision process transitions and making it suitable for conventional equipment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG UNIV
- Filing Date
- 2026-05-12
- Publication Date
- 2026-06-09
AI Technical Summary
Existing additive and subtractive composite manufacturing technologies suffer from problems such as thermal stress caused by temperature gradients, insufficient interfacial bonding, and unstable molten pools, which affect forming accuracy and bonding strength.
By generating interface preheating paths and transition support paths, the alternating process of adding and subtracting materials is dynamically controlled. Taking into account geometric features, blank allowance, and thermal stress risks, the original processing path is reconstructed to achieve a smooth transition between processes.
It improves the quality of interface bonding, reduces thermal stress concentration, ensures the stability of the molten pool and the forming accuracy, and is suitable for conventional equipment without changing the part design.
Smart Images
Figure CN122174520A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of additive and subtractive composite manufacturing technology, and in particular to a method for generating and controlling the transition path of alternating additive and subtractive composite manufacturing processes. Background Technology
[0002] Additive manufacturing technology uses programmable high-energy beams or deposition devices to achieve moldless net-shape forming of three-dimensional solids, effectively simplifying the manufacturing process of complex spatial structures. Compared to traditional subtractive or equal-material manufacturing processes, this technology avoids geometric constraints through layered manufacturing, enabling the creation of complex structures with topology-optimized structures and internal flow channels—features that are impossible to achieve with traditional machining methods. It eliminates process feasibility limitations and reduces material loss rates, and is currently widely used in aerospace, medical, automotive, and military industries. However, current mainstream additive manufacturing technologies suffer from mechanistic defects in forming accuracy and surface roughness, and cannot reach the quality levels of subtractive manufacturing in the short term.
[0003] Additive-subtractive composite manufacturing combines two processes, leveraging the advantages of additive manufacturing for complex structures while using machining to compensate for shortcomings in geometric accuracy and surface quality, resulting in a strong complementary effect. The introduction of composite manufacturing reduces the precision requirements for blank manufacturing in the additive manufacturing stage. Furthermore, since the blank position is known after combining the two processes, tool setting-free machining can be achieved, improving the precision of the manufacturing system. Moreover, the blank produced by additive manufacturing is highly precise, significantly reducing cutting allowances compared to direct subtractive manufacturing, and also improving tool accessibility.
[0004] However, the coupling of additive and subtractive manufacturing processes also introduces some new problems. For example, a large temperature gradient exists during additive deposition, and thermal stress is generated during material cooling and solidification. When the stress exceeds the material's yield strength, plastic strain occurs within the material, causing deformation. After subtractive milling of the additive blank, the workpiece temperature drops rapidly, and impurities such as cutting fluid and chips remain on the surface. If additive deposition is performed directly on it, it can easily lead to insufficient metallurgical bonding at the interface, affecting the bonding strength. At the same time, after subtractive machining, the local blank allowance may not be sufficient to support the normal deposition of the subsequent additive molten pool, resulting in molten pool collapse, unstable edge forming, or even an inability to smoothly transition the process.
[0005] To address these issues, existing technologies have proposed various solutions. For example, Chinese patent document CN118578067A discloses a method for additive-subtractive composite manufacturing with a spacer layer. This method involves setting a spacer layer during the additive-subtractive composite manufacturing process and calculating the spacer layer height based on experimentally obtained interface depression values to improve the depression phenomenon at the interface. This method mainly achieves interface compensation through tool selection and control of the maximum continuous additive height, focusing on the optimization of machining parameters at the geometric level. However, this method primarily relies on pre-experimental data to determine the spacer layer height and does not involve a comprehensive analysis of the thermal stress risk at alternating interfaces and the molten pool support state.
[0006] For example, Chinese patent document CN118635811A discloses a forming method and system for metal additive-subtractive composite processing. This method improves the molten pool support conditions by chamfering the alternating interfaces after subtractive processing and adjusting the printing area's orientation using a cradle-type work platform to keep the deposition layer parallel to the print head's working surface. This method achieves transition support through geometric adjustment and equipment orientation control, relies on real-time orientation adjustment of a multi-axis device, and involves modifications to the original model during processing. Therefore, it represents an improvement solution at the structural and equipment levels. Summary of the Invention
[0007] This invention provides a method for generating and controlling the transition path of alternating additive and subtractive manufacturing processes. Without changing the three-dimensional model of the part, the method dynamically generates interface preheating paths and transition support paths by comprehensively judging the geometric features, blank allowance distribution and thermal stress risk of the alternating interface area, and reconstructs the original processing path to achieve a smooth transition of additive and subtractive manufacturing processes.
[0008] A method for generating and controlling the transition path of alternating additive and subtractive manufacturing processes includes the following steps: (1) Obtain the three-dimensional data model of the workpiece to be processed, including the additive blank model and the target forming model; determine the timing of alternating additive and subtractive processing based on the difference area between the target forming model and the additive blank model, and generate the original additive and subtractive composite manufacturing processing path; (2) Based on the alternation timing, the three-dimensional data model is divided into regions, the slice contour data of the alternation interface is extracted, and the interface normal vector is calculated; (3) Calculate the maximum allowable overhang angle of the alternating interface region according to the preset process parameters; calculate the overhang angle value at the alternating node, and determine whether an overhang structure is formed between the blank structure after subtractive processing and the subsequent additive deposition structure during the alternating process. (4) Perform spatial mapping analysis on the overhanging structure and blank allowance of the model after material reduction during the alternation of addition and subtraction. When the local blank allowance is less than the preset melt pool width, calculate the number of transition support layers based on the blank allowance and the single-layer deposition height and generate the addition and subtraction transition support path. (5) Determine whether there is a risk of thermal stress concentration at the interface based on the geometric structural characteristics of the alternating interface region. If there is a risk of thermal stress concentration, generate a preheating scan path for the alternating interface. (6) Insert the addition / reduction transition support path and the preheating scan path into the original addition / reduction material processing path, reconstruct the original addition / reduction material processing path, update the processing code and perform composite processing.
[0009] This invention dynamically generates interface preheating paths and transition support paths at the alternating nodes of additive and subtractive manufacturing. Without changing the part design model, it reconstructs the original processing path, achieving a smooth transition in the additive and subtractive composite manufacturing process, improving interface bonding quality, reducing stress concentration, and improving overall forming accuracy.
[0010] In this invention, the additive manufacturing method includes powder feeding and wire feeding, and the subtractive milling method includes three-axis and five-axis CNC milling. Before path planning and processing, the process method to be used is determined, such as three-axis powder feeding additive manufacturing + five-axis CNC milling.
[0011] Furthermore, before generating the original additive and subtractive composite manufacturing process path in step (1), appropriate additive processing parameters, including heat source power, scanning speed, scanning width, and deposition layer thickness, should be selected based on the complexity of the workpiece structure and the surface processing accuracy requirements. Appropriate subtractive cutting tools, such as flat milling cutters, ball end mills, and drum end mills, should also be selected.
[0012] In step (2), the extracted slice contour data is in the format of point cloud, patch or continuous contour line, etc.
[0013] In step (3), the surface of the workpiece after subtractive processing is used as the support reference surface. Combined with the subsequent additive deposition direction, the overhang angle value is calculated by the angle between the interface normal vector and the deposition direction vector. The formula is: ; in, This is the suspension angle value, which takes the value of... ; For the interface normal vector, This is the deposition direction vector.
[0014] In step (3), the overhanging structure is formed by comparing the blank allowance of the N+1th additive model with the Nth subtractive model size.
[0015] In step (4), the blank allowance is the interpolation between the part size after the Nth subtraction and the part size after the N+1th addition.
[0016] In step (4), the number of transition support layers is calculated based on the blank allowance and the single-layer deposition height, and then rounded according to the following formula: ; in, The number of support layers for the transition layer. This is the allowance for the blank; This refers to the overlap ratio of the molten pool. The angle between the additive manufacturing tool tip position vector and the deposition direction. The overhang angle, , ; Molten pool width, The height of the molten pool is determined by the additive manufacturing process parameters.
[0017] In step (5), the geometric structural features of the alternating interface region include the rate of change of interface curvature and the rate of change of cross-sectional area.
[0018] In step (6), when reconstructing the original additive and subtractive machining path, the constraints of tool motion continuity, energy input smoothness and machine tool acceleration must be met.
[0019] In step (6), the addition / reduction transition support path and the preheating scanning path are dynamically inserted into the original addition / reduction material processing path according to the corresponding alternation timing.
[0020] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention makes a comprehensive judgment based on the geometric features of alternating interfaces, the distribution of blank allowance, and the state of heat input to achieve path-level dynamic control, rather than simply relying on interval layer compensation or equipment attitude adjustment, thus improving the flexibility of transition control.
[0021] 2. This invention removes residual surface impurities from the subtractive process by inserting an interface preheating path at alternating nodes, while effectively reducing the interface temperature gradient, alleviating thermal stress concentration, and improving the interface bonding strength.
[0022] 3. This invention dynamically generates the path for adding or subtracting transition supports by analyzing the blank allowance space mapping, ensuring stable forming of the molten pool and improving the stability of the composite manufacturing process of additive and subtractive materials.
[0023] 4. This invention does not rely on special tool structures or multi-axis attitude adjustment devices and can be implemented on conventional three-axis or five-axis additive and subtractive composite equipment, making it highly applicable to engineering projects.
[0024] 5. This invention achieves smooth process transition by inserting preheating path segments and transition support path segments into the original material addition and subtraction processing path. Without changing the original design model of the part, it achieves alternating control of material addition and subtraction by dynamically inserting transition processing paths, thereby improving the versatility and scalability of the method. Attached Figure Description
[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0026] Figure 1 This is a flowchart of the overall method of the present invention.
[0027] Figure 2 This is a schematic diagram illustrating the exemplary components and the timing of their alternation in an embodiment of the present invention.
[0028] Figure 3 It is a schematic diagram of the alternating interface slice outlines at each stage of additive and subtractive composite processing.
[0029] Figure 4 This is a schematic diagram of the blank allowance space mapping before and after alternating increases and decreases.
[0030] Figure 5 This is a schematic diagram for calculating the overhang angle.
[0031] Figure 6 These are schematic diagrams of different types of blank hanging structures.
[0032] Figure 7 This is a schematic diagram for calculating the number of transition support path layers.
[0033] Figure 8 This is a schematic diagram of the transition support.
[0034] Figure 9 This is a schematic diagram of the alternating interface preheating path.
[0035] Figure 10 It is a flowchart of dynamic reconstruction of the manufacturing process path for additive and subtractive composite materials. Detailed Implementation
[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0037] It should be noted that, unless otherwise specified, the features in the following embodiments and implementation methods can be combined with each other.
[0038] Figure 1 As shown, a method for generating and controlling the transition path of alternating additive and subtractive composite manufacturing processes includes steps such as model acquisition, extraction of alternating interface features, determination of overhanging structures, analysis of blank allowance, generation of transition support path, generation of interface preheating path, and path reconstruction.
[0039] In this embodiment, the additive manufacturing method is laser powder feeding additive manufacturing, and the subtractive manufacturing method is five-axis CNC milling. Of course, in other embodiments, wire feeding additive manufacturing or three-axis milling can also be used.
[0040] Figure 2 As shown, taking a tee pipe part as an example, this part has a large length-to-diameter ratio, and both the inner and outer walls require subtractive machining. Traditional machining methods cannot properly machine the inner wall due to the inaccessibility of the cutting tool. Therefore, a composite machining method of additive and subtractive machining is needed to achieve the part's shape. The method is determined by analyzing the part model and the selected machining method. Figure 2 The timing of the increase and decrease is shown.
[0041] Figure 3 As shown, the model is segmented at alternating nodes, and the slice contour data of the alternating interfaces is extracted. The slice contour data may include various forms such as point clouds, patches, and continuous contour lines. Figure 3 In the middle, A represents the outline of the interface that alternates between the first and fourth additions and subtractions. Figure 3 B in the middle is the outline of the interface that alternates between the fifth increase and decrease.
[0042] Figure 4 The diagram shows the dimensions of the model after the Nth subtractive process, the N+1th additive process, and the N+1th subtractive process. Considering potential surface defects during the additive process, the additive model has a certain blank allowance compared to the precise subtractive model. This allowance, together with the Nth subtractive model, forms a new overhanging structure. Whether a support path segment needs to be inserted is determined by judging whether the angle between the blank overhanging structures exceeds the maximum allowable overhang angle.
[0043] Overhang angle like Figure 5 As shown, from the interface normal vector With the deposition direction vector The calculation yielded: , The maximum permissible overhang angle value Determined by additive manufacturing process parameters, when The presence of a suspended structure is determined at that time.
[0044] Figure 6The diagram shows several different blank hanging structures. Types A and B require a support structure to ensure a smooth transition to subsequent additive manufacturing processes. Type C requires determining the hanging angle to decide whether a support structure is needed. Type D can achieve support for subsequent additive manufacturing processes based on its own dimensions.
[0045] like Figure 7 As shown, the calculation of the number of transition support layers for additive and subtractive manufacturing varies depending on the additive manufacturing method. For five-axis additive manufacturing, the support path can be optimized by adjusting the deposition head attitude, while for three-axis additive manufacturing, the support path is determined based on the overlap rate of multiple molten pools and the maximum overhang angle. For example... Figure 4 , Figure 6 As shown, define the blank allowance. This represents the difference between the part size after the Nth subtraction process and the theoretical additive size after the (N+1)th additive process. The weld pool width is determined based on the additive manufacturing process parameters. and molten pool height .
[0046] The number of support layers is according to Integer calculation, where, This is the allowance for the blank; This refers to the overlap ratio of the molten pool. The angle between the additive manufacturing tool tip position vector and the deposition direction. The overhang angle, , ; Molten pool width, This represents the height of the molten pool.
[0047] like Figure 8 As shown, after completing the transition support processing of the inner and outer contours, a normal transition between additive and subtractive processes can be achieved, avoiding the problem of poor additive printing quality or even failure to form after subtractive processing.
[0048] After subtractive milling of an additive blank, the workpiece temperature drops rapidly. Thermal stress is generated during the material's cooling and solidification process. When this stress exceeds the material's yield strength, plastic strain occurs within the material, causing deformation. Simultaneously, impurities such as cutting fluid and chips remain on the surface. Direct additive deposition on this material can easily lead to insufficient interfacial metallurgical bonding, affecting the bonding strength. For example... Figure 9As shown, the rate of change of interface curvature or the rate of change of cross-sectional area are calculated in the alternating interface region. When the rate exceeds a preset threshold, it is determined that a preheating path needs to be inserted during the alternating process of adding and subtracting materials. The risk threshold is obtained through pre-experimentation. The generation strategy for the preheating path is an outer contour line, an inner contour line, and an inner fill line. The inner and outer contour lines are obtained by reading the slice contour data of the alternating interface of adding and subtracting materials. The path strategy for the inner fill line is not limited to unidirectional, reciprocating, zigzag, contour offset, and cross-grid forms, depending on the specific processing requirements. The energy input per unit area is controlled by adjusting parameters such as laser power and scanning speed.
[0049] like Figure 10 As shown, after generating the transition support and interface preheating path for the alternating addition and subtraction process, dynamic reconstruction is performed based on the previously described addition and subtraction path. This path reconstruction satisfies constraints on tool motion continuity, energy input smoothness, and machine tool acceleration. The transition support path and preheating path are then inserted into the original machining path to generate the final code.
[0050] Thus, by using the aforementioned method, without making geometric modifications to the part model or changing the part design outline, a smooth transition between addition and subtraction is achieved only at the machining path level. At the same time, the problem of thermal stress concentration during the addition and subtraction process is solved, as well as the problem of poor additive machining quality after subtraction during the addition and subtraction process, or even the inability of the molten pool to support the material, which leads to the inability to form normally.
[0051] The method for generating and controlling the transition path of alternating processes in additive and subtractive composite manufacturing proposed in this invention is applicable to the processing of any part, any additive manufacturing process, and any three-axis and five-axis additive and subtractive composite equipment. It does not require a special chamfering structure or attitude adjustment mechanism, is easy to integrate into existing CAM systems, and has wide applicability.
[0052] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for generating and controlling the transition path of alternating additive and subtractive manufacturing processes, characterized in that, include: (1) Obtain the three-dimensional data model of the workpiece to be processed, including the additive blank model and the target forming model; determine the timing of alternating additive and subtractive processing based on the difference area between the target forming model and the additive blank model, and generate the original additive and subtractive composite manufacturing processing path; (2) Based on the alternation timing, the three-dimensional data model is divided into regions, the slice contour data of the alternation interface is extracted, and the interface normal vector is calculated; (3) Calculate the maximum allowable overhang angle of the alternating interface region according to the preset process parameters; calculate the overhang angle value at the alternating node, and determine whether an overhang structure is formed between the blank structure after subtractive processing and the subsequent additive deposition structure during the alternating process. (4) Perform spatial mapping analysis on the overhanging structure and blank allowance of the model after material reduction during the alternation of addition and subtraction. When the local blank allowance is less than the preset melt pool width, calculate the number of transition support layers based on the blank allowance and the single-layer deposition height and generate the addition and subtraction transition support path. (5) Determine whether there is a risk of thermal stress concentration at the interface based on the geometric structural characteristics of the alternating interface region. If there is a risk of thermal stress concentration, generate a preheating scan path for the alternating interface. (6) Insert the addition / reduction transition support path and the preheating scan path into the original addition / reduction material processing path, reconstruct the original addition / reduction material processing path, update the processing code and perform composite processing.
2. The method for generating and controlling the alternating transition paths in additive and subtractive composite manufacturing processes according to claim 1, characterized in that, In step (2), the extracted slice contour data is in the format of point cloud, patch or continuous contour line.
3. The method for generating and controlling the alternating transition paths in additive and subtractive composite manufacturing processes according to claim 1, characterized in that, In step (3), the surface of the workpiece after subtractive processing is used as the support reference surface. Combined with the subsequent additive deposition direction, the overhang angle value is calculated by the angle between the interface normal vector and the deposition direction vector. The formula is: ； in, This is the suspension angle value, which takes the value of... ; For the interface normal vector, This is the deposition direction vector.
4. The method for generating and controlling the alternating transition paths in additive and subtractive composite manufacturing processes according to claim 1, characterized in that, In step (3), the overhanging structure is formed by comparing the blank allowance of the N+1th additive model with the Nth subtractive model size.
5. The method for generating and controlling the alternating transition paths in additive and subtractive composite manufacturing processes according to claim 1, characterized in that, In step (4), the blank allowance is the interpolation between the part size after the Nth subtraction and the part size after the N+1th addition.
6. The method for generating and controlling the alternating transition paths in additive and subtractive composite manufacturing processes according to claim 1, characterized in that, In step (4), the number of transition support layers is calculated based on the blank allowance and the single-layer deposition height, and then rounded according to the following formula: ； in, The number of support layers for the transition layer. This is the allowance for the blank; This refers to the overlap ratio of the molten pool. The angle between the additive manufacturing tool tip position vector and the deposition direction. The overhang angle, , ; Molten pool width, This represents the height of the molten pool.
7. The method for generating and controlling alternating transition paths in additive and subtractive composite manufacturing processes according to claim 1, characterized in that, In step (5), the geometric structural features of the alternating interface region include the rate of change of interface curvature and the rate of change of cross-sectional area.
8. The method for generating and controlling the alternating transition paths in additive and subtractive composite manufacturing processes according to claim 1, characterized in that, In step (6), when reconstructing the original additive and subtractive machining path, the constraints of tool motion continuity, energy input smoothness and machine tool acceleration must be met.
9. The method for generating and controlling the alternating transition paths in additive and subtractive composite manufacturing processes according to claim 1, characterized in that, In step (6), the addition / reduction transition support path and the preheating scanning path are dynamically inserted into the original addition / reduction material processing path according to the corresponding alternation timing.