A powder bed and five-axis hybrid additive and subtractive manufacturing method

Abstract

A composite manufacturing method based on a powder bed and five-axis additive and subtractive materials includes model preprocessing: performing model adaptive compensation on the basis of a design model, repairing the compensated model, and obtaining an additive model; decomposition and reconstruction: decomposing the additive model to obtain multiple sub-models for which inner surface tool paths can be planned at one time, and then performing additive manufacturing and CNC machining alternately on the sub-models in a construction order until all sub-models are machined; post-processing: after completing the composite machining of all sub-models, it is necessary to remove the support structure and mill the outer surface of the part; in addition, after removing the influence of the powder bed and support, some unmachined internal structures are remachined to obtain the final required parts; the present invention can realize the manufacturing of parts with complex internal structures that are difficult to machine by traditional CNC machining, and provide technical support for the integrated precision manufacturing of parts with complex internal structures.

Description

Technical Field

[0001] The present invention relates to the technical field of additive and subtractive composite manufacturing, and in particular to a powder bed and five-axis additive and subtractive composite manufacturing method. Background Art

[0002] Additive-subtractive composite manufacturing technology combines the advantages of high design freedom of additive manufacturing and high surface accuracy of CNC machining, eliminates the "step effect" caused by the discrete stacking principle of additive manufacturing, improves the surface accuracy of additively manufactured parts, expands the manufacturability of CNC machining, and provides a solution for the integrated precision manufacturing of parts that are difficult to manufacture by CNC machining (such as parts with complex internal structures).

[0003] There are two main additive methods for metal additive and subtractive composite manufacturing: direct energy deposition (DED) and powder bed fusion (PBF). Among them, composite manufacturing equipment using DED as the additive method can be realized by integrating a cladding head on a five-axis CNC machine tool. The equipment is easy to manufacture and control, and is suitable for the rapid manufacturing and repair of large parts. Compared with the DED process, the composite manufacturing method based on the PBF process has higher surface accuracy, can form fine structures, and is more suitable for the integrated precision manufacturing of complex internal structures (such as parts with internal flow channels). It has broad application prospects in aerospace, automotive, biomedicine and other fields.

[0004] Existing additive and subtractive composite manufacturing methods ([1] VTLe, H. Paris, G. Mandil, The development of a strategy for direct part reuse using additive and subtractive manufacturing technologies, Addit. Manuf. 22 (2018) 687–699; [2] ST Newman, ZC Zhu, V. Dhokia, A. Shokrani, Process planning for additive and subtractive manufacturing technologies, CIRP Ann.—Manuf. Technol. 64 (2015) 467–470;) focus on the repair process of multiple parts and only use the model's own characteristics to plan the operation sequence between additive manufacturing and CNC machining in the manufacturing stage. However, PBF-based additive and subtractive composite manufacturing is limited by the influence of the powder bed, its construction direction is single, and the swing head cannot be processed below the surface of the powder bed during the composite manufacturing process. Therefore, the current additive and subtractive composite manufacturing method is only applicable to DED additive and subtractive composite manufacturing with high degrees of freedom, and is not applicable to PBF additive and subtractive composite manufacturing suitable for integrated precision manufacturing of complex internal structures. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a powder bed and five-axis additive and subtractive composite manufacturing method, which fully considers the influence of the PBF process characteristics and constraints on the CNC machining process, and can realize the manufacturing of parts with complex internal structures that are difficult to process with traditional CNC machining, which is beneficial to the improvement of part surface quality and shape control in additive and subtractive composite manufacturing.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A powder bed and five-axis additive and subtractive composite manufacturing method, comprising the following steps:

[0008] (a) Model preprocessing: Adaptive model compensation is performed on the design model. The compensated model is then checked for STL errors. If errors are found, the model is repaired until a complete, error-free, and watertight STL model is formed. This model is then used as the additive model for the entire additive and subtractive manufacturing process for subsequent processing.

[0009] (b) Decomposition and reconstruction: The additive model is decomposed to obtain multiple sub-models for planning the inner surface tool path at one time. The sub-models are then reconstructed alternately according to the construction order until all sub-models are compositely manufactured;

[0010] (c) Post-processing: After all sub-models are completed, the support structure needs to be removed and the outer surface needs to be milled; in addition, after removing the powder bed and support influence, some unprocessed internal structures are reprocessed to obtain the final required parts.

[0011] The model adaptive compensation rule in step (a) is to expand the outer contour of the model and shrink the inner contour to achieve the effect of leaving a suitable finishing allowance. This step is achieved by developing a model adaptive compensation algorithm.

[0012] The adaptive meaning is: under certain equipment, materials and processes, the model deviation caused by the additive process is compensated for according to different model characteristics. In addition to leaving a finishing allowance, the model compensation also needs to compensate for the model deviation caused by the additive process. The adaptive rules are explored by printing models at different tilt angles and measuring the length and angle deviations between the actual size and the design size.

[0013] The basic idea of the model adaptive compensation algorithm is as follows: to leave a finishing allowance, the plane where each triangular facet in the original model is located is translated toward the outside of the model along the normal vector direction, that is, by the sum of the finishing allowance and the model deviation during the additive process; the new three vertex coordinates of each triangular facet are obtained by calculating the intersection of each plane after translation, and the normal vector is recalculated; the three vertices and normal vectors of each triangular facet after transformation are output into STL format according to the rules to obtain the compensated model.

[0014] The mathematical principle of the model adaptive compensation algorithm for solving the new vertices after the translation of each triangle is as follows:

[0015] Assume that the coordinates of a vertex before the change are M0 = (x0, y0, z0), and the coordinates after the transformation are M. The triangles around point M0 are distributed on n independent planes, and their independent plane normal vectors are: When the adaptive rule is not considered, the translation distance of each triangle along the normal vector direction is d;

[0016] When the triangles around a vertex are distributed in the same plane, that is, when n=1, the vertex transformation rule is regarded as a translation distance d along the direction of the normal vector of the plane, that is, the coordinate transformation formula of the vertex is:

[0017]

[0018] When the triangles around a vertex are distributed in two planes, that is, when n=2, the vertex transformation rule is regarded as a translation distance D along the direction of the resultant vector of the two planes, that is, the coordinate transformation formula of the vertex is:

[0019]

[0020] When the triangles around a vertex are distributed on three or more planes, that is, when n≥3, the problem of converting the changed vertex coordinates into the intersection point of multiple planes is solved. The coordinate transformation formula of the vertex is:

[0021] arg min‖Am-b‖

[0022] Among them, A is the plane equation coefficient matrix, m is the coordinate of the point after transformation, and b is the constant term. Its expression is as follows:

[0023]

[0024] m=(x,y,z) T

[0025]

[0026] The translation direction and distance of each facet are adjusted according to the adaptive rule to the normal vector direction in the above coordinate transformation rule. And the distance d is corrected to achieve model adaptive compensation.

[0027] After changing the adaptive rules, the model adaptive compensation is also applied to other forms of additive and subtractive composite manufacturing, realizing the reservation of finishing allowances in the additive and subtractive composite manufacturing process from the model level.

[0028] The step (b) includes three stages: model decomposition, inner surface tool path planning, and model reconstruction;

[0029] The model decomposition stage involves decomposing the additive model into multiple sub-models for planning inner surface machining paths at a single time using multiple cutting planes perpendicular to the build direction, based on the internal structural features of the additive model and the specified placement angle and machining accuracy requirements, and outputting a sub-model build sequence.

[0030] The CNC machining during the inner surface tool path planning stage only processes the inner surface of the part. When planning the machining tool path, each sub-model after the additive model is decomposed is used as a blank, and the design model is used as the target component. The inner surface tool path planning stage will generate the same number of machining tool path files as the sub-models.

[0031] The model reconstruction stage is to perform additive manufacturing and CNC machining alternately on the sub-models obtained in the model decomposition stage and the machining tool path files obtained in the inner surface tool path planning stage according to the construction sequence according to the machining accuracy requirements until all sub-models are compositely manufactured.

[0032] The reprocessing in step (c) refers to the following: during the composite manufacturing process of the additive model in the decomposition and reconstruction stage, the inner surface of the part cannot be fine-machined due to the limitations of CNC machining due to the process characteristics of PBF; after removing the influence of powder and support, the unprocessed inner surface of the part is re-finished using a five-axis machine tool.

[0033] The equipment used in the powder bed and five-axis additive and subtractive material composite manufacturing method includes an atmosphere protection shell 1, a five-axis oscillating head 2 is provided inside the atmosphere protection shell 1, a tool 9 is connected to the bottom of the five-axis oscillating head 2, the five-axis oscillating head 2 is connected to a linear motor 10, and a laser galvanometer 3 is connected to the linear motor 10; a powder scraper 4 is provided at the bottom of the atmosphere protection shell 1; a forming base plate 7 is provided at the middle part of the lower part of the atmosphere protection shell 1, a powder bin 5 and a powder top mechanism 6 are provided on one side, and a powder collecting bin 8 is provided on the other side; the function of the atmosphere protection shell 1 is to form a low-oxygen environment to prevent the powder from overburning.

[0034] The beneficial effects of the present invention are:

[0035] (1) The present invention comprehensively considers the influence of PBF process characteristics and constraints on the CNC machining process, and divides the powder bed and five-axis additive and subtractive material composite manufacturing method into three steps: model preprocessing, decomposition and reconstruction, and post-processing, which is conducive to achieving integrated precision of parts with complex internal structures.

[0036] (2) The model adaptive compensation algorithm adopted in the present invention has the advantages of universality, accuracy and speed, which can reduce the tedious and error-prone situation of manual compensation of complex structural parts, and is beneficial to the improvement of part surface quality and shape control in additive and subtractive composite manufacturing.

[0037] (3) The present invention adopts a reprocessing process in the post-processing step, which can allow some unprocessed areas in the decomposition and reconstruction stage to be processed again after removing the influence of the powder bed and support, which is beneficial to improving the overall surface quality of the parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Flowchart of the present invention.

[0039] Figure 2 Schematic diagram of the adaptive compensation rule of the model of the present invention.

[0040] Figure 3Schematic diagram of the basic idea of the model adaptive compensation algorithm of the present invention; Figure (a) shows that the triangular facets around a vertex are distributed in the same plane, Figure (b) shows that the triangular facets around a vertex are distributed in two planes; Figure (c) shows that the triangular facets around a vertex are distributed in three or more planes.

[0041] Figure 4 Schematic diagram of the equipment used in the present invention.

[0042] Figure 5 Schematic diagram of alternating additive manufacturing and CNC machining according to the present invention.

[0043] Figure 6 Schematic diagram of the effect of different model placement angles on the internal processable area of the present invention; Figure (a) is horizontal placement, and Figure (b) is tilted placement.

[0044] Figure 7 Schematic diagram of the additive and subtractive composite manufacturing process of a complex internal cavity part according to an embodiment of the present invention. DETAILED DESCRIPTION

[0045] The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0046] Reference Figure 1 , a powder bed and five-axis additive and subtractive composite manufacturing method, comprising the following steps:

[0047] (a) Model preprocessing: Because the surface accuracy of additive and subtractive manufacturing parts is guaranteed by CNC, considering the finishing allowance, it is necessary to perform model adaptive compensation based on the design model to obtain the additive model. In addition, to prevent the compensated additive model from generating STL errors (such as intersecting triangles), the compensated model needs to be repaired until a complete, error-free, and watertight STL model is formed. This model can then be used as the additive model for the entire additive and subtractive manufacturing process for subsequent processing.

[0048] (b) Decomposition and reconstruction: Taking into account the PBF process characteristics and the impact of constraints on the NC machining process and model features, the additive model obtained in step (a) is decomposed to obtain multiple sub-models for planning the inner surface tool path at one time. The sub-models are then reconstructed alternately in the construction order until all sub-models are compositely manufactured;

[0049] (c) Post-processing: After all sub-models are completed, the support structure needs to be removed and the outer surface needs to be milled; in addition, after removing the powder bed and support influence, some unprocessed internal structures are reprocessed to obtain the final required parts.

[0050] Reference Figure 2The model adaptive compensation rule is to expand the outer contour of the model and shrink the inner contour to achieve the effect of leaving an appropriate finishing allowance. Model compensation can be achieved manually through CAD software, but when faced with parts with more complex structures, manual compensation is often cumbersome and prone to errors. In addition, manual compensation cannot make adaptive adjustments to different areas based on the process characteristics of PBF. Therefore, the development of a model adaptive compensation algorithm will improve the finishing allowance in terms of time, effect, adaptability, and other aspects.

[0051] The adaptive meaning is: under certain equipment, materials and processes, the model deviation caused by the additive process is compensated for according to different model characteristics. This is because the finishing allowance is generally small. During the printing process, the equipment, materials, processes and model characteristics (mainly the inclination angle of the triangular facets) may also cause inconsistencies in the actual model and the designed model size. If this deviation accumulates and exceeds the value of the finishing allowance, it will be detrimental to the progress of CNC machining; therefore, in addition to leaving a finishing allowance, model compensation also needs to compensate for the model deviation caused by the additive process; the adaptive rules are explored by printing models at different inclination angles and measuring the length and angle deviations between the actual size and the designed size.

[0052] Reference Figure 3 The basic idea of the model adaptive compensation algorithm is as follows: in order to leave a finishing allowance, the plane where each triangle facet in the original model is located is translated toward the outside of the model along the normal vector direction, that is, the sum of the finishing allowance and the model deviation during the additive process; the new three vertex coordinates of each triangle facet are obtained by calculating the intersection points of each plane after translation, and the normal vector is recalculated; the three vertices and normal vectors of each triangle facet after transformation are output into STL format according to the rules, and the compensated model can be obtained.

[0053] The mathematical principle of the model adaptive compensation algorithm for solving the new vertices after the translation of each triangle is as follows:

[0054] Without loss of generality, assume that the coordinates of a vertex before the change are M0 = (x0, y0, z0), and the coordinates after the transformation are M. The triangles around point M0 are distributed on n independent planes, and their independent plane normal vectors are: When the adaptive rule is not considered, the translation distance of each triangle along the normal vector direction is d;

[0055] like Figure 3 As shown in (a), when the triangles around a vertex are distributed in the same plane, that is, when n = 1, the vertex transformation rule can be regarded as a translation distance d along the direction of the normal vector of the plane, that is, the coordinate transformation formula of the vertex is:

[0056]

[0057] like Figure 3 As shown in (b), when the triangles around a vertex are distributed in two planes, that is, when n = 2, the vertex transformation rule can be regarded as a translation distance D along the direction of the resultant vector of the two planes, that is, the coordinate transformation formula of the vertex is:

[0058]

[0059] like Figure 3 As shown in (c), when the triangles around a vertex are distributed on three or more planes, that is, when n ≥ 3, solving the changed vertex coordinates can be transformed into the problem of finding the intersection of multiple planes, that is, the vertex coordinate transformation formula is:

[0060] arg min‖Am-b‖

[0061] Among them, A is the plane equation coefficient matrix, m is the coordinate of the point after transformation, and b is the constant term. Its expression is as follows:

[0062]

[0063] m=(x,y,z) T

[0064]

[0065] The translation direction and distance of each facet are adjusted according to the adaptive rules explored in the experiment to the normal vector direction in the above coordinate transformation rules. Model adaptive compensation can be achieved by correcting the distance d.

[0066] After changing the adaptive rules, the model adaptive compensation is also applied to other forms of additive and subtractive composite manufacturing, realizing the reservation of finishing allowances in the additive and subtractive composite manufacturing process from the model level.

[0067] Reference Figure 1 , said step (b) includes three stages: model decomposition, inner surface tool path planning and model reconstruction;

[0068] The model decomposition stage involves decomposing the additive model into multiple sub-models for planning inner surface machining paths at a single time using multiple cutting planes perpendicular to the build direction, based on the internal structural features of the additive model and the specified placement angle and machining accuracy requirements, and outputting a sub-model build sequence.

[0069] In the inner surface toolpath planning stage, in order to improve manufacturing efficiency and prevent damage to the support structure, the CNC machining at this time only processes the inner surface of the part. When planning the machining toolpath, the sub-models after the additive model is decomposed are used as the blank, and the design model is used as the target component. The inner surface toolpath planning stage will generate the same number of machining toolpath files as the sub-models.

[0070] The model reconstruction stage is to perform additive manufacturing and CNC machining alternately on the sub-models obtained in the model decomposition stage and the machining tool path files obtained in the inner surface tool path planning stage according to the construction sequence according to the machining accuracy requirements until all sub-models are completed.

[0071] The reprocessing in step (c) refers to the following: during the composite manufacturing process of the additive model in the decomposition and reconstruction stage, the inner surface of the part cannot be fine-machined due to the limitations of CNC machining due to the process characteristics of PBF (such as the inability of the swing head to perform machining below the upper surface of the powder bed and interference with the support structure); after removing the influence of the powder and support, the unprocessed inner surface of the part is re-processed using a five-axis machine tool.

[0072] Reference Figure 4 The equipment used in the powder bed and five-axis additive and subtractive composite manufacturing method includes: an atmosphere protection shell 1, a five-axis oscillating head 2, a laser galvanometer 3, a powder spreading scraper 4, a powder bin 5, a powder pushing mechanism 6, a forming substrate 7, a powder collecting bin 8, a tool 9 and a linear motor 10; the atmosphere protection shell 1 is provided with a five-axis oscillating head 2, the bottom of the five-axis oscillating head 2 is connected to the tool 9, the five-axis oscillating head 2 is connected to the linear motor 10, and the linear motor 10 is connected to the laser galvanometer 3; the bottom of the atmosphere protection shell 1 is provided with a powder spreading scraper 4;

[0073] A forming base plate 7 is provided in the middle of the lower portion of the atmosphere protection housing 1, a powder bin 5 and a powder ejecting mechanism 6 are provided on one side, and a powder collecting bin 8 is provided on the other side;

[0074] The atmosphere protection shell 1 is used to form a low-oxygen environment to prevent the powder from being over-burned; the powder collecting bin 8 is used to collect excess powder during the powder spreading process.

[0075] Reference Figure 4 、 Figure 5 , additive manufacturing and CNC machining are carried out alternately, that is, the bottom sequence sub-model 1101 is first formed by additive manufacturing. The specific additive manufacturing process is as follows: driven by the linear motor 10, the laser galvanometer 3 moves to the center position of the forming substrate 7 and prints layer by layer. At this time, the powder pushing mechanism 6 pushes the powder bin 5 upward, the forming substrate 7 moves downward, and the powder spreading scraper 4 moves back and forth until the entire sub-model 1101 is printed;

[0076] After the sub-model 1101 is printed, the laser galvanometer 3 is driven by the linear motor 10 to withdraw from the center of the forming substrate 7, and the five-axis rotary head 2 is moved to a suitable position to perform CNC machining on the sub-model 1101. At this time, the powder spreading scraper 4, the powder pushing mechanism 6, and the forming substrate 7 remain stationary. When the sub-model 1101 is machined according to the planned tool path, the sub-model 1102 manufactured by the additive and subtractive composite manufacturing of the bottom sequence can be obtained.

[0077] When the additive and subtractive composite manufacturing of the bottom sequence sub-model 1102 is completed, the five-axis rotary head 2 is withdrawn, the laser galvanometer 3 is moved to the center of the forming substrate 7, and additive manufacturing is continued on the sub-model 1102 to construct the next sequence sub-model 1103; this process repeats the process of additive manufacturing and CNC machining of each sub-model according to the construction sequence until all sub-models are composited and completed.

[0078] Reference Figure 6 The location of the cutting surface should be determined according to the model placement angle and internal structure. Taking the “J”-shaped inner flow channel as an example, if the model is to be manufactured in an integrated and precise manner, different cutting surfaces should be used to cut the model into multiple sub-models according to the structural characteristics of the inner flow channel (generally, the inner top surface / edge is selected as the cutting surface). Figure 6 As shown in (a), when the model is placed horizontally, three cutting planes P1, P2, and P3 are selected to divide the model into four sub-models, and then each sub-model is subjected to additive and subtractive composite manufacturing in turn according to the construction order. At this time, most of the inner surfaces can be fine-machined, but the inner surfaces s1, s2, and s3 cannot be fine-machined in step (b) due to the limitations of the powder bed and the model itself; as shown in Figure 6 (b), when the model is placed tilted, four cutting planes P1, P2, P3, and P4 are selected to divide the model into five sub-models. Due to the tilt of the model, an external support structure is required; after all sub-models have been manufactured by additive and subtractive composite manufacturing, only the inner surfaces s3 and s4 between the cutting planes P2 and P3 cannot be fine-machined.

[0079] Reference Figure 6 The reprocessing means that after removing the influence of factors such as the powder bed and the support, the inner surface that has not been processed in step (b) can be re-processed; Figure 6 In (a), the inner surfaces s1 and s3 are machined, but the inner surface s2 cannot be machined due to the limitations of the model characteristics; Figure 6 In (b), the inner surfaces s3 and s4 in the areas between the cutting planes P2 and P3 can be reprocessed after the support and powder are removed.

[0080] Reference Figure 7 The present invention is used to illustrate a composite manufacturing method based on powder bed and five-axis additive and subtractive materials, using a certain complex internal cavity part. Figure 7 The design model has a side V-shaped inner cavity, which can be divided into three sections with rounded corners. Using traditional multi-axis CNC machining, the inner surface of the middle section cannot be machined. If additive manufacturing is used, the inner cavity surface will be rough due to the adhesion of unmelted powder. The present invention uses a powder bed and five-axis additive and subtractive composite manufacturing method to achieve integrated precision manufacturing of this inner cavity model. The specific manufacturing process is as follows:

[0081] First, the design model is adaptively compensated and STL repaired (a1) to obtain an additive model with appropriate finishing allowance; the horizontal placement direction is selected, and the dividing surface (b1) is selected according to the internal cavity characteristics (corner) of the additive model. The additive model is divided into three sub-models (b2) according to the selected dividing surfaces P1 and P2. The sub-models are alternately subjected to additive manufacturing and CNC machining (b3) to (b8) in accordance with the construction order, wherein steps (b3), (b5), and (b7) are additive manufacturing processes; (b4), (b6), and (b8) are CNC machining processes, and the CNC machining area is only the inner surface of the cavity; when the three sub-models are all compositely manufactured, the model is removed from the powder bed, and the planned surface machining tool path is performed (c1), and the outer surface of the model is milled (c2) to obtain the final integrated precision-formed inner cavity part.

[0082] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A powder bed and five-axis additive and subtractive composite manufacturing method, characterized in that: The following steps are involved: (a) Model preprocessing: Adaptive model compensation is performed on the design model. The compensated model is then checked for STL errors. If errors are found, the model is repaired until a complete, error-free, and watertight STL model is formed. This model is then used as the additive model for the entire additive and subtractive manufacturing process for subsequent processing. (b) Decomposition and reconstruction: The additive model is decomposed to obtain multiple sub-models for planning the inner surface tool path at one time. The sub-models are then reconstructed alternately according to the construction order until all sub-models are compositely manufactured; (c) Post-processing: After all sub-models are composited, support structures are removed and the outer surface is milled. In addition, after removing the powder bed and support effects, some of the unmachined internal structure is re-machined to obtain the final desired part. The model adaptive compensation rule in step (a) is to expand the outer contour of the model and shrink the inner contour to achieve the effect of leaving a suitable finishing allowance. This step is achieved by developing a model adaptive compensation algorithm; Adaptive design means compensating for model deviations caused by the additive process based on the specific equipment, materials, and processes used. Model compensation not only requires leaving a finishing allowance, but also compensates for model deviations caused by the additive process. Adaptive rules are explored by printing models at different tilt angles and measuring the length and angle deviations between the actual and designed dimensions. The basic idea of the model adaptive compensation algorithm is as follows: to leave a finishing allowance, the plane where each triangular facet in the original model is located is translated toward the outside of the model along the normal vector direction, that is, by the sum of the finishing allowance and the model deviation during the additive process; the new three vertex coordinates of each triangular facet are obtained by calculating the intersection of each plane after translation, and the normal vector is recalculated; the three vertices and normal vector of each triangular facet after transformation are output into STL format according to the rules, thus obtaining the compensated model.

2. The method according to claim 1, characterized in that The mathematical principle of the model adaptive compensation algorithm for solving the new vertices after the translation of each triangle is as follows: Assume that the coordinates of a vertex before the change are , the transformed coordinates are , The triangles around the point are distributed in On independent planes, their independent plane normal vectors are: , when the adaptive rule is not considered, the translation distance of each triangle along the normal vector direction is ; When the triangles around a vertex are distributed on the same plane, that is, When the vertex transformation rule is regarded as a translation distance along the normal vector direction of the plane , that is, the coordinate transformation formula of the vertex is: When the triangles around a vertex are distributed on two planes, that is, When the vertex transformation rule is regarded as a translation distance along the direction of the two plane vectors , that is, the coordinate transformation formula of the vertex is: When the triangles around a vertex are distributed on three or more planes, that is, When , solving the changed vertex coordinates is transformed into the problem of finding the intersection of multiple planes, that is, the vertex coordinate transformation formula is: in, is the plane equation coefficient matrix, is the coordinate of the point after transformation, is a constant term, and its expression is as follows: The translation direction and distance of each facet are adjusted according to the adaptive rule to the normal vector direction in the above coordinate transformation rule. and distance Making corrections means realizing model adaptive compensation.

3. The method according to claim 1, characterized in that After changing the adaptive rules, the model adaptive compensation is also applied to other forms of additive and subtractive composite manufacturing, realizing the reservation of finishing allowances in the additive and subtractive composite manufacturing process from the model level.

4. The method according to claim 1, wherein The step (b) includes three stages: model decomposition, inner surface tool path planning, and model reconstruction; The model decomposition stage involves decomposing the additive model into multiple sub-models for planning inner surface machining paths at a single time using multiple cutting planes perpendicular to the build direction, based on the internal structural features of the additive model and the specified placement angle and machining accuracy requirements, and outputting a sub-model build sequence. The CNC machining during the inner surface tool path planning stage only processes the inner surface of the part. When planning the machining tool path, each sub-model after the additive model is decomposed is used as a blank, and the design model is used as the target component. The inner surface tool path planning stage will generate the same number of machining tool path files as the sub-models. The model reconstruction stage is to perform additive manufacturing and CNC machining alternately on the sub-models obtained in the model decomposition stage and the machining tool path files obtained in the inner surface tool path planning stage according to the construction sequence according to the machining accuracy requirements until all sub-models are compositely manufactured.

5. The method according to claim 1, characterized in that The reprocessing in step (c) refers to the following: during the composite manufacturing process of the additive model at the decomposition and reconstruction stage, the internal surface of the part cannot be finely machined due to the limitations of CNC machining due to the process characteristics of PBF; After removing the influence of powder and support, the unprocessed inner surface of the part is refined again using a five-axis machine tool.

6. The device used in the powder bed and five-axis additive and subtractive composite manufacturing method according to claim 1, characterized in that: The invention comprises an atmosphere protection shell (1), wherein a five-axis oscillating head (2) is provided inside the atmosphere protection shell (1), a tool (9) is connected to the bottom of the five-axis oscillating head (2), the five-axis oscillating head (2) is connected to a linear motor (10), and the linear motor (10) is connected to a laser galvanometer (3); a powder spreading scraper (4) is provided at the bottom of the atmosphere protection shell (1); a forming base plate (7) is provided at the middle part of the lower part of the atmosphere protection shell (1), a powder bin (5) and a powder top mechanism (6) are provided on one side, and a powder collecting bin (8) is provided on the other side; the atmosphere protection shell (1) functions to form a low-oxygen environment to prevent the powder from being overburned.

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