3D printing continuous fiber reinforced composite material path planning method based on absolute maximum principal stress direction

Abstract

The invention relates to the technical field of additive manufacturing, and discloses a 3D printing continuous fiber reinforced composite material path planning method based on the absolute maximum principal stress direction, and the method comprises the steps: building a three-dimensional model of a to-be-formed structural member, carrying out the slicing processing of the three-dimensional model, and obtaining a two-dimensional model of the to-be-formed structural member and the geometric characteristics of the two-dimensional model; material parameters and load constraints are set for a to-be-formed structural part needing additive manufacturing according to the requirements of forming materials and structural working conditions, finite element simulation is carried out, and a finite element simulation calculation result of a unit is exported; on the basis of a finite element simulation calculation result, an original contour line based on the stress direction is obtained through calculation; and on the basis of the calculated contour line in the stress direction, the additive manufacturing path of the to-be-formed structural part is obtained. The effect of improving the mechanical property of the continuous fiber composite material structure is achieved, and the mechanical property of a composite material component is improved on the premise of the same fiber content.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing technology, and in particular to a 3D printing continuous fiber reinforced composite material path planning method based on the direction of absolute maximum principal stress. Background Art

[0002] FDM (Fused deposition molding) technology is an additive manufacturing method based on thermoplastic composite materials. It combines the characteristics of rapid prototyping technology and material deposition technology. It uses thermoplastic composite wire as raw material, heats it to a molten state using a heating nozzle, and layers the three-dimensional model according to the STL model of the molded part through slicing software. The movement path of the nozzle is planned, and the molten material is extruded layer by layer and cooled and solidified, thereby realizing direct manufacturing of complex shapes.

[0003] In the deposition molding process of continuous fiber reinforced thermoplastic composites, the additive manufacturing path directly affects the part structure. Currently, the more mature filling path planning schemes in the industry mainly use the Z-shaped method, streamline method, etc. Because the above filling path planning schemes do not take into account the anisotropy and continuity of continuous fibers, the geometric characteristics of the structure, the influence of the additive manufacturing process, and the reason why continuous fibers transfer stress along the load direction, they will have problems such as poor mechanical properties and many fiber shearing times.

[0004] In the prior art, Chinese patent 202110972007.X discloses a 3D printing continuous fiber reinforcement path planning method based on the principal stress trajectory line, and proposes a method of forming a continuous fiber reinforcement path according to the number of interpolation points N in the design domain and the principal stress direction information of the extracted nodes. However, the structure of the component obtained by this method does not take into account the process parameters of additive manufacturing and the geometric characteristics of the structure. Although the continuous fiber direction of the stress curve planning is guaranteed to be parallel to the load direction, it reduces the integrity and applicability of the structure to be formed. Summary of the invention

[0005] To solve the above problems, the present invention discloses an additive manufacturing path planning method based on stress direction and an additive manufacturing method, which are used to fit the original contour shape of the slice of the structural part to be formed as much as possible, improve the mechanical properties of the structural part to be formed, and improve the mechanical properties of the composite components under the premise of the same fiber content.

[0006] A method for additive manufacturing path planning based on stress direction comprises the following steps:

[0007] Step 1: Establish a three-dimensional model of the structural part to be formed, and slice the three-dimensional model to obtain a two-dimensional model of the structural part to be formed and its geometric features;

[0008] Step 2: Set material parameters and load constraints for the structural parts to be manufactured by additive manufacturing according to the requirements of molding materials and structural working conditions, and perform finite element simulation. Calculate the corresponding relationship between the unit and the node obtained by finite element simulation to obtain the coordinate data and principal stress data of the unit, and derive the finite element simulation calculation results of the unit;

[0009] Step 3: Based on the finite element simulation calculation results, an additive manufacturing path planning method based on stress direction is constructed. The original contour line based on stress direction is calculated by performing linear fitting analysis on the finite element simulation calculation results of the unit;

[0010] Step 4: Based on the calculated stress direction contour, the additive manufacturing path of the to-be-molded structural part is obtained according to the structural constraints of the molded structural part and the additive manufacturing process constraints.

[0011] Furthermore, the specific steps of step 2 are:

[0012] Step 21: By considering the molding materials and structural working conditions required for the structure to be molded, the material parameters of density, Young's modulus, and Poisson's ratio of the additive manufacturing molding materials of the structure to be molded, as well as the load constraints of the force magnitude, force form, force direction, constraint position, and constraint method of the structure to be molded under actual working conditions are obtained, and the load constraint conditions are simplified according to the actual conditions of the finite element simulation software to obtain the material parameters and load constraints of the structure to be molded by finite element simulation.

[0013] Step 22: Calculate using commercial finite element simulation software, query and export finite element simulation results including node number, node coordinates, node unit, unit number, nodes included in the unit, unit S11 direction stress, unit S22 direction stress and unit S12 direction stress.

[0014] Step 23: Obtain the node corresponding to each unit number through the unit number, the nodes contained in the unit and the unit to which the node belongs, and calculate the unit coordinates of each unit number according to the node number and the node coordinates, and correspond and export the unit number, unit coordinates, unit S11 direction stress, unit S22 direction stress and unit S12 direction stress.

[0015] Furthermore, in step 3, according to the material mechanics formula and the relationship between the node coordinates and the node and the unit, an additive manufacturing path planning method based on the stress direction is constructed, and based on the finite element simulation calculation results, an additive manufacturing path planning method based on the stress direction is constructed, and the original contour line based on the stress direction is calculated by performing a linear fitting analysis on the finite element simulation calculation results of the unit, specifically:

[0016] Step 31: Process the finite element simulation calculation structure, and number the elements as e1, e2, ..., en in order from left to right and from bottom to top according to the element number, element coordinates, element S11 direction stress, element S22 direction stress and element S12 direction stress data obtained in step 2, where n ≥ 2;

[0017] Step 32: According to the material mechanics formula, the maximum principal stress vector and the minimum principal stress vector of each unit are calculated through the unit S11 direction stress, the unit S22 direction stress and the unit S12 direction stress, and are recorded as nmaxs, nmaxa, nmins, nmina in sequence according to the unit number, where n is the unit number, s represents the modulus of the principal stress vector, and a represents the direction of the principal stress vector;

[0018] Step 33: Process mmaxs, mmaxa, mmins, mmina of unit cell m in turn, where m is the unit number; if the ratio of mmins to mmaxs is less than 1, the stress vector of unit m is ms=mmaxs, ma=mmaxa, otherwise ms=mmins, ma=mmina;

[0019] Step 34: Starting from the unit with unit number m, compare the ma of unit m with other surrounding units, where m is the unit number. If the difference between the ma of unit m and other surrounding units is within the set range, it is defined as an approximate unit, and linear fitting calculation is performed on the approximate unit according to its ma, and unit lines are obtained in sequence, and the unit lines are connected in series to form the original contour line based on the stress direction. The set range refers to the range set by the fitting algorithm, specifically the absolute value of the difference between the ma of unit m and other surrounding units is less than the set value of the fitting algorithm. Linear fitting calculation refers to linear fitting of units in the approximate unit data group, specifically linear fitting calculation of the unit coordinates and unit stress vector of each unit in the approximate unit data group.

[0020] When the above technical solution is adopted, the additive manufacturing path connection formed according to the above path planning is more in line with the original contour shape of the component to be formed, ensuring that the print head runs continuously at the rated speed for a long distance, reducing the number of lifts and the idle distance, and can effectively reduce the stress concentration of the component to be formed. At the same time, the structural flatness is improved, the molding quality of the parts is improved, and the traditional molding path is avoided. The sharp corners at the edge of the part are avoided. During the actual printing process, the print head travel speed changes frequently, and the print head lifting process will lead to poor interlayer performance in the actual printing process, and the continuous fiber reinforced thermoplastic composite material is sheared more, resulting in material waste and faults inside the part.

[0021] Furthermore, the step 4 obtains the additive manufacturing path of the structure to be formed based on the calculated stress direction contour line according to the structural constraints of the formed structure and the additive manufacturing process constraints, specifically:

[0022] Step 41: The number of contour offsets c of the original contour line based on the stress direction is calculated by the minimum width w of the structure calculated in step 1 and the track spacing d in the additive manufacturing process constraint, and whether the structure can be drawn in one stroke is obtained by the number of structural singular points calculated in step 1. According to the original contour line based on the stress direction, the original contour line based on the stress direction is processed with contour offsets from the outside to the inside according to the structural geometry, and c contour lines based on the stress direction are obtained, which are numbered i 1, i 2...in from the outside to the inside, where n≤c. The offset distance of the contour line is d, d is the track spacing size in the additive manufacturing process constraint, the minimum width w of the structure to which it belongs is the smallest width in the structure to be formed, and the number of contour offsets c is calculated as w / d.

[0023] When the above technical solution is adopted, through the geometric dimension constraints of the structure and the process parameter constraints of additive manufacturing, not only the structural characteristics but also the process conditions are taken into consideration in path planning, which is conducive to the planning of the additive manufacturing printing path, making the path more uniform and improving the printing quality.

[0024] Connecting adjacent contour lines between each of the contour lines obtained by offset in series to form a path line, and obtaining an additive manufacturing path for the structure to be formed. Specifically comprising:

[0025] Step 42: Connect from the starting point of contour im+1 to the end point of contour im+1 on contour line im+1, enter contour line im+2 along the line connecting the end point of contour line im+1 and the starting point of contour line im+2, and complete the path connection from contour line i 1 to contour line in in sequence, connect the adjacent contour lines between each of the contour lines obtained by biasing into a path connection line, and obtain the additive manufacturing path of the structural part to be formed.

[0026] An additive manufacturing method utilizes the above-mentioned additive manufacturing path planning method to plan a printing path, adopts a material extrusion method, melt-deposit the to-be-molded part according to the planned molding path, and molds the to-be-molded part layer by layer.

[0027] When the above technical solution is adopted, the additive manufacturing path planning method is applied to the fused deposition modeling additive manufacturing method, which can improve the molding quality and application scope of the fused deposition modeling technology.

[0028] Beneficial effects of the present invention:

[0029] 1. Compared with the prior art, the present invention obtains the original contour line based on the stress direction by algorithmically processing the finite element calculation results. According to the original contour line based on the stress direction, the structural constraints of the molded structure and the additive manufacturing process constraints, the additive manufacturing process constraints of the layer spacing and the track spacing are substituted, and the original contour line based on the stress direction is subjected to contour offset processing to obtain the final specific path of the intelligent additive manufacturing path planning based on the stress direction, which can fully fill the structure to be molded, ensure that the print head runs at the rated speed for a long distance, reduce the number of shearing times and frequent large curvature turns, which is beneficial to improving the mechanical properties and stress transfer of the structure to be molded, reducing the stress concentration status, and the printing path largely fits the original contour shape of the part.

[0030] 2. The specific path of additive manufacturing path planning obtained by the present invention based on the contour line based on stress direction obtained by linear fitting, the structural constraints of the formed structural parts and the constraints of the additive manufacturing process can avoid the low path filling rate of the traditional additive manufacturing path when printing the structural parts to be formed, especially when printing continuous fiber reinforced thermoplastic composite materials that need to ensure continuity and integrity, as well as complex, frame and beam structures to be formed. The traditional path has the disadvantages of poor path filling rate, failure to fit the original contour shape of the structural parts to be formed, and many path cutting times. The technical solution of the present invention can effectively improve the mechanical properties of the structural parts to be formed, reduce the number of printing and cutting times, and improve the production efficiency and product qualification rate of the structural parts to be formed. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A flow chart of a method for additive manufacturing path planning based on stress direction provided by an embodiment of the present invention;

[0032] Figure 2 It is a schematic diagram of the Z-shaped additive manufacturing path of the prior art;

[0033] Figure 3 It is a data processing diagram of finite element simulation data results according to an embodiment of the present invention;

[0034] Figure 4 A schematic diagram of connecting data processing results based on stress directions according to an embodiment of the present invention;

[0035] Figure 5 A schematic diagram of the stress-based additive manufacturing path planning result obtained in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the accompanying drawings, and the words "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0037] like Figure 2 As shown in the figure, the Z-shaped additive manufacturing path used in the traditional process produces relatively sharp corners at the edge of the part. During the actual printing process, the travel speed of the print head changes frequently. The lifting process of the print head will lead to poor interlayer performance in the actual printing process, and the continuous fiber reinforced thermoplastic composite material is sheared more, resulting in material waste and faults inside the part.

[0038] To solve the above problems, Figure 1 As shown, the embodiment of the present invention discloses an additive manufacturing path planning method based on stress direction and an additive manufacturing method, comprising the following steps:

[0039] S1: Step 1: Establish a three-dimensional model of the structural part to be formed, and slice the three-dimensional model to obtain a two-dimensional model of the structural part to be formed and its geometric features;

[0040] S2: According to the requirements of molding materials and structural working conditions, material parameters and load constraints are set for the structural parts to be manufactured by additive manufacturing, and finite element simulation is performed. The coordinate data and principal stress data of the unit are obtained by calculating the corresponding relationship between the unit and the node obtained by the finite element simulation, and the finite element simulation calculation results of the unit are derived;

[0041] S3: Based on the finite element simulation calculation results, an additive manufacturing path planning method based on stress direction is constructed. The original contour line based on stress direction is calculated by performing linear fitting analysis on the finite element simulation calculation results of the unit;

[0042] S4: Based on the calculated stress direction contour, according to the structural constraints of the molded structural parts and the additive manufacturing process constraints, the additive manufacturing path of the to-be-molded structural parts is obtained.

[0043] Specifically, the above step S3 includes:

[0044] S301: Processing the finite element simulation calculation structure, according to the unit number, unit coordinates, unit S11 direction stress, unit S22 direction stress and unit S12 direction stress data obtained in step 2, in the order of rows from left to right and columns from bottom to top, numbering the units as e1, e2...en in sequence, where n≥2;

[0045] S302: According to the material mechanics formula, the maximum principal stress vector and the minimum principal stress vector of each unit are obtained through the unit S11 direction stress, the unit S22 direction stress and the unit S12 direction stress, and are recorded as nmaxs, nmaxa, nmins, nmina in sequence according to the unit number, where n is the unit number;

[0046] S303: Process mmaxs, mmaxa, mmins, mmina of unit cell m in turn, where m is the unit number; if the ratio of mmins to mmaxs is less than 1, the stress vector of unit m is ms=mmaxs, ma=mmaxa, otherwise ms=mmins, ma=mmina.

[0047] S304: Starting from the unit labeled m, compare the ma of unit m with that of other surrounding units, where m is the unit number. If the difference between the ma of unit m and that of other surrounding units is within the set range, it is defined as an approximate unit. A linear fitting calculation is performed on the approximate unit according to its ma, and unit lines are obtained in sequence. The unit lines are connected in series to form the original contour line based on the stress direction.

[0048] When the above technical solution is adopted, the additive manufacturing path connection formed according to the above path planning is more in line with the original contour shape of the component to be formed, ensuring that the print head runs continuously at the rated speed for a long distance, reducing the number of lifts and the idle distance, and can effectively reduce the stress concentration of the component to be formed. At the same time, the structural flatness is improved, the molding quality of the parts is improved, and the traditional molding path is avoided. The sharp corners at the edge of the part are avoided. During the actual printing process, the print head travel speed changes frequently, and the print head lifting process will lead to poor interlayer performance in the actual printing process, and the continuous fiber reinforced thermoplastic composite material is sheared more, resulting in material waste and faults inside the part.

[0049] Step S4 is specifically as follows:

[0050] S401: The number of contour offsets c of the original contour line based on the stress direction is calculated by the minimum width w of the structure calculated in step 1 and the track spacing d in the additive manufacturing process constraint, and whether the structure can be drawn in one stroke is obtained by the number of structural singular points calculated in step 1. According to the original contour line based on the stress direction, the original contour line based on the stress direction is processed with contour offsets from the outside to the inside according to the structural geometry, and c contour lines based on the stress direction are obtained, which are numbered from the outside to the inside as i 1, i2...in, where n≤c. .

[0051] S402: Connect from the starting point of contour im+1 to the end point of contour im+1 on contour im+1, enter contour im+2 along the line connecting the end point of contour im+1 and the starting point of contour im+2, complete the path connection from contour line i1 to contour line in in sequence, connect adjacent contour lines between each of the contour lines obtained by offset into a path connection line, and obtain the additive manufacturing path of the structural part to be formed.

[0052] The present invention also discloses an additive manufacturing method, which utilizes the additive manufacturing path planning method implemented in the present invention to perform path planning for an additive manufacturing structure: using material extrusion, the material is extruded and molded on the part to be molded according to the planned printing path, and the molded part is molded layer by layer.

[0053] In the case of adopting the above technical solution, the additive manufacturing path planning method described in the first aspect is applied to the fused deposition modeling additive manufacturing method, which can improve the molding quality and application range of the fused deposition modeling technology.

[0054] The present invention is applicable to continuous fiber reinforced thermoplastic composite materials that need to ensure continuity and integrity, as well as parts with complex, frame and beam structures, and can effectively improve the surface quality of products.

[0055] The present invention is briefly described below by taking a curved beam structure as an example:

[0056] S1: Import the curved beam structure to be formed, slice the three-dimensional model, obtain the two-dimensional model corresponding to the structure to be formed, and extract its geometric features: the bounding box is 150mm long, 25mm wide, and 4mm thick, the minimum size of the structure is 1.2mm, and the number of singular points is 2.

[0057] S2: By considering the molding materials and structural working conditions required for the structural parts to be formed, the material parameters of the additive manufacturing molding materials for the curved beam structural parts are obtained, including a density of 1.33g / cm3, a Young's modulus of 25520MPa, and a Poisson's ratio of 0.31, and the force magnitude of the structural parts to be formed under actual working conditions is 500N, the force form is concentrated force, the force direction is the negative direction of the Y-axis, the constraint position is the lower left corner and the lower right corner of the curved beam structural part, and the constraint method is a fixed load constraint.

[0058] S3: Calculate through commercial finite element simulation software, query and export finite element simulation results including node number, node coordinates, unit to which the node belongs, unit number, nodes included in the unit, unit S11 directional stress, unit S22 directional stress and unit S12 directional stress.

[0059] S4: Import the finite element simulation results into this method and obtain Figure 3The finite element simulation calculation results of the structural component unit to be formed are shown in FIG. Based on the finite element simulation calculation results, the linear fitting calculation of the approximate unit is performed and substituted into the additive manufacturing path planning method based on the stress direction to obtain the following Figure 4 The original stress direction-based contours are shown;

[0060] S5: According to the structural geometric characteristics and additive manufacturing process constraints, the channel spacing is 0.6 mm, and the following is obtained: Figure 5 The two-dimensional additive manufacturing path of the structural part to be formed is shown. Compared with the traditional uniform continuous fiber reinforcement path, the mechanical properties of the continuous fiber reinforcement path specimen based on the principal stress trajectory are significantly improved.

[0061] In summary, the additive manufacturing path planning method based on stress direction proposed in the present invention, the additive manufacturing path connection formed according to the above path planning, is more in line with the original contour shape of the component to be formed, ensuring that the print head runs continuously at the rated speed for a long distance, reducing the number of lifts and the idle distance, and can effectively reduce the stress concentration of the component to be formed, while improving the structural flatness, improving the forming quality of the parts, and avoiding the traditional forming path causing relatively sharp corners at the edge of the parts. In the actual printing process, the print head travel speed changes frequently, and the print head lifting process will lead to poor interlayer performance in the actual printing process, and the continuous fiber reinforced thermoplastic composite material is sheared more, resulting in material waste and faults inside the parts.

[0062] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above-mentioned implementation mode, but also include technical schemes composed of any combination of the above technical features.

Claims

1. A path planning method for 3D printing continuous fiber reinforced composite materials based on the direction of absolute maximum principal stress, characterized in that: The following steps are involved: Step 1: Establish a three-dimensional model of the structural part to be formed, and slice the three-dimensional model to obtain a two-dimensional model of the structural part to be formed and its geometric features; Step 2: Set material parameters and load constraints for the structural parts to be manufactured by additive manufacturing according to the requirements of molding materials and structural working conditions, and perform finite element simulation. Calculate the corresponding relationship between the unit and the node obtained by finite element simulation to obtain the coordinate data and principal stress data of the unit, and derive the finite element simulation calculation results of the unit; Step 3: Based on the finite element simulation calculation results, an additive manufacturing path planning method based on stress direction is constructed. The original contour line based on stress direction is calculated by performing linear fitting analysis on the finite element simulation calculation results of the unit; Step 4: Based on the calculated stress direction contour, the additive manufacturing path of the to-be-molded structural part is obtained according to the structural constraints of the molded structural part and the additive manufacturing process constraints.

2. A 3D printing continuous fiber reinforced composite material path planning method based on the absolute maximum principal stress direction according to claim 1, characterized in that: The specific steps of step 1 are: A three-dimensional model of the structure to be formed is established in computer-aided design software or three-dimensional modeling software, the three-dimensional model is sliced ​​to obtain a two-dimensional model of the structure to be formed, and the geometric features of the bounding box, the minimum width dimension of the structure and the number of singular points of the two-dimensional model of the structure to be formed are extracted.

3. The method for path planning of 3D printing continuous fiber reinforced composite materials based on the direction of absolute maximum principal stress according to claim 1, characterized in that: The specific steps of step 2 are: Step 21: By considering the molding materials and structural working conditions required for the structure to be molded, the material parameters of density, Young's modulus, and Poisson's ratio of the additive manufacturing molding materials of the structure to be molded, as well as the force magnitude, force form, force direction, constraint position, and load constraints of the constraint method of the structure to be molded under actual working conditions are obtained, and the load constraint conditions are simplified according to the actual conditions of the finite element simulation software to obtain the material parameters and load constraints of the structure to be molded by finite element simulation; Step 22: Calculate using commercial finite element simulation software, query and export finite element simulation results including node number, node coordinates, unit to which the node belongs, unit number, nodes included in the unit, unit S11 direction stress, unit S22 direction stress and unit S12 direction stress; Step 23: Obtain the node corresponding to each unit number through the unit number, the nodes contained in the unit and the unit to which the node belongs, and calculate the unit coordinates of each unit number according to the node number and the node coordinates, and correspond and export the unit number, unit coordinates, unit S11 direction stress, unit S22 direction stress and unit S12 direction stress.

4. The method for path planning of 3D printing continuous fiber reinforced composite materials based on the direction of absolute maximum principal stress according to claim 1, characterized in that: The step 3 is specifically as follows: Step 31: Process the finite element simulation calculation structure, and number the elements as e1, e2, ..., en in order from left to right and from bottom to top according to the element number, element coordinates, element S11 direction stress, element S22 direction stress and element S12 direction stress data obtained in step 2, where n ≥ 2; Step 32: According to the material mechanics formula, the maximum principal stress vector and the minimum principal stress vector of each unit are calculated through the unit S11 direction stress, the unit S22 direction stress and the unit S12 direction stress, and are recorded as nmaxs, nmaxa, nmins, nmina in sequence according to the unit number, where n is the unit number, s represents the modulus of the principal stress vector, and a represents the direction of the principal stress vector; Step 33: Calculate the principal stress vector of each unit cell in turn. Take the unit cell with unit number m as an example, and process mmaxs, mmaxa, mmins, and mmina of unit m, where m is the unit number. If the ratio of mmins to mmaxs is less than 1, the principal stress vector of unit m is ms=mmaxs, ma=mmaxa, otherwise ms=mmins, ma=mmina. Step 34: Starting from the unit labeled m, compare the ma of unit m with that of other surrounding units, where m is the unit number. If the difference between the ma of unit m and other surrounding units is within the set range, it is defined as an approximate unit. A linear fitting calculation is performed on the approximate unit based on its ma to obtain the fitting line of the approximate unit. The fitting lines of the approximate unit are connected in series to form the original contour line based on the stress direction.

5. The method for path planning of 3D printing continuous fiber reinforced composite materials based on the direction of absolute maximum principal stress according to claim 4, characterized in that: The set range refers to the range set by the fitting algorithm, specifically, the absolute value of the difference between the unit m and the ma of other surrounding units is less than the set value of the fitting algorithm. Linear fitting calculation refers to linear fitting of the units in the approximate unit data group, specifically, linear fitting calculation of the unit coordinates and unit absolute principal stress vector of each unit in the approximate unit data group.

6. The method for path planning of 3D printing continuous fiber reinforced composite materials based on the direction of absolute maximum principal stress according to claim 1, characterized in that: The step 4 obtains the additive manufacturing path of the structure to be formed based on the calculated stress direction contour line according to the structural constraints of the formed structure and the additive manufacturing process constraints, specifically: Step 41: The minimum width w of the structure calculated in step 1 and the track spacing d in the additive manufacturing process constraint are used to calculate the number of contour offsets c of the original stress-direction-based contour line, and the number of structural singular points calculated in step 1 is used to determine whether the structure can be drawn in one stroke. According to the original contour line based on the stress direction, the original contour line based on the stress direction is processed with contour offset in sequence from the outside to the inside according to the structural geometry, and c contour lines based on the stress direction are obtained, which are numbered as i 1, i2...in from the outside to the inside, where n≤c; the offset distance of the contour line is the additive manufacturing process parameter track spacing d, and the minimum width w of the structure to which it belongs is the smallest width in the structure to be formed, which can be calculated as the contour offset number c is w / d. Step 42: Connect from the starting point of contour im+1 to the end point of contour im+1 on contour line im+1, enter contour line im+2 along the line connecting the end point of contour line im+1 and the starting point of contour line im+2, and complete the path connection from contour line i 1 to contour line in in sequence, connect the adjacent contour lines between each of the contour lines obtained by biasing into a path connection line, and obtain the additive manufacturing path of the structural part to be formed.

7. An additive manufacturing application of a 3D printing continuous fiber reinforced composite material path planning method based on the direction of absolute maximum principal stress, characterized in that: The additive manufacturing path planning method based on stress direction as described in any one of claims 1 to 5 is used to plan the additive manufacturing path of the structural part to be formed: the material is extruded to form the part to be formed according to the planned printing path, and the formed part is formed layer by layer.

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