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

Abstract

The application relates to the field of additive manufacturing technology and discloses a 3D printing continuous fiber reinforced composite material path planning method based on the absolute maximum principal stress direction, which comprises the following steps: establishing a three-dimensional model of a structure to be formed, performing slice processing on the three-dimensional model to obtain a two-dimensional model of the structure to be formed and geometric characteristics thereof; setting material parameters and load constraints for the structure to be formed which needs to be subjected to additive manufacturing according to the requirements of forming materials and structure working conditions, and performing finite element simulation to derive finite element simulation calculation results of units; based on the finite element simulation calculation results, an original contour line based on a stress direction is calculated; and based on the calculated contour line based on the stress direction, an additive manufacturing path of the structure to be formed is obtained. The application improves the effect of improving the mechanical properties of continuous fiber composite material structures and improves the mechanical properties of composite material components under the premise of the same fiber content.

Description

TECHNICAL FIELD

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

[0002] FDM (Fused deposition molding) technology is an additive manufacturing method based on thermoplastic composites, which combines the characteristics of rapid prototyping technology and material deposition technology. It uses thermoplastic composite filaments as raw materials, heats them to a molten state using a heated nozzle, processes the three-dimensional model into layers using slicing software according to the STL model of the molded part, plans the movement path of the nozzle, and extrudes the molten material layer by layer and cools it to solidify, thereby realizing the direct manufacturing of complex shapes.

[0003] In the deposition molding process of continuous fiber reinforced thermoplastic composites, the additive manufacturing path directly affects the organization structure of the part. The current industry's more mature filling path planning scheme mainly uses Z-shaped method, streamline method, etc. The above filling path planning scheme does not consider 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 transmit stress along the load direction, resulting in poor mechanical properties, multiple fiber shearing, etc.

[0004] In the prior art, Chinese patent 202110972007.X discloses a 3D printing continuous fiber reinforced path planning method based on principal stress trajectory, which proposes a continuous fiber reinforced path formed by the number of interpolation points N in the design domain and the principal stress direction information of the extracted nodes. However, the structure 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 ensures parallelism with the load direction, but reduces the integrity and applicability of the structure to be formed. SUMMARY

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

[0006] An additive manufacturing path planning method based on stress direction, comprising the following steps:

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

[0008] Step 2: setting material parameters and load constraints for the to-be-formed structure that needs to be additively manufactured according to the requirements of the forming material and the structure working condition, and performing finite element simulation, obtaining the coordinate data and principal stress data of the element by calculating the corresponding relationship between the element and the node obtained from the finite element simulation, and exporting the finite element simulation calculation results of the element;

[0009] Step 3: based on the finite element simulation calculation results, constructing a stress direction-based additive manufacturing path planning method, calculating the original stress direction-based contour line by linear fitting analysis of the finite element simulation calculation results of the element;

[0010] Step 4: based on the calculated stress direction contour line, obtaining the additive manufacturing path of the to-be-formed structure according to the structural constraints and additive manufacturing process constraint requirements of the formed structure.

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

[0012] Step 21: obtaining the material parameters of the additive manufacturing forming material of the to-be-formed structure, including the density, Young's modulus and Poisson's ratio, and the load constraints of the to-be-formed structure under actual working conditions, including the stress size, stress form, stress direction, constraint position and constraint method, by considering the required forming material and structure working condition of the to-be-formed structure, and simplifying the load constraint according to the actual situation of the finite element simulation software,

[0013] Step 22: calculating by using a commercial finite element simulation software, querying and exporting the finite element simulation results including node number, node coordinates, node belonging element, element number, element containing nodes, element S11 direction stress, element S22 direction stress and element S12 direction stress,

[0014] Step 23: obtaining the node corresponding to each element number by using the element number, element containing nodes and node belonging element, and calculating the element coordinates of each element number according to the node number and node coordinates, and corresponding the element number, element coordinates, element S11 direction stress, element S22 direction stress and element S12 direction stress and exporting them.

[0015] Further, step 3 constructs a stress direction-based additive manufacturing path planning method according to the material mechanics formula and the relationship between the node coordinates and the node and the element, and based on the finite element simulation calculation results, constructs a stress direction-based additive manufacturing path planning method, calculates the original stress direction-based contour line by linear fitting analysis of the finite element simulation calculation results of the element, which is specifically:

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

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

[0018] Step 33: sequentially processing mmaxs, mmaxa, mmins and mmina of the element cell m, where m is the element number; if the ratio of mmins to mmaxs is less than 1, the stress vector of the element m is ms=mmaxs and ma=mmaxa, otherwise ms=mmins and ma=mmina;

[0019] Step 34: starting from the element with element number m, comparing the ma of the element m with the ma of the surrounding elements, if the difference between the ma of the element m and the ma of the surrounding elements is within a set range, the element is defined as an approximate element, and a linear fitting calculation is performed on the approximate element according to its ma to sequentially obtain element connecting lines, and the element connecting lines are connected in series to form the original stress direction-based contour line. The set range refers to that the absolute value of the difference between the ma of the element m and the ma of the surrounding elements is less than the set value of the fitting algorithm. The linear fitting calculation refers to linear fitting of the elements in the approximate element data group, specifically linear fitting calculation of the element coordinates and element stress vectors of each element in the approximate element data group.

[0020] In the case of the above technical solution, the additive manufacturing path connecting line formed according to the above path planning is more consistent with the original contour shape of the to-be-formed component, ensures continuous operation of the printing nozzle at a rated speed for a long distance, reduces the lifting frequency and empty running distance, can effectively reduce the stress concentration of the to-be-formed component, improves the structure flatness and the forming quality of the part, avoids the generation of relatively sharp sharp corners at the edges of the part caused by the traditional forming path, and avoids the frequent change of the printing nozzle travel speed in the real printing process, the lifting process of the printing nozzle causes poor interlayer performance in the real printing process, and the continuous fiber reinforced thermoplastic composite is cut more, resulting in material waste and the presence of faults in the part.

[0021] Further, the step 4 obtains the additive manufacturing path of the to-be-formed structural part according to the structural constraint of the formed structural part and the constraint requirement of the additive manufacturing process based on the profile line of the calculated stress direction, specifically as follows:

[0022] Step 41: the number of profile offsets c of the original stress direction-based profile line is calculated by the structural minimum width w 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 stress direction-based profile line, the original stress direction-based profile line is sequentially profile offset processed from outside to inside according to the structural geometry to obtain c stress direction-based profile lines, which are numbered from outside to inside as i 1, i 2,..., i n, where n≤c. The offset distance of the profile line is d, d is the track spacing size in the additive manufacturing process constraint, the minimum width w of the structure is the minimum size in the to-be-formed structure, and the number of profile offsets c is calculated by w / d.

[0023] In the case of adopting the above technical solution, the structural features and process conditions are considered in the path planning through the geometric size constraint of the structure and the process parameter constraint of the additive manufacturing, which is beneficial to the planning of the additive manufacturing printing path, the path is more uniform, and the printing quality is improved.

[0024] Each of the profile lines obtained by offsetting is connected in series to form a path connection line between adjacent profile lines, and the additive manufacturing path of the to-be-formed structural part is obtained. Specifically, it includes:

[0025] Step 42: connecting from the starting point of the profile im+1 to the terminal point of the profile im+1 in the direction of the profile im+1, entering the profile im+2 along the connection line between the terminal point of the profile im+1 and the starting point of the profile im+2, and sequentially completing the path connection of the profile i 1 to the profile i n. Each of the profile lines obtained by offsetting is connected in series to form a path connection line between adjacent profile lines, and the additive manufacturing path of the to-be-formed structural part is obtained.

[0026] An additive manufacturing method utilizes the additive manufacturing path planning method to plan the printing path, and utilizes the material extrusion to melt and deposit the to-be-formed part according to the formed path, and forms the to-be-formed part layer by layer.

[0027] In the case of adopting the above technical solution, the additive manufacturing path planning method is applied to the fused deposition modeling additive manufacturing method, and the forming quality and application range of the fused deposition modeling technology can be improved.

[0028] The beneficial effects of the present application are as follows:

[0029] 1. Compared with the prior art, the original stress direction based contour line is obtained by algorithm processing the finite element calculation result, the stress direction based contour line is subjected to contour offset processing according to the original stress direction based contour line, the structure constraint of the formed structural part and the additive manufacturing process constraint requirement, the additive manufacturing process constraint condition of the layer spacing and the path spacing, and the final stress direction based intelligent additive manufacturing path planning specific path is obtained, the formed structural part can be filled sufficiently, the printing head can run for a long distance at a rated speed, the shearing frequency and the frequent large curvature turning are reduced, the mechanical properties and stress transmission of the formed structural part are improved, the stress concentration is reduced, and the printing path is attached to the original contour shape of the part to a great extent.

[0030] 2. The stress direction based contour line obtained by linear fitting, the structure constraint of the formed structural part and the additive manufacturing process constraint requirement, and the additive manufacturing path planning specific path can avoid the low path filling rate of the traditional additive manufacturing path when printing the formed structural part, especially when printing the continuous fiber reinforced thermoplastic composite material and the complex, frame and beam structure formed structural part which needs to ensure continuity and integrity, the traditional path has the defects of poor path filling rate, not attached to the original contour shape of the formed structural part, and high shearing frequency, and the technical scheme of the present application can effectively improve the mechanical properties of the formed structural part, reduce the printing shearing frequency, improve the production efficiency of the formed structural part and the product qualification rate. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The stress direction based additive manufacturing path planning method flow chart provided for the embodiment of the present application;

[0032] Figure 2 The Z-shaped additive manufacturing path schematic diagram for the prior art;

[0033] Figure 3 The data processing diagram of the finite element simulation data result for the embodiment of the present application;

[0034] Figure 4 The schematic diagram of the data processing result based on the stress direction connection for the embodiment of the present application;

[0035] Figure 5 The stress based additive manufacturing path planning route result schematic diagram for the embodiment of the present application. DETAILED DESCRIPTION

[0036] The present application is further illustrated by the accompanying drawings and specific embodiments, and it should be understood that the following specific embodiments are only used to illustrate the present application and not to limit the scope of the present application. It should be noted that the words "front", "back", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings, and the words "in" and "out" refer to the directions towards or away from the geometric center of a particular component.

[0037] As shown in the conventional process, a zigzag additive manufacturing path is used to generate relatively sharp sharp corners at the edges of the part, the printing head travel speed changes frequently during the actual printing process, the printing head lifting process will cause the interlayer performance to be poor during the actual printing process, and the continuous fiber reinforced thermoplastic composite is cut more, resulting in material waste and internal fault of the part. Figure 2

[0038] To solve the above problems, as shown in the Figure 1 The embodiment of the present application 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 structure to be formed, slice the three-dimensional model, and obtain a two-dimensional model of the structure to be formed and its geometric characteristics;

[0040] S2: According to the requirements of the forming material and the structure working condition, set the material parameters and load constraints of the structure to be formed which needs to be additively manufactured, and carry out finite element simulation, calculate the coordinate data and principal stress data of the element by calculating the corresponding relationship between the element and the node obtained by finite element simulation, and export the finite element simulation calculation results of the element;

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

[0042] S4: Based on the stress direction contour line calculated, according to the structure constraint and additive manufacturing process constraint requirement of the formed structure, the additive manufacturing path of the structure to be formed is obtained.

[0043] Specifically, the above step S3 comprises:

[0044] S301: Process the finite element simulation calculation structure, according to the element number, element coordinate, element S11 direction stress, element S22 direction stress and element S12 direction stress data obtained in step 2, according to the order of row from left to right and column from bottom to top, the element number is e1, e2......en, 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 by the unit S11 direction stress, the unit S22 direction stress and the unit S12 direction stress: and, which are sequentially recorded as nmaxs, nmaxa, nmins, nmina according to the unit number, wherein n is the unit number;

[0046] S303: The mmaxs, mmaxa, mmins and mmina of the unit cell m are processed in turn, wherein m is the unit number; if the ratio of mmins and 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 with unit number m, the ma of unit m is compared with that of other surrounding units, if the difference between the ma of unit m and that of other surrounding units is within a certain range, it is defined as an approximate unit, and the ma of the approximate unit is linearly fitted to obtain a unit connecting line in turn, and the unit connecting lines are connected in series to form the original stress direction based contour line.

[0048] In the case of the above technical solution, the additive manufacturing path connecting line formed according to the above path planning is more consistent with the original contour shape of the to-be-formed component, ensures the continuous operation of the printing nozzle at the rated speed for a long distance, reduces the lifting frequency and empty driving distance, can effectively reduce the stress concentration of the to-be-formed component, improves the structure flatness, improves the forming quality of the part, avoids the generation of relatively sharp corners at the edge of the part caused by the traditional forming path, the printing nozzle travel speed changes frequently in the real printing process, the printing nozzle lifting process will cause the interlayer performance to be poor in the real printing process, and the continuous fiber reinforced thermoplastic composite is cut more, causing material waste and the phenomenon of internal fault in the part.

[0049] Step S4 is specifically:

[0050] S401: The number of contour offsets c of the original stress direction based contour line is calculated by the structure minimum width w calculated in step 1 and the path spacing d in the additive manufacturing process constraint, and whether the structure can be drawn in one stroke is obtained by the structure singularity number calculated in step 1. According to the original stress direction based contour line, the original stress direction based contour line is processed according to the structure geometry from outside to inside to obtain c stress direction based contour lines, which are numbered from outside to inside as i1, i2...in, wherein n≤c.

[0051] S402: connecting from the starting point of the contour im+1 to the end point of the contour im+1 on the contour line im+1, entering the contour line im+2 along the connecting line between the end point of the contour line im+1 and the starting point of the contour line im+2, and sequentially completing the path connection of the contour line i 1 to the contour line i n, connecting the adjacent contour lines in series to obtain the additive manufacturing path of the to-be-formed structure.

[0052] The application further discloses an additive manufacturing method, which utilizes the additive manufacturing path planning method to plan the additive manufacturing path of a to-be-formed structure.

[0053] In the case of the technical scheme, the additive manufacturing path planning method of the first aspect is applied to the fused deposition modeling additive manufacturing method, so that the forming quality and application range of the fused deposition modeling technology can be improved.

[0054] The application is suitable for continuous fiber reinforced thermoplastic composite materials that need to ensure continuity and integrity, and parts of complex, frame and beam structures, and can effectively improve the surface quality of products.

[0055] The application will be briefly described below by taking a curved beam structure as an example.

[0056] S1: introducing a to-be-formed curved beam structure, performing slice processing on the three-dimensional model to obtain a two-dimensional model corresponding to the to-be-formed structure, and extracting geometric features as follows: the bounding box is 150 mm long, 25 mm wide, and 4 mm thick, the minimum size of the structure is 1.2 mm, and the number of singular points is 2.

[0057] S2: obtaining material parameters of the additive manufacturing of the curved beam structure, including a density of 1.33 g / cm3, a Young's modulus of 25520 MPa, and a Poisson's ratio of 0.31, and stress of the to-be-formed structure under actual working conditions is 500 N, stress form is concentrated force, stress direction is the negative direction of the Y axis, constraint position is the lower left corner and the lower right corner of the curved beam structure, and constraint mode is fixed load constraint.

[0058] S3: performing calculation by using a commercial finite element simulation software, and querying and exporting finite element simulation results including node serial number, node coordinates, nodes belonging to the unit, unit serial number, nodes contained in the unit, unit S11 direction stress, unit S22 direction stress and unit S12 direction stress.

[0059] S4: importing the finite element simulation results into the method to obtain, for example, Figure 3The finite element simulation calculation result of the shown to-be-formed structure unit is based on the finite element simulation calculation result, the linear fitting calculation is carried out on the approximate unit, the additive manufacturing path planning method based on the stress direction is substituted, and the original stress direction-based contour line as shown in Figure 4 is obtained.

[0060] S5: according to the structure geometric characteristics and the additive manufacturing process constraint requirement, the inter-path distance is 0.6mm, and the two-dimensional additive manufacturing path of the to-be-formed structure as shown in Figure 5 is obtained. Compared with the traditional uniform continuous fiber reinforced path, the mechanical property of the continuous fiber reinforced path sample based on the principal stress trajectory is obviously improved.

[0061] In summary, the additive manufacturing path planning method based on the stress direction is proposed, the additive manufacturing path connection line formed according to the above path planning is more suitable for the original contour shape of the to-be-formed component, the printing nozzle can continuously run for a long distance at the rated speed, the lifting frequency and the empty running distance are reduced, the stress concentration of the to-be-formed component can be effectively reduced, the structure flatness is improved, the forming quality of the part is improved, the sharp corners at the edge of the part caused by the traditional forming path are avoided, the printing nozzle running speed changes frequently in the real printing process, the lifting process of the printing nozzle will cause the interlayer performance to be poor in the real printing process, and the continuous fiber reinforced thermoplastic composite is cut more, which causes material waste and the phenomenon that there are faults in the part.

[0062] The technical means disclosed in the scheme of the present application is not limited to the technical means disclosed in the above-mentioned embodiments, but also includes the technical scheme 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, Includes the following steps: 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: Based on the requirements of the molding material and structural conditions, set the material parameters and load constraints for the structural parts to be manufactured by additive manufacturing, and perform finite element simulation. Calculate the coordinate data and principal stress data of the elements by analyzing the correspondence between the elements and nodes obtained from the finite element simulation, and export the finite element simulation calculation results of the elements. Step 3: Based on the finite element simulation results, construct an additive manufacturing path planning method based on stress direction. By performing linear fitting analysis on the finite element simulation results of the elements, the original contour line based on the stress direction is calculated. Specifically, Step 3 involves: Step 31: Process the finite element simulation calculation structure. Based on the element number, element coordinates, stress in the S11 direction, stress in the S22 direction, and stress in the S12 direction obtained in Step 2, number the elements as e1, e2, ..., en in the order of rows from left to right and columns from bottom to top, where n≥2. Step 32: According to the formulas of mechanics of materials, calculate the maximum principal stress vector and the minimum principal stress vector of each element through the stress in the S11 direction, the S22 direction, and the S12 direction. Record them as nmaxs, nmaxa, nmins, and nmina in sequence according to the element number, where n is the element number, s represents the magnitude of the principal stress vector, and a represents the direction of the principal stress vector. Step 33: Calculate the principal stress vector of each cell in sequence. Taking cell m as an example, process mmaxs, mmaxa, mmins, and mmina of cell m, where m is the cell number. If the ratio of mmins to mmaxs is less than 1, then the principal stress vector of cell m is ms=mmaxs, ma=mmaxa; otherwise, ms=mmins, ma=mmina. Step 34: Starting from the unit with unit number m, compare the ma of unit m with that of the surrounding units, where m is the unit number. If the difference between unit m and the ma of the surrounding units is within the set range, then define it as an approximate unit. Perform linear fitting calculation on the approximate unit based on its ma to obtain the fitting line of the approximate unit. Connect the fitting lines of the approximate unit to form the original contour line based on the stress direction. Step 4: Based on the calculated stress direction contour, and according to the structural constraints and additive manufacturing process constraints of the formed component, obtain the additive manufacturing path for the component to be formed; specifically, Step 4 involves: Step 41: Using the minimum structural width w calculated in Step 1 and the channel spacing d in the additive manufacturing process constraints, calculate the original number of contour offsets c based on the stress direction. Determine whether the structure can be drawn in one stroke using the number of structural singularities calculated in Step 1. Based on the original stress direction contours, sequentially perform contour offset processing on the original stress direction contours from the outside in according to the structural geometry, obtaining c stress direction contours, numbered i1, i2...in from the outside in, where n≤c; the offset distance of the contours is the channel spacing d in the additive manufacturing process parameter, the minimum structural width w is the smallest width in the structure to be formed, and the number of contour offsets c is calculated as w / d. Step 42: Connect from the starting point of contour line im+1 to the ending point of contour line im+1. Enter contour line im+2 along the line connecting the ending point of contour line im+1 and the starting point of contour line im+2. Complete the path connection from contour line i1 to contour line in in sequence. Connect adjacent contour lines between each contour line obtained by offset to form a path connection line to obtain the additive manufacturing path of the structure to be formed.

2. The path planning method for 3D printed continuous fiber reinforced composite materials based on the absolute maximum principal stress direction according to claim 1, characterized in that, The specific steps of step 1 are as follows: a three-dimensional model of the structural component 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, minimum width dimension and number of singularities of the two-dimensional model of the structure to be formed are extracted.

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

4. The path planning method for 3D printed continuous fiber reinforced composite materials based on the absolute maximum principal stress direction according to claim 1, characterized in that, The set range refers to the range set by the fitting algorithm. Specifically, the absolute value of the difference between element m and the ma of other surrounding elements is less than the set value of the fitting algorithm. Linear fitting calculation refers to performing linear fitting on elements within the approximate element data group. Specifically, it involves performing linear fitting calculation on the element coordinates and absolute principal stress vector of each element within the approximate element data group.

5. An additive manufacturing application of a path planning method for 3D printing continuous fiber reinforced composite materials based on the absolute maximum principal stress direction, characterized in that, Using the stress-direction-based additive manufacturing path planning method according to any one of claims 1 to 4, the additive manufacturing path of the structural part to be formed is planned: by material extrusion, the part to be formed is extruded and formed layer by layer according to the planned printing path.

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