Integrated control method for strength, rigidity and randomness of 3D printing structural part

Abstract

The invention belongs to the technical field of additive manufacturing, and particularly discloses a 3D printing structural part strength, rigidity and randomness integrated control method which comprises the following steps: S1, selecting a printing material according to mechanical requirements; s2, printing parameters are determined; s3, determining a printing parameter range; s4, printing parameter selection values are determined; s5, performing orthogonal test combination to print parameters; s6, performing a mechanical test; s7, fitting a multivariable regression model; s8, analyzing the stress of the structural member; s9, carrying out structural part region division; s10, printing parameter combination endowing; and S11, 3D printing is conducted. According to the integrated control method for the strength, the rigidity and the randomness of the 3D printing structural component, regional integrated optimization of the strength, the rigidity and the randomness of the target component is taken as a target, the components are dominantly divided through tension and compression and the strength and rigidity randomness, and different printing parameters are given, so that the components meet the strength requirement, and meanwhile, the strength, the rigidity and the randomness of the target component are greatly improved. And higher rigidity and lower randomness are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a method for integrated control of strength, stiffness and randomness of 3D printed structural parts. Background Art

[0002] Melt extrusion technology is one of the technologies widely used in additive manufacturing. Melt extrusion technology sends thermoplastic filaments to the heating end to melt them within a specific temperature range, then extrude them through the nozzle, cool and bond them on the printing plate, and stack them layer by layer. After the entire 3D printing process, the mechanical properties of the filaments will change significantly, which in turn affects the mechanical properties of the printed product.

[0003] During the melt extrusion printing process, various machine parameters such as nozzle temperature, base speed, extrusion layer height, trace width and filling rate can also be adjusted according to needs. Different printing parameter settings have a great influence on the mechanical properties of the printed components when the material is the same. The strength of the printed components produced by different printing equipment is also different, making it difficult to obtain printed products with stable performance.

[0004] In the prior art, the improvement of the performance of printed components is mainly focused on improving strength. For example, the invention patent application with publication number CN117172070A discloses a method for optimizing component 3D printing parameters based on mechanical guidance. Through orthogonal experiments and signal-to-noise ratio analysis, the optimization control of printing parameters for strength is considered, but the stiffness is not considered, and the randomness of the printed components is not guaranteed to be minimized, making it difficult to ensure the performance stability of 3D printed products. Only some areas of the printed components have large stress and strain, and the strength redundancy of some areas is still large. While ensuring that the strength of the 3D printed structural parts meets the requirements, the strength redundancy area can be given parameters with higher stiffness and lower randomness, ensuring strength while improving the stiffness and stability of the structure.

[0005] Therefore, it is necessary to provide an integrated control method for the strength, stiffness and randomness of 3D printed structural parts to solve the above problems. Summary of the invention

[0006] The purpose of the present invention is to provide a method for integrated control of strength, stiffness and randomness of 3D printed structural parts. On the basis of considering the actual force type composition and printing principle, the regional integration of strength, stiffness and randomness of the target component is taken as the optimization goal, the components are divided by tension, compression, strength, stiffness and randomness, and different printing parameters are assigned, so that the components meet the strength requirements while having higher stiffness and lower randomness.

[0007] To achieve the above object, the present invention provides a method for integrated control of strength, stiffness and randomness of 3D printed structural parts, comprising the following steps: S0, build material property library; S1. Select 3D printing materials according to mechanical requirements; S2. Determine printing parameters that affect mechanical properties; S3, determining the printing parameter range: determining the maximum and minimum values ​​of each printing parameter from the molding perspective to obtain the printing parameter range; S4, determine the selected values ​​of printing parameters: select 3-5 values ​​of the same number at equal intervals for each printing parameter; S5. Orthogonal test combination printing parameters: obtaining a printing parameter combination based on an orthogonal test design, wherein the printing parameters are factors in the orthogonal test, and the selected values ​​of the printing parameters are levels in the orthogonal test; S6, mechanical test: using the printing parameter combination obtained in S5 to print the tension standard specimen and the compression standard specimen respectively, and conduct mechanical tests to obtain mechanical test data; S7, multivariate regression model fitting: obtain the regression matrix of strength, stiffness, randomness and printing parameters; S8. Stress analysis of structural parts: Conduct finite element analysis on structural parts to obtain stress and strain predictions of various parts; S9. Structural parts area division: Structural parts area is divided according to the tension and compression state, stiffness and strength randomness dominant relationship; S10, assigning printing parameter combinations: assigning printing parameter combinations according to the structural parts area division; S11, 3D printing of structural parts: combining slicing and printing according to the given printing parameters.

[0008] Preferably, in S0, the material property library includes actual 3D printing materials and the strength, stiffness and elastic modulus of the 3D printing materials.

[0009] Preferably, in S2, the printing parameters include one or more of layer height, line width, nozzle temperature and printing speed.

[0010] Preferably, in S3, the printing parameter range is determined by the molding effect of the target structural part through trial printing.

[0011] Preferably, in S4, the number of selected values ​​of the printing parameters is n , the specific range of printing parameter selection values ​​is: ; in, The minimum value among the selected values ​​for the print parameters, The maximum value among the selected values ​​for the print parameters. The number of values ​​selected for the print parameter, Select values ​​for printing parameters No. A selected value, =1,2,…,max.

[0012] Preferably, in S6, the tensile standard specimen and the compressive standard specimen are one of ASTM, ISO or GB, and the mechanical test data include one or more of tensile strength, tensile stiffness, tensile elastic modulus, compressive strength, compressive stiffness and compressive elastic modulus.

[0013] Preferably, in S7, the data of the multivariate regression model fitting comes from S6 to finally obtain the regression matrix of each printing parameter A, B, C, ..., and strength Sr, stiffness Si and randomness R: ; in, is a vector of print parameters, is the regression coefficient matrix, is the vector of mechanical properties, is the error vector.

[0014] Preferably, in S8, the stress analysis of the structural member adopts finite element method, and priority is given to ensuring that the strength of the structural member meets the requirements. The data adopted by the finite element method come from the mechanical test data of the tensile quasi-specimen with the highest tensile strength and the compressive standard specimen with the highest compressive strength in S6.

[0015] Preferably, in S9, the strength of the material obtained in S5 , stiffness , Randomness The stress and strain prediction results obtained by S8 are divided into regions as follows: Randomness-dominated area: The area in the target structural part where the finite element stress is less than 30% of the strength is the randomness-dominated area; Strength-dominated area: When the finite element stress of the area in the target structural part is ≥ 70% of the strength, it is the strength-dominated area; Stiffness-dominated region: When the finite element stress of the region in the target structural part is less than 70% and ≥30% of the strength, it is the stiffness-dominated region; According to the positive and negative stress values ​​of the finite element analysis of S8, the target structural parts are first divided into tension zones and compression zones, and the zone types include tension strength zone, compression strength zone, tension stiffness zone, compression stiffness zone, tension random zone, and compression random zone; The strength was quantified by selecting the average value of the peak value of the mechanical test curve; The quantification method of stiffness is to select the average value of the tangent line of the elastic segment of the mechanical test curve; The randomness comes from strength and stiffness respectively, and the quantitative formula is as follows: ; in, is the standard deviation of the mechanical test data, is the mean value of mechanical test data.

[0016] Preferably, S10 is specifically: Tensile strength zone: the printing parameter combination that gives the highest printable tensile strength; Compressive strength zone: the printing parameter combination that gives the highest compressive strength to the printable; Tensile stiffness zone: a printing parameter combination that gives the highest printable tensile stiffness and a tensile strength not less than the regional stress; Compressive stiffness zone: a printing parameter combination that gives the highest printable compressive stiffness and a compressive strength not less than the regional stress; Tensile random zone: the printing parameter combination that gives the lowest printable tensile randomness and a tensile strength not less than the regional stress; Stress random zone: The printing parameter combination that gives the lowest printable stress randomness and a stress strength not less than the regional stress.

[0017] Therefore, the present invention adopts the above-mentioned 3D printed structural component strength stiffness and randomness integrated control method, and the beneficial effects are as follows: The present invention takes into account the actual force type composition and printing principle, and according to actual needs, takes the regional integration of the strength, stiffness and randomness of the target component as the optimization goal, integrates the control of the strength, stiffness and randomness of the structural parts, divides the components by tension, compression, strength, stiffness and randomness to determine the required manufacturing parameters of the components under specific target force conditions, controls the performance and randomness of the structural parts, and makes the components meet the strength requirements while having higher stiffness and lower randomness.

[0018] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a flow chart of an embodiment of a method for integrated control of strength, stiffness and randomness of a 3D printed structural part according to the present invention; Figure 2 is the test result of a standard tensile specimen of an embodiment of a method for integrated control of strength, stiffness and randomness of a 3D printed structural component of the present invention, wherein (a) is the tensile strength, and (b) is the tensile elastic modulus; Figure 3 is the test result of a standard compressive specimen of an embodiment of a method for integrated control of strength, stiffness and randomness of a 3D printed structural component of the present invention, wherein (a) is the compressive strength, and (b) is the compressive elastic modulus; Figure 4It is a component tension and compression distribution diagram of an embodiment of a method for integrated control of strength, stiffness and randomness of a 3D printed structural component of the present invention; Figure 5 It is a component area division diagram of an embodiment of a method for integrated control of strength, stiffness and randomness of a 3D printed structural component of the present invention; Figure 6 It is the printing parameter optimization result of an embodiment of a method for integrated control of strength, stiffness and randomness of a 3D printed structural part of the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0021] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0022] Embodiment 1 like Figure 1 As shown, a method for integrated control of strength, stiffness and randomness of 3D printed structural parts includes material level and structural level. Material level: a 3D printing material parameter combination prediction method based on multivariate regression, establishing the relationship between the strength, stiffness, randomness of the material and the 3D printing parameter combination; structural level: a 3D printing parameter combination allocation method for structural parts based on force analysis and mechanical requirements, that is, based on the analysis results of the structural parts by finite element, the structural parts are divided into regions according to the tension and compression state, strength stiffness and randomness dominant relationship, and different printing parameters are assigned. Among them, S0 and S1 are preparation methods; S2-S7 are the specific steps of the material level method; S8-S11 are the specific steps of the structural level method, which are as follows: S0, build material property library: enter the existing actual 3D printing materials and the strength, stiffness and elastic modulus of 3D printing materials into the material property library. First, select roughly matching materials from the property data of existing 3D printing materials. The source of material properties in the material property library is directly given by the manufacturer or accumulated in previous experiments, and is only used as a reference value to facilitate S1 to select materials.

[0023] S1. Select 3D printing materials based on mechanical requirements: Select appropriate 3D printing materials based on the strength, stiffness and other mechanical requirements of the printed structural parts.

[0024] S2. Determine the printing parameters that have the greatest impact on mechanical properties: Determine the printing parameters that have the greatest impact based on the characteristics of the 3D printing material. In this embodiment, the printing parameters that have the greatest impact on the mechanical properties of FDM type 3D printing are generally layer height, line width, nozzle temperature and printing speed.

[0025] S3, determine the printing parameter range: determine the maximum and minimum values ​​of each printing parameter from the molding angle to obtain the printing parameter range. In this embodiment, the printing parameter range is determined by the molding effect of the target structural part of the trial printing.

[0026] S4, determine the selected values ​​of the printing parameters: each printing parameter is equally spaced and selected with the same number of 3-5 values. In this embodiment, the selected value range of the printing parameter is determined by S3, and the number of selected values ​​of each printing parameter is the same. n , then the range of printing parameter selection values ​​is: ; Where: Select the minimum value for the printing parameter; The maximum value among the selected values ​​for the printing parameters; The number of values ​​selected for the print parameters; For printing parameters No. Selected values ​​( =1,2,…,max).

[0027] S5. Orthogonal test combination printing parameters: obtain a printing parameter combination based on the orthogonal test design. In this embodiment, in the orthogonal test combination printing parameters, the printing parameters are factors in the orthogonal test, and the selected printing parameter values ​​are levels in the orthogonal test.

[0028] S6, mechanical test: Use the printing parameter combination obtained in S5 to print the tensile quasi-test piece and the compressive standard test piece respectively, and perform mechanical tests to obtain mechanical test data. In this embodiment, the tensile quasi-test piece and the compressive standard test piece printed in the mechanical test refer to one of ASTM, ISO, and GB, and the specific specification is determined by the material used.

[0029] S7, multivariate regression model fitting: obtain the regression matrix of strength, stiffness, randomness and printing parameters. In this embodiment, the data of the multivariate regression model fitting comes from S6, and finally obtains the regression matrix of each printing parameter (A, B, C, ...,) and strength (Sr), stiffness (Si) and randomness (R): ; In the formula is a vector of printing parameters; is the regression coefficient matrix; is the vector of mechanical properties; is the error vector.

[0030] S8. Stress analysis of structural parts: Conduct finite element analysis on structural parts to obtain stress and strain predictions for each part, giving priority to ensuring that the strength of the structural parts meets the requirements.

[0031] S9. Structural component area division: The component area is divided according to the tension and compression state, stiffness, strength and randomness dominant relationship. According to the positive and negative stress values ​​of the finite element analysis in S8, the target structural component is first divided into a tensile zone and a compressive zone. Therefore, the data used by the finite element come from the mechanical test data of the specimens with the highest tensile strength and compressive strength in S6. Combined with the dominant relationship between strength, stiffness and randomness of the target structural component, the structural component is divided into six types of areas: tensile strength zone, compressive strength zone, tensile stiffness zone, compressive stiffness zone, tensile random zone, and compressive random zone. The method for determining the dominant relationship between strength, stiffness and randomness of a certain area is as follows: According to the strength of the material obtained in S5 , stiffness , Randomness The data and analysis results of the finite element analysis in S8 are as follows: Randomness Dominant Region: The finite element stress of the region in the target structure <Strength 30% is the randomness-dominated area.

[0032] Strength Dominant Region: The finite element stress of the region in the target structure ≥ Strength When it is 70%, it is the intensity-dominated area.

[0033] Stiffness Dominant Region: The stress of the finite element in the region of the target structure <Strength When the stiffness is 70% and ≥30%, it is the stiffness dominant area.

[0034] The strength is quantified by taking the average value of the peak value of the mechanical test curve.

[0035] The method to quantify the stiffness is to select the average value of the tangent of the elastic segment of the mechanical test curve.

[0036] The randomness comes from strength and stiffness respectively, and the quantitative formula is as follows: ; in, is the standard deviation of the mechanical test data, is the mean value of mechanical test data.

[0037] S10, Printing parameter combination assignment: assign printing parameter combinations according to the structural component area division. Based on the multivariate regression model constructed in S7 to calculate the printing parameters, the printing parameter combination assignment in S10 divides the component into six areas: Tensile Strength Zone: The combination of printing parameters that gives the highest tensile strength of the printable.

[0038] Compressive Strength Zone: The combination of printing parameters that gives the highest compressive strength to the printable.

[0039] Tensile stiffness zone: The printing parameter combination that gives the highest printable tensile stiffness and a tensile strength not less than the regional stress.

[0040] Compressive stiffness zone: The printing parameter combination that gives the highest printable compressive stiffness and a compressive strength not less than the regional stress.

[0041] Tensile random zone: The printing parameter combination that gives the lowest printable tensile randomness and a tensile strength not less than the regional stress.

[0042] Stress random zone: The printing parameter combination that gives the lowest printable stress randomness and a stress strength not less than the regional stress.

[0043] S11, 3D printing of structural parts: combining slicing and printing according to the given printing parameters.

[0044] Embodiment 2 Using the method of Example 1, based on the materials in the 3D printing material attribute library, polylactic acid (PLA) material was selected as the research object according to the requirements. According to the characteristics of PLA material, the printing parameters that have a greater impact on its mechanical properties are layer height, nozzle temperature and printing speed.

[0045] Combined with the molding temperature of PLA material 195℃-215℃, the range of nozzle temperature was determined. According to the speed of the printer, the range of printing speed was determined to be 50mm / s-70mm / s. Combined with molding quality and efficiency, the range of layer height was 0.20mm-0.30mm.

[0046] For each printing parameter, three values ​​of the same number are selected at equal intervals, such as the printing speed (A) 50mm / s ( )、60mm / s( )、70mm / s( ), nozzle temperature (B) 195℃ ( )、205℃( ) and 215℃( ), layer height (C) 0.20mm ( )、0.25mm( ) and 0.30mm( ). Then the orthogonal test combination is three factors and three levels L9(3 3 ), as shown in Table 1.

[0047] Table 1 Orthogonal test combinations ;

[0048] ASTM D638-2014 and ASTM D695 were used to print the tension standard specimens and the compression standard specimens respectively under the obtained printing parameter combinations, and mechanical tests were carried out respectively. The mechanical test data results are shown in Figure 2 and Figure 3 shown.

[0049] The multivariate regression model is used to fit the mechanical test results to obtain the regression matrix of strength, stiffness, randomness and printing parameters. The data for the multivariate regression model fitting comes from the regression matrix of each printing parameter (A, B, C) and strength (Sr), stiffness (Si) and randomness (R): ; Where: is a vector of printing parameters; is the regression coefficient matrix; is the vector of mechanical properties; is the error vector.

[0050] In this embodiment, the stretched regression coefficient matrix : [4.29397545e-02 1.48807179e+01 -3.25070769e-02 2.08546476e-011.11938109e+01 4.17655046e-02 -3.16225765e+01 -1.58276433e+03 -1.20941617e+01] In this embodiment, the stretched error vector for: [-2.86651579e+03 2.51574537e+02 3.10228331e+05 -3.01455481e+033.43447006e+02 3.26057907e+05 -3.16612799e+03 3.05141643e+02 3.41881555e+05 -2.86930386e+03 4.65276729e+02 3.10542340e+05 -3.01332282e+03 6.76075130e+023.26369077e+05 -3.16151760e+03 5.04512933e+02 3.42195300e+05 -2.86697360e+036.94308519e+02 3.10858565e+05 -3.01916986e+03 4.11895155e+02 3.26687647e+05 -3.16336292e+03 7.04407557e+02 3.42515430e+05] In this embodiment, the compressed regression coefficient matrix : [-4.64348004e-02 2.01499077e+00 -2.04965338e-02 3.65098479e-011.06812636e+01 7.68021500e-03 -6.80488257e+01 -1.80281682e+03 4.59824888e+00] In this embodiment, the compressed error vector for: [-3.31968508e+02 -7.31208609e+01 3.54951902e+05 -3.53746846e+02 -1.99196714e+02 3.72980893e+05 -3.77118703e+02 -6.19804567e+02 3.91008036e+05-3.40450048e+02 -3.82504614e+02 3.55632128e+05 -3.50780767e+02 -4.86399648e+02 3.73660420e+05 -3.75103549e+02 -4.05932002e+02 3.91690166e+05 -3.36550290e+02 -2.20666381e+02 3.56312461e+05 -3.59953387e+02 -4.96588234e+023.74341443e+05 -3.70712553e+02 -2.51867936e+02 3.92368986e+05] First, if Figure 4 As shown, finite element analysis is performed on the component to obtain stress and strain predictions for each part. According to the positive and negative stress values ​​in the finite element analysis, the target structural member is first divided into a tensile zone (purple) and a compressive zone (gray).

[0051] Then, Figure 2 and Figure 3 The mechanical test data of the specimens with the highest tensile strength (tensile strength 40.41 MPa, tensile elastic modulus 3125 MPa) and the highest compressive strength (compressive strength 59.50 MPa, compressive elastic modulus 2070 MPa) were assigned to the tension zone and the compression zone, respectively.

[0052] Then, if Figure 5 As shown in the figure, the component area is divided according to the tensile and compressive state, the stiffness and strength randomness dominant relationship, the printing parameters are calculated based on the multivariate regression model, and the printing parameter combination is assigned. The component is divided into 6 areas, of which the orange is the tensile strength area ( ≥Tensile strength 70% of the total), the printing parameters are: T6: printing speed 60mm / s, nozzle temperature 215℃, printing layer height 0.25mm; pink is the compressive strength area ( ≥Compression strength 70% of the total), the printing parameters are: C5: printing speed 60mm / s, nozzle temperature 205℃, printing layer height 0.20mm. Green is the tensile stiffness area ( <Tensile strength 70% and ≥30%), the printing parameters are: T9: printing speed 70mm / s, nozzle temperature 215℃, printing layer height 0.20mm; red is the compressive stiffness area ( <Compression strength 70% and ≥30%), the printing parameters are: C1: printing speed 50mm / s, nozzle temperature 195℃, printing layer height 0.20mm; blue is the tensile random area ( <Tensile strength 30% of the total area), the printing parameters are: T8: printing speed 70mm / s, nozzle temperature 205℃, printing layer height 0.30mm; yellow is the random area under pressure ( <Compression strength The printing parameters are: C4: printing speed 60mm / s, nozzle temperature 195℃, printing layer height 0.30mm.

[0053] Slice and print according to the given printing parameter combination. Use the 3D printing slicing algorithm to convert the control printing parameter combination obtained by analysis into specific instructions for slicing printing and manufacturing. Except for the printing speed, nozzle temperature and layer height that are modified according to needs, the other settings remain the same to obtain 3D printed structural parts.

[0054] Experimental Testing The 3D printed structural part obtained in Example 2 was subjected to a compression test. The test results are as follows: Figure 6 shown.

[0055] The first group corresponds to printing parameter T6, that is, the entire structure is built using printing parameter T6. Similarly, the second group corresponds to printing parameter C5, the third group corresponds to printing parameter T9, the fourth group corresponds to printing parameter C1, the fifth group corresponds to printing parameter T8, the sixth group corresponds to printing parameter C4, and the seventh group is based on Figure 5 The partitions are assigned corresponding printing parameters.

[0056] Depend on Figure 6 It can be seen that the first and second groups respectively use the parameters with the best tensile and compressive strength, and the corresponding lattice structure has a larger ultimate bearing capacity, but smaller stiffness and greater randomness; the third and fourth groups respectively use the printing parameters with the best tensile and compressive stiffness, and the corresponding lattice structure has a larger stiffness, but smaller strength and greater randomness; the fifth and sixth groups respectively use the printing parameters with the smallest tensile and compressive randomness, and the corresponding lattice structure has the smallest randomness, but smaller strength and smaller stiffness; the seventh group is based on Figure 6The optimal printing parameters are used for each partition. Under this combination of printing parameters, the lattice structure has the highest strength, the highest stiffness, and the lowest randomness. The tension area of ​​the entire structure is larger than the compression area. In the performance direction, the performance of the optimal printing parameters corresponding to tension will be slightly higher than that corresponding to the optimal printing parameters for compression.

[0057] Therefore, the present invention adopts the above-mentioned integrated control method of strength, stiffness and randomness of 3D printed structural parts, takes the regional integrated optimization of the strength, stiffness and randomness of the target component as the goal, divides the components by tension, compression, strength, stiffness and randomness, and assigns different printing parameters, so that the components meet the strength requirements while having higher stiffness and lower randomness.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts, characterized in that: The following steps are involved: S0, build material property library; S1. Select 3D printing materials according to mechanical requirements; S2. Determine printing parameters that affect mechanical properties; S3, determining the printing parameter range: determining the maximum and minimum values ​​of each printing parameter from the molding perspective to obtain the printing parameter range; S4, determine the selected values ​​of printing parameters: select 3-5 values ​​of the same number at equal intervals for each printing parameter; S5. Orthogonal test combination printing parameters: obtaining a printing parameter combination based on an orthogonal test design, wherein the printing parameters are factors in the orthogonal test, and the selected values ​​of the printing parameters are levels in the orthogonal test; S6, mechanical test: using the printing parameter combination obtained in S5 to print the tension standard specimen and the compression standard specimen respectively, and conduct mechanical tests to obtain mechanical test data; S7, multivariate regression model fitting: obtain the regression matrix of strength, stiffness, randomness and printing parameters; S8. Stress analysis of structural parts: Conduct finite element analysis on structural parts to obtain stress and strain predictions of various parts; S9. Structural parts area division: Structural parts area is divided according to the tension and compression state, stiffness and strength randomness dominant relationship; S10, assigning printing parameter combinations: assigning printing parameter combinations according to the structural parts area division; S11, 3D printing of structural parts: combining slicing and printing according to the given printing parameters.

2. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 1, characterized in that: In S0, the material property library includes actual 3D printing materials and the strength, stiffness and elastic modulus of the 3D printing materials.

3. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 1, characterized in that: In S2, the printing parameters include one or more of layer height, line width, nozzle temperature and printing speed.

4. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 1, characterized in that: In S3, the printing parameter range is determined by the molding effect of the target structural part through trial printing.

5. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 1, characterized in that: In S4, the number of selected values ​​of the printing parameters is n , the range of printing parameter selection values ​​is as follows: ； in, The minimum value among the selected values ​​for the print parameters, The maximum value among the selected values ​​for the print parameters. The number of values ​​selected for the print parameter, Select values ​​for printing parameters No. A selected value, =1,2,…,max.

6. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 1, characterized in that: In S6, the tension standard specimen and the compression standard specimen are one of ASTM, ISO or GB, and the mechanical test data include one or more of tensile strength, tensile stiffness, tensile elastic modulus, compressive strength, compressive stiffness and compressive elastic modulus.

7. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 1, characterized in that: In S7, the data of the multivariate regression model fitting comes from S6, and finally the regression matrix of each printing parameter A, B, C, ..., and strength Sr, stiffness Si and randomness R is obtained: ； in, is a vector of print parameters, is the regression coefficient matrix, is the vector of mechanical properties, is the error vector.

8. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 1, characterized in that: In S8, the stress analysis of the structural parts adopts finite element method, and priority is given to ensuring that the strength of the structural parts meets the requirements. The data adopted by the finite element method come from the mechanical test data of the tensile quasi-specimen with the highest tensile strength and the compressive standard specimen with the highest compressive strength in S6.

9. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 1, characterized in that: In S9, the strength of the material obtained in S5 , stiffness , Randomness The stress and strain prediction results obtained by S8 are divided into regions as follows: Randomness-dominated area: The area in the target structural part where the finite element stress is less than 30% of the strength is the randomness-dominated area; Strength-dominated area: When the finite element stress of the area in the target structural part is ≥ 70% of the strength, it is the strength-dominated area; Stiffness-dominated region: When the finite element stress of the region in the target structural part is less than 70% and ≥30% of the strength, it is the stiffness-dominated region; According to the positive and negative stress values ​​of the finite element analysis of S8, the target structural parts are first divided into tension zones and compression zones, and the zone types include tension strength zone, compression strength zone, tension stiffness zone, compression stiffness zone, tension random zone, and compression random zone; The strength was quantified by selecting the average value of the peak value of the mechanical test curve; The quantification method of stiffness is to select the average value of the tangent line of the elastic segment of the mechanical test curve; The randomness comes from strength and stiffness respectively, and the quantitative formula is as follows: ； in, is the standard deviation of the mechanical test data, is the mean value of mechanical test data.

10. A method for integrated control of strength, stiffness and randomness of 3D printed structural parts according to claim 9, characterized in that: S10 is as follows: Tensile strength zone: the printing parameter combination that gives the highest printable tensile strength; Compressive strength zone: the printing parameter combination that gives the highest compressive strength to the printable; Tensile stiffness zone: a printing parameter combination that gives the highest printable tensile stiffness and a tensile strength not less than the regional stress; Compressive stiffness zone: a printing parameter combination that gives the highest printable compressive stiffness and a compressive strength not less than the regional stress; Tensile random zone: the printing parameter combination that gives the lowest printable tensile randomness and a tensile strength not less than the regional stress; Stress random zone: The printing parameter combination that gives the lowest printable stress randomness and a stress strength not less than the regional stress.

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