CN117454451A - Temperature field numerical simulation method and system for laser sintering 3D printing process - Google Patents
Temperature field numerical simulation method and system for laser sintering 3D printing process Download PDFInfo
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Abstract
The invention discloses a temperature field numerical simulation method and system in a laser sintering 3D printing process, and relates to the technical field of numerical simulation. The technical key points of the invention include: establishing a geometric model to be simulated, and determining basic requirement parameters to be simulated; converting the geometric model to be simulated into a slice model and a general model; slicing the slice model to obtain a motion control file with G codes; extracting coordinates of a laser scanning target point and moving speed data according to the moving control file to obtain a laser scanning path point location data table; dividing the general model in numerical simulation software, performing grid division on a geometric division result to finish load loading, setting a circulating instruction and a time parameter, setting a solving mode as a transient solver, and finishing a numerical simulation operation pretreatment process; and carrying out numerical simulation solution and post-processing to obtain a temperature field numerical simulation result. The invention can identify and track the temperature state of each target point in the laser sintering process.
Description
Technical Field
The invention relates to the technical field of numerical simulation, in particular to a temperature field numerical simulation method and system in a laser sintering 3D printing process.
Background
The laser sintering technology has irreplaceable unique advantages in the field of additive manufacturing because of its efficient material utilization, wide material adaptability, free forming modes, unique self-supporting forming modes, and distinction from other additive manufacturing forms. For the laser sintering technology, the accurate temperature field numerical simulation result has important practical value and guiding significance in the aspects of analyzing the problem of the printing process, determining a reasonable laser scanning path in the printing process, determining a reasonable posture of a printed piece, simplifying the precision prediction difficulty, improving the precision grade and the like. The main manifestations are the following: (1) The temperature field numerical simulation result can be used for analyzing the temperature change gradient and the temperature state in the workpiece in the forming process, and is beneficial to analyzing and determining the influence relationship of the temperature field on the problems of related precision performance and the like. (2) Under the condition that other parameters are the same, different laser scanning paths can enable the local or whole temperature field state of the workpiece to form different results, so that the final workpiece result is affected, and more reasonable laser scanning paths can be selected through the temperature field numerical simulation result. (3) Different geometric characteristics of the workpiece can achieve different forms due to different geometric postures of the workpiece, for example, a plane can form a horizontal or vertical or inclined surface state, a curved surface can be concave upwards or concave downwards, different final effects can be generated, and therefore, the temperature field numerical simulation result can be used for more facilitating analysis of advantages and disadvantages of various forms and assisting in reasonably selecting reasonable postures of printed workpieces. (4) Based on the fact that the accuracy result of the workpiece is further affected due to the fact that heat is excessively accumulated in some laser sintering materials, the temperature field numerical simulation result can assist in judging the whole temperature state of the workpiece and the temperature gradient of the forming boundary, prediction in the aspect of workpiece accuracy influence is facilitated, and accuracy grade of the workpiece is further improved in an auxiliary mode.
In the existing related numerical simulation research in the aspect of 3D printing, for example, in the aspects of technical types such as fused deposition, laser cladding and the like, related comments and articles are related to the related research on numerical simulation technology, modeling process, forming process, material characteristics, process parameters and solving modes; and parameter optimization problems, result consistency problems and calculation scale problems based on the parameters. However, there are few reports on the problem of numerical simulation of laser sintering, and due to the difference in principle, there are few numerical simulation methods that can be used as a reference in the field of related additive manufacturing, and most of them are based on the content of numerical simulation in terms of simplifying and optimizing.
In some existing papers and research contents related to numerical simulation related to laser sintering, the core simulation contents are basically single-layer or 2-4-layer manual program simulation processing methods; or the conformity degree of the related process principle and the laser sintering working form is lower; or the related functions or parameters are constant according to manual input, and the degree of freedom of parameter control is low; either undersize or too simple of the model part; or the laser scanning path is too single, the parameter management is small, and the degree of freedom of the simulation model is low; or the reasonable model setting cannot be performed based on different working conditions of thermodynamic and heat transfer modes, such as heat conduction, convection, phase change and heat radiation, so that the description of the corresponding forming process of laser sintering is too simplified. Therefore, in the material heat conduction state, the convection heat exchange effect of the powder bed and the heat cavity, the phase change tracking of the sintering molten pool, the radiation heating effect of the heater and other problems have poor numerical simulation effect, and the model processing of the integrity or the actual model fitting prediction is insufficient.
Because of the working principle characteristics of laser sintering, the light spot size is less than 0.5mm, the scanning interval is less than 0.4mm, the layer thickness is less than 0.2mm, the size difference from the model on the macro scale of tens or hundreds of millimeters is too large, a single sintering layer requires light spots to reciprocate hundreds of times, the number of units to be operated, the number of target surfaces, and the time variation are too many (possibly thousands of repeated selection operations), so that manual interaction operation of operators is performed, and the numerical simulation of laser sintering becomes too inefficient or difficult to complete.
Disclosure of Invention
In view of the above problems, the invention provides a temperature field numerical simulation method and a system for a laser sintering 3D printing process.
According to an aspect of the present invention, a method for simulating a temperature field value in a laser sintering 3D printing process is provided, which includes the following steps:
s1: establishing a geometric model to be simulated by using modeling software, and correspondingly determining basic requirement parameters to be simulated according to an actual laser sintering 3D printing process;
s2: converting the geometric model to be simulated into a slicing model which can be identified by 3D printing general slicing software;
s3: setting parameters of 3D printing general slicing software as the basic requirement parameters to be simulated, slicing the slicing model by using the 3D printing general slicing software, and obtaining a motion control file with G codes;
S4: extracting coordinates of a laser scanning target point and moving speed data according to the movement control file, and sorting to obtain slice layer thickness parameters, laser scanning path parameters, laser scanning speed parameters and laser scanning time parameters, so as to obtain a laser scanning path point position data table;
s5: converting the geometric model to be simulated into a general model for retaining model body characteristic information;
s6: importing the general model and the basic requirement parameters to be simulated into numerical simulation software, and completing numerical simulation initialization;
s7: in numerical simulation software, the universal model is segmented according to the laser scanning path point location data table to obtain a geometric segmentation result; performing grid division on the geometric division result by combining the basic requirement parameters to be simulated to obtain a grid division result;
s8: in numerical simulation software, loading is completed based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated, and a loading result is obtained;
s9: in numerical simulation software, setting a circulation instruction and a time parameter based on a geometric segmentation result, a laser scanning time parameter and a load loading result, and setting a solving mode as a transient solver based on a grid division result to finish a numerical simulation operation pretreatment process;
S10: and carrying out numerical simulation solution by using numerical simulation software, and carrying out post-processing to obtain a temperature field numerical simulation result.
Further, the basic requirement parameters to be simulated in S1 include physical characteristic parameters of the 3D printing material, geometric dimensions of the geometric model to be simulated in the X, Y, Z direction, laser absorptivity, laser power, laser spot radius, scanning interval in the sintering process, maximum unit size of the sintering region, and cooling time of layer circulation.
Further, in S7, the process of performing segmentation processing on the generic model according to the laser scanning path point location data table to obtain a geometric segmentation result includes: selecting a geometric body number corresponding to the geometric model to be simulated; performing cyclic segmentation on the universal model corresponding to the geometric model to be simulated by using a working plane coordinate system, and performing cyclic segmentation according to the slice thickness parameters; and (3) carrying out surface segmentation or body segmentation on the sintered upper surface of each segmented layer body according to the laser scanning path parameters.
Further, in S8, based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated, the process of completing load loading includes: applying heat source load to the region where laser is sintering according to an actual laser scanning flow by adopting a Gaussian surface heat source mode, applying convective heat transfer load to other regions by adopting a convective heat transfer mode, performing a cyclic loading process according to slice layer thickness parameters of laser sintering, sequentially activating units from a layer unit corresponding to a Z minimum value to a layer unit corresponding to a Z maximum value, and applying corresponding loads; in the cyclic loading process, according to the coordinates of a laser target point in a laser scanning path point position data table, corresponding to laser scanning time parameters, a surface needing to be loaded is selected on the upper surface of an activated unit to be loaded.
Further, in S8, the gaussian surface heat source is a function parameter table result obtained according to the basic requirement parameters to be simulated, and in each cycle sub-step in the cyclic loading process, the corresponding function parameter table result is updated according to the laser scanning path parameter X and Y coordinate results.
Further, in S9, the time parameter is obtained by calculating according to the motion speed data and the length of the geometric model to be simulated in the direction X, Y, Z.
Further, the specific process of S9 includes: obtaining reference operation time according to the laser scanning time parameters, subdividing the reference operation time by combining the basic requirement parameters to be simulated to obtain subdivision operation time, setting a circulation instruction and time parameters by using the subdivision operation time, and setting a solving mode as a transient solver.
According to another aspect of the present invention, a temperature field numerical simulation system for a laser sintering 3D printing process is provided, the system comprising:
the model and parameter establishing module is used for establishing a geometric model to be simulated by using modeling software and correspondingly determining basic requirement parameters to be simulated according to an actual laser sintering 3D printing process; the basic requirement parameters to be simulated comprise physical characteristic parameters of the 3D printing material, the geometric dimension of the geometric model to be simulated in the X, Y, Z direction, the laser absorptivity, the laser power, the laser spot radius, the scanning interval in the sintering process, the maximum unit size of the sintering region and the cooling time of layer circulation;
The model conversion module is used for converting the geometric model to be simulated into a slicing model which can be identified by the 3D printing general slicing software; converting the geometric model to be simulated into a general model for retaining model body characteristic information;
the motion control file acquisition module is used for setting parameters of the 3D printing general slicing software as the basic requirement parameters to be simulated, slicing the slicing model by using the 3D printing general slicing software, and acquiring a motion control file with G codes;
the scanning path data acquisition module is used for extracting coordinates of a laser scanning target point and moving speed data according to the moving control file, and collating and obtaining slice layer thickness parameters, laser scanning path parameters, laser scanning speed parameters and laser scanning time parameters so as to obtain a laser scanning path point position data table;
the numerical simulation preprocessing module is used for importing the general model and the basic requirement parameters to be simulated into numerical simulation software and completing numerical simulation initialization; dividing the general model according to the laser scanning path point location data table to obtain a geometric division result; performing grid division on the geometric division result by combining the basic requirement parameters to be simulated to obtain a grid division result; based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated, loading the load is completed, and a load loading result is obtained; setting a circulation instruction and a time parameter based on a geometric segmentation result, a laser scanning time parameter and a load loading result, and setting a solving mode as a transient solver based on a grid division result to finish a numerical simulation operation pretreatment process; the time parameter is obtained by calculation according to the movement speed data and the length of the geometric model to be simulated in the X, Y, Z direction;
And the numerical simulation post-processing module is used for carrying out numerical simulation solving by utilizing numerical simulation software and carrying out post-processing to obtain a temperature field numerical simulation result.
Further, the process of performing segmentation processing on the general model according to the laser scanning path point location data table in the numerical simulation preprocessing module to obtain a geometric segmentation result includes: selecting a geometric body number corresponding to the geometric model to be simulated; performing cyclic segmentation on the universal model corresponding to the geometric model to be simulated by using a working plane coordinate system, and performing cyclic segmentation according to the slice thickness parameters; performing surface segmentation or body segmentation on the sintering upper surface of each segmented layer according to the laser scanning path parameters; the process for completing load loading based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated comprises the following steps: applying heat source load to the region where laser is sintering according to an actual laser scanning flow by adopting a Gaussian surface heat source mode, applying convective heat transfer load to other regions by adopting a convective heat transfer mode, performing a cyclic loading process according to slice layer thickness parameters of laser sintering, sequentially activating units from a layer unit corresponding to a Z minimum value to a layer unit corresponding to a Z maximum value, and applying corresponding loads; in the cyclic loading process, according to the coordinates of a laser target point in a laser scanning path point position data table, corresponding to laser scanning time parameters, a surface needing to be loaded is selected on the upper surface of an activated unit to be loaded.
Further, the gaussian surface heat source in the numerical simulation preprocessing module is a function parameter table result obtained according to the basic requirement parameters to be simulated, and in each circulation sub-step in the circulation loading process, the corresponding function parameter table result is updated according to the laser scanning path parameters X and Y coordinate results.
The beneficial technical effects of the invention are as follows:
according to the invention, based on a laser motion control path of an actual printing process, temperature field numerical simulation is carried out, and a numerical simulation solving process which effectively approximates to an actual forming process is obtained; according to the actual printing requirement, relevant technical parameters are adjusted, and the corresponding adjustment of the G code and the parameters of the numerical simulation process is realized; the temperature state of each target point in the laser sintering process can be identified and tracked.
Compared with the prior art, the invention has the following advantages:
(1) By using the numerical simulation method of the temperature field in the laser sintering 3D printing process to carry out simulation, the actual laser sintering forming process can be more practically attached, and related operation parameters are rich and adjustable: the method comprises the steps of laser energy parameters, light spot radius, energy absorptivity and energy peak value; the scanning interval of laser, the scanning speed of laser and the energy distribution form of laser; adjusting convection, heat conduction, radiation and other environmental conditions of each region in the forming process; based on the change of the area of the time state, such as the adjustment of the area load with the change of time, the heat exchange time interval between the scanning layers, etc.
(2) And by combining G code motion control, the consistency of theoretical parameters and actual state parameters is ensured, and model revision is conveniently carried out on the process characteristics of materials and equipment, so that the effectiveness and the improvability of numerical simulation operation are improved.
(3) According to the input value of the basic parameters to be simulated, the grid number of the model can be conveniently regulated, if the calculation force is sufficient, the parameters can be integrally modified to improve the unit number to carry out finer operation, and the grid number of the local area can be modified to obtain the grid unit with finer unit size, when the grid unit is small enough to be about 0.05mm, the path change, the optical characteristic change and the material change in the printing process can be analyzed with high precision, and the high-precision simulation result of the local laminating actual process can be obtained.
(4) The invention supports stress operation, and the thermal stress operation result of the model can be obtained by carrying out post-treatment on the result of temperature field operation and carrying out secondary coupling operation.
Drawings
The invention may be better understood by reference to the following description taken in conjunction with the accompanying drawings, which are included to provide a further illustration of the preferred embodiments of the invention and to explain the principles and advantages of the invention, together with the detailed description below.
Fig. 1 is a flowchart of a temperature field numerical simulation method in a laser sintering 3D printing process according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of an original geometric model in an embodiment of the present invention.
FIG. 3 is a schematic representation of slicing results in an embodiment of the present invention.
FIG. 4 is a diagram illustrating the contents of a G code file according to an embodiment of the present invention.
Fig. 5 is a schematic diagram of a spot track and a planar division effect in an embodiment of the present invention.
FIG. 6 is a graph showing the result of dividing the thickness of the circulating layer in the embodiment of the invention.
FIG. 7 is a schematic diagram of a cyclic single-layer segmentation result in an embodiment of the present invention.
FIG. 8 is a graph showing an example of the result cloud of the laser sintering numerical simulation temperature field in the embodiment of the invention.
Fig. 9 is a graph showing an example of the temperature change curve at the point KP1 in the temperature field according to the embodiment of the invention.
Detailed Description
In order that those skilled in the art will better understand the present invention, exemplary embodiments or examples of the present invention will be described below with reference to the accompanying drawings. It is apparent that the described embodiments or examples are only implementations or examples of a part of the invention, not all. All other embodiments or examples, which may be made by one of ordinary skill in the art without undue burden, are intended to be within the scope of the present invention based on the embodiments or examples herein.
In order to achieve the technical purpose, the embodiment of the invention provides a temperature field numerical simulation method in a laser sintering 3D printing process, which can enable printing temperature field analysis and stress field analysis to be more detailed, can observe transient changes of a printing path and distribution and directivity of an integral temperature field and stress field of a formed part, and simultaneously obtains larger thermal stress area number increase, simulation precision is improved, and is convenient for actual experiment comparison analysis and analysis for improving quality of the formed part.
Fig. 1 is a flowchart of a temperature field numerical simulation method for a laser sintering 3D printing process according to an embodiment of the present invention, as shown in fig. 1, the method includes the following steps:
s1: establishing a geometric model to be simulated by using modeling software, and correspondingly determining basic requirement parameters to be simulated according to an actual laser sintering 3D printing process;
s2: converting the geometric model to be simulated into a slicing model which can be identified by 3D printing general slicing software;
s3: setting parameters of 3D printing general slicing software as the basic requirement parameters to be simulated, slicing the slicing model by using the 3D printing general slicing software, and obtaining a motion control file with G codes;
s4: extracting coordinates of a laser scanning target point and moving speed data according to the movement control file, and sorting to obtain slice layer thickness parameters, laser scanning path parameters, laser scanning speed parameters and laser scanning time parameters, so as to obtain a laser scanning path point position data table;
S5: converting the geometric model to be simulated into a general model for retaining model body characteristic information;
s6: importing the general model and the basic requirement parameters to be simulated into numerical simulation software, and completing numerical simulation initialization;
s7: in numerical simulation software, the universal model is segmented according to the laser scanning path point location data table to obtain a geometric segmentation result; performing grid division on the geometric division result by combining the basic requirement parameters to be simulated to obtain a grid division result;
s8: in numerical simulation software, loading is completed based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated, and a loading result is obtained;
s9: in numerical simulation software, setting a circulation instruction and a time parameter based on a geometric segmentation result, a laser scanning time parameter and a load loading result, and setting a solving mode as a transient solver based on a grid division result to finish a numerical simulation operation pretreatment process;
s10: and carrying out numerical simulation solution by using numerical simulation software, and carrying out post-processing to obtain a temperature field numerical simulation result.
The method starts from step S1, in step S1, a geometric model to be simulated is firstly established by modeling software, and basic requirement parameters to be simulated are correspondingly determined according to an actual laser sintering 3D printing process. The basic requirement parameters to be simulated comprise physical characteristic parameters of the 3D printing material, the geometric dimension of the geometric model to be simulated in the X, Y, Z direction, the laser absorptivity, the laser power, the laser spot radius, the scanning interval in the sintering process, the maximum unit size of the sintering region and the cooling time of the layer circulation.
According to the embodiment of the invention, the geometric model to be simulated is obtained by establishing a geometric data model by using modeling software which is common in the market, such as an original geometric model file shown in fig. 2. And further carrying out expected judgment and analysis on the molding process, and determining basic requirement parameters of the simulation process. It should be noted that the geometric model to be simulated is an internal continuous entity, and may not be an array of a single model or a non-contact combination of multiple models.
By way of example, the recommended tensile sample piece according to the standard GB/T9314-2008/ISO 178:2001 has a specific dimension of length l:80mm; width b is 10mm; thickness h:4mm; the relevant requirement parameters are the requirement parameters correspondingly set in the actual processing requirement state, and the specific parameters of the adopted basic SI international unit system (m, kg, s, K) are as follows:
lx=0.08-! Length of the material in X direction 10mm
Ly=0.01-! Length of material in Y direction 10mm
Lz=0.004-! Length of material in Z direction 4mm
Abs=0.95-! Laser absorptivity of material
Power_laser=15-! Power W of laser
R_laser=0.0002-! Laser spot radius, r=2mm
Vx=2-! Laser scanning speed (m/s)
QM＝2*Abs*Power_Laser/(3.1415*R_Laser**2)
L_size=0.0004-! Scan pitch of sintering process
S_size=0.0001-! Setting the maximum unit size of the sintering area
Hsize=0.0001-! Defining layer thickness, defaulting to 0.1mm
T_cold=5-! Cooling time in s for layer circulation
Wherein LX, LY, LZ should correspond to the basic dimensions of the geometric model; abs, power_laser, QM constitute the expression form of Laser energy, specifically taking planar gaussian heat source as an example; VX is the Laser scanning speed in the Laser sintering process, and R_Laser is the Laser sintering focusing and the spot radius size of the powder bed surface; h_size is a layer thickness parameter and should correspond to a slice setting parameter; the S_size is a reference variable of grid division in the ANSYS model preprocessing process, the size after grid division is required to take the S_size as a reference value, in principle, the value of the S_size is not smaller than H_size, the smaller the S_size is, the more the grid number is, the larger the calculation scale is, the higher the solution precision is, and the same calculation scale is also, the invention is to adjust the number of units of numerical simulation calculation by using the S_size so as to control the calculation scale; l_size is the scan pitch; in the actual laser sintering process, a powder spreading process exists, and after the interlayer complaint unit is changed, a section of preheating and convection heat exchange state body is needed, and the powder spreading time is represented by T_cold to participate in operation.
And then, executing step S2, and converting the geometric model to be simulated into a slicing model which can be identified by the 3D printing general slicing software.
According to the embodiment of the invention, by using general 3D modeling software, such as UG_NX software, an 'STL' file can be obtained in a derived mode, and the format file only retains the simplified external surface triangular patch information of the model, and can be identified by 3D printing related slicing software as a general format and used for slicing operation. The slicing model is a generic file that can be read by the slicing element and can be adjusted according to the slicing software used.
And then executing step S3, setting parameters of the 3D printing general slicing software as the basic requirement parameters to be simulated, and slicing the slicing model by using the 3D printing general slicing software to obtain a motion control file with G codes.
According to the embodiment of the invention, the motion control G code based on the numerical control technology is a basic code obtained by planning and calculating a laser scanning path by slicing software based on the laser sintering technology, and the control motion of the laser sintering forming equipment is controlled by the G code. Slicing operation is carried out by using slicing software supported by corresponding laser sintering equipment through 3D numerical simulation, slicing related parameters are required to be set according to the actual laser sintering molding process, and finally slicing results shown in fig. 3 are obtained. Further, the motion control G code file is automatically generated through a software export function, and the content of the G code file is shown in fig. 4. The G code file contains motion control information, mainly including the X, Y, Z point coordinates of the 1 st point, the 2 nd point … to the last nth point, which are sequentially read, and its motion speed information.
As an example, CURA software, which is open-source on the market, is employed, wherein the parameters that need to be set for consistency are: the moving speed corresponds to the laser scanning speed VX, and the numerical value is 2000mm/s; the scanning interval corresponds to L_size, and the numerical value is 0.4mm; the thickness of the slice layer corresponds to the thickness H_size, and the numerical value is 0.1mm; the diameter of the scanning nozzle corresponds to the radius R_laser of the Laser spot, the numerical value is 0.2mm, a slicing result file is obtained, and a motion path preview schematic diagram is shown in fig. 3.
And then executing step S4, extracting coordinates of a laser scanning target point and moving speed data according to the moving control file, and finishing to obtain slice layer thickness parameters, laser scanning path parameters, laser scanning speed parameters and laser scanning time parameters, thereby obtaining a laser scanning path point position data table.
According to the embodiment of the invention, the laser scanning route point location data table extracts the coordinates and the movement speed data of the laser scanning target point corresponding to the actual laser sintering 3D printing process, and the data information in the laser scanning route point location data table comprises: slice layer thickness parameters, laser scanning path parameters, laser scanning speed parameters and laser scanning time parameters; according to the Z coordinate result of slice thickness parameter, the method can be used for guiding the geometrical body segmentation process in the Z direction in S7; the X and Y coordinate results according to the laser scanning path parameters can be used for guiding the geometrical plane segmentation process in the plane direction in the S7; according to the laser scanning speed parameter, the method can be used for guiding the loading process of the S8; the laser scanning time parameter can be used for guiding the loading process of the S8. The point location data table is used for reading the motion control file with the G code and obtaining the corresponding scanning path data point number, the corresponding coordinate position, the scanning speed between the two points and the total data point number. The obtained key points of the Laser scanning path are automatically segmented by slicing software according to the scanning interval L_size and the Laser spot size R_laser according to the model geometric form, and examples are shown in the following table. The Laser scanning path point location data table is obtained by intersecting a single-layer boundary through a motion control file with G codes by using Laser spot size R_laser paranoid operation.
As an example, the center of the bottom surface of the model is a far coordinate point, so the path starting point is the spot offset point K1 (X-39.8, Y4.98, Z0) of the fourth quadrant limit point (X-40, Y5, Z0), so the single-layer plane is divided into a plurality of areas according to the scanned path, and the dividing key points are the corresponding KP key points, as shown in fig. 5.
And then, executing step S5, and converting the geometric model to be simulated into a general model with model body characteristic information reserved.
According to the embodiment of the invention, the general 3D modeling software, such as UG_NX software, can be used for obtaining the ". X_t" file in an export mode, the format file only keeps the body characteristic information of the model, the seat general format has strong readability and low file reading failure rate, and the file can be identified and imported or exported by most 3D digital-analog related software, thereby being beneficial to importing the numerical simulation software to realize the consistency requirement of the numerical simulation model and the printing model. The universal model is a universal file containing characteristic information of the geometric model to be simulated, is generally a recognizable 3D digital model in the field of computer-aided design, such as ". X_t", ". Igs" or ". Stp" format files, and the files can be recognized and imported by software such as UG, SW, CREO, ANSYS, etc., so that basic information of the original geometric model is obtained from the universal model.
And then executing step S6, importing the general model and the basic requirement parameters to be simulated into numerical simulation software, and completing numerical simulation initialization.
According to embodiments of the present invention, the numerical simulation software may employ ANSYS software or other numerical simulation software. Wherein ANSYS software integrates a language for secondary development and software operation-APDL language. Thus, APDL language can be utilized to develop a laser sintering 3D printing process temperature field numerical simulation. The numerical simulation initialization process is to perform initialization setting on a temperature field (specifically, a thermal transmission function) by using physical characteristic parameters in basic requirement parameters to be simulated, taking ANSYS software as an example, a type solid70 of a thermal transmission arithmetic unit is suitable, physical characteristic parameters (including a heat conduction coefficient of a material, a density of the material, a specific heat of the material, a poisson ratio of the material, a convection heat coefficient of the material, a laser energy model participating in operation, an ambient temperature and a laser scanning speed) in the basic requirement parameters to be simulated, the corresponding parameters can be constants, variables and functional relations, and the variables and the functions can be corresponding and the solving scale and the operation requirement are simplified to be constants.
Step S7 is executed, and in numerical simulation software, the universal model is segmented according to the laser scanning path point location data table to obtain a geometric segmentation result; and combining the basic requirement parameters to be simulated to carry out grid division on the geometric division result, so as to obtain a grid division result.
According to the embodiment of the invention, the geometric segmentation result, namely the geometric segmentation file, is written based on APDL language, and the laser scanning path point position data table can be used for determining how many layers a model is divided into, what the scanning path of each layer is, and how to segment each layer is needed for the purpose. The scan path only supports laser sintering 3D printing with straight line filling inside.
The core requirement of the geometric segmentation file is to segment the geometric model based on the actual laser sintering laser scanning path. The purpose is to make the operation load loading of the digital simulation process more convenient and accurate, and the actual working condition is attached. For this purpose the segmentation of the geometric model needs to be divided into the following steps:
(1) Firstly, the geometric body number corresponding to the segmentation target geometric model in the numerical simulation software is required to be selected, and the selection method is to select the command statement according to APDL language. In the selection process, the geometric centroid is also known, and the selection of the target geometric body is completed by adopting an absolute coordinate mode because the characteristic parameters of the definite geometric body, including LX, LY and LZ values corresponding to the length, the width and the height of the geometric body, are known.
(2) The target geometry is circularly segmented by using an artificially controllable working plane coordinate system, and the segmentation of the target geometry is circularly segmented according to slice layer thickness parameters-layer thickness h_size by using DO circulation sentences so as to realize the circulation operation process of the death-causing unit, as shown in fig. 6.
(3) The sintered upper surface of each layer is divided according to the laser scanning path parameters, wherein, because the example adopts the energy source of Gaussian surface heat source seat numerical simulation, the surface division mode is adopted, and if a body heat source is adopted, the layers are required to be divided again according to the laser scanning path, as shown in fig. 7.
The grid division process is to divide the geometric division result into grids according to the basic requirement parameters to be simulated, and the cell size and the cell configuration of the grid division are controlled by the basic parameters to be simulated.
As an example, in ANSYS numerical simulation software, a generic model is imported using a-paramin command; selecting a specific target volume using the VSEL command; establishing the key points in the S4 by using a K command; GET the number with GET command; moving the working coordinate system by utilizing a wpob command; dividing a target body by using a VSBW command through a working coordinate system; selecting a target KP key point by using the KSEL command; drawing a straight line by using an LSTR command; selecting a target plane to be segmented by using the ASEL command; dividing a target plane by using an ASBL command; the command uses DO circulation effect to realize automatic circulation division of the object according to slice thickness and automatic circulation division of the object surface according to scan interval.
And then executing step S8, and completing load loading based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated in numerical simulation software to obtain a load loading result.
According to the embodiment of the invention, a heat source load is applied to a region where laser is sintering according to an actual laser scanning flow, a convection heat transfer load is applied to other regions, and the application of the load needs to consider the flow problems corresponding to the actual existence of units, all units are killed first, a cyclic loading process is performed according to slice layer thickness parameters of laser sintering, and units are activated in sequence from a layer unit corresponding to a Z minimum value to a layer unit corresponding to a Z maximum value and a corresponding load is applied.
And in the cyclic transportation loading process, according to the coordinates of laser target points in a laser scanning path point position data table and corresponding laser scanning time parameters, selecting a surface to be loaded on the upper surface of an activated unit for loading.
The Gaussian surface heat source is a function parameter table result obtained according to the simulation basic requirement parameters. In the Gaussian surface heat source loading process, corresponding function parameter table results are updated according to laser scanning path parameter X and Y coordinate results in each circulation sub-step in the circulation loading process.
And adding the heat convection load to other areas in a heat convection mode according to an actual laser scanning flow, and selecting a surface to be loaded on the upper surface of the unit being activated to load according to the laser target point coordinates in the laser scanning path point position data table and corresponding laser scanning time parameters.
As an example, if ANSYS numerical simulation software is adopted, the load loading result, that is, the load loading file, is written based on APDL language, and the loading direction, the forming direction, the target surface sequence of loading each layer, the laser scanning sequence, and the time period between layers can be determined by using the laser scanning path point location data table.
In the load loading process, a region for settling a Gaussian heat source needs to be locally loaded, because of the load characteristic of ANSYS software, heat FLUX FLUX of surface input energy and a CONV command of convection heat exchange are mutually exclusive, FLUX heat source load is required to be applied to a region where laser is sintering according to a laser scanning flow, convection heat exchange load is required to be applied to other regions, the flow problem of a dead unit is required to be considered in load application, all units are killed firstly, cyclic operation is carried out according to the layer height of laser sintering, and the units are activated in sequence and corresponding loads are applied.
Using EKILL, commanding to kill all cells, activating and operating in sequence in the subsequent DO cycle; in the layer circulation, using the unit of the layer height selected target to generate, and using the EALIVE command to activate the corresponding unit; in the single-layer laser sintering process, cyclic loading is carried out by using a surface segmentation result, and a corresponding target surface is selected by using an ASEL command, wherein the target surface load in the whole cyclic layer is deleted first, the target surface is reselected again and the load is applied, so that the problem of operation load conflict can be prevented.
Wherein the problem is upper at the heat source, ". DEL, GAUSS1" to "| -! The End of the evaluation "read-in work cause command for Gaussian function is a standard code input by ANSYS software, so the invention is not explained. Because ANSYS software does not support the real-time updating of the variables of the functions, in the numerical simulation process, the cyclic assignment variables i_gaus, j_gaus and K_gaus are introduced into the Gaussian heat source function to realize the loading of the cyclic Gaussian heat source function; and in the cyclic loading process, repeating the deleting of the existing heat source function, and further re-reading the values of the cyclic variables i_gaus, j_gaus and K_gaus according to the time relation, wherein the variables of the heat source function are the latest parameters in the cyclic operation process, i_gaus, j_gaus and K_gaus correspond to the cyclic time parameters in the X direction of the layer, the cyclic time parameters in the Y direction of the layer and the sintering time parameters of the complete 1 layer.
Step S9 is executed, in numerical simulation software, a circulation instruction and a time parameter are set based on a geometric segmentation result, a laser scanning time parameter and a load loading result, a solving mode is set as a transient solver based on a grid division result, and a numerical simulation operation preprocessing process is completed; the time parameter is obtained by calculation according to the movement speed data and the length of the geometric model to be simulated in the X, Y, Z direction.
According to the embodiment of the invention, the reference operation time is obtained according to the laser scanning time parameter, the reference operation time is subdivided by combining the basic requirement parameter to be simulated, the subdivision operation time is obtained, the circulation instruction and the time parameter of the numerical simulation software are set by utilizing the subdivision operation time, and the solving mode is set as a transient solver. For example, taking the model of x=10mm, y=80 mm, the laser spot radius of 0.2mm, and the laser scanning speed of 2000mm/s, if the scanning time of the single line after segmentation is 0.0398s, the reference operation time is 0.0398s, if the rounding setting operation subdivision is 398, that is, each operation time sub-step is 0.0001s, and for effective convergence when solving, the software will automatically set the time parameter (where the time parameter is smaller than the time sub-step), where the time parameter can be manually set as expected so as to obtain a finer numerical simulation operation result.
And finally, executing step S10, carrying out numerical simulation solution by using numerical simulation software, and carrying out post-processing to obtain a temperature field numerical simulation result. The numerical simulation solving and post-processing processes are all in the prior art, and the invention is not repeated.
By way of example, a temperature change curve at a specific point in time can be plotted using post-processing commands, as shown in fig. 8 and 9, and fig. 8 is a graph of a cloud of laser sintering numerical simulation temperature field results. Fig. 9 is a graph showing an example of the temperature change curve at the point KP1 of the temperature field.
In summary, the temperature field numerical simulation method for the laser sintering 3D printing process can obtain a high-precision computer numerical simulation result consistent with the laser scanning path of the laser sintering forming process, and combines G code laser scanning path control of slicing software to realize a high-efficiency vivid numerical simulation modeling method, thereby providing an intuitive modeling method for the laser sintering numerical simulation process.
Another embodiment of the present invention provides a temperature field numerical simulation system for a laser sintering 3D printing process, the system comprising:
the model and parameter establishing module is used for establishing a geometric model to be simulated by using modeling software and correspondingly determining basic requirement parameters to be simulated according to an actual laser sintering 3D printing process; the basic requirement parameters to be simulated comprise physical characteristic parameters of the 3D printing material, the geometric dimension of the geometric model to be simulated in the X, Y, Z direction, the laser absorptivity, the laser power, the laser spot radius, the scanning interval in the sintering process, the maximum unit size of the sintering region and the cooling time of layer circulation;
The model conversion module is used for converting the geometric model to be simulated into a slicing model which can be identified by the 3D printing general slicing software; converting the geometric model to be simulated into a general model for retaining model body characteristic information;
the motion control file acquisition module is used for setting parameters of the 3D printing general slicing software as the basic requirement parameters to be simulated, slicing the slicing model by using the 3D printing general slicing software, and acquiring a motion control file with G codes;
the scanning path data acquisition module is used for extracting coordinates of a laser scanning target point and moving speed data according to the moving control file, and collating and obtaining slice layer thickness parameters, laser scanning path parameters, laser scanning speed parameters and laser scanning time parameters so as to obtain a laser scanning path point position data table;
the numerical simulation preprocessing module is used for importing the general model and the basic requirement parameters to be simulated into numerical simulation software and completing numerical simulation initialization; dividing the general model according to the laser scanning path point location data table to obtain a geometric division result; performing grid division on the geometric division result by combining the basic requirement parameters to be simulated to obtain a grid division result; based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated, loading the load is completed, and a load loading result is obtained; setting a circulation instruction and a time parameter based on a geometric segmentation result, a laser scanning time parameter and a load loading result, and setting a solving mode as a transient solver based on a grid division result to finish a numerical simulation operation pretreatment process; the time parameter is obtained by calculation according to the movement speed data and the length of the geometric model to be simulated in the X, Y, Z direction;
And the numerical simulation post-processing module is used for carrying out numerical simulation solving by utilizing numerical simulation software and carrying out post-processing to obtain a temperature field numerical simulation result.
In this embodiment, preferably, the process of performing segmentation processing on the generic model according to the laser scanning path point location data table in the numerical simulation preprocessing module to obtain a geometric segmentation result includes: selecting a geometric body number corresponding to the geometric model to be simulated; performing cyclic segmentation on the universal model corresponding to the geometric model to be simulated by using a working plane coordinate system, and performing cyclic segmentation according to the slice thickness parameters; performing surface segmentation or body segmentation on the sintering upper surface of each segmented layer according to the laser scanning path parameters; the process for completing load loading based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated comprises the following steps: applying heat source load to the region where laser is sintering according to an actual laser scanning flow by adopting a Gaussian surface heat source mode, applying convective heat transfer load to other regions by adopting a convective heat transfer mode, performing a cyclic loading process according to slice layer thickness parameters of laser sintering, sequentially activating units from a layer unit corresponding to a Z minimum value to a layer unit corresponding to a Z maximum value, and applying corresponding loads; in the cyclic loading process, according to the coordinates of a laser target point in a laser scanning path point position data table, corresponding to laser scanning time parameters, a surface needing to be loaded is selected on the upper surface of an activated unit to be loaded.
In this embodiment, preferably, the gaussian surface heat source in the numerical simulation preprocessing module is a function parameter table result obtained according to the basic requirement parameters to be simulated, and in each circulation sub-step in the circulation loading process, the corresponding function parameter table result is updated according to the laser scanning path parameters X and Y coordinate results.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of the above description, will appreciate that other embodiments are contemplated within the scope of the invention as described herein. The disclosure of the present invention is intended to be illustrative, but not limiting, of the scope of the invention, which is defined by the appended claims.
Claims (10)
1. The numerical simulation method for the temperature field in the laser sintering 3D printing process is characterized by comprising the following steps of:
s1: establishing a geometric model to be simulated by using modeling software, and correspondingly determining basic requirement parameters to be simulated according to an actual laser sintering 3D printing process;
s2: converting the geometric model to be simulated into a slicing model which can be identified by 3D printing general slicing software;
s3: setting parameters of 3D printing general slicing software as the basic requirement parameters to be simulated, slicing the slicing model by using the 3D printing general slicing software, and obtaining a motion control file with G codes;
S4: extracting coordinates of a laser scanning target point and moving speed data according to the movement control file, and sorting to obtain slice layer thickness parameters, laser scanning path parameters, laser scanning speed parameters and laser scanning time parameters, so as to obtain a laser scanning path point position data table;
s5: converting the geometric model to be simulated into a general model for retaining model body characteristic information;
s6: importing the general model and the basic requirement parameters to be simulated into numerical simulation software, and completing numerical simulation initialization;
s7: in numerical simulation software, the universal model is segmented according to the laser scanning path point location data table to obtain a geometric segmentation result; performing grid division on the geometric division result by combining the basic requirement parameters to be simulated to obtain a grid division result;
s8: in numerical simulation software, loading is completed based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated, and a loading result is obtained;
s9: in numerical simulation software, setting a circulation instruction and a time parameter based on a geometric segmentation result, a laser scanning time parameter and a load loading result, and setting a solving mode as a transient solver based on a grid division result to finish a numerical simulation operation pretreatment process;
S10: and carrying out numerical simulation solution by using numerical simulation software, and carrying out post-processing to obtain a temperature field numerical simulation result.
2. The method according to claim 1, wherein the parameters required for the simulation in S1 include physical characteristic parameters of the 3D printing material, geometric dimensions of the geometric model to be simulated in X, Y, Z direction, laser absorptivity, laser power, laser spot radius, scan interval of the sintering process, maximum unit size of the sintering region, and cooling time of the layer cycle.
3. The method for simulating the temperature field values in the laser sintering 3D printing process according to claim 1, wherein the step S7 of segmenting the generic model according to the laser scanning path point location data table to obtain the geometric segmentation result comprises: selecting a geometric body number corresponding to the geometric model to be simulated; performing cyclic segmentation on the universal model corresponding to the geometric model to be simulated by using a working plane coordinate system, and performing cyclic segmentation according to the slice thickness parameters; and (3) carrying out surface segmentation or body segmentation on the sintered upper surface of each segmented layer body according to the laser scanning path parameters.
4. The method for simulating the temperature field value in the laser sintering 3D printing process according to claim 1, wherein the step S8 of completing the loading process based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated comprises: applying heat source load to the region where laser is sintering according to an actual laser scanning flow by adopting a Gaussian surface heat source mode, applying convective heat transfer load to other regions by adopting a convective heat transfer mode, performing a cyclic loading process according to slice layer thickness parameters of laser sintering, sequentially activating units from a layer unit corresponding to a Z minimum value to a layer unit corresponding to a Z maximum value, and applying corresponding loads; in the cyclic loading process, according to the coordinates of a laser target point in a laser scanning path point position data table, corresponding to laser scanning time parameters, a surface needing to be loaded is selected on the upper surface of an activated unit to be loaded.
5. The method according to claim 4, wherein the gaussian surface heat source in S8 is a function parameter table result obtained according to basic requirement parameters to be simulated, and the corresponding function parameter table result is updated according to the laser scanning path parameter X, Y coordinate result in each cycle sub-step in the cyclic loading process.
6. The method according to claim 2, wherein the time parameter in S9 is obtained by calculating according to the movement speed data and the length of the geometric model to be simulated in the direction X, Y, Z.
7. A method for simulating the temperature field value of a laser sintering 3D printing process according to any one of claims 1-6, wherein the specific process of S9 comprises: obtaining reference operation time according to the laser scanning time parameters, subdividing the reference operation time by combining the basic requirement parameters to be simulated to obtain subdivision operation time, setting a circulation instruction and time parameters by using the subdivision operation time, and setting a solving mode as a transient solver.
8. A laser sintering 3D printing process temperature field numerical simulation system, comprising:
the model and parameter establishing module is used for establishing a geometric model to be simulated by using modeling software and correspondingly determining basic requirement parameters to be simulated according to an actual laser sintering 3D printing process; the basic requirement parameters to be simulated comprise physical characteristic parameters of the 3D printing material, the geometric dimension of the geometric model to be simulated in the X, Y, Z direction, the laser absorptivity, the laser power, the laser spot radius, the scanning interval in the sintering process, the maximum unit size of the sintering region and the cooling time of layer circulation;
The model conversion module is used for converting the geometric model to be simulated into a slicing model which can be identified by the 3D printing general slicing software; converting the geometric model to be simulated into a general model for retaining model body characteristic information;
the motion control file acquisition module is used for setting parameters of the 3D printing general slicing software as the basic requirement parameters to be simulated, slicing the slicing model by using the 3D printing general slicing software, and acquiring a motion control file with G codes;
the scanning path data acquisition module is used for extracting coordinates of a laser scanning target point and moving speed data according to the moving control file, and collating and obtaining slice layer thickness parameters, laser scanning path parameters, laser scanning speed parameters and laser scanning time parameters so as to obtain a laser scanning path point position data table;
the numerical simulation preprocessing module is used for importing the general model and the basic requirement parameters to be simulated into numerical simulation software and completing numerical simulation initialization; dividing the general model according to the laser scanning path point location data table to obtain a geometric division result; performing grid division on the geometric division result by combining the basic requirement parameters to be simulated to obtain a grid division result; based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated, loading the load is completed, and a load loading result is obtained; setting a circulation instruction and a time parameter based on a geometric segmentation result, a laser scanning time parameter and a load loading result, and setting a solving mode as a transient solver based on a grid division result to finish a numerical simulation operation pretreatment process; the time parameter is obtained by calculation according to the movement speed data and the length of the geometric model to be simulated in the X, Y, Z direction;
And the numerical simulation post-processing module is used for carrying out numerical simulation solving by utilizing numerical simulation software and carrying out post-processing to obtain a temperature field numerical simulation result.
9. The system for simulating the temperature field value of the laser sintering 3D printing process according to claim 8, wherein the process of performing segmentation processing on the generic model according to the laser scanning path point location data table in the numerical simulation preprocessing module to obtain the geometric segmentation result comprises: selecting a geometric body number corresponding to the geometric model to be simulated; performing cyclic segmentation on the universal model corresponding to the geometric model to be simulated by using a working plane coordinate system, and performing cyclic segmentation according to the slice thickness parameters; performing surface segmentation or body segmentation on the sintering upper surface of each segmented layer according to the laser scanning path parameters; the process for completing load loading based on the laser scanning path point location data table, the geometric segmentation result and the basic requirement parameters to be simulated comprises the following steps: applying heat source load to the region where laser is sintering according to an actual laser scanning flow by adopting a Gaussian surface heat source mode, applying convective heat transfer load to other regions by adopting a convective heat transfer mode, performing a cyclic loading process according to slice layer thickness parameters of laser sintering, sequentially activating units from a layer unit corresponding to a Z minimum value to a layer unit corresponding to a Z maximum value, and applying corresponding loads; in the cyclic loading process, according to the coordinates of a laser target point in a laser scanning path point position data table, corresponding to laser scanning time parameters, a surface needing to be loaded is selected on the upper surface of an activated unit to be loaded.
10. The system according to claim 9, wherein the gaussian surface heat source in the numerical simulation preprocessing module is a function parameter table result obtained according to basic requirement parameters to be simulated, and in each circulation sub-step in the circulation loading process, the corresponding function parameter table result is updated according to the laser scanning path parameters X and Y coordinate results.
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