Finite element simulation method and system, computer device and storage medium

Abstract

The application discloses a finite element simulation method and system, a computer device and a computer readable storage medium; the printing path is discretized into multiple segments according to time steps, a basic unit is arranged in each segment and is activated according to a time sequence of printing, in the process of simulating printing, a thermal contact and a mechanical contact are arranged on the surface of the basic unit, a temperature field and a stress field are coupled for calculation, and a result close to actual printing is obtained through a thermal-force-chemical fully coupled finite element simulation method; in addition, initial residual stress is considered for simulating the printing process, and the finite element simulation method can be used for analyzing the deformation condition of a printed part caused by the initial residual stress; temperature data and strain data obtained through calculation can be used for evaluating the performance of a printed object under different printing parameter settings, and the finite element simulation method can provide data to support adjustment of printing parameters.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of computer data processing, and in particular, to a finite element simulation method and system for fused deposition printing, a computer device, and a computer readable storage medium. BACKGROUND

[0002] In existing fused deposition printing slicing software, the printing path and printing parameters are determined in a pure geometric manner, which cannot effectively guarantee the printing speed and the performance of the final printed product, such as shape distortion, interlayer adhesion, elastic modulus, and strength. It is difficult to track the change state of the material temperature field and stress field of the printing process based on the existing slicing technology to analyze the printing process and evaluate the performance of the obtained object to adjust the printing path and printing parameters, and at the same time, high economic cost and time cost need to be borne. SUMMARY

[0003] In view of the above-mentioned shortcomings of the related art, the purpose of the present application is to provide a finite element simulation method and system, a computer device, and a computer readable storage medium to solve the technical problems that it is difficult to track the change state of the material temperature field and stress field of the printing process in the prior art, and at the same time, high economic cost and time cost need to be borne.

[0004] To achieve the above-mentioned purposes and other related purposes, the present application discloses a finite element simulation method of a three-dimensional model of an object, comprising the following steps: reading G-Code data of the three-dimensional model of the object and setting printing information, the printing information including attribute information of a printing material; discretizing a printing path in the G-Code data according to a preset time step to obtain position information of a starting point and an ending point of each time step; determining a basic unit that needs to be activated for each time step according to a printing time sequence of the printing path, the basic unit being preset based on the three-dimensional model of the object; sequentially activating the basic unit in the three-dimensional model of the object according to the printing time sequence of the printing path and the determined time step; and using a preset model to perform coupled simulation calculation on each activated basic unit in the three-dimensional model of the object to obtain a simulation result describing a dynamic temperature field distribution and / or a dynamic residual stress field distribution of the printing material in the three-dimensional model of the object over time during the printing process.

[0005] In some embodiments of the first aspect of the present application, the G-Code data includes one or more of the following information: a printing path of a print head, a moving speed of the print head, a printing material output speed, a printing material heating temperature, and a component plate heating temperature of a printing device.

[0006] In some embodiments of the first aspect of the application, the printing information further comprises device parameter information, the device parameter information comprising: printing substrate temperature, printing chamber temperature, extrusion head diameter, extrusion head temperature, filament maximum heating temperature.

[0007] In some embodiments of the first aspect of the application, the attribute information of the printing material comprises one or more of: filament type, filament diameter, and filament cross-sectional shape.

[0008] In some embodiments of the first aspect of the application, the step of discretizing the printing path in the G-Code data according to the preset time step to obtain the position information of the start point and the end point of each time step comprises: establishing a coordinate system for the printing path in the G-Code data; obtaining the printing sequence and the printing speed of the printing path from the G-Code data to obtain the printing time sequence of the printing path; grid dividing the printing path according to the preset time step to discretize into a plurality of segments, so that each segment corresponds to its preset time step; recording the start point coordinates and the end point coordinates of each time step.

[0009] In some embodiments of the first aspect of the application, in the step of determining the basic unit to be activated at each time step according to the printing time sequence of the printing path, the basic unit is a rod unit.

[0010] In some embodiments of the first aspect of the application, the finite element simulation method further comprises the step of: establishing heat transfer contact and / or mechanical contact between the rod unit of the current printing layer and the rod unit of the corresponding previous printing layer in the three-dimensional model of the object according to the relative position between the current printing layer and the previous printing layer.

[0011] In some embodiments of the first aspect of the application, the step of establishing heat transfer contact and / or mechanical contact is to establish interlayer adhesion between the rod unit of the current printing layer and the rod unit of the corresponding previous printing layer in the three-dimensional model of the object.

[0012] In some embodiments of the first aspect of the application, in the step of determining the basic unit to be activated at each time step according to the printing time sequence of the printing path, the basic unit is a hexahedral unit.

[0013] In some embodiments of the first aspect of the application, the step of determining the basic unit to be activated at each time step according to the printing time sequence of the printing path comprises: establishing a simulation domain according to the preset basic unit and the profile of the three-dimensional model of the object; in the simulation domain, determining the basic unit to be activated at each time step according to the printing time sequence of the printing path.

[0014] In some embodiments of the first aspect of the application, the finite element simulation method further comprises the step of establishing an envelope range along the printing path in the simulation domain according to the attribute information of the printing material.

[0015] In some embodiments of the first aspect of the application, the step of determining the basic unit to be activated at each time step further comprises the step of setting a judgment condition: judging whether the basic unit is in the envelope range, if it is in the envelope range, activating the unit; if it is not in the envelope range, not activating the unit.

[0016] In some embodiments of the first aspect of the application, the step of determining the basic unit to be activated at each time step further comprises: according to the printing time sequence, assigning a direction vector to the basic unit to be activated in the printing path, so that the material direction of each basic unit in the printing path is in line with the direction of the printing path.

[0017] In some embodiments of the first aspect of the application, the finite element simulation method further comprises the step of obtaining the initial residual stress of the printing material, and based on the initial residual stress, using a preset model to perform coupled temperature displacement simulation on the three-dimensional model of the object.

[0018] In some embodiments of the first aspect of the application, in the step of using a preset model to perform coupled simulation calculation on the three-dimensional model of the object, the coupled simulation calculation is a coupled simulation calculation under a preset boundary condition, and the boundary condition includes a thermal convection boundary condition and / or a thermal radiation boundary condition.

[0019] In some embodiments of the first aspect of the application, in the step of using a preset model to perform coupled simulation calculation on the three-dimensional model of the object, the preset model includes a linear viscoelastic model for describing the mechanical deformation of the printing material, or / and an orthotropic thermal conduction model or an orthotropic thermal conduction model for describing the thermal conduction behavior of the printing material.

[0020] The application also discloses a finite element simulation system of a three-dimensional model of an object in a second aspect, which comprises: a preprocessing module, which is used to read G-Code data of the three-dimensional model of the object and set printing information, and to disperse a printing path in the G-Code data according to a preset time step when a dispersion instruction is received, to obtain position information of a starting point and an ending point of each time step, and the printing information comprises attribute information of a printing material; a generation module, which is used to determine a basic unit that needs to be activated in each time step according to a printing time sequence of the printing path when a generation instruction is received, and the basic unit is preset based on the three-dimensional model of the object; an activation module, which is used to sequentially activate the basic unit in the three-dimensional model of the object according to the printing time sequence of the printing path and the determined time step when an activation instruction is received; and a simulation calculation module, which is used to perform coupled simulation calculation on each activated basic unit in the three-dimensional model of the object by using a preset model, so as to obtain a simulation result describing a dynamic temperature field distribution and / or a dynamic residual stress field distribution of the printing material in the three-dimensional model of the object in a printing process.

[0021] In some embodiments of the second aspect of the application, the step of dispersing the printing path in the G-Code data by the preprocessing module comprises: establishing a coordinate system for the printing path in the G-Code data; obtaining a printing sequence and a printing speed of the printing path from the G-Code data, so as to obtain a printing time sequence of the printing path; performing grid division on the printing path according to a preset time step, so as to disperse the printing path into a plurality of segments, so that each segment corresponds to a preset time step; and recording starting point coordinates and ending point coordinates of each time step.

[0022] In some embodiments of the second aspect of the application, the basic unit in the generation module is a rod unit.

[0023] In some embodiments of the second aspect of the application, the generation module is further used to establish heat transfer contact and / or mechanical contact between rod units of a current printing layer and corresponding rod units of a previous printing layer in the three-dimensional model of the object according to a relative position between the current printing layer and the previous printing layer in the three-dimensional model of the object.

[0024] In some embodiments of the second aspect of the application, the establishment of the heat transfer contact and / or the mechanical contact is the establishment of interlayer adhesion between rod units of a current printing layer and corresponding rod units of a previous printing layer in the three-dimensional model of the object.

[0025] In some embodiments of the second aspect of the application, the basic unit in the generation module is a hexahedral unit.

[0026] In some embodiments of the second aspect of the application, the generating module is configured to determine the basic unit to be activated at each time step according to the printing time sequence of the printing path by establishing a simulation domain according to the preset basic unit and the profile of the three-dimensional model of the object; and determining the basic unit to be activated at each time step according to the printing time sequence of the printing path in the simulation domain.

[0027] In some embodiments of the second aspect of the application, the generating module is further configured to establish an envelope range along the printing path in the simulation domain according to the attribute information of the printing material.

[0028] In some embodiments of the second aspect of the application, the generating module is further configured to determine whether the basic unit is within the envelope range, and if the basic unit is within the envelope range, activate the basic unit; and if the basic unit is not within the envelope range, do not activate the basic unit.

[0029] In some embodiments of the second aspect of the application, the generating module is further configured to assign a direction vector to the basic unit to be activated in the printing path according to the printing time sequence, so that the material direction of each basic unit in the printing path is consistent with the direction of the printing path.

[0030] In some embodiments of the second aspect of the application, the preprocessing module is further configured to obtain an initial residual stress of the printing material, so that the simulation computing module performs coupled temperature displacement simulation on the three-dimensional model of the object based on the initial residual stress and using a preset model.

[0031] In some embodiments of the second aspect of the application, the coupled simulation calculation in the simulation computing module is a coupled simulation calculation under a preset boundary condition, and the boundary condition includes a thermal convection boundary condition and / or a thermal radiation boundary condition.

[0032] In some embodiments of the second aspect of the application, the preset model includes a linear viscoelastic model for describing the mechanical deformation of the printing material, and / or an orthotropic thermal conduction model or an isotropic thermal conduction model for describing the thermal conduction behavior of the printing material.

[0033] The application also discloses a computer device in a third aspect, comprising: a storage device for storing at least one program and a preset simulation calculation model; a processing device connected with the storage device, used for executing the at least one program to call the at least one program in the storage device to execute and realize the finite element simulation method in any implementation manner disclosed in the first aspect of the application; and a display device for displaying the simulation result of the dynamic temperature field distribution and / or dynamic residual stress field distribution of the printing material of the three-dimensional model of the object in the printing process.

[0034] The application also discloses a computer readable storage medium in a fourth aspect, storing at least one program, which is executed by a processor to realize the finite element simulation method in any implementation manner disclosed in the first aspect of the application.

[0035] In summary, the finite element simulation method and system provided by the application have the following beneficial effects: the printing path is discretized into a plurality of segments according to time steps, a basic unit is arranged in each segment and activated according to the time sequence of printing, in the process of simulating printing, a linear viscoelastic model is used to describe the mechanical deformation of the material, and the temperature-dependent relaxation behavior and flow shear phenomenon of the material are considered, thermal contact and mechanical contact are arranged on the surface of the basic unit, and the temperature field and the stress field are calculated, and the result close to the actual printing is obtained through the thermal-mechanical-chemical fully coupled finite element simulation method; in addition, the finite element simulation method considers the initial residual stress for printing process simulation, and can be used for analyzing the deformation condition of the printed object caused by the initial residual stress, and the temperature data and strain data obtained through calculation can be used to evaluate the performance of the printed object under different printing parameter settings, and the finite element simulation method can provide data to support the adjustment of the printing parameters. BRIEF DESCRIPTION OF DRAWINGS

[0036] The specific features of the application involved in the application are shown in the appended claims. The features and advantages of the application involved can be better understood by referring to the exemplary embodiments described in detail below and the accompanying drawings. A brief description of the drawings is as follows:

[0037] Figure 1 A flowchart showing the execution mode of step S11 in an embodiment of the finite element simulation method of the application is shown.

[0038] Figure 2 A simplified schematic diagram showing the printing path in an embodiment of the finite element simulation method of the application is shown.

[0039] Figure 3 A flowchart showing the execution mode of step S11 in an embodiment of the finite element simulation method of the application is shown. Figure 1

[0040] ​Figure 4 A simplified schematic diagram showing the discretized print path in the finite element simulation method of the present application in an embodiment.

[0041] Figure 5a A simplified model schematic diagram showing the finite element simulation method of the present application in simulating printing.

[0042] Figure 5b A simplified model schematic diagram showing the finite element simulation method of the present application in simulating printing.

[0043] Figure 6a A simplified structure schematic diagram showing the finite element simulation method of the present application in simulating printing.

[0044] Figure 6b A simplified structure schematic diagram showing the finite element simulation method of the present application in simulating printing.

[0045] Figure 7a A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment. Figure 1 A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment.

[0046] Figure 7b A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment. Figure 1 A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment.

[0047] Figure 7c A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment. Figure 7b A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment.

[0048] Figure 8a A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment.

[0049] Figure 8b A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment.

[0050] Figure 8c A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment.

[0051] Figure 8d A simplified schematic diagram showing the execution process of step S12 in the method of the present application in an embodiment.

[0052] Figure 9 A simplified structure schematic diagram showing the finite element simulation system of the present application in an embodiment.

[0053] Figure 10 A simplified structure schematic diagram showing the computer device of the present application in an embodiment. DETAILED DESCRIPTION

[0054] The present application is herein described, by way of example only, with the understanding that

[0055] In the following description, reference is made to the accompanying drawings which form a part hereof, and in which are shown, by way of illustration, several embodiments of the present application. It is understood that other embodiments can be utilized and mechanical, structural, electrical, and operational changes can be made without departing from the spirit and scope of the present disclosure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of various embodiments of the present application are defined by the appended claims. The terminology used herein is for the purpose of describing

[0056] Further, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including" when used herein, specify the presence of stated features, steps, operations, elements, components, items, and / or groups but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, items, and / or groups thereof. As used herein, the terms "or" and "and / or" are to be interpreted as inclusive, i.e., as meaning one or more of the stated items is present. Therefore, "A, B or C" or "A, B and / or C" means any of the following: A; B; C; A and B; A and C; B and C; A, B and C. An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.

[0057] In 3D printing processes, for example, in a 3D printing process of the fused deposition process, also known as FDM printing (Fused Deposition Modelling, FDM for short), the material is added in a high-temperature fluid state and then extruded and cooled. During the printing process, the material is gradually increased in a molten state or brought into a molten state by a moving heat source (such as a heating element), and then cooled on a continuously evolving surface.

[0058] For the convenience of the description of the finite element simulation method and system provided by the present application, the coordinate system used in the embodiments of the present application is a right-angle three-dimensional coordinate, and the directions of the three-dimensional coordinate are X, Y and Z directions. Corresponding to the actual printing simulated, the Z direction is the normal direction of the horizontal plane, that is, the direction generally perpendicular to the printing work surface.

[0059] Please refer to Figure 1 , which shows the flowchart of the finite element simulation method of the present application in an embodiment.

[0060] For example, the finite element simulation method can be executed in a device with processing function, such as a processor using an optional preset density of any type of mesh to discretize the representation of the real-world object into a plurality of finite elements, wherein the finite element is a description of a geometric part of the real-world object. The device can be any computing device with mathematical and logical operations, data processing capabilities, including but not limited to: personal computer devices, single servers, server clusters, distributed servers, cloud servers, etc.

[0061] In embodiments of the present application, the finite element simulation method simulates real physical systems (such as geometry and load conditions) using a mathematical approximation method, and in particular, the finite element simulation method provided by the present application can be used to simulate the 3D printing process in reality, such as FDM printing.

[0062] As shown, the finite element simulation method comprises the following steps:

[0063] In step S10, the G-Code data of the object three-dimensional model and the set printing information are read, and the printing information includes the attribute information of the printing material.

[0064] The object three-dimensional model can be any designed three-dimensional model, and generally is a three-dimensional model corresponding to an object entity for 3D printing, such as a mold model, a medical jig model, a customized commodity model such as a shoe sole model or a tooth model, etc. In some embodiments, S10 includes a step of converting the object three-dimensional model into G-Code data or directly generating a three-dimensional model represented by G-Code data. The object three-dimensional model can be generated by computer-aided design (CAD) software, and in practice, the software used to realize three-dimensional modeling includes but is not limited to Autocad, Aurodesk123D, Tinkercad, Solidworks, Pro-E, Catia, Cimatron, Sketchup, OpenScad, UG, 3D max, maya, Rhino, Blender, etc.

[0065] The G-Code data is primarily a numerical control programming language, which can have multiple versions of representation in practice. The data of the object three-dimensional model can be in any known format, including but not limited to the Standard Tessellation Language (STL) or Stereo Lithography Contour (SLC) format, Virtual Reality Modeling Language (VRML), Additive Manufacturing File (AMF) format, Drawing Exchange Format (DXF), Polygon File Format (PLY), or any other format suitable for Computer-Aided Design (CAD).

[0066] In practice, the G-Code data includes a series of spatial coordinate points with an execution sequence, and the G-Code data of the object three-dimensional model is a three-dimensional model represented in a coordinate and time sequence or an execution sequence, for example, the G-Code data is input into a computing device with a processing function, and a path formed according to the sequence of each spatial coordinate point of the G-Code data constitutes the object three-dimensional model.

[0067] Specifically, the process of reading the G-Code data and setting the printing information can be performed by a processing device, and subsequent processing is performed on the read data. In some embodiments, the processing process can be implemented in a finite element system of the processing device.

[0068] In some embodiments, the G-Code data includes one or more of the following information: a printing path of a print head, a moving speed of the print head, a printing material output speed, a printing material heating temperature, and a component plate heating temperature of a printing device.

[0069] In general, in FDM printing, a hot-melt material in the form of a filament is fed into a hot-melt nozzle through a filament feeding mechanism (usually a roller). The filament material is heated and melted in the nozzle, while the nozzle moves along the part layer profile and the filling track, and the melted material is extruded and deposited at the specified location to solidify and form a model, which is bonded to the already formed material of the previous layer, and the layers are stacked to finally form a product model.

[0070] It should be understood that the print head is a heating head (also known as a heating nozzle, a spray head, or a nozzle) in a 3D printing device of the FDM type, which is used to heat and melt the filament material as the 3D printing raw material into a liquid state and then apply it on the component plate; the component plate (also known as a component platform or a printing platform) is a platform for attaching the target 3D component, which can move along the vertical Z-axis according to the signals provided by the computer-operated controller.

[0071] In the finite element simulation method of the present application, the print head can be a virtual print head such as a virtual model in a simulation software or a functionally equivalent print head. Parameters defined by the print head such as print path, print head moving speed, heating temperature of the print head as a moving heat source, etc. can be set based on the print head data in actual printing or can be set artificially. In some embodiments of the finite element simulation, the print head can be used as the starting point of the delivery of the printing material, and is displayed as a cross section whose position is determined by the print path and the print head moving speed. Among them, the functionally equivalent print head is realized by assigning the influence of the print head to the printing material, such as the process of assigning the printing material to follow the predetermined path of the print head to increase, the temperature influence of the print head on the extruded printing material, etc. In the finite element simulation method of the embodiment, there is no need to establish a print head model.

[0072] Please refer to Figure 2 , which shows a simplified schematic diagram of the print path in an embodiment of the finite element simulation method of the present application.

[0073] The print path is a series of coordinate points arranged in a certain order, and based on the print head moving speed information, the simulation time corresponding to each coordinate point in the print path can be determined. As shown in Figure 2 , the spatial coordinate points can be three-dimensional coordinate points, and in some embodiments, they can also be a plurality of groups of two-dimensional coordinate points such as X and Y direction coordinate points, each group of two-dimensional coordinate points sharing a Z coordinate, that is, the print path is a plurality of groups of discontinuous print paths, each group of print paths being in the same horizontal plane.

[0074] The output speed of the printing material is the speed of adding material in the printing environment with the print head as the starting point. The heating temperature of the printing material is the initial temperature of the material when it is extruded or output from the print head. The component plate heating temperature of the printing device corresponds to the component plate temperature in actual printing, which can be a constant temperature contact surface or a contact surface that heats up or cools down in a predetermined manner in the finite element simulation environment, and the contact surface is the receiving surface of the first layer of printing material, that is, the bottom surface of the model.

[0075] In some embodiments, the printing information further comprises device parameter information, the device parameter information comprising printing base temperature, printing chamber temperature (also referred to as forming chamber), printing head diameter, printing head temperature, and printing material maximum heating temperature.

[0076] The printing substrate temperature is the temperature of a member plate for carrying a printed object. Generally, the printing substrate temperature is a preset constant value. In the simulation method of the present application, the boundary condition at the bottom of the model is a constant temperature with a preset fixed value, which is used to simulate the printing substrate temperature in printing. Alternatively, the temperature of the printing substrate is a non-constant value, and the temperature at the bottom of the model is set as a temperature variation function of the printing substrate in simulation.

[0077] The printing chamber temperature corresponds to the temperature in the forming chamber in actual printing. In the finite element simulation environment, the printing chamber temperature can correspond to the temperature in a preset chamber volume. The chamber volume can be composed of selected planes or curved surfaces, and heat exchange conditions and material types equivalent to the actual chamber are applied or defined to simulate the real printing scenario. In some embodiments, the printing chamber temperature in the finite element simulation can be defined by an equivalent heating or cooling speed of the printing environment, which can be defined by a heat conduction formula or an empirical formula based on the boundary conditions of the actual printing environment.

[0078] The printing head generally has a circular cross-section and a polygonal cross-section (such as a square, rectangular, rhombic, pentagonal, or hexagonal cross-section). The printing head diameter can determine the cross-section of the printing material delivered to the printing chamber for cooling and forming. In some embodiments, the printing head shape can be other geometric shapes, and the geometric parameters are defined according to the preset printing head shape.

[0079] The printing head temperature can be used as a moving heat source for the printing material. The influence of the printing head temperature on the printing material is the heat conduction between the internal contour of the printing head and the molten printing material inside the printing head.

[0080] The printing material maximum heating temperature is the upper limit of the temperature allowed for maintaining the performance of the printed object during the process of melting, extruding, and cooling and forming of the specific printing material. For example, a temperature that is too high can cause warping and shrinkage of the printing material. Based on the printing information as a temperature limit condition, the results obtained by the finite element simulation method for simulating and analyzing the printing process can avoid damaging the printing quality due to temperature in actual printing.

[0081] The printing material includes PLA (Polylactic acid), ABS (Acrylonitrile Butadiene Styrene), polyurethane TPU, TPE material (thermoplastic elastomer), thermoplastic elastomer, nylon, carbon fiber material (for example, Carbon Fiber), semi-crystalline thermoplastic, Metal PLA / Metal ABS metal texture PLA / ABS material, PEEK material, FDM conductive wire material, Glow-in-the-Dark night light material (such as adding different colors of fluorescent agents in PLA or ABS), Wood wood texture material (by mixing a certain amount of wood fibers in PLA), and the like.

[0082] The attribute information of the printing material is characteristic information related to the material type, which can be parameter information corresponding to different characteristics of different materials, such as physical properties such as specific heat capacity or thermal conductivity, density, melting point, glass transition temperature, mechanical properties, chemical properties, and the like.

[0083] In some embodiments, the attribute information of the printing material includes one or more of wire material type, wire material diameter, and wire material cross-sectional shape. The wire material type is the printing material type, and the corresponding different information determined by the material characteristics such as thermal conductivity, specific heat capacity, glass transition temperature, and elastic modulus can be obtained from the determined wire material type information.

[0084] The wire material diameter is the diameter of the printing material extruded from the print head. In some embodiments, the wire material has a circular cross-section, and the extrusion speed of the wire material can be obtained by defining the print head moving speed and the wire material diameter.

[0085] The wire material cross-sectional shape is the wire material cross-sectional shape used for stacking to form a component during the cooling process of the wire material on the continuously evolving surface after being extruded from the print head. Generally, in an ideal case, the wire material cross-sectional shape is the same shape at the print head position, and then based on the heat transfer state and mechanical state of different regions in the printing, the wire material cross-sectional shape after forming can evolve into different shapes. In an embodiment of the finite element simulation method, the wire material cross-sectional shape is the wire material cross-sectional shape at the extrusion position of the print head.

[0086] In step S11, the printing path in the G-Code data is discretized according to a preset time step to obtain the position information of the starting point and the ending point of each time step.

[0087] The preset time step is a human-settable time interval. The continuous printing path in the G-Code data or a section of the printing path corresponding to a longer printing time is discretized at the preset time interval to form a plurality of printing paths corresponding to the time intervals. The printing paths between the time intervals are connected end to end, and the starting point and the ending point of the printing path corresponding to each time interval, i.e., the preset real-time step, are obtained.

[0088] Referring to Figure 3 , shown as Figure 1 The flowchart of step S11 in an embodiment is shown in FIG. 1. As shown in the figure, the step of discretizing the printing path and obtaining the starting point and the ending point of each time step includes:

[0089] In step S110, a coordinate system is established for the printing path in the G-Code data.

[0090] Generally, the coordinate system corresponding to the path coordinate points in the printing path in the G-Code data read by the processing device in S100 is included. In some embodiments, the original printing path coordinate system can be used after reading the G-Code data, or a new coordinate system is established and subsequent coordinate transformation of the printing path in the new coordinate system is performed. For example, another three-dimensional rectangular coordinate system is established, the printing path of the G-Code data is translated or folded, and the spatial coordinates of the printing path in the new coordinate system are obtained.

[0091] In step S111, the printing order and the printing speed of the printing path are obtained from the G-Code data to obtain the printing time sequence of the printing path.

[0092] Based on the printing path with the determined coordinate position, the order of the coordinate points in the printing path, i.e., the printing order, and the printing speed are obtained. The printing speed can be directly obtained from the printing head moving speed, or obtained based on the filament diameter or the filament cross-sectional shape and the extrusion speed. Based on the printing path, the printing order, and the printing speed information, the coordinate position and the printing speed corresponding to any intercepted end of the printing path can be obtained, and it is easy to know that the time point corresponding to different coordinate points can be known from the relationship between the path and the speed. In some embodiments, the starting point in the printing path is set as the zero time point, the time corresponding to each coordinate point is obtained through the printing order and the printing speed, and the time sequence is obtained.

[0093] In an actual scenario, after reading the G-Code data in the finite element system of the processing device, a coordinate system can be automatically established and the time sequence of the printing path can be obtained.

[0094] In step S112, the printing path is meshed according to the preset time step to be discretized into a plurality of segments, so that each segment corresponds to its preset time step.

[0095] In some embodiments, the coordinate point information of the printing path in the G-Code data is coordinate point information at the turning points of the path, for example, in a continuous line segment, the coordinate points at the two ends of the line segment are included in the printing path.

[0096] The preset time steps are used to segment the printing process, for example, a printing path that is completed in 10s is divided into 10 segments, each of which is 1s long. In some embodiments, each time step is of the same length from the start to the end of the printing process. In some embodiments, the lengths of the time steps are different, for example, the time steps can be 1s and 2s or other settable time periods.

[0097] Referring to FIG. 1, a simplified schematic diagram of the discretized printing path in an embodiment of the finite element simulation method of the present application is shown. As shown in FIG. 1, the printing path is divided into discrete units corresponding to the time steps after grid division. Figure 4 As shown in FIG. 1, the printing path is divided into a plurality of discrete points on the path, i.e., nodes on the path, after grid division, to form a plurality of adjacent discrete unit segments. Among them, a unit segment between two adjacent discrete points corresponds to the printing distance in a time step, for example, 1s. Figure 4 Figure 4 The grid division is performed on a certain range including the printing path in the current coordinate system, and the discrete points on the printing path are obtained by the intersection of the grid and the printing path. Generally, the grid division step includes the selection of the grid type and the grid size. In an embodiment, the basic unit of the grid type used is a square grid on a plane, or a cubic grid in a body. After determining the grid type, the grid parameters are determined according to the preset time steps and the printing speed, or the grid length can be determined based on the number of line segments to divide the printing path. Then, the discrete points formed by the intersection of the printing path and the grid unit are obtained by dividing the grid. Through finite element grid division, the printing path is discretized into a plurality of finite elements in the simulated actual environment.

[0098] In some embodiments, a hybrid grid division is used to obtain discrete units corresponding to different time steps.

[0099] In some embodiments, the grid length is determined by fixing the time step or equally dividing the segments based on the number of line segments, so that the printing head moves the same distance in each time step.

[0100] In some embodiments, the grid length is determined by fixing the time step or equally dividing the segments based on the number of line segments, so that the printing head moves the same distance in each time step.

[0101] In step S113, the start and end coordinates of each time step are recorded. ​

[0102] The starting point coordinates and the end point coordinates of each time step are discrete point coordinates after grid division, and the discrete point coordinates corresponding to each time step are recorded. According to the selected time step, different starting point coordinates and end point coordinates can be obtained, for example, if the desired time step is 1s, the starting point coordinates and the end point coordinates of the print head movement path corresponding to each 1s time step are obtained. As shown in Figure 3 The two adjacent discrete point coordinates corresponding to the printing path correspond to the starting point coordinates and the end point coordinates in one time step.

[0103] Please continue to refer to Figure 1 In step S12, the basic unit to be activated in each time step is determined according to the printing time sequence of the printing path, wherein the basic unit is preset based on the three-dimensional model of the object.

[0104] In some embodiments, the basic unit is a rod unit. The rod unit is a rod unit connecting the starting point coordinates and the end point coordinates in each time step. Specifically, the diameter or cross-sectional shape of the rod unit is consistent with the diameter or cross-sectional shape of the filament in the G-Code data, and the basic rod unit in each time step corresponds to the printing segment extruded by the print head in the actual printing in the time step.

[0105] In one implementation, the rod unit is determined in the following manner: based on the discrete printing path, the starting point and the end point coordinates of each time step are obtained, the diameter or cross-sectional shape of the rod unit is determined based on the diameter or cross-sectional shape of the filament in the G-Code data, the starting point and the end point coordinates of the time step are taken as the geometric center of the rod unit cross section, and the rod unit connecting the two cross sections is constructed.

[0106] After determining the rod unit based on the discrete time step, the three-dimensional model of the object composed of the rod unit can be obtained. In some embodiments, S12 further includes the step of establishing heat transfer contact and / or mechanical contact between the rod unit of the current printing layer and the rod unit of the corresponding previous printing layer in the three-dimensional model of the object according to the relative position between the current printing layer and the previous printing layer.

[0107] In the embodiments provided in the present application, the order of the printing layer definition is the time sequence, for example, the printing layer printed first at the bottom of the model is the first printing layer, and the second printing layer printed immediately on the first printing layer is the next printing layer. According to the relative position between the current printing layer and the previous printing layer in the three-dimensional model, based on the preset judgment condition for the position relationship, it is determined whether to establish a heat transfer contact or / and a mechanical contact between the current layer rod element and the previous printing layer rod element, and the specific contact type, the mechanical contact and the heat transfer contact can be used to describe the bonding behavior of the materials between different printing layers. Based on the grid division step in S11, after the heat transfer contact is established, the nonlinear transient heat conduction problem can be approximately expressed as a linear equation set.

[0108] It should be understood that the heat transfer contact and the mechanical contact between different printing layers exist at the same time, the heat transfer process between the printing layers is the heat convection between the extruded materials in the molten state, and the heat conduction between the bonded solid models changes over time during the solidification process of the printing material, when the mechanical contact does not occur between the printing layers, the thermal boundary condition of the surface of the printing layer is the thermal radiation with the printing chamber, and there is no direct heat transfer contact between the printing layers. In some embodiments, when the heat transfer contact and the mechanical contact between the printing layers are established in the finite element system of the processing device, one of the mechanical contact or the heat transfer contact, such as the mechanical contact, can be selected, and the finite element system can automatically identify the model surface to generate the heat transfer contact between the printing layers; of course, the mechanical contact and the heat transfer contact can also be established at the same time.

[0109] In a specific implementation, the step of establishing the heat transfer contact and / or the mechanical contact is to establish the interlayer bonding between the rod element of the current printing layer and the rod element of the corresponding previous printing layer in the three-dimensional model of the object. In some embodiments, the rod elements of different printing layers formed by connecting the start point and the end point of the time step are in a mutually separated slidable state, and in actual printing, for example, FDM printing, the different printing layers are in a mutually bonded state, the interlayer bonding between the rod element of the current printing layer and the rod element of the corresponding previous printing layer is established to simulate the actual printing situation, and the interlayer bonding can be realized by increasing the contact constraint.

[0110] Please refer to Figure 5a , Figure 5b , which shows a simplified schematic diagram of the rod element basic unit model in the finite element simulation method of the present application in the simulation of printing. Figure 5a , Figure 5b shows the process of setting the basic unit that needs to be activated for the first printing layer of the three-dimensional object model, wherein, Figure 5a to simplify the process of dynamically adding basic units in the model, Figure 5b corresponding to the actual shape of the object model simulated in the printing.

[0111] Referring to Figure 6a , Figure 6b , shows a simplified schematic diagram of the basic element model of the rod element in the finite element simulation method of the present application in simulating printing. Figure 6a To continue Figure 5a The simulation process determines the basic elements that need to be activated in the second printing layer in the simplified model, Figure 6b The actual shape of the object model in the second printing layer for simulating printing. Figure 6a A in the above is an enlarged schematic diagram of the interlayer bonding established, as shown, the basic elements between the upper and lower layers in A are bonded together through the interlayer bonding provided between different printing layers, B shows a cross-sectional schematic diagram of the printing element in the part of the model without interlayer bonding. Through the increased interlayer bonding shown in B, the printing elements of adjacent layers are converted from a relatively slidable state to a bonded state, and heat transfer contact and mechanical contact can be provided between the printing elements based on the interlayer bonding.

[0112] The heat transfer contact includes heat exchange and temperature boundary conditions on the contact boundary, the relative positions between the rod elements are used to determine whether a contact boundary is formed and the type of boundary condition, such as one or more of a specific temperature distribution on the boundary of the given model, a given heat flow on the boundary, or a given convective heat transfer condition, a given radiation heat dissipation condition, and the corresponding heat transfer coefficient, convective heat transfer coefficient, and radiation rate are selected and defined based on the type of boundary condition. In some embodiments, the heat exchange and temperature boundary conditions include thermal radiation boundary conditions and thermal convection boundary conditions, as well as thermal conduction.

[0113] In some embodiments, the position relationship between the previous printing layer and the current printing layer is determined based on the contact detection to establish the interlayer bonding. For example, when the contact detection result is the existence of general contact or interference contact, etc., a contact constraint is applied to the surface of the rod element based on this, and convective heat transfer between the upper and lower layers is established on the contact surface of the rod element model, and the rest of the surface of the rod element and the radiation heat dissipation of the printing chamber. In particular, for the first printing layer, that is, the printing layer that is simulated to be bonded to the component plate in real printing, the surface of the rod element also includes thermal contact with the component plate.

[0114] The mechanical contact is used to simulate the mechanical environment of the object material in printing, considering the mechanical action between different printing layers during the cooling and solidification process of the printing material from the molten state, so that the analysis of the strain process of the printing material obtained thereby integrates the strain caused by temperature and the strain caused by extrusion stress between different printing layers.

[0115] After establishing the beam elements and the interlayer adhesion between different printing layers, the basic elements needed to be activated are determined according to the printing time sequence of the printing path, and the basic elements needed to be activated in each time step are the beam elements connecting the starting point and the ending point in the time step. By determining the beam element activation sequence, the process of the print head extruding material in the actual printing can be simulated, and the region in the beam element profile is endowed with the properties of material and interlayer adhesion according to the activation sequence.

[0116] In some embodiments, in the step S12 of determining the basic elements needed to be activated in each time step according to the printing time sequence of the printing path, the basic elements are hexahedrons.

[0117] Generally, the size of the basic elements is of an order of magnitude much smaller than the order of magnitude of the diameter of the wire, and the profile of the three-dimensional model of the object is determined to add the printing material properties to the basic elements in the region. Since the surface of the extruded wire in the printing model is usually an arc surface such as the side surface of a cylinder, the basic elements are set to be small enough hexahedron elements to be accumulated by the basic elements in the form of differentiation to form the corresponding three-dimensional model of the object. Specifically, the hexahedron elements can be cubes. The smaller the size of the basic elements is when the basic elements are set, the closer the determined activated basic elements are to the range of the three-dimensional model of the object.

[0118] The three-dimensional model of the object can be determined by the printing path and the diameter of the print head, and the three-dimensional profile of the object can be obtained after the processing device performing the finite element simulation method reads the G-Code data.

[0119] In some embodiments, S12 includes: establishing a simulation domain according to a preset basic element and a profile of the three-dimensional model of the object; and in the simulation domain, determining the basic elements needed to be activated in each time step according to the printing time sequence of the printing path.

[0120] The simulation domain can be used to determine the calculation domain of the heat-mechanical-chemical coupling calculation in the subsequent simulation printing process. Generally, the larger the range of the simulation domain is, the closer it is to the printing state in the actual production. In the finite element simulation, in order to reduce the consumption of computing resources and the calculation time, the range of the simulation domain includes the three-dimensional model of the object, the equivalent printing chamber boundary, and the component plate, and the indoor environment of the printing device is equivalent to the boundary of the simulation domain.

[0121] In the determined simulation domain, the basic unit to be activated in each time step is determined according to the time sequence of the printing path. In the process of activating the basic unit in the time sequence, which corresponds to the actual printing process, the basic unit to be activated in each time step is determined in advance. Specifically, the basic unit to be activated corresponds to the printing material extruded by the printing head in printing, and the spatial range of the printing material extruded in each time step can be determined by the known three-dimensional model information of the object and the selected time step information. The time step information includes the start point and end point coordinate information of the time step obtained in S11. For example, corresponding to the actual printing, the spatial range occupied by the printing material extruded by the printing head moving from the start point coordinate to the end point coordinate of a time step in the range of the basic unit activated in the time step.

[0122] In some implementations, S12 further includes the step of establishing an envelope range along the printing path according to the attribute information of the printing material in the simulation domain.

[0123] The attribute information of the printing material used mainly includes at least one of the printing head diameter, the filament diameter, or the filament cross-sectional shape. Based on the attribute information, the envelope range is established along the printing path. The envelope range is a three-dimensional space region, and the discrete points of the time steps on the printing path are taken as the start point and the end point. In one implementation, for a certain determined time step, the printing head diameter or the filament diameter is taken as the diameter to establish a vertical circular cross-section with the time step start point and end point coordinates as the centers, and the start point and end point circular cross-sections are connected by a smooth arc surface to form the envelope range in the time step. Alternatively, the time step start point and end point coordinates are taken as the geometric centers of the filament cross-section to establish a vertical filament cross-section, and the start point and end point cross-sections are connected to form the corresponding envelope range.

[0124] In some implementations, the step of determining the basic unit to be activated in each time step further includes the step of setting a judgment condition: judging whether the basic unit is within the envelope range, if it is within the envelope range, activating the unit; if it is not within the envelope range, not activating the unit. Specifically, whether the basic unit is within the envelope range is determined by the profile of the envelope range in the time step. For the basic unit intersecting the interface of the envelope range profile, a preset rule can be used for judgment. For example, if more than 50% of the volume of the basic unit is within the envelope range, it is determined as the basic unit to be activated. The preset judgment rule can be a rule preset in the finite element system of the processing device.

[0125] In the subsequent simulation printing, whether the basic unit is within the envelope range is judged in each time step, and the basic unit within the envelope range is activated according to the movement path of the printing head.

[0126] Please refer to Figure 7a ,Figure 7b 、 Figure 7c , shows a schematic diagram of the process of determining the envelope range and the basic units to be activated in step S12 in an embodiment. As shown in Figure 7a , the print path can be obtained by reading the G-Code data, and in Figure 7b , the envelope range is established based on the print path and the cross-sectional shape of the filament, the diameter of the filament or the diameter of the print head in the print information of the G-Code data as shown in Figure 7a . Figure 7c is a schematic diagram of the cross-section C in Figure 7b , as shown in Figure 7c , each square represents a basic unit, and the circular cross-section is the cross-section C of the envelope range. It is determined whether each basic unit is within the envelope range, and the selected area in Figure 7c is the basic unit within the envelope range, which is set as the basic unit to be activated.

[0127] In some embodiments, the step of determining the basic units to be activated at each time step further comprises: assigning a direction vector to the basic units to be activated in the print path according to the print time sequence, so that the material direction of each basic unit in the print path is consistent with the direction of the print path.

[0128] The material direction includes the local material direction of the basic unit at each time step. The direction of the basic unit is determined by the direction of the print path, for example, in a model with rod units as basic units, the print material direction is consistent with the extension direction of the rod unit, and in a model with hexahedrons as basic units, the print material direction is the direction of the print path or the tangent direction of the print path at the time step.

[0129] After setting the material direction to be consistent with the direction of the print path, in the subsequent print simulation, the print material is assigned with orthogonal anisotropic or transverse isotropic material properties.

[0130] In step S13, the basic units in the three-dimensional model of the object are sequentially activated according to the print time sequence of the print path and the determined basic units at each time step.

[0131] Based on the predetermined print path and the basic units to be activated at each time step, in the process of activating the basic units according to the time steps, the dynamic additive process is realized according to the material properties, print property information and boundary condition information of the print environment in the preset G-code data. When the rod units or the basic units within the envelope range are activated at each time step, the activated basic units are assigned with the material properties, and the speed of the activated basic units corresponds to the moving speed of the print head in the G-code data.

[0132] Generally, the temperature field in FDM printing is a transient heat transfer analysis. In some embodiments, for a simulation method using hexahedron as a basic unit, the step S13 further includes a step of re-identifying the model surface at each time step and assigning a thermal convection boundary condition and a thermal radiation boundary condition to the surface of the model to describe the influence of the ambient temperature during the printing process with dynamic boundary conditions. In each time step, the temperature of the basic unit just activated is equal to the temperature of the print head, and the other units are calculated by assigning a thermal convection boundary condition and a thermal radiation boundary condition, coupling the stress-strain model through the heat conduction model to obtain the temperature field and stress field varying with time and space.

[0133] In the actual printing or simulation printing process, the print head starts to extrude the printing material to form a continuously evolving surface. Each time step of the printing process corresponds to different basic units and different spatial positions. In each time step, the model surface is re-identified to simulate the boundary conditions formed when contact occurs in the actual printing process. That is, the boundary conditions are dynamic boundary conditions. For example, the model surface is identified when the basic unit is activated in the current time step, and the thermal radiation boundary condition in the printing chamber and the thermal convection boundary condition between the bonded printing layer are added.

[0134] Please refer to Figure 8a 、 Figure 8b 、 Figure 8c 、 Figure 8d , which respectively show simplified schematic diagrams of the activation of basic units in time steps in an embodiment, i.e., simplified schematic diagrams of the printing simulation process. As shown in the figures, Figure 8a , Figure 8b , Figure 8c , Figure 8d The basic units are activated in the time sequence of the printing path and then accumulated layer by layer. In each time step, the basic units in the three-dimensional model of the object are activated, i.e., the process of assigning material properties and temperature boundary conditions, stress conditions to the basic units in the three-dimensional model of the object according to the time step. The three-dimensional model of the object as a whole presents a dynamic additive layer-by-layer accumulation and bonding effect to simulate the process of material extrusion from the print head in the actual printing.

[0135] In step S14, the activated basic units in the three-dimensional model of the object are coupled and simulated by using a preset model to obtain a simulation result describing the dynamic temperature field distribution and / or dynamic residual stress field distribution of the printing material in the three-dimensional model of the object varying with time during the printing process.

[0136] In some embodiments, the coupling simulation in step S14 is a coupling simulation with preset boundary conditions, which include thermal convection boundary conditions and / or thermal radiation boundary conditions. Specifically, the boundary conditions include heat transfer boundary conditions and mechanical contact boundary conditions, wherein the basic unit thermal boundary conditions are the heat exchange conditions between the basic unit and the external environment and different printing layer units, including convective heat exchange between the component plate with constant temperature at the bottom of the model, internal negative heat sources caused by environmental cooling, convection between different printing layers, and cooling caused by printing chamber radiation.

[0137] In some embodiments, the preset model includes a linear viscoelastic model for describing the mechanical deformation of the printing material, or / and an orthotropic thermal conduction model or an orthotropic thermal conduction model for describing the thermal conduction behavior of the printing material.

[0138] Specifically, the linear viscoelastic model can be a multi-branch thermal viscoelastic model, which takes into account the temperature-dependent relaxation behavior of the material and the flow shear phenomenon. Wherein the mechanical behavior of the material is related to the temperature, the total strain in printing is composed of thermal strain and elastic strain, the change of the material at each time step is described by a thermo-mechanical-chemical coupling model, the obtained simulation results consider the material properties, temperature and mechanical state, and the interaction between temperature and stress and strain, and the final deformation data is more consistent with the actual printing state, which can reduce the simulation error.

[0139] In some embodiments, during the simulation calculation, one of the stress nephogram corresponding to the residual stress field, the displacement nephogram corresponding to the deformation, or the temperature nephogram corresponding to the temperature field can be selected to be displayed. It should be understood that in the calculation, the temperature field and the stress field are completely coupled, and the transient temperature field and the residual stress field can be obtained simultaneously in each time calculation. The dynamic temperature field and the residual stress field varying with time are obtained in any time step or the entire process of simulating printing. In the processing device for executing the finite element simulation method, multiple ones can also be selected to be displayed simultaneously.

[0140] In some embodiments, the finite element simulation method further includes a step of obtaining the initial residual stress of the printing material, and based on the initial residual stress, a coupling temperature displacement simulation is performed on the three-dimensional model of the object by using the preset model.

[0141] The initial residual stress is taken as an initial condition of the printing process simulation. Generally, the residual stress at the initial printing moment will affect the printing until the end of the printing. The initial residual stress has certain influence on the formed printed object, such as causing material deformation and cracking. In the finite element simulation method, the initial residual stress is considered to obtain the printing analysis result, which can be used to control the forming process in actual printing, such as adjusting the printing parameters, to weaken the damage of the initial residual stress to the printing quality.

[0142] Generally, in actual FDM printing, the bonding strength of the interlayer bonding caused by the thermal expansion extrusion contact between different printing layers has a great influence on the mechanical properties of the printed object. The temperature of the filament contact interface and the diffusion time of the polymer molecules of the printing material affect the bonding quality of the filament, so it is necessary to perform thermal analysis on the accumulation process of the filament and study the variation law of the filament temperature with the forming parameters. Therefore, the temperature field and strain field state in the printing process are studied, and the thermal history data from printing to cooling forming are formed to provide data support for improving the performance of the printed object in production. Based on the finite element simulation method, the printing process and the printing environment can be reproduced multiple times to obtain theoretical data, and the cost and time consumption in the performance evaluation mode through multiple actual printing can be reduced.

[0143] The finite element simulation method provided by the present application discretizes the printing path into multiple segments according to time steps, sets basic units in each segment and activates according to the time sequence of printing. In the simulation of the printing process, a linear viscoelastic model is used to describe the mechanical deformation of the material, and the temperature-dependent relaxation behavior and flow shear phenomenon of the material are considered. Thermal contact and mechanical contact are set on the surface of the basic unit, and the temperature field and stress field are coupled for calculation. The thermal-mechanical-chemical fully coupled finite element simulation method obtains results close to actual printing. Furthermore, the finite element simulation method of the present application considers the initial residual stress for printing process simulation, which can be used to analyze the deformation of the printed object caused by the initial residual stress. The temperature data and strain data obtained by calculation can evaluate the performance of the printed object under different printing parameter settings. The finite element simulation method can provide data to support the adjustment of the printing parameters.

[0144] In a second aspect, the present application further provides a finite element simulation system of an object three-dimensional model. Please refer to Figure 9 , which shows a simplified structure schematic diagram of the finite element simulation system in an embodiment of the present application, as Figure 9 shown, the finite element simulation system 2 comprises a preprocessing module 21, a generation module 22, an activation module 23 and a simulation calculation module 24.

[0145] The preprocessing module 21 reads the G-Code data of the object three-dimensional model and the set printing information, and the printing information includes the attribute information of the printing material.

[0146] The object three-dimensional model can be any designed three-dimensional model, and is generally a three-dimensional model corresponding to an object entity for 3D printing, such as a mold model, a medical tool model, a customized commodity model such as a shoe sole model or a tooth model, and the like. In some embodiments, the preprocessing module 2121 can also convert the object three-dimensional model into G-Code data or directly generate a three-dimensional model represented by G-Code data. The object three-dimensional model can be generated by modeling software, for example, by computer-aided design (CAD) software to generate an object three-dimensional model. In practice, software used to implement three-dimensional modeling includes, but is not limited to, Autocad, Aurodesk123D, Tinkercad, Solidworks, Pro-E, Catia, Cimatron, Sketchup, OpenScad, UG, 3D max, maya, Rhino, Blender, and the like.

[0147] The G-Code data is mainly a numerical control programming language, which can have multiple versions of representations in practice. The data of the object three-dimensional model can be in any known format, including but not limited to Standard Tessellation Language (STL) or Stereo Lithography Contour (SLC) format, Virtual Reality Modeling Language (VRML), Additive Manufacturing File (AMF) format, Drawing Exchange Format (DXF), Polygon File Format (PLY), or any other format suitable for Computer-Aided Design (CAD).

[0148] In practice, G-Code data includes a series of spatial coordinate points with an execution order, and the G-Code data of the object three-dimensional model is a three-dimensional model represented by coordinates and time series or an execution order. For example, when the G-Code data is input into a computing device with processing functions, a path formed in accordance with the order of each spatial coordinate point of the G-Code data constitutes the object three-dimensional model.

[0149] Specifically, the process of reading the G-Code data and setting the printing information can be performed by a processing device, and subsequent processing of the read data can be implemented in a finite element system of the processing device in some embodiments.

[0150] In some embodiments, the G-Code data comprises one or more of a print path of the print head, a movement speed of the print head, a print material output speed, a print material heating temperature, a build plate heating temperature of the printing device.

[0151] In FDM printing, a filament of thermoplastic material is fed through a filament feeding mechanism (typically a roller) into a hot melt nozzle, where the filament is heated and melted, while the nozzle is moved along the part layer contour and fill trajectories, and the melted material is extruded and deposited at the designated location to solidify and form a bond with the already formed material of the previous layer, and the layers are stacked to form the final product model.

[0152] It should be understood that the print head is a heating head (also known as a heating nozzle, a nozzle or a nozzle) in a 3D printing device of the FDM type, which is used to heat and melt the filament as the raw material of 3D printing into a liquid material to be applied on the build plate; the build plate (also known as a build platform or a printing platform) is a platform for attaching the target 3D component, which can be moved along the vertical Z-axis according to the signals provided by the computer-operated controller.

[0153] In the finite element simulation system of the present application, the print head can be a virtual print head such as a virtual modeled print head in a simulation software or a functionally equivalent print head. The parameters defined by the print head such as the print path, the print head movement speed, the heating temperature with the print head as the moving heat source, etc. can be set based on the print head data in actual printing, or can be set artificially. In some embodiments of the finite element simulation, the print head can be used as the starting point of the delivery of the printing material, and is displayed as a cross section whose position is determined by the print movement speed and the print path.

[0154] Please continue to refer to Figure 2 As shown in the figure, the print path is a series of coordinate points arranged in a sequence, and based on the print head movement speed information, the simulation time corresponding to each coordinate point in the print path can be determined. The spatial coordinate points can be three-dimensional coordinate points, and in some embodiments, they can also be a plurality of groups of two-dimensional coordinate points such as X and Y direction coordinate points, each group of two-dimensional coordinate points sharing a Z coordinate, that is, the print path is a plurality of groups of print paths that are discontinuous, and each group of print paths is in the same horizontal plane.

[0155] The output speed of the printing material is the speed of adding material in the printing environment starting from the print head. The heating temperature of the printing material is the initial temperature of the material when it is extruded or output from the print head. The component plate heating temperature of the printing device corresponds to the component plate temperature in actual printing, which can be a constant temperature contact surface in the finite element simulation environment or a contact surface that heats up or cools down at a predetermined rate, and the contact surface is the receiving surface of the first layer of printing material, that is, the bottom surface of the model.

[0156] In some embodiments, the printing information further includes device parameter information, and the device parameter information includes a printing base temperature, a printing chamber temperature (also referred to as a forming chamber), a print head diameter, a print head temperature, and a printing material maximum heating temperature.

[0157] The printing substrate temperature is the temperature of the component plate for carrying the printed object. Generally, the printing substrate temperature is a predetermined constant value. In the simulation method of the present application, the boundary condition at the bottom of the model is a constant temperature with a predetermined fixed value, which is used to simulate the printing substrate temperature in printing. Alternatively, the temperature of the printing substrate is a non-constant value, and the temperature at the bottom of the model is set as a temperature variation function of the printing substrate in the simulation.

[0158] The printing chamber temperature corresponds to the temperature in the forming chamber in actual printing, which can correspond to the temperature in a predetermined chamber volume in the finite element simulation environment. The chamber volume can be composed of selected planes or curved surfaces, and heat exchange conditions and material types equivalent to the actual chamber are applied or defined to simulate the real printing scenario. In some embodiments, the printing chamber temperature in the finite element simulation can be defined by the equivalent heating or cooling speed of the printing environment, which can be defined by a heat conduction formula or an empirical formula based on the boundary conditions of the actual printing environment.

[0159] The print head is usually circular in cross-section and polygonal in cross-section (such as square, rectangular, rhombic, pentagonal, or hexagonal cross-section), and the cross-section of the printing material delivered to the printing chamber for cooling and forming can be determined by the print head diameter. In some embodiments, the print head shape can be other geometric shapes, and geometric parameters are defined according to the predetermined print head shape.

[0160] The print head temperature can be used as a moving heat source for the printing material, and the effect of the print head temperature on the printing material is manifested as heat conduction between the internal contour of the print head and the molten printing material inside the print head.

[0161] The maximum heating temperature of the printing material is the upper limit of the temperature allowed to maintain the performance of the printed object during the process of melting, extrusion, and cooling of the specific printing material, for example, a temperature that is too high will cause warping and shrinkage of the printing material. Based on the printing information as a temperature limit condition, the results obtained by the finite element simulation method for the simulation analysis of the printing process will not damage the printing quality due to temperature in actual printing.

[0162] The printing material includes PLA (Polylactic acid), ABS (Acrylonitrile Butadiene Styrene), polyurethane TPU, TPE material (thermoplastic elastomer), thermoplastic elastomer, nylon, carbon fiber material (such as Carbon Fiber), semi-crystalline thermoplastic, Metal PLA / Metal ABS metal texture PLA / ABS material, PEEK material, FDM conductive wire, Glow-in-the-Dark night light material (such as adding different colors of fluorescent agents in PLA or ABS), Wood wood texture material (by mixing a certain amount of wood fiber in PLA), etc.

[0163] The attribute information of the printing material is characteristic information related to the type of the material, which can be parameter information corresponding to different characteristics of different materials, such as physical properties such as specific heat capacity or thermal conductivity, density, melting point, glass transition temperature, mechanical properties, chemical properties, etc.

[0164] In some embodiments, the attribute information of the printing material includes one or more of the type of the wire material, the diameter of the wire material, and the cross-sectional shape of the wire material. The type of the wire material is the type of the printing material, and the corresponding information determined by the material characteristics such as thermal conductivity, specific heat capacity, glass transition temperature, and elastic modulus can be obtained from the determined wire material type information.

[0165] The diameter of the wire material is the diameter of the printing material extruded from the print head, and in some embodiments, the wire material has a circular cross-section, and the extrusion speed of the wire material can be obtained by defining the moving speed of the print head and the diameter of the wire material.

[0166] The cross-sectional shape of the wire material is the cross-sectional shape of the wire material used to stack the formed components during the cooling process of the wire material on the continuously evolving surface after being extruded from the print head. Generally, in an ideal case, the cross-sectional shape of the wire material is the same at the position of the print head, and then based on the heat transfer state and mechanical state of different regions in the printing, the cross-sectional shape of the wire material after forming may evolve into different forms. In an embodiment of the finite element simulation method, the cross-sectional shape of the wire material is the cross-sectional shape of the wire material at the position of the print head just after being extruded.

[0167] The pre-processing module 21 discretizes the printing path in the G-Code data according to the preset time step upon receiving the discrete instruction, and obtains the position information of the starting point and the ending point of each time step.

[0168] In an implementation, the discrete instruction can be obtained based on the input by the interactive interface of the system, and the finite element system invokes the pre-processing module 21 to perform the discretization operation on the printing path after receiving the instruction.

[0169] The preset time step is a time interval that can be set artificially, and the continuous printing path in the G-Code data or a section of the printing path corresponding to a long printing time is discretized at the preset time interval to form a plurality of printing paths corresponding to the time intervals, the printing paths between the time intervals are connected end to end, and the starting point and the ending point of the printing path corresponding to each time interval, i.e., the preset time step, are obtained.

[0170] In some embodiments, when the pre-processing module 21 performs the discretization operation on the printing path, the pre-processing module discretizes the printing path in the G-Code data, which includes establishing a coordinate system for the printing path in the G-Code data.

[0171] Generally, in the G-Code data read by the pre-processing module 21, the printing path includes a coordinate system corresponding to the path coordinate points, and in some embodiments, the pre-processing module 21 can use the original printing path coordinate system after reading the G-Code data, or a new coordinate system is established and subsequent coordinate transformation of the printing path in the new coordinate system is performed. For example, the pre-processing module 21 establishes another three-dimensional rectangular coordinate system, translates or folds the printing path of the G-Code data, and obtains the spatial coordinates of the printing path in the new coordinate system.

[0172] The step of performing the discretization operation on the printing path by the pre-processing module 21 further includes obtaining the printing order and the printing speed of the printing path from the G-Code data to obtain the printing time sequence of the printing path.

[0173] The pre-processing module 21 obtains the printing order of the coordinate points in the printing path and the printing speed based on the printing path with the determined coordinate positions. The printing speed can be directly obtained from the printing head moving speed, or obtained based on the filament diameter or the filament cross-sectional shape and the extrusion speed. Based on the printing path, the printing order and the printing speed information, the coordinate position and the printing speed corresponding to any intercepted section of the printing path can be obtained, and the time points corresponding to different coordinate points can be easily known from the relationship between the path and the speed. In some embodiments, the starting point in the printing path is set as the zero time point, and the time corresponding to each coordinate point is obtained through the printing order and the printing speed, so that the time sequence is obtained.

[0174] In some scenarios, the finite element simulation system can automatically establish a coordinate system and obtain a time sequence of the printing path after reading the G-Code data.

[0175] The step of discretizing the printing path in the G-Code data by the preprocessing module 21 further includes grid dividing the printing path according to a preset time step to discretize the printing path into a plurality of segments, so that each segment corresponds to a preset time step.

[0176] In some embodiments, the coordinate point information of the printing path in the G-Code data is coordinate point information at a turning angle of the path, for example, in a continuous line segment, the printing path includes coordinates at both ends of the line segment.

[0177] The preset time step is used to segment the printing process, for example, a segment of the printing path completed in 10s is discretized into 10 segments with a time step of 1s. In some embodiments, each time step is equal in length from the start to the end of the printing process. In some embodiments, the time steps have different lengths, for example, the time steps can be 1s and 2s or other settable time periods.

[0178] Please continue to refer to Figure 4 As shown, the printing path is discretized into a plurality of discrete units corresponding to the time steps after grid division. Figure 4 In the illustrated embodiment, the continuous printing path is in the same printing layer, and a plurality of discrete points, i.e., nodes on the path, are formed on the printing path after grid division, forming a plurality of contiguous discrete unit segments. One unit segment between two adjacent discrete points corresponds to a printing distance in a time step, such as 1s.

[0179] The grid division is performed on a certain range including the printing path in the current coordinate system, and the discrete points on the printing path are obtained by the intersection of the grid and the printing path. Generally, the grid division step further includes selection of a grid type and a grid size. In an embodiment, the basic unit of the grid type used is a square grid on a plane, or a cubic grid in a volume. After determining the grid type, the grid parameters are determined according to the preset time step and the printing speed to determine the edge length of the grid basic unit, or the grid edge length can be determined based on the number of line segments to divide the printing path. Then, the discrete points formed by the intersection of the printing path and the grid unit are obtained by dividing the grid. Through finite element grid division, the printing path is discretized into a plurality of finite elements in the simulated actual environment.

[0180] In some embodiments, a hybrid grid division is used to obtain discrete units corresponding to different time steps.

[0181] In some embodiments, the printing path is divided into discrete units of equal length from line segments of different lengths by fixing a time step or equal segmentation based on the number of line segments, so that the printing head moves the same distance in each time step.

[0182] The step of discretizing the printing path in the G-Code data by the preprocessing module 21 further comprises recording the start point coordinates and end point coordinates of each time step.

[0183] The start point coordinates and end point coordinates of each time step are the discrete point coordinates after grid division. Different start point coordinates and end point coordinates can be obtained according to the selected time step, for example, if the desired time step is 1 s, the start point coordinates and end point coordinates of the printing head movement path corresponding to each 1 s time step are obtained. As shown in the figure, the two adjacent discrete point coordinates of the printing path correspond to the start point coordinates and end point coordinates of a time step. Figure 3

[0184] The generation module 22 is configured to determine the basic unit to be activated in each time step according to the printing time sequence of the printing path when receiving a generation instruction, and the basic unit is preset based on the three-dimensional model of the object.

[0185] In some embodiments, the basic unit in the generation module is a rod unit. The rod unit is a rod unit connecting the start point coordinates and end point coordinates in each time step. Specifically, the diameter or cross-sectional shape of the rod unit is consistent with the diameter or cross-sectional shape of the wire in the G-Code data, and the basic rod unit in each time step corresponds to the printing segment extruded by the printing head in the actual printing in the time step.

[0186] In one implementation, the rod unit is determined as follows: based on the discretized printing path, the start point and end point coordinates of each time step are obtained, the diameter or cross-sectional shape of the rod unit is determined based on the diameter or cross-sectional shape of the wire in the G-Code data, the start point and end point coordinates of the time step are taken as the geometric center of the rod unit cross section, and the rod unit connecting the two cross sections is constructed.

[0187] After determining the rod unit based on the discrete time step, the three-dimensional model of the object composed of the rod unit can be obtained. In some embodiments, the generation module 22 establishes heat transfer contact and / or mechanical contact between the rod unit of the current printing layer and the rod unit of the corresponding previous printing layer in the three-dimensional model of the object according to the relative position between the current printing layer and the previous printing layer.

[0188] ​In the embodiments provided in the present application, the order of the printing layer definition is the time sequence, for example, the printing layer printed first at the bottom of the model is the first printing layer, and the second printing layer printed immediately on the first printing layer is the next printing layer. According to the relative position between the current printing layer and the previous printing layer in the three-dimensional model, based on the preset judgment condition of the position relationship, it is determined whether to establish a heat transfer contact or / and a mechanical contact between the current layer rod element and the previous printing layer rod element, and the specific contact type, the mechanical contact and the heat transfer contact can be used to describe the bonding behavior of the materials between different printing layers. Based on the state of the grid division that has been completed, after the heat transfer contact is established, the nonlinear transient heat conduction problem can be approximately expressed as a linear equation set.

[0189] It should be understood that the heat transfer contact and the mechanical contact between different printing layers exist at the same time, the heat transfer process between the printing layers is the heat convection between the extruded materials in the molten state, and the heat conduction between the bonded solid models changes over time during the solidification process of the printing material, when the mechanical contact does not occur between the printing layers, the thermal boundary condition of the surface of the printing layer is the thermal radiation with the printing chamber, and there is no direct heat transfer contact between the printing layers. In some embodiments, when the heat transfer contact and the mechanical contact between the printing layers are established in the finite element system of the processing device, one of the mechanical contact or the heat transfer contact, such as the mechanical contact, can be selected, and the finite element system can automatically identify the model surface to generate the heat transfer contact between the printing layers; of course, the mechanical contact and the heat transfer contact can also be established at the same time.

[0190] In a specific implementation, the generation module 22 establishes the heat transfer contact and / or the mechanical contact by establishing the interlayer bonding between the rod element of the current printing layer and the rod element of the corresponding previous printing layer in the three-dimensional model of the object. In some embodiments, the rod elements of different printing layers formed by connecting the start point and the end point of the time step are in a mutually separated slidable state, and in actual printing, for example, FDM printing, the different printing layers are in a mutually bonded state, the interlayer bonding between the rod element of the current printing layer and the rod element of the corresponding previous printing layer is established to simulate the actual printing situation, and the interlayer bonding can be realized by increasing the contact constraint.

[0191] Please continue to refer to Figure 5a 、 Figure 5b As the finite element simulation system of the present application processes the three-dimensional model of the object, the simplified schematic diagram of the rod element basic unit model in the simulation of printing is shown. Figure 5a 、 Figure 5b The process of setting the basic unit that needs to be activated in the first printing layer of the three-dimensional object model is shown. Figure 5a To simplify the process of dynamically increasing the basic unit in the model, Figure 5bThe actual shape of the object model corresponding to the simulated printing.

[0192] Please continue to refer to Figure 6a 、 Figure 6b As the finite element simulation system of the present application is in the process of processing the three-dimensional model of the object, the simplified schematic diagram of the rod element basic unit model in the simulation of printing. Figure 6a To continue Figure 5a The simulation process determines the basic units that need to be activated in the second printing layer in the simplified model, Figure 6b The actual shape of the object model corresponding to the simulated printing in the second printing layer. Figure 6a A in the above is an enlarged schematic diagram of the interlayer bonding established, as shown, the different printing layers in A are bonded together through the interlayer bonding provided between the upper and lower layers of basic units, B shows a cross-sectional schematic diagram of the printing unit in the part of the model without interlayer bonding. Through the increased interlayer bonding shown in B, the printing units of adjacent layers are converted from a relatively slidable state to a bonded state, and heat transfer contact and mechanical contact can be provided between the printing units based on the interlayer bonding.

[0193] The heat transfer contact includes heat exchange and temperature boundary conditions on the contact boundary, the mutual position between the rod elements is used to determine whether a contact boundary is formed and the type of boundary condition, such as one or more of a specific temperature distribution on the boundary of the given model, a given heat flow on the boundary, or a given convective heat transfer condition, a given radiation heat dissipation condition, and the corresponding heat transfer coefficient, convective heat transfer coefficient, and radiation rate are selected and defined based on the type of boundary condition. In some embodiments, the heat exchange and temperature boundary conditions include thermal radiation boundary conditions and thermal convection boundary conditions, as well as thermal conduction.

[0194] In some embodiments, the position relationship between the previous printing layer and the current printing layer is determined based on the contact detection to establish the interlayer bonding. For example, when the contact detection result is the existence of general contact or interference contact, etc., a contact constraint is applied to the surface of the rod element based on this, and convective heat transfer between the upper and lower layers is established on the contact surface of the rod element model, and the rest of the surface of the rod element and the radiation heat dissipation of the printing chamber. In particular, for the first printing layer, that is, the printing layer simulated in the actual printing bonded to the component plate, the surface of the rod element also includes thermal contact with the component plate.

[0195] The mechanical contact is used to simulate the mechanical environment of the object material in the printing, and the mechanical action between different printing layers is considered in the process of cooling and solidification of the printing material from the molten state, so that the analysis of the strain process of the printing material obtained comprehensively considers the strain caused by temperature and the strain caused by extrusion stress between different printing layers.

[0196] The generating module 22 determines the basic units to be activated at each time step according to the printing time sequence of the printing path, where the basic units to be activated at each time step are the rod units connecting the start point and the end point in the time step. By determining the sequence of the rod units to be activated, the process of the printing head extruding material in the actual printing can be simulated, and the region in the profile of the rod unit is endowed with the properties of the material and the interlayer adhesion according to the activation sequence.

[0197] In some embodiments, the generating module 22, in the step of determining the basic units to be activated at each time step according to the printing time sequence of the printing path, the basic units are hexahedrons.

[0198] Generally, the size of the basic units is of the order of magnitude much smaller than the diameter of the filament, and the profile of the three-dimensional model of the object is determined to add the property of the printing material to the basic units in the region. Since the surface of the extruded filament in the printing model is usually an arc surface such as the side surface of a cylinder, the basic units are set to be small enough hexahedron units to be accumulated in the form of differential to form the corresponding three-dimensional model of the object. Specifically, the hexahedron units can be cubes. The smaller the size of the basic units is, the closer the determined activated basic units are to the range of the three-dimensional model of the object.

[0199] The three-dimensional model of the object can be determined by the printing path and the diameter of the printing head, and the three-dimensional profile of the object can be obtained after the processing device performing the finite element simulation method reads the G-Code data.

[0200] In some embodiments, the generating module 22, in the step of determining the basic units to be activated at each time step according to the printing time sequence of the printing path, includes: establishing a simulation domain according to the preset basic units and the profile of the three-dimensional model of the object; and in the simulation domain, determining the basic units to be activated at each time step according to the printing time sequence of the printing path.

[0201] The simulation domain can be used to determine the calculation domain of the thermal-mechanical-chemical coupling calculation in the subsequent simulation printing process. Generally, the larger the range of the simulation domain is, the closer it is to the printing state in the actual production. In the finite element simulation, in order to reduce the consumption of computing resources and the calculation time, the range of the simulation domain includes the three-dimensional model of the object, the equivalent printing chamber boundary, and the component plate, and the indoor environment where the printing device is located is equivalent to the boundary of the simulation domain.

[0202] In the determined simulation domain, the basic unit to be activated in each time step is determined according to the time sequence of the printing path. In the process of activating the basic unit in the time sequence, which corresponds to the actual printing process, the basic unit to be activated in each time step is determined in advance. Specifically, the basic unit to be activated corresponds to the printing material extruded by the print head in printing. By means of the known three-dimensional model information of the object and the selected time step information, the spatial range of the printing material extruded in each time step can be determined. The time step information includes the start point and end point coordinate information of the time step obtained by the preprocessing module 21 in S11. For example, corresponding to the actual printing, the spatial range occupied by the printing material extruded by the print head moving from the start point coordinate to the end point coordinate of a time step in the range of the basic unit activated in the time step.

[0203] In some implementations, the step of determining the basic unit to be activated in each time step according to the printing time sequence of the printing path by the generating module 22 further includes: establishing an envelope range along the printing path according to the attribute information of the printing material in the simulation domain.

[0204] The attribute information of the printing material used mainly includes at least one of the print head diameter, the filament diameter or the filament cross-sectional shape. Based on the attribute information, an envelope range is established along the printing path. The envelope range is a three-dimensional space region, and the discrete points of the time steps on the printing path are taken as the start point and end point. In one implementation, for a certain determined time step, the print head diameter or the filament diameter is taken as the diameter to establish a vertical circular cross-section with the time step start point and end point coordinates as the centers, and the start point and end point circular cross-sections are connected by a smooth arc surface to form the envelope range in the time step. Alternatively, the time step start point and end point coordinates are taken as the geometric centers of the filament cross-section to establish a vertical filament cross-section, and the start point and end point cross-sections are connected to form the corresponding envelope range.

[0205] In some implementations, the generating module 22 is further configured to determine whether the basic unit is within the envelope range, and if it is within the envelope range, the unit is activated; if it is not within the envelope range, the unit is not activated.

[0206] In some embodiments, the step of determining the basic cells that need to be activated at each time step further comprises a step of setting a judging condition: judging whether the basic cell is within the envelope range, if it is within the envelope range, then activate the cell; if it is not within the envelope range, then do not activate the cell. Specifically, whether the basic cell is within the envelope range contour is determined by the envelope range contour at the time step, for the basic cell that intersects the envelope range contour interface, a preset rule can be used for judgment, for example, if more than 50% of the volume of the basic cell is within the envelope range, then it is determined that the basic cell needs to be activated, and the preset judging rule can be a rule preset in the finite element system of the processing device.

[0207] In subsequent simulation printing, at each time step, it is judged whether the basic cell is within the envelope range, and the basic cell within the envelope range is activated according to the print head moving path.

[0208] Please continue to refer to Figure 7a 、 Figure 7b 、 Figure 7c , which can be shown as a schematic diagram of the process of the generating module 22 determining the envelope range and the basic cells that need to be activated in an embodiment. As shown in Figure 7a , the print path can be obtained by reading the G-Code data, and in Figure 7b , the envelope range is established based on the print path and the filament cross-sectional shape, filament diameter or print head diameter in the print information of the G-Code data as shown in Figure 7a . Figure 7c For Figure 7b , it is a schematic diagram of the cross section C, as shown in Figure 7c , each square represents a basic cell, and the circular cross section is the cross section C of the envelope range. It is judged whether each basic cell is within the envelope range, and the selected area in Figure 7c is the basic cell within the envelope range, which is set as the basic cell that needs to be activated.

[0209] In some embodiments, the generating module is further configured to assign a direction vector to the basic cell that needs to be activated in the print path according to the print time sequence, so that the material direction of each basic cell in the print path is in line with the direction of the print path.

[0210] The material direction includes the local material direction of the basic cell at each time step, and the direction of the basic cell is determined by the direction of the print path, for example, in a model with a rod cell as the basic cell, the print material direction is in line with the extension direction of the rod cell, and in a model with a hexahedron as the basic cell, the print material direction is the print path direction or the tangent direction of the print path at the time step.

[0211] After setting the material direction to follow the printing path direction, the printing material is assigned with orthotropic or isotropic material properties in the subsequent printing simulation.

[0212] The activation module 23 is configured to sequentially activate the basic cells in the three-dimensional model of the object according to the printing time sequence of the printing path and the determined time steps upon receiving the activation instruction.

[0213] In particular, the process performed by the activation module 23 corresponds to the process of melting the basic material by the printing head in the actual FDM printing. In the simulation printing, the activation module 23 and the simulation calculation module 24 are in working state at the same time, so as to track the changes of the temperature field and the stress field calculated by the simulation calculation module 24 from the beginning of the printing to the formation of the printed object while simulating the printing process.

[0214] In the process of activating the basic cells according to the time steps, the activation module 23 implements the dynamic additive process according to the material properties, printing properties information and boundary condition information of the printing environment in the preset G-code data. When the basic cells in the rod cell or the envelope range are activated in each time step, the activated basic cells are assigned with the material properties, and the speed of activating the basic cells corresponds to the moving speed of the printing head in the G-code data.

[0215] Generally, the temperature field in the FDM printing is transient heat transfer analysis. In some embodiments, for the simulation method with hexahedron as the basic cell, the step S13 further includes the step of re-identifying the model surface in each time step and assigning the thermal convection boundary condition and the thermal radiation boundary condition on the surface of the model, so as to describe the influence of the environmental temperature in the printing process by the dynamic boundary condition. In each time step, the temperature of the just activated basic cell is equal to the temperature of the printing head, and the other cells are calculated by assigning the thermal convection boundary condition and the thermal radiation boundary condition, coupling the stress-strain model by the heat conduction model to obtain the temperature field and the stress field varying with time and space.

[0216] In the actual printing or simulation printing process, the printing head starts to extrude the printing material to form a continuously evolving surface. Each time step in the time sequence corresponds to different basic cells and different spatial positions. In each time step, the model surface is re-identified to simulate the boundary condition formed when the actual printing process occurs, that is, the boundary condition is a dynamic boundary condition. For example, the model surface is identified in the current time step when the basic cell is activated, and the thermal convection boundary condition between the thermal radiation boundary condition in the printing chamber and the bonded printing layer is added.

[0217] Please continue to refer to Figure 8a ,Figure 8b 、 Figure 8c 、 Figure 8d , which is a simplified schematic diagram of the printing simulation process. As shown in the figure, Figure 8a , Figure 8b , Figure 8c , Figure 8d is a process of accumulating layer by layer after the time sequence basic unit conforming to the printing path is activated. The activation module 23 activates the basic unit in the three-dimensional model of the object in each time step, that is, the process of assigning the material attribute and the temperature boundary condition, the stress condition to the basic unit in the three-dimensional model of the object conforming to the time step. The three-dimensional model of the object as a whole presents the effect of dynamic additive layer-by-layer accumulation and bonding to simulate the process of material extrusion from the printing head in actual printing.

[0218] The simulation calculation module 24 is configured to perform coupled simulation calculation on the activated basic units in the three-dimensional model of the object by using a preset model to obtain simulation results describing the dynamic temperature field distribution and / or the dynamic residual stress field distribution of the printing material in the three-dimensional model of the object changing with time during the printing process.

[0219] In some embodiments, the coupled simulation calculation performed by the simulation calculation module 24 is coupled simulation calculation under preset boundary conditions, which include heat convection boundary conditions and / or heat radiation boundary conditions. Specifically, the boundary conditions include heat transfer boundary conditions and mechanical contact boundary conditions, wherein the basic unit thermal boundary conditions are the heat exchange conditions between the basic unit and the external environment and different printing layer units, including: convective heat exchange between the model bottom constant temperature component plate, internal negative heat source caused by environmental cooling, and cooling caused by convection between different printing layers and printing chamber radiation.

[0220] In some embodiments, the preset model includes a linear viscoelastic model for describing the mechanical deformation of the printing material, or / and an orthotropic thermal conduction model or an orthotropic thermal conduction model for describing the thermal conduction behavior of the printing material.

[0221] Specifically, the linear viscoelastic model can be a multi-branch thermal viscoelastic model, which considers the temperature-dependent relaxation behavior of the material and the flow shear phenomenon. Wherein, the mechanical behavior of the material is related to the temperature, the total strain in printing is composed of thermal strain and elastic strain, the change of the material in each time step is described by a thermo-mechanical-chemical coupling model, the obtained simulation results consider the material properties, temperature and mechanical state, and the interaction between temperature and stress and strain, and the final deformation data is more consistent with the actual printing state, which can reduce the simulation error.

[0222] In some embodiments, during the simulation calculation, one of the stress nephogram corresponding to the residual stress field, the displacement nephogram corresponding to the deformation, or the temperature nephogram corresponding to the temperature field can be selected to be displayed, and it should be understood that, in the calculation, the temperature field is completely coupled with the stress field, and the transient temperature field and the residual stress field can be obtained simultaneously at each time of calculation, and the dynamic temperature field and the residual stress field varying with time can be obtained at any time step or during the entire simulation printing, and multiple ones can be selected to be displayed simultaneously in the finite element system.

[0223] In some embodiments, the preprocessing module 21 is further configured to obtain the initial residual stress of the printing material, so that the simulation calculation module 24 performs coupled temperature displacement simulation on the three-dimensional model of the object based on the initial residual stress by using a preset model.

[0224] The initial residual stress is used as an initial condition of the printing process simulation, and the residual stress at the initial printing time will affect the printing until the end of the printing. The initial residual stress has a certain influence on the formed printed object, such as causing material deformation and cracking. In the finite element simulation method, the initial residual stress is considered to obtain the printing analysis result, which can be used to control the forming process in actual printing, such as adjusting the printing parameters, to weaken the damage of the initial residual stress to the printing quality.

[0225] The finite element simulation system provided in the present application discretizes the printing path into multiple segments according to time steps, sets a basic unit in each segment and activates according to the time sequence of printing, adopts a linear viscoelastic model to describe the mechanical deformation of the material during the simulation printing, considers the temperature-dependent relaxation behavior and flow shear phenomenon of the material, sets thermal contact and mechanical contact on the surface of the basic unit, and performs calculation by coupling the temperature field and the stress field. The results close to the actual printing are obtained by the fully coupled thermal-mechanical-chemical finite element simulation method. Furthermore, the finite element simulation system considers the initial residual stress for printing process simulation, can be used to analyze the deformation of the printed object caused by the initial residual stress, and the temperature data and strain data obtained by calculation can be used to evaluate the performance of the printed object under different printing parameter settings. The finite element simulation system can provide data to support the adjustment of the printing parameters.

[0226] In a third aspect, the present application further provides a computer device, such as Figure 10 As shown, a simplified structure schematic diagram of the computer device in an embodiment of the present application is shown. As shown, the computer device comprises a storage device 31, a processing device 32, and a display device 33.

[0227] The storage device 31 is configured to store at least one program and a preset simulation calculation model.

[0228] In some embodiments, the storage device 31 is, for example, a network attached storage device accessed via RF circuitry or an external port and a communications network, which can be the Internet, one or more intranets, local area networks, wide area networks, storage area networks, etc., or a suitable combination thereof. A storage device controller can control access to the storage device 31 by other components of the device, such as the CPU and peripheral interfaces. The storage device 31 optionally includes a high-speed random access memory, and also optionally includes a non-volatile memory, such as one or more disk storage devices, flash storage devices, or other non-volatile solid-state storage devices. Access to the memory by other components of the device, such as the CPU and peripheral interfaces, is controlled by the memory controller.

[0229] In some embodiments, the storage device 31 can also include volatile memory, such as random access memory, and storage memory, such as read-only memory, flash memory, hard disk or solid state disk.

[0230] The processing device 32 is connected to the storage device 31, and is configured to execute the at least one program to call the storage device to perform and implement the finite element simulation method according to any one of the embodiments of the present application. Figure 1 The processing device 32 is connected to the storage device 31, and is configured to execute the at least one program to call the storage device to perform and implement the finite element simulation method according to any one of the embodiments of the present application.

[0231] In some embodiments, the processing device 32 includes an integrated circuit chip with signal processing capability, or a general-purpose processor, which can be a microprocessor or any conventional processor, etc., such as a central processing unit. For example, it can be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a discrete gate or transistor logic device, a discrete hardware component, which can implement or execute the disclosed methods, steps and logic block diagrams in the embodiments of the present application, for example, to perform the finite element simulation method according to any one of the embodiments of the present application. Figures 1 to 8d The processing device 32 is connected to the storage device 31, and is configured to execute the at least one program to call the storage device to perform and implement the finite element simulation method according to any one of the embodiments of the present application.

[0232] The display device 33 is configured to display the simulation results of the dynamic temperature field distribution and / or the dynamic residual stress field distribution of the object three-dimensional model in the printing process.

[0233] The display device 33 performs specific tasks according to the data and instructions received from the information processing system, such as a computer device, and outputs information including text, graphics, tactile, audio, video, etc.

[0234] The display device 33 also serves as an interactive interface, for example, the computer device is loaded with a finite element system according to the second aspect of the present application, and when performing operations such as discrete printing path, setting envelope range, generating basic unit, simulation calculation, activating basic unit, etc., instructions can be generated through the display interface.

[0235] The finite element simulation method performed by the processing device 32 in coordination with the storage device 31 discretizes the printing path into a plurality of segments according to time steps, sets a basic unit in each segment and activates according to the time sequence of printing, adopts a linear viscoelastic model to describe the mechanical deformation of the material during the simulation of printing, considers the temperature-dependent relaxation behavior and flow shear phenomenon of the material, sets thermal contact and mechanical contact on the surface of the basic unit, and calculates the temperature field and stress field in coupling, so as to obtain a result close to the actual printing through the full coupling of thermal-mechanical-chemical finite element simulation method. Furthermore, the finite element simulation method of the present application considers the initial residual stress for printing process simulation, and can be used to analyze the deformation of the printed part caused by the initial residual stress. The temperature data and strain data obtained by calculation can be used to evaluate the performance of the printed object under different printing parameter settings. The finite element simulation method can provide data to support the adjustment of printing parameters.

[0236] In some embodiments, during the simulation calculation, the display device 33 can select to display one of a stress contour corresponding to the residual stress field, a displacement contour of deformation, or a temperature contour corresponding to the temperature field based on the received instructions. It should be understood that in the calculation, the temperature field and the residual stress field are fully coupled, and the transient temperature field and the stress field can be obtained simultaneously at each time of calculation. The dynamic temperature field and the residual stress field varying with time are obtained in the time step or the entire process of simulating printing. The display device 33 can also select to display multiple simultaneously.

[0237] The present application also provides a computer-readable storage medium storing at least one program in a fourth aspect. Wherein, the at least one program, when invoked by a processor, performs and implements the finite element simulation method as described in any of the embodiments of the present application. Figures 1 to 8d The finite element simulation method as described in any of the embodiments of the present application.

[0238] The functions, if implemented in the form of software function units and sold or used as independent products, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application.

[0239] In the embodiments provided by the present application, the computer readable and writable storage medium can include read-only memory, random access memory, EEPROM, CD-ROM or other optical disk storage device, magnetic disk storage device or other magnetic storage device, flash memory, U disk, mobile hard disk, or any other medium capable of storing desired program code in the form of instructions or data structures and capable of being accessed by a computer. In addition, any connection can be appropriately referred to as a computer readable medium. For example, if instructions are sent from a website, server or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology such as infrared, radio and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL or wireless technology such as infrared, radio and microwave is included in the definition of the medium. However, it should be understood that the computer readable and writable storage medium and the data storage medium do not include connections, carriers, signals or other transitory media, but are intended for non-transitory, tangible storage media. As used in the application, magnetic disks and optical disks include compact discs (CD), laser discs, optical discs, digital versatile discs (DVD), floppy disks and Blu-ray discs, wherein magnetic disks usually magnetically copy data, and optical disks use laser to optically copy data.

[0240] In one or more example aspects, the functions described by the computer program of the finite element simulation method described in the present application can be implemented in hardware, software, firmware or any combination thereof. When implemented in software, these functions can be stored or transmitted as one or more instructions or codes on a computer readable medium. The steps of the method or algorithm disclosed in the present application can be embodied in a processor executable software module, wherein the processor executable software module can be located on a tangible, non-transitory computer readable and writable storage medium. The tangible, non-transitory computer readable and writable storage medium can be any available medium accessible by a computer.

[0241] The flow diagrams and the block diagrams in above-described figures of this application illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to various embodiments of this application. In this regard, each block in the flow diagrams and the block diagrams can represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the block can occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flow diagrams, and combinations thereof, can be implemented by special purpose hardware-based systems that perform the specified functions or operations, or combinations of special purpose hardware and computer instructions.

[0242] The above-described embodiments of the application are merely descriptive and are not intended to limit the scope of the application. Any modifications or changes to the described embodiments are considered to be within the scope of the application. Therefore, the scope of the application is defined by the appended claims.

Claims

1. A method of finite element modeling of a three-dimensional model of an object, characterized by, The method comprises the following steps: reading G-Code data of the three-dimensional model of the object and printing information set, the printing information comprising attribute information of printing material; discretizing the printing path in the G-Code data according to a preset time step to obtain position information of a starting point and an ending point of each time step; wherein the step of discretizing the printing path in the G-Code data according to a preset time step to obtain position information of a starting point and an ending point of each time step comprises: establishing a coordinate system for the printing path in the G-Code data; obtaining printing sequence and printing speed of the printing path from the G-Code data to obtain a printing time sequence of the printing path; grid dividing the printing path according to a preset time step to discretize into multiple segments, so that each segment corresponds to its preset time step; recording the starting point coordinates and the ending point coordinates of each time step; determining the basic unit to be activated at each time step according to the printing time sequence of the printing path, the basic unit being preset based on the three-dimensional model of the object; wherein the basic unit is a rod unit or a hexahedral unit; establishing heat transfer contact and / or mechanical contact between the rod unit of the current printing layer and the rod unit of the corresponding previous printing layer in the three-dimensional model of the object according to the relative position between the current printing layer and the previous printing layer; the step of establishing heat transfer contact and / or mechanical contact is to establish interlayer adhesion between the rod unit of the current printing layer and the rod unit of the corresponding previous printing layer in the three-dimensional model of the object; sequentially activating the basic units in the three-dimensional model of the object according to the printing time sequence of the printing path and the determined time step; performing coupling simulation calculation on each activated basic unit in the three-dimensional model of the object by using a preset model to obtain simulation results describing the dynamic temperature field distribution and / or dynamic residual stress field distribution of the printing material in the three-dimensional model of the object over time during the printing process.

2. The finite element simulation method of claim 1, wherein, The G-Code data comprises one or more of the following information: printing path of the printing head, moving speed of the printing head, printing material output speed, printing material heating temperature, and component plate heating temperature of the printing equipment.

3. The finite element simulation method of claim 1, wherein, The printing information further comprises equipment parameter information, and the equipment parameter information comprises: printing substrate temperature, printing chamber temperature, extrusion head diameter, extrusion head temperature, and maximum heating temperature of the filament.

4. The finite element simulation method of claim 1, wherein, The attribute information of the printing material comprises one or more of the following information: filament type, filament diameter, and filament cross-sectional shape.

5. The finite element simulation method of claim 1, wherein, The step of determining the basic unit to be activated at each time step according to the printing time sequence of the printing path comprises: establishing a simulation domain according to the preset basic unit and the profile of the three-dimensional model of the object; in the simulation domain, determining the basic unit to be activated at each time step according to the printing time sequence of the printing path.

6. The finite element simulation method of claim 5, wherein, The method further comprises the step of establishing an envelope range along the printing path in the simulation domain according to the attribute information of the printing material.

7. The finite element simulation method of claim 6, wherein, The step of determining the basic unit to be activated at each time step further comprises a step of setting a judgment condition: judging whether the basic unit is within the envelope range, if yes, activating the unit; if not, not activating the unit.

8. The finite element simulation method of claim 1, wherein, The step of determining the basic unit to be activated at each time step further comprises: assigning a direction vector to the basic unit to be activated in the printing path according to the printing time sequence, so that the material direction of each basic unit in the printing path is consistent with the direction of the printing path.

9. The finite element simulation method of claim 1, wherein, Further comprising a step of obtaining the initial residual stress of the printing material, so as to perform coupled temperature displacement simulation on the three-dimensional model of the object by using a preset model based on the initial residual stress.

10. The finite element simulation method of claim 1, wherein, In the step of performing coupled simulation calculation on the three-dimensional model of the object by using a preset model, the coupled simulation calculation is a coupled simulation calculation under preset boundary conditions, and the boundary conditions include a heat convection boundary condition and / or a heat radiation boundary condition.

11. The finite element simulation method of claim 1 or 10, wherein, In the step of performing coupled simulation calculation on the three-dimensional model of the object by using a preset model, the preset model includes a linear viscoelastic model for describing the mechanical deformation of the printing material, or / and an orthotropic thermal conduction model or an orthotropic thermal conduction model for describing the thermal conduction behavior of the printing material.

12. A finite element modeling system for a three-dimensional model of an object, comprising: Comprise: A preprocessing module is configured to read G-Code data of the three-dimensional model of the object and set printing information, and obtain position information of a starting point and an ending point of each time step by discretizing a printing path in the G-Code data according to a preset time step when a discrete instruction is received, wherein the printing information comprises attribute information of a printing material; wherein the step of discretizing the printing path in the G-Code data according to the preset time step to obtain the position information of the starting point and the ending point of each time step comprises: establishing a coordinate system for the printing path in the G-Code data; obtaining a printing sequence and a printing speed of the printing path from the G-Code data to obtain a printing time sequence of the printing path; performing grid division on the printing path according to the preset time step to discretize the printing path into a plurality of segments, so that each segment corresponds to a preset time step; and recording starting point coordinates and ending point coordinates of each time step; A generating module is configured to determine a basic unit to be activated at each time step according to a printing time sequence of the printing path when a generation instruction is received, wherein the basic unit is preset based on the three-dimensional model of the object; wherein the basic unit is a rod element or a hexahedral element; and the generating module is further configured to establish a heat transfer contact and / or a mechanical contact between a rod element of a current printing layer and a rod element of a corresponding previous printing layer in the three-dimensional model of the object according to a relative position between the current printing layer and the previous printing layer, wherein the heat transfer contact and / or the mechanical contact is a layer adhesion between the rod element of the current printing layer and the rod element of the corresponding previous printing layer in the three-dimensional model of the object. an activation module configured to activate, upon receiving the activation instruction, the basic cells in the three-dimensional model of the object in sequence according to the printing time sequence of the printing path and the determined time steps; an analog computation module configured to perform coupled analog computation on the activated basic cells in the three-dimensional model of the object by using a preset model, to obtain analog results describing the dynamic temperature field distribution and / or the dynamic residual stress field distribution of the printing material in the three-dimensional model of the object over time during the printing process.

13. The finite element modeling system of claim 12, wherein, The step of determining the basic cells to be activated at each time step by the generating module according to the printing time sequence of the printing path comprises: establishing an analog domain according to the preset basic cells and the contour of the three-dimensional model of the object; in the analog domain, determining the basic cells to be activated at each time step according to the printing time sequence of the printing path.

14. The finite element modeling system of claim 13, wherein, The generating module is further configured to establish an envelope range along the printing path in the analog domain according to the attribute information of the printing material.

15. The finite element modeling system of claim 14, wherein, The generating module is further configured to determine whether the basic cells are within the envelope range, and if so, activate the cells; if not, do not activate the cells.

16. The finite element modeling system of claim 12, wherein, The generating module is further configured to assign a directional vector to the basic cells to be activated in the printing path according to the printing time sequence, so that the material direction of the basic cells in the printing path is consistent with the direction of the printing path.

17. The finite element modeling system of claim 12, wherein, The preprocessing module is further configured to obtain the initial residual stress of the printing material, so that the analog computation module performs coupled temperature displacement analog computation on the three-dimensional model of the object by using a preset model based on the initial residual stress.

18. The finite element modeling system of claim 12, wherein, The coupled analog computation in the analog computation module is coupled analog computation under preset boundary conditions, which include thermal convection boundary conditions and / or thermal radiation boundary conditions.

19. The finite element modeling system of claim 12 or 18, wherein, The preset model includes a linear viscoelastic model for describing the mechanical deformation of the printing material, or / and an orthotropic thermal conduction model or an isotropic thermal conduction model for describing the thermal conduction behavior of the printing material.

20. A computer device, comprising: comprise: a storage device configured to store at least one program and a preset analog computation model; a processing device connected to the storage device, configured to execute the at least one program to call the at least one program in the storage device to perform and implement the finite element analog method according to any one of claims 1-11; a display device configured to display the analog results describing the dynamic temperature field distribution and / or the dynamic residual stress field distribution of the printing material in the three-dimensional model of the object over time during the printing process.

21. A computer-readable storage medium, characterized in that, at least one program, which is executed by a processor to implement the finite element analog method according to any one of claims 1-11.

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