FDM optimal printing speed range determination method based on multi-path temperature field simulation

Abstract

The invention discloses an FDM optimal printing speed range determination method based on multipath temperature field simulation, and the method comprises the following steps: carrying out simulation through employing Ansys Workbench software, and building a simulation model of an FDM forming process; defining the material attribute of the formed part, and carrying out proper grid division; and carrying out life and death unit setting on the formed part, activating different printing forming processes according to a specified printing path to simulate an actual printing process, obtaining a temperature field simulation result of the printed part, and analyzing and determining an optimal printing speed range under different printing paths. The invention aims to research and find out the optimal printing speed range including the filling speed and the jumping speed by analyzing the temperature fields of different printing paths at different printing speeds based on the FDM technology so as to meet the performance requirements in practical application and balance the printing efficiency and precision.

Description

[0001] The present invention relates to the field of 3D printing technology, and in particular to a method for determining an optimal printing speed range based on temperature field simulation of an FDM molding process. Background Art

[0002] The continuous development of 3D printing technology has spawned a variety of different printing technologies. Five common technologies, depending on the molding process and materials used, include: Stereolithography (SLA), Selective Laser Sintering (SLS), Layered Object Manufacturing (LOM), 3D Deposition Modeling (3DP), and Fused Deposition Modeling (FDM). Each technology has its own unique advantages and applications. FDM is a relatively mature 3D printing technology and is widely used in product prototyping and design verification. Its principle is to heat a thermoplastic material through a nozzle until it melts, then deposit it layer by layer to ultimately create the desired three-dimensional object. Due to its low equipment cost, ease of operation, and wide range of materials, FDM has become the preferred technology for prototyping, functional verification, and small-batch production in many industrial fields. The advantages of FDM technology lie not only in its low cost and high operational efficiency, but also in its ability to work with a variety of thermoplastic materials, such as PLA, ABS, and nylon, which has led to its widespread application across multiple industries.

[0003] Different path planning methods can lead to significant differences in temperature field distribution during the FDM molding process, directly affecting the range of the optimal printing speed. The optimal printing speed is closely related to the quality and efficiency of the printed product and is one of the important factors affecting the molding process. In practical applications, the path planning method determines the movement trajectory and filling strategy of the nozzle, thereby affecting the temperature distribution of each layer of material. Currently, there is a lack of systematic research on the impact of different path planning methods on the optimal printing speed. Different path planning methods require different optimal printing speeds during the printing process, and sufficient theoretical analysis and empirical research have not been carried out. For example, some path planning methods may be able to better disperse heat under certain conditions and maintain a relatively uniform temperature field distribution, making them suitable for higher printing speeds; while others may require slower printing speeds to avoid local overheating or uneven cooling to ensure product quality.

[0004] Therefore, it is necessary to consider the influence of temperature field distribution based on the model's molding accuracy and printing efficiency, and propose a method to study the optimal printing speed based on the temperature field of the FDM molding process. By simulating the temperature field changes under different path planning methods, the influence of the temperature field on the optimal printing speed range is explored, providing a theoretical basis for formulating a more reasonable printing speed. Summary of the Invention

[0005] In view of this, the present invention proposes a method for determining an optimal FDM printing speed range based on multi-path temperature field simulation to solve the problems existing in the above-mentioned background technology.

[0006] The technical solution of the present invention is to provide a method for determining the optimal printing speed range of FDM based on multi-path temperature field simulation, the specific steps of which are as follows:

[0007] Step 1: Use Ansys Workbench software to simulate and build a simulation model of the FDM molding process; Step 1 includes the following steps:

[0008] (1) Design the model according to the actual rectangular size, and set the length, width and height to 16mm*8mm*2mm.

[0009] Step 2: Define the material properties of the molded part and perform appropriate mesh division. Step 2 includes two steps:

[0010] (1) Set material parameters in the simulation model and apply the physical properties of the printed material at different temperatures to the model based on the actual material properties;

[0011] (2) Divide the rectangular model into grids, and control the grid size to 0.4mm*0.4mm*0.2mm.

[0012] Step 3: Set the birth and death units for the molded part and activate different printing processes according to the specified printing path to simulate the actual printing process. Step 3 includes two steps:

[0013] (1) The life and death process of the unit is realized by modifying the unit body stiffness. When the unit stiffness is multiplied by a very small reduction coefficient, the output of the unit is close to 0, which can be regarded as the unit being "killed". When the reduction coefficient of the unit stiffness is changed to 1, the output of the unit returns to the initial value of the system, which can be regarded as the unit being "activated". The activation and killing process of the unit is controlled to simulate the melting and accumulation process of the material during the printing process;

[0014] (2) The unit activation time is set to 0.02s, and the simulation model is set to have 8000 analysis steps. The units in the meshed model are numbered, and the corresponding units are activated by selecting specific unit numbers. The order of activated units is controlled to simulate different printing paths during the molding process.

[0015] Step 4: Using the temperature results during the printing process as the load to solve, obtain the temperature field of the printed part and analyze and determine the optimal printing speed range under different printing paths; Step 4 includes two steps:

[0016] (1) Applying nozzle temperature to the selected activated unit, adjusting the printing speed by controlling the duration of temperature application, applying air convection and heat conduction models to the activated unit to calculate the temperature field of the simulation model, and obtaining a continuously changing temperature field cloud map and a curve diagram of node temperature change over time based on the temperature field;

[0017] (2) According to the melting temperature range of PLA material (150℃ to 180℃), combined with the temperature field cloud map, the curve diagram of node temperature change over time and the exported data, the temperature distribution characteristics under different printing paths are analyzed and the optimal printing speed range including filling speed and jump speed is determined.

[0018] Compared with the prior art, the present invention provides a method for determining the optimal printing speed range based on the temperature field of the FDM molding process, which has the following beneficial effects:

[0019] 1. Optimize the balance between printing efficiency and precision. Based on the temperature field simulation during the FDM molding process, we study the optimal printing speed and determine the optimal printing speed range under different printing paths, thereby improving printing efficiency while ensuring printing quality.

[0020] 2. Improve printing quality and molding stability. By analyzing the temperature field changes under different printing paths, the heat conduction process can be better controlled, avoiding printing defects such as warping and deformation caused by uneven temperature, thereby improving the accuracy and stability of printed parts. This helps to produce high-quality 3D printed parts, which is especially important in industrial applications with high precision requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the overall process of the present invention;

[0022] Figure 2 It is a detailed diagram of the overall process of the present invention;

[0023] Figure 3 This is a mesh division result diagram of the simulation model of the present invention;

[0024] Figure 4 Schematic diagram of three path activation methods used in the present invention;

[0025] Figure 5 This is the temperature field distribution cloud diagram of the Z-shaped path at different filling speeds of the present invention;

[0026] Figure 6 This is a graph showing the change of node temperature over time at different filling speeds for the Z-shaped path of the present invention;

[0027] Figure 7 This is a temperature field distribution cloud diagram of the contour offset path at different filling speeds of the present invention;

[0028] Figure 8 This is a graph showing the change of node temperature over time at different filling speeds for the contour offset path of the present invention;

[0029] Figure 9 The temperature field distribution cloud diagram of the unidirectional reciprocating straight path of the present invention at different jump speeds;

[0030] Figure 10 This is a graph showing the temperature change of nodes over time at different jump speeds for a unidirectional reciprocating straight line path according to the present invention; DETAILED DESCRIPTION

[0031] The technical solution of the present invention is further described below with reference to the accompanying drawings and specific embodiments:

[0032] The present invention encompasses any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention. In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without the description of these details.

[0033] like Figure 1 As shown, the present invention provides a method for determining an optimal printing speed range based on the temperature field of an FDM molding process, comprising the following steps:

[0034] Step 1: Use Ansys Workbench software to build a simulation model of the FDM molding process;

[0035] Step 2: Define the material properties of the simulation model and perform appropriate meshing;

[0036] Step 3: Set up the life and death unit of the simulation model and activate different printing processes according to the specified printing path to simulate the actual printing process;

[0037] Step 4: Use the temperature results during the printing process as the load to solve, obtain the temperature field of the printed part, and analyze and determine the optimal printing speed range under different printing paths.

[0038] Detailed steps as follows Figure 2As shown, based on 3D printing FDM technology, this paper proposes a method to determine the optimal printing speed range for different paths based on changes in the material's melt temperature during the molding process temperature field simulation. First, finite element modeling was performed using Ansys Workbench software, with the length, width, and height dimensions set to 16mm*8mm*2mm. Material properties of PLA, the material used in this experiment, including density, thermal conductivity, elastic modulus, and Poisson's ratio, were set, and the model was meshed with a grid size of 0.4mm*0.4mm*0.2mm. Next, birth and death units were set in the model, and different printing processes were activated according to the specified printing path, including a zigzag path, an outward-to-inward contour offset path, and a unidirectional reciprocating straight path. The molding process under different printing paths was simulated using different activation methods. Finally, the molded part was subjected to temperature field simulation, and the data derived from the model nodes was analyzed to determine the optimal printing speed range for different paths. The optimal printing speed range was selected to have a value interval of 20°C. This method can achieve higher manufacturing precision for printed models and improve printing efficiency while maintaining printing accuracy.

[0039] The following is a detailed explanation of each of the four steps.

[0040] Step 1: Use Ansys Workbench software to simulate and build a simulation model of the FDM molding process; Step 1 includes the following steps:

[0041] (1) Design the model according to the actual rectangular parallelepiped size, and set the length, width and height to 16mm*8mm*2mm;

[0042] Step 2: Define the material properties of the simulation model and perform appropriate meshing. Step 2 includes two steps:

[0043] (1) Set the material parameters in the simulation model, where the density is 1280 kg / m 3 , thermal conductivity 0.25W / m·℃, elastic modulus 3500MPa, Poisson's ratio 0.35, etc., assuming that its density, thermal conductivity, etc. do not change with temperature. In order to solve the problem of latent heat of phase change, the equivalent specific heat capacity method is used to simulate the actual printing process, and the physical properties of the printing material at different temperatures are applied to the model based on the actual material properties.

[0044] The equivalent specific heat capacity method is a common technique used to simplify transient heat conduction problems in thermal analysis. This method reduces computational complexity by converting a complex unsteady-state heat conduction problem into a relatively simplified steady-state problem. The formula is as follows:

[0045] ce=c+L0

[0046] Among them, c eis the equivalent specific heat capacity, also called effective specific heat capacity, which includes the true specific heat capacity of the object and the increase in specific heat capacity caused by latent heat; L0 is the increase in specific heat capacity.

[0047] (2) The rectangular parallelepiped model is meshed, and the mesh size is controlled to 0.4mm*0.4mm*0.2mm. The duration of each analysis step, i.e., the unit activation time, is 0.02s. There are 8000 analysis steps in total. The model meshing results are as follows: Figure 3 As shown, the black point is the selected node, which is located at the junction of the first and second layer mesh surfaces.

[0048] Step 3: Set the birth and death units for the molded part and activate different printing processes according to the specified printing path to simulate the actual printing process. Step 3 includes two steps:

[0049] (1) The life and death process of the unit is realized by modifying the unit body stiffness. When the unit stiffness is multiplied by a very small reduction coefficient, the output of the unit is close to 0, which can be regarded as the unit being "killed". When the reduction coefficient of the unit stiffness is changed to 1, the output of the unit returns to the initial value of the system, which can be regarded as the unit being "activated". The activation and killing process of the unit is controlled to simulate the melting and accumulation process of the material during the printing process;

[0050] (2) The unit activation time is set to 0.02s, and the simulation model is set to 8000 analysis steps. The units in the mesh model are numbered, and the corresponding units are activated by selecting specific unit numbers. The different printing paths in the molding process are simulated by controlling the order of the activated units, such as Figure 4 Schematic diagram of three path activation methods shown.

[0051] Step 4: Use the temperature results during the printing process as the load to solve, obtain the temperature field of the printed part and analyze and determine the optimal printing speed range under different printing paths. Step 4 includes two steps:

[0052] (1) During the actual printing process, loads are applied to the divided units. In ANSYS thermal analysis, the loads applied to each unit generally include temperature and heat convection. For FDM technology, the filament has the same temperature as the nozzle when it is heated and extruded. Therefore, the newly deposited filament can be regarded as the system heat source. The nozzle temperature, that is, the temperature of the newly extruded filament, is set to 210°C. This temperature is the most commonly set nozzle temperature.

[0053] For FDM technology, the model of material heating in the print head belongs to steady-state thermal analysis, the process of material extrusion from the print head belongs to transient thermal analysis, and the temperature field change during the FDM material stacking process belongs to nonlinear transient thermal analysis. The heat transfer within each unit cell can be described by the nonlinear transient heat conduction differential equation as shown below:

[0054]

[0055] Where ρ is the material density; c is the specific heat capacity of the material; k x 、k y 、k z They represent the heat conduction coefficients along the x, y, and z directions respectively; T is temperature; t is time; Q=Q(x,y,z,t) is the heat source density inside the object.

[0056] When solving differential equations, we must first clarify the initial conditions and boundary conditions. The initial conditions refer to the initial temperature distribution of the object. The expression is as follows:

[0057] T0=T(x,y,z,t)| t＝0

[0058] In the temperature field simulation of the FDM molding process, the third type of boundary condition is mainly used: given the convective heat transfer value between the material and the air, the convective heat transfer coefficient between the molded part and the air medium at room temperature and the room temperature is expressed as follows:

[0059]

[0060] Where h is the convective heat transfer coefficient; T a is the surface temperature of the model; T s is the fluid temperature.

[0061] The printing speed is adjusted by controlling the duration of temperature application. Air convection and heat conduction models are applied to the activated units to calculate the temperature field of the simulation model, such as Figure 5 、 Figure 7 、 Figure 9 As shown in the figure, the temperature variation curve of the selected node with time is as follows Figure 6 、 Figure 8 、 Figure 10 As shown;

[0062] (2) Based on the melting temperature range of PLA material (150℃ to 180℃), combined with the temperature field cloud map, the node temperature change curve over time and the derived data, the specific research methods and conclusions are as follows:

[0063] according to Figure 5It can be concluded that at different filling speeds, the Z-shaped path shows a significant temperature gradient distribution, and the high-temperature areas mainly appear at the corners of the path and the position just after printing. The temperature gradient distribution is correlated with the filling speed. As the filling speed increases, the overall temperature field shows a higher temperature distribution. At low filling speeds, the material fills slowly and the heat dissipation time is longer, resulting in a larger temperature difference across the entire region and a more obvious temperature gradient difference. At high filling speeds, the material fills quickly and the heat dissipation time is shortened, so the overall temperature is higher and the temperature gradient is smaller. The smaller temperature difference also helps to reduce deformation and other defects caused by thermal stress, thereby ensuring the molding accuracy of the final product.

[0064] according to Figure 6 It can be concluded that at different filling speeds, the temperature of all nodes shows a curve shape that shows an initial rapid rise followed by a gradual decay and stabilization. This indicates that the material heats up rapidly in the early stages of flow due to heating during the extrusion process, and then gradually drops due to heat conduction and heat dissipation caused by material flow. The temperature curves at different speeds gradually converge to a similar steady-state temperature range within 2000s. The node temperatures at different filling speeds after printing the first layer of the path at the export node are shown in the following table:

[0065]

[0066] PLA material typically melts between 150°C and 180°C. A fill speed of 60 mm / s is considered ideal. At this speed, the node temperature reaches approximately 119°C. Meanwhile, at 80 mm / s, the node temperature reaches 140.88°C, close to the upper melting temperature limit of PLA material. This effectively controls heat accumulation, preventing overheating while maintaining good printing accuracy and efficiency. Therefore, a reasonable fill speed range for a zigzag path is between 60 mm / s and 80 mm / s, ensuring thermal control and excellent print quality during printing.

[0067] according to Figure 7 It can be concluded that when the molded part is filled from the outside in during the 3D printing process, this filling sequence results in the highest temperature in the center of the molded part, forming a distinct elliptical temperature distribution. As the temperature moves away from the center, it gradually decreases, forming a uniform and smooth temperature gradient. The contour-biased filling method from the outside in and the appropriate temperature distribution design play a significant role in improving the strength, stability, and overall quality of the printed part. By controlling the filling speed and thus influencing the temperature distribution, the internal stress distribution of the molded part can be effectively optimized, ensuring better adaptability during the cooling process.

[0068] according to Figure 8It can be concluded that as the filling speed gradually increases from 20 mm / s to 80 mm / s, the temperature difference at the node gradually becomes smaller and more uniform after printing each layer of the path. Unlike the Z-shaped path, the temperature at the node gradually decreases when printing the same layer. The direction of the contour offset path affects the temperature distribution at the node. When printing a layer of path, the temperature at the node shows a sawtooth pattern of continuous increase and decrease. The heat transfer law of this path also makes the overall temperature distribution change slightly after printing four layers of path. Compared with the Z-shaped path, the contour offset path can better optimize thermal management, improve the accuracy of temperature control, and thus reduce printing defects caused by temperature fluctuations. The node temperature at different filling speeds after printing the first layer of path at the export node is shown in the following table:

[0069]

[0070] Find the fill speed at which the node temperature is lower than the lowest melting temperature of the PLA material after printing the first layer. Combined with the commonly used fill speed of 60 mm / s, it can be obtained that the optimal fill speed range for the contour offset path is 40 mm / s to 60 mm / s. The reason for not taking 80 mm / s is that when the first layer is printed, the temperature at the node is still within the melting temperature of the PLA material. Excessive material temperature will cause printing quality problems. The reason for not taking 20 mm / s is that from the perspective of comprehensive printing efficiency, 40 mm / s is more efficient while ensuring printing quality.

[0071] according to Figure 9 It can be concluded that under the same jump distance conditions, different jump speeds have little effect on the overall temperature distribution of the model, and the overall temperature distribution remains consistent. The jump speed has a more obvious effect on the local temperature field distribution at the jump position.

[0072] according to Figure 10 The node temperatures at different filling speeds after printing the first layer of the path at the node can be exported as shown in the following table:

[0073]

[0074] When the jump speed reaches 90 mm / s, the temperature change trend with the jump speed slows down significantly, and the influence of the jump speed on the node temperature becomes smaller and smaller. It is most appropriate to select 90 mm / s to 110 mm / s as the optimal jump speed range using the same method.

[0075] The above can be understood as providing a specific description of the implementation of the present invention, and should not be understood as limiting the present invention to the embodiments. Based on the ideas of the present invention, those skilled in the art can use equivalent deformation, change, modification and substitution.

Claims

1. A method for determining the optimal printing speed range of FDM based on multi-path temperature field simulation, characterized in that: The following steps are involved: Step 1: Use Ansys Workbench software to simulate and build a simulation model of the FDM molding process; Step 2: Define the material properties of the molded part and perform appropriate mesh division; Step 3: Set the birth and death units for the molded part and activate different printing processes according to the specified printing path to simulate the actual printing process; Step 4: Use the temperature results during the printing process as the load to solve, obtain the temperature field of the printed part, and analyze and determine the optimal printing speed range under different printing paths.

2. The method for studying the optimal printing speed range based on the temperature field of the FDM molding process according to claim 1 is characterized in that: The step 1 includes a step: (1) Design the model according to the actual rectangular size, and set the length, width and height to 16mm*8mm*2mm.

3. The method for studying the optimal printing speed range based on the temperature field of the FDM molding process according to claim 2, characterized in that: The second step includes two steps: (1) Set material parameters in the simulation model and apply the physical properties of the printed material at different temperatures to the model based on the actual material properties; (2) Divide the rectangular model into grids, and control the grid size to 0.4mm*0.4mm*0.2mm.

4. The method for studying the optimal printing speed range based on the temperature field of the FDM molding process according to claim 3 is characterized in that: The step three includes two steps: (1) The life and death process of the unit is realized by modifying the unit body stiffness. When the unit stiffness is multiplied by a very small reduction coefficient, the output of the unit is close to 0, which can be regarded as the unit being "killed". When the unit stiffness reduction coefficient is changed to 1, the output of the unit returns to the initial value of the system, which can be regarded as the unit being "activated". The activation and killing process of the unit is controlled to simulate the melting and accumulation process of the material during the printing process; (2) The unit activation time is set to 0.02s, and the simulation model is set to have 8000 analysis steps. The units in the meshed model are numbered, and the corresponding units are activated by selecting specific unit numbers. The order of activated units is controlled to simulate different printing paths during the molding process.

5. The method for determining the optimal printing speed range of FDM based on multi-path temperature field simulation according to claim 4 is characterized in that: The step 4 includes two steps: (1) Applying nozzle temperature to the selected activated unit, adjusting the printing speed by controlling the duration of temperature application, applying air convection and heat conduction models to the activated unit to calculate the temperature field of the simulation model, and obtaining a continuously changing temperature field cloud map and a curve diagram of node temperature change over time based on the temperature field; (2) According to the melting temperature range of PLA material, combined with the temperature field cloud map, the curve diagram of node temperature change over time and the exported data, the temperature distribution characteristics under different printing paths are analyzed and the optimal printing speed range including filling speed and jump speed is determined.

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