3D printing flow control method and device, equipment and storage medium

Abstract

According to the 3D printing flow control method, device and equipment and the storage medium, the flowing property parameters of consumables at the specific printing temperature are determined, and the theoretical corresponding relation between the extrusion flow and the extrusion pressure is determined according to the flowing property parameters of the consumables; the theoretical corresponding relation between the extrusion flow and the extrusion pressure is input into the 3D printer for printing testing, the actual extrusion pressure of a printing nozzle is detected through a pressure sensor, and the theoretical extrusion pressure is adjusted according to the fed-back actual extrusion pressure so as to determine the actual corresponding relation between the extrusion flow and the extrusion pressure; and the extrusion flow is accurately controlled through the extrusion pressure.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing technology, and in particular to a 3D printing nozzle flow control method, device, equipment and storage medium. Background Art

[0002] With the rapid development of 3D printing technology, its application scope has expanded from prototyping to end product manufacturing, medical equipment, aerospace and other fields. The core of 3D printing technology lies in the ability to transform digital models into physical entities, and one of the keys to this process is the control of the extrusion flow of the 3D printing nozzle.

[0003] Among them, multiple factors such as the type of consumables, printing temperature, and nozzle size will affect the preset extrusion flow rate of the nozzle in the 3D printing equipment, resulting in inaccurate preset extrusion flow rate of the nozzle, and ultimately causing deviations in the size of the printed 3D finished product, affecting the quality of the finished product. Therefore, it is necessary to adjust the extrusion flow rate of the nozzle based on factors such as the type of consumables, printing temperature, and nozzle size to accurately control the flow rate. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a 3D printing nozzle flow control method, device, equipment and storage medium, which accurately controls the extrusion flow of consumables by adjusting the extrusion stress of the 3D nozzle.

[0005] In order to achieve this purpose, the technical concept of the present invention is to determine the flow performance parameters of the consumables at a specific printing temperature, determine the theoretical correspondence between the extrusion flow rate and the extrusion pressure based on the flow performance parameters of the consumables, input the theoretical correspondence between the extrusion flow rate and the extrusion pressure into the 3D printer for printing test, and detect the actual extrusion pressure of the print head through a pressure sensor, adjust the theoretical extrusion pressure according to the feedback of the actual extrusion pressure to determine the actual correspondence between the extrusion flow rate and the extrusion pressure, and accurately control the extrusion flow rate through the extrusion pressure.

[0006] One of the purposes of the present invention is to disclose a 3D printing flow control method, comprising the following steps: Step S1: Select printing consumables; Step S2: Determine the appropriate printing temperature T of the consumables; Step S3: determining the flow performance parameters of the consumables at the corresponding printing temperature T; Step S4: determining the relationship between the theoretical extrusion pressure p and the extrusion flow rate Q; Step S5: writing a control program based on the relationship between the theoretical extrusion pressure p and the extrusion flow rate Q and inputting it into the storage module of the 3D printer; Step S6: calibrating the extrusion pressure of the printer nozzle assembly, including: Step S61: Calculate the extrusion flow rates Q1, Q2, Q3, ... Q according to the corresponding relationship between the theoretical extrusion pressure p and the extrusion flow rate Q. N Theoretical extrusion pressure p1, p2, p3, ... p N ; Step S62: Setting the working parameters of the 3D printer, including the printing temperature T, the extrusion flow rates Q1, Q2, Q3, ... Q N ; Step S63: Execute the printing task, and record the actual extrusion pressures P1' and P2 through the pressure sensor in the printer nozzle assembly. ’ , P3', ... P N '; Step S64: Calculate stress deviation △P1=P1'-P1, △P2=P2'-P2, △P3=P3'-P3......△P N =P N '-P N ; The corresponding relationship between the pressure deviation △P and the theoretical extrusion pressure P is obtained by fitting: ; Step S65: Obtain the corresponding relationship between the corrected actual extrusion pressure p' and the extrusion flow rate Q: ; Among them, N≥5.

[0007] Furthermore, a 3D printing flow control method further includes: Step S7: repeating steps 1-6, and obtaining the corresponding relationship between the actual extrusion pressure p' and the extrusion flow rate Q of consumable 2, consumable 3, ..., consumable n in sequence, wherein n≥3; Step S8: compile a nozzle flow control program based on the corresponding relationship between the appropriate working temperature T, flow performance parameters, actual extrusion pressure p' and extrusion flow rate Q of each consumable, and input it into the storage module of the 3D printer.

[0008] Further, step S3 includes: Step S31: selecting a flow model that the fluid conforms to according to the flow state of the consumables; wherein the flow model is one of a power law fluid, a Bingham Plastic fluid, and a Herschel-Bulkley Fluid.

[0009] Step S32: Determine the flow performance parameters in the flow model through experiments:

[0010] Specifically, a rheometer is used to measure the shear rate corresponding to a series of shear stresses of the consumables, and data fitting is performed to obtain the flow performance parameters of the consumables; the flow performance parameters include at least one of yield stress τ0, plastic viscosity μ, consistency coefficient k, and rheological index n.

[0011] Further, step S4 includes: Determine the nozzle assembly type, and determine the relationship between the theoretical extrusion pressure p and the extrusion flow rate Q based on the nozzle assembly type.

[0012] Another object of the present invention is to disclose a 3D printing device, comprising: Input module, used to input consumable material, nozzle assembly type, printing speed and printing model; A storage module storing the above-mentioned nozzle flow control program; A transmission module, used for transmitting the information input by the above input module to the control module; The control module receives the information input from the transmission module, calls the nozzle flow control program in the storage module, and controls the nozzle assembly module to perform work; The nozzle assembly module includes a heating module and an extrusion module, and the extrusion module has a built-in pressure sensor.

[0013] Another object of the present invention is to disclose a 3D printing device, which includes a processor and a memory, wherein the memory is used to store the above-mentioned nozzle flow control program, and the processor is used to call the nozzle flow control program in the memory so that the 3D printing device performs printing according to the nozzle flow control program.

[0014] Another object of the present invention is to disclose a computer-readable storage medium storing the above-mentioned nozzle flow control program. When the nozzle flow control program is run on a 3D printing device, the 3D printing device performs printing work according to the nozzle flow control program.

[0015] The present invention has the following beneficial technical effects: The theoretical correspondence between extrusion flow and extrusion pressure is determined by the flow performance parameters of the printing consumables, so that the extrusion flow of the consumables can be controlled by the extrusion pressure. The actual extrusion pressure of the printing nozzle is detected by the pressure sensor, and the theoretical extrusion pressure is adjusted according to the feedback of the actual extrusion pressure, thereby improving the control accuracy of the extrusion flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a workflow diagram of the 3D printing flow control method in Example 1; Figure 2 It is a schematic diagram of the structure of the nozzle assembly; Figure 3 This is the force analysis diagram of the resin in the cylindrical part; Figure 4 This is the stress analysis diagram of the resin of the truncated cone; Figure 5 It is a schematic diagram of the structure of a 3D printing device; Figure 6 Schematic diagram of the 3D printing equipment structure. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Embodiment 1

[0018] A 3D printing flow control method, the workflow is as follows Figure 1 As shown, the printing consumables are selected from polylactide resin, including the following steps: Step S1: selecting polylactic acid (PLA); Step S2: Select 240°C as the printing temperature T according to the empirical value; Step S3: Determine the flow performance parameters of polylactide resin at a printing temperature T of 240°C. The flow state of polylactide resin conforms to power law fluid, and the shear stress (Pa) and shear rate γ ˙(s -1 ) conforms to the power law model: (1); Where: k is the consistency coefficient (Pa·s), n is the rheological index; Through experiments, the values ​​of the consistency coefficient k and rheological index n in the power law model are determined, including: Step S31: Using a rheometer, measure a series of corresponding shear rates of polylactide resin γ ˙, shear stress ; Step S32: draw a graph with the x-axis being log(γ˙) and the y-axis being log(τ); Step S33: Fitting a straight line and calculating the values ​​of k and n; Step S34: using the calculated values ​​of k and n to predict the shear stress at other shear rates, and comparing with the experimental data to evaluate the accuracy of the model; Step S4: Determine the relationship between the theoretical extrusion pressure p and the extrusion flow rate Q. The shape of the nozzle assembly is as follows: Figure 2 As shown, the upper part is a cylinder 8, and the lower part is a truncated cone 9, including: Step S41: determining the upper and lower pressure difference of the resin in the cylindrical part of the printer nozzle assembly, including: The force analysis of the polylactide resin liquid column with radius r is performed (ignoring the weight of the liquid column), as follows: Figure 3 As shown, the force model is obtained: (2); Where: p 圆柱 =p 上 -p 下 , represents the difference in upper and lower stresses on the liquid column, and L is the length of the cylinder; Combining equations (1) and (2), the integral is performed from the radius r to the cylinder radius R. Since the flow velocity of the polylactide resin is 0 at the cylinder wall, that is, when r=R, the flow velocity of the polylactide resin at the radius r can be obtained as : (3); Integrating the resin flow rate from 0 to the cylinder radius R, the flow rate Q is: (4); Get the pressure difference The relationship with flow Q is: (5); set up ,but ; Step S42: determining the upper and lower pressure difference of the resin in the truncated cone portion of the printer nozzle assembly, including: Let the radius of the upper surface of the cone be R 上 , the radius of the lower surface of the frustum is R 下 , the cone angle of the truncated cone is 2a. At a distance of z from the apex of the truncated cone, a resin microelement with a thickness of dz is taken for force analysis, such as Figure 4 As shown, it can be seen that the resin microelement with thickness dz is similar to a cylinder with thickness dz. The force model is obtained from the above formula (5): (6); in is the upper and lower pressure difference of the resin microelement with thickness dz; Since the pressure at the bottom surface of the cone is 0, the pressure difference inside the cone can be obtained by integrating from the bottom surface to the top surface of the cone. : = (7); set up ,but ; Step S43: Determine the theoretical extrusion pressure p of the printer nozzle assembly: (8).

[0019] Step S5: writing a control program based on the corresponding relationship between the theoretical extrusion pressure p and the extrusion flow rate Q and inputting it into the storage module of the 3D printer; Step S6: calibrating the extrusion pressure of the printer nozzle assembly, including: Step S61: Calculate theoretical extrusion pressures p1, p2, p3, p4, p5 of extrusion flow rates Q1, Q2, Q3, Q4, Q5 according to the corresponding relationship between theoretical extrusion pressure p and extrusion flow rate Q; Step S62: setting the working parameters of the 3D printer, including selecting the printing temperature T as 240°C, the printing speed V, and the extrusion flow rates Q1, Q2, Q3, Q4, and Q5; Step S63: Execute the printing task and record the actual extrusion stress P1', P2 through the pressure sensor in the printer nozzle assembly ’ , P3', P4', P5'; Step S64: Calculate the pressure deviation △P1=P1'-P1, △P2=P2'-P2, △P3=P3'-P3, △P4=P4'-P4, △P5=P5'-P5; plot the pressure deviation △P as the Y-axis and the theoretical extrusion stress P as the x-axis, and fit the corresponding relationship between the pressure deviation △P and the theoretical extrusion stress P: ; Step S65: Obtain the corresponding relationship between the corrected actual extrusion stress p' and the extrusion flow rate Q: ; Step S7: compile a nozzle flow control program based on the corresponding relationship between the appropriate working temperature T240°C, consistency coefficient k, rheological index n, actual extrusion stress p' and extrusion flow rate Q of the polylactide resin, and input it into the storage module of the 3D printer. Embodiment 2

[0020] A 3D printing device, such as Figure 5 As shown, including: Input module 1, used to input consumable material, nozzle assembly type, printing speed and printing model; Storage module 2, storing the nozzle flow control program in embodiment 1; The transmission module 3 is used to transmit the information input by the input module 1 to the control module 4; The control module 4 receives the information input from the transmission module 3, and calls the nozzle flow control program in the storage module 2 to control the nozzle assembly module 5 to perform printing; The nozzle assembly module 5 includes a heating module and an extrusion module, and the extrusion module has a built-in pressure sensor. Embodiment 3

[0021] A 3D printing device, such as Figure 6 As shown, it includes a processor 6 and a memory 7, the memory 7 is used to store the nozzle flow control program in Example 1, and the processor 6 is used to call the nozzle flow control program in the memory 7, so that the 3D printing device performs printing according to the nozzle flow control program.

[0022] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A 3D printing flow control method, comprising the following steps: Step S1: Select printing consumables; Step S2: Determine the appropriate printing temperature T for the consumables; Step S3: determining the flow performance parameters of the consumables at the corresponding printing temperature T; Step S4: determining the relationship between the theoretical extrusion pressure p and the extrusion flow rate Q; Step S5: writing a control program based on the relationship between the theoretical extrusion pressure p and the extrusion flow rate Q and inputting it into the storage module of the 3D printer; Step S6: calibrating the extrusion pressure of the printer nozzle assembly, including: Step S61: Calculate the extrusion flow rates Q1, Q2, Q3, ... Q according to the corresponding relationship between the theoretical extrusion pressure p and the extrusion flow rate Q. N Theoretical extrusion pressure p1, p2, p3, ... p N ; Step S62: Setting the working parameters of the 3D printer, including the printing temperature T, the extrusion flow rates Q1, Q2, Q3, ... Q N ; Step S63: Execute the printing task, and record the actual extrusion pressures P1' and P2 through the pressure sensor in the printer nozzle assembly. ’ , P3', ... P N '; Step S64: Calculate stress deviation △P1=P1'-P1, △P2=P2'-P2, △P3=P3'-P3......△P N =P N '-P N ; The corresponding relationship between the pressure deviation △P and the theoretical extrusion pressure P is obtained by fitting: ； Step S65: Obtain the corresponding relationship between the corrected actual extrusion pressure p' and the extrusion flow rate Q: ； Among them, N≥5.

2. A 3D printing flow control method as claimed in claim 1, further comprising: Step S7: repeating steps 1-6, and obtaining the corresponding relationship between the actual extrusion pressure p' and the extrusion flow rate Q of consumable 2, consumable 3, ..., consumable n in sequence, wherein n≥3; Step S8: compile a nozzle flow control program based on the corresponding relationship between the appropriate working temperature T, flow performance parameters, actual extrusion pressure p' and extrusion flow rate Q of each consumable, and input it into the storage module of the 3D printer.

3. A 3D printing flow control method as claimed in claim 2, wherein: Step S3 includes: Step S31: selecting a flow model that the fluid conforms to according to the flow state of the consumables, wherein the flow model is one of a power law fluid, a Bingham Plastic fluid, and a Herschel-Bulkley Fluid; Step S32: Determine the flow performance parameters in the flow model through experiments: A rheometer is used to measure the shear rates corresponding to a series of shear stresses of the consumables, and data fitting is performed to obtain the flow performance parameters of the consumables; the flow performance parameters include at least one of yield stress τ0, plastic viscosity μ, consistency coefficient k, and rheological index n.

4. A 3D printing flow control method as claimed in claim 2, wherein: Step S4 includes: Determine the nozzle assembly type, and determine the relationship between the theoretical extrusion pressure p and the extrusion flow rate Q based on the nozzle assembly type.

5. A 3D printing device, comprising: Input module, used to input consumable material, nozzle assembly type, printing speed and printing model; A storage module storing the nozzle flow control program according to any one of claims 2 to 4; A transmission module, used for transmitting the information input by the above input module to the control module; The control module receives the information input from the transmission module, and calls the nozzle flow control program in the storage module to control the nozzle assembly module to perform work; The nozzle assembly module includes a heating module and an extrusion module, and the extrusion module has a built-in pressure sensor.

6. A 3D printing device, comprising a processor and a memory, wherein the memory is used to store the nozzle flow control program in any one of claims 2 to 4, and the processor is used to call the nozzle flow control program in the memory so that the 3D printing device performs printing according to the nozzle flow control program.

7. A computer-readable storage medium storing the nozzle flow control program according to any one of claims 2 to 4, wherein when the nozzle flow control program is run on a 3D printing device, the 3D printing device performs printing according to the nozzle flow control program.

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