Dynamic compensation control method based on material switching delay in multi-nozzle 3D printing

Abstract

The invention discloses a dynamic compensation control method based on material switching delay in multi-nozzle 3D printing, which relates to the field of 3D printing, and comprises the following steps: establishing a model of influence of temperature on viscosity, and analyzing to obtain a first actual viscosity of a current material and a second actual viscosity of a target material; analyzing to obtain residual points; the residual distribution condition of the current material in the nozzle; forming an allowable time difference when the nozzle switches the current material to the target material; dividing the allowable time difference into an acceleration time period and a filling time period; calculating to obtain a first extrusion speed of the extruder in the acceleration time period; calculating to obtain a second extrusion speed of the extruder in the filling time period; and performing dynamic compensation according to the first extrusion speed and the second extrusion speed. The first extrusion speed and the second extrusion speed are obtained by establishing the influence model of the temperature on the viscosity, it is guaranteed that the time of the whole material switching process is limited to be the allowable time difference, and therefore the generated error is also within the acceptable range.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing, and specifically to a dynamic compensation control method for material switching delay in multi-nozzle 3D printing. Background Art

[0002] When performing multi-material printing in 3D printing, material switching delay is a common technical challenge in 3D printing, which will affect the printing quality and efficiency. During printing, in order to ensure smoothness, the nozzle does not stop moving. When switching materials, the previous material will remain in the nozzle, which will pose a certain obstacle to filling the nozzle with the material to be replaced. At the same time, the viscosity of the material to be replaced is different from that of the previous material. Therefore, the time it takes to fill the nozzle varies depending on the combined situation of the viscosity of the material to be replaced and the viscosity of the previous material, which will result in different delay times and cause uncontrollable printing errors. Summary of the Invention

[0003] To solve the above technical problems, a dynamic compensation control method for material switching delay in multi-nozzle 3D printing is provided, and this technical solution solves the problems raised in the above background art.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows: A dynamic compensation control method for material switching delay in multi-nozzle 3D printing, comprising: Obtain the flow channel structure of the nozzle, obtain the current material ejected from the nozzle, obtain the target material to be replaced by the nozzle, obtain the first viscosity of the current material and the second viscosity of the target material, and obtain the real-time extrusion speed of the extruder that controls the ejection of the nozzle. Among them, the temperature when obtaining the first viscosity and the second viscosity is the preset temperature, and the preset temperature is any temperature at which the material is a fluid when heated. Establish an influence model of temperature on viscosity, obtain the real-time average temperature inside the flow channel structure, and analyze to obtain the first actual viscosity of the current material and the second actual viscosity of the target material. Based on the flow channel structure of the nozzle, analyze to obtain at least one residual point. Based on the residual point and the first viscosity of the current material, estimate the residual distribution of the current material in the nozzle when switching materials. Obtain the allowable error area of 3D printing, obtain the moving speed of the nozzle, and form an allowable time difference for the nozzle to switch the current material to the target material based on the allowable error area of 3D printing and the moving speed of the nozzle. Divide the allowable time difference into an acceleration time period and a filling time period. Based on the second viscosity of the target material, calculate the first extrusion speed of the extruder in the acceleration time period. Based on the residual distribution and the second viscosity of the target material, the second extrusion speed of the extruder during the filling period is calculated; Dynamic compensation is performed according to the first extrusion speed and the second extrusion speed.

[0005] Preferably, the step of establishing the influence model of temperature on viscosity includes the following steps: Obtain the temperature value range when the nozzle is operating, and equally divide the temperature value range at equal intervals to obtain at least one identification point; Take the identification point with the smallest value as the reference identification point; Obtain the viscosity of the sample material under the condition that the temperature is equal to the value of the identification point as the sample viscosity, and take the sample viscosity corresponding to the reference identification point as the sample reference viscosity; The sample viscosity is compared with the sample reference viscosity to obtain a sample coefficient, and the value of the identification point is compared with the value of the reference identification point to obtain a temperature coefficient; The temperature coefficient and the sample coefficient are paired and fitted to obtain a viscosity fitting function.

[0006] Preferably, the step of analyzing and obtaining the first actual viscosity of the current material and the second actual viscosity of the target material includes the following steps: Take at least one sampling point uniformly inside the flow channel structure, and use the end of the nozzle as the reference sampling point; When the heating temperature of the material in the nozzle is the preset temperature in advance, take the average value of the temperatures of at least one sampling point to obtain the sampling average temperature, and obtain the temperature of the reference sampling point as the sampling reference temperature; The sampling average temperature is compared with the sampling reference temperature to obtain a regulation coefficient; During the material switching process, the actual temperature at the reference sampling point is obtained in real time through infrared identification, and the actual temperature is multiplied by the regulation coefficient to obtain the real-time average temperature; The real-time average temperature is divided by the preset temperature to obtain the actual temperature coefficient, and the actual temperature coefficient is substituted into the viscosity fitting function to obtain the actual ratio; The first viscosity is multiplied by the actual ratio to obtain the first actual viscosity, and the second viscosity is multiplied by the actual ratio to obtain the second actual viscosity.

[0007] Preferably, the step of analyzing and obtaining at least one residual point based on the flow channel structure of the nozzle includes the following steps: Take the vertically downward direction as the spraying direction of the nozzle, draw a ray in the spraying direction at the sampling point to obtain a characteristic ray, take the position where the characteristic ray intersects the flow channel structure for the first time as the residual point, and perform duplicate removal on the coincident residual points to obtain at least one residual point.

[0008] Preferably, the step of estimating the residual distribution of the current material in the nozzle when the material is switched includes the following steps: Take the area where the residual points exist in the runner structure as the characteristic area, use the residual points as lattice points, and divide the characteristic area into at least one characteristic block, with the vertices of the characteristic block being the residual points; Take the center of the characteristic block as the characteristic point, obtain the tangent plane of the inner wall of the runner structure at the characteristic point, and take the distance between the top edge and the bottom edge of the characteristic block as the characteristic distance; Obtain the real-time speed of the nozzle spraying the current material. According to the Newton viscosity formula, multiply the product of the real-time speed divided by the characteristic distance and the first actual viscosity to obtain the viscous resistance; Obtain the load capacity upper limit of the characteristic block, and satisfy that the component of the load capacity upper limit along the tangent plane of the characteristic block is equal to the viscous resistance; Divide the load capacity upper limit by the acceleration due to gravity to obtain the mass upper limit, and summarize the characteristic block and its corresponding mass upper limit to obtain the residual distribution of the current material.

[0009] Preferably, the steps for forming the allowable time difference for the nozzle to switch the current material to the target material based on the allowable error area of 3D printing and the moving speed of the nozzle include the following: Obtain the diameter of the nozzle of the nozzle, and take the ratio of the allowable error area to the diameter of the nozzle as the upper limit of the moving length; Divide the upper limit of the moving length by the moving speed of the nozzle to obtain the allowable time difference.

[0010] Preferably, the steps for dividing the allowable time difference into an acceleration time period and a filling time period include the following: Take the position closest to the nozzle of the nozzle in the runner structure as the end of the runner structure, and take the position farthest from the nozzle of the nozzle in the runner structure as the initial end of the runner structure; Take the characteristic block with the farthest distance from the end of the runner structure as the target characteristic block, take the distance from the target characteristic block to the end of the runner structure as the second distance, and take the distance from the target characteristic block to the initial end of the runner structure as the first distance; Superimpose the second actual viscosity and the first actual viscosity to obtain the third actual viscosity. Multiply the second distance by the third actual viscosity to obtain the filling coefficient, and multiply the first distance by the second actual viscosity to obtain the acceleration coefficient; Divide the allowable time difference into an acceleration time period and a filling time period, and satisfy that the ratio of the lengths of the acceleration time period and the filling time period is equal to the ratio of the acceleration coefficient to the filling coefficient.

[0011] Preferably, the steps for calculating the first extrusion speed of the extruder for the acceleration time period include the following: The region from the target feature block to the initial end of the flow channel structure is taken as the first region. Taking the first extrusion speed as an unknown, according to Newton's viscosity formula, the first resistance is obtained by multiplying the second actual viscosity after dividing the first extrusion speed by the first distance; Multiply half of the volume of the first region by the density of the target material to obtain the first mass; Divide the first resistance by the first mass to obtain the first acceleration. Subtract the product of the first acceleration and the length of the acceleration time period from the first extrusion speed to obtain the first weakened speed; Use the first velocity-displacement relationship to solve for the first extrusion speed; The first velocity-displacement relationship is as follows: , where a is the first extrusion speed, b is the first weakened speed, c is the first acceleration, and X is the first distance.

[0012] Preferably, the second extrusion speed of the extruder for calculating the filling time period includes the following steps: Taking the second extrusion speed as an unknown, according to Newton's viscosity formula, the second resistance is obtained by multiplying the second actual viscosity after dividing the second extrusion speed by the first distance; Divide the second resistance by the first mass to obtain the second acceleration, and use the second velocity-displacement relationship to obtain the second weakened speed; Subtract the product of the second acceleration and the length of the acceleration time period from the first extrusion speed to obtain the second weakened speed; According to Newton's viscosity formula, the third resistance is obtained by multiplying the third actual viscosity after dividing the second weakened speed by the second distance; The region from the target feature block to the end of the flow channel structure is taken as the second region. Multiply half of the volume of the second region by the density of the target material to obtain the second mass. Accumulate half of all the mass upper limits with the second mass to obtain the third mass; Divide the third resistance by the third mass to obtain the third acceleration. Subtract the product of the third acceleration and the length of the filling time period from the second weakened speed to obtain the third weakened speed; Use the third velocity-displacement relationship to solve for the second extrusion speed; The second velocity-displacement relationship is as follows: , where e is the second extrusion speed, d is the second weakened speed, f is the second acceleration, and X is the first distance; The third velocity-displacement relationship is as follows: , where e is the second extrusion speed, h is the third weakened speed, i is the third acceleration, and Y is the second distance.

[0013] Preferably, the dynamic compensation based on the first extrusion speed and the second extrusion speed includes the following steps: Based on the relationship that the ratio of the real-time extrusion speed to the target extrusion speed is equal to the ratio of the first actual viscosity to the second actual viscosity, calculate the target extrusion speed; When switching materials, the extruder operates at the first extrusion speed for a first duration, and the length of the first duration is equal to the length of the acceleration period; When reaching the first duration, the extruder operates at the second extrusion speed for a second duration, and the length of the second duration is equal to the length of the filling period, and when the switching is completed, the extruder performs the printing operation at the target extrusion speed.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: By establishing an influence model of temperature on viscosity, obtaining the first actual viscosity and the second actual viscosity, and obtaining the first extrusion speed and the second extrusion speed, it is possible to estimate the first actual viscosity of the current material and the second actual viscosity of the target material according to the influence of temperature on viscosity, and estimate the residual distribution of the current material in the nozzle according to the situation of the flow channel structure, so as to set the first extrusion speed and the second extrusion speed of the extruder during the material switching process. The first extrusion speed is used to reach the residual distribution position of the current material, and the second extrusion speed is used to extrude the residual of the current material and fill the nozzle with the target material. By setting the first extrusion speed and the second extrusion speed, the time of the entire material switching process is ensured to be limited to the allowable time difference. Thus, even if the moving speed of the nozzle remains unchanged, the generated error is within an acceptable range, and since the viscosity of the material changes, the subsequent extrusion speed is also changed to ensure that the spraying speed of the nozzle is consistent with the speed before the material switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic flowchart of the dynamic compensation control method for material switching delay in 3D printing based on multiple nozzles of the present invention; Figure 2 It is a schematic flowchart of establishing an influence model of temperature on viscosity of the present invention; Figure 3 It is a schematic flowchart of analyzing and obtaining the first actual viscosity of the current material and the second actual viscosity of the target material of the present invention; Figure 4 It is a schematic flowchart of estimating the residual distribution of the current material in the nozzle when switching materials of the present invention; Figure 5 It is a schematic flowchart of forming an allowable time difference for the nozzle to switch the current material to the target material based on the allowable error area of 3D printing and the moving speed of the nozzle of the present invention; Figure 6Schematic diagram of the process of the present invention that divides the time difference into an acceleration period and a filling period; Figure 7 Schematic diagram of the process of calculating the first extrusion speed of the extruder during the acceleration period in the present invention; Figure 8 Schematic diagram of the process of calculating the second extrusion speed of the extruder during the filling period in the present invention; Figure 9 Schematic diagram of the process of performing dynamic compensation according to the first extrusion speed and the second extrusion speed in the present invention. Detailed implementation manners

[0016] The following description is used to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments in the following description are only examples, and those skilled in the art can think of other obvious variations.

[0017] Refer to Figure 1 As shown, a dynamic compensation control method based on material switching delay in multi-nozzle 3D printing includes: Obtain the flow channel structure of the nozzle, obtain the current material ejected from the nozzle, obtain the target material to be replaced by the nozzle, obtain the first viscosity of the current material and the second viscosity of the target material, and obtain the real-time extrusion speed of the extruder that controls the ejection of the nozzle. Among them, the temperature when the first viscosity and the second viscosity are obtained is the preset temperature, and the preset temperature is any temperature when the material is in a fluid state when heated. Establish an influence model of temperature on viscosity, obtain the real-time average temperature inside the flow channel structure, and analyze to obtain the first actual viscosity of the current material and the second actual viscosity of the target material; Based on the flow channel structure of the nozzle, analyze to obtain at least one residual point; Based on the residual point and the first viscosity of the current material, estimate the residual distribution of the current material in the nozzle when material switching is performed; Obtain the allowable error area of 3D printing, obtain the moving speed of the nozzle, and based on the allowable error area of 3D printing and the moving speed of the nozzle, form an allowable time difference for the nozzle to switch the current material to the target material; Divide the allowable time difference into an acceleration period and a filling period; Based on the second viscosity of the target material, calculate the first extrusion speed of the extruder during the acceleration period; Based on the residual distribution and the second viscosity of the target material, calculate the second extrusion speed of the extruder during the filling period; Perform dynamic compensation according to the first extrusion speed and the second extrusion speed.

[0018] The processing of multiple nozzles is the same as that of a single nozzle. As long as the processing of a single nozzle is synchronized to the remaining nozzles, the nozzles will also move during the switching process. Therefore, during the switching process, the printing made is not meeting the requirements. However, as long as the time of this part is controlled small enough, the error is acceptable. But since the first viscosity of the current material and the second viscosity of the target material are different, and during printing, the temperature in the runner structure may also be affected by the ambient temperature, resulting in slight differences, the time taken for the extruder to complete the material switching at the same extrusion speed will change. As a result, it may lead to too long a switching time, causing the printing error caused by the switching process to be too large, thereby affecting the printing effect. To avoid this situation, a series of algorithms are set to regulate the extrusion speed of the extruder, thus ensuring the switching time.

[0019] Refer to Figure 2 As shown, the steps for establishing the influence model of temperature on viscosity are as follows: Obtain the temperature value range when the nozzle is operating, and equally divide the temperature value range at intervals to obtain at least one identification point; Take the identification point with the smallest value as the reference identification point; Obtain the viscosity of the sample material under the condition that the temperature is equal to the value of the identification point as the sample viscosity, and take the sample viscosity corresponding to the reference identification point as the sample reference viscosity; Divide the sample viscosity by the sample reference viscosity to obtain the sample coefficient, and divide the value of the identification point by the value of the reference identification point to obtain the temperature coefficient; Pair and fit the temperature coefficient and the sample coefficient to obtain the viscosity fitting function.

[0020] Refer to Figure 3 As shown, the steps for analyzing and obtaining the first actual viscosity of the current material and the second actual viscosity of the target material are as follows: Uniformly take at least one sampling point inside the runner structure, and take the end of the nozzle as the reference sampling point; When the heating temperature of the material in the nozzle is the preset temperature in advance, take the average value of the temperatures of at least one sampling point to obtain the sampling average temperature, and obtain the temperature of the reference sampling point as the sampling reference temperature; Divide the sampling average temperature by the sampling reference temperature to obtain the regulation coefficient; During the material switching process, obtain the actual temperature at the reference sampling point in real time through infrared identification, and multiply the actual temperature by the regulation coefficient to obtain the real-time average temperature; Divide the real-time average temperature by the preset temperature to obtain the actual temperature coefficient, and substitute the actual temperature coefficient into the viscosity fitting function to obtain the actual ratio; Multiply the first viscosity by the actual ratio to obtain the first actual viscosity, and multiply the second viscosity by the actual ratio to obtain the second actual viscosity.

[0021] During actual switching, due to different temperatures, the viscosity will change. The first viscosity of the current material and the second viscosity of the target material are obtained under the condition of a preset temperature, but the actual temperature is the real-time average temperature. Therefore, it is necessary to perform proportional conversion through the established influence model of temperature on viscosity to obtain the first actual viscosity and the second actual viscosity. Because according to the establishment process of the influence model of temperature on viscosity, the ratio of the first actual viscosity to the first viscosity corresponds to the actual ratio, and the ratio of the second actual viscosity to the second viscosity corresponds to the actual ratio.

[0022] Based on the flow channel structure of the nozzle, analyzing to obtain at least one residual point includes the following steps: Take the vertically downward direction as the spraying direction of the nozzle, draw a ray at the sampling point along the spraying direction to obtain a characteristic ray, and take the position where the characteristic ray first intersects the flow channel structure as the residual point. Remove duplicate residual points to obtain at least one residual point.

[0023] During spraying, the inside of the flow channel structure gradually narrows. Therefore, when the current material is sprayed, residues will be generated at the blocked positions, and these residues will hinder the subsequent material switching. Therefore, it is necessary to obtain the residue distribution of the current material and then incorporate it into the consideration of switching.

[0024] Refer to Figure 4 As shown, estimating the residue distribution of the current material in the nozzle during material switching includes the following steps: Take the area where the residual points exist in the flow channel structure as the characteristic area, use the residual points as grid points, and divide the characteristic area into at least one characteristic block. The vertices of the characteristic block are the residual points; Take the center of the characteristic block as the characteristic point, obtain the tangent plane of the inner wall of the flow channel structure at the characteristic point, and take the distance between the top edge and the bottom edge of the characteristic block as the characteristic distance; Obtain the real-time speed of the nozzle spraying the current material. According to the Newton viscosity formula, multiply the real-time speed divided by the characteristic distance by the first actual viscosity to obtain the viscous resistance; Obtain the load capacity upper limit of the characteristic block, such that the component of the load capacity upper limit along the tangent plane of the characteristic block is equal to the viscous resistance; Divide the load capacity upper limit by the acceleration due to gravity to obtain the mass upper limit, and summarize the characteristic block and its corresponding mass upper limit to obtain the residue distribution of the current material.

[0025] Newton's viscosity formula is E = F / (dv / dy), where E is viscosity, F is viscous resistance, and dv / dy is the ratio of velocity to moving distance in an extremely short time. Here, since the residue is caused by the current material stopping being extruded, the time is extremely short. Thus, the real-time velocity divided by the characteristic distance can be used as dv / dy, enabling the calculation of viscous resistance. From the force analysis, the upper limit of the mass remaining on the characteristic block can be obtained.

[0026] Refer to Figure 5 As shown, based on the allowable error area of 3D printing and the moving speed of the nozzle, forming the allowable time difference for the nozzle to switch the current material to the target material includes the following steps: Obtain the diameter of the nozzle of the nozzle head, and use the ratio of the allowable error area to the diameter of the nozzle as the upper limit of the moving length; Divide the upper limit of the moving length by the moving speed of the nozzle head to obtain the allowable time difference.

[0027] Refer to Figure 6 As shown, dividing the allowable time difference into an acceleration time period and a filling time period includes the following steps: Take the position in the runner structure closest to the nozzle of the nozzle head as the end of the runner structure, and the position in the runner structure farthest from the nozzle of the nozzle head as the initial end of the runner structure; Take the characteristic block farthest from the end of the runner structure as the target characteristic block, take the distance from the target characteristic block to the end of the runner structure as the second distance, and take the distance from the target characteristic block to the initial end of the runner structure as the first distance; Superimpose the second actual viscosity and the first actual viscosity to obtain the third actual viscosity. Multiply the second distance by the third actual viscosity to obtain the filling coefficient, and multiply the first distance by the second actual viscosity to obtain the acceleration coefficient; Divide the allowable time difference into an acceleration time period and a filling time period, such that the ratio of the lengths of the acceleration time period and the filling time period is equal to the ratio of the acceleration coefficient to the filling coefficient.

[0028] The acceleration time period is the time taken for the target material to reach the residual distribution of the current material, and the filling time period is the time taken for the target material to extrude the residue of the current material and complete the switching. Its time is allocated based on the comprehensive consideration of the moving distance and the viscosity in the moving distance. Only the target material moves in the first distance, so the acceleration coefficient is the product of the first distance and the second actual viscosity. The second distance is the distance for the target material to extrude the residue of the current material, so the viscosity is the third actual viscosity, that is, the superposition of the second actual viscosity and the first actual viscosity. Thus, the filling coefficient is the product of the second distance and the third actual viscosity.

[0029] Refer to Figure 7 As shown, calculating the first extrusion speed of the extruder in the acceleration time period includes the following steps: The region from the target feature block to the initial end of the flow channel structure is taken as the first region. Taking the first extrusion speed as an unknown, according to Newton's viscosity formula, the first resistance is obtained by multiplying the second actual viscosity after dividing the first extrusion speed by the first distance. Multiply half of the volume of the first region by the density of the target material to obtain the first mass. Divide the first resistance by the first mass to obtain the first acceleration. Subtract the product of the first acceleration and the length of the acceleration time period from the first extrusion speed to obtain the first weakened speed. Use the first velocity-displacement relationship to solve for the first extrusion speed. The first velocity-displacement relationship is as follows: , where a is the first extrusion speed, b is the first weakened speed, c is the first acceleration, and X is the first distance.

[0030] The first extrusion speed needs to ensure that the time taken for the target material to travel the first distance is equal to the length of the acceleration time period. Here, due to the effect of viscosity, when the target material leaves the extruder, it is in a decelerated motion. Therefore, the first extrusion speed can be solved by the velocity-displacement formula, but the acceleration during the deceleration process needs to be obtained. Actually, it is a deceleration, but for the sake of conforming to the habit of physical terms, it is still named acceleration. Furthermore, the first resistance generated by viscosity needs to be obtained, which is consistent with the principle of using Newton's viscosity formula before. Since the switching time is very short, the same principle can be used to obtain the first resistance. However, when calculating the first acceleration, the mass on which the first resistance acts needs to be determined. Since the target material gradually fills the first region, the initial mass is 0, and the final mass is the mass when the first region is filled with the target material. Therefore, the mass of the whole process can be regarded as the average of the two, and thus the first mass is obtained. Then, the first acceleration can be calculated from this.

[0031] Refer to Figure 8 As shown, calculating the second extrusion speed of the extruder during the filling time period includes the following steps: Taking the second extrusion speed as an unknown, according to Newton's viscosity formula, the second resistance is obtained by multiplying the third actual viscosity after dividing the second extrusion speed by the first distance. Divide the second resistance by the first mass to obtain the second acceleration, and use the second velocity-displacement relationship to obtain the second weakened speed. Subtract the product of the second acceleration and the length of the acceleration time period from the first extrusion speed to obtain the second weakened speed. According to Newton's viscosity formula, the third resistance is obtained by multiplying the third actual viscosity after dividing the second weakened speed by the second distance. The area from the target feature block to the end of the flow channel structure is taken as the second area. Multiply half of the volume of the second area by the density of the target material to obtain the second mass. Add half of all the mass limits to the second mass to obtain the third mass; Divide the third resistance by the third mass to obtain the third acceleration. Subtract the product of the third acceleration and the length of the filling time period from the second weakened velocity to obtain the third weakened velocity; Use the third velocity-displacement relationship to solve for the second extrusion velocity; The second velocity-displacement relationship is as follows: , where e is the second extrusion velocity, d is the second weakened velocity, f is the second acceleration, and X is the first distance; The third velocity-displacement relationship is as follows: , where e is the second extrusion velocity, h is the third weakened velocity, i is the third acceleration, and Y is the second distance.

[0032] Here, since the extrusion velocity of the extruder becomes the second extrusion velocity, the velocity at the time of reaching the target feature block will also change accordingly. As long as the second acceleration during this process is calculated, the second weakened velocity can be obtained. The principle used here is exactly the same as the principle for obtaining the first acceleration; The second weakened velocity is the velocity at which the target feature block is reached, that is, the velocity at the remaining initial position of the current material; After that, the target material will extrude the remaining current material at the second weakened velocity and complete the filling. In the same way, the third resistance can be calculated, but the mass on which the third resistance acts is somewhat different from before. The third resistance is the resistance to the material in the second area. Initially, the acting mass is 0, and finally, the acting mass is the mass filled by the target material in the second area. However, during the filling process, the remaining current material is also gradually extruded. Therefore, the acting mass can be regarded as the third mass. Thus, the third acceleration is calculated, and then the equation is obtained, and the second extrusion velocity is solved.

[0033] Refer to Figure 9 As shown, the dynamic compensation based on the first extrusion velocity and the second extrusion velocity includes the following steps: Based on the relationship that the ratio of the real-time extrusion velocity to the target extrusion velocity is equal to the ratio of the first real viscosity to the second real viscosity, calculate the target extrusion velocity; When switching materials, the extruder operates at the first extrusion velocity for the first duration, and the length of the first duration is equal to the length of the acceleration time period; When the first duration is reached, the extruder operates at a second extrusion speed for a second duration, the length of the second duration being equal to the length of the filling period, and when the switching is completed, the extruder performs a printing operation at a target extrusion speed.

[0034] Due to the difference in viscosity, therefore, during actual spraying, in order to maintain a consistent spraying speed, the extrusion speed needs to be changed proportionally, and thus, the target extrusion speed is calculated.

[0035] Furthermore, this solution also proposes a storage medium on which a computer-readable program is stored. When the computer-readable program is called, it executes the above-mentioned dynamic compensation control method for material switching delay in multi-nozzle 3D printing.

[0036] It can be understood that the storage medium can be a magnetic medium, such as a floppy disk, a hard disk, or a magnetic tape; an optical medium, such as a DVD; or a semiconductor medium, such as a solid-state drive (SSD).

[0037] In summary, the advantages of the present invention are as follows: By establishing an influence model of temperature on viscosity, obtaining the first actual viscosity and the second actual viscosity, and obtaining the first extrusion speed and the second extrusion speed, it is possible to estimate the first actual viscosity of the current material and the second actual viscosity of the target material according to the influence of temperature on viscosity, and estimate the residual distribution of the current material in the nozzle according to the situation of the flow channel structure, so as to set the first extrusion speed and the second extrusion speed of the extruder during the material switching process. The first extrusion speed is used to reach the position of the residual distribution of the current material, and the second extrusion speed is used to extrude the residual of the current material and fill the nozzle with the target material. By setting the first extrusion speed and the second extrusion speed, the time of the entire material switching process is ensured to be limited to the allowable time difference. Thus, even if the moving speed of the nozzle remains unchanged, the generated error is within an acceptable range, and since the viscosity of the material changes, the subsequent extrusion speed is also changed to ensure that the spraying speed of the nozzle is consistent with the speed before material switching.

[0038] The above shows and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification is only the principle of the present invention. Without departing from the spirit and scope of the present invention, various changes and improvements will occur to the present invention, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A dynamic compensation control method for material switching delay in multi-nozzle 3D printing, characterized in that, Including: Obtain the flow channel structure of the nozzle, obtain the current material ejected from the nozzle, obtain the target material to be replaced by the nozzle, obtain the first viscosity of the current material and the second viscosity of the target material, obtain the real-time extrusion speed of the extruder that controls the ejection of the nozzle, where the temperature when the first viscosity and the second viscosity are obtained is the preset temperature, and the preset temperature is any temperature when the material is in a fluid state when heated; Establish an influence model of temperature on viscosity, obtain the real-time average temperature inside the flow channel structure, and analyze to obtain the first actual viscosity of the current material and the second actual viscosity of the target material; Based on the flow channel structure of the nozzle, analyze to obtain at least one residual point; Based on the residual point and the first viscosity of the current material, estimate the residual distribution of the current material in the nozzle when the material is switched; Obtain the allowable error area of 3D printing, obtain the moving speed of the nozzle, and based on the allowable error area of 3D printing and the moving speed of the nozzle, form an allowable time difference for the nozzle to switch the current material to the target material; Divide the allowable time difference into an acceleration time period and a filling time period; Based on the second viscosity of the target material, calculate the first extrusion speed of the extruder in the acceleration time period; Based on the residual distribution and the second viscosity of the target material, calculate the second extrusion speed of the extruder in the filling time period; Perform dynamic compensation according to the first extrusion speed and the second extrusion speed.

2. The dynamic compensation control method for material switching delay in multi-nozzle 3D printing according to claim 1, characterized in that The establishing the influence model of temperature on viscosity includes the following steps: Obtain the temperature value range when the nozzle is operating, equally spaced divide the temperature value range to obtain at least one identification point; Take the identification point with the smallest value as the reference identification point; Obtain the viscosity of the sample material under the condition that the temperature is equal to the value of the identification point as the sample viscosity, and take the sample viscosity corresponding to the reference identification point as the sample reference viscosity; Divide the sample viscosity by the sample reference viscosity to obtain the sample coefficient, and divide the value of the identification point by the value of the reference identification point to obtain the temperature coefficient; Pair and fit the temperature coefficient and the sample coefficient to obtain a viscosity fitting function.

3. The dynamic compensation control method for material switching delay in multi-nozzle 3D printing according to claim 2, wherein The analyzing to obtain the first actual viscosity of the current material and the second actual viscosity of the target material includes the following steps: Uniformly take at least one sampling point inside the flow channel structure, and take the end of the nozzle as the reference sampling point; When the heating temperature of the material in the nozzle is the preset temperature in advance, take the average value of the temperatures of at least one sampling point to obtain the sampling average temperature, and obtain the temperature of the reference sampling point as the sampling reference temperature; Divide the sampling average temperature by the sampling reference temperature to obtain the regulation coefficient; During the material switching process, obtain the actual temperature at the reference sampling point in real time through infrared identification, and multiply the actual temperature by the regulation coefficient to obtain the real-time average temperature; Divide the real-time average temperature by the preset temperature to obtain the actual temperature coefficient, substitute the actual temperature coefficient into the viscosity fitting function to obtain the actual ratio; Multiply the first viscosity by the actual ratio to obtain the first actual viscosity, and multiply the second viscosity by the actual ratio to obtain the second actual viscosity.

4. The dynamic compensation control method for material switching delay in multi-nozzle 3D printing according to claim 3, wherein The analyzing to obtain at least one residual point based on the flow channel structure of the nozzle includes the following steps: Taking the vertically downward direction as the spraying direction of the nozzle, a ray is drawn at the sampling point along the spraying direction to obtain a characteristic ray. The position where the characteristic ray first intersects the flow channel structure is taken as the residual point, and the overlapping residual points are processed to remove duplicates, obtaining at least one residual point.

5. The dynamic compensation control method for material switching delay in multi-nozzle 3D printing according to claim 4, wherein When estimating the residual distribution of the current material in the nozzle during material switching, the following steps are included: The area where the residual points exist in the flow channel structure is taken as the characteristic area. Using the residual points as grid points, the characteristic area is divided into at least one characteristic block, and the vertices of the characteristic block are the residual points; The center of the characteristic block is taken as the characteristic point. The tangent plane of the inner wall of the flow channel structure at the characteristic point is obtained, and the distance between the top edge and the bottom edge of the characteristic block is taken as the characteristic distance; The real-time velocity of the nozzle spraying the current material is obtained. According to the Newton viscosity formula, the viscous resistance is obtained by multiplying the first actual viscosity after dividing the real-time velocity by the characteristic distance; The load upper limit of the characteristic block is obtained, and it is satisfied that the component of the load upper limit along the tangent plane of the characteristic block is equal to the viscous resistance; The load upper limit is divided by the gravitational acceleration to obtain the mass upper limit. The characteristic blocks and their corresponding mass upper limits are summarized to obtain the residual distribution of the current material.

6. The dynamic compensation control method based on material switching delay in multi-nozzle 3D printing according to claim 5, wherein Forming the allowable time difference for the nozzle to switch the current material to the target material based on the allowable error area of 3D printing and the moving speed of the nozzle includes the following steps: The diameter of the nozzle of the nozzle is obtained, and the ratio of the allowable error area to the diameter of the nozzle is taken as the upper limit of the moving length; The upper limit of the moving length is divided by the moving speed of the nozzle to obtain the allowable time difference.

7. The dynamic compensation control method for material switching delay in multi-nozzle 3D printing according to claim 6, characterized in that Dividing the allowable time difference into an acceleration time period and a filling time period includes the following steps: The position in the flow channel structure closest to the nozzle of the nozzle is taken as the end of the flow channel structure, and the position in the flow channel structure farthest from the nozzle of the nozzle is taken as the initial end of the flow channel structure; The characteristic block farthest from the end of the flow channel structure is taken as the target characteristic block. The distance from the target characteristic block to the end of the flow channel structure is taken as the second distance, and the distance from the target characteristic block to the initial end of the flow channel structure is taken as the first distance; The second actual viscosity and the first actual viscosity are superimposed to obtain the third actual viscosity. The second distance is multiplied by the third actual viscosity to obtain the filling coefficient, and the first distance is multiplied by the second actual viscosity to obtain the acceleration coefficient; The allowable time difference is divided into an acceleration time period and a filling time period, and it is satisfied that the ratio of the lengths of the acceleration time period and the filling time period is equal to the ratio of the acceleration coefficient to the filling coefficient.

8. The dynamic compensation control method for material switching delay in multi-nozzle 3D printing according to claim 7, characterized in that Calculating the first extrusion speed of the extruder during the acceleration time period includes the following steps: The area from the target characteristic block to the initial end of the flow channel structure is taken as the first area. Taking the first extrusion speed as an unknown, according to the Newton viscosity formula, the first resistance is obtained by multiplying the second actual viscosity after dividing the first extrusion speed by the first distance; Half of the volume of the first area is multiplied by the density of the target material to obtain the first mass; The first resistance is divided by the first mass to obtain the first acceleration. The first extrusion speed minus the product of the first acceleration and the length of the acceleration time period is obtained as the first weakened speed; Using the first velocity-displacement relationship formula to solve for the first extrusion speed; The first speed-displacement relationship is as follows: , Among them, a is the first extrusion speed, b is the first speed after weakening, c is the first acceleration, and X is the first distance.

9. The dynamic compensation control method based on the material switching delay in multi-nozzle 3D printing according to claim 8, wherein The steps for calculating the second extrusion speed of the extruder during the filling time period are as follows: Regarding the second extrusion speed as an unknown, according to the Newton viscosity formula, the second resistance is obtained by multiplying the second actual viscosity after dividing the second extrusion speed by the first distance. The second resistance is divided by the first mass to obtain the second acceleration, and the second speed-displacement relationship is used to obtain the second speed after weakening. The first extrusion speed minus the product of the second acceleration and the length of the acceleration time period gives the second speed after weakening. According to the Newton viscosity formula, the third resistance is obtained by multiplying the third actual viscosity after dividing the second speed after weakening by the second distance. The region from the target feature block to the end of the flow channel structure is taken as the second region. Half of the volume of the second region is multiplied by the density of the target material to obtain the second mass. Half of all the mass upper limits is accumulated with the second mass to obtain the third mass. The third resistance is divided by the third mass to obtain the third acceleration. The second speed after weakening minus the product of the third acceleration and the length of the filling time period gives the third speed after weakening. The third speed-displacement relationship is used to solve for the second extrusion speed. The second velocity-displacement relation is as follows: , Among them, e is the second extrusion speed, d is the second speed after weakening, f is the second acceleration, and X is the first distance. The third speed-displacement relationship is as follows: , Among them, e is the second extrusion speed, h is the third speed after weakening, i is the third acceleration, and Y is the second distance.

10. The dynamic compensation control method for material switching delay in multi-nozzle 3D printing according to claim 9, characterized in that The steps for performing dynamic compensation based on the first extrusion speed and the second extrusion speed are as follows: Based on the relationship that the ratio of the real-time extrusion speed to the target extrusion speed is equal to the ratio of the first actual viscosity to the second actual viscosity, the target extrusion speed is calculated. When switching materials, the extruder operates at the first extrusion speed for the first duration, and the length of the first duration is equal to the length of the acceleration time period. When the first duration is reached, the extruder operates at the second extrusion speed for the second duration, and the length of the second duration is equal to the length of the filling time period. When the switching is completed, the extruder performs the printing operation at the target extrusion speed.

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