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

Abstract

The present 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, including: establishing a temperature influence model on viscosity, analyzing and obtaining a first actual viscosity of the current material and a second actual viscosity of the target material; analyzing and obtaining residual points; the residual distribution of the current material in the nozzle; forming an allowable time difference for the nozzle to switch the current material to the target material; dividing the allowable time difference into an acceleration time period and a filling time period; calculating a first extrusion speed of the extruder in the acceleration time period; calculating a second extrusion speed of the extruder in the filling time period; and performing dynamic compensation based on the first extrusion speed and the second extrusion speed. By establishing a temperature influence model on viscosity and obtaining the first extrusion speed and the second extrusion speed, it is ensured that the time of the entire material switching process is limited to the allowable time difference, thereby keeping the error generated within an acceptable range.

Description

Technical Field

[0001] The present invention relates to the field of 3D printing, and in particular to a dynamic compensation control method based on 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 affects 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 cause a certain obstruction to the nozzle filling 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 with the combined viscosity of the material to be replaced and the viscosity of the previous material, which will lead to different delay times, which will cause uncontrollable printing errors. Summary of the Invention

[0003] In order to solve the above technical problems, a dynamic compensation control method based on material switching delay in multi-nozzle 3D printing is provided. This technical solution solves the problems raised in the above background technology.

[0004] In order to achieve the above objects, the technical solution adopted by the present invention is:

[0005] A dynamic compensation control method based on material switching delay in multi-nozzle 3D printing includes:

[0006] Obtaining the flow channel structure of the nozzle, obtaining the current material being sprayed by the nozzle, obtaining the target material to be replaced by the nozzle, obtaining the first viscosity of the current material and the second viscosity of the target material, and obtaining the real-time extrusion speed of the extruder that controls the nozzle spraying, wherein the temperature at which the first viscosity and the second viscosity are obtained are both preset temperatures, which are any temperatures when the material is fluid when heated;

[0007] Establish a temperature-viscosity impact model, obtain the real-time average temperature inside the flow channel structure, and analyze and obtain the first actual viscosity of the current material and the second actual viscosity of the target material;

[0008] Based on the flow channel structure of the nozzle, at least one residual point is obtained through analysis;

[0009] 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;

[0010] Obtaining the allowable error area of ​​3D printing and the movement speed of the nozzle, and 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 movement speed of the nozzle;

[0011] The allowed time difference is divided into an acceleration period and a filling period;

[0012] Calculating a first extrusion speed of the extruder during an acceleration period based on a second viscosity of the target material;

[0013] Calculating a second extrusion speed of the extruder during a filling time period based on the residual distribution and a second viscosity of the target material;

[0014] Dynamic compensation is performed according to the first extrusion speed and the second extrusion speed.

[0015] Preferably, the establishment of the temperature-viscosity effect model comprises the following steps:

[0016] Obtaining a temperature value range when the nozzle is operating, dividing the temperature value range into equal intervals, and obtaining at least one identification point;

[0017] The identification point with the smallest value is used as the benchmark identification point;

[0018] Obtaining 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 using the sample viscosity corresponding to the reference identification point as the sample reference viscosity;

[0019] The sample viscosity is compared with the sample reference viscosity to obtain the sample coefficient, and the identification point is compared with the reference identification point value to obtain the temperature coefficient;

[0020] The temperature coefficients are paired with the sample coefficients and fitted to obtain the viscosity fitting function.

[0021] Preferably, the analyzing and obtaining the first actual viscosity of the current material and the second actual viscosity of the target material comprises the following steps:

[0022] Take at least one sampling point evenly inside the flow channel structure, and use the nozzle end as the reference sampling point;

[0023] When the heating temperature of the material in the nozzle is pre-set, the temperature of at least one sampling point is averaged to obtain the sampling average temperature, and the temperature of the reference sampling point is obtained as the sampling reference temperature;

[0024] Compare the sampling average temperature with the sampling reference temperature to obtain the control coefficient;

[0025] During the material switching process, the actual temperature at the reference sampling point is obtained in real time through infrared recognition. The actual temperature is multiplied by the control coefficient to obtain the real-time average temperature;

[0026] The real-time average temperature is divided by the preset temperature to obtain the actual temperature coefficient, which is then substituted into the viscosity fitting function to obtain the actual ratio.

[0027] The first viscosity is multiplied by the actual ratio to obtain a first actual viscosity, and the second viscosity is multiplied by the actual ratio to obtain a second actual viscosity.

[0028] Preferably, the analyzing and obtaining at least one residual point based on the flow channel structure of the nozzle comprises the following steps:

[0029] The vertical downward direction is used as the spray direction of the nozzle, and a ray is drawn along the spray direction at the sampling point to obtain a characteristic ray. The position where the characteristic ray first intersects the flow channel structure is used as the residual point. The overlapping residual points are deduplicated to obtain at least one residual point.

[0030] Preferably, the estimating the residual distribution of the current material in the nozzle when switching materials includes the following steps:

[0031] The area where the residual points exist in the flow channel structure is regarded as a feature area, and the residual points are used as grid points to divide the feature area into at least one feature block, where the vertices of the feature block are the residual points;

[0032] The center of the feature block is used as the feature point, and the tangent plane of the inner wall of the flow channel structure at the feature point is obtained. The distance between the top edge of the feature block and the bottom edge of the feature block is used as the feature distance.

[0033] Get the real-time speed of the current material being ejected by the nozzle. According to the Newtonian viscosity formula, the real-time speed is divided by the characteristic distance and then multiplied by the first actual viscosity to obtain the viscous resistance.

[0034] Obtain the upper load limit of the characteristic block, satisfying that the component of the upper load limit along the tangent plane of the characteristic block is equal to the viscous resistance;

[0035] The load limit is divided by the gravitational acceleration to obtain the mass limit. The characteristic blocks and their corresponding mass limits are summarized to obtain the residual distribution of the current material.

[0036] Preferably, 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 movement speed of the nozzle includes the following steps:

[0037] Obtain the nozzle diameter of the printhead, and use the ratio of the allowable error area to the nozzle diameter as the upper limit of the moving length;

[0038] The upper limit of the moving length is divided by the moving speed of the nozzle to obtain the allowable time difference.

[0039] Preferably, dividing the allowed time difference into an acceleration time period and a filling time period comprises the following steps:

[0040] The position of the flow channel structure closest to the nozzle of the nozzle is regarded as the end of the flow channel structure, and the position of the flow channel structure farthest from the nozzle of the nozzle is regarded as the initial end of the flow channel structure;

[0041] The feature block farthest from the end of the flow channel structure is used as the target feature block, the distance from the target feature block to the end of the flow channel structure is used as the second distance, and the distance from the target feature block to the initial end of the flow channel structure is used as the first distance;

[0042] The second actual viscosity is superimposed on the first actual viscosity 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;

[0043] The allowed time difference is divided into an acceleration period and a filling period, and the ratio of the length of the acceleration period to the length of the filling period is equal to the ratio of the acceleration factor to the filling factor.

[0044] Preferably, the calculating of the first extrusion speed of the extruder during the acceleration time period comprises the following steps:

[0045] The area from the target feature block to the initial end of the flow channel structure is taken as the first area, and the first extrusion speed is taken as the unknown. According to the Newtonian viscosity formula, the first extrusion speed is divided by the first distance and then multiplied by the second actual viscosity to obtain the first resistance;

[0046] Half the volume of the first region is multiplied by the density of the target material to obtain a first mass;

[0047] The first resistance is divided by the first mass to obtain a first acceleration, and the first extrusion velocity is subtracted from the first acceleration multiplied by the length of the acceleration time period to obtain a first weakened velocity;

[0048] Using the first velocity-displacement relationship, the first extrusion velocity is obtained;

[0049] The first velocity-displacement relationship is as follows: ,

[0050] Wherein, a is the first extrusion velocity, b is the first weakened velocity, c is the first acceleration, and X is the first distance.

[0051] Preferably, the calculating of the second extrusion speed of the extruder for the filling time period comprises the following steps:

[0052] The second extrusion speed is taken as an unknown number. According to the Newtonian viscosity formula, the second extrusion speed is divided by the first distance and then multiplied by the second actual viscosity to obtain the second resistance.

[0053] The second resistance is divided by the first mass to obtain the second acceleration, and the second velocity-displacement relationship is used to obtain the second weakened velocity;

[0054] The second weakened velocity is obtained by subtracting the product of the second acceleration and the length of the acceleration time period from the first extrusion velocity;

[0055] According to the Newton viscosity formula, the second weakened speed is divided by the second distance and then multiplied by the third actual viscosity to obtain the third resistance;

[0056] The area from the target feature block to the end of the flow channel structure is taken as the second area, half of the volume of the second area is multiplied by the density of the target material to obtain the second mass, and half of all mass upper limits are added to the second mass to obtain the third mass;

[0057] The third resistance is divided by the third mass to obtain a third acceleration, and the second weakened velocity is subtracted from the product of the third acceleration and the length of the filling time period to obtain a third weakened velocity;

[0058] The second extrusion speed is obtained by using the third speed-displacement relationship;

[0059] The second velocity displacement relationship is as follows: ,

[0060] Wherein, e is the second extrusion velocity, d is the second weakened velocity, f is the second acceleration, and X is the first distance;

[0061] The third velocity displacement relationship is as follows: ,

[0062] Wherein, e is the second extrusion velocity, h is the third weakened velocity, i is the third acceleration, and Y is the second distance.

[0063] Preferably, the dynamic compensation according to the first extrusion speed and the second extrusion speed comprises the following steps:

[0064] The target extrusion speed is calculated based on a relationship that a ratio of the real-time extrusion speed to the target extrusion speed is equal to a ratio of the first actual viscosity to the second actual viscosity;

[0065] When switching materials, the extruder operates at a first extrusion speed for a first time period, where the length of the first time period is equal to the length of the acceleration time period;

[0066] When the first duration is reached, the extruder operates at a second extrusion speed for a second duration, where the length of the second duration is equal to the length of the filling time period, and when the switching is completed, the extruder performs the printing operation at the target extrusion speed.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] By establishing a model of the influence 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, the first actual viscosity of the current material and the second actual viscosity of the target material can be estimated according to the influence of temperature on viscosity, and the residual distribution of the current material in the nozzle can be estimated according to 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 residue 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 limited to the allowable time difference. Therefore, even if the nozzle movement speed remains unchanged, the error generated is within an acceptable range. In addition, due to the change in the viscosity of the material, the subsequent extrusion speed is also changed to ensure that the nozzle injection speed is consistent with the speed before the material switching. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 Schematic diagram of the flow of the dynamic compensation control method based on material switching delay in multi-nozzle 3D printing of the present invention;

[0070] Figure 2 A schematic diagram of a process for establishing a temperature-viscosity effect model according to the present invention;

[0071] Figure 3 A schematic diagram of a process for analyzing and obtaining a first actual viscosity of a current material and a second actual viscosity of a target material according to the present invention;

[0072] Figure 4 A schematic flow chart of the residual distribution of the current material in the nozzle when the material is switched for estimation according to the present invention;

[0073] Figure 5 This is a flow chart of the invention 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 movement speed of the nozzle;

[0074] Figure 6 Schematic diagram of a flow chart of dividing the allowed time difference into an acceleration time period and a filling time period according to the present invention;

[0075] Figure 7 A schematic flow chart of calculating a first extrusion speed of an extruder during an acceleration time period according to the present invention;

[0076] Figure 8 A schematic flow chart of calculating a second extrusion speed of an extruder for obtaining a filling time period according to the present invention;

[0077] Figure 9It is a schematic diagram of the process of performing dynamic compensation according to the first extrusion speed and the second extrusion speed of the present invention. DETAILED DESCRIPTION

[0078] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are merely examples, and those skilled in the art may conceive of other obvious variations.

[0079] Reference Figure 1 As shown, the dynamic compensation control method based on material switching delay in multi-nozzle 3D printing includes:

[0080] Obtaining the flow channel structure of the nozzle, obtaining the current material being sprayed by the nozzle, obtaining the target material to be replaced by the nozzle, obtaining the first viscosity of the current material and the second viscosity of the target material, and obtaining the real-time extrusion speed of the extruder that controls the nozzle spraying, wherein the temperature at which the first viscosity and the second viscosity are obtained are both preset temperatures, which are any temperatures when the material is fluid when heated;

[0081] Establish a temperature-viscosity impact model, obtain the real-time average temperature inside the flow channel structure, and analyze and obtain the first actual viscosity of the current material and the second actual viscosity of the target material;

[0082] Based on the flow channel structure of the nozzle, at least one residual point is obtained through analysis;

[0083] 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;

[0084] Obtaining the allowable error area of ​​3D printing and the movement speed of the nozzle, and 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 movement speed of the nozzle;

[0085] The allowed time difference is divided into an acceleration period and a filling period;

[0086] Calculating a first extrusion speed of the extruder during an acceleration period based on a second viscosity of the target material;

[0087] Calculating a second extrusion speed of the extruder during a filling time period based on the residual distribution and a second viscosity of the target material;

[0088] Dynamic compensation is performed according to the first extrusion speed and the second extrusion speed.

[0089] The processing of multiple nozzles is consistent with that of a single nozzle. It is sufficient to synchronize the processing of a single nozzle to the remaining nozzles. When switching, the nozzle will also move. Therefore, during the switching process, the printing it produces does not meet the demand. However, as long as the time for controlling this part is small enough, the error is acceptable. However, since the first viscosity of the current material and the second viscosity of the target material are different, and the temperature in the flow channel structure may also be affected by the ambient temperature during printing, resulting in slight differences, the time it takes for the extruder to complete the material switching will change at the same extrusion speed. This may cause the switching time to be too long, resulting in excessive printing errors caused by the switching process, which in turn affects the printing effect. In order to avoid this situation, a series of algorithms are set to regulate the extrusion speed of the extruder to ensure the switching time.

[0090] Reference Figure 2 As shown in Figure 2, establishing a model for the effect of temperature on viscosity includes the following steps:

[0091] Obtaining a temperature value range when the nozzle is operating, dividing the temperature value range into equal intervals, and obtaining at least one identification point;

[0092] The identification point with the smallest value is used as the benchmark identification point;

[0093] Obtaining 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 using the sample viscosity corresponding to the reference identification point as the sample reference viscosity;

[0094] The sample viscosity is compared with the sample reference viscosity to obtain the sample coefficient, and the identification point is compared with the reference identification point value to obtain the temperature coefficient;

[0095] The temperature coefficients are paired with the sample coefficients and fitted to obtain the viscosity fitting function.

[0096] Reference Figure 3 As shown, analyzing and obtaining the first actual viscosity of the current material and the second actual viscosity of the target material includes the following steps:

[0097] Take at least one sampling point evenly inside the flow channel structure, and use the nozzle end as the reference sampling point;

[0098] When the heating temperature of the material in the nozzle is pre-set, the temperature of at least one sampling point is averaged to obtain the sampling average temperature, and the temperature of the reference sampling point is obtained as the sampling reference temperature;

[0099] Compare the sampling average temperature with the sampling reference temperature to obtain the control coefficient;

[0100] During the material switching process, the actual temperature at the reference sampling point is obtained in real time through infrared recognition. The actual temperature is multiplied by the control coefficient to obtain the real-time average temperature;

[0101] The real-time average temperature is divided by the preset temperature to obtain the actual temperature coefficient, which is then substituted into the viscosity fitting function to obtain the actual ratio.

[0102] The first viscosity is multiplied by the actual ratio to obtain a first actual viscosity, and the second viscosity is multiplied by the actual ratio to obtain a second actual viscosity.

[0103] During actual switching, the viscosity will change due to temperature differences. The first viscosity of the current material and the second viscosity of the target material are obtained under preset temperature conditions, but the actual temperature is the real-time average temperature. Therefore, it is necessary to perform proportional conversion through the established temperature effect model on viscosity to obtain the first actual viscosity and the second actual viscosity. Because according to the establishment process of the temperature effect model 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.

[0104] Based on the flow channel structure of the nozzle, analyzing and obtaining at least one residual point includes the following steps:

[0105] The vertical downward direction is used as the spray direction of the nozzle, and a ray is drawn along the spray direction at the sampling point to obtain a characteristic ray. The position where the characteristic ray first intersects the flow channel structure is used as the residual point. The overlapping residual points are deduplicated to obtain at least one residual point.

[0106] During injection, the flow channel structure gradually shrinks. Therefore, after the current material is injected, residues will be generated at the obstructed position. These residues will hinder the subsequent material switching. Therefore, it is necessary to obtain the residual distribution of the current material and then take it into consideration when switching.

[0107] Reference Figure 4 As shown in the figure, estimating the residual distribution of the current material in the nozzle when switching materials includes the following steps:

[0108] The area where the residual points exist in the flow channel structure is regarded as a feature area, and the residual points are used as grid points to divide the feature area into at least one feature block, and the vertices of the feature block are the residual points;

[0109] The center of the feature block is used as the feature point, the tangent plane of the inner wall of the flow channel structure at the feature point is obtained, and the distance between the top edge of the feature block and the bottom edge of the feature block is used as the feature distance;

[0110] Get the real-time speed of the current material being ejected by the nozzle. According to the Newtonian viscosity formula, the real-time speed is divided by the characteristic distance and then multiplied by the first actual viscosity to obtain the viscous resistance.

[0111] Obtain the upper load limit of the characteristic block, satisfying that the component of the upper load limit along the tangent plane of the characteristic block is equal to the viscous resistance;

[0112] The load limit is divided by the gravitational acceleration to obtain the mass limit. The characteristic blocks and their corresponding mass limits are summarized to obtain the residual distribution of the current material.

[0113] The Newtonian viscosity formula is E=F / (dv / dy), where E is viscosity, F is viscous resistance, and dv / dy is the ratio of speed to distance traveled in a very short time. Here, since the residue is caused by the current material stopping being extruded, the time is extremely short. The real-time speed can be divided by the characteristic distance as dv / dy to calculate the viscous resistance. Based on force analysis, the upper limit of the mass remaining in the characteristic block can be obtained.

[0114] Reference Figure 5 As shown, based on the allowable error area of ​​3D printing and the movement 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:

[0115] Obtain the nozzle diameter of the printhead, and use the ratio of the allowable error area to the nozzle diameter as the upper limit of the moving length;

[0116] The upper limit of the moving length is divided by the moving speed of the nozzle to obtain the allowable time difference.

[0117] Reference Figure 6 As shown, dividing the allowed time difference into the acceleration period and the filling period includes the following steps:

[0118] The position of the flow channel structure closest to the nozzle of the nozzle is regarded as the end of the flow channel structure, and the position of the flow channel structure farthest from the nozzle of the nozzle is regarded as the initial end of the flow channel structure;

[0119] The feature block farthest from the end of the flow channel structure is used as the target feature block, the distance from the target feature block to the end of the flow channel structure is used as the second distance, and the distance from the target feature block to the initial end of the flow channel structure is used as the first distance;

[0120] The second actual viscosity is superimposed on the first actual viscosity 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;

[0121] The allowed time difference is divided into an acceleration period and a filling period, and the ratio of the length of the acceleration period to the length of the filling period is equal to the ratio of the acceleration factor to the filling factor.

[0122] The acceleration time period is the time it takes for the target material to reach the residual distribution of the current material, and the filling time period is the time it takes for the target material to extrude the residual of the current material and complete the switching. The time is allocated based on the combined movement distance and viscosity in the movement distance. In the first distance, only the target material moves, so the acceleration coefficient is the first distance multiplied by the second actual viscosity. The second distance is when the target material extrude the residual of the current material. Therefore, the viscosity is the third actual viscosity, that is, the superposition of the second actual viscosity and the first actual viscosity. Therefore, the filling coefficient is the second distance multiplied by the third actual viscosity.

[0123] Reference Figure 7 As shown, calculating the first extrusion speed of the extruder during the acceleration time period includes the following steps:

[0124] The area from the target feature block to the initial end of the flow channel structure is taken as the first area, and the first extrusion speed is taken as the unknown. According to the Newtonian viscosity formula, the first extrusion speed is divided by the first distance and then multiplied by the second actual viscosity to obtain the first resistance;

[0125] Half the volume of the first region is multiplied by the density of the target material to obtain a first mass;

[0126] The first resistance is divided by the first mass to obtain a first acceleration, and the first extrusion velocity is subtracted from the first acceleration multiplied by the length of the acceleration time period to obtain a first weakened velocity;

[0127] Using the first velocity-displacement relationship, the first extrusion velocity is obtained;

[0128] The first velocity-displacement relationship is as follows: ,

[0129] Wherein, a is the first extrusion velocity, b is the first weakened velocity, c is the first acceleration, and X is the first distance.

[0130] The first extrusion speed needs to ensure that the time it takes for the target material to complete the first distance is equal to the length of the acceleration time period. Due to the effect of viscosity, when the target material leaves the extruder, it is a deceleration motion. Therefore, the first extrusion speed can be solved by the velocity-displacement formula, but the acceleration of the deceleration process needs to be obtained. It is actually deceleration, but in order to conform to the habit of physical naming, it is still named acceleration. Then, 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 of the first resistance needs to be determined. Since the target material gradually fills the first area, the initial mass is 0, and the final mass is the mass of the first area filled with the target material. Therefore, the mass of the entire process can be regarded as the average of the two, thus obtaining the first mass, and thus the first acceleration can be calculated.

[0131] Reference Figure 8 As shown, calculating the second extrusion speed of the extruder during the filling time period includes the following steps:

[0132] The second extrusion speed is taken as an unknown number. According to the Newtonian viscosity formula, the second extrusion speed is divided by the first distance and then multiplied by the second actual viscosity to obtain the second resistance.

[0133] The second resistance is divided by the first mass to obtain the second acceleration, and the second velocity-displacement relationship is used to obtain the second weakened velocity;

[0134] The second weakened velocity is obtained by subtracting the product of the second acceleration and the length of the acceleration time period from the first extrusion velocity;

[0135] According to the Newton viscosity formula, the second weakened speed is divided by the second distance and then multiplied by the third actual viscosity to obtain the third resistance;

[0136] The area from the target feature block to the end of the flow channel structure is taken as the second area, half of the volume of the second area is multiplied by the density of the target material to obtain the second mass, and half of all mass upper limits are added to the second mass to obtain the third mass;

[0137] The third resistance is divided by the third mass to obtain a third acceleration, and the second weakened velocity is subtracted from the product of the third acceleration and the length of the filling time period to obtain a third weakened velocity;

[0138] The second extrusion speed is obtained by using the third speed-displacement relationship;

[0139] The second velocity displacement relationship is as follows: ,

[0140] Wherein, e is the second extrusion velocity, d is the second weakened velocity, f is the second acceleration, and X is the first distance;

[0141] The third velocity displacement relationship is as follows: ,

[0142] Wherein, e is the second extrusion velocity, h is the third weakened velocity, i is the third acceleration, and Y is the second distance.

[0143] Here, since the extruder's extrusion speed becomes the second extrusion speed, the speed when reaching the target feature block will also change. As long as the second acceleration of this process is calculated, the second weakened speed can be obtained. The principle used here is exactly the same as the principle of obtaining the first acceleration.

[0144] The second post-weakening speed is the speed at which the target feature block is reached, that is, the speed at which the residual initial position of the current material is reached;

[0145] Afterwards, the target material will extrude the remnants of the current material at the second weakened speed and complete the filling. The third resistance can be calculated in the same way, but the mass of the third resistance here is somewhat different from before. The third resistance is the resistance to the material in the second area. Initially, the mass of the action is 0, and the final mass of the action is the mass filled by the target material in the second area. However, during the filling process, the remnants of the current material are gradually squeezed out. Therefore, the mass of the action can be regarded as the third mass. From this, the third acceleration is calculated, and then the equation is obtained, and the second extrusion speed is solved.

[0146] Reference Figure 9 As shown, performing dynamic compensation according to the first extrusion speed and the second extrusion speed includes the following steps:

[0147] The target extrusion speed is calculated based on a relationship that a ratio of the real-time extrusion speed to the target extrusion speed is equal to a ratio of the first actual viscosity to the second actual viscosity;

[0148] When switching materials, the extruder operates at a first extrusion speed for a first time period, where the length of the first time period is equal to the length of the acceleration time period;

[0149] When the first duration is reached, the extruder operates at a second extrusion speed for a second duration, where the length of the second duration is equal to the length of the filling time period, and when the switching is completed, the extruder performs the printing operation at the target extrusion speed.

[0150] Due to the difference in viscosity, in order to maintain the consistency of the injection speed during actual injection, the extrusion speed must be changed proportionally, and thus the target extrusion speed is calculated.

[0151] Furthermore, the present solution also proposes a storage medium having a computer-readable program stored thereon, which, when called, executes the above-mentioned dynamic compensation control method based on material switching delay in multi-nozzle 3D printing.

[0152] It is understandable that the storage medium may 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 disk (SSD).

[0153] In summary, the advantages of the present invention are: by establishing a model of the influence 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, the first actual viscosity of the current material and the second actual viscosity of the target material can be estimated according to the influence of temperature on viscosity, and the residual distribution of the current material in the nozzle can be estimated according to the flow channel structure, so that the first extrusion speed and the second extrusion speed of the extruder during the material switching process are set, 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 residue 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 limited to the allowable time difference. Therefore, even if the nozzle movement speed remains unchanged, the error generated is within an acceptable range, and since the viscosity of the material changes, the subsequent extrusion speed is also changed to ensure that the nozzle injection speed is consistent with the speed before the material switching.

[0154] 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 to the above embodiments. The above embodiments and descriptions merely illustrate the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. 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: include: Obtaining the flow channel structure of the nozzle, obtaining the current material being sprayed by the nozzle, obtaining the target material to be replaced by the nozzle, obtaining the first viscosity of the current material and the second viscosity of the target material, and obtaining the real-time extrusion speed of the extruder that controls the nozzle spraying, wherein the temperature at which the first viscosity and the second viscosity are obtained are both preset temperatures, which are any temperatures when the material is fluid when heated; Establish a temperature-viscosity impact model, obtain the real-time average temperature inside the flow channel structure, and analyze and 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, at least one residual point is obtained through analysis; 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; Obtaining the allowable error area of ​​3D printing and the movement speed of the nozzle, and 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 movement speed of the nozzle; The allowed time difference is divided into an acceleration period and a filling period; Calculating a first extrusion speed of the extruder during an acceleration period based on a second viscosity of the target material; Calculating a second extrusion speed of the extruder during a filling time period based on the residual distribution and a second viscosity of the target material; Perform dynamic compensation according to the first extrusion speed and the second extrusion speed; The dynamic compensation according to the first extrusion speed and the second extrusion speed comprises the following steps: The target extrusion speed is calculated based on a relationship that a ratio of the real-time extrusion speed to the target extrusion speed is equal to a ratio of the first actual viscosity to the second actual viscosity; When switching materials, the extruder operates at a first extrusion speed for a first time period, where the length of the first time period 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, where the length of the second duration is equal to the length of the filling time period, and when the switching is completed, the extruder performs the printing operation at the target extrusion speed.

2. The dynamic compensation control method based on material switching delay in multi-nozzle 3D printing according to claim 1, characterized in that: The model for establishing the influence of temperature on viscosity comprises the following steps: Obtaining a temperature value range when the nozzle is operating, dividing the temperature value range into equal intervals, and obtaining at least one identification point; The identification point with the smallest value is used as the benchmark identification point; Obtaining 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 using 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 the sample coefficient, and the identification point is compared with the reference identification point value to obtain the temperature coefficient; The temperature coefficients are paired with the sample coefficients and fitted to obtain the viscosity fitting function.

3. The dynamic compensation control method based on material switching delay in multi-nozzle 3D printing according to claim 2, characterized in that: The analyzing and obtaining the first actual viscosity of the current material and the second actual viscosity of the target material comprises the following steps: Take at least one sampling point evenly inside the flow channel structure, and use the nozzle end as the reference sampling point; When the heating temperature of the material in the nozzle is pre-set, the temperature of at least one sampling point is averaged to obtain the sampling average temperature, and the temperature of the reference sampling point is obtained as the sampling reference temperature; Compare the sampling average temperature with the sampling reference temperature to obtain the control coefficient; During the material switching process, the actual temperature at the reference sampling point is obtained in real time through infrared recognition. The actual temperature is multiplied by the control 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, which is then substituted into the viscosity fitting function to obtain the actual ratio. The first viscosity is multiplied by the actual ratio to obtain a first actual viscosity, and the second viscosity is multiplied by the actual ratio to obtain a second actual viscosity.

4. The dynamic compensation control method based on material switching delay in multi-nozzle 3D printing according to claim 3, characterized in that: The analysis of the flow channel structure of the nozzle to obtain at least one residual point includes the following steps: The vertical downward direction is used as the spray direction of the nozzle, and a ray is drawn along the spray direction at the sampling point to obtain a characteristic ray. The position where the characteristic ray first intersects the flow channel structure is used as the residual point. The overlapping residual points are deduplicated to obtain at least one residual point.

5. The dynamic compensation control method based on material switching delay in multi-nozzle 3D printing according to claim 4, characterized in that: The estimation of the residual distribution of the current material in the nozzle during material switching includes the following steps: The area where the residual points exist in the flow channel structure is regarded as a feature area, and the residual points are used as grid points to divide the feature area into at least one feature block, where the vertices of the feature block are the residual points; The center of the feature block is used as the feature point, and the tangent plane of the inner wall of the flow channel structure at the feature point is obtained. The distance between the top edge of the feature block and the bottom edge of the feature block is used as the feature distance. Get the real-time speed of the current material being ejected by the nozzle. According to the Newtonian viscosity formula, the real-time speed is divided by the characteristic distance and then multiplied by the first actual viscosity to obtain the viscous resistance. Obtain the upper load limit of the characteristic block, satisfying that the component of the upper load limit along the tangent plane of the characteristic block is equal to the viscous resistance; The load limit is divided by the gravitational acceleration to obtain the mass limit. The characteristic blocks and their corresponding mass 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, characterized in that: The method 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 movement speed of the nozzle includes the following steps: Obtain the nozzle diameter of the printhead, and use the ratio of the allowable error area to the nozzle diameter 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 based on material switching delay in multi-nozzle 3D printing according to claim 6, characterized in that: The step of dividing the allowed time difference into an acceleration time period and a filling time period comprises the following steps: The position of the flow channel structure closest to the nozzle of the nozzle is regarded as the end of the flow channel structure, and the position of the flow channel structure farthest from the nozzle of the nozzle is regarded as the initial end of the flow channel structure; The feature block farthest from the end of the flow channel structure is used as the target feature block, the distance from the target feature block to the end of the flow channel structure is used as the second distance, and the distance from the target feature block to the initial end of the flow channel structure is used as the first distance; The second actual viscosity is superimposed on the first actual viscosity 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 allowed time difference is divided into an acceleration period and a filling period, and the ratio of the length of the acceleration period to the length of the filling period is equal to the ratio of the acceleration factor to the filling factor.

8. The dynamic compensation control method based on material switching delay in multi-nozzle 3D printing according to claim 7, characterized in that: The calculation of the first extrusion speed of the extruder during the acceleration time period comprises the following steps: The area from the target feature block to the initial end of the flow channel structure is taken as the first area, and the first extrusion speed is taken as the unknown. According to the Newtonian viscosity formula, the first extrusion speed is divided by the first distance and then multiplied by the second actual viscosity to obtain the first resistance; Half the volume of the first region is multiplied by the density of the target material to obtain a first mass; The first resistance is divided by the first mass to obtain a first acceleration, and the first extrusion velocity is subtracted from the first acceleration multiplied by the length of the acceleration time period to obtain a first weakened velocity; Using the first velocity-displacement relationship, the first extrusion velocity is obtained; The first velocity-displacement relationship is as follows: , Wherein, a is the first extrusion velocity, b is the first weakened velocity, c is the first acceleration, and X is the first distance.

9. The dynamic compensation control method based on material switching delay in multi-nozzle 3D printing according to claim 8, characterized in that: The calculation of the second extrusion speed of the extruder for the filling time period comprises the following steps: The second extrusion speed is taken as an unknown number. According to the Newtonian viscosity formula, the second extrusion speed is divided by the first distance and then multiplied by the second actual viscosity to obtain the second resistance. The second resistance is divided by the first mass to obtain the second acceleration, and the second velocity-displacement relationship is used to obtain the second weakened velocity; The second weakened velocity is obtained by subtracting the product of the second acceleration and the length of the acceleration time period from the first extrusion velocity; According to the Newton viscosity formula, the second weakened speed is divided by the second distance and then multiplied by the third actual viscosity to obtain the third resistance; The area from the target feature block to the end of the flow channel structure is taken as the second area, half of the volume of the second area is multiplied by the density of the target material to obtain the second mass, and half of all mass upper limits are added to the second mass to obtain the third mass; The third resistance is divided by the third mass to obtain a third acceleration, and the second weakened velocity is subtracted from the product of the third acceleration and the length of the filling time period to obtain a third weakened velocity; The second extrusion speed is obtained by using the third speed-displacement relationship; The second velocity displacement relationship is as follows: , Wherein, 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: , Wherein, e is the second extrusion velocity, h is the third weakened velocity, i is the third acceleration, and Y is the second distance.

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