Flow calibration method for 3D printer

Abstract

The invention discloses a flow calibration method for a 3D printer, and the method comprises the steps: controlling an extruder to switch the extrusion speed in more than one extrusion period, and controlling the extruder to extrude a printing material; controlling the sensor to obtain the distance change of the extruder relative to the sensor in the extrusion period; and obtaining a target flow calibration parameter of the extruder according to the distance change of the extruder relative to the sensor in the extrusion period.

Description

Technical Field

[0001] This invention relates to the field of 3D printing, and more specifically to a flow calibration method for 3D printers. Background Technology

[0002] like Figure 1 As shown, during 3D printing, the viscoelastic properties of the polymer filament cause lag in the volumetric flow rate at the extrusion gear inlet and nozzle outlet during acceleration and deceleration, preventing them from being as synchronous as ideally rigid. This leads to defects such as insufficient or excessive filament and uneven corners during printing; these defects are particularly pronounced when printing at high speeds and for intricate surfaces. Different materials (such as common PLA / PETG / TPU) and filaments from different manufacturers exhibit varying lag properties. Currently, each time a filament is changed, the system needs to be manually recalibrated by scribing lines and visually selecting appropriate flow parameters. At high speeds or with large amounts of material, this manual scribing method is inefficient, inaccurate, and provides a poor user experience, necessitating automated calibration.

[0003] There is a need in this field to develop an improved, faster, more accurate, and more reliable flow calibration technology to mitigate or overcome the aforementioned technical deficiencies and to obtain other beneficial technical effects.

[0004] The information included in this background section of the present invention specification, including any references cited herein and any descriptions or discussions thereof, is included for technical reference purposes only and is not intended to limit the scope of the invention. Summary of the Invention

[0005] The present invention is proposed in view of the foregoing and other further ideas.

[0006] According to one aspect of the present invention, a flow calibration method for a 3D printer is proposed, the 3D printer comprising: a printhead assembly including a hot-end assembly having a nozzle, an extruder feeding material to the nozzle, and a sensor configured to acquire a distance change signal of the extruder relative to the sensor at different extrusion speeds; and a controller configured to control the extruder to feed material at different extrusion speeds, wherein the method comprises: The extruder is controlled to switch the extrusion speed within one or more extrusion cycles, and the extruder is controlled to extrude printing material. The sensor is controlled to acquire the change in distance between the extruder and the sensor during the extrusion cycle; and The target flow calibration parameters of the extruder are obtained based on the change in distance between the extruder and the sensor during the extrusion cycle.

[0007] In one embodiment, controlling the extruder to switch the extrusion speed and control the extruder to extrude printing material within one or more extrusion cycles includes: During the first extrusion cycle, the extrusion speed is switched from a first extrusion speed to a second extrusion speed, and the extruder is controlled to extrude the printing material.

[0008] In one embodiment, obtaining the target flow calibration parameters of the extruder based on the distance change of the extruder relative to the sensor during the extrusion cycle includes: The initial flow calibration parameter k0 of the extruder is obtained based on the change in distance between the extruder and the sensor during the first extrusion cycle.

[0009] In one embodiment, controlling the extruder to switch the extrusion speed and control the extruder to extrude printing material within one or more extrusion cycles further includes: During the second extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed, and the extruder is controlled to extrude the printing material.

[0010] In one embodiment, obtaining the target flow calibration parameters of the extruder based on the distance change of the extruder relative to the sensor during the extrusion cycle further includes: The target flow calibration parameters are obtained based on the changes in the distance between the extruder and the sensor during the first and second extrusion cycles.

[0011] In one embodiment, the first extrusion cycle includes a first extrusion speed switching cycle and a first constant speed cycle, and the second extrusion cycle includes a second extrusion speed switching cycle.

[0012] In one embodiment, obtaining the target flow calibration parameter based on the distance change of the extruder relative to the sensor during the first extrusion cycle and the second extrusion cycle includes: Multiple secondary flow calibration parameters are taken adjacent to the primary flow calibration parameter k0 and recorded as secondary flow calibration parameter k. n ; The steps of the flow calibration method are performed using the secondary flow calibration parameters, and the curves between time and distance changes corresponding to the secondary flow calibration parameters are obtained; and The integral area difference S(k) between the integral area S1 of the distance change over time in the first uniform speed cycle and the integral area S2 of the distance change over time in the second extrusion speed switching cycle corresponding to the secondary flow calibration parameters is obtained. n ).

[0013] In one embodiment, obtaining the target flow calibration parameter based on the distance change of the extruder relative to the sensor during the first extrusion cycle and the second extrusion cycle further includes: Determine the difference S(k) between adjacent integral areas. n Whether the signs are opposite or whether one of them is zero, when the integral area difference S(k) n () opposite signs or one of them is zero, and two adjacent k n If the difference is less than the specified step size, then S(k) will be... n When the sign changes, the average value of the two secondary flow calibration parameters or one of them, or S(k) n The k corresponding to ) being zero n Record as target flow calibration parameters; and When the integral area difference S(k) n If the sign is not opposite or not equal to zero, then the primary flow calibration parameter is reacquired until the adjacent integral area difference S(k) is reached. n (Different sign)

[0014] In one embodiment, obtaining the coordinates of the time and distance changes of the first extrusion speed switching cycle to obtain the primary flow calibration parameter k0 includes: The distance change in the coordinates is obtained as (1-e) -n The coordinates of ) are obtained, and the distance change is (1-e) -n The x-coordinate nk corresponding to the coordinates of ) is a positive integer; and The primary flow calibration parameter k0 is calculated using the horizontal axis, where the primary flow calibration parameter k0 is the average of k.

[0015] In one embodiment, switching the extrusion speed from a first extrusion speed to a second extrusion speed during the first extrusion cycle and controlling the extruder to extrude printing material further includes: A sine and cosine periodic velocity motion signal is input to the extruder.

[0016] In one embodiment, obtaining the coordinates of the time and distance changes of the first extrusion speed switching cycle to obtain the primary flow calibration parameter k0 includes: Acquire the output sine and cosine periodic velocity motion signal of the extruder; Calculate the phase difference or amplitude ratio between the input sine / cosine periodic velocity motion signal and the output sine / cosine periodic velocity motion signal; and The primary flow calibration parameter k0 is obtained by the phase difference or the amplitude ratio.

[0017] In one embodiment, the integral area difference S(k) between the integral area S1 of the distance change versus time of the first uniform speed cycle corresponding to the secondary flow calibration parameter and the integral area S2 of the distance change versus time of the second extrusion speed switching cycle is obtained. n ),include: Get multiple (k) n S(k) n The target flow calibration parameters are obtained by finding the intersection of the linear regression equation of the coordinate points with the x-axis.

[0018] In one embodiment, switching the extrusion speed from a first extrusion speed to a second extrusion speed during a first extrusion cycle and controlling the extruder to extrude printing material includes: During the first extrusion cycle, the extrusion speed is switched from the first extrusion speed to the second extrusion speed using the first-stage flow calibration parameter and the second-stage flow calibration parameter, respectively, and the extruder is controlled to extrude the printing material.

[0019] In one embodiment, obtaining the target flow calibration parameters of the extruder based on the distance change of the extruder relative to the sensor during the extrusion cycle includes: During the second extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed using the first-stage flow calibration parameter and the second-stage flow calibration parameter, respectively, and the extruder is controlled to extrude the printing material. Obtain the integral area difference S(k) between the integral area S1 of the distance change over time during the first uniform speed cycle and the integral area S2 of the distance change over time during the second extrusion speed switching cycle corresponding to the first-stage flow calibration parameters and the second-stage flow calibration parameters. n );and Determine the integral area difference S(k) corresponding to the first-stage flow calibration parameters. n The integral area difference S(k) between the second-stage flow calibration parameters and the parameters of the second-stage flow calibration is... n Is the product of () and () less than 0?

[0020] In one embodiment, obtaining the target flow calibration parameters of the extruder based on the distance change of the extruder relative to the sensor during the extrusion cycle further includes: As described above, the integral area difference S(k) corresponding to the first-stage flow calibration parameters is... n The integral area difference S(k) between the second-stage flow calibration parameters and the parameters of the second-stage flow calibration is... n If the product of the first-level flow calibration parameter and the second-level flow calibration parameter is less than 0, the target flow calibration parameter is obtained by bisection using the first-level flow calibration parameter and the second-level flow calibration parameter as the interval.

[0021] In one embodiment, controlling the extruder to switch the extrusion speed and control the extruder to extrude printing material within one or more extrusion cycles includes: During the first extrusion cycle, the extrusion speed is switched from a first extrusion speed to a second extrusion speed based on the first-stage flow calibration parameters, and the extruder is controlled to extrude printing material. During the second extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed based on the first-stage flow calibration parameters, and the extruder is controlled to extrude the printing material. During the third extrusion cycle, the extrusion speed is switched from the first extrusion speed to the second extrusion speed based on the second-stage flow calibration parameters, and the extruder is controlled to extrude the printing material; and During the fourth extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed based on the second-stage flow calibration parameters, and the extruder is controlled to extrude the printing material. Triangular wave periodic motion signals are input to the extruder during the first extrusion cycle, the second extrusion cycle, the third extrusion cycle, and the fourth extrusion cycle.

[0022] In one embodiment, controlling the extruder to switch the extrusion speed and control the extruder to extrude printing material within one or more extrusion cycles includes: The target flow calibration parameters are obtained based on the distance changes of the extruder relative to the sensor during the first extrusion cycle, the second extrusion cycle, the third extrusion cycle, and the fourth extrusion cycle, wherein the first extrusion cycle and the third extrusion cycle are acceleration phases, and the second extrusion cycle and the fourth extrusion cycle are deceleration phases.

[0023] In one embodiment, obtaining the target flow calibration parameter based on the distance change of the extruder relative to the sensor during the first extrusion cycle, the second extrusion cycle, the third extrusion cycle, and the fourth extrusion cycle further includes: The distance peak value of the output signal at the nozzle outlet of the extruder is obtained, and the target flow calibration parameter is obtained through the distance peak value.

[0024] In one embodiment, obtaining the preliminary flow calibration parameter k0 of the extruder based on the distance change of the extruder relative to the sensor during the first extrusion cycle includes: Obtain the V of the extruder during the first extrusion cycle out V0, V in The corresponding value with time t, via V out =(V0-Vin )*e (-1 / k0)*t + V in The initial flow calibration parameter k0 is obtained. Among them, V out V is the nozzle exit extrusion speed, V0 is the initial extrusion speed, and V in t is the inlet extrusion speed, and t is the extrusion time.

[0025] Further embodiments of the present invention can achieve other advantageous technical effects not listed hereafter, which may be partially described below and can be expected and understood by those skilled in the art after reading the present invention. Attached Figure Description

[0026] The above-described features and advantages of these embodiments, as well as other features and advantages, and the ways in which they are implemented, will become more apparent from the following description in conjunction with the accompanying drawings, and embodiments of the invention will be better understood.

[0027] Figure 1 This is a diagram illustrating the flow error caused by input / output lag during the printing process of printing materials. Figure 2 This is a schematic diagram of a printhead assembly of a 3D printer in one embodiment of this application; Figure 3 This is a schematic diagram of a printhead assembly of a 3D printer in another embodiment of this application; Figure 4 In one embodiment, the outlet extrusion speed V out A graph showing how the time t changes the time. Figure 5 This is a graph showing the change of the outlet output distance D(t) with time t in one embodiment; Figure 6 This is a graph showing the change of inlet input velocity Vin / outlet output velocity Vout over time t in one embodiment. Figure 7 yes Figure 6 The graphs showing the changes in outlet output speed and outlet output distance over time t in the embodiment; Figure 8 This is a graph showing the time versus distance variation D(t)' of the extruder at different extrusion speeds in one embodiment; Figure 9 This is a schematic diagram illustrating the acquisition of k0' during the target flow calibration parameter acquisition process in one embodiment; Figure 10 This is a graph showing the change of the inlet input velocity Vin with time t in one embodiment; Figure 11 Is Figure 10 A graph showing the variation of the output-input distance D(t) with time t in the embodiment; and Figure 12 Is Figure 10 The diagram shows the relationship between slope A and the target flow calibration parameters in the embodiment. Detailed Implementation

[0028] In the following description of the accompanying drawings and detailed embodiments, details of one or more embodiments of the invention will be set forth. Other features, objects, and advantages of the invention will become apparent from these descriptions, drawings, and claims.

[0029] It should be understood that the illustrated and described embodiments are not limited in application to the details of the construction and arrangement of the components set forth in the following description or illustrated in the drawings. The illustrated embodiments may be other embodiments and can be implemented or performed in various ways. The examples are provided by way of explanation rather than limitation of the disclosed embodiments. Indeed, it will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the invention without departing from the scope or spirit of the disclosure. For example, features illustrated or described as part of one embodiment may be used with another embodiment to still produce another embodiment. Therefore, this disclosure covers such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0030] Similarly, it is understood that the phrases and terms used in this document are for descriptive purposes and should not be considered restrictive. The use of “including,” “contains,” or “has,” and their variations, in this document is intended to include, in an open-ended manner, the items listed thereafter, their equivalents, and any additional items.

[0031] The term "3D printer" includes not only three-dimensional printing equipment in the general sense of the art, such as industrial-grade 3D printers, including consumer-grade 3D printers, but also laser processing equipment with 3D printing capabilities and 3D printing equipment with laser processing capabilities, all of which fall within the scope of "3D printer" in this application.

[0032] In this application, the "3D printer" may include the function of constructing objects by layering and stacking three-dimensional solids using powdered metal or plastic and other bondable materials through methods such as spraying adhesive or extrusion, and may also selectively include laser processing function depending on the application.

[0033] The present invention will now be described in more detail with reference to specific embodiments thereof.

[0034] 3D printer like Figure 2As shown, the 3D printer includes: a printhead assembly, which includes a hot-end assembly 1 with a nozzle 11, an extruder 2 feeding material to the nozzle 11, and a sensor 3 configured to acquire distance or position change signals of the hot-end assembly 1 relative to the sensor 3 at different extrusion speeds; and a controller (not shown), configured to control the extruder 2 to feed material at different extrusion speeds. The printing material m is extruded from the nozzle 11 under the drive of the extruder 2. In addition to the nozzle 11, the hot-end assembly 1 also includes a heating block and heat dissipation fins.

[0035] Sensor 3 may include a coil eddy current sensor, Hall sensor, inductive sensor, capacitive sensor, or mechanical sensor, etc. The working principle of sensor 3 is based on the changes in the distance between the object being measured and the sensor, which cause changes in the coil frequency, voltage, inductance, capacitance, deformation, or force of sensor 3. For example, the working principle of a coil eddy current sensor is based on Faraday's principle of electromagnetic induction. When a metal conductor is placed in a changing magnetic field or moves through a magnetic field cutting magnetic lines of force, an induced current in the form of eddies will be generated within the conductor. This current is called an eddy current, and the phenomenon is called the eddy current effect. Based on this effect, a coil eddy current sensor can accurately measure the relative positional change between the measured metal object and the sensor end face, such as... Figure 2 As shown.

[0036] like Figure 3 As shown, sensor 3 can also be a mechanical sensor and is mounted on the cantilever beam of the printhead assembly. The cantilever beam is a part of the printhead assembly that is prone to deformation when the extruder 2 feeds material. When the extruder 2 feeds material at different extrusion speeds, the cantilever beam will deform to different degrees, thereby changing the relative position of the measured object and the sensor, and then calculating based on the linear relationship between the exit speed and distance.

[0037] like Figure 2 and 3 As shown, sensor 3 can be mounted on the printhead assembly. Specifically, sensor 3 can be mounted on the extruder 2 of the printhead assembly and opposite the hot-end assembly 1 to detect changes in the distance or position of the hot-end assembly 1 relative to sensor 3 at different extrusion speeds. During 3D printing, extruder 2 has an extrusion wheel for driving material feeding. When the extrusion wheel extrudes the filament, the extruder 2 or other components of the printhead assembly are subjected to force and deformation, resulting in minute displacements or vibration frequencies, which in turn cause changes in the distance between sensor 3 and the hot-end assembly 1. Therefore, by acquiring the distance change of the hot-end assembly 1 relative to sensor 3 at different extrusion speeds, the force changes of extruder 2 at different extrusion speeds can be identified.

[0038] Flow calibration method The flow calibration method includes: Control the extruder to switch extrusion speeds and control the extruder to extrude printing material within one or more extrusion cycles; The control sensor acquires the change in distance between the extruder and the sensor during the extrusion cycle; and The target flow calibration parameters of the extruder are obtained based on the change in distance between the extruder and the sensor during the extrusion cycle.

[0039] Among these, controlling the extruder to switch extrusion speeds and control the extruder to extrude printing material within one or more extrusion cycles includes: During the first extrusion cycle, the extrusion speed is switched from the first extrusion speed to the second extrusion speed, and the extruder is controlled to extrude the printing material.

[0040] The target flow calibration parameters for the extruder are obtained based on the change in distance between the extruder and the sensor during the extrusion cycle, including: The initial flow calibration parameter k0 of the extruder is obtained based on the change in distance between the extruder and the sensor during the first extrusion cycle.

[0041] The following provides several examples of obtaining the initial flow calibration parameter k0 of the extruder.

[0042] In one embodiment, such as Figure 4 As shown, the relationship between the outlet extrusion speed of the nozzle 11 of the extruder 2 and the flow calibration parameters and extrusion time during 3D printing can be expressed as: V out =(V0-V in )*e (-1 / k0)*t + V in Among them, V out V is the outlet extrusion speed of nozzle 11, V0 is the initial extrusion speed, and V in t is the inlet extrusion speed, and t is the extrusion time.

[0043] Therefore, the outlet extrusion speed of nozzle 11 is a function of the flow calibration parameter and the extrusion time. Furthermore, the outlet extrusion speed V of nozzle 11... out It has a linear relationship with the change in distance. Therefore, V out The trend of the curve is the same as the trend of the curve showing the change in distance between extruder 2 and sensor 3. The curve showing the change in distance from sensor 3 can be used to replace V. out Curve. In V out V0, V in If the data can be obtained from the controller, the primary flow calibration parameter k0 can be calculated.

[0044] In one embodiment, such as Figure 5As shown, based on the change in distance between the extruder 2 and the sensor 3 during the first extrusion cycle, the preliminary flow calibration parameter k0 of the extruder 2 is obtained, including: The distance change D(t)' in the coordinate system is obtained as (1-e -n The coordinates of ) are obtained, and the distance change D(t)' is (1-e -n The x-coordinate nk corresponds to the coordinate of ), where n is a positive integer; and the primary flow calibration parameter k0 is calculated through the x-coordinate, where the primary flow calibration parameter k0 is the average of k.

[0045] Specifically, the steps to obtain the initial flow calibration parameter k0 of the extruder include: Control the extruder to accelerate from a first extrusion speed to a second extrusion speed at a predetermined acceleration; The sensor acquires the correspondence between the time t at the nozzle exit and the distance change D(t)'=D(t) / D (where the exit speed and the distance change are linearly related). D(t) is the distance corresponding to different times t during the acceleration of the extrusion speed from the first extrusion speed to the second extrusion speed. D is the amplitude of the curve of time versus distance during the first extrusion speed switching cycle, that is, the distance D during the acceleration of the extrusion speed from the first extrusion speed to the second extrusion speed. D(t) / D represents the distance change. Obtain the value at time t=k0 when the distance change D(t)'=63.2%, the value at time t=2k0 when the distance change D(t)'=86.5%, the value at time t=3k0 when the distance change D(t)'=95.0%, and the value at time t=4k0 when the distance change D(t) / DD(t)'=98.2%. After calculating k0 corresponding to each of the above distance changes D(t)', the average value is taken to obtain the initial flow calibration parameter k0 of the extruder.

[0046] In one embodiment, such as Figure 6 and 7 As shown, switching the extrusion speed from the first extrusion speed to the second extrusion speed during the first extrusion cycle and controlling the extruder to extrude the printing material includes: inputting a sine and cosine periodic speed motion signal to the extruder.

[0047] Specifically, the coordinates of the time and distance changes during the first extrusion speed switching cycle are obtained to acquire the primary flow calibration parameter k0, including: Acquire the output sine and cosine periodic velocity motion signal of the extruder; Calculate the phase difference or amplitude ratio between the input sine / cosine periodic velocity motion signal and the output sine / cosine periodic velocity motion signal; and The primary flow calibration parameter k0 is obtained by using the phase difference or amplitude ratio.

[0048] Specifically, the steps to obtain the primary flow calibration parameter k0 include: The extruder is controlled by inputting a sinusoidal-cosine periodic speed motion signal: the period is T, the phase is φ (in), the peak is VF (in), and the trough is VG (in); The sensor acquires the time t at the nozzle exit and the corresponding distance change (the exit velocity and distance change are linearly related). Obtain the input phase φ(in), input velocity peak VF(in), and input velocity trough VG(in); Obtain the output distance phase φ(out), output distance peak DF(out), and output distance trough DG(out); By using the proportional relationship between output distance and output speed, the output speeds VF(out) and VG(out) can be obtained from the output distances DF(out) and DG(out). Calculate the phase difference between input and output velocities δφ=φ(out)-φ(in) and the amplitude ratio of output velocity to input velocity i=[VF(out)-VG(out)] / [VF(in)-VG(in)] under period T (where ω=2π / T); By inputting ω and δφ or ω and i, substitute δφ=-arctan(ω*k0) and The initial k0 value is calculated.

[0049] The following provides several examples of obtaining the target flow calibration parameters for the extruder.

[0050] In one embodiment, such as Figure 8 As shown, controlling the extruder to switch extrusion speeds and control the extruder to extrude printing material within one or more extrusion cycles also includes: During the second extrusion cycle T2, the extrusion speed is switched from the second extrusion speed V2 to the third extrusion speed V3, and the extruder 2 is controlled to extrude the printing material.

[0051] The method for obtaining the target flow calibration parameters of the extruder 2 based on the distance change of the extruder 2 relative to the sensor 3 during the extrusion cycle also includes: The target flow calibration parameters are obtained based on the change in distance between the extruder 2 and the sensor 3 during the first extrusion cycle T1 and the second extrusion cycle T2.

[0052] The first extrusion cycle T1 includes a first extrusion speed switching cycle T11 and a first constant speed cycle T12, and the second extrusion cycle T2 includes a second extrusion speed switching cycle T21.

[0053] The target flow calibration parameters are obtained based on the distance changes between the extruder 2 and the sensor 3 during the first extrusion cycle T1 and the second extrusion cycle T2, including: The primary flow calibration parameter k0 is taken from multiple secondary flow calibration parameters and recorded as secondary flow calibration parameter k. n (n is an integer greater than 0); The steps of performing the flow calibration method using secondary flow calibration parameters and obtaining the curves between time and distance corresponding to the secondary flow calibration parameters; and Obtain the integral area S(k) of the distance change versus time integral area S1 of the first uniform speed period T12 and the integral area S2 of the distance change versus time integral area S2 of the second extrusion speed switching period T21 corresponding to the secondary flow calibration parameters. n ).

[0054] The method for obtaining the target flow calibration parameters based on the distance changes between the extruder 2 and the sensor 3 during the first extrusion cycle T1 and the second extrusion cycle T2 also includes: Determine the difference S(k) between adjacent integral areas. n Whether the signs are opposite or whether one of them is zero, when the integral area difference S(k) n () opposite signs or one of them is zero, and two adjacent k n If the difference is less than the specified step size, such as 0.004, then S(k) will be... n When the sign changes, the average value of the two secondary flow calibration parameters or one of them, or S(k) n The k corresponding to ) being zero n Record as target flow calibration parameters; and When the adjacent integral area difference S(k) n If the sign is not opposite or not equal to zero, then the primary flow calibration parameter is reacquired until the adjacent integral area difference S(k) is reached. n If the two adjacent secondary flow calibration parameters have different signs and are less than the specified step size, such as 0.004.

[0055] like Figure 8 As shown, the first extrusion cycle T1 may include a first extrusion speed switching cycle T11 and a first constant speed cycle T12. In one embodiment, the second extrusion speed V2 is greater than the first extrusion speed V1, that is, the extrusion speed is accelerated from the first extrusion speed V1 to the second extrusion speed V2 within the first extrusion cycle T1. Within the first extrusion speed switching cycle T11, the extrusion speed will be continuously changing until the extrusion speed reaches the second extrusion speed V2, and then a predetermined distance will be extruded at a constant speed of the second extrusion speed V2.

[0056] like Figure 8As shown, during the first extrusion speed switching cycle T11, because it is in the acceleration phase, if the extruder's flow rate is not calibrated, the flow rate of the hot-end component will be relatively too slow due to the increased extrusion speed, resulting in lines that are too thin or too short when the printhead moves at high speed. At this time, it is necessary to calibrate the extruder's flow rate to ensure that the printed lines meet the expected width and height.

[0057] This flow calibration method also includes: like Figure 8 As shown, the second extrusion cycle T2 may include a second extrusion speed switching cycle T21 and a second constant speed cycle T22. In one embodiment, the second extrusion speed V2 is greater than the third extrusion speed V3, that is, the extrusion speed is reduced from the second extrusion speed V2 to the third extrusion speed V3 within the second extrusion cycle T2. Within the second extrusion speed switching cycle T21, the extrusion speed will be continuously changing until the extrusion speed reaches the third extrusion speed V3, and then a predetermined distance will be extruded at a constant speed of the third extrusion speed V3.

[0058] like Figure 8 As shown, during the second extrusion speed switching cycle T21, because it is in the deceleration phase, if the extruder flow rate is not calibrated, the flow rate of the hot-end component will be relatively too fast due to the reduced extrusion speed, resulting in lines that are too wide or overlapped when the printhead moves at low speed. At this time, it is necessary to calibrate the extruder flow rate to ensure that the printed lines meet the expected width and height.

[0059] like Figure 8 As shown, the third extrusion speed V3 can also be equal to the first extrusion speed V1. That is, the extrusion speed is reduced from the second extrusion speed V2 to the first extrusion speed V1 within the second extrusion cycle T2. Of course, the third extrusion speed V3 can also be any other extrusion speed different from the first extrusion speed V1.

[0060] Specifically, in this embodiment, the steps of the target flow calibration parameter acquisition process include: The primary flow calibration parameter k0 is taken from multiple secondary flow calibration parameters and recorded as secondary flow calibration parameter k. n ; The steps of performing the flow calibration method with secondary flow calibration parameters are described, and the curves of time versus distance changes corresponding to the secondary flow calibration parameters are obtained. Obtain the integral area difference S(k) between the integral area S1 of the distance change versus time during the first uniform speed cycle and the integral area S2 of the distance change versus time during the second extrusion speed switching cycle corresponding to the secondary flow calibration parameters. n );and Determine the difference S(k) between adjacent integral areas n Is there a sign difference or does S(k) exist?n ) equals 0.

[0061] The integral area S1 of the distance change versus time in the first uniform speed cycle represents the extrusion flow area in the first uniform speed cycle, and the integral area S2 of the distance change versus time in the second extrusion speed switching cycle represents the extrusion flow area in the second extrusion speed switching cycle. The difference in integral area S(k n ) represents the difference in extrusion flow area between the first uniform speed cycle and the second extrusion speed switching cycle.

[0062] When the integral area difference S(k) n Two k with opposite signs and adjacent k n If the difference is less than the specified step size, then S(k) will be... n The average value of the two secondary flow calibration parameters corresponding to the sign change is recorded as the target flow calibration parameter. When the integral area difference S(k n When S(k) equals 0, then S(k) will be... n When the integral area difference S(k) equals 0, the corresponding secondary flow calibration parameter is recorded as the target flow calibration parameter. n If the signs are not different, the primary flow calibration parameters are reacquired, and the steps of the target flow calibration parameter acquisition process are executed.

[0063] Specifically, multiple secondary flow calibration parameters are taken from the primary flow calibration parameter k0 and recorded as secondary flow calibration parameter k. n include: Based on the primary flow calibration parameter k0, multiple secondary flow calibration parameters are taken with a step size d and recorded as secondary flow calibration parameters k. n .

[0064] Specifically, based on the primary flow calibration parameter k0, multiple secondary flow calibration parameters are taken with a step size d and recorded as secondary flow calibration parameters k. n include: A range [k0-δ, k0+δ] is generated centered on the primary flow calibration parameter k0, where δ is a constant between 0 and 1; and Within the interval [k0-δ, k0+δ], take multiple secondary flow calibration parameters with a step size d, and record them as secondary flow calibration parameters k. n , Where k n It is an arithmetic sequence with common difference d. n It can be represented as k0-n*d and k0+n*d, where n is a natural number.

[0065] For example, if k0 = 0.04 is calculated and δ is set to 0.03, then the interval [0.01, 0.07] is obtained. Within this interval, a point is taken with d = 0.005 to obtain the secondary flow calibration parameter k. nThe secondary flow calibration parameter k n Including 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, and 0.055.

[0066] When the integral area difference S(k) n () opposite signs or one of them is zero, and two adjacent k n If the difference is less than the specified step size, then S(k) will be... n When the sign changes, the average value of the two secondary flow calibration parameters or one of them, or S(k) n The k corresponding to ) being zero n Record these as target flow calibration parameters.

[0067] For example, when S(k) n When the k value corresponding to the sign change is 0.045 and 0.04, if the difference between 0.0045 and 0.004 is less than the specified step size, then the target flow calibration parameter is the average of the two, which is 0.0425.

[0068] When the integral area difference S(k) n If the signs are not different, then the primary flow calibration parameters are reacquired, and the steps of the target flow calibration parameter acquisition process are executed. The steps of the target flow calibration parameter acquisition process include: The primary flow calibration parameter k0 is taken from multiple secondary flow calibration parameters and recorded as secondary flow calibration parameter k. n ; The steps of performing the flow calibration method with secondary flow calibration parameters are described, and the curves of time versus distance changes corresponding to the secondary flow calibration parameters are obtained. Obtain the integral area difference S(k) between the integral area S1 of the distance change versus time during the first uniform speed cycle and the integral area S2 of the distance change versus time during the second extrusion speed switching cycle corresponding to the secondary flow calibration parameters. n );and Determine the difference in integral area S(k) n () Whether the signs are different.

[0069] Reacquiring the primary flow calibration parameters includes: Get (k) n S(k) n The linear regression equation of the coordinate points intersects the x-axis at point k0', and the target flow calibration parameter acquisition process is re-executed using k0'. Where k0' is the primary flow calibration parameter.

[0070] In one embodiment, such as Figure 9 As shown, (k) is obtained through the linear regression equation. n S(k) nThe coordinates of the points, such as (k1, S(k1)), (k2, S(k2)), and (k3, S(k3)), are used to generate a univariate linear regression equation, and the intersection point k0' of this univariate linear regression equation with the x-axis is calculated. Here, k0' is the reacquired primary flow calibration parameter, and the target flow calibration parameter acquisition process is re-executed with k0'.

[0071] In one embodiment, the integral area difference S(k) between the integral area S1 of the distance change versus time during the first uniform speed cycle and the integral area S2 of the distance change versus time during the second extrusion speed switching cycle corresponding to the secondary flow calibration parameters is obtained. n ),include: Get multiple (k) n S(k) n The target flow calibration parameters are obtained by finding the intersection of the linear regression equation of the coordinate points with the x-axis.

[0072] Specifically, switching the extrusion speed from a first extrusion speed to a second extrusion speed during the first extrusion cycle and controlling the extruder to extrude the printing material includes: During the first extrusion cycle, the extrusion speed is switched from the first extrusion speed to the second extrusion speed using the first-stage flow calibration parameter and the second-stage flow calibration parameter, respectively, and the extruder is controlled to extrude the printing material.

[0073] The target flow calibration parameters for the extruder are obtained based on the change in distance between the extruder and the sensor during the extrusion cycle, including: During the second extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed using the first-stage flow calibration parameters and the second-stage flow calibration parameters, respectively, and the extruder is controlled to extrude the printing material. Obtain the integral area difference S(k) between the integral area S1 of the distance change versus time during the first uniform speed cycle and the integral area S2 of the distance change versus time during the second extrusion speed switching cycle corresponding to the first and second stage flow calibration parameters. n );and Determine the integral area difference S(k) corresponding to the first-stage flow calibration parameters. n The integral area difference S(k) between the second-stage flow calibration parameters and the second-stage flow calibration parameters n Is the product of () and () less than 0?

[0074] The method for obtaining the target flow calibration parameters of the extruder based on the change in distance between the extruder and the sensor during the extrusion cycle also includes: For example, the integral area difference S(k) corresponding to the first-stage flow calibration parameters n The integral area difference S(k) between the second-stage flow calibration parameters and the second-stage flow calibration parameters nIf the product of the first-stage flow calibration parameter and the second-stage flow calibration parameter is less than 0, the target flow calibration parameter is obtained by bisection using the first-stage flow calibration parameter and the second-stage flow calibration parameter as the interval.

[0075] Specifically, the steps to obtain the target flow calibration parameters for the extruder include: Assign a positive interval to the secondary flow calibration parameter kn, for example, kn∈[0,a]; The extruder is controlled to switch from the first extrusion speed to the second extrusion speed using the first-stage flow calibration parameter 0 and the second-stage flow calibration parameter a, respectively. The sensor acquires the time t and distance change at the nozzle exit (the exit velocity and distance change are linearly related). Calculate the values ​​of S(0) and S(a) corresponding to k=0 and k=a, such that S(0)*S(a)<0; Calculate the midpoint c = a / 2 of the interval, and calculate the value of S(c); Determine the sign of S(c): a) If S(c) = 0, then c is the target flow calibration parameter. b) If S(c) and S(0) have the same sign, then the target flow calibration parameter is in the interval [c, a], update 0 = c. c) If S(c) and S(a) have the same sign, then the target flow calibration parameter is in the interval [0, c], and a = c is updated; Repeat steps b) and c) until the adjacent k(n+1)-kn < 0.004 is satisfied, then the value of [kn+k(n+1)] / 2 is the target flow calibration parameter.

[0076] In one embodiment, such as Figure 10-12 As shown, controlling the extruder to switch extrusion speeds and extrude printing material within one or more extrusion cycles includes: During the first extrusion cycle, the extrusion speed is switched from the first extrusion speed to the second extrusion speed based on the first primary flow calibration parameters, and the extruder is controlled to extrude the printing material. During the second extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed based on the first-stage flow calibration parameters, and the extruder is controlled to extrude the printing material. During the third extrusion cycle, the extrusion speed is switched from the first extrusion speed to the second extrusion speed based on the second-stage flow calibration parameters, and the extruder is controlled to extrude the printing material; and During the fourth extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed based on the second-stage flow calibration parameters, and the extruder is controlled to extrude the printing material. Triangular wave periodic motion signals are input to the extruder during the first, second, third, and fourth extrusion cycles.

[0077] Among these, controlling the extruder to switch extrusion speeds and control the extruder to extrude printing material within one or more extrusion cycles includes: The target flow calibration parameters are obtained based on the changes in the distance between the extruder and the sensor during the first, second, third, and fourth extrusion cycles, where the first and third extrusion cycles are acceleration phases and the second and fourth extrusion cycles are deceleration phases.

[0078] The method for obtaining target flow calibration parameters based on the changes in the distance between the extruder and the sensor during the first, second, third, and fourth extrusion cycles also includes: The distance peak value of the output signal at the nozzle outlet of the extruder is obtained, and the target flow calibration parameters are obtained through the distance peak value.

[0079] Specifically, such as Figure 10-12 As shown, the steps to obtain the target flow calibration parameters include: The extruder is controlled to switch from a first extrusion speed V1 to a second extrusion speed V2, and then back to the first extrusion speed V1. This means the extruder is controlled to perform triangular wave periodic motion. During the first extrusion cycle T1 and the second extrusion cycle T2, the first-stage flow calibration parameter k=c; during the third extrusion cycle T3 and the fourth extrusion cycle T4, the second-stage flow calibration parameter k=2c; during the fifth extrusion cycle T5 and the sixth extrusion cycle T6, the third-stage flow calibration parameter k=3c; and during the seventh extrusion cycle T7 and the eighth extrusion cycle T8, the fourth-stage flow calibration parameter k=4c (where c is a non-zero constant). The sensor acquires the relationship between the time t at the nozzle exit and the distance D(t). Where, when k=c, D(t)=df1, when k=2c, D(t)=df2, when k=3c, D(t)=df3, when k=4c, D(t)=df4, and calculate the slope value A of the above (D(t), t) coordinates, where df1-df4 is the distance peak value; Through the monotonic function TA function ( Figure 12 ), to obtain the target flow calibration parameters.

[0080] Alternatively, in this embodiment, the target flow calibration parameters can also be obtained as follows: when Figure 11 The output distances D(t) to a certain peak value df1, df2, df3, df4 and Figure 10When the difference between the peak input velocity V2 / λ and the peak input velocity is less than the specified value Δd, for example (df2-V2 / λ)<Δd, k=2c corresponding to df2 is used as the target flow calibration parameter.

[0081] Alternatively, in this embodiment, the target flow calibration parameters can also be obtained as follows: For the nozzle outlet D(t) Figure 11 Integral as follows: When k=c, integrate over two periods, T1 and T2. When k=2c, the integral is performed over two periods, T3 and T4. When k=3c, integrate over two periods, T5 and T6. When k=4c, the integral is performed over two periods, T7 and T8. When k = different values ​​of c, the integral value of the output distance D(t) is the same as... Figure 10 When the difference between the input speed Vin / 2[λ(T1+T2)] and the input speed is less than the specified value Δd, the k value corresponding to the integral value is used as the target flow calibration parameter.

[0082] The foregoing description of several embodiments of the invention has been provided for illustrative purposes. The foregoing description is not intended to be exhaustive, nor is it intended to limit the invention to the precise steps and / or forms disclosed; clearly, many modifications and variations can be made in light of the teachings above. The scope of the invention and all its equivalents are intended to be defined by the appended claims.

Claims

1. A flow calibration method for a 3D printer, characterized in that, The 3D printer includes: a printhead assembly comprising a hot-end assembly with a nozzle, an extruder feeding material to the nozzle, and a sensor configured to acquire distance change signals of the extruder relative to the sensor at different extrusion speeds; and a controller configured to control the extruder to feed material at different extrusion speeds. The method includes: The extruder is controlled to switch the extrusion speed within one or more extrusion cycles, and the extruder is controlled to extrude printing material. The sensor is controlled to acquire the change in distance between the extruder and the sensor during the extrusion cycle; and The target flow calibration parameters of the extruder are obtained based on the change in distance between the extruder and the sensor during the extrusion cycle.

2. The flow calibration method according to claim 1, characterized in that, Controlling the extruder to switch the extrusion speed and control the extruder to extrude printing material within one or more extrusion cycles includes: During the first extrusion cycle, the extrusion speed is switched from a first extrusion speed to a second extrusion speed, and the extruder is controlled to extrude the printing material.

3. The flow calibration method according to claim 2, characterized in that, The step of obtaining the target flow calibration parameters of the extruder based on the distance change of the extruder relative to the sensor during the extrusion cycle includes: The initial flow calibration parameter k0 of the extruder is obtained based on the change in distance between the extruder and the sensor during the first extrusion cycle.

4. The flow calibration method according to claim 3, characterized in that, The method of controlling the extruder to switch the extrusion speed and controlling the extruder to extrude printing material within one or more extrusion cycles further includes: During the second extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed, and the extruder is controlled to extrude the printing material.

5. The flow calibration method according to claim 4, characterized in that, The step of obtaining the target flow calibration parameters of the extruder based on the distance change of the extruder relative to the sensor during the extrusion cycle further includes: The target flow calibration parameters are obtained based on the changes in the distance between the extruder and the sensor during the first and second extrusion cycles.

6. The flow calibration method according to claim 5, characterized in that, The first extrusion cycle includes a first extrusion speed switching cycle and a first constant speed cycle, and the second extrusion cycle includes a second extrusion speed switching cycle.

7. The flow calibration method according to claim 6, characterized in that, The step of obtaining the target flow calibration parameters based on the distance changes of the extruder relative to the sensor during the first extrusion cycle and the second extrusion cycle includes: Multiple secondary flow calibration parameters are taken adjacent to the primary flow calibration parameter k0 and recorded as secondary flow calibration parameter k. n ; The steps of the flow calibration method are performed using the secondary flow calibration parameters, and the curves between time and distance changes corresponding to the secondary flow calibration parameters are obtained; and The integral area difference S(k) between the integral area S1 of the distance change over time in the first uniform speed cycle and the integral area S2 of the distance change over time in the second extrusion speed switching cycle corresponding to the secondary flow calibration parameters is obtained. n ).

8. The flow calibration method according to claim 7, characterized in that, The step of obtaining the target flow calibration parameter based on the distance change of the extruder relative to the sensor during the first extrusion cycle and the second extrusion cycle further includes: Determine the difference S(k) between adjacent integral areas. n Whether the signs are opposite or whether one of them is zero, when the integral area difference S(k) n () opposite signs or one of them is zero, and two adjacent k n If the difference is less than the specified step size, then S(k) will be... n When the sign changes, the average value of the two secondary flow calibration parameters or one of them, or S(k) n The k corresponding to ) being zero n Record as target flow calibration parameters; and When the adjacent integral area difference S(k) n If the sign is not opposite or not equal to zero, then the primary flow calibration parameter is reacquired until the adjacent integral area difference S(k) is reached. n (Different sign) 9. The flow calibration method according to claim 3, characterized in that, The step of obtaining the coordinates of the time and distance changes of the first extrusion speed switching cycle to obtain the primary flow calibration parameter k0 includes: The distance change in the coordinates is obtained as (1-e) -n The coordinates of ) are obtained, and the distance change is (1-e) -n The x-coordinate nk corresponding to the coordinates of ) is a positive integer; and The primary flow calibration parameter k0 is calculated using the horizontal axis, where the primary flow calibration parameter k0 is the average of k.

10. The flow calibration method according to claim 3, characterized in that, The step of switching the extrusion speed from a first extrusion speed to a second extrusion speed during the first extrusion cycle and controlling the extruder to extrude printing material further includes: A sine and cosine periodic velocity motion signal is input to the extruder.

11. The flow calibration method according to claim 10, characterized in that, The step of obtaining the coordinates of the time and distance changes of the first extrusion speed switching cycle to obtain the primary flow calibration parameter k0 includes: Acquire the output sine and cosine periodic velocity motion signal of the extruder; Calculate the phase difference or amplitude ratio between the input sine / cosine periodic velocity motion signal and the output sine / cosine periodic velocity motion signal; and The primary flow calibration parameter k0 is obtained by the phase difference or the amplitude ratio.

12. The flow calibration method according to claim 7, characterized in that, The integral area difference S(k) between the integral area S1 of the distance change and time of the first uniform speed cycle corresponding to the secondary flow calibration parameters and the integral area S2 of the distance change and time of the second extrusion speed switching cycle is obtained. n ),include: Get multiple (k) n S(k) n The target flow calibration parameters are obtained by finding the intersection of the linear regression equation of the coordinate points with the x-axis.

13. The flow calibration method according to claim 6, characterized in that, The step of switching the extrusion speed from a first extrusion speed to a second extrusion speed during the first extrusion cycle and controlling the extruder to extrude printing material includes: During the first extrusion cycle, the extrusion speed is switched from the first extrusion speed to the second extrusion speed using the first-stage flow calibration parameter and the second-stage flow calibration parameter, respectively, and the extruder is controlled to extrude the printing material.

14. The flow calibration method according to claim 13, characterized in that, The step of obtaining the target flow calibration parameters of the extruder based on the distance change of the extruder relative to the sensor during the extrusion cycle includes: During the second extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed using the first-stage flow calibration parameter and the second-stage flow calibration parameter, respectively, and the extruder is controlled to extrude the printing material. Obtain the integral area difference S(k) between the integral area S1 of the distance change over time during the first uniform speed cycle and the integral area S2 of the distance change over time during the second extrusion speed switching cycle corresponding to the first-stage flow calibration parameters and the second-stage flow calibration parameters. n );and Determine the integral area difference S(k) corresponding to the first-stage flow calibration parameters. n The integral area difference S(k) between the second-stage flow calibration parameters and the parameters of the second-stage flow calibration is... n Is the product of () and () less than 0? 15. The flow calibration method according to claim 14, characterized in that, The step of obtaining the target flow calibration parameters of the extruder based on the distance change of the extruder relative to the sensor during the extrusion cycle further includes: As described above, the integral area difference S(k) corresponding to the first-stage flow calibration parameters is... n The integral area difference S(k) between the second-stage flow calibration parameters and the parameters of the second-stage flow calibration is... n If the product of the first-level flow calibration parameter and the second-level flow calibration parameter is less than 0, the target flow calibration parameter is obtained by bisection using the first-level flow calibration parameter and the second-level flow calibration parameter as the interval.

16. The flow calibration method according to claim 2, characterized in that, Controlling the extruder to switch the extrusion speed and control the extruder to extrude printing material within one or more extrusion cycles includes: During the first extrusion cycle, the extrusion speed is switched from a first extrusion speed to a second extrusion speed based on the first-stage flow calibration parameters, and the extruder is controlled to extrude printing material. During the second extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed based on the first-stage flow calibration parameters, and the extruder is controlled to extrude the printing material. During the third extrusion cycle, the extrusion speed is switched from the first extrusion speed to the second extrusion speed based on the second-stage flow calibration parameters, and the extruder is controlled to extrude the printing material; and During the fourth extrusion cycle, the extrusion speed is switched from the second extrusion speed to the third extrusion speed based on the second-stage flow calibration parameters, and the extruder is controlled to extrude the printing material. Triangular wave periodic motion signals are input to the extruder during the first extrusion cycle, the second extrusion cycle, the third extrusion cycle, and the fourth extrusion cycle.

17. The flow calibration method according to claim 16, characterized in that, Controlling the extruder to switch the extrusion speed and control the extruder to extrude printing material within one or more extrusion cycles includes: The target flow calibration parameters are obtained based on the distance changes of the extruder relative to the sensor during the first extrusion cycle, the second extrusion cycle, the third extrusion cycle, and the fourth extrusion cycle, wherein the first extrusion cycle and the third extrusion cycle are acceleration phases, and the second extrusion cycle and the fourth extrusion cycle are deceleration phases.

18. The flow calibration method according to claim 17, characterized in that, The method of obtaining the target flow calibration parameter based on the distance change of the extruder relative to the sensor during the first extrusion cycle, the second extrusion cycle, the third extrusion cycle, and the fourth extrusion cycle further includes: The distance peak value of the output signal at the nozzle outlet of the extruder is obtained, and the target flow calibration parameter is obtained through the distance peak value.

19. The flow calibration method according to claim 3, characterized in that, The step of obtaining the preliminary flow calibration parameter k0 of the extruder based on the change in distance between the extruder and the sensor during the first extrusion cycle includes: Obtain the V of the extruder during the first extrusion cycle out V0, V in The corresponding value with time t, via V out =(V0-V in )*e (-1 / k0)*t + V in The initial flow calibration parameter k0 is obtained. Among them, V out V is the nozzle exit extrusion speed, V0 is the initial extrusion speed, and V in t is the inlet extrusion speed, and t is the extrusion time.

Images