Electrofluidic on-demand printing substrate active leveling device and method

Abstract

The application discloses a kind of electrofluid printing substrate active leveling device and leveling method, its device includes movable printing platform, droplet observation module, work computer and main control board, and printing platform top is equipped with printing substrate;Printing platform is used to carry out electrofluid printing on demand on printing substrate;Droplet observation module is used to observe the process of droplet ejection in the printing process of printing platform on printing substrate;Work computer is connected with main control board, and the leveling of printing platform and printing substrate is controlled by motion interpolation program control printing platform movement displacement;Main control board is used to control the observation of three-axis motion of printing platform, droplet observation module and the waveform output of control high-voltage power supply;The height of the nozzle distance substrate can be controlled to 0.8-1 microns by the application, reduces the electric field intensity fluctuation of electrostatic field, improves the stability and consistency of electrofluid printing;Actual Z-axis movement height is realized by calculation to level plane substrate;It has the advantages of high leveling precision, stability and good consistency.

Description

Technical Field

[0001] This invention belongs to the field of electro-hydraulic inkjet printing technology, and particularly relates to an active leveling device and method for electro-hydraulic on-demand printing substrates. Background Technology

[0002] Electrohydrodynamic (EHD) jetting is a novel printing technology that uses an electric field to pull liquid out of a nozzle, creating high-resolution prints. Its working principle involves applying a pulsed high voltage between the nozzle and the substrate. Under this high voltage, the liquid is subjected to an electric field, causing it to move within the nozzle. Once the electric field exceeds the surface tension, a jet much smaller than the nozzle diameter is formed. After the voltage is turned off, a droplet much smaller than the nozzle diameter is formed, achieving a maximum resolution of 50 nm. EHD jetting technology has become a promising candidate for micro / nanoscale additive manufacturing. It holds promise for applications in sensors, flexible electronics, and bioengineering.

[0003] Electrohydraulic inkjet printing technology is highly sensitive to the height between the printhead and the substrate due to its inherent mechanism. Machining and installation errors of mechanical parts can typically reach hundreds of micrometers, which significantly reduces the stability and consistency of electrohydraulic printing.

[0004] Because electrohydrodynamic printing requires applying high voltage to the nozzle and grounding the substrate, droplets are printed under the drive of this electric field. This printing method is extremely sensitive to the height between the nozzle and the substrate. To address this issue, patent application CN202410376139.X uses a mechanical device to adjust the angle of the electrohydrodynamic nozzle in two degrees of freedom, making it perpendicular to the normal direction of the substrate. However, it cannot achieve high-precision control over the height between the nozzle and the substrate, making it unsuitable for on-demand electrohydrodynamic printing. Summary of the Invention

[0005] To overcome the problems existing in the prior art, the present invention aims to provide an active leveling device and method for electro-hydraulic on-demand printing substrates. The leveling method combines camera observation and the high-precision characteristics of capacitive sensors, which greatly improves the stability and consistency of electro-hydraulic on-demand printing. Through the real-time nature of electrical leveling, the relative height between the printhead and the substrate remains constant during the printing process, ensuring the uniformity and consistency of the printing. It has the advantages of high leveling accuracy, good stability and consistency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An active leveling device for on-demand printing of electrofluid substrates includes a movable printing platform 3, a droplet observation module 4, a working computer, and a main control board. A printing substrate 10 is mounted on top of the printing platform 3. The printing platform 3 is used for on-demand printing of electrofluid on the printing substrate 10. The droplet observation module 4 is used to observe the droplet ejection process during the printing process of the printing platform 3 on the printing substrate 10. The working computer stores a control interface for generating G-code for path planning and sending G-code. The signal connection terminal of the working computer is connected to the data transmission terminal of the main control board, and the movement displacement of the printing platform 3 and the leveling of the printing substrate 10 are controlled by a motion interpolation program. The main control board is used to control the three-axis movement of the printing platform 3, the observation of the droplet observation module 4, and the waveform output of the high-voltage power supply.

[0008] The main control board integrates a stepper motor controller, a microdroplet observation module, and an ADC module. The main control board is connected to a high-voltage power supply through the ADC module. The main control board receives the output data of the working computer through a serial port, processes and converts the data, and outputs a 0 to ±10V waveform signal. It controls the high-voltage power supply to output a corresponding 0 to ±3kV waveform signal. The positive terminal of the high-voltage power supply is connected to the metal wire of the conductive nozzle 2, and the negative terminal is connected to the wire of the printing substrate 10.

[0009] The printing platform 3 adopts an XYZ three-axis motion mechanism. Each XYZ three-axis motion mechanism is driven by a stepper motor on its respective movement trajectory. The stepper motor controller of the main control board is connected to the working computer through a signal line. Each stepper motor controller of the motion axis uses an independent timer to send pulses. The path planning generated G instruction code stored in the working computer is the high-voltage control instruction G12 XYZ Fr d wp b, where G12 represents on-demand point printing, X, Y, and Z are the motion displacement coordinates of the three axes, F represents the overall motion speed of the printing device, and r, d, w, p, and b are the parameter values ​​of the pulse waveform of the high-voltage power supply.

[0010] The conductive nozzle 2 contains a conductive metal wire. A contact capacitive sensor 5 for capturing position points on the printing substrate is installed on one side of the conductive nozzle 2. The signal receiving terminal at one end of the contact capacitive sensor 5 is connected to the metal wire inside the conductive nozzle 2 through a differential line, and the signal receiving terminal at the other end is connected to the wire of the printing substrate 10 through a differential line.

[0011] The droplet observation module 4 includes a camera support 6 mounted on one side of the printing platform 3 and a flash lamp support 7 mounted on the other side; the camera support 6 holds an observation camera 8 by means of a clamp, and the flash lamp support 7 holds a flash lamp 9 by means of a clamp; the signal transmission ends of the observation camera 8 and the flash lamp 9 are connected to the working computer via a signal line for observing the droplet ejection process during the on-demand printing of electrofluid.

[0012] A leveling method for an active leveling device for on-demand electrofluid printing substrates, comprising the following specific steps:

[0013] The first step is to control the X, Y, and Z axis motion of the inkjet printing platform 3 by using a multi-axis linkage linear interpolation algorithm through a stepper motor controller, and to coordinate the control of the contact capacitive sensor 5 and the microdroplet observation module 4 to obtain the coordinate points on the printing substrate 10.

[0014] The second step is to input the coordinate points obtained in the first step into the working computer, and according to the substrate surface fitting algorithm, solve the motion compensation coefficients of each axis in the XYZ three-axis motion mechanism of the inkjet printing platform 3. The obtained compensation coefficients are sent to the stepper motor controller through the serial port of the working computer. The stepper motor controller parses the compensation coefficients and obtains the actual Z-axis motion height through the compensation calculation formula.

[0015] The third step involves the working computer sending specific motion commands via serial port. The path planning stored in the working computer generates G-code, i.e., high-voltage control commands (G12 XYZ Fr d wp b), to the stepper motor controller, the droplet observation module, and the ADC module. The stepper motor controller parses the motion commands to obtain the specific displacements of the X, Y, and Z axes and calculates the compensation height Δz in real time. The ADC module parses the printing commands, ultimately achieving real-time leveling and printing.

[0016] The multi-axis linkage linear interpolation algorithm described in the first step includes a coarse interpolation algorithm and a fine interpolation algorithm; the specific coarse interpolation algorithm is as follows:

[0017] First, based on the displacements within the X, Y, and Z axes, determine the longest axis and set it as L. F1 is the velocity of the longest axis.

[0018] When the axis of longest displacement during motion is the X-axis, the number of interpolation N1 on the X-axis and the pulse time T1 for each pulse step of the X-axis stepper motor are:

[0019]

[0020] Where L1 is the movement distance along the X-axis, and h is the movement step size of one pulse;

[0021] Interpolate the Y-axis motion into the X-axis, and calculate the number of interpolation N2 on the Y-axis and the pulse time T2 for each step of the Y-axis stepper motor:

[0022]

[0023] Where L2 is the movement distance along the Y-axis, and h is the movement step size of one pulse;

[0024] Interpolate the Z-axis motion into the X-axis, and calculate the number of interpolation N3 for the Z-axis and the pulse time T3 for each step of the Z-axis stepper motor:

[0025]

[0026] Where L3 is the movement distance along the Z-axis, and h is the movement step size of one pulse;

[0027] Then, a fine interpolation algorithm is used to make the X, Y, and Z axes move and stop simultaneously.

[0028] The specific fine interpolation algorithm is as follows:

[0029] The fine interpolation algorithm calls the timers of each of the three motion axes X, Y, and Z. It divides the pulse time of each step of the stepper motor in coarse interpolation into half of the pulse time and sends it as a high level, while sending the other half as a low level. These pulses are loaded into the timers to implement timer interrupts, which control the stepper motor movement. Ultimately, the fast axis moves as the slow axis moves, i.e., all three axes move and stop at the same time.

[0030] The first step involves the coordinated control of the contact capacitive sensor 5 and the droplet observation module 4 to obtain coordinate points on the printed substrate 10. The specific steps are as follows:

[0031] The working computer controls the X, Y, and Z axes of motion along the printing substrate 10 via a stepper motor controller, while simultaneously controlling the flash lamp 9 in the droplet observation module 4 to emit light at a set frequency. The observation camera 8 acquires the relative position of the nozzle of the conductive nozzle 2 to the printing substrate 10. First, the conductive nozzle 2 is brought into contact with the printing substrate 10, and the average value of multiple different positions along the X, Y, and Z axes is calculated as a reference point for the contact capacitive sensor. Then, the conductive nozzle 2 is raised, and the X and Y axes are moved along the printing substrate 10 to one of the points, lowering the Z-axis height. When the nozzle of the conductive nozzle 2 contacts the substrate 10, the contact capacitive sensor 5 samples the data. A difference of ±500 from the reference value is used as a marker point, and the coordinates of this X, Y, and Z axes are recorded. The sampling formula of the contact capacitive sensor 5 is as follows:

[0032]

[0033] In the formula, f sensor f is the input frequency of a certain channel of a contact capacitive sensor. ref It is the reference frequency of the contact capacitive sensor;

[0034] Continue in this manner to complete the measurement of the remaining coordinate points.

[0035] The specific method for the second step is as follows:

[0036] Input the coordinate points obtained in the first step into the working computer, and calculate the X-axis, Y-axis, and Z-axis compensation coefficients based on the obtained coordinate points according to the substrate surface fitting algorithm. The specific calculation formula for the compensation coefficients is as follows:

[0037] ΔZ=X×b1+Y×b2+b3 2-1

[0038] In the formula, X and Y are the measured coordinate points, b1 is the compensation coefficient of the X-axis, b2 is the compensation coefficient of the Y-axis, and b3 is the height compensation coefficient.

[0039] The calculated compensation coefficients are sent to the stepper motor controller via the serial port of the working computer. After parsing the compensation coefficients b1, b2, and b3, the stepper motor controller modifies the height compensation coefficient in the stepper motor controller and obtains the actual Z-axis movement height through the compensation calculation formula.

[0040] b3 = X × b1 + Y × b2 2-2

[0041] Z = z + b3 2-3

[0042] Where Z is the actual movement height and z is the commanded height.

[0043] The specific method for the third step is as follows:

[0044] Specific motion commands and high-voltage control commands G12 XYZ Frdwpb are set for the working computer. G12 represents on-demand dot printing, X, Y, and Z are the motion displacement coordinates of the three axes, F represents the overall motion speed of the printing equipment, and r, d, w, p, and b are the parameter values ​​of the high-voltage power supply pulse waveform, where r represents the rise time, d represents the voltage duration, w represents the transition time, p represents the peak voltage, and b represents the bias voltage. These commands are sent to the main control board via serial port. The ADC module processes and converts the acquired pulse waveform parameter values ​​r, d, w, p, and b, outputting a 0~±10V DC low-voltage waveform signal. The high-voltage power supply is then controlled to output a 0~±3kV DC high-voltage waveform signal, which is applied to the conductive printhead 2. Simultaneously, the stepper motor controller calculates the required compensation Δz in real time based on the X, Y, and Z motion displacement coordinates of the motion commands and the height compensation coefficient in the stepper motor controller. The X, Y, and Z axis motion mechanisms are linked to achieve synergy between printing and height compensation. The specific process is as follows:

[0045] First, based on the target positions X1, Y1, Z1 on the X, Y, and Z axes and the compensation coefficients b1, b2, calculate the compensation formula for errorz:

[0046] errorz=X1×b1+Y1×b2 3-1

[0047] Z = errorz + Z1 3-2

[0048] Secondly, after obtaining the actual target positions X1, Y1, and Z1 of the X, Y, and Z axes, the pulse times of the three axes are obtained by solving the multi-axis linkage linear interpolation algorithm in the first step, and the timers of the three motion axes X, Y, and Z are called to realize pulse transmission, and at the same time determine whether the motion of the three motion axes X, Y, and Z has reached the printing position.

[0049] The specific method for determining whether the XYZ three motion axes have reached the printing position is as follows:

[0050] The entire motion trajectory of the printing substrate 10 is divided into many points. 0 represents no printing at this point, and 1 represents printing at this point. Then, 0 or 1 is appended to the end of the g-code command sent by the working computer, which is then sent to the main control board. After receiving the command, the main control board performs mapping processing. PO represents the normalized value of the current interpolation progress, RC represents the real-time interpolation steps, AC represents the total number of interpolation steps, PI represents the normalized value of the image row count, PRC represents the current row count, and PAC represents the total row count. The formula is as follows:

[0051]

[0052] The current interpolation progress normalization value PO is compared with the normalization value of the image row number PI. If PO is greater than PI, the high-voltage power supply is controlled to print.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1. Due to installation errors of the electrohydraulic printing platform, machining errors of the printing substrate, and installation errors, the height control error between the printhead and the substrate can reach 100-500 micrometers. This invention uses a multi-axis linkage linear interpolation algorithm to control the XYZ three-axis motion of the printing platform 3, which can control the height between the printhead and the substrate to 0.8-1 micrometer, reducing the fluctuation of the electric field strength of the electrostatic field and greatly improving the stability and consistency of electrohydraulic printing. The printing experiment in Figure 4 shows that the droplet size of the electrohydraulic print is consistent, verifying the feasibility of active leveling.

[0055] 2. This invention mainly focuses on electrical leveling. Through interpolation algorithms, the leveling accuracy of this invention reaches the sub-micron level, which is higher than that of previous mechanical leveling (mechanical leveling accuracy is difficult to reach the sub-micron level). Mechanical leveling requires the design of corresponding mechanical structures for different motion devices. The electrical leveling of this invention has very low requirements for mechanical structures, can be applied to different devices, has strong consistency, and the hardware cost can be controlled within 100 yuan, which is much lower than the price of mechanical leveling.

[0056] 3. According to the substrate surface fitting algorithm, the present invention solves the motion compensation coefficient of each axis in the XYZ three-axis motion mechanism of the inkjet printing platform 3. The obtained compensation coefficient is sent to the stepper motor controller through the serial port of the working computer. The stepper motor controller parses the compensation coefficient and obtains the actual Z-axis motion height through the compensation calculation formula, which can not only realize the leveling of the planar substrate.

[0057] In summary, to achieve more accurate measurement of position points on the substrate, this invention employs a contact capacitive sensor 5 and an observation camera to capture position points on the substrate 10; each motion axis uses an independent timer to send pulses, which reduces speed fluctuations to a certain extent and ultimately achieves synchronization of multi-axis motion (simultaneous movement and simultaneous stopping), avoiding lag in Z-axis height compensation. When the movement reaches the designated position, the Z-axis is also compensated simultaneously and printed on demand. This method ensures the stability and consistency of printing. Attached Figure Description

[0058] Figure 1 This is a structural diagram of the device of the present invention.

[0059] Figure 2 This is a diagram showing the connection relationships of the device according to the present invention.

[0060] Figure 3 This is a schematic diagram of the substrate plane leveling compensation of the present invention.

[0061] Figure 4 shows the printing results of the printing experiment using the method of the present invention. Figure 4(a) shows high-precision printing without satellite droplets; Figure 4(b) shows large-area printing on demand; and Figure 4(c) shows printing the Xidian University logo on demand.

[0062] Figure 5 This is a flowchart of the leveling method of the present invention.

[0063] In the diagram: 1. Support; 2. Conductive nozzle; 3. Printing platform; 4. Droplet observation module; 5. Contact capacitive sensor; 6. Camera support; 7. Flash lamp support; 8. Observation camera; 9. Flash lamp; 10. Substrate. Detailed Implementation

[0064] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0065] See Figure 1 , Figure 2An active leveling device for on-demand printing of electrofluid substrates includes a movable printing platform 3, a droplet observation module 4, a working computer, and a main control board. A printing substrate 10 is mounted on top of the printing platform 3. The printing platform 3 is used for on-demand printing of electrofluid on the printing substrate 10. The droplet observation module 4 is used to observe the droplet ejection process during printing on the printing substrate 10. The working computer stores a control interface for generating G-code for path planning and sending G-codes. The signal connection terminal of the working computer is connected to the data transmission terminal of the main control board, controlling the movement and displacement of the printing platform 3 and the leveling of the printing substrate 10 through a motion interpolation program. The main control board controls the three-axis movement of the printing platform 3, the observation by the droplet observation module 4, and the waveform output of the high-voltage power supply.

[0066] The main control board integrates a stepper motor controller, a microdroplet observation module, and an ADC module. The main control board is connected to a high-voltage power supply through the ADC module. The main control board receives the output data of the working computer through a serial port, processes and converts the data, and outputs a 0 to ±10V waveform signal. It controls the high-voltage power supply to output a corresponding 0 to ±3kV waveform signal. The positive terminal of the high-voltage power supply is connected to the metal wire of the conductive nozzle 2, and the negative terminal is connected to the wire of the printing substrate 10.

[0067] The printing platform 3 adopts an XYZ three-axis motion mechanism. Each XYZ three-axis motion mechanism is driven by a stepper motor on its respective movement trajectory. The stepper motor controller of the main control board is connected to the working computer through a signal line. Each stepper motor controller of the motion axis uses an independent timer to send pulses. The path planning generated G instruction code stored in the working computer is the high-voltage control instruction G12 XYZ Fr d wp b, where G12 represents on-demand point printing, X, Y, and Z are the motion displacement coordinates of the three axes, F represents the overall motion speed of the printing device, and r, d, w, p, and b are the parameter values ​​of the pulse waveform of the high-voltage power supply.

[0068] A conductive nozzle 2, perpendicular to the printing substrate 10, is mounted on the top of the printing substrate 10 via a support 1. The conductive nozzle 2 contains conductive metal wires, and a contact capacitive sensor 5 for capturing position points on the printing substrate is mounted on one side of the conductive nozzle 2. The signal receiving terminal at one end of the contact capacitive sensor 5 is connected to the metal wire inside the conductive nozzle 2 via a differential line, and the signal receiving terminal at the other end is connected to the wire of the printing substrate 10 via a differential line.

[0069] The droplet observation module 4 includes a camera support 6 mounted on one side of the printing platform 3 and a flash lamp support 7 mounted on the other side; the camera support 6 holds an observation camera 8 for capturing position points on the printing substrate by means of a clamp, and the flash lamp support 7 holds a flash lamp 9 by means of a clamp; the signal transmission ends of the observation camera 8 and the flash lamp 9 are connected to the working computer through a signal line for observing the process of droplet ejection during the on-demand printing of electrofluid.

[0070] A leveling method for an active leveling device for on-demand electro-hydraulic printing substrates, see [link to relevant documentation]. Figure 5 The specific steps are as follows:

[0071] The first step is to control the X, Y, and Z axis motion of the inkjet printing platform 3 by using a multi-axis linkage linear interpolation algorithm through a stepper motor controller, and to coordinate the control of the contact capacitive sensor 5 and the microdroplet observation module 4 to obtain the coordinate points on the printing substrate 10.

[0072] The second step is to input the coordinate points obtained in the first step into the working computer, and according to the substrate surface fitting algorithm, solve the motion compensation coefficients of each axis in the XYZ three-axis motion mechanism of the inkjet printing platform 3. The obtained compensation coefficients are sent to the stepper motor controller through the serial port of the working computer. The stepper motor controller parses the compensation coefficients and obtains the actual Z-axis motion height through the compensation calculation formula.

[0073] The third step involves the working computer sending specific motion commands via serial port. The path planning stored in the working computer generates G-code, i.e., high-voltage control commands (G12 XYZ Fr d wp b), to the stepper motor controller, the droplet observation module, and the ADC module. The stepper motor controller parses the motion commands to obtain the specific displacements of the X, Y, and Z axes and calculates the compensation height Δz in real time. The ADC module parses the printing commands, ultimately achieving real-time leveling and printing.

[0074] The multi-axis linkage linear interpolation algorithm described in the first step includes a coarse interpolation algorithm and a fine interpolation algorithm. Since we are using a stepper motor, the speed fluctuation will not be caused by the time difference of adjacent pulses within 5us. Therefore, it is necessary to use the interpolation algorithm to achieve simultaneous movement and stopping of each motion axis.

[0075] The specific coarse interpolation algorithm is as follows:

[0076] First, based on the displacements within the X, Y, and Z axes, determine the longest axis and set it as L. F1 is the velocity of the longest axis.

[0077] When the axis of longest displacement during motion is the X-axis, the number of interpolation N1 on the X-axis and the pulse time T1 for each pulse step of the X-axis stepper motor are:

[0078]

[0079] Where L1 is the movement distance along the X-axis, and h is the movement step size of one pulse;

[0080] Interpolate its Y-axis motion into the X-axis, and calculate the number of interpolation N2 on the Y-axis and the pulse time T2 for each step of the Y-axis stepper motor:

[0081]

[0082] Where L2 is the movement distance along the Y-axis, and h is the movement step size of one pulse;

[0083] Interpolate its Z-axis motion into the X-axis, and calculate the number of interpolation N3 on the Z-axis and the pulse time T3 for each step of the Z-axis stepper motor:

[0084]

[0085]

[0086] Where L3 is the movement distance along the Z-axis, and h is the movement step size of one pulse;

[0087] Then, a fine interpolation algorithm is used to make the three axes move and stop simultaneously.

[0088] The specific fine interpolation algorithm is as follows:

[0089] The fine interpolation algorithm calls the timers of each of the three motion axes X, Y, and Z. It divides the pulse time of each step of the stepper motor in coarse interpolation into half of the pulse time and sends it as a high level, while sending the other half as a low level. These pulses are loaded into the timers to implement timer interrupts, which control the stepper motor movement. Ultimately, the fast axis moves as the slow axis moves, i.e., all three axes move and stop at the same time.

[0090] By using an independent timer to send pulses for each motion axis, speed fluctuations are reduced to a certain extent, ensuring the accuracy of coordinate acquisition.

[0091] The first step involves the coordinated control of the contact capacitive sensor 5 and the droplet observation module 4 to obtain coordinate points on the printed substrate 10. The specific steps are as follows:

[0092] The working computer controls the XYZ motion axes to move longitudinally and laterally along the printing substrate 10 via a stepper motor controller, while simultaneously controlling the flash lamp 9 in the droplet observation module 4 to emit light at a set frequency. The observation camera 8 acquires the relative position of the nozzle of the conductive nozzle 2 to the substrate 10. First, the conductive nozzle 2 is brought into contact with the printing substrate 10, and the average value of multiple different XYZ motion points is calculated as a reference point for the capacitive sensor. Then, the conductive nozzle 2 is raised, and the X and Y motion axes are controlled to move along the printing substrate 10 to one of the points, lowering the Z-axis height. When the nozzle of the conductive nozzle 2 contacts the substrate 10, the contact capacitive sensor 5 samples the data. The difference between the sampled value and the reference value within ±500 is used as a marker point, and the XYZ motion axis coordinates are recorded. The sampling formula of the contact capacitive sensor 5 is as follows:

[0093]

[0094] In the formula, f sensor f is the input frequency of a certain channel of a contact capacitive sensor. ref It is the reference frequency of the contact capacitive sensor;

[0095] The remaining coordinate points are measured in this manner. We use a 28-bit capacitive sensor; this measurement method can control the error to below 1µm. The specific mounting details are as follows... Figure 1 As shown.

[0096] The specific method for the second step is as follows:

[0097] Input the coordinate points obtained in the first step into the working computer, and according to the substrate surface fitting algorithm, the fitting surface is as follows. Figure 2 As shown; that is, the compensation coefficients for the X-axis, Y-axis, and Z-axis are calculated based on the obtained coordinate points. The specific calculation formula for the compensation coefficients is as follows:

[0098] ΔZ=X×b1+Y×b2+b3 2-1

[0099] In the formula, X and Y are the measured coordinate points, b1 is the compensation coefficient of the X-axis, b2 is the compensation coefficient of the Y-axis, and b3 is the height compensation coefficient.

[0100] The calculated compensation coefficients are sent to the stepper motor controller via the serial port of the working computer. After parsing the compensation coefficients b1, b2, and b3, the stepper motor controller modifies the height compensation coefficient in the stepper motor controller and obtains the actual Z-axis movement height through the compensation calculation formula.

[0101] b3 = X × b1 + Y × b2 2-2

[0102] Z = z + b3 2-3

[0103] Where Z is the actual movement height and z is the commanded height. Figure 3 This is a schematic diagram of substrate plane leveling compensation.

[0104] The specific method for the third step is as follows:

[0105] Specific motion commands and high-voltage control commands G12 XYZ Fr dw pb are set on the working computer. G12 represents on-demand dot printing, X, Y, and Z are the motion displacement coordinates of the three axes, F represents the overall motion speed of the printing equipment, and r, d, w, p, and b are the parameter values ​​of the pulse waveform of the high-voltage power supply, where r represents the rise time, d represents the voltage duration, w represents the transition time, p represents the peak voltage, and b represents the bias voltage. These commands are sent to the main control board via serial port. The ADC module processes and converts the acquired pulse waveform parameter values ​​r, d, w, p, and b, outputting a 0~±10V DC low-voltage waveform signal. The high-voltage power supply is then controlled to output a 0~±3kV DC high-voltage waveform signal, which is applied to the conductive printhead 2. Simultaneously, the stepper motor controller calculates the required compensation Δz in real time based on the X, Y, and Z motion displacement coordinates of the motion commands and the height compensation coefficient in the stepper motor controller. The X, Y, and Z axis motion mechanisms are linked to achieve synergy between printing and height compensation. The specific process is as follows:

[0106] First, based on the target positions X1, Y1, Z1 on the X, Y, and Z axes and the compensation coefficients b1, b2, calculate the compensation formula for errorz:

[0107] errorz=X1×b1+Y1×b2 3-1

[0108] Z = errorz + Z1 3-2

[0109] Secondly, after obtaining the actual target positions X1, Y1, and Z1 of the X, Y, and Z axes, the pulse times of the three axes are obtained by solving the multi-axis linkage linear interpolation algorithm in the first step, and the timers of the three motion axes X, Y, and Z are called to realize pulse transmission, and at the same time determine whether the motion of the three motion axes X, Y, and Z has reached the printing position.

[0110] The specific judgment method is as follows:

[0111] The conditions for ejection by the conductive nozzle 2 are mapped linearly across the entire spatial distance. The entire motion trajectory of the printing substrate 10 is divided into many points, where 0 represents no printing and 1 represents printing. The 0 or 1 is then appended to the end of the g-code instruction sent by the working computer, which is then sent to the main control board. Upon receiving the instruction, the main control board performs mapping processing. PO represents the normalized value of the current interpolation progress, RC represents the real-time interpolation steps, AC represents the total number of interpolation steps, PI represents the normalized value of the image row count, PRC represents the current row count, and PAC represents the total row count. The formula is as follows:

[0112]

[0113] The system compares the current interpolation progress normalized value PO with the normalized value of the image row count PI. If PO is greater than PI, the high-voltage power supply is controlled to start printing. Each motion axis uses an independent timer to send pulses, which reduces speed fluctuations to some extent and ultimately achieves synchronization of multi-axis motion (simultaneous movement and simultaneous stopping). This avoids lag in Z-axis height compensation. When the motion reaches the designated position, the Z-axis also completes compensation simultaneously and prints on demand. This method ensures printing stability and consistency.

[0114] The printing experiments in Figure 4 show that: Figure 4(a) shows that the droplet size of the electrofluid printed on demand is consistent, reducing the number of satellite droplets; Figures 4(b) and 4(c) show that the present invention can achieve large-area on-demand printing as well as normal on-demand printing, ensuring the stability of printing, solving the problem of poor stability and consistency of current electrofluid printing, and verifying the feasibility of the active leveling of the present invention.

[0115] Figure 3 As can be seen from the leveling compensation and printing steps, this method breaks free from the limitations of traditional mechanical leveling. The core leveling method is not limited to this printing device; it can also achieve higher precision leveling on other printing devices. This invention reduces the cost of traditional mechanical leveling while improving the leveling accuracy of electro-hydraulic printing devices. It can be adjusted in real time without cumulative error.

[0116] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An active leveling device for an on-demand electrofluid printing substrate, characterized in that: The system includes a mobile printing platform (3), a droplet observation module (4), a working computer, and a main control board. A printing substrate (10) is mounted on top of the printing platform (3). A conductive nozzle (2) perpendicular to the printing substrate (10) is mounted on the printing substrate (10) via a support (1). The printing platform (3) is used to perform on-demand printing of electrofluids on the printing substrate (10). The droplet observation module (4) is used to observe the process of droplet ejection during the printing process of the printing platform (3) on the printing substrate (10). The working computer stores a control interface for generating G-code for path planning and sending G-code. The signal connection terminal of the working computer is connected to the data transmission terminal of the main control board. The motion interpolation program controls the movement displacement of the printing platform (3) and the leveling of the printing substrate (10). The main control board is used to control the three-axis movement of the printing platform (3), the observation of the droplet observation module (4), and the waveform output of the high-voltage power supply.

2. The active leveling device for an on-demand electrofluid printing substrate according to claim 1, characterized in that: The main control board integrates a stepper motor controller, a microdroplet observation module, and an ADC module. The main control board is connected to a high-voltage power supply through the ADC module. The main control board receives the output data of the working computer through the serial port, processes and converts the data, and outputs a 0~±10V waveform signal. It controls the high-voltage power supply to output a corresponding 0~±3kV waveform signal. The positive terminal of the high-voltage power supply is connected to the metal wire of the conductive nozzle (2), and the negative terminal is connected to the wire of the printing substrate (10). The printing platform (3) adopts an XYZ three-axis motion mechanism. The XYZ three-axis motion mechanism is driven by stepper motors on its respective movement trajectory. The stepper motor controller of the main control board is connected to the working computer through a signal line. Each motion axis stepper motor controller uses an independent timer to send pulses. The path planning generated G instruction code stored in the working computer is the high-voltage control instruction G12XYZ Fr d wp b, where G12 represents on-demand point printing, X, Y, and Z are the motion displacement coordinates of the three axes, F represents the overall motion speed of the printing equipment, and r, d, w, p, and b are the parameter values ​​of the pulse waveform of the high-voltage power supply.

3. The active leveling device for an on-demand electrofluid printing substrate according to claim 1, characterized in that: The conductive nozzle (2) contains a conductive metal wire. A contact capacitive sensor (5) for capturing position points on the printing substrate is installed on one side of the conductive nozzle (2). The signal receiving terminal at one end of the contact capacitive sensor (5) is connected to the metal wire inside the conductive nozzle (2) through a differential line, and the signal receiving terminal at the other end is connected to the wire of the printing substrate (10) through a differential line.

4. The active leveling device for an on-demand electrofluid printing substrate according to claim 1, characterized in that: The droplet observation module (4) includes a camera support (6) installed on one side of the printing platform (3) and a flash lamp support (7) installed on the other side; the camera support (6) holds the observation camera (8) by a clamp, and the flash lamp support (7) holds the flash lamp (9) by a clamp; the signal transmission ends of the observation camera (8) and the flash lamp (9) are connected to the working computer through a signal line for observation of the droplet ejection process during the on-demand printing of electrofluid.

5. A leveling method for an active leveling device for an on-demand electrofluid printing substrate according to any one of claims 1 to 4, characterized in that: The specific steps are as follows: The first step is to control the X, Y, and Z axis motion of the inkjet printing platform (3) by using a multi-axis linkage linear interpolation algorithm through a stepper motor controller, and to coordinate the control of the contact capacitive sensor (5) and the droplet observation module (4) to obtain the coordinate points on the printing substrate (10); The second step is to input the coordinate points obtained in the first step into the working computer, and according to the substrate surface fitting algorithm, solve the motion compensation coefficients of each axis in the XYZ three-axis motion mechanism of the inkjet printing platform (3). The obtained compensation coefficients are sent to the stepper motor controller through the serial port of the working computer. The stepper motor controller parses out the compensation coefficients and obtains the actual Z-axis motion height through the compensation calculation formula. The third step involves the working computer sending specific motion commands via serial port. The path planning stored in the working computer generates G-code, i.e., high-voltage control commands (G12XYZ Fr d wp b), to the stepper motor controller, the droplet observation module, and the ADC module. The stepper motor controller parses the motion commands to obtain the specific displacements of the X, Y, and Z axes and calculates the compensation height Δz in real time. The ADC module parses the printing commands, ultimately achieving real-time leveling and printing.

6. The leveling method of the active leveling device for on-demand electro-hydraulic printing substrate according to claim 5, characterized in that: The multi-axis linkage linear interpolation algorithm described in the first step includes a coarse interpolation algorithm and a fine interpolation algorithm; the specific coarse interpolation algorithm is as follows: First, based on the displacements within the X, Y, and Z axes, determine the longest axis and set it as L. F1 is the velocity of the longest axis. When the axis of longest displacement during motion is the X-axis, the number of interpolation steps N1 on the X-axis and the pulse time T1 for each pulse step of the X-axis stepper motor are: Where L1 is the movement distance along the X-axis, and h is the movement step size of one pulse; Interpolate the Y-axis motion into the X-axis, and calculate the number of interpolation N2 on the Y-axis and the pulse time T2 for each step of the Y-axis stepper motor: Where L2 is the movement distance along the Y-axis, and h is the movement step size of one pulse; Interpolate the Z-axis motion into the X-axis, and calculate the number of interpolation N3 for the Z-axis and the pulse time T3 for each step of the Z-axis stepper motor: Where L3 is the movement distance along the Z-axis, and h is the movement step size of one pulse; Then, a fine interpolation algorithm is used to make the X, Y, and Z axes move and stop simultaneously. The specific fine interpolation algorithm is as follows: The fine interpolation algorithm calls the timers of each of the three motion axes X, Y, and Z. It divides the pulse time of each step of the stepper motor in coarse interpolation into half of the pulse time and sends it as a high level, while sending the other half as a low level. These pulses are loaded into the timers to implement timer interrupts, which control the stepper motor movement. Ultimately, the fast axis moves as the slow axis moves, i.e., all three axes move and stop at the same time.

7. The leveling method of the on-demand electrofluid printing substrate active leveling device according to claim 5, characterized in that: The first step involves the coordinated control of the contact capacitive sensor (5) and the droplet observation module (4) to obtain the coordinate points on the printed substrate (10). The specific steps are as follows: The working computer controls the X, Y, and Z motion axes to move along the printing substrate (10) in both directions via a stepper motor controller, while simultaneously controlling the flash lamp (9) in the droplet observation module (4) to emit light at a set frequency. The observation camera (8) then acquires the relative position of the nozzle of the conductive nozzle (2) and the printing substrate (10). First, the conductive nozzle (2) is brought into contact with the printing substrate (10), and the average value of multiple different positions of the X, Y, and Z motion axes is calculated as the reference point for the contact capacitive sensor. Then, the conductive nozzle (2) is lifted, and the X and Y motion axes are moved along the printing substrate (10) to one of the points, and the height of the Z axis is lowered. When the nozzle of the conductive nozzle (2) contacts the substrate (10), the contact capacitive sensor (5) samples the data. The difference between the sampled value and the reference value is ±500, which can be used as a marker point. The coordinates of this X, Y, and Z motion axes are recorded. The sampling formula of the contact capacitive sensor (5) is as follows: In the formula, f sensor f is the input frequency of a certain channel of the contact capacitive sensor (5). ref It is the reference frequency of the contact capacitive sensor (5); Continue in this manner to complete the measurement of the remaining coordinate points.

8. The leveling method of the active leveling device for on-demand electrofluid printing substrate according to claim 5, characterized in that: The specific method for the second step is as follows: Input the coordinate points obtained in the first step into the working computer, and calculate the X-axis, Y-axis, and Z-axis compensation coefficients based on the obtained coordinate points according to the substrate surface fitting algorithm. The specific calculation formula for the compensation coefficients is as follows: ΔZ=X×b1+Y×b2+b3 2-1 In the formula, X and Y are the measured coordinate points, b1 is the compensation coefficient of the X-axis, b2 is the compensation coefficient of the Y-axis, and b3 is the height compensation coefficient. The calculated compensation coefficients are sent to the stepper motor controller via the serial port of the working computer. After parsing the compensation coefficients b1, b2, and b3, the stepper motor controller modifies the height compensation coefficient in the stepper motor controller and obtains the actual Z-axis movement height through the compensation calculation formula. b3 = X × b1 + Y × b2 2-2 Z = z + b3 2-3 Where Z is the actual movement height and z is the commanded height.

9. The leveling method of the active leveling device for on-demand electrofluid printing substrate according to claim 5, characterized in that: The specific method for the third step is as follows: The specific motion command and high voltage control command G12XYZ Fr dw pb are set for the working computer. G12 represents on-demand point printing, X, Y, and Z are the motion displacement coordinates of the three axes, F represents the overall motion speed of the printing equipment, and r, d, w, p, and b are the parameter values ​​of the pulse waveform of the high voltage power supply. r represents the rise time, d represents the voltage duration, w represents the transition time, p represents the peak voltage, and b represents the bias voltage. The command is sent to the main control board through the serial port. The parameter values ​​r, d, w, p, and b of the obtained pulse waveform are processed and converted by the ADC module and output a 0~±10V DC low voltage waveform signal. The high voltage power supply is controlled to output a 0~±3kV DC high voltage waveform signal. The waveform signal is loaded onto the conductive nozzle (2). At the same time, the stepper motor controller calculates the required compensation ΔZ in real time according to the motion displacement coordinates of X, Y, and Z of the motion command and the height compensation coefficient in the stepper motor controller. The X, Y, and Z three-axis motion mechanisms are linked to achieve the synergy between printing and height compensation. The specific process is as follows: First, based on the target positions X1, Y1, Z1 on the X, Y, and Z axes and the compensation coefficients b1 and b2, calculate the compensation formula for errorz: errorz=X1×b1+Y1×b2 3-1 Z = errorz + Z1 3-2 Secondly, after obtaining the actual target positions X1, Y1, and Z1 of the X, Y, and Z axes, the pulse times of the three axes are obtained by solving the multi-axis linkage linear interpolation algorithm in the first step, and the timers of the three motion axes X, Y, and Z are called to realize pulse transmission, and at the same time determine whether the motion of the three motion axes X, Y, and Z has reached the printing position.

10. The leveling method of the active leveling device for on-demand electrofluid printing substrate according to claim 9, characterized in that: The specific method for determining whether the XYZ three motion axes have reached the printing position is as follows: The entire motion trajectory of the printing substrate (10) is divided into many points. 0 represents that the point is not printed and 1 represents that the point is to be printed. Then, 0 or 1 is appended to the end of the g code instruction sent by the working computer and sent to the main control board through the working computer. After receiving the instruction, the main control board will perform mapping processing. PO represents the normalized value of the current interpolation progress, RC represents the real-time interpolation step number, AC represents the total interpolation step number, PI represents the normalized value of the number of image rows, PRC represents the current number of rows, and PAC represents the total number of rows. The formula is as follows: The current interpolation progress normalization value PO is compared with the normalization value of the image row number PI. If PO is greater than PI, the high-voltage power supply is controlled to print.

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