Active leveling device and leveling method for electrofluid on-demand printing substrate

Abstract

The invention relates to an active leveling device and method for an electrofluid on-demand printing substrate, the device comprises a mobile jet printing platform, a microdroplet observation module, a working computer and a main control board, and the top of the jet printing platform is provided with a printing substrate; the jet printing platform is used for carrying out electrofluid on-demand printing on the printing substrate; the micro-droplet observation module is used for observing the micro-droplet jetting process of the jet printing platform in the printing substrate printing process; the working computer is connected with the main control board, and controls the movement displacement of the jet printing platform and the leveling of the printing substrate through a motion interpolation program; the main control board is used for controlling the three-axis movement of the jet printing platform, the observation of the microdroplet observation module and the waveform output of the high-voltage power supply; according to the invention, the height from the nozzle to the substrate can be controlled to be 0.8-1 micron, the electric field intensity fluctuation of the electrostatic field is reduced, and the stability and consistency of electrofluid jet printing are improved; the leveling of the plane substrate is realized through the calculated actual Z-axis movement height; the leveling device has the advantages of high leveling precision and good stability and consistency.

Description

Technical Field

[0001] The invention belongs to the technical field of electrofluid printing, and in particular relates to an active leveling device and a leveling method for an electrofluid on-demand printing substrate. Background Art

[0002] Electrofluidic jet-on-demand is a new printing technology that uses electric field force to pull liquid out of the nozzle to form a high-resolution print. Its working principle is to apply pulsed high voltage between the nozzle and the substrate. Under the action of high voltage, the liquid is affected by the electric field force, and the liquid in the nozzle begins to move. Once the electric field force 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, with a maximum resolution of 50nm. Electrofluidic jet-on-demand technology has become a strong candidate technology for micro-nanoscale additive manufacturing. It is expected to be used in sensors, flexible electronic devices, and bioengineering.

[0003] Due to its inherent mechanism, electrofluidic printing technology is very sensitive to the height between the nozzle and the substrate. The processing and installation errors of mechanical parts usually reach hundreds of microns, which significantly reduces the stability and consistency of electrofluidic printing.

[0004] Since electrofluid printing requires high voltage to be applied to the nozzle and the substrate to be grounded, and the droplets are printed under the drive of this electric field force, this printing method is extremely sensitive to the height between the nozzle and the substrate. To address this problem, the patent application with application number CN202410376139.X uses a mechanical device to achieve the angle adjustment of the two degrees of freedom of the electrofluid nozzle, so that it can be perpendicular to the normal direction of the substrate, but the height between the nozzle and the substrate cannot be controlled with high precision, which is not suitable for electrofluid on-demand printing. Summary of the invention

[0005] In order to overcome the problems existing in the above-mentioned prior art, the purpose of the present invention is to provide an active leveling device and leveling method for electrofluid on-demand printing of substrates. The adopted leveling method combines camera observation and the high-precision characteristics of capacitive sensors, which greatly improves the stability and consistency of electrofluid on-demand printing; through the real-time electrical leveling, the relative height between the nozzle and the substrate is guaranteed to remain unchanged during the printing process, ensuring the uniformity and consistency of printing; it has the advantages of high leveling accuracy, good stability and consistency.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] An active leveling device for on-demand printing of an electrofluid substrate comprises a movable printing platform 3, a droplet observation module 4, a working computer and a main control board, wherein a printing substrate 10 is mounted on the 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 for observing the process of droplet ejection by the printing platform 3 during the printing of the printing substrate 10; the working computer stores a control interface for generating G instruction codes through path planning and sending G instructions, the signal connection end of the working computer is connected to the data transmission end 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 motion 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 droplet 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 output data from a working computer through a serial port, processes and converts the data, and outputs a 0-±10v waveform signal. The high-voltage power supply is controlled to output a corresponding 0-±3kV waveform signal. The positive electrode of the high-voltage power supply is connected to the metal wire of the conductive nozzle 2, and the negative electrode is connected to the wire of the printing substrate 10.

[0009] The printing platform 3 adopts an XYZ three-axis motion mechanism, and the XYZ three-axis motion mechanism is driven by a stepper motor on its respective moving trajectory. The stepper motor controller of the main control board is connected to the working computer through a signal line, and the stepper motor controller of each motion axis uses an independent timer to send pulses; the path planning stored in the working computer generates a G instruction code as a high-voltage control instruction G12 XYZ F rd wp b, wherein G12 represents on-demand point printing, X, Y, and Z are respectively 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 respectively the parameter values ​​of the pulse waveform of the high-voltage power supply.

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

[0011] The droplet observation module 4 includes a camera support seat 6 installed on one side of the printing platform 3 and a flash light support seat 7 installed on the other side; an observation camera 8 is clamped on the camera support seat 6, and a flash light 9 is clamped on the flash light support seat 7; the signal transmission ends of the observation camera 8 and the flash light 9 are connected to the working computer through signal lines for process observation of droplet ejection during on-demand printing of electrofluid.

[0012] A leveling method for an electrofluid on-demand printing substrate active leveling device, the specific steps are as follows:

[0013] In the first step, a multi-axis linear interpolation algorithm is used to control the X, Y, and Z axis motions of the printing platform 3 through a stepper motor controller, and the contact capacitance sensor 5 and the droplet observation module 4 are coordinated to obtain the coordinate points on the printing substrate 10;

[0014] In the second step, the coordinate points obtained in the first step are input into the working computer, and the motion compensation coefficients of each axis in the XYZ three-axis motion mechanism of the printing platform 3 are solved according to the substrate surface fitting algorithm, and 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] In the third step, the working computer sends specific motion instructions through the serial port, and the path planning stored in the working computer generates the G instruction code, namely the high-voltage control instruction (G12 XYZ F rd wp b) to the stepper motor controller, the droplet observation module, and the ADC module. The stepper motor controller parses the motion instructions to obtain the specific movement displacement of the X, Y, and Z axes, and solves the compensation height Δz in real time. The ADC module parses the printing instructions, and finally realizes real-time leveling and printing.

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

[0017] First, according to the displacement of the X, Y, and Z axes, the longest axis is determined and set as L. F1 is the movement speed of the longest axis.

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

[0019]

[0020] Among them, L1 is the movement distance of the X axis, and h is the movement step length of a pulse;

[0021] Insert the movement of the Y axis into the X axis, calculate the number of interpolation times N2 of the Y axis and the pulse time T2 of each step of the Y axis stepper motor:

[0022]

[0023] Among them, L2 is the movement distance of the Y axis, and h is the movement step length of a pulse;

[0024] Insert the movement of the Z axis into the X axis, calculate the number of interpolation times N3 of the Z axis and the pulse time T3 of each step of the Z axis stepper motor:

[0025]

[0026] Among them, L3 is the movement distance of the Z axis, and h is the movement step length of a pulse;

[0027] Then, a fine interpolation algorithm is performed 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 the three motion axes X, Y, and Z, and divides the pulse time of each step of the stepper motor in the coarse interpolation into half to send a high level and the other half to send a low level, which are loaded into each timer to realize timed interruption and control the movement of the stepper motor respectively, ultimately achieving the effect of the fast axis equal to the slow axis, that is, the three axes move and stop at the same time.

[0030] The first step is to collaboratively control the contact capacitance sensor 5 and the droplet observation module 4 to obtain the coordinate points on the printing substrate 10. The specific steps are as follows:

[0031] The working computer controls the X, Y, and Z axes of motion to move vertically and horizontally along the printed substrate 10 through a stepper motor controller, and controls the flash lamp 9 in the droplet observation module 4 to emit light at a set frequency, and the observation camera 8 obtains the relative position of the nozzle of the conductive nozzle 2 and the printed substrate 10; first, the conductive nozzle 2 is brought into contact with the printed substrate 10, and the average value of multiple different position points of the X, Y, and Z axes of motion is controlled to be taken as the reference reference point of the contact capacitance sensor; then the conductive nozzle 2 is lifted, and the X and Y axes of motion are controlled to move to one point along the printed substrate 10, and the Z axis height is lowered. When the nozzle of the conductive nozzle 2 contacts the substrate 10, the contact capacitance sensor 5 is sampled. The sampling value differs from the reference value by ±500, which can be used as a marking point. The coordinates of the X, Y, and Z axes of motion are recorded. The sampling formula of the contact capacitance sensor 5 is as follows:

[0032]

[0033] In the formula, f sensor is the input frequency of a channel of the contact capacitance sensor, f ref is the reference frequency of the contact capacitance sensor;

[0034] The measurement of the remaining coordinate points is completed in this way.

[0035] The specific method of the second step is:

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

[0037] Z=X×b1+Y×b2+b3 2-1

[0038] In the formula, X, Y, Z 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 coefficient is sent to the stepper motor controller through the serial port of the working computer. After the stepper motor controller analyzes the compensation coefficients b1, b2, and b3, it modifies the height compensation coefficient in the stepper motor controller and obtains the actual Z-axis motion height through the compensation calculation formula:

[0040] b3=X×b1+Y×b2 2-2

[0041] Z=z+b3 2-3

[0042] Among them, Z is the actual movement height and z is the command height.

[0043] The specific method of the third step is:

[0044] Set specific motion instructions and high-voltage control instructions G12 XYZ F r dw pb for the working computer, G12 represents on-demand point printing, X, Y, Z are the motion displacement coordinates of the three axes, F represents the overall motion speed of the printing device, r, d, w, p, b are the parameter values ​​of the pulse waveform of the high-voltage power supply, r represents the rising edge time, d represents the voltage duration, w represents the transition time, p represents the peak voltage, and b represents the bias voltage; send it to the main control board through the serial port, and convert the acquired pulse waveform parameter values ​​r, d, w, p, b through the ADC module to output a 0~±10V DC low-voltage waveform signal; and control the high-voltage power supply to output a 0~±3kV DC high-voltage waveform signal, and load the waveform signal on the conductive nozzle 2. At the same time, the stepper motor controller calculates the Δz that needs to be compensated in real time according to the motion displacement coordinates of X, Y, Z of the motion instruction and the height compensation coefficient in the stepper motor controller, and the X, Y, Z three-axis motion mechanism is linked to achieve the synergy of printing and height compensation; the specific process is as follows:

[0045] First, according to the X, Y, and Z axis target positions X1, Y1, Z1 and the compensation coefficients b1 and b2, the compensation formula for errorz is calculated:

[0046] errorz=X1×b1+Y1×b2 3-1

[0047] Z=errorz+Z1 3-2

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

[0049] The specific method for judging whether the movement of the three motion axes XYZ reaches the printing position is:

[0050] The entire motion trajectory of the printing substrate 10 is divided into many points, 0 represents that this point is not printed, and 1 represents that this point is to be printed, and then 0 or 1 is attached 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 do mapping processing, and use PO to represent the normalized value of the current interpolation progress, RC to represent the real-time interpolation steps, AC to represent the total interpolation steps, PI to represent the normalized value of the number of image rows, PRC to represent the current number of rows, and PAC to represent the total number of rows. The formula is as follows:

[0051]

[0052] According to the comparison between the current interpolation progress normalized value PO and the normalized value of the number of image rows PI, if PO is greater than PI, the high voltage power supply is controlled to print.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] 1. Due to the installation error of the electrofluid printing platform, the machining error of the printing substrate and the installation error, the height control error of the nozzle from the substrate can reach 100-500 microns. The present invention controls the XYZ three-axis motion of the printing platform 3 by adopting a multi-axis linkage linear interpolation algorithm, so that the height of the nozzle from the substrate can be controlled at 0.8-1 microns, which reduces the electric field intensity fluctuation of the electrostatic field and greatly improves the stability and consistency of electrofluid printing. The printing experiment in Figure 4 shows that the droplet size printed on demand by the electrofluid is consistent, which verifies the feasibility of active leveling.

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

[0056] 3. The present invention solves the motion compensation coefficient of each axis in the XYZ three-axis motion mechanism of the printing platform 3 according to the substrate surface fitting algorithm, and sends the obtained compensation coefficient 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 flat substrate.

[0057] In summary, in order to achieve more accurate measurement of position points on the substrate, the present invention adopts a contact capacitive sensor 5 and an observation camera to capture the position points on the substrate 10; each moving axis uses an independent timer to send pulses to reduce speed fluctuations to a certain extent, and finally achieve the synchronization of multi-axis motion (moving and stopping at the same time), avoiding the compensation lag of the Z-axis height. When moving to the specified position, the Z-axis also completes the compensation at the same time and prints on demand. In this way, the stability and consistency of printing can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0059] Figure 2 It is a device connection diagram of the present invention.

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

[0061] FIG4 is a diagram showing the printing results of the printing experiment of the method of the present invention, wherein FIG4(a) is a high-precision printing without satellite droplets; FIG4(b) is a large-area printing on demand; and FIG4(c) is a printing of the Xidian University school emblem on demand.

[0062] Figure 5 It is a flow chart of the leveling method of the present invention.

[0063] In the figure: 1. support, 2. conductive nozzle, 3. printing platform, 4. droplet observation module, 5. contact measurement module, 6. camera support, 7. observation fixture, 8. observation camera; 9. flash; 10. substrate. DETAILED DESCRIPTION

[0064] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0065] See also Figure 1 , Figure 2, an active leveling device for on-demand printing of an electrofluid substrate, comprising 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 the 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 for observing the process of droplet ejection of the printing platform 3 during the printing of the printing substrate 10; the working computer stores a control interface for generating G instruction codes and sending G instructions through path planning, the signal connection end of the working computer is connected to the data transmission end 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 motion of the printing platform 3, the observation of 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 droplet 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 output data from a working computer through a serial port, processes and converts the data, and outputs a 0-±10v waveform signal. The high-voltage power supply is controlled to output a corresponding 0-±3kV waveform signal. The positive electrode of the high-voltage power supply is connected to the metal wire of the conductive nozzle 2, and the negative electrode is connected to the wire of the printing substrate 10.

[0067] The printing platform 3 adopts an XYZ three-axis motion mechanism, and the XYZ three-axis motion mechanism is driven by a stepper motor on its respective moving trajectory. The stepper motor controller of the main control board is connected to the working computer through a signal line, and the stepper motor controller of each motion axis uses an independent timer to send pulses; the path planning stored in the working computer generates a G instruction code as a high-voltage control instruction G12 XYZ F rd wp b, wherein G12 represents on-demand point printing, X, Y, and Z are respectively 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 respectively the parameter values ​​of the pulse waveform of the high-voltage power supply.

[0068] A conductive nozzle 2 perpendicular to the printed substrate 10 is installed above the printed substrate 10 through a support 1, and the conductive nozzle 2 contains a conductive metal wire. A contact capacitance sensor 5 for capturing a position point on the printed substrate is installed on one side of the conductive nozzle 2; a signal receiving terminal at one end of the contact capacitance sensor 5 is connected to the metal wire in the conductive nozzle 2 through a differential line, and a signal receiving terminal at the other end is connected to the wire of the printed substrate 10 through a differential line.

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

[0070] A leveling method for an active leveling device for electrofluidic on-demand printing of substrates, see Figure 5 , the specific steps are as follows:

[0071] In the first step, a multi-axis linear interpolation algorithm is used to control the X, Y, and Z axis motions of the printing platform 3 through a stepper motor controller, and the contact capacitance sensor 5 and the droplet observation module 4 are coordinated to obtain the coordinate points on the printing substrate 10;

[0072] In the second step, the coordinate points obtained in the first step are input into the working computer, and the motion compensation coefficients of each axis in the XYZ three-axis motion mechanism of the printing platform 3 are solved according to the substrate surface fitting algorithm, and 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] In the third step, the working computer sends specific motion instructions through the serial port, and the path planning stored in the working computer generates the G instruction code, namely the high-voltage control instruction (G12 XYZ F rd wp b) to the stepper motor controller, the droplet observation module, and the ADC module. The stepper motor controller parses the motion instructions to obtain the specific movement displacement of the X, Y, and Z axes, and solves the compensation height Δz in real time. The ADC module parses the printing instructions, and finally realizes 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 use a stepper motor, the time difference between adjacent pulses within 5us will not cause speed fluctuations, so the interpolation algorithm is needed to achieve simultaneous movement and stopping of each motion axis.

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

[0076] First, according to the displacement of the X, Y, and Z axes, the longest axis is determined and set as L. F1 is the movement speed of the longest axis.

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

[0078]

[0079] Among them, L1 is the movement distance of the X axis, and h is the movement step length of a pulse;

[0080] Insert the movement of the Y axis into the X axis, calculate the number of interpolation times N2 of the Y axis and the pulse time T2 of each step of the Y axis stepper motor:

[0081]

[0082] Among them, L2 is the movement distance of the Y axis, and h is the movement step length of a pulse;

[0083] Insert the movement of the Z axis into the X axis, calculate the number of interpolation times N3 of the Z axis and the pulse time T3 of each step of the Z axis stepper motor:

[0084]

[0085]

[0086] Among them, L3 is the movement distance of the Z axis, and h is the movement step length of a pulse;

[0087] Then, a fine interpolation algorithm is performed 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 the three motion axes X, Y, and Z, and divides the pulse time of each step of the stepper motor in the coarse interpolation into half to send a high level and the other half to send a low level, which are loaded into each timer to realize timed interruption and control the movement of the stepper motor respectively, ultimately achieving the effect of the fast axis equal to the slow axis, that is, the three axes move and stop at the same time.

[0090] Each motion axis uses an independent timer to send pulses, which reduces speed fluctuations to a certain extent and ensures the accuracy of coordinate acquisition.

[0091] The first step is to collaboratively control the contact capacitance sensor 5 and the droplet observation module 4 to obtain the coordinate points on the printing substrate 10. The specific steps are as follows:

[0092] The working computer controls the XYZ motion axis to move vertically and horizontally along the printing substrate 10 through the stepper motor controller, and controls the flash lamp 9 in the droplet observation module 4 to emit light according to the set frequency, and the observation camera 8 obtains the relative position of the nozzle of the conductive nozzle 2 and the substrate 10; first, the conductive nozzle 2 is brought into contact with the printing substrate 10, and the XYZ motion is controlled to obtain the average value at multiple different positions as the reference reference point of the capacitive sensor; then the conductive nozzle 2 is lifted, and the X and Y motion axes are controlled to move to one point along the printing substrate 10, and the Z axis height is lowered. When the nozzle of the conductive nozzle 2 contacts the substrate 10, the contact capacitive sensor 5 is sampled. The sampling value differs from the reference value by ±500, which can be used as a marking point to record the coordinates of the XYZ motion axis. The sampling formula of the contact capacitive sensor 5 is as follows:

[0093]

[0094] In the formula, f sensor is the input frequency of a channel of the contact capacitance sensor, f ref is the reference frequency of the contact capacitance sensor;

[0095] The remaining coordinate points are measured in the same way. We use a 28-bit capacitive sensor. This measurement method can control the error to less than 1um. The specific relationship is as follows: Figure 1 shown.

[0096] The specific method of the second step is:

[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 of the X-axis, Y-axis and Z-axis are calculated according to the acquired coordinate points. The specific compensation coefficient calculation formula is as follows:

[0098] Z=X×b1+Y×b2+b3 2-1

[0099] In the formula, X, Y, Z 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 coefficient is sent to the stepper motor controller through the serial port of the working computer. After the stepper motor controller analyzes the compensation coefficients b1, b2, and b3, it modifies the height compensation coefficient in the stepper motor controller and obtains the actual Z-axis motion height through the compensation calculation formula:

[0101] b3=X×b1+Y×b2 2-2

[0102] Z=z+b3 2-3

[0103] Among them, Z is the actual movement height and z is the command height. Figure 3 Schematic diagram of substrate plane leveling compensation.

[0104] The specific method of the third step is:

[0105] Set specific motion instructions and high-voltage control instructions G12 XYZF rdwpb for the working computer, G12 represents on-demand point printing, X, Y, Z are the motion displacement coordinates of the three axes, F represents the overall motion speed of the printing device, r, d, w, p, b are the parameter values ​​of the pulse waveform of the high-voltage power supply, r represents the rising edge time, d represents the voltage duration, w represents the transition time, p represents the peak voltage, and b represents the bias voltage; send it to the main control board through the serial port, and convert the acquired pulse waveform parameter values ​​r, d, w, p, b through the ADC module to output a 0~±10V DC low-voltage waveform signal; and control the high-voltage power supply to output a 0~±3kV DC high-voltage waveform signal, and load the waveform signal on the conductive nozzle 2. At the same time, the stepper motor controller calculates the Δz that needs to be compensated in real time according to the motion displacement coordinates of X, Y, Z of the motion instruction and the height compensation coefficient in the stepper motor controller, and the X, Y, Z three-axis motion mechanism is linked to achieve the synergy of printing and height compensation; the specific process is as follows:

[0106] First, according to the X, Y, and Z axis target positions X1, Y1, Z1 and the compensation coefficients b1 and b2, the compensation formula for errorz is calculated:

[0107] errorz=X1×b1+Y1×b2 3-1

[0108] Z=errorz+Z1 3-2

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

[0110] The specific judgment method is:

[0111] The condition for the conductive nozzle 3 to spray is to map to the entire spatial distance in a linear manner, and the entire motion trajectory of the printing substrate 10 is divided into many points. 0 represents that this point is not sprayed, and 1 represents that this point is to be sprayed. Then 0 or 1 is attached 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 do mapping processing, using PO to represent the normalized value of the current interpolation progress, RC to represent the real-time interpolation steps, AC to represent the total interpolation steps, PI to represent the normalized value of the number of image rows, PRC to represent the current number of rows, and PAC to represent the total number of rows. The formula is as follows:

[0112]

[0113] According to the current interpolation progress normalization value PO and the normalization value of the number of image rows, PI is compared. If PO is greater than PI, the high voltage power supply is controlled to print. Each motion axis uses an independent timer to send pulses to reduce speed fluctuations to a certain extent, and finally achieve the synchronization of multi-axis motion (moving and stopping at the same time), avoiding the Z-axis height compensation lag. When moving to the specified position, the Z-axis also completes the compensation at the same time and prints on demand. In this way, the stability and consistency of printing can be guaranteed.

[0114] It can be seen from the printing experiment of Figure 4 that: Figure 4(a) shows that the droplets printed on demand by the electrofluid are of uniform size, reducing 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 current problems of poor stability and consistency in electrofluid printing, and verifying the feasibility of the active leveling of the present invention.

[0115] Figure 3 It can be seen from the leveling compensation and printing steps that this method gets rid of the limitations of traditional mechanical leveling. The core leveling method of this method is not limited to this printing device. In other printing devices, higher-precision leveling can also be achieved. The present invention reduces the cost of traditional mechanical leveling and improves the leveling accuracy of electrofluid printing equipment. It can be adjusted in real time without cumulative errors.

[0116] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. An electrofluidic on-demand printing substrate active leveling device, characterized in that: The invention comprises a mobile printing platform (3), a droplet observation module (4), a working computer and a main control board, wherein a printing substrate (10) is installed on the top of the printing platform (3); the printing platform (3) is used for printing an electric fluid on the printing substrate (10) on demand; the droplet observation module (4) is used for observing the process of droplet ejection by the printing platform (3) during the printing process of the printing substrate (10); the working computer stores a control interface for generating G instruction codes for path planning and sending G instructions; the signal connection end of the working computer is connected to the data transmission end 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 motion 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 electrofluidic on-demand printing substrate active leveling device according to claim 1, characterized in that: The main control board integrates a stepper motor controller, a droplet 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 output data from a working computer through a serial port, processes and converts the data, and outputs a 0-±10v waveform signal. The high-voltage power supply is controlled to output a corresponding 0-±3kV waveform signal. The positive electrode of the high-voltage power supply is connected to the metal wire of the conductive nozzle 2, and the negative electrode is connected to the wire of the printing substrate (10); The printing platform 3 adopts an XYZ three-axis motion mechanism, and the XYZ three-axis motion mechanism is driven by a stepper motor on its respective moving trajectory. The stepper motor controller of the main control board is connected to the working computer through a signal line, and the stepper motor controller of each motion axis uses an independent timer to send pulses; the path planning stored in the working computer generates a G instruction code as a high-voltage control instruction G12 XYZF rdwpb, wherein 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.

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

4. The electrofluidic on-demand printing substrate active leveling device according to claim 1, characterized in that: The micro-droplet observation module (4) comprises a camera support seat (6) installed on one side of the printing platform (3) and a flash light support seat (7) installed on the other side; an observation camera (8) is clamped on the camera support seat (6) by a clamp, and a flash light (9) is clamped on the flash light support seat (7) by a clamp; the signal transmission ends of the observation camera (8) and the flash light (9) are connected to the working computer through signal lines for process observation of micro-droplet ejection during the electro-fluid on-demand printing process.

5. A leveling method for an electrofluidic on-demand printing substrate active leveling device 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 three-axis motion of the printing platform (3) through a stepper motor controller using a multi-axis linkage linear interpolation algorithm, and coordinately control the contact capacitance sensor (5) and the droplet observation module (4) to obtain the coordinate points on the printing substrate (10); In the second step, the coordinate points obtained in the first step are input into the working computer, and the motion compensation coefficients of each axis in the XYZ three-axis motion mechanism of the printing platform (3) are solved according to the substrate surface fitting algorithm, and 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; In the third step, the working computer sends specific motion instructions through the serial port, and the path planning stored in the working computer generates the G instruction code, namely the high-voltage control instruction (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 instructions to obtain the specific movement displacement of the X, Y, and Z axes, and solves the compensation height Δz in real time. The ADC module parses the printing instructions, and finally realizes real-time leveling and printing.

6. The leveling method of the electrofluidic on-demand printing substrate active leveling device according to claim 5, characterized in that: The multi-axis linkage linear interpolation algorithm described in the first step includes a rough interpolation algorithm and a fine interpolation algorithm; the specific rough interpolation algorithm is as follows: First, according to the displacement of the X, Y, and Z axes, the longest axis is determined and set as L. F1 is the movement speed of the longest axis. When the longest displacement axis in the motion is the X-axis, the number of interpolation times N1 of the X-axis and the pulse time T1 of each pulse step of the X-axis stepper motor are: Among them, L1 is the movement distance of the X axis, and h is the movement step length of a pulse; Insert the movement of the Y axis into the X axis, calculate the number of interpolation times N2 of the Y axis and the pulse time T2 of each step of the Y axis stepper motor: Among them, L2 is the movement distance of the Y axis, and h is the movement step length of a pulse; Insert the movement of the Z axis into the X axis, calculate the number of interpolation times N3 of the Z axis and the pulse time T3 of each step of the Z axis stepper motor: Among them, L3 is the movement distance of the Z axis, and h is the movement step length of a pulse; Then, a fine interpolation algorithm is performed 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 the three motion axes X, Y, and Z, and divides the pulse time of each step of the stepper motor in the coarse interpolation into half to send a high level and the other half to send a low level, which are loaded into each timer to realize timed interruption and control the movement of the stepper motor respectively, ultimately achieving the effect of the fast axis equal to the slow axis, that is, the three axes move and stop at the same time.

7. The leveling method of the electrofluidic on-demand printing substrate active leveling device according to claim 5, characterized in that: The first step of collaboratively controlling the contact capacitance sensor (5) and the droplet observation module (4) to obtain the coordinate points on the printing substrate (10) is as follows: The working computer controls the X, Y, and Z movement axes to move vertically and horizontally along the printing substrate (10) through a stepper motor controller, and controls the flash lamp (9) in the droplet observation module (4) to emit light according to a set frequency, and the observation camera (8) obtains 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 X, Y, and Z movement axes are controlled to obtain an average value at multiple different position points as a reference reference point of the contact capacitance sensor; then, the conductive nozzle (2) is lifted, and the X, Y movement axes are controlled to move to one point along the printing substrate (10), and the Z axis height is lowered. When the nozzle of the conductive nozzle (2) contacts the substrate (10), the contact capacitance sensor (5) performs sampling. The sampling value differs from the reference value by ±500, which can be used as a marking point. The coordinates of the X, Y, and Z movement axes are recorded. The sampling formula of the contact capacitance sensor 5 is as follows: In the formula, f sensor is the input frequency of a channel of the contact capacitance sensor, f ref is the reference frequency of the contact capacitance sensor; The measurement of the remaining coordinate points is completed in this way.

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

9. The leveling method of the electrofluidic on-demand printing substrate active leveling device according to claim 5, characterized in that: The specific method of the third step is: The working computer is set with specific motion instructions and high-voltage control instructions G12 XYZF rdwpb, 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, r, d, w, p, and b are the parameter values ​​of the pulse waveform of the high-voltage power supply, r represents the rising edge time, d represents the voltage duration, w represents the transition time, p represents the peak voltage, and b represents the bias voltage; the instructions are sent to the main control board through the serial port, and the acquired pulse waveform parameter values ​​r, d, w, p, and b are processed and converted by the ADC module to 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, and the waveform signal is loaded on the conductive nozzle (2); at the same time, the stepper motor controller calculates the Δz that needs to be compensated in real time according to the motion displacement coordinates of X, Y, and Z of the motion instructions and the height compensation coefficient in the stepper motor controller, and the X, Y, and Z three-axis motion mechanisms are linked to achieve the synergy of printing and height compensation; the specific process is as follows: First, according to the X, Y, and Z axis target positions X1, Y1, Z1 and the compensation coefficients b1 and b2, the compensation formula for errorz is calculated: errorz=X1×b1+Y1×b2 3-1 Z=errorz+Z1 3-2 Secondly, after obtaining the actual X, Y, Z axis target positions X1, Y1, Z1, the pulse time of the three axes is obtained according to the first step of the multi-axis linkage linear interpolation algorithm, and the timers of the three motion axes of X, Y, and Z are called to realize pulse sending, and at the same time determine whether the three motion axes of X, Y, and Z have reached the printing position.

10. The leveling method of the electrofluidic on-demand printing substrate active leveling device according to claim 9, characterized in that: The specific method for judging whether the movement of the three motion axes XYZ reaches the printing position is: The entire motion trajectory of the printing substrate (10) is divided into a plurality of points, 0 represents that this point is not to be printed, and 1 represents that this point is to be printed, and then 0 or 1 is attached to the end of the g code command sent by the working computer, and sent to the main control board through the working computer. After receiving the command, the main control board will perform mapping processing, and use PO to represent the normalized value of the current interpolation progress, RC to represent the real-time interpolation steps, AC to represent the total interpolation steps, PI to represent the normalized value of the number of image rows, PRC to represent the current number of rows, and PAC to represent the total number of rows. The formula is as follows: According to the comparison between the current interpolation progress normalized value PO and the normalized value of the number of image rows PI, if PO is greater than PI, the high voltage power supply is controlled to print.

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