CN110370648B - Multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system and method - Google Patents
Multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system and method Download PDFInfo
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 96
- 238000000034 method Methods 0.000 title claims abstract description 29
- 238000010146 3D printing Methods 0.000 title claims abstract description 21
- 239000007788 liquid Substances 0.000 claims abstract description 94
- 239000007921 spray Substances 0.000 claims abstract description 60
- 238000001514 detection method Methods 0.000 claims abstract description 23
- 238000005507 spraying Methods 0.000 claims description 29
- 239000003990 capacitor Substances 0.000 claims description 21
- 238000013016 damping Methods 0.000 claims description 19
- 238000002347 injection Methods 0.000 claims description 9
- 239000007924 injection Substances 0.000 claims description 9
- 238000004364 calculation method Methods 0.000 claims description 8
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- 230000002159 abnormal effect Effects 0.000 claims description 5
- 230000003068 static effect Effects 0.000 claims description 3
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- 238000004458 analytical method Methods 0.000 claims description 2
- 238000010521 absorption reaction Methods 0.000 claims 1
- 230000000694 effects Effects 0.000 description 12
- 238000007639 printing Methods 0.000 description 7
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- 239000000463 material Substances 0.000 description 2
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- 238000000465 moulding Methods 0.000 description 2
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/30—Auxiliary operations or equipment
- B29C64/386—Data acquisition or data processing for additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/30—Auxiliary operations or equipment
- B29C64/386—Data acquisition or data processing for additive manufacturing
- B29C64/393—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y50/00—Data acquisition or data processing for additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y50/00—Data acquisition or data processing for additive manufacturing
- B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
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- Optics & Photonics (AREA)
- Ink Jet (AREA)
Abstract
The invention discloses a multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system and method, which comprises a nozzle driving circuit, a multichannel gating circuit, a piezoelectric signal acquisition circuit and a monitoring unit, wherein the nozzle driving circuit is used for providing a driving signal to enable a piezoelectric nozzle to jet; the multichannel gating circuit is used for providing multichannel alternate gating signals to realize alternate monitoring of the multiple spray holes of the piezoelectric nozzle; the piezoelectric signal acquisition circuit acquires residual vibration signals in a flow passage cavity of the piezoelectric nozzle in a self-induction detection mode; the monitoring unit comprises a driving voltage monitoring module, a liquid viscosity monitoring module, an ink supply pressure monitoring module and a liquid drop ejection speed calculating module and is used for monitoring the working state of the piezoelectric nozzle. The invention can effectively identify the fault type and the cause, improve the monitoring accuracy and facilitate the user to adopt effective measures; meanwhile, an external sensor is not needed, and the hardware cost is reduced in a mode of alternate monitoring; the monitoring can be carried out in the working process of the spray head, and the monitoring flexibility is improved.
Description
Technical Field
The invention belongs to the technical field of advanced manufacturing, and particularly relates to a multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system and method.
Background
3D printing is a revolutionary manufacturing process that has evolved from the mid-nineties of the last century. Based on the principle of material accumulation molding, the method starts from a three-dimensional CAD model of a part, carries out discretization slicing and layering processing on the model, then manufactures two-dimensional data layer by layer and finally accumulates the two-dimensional data into a three-dimensional entity, and realizes the molding and manufacturing of workpieces. The micro-droplet jetting technology is widely applied to 3D printing, however, as the nozzle belongs to a precise device, jetting faults such as over-limit of driving voltage, high viscosity plug, imbalance of ink supply pressure and the like are easily caused, the faults can only be found under ink observation equipment at present, a large amount of time is required for maintaining the nozzle, and the printing quality is seriously influenced.
At present, the research for detecting the spray state of the spray head at home and abroad comprises:
(1) the method comprises the steps that a residual vibration signal in a nozzle flow channel cavity is extracted by utilizing a self-induction mode of a piezoelectric nozzle to analyze, and a variance algorithm is adopted to detect the spraying state of the nozzle;
(2) the Hangzhou electronic science and technology university carries out image acquisition of ink drop ejection through a CCD high-speed camera, extracts ink drop forms by using an area growing method, and calculates the speed and the volume of ink drops.
The above method has the following problems: specific fault types cannot be effectively identified, and corresponding measures are not facilitated to be taken; detection can only be carried out at a fixed position, and the detection efficiency is influenced.
Disclosure of Invention
The invention aims to solve the technical problem that the defects in the prior art are overcome, and the system and the method for identifying the fault and monitoring the state of the multi-channel piezoelectric 3D printing nozzle can effectively identify the fault type, calculate the speed of liquid drops, improve the detection accuracy, detect the nozzle in the printing motion process, are not limited by the position of the nozzle, and greatly improve the detection flexibility.
The invention adopts the following technical scheme:
a multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system comprises a nozzle driving circuit, a multichannel gating circuit, a piezoelectric signal acquisition circuit and a monitoring unit, wherein the nozzle driving circuit is used for providing a driving signal to enable a piezoelectric nozzle to jet; the multichannel gating circuit is used for providing multichannel alternate gating signals to realize alternate monitoring of the multiple spray holes of the piezoelectric nozzle; the piezoelectric signal acquisition circuit acquires residual vibration signals in a flow passage cavity of the piezoelectric nozzle in a self-induction detection mode; the monitoring unit comprises a driving voltage monitoring module, a liquid viscosity monitoring module, an ink supply pressure monitoring module and a liquid drop ejection speed calculating module and is used for monitoring the working state of the piezoelectric nozzle.
Specifically, the piezoelectric signal acquisition circuit comprises a spray head circuit and an equivalent circuit, and the equivalent circuit comprises a divider resistor R2Equivalent capacitance C with the nozzleeThe nozzle circuit comprises a voltage dividing resistor R1And static capacitance C of the nozzlepAnd C isp＝Ce，R1＝R2Input drive voltage VinDivided into two paths, one path passes through a resistor R2And a capacitor CeGrounded, the other path is through a resistor R1And a capacitor CpVoltage V at capacitor end in grounding, equivalent circuit2And voltage V at capacitor end in spray head circuit1Output signal V processed by piezoelectric signal acquisition circuitoutAnd the data acquisition system is connected with the data acquisition system and is used for outputting a final result.
The piezoelectric signal acquisition circuit is divided into two paths, one path is connected with the multichannel gating switch and used for extracting the voltage of a spray head capacitor end in the spray head circuit, and the other path is connected with an equivalent capacitor C in the equivalent circuitneThe remote ground end of the equivalent circuit is connected and used for extracting the end voltage of the equivalent capacitor in the equivalent circuit; the multi-channel gating switch receives the gating signal and is connected with the multi-orifice spray head.
Further, the equivalent circuit comprises a voltage dividing resistor RrAnd an equivalent capacitance CneSelf-induced voltage signal V of the nth nozzlenEquivalent voltage signal V of equivalent circuitrProcessed by a piezoelectric signal acquisition circuit to obtain an output signal VnoutThe data acquisition system is connected with the data acquisition system and used for outputting a final result; input voltage V provided by drive signal generatorninA voltage dividing resistor R divided into two paths, one path passes through the measured orifice circuitnAnd the back of the spray hole circuit is grounded and is used for leading the spray of the spray head to generate a self-induction signal VnThe other path is through a divider resistor R of an equivalent circuitrAnd equivalent capacitance CneRear ground for transmissionOutput an equivalent voltage signal VrAnd R isr＝Rn。
The invention also provides a fault identification and state monitoring method of the multichannel piezoelectric type 3D printing nozzle, which comprises the steps of converting residual vibration signals in a piezoelectric nozzle runner cavity into voltage signals by using a multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system in a self-induction detection mode, acquiring and analyzing the voltage signals to obtain corresponding characteristic parameters when a fault occurs, establishing an algorithm model between an injection fault and the characteristic parameters and between a liquid drop speed and the characteristic parameters, and indicating that the fault occurs when the characteristic parameters corresponding to all factors in a driving voltage monitoring module, a liquid viscosity monitoring module, an ink supply pressure monitoring module and a liquid drop injection speed calculation module exceed a threshold value.
Specifically, the driving voltage monitoring is judged by taking a sharp angle amplitude in a self-induction signal as a characteristic parameter, the sharp angle amplitude is the first sharp angle amplitude of the collected self-induction signal, a certain selected spray hole is sprayed through a spray head driving circuit, a piezoelectric signal collecting circuit and a data collecting system are adopted to extract and collect a pressure wave signal in a piezoelectric spray head flow channel cavity, when the spray head driving voltage is too small, the liquid drop spraying speed is lower than a normal value or the driving voltage is too large, so that satellite liquid drops are generated around main liquid drops, an indicator lamp corresponding to the driving voltage is lightened, and the liquid drop spraying fault caused by the voltage is indicated.
Specifically, the monitoring of the liquid viscosity is judged by taking a damping ratio in a self-induction signal as a characteristic parameter, the damping ratio is obtained by calculating an attenuation damping ratio of collected residual vibration at the tail of the self-induction signal, a certain selected spray hole is sprayed by a spray head driving circuit, a piezoelectric signal collecting circuit and a data collecting system are adopted to extract and collect pressure wave signals in a flow channel cavity of the piezoelectric spray head, and when the viscosity of the sprayed liquid is too high, the liquid drop spraying speed is lower than a normal value or the liquid drop viscosity is very low, so that a liquid column at the tail of a main liquid drop is long, an indicator lamp corresponding to the liquid viscosity is lightened, and the liquid drop spraying fault caused by the viscosity is indicated.
Specifically, the ink supply pressure monitoring is judged by taking a phase in a self-induction signal as a characteristic parameter, the phase is obtained by calculating the phase of the collected self-induction signal, a nozzle driving circuit is used for jetting a selected nozzle, a piezoelectric signal collecting circuit and a data collecting system are used for extracting and collecting pressure wave signals in a flow channel cavity of the piezoelectric nozzle, when the ink supply pressure is too small, liquid drops are gathered in the nozzle and cannot be jetted, or when the ink supply pressure is too large, air bubbles sucked into the nozzle and cannot be jetted, an indicator light corresponding to the ink supply pressure is lightened, and the liquid drop jetting failure caused by the pressure is indicated.
Specifically, the liquid drop spraying speed calculation scheme is obtained by calculating a regression model, a certain selected spraying hole is sprayed through a spraying head driving circuit, a piezoelectric signal acquisition circuit and a data acquisition system are adopted to extract and acquire pressure wave signals in a piezoelectric spraying head flow passage cavity, when the spraying condition is within a normal range, the normal spraying state is indicated, and the spraying speed of the liquid drops is reflected through the speed value calculated by the regression model.
Further, the characteristic value judging step is as follows:
s1, reading the piezoelectric signal, and sequentially judging the amplitude characteristic value of the time domain sharp angle, the characteristic value of the residual vibration damping ratio and the frequency domain phase characteristic value;
s2, when the characteristic value of the amplitude of the sharp angle of the time domain, the characteristic value of the residual vibration damping ratio and the characteristic value of the phase of the frequency domain are normal, calculating the speed of the liquid drop and ending;
and S3, when any one of the characteristic value of the time domain sharp angle amplitude, the characteristic value of the residual vibration damping ratio and the characteristic value of the frequency domain phase is abnormal, directly ending.
Compared with the prior art, the invention has at least the following beneficial effects:
the invention relates to a multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system, which adopts a time-sharing multiplexing detection scheme, realizes the alternate detection of multiple spray holes by designing a multichannel gating circuit, greatly reduces the hardware cost and the circuit power consumption, simultaneously ensures the detection efficiency, can convert a tiny pressure wave signal in a piezoelectric nozzle flow channel cavity into a self-induction voltage signal for extraction and analysis, improves the detection accuracy, can detect in the nozzle printing motion process, is not limited by the position of a nozzle, and greatly improves the detection flexibility.
Furthermore, the whole size of the detection circuit is small, the piezoelectric effect of the piezoelectric nozzle is utilized, an additional sensor is not needed, the detection circuit is convenient to install on the nozzle for monitoring, the detection circuit can be further packaged inside the nozzle, and technical support is provided for manufacturing of the piezoelectric nozzle.
The invention also discloses a fault identification and state monitoring method for the multichannel piezoelectric type 3D printing nozzle, which can simultaneously detect fault factors such as driving voltage, liquid viscosity, ink supply pressure and the like when the nozzle is abnormally sprayed, and when the spraying fault occurs due to one or more factors, the corresponding state indication reflects, so that the fault category can be effectively identified, and a user can take treatment measures in time; the liquid drop spraying speed can be calculated when the spray head sprays normally, and a user can optimize the spraying parameters conveniently to control the liquid drop spraying speed within a proper range.
Furthermore, whether the injection fault caused by the driving voltage overrun exists or not is directly judged by monitoring the size of the driving voltage, and a user is reminded to adjust the driving voltage. For example, when the ejection voltage is too small, the density of the 3D printed part is affected because the droplet velocity and volume are small due to insufficient driving force, and when the ejection voltage is too large, the resolution of the 3D printed part is reduced because a part of micro droplets are generated around the droplets due to too large driving force.
Furthermore, whether the ejection fault caused by the liquid viscosity discomfort exists or not is directly judged by monitoring the size of the liquid viscosity, and a user is reminded to eject by adopting liquid with proper viscosity. For example, when the viscosity of the liquid is too high, the nozzle may be blocked and not ejected, and when the viscosity of the liquid is too low, the tail of the main droplet may have a long liquid column, and finally, the surface of the printing medium may have droplet spread.
Furthermore, whether an injection fault caused by abnormal ink supply pressure exists or not is directly judged by monitoring the size of the ink supply pressure, and a user is reminded to adjust the ink supply pressure. For example, when the ink supply pressure is too low, the ink droplets may be extruded and hung on the surface of the nozzle holes and finally fall on the printing medium to damage the printed surface, and when the ink supply pressure is too high, air may be sucked into the nozzle holes to disorder the ejected ink droplets.
Furthermore, the real-time speed of the liquid drops is obtained through calculation of the characteristic parameters, the spray head does not need to be moved to a specific position for observation, the measurement time and space are saved, the measurement process is simplified, and meanwhile, a user can adjust corresponding process parameters through a real-time speed monitoring result to realize optimal control of the speed of the liquid drops.
Furthermore, the states of the driving factors and the speeds of the liquid drops are obtained by calculating and comparing and judging the characteristic values, and when any index is abnormal, the corresponding state indicator lamp is immediately lightened to remind a user of the occurrence of a corresponding fault.
In summary, the present invention provides a system and a method for identifying a fault and monitoring a state of a multi-channel piezoelectric 3D printing nozzle, which extract a self-induced signal from the inside of the nozzle by using a self-induced detection method without using an additional sensor, and calculate and determine a characteristic parameter of the self-induced signal to obtain an ejection state of the nozzle. The fault type and the cause can be effectively identified, the monitoring accuracy is improved, and the user can conveniently adopt effective measures; meanwhile, an external sensor is not needed, the problem of inconvenience in sensor installation is solved, and the hardware cost is reduced in a mode of alternate monitoring; the monitoring can be carried out in the working process of the spray head, the spray head is not restricted by the position of the spray head, and the monitoring flexibility is improved.
The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.
Drawings
FIG. 1 is a schematic diagram of a piezoelectric signal acquisition circuit for converting a pressure wave signal in a flow channel of a piezoelectric nozzle into an electrical signal in a self-induction manner;
FIG. 2 is a schematic diagram of a multi-channel rotation monitoring circuit;
FIG. 3 is a diagram of self-induced signals collected using a piezoelectric signal collection circuit and a data collection system;
FIG. 4 is a flow chart of the spray status monitoring of the spray head;
FIG. 5 is a schematic view of condition monitoring based on regression model and algorithm development;
FIG. 6 is a graph showing the effect of monitoring insufficient driving voltage resulting in too low droplet velocity;
FIG. 7 is a graph showing the effect of monitoring the drop velocity that is too low due to the high viscosity of the liquid;
fig. 8 is a graph showing the monitoring effect of the ink supply pressure negative pressure being too small to cause the liquid droplets to be accumulated on the surface of the nozzle hole.
Detailed Description
The invention provides a multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system and method. Compared with the traditional injection state monitoring mode based on video, the invention can realize the monitoring of the injection state of the spray head in the moving and printing process of the spray head without being limited by the position of the spray head; meanwhile, the invention realizes the state monitoring of the multiple spray holes by adopting an alternate monitoring mode, thereby greatly reducing the hardware cost, improving the detection efficiency and further ensuring the working stability and reliability of the printing head.
The invention relates to a fault identification and state monitoring system for a multichannel piezoelectric type 3D printing nozzle, which comprises a nozzle driving circuit, a multichannel gating circuit, a piezoelectric signal acquisition circuit and a monitoring unit, wherein the nozzle driving circuit is used for providing a driving signal to enable the piezoelectric nozzle to jet; the multichannel gating circuit is used for providing multichannel alternate gating signals to realize the scheme of alternately monitoring the multiple spray holes of the piezoelectric nozzle; the piezoelectric signal acquisition circuit acquires residual vibration signals in a flow passage cavity of the piezoelectric nozzle in a self-induction detection mode; the monitoring unit is used for presenting the state detection result of the piezoelectric nozzle to a user.
Referring to FIG. 1, the piezoelectric signal collecting circuit includesA spray head circuit and an equivalent circuit, the equivalent circuit comprises a divider resistor R2Equivalent capacitance C with the nozzleeThe nozzle circuit comprises a voltage dividing resistor R1And static capacitance C of the nozzlepAnd C isp＝Ce，R1＝R2Input drive voltage VinDivided into two paths, one path passes through a resistor R2And a capacitor CeGrounded, the other path is through a resistor R1And a capacitor CpVoltage V at capacitor end in grounding, equivalent circuit2And voltage V at capacitor end in spray head circuit1Output signal V processed by piezoelectric signal acquisition circuitoutAnd the data acquisition system is connected with the data acquisition system and is used for outputting a final result.
Referring to fig. 2, the multi-channel gating circuit includes an equivalent circuit, a driving signal generator, a multi-channel gating switch and a multi-orifice nozzle, the piezoelectric signal collecting circuit is divided into two paths, one path is connected to the multi-channel gating switch for extracting the voltage of the nozzle capacitor terminal in the nozzle circuit, and the other path is connected to the equivalent capacitor C in the equivalent circuitneThe remote end of the equivalent circuit is connected and used for extracting the end voltage of the equivalent capacitor in the equivalent circuit; the multi-channel gating switch receives the gating signal and is connected with the multi-orifice spray head.
The equivalent circuit comprises a voltage dividing resistor RrAnd an equivalent capacitance CneSelf-induced voltage signal V of the nth nozzlenEquivalent voltage signal V of equivalent circuitrProcessed by a piezoelectric signal acquisition circuit to obtain an output signal VnoutThe data acquisition system is connected with the data acquisition system and used for outputting a final result; input voltage V provided by drive signal generatorninA voltage dividing resistor R divided into two paths, one path passes through the measured orifice circuitnAnd the back of the spray hole circuit is grounded and is used for leading the spray of the spray head to generate a self-induction signal VnThe other path is through a divider resistor R of an equivalent circuitrAnd equivalent capacitance CneRear ground for outputting equivalent voltage signal VrAnd R isr＝Rn。
Wherein, thFor single channel strobe duration, tsThe interval time for gating adjacent channels can be set by setting thAdjustable single-way valveThe strobe time.
The monitoring unit comprises a driving voltage monitoring module, a liquid viscosity monitoring module, an ink supply pressure monitoring module and a liquid drop ejection speed calculating module.
The working principle of the invention is as follows:
1. piezoelectric materials have a piezoelectric effect, which allows piezoelectric plates to act as both actuators and sensors in a showerhead system.
2. When the piezoelectric plate is used as a sensor, the internal current of the piezoelectric plate comprises two parts, namely current generated by charge and discharge effects and current generated by residual pressure waves through the piezoelectric effect.
3. The jet state of the nozzle can affect the residual pressure wave and further affect the current inside the piezoelectric plate, so the current of the piezoelectric plate is collected to analyze the jet state of the nozzle.
4. The differential characteristics of the self-induction detection circuit are used to extract the current generated by the pressure wave and convert it into a voltage signal.
5. And collecting and analyzing the self-induced voltage signal, and establishing an algorithm model between the jetting fault and the characteristic parameter and between the droplet speed and the characteristic parameter.
6. Based on the model, the development state monitoring system monitors the spray state of the spray head and identifies the spray failure.
Referring to fig. 4, a method for identifying a fault and monitoring a state of a multi-channel piezoelectric 3D printing nozzle includes converting a residual vibration signal in a flow channel cavity of the piezoelectric nozzle into a voltage signal in a self-induction detection mode, collecting and analyzing the voltage signal to obtain a characteristic parameter corresponding to the fault, establishing an algorithm model between an ejection fault and the characteristic parameter and between a droplet speed and the characteristic parameter, and turning on an alarm lamp when the characteristic parameter corresponding to each factor in a driving voltage monitoring module, a liquid viscosity monitoring module, an ink supply pressure monitoring module and a droplet ejection speed calculation module exceeds a set threshold.
The driving voltage monitoring scheme is characterized in that a sharp angle amplitude in a self-induction signal is used as a characteristic parameter for judgment, the sharp angle amplitude is the first sharp angle amplitude of the collected self-induction signal, and when the sharp angle amplitude exceeds a set threshold value, the driving voltage is considered to cause an injection fault;
the liquid viscosity monitoring scheme is characterized in that the damping ratio in the self-induction signal is used as a characteristic parameter to judge, the damping ratio is obtained by calculating the damping ratio of the attenuation of the residual vibration at the tail of the collected self-induction signal, the calculation method is the amplitude ratio of adjacent wave crests or wave troughs, and when the damping ratio exceeds a set threshold value, the liquid viscosity is considered to cause the ejection fault;
the ink supply pressure monitoring scheme is characterized in that the phase in the self-induction signal is used as a characteristic parameter to be judged, the phase is obtained by calculating the phase corresponding to the second-order frequency of the collected self-induction signal, and when the phase exceeds a set threshold, the ink supply pressure is considered to cause the ejection fault;
the droplet ejection speed calculation scheme is obtained by regression model calculation.
The liquid drop spraying speed is calculated by a regression model established among all characteristic parameters, the regression model is obtained based on experimental data fitting and basically consistent with a dynamic model of the piezoelectric spray head spraying process, the experimental factors are driving voltage, liquid viscosity and ink supply pressure, and the dependent variable is the liquid drop speed.
The eigenvalues are judged as follows:
reading a piezoelectric signal, and sequentially judging a time domain sharp angle amplitude characteristic value, a residual vibration damping ratio characteristic value and a frequency domain phase characteristic value;
when the amplitude characteristic value of the time domain sharp angle, the characteristic value of the residual vibration damping ratio and the frequency domain phase characteristic value are normal, respectively calculating the liquid drop speed and then finishing;
and when the amplitude characteristic value of the sharp angle of the time domain, the characteristic value of the residual vibration damping ratio and the characteristic value of the phase of the frequency domain are abnormal, the method is finished directly.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of the embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In one example, a nozzle driving circuit is used for spraying a selected nozzle, a piezoelectric signal acquisition circuit and a data acquisition system are used for extracting and acquiring pressure wave signals in a piezoelectric nozzle flow channel cavity, and when the driving voltage of the nozzle is too low, the liquid drop spraying speed is lower than a normal value, or the driving voltage is too high, so that satellite liquid drops are generated around main liquid drops, a voltage indicator lamp on a monitoring software interface is on at the moment, and liquid drop spraying faults caused by voltage are indicated.
In one example, a nozzle driving circuit is used for jetting a selected nozzle, a piezoelectric signal acquisition circuit and a data acquisition system are used for extracting and acquiring pressure wave signals in a piezoelectric nozzle flow channel cavity, and when the viscosity of jetted liquid is too high, the jetting speed of liquid drops is lower than a normal value or the viscosity of the liquid drops is very low, so that a liquid column at the tail of a main liquid drop is long, a viscosity indicator lamp on a monitoring software interface is on, and the phenomenon that the liquid drop jetting fault is caused by the viscosity is indicated.
In one example, a nozzle driving circuit is used for jetting a selected nozzle, a piezoelectric signal acquisition circuit and a data acquisition system are used for extracting and acquiring pressure wave signals in a piezoelectric nozzle flow channel cavity, when ink supply pressure negative pressure is too small, liquid drops are gathered in the nozzle and cannot be jetted, or when ink supply pressure negative pressure is too large, air bubbles are sucked into the nozzle and cannot be jetted, pressure indicating lamps on a monitoring software interface are all lightened, and liquid drop jetting faults caused by pressure are indicated.
In one example, a selected spray hole is sprayed through a spray head driving circuit, a piezoelectric signal acquisition circuit and a data acquisition system are adopted to extract and acquire pressure wave signals in a piezoelectric spray head flow passage cavity, when the spraying conditions are within a normal range, indicator lamps of all factors on a monitoring software interface are normal at the moment, the normal spraying state is indicated, meanwhile, the spraying speed of liquid drops can be reflected through a speed value calculated through a regression model, the calculated speed value is basically consistent with an actual value measured by an ink observation device, and the state monitoring software can effectively calculate the liquid drop speed.
In one example, a nozzle with 16 nozzle holes is sprayed by a nozzle driving circuit and a multi-channel gating circuit in turn, a piezoelectric signal acquisition circuit is adopted to acquire residual vibration signals in a flow channel cavity, and the liquid drop spraying speed of each nozzle hole is calculated by monitoring software, so that the liquid drop speed monitoring of the multiple nozzle holes can be realized.
Referring to fig. 5, a state monitoring software interface developed based on a regression model and an algorithm includes modules of serial port configuration, sampling setting, waveform display, monitoring state result display, etc., and the interface can directly and effectively display the cause of the ejection failure of the nozzle and the speed of liquid drops during normal ejection;
in fig. 6 to 8, the left side is a monitoring interface, the right side black dots are real-time images of droplets collected by an ink observing device, and the droplet speed can be measured to perform comparison verification on the monitoring effect of the present invention, the ink observing device is a miwatch device of minjie, in the state of hough, the droplet position is closer to the upper part, the droplet speed is lower, when the droplet speed is lower than a reference value, an ejection failure is considered to occur, and the reference speed is set to 5m/s in the present invention.
Referring to fig. 6, for the monitoring effect of the insufficient driving voltage causing the too low droplet speed, the driving voltage is artificially reduced to make the droplet speed become 4.49m/s, which is the fault state, and the state indicator light variable corresponding to the driving voltage at this time represents the fault caused by the driving voltage;
referring to fig. 7, for the monitoring effect of the liquid viscosity being greater and causing the speed of the liquid drop to be too low, the high-viscosity liquid drop is replaced to be ejected, the speed of the liquid drop measured by the ink observing device is 2.88m/s, that is, the liquid drop is in a fault state, and at this time, the indicator light corresponding to the liquid viscosity is turned on to indicate the fault caused by the viscosity of the ejected liquid;
referring to fig. 8, in order to monitor the effect that the ink supply pressure is too high and the liquid drops are accumulated on the surface of the nozzle, the ink supply pressure is artificially increased to cause the liquid drops to be accumulated on the surface of the nozzle, which is a failure state, and at this time, the indicator light variable corresponding to the ink supply pressure indicates a failure caused by the ink supply pressure.
The monitoring effects of fig. 6-8 show that when an actual ejection failure occurs, the invention can immediately remind a user that the nozzle fails and can effectively identify the type of the failure, thereby avoiding blind processing.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (8)
1. A fault identification and state monitoring method for a multichannel piezoelectric type 3D printing nozzle is characterized in that a self-induction detection mode is adopted to convert residual vibration signals in a flow channel cavity of the piezoelectric nozzle into voltage signals for collection and analysis to obtain corresponding characteristic parameters when a fault occurs, an algorithm model between an injection fault and the characteristic parameters and between a liquid drop speed and the characteristic parameters is established, and the fault occurs when the characteristic parameters corresponding to all factors in a driving voltage monitoring module, a liquid viscosity monitoring module, an ink supply pressure monitoring module and a liquid drop injection speed calculation module exceed a threshold value;
the driving voltage monitoring is judged by taking a sharp angle amplitude in a self-induction signal as a characteristic parameter, the sharp angle amplitude is the first sharp angle amplitude of the collected self-induction signal, a certain selected spray hole is sprayed by a spray head driving circuit, a piezoelectric signal collecting circuit and a data collecting system are adopted to extract and collect a pressure wave signal in a flow channel cavity of a piezoelectric spray head, and when the spray head driving voltage is too small to cause that the liquid drop spraying speed is lower than a normal value or the driving voltage is too large to cause that satellite liquid drops are generated around a main liquid drop, an indicator lamp corresponding to the driving voltage is lightened, which indicates that the liquid drop spraying fault is caused by the voltage;
the monitoring of the liquid viscosity is judged by taking a damping ratio in a self-induction signal as a characteristic parameter, the damping ratio is obtained by calculating an attenuation damping ratio of collected residual vibration at the tail of the self-induction signal, a certain selected spray hole is sprayed by a spray head driving circuit, a piezoelectric signal collecting circuit and a data collecting system are adopted to extract and collect pressure wave signals in a flow channel cavity of the piezoelectric spray head, and when the viscosity of the sprayed liquid is too high, the liquid drop spraying speed is lower than a normal value or the liquid drop viscosity is very low, so that a liquid column at the tail of a main liquid drop is long, an indicator lamp corresponding to the liquid viscosity is lightened, and the liquid drop spraying fault caused by the viscosity is indicated.
2. The method as claimed in claim 1, wherein the monitoring of the ink supply pressure is determined by using a phase in the self-induced signal as a characteristic parameter, the phase is calculated from the phase of the collected self-induced signal, the nozzle driving circuit is used for ejecting a selected nozzle, the piezoelectric signal collecting circuit and the data collecting system are used for extracting and collecting a pressure wave signal in the flow channel cavity of the piezoelectric nozzle, when the ink supply pressure is too low to cause the accumulation of liquid drops in the nozzle to fail to eject or when the ink supply pressure is too high to cause the absorption of air bubbles in the nozzle to fail to eject, an indicator light corresponding to the ink supply pressure is turned on to indicate that the liquid drop ejection failure is caused by the pressure.
3. The method of claim 1, wherein the calculation scheme of the droplet ejection speed is obtained by a regression model, a selected nozzle is ejected by the nozzle driving circuit, a piezoelectric signal acquisition circuit and a data acquisition system are used for extracting and acquiring pressure wave signals in the piezoelectric nozzle flow channel cavity, when the ejection condition is within a normal range, the piezoelectric nozzle flow channel cavity is indicated to be in a normal ejection state, and the speed value calculated by the regression model reflects the ejection speed of the droplet.
4. The method according to claim 1, 2 or 3, wherein the characteristic value judging step is as follows:
s1, reading the piezoelectric signal, and sequentially judging the amplitude characteristic value of the time domain sharp angle, the characteristic value of the residual vibration damping ratio and the frequency domain phase characteristic value;
s2, when the characteristic value of the amplitude of the sharp angle of the time domain, the characteristic value of the residual vibration damping ratio and the characteristic value of the phase of the frequency domain are normal, calculating the speed of the liquid drop and ending;
and S3, when any one of the characteristic value of the time domain sharp angle amplitude, the characteristic value of the residual vibration damping ratio and the characteristic value of the frequency domain phase is abnormal, directly ending.
5. The multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system is characterized in that the multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring method of claim 1 is adopted, and the multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring method comprises a nozzle driving circuit, a multichannel gating circuit, a piezoelectric signal acquisition circuit and a monitoring unit, wherein the nozzle driving circuit is used for providing a driving signal to enable a piezoelectric nozzle to jet; the multichannel gating circuit is used for providing multichannel alternate gating signals to realize alternate monitoring of the multiple spray holes of the piezoelectric nozzle; the piezoelectric signal acquisition circuit acquires residual vibration signals in a flow passage cavity of the piezoelectric nozzle in a self-induction detection mode; the monitoring unit comprises a driving voltage monitoring module, a liquid viscosity monitoring module, an ink supply pressure monitoring module and a liquid drop ejection speed calculating module and is used for monitoring the working state of the piezoelectric nozzle.
6. The system of claim 5, wherein the piezoelectric signal acquisition circuit comprises a nozzle circuit and an equivalent circuit, and the equivalent circuit comprises a voltage dividing resistor R2Equivalent capacitance C with the nozzleeThe nozzle circuit comprises a voltage dividing resistor R1And static capacitance C of the nozzlepAnd C isp＝Ce，R1＝R2Input drive voltage VinDivided into two paths, one path passes through a resistor R2And a capacitor CeGrounded, the other path is through a resistor R1And a capacitor CpVoltage V at capacitor end in grounding, equivalent circuit2And voltage V at capacitor end in spray head circuit1Output signal V processed by piezoelectric signal acquisition circuitoutConnected with data acquisition system for outputting final dataAnd (6) obtaining the result.
7. The multi-channel piezoelectric type 3D printing nozzle fault identification and state monitoring system as claimed in claim 5, wherein the multi-channel gating circuit comprises an equivalent circuit, a driving signal generator, a multi-channel gating switch and a multi-orifice nozzle, the piezoelectric signal acquisition circuit is divided into two paths, one path is connected with the multi-channel gating switch and used for extracting the terminal voltage of a nozzle capacitor in the nozzle circuit, and the other path is connected with an equivalent capacitor C in the equivalent circuitneThe remote ground end of the equivalent circuit is connected and used for extracting the end voltage of the equivalent capacitor in the equivalent circuit; the multi-channel gating switch receives the gating signal and is connected with the multi-orifice spray head.
8. The system of claim 7, wherein the equivalent circuit comprises a voltage divider resistor RrAnd an equivalent capacitance CneSelf-induced voltage signal V of the nth nozzlenEquivalent voltage signal V of equivalent circuitrProcessed by a piezoelectric signal acquisition circuit to obtain an output signal VnoutThe data acquisition system is connected with the data acquisition system and used for outputting a final result; input voltage V provided by drive signal generatorninA voltage dividing resistor R divided into two paths, one path passes through the measured orifice circuitnAnd the back of the spray hole circuit is grounded and is used for leading the spray of the spray head to generate a self-induction signal VnThe other path is through a divider resistor R of an equivalent circuitrAnd equivalent capacitance CneRear ground for outputting equivalent voltage signal VrAnd R isr＝Rn。
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| CN201910592645.1A CN110370648B (en) | 2019-07-03 | 2019-07-03 | Multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system and method |
| PCT/CN2020/098572 WO2021000798A1 (en) | 2019-07-03 | 2020-06-28 | Fault identification and state monitoring system and method for multi-channel piezoelectric 3d printing spray head |
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| CN110370648B (en) * | 2019-07-03 | 2020-07-28 | 西安交通大学 | Multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system and method |
| US11717910B2 (en) * | 2020-11-03 | 2023-08-08 | General Electric Company | Monitoring operation of electron beam additive manufacturing with piezoelectric crystals |
| CN114179518B (en) * | 2021-11-25 | 2023-01-06 | 华南理工大学 | Micro-pressure electric spray head based on iris turbofan and nozzle aperture adjusting and controlling method |
| CN115014590B (en) * | 2022-06-16 | 2023-10-20 | 东华大学 | Piezoelectric sensor and preparation method thereof |
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| CN204398329U (en) * | 2014-11-27 | 2015-06-17 | 成都瑞途电子有限公司 | A kind of nozzle temperature monitoring alarm for 3D printer |
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| US5784279A (en) * | 1995-09-29 | 1998-07-21 | Bpm Technology, Inc. | Apparatus for making three-dimensional articles including moving build material reservoir and associated method |
| US9623605B2 (en) * | 2012-09-12 | 2017-04-18 | International Business Machines Corporation | Thermally cross-linkable photo-hydrolyzable inkjet printable polymers for microfluidic channels |
| US20160039148A1 (en) * | 2014-08-05 | 2016-02-11 | Delaware Capital Formation, Inc. | 3-d printer having motion sensors |
| CN105881898B (en) * | 2016-04-05 | 2018-04-10 | 北京恒创增材制造技术研究院有限公司 | A kind of new type colorful printing head |
| CN105861308B (en) * | 2016-04-13 | 2018-03-02 | 西安交通大学 | The cell 3D printing device and method that a kind of more droplets precisely spray |
| CN110370648B (en) * | 2019-07-03 | 2020-07-28 | 西安交通大学 | Multichannel piezoelectric type 3D printing nozzle fault identification and state monitoring system and method |
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| CN204398329U (en) * | 2014-11-27 | 2015-06-17 | 成都瑞途电子有限公司 | A kind of nozzle temperature monitoring alarm for 3D printer |
Non-Patent Citations (2)
| Title |
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| Inkjet jet failures and their detection using piezo self-sensing;Kye-Si Kwon, Yun-Sik Choi. et al;《Sensors and Actuators A: Physical》;20131031;335-341 * |
| Low-cost and high speed monitoring system for a multi-nozzle piezo inkjet head;Kye-Si Kwon, Yun-Sik Choi. et al;《Sensors and Actuators A: Physical》;20120731;154-165 * |
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