Fish-eye terminal anti-crystal slag precision stamping processing control method

Abstract

The invention relates to a fisheye terminal crystal slag prevention precision stamping machining control method. The method comprises the steps that a friction volt potential standard response is established based on a mold of a pre-machined micro-nano structure; a transient friction volt potential is collected in real time by using a suspension ground potential technology; a dynamic differential capacitance spectrum of the lubricating oil film is collected, and the molecular orientation order degree is analyzed; performing time sequence correlation analysis on the potential variation characteristic and the dispersion characteristic, and judging that the phase is a microscopic nucleation stage of the crystal slag when the polarity is detected to be overturned and the order degree is dropped; and the electrostatic minimal quantity lubrication system is triggered, and the charged oil mist is driven by a high-gradient electrostatic field induced by the micro-nano structure to be adsorbed to the friction hot spots in a targeted mode. The method has the advantages that the microcosmic early warning of crystal slag nucleation is realized, and self-aligned targeted lubrication is achieved.

Description

Technical Field

[0001] This application relates to the field of precision machining, and in particular to a precision stamping control method for preventing crystal slag formation in fisheye terminals. Background Technology

[0002] As a key precision component in connectors, fisheye terminals, with their unique gradient thickness elastic arm and rounded inner corner structure, place high precision demands on the stamping process. During high-speed continuous stamping production, continuous mechanical friction and plastic deformation occur between the die and the indium-plated layer. Because indium metal is relatively soft and prone to adhesion, poor lubrication or microscopic defects on the die surface can easily lead to metal lattice breakage at the contact interface, inducing tiny metal chips, or slag. The formation of slag not only scratches the die surface but also adheres to the conductive contact surface of the terminal, causing unstable contact resistance and even electrical failure.

[0003] Existing stamping die monitoring technologies primarily focus on capturing macroscopic physical quantities, such as monitoring heat accumulation through temperature sensors, analyzing mechanical impact through vibration sensors, or detecting material fracture signals using acoustic emission technology. However, changes in these physical quantities are often delayed, typically only being detected by the system when slag has already formed and accumulated to a certain extent, causing significant temperature increases or abnormal vibrations in the die. By this time, irreversible physical damage may have already occurred on the die surface, making early identification and intervention difficult during the microscopic nucleation stage of slag formation. Furthermore, single-dimensional monitoring signals are easily interfered with by machine tool environmental noise, making it difficult to accurately distinguish between normal process fluctuations and early fault symptoms.

[0004] Furthermore, in terms of lubrication control, traditional timed and metered oil injection or flooding lubrication methods are ill-suited to the complex geometry of fisheye terminals. Lubricating oil mist struggles to effectively overcome resistance and penetrate to the root of gradually thickening areas or minute rounded corner regions, resulting in these high-stress concentration areas frequently being under-lubricated and becoming areas prone to crystal slag formation. Existing control methods lack the ability to perceive the microscopic state of the lubricating oil film in real time, and cannot dynamically adjust lubrication strategies based on the orderliness of the oil film molecular arrangement or the electron transfer activity at the contact interface. Summary of the Invention

[0005] In order to characterize the contact state in real time at the electronic and molecular microscopic level and realize an adaptive targeted lubrication control method, this application provides a precision stamping control method for preventing crystal slag formation in fisheye terminals.

[0006] This application provides a precision stamping processing control method for preventing crystal slag formation in fisheye terminals, which adopts the following technical solution:

[0007] A method for controlling the precision stamping process of fisheye terminals to prevent crystal slag formation, used in the processing of fisheye terminals, the method comprising the following steps:

[0008] S1. During the trial stamping stage, the standard response of the tribovoltaic potential of the interface between the pre-processed indium plating layer on the fisheye terminal and the stamping die during plastic deformation is obtained based on normal stamping conditions. The surface of the fisheye forming insert of the stamping die is pre-processed with micro-nano structures. The micro-nano structures are used to increase the contact specific surface area to enhance the signal-to-noise ratio of the tribovoltaic effect at the contact interface, and to construct a non-uniformly distributed high-gradient electrostatic field in the friction contact area. The transient tribovoltaic potential is used to characterize the electron-hole pair separation state caused by the deformation of the metal lattice.

[0009] S2. During the stamping stage, the die-terminal electrical circuit is configured to a floating ground potential measurement mode to collect the transient triboelectric potential generated by the stamping die and the fisheye terminal in real time.

[0010] S3. During the mold closing and downward movement stages and the bottom dead center holding pressure stage, a frequency sweep signal of a preset frequency band is continuously applied to the mold-terminal electrical circuit to acquire the dynamic differential capacitance spectrum of the lubricating oil film to obtain its dispersion characteristics and to resolve the molecular orientation order; wherein, the mold-terminal electrical circuit is a conductive circuit composed of the stamping mold and the fisheye terminal;

[0011] S4. Within the bottom dead center holding window before the end of a single stamping stroke, the transient triboelectric potential is compared with the standard response of the triboelectric potential to extract and identify potential change features; the potential change features are correlated with the dispersion characteristics obtained in the current bottom dead center holding stage. When the potential change feature corresponding to the stamping stroke is detected to show polarity reversal and the molecular orientation order degree drops to the preset molecular orientation order degree threshold, it is determined to be the micro-nucleation stage of slag derived from coating lattice breakage.

[0012] S5. Based on the discrimination results of the micro-nucleation stage of crystal slag, the electrostatic micro-lubrication system is triggered to spray lubricating oil mist with specific polar charges into the forming area. The high gradient electrostatic field induced by the micro-nano structure in the area of ​​severe friction drives the lubricating oil mist to migrate autonomously along the electric field lines and preferentially adsorb to the friction hot spot area with the highest potential.

[0013] Optionally, the fisheye terminal has a gradually thickened elastic arm structure and rounded inner wall corners; the triboelectric potential standard response obtained in step S1 is determined based on the specific potential waveform characteristics excited by the non-uniform stress distribution gradient and specific plastic deformation rate generated by the gradually thickened elastic arm structure during plastic deformation; the specific potential waveform characteristics are different from the potential response of a cantilever beam structure with uniform thickness.

[0014] Optionally, S2 includes:

[0015] S21. Electrically isolate the lower die base of the stamping die from the main body of the press by using insulating ceramic material, and establish the die-terminal electrical circuit;

[0016] S22. Control the multiplexer to switch the mold-terminal electrical circuit to the differential charge acquisition channel, using the non-working area of ​​the stamping mold as the reference ground potential, and acquire the differential charge signal between the fisheye molding insert and the fisheye terminal's gradually thickened elastic arm structure based on the differential charge amplifier; wherein, the differential charge amplifier is installed on the insulating sidewall of the lower mold base and moves synchronously with the mold;

[0017] S23. Determine the region where the gradual thickness elastic arm structure undergoes maximum plastic deformation, use the differential mode charge signal to characterize the electron escape behavior induced by high strain rate in this region, and after filtering out the common mode electromagnetic interference generated by the operation of the punch press, convert the processed differential mode charge signal into the transient triboelectric potential.

[0018] Optionally, for stamping cold start conditions, the method further includes the following steps:

[0019] During the stamping stage, the control power module applies a DC bias voltage between the stamping die and the fisheye terminal;

[0020] The DC bias voltage induces a dielectric wetting effect, which reduces the contact angle of the cold lubricating oil on the surface of the fisheye molded insert; wherein, the contact angle refers to the angle between the tangent of the liquid-gas interface of the lubricating oil droplet and the solid-liquid interface of the fisheye molded insert.

[0021] The input circuit of the mold-terminal electrical circuit is configured to be AC ​​coupling mode. The DC component of the DC bias voltage is isolated by the DC blocking capacitor and the power supply ripple interference is filtered out. Only the AC component of the transient triboelectric potential superimposed on the DC bias voltage is extracted as the basis for the S4 comparison.

[0022] The DC bias voltage is maintained until the lubricating oil overcomes the surface tension under the drive of the electric field force and spreads and penetrates into the root of the gradually thickened fisheye terminal and the micro-gap of the inner wall rounded corner.

[0023] Optionally, S3 includes:

[0024] S31. Control the multiplexer to switch the mold-terminal electrical circuit to the high-frequency impedance analysis channel, continuously injecting frequency range coverage. Hz to A frequency sweep signal with a preset frequency band of Hz is used to measure the current response of the high-frequency impedance analysis channel and calculate the dynamic differential capacitance spectrum.

[0025] S32. Decompose the acquired dynamic differential capacitance spectrum into real capacitance and imaginary capacitance, and construct a complex capacitance plane trajectory feature that reflects the evolution of real capacitance and imaginary capacitance with frequency using real capacitance as the abscissa and imaginary capacitance as the ordinate.

[0026] S33. Extract the polarization intensity intercept difference of the complex capacitor plane trajectory feature on the real axis as the dispersion characteristic, wherein the polarization intensity intercept difference is used to characterize the degree of polarization response hysteresis of the lubricating oil film under frequency sweep electric field excitation.

[0027] S34. Calculate the dielectric loss peak of the imaginary capacitance as a function of frequency, and extract the frequency domain response bandwidth of the dielectric loss peak, wherein the frequency domain response bandwidth corresponds to the half-width at half maximum (WHM) of the dielectric loss peak.

[0028] S35. Based on the Boltzmann distribution function, establish a mapping model between the frequency domain response bandwidth and the dispersion of oil film molecular arrangement, and normalize the reciprocal of the frequency domain response bandwidth to obtain the molecular orientation order; wherein, the narrower the frequency domain response bandwidth, the more consistent the arrangement of oil film molecules under pressure holding state, and the higher the molecular orientation order.

[0029] S3 further includes:

[0030] S301. Extract the data segment of the dynamic differential capacitance spectrum during the downward phase of the closing mode, and establish a space charge distribution characteristic curve that reflects the nonlinear relationship between the reciprocal square of the lubricating oil film capacitance and the bias voltage;

[0031] S302. Extract the linear region slope and voltage axis intercept of the space charge distribution characteristic curve, use the linear region slope to analyze the charge carrier concentration in the lubricating oil film, and combine it with the built-in potential determined by the voltage axis intercept to calculate the physical thickness of the charge depletion layer in the lubricating oil film as the effective space charge region width through Poisson equation inversion.

[0032] S303. When it is detected that the width of the effective space charge region decreases exponentially to a preset nanometer threshold and the dynamic differential capacitance spectrum shows negative capacitance characteristics, it is determined that the lubricating oil film is about to undergo quantum tunneling breakdown, and S5 is forcibly triggered before the stamping die and the fisheye terminal make physical contact.

[0033] Optionally, S4 includes:

[0034] S41. Within the pressure holding window at the bottom dead center before the end of a single stamping stroke, the transient triboelectric potential and the standard response of the triboelectric potential are compared in the time domain, and the deviation between the two is extracted as the potential variation feature.

[0035] S42. The potential change characteristics are correlated with the dispersion characteristics of the dynamic differential capacitance spectrum obtained in the current lower dead point holding stage, and the causal relationship between the two is analyzed.

[0036] S43. Synchronously read the data from the fiber optic probe arranged in the non-contact area of ​​the mold, wherein the fiber optic probe is used to collect the photon count released at the interface between the stamping mold and the fisheye terminal during plastic deformation.

[0037] S44. Only when the potential change characteristic is detected to be a polarity reversal, the molecular orientation order drops to a preset order threshold, and the instantaneous value of the triboluminescence photon count corresponding to the indium oxide energy level transition wavelength is simultaneously detected to exceed three times the standard deviation of the environmental background photon count baseline, is it confirmed to be the micro-nucleation stage of the slag, so as to exclude the false positive signal of potential caused by the piezoelectric effect.

[0038] Optionally, S5 includes:

[0039] S51. Monitor the residual surface potential of the stamping die surface in real time;

[0040] S52. When the residual surface potential is detected to exceed the preset saturation threshold, it is determined that an electrostatic shielding field has been formed on the surface of the stamping die, wherein the electrostatic shielding field will hinder the adsorption of subsequent charged oil mist;

[0041] S53. Control the polarity of the high-voltage generator of the electrostatic micro-lubrication system to reverse, spraying lubricating oil mist with a charge opposite to the current residual surface potential polarity to neutralize the accumulated charge on the surface of the stamping die, thereby eliminating the electrostatic shielding field and maintaining the continuous targeted adsorption capacity; wherein, the high-voltage generator is used to generate a high-voltage electrostatic field at the nozzle, causing the flowing lubricating oil mist droplets to carry an electrostatic charge of a specific polarity through corona discharge or inductive electrification effect.

[0042] Optionally, S5 further includes:

[0043] S501. Real-time acquisition of the punching frequency data of the stamping die and the pneumatic stagnation pressure at the moment of die closure;

[0044] S502. The stroke frequency and the aerodynamic stagnation pressure are weighted and evaluated. When the evaluation result exceeds the preset wind barrier threshold, it is determined that there is an aerodynamic wind barrier that hinders continuous spray adsorption in the current working condition.

[0045] S503. In response to the determination result, the output mode of the electrostatic micro-lubrication system is switched from continuous spray to high-pressure pulse injection mode;

[0046] S504. Control the high-pressure generator to apply a pulsed electric field between the nozzle and the stamping die, and adjust the charging frequency of the oil mist droplets to maintain synchronous resonance with the frequency of the pulsed electric field;

[0047] S505. The peak electric field intensity of the pulsed electric field is used to generate a transient electric field force, which drives the oil mist particles to gain kinetic energy that exceeds the resistance of the closed airflow of the mold, so that the oil mist particles penetrate the aerodynamic wind barrier with a ballistic trajectory and bombard the surface of the stamping mold.

[0048] In summary, this application includes at least one of the following beneficial technical effects:

[0049] 1. This method abandons traditional lagging monitoring methods based on macroscopic physical quantities (such as crack acoustic waves and temperature rise), such as acoustic emission or thermal imaging, and establishes a correlation between tribovoltaic potential and microscopic lattice deformation. By acquiring interface electron transfer signals in real time through levitation ground potential technology, it can issue early warnings at the microsecond level when the metal lattice just breaks and electron bonds break (i.e., the slag nucleation stage). This allows for the detection of potential problems thousands of stamping cycles earlier than traditional methods, solving the problem of slag being scrapped as soon as it is detected.

[0050] 2. Perform time-series correlation analysis on the dynamic signals of the stamping stage and the quasi-static signals of the bottom dead center holding stage. Use the polarity reversal of the dynamic potential as a suspected signal and the orderly drop of the static oil film as a confirmation signal. Use spatiotemporal coupling logic to eliminate occasional interference (such as electromagnetic noise or mechanical vibration) of a single signal.

[0051] 3. Addressing the challenges of lubrication due to the gradual thickness and rounded corners of fisheye terminals, this application utilizes pre-fabricated micro / nano structures to induce a high-gradient electrostatic field at friction hotspots (high potential points), coupled with an electrostatic micro-lubrication system to emit charged oil mist. This mechanism leverages Coulomb force to drive the lubricant along the electric field lines, actively overcoming capillary resistance and precisely adsorbing it onto the most severely worn areas, achieving self-aligned targeted lubrication without mechanical positioning. Furthermore, special control strategies designed for cold starts (electrowetting-assisted spreading) and high-speed stamping (pulse electric field ballistic penetration) ensure the lubrication system remains highly efficient and reliable even under extreme operating conditions. Attached Figure Description

[0052] Figure 1 A schematic diagram of a fisheye terminal is shown in one embodiment of the present invention.

[0053] Figure 2 A flowchart illustrating a precision stamping process control method for preventing crystal slag formation in fisheye terminals according to an embodiment of the present invention is shown. Detailed Implementation

[0054] The present application will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the application and are not intended to limit the scope of the application.

[0055] In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of the inventive concept. As part of this specification, some of the accompanying drawings of this disclosure are block diagrams illustrating structures and devices to avoid complicating the disclosed principles. For clarity, not all features of the actual embodiment need to be described. Furthermore, the language used in this disclosure has been primarily chosen for readability and instructional purposes and may not have been chosen to define or limit the subject matter of the invention, thus requiring the necessary claims to determine such inventive subject matter. References to “an embodiment” or “an embodiment” in this disclosure mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment, and multiple references to “an embodiment” or “an embodiment” should not be construed as necessarily referring to the same embodiment.

[0056] Unless explicitly defined, the terms “a,” “an,” and “the” are not intended to refer to a singular entity, but rather to include a general category whose specific examples can be used for illustration. Therefore, the use of the terms “a” or “an” can mean any number of at least one, including “a,” “one or more,” “at least one,” and “one or more.” The term “or” means any of the options and any combination of the options, including all options unless explicitly indicated that the options are mutually exclusive. The phrase “at least one of” when combined with a list of items refers to a single item in the list or any combination of items in the list. The phrase does not require all items listed unless explicitly defined as such.

[0057] Reference Figure 1 Fisheye terminals, as core components in automotive electronics and industrial connectors, are typically made of copper alloy substrates with an indium or tin-indium alloy plating, generally ranging from a few micrometers to tens of micrometers in thickness. This plating primarily provides excellent conductive contact performance and oxidation protection, while utilizing the rheological properties of soft metals to fill microscopic gaps during crimping, reducing contact resistance. The structural features of fisheye terminals include a gradually thickening elastic arm and rounded inner corners. This design aims to provide uniform radial pressure during crimping, ensuring reliable connection.

[0058] The processing of fisheye terminals primarily relies on high-speed precision stamping technology, using multi-station progressive dies to continuously punch, bend, and form metal strips. A single processing cycle, or one complete stroke of the press, can be divided into three key stages based on the slide's trajectory: First, the die-closing and downward movement stage, from the moment the slide leaves the top dead center (0°) until the punch just touches the indium plating layer of the fisheye terminal. During this stage, the die rapidly approaches the workpiece, and as the gap narrows dramatically, the air between the die and the workpiece is intensely compressed and ejected outwards, generating significant aerodynamic effects. Second, the stamping and forming stage, from the moment the punch contacts the material until the slide reaches the bottom dead center (180°). This stage is the core of the processing; the pressure rises sharply, forcing the metal material to undergo intense plastic deformation to form the fisheye structure. The slippage and fracture of the metal lattice lead to significant electron transfer at the contact interface, which is the core window for generating the tribovoltaic potential. Finally, the bottom dead center holding stage, where the slide reaches the bottom of its stroke and pauses briefly before beginning its return stroke (360°). At this stage, the mold and the workpiece are in a relatively static state, the contact pressure reaches its peak, and the lubricating oil film between the interfaces is compressed to its limit thickness. At this time, the electromagnetic environment and mechanical vibration are relatively stable, which is suitable for high-precision static capacitance spectrum measurement.

[0059] During the stamping process, due to the softness and high viscosity of indium metal, the metal lattice on the coating surface is prone to breakage and detachment under intense friction and plastic deformation, forming tiny metal particles, i.e., slag. The main causes of slag formation include dry friction due to insufficient lubrication, mechanical scratching caused by the microscopic roughness of the die surface, and metal softening and adhesion caused by localized high temperatures. Slag is typically in the micrometer range. Although tiny, it is extremely harmful. It not only adheres to the die surface, accelerating die wear, but also remains on the terminal contact surface, leading to unstable contact resistance, signal transmission interruption, and even short circuit failure. The difficulty in preventing slag formation lies in the fact that slag formation often begins at the microscopic nucleation stage, and its location is hidden, making it difficult to detect in time by conventional macroscopic monitoring methods. By the time it is discovered, it often results in the scrapping of a large number of products.

[0060] Therefore, this application proposes a precision stamping control method for preventing crystal slag formation in fisheye terminals. The core of this method lies in constructing a closed-loop control system integrating sensing and control. By pre-setting functional micro / nano structures on the surface of the stamping die, the method utilizes an interface electron transfer mechanism to convert microscopic metal lattice deformation and fracture into a real-time captureable transient potential signal. Simultaneously, it utilizes the electrostatic field characteristics generated by this texture to assist lubrication. Furthermore, this method combines dielectric spectral analysis of the microscopic molecular order of the lubricating oil film, achieving multi-dimensional spatiotemporal fusion discrimination from dynamic triboelectronic signals to static oil film dielectric properties. This enables precise identification of microscopic nucleation signs before macroscopic crystal slag accumulation and triggers electrostatically driven adaptive targeted lubrication, thereby actively suppressing crystal slag defects during precision stamping. Specifically, refer to... Figure 2 The method includes the following steps S1-S5.

[0061] S1. During the trial stamping stage, the standard response of the tribovoltaic potential of the interface between the pre-processed indium plating layer on the fisheye terminal and the stamping die during plastic deformation is obtained based on normal stamping conditions. The surface of the fisheye forming insert of the stamping die is pre-processed with micro-nano structures. The micro-nano structures are used to increase the contact specific surface area to enhance the signal-to-noise ratio of the tribovoltaic effect at the contact interface, and to construct a non-uniformly distributed high-gradient electrostatic field in the friction contact area. The transient tribovoltaic potential is used to characterize the electron-hole pair separation state caused by the deformation of the metal lattice.

[0062] The trial stamping stage refers to a small-batch trial run conducted before formal mass production, using qualified raw materials and standard process parameters. Its purpose is to confirm the mold condition and collect baseline data. The tribovoltaic potential standard response is a waveform characteristic representing a defect-free, normal processing state, recorded during this stage using high-precision measuring equipment. The purpose of establishing this standard response is to provide a reference for subsequent comparisons; any abnormal fluctuations deviating from this reference system may indicate the occurrence of processing defects. This potential response arises from electron transitions at the semiconductor or metal oxide interface during dynamic friction and plastic deformation. Its waveform amplitude and frequency are influenced by contact pressure, deformation rate, and the material's band structure.

[0063] Fisheye forming inserts are core components in stamping dies that directly contact and shape the fisheye terminals. The micro / nano structures pre-processed on their surfaces are typically micron-scale arrays formed by laser etching or chemical etching. From a signal-to-noise ratio perspective, these micro / nano structures significantly increase the microscopic contact surface area between the die and the terminal, allowing more interface atoms to participate in the triboelectric process, thus amplifying the originally weak triboelectric voltaic signal several times and effectively enhancing the signal-to-noise ratio. Without micro / nano structures, the contact area of ​​a smooth surface is limited, resulting in minimal electron transfer and a potential signal often only at the microvolt level, easily drowned out by the electromagnetic noise of machine tool operation, making effective monitoring impossible. From an electrostatic field perspective, the tip effect of the micro / nano structures can create a non-uniformly distributed high-gradient electrostatic field around them, providing a physical basis for subsequent electrostatic adsorption lubrication. The transient tribovoltaic potential can characterize the electron-hole pair separation state because when the metal lattice undergoes severe deformation, the atomic bonds at the grain boundaries break, releasing non-equilibrium charge carriers. These charge carriers separate and move directionally under the influence of the built-in electric field at the interface, forming a transient current. Its macroscopic manifestation is a measurable change in potential. Therefore, the fluctuation of potential directly reflects the severity of lattice deformation and microscopic fracture behavior.

[0064] For example, during the trial stamping stage, this embodiment uses a high-speed precision stamping press with a stamping frequency set to 800 SPM. The standard response of the triboelectric potential between the pre-processed indium plating layer on the fisheye terminal and the stamping die interface during plastic deformation is obtained based on normal stamping conditions. The surface of the fisheye forming insert of the stamping die is pre-processed with micro / nano structures. In this embodiment, these micro / nano structures are fabricated using femtosecond laser etching technology, and their characteristic dimensions are hexagonal array pits with a diameter of 5 μm, a depth of 2 μm, and a spacing of 8 μm.

[0065] Optionally, the fisheye terminal has a gradually thickened elastic arm structure and rounded inner wall corners; the triboelectric potential standard response obtained in step S1 is determined based on the specific potential waveform characteristics excited by the non-uniform stress distribution gradient and specific plastic deformation rate generated by the gradually thickened elastic arm structure during plastic deformation; the specific potential waveform characteristics are different from the potential response of a cantilever beam structure with uniform thickness.

[0066] S2. During the stamping stage, the die-terminal electrical circuit is configured to a floating ground potential measurement mode to collect the transient triboelectric potential generated by the stamping die and the fisheye terminal in real time.

[0067] Floating ground potential measurement technology is a highly sensitive method for extracting weak signals. Its core lies in the electrical isolation between the reference ground potential of the measurement system and the absolute ground potential of the earth. In complex industrial stamping environments, machine tool bodies are usually connected to high-power servo motors, frequency converters, and various control circuits. When these devices are running, they inject extremely strong high-frequency common-mode electromagnetic interference into the machine tool's metal frame (i.e., the earth), with amplitudes often reaching tens of volts.

[0068] If a traditional common-ground measurement method is used, directly connecting the ground wire of the measuring instrument to the machine tool body, then these high-intensity background noises will be directly coupled into the measurement circuit. Since the triboelectric potential to be measured is usually only in the microvolt to millivolt range, this huge difference in magnitude will cause the effective signal to be instantly and completely submerged by the background noise, making it impossible to identify any valuable waveform features. The floating ground potential measurement mode cuts off the conductive connection between the measurement circuit and the machine tool ground through physical isolation, constructing a reference frame independent of the ground. This is similar to the physical principle that "a bird standing on a high-voltage line will not get electrocuted." At this time, the measurement system no longer cares about the absolute voltage of the mold or terminal relative to the ground (even if the voltage contains huge common-mode interference), but focuses on capturing the tiny potential difference between the two floating nodes, the mold and the terminal, thereby achieving high signal-to-noise ratio acquisition of weak triboelectric signals in a strong interference environment.

[0069] Specifically, S2 includes S21-S23.

[0070] S21. Electrically isolate the lower die base of the stamping die from the main body of the press by using insulating ceramic material, and establish the die-terminal electrical circuit.

[0071] In this step, insulating ceramic materials (such as high-purity alumina or zirconia ceramic plates) are selected as the physical barrier medium between the lower die and the press table due to their extremely high volume resistivity and excellent compressive strength. Their primary function is to cut off the charge leakage path, preventing triboelectric charges generated at the die-terminal interface from being directly conducted to the ground through the metal machine tool, ensuring that charges can effectively accumulate on the die surface. Through this electrical isolation, the stamping die, the fisheye terminal, and the external wires connecting them together constitute a single-electrode triboelectric nanogenerator system. In this system, the periodic contact and separation, friction and sliding processes between the fisheye terminal and the die insert drive dynamic changes in the interface electronic potential barrier, thereby driving free electrons to flow back and forth in the external load circuit to balance the interface potential difference, thus constructing a self-driven, suspended contact electrification measurement circuit that reflects the microscopic contact state.

[0072] S22. Control the multiplexer to switch the mold-terminal electrical circuit to the differential charge acquisition channel, using the non-working area of ​​the stamping mold as the reference ground potential, and acquire the differential charge signal between the fisheye molding insert and the fisheye terminal's gradually thickened elastic arm structure based on the differential charge amplifier; wherein, the differential charge amplifier is installed on the insulating sidewall of the lower mold base and moves synchronously with the mold.

[0073] The multiplexer plays a crucial signal routing role. Based on instructions from the control system, it changes the connection object of the mold-terminal electrical circuit, switching the circuit from a high-impedance open-circuit state or subsequent impedance analysis channel to a differential acquisition channel specifically for weak charge measurement. The selection of the reference ground potential is critical for establishing the differential charge acquisition channel. This embodiment does not choose earth or an unstable terminal side as the reference; instead, it specifically selects a non-working area of ​​the stamping die that does not participate in forming contact as a "floating reference ground." This is because this area is on the same physical entity as the forming insert, and the electromagnetic environmental noise (common-mode interference) induced by both from the machine tool is almost identical, but the non-working area does not generate triboelectric charge. Based on the "virtual ground" characteristic of the differential charge amplifier, the input terminals are connected to the fisheye forming insert (signal terminal) and the non-working area (reference terminal), respectively. The amplifier only integrates and amplifies the charge difference between the two terminals. Since the elastic arm structure with gradually varying thickness undergoes the most severe deformation during molding, the amount of charge transfer on its surface is significantly higher than that in other areas. Therefore, the signal output by the differential amplifier is the differential charge signal that accurately reflects the microscopic deformation state of this specific structure after the common-mode noise has been removed.

[0074] S23. Determine the region where the gradual thickness elastic arm structure undergoes maximum plastic deformation, use the differential mode charge signal to characterize the electron escape behavior induced by high strain rate in this region, and after filtering out the common mode electromagnetic interference generated by the operation of the punch press, convert the processed differential mode charge signal into the transient triboelectric potential.

[0075] Mounting the differential charge amplifier on the insulated sidewall of the lower mold base and moving synchronously with the mold offers significant engineering advantages through in-situ amplification. It shortens the transmission path of weak signals from several meters to the centimeter level, physically reducing the parasitic capacitance and electromagnetic coupling effects that may occur with long wires in high-frequency interference environments, thus ensuring the purity of the original signal before it enters the amplifier.

[0076] The reason for focusing on the region of maximum plastic deformation in the gradually thickened elastic arm structure is that, according to solid-state physics and triboelectronics principles, the intensity of the tribovoltaic effect in metallic materials is positively correlated with the strain rate of their crystal lattice. In this region of maximum deformation, the metallic lattice undergoes the most intense slip and dislocation movements, reaching its peak strain rate. This high-strain-rate mechanical state can break the electron-binding barrier at grain boundaries, inducing non-thermal equilibrium electron emission, i.e., electron escape behavior. The differential-mode charge signal essentially records the amount of charge transfer between interfaces, thus accurately characterizing the intensity of this microscopic electron escape induced by high strain rate.

[0077] During signal processing, electromagnetic interference generated by the punch press operation simultaneously affects both the formed insert and the non-working area, with essentially the same amplitude and phase, constituting a common-mode interference signal. The differential charge amplifier, utilizing its high common-mode rejection ratio, subtracts the signals from its two input terminals, physically canceling out the common-mode electromagnetic interference and retaining only the differential-mode signal reflecting the interface friction state. Finally, based on the electrometer principle, the system linearly maps the processed pure charge quantity into a transient triboelectric potential in the voltage dimension using the system's equivalent capacitance parameters.

[0078] Optionally, for stamping cold start conditions, the method further includes the following step ad.

[0079] a. During the stamping stage, the control power module superimposes a DC bias voltage between the stamping die and the fisheye terminal.

[0080] b. The dielectric wetting effect is induced by the DC bias voltage, which reduces the contact angle of the cold lubricating oil on the surface of the fisheye molded insert; wherein the contact angle refers to the angle between the tangent of the liquid-gas interface of the lubricating oil droplet and the solid-liquid interface of the fisheye molded insert.

[0081] c. Configure the input circuit of the mold-terminal electrical circuit to AC coupling mode, use a DC blocking capacitor to isolate the DC component of the DC bias voltage, and filter out power supply ripple interference, extracting only the AC component of the transient triboelectric potential superimposed on the DC bias voltage as the basis for the S4 comparison.

[0082] d. Maintain the DC bias voltage until the lubricating oil overcomes the surface tension under the drive of the electric field force and spreads and penetrates into the root of the gradually thickened fisheye terminal and the micro-gap of the inner wall rounded corner.

[0083] During the cold start phase of stamping equipment, the lubricating oil is typically at a low temperature, with a kinematic viscosity significantly higher than that at normal operating temperature, resulting in poor fluidity. The root of the fisheye terminal's gradient thickness and the rounded corners of its inner wall constitute a microscopic slit structure with a large depth-to-width ratio. In the extremely short contact time of high-frequency stamping, the high-viscosity, cold lubricating oil cannot overcome surface tension and quickly penetrate these critical friction areas using its own gravity or weak natural capillary action, easily leading to dry friction damage in the initial cold start phase. The dielectric wetting effect alters the surface tension balance of the solid-liquid interface by applying a DC bias voltage between the die and the terminal, forming a capacitor. According to the Yang-Lippman equation, the applied electric field reduces the solid-liquid interfacial energy, resulting in a significant reduction in the contact angle of lubricating oil droplets on the surface of the fisheye molding insert. Macroscopically, this manifests as the oil droplets changing from a contracted spherical shape to a spread-out flat shape, significantly enhancing wetting performance.

[0084] However, acquiring weak triboelectric signals while applying a high-amplitude DC bias voltage presents significant signal processing challenges. The DC bias voltage is typically tens of volts, while the triboelectric signal is only in the millivolt or even microvolt range. Direct coupling would cause the large DC component to instantly saturate a highly sensitive charge amplifier, completely drowning out the effective signal. Therefore, the system employs an AC coupling mode, connecting a high-voltage DC-blocking capacitor in series in the measurement circuit. Utilizing the capacitor's impedance characteristic of passing AC and blocking DC, this capacitor presents infinite impedance to the DC bias voltage, completely isolating it from the detection circuit. Simultaneously, it presents extremely low impedance to high-frequency transient triboelectric pulses, allowing them to pass without loss. This circuit topology achieves spectral separation between the driving voltage and the detection signal, ensuring that while using a high voltage to drive the lubricating oil spread, the tiny AC potential component superimposed on the DC fundamental wave can still be clearly extracted, achieving non-interference between lubrication intervention and condition monitoring. Under the continuous action of the electric field, the polarized lubricating oil molecules gain directional driving force. This driving force, combined with the improved wettability brought about by the reduction of the contact angle, overcomes the high surface tension resistance of the cold oil, causing the lubricating oil to spread along the electric field gradient direction and quickly penetrate and fill the rounded corners and root gaps of the fisheye terminal that are difficult to lubricate.

[0085] S3. During the mold closing and downward movement stages and the bottom dead center holding pressure stage, a preset frequency sweep signal is continuously applied to the mold-terminal electrical circuit to acquire the dynamic differential capacitance spectrum of the lubricating oil film to obtain its dispersion characteristics and to resolve the molecular orientation order; wherein, the mold-terminal electrical circuit is a conductive circuit composed of the stamping mold and the fisheye terminal.

[0086] The choice to perform frequency sweep measurements during the die-closing descent and bottom dead center holding phases is based on a precise consideration of the electromagnetic environment and physical state of the stamping process. During the stamping process, the die and the workpiece undergo intense relative sliding and plastic deformation, resulting in rapidly changing contact resistance accompanied by strong triboelectric potential interference. Under these conditions, obtaining accurate data through high-sensitivity impedance analysis is extremely difficult. Conversely, the die-closing descent phase represents a quasi-static or micro-contact state before contact, while the bottom dead center holding phase involves the die and workpiece in a mechanically locked, relatively static state. The contact pressure is stable and there is no severe triboelectric noise, providing the optimal quiet window for measuring the dielectric properties of the lubricating oil film.

[0087] A swept-frequency signal, as an active excitation source, can stimulate polarization responses at different scales within the lubricating oil film by injecting a continuously varying frequency alternating electric field into the circuit. The dynamic differential capacitance spectrum is not simply a record of capacitance values, but rather reflects the dynamic response function of the oil film as a dielectric material to its charge storage capacity (real part) and energy dissipation capacity (imaginary part) under different frequency electric field driving. By measuring the current amplitude and phase hysteresis of the circuit under swept-frequency excitation, and using Fast Fourier Transform (FFT) or lock-in amplification techniques, the complex impedance at the corresponding frequency can be calculated, thus deriving the dynamic differential capacitance spectrum.

[0088] Dispersion characteristics primarily characterize the relaxation behavior of the polarization mechanisms within the oil film (such as electronic polarization, atomic polarization, and dipole orientation polarization) as frequency changes, reflecting the macroscopic continuity and uniformity of the oil film. Molecular orientation order, on the other hand, delves into the microscopic level, characterizing the degree of orderly arrangement of the oil film molecular chains under extremely high pressure and shear force. Higher order indicates a denser molecular arrangement and stronger resistance to shearing and fracturing; conversely, low order suggests the possible presence of microscopic pores, broken molecular chains, or disordered arrangement within the oil film, representing an early potential risk for slag nucleation.

[0089] Specifically, S3 includes S31-S35.

[0090] S31. Control the multiplexer to switch the mold-terminal electrical circuit to the high-frequency impedance analysis channel, continuously injecting frequency range coverage. Hz to The current response of the high-frequency impedance analysis channel is measured and the dynamic differential capacitance spectrum is calculated using a frequency sweep signal with a preset frequency band of Hz.

[0091] The frequency range of the preset frequency band sweep signal is selected based on the characteristic time constant of the polarization relaxation of lubricating oil molecules. Frequency lower than... At frequencies above Hz, measurement results are easily dominated by electrode polarization effects and the diffusion behavior of impurity ions in the interfacial double layer, masking the dielectric response characteristics of the oil film itself; while at frequencies higher than Hz, the results are more susceptible to interference. At Hz, the rate of change of the electric field exceeds the orientation response limit of the lubricating oil macromolecular dipoles, making it difficult to excite effective orientation polarization. Therefore, selecting Hz to The Hz frequency band can accurately cover the dipole relaxation range of organic lubricant molecules, making it an ideal window for detecting the orientation state and microstructure of oil film molecules.

[0092] The process of calculating the dynamic differential capacitance spectrum through a high-frequency impedance analysis channel is based on the principle of complex impedance analysis. The system applies a small-amplitude sinusoidal AC voltage excitation to the loop, and a lock-in amplifier is used to synchronously acquire the amplitude and phase angle of the current response signal fed back from the loop. According to Ohm's law in the complex frequency domain, the ratio of the voltage vector to the current vector is analyzed as the system's complex impedance, and its reciprocal, the complex admittance, is then obtained. Based on the equivalent circuit model of the lubricating oil film, it is considered as a parallel structure of leakage resistance and capacitance. By separating the imaginary part of the complex admittance and dividing it by the angular frequency, the complex capacitance data at the corresponding frequency can be decoupled and calculated.

[0093] Dynamic differential capacitance spectroscopy is a spectral dataset describing the evolution of the complex capacitance of an oil film as a function of excitation frequency. It not only contains a single capacitance value but also rich information about the dielectric response of the oil film at different time scales. The real part of the spectrum reflects the charge storage capacity and polarization intensity of the oil film under an electric field, directly related to the thickness and compactness of the film. The imaginary part reflects the dissipation of electric field energy within the oil film, corresponding to molecular friction and relaxation losses. Dynamic differential capacitance spectroscopy is equivalent to a dielectric fingerprint of the oil film's microscopic state, revealing the disordered molecular chain arrangement and discontinuities in the microstructure that cannot be detected by single-frequency measurements.

[0094] S32. The acquired dynamic differential capacitance spectrum is decomposed into real capacitance and imaginary capacitance. The real capacitance is used as the abscissa and the imaginary capacitance is used as the ordinate to construct a complex capacitance plane trajectory feature that reflects the evolution of the real capacitance and imaginary capacitance with frequency.

[0095] In dielectric physics, lubricating oil films are not ideal insulating capacitors, but rather viscoelastic media with energy dissipation characteristics. When an alternating electric field is applied to the oil film, there is a phase difference between its internal electric displacement vector and electric field intensity vector, which necessitates expressing its permittivity, which describes its dielectric response, in complex form. Therefore, the dynamic differential capacitance spectrum can be mathematically decomposed into real and imaginary capacitance. The real capacitance represents the oil film's ability to store electrostatic energy under the influence of an electric field, physically corresponding to the degree of polarization of the oil film molecules, i.e., how much charge is bound to the interface or molecular chains; the imaginary capacitance represents the oil film's ability to dissipate electric field energy during polarization, physically corresponding to dielectric losses caused by intermolecular frictional heat generation or carrier migration. Both are indispensable and together constitute the complete electrical physical picture of the oil film.

[0096] The complex capacitance plane trajectory feature is constructed by using the real capacitance value at the same frequency as the abscissa and the imaginary capacitance value as the ordinate, plotting a series of data points during the frequency sweep process as a continuous curve on the complex plane. The physical significance of this trajectory lies in its intuitive representation of the entire dielectric relaxation process of the oil film. In the ideal Debye relaxation model, this trajectory appears as a semicircle; however, in actual lubricating oil films, due to the diversity of molecular structures and the disorder of their arrangement, the trajectory usually appears as a flattened arc. The shape, radius, and center position of this arc contain information about the distribution of relaxation times of oil film molecules, and can sensitively reflect whether phase separation of molecular arrangement or non-homogeneous evolution of the microstructure has occurred within the oil film.

[0097] S33. Extract the polarization intensity intercept difference of the complex capacitor plane trajectory feature on the real axis as the dispersion characteristic, wherein the polarization intensity intercept difference is used to characterize the degree of polarization response hysteresis of the lubricating oil film under frequency sweep electric field excitation.

[0098] The polarization intercept difference physically corresponds to the distance between the two intersection points of the complex capacitance plane trajectory and the real axis, i.e., the difference between the low-frequency capacitance limit corresponding to the static dielectric constant and the high-frequency capacitance limit corresponding to the optical frequency dielectric constant. The magnitude of this difference directly reflects the total ability of dipoles within the lubricating oil film to undergo reorientation polarization under the influence of an electric field. A large polarization intercept difference indicates that oil film molecules can be fully polarized under a low-frequency electric field, but under a high-frequency electric field, polarization cannot keep up with the change in electric field, resulting in a significant polarization response hysteresis. This hysteresis is not constant but is closely related to the viscosity of the oil film and the intermolecular forces. When precursor particles for slag nucleation appear within the oil film, these particles hinder the free rotation of surrounding molecules, slowing down the polarization establishment process and thus altering the hysteresis characteristics of the polarization response, causing an abnormal shift in the polarization intercept difference.

[0099] S34. Calculate the dielectric loss peak of the imaginary capacitance as a function of frequency, and extract the frequency domain response bandwidth of the dielectric loss peak, wherein the frequency domain response bandwidth corresponds to the half-width at half maximum (WHM) of the dielectric loss peak.

[0100] In dielectric spectroscopy analysis, the curve of the imaginary capacitance versus frequency typically exhibits one or more characteristic loss peaks, the frequency of which corresponds to the central relaxation frequency of the molecules. The frequency domain response bandwidth, i.e., the full width at half maximum (FWHM) of the dielectric loss peak, is a key indicator of the dispersion of the relaxation time distribution of molecules within the lubricating oil film. According to the principles of statistical physics, the FWHM of the dielectric loss peak is positively correlated with the disorder of molecular arrangement. A narrow frequency domain response bandwidth means that the relaxation times of the vast majority of oil film molecules are concentrated within a very small range, indicating a highly uniform microscopic environment and orderly arrangement of the molecules. Conversely, a significantly broad frequency domain response bandwidth indicates an extremely wide range of molecular relaxation time distribution, suggesting the existence of various microscopic regions with different states within the oil film, and a high degree of non-uniformity and disorder in molecular arrangement. This increased disorder is often a direct manifestation of structural collapse or microscopic fracture of the oil film under localized high pressure.

[0101] S35. Based on the Boltzmann distribution function, establish a mapping model between the frequency domain response bandwidth and the dispersion of oil film molecular arrangement, and normalize the reciprocal of the frequency domain response bandwidth to obtain the molecular orientation order; wherein, the narrower the frequency domain response bandwidth, the more consistent the arrangement of oil film molecules under pressure holding state, and the higher the molecular orientation order.

[0102] The logic of mapping the frequency domain response bandwidth to the molecular orientation order using statistical thermodynamics principles lies in the fact that the orientation state of lubricating oil film molecules essentially follows a statistical distribution of thermal motion based on the principle of minimizing energy. Under a high-voltage electrostatic field environment with pressure held at the bottom dead center, the orientation potential energy of the oil film molecules competes with their thermal kinetic energy, and the probability distribution of their orientation angles follows the Boltzmann distribution law. The frequency domain response bandwidth of the dielectric loss peak directly reflects the variance or dispersion of this statistical distribution; that is, the wider the bandwidth, the more diffuse the probability density distribution of molecular orientation deviating from the direction of the main electric field, and the higher the entropy of the system. By establishing a mathematical mapping model, the frequency domain response bandwidth is regarded as a characteristic parameter describing the degree of dispersion of molecular arrangement. Using its reciprocal relationship to construct an order index and performing normalization, the abstract spectral width can be transformed into a dimensionless scalar between 0 and 1. When the scalar approaches 1, it corresponds to an extremely narrow response bandwidth, indicating that the vast majority of molecules have overcome thermal perturbation and achieved a highly consistent ordered arrangement along the direction of the electric field; when the scalar decreases significantly, it quantitatively reveals that there is a randomization trend of molecular orientation inside the oil film, indicating the degradation of the microstructure of the lubricating film.

[0103] To further enhance the system's early warning capability for extreme operating conditions, especially for potential breakdown failures of the lubricating oil film when it is extremely thin, this embodiment designs a quantum tunneling precursor identification mechanism based on S3. It utilizes semiconductor physics analysis methods to detect the space charge distribution within the oil film during the mold closing and downward movement phase, before the mold and terminals have physically contacted each other. Once it is detected that the effective insulating layer thickness has decreased to the quantum tunneling critical value due to excessive compression or microscopic defects, a highest-priority blocking or intervention command is issued before physical damage occurs. Therefore, S3 also includes S301-S303.

[0104] S301. Extract the data segment of the dynamic differential capacitance spectrum during the downward phase of the closing mode, and establish a space charge distribution characteristic curve reflecting the nonlinear relationship between the reciprocal square of the lubricating oil film capacitance and the bias voltage.

[0105] The principle for extracting data segments of the dynamic differential capacitance spectrum during the mold closing and downward movement is based on the correspondence between the mold stroke and the physical state of the oil film. Specifically, the system only extracts data from the start of the mold's downward movement until one microsecond before contact with the terminal plating (i.e., the tiny window from the formation of the aerodynamic wind barrier to the point of contact). During this stage, the lubricating oil film is in a non-pressurized or slightly pressurized state, and its electrical properties have not yet been severely disturbed by mechanical deformation, best reflecting the semiconductor interface properties of the oil film itself. The established space charge distribution characteristic curve is commonly referred to in physics as the Mott-Schottky curve. This curve is expressed as the inverse square of the capacitance (… The curve is plotted with the applied DC bias voltage (V) on the x-axis. Its physical meaning lies in revealing the variation of the capacitance characteristics of the depletion layer (or space charge region) at the interface with the applied voltage. In an ideal semiconductor-electrolyte or metal-insulator-metal interface, the linear portion of this curve directly reflects the doping concentration or defect density distribution of the space charge region near the interface. By analyzing this curve, the invisible microscopic charge distribution of the oil film can be transformed into visible geometric features.

[0106] S302. Extract the slope of the linear region and the voltage axis intercept of the space charge distribution characteristic curve, use the slope of the linear region to analyze the charge carrier concentration in the lubricating oil film, and combine it with the built-in potential determined by the voltage axis intercept to calculate the physical thickness of the charge depletion layer in the lubricating oil film as the effective space charge region width through Poisson equation inversion.

[0107] First, the carrier concentration is derived from the curve slope; second, the built-in potential is determined from the intercept; and finally, the physical thickness is calculated by combining the two. Specifically, the principle of extracting the linear region slope to analyze the charge carrier concentration is based on the Mott-Schottky relation, which shows that the slope of the inverse square of the capacitance as a function of voltage is inversely proportional to the donor or acceptor impurity concentration (i.e., charge carrier concentration) within the semiconductor (equivalent to a lubricating oil film). A steeper slope indicates a lower carrier concentration; a gentler slope indicates a higher carrier concentration. Simultaneously, the voltage axis intercept (i.e., ...) The voltage value at which the charge concentration is zero (=0) physically corresponds to the difference between the flat-band potential and the built-in potential, from which the height of the built-in potential at the interface can be determined. Finally, based on the solution of the Poisson equation under the depletion layer approximation, the analytically obtained carrier concentration and built-in potential are substituted into the depletion layer width formula to calculate the physical thickness of the charge depletion layer in the lubricating oil film. This thickness is the width of the effective space charge region that blocks electron transitions.

[0108] S303. When it is detected that the width of the effective space charge region decreases exponentially to a preset nanometer threshold and the dynamic differential capacitance spectrum shows negative capacitance characteristics, it is determined that the lubricating oil film is about to undergo quantum tunneling breakdown, and S5 is forcibly triggered before the stamping die and the fisheye terminal make physical contact.

[0109] In this step, the determination of quantum tunneling breakdown is based on two significant microscopic precursor characteristics: First, the effective space charge region width decays exponentially. According to the principles of quantum mechanics, the probability of electron tunneling is exponentially negatively correlated with the barrier width (i.e., oil film thickness). When the thickness decays to the nanometer threshold (usually 1-3 nm), the tunneling probability increases sharply, and the originally insulating oil film will instantly become conductive. Second, the dynamic differential capacitance spectrum shows negative capacitance characteristics. This is usually due to charge injection or nonlinear polarization response at the interface, causing the current phase to lead the voltage, which is a typical electrical fingerprint of the medium about to undergo avalanche breakdown or tunneling effect. The reason for designing this logic to "short-circuit" or skip the subsequent S4 determination step is that once the above precursors are detected, it means that lubrication failure is imminent. If we wait for the data acquisition and correlation analysis of S2 (potential) and S3 (order degree) in the S4 step to be completed, physical contact and damage may have already occurred. Therefore, establishing such a high-speed early warning channel before contact can forcibly trigger the lubrication intervention of S5 within a microsecond window before physical damage occurs.

[0110] For example, in this embodiment, the preset nanometer threshold is set to 3nm. When the calculated effective space charge region width is less than 3nm and the differential capacitance spectrum phase angle shows a leading trend (i.e., exhibiting negative capacitance), the system determines that the risk of insulation failure is extremely high, and forcibly triggers the execution of S5 before the stamping die and the fisheye terminal make physical contact.

[0111] S4. Within the bottom dead center holding window before the end of a single stamping stroke, the transient triboelectric potential is compared with the standard response of the triboelectric potential to extract and identify potential anomaly features; the potential anomaly features are correlated with the dispersion characteristics obtained in the current bottom dead center holding stage. When the potential anomaly feature corresponding to the stamping stroke is detected to show polarity reversal and the molecular orientation order degree drops to the preset molecular orientation order degree threshold, it is determined to be the micro-nucleation stage of slag derived from coating lattice breakage.

[0112] The final determination is made within the holding pressure window at the bottom dead center before the end of a single stamping stroke because this is a point where a complete physical stroke is about to end and the next stroke has not yet begun. At this time, the dynamic potential data of the stamping stage has been collected, and the static dielectric data of the holding pressure stage has just been acquired, so the system has complete data for this stroke to make a determination.

[0113] The correlation analysis between potential change characteristics and dispersion characteristics constructs a causal chain: the polarity reversal of the transient triboelectric potential captured in stage S2 is the cause, which indicates that at the moment of violent deformation, the metal lattice underwent abnormal fracture or slippage, resulting in a sudden change in the direction of electron transfer. This is merely a dynamic signal of suspected damage. The drop in molecular orientation order obtained in stage S3 is the effect, which indicates that at the moment of maximum pressure, the microstructure of the lubricating oil film did indeed collapse or become disordered, verifying the authenticity of the previous dynamic signal and providing static evidence of damage.

[0114] This complete chain of evidence, combining dynamic process quantities with static state quantities, can effectively reduce the false alarm rate. If there is only a potential reversal without a drop in order, it may simply be an occasional electromagnetic interference or mechanical vibration; if there is only a drop in order without a potential reversal, it may simply be normal rheological fluctuations in the oil film. Only when the two show a strict causal correspondence in the timing of the same stroke can the system confirm and determine that it is microscopic nucleation of slag, thereby eliminating the random error of a single signal source and significantly improving the accuracy of fault identification.

[0115] In the specific parameter settings of this embodiment, the preset molecular orientation order threshold is set to 0.75 (normalized value). That is, when the molecular orientation order calculated by the system drops from 0.92±0.03 under normal conditions to below 0.75, and the tribovoltaic potential is simultaneously detected to change abruptly from positive (e.g. +15mV) to negative (e.g. −25mV), the system confirms that the slag nucleation determination is established.

[0116] Specifically, S4 includes S41-S44.

[0117] S41. Within the pressure holding window at the bottom dead center before the end of a single stamping stroke, the transient triboelectric potential and the standard response of the triboelectric potential are compared in the time domain, and the deviation between the two is extracted as the potential variation feature.

[0118] The reason for comparing the real-time acquired transient triboelectric potential with the pre-acquired standard response in the time domain is that stamping is a highly nonlinear dynamic process, and the trajectory of its potential signal over time contains rich process information. The standard response represents a reference waveform under ideal lubrication and defect-free conditions, reflecting the normal plastic deformation path. Through time-domain comparison, the system can calculate the differences in amplitude, phase, and waveform envelope between the real-time waveform and the reference waveform point by point. The extracted deviation (i.e., potential anomaly characteristics) is not just a simple numerical difference, but more importantly, it captures the time point and shape of signal abrupt changes. For example, if a sharp negative pulse appears at a specific millisecond, it often corresponds to the instant of micro-lattice fracture. This time-domain-based comparison can distinguish normal process fluctuations (such as overall shifts caused by small changes in material thickness) from abnormal defect signals (such as local abrupt changes caused by slag nucleation).

[0119] S42. The potential change characteristics are correlated with the dispersion characteristics of the dynamic differential capacitance spectrum obtained during the current lower dead center holding stage, and the causal relationship between the two is analyzed.

[0120] The core of temporal correlation lies in establishing a logical mapping of physical events along the timeline. The system timestamps the potential change characteristics extracted in stage S2 (stamping) and marks them as event A (the moment the suspected damage occurred); it timestamps the dispersion anomalies obtained in stage S3 (holding pressure) and marks them as event B (the moment the damage consequences manifested). Since the stamping process is a unidirectional time flow, event A must occur before event B.

[0121] Analyzing whether a causal relationship exists between the two involves checking whether the nature of event A is sufficient to cause the result of event B. Specifically, the system searches a pre-defined fault mode library. For example, if event A is characterized by a potential polarity reversal (meaning a change in the direction of interface electron transfer, usually caused by coating cracking), and the immediately following event B is characterized by a sharp decrease in molecular orientation order (meaning a disordered microstructure of the oil film, usually caused by rough surfaces or particle disturbance), then there is a strong causal chain between the two in terms of physical mechanism. If there is only A without B, or if B appears before A (a logical paradox, possibly noise), then a causal correspondence is not considered.

[0122] S43. Synchronously read the data from the fiber optic probe arranged in the non-contact area of ​​the mold, wherein the fiber optic probe is used to collect the photon count released at the interface between the stamping mold and the fisheye terminal during plastic deformation.

[0123] Synchronization here refers to strictly aligning the phases of the fiber optic probe's data acquisition clock, transient triboelectric potential acquisition clock, and dynamic differential capacitance spectrum acquisition clock. This ensures that all physical quantities correspond to the same millisecond-level time axis coordinates, thereby achieving accurate reproduction of multidimensional signals within a single stamping stroke. The photon counting results acquired by the fiber optic probe are directly affected by the band structure and micro-fracture intensity of the contact interface material. In particular, for the indium oxide layer on the surface of the fisheye terminal, lattice breakage or peeling is accompanied by triboluminescence at a specific wavelength. The purpose of introducing a fiber optic probe for optical-assisted verification is to introduce a physical criterion independent of the electrical signal. Since the triboelectric potential is easily modulated by electromagnetic interference or changes in contact resistance, a single electrical characteristic may have multiple interpretations. Triboluminescence, on the other hand, only occurs when the chemical bonds of the material break or undergo severe lattice rearrangement, providing direct optical evidence of micro-damage. By introducing this dimension of monitoring, it is possible to effectively distinguish between simple elastic contact (no light) and destructive plastic damage (light).

[0124] S44. Only when the potential change characteristic is detected to be a polarity reversal, the molecular orientation order drops to a preset order threshold, and the instantaneous value of the triboluminescence photon count corresponding to the indium oxide energy level transition wavelength is simultaneously detected to exceed three times the standard deviation of the environmental background photon count baseline, is it confirmed to be the micro-nucleation stage of the slag, so as to exclude the false positive signal of potential caused by the piezoelectric effect.

[0125] Three standard deviations (3σ) have a clear quantitative significance in statistical signal processing, representing the significance level of a signal deviating from the mean of background noise. According to the normal distribution theory, when the signal intensity exceeds three standard deviations from the background baseline, the probability that the signal originates from random noise is less than 0.3%, i.e., the confidence level reaches 99.7%. This stringent statistical threshold ensures that the photon bursts captured by the system are real physical events, rather than ambient light fluctuations or thermal noise.

[0126] In precision stamping processes, die materials or piezoelectric ceramic sensors often exhibit piezoelectric effects, producing significant potential spikes under high-pressure impact. These spikes are easily misinterpreted as triboelectric anomalies (S2 false positive). However, a pure piezoelectric response is an intrinsic physical property of the material and does not lead to microstructural disorder in the lubricating oil film (S3 normal) or the release of photons due to chemical bond breakage (S43 normal). Therefore, only when the potential reversal representing an abnormal electron transfer, the drop in orderliness representing dielectric layer disruption, and the photon burst representing lattice breakage occur simultaneously, and these three chains of evidence converge in space and time, can the microscopic nucleation stage of slag be definitively identified. For example, in a single stamping operation, if only a voltage surge is detected without a photon signal, the system will automatically identify it as mechanical vibration or piezoelectric interference and will not trigger an alarm; only when all three are present will the system confirm that slag is being generated.

[0127] S5. Based on the discrimination results of the micro-nucleation stage of crystal slag, the electrostatic micro-lubrication system is triggered to spray lubricating oil mist with specific polar charges into the forming area. The high gradient electrostatic field induced by the micro-nano structure in the area of ​​severe friction drives the lubricating oil mist to migrate autonomously along the electric field lines and preferentially adsorb to the friction hot spot area with the highest potential.

[0128] The triggering logic of the electrostatic micro-lubrication system follows the principle of on-demand intervention. The system is normally in standby or low-flow maintenance mode. Only when step S4 confirms the signal of micro-nucleation of slag does the controller instantaneously activate the high-voltage electrostatic generator and micro-pump to release micro-nano-scale lubricating oil mist with a specific polarity charge (usually set to the opposite polarity to the induced charge on the mold surface) into the mold cavity. This triggering mechanism avoids the excessive lubrication and environmental pollution caused by traditional continuous oil spraying.

[0129] In this process, there is an intrinsic physical correspondence between the friction hotspot region and the high-gradient electrostatic field. The friction hotspot region is the area where the fisheye terminal deforms most severely, experiences the greatest contact pressure, and suffers the most severe lattice breakage. According to the principle of triboelectric charging and the tip discharge effect, these regions have the highest surface charge density, and due to the presence of the micro-nano structures prefabricated in step S1, the radius of curvature at the micro-tip is extremely small, resulting in an order-of-magnitude increase in the electric field strength at that location. In short, the area with the most severe wear is where the surface potential is highest and the electric field gradient is steepest.

[0130] Traditional spray lubrication relies on airflow, making it difficult to penetrate blind holes or leeward surfaces. However, charged oil mist particles, upon entering a high-gradient electrostatic field, are subject to strong electrostatic attraction (F=qE). Because the electric field strength E at the friction hotspot is much higher than in the surrounding flat area, the oil mist particles automatically accelerate along the curved electric field lines, like iron filings attracted by a magnet, preferentially flying towards and depositing at the friction hotspot with the highest potential. This physical self-adsorption effect enables self-aligned targeted lubrication without any mechanical vision positioning or nozzle movement, ensuring that the lubricant precisely covers the microscopic damage points that require the most protection.

[0131] Specifically, S5 includes S51-S53.

[0132] S51. Monitor the residual surface potential of the stamping die surface in real time.

[0133] During the long-term operation of an electrostatic micro-lubrication system, if a single-polarity charged oil mist, such as continuously spraying positively charged oil droplets, is continuously sprayed onto the mold surface, the mold, being in a suspended and insulated state, cannot release the charge through a grounding circuit. This leads to the continuous accumulation of the same charge on the insulating layer or lubricating oil film surface of the mold. As the accumulated charge density increases, an electrostatic field with the same polarity as the incident oil droplets gradually forms on the mold surface—an electrostatic shielding field. According to Coulomb's law, this shielding field generates a strong electrostatic repulsive force against subsequent incoming charged oil droplets of the same polarity. When this repulsive force increases sufficiently to counteract the electrostatic adsorption force and the airflow carrying force, the oil mist particles will be pushed away from the target area, unable to effectively adhere to the mold surface, resulting in the failure of targeted adsorption and even creating lubrication blind spots.

[0134] S52. When the residual surface potential is detected to exceed the preset saturation threshold, it is determined that an electrostatic shielding field has been formed on the surface of the stamping die, wherein the electrostatic shielding field will hinder the adsorption of subsequent charged oil mist.

[0135] The physical meaning of the preset saturation threshold is the surface potential value when the repulsive electric field strength generated by the accumulated charge on the mold surface reaches a critical state. At this critical state, the negative work done by the electrostatic shielding field on the incident charged oil droplet is close to the sum of the droplet's kinetic energy and electrostatic potential energy, meaning that subsequent oil droplets will find it difficult to penetrate the barrier and contact the mold surface. The purpose of setting this threshold is to quantify the severity of the electrostatic shielding effect, serving as a critical criterion for triggering polarity reversal control and preventing the system from continuing to operate in an ineffective adsorption state.

[0136] S53. Control the polarity of the high-voltage generator of the electrostatic micro-lubrication system to reverse, spraying lubricating oil mist with a charge opposite to the current residual surface potential polarity to neutralize the accumulated charge on the surface of the stamping die, thereby eliminating the electrostatic shielding field and maintaining the continuous targeted adsorption capacity; wherein, the high-voltage generator is used to generate a high-voltage electrostatic field at the nozzle, causing the flowing lubricating oil mist droplets to carry an electrostatic charge of a specific polarity through corona discharge or inductive electrification effect.

[0137] The physical mechanism of the polarity reversal strategy lies in utilizing the neutralization effect of opposite charges to eliminate electrostatic shielding. When the system detects the formation of a shielding field, it controls the high-voltage generator to output a reverse high voltage, for example, switching from positive high voltage to negative high voltage, causing the oil mist particles ejected from the nozzle to carry a negative charge. When these anti-charged droplets fly towards the positively charged mold surface, they are not only accelerated by extremely strong Coulomb attraction, but also recombine with the accumulated positive charge on the surface at the moment of contact, thereby rapidly reducing the residual potential of the mold surface. This process is essentially an electrostatic cleaning of the mold surface, eliminating the shielding field that hinders adsorption, restoring the mold surface's ability to adsorb subsequent oil droplets, and ensuring the continuity and stability of the lubrication process.

[0138] The specific principle behind the generation of charged oil mist by a high-voltage generator mainly relies on corona discharge or induction charging. In corona discharge mode, the high-voltage generator produces an extremely high-intensity non-uniform electric field at the nozzle tip, ionizing the air molecules around the nozzle and generating a large number of free ions. These ions collide with and attach to the sprayed oil mist droplets under the influence of the electric field, charging them. In induction charging mode, the high-voltage electrode does not directly contact the liquid, but instead establishes a strong induced electric field in the area where the liquid breaks into droplets. This causes the droplets to induce a charge with opposite polarity to the electrode at the moment of separation, thus achieving efficient charging.

[0139] It should be noted that although the "high gradient electrostatic field" and the "electrostatic shielding field" in this embodiment both belong to the field of electrostatics, they are fundamentally different in terms of physical properties and mechanisms of action.

[0140] First, the high-gradient electrostatic field is a localized dynamic field at the microscale. This electric field originates from the micro / nanostructures prefabricated in step S1. At the instant of frictional contact, due to edge effects and tip discharge effects, charges preferentially accumulate at the tips or edges of the microtexture, resulting in a maximum electric field intensity gradient (high ∇E value) in this tiny region (micrometer scale). According to the principles of dielectric force or strong Coulomb attraction, this localized high-gradient field exhibits a strong traction force on charged oil mist particles, enabling it to precisely "grab" and lock the oil mist particles onto the microscopic contact points with the most severe wear, thereby achieving targeted lubrication.

[0141] Secondly, the electrostatic shielding field is a macroscopic overall resistance field. This electric field originates from the long-term spraying of unipolar (e.g., positive) charged oil mist from an electrostatic micro-lubrication system onto the surface of an insulated, suspended mold. As the spraying time progresses, unneutralized positive charges gradually accumulate across the entire mold cavity surface, forming a relatively uniformly distributed macroscopic potential layer. According to the principle of repulsion between like charges, this macroscopic electric field exhibits Coulomb repulsion against subsequently arriving positively charged oil mist particles. When the accumulated potential exceeds a preset saturation threshold, the macroscopic repulsion overcomes the microscopic attraction and airflow carrying force, causing the oil mist particles to be pushed away before reaching the effective adsorption range of the micro / nano texture, thus forming the so-called "electrostatic shielding."

[0142] Therefore, the polarity reversal strategy in step S53 is essentially about eliminating the overall resistance field at the macroscopic level while preserving the local dynamic field generation mechanism at the microscopic level. By neutralizing the redundant charges accumulated on the surface, the macroscopic surface potential is reset to near zero potential, allowing the local high gradient field at the micro / nano texture to once again dominate the adsorption process of oil mist particles, ensuring the continued effectiveness of the targeted lubrication mechanism.

[0143] Furthermore, to address the issue of lubricating oil mist adhesion difficulties under ultra-high-speed stamping conditions, one embodiment of this application introduces a pulsed electric field ballistic injection mechanism to ensure forced lubrication of the mold surface even under extreme airflow interference. Specifically, S5 also includes S501-S505.

[0144] S501. Real-time acquisition of the punching frequency data of the stamping die and the pneumatic stagnation pressure at the moment the die closes.

[0145] S502. The stroke frequency and the aerodynamic stagnation pressure are weighted and evaluated. When the evaluation result exceeds the preset wind barrier threshold, it is determined that there is an aerodynamic wind barrier that hinders continuous spray adsorption in the current working condition.

[0146] During high-speed stamping, especially when the stamping frequency exceeds several hundred times per minute, the die closing speed is extremely fast. Air between the upper and lower dies, unable to escape in time, is instantly and violently compressed and ejected outwards at near-sonic speeds—a phenomenon known as the air barrier or air cushion effect. This high-speed airflow forms a high-pressure aerodynamic protective layer around the die, with a stagnation pressure far exceeding ambient atmospheric pressure. In conventional continuous spraying modes, the tiny oil mist particles are extremely light and have low kinetic energy. When they approach the die, they are directly dispersed or bounced off by this powerful airflow, unable to penetrate the air barrier to reach the deeper structures of the die surface (such as rounded corners), leading to lubrication failure. Therefore, a detection-judgment logic is introduced to monitor the aerodynamic stagnation pressure in real time. Only when the evaluation results show that the air barrier strength is sufficient to prevent oil mist adsorption does the system activate a special penetration mode, avoiding wasted energy or excessive oil mist generation under low-speed conditions.

[0147] S503. In response to the determination result, the output mode of the electrostatic micro-lubrication system is switched from continuous spray to high-pressure pulse injection mode.

[0148] S504. Control the high-voltage generator to apply a pulsed electric field between the nozzle and the stamping die, and adjust the charging frequency of the oil mist droplets to maintain synchronous resonance with the frequency of the pulsed electric field.

[0149] S505. The peak electric field intensity of the pulsed electric field is used to generate a transient electric field force, which drives the oil mist particles to gain kinetic energy that exceeds the resistance of the closed airflow of the mold, so that the oil mist particles penetrate the aerodynamic wind barrier with a ballistic trajectory and bombard the surface of the stamping mold.

[0150] To address the problem of high-speed airflow obstruction, S503-S505 employs a "pulse ballistic injection" physical mechanism. Its core principle is based on the electric field force formula. In pulse mode, the high-voltage generator no longer outputs a constant voltage, but instead outputs a high-voltage pulse with an extremely short duty cycle, resulting in an instantaneous peak electric field intensity. The field strength is significantly higher than the average field strength in continuous mode. Simultaneously, by adjusting the synchronous resonance between the oil mist charging frequency and the pulsed electric field frequency, it is ensured that the oil droplets carry the maximum charge q precisely at the moment the electric field peak arrives, thus obtaining the maximum transient electric force. This enormous transient force endows the oil mist particles with extremely high initial velocity and kinetic energy, causing their trajectory to no longer be the Brownian motion of drifting with the airflow, but rather a straight ballistic trajectory similar to a bullet shot, forcibly penetrating the aerodynamic wind barrier generated by the high-speed closure and striking the surface of the stamping die.

[0151] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0152] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is used as an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0153] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for controlling the precision stamping process of fisheye terminals to prevent crystal slag formation, characterized in that, The method for processing fisheye terminals includes the following steps: S1. During the trial stamping stage, the standard response of the tribovoltaic potential of the interface between the pre-processed indium plating layer on the fisheye terminal and the stamping die during plastic deformation is obtained based on normal stamping conditions. The surface of the fisheye forming insert of the stamping die is pre-processed with micro-nano structures. The micro-nano structures are used to increase the contact specific surface area to enhance the signal-to-noise ratio of the tribovoltaic effect at the contact interface, and to construct a non-uniformly distributed high-gradient electrostatic field in the friction contact area. The transient tribovoltaic potential is used to characterize the electron-hole pair separation state caused by the deformation of the metal lattice. S2. During the stamping stage, the die-terminal electrical circuit is configured to a floating ground potential measurement mode to collect the transient triboelectric potential generated by the stamping die and the fisheye terminal in real time. S3. During the mold closing and downward movement stages and the bottom dead center holding pressure stage, a frequency sweep signal of a preset frequency band is continuously applied to the mold-terminal electrical circuit to acquire the dynamic differential capacitance spectrum of the lubricating oil film to obtain its dispersion characteristics and to resolve the molecular orientation order; wherein, the mold-terminal electrical circuit is a conductive circuit composed of the stamping mold and the fisheye terminal; S4. Within the bottom dead center holding window before the end of a single stamping stroke, the transient triboelectric potential is compared with the standard response of the triboelectric potential to extract and identify potential change features; the potential change features are correlated with the dispersion characteristics obtained in the current bottom dead center holding stage. When the potential change feature corresponding to the stamping stroke is detected to show polarity reversal and the molecular orientation order degree drops to the preset molecular orientation order degree threshold, it is determined to be the micro-nucleation stage of slag derived from coating lattice breakage. S5. Based on the discrimination results of the micro-nucleation stage of crystal slag, the electrostatic micro-lubrication system is triggered to spray lubricating oil mist with specific polar charges into the forming area. The high gradient electrostatic field induced by the micro-nano structure in the area of ​​severe friction drives the lubricating oil mist to migrate autonomously along the electric field lines and preferentially adsorb to the friction hot spot area with the highest potential.

2. The method for controlling the precision stamping process of fisheye terminals to prevent crystal slag formation according to claim 1, characterized in that, The fisheye terminal has a gradually thickened elastic arm structure and rounded inner wall corners; the triboelectric potential standard response obtained in step S1 is determined based on the specific potential waveform characteristics excited by the non-uniform stress distribution gradient and specific plastic deformation rate generated by the gradually thickened elastic arm structure during plastic deformation; the specific potential waveform characteristics are different from the potential response of the cantilever beam structure with uniform thickness.

3. The method for controlling the precision stamping process of fisheye terminals to prevent crystal slag formation according to claim 1, characterized in that, S2 includes: S21. Electrically isolate the lower die base of the stamping die from the main body of the press by using insulating ceramic material, and establish the die-terminal electrical circuit; S22. Control the multiplexer to switch the mold-terminal electrical circuit to the differential charge acquisition channel, using the non-working area of ​​the stamping mold as the reference ground potential, and acquire the differential charge signal between the fisheye molding insert and the fisheye terminal's gradually thickened elastic arm structure based on the differential charge amplifier; wherein, the differential charge amplifier is installed on the insulating sidewall of the lower mold base and moves synchronously with the mold; S23. Determine the region where the gradual thickness elastic arm structure undergoes maximum plastic deformation, use the differential mode charge signal to characterize the electron escape behavior induced by high strain rate in this region, and after filtering out the common mode electromagnetic interference generated by the operation of the punch press, convert the processed differential mode charge signal into the transient triboelectric potential.

4. The method for controlling the precision stamping process of fisheye terminals to prevent crystal slag formation according to claim 1, characterized in that, For cold start conditions in stamping operations, the method further includes the following steps: During the stamping stage, the control power module applies a DC bias voltage between the stamping die and the fisheye terminal; The DC bias voltage induces a dielectric wetting effect, which reduces the contact angle of the cold lubricating oil on the surface of the fisheye molded insert; wherein, the contact angle refers to the angle between the tangent of the liquid-gas interface of the lubricating oil droplet and the solid-liquid interface of the fisheye molded insert. The input circuit of the mold-terminal electrical circuit is configured to be AC ​​coupling mode. The DC component of the DC bias voltage is isolated by the DC blocking capacitor and the power supply ripple interference is filtered out. Only the AC component of the transient triboelectric potential superimposed on the DC bias voltage is extracted as the basis for the S4 comparison. The DC bias voltage is maintained until the lubricating oil overcomes the surface tension under the drive of the electric field force and spreads and penetrates into the root of the gradually thickened fisheye terminal and the micro-gap of the inner wall rounded corner.

5. The precision stamping processing control method for preventing crystal slag formation in fisheye terminals according to claim 1, characterized in that, S3 includes: S31. Control the multiplexer to switch the mold-terminal electrical circuit to the high-frequency impedance analysis channel, continuously injecting frequency range coverage. Hz to A frequency sweep signal with a preset frequency band of Hz is used to measure the current response of the high-frequency impedance analysis channel and calculate the dynamic differential capacitance spectrum. S32. Decompose the acquired dynamic differential capacitance spectrum into real capacitance and imaginary capacitance, and construct a complex capacitance plane trajectory feature that reflects the evolution of real capacitance and imaginary capacitance with frequency using real capacitance as the abscissa and imaginary capacitance as the ordinate. S33. Extract the polarization intensity intercept difference of the complex capacitor plane trajectory feature on the real axis as the dispersion characteristic, wherein the polarization intensity intercept difference is used to characterize the degree of polarization response hysteresis of the lubricating oil film under frequency sweep electric field excitation. S34. Calculate the dielectric loss peak of the imaginary capacitance as a function of frequency, and extract the frequency domain response bandwidth of the dielectric loss peak, wherein the frequency domain response bandwidth corresponds to the half-width at half maximum (WHM) of the dielectric loss peak. S35. Based on the Boltzmann distribution function, establish a mapping model between the frequency domain response bandwidth and the dispersion of oil film molecular arrangement, and normalize the reciprocal of the frequency domain response bandwidth to obtain the molecular orientation order; wherein, the narrower the frequency domain response bandwidth, the more consistent the arrangement of oil film molecules under pressure holding state, and the higher the molecular orientation order.

6. The precision stamping processing control method for preventing crystal slag formation in fisheye terminals according to claim 1, characterized in that, S3 further includes: S301. Extract the data segment of the dynamic differential capacitance spectrum during the downward phase of the closing mode, and establish a space charge distribution characteristic curve that reflects the nonlinear relationship between the reciprocal square of the lubricating oil film capacitance and the bias voltage; S302. Extract the linear region slope and voltage axis intercept of the space charge distribution characteristic curve, use the linear region slope to analyze the charge carrier concentration in the lubricating oil film, and combine it with the built-in potential determined by the voltage axis intercept to calculate the physical thickness of the charge depletion layer in the lubricating oil film as the effective space charge region width through Poisson equation inversion. S303. When it is detected that the width of the effective space charge region decreases exponentially to a preset nanometer threshold and the dynamic differential capacitance spectrum shows negative capacitance characteristics, it is determined that the lubricating oil film is about to undergo quantum tunneling breakdown, and S5 is forcibly triggered before the stamping die and the fisheye terminal make physical contact.

7. The method for controlling the precision stamping process of fisheye terminals to prevent crystal slag formation according to claim 1, characterized in that, S4 includes: S41. Within the pressure holding window at the bottom dead center before the end of a single stamping stroke, the transient triboelectric potential and the standard response of the triboelectric potential are compared in the time domain, and the deviation between the two is extracted as the potential variation feature. S42. The potential change characteristics are correlated with the dispersion characteristics of the dynamic differential capacitance spectrum obtained in the current lower dead point holding stage, and the causal relationship between the two is analyzed. S43. Synchronously read the data from the fiber optic probe arranged in the non-contact area of ​​the mold, wherein the fiber optic probe is used to collect the photon count released at the interface between the stamping mold and the fisheye terminal during plastic deformation. S44. Only when the potential change characteristic is detected to be a polarity reversal, the molecular orientation order drops to a preset order threshold, and the instantaneous value of the triboluminescence photon count corresponding to the indium oxide energy level transition wavelength is simultaneously detected to exceed three times the standard deviation of the environmental background photon count baseline, is it confirmed to be the micro-nucleation stage of the slag, so as to exclude the false positive signal of potential caused by the piezoelectric effect.

8. The method for controlling the precision stamping process of fisheye terminals to prevent crystal slag formation according to claim 1, characterized in that, S5 includes: S51. Monitor the residual surface potential of the stamping die surface in real time; S52. When the residual surface potential is detected to exceed the preset saturation threshold, it is determined that an electrostatic shielding field has been formed on the surface of the stamping die, wherein the electrostatic shielding field will hinder the adsorption of subsequent charged oil mist; S53. Control the polarity of the high-voltage generator of the electrostatic micro-lubrication system to reverse, spraying lubricating oil mist with a charge opposite to the current residual surface potential polarity to neutralize the accumulated charge on the surface of the stamping die, thereby eliminating the electrostatic shielding field and maintaining the continuous targeted adsorption capacity; wherein, the high-voltage generator is used to generate a high-voltage electrostatic field at the nozzle, causing the flowing lubricating oil mist droplets to carry an electrostatic charge of a specific polarity through corona discharge or inductive electrification effect.

9. The method for controlling the precision stamping process of fisheye terminals to prevent crystal slag formation according to claim 1 or 8, characterized in that, S5 includes: S501. Real-time acquisition of the punching frequency data of the stamping die and the pneumatic stagnation pressure at the moment of die closure; S502. The stroke frequency and the aerodynamic stagnation pressure are weighted and evaluated. When the evaluation result exceeds the preset wind barrier threshold, it is determined that there is an aerodynamic wind barrier that hinders continuous spray adsorption in the current working condition. S503. In response to the determination result, the output mode of the electrostatic micro-lubrication system is switched from continuous spray to high-pressure pulse injection mode; S504. Control the high-pressure generator to apply a pulsed electric field between the nozzle and the stamping die, and adjust the charging frequency of the oil mist droplets to maintain synchronous resonance with the frequency of the pulsed electric field; S505. The peak electric field intensity of the pulsed electric field is used to generate a transient electric field force, which drives the oil mist particles to gain kinetic energy that exceeds the resistance of the closed airflow of the mold, so that the oil mist particles penetrate the aerodynamic wind barrier with a ballistic trajectory and bombard the surface of the stamping mold.

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