Intelligent regulation and control system for large-scale production forming of cubic zirconia material

Abstract

The invention relates to the technical field of intraocular lens growth, and discloses an intelligent regulation and control system for large-scale production forming of a cubic zirconia material. Comprising a central cooperative control module, a partition cooling data monitoring module, a contact thermal resistance liquid level analysis module, a vertical temperature gradient construction module and an induction energy dynamic matching module, and the partition cooling data monitoring module, the contact thermal resistance liquid level analysis module, the vertical temperature gradient construction module and the induction energy dynamic matching module are connected through a bus. The vertical temperature gradient construction module constructs a vertical heat flow channel by adjusting the flow velocity difference of cooling water on the side wall and the bottom. The induction energy dynamic matching module dynamically adjusts the radio frequency output power according to the liquid level height; the central cooperative control module overall plans the whole process of raw material melting, crystal growth and annealing shutdown according to thermodynamic characteristics. The technical problems that the liquid level of the high-temperature melt is difficult to monitor and the thermal field is difficult to control are solved, automatic closed-loop control over crystal growth is achieved, and the structural uniformity and the yield of large-size single crystals are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of artificial crystal growth technology, specifically to an intelligent control system for the large-scale production and molding of cubic zirconia materials. Background Technology

[0002] Cubic zirconia, with its high hardness, high refractive index, and excellent chemical stability, is widely used in artificial gemstones, laser window materials, and high-temperature refractory materials. Since pure zirconia exists as a monoclinic crystal at room temperature, yttrium oxide or calcium oxide is typically added as a stabilizer during production to obtain a stable cubic crystal phase at room temperature. Given its high melting point of 2750℃, conventional refractory or precious metal crucibles cannot withstand this high temperature and are prone to introducing impurities. Therefore, the cold crucible skeleton melting method (CCSM) has become the mainstream process for preparing such high-melting-point oxide crystals. This process utilizes high-frequency electromagnetic induction coupling to heat the raw material inside a cold crucible, combined with forced heat dissipation through a water-cooled copper crucible wall. This causes the material near the inner wall of the crucible to form a solid sintered shell as a self-supporting container, thus achieving high-temperature melting and crystallization in an environment free from refractory contamination.

[0003] In existing cold crucible melting processes, monitoring the melt state and constructing the thermal field present technical challenges. Due to the high temperature, strong electromagnetic radiation, and high brightness characteristics of the melting environment, contact sensors struggle to operate stably for extended periods. Non-contact measurements are often affected by volatiles and surface crusting within the furnace, making it difficult to obtain accurate real-time liquid level data. The production process relies heavily on manual judgment. Furthermore, conventional cooling systems typically employ uniform cooling parameters for the crucible sidewalls and bottom, causing heat from the melt to tend to conduct radially towards the sidewalls. This predominantly radial temperature gradient tends to guide crystal growth horizontally, making it difficult to form a suitable vertical axial heat flow channel for large-size single crystal growth, thus limiting the effective crystallization volume of the single crystal.

[0004] On the other hand, crystal growth is a process of dynamic evolution of load characteristics. As the crystallization interface advances from bottom to top, the ratio of conductive liquid phase to insulating solid phase in the crucible continuously changes, causing the equivalent load impedance of the induction coil to drift. Using constant power output or discontinuous adjustment methods makes it difficult to adapt to the dynamic power density requirements caused by changes in liquid phase volume. Furthermore, mechanical traction mechanisms typically operate at a preset speed, making it difficult to respond in real time to the actual crystallization rate affected by thermal field fluctuations. If the energy supply parameters and mechanical motion parameters lack real-time closed-loop linkage, deviations may occur between the solid-liquid interface advancement speed and the traction speed, thereby affecting the crystal growth quality and batch stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an intelligent control system for the large-scale production and molding of cubic zirconia materials, which solves the problems of the inability to monitor the high-temperature melt level in real time, the difficulty in constructing vertical heat flow channels, and the low matching degree between radio frequency induction energy and crystal growth rate in traditional cold crucible melting processes.

[0006] To achieve the above objectives, this invention provides a large-scale intelligent control system for the production and molding of cubic zirconia materials, comprising a central collaborative control module, a zoned cooling data monitoring module, a contact thermal resistance level analysis module, a vertical temperature gradient construction module, and an inductive energy dynamic matching module. The central collaborative control module establishes communication connections with the zoned cooling data monitoring module, the contact thermal resistance level analysis module, the vertical temperature gradient construction module, and the inductive energy dynamic matching module via an industrial fieldbus. This allows for comprehensive lifecycle control, coordinating the execution of phased control strategies for raw material melting, crystal growth, and annealing shutdown based on the thermodynamic characteristics of different stages of crystal growth.

[0007] The zoned cooling data monitoring module is equipped with physically isolated sidewall and bottom cooling circuits for independently acquiring thermal parameters of the bottom and sidewall water paths of the cold crucible. The module obtains real-time fluid data by installing temperature sensors and flow transmitters at the inlet and outlet of the sidewall and bottom, respectively. Based on the principle of thermodynamic energy conservation, the module calculates the product of the specific heat capacity of the cooling medium, the density-corrected mass flow rate, and the temperature difference between the outlet and inlet to calculate the sidewall heat loss power and bottom heat loss power in real time, while simultaneously acquiring the total input energy reference of the RF power supply, providing a quantitative basis for subsequent thermal field analysis.

[0008] The contact thermal resistance level analysis module is configured to invert the liquid level state of high-temperature melt using indirect thermal parameters. Based on the physical difference in thermal conductivity between liquid and solid zirconium oxide to the inner wall of a cold crucible, the module uses a normalized power attenuation model to invert the real-time liquid level. Specifically, the module first establishes the stable thermal power of the sidewall water channel when the raw material is completely melted and the liquid level reaches its maximum value as the full-load liquid phase thermal power benchmark, and establishes the stable thermal power of the sidewall water channel when the material is completely solidified as the all-solid background thermal power benchmark. The real-time melt level height calculated by the module is proportional to the difference between the real-time sidewall heat loss power and the all-solid background thermal power benchmark, and inversely proportional to the difference between the full-load liquid phase thermal power benchmark and the all-solid background thermal power benchmark. Geometric correction is performed using a crucible shape correction coefficient to output the real-time height of the melt level relative to the bottom of the crucible.

[0009] The vertical temperature gradient construction module is configured to modify boundary heat transfer conditions through fluid dynamics during the crystal growth stage. It controls the bottom water channel to maintain a high turbulent flow velocity, utilizing the convective heat transfer characteristics of the fluid to keep the bottom copper wall at a low temperature close to the inlet water temperature, thus constructing an axial heat dissipation channel with low interfacial thermal resistance. Simultaneously, the module performs closed-loop control based on the real-time temperature difference of the sidewall water channel. By reducing the valve opening and flow rate, it raises the sidewall outlet water temperature to a target set value close to boiling, thereby maintaining a high-temperature water film on the inner wall of the sidewall copper tube to form a high thermal resistance boundary layer. By establishing the thermal boundary difference between the high thermal resistance of the sidewall and the low thermal resistance of the bottom, the module redirects the originally divergent heat flow vector to a vertical direction pointing from the center of the high-temperature melt to the bottom of the low-temperature crucible, guiding the crystal to grow directionally from bottom to top. Furthermore, the module is equipped with a vaporization safety threshold monitoring program. When the outlet water temperature exceeds the safety alarm value or the flow rate exhibits gas-liquid two-phase flow characteristics, it forcibly increases the valve opening to prevent equipment damage caused by critical heat load.

[0010] The inductive energy dynamic matching module is configured to maintain the microstructural uniformity of the crystallization interface. It incorporates a constant power density control model that maps the real-time melt level to the remaining liquid phase melt volume and adjusts the RF power supply based on a linear attenuation algorithm. The target output power set by the inductive energy dynamic matching module is equal to the sum of the system's base power loss and the power required by the liquid phase. The power required by the liquid phase is determined by the product of the optimal melt power density constant per unit volume, the effective cross-sectional area inside the cold crucible, and the real-time melt level. Furthermore, the inductive energy dynamic matching module integrates an automatic frequency tracking program that monitors the phase difference of the oscillation circuit in real time during crystal growth. When it detects load impedance drift caused by a decrease in conductive liquid phase and an increase in insulating solid phase within the crucible, it automatically adjusts the driving frequency to maintain resonance.

[0011] The central collaborative control module is equipped with a thermal balance determination and dynamic speed matching strategy. During the raw material melting stage, the central collaborative control module monitors the rate of change of sidewall heat loss power. When the absolute value of the rate of change is less than a preset stability threshold within a continuous sampling period, the system is determined to have reached steady state and the reference power is locked. During the crystal growth stage, the central collaborative control module calculates the liquid level descent speed derived from the liquid level height change rate and compares it with the mechanical descent speed of the servo mechanism: if the liquid level descent speed is less than the mechanical descent speed, the central collaborative control module automatically sends a command to reduce the mechanical descent speed or fine-tune to increase the cooling intensity; if the liquid level descent speed is greater than the mechanical descent speed, it sends a command to increase the mechanical descent speed, thereby achieving dynamic coupling between the solid-liquid interface propulsion speed and the mechanical traction speed.

[0012] After crystal growth is complete, the central coordinating control module is configured to perform programmed annealing. The central coordinating control module employs an exponential power attenuation strategy to release thermal stress in the crystal, controlling the output power of the RF power supply to decrease exponentially over time, with the attenuation rate determined by the annealing time constant. This annealing time constant is set based on the thermal expansion coefficient and thermal conductivity of the zirconia crystal, ensuring that the temperature change rate during the cooling process does not exceed the crystal's critical thermal shock threshold.

[0013] This invention provides an intelligent control system for the large-scale production and molding of cubic zirconia materials. It has the following beneficial effects: 1. This invention utilizes a contact thermal resistance level analysis module to establish a normalized power attenuation model based on the sidewall heat loss power, taking advantage of the physical difference in heat conduction efficiency between the liquid and solid phases on the inner wall of a cold crucible. This mechanism enables non-contact real-time monitoring of the high-temperature molten liquid level within a sealed cold crucible, effectively overcoming the technical challenges of traditional contact sensor failure and large errors in manual visual inspection under extreme high temperatures and strong electromagnetic environments. It provides a precise quantitative feedback benchmark for the automated closed-loop control of crystal growth.

[0014] 2. This invention implements a differentiated cooling strategy of high-temperature throttling on the sidewalls and low-temperature full-speed cooling at the bottom by constructing a vertical temperature gradient module. This creates a high thermal resistance gas-liquid two-phase boundary layer on the sidewalls while maintaining a low thermal resistance heat dissipation channel at the bottom. This reconstruction of thermal boundary conditions forces the heat flow vector inside the melt to change from the traditional radial divergence to axial vertical conduction, thereby establishing a suitable vertical temperature gradient for large-size single crystal growth within the cold crucible. This effectively suppresses the generation of disordered crystal nuclei and promotes bottom-up directional crystallization.

[0015] 3. This invention, through the linkage of a central collaborative control module and an inductive energy dynamic matching module, automatically adjusts the RF power output based on real-time liquid level data to maintain a constant power density, and dynamically corrects the mechanical traction speed according to the liquid level descent rate. This closed-loop collaborative mechanism eliminates the lag and uncertainty inherent in traditional manual experience-based adjustments, ensuring precise matching between the solid-liquid interface propulsion speed and the mechanical movement speed, significantly improving the stability of the production process and the structural uniformity and yield of large-size cubic zirconia single crystals. Attached Figure Description

[0016] Figure 1 This is a system framework diagram of the present invention; Figure 2 This is a schematic diagram illustrating the structure and heat flow detection principle of the partitioned cooling data monitoring module of the present invention; Figure 3 This is a schematic diagram of the liquid level inversion model and calculation logic of the contact thermal resistance liquid level analysis module of the present invention; Figure 4This is a schematic diagram of the control logic and thermal field morphology of the vertical temperature gradient construction module of the present invention; Figure 5 This is a schematic diagram of the closed-loop control logic of the inductive energy dynamic matching module of the present invention.

[0017] Among them, 10 is the zoned cooling data monitoring module; 20 is the contact thermal resistance liquid level analysis module; 30 is the vertical temperature gradient construction module; 40 is the induction energy dynamic matching module; and 50 is the central collaborative control module. Detailed Implementation

[0018] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] See attached document Figure 1 , Figure 1 This is a schematic diagram of a large-scale intelligent control system for the molding of cubic zirconia materials according to an embodiment of the present invention. The present invention provides a large-scale intelligent control system for the molding of cubic zirconia materials, comprising: The partitioned cooling data monitoring module 10 is used to independently collect the inlet and outlet temperature difference and real-time flow of the water channel at the bottom and side walls of the cold crucible, and simultaneously monitor the output power parameters of the induction heating power supply, providing real-time thermodynamic basic data for the system. The contact thermal resistance liquid level analysis module 20 is used to calculate the effective contact area between the high-temperature liquid phase and the side wall by calculating the attenuation ratio of the heat transfer efficiency of liquid and solid zirconium oxide to the inner wall of the copper crucible, and thus infer the real-time height of the melt level. The vertical temperature gradient construction module 30 is used to maintain the sidewall water temperature at near boiling point during the crystal growth stage by precise throttling. It uses a high-temperature water film to construct a high thermal resistance water barrier to minimize the sidewall heat exchange temperature difference. Combined with the bottom water channel that maintains low-temperature full-speed operation, it forces the heat flow to the bottom of the crucible to construct a vertically upward crystal growth channel. The inductive energy dynamic matching module 40 is used to automatically adjust the output power of the radio frequency generator according to the real-time height of the melt surface, so as to ensure that the power density received by the melt per unit volume is constant, maintain the energy supply and demand balance during the crystallization process, and prevent the melt from boiling again or crystallizing randomly. The central coordination control module 50 is used to coordinate the entire life cycle control: during the raw material melting stage, it controls the two water flows to run at full speed; during the crystal growth stage, it calls the vertical temperature gradient construction module 30 to lock the growth direction; and during the annealing stage, it executes a low flow rate heat preservation strategy to slow down the cooling rate and prevent the finished product from cracking.

[0020] The implementation methods of each of the above functional modules will be explained in detail below, based on specific physical principles and control logic.

[0021] See attached document Figure 2 , Figure 2 A schematic diagram of the hardware connection and data acquisition logic of an intelligent control system for the large-scale production and molding of cubic zirconia materials according to an embodiment of the present invention is shown. The zoned cooling data monitoring module 10 of this embodiment includes physically isolated cooling circulation pipelines, sensor components, and a data processing terminal for performing calculations. The specific implementation steps and structural features are as follows: S101: Construct an independent physical channel for heat exchange; The cold crucible furnace body adopts a split water circuit design, dividing the cooling circuit of the cold crucible into two independent loops. The first loop is the sidewall cooling circuit, with its inlet and outlet water pipes directly connected to the copper tube array forming the crucible sidewall. The second loop is the bottom cooling circuit, with its inlet and outlet water pipes directly connected to the copper assembly forming the crucible base. Each system is equipped with independent inlet and outlet water manifolds, and each outlet water pipe is fitted with an independent electrically controlled regulating valve. The electrically controlled regulating valve is equipped with an analog control interface, enabling continuous adjustment of the valve opening within a stroke range of 0% to 100% based on a control signal, thereby achieving independent and precise adjustment of the cooling water flow rate through the sidewall and bottom.

[0022] S102: Real-time acquisition of sidewall thermal parameters; Platinum resistance temperature sensors are installed at the inlet and outlet of the sidewall cooling circuit to detect the inlet and outlet temperatures of the cooling water in real time. Simultaneously, a flow transmitter is installed on the main pipe of the sidewall circuit to detect the real-time volumetric flow rate through the copper pipe in the sidewall. These sensors convert the collected analog signals into digital signals and transmit them to the central control unit. The central control unit performs calculations based on the principle of thermodynamic energy conservation: first, it consults a pre-stored water density table based on the real-time water temperature data to obtain the water density value at the current temperature; then, it multiplies the real-time volumetric flow rate by the water density value to obtain the mass flow rate; finally, it multiplies the specific heat constant of the water, the mass flow rate, and the temperature difference between the inlet and outlet to calculate the sidewall heat loss power.

[0023] S103: Real-time acquisition of bottom thermal parameters; Using the same hardware configuration standards and calculation logic as in step S102, temperature sensors are placed at the inlet and outlet of the bottom cooling circuit, and flow sensors are placed in the pipeline. The system independently collects the inlet and outlet water temperature difference and volumetric flow rate data of the bottom water path. Similarly, using the product of water's specific heat capacity, density-corrected mass flow rate, and temperature difference, the bottom heat loss power is calculated. Through step S103, the system can obtain the radial heat dissipation power in the direction of the cold crucible sidewall and the axial heat dissipation power in the direction of the bottom.

[0024] S104: Synchronous monitoring of the input energy source; The system communicates with the control interface of the RF induction heating power supply via an industrial bus, reading the power supply's output voltage, output current, and oscillation frequency parameters in real time. For high-frequency oscillators using DC power, the system acquires the DC-side input power; for direct-output power supplies, the system acquires the product of the anode voltage and anode current or directly reads the power count value. The power count value serves as the system's total input energy reference, used for subsequent energy balance comparison with the heat carried away by the cooling water.

[0025] S105: Comprehensive data processing and state mapping; The central control unit synchronously receives data from S102, S103, and S104 at a fixed sampling period (e.g., 10 milliseconds to 100 milliseconds). The system not only records instantaneous values ​​but also establishes a time-series database, recording the trend curves of the aforementioned thermal parameters over time. The calculated sidewall heat loss power and bottom heat loss power are used as input variables for the subsequent contact thermal resistance level analysis module 20 and vertical temperature gradient construction module 30.

[0026] For the specific selection, installation method and signal wiring process of the platinum resistance thermometer, flow transmitter, electric regulating valve and PLC controller involved in the above steps, those skilled in the art can make the selection according to the actual working conditions. These are mature technologies in the field of automation control and will not be elaborated here.

[0027] See attached document Figure 3 , Figure 3 A schematic diagram illustrating the logic flow and operational principle of the contact thermal resistance level analysis module according to an embodiment of the present invention is shown. The contact thermal resistance level analysis module 20 analyzes the melt state inside the crucible based on changes in thermodynamic boundary conditions. The specific implementation steps are as follows: S201: Establish the heat flow reference state; After the cold crucible has been fed and entered the full-power melting stage, when the partition cooling data monitoring module 10 detects that the heat power carried away by the side wall water channel no longer increases and remains at the steady-state peak, the contact thermal resistance level analysis module 20 determines that the material in the crucible is now in a completely liquid phase state and the liquid level height has reached its initial maximum value. At this time, the contact thermal resistance level analysis module 20 reads and locks the real-time heat power value of the side wall water channel at the current moment and marks it as the full-load liquid phase heat power reference (…). Simultaneously, the system sets an all-solid-state background thermal power reference (…). This value can be obtained through experimental calibration; it represents the stable thermal power of the sidewall water passages when the material inside the crucible is completely solidified into a crystalline state under the same induction power. These two values ​​define the effective dynamic range of thermal power change during the transition from a fully liquid phase to a fully solid phase.

[0028] S202: Establish a physical mapping model between contact thermal resistance and liquid level; This step is based on the physical mechanism of heat transfer: convective heat transfer mainly occurs between the liquid zirconia melt and the inner wall of the copper crucible, resulting in low interfacial thermal resistance and high heat flux density. Conversely, solid-state heat conduction mainly occurs between the solid zirconia crystal and the inner wall of the copper crucible, and due to the air gap created by solid-state contraction, its interfacial thermal resistance is high, resulting in low heat flux density. Therefore, under the premise of constant input power, the total heat carried away by the sidewall water channels is positively correlated with the effective contact area of ​​the high-temperature liquid melt covering the sidewall.

[0029] S203: Algorithm implementation for real-time liquid level height; During crystal growth, as the crystal grows from bottom to top, the solid phase region gradually replaces the liquid phase region that was originally in contact with the sidewall, causing the total heat power monitored by the sidewall water channel to gradually decrease. The contact thermal resistance level analysis module 20 analyzes the heat loss power of the sidewall in real time. The real-time height of the melt surface was calculated using a normalized power decay model. : ; in, express The effective height of the melt surface relative to the bottom of the crucible, calculated at any time; This represents the initial total height of the liquid level when the material in the crucible is completely melted. This value is a known geometric parameter of the equipment and is expressed in millimeters. This indicates that the partition cooling data monitoring module 10 is in The sidewall water channel heat loss power is calculated in real time. This indicates that the full-load liquid phase thermal power reference determined in step S201 corresponds to a liquid level height of... Thermal power state at that time; This represents the all-solid background thermal power reference determined in step S201, corresponding to the thermal power state when the liquid level height approaches 0. This represents the crucible shape correction factor. For a standard cylindrical crucible, The value is 1; for irregularly shaped crucibles with tapered or cross-sectional changes, the crucible shape correction coefficient is obtained by fitting known liquid level and power data, and is used to correct the influence of geometric nonlinearity on the heat dissipation area.

[0030] S204: Signal smoothing and status output; Given that turbulent disturbances during the cooling water flow process may cause instantaneous power fluctuations, the contact thermal resistance level analysis module 20 outputs the following in step S203: The data is processed using a moving average filtering method with a time window of 1 to 5 seconds to remove high-frequency noise interference. The processed liquid level data is transmitted in real time to the inductive energy dynamic matching module 40 and the vertical temperature gradient construction module 30 as feedback control variables for adjusting the radio frequency power and the opening of the water valve.

[0031] See attached document Figure 4 , Figure 4 A schematic diagram of the control logic and thermal field morphology of a vertical temperature gradient construction module according to an embodiment of the present invention is shown. The vertical temperature gradient construction module 30 modifies the thermodynamic boundary conditions of the cold crucible through fluid dynamics control, thereby reconstructing the heat flow transport path inside the melt. Specific implementation methods and technical details are as follows: S301: Triggering and initialization of crystal growth mode; Once the contact thermal resistance level analysis module 20 determines that the melt surface is stable and the raw material is completely melted, the system enters the crystal growth stage. The vertical temperature gradient construction module 30 executes a differentiated cooling strategy, switching the cooling mode from full-power cooling to a zoned control mode for the bottom and sidewalls. At this time, the vertical temperature gradient construction module 30 reads the current sidewall inlet water temperature and atmospheric pressure parameters, and sets the target outlet water temperature for the sidewall cooling water (…). To prevent film boiling of cooling water inside the copper pipes from damaging the equipment, the target temperature is set below the safe value of water boiling point at local atmospheric pressure, typically between 90°C and 95°C, to retain a safety margin of subcooling to prevent vaporization.

[0032] S302: Maintaining the low thermal resistance heat dissipation channel at the bottom; The vertical temperature gradient construction module 30 controls the electric regulating valve of the bottom water channel to remain fully open, or adjusts the pump frequency to keep the flow velocity of the bottom water channel in a high-turbulence region, maintaining a high Reynolds number. This operation ensures a high convective heat transfer coefficient between the bottom copper crucible and the cooling water, ensuring that the bottom copper wall remains at a low temperature close to the inlet water temperature. At this time, the bottom of the crucible exhibits low interfacial thermal resistance characteristics to the high-temperature melt, forming the main channel for heat dissipation.

[0033] S303: Dynamic construction of high thermal water barrier on the sidewall; The vertical temperature gradient construction module 30, based on the real-time temperature difference of the sidewall water channel, employs a PID closed-loop control algorithm, according to the parameters set in step S301. The opening of the electric regulating valve on the side wall is continuously adjusted to the set value. By reducing the valve opening, the mass flow rate of the cooling water in the side wall is reduced, increasing the residence time of the water in the copper tube of the side wall. This causes the sensible heat exchange to approach its limit, resulting in an increase in the outlet water temperature, which is then maintained at a certain level. Nearby. During this process, the system follows the energy conservation law shown in the following equation, which characterizes the thermodynamic equilibrium conditions required to maintain the high water temperature: ; In the formula: This represents the mass flow rate of cooling water required to maintain a high sidewall temperature. This indicates the real-time heat load currently borne by the sidewall copper crucible, calculated and fed back in real time by the partitioned cooling data monitoring module 10. This represents the specific heat capacity constant of cooling water; This indicates the set target temperature for the water outlet from the side wall, which is set to a critical temperature close to boiling. This indicates the real-time monitored sidewall inlet water temperature.

[0034] By maintaining the outlet water temperature at a high temperature, the heat exchange temperature difference between the sidewall cooling water and the copper wall is controlled to a minimum. According to Newton's law of cooling, the heat exchange efficiency of the sidewall decreases significantly. At this time, the high-temperature water film forms a dynamic thermal resistance boundary layer on the inner wall of the sidewall copper tube, making the sidewall exhibit a high thermal resistance thermal boundary property for the melt.

[0035] S304: Redirection of heat flux vector and directional crystallization; Because the thermal resistance at the bottom in step S302 is much smaller than the thermal resistance of the sidewall in step S303, the thermal field distribution inside the melt is reconstructed. Under this thermodynamic boundary condition, the system invokes a precision servo lifting mechanism that supports the cold crucible furnace body, working in conjunction with a fixed-position radio frequency induction coil. The radio frequency induction coil continuously inputs electromagnetic energy into the upper region of the melt inside the crucible, maintaining the liquid phase temperature gradient of the upper melt; simultaneously, the precision servo lifting mechanism drives the cold crucible to move vertically downward relative to the radio frequency induction coil at a preset crystal growth rate (e.g., 5 mm / h to 15 mm / h). The heat flow vector that originally radiated outwards is redirected, forming a vertical heat flow channel pointing from the center of the high-temperature melt to the bottom of the low-temperature crucible. According to the physical law that the crystal growth direction is opposite to the heat flow direction, the solid-liquid interface, i.e., the crystallization front, is constrained by the thermal field gradient and grows vertically upwards from the bottom of the crucible as the starting point of the plane.

[0036] S305: Critical control of vaporization safety threshold; During the implementation of the high-temperature throttling strategy, the vertical temperature gradient construction module 30 continuously monitors the pressure drop and temperature fluctuation of the water flow on the sidewall. Once the outlet water temperature exceeds the preset safety alarm value (e.g., 98°C) or the flow rate shows fluctuations characteristic of gas-liquid two-phase flow, indicating that the system is approaching the critical heat flux threshold, the vertical temperature gradient construction module 30 will immediately execute a safety intervention procedure, forcibly increasing the opening of the electric regulating valve to increase the flow rate until the temperature drops back to the safe range, preventing the copper crucible from melting through due to local vaporization.

[0037] The parameter tuning methods for PID controllers and the mechanical action characteristics of electric regulating valves are well-known technologies in the field of automation control. Those skilled in the art can adjust them according to actual working conditions, so they will not be elaborated here.

[0038] See attached document Figure 5 , Figure 5 A schematic diagram of the closed-loop control logic of the inductive energy dynamic matching module according to an embodiment of the present invention is shown. The inductive energy dynamic matching module 40 performs adaptive regulation of power density based on a correlation model between melt geometry and electromagnetic coupling efficiency. Specific implementation methods and technical details are as follows: S401: Synchronization mapping of load status parameters; The induction energy dynamic matching module 40 reads the real-time melt level height data calculated by the contact thermal resistance level analysis module 20 via its internal data bus. Simultaneously, the induction energy dynamic matching module 40 retrieves the crucible's geometric dimensions, including its inner diameter and cross-sectional area, from its memory. Based on the product of the real-time melt level height and the cross-sectional area, the system calculates the remaining volume of liquid melt in the crucible at the current moment. Step S401 converts the melt level signal derived from the thermal parameters into a volume signal of the electromagnetic load, thus establishing the real-time energy application target of the induction heating system.

[0039] S402: Construction of a constant power density control model; To ensure the uniformity of the microstructure at the crystal growth interface and prevent secondary boiling or bubble inclusions caused by a significant increase in energy received per unit volume of remaining melt due to a drop in the liquid level, the system implements a constant power density control strategy. The inductive energy dynamic matching module 40 uses a linear attenuation algorithm to calculate the theoretical set power that the RF power supply should output at the current moment.

[0040] The system calculates the target output power of the RF generator based on the following power-volume matching formula. ): ; In the formula: express The target power setting value that the radio frequency induction heating power supply should output at any given time; This represents the basic power loss required to maintain system operation and keep the solid crystal warm. The basic power loss is obtained by experimental calibration of the system under full load and full melting conditions, and includes the structural loss of the cold crucible and the transmission loss of the pipeline. This represents the optimal melt power density constant per unit volume for the process setting. The optimal melt power density constant per unit volume characterizes the electromagnetic energy required to maintain a unit volume of zirconium oxide in a molten state. This represents the effective cross-sectional area inside the cold crucible, which is a constant for cylindrical crucibles. This indicates the real-time melt level height input by the contact thermal resistance level analysis module 20.

[0041] S403: Execution and adjustment of RF output parameters; The inductive energy dynamic matching module 40 will calculate the... The real-time power input collected by the partitioned cooling data monitoring module 10 is used as the process feedback value (PV) as the setpoint (SP) of the PID controller. After the controller performs deviation calculation, it sends an analog control signal to the power regulation unit of the RF generator. For the vacuum tube self-excited oscillating power supply, the system adjusts the conduction angle of the primary side regulating thyristor of the anode high-voltage transformer, thereby changing the anode voltage; for the all-solid-state power supply, the system adjusts the duty cycle of the inverter bridge or the DC bus voltage. Through the above adjustments, the system controls the actual output power of the power supply to decrease linearly following the trajectory of the liquid level drop, always maintaining the melt in a state of critical melting thermodynamic equilibrium.

[0042] S404: Automatic frequency tracking of load impedance drift; As the crystal growth height increases, the conductive liquid phase in the crucible decreases while the insulating solid phase increases, causing a drift in the equivalent load impedance and resonant frequency of the induction coil. The dynamic matching module 40 for induction energy integrates a phase-locked loop (PLL) frequency tracking subroutine, which monitors the phase difference of the oscillation circuit in real time while adjusting the power amplitude. When phase lock-up or increased reflected power is detected, the system automatically adjusts the driving frequency of the oscillation circuit to ensure that the induction heating power supply always operates in a quasi-resonant state, maintains the power factor in the high-efficiency range, and avoids nonlinear interference to the crystal growth rate caused by energy transfer efficiency fluctuations due to impedance mismatch.

[0043] The specific topology of the phase-locked loop circuit and the principle of the rectifier-inverter circuit inside the RF power supply involved in the above control process are well-known technologies in the field of power electronics. Those skilled in the art can refer to relevant design manuals to implement them, and will not be elaborated here.

[0044] The central collaborative control module 50 establishes data connections with the zoned cooling data monitoring module 10, the contact thermal resistance liquid level analysis module 20, the vertical temperature gradient construction module 30, and the inductive energy dynamic matching module 40 via an industrial fieldbus, and executes a phased control strategy based on the thermodynamic characteristics of different stages of crystal growth. The specific implementation steps are as follows: S501: High-power melting and safety redundancy establishment; At the initial stage of process startup, the central collaborative control module 50 sends a full-power output command to the RF power supply and a forced command to the actuators of the cooling system, setting the opening of the electric regulating valves on the side walls and bottom to 100% to ensure that the cooling water flow rate reaches its maximum value. During this stage, a high-frequency electromagnetic field is used to establish eddy currents in the zirconium scrap within the cold crucible. Induction heating is then used to melt the cold crucible, and strong cooling is employed to form a stable solid cold skin protective layer on the inner wall of the copper crucible, preventing direct contact between the high-temperature molten metal and the copper wall from causing equipment damage.

[0045] S502: Thermal balance determination and baseline locking; As the smelting process continues, the central collaborative control module 50 continuously monitors the rate of change of sidewall heat loss power fed back by the zoned cooling data monitoring module 10. When the absolute value of the rate of change is detected to be less than a preset stability threshold over multiple consecutive sampling periods, the system determines that the raw material has completely melted and the melt flow field has reached a steady state. At this time, the central collaborative control module 50 triggers the contact thermal resistance level analysis module 20 to execute the reference sampling program and lock the current full-load heat power as... and retrieve the corresponding data from the database. Complete the initialization and calibration of the liquid level soft measurement model.

[0046] S503: Construction and Coupling Adaptation of Growth Gradients; After the reference locking is completed, the system automatically switches to crystal growth mode. The central coordination control module 50 sends a start signal to the vertical temperature gradient construction module 30, activating the high-temperature throttling control of the sidewall water channel, raising the sidewall outlet water temperature to the target set value, and establishing a vertical heat flow channel. Simultaneously, the system activates the inductive energy dynamic matching module 40, which adjusts the output power of the RF power supply according to the liquid level and starts the precision servo lifting mechanism to drive the cold crucible to move downward relative to the induction coil at a preset process speed, starting the directional crystallization process.

[0047] S504: Closed-loop synergy in dynamic growth process; During the main stage of crystal growth, the central collaborative control module 50 executes parallel control procedures: 1. Call the contact thermal resistance liquid level analysis module 20 to calculate the melt level height in real time. and its rate of change ; 2. The data is transmitted to the inductive energy dynamic matching module 40, which calculates and adjusts the output power of the RF power supply to maintain a constant power density. 3. Calculate the rate of liquid level drop ( ) and the mechanical descent speed of the servo mechanism ( The deviation between ) if This indicates that the crystallization rate lags behind the mechanical traction rate, and the central coordination control module 50 will send a command to reduce the rate. Alternatively, fine-tune the cooling intensity of the vertical temperature gradient building module 30 to increase it, and vice versa. This enables dynamic matching between the propulsion speed at the solid-liquid interface and the mechanical motion speed. 4. Monitor the real-time temperature and flow rate fed back by the monitoring module 10 for the cooling data of the monitoring zone. If abnormal fluctuations occur, immediately implement flow intervention through the vertical temperature gradient construction module 30.

[0048] S505: Programmed Annealing and Controlled Shutdown When the Calculated Liquid Level Height Approaching 0, and the real-time sidewall thermal power is close to the all-solid background thermal power benchmark. At this point, the central collaborative control module 50 determines that crystal growth has ended. The system enters the in-situ annealing stage, stops the descent of the cold crucible, and executes an exponential power decay strategy to release the thermal stress inside the crystal. The power control during the annealing stage follows the following exponential decay model: ; In the formula: This represents the power output power setting value at time t during the annealing stage; The power output power indicates the time when crystal growth ends, i.e., the time when step S504 ends. The base of the natural logarithm (Euler's number) is a constant of 2.71828. Indicates the duration after entering the annealing stage; This represents the annealing time constant, which is related to the thermal expansion coefficient and thermal conductivity of zirconia crystals and is used to control the cooling rate to not exceed the critical thermal shock threshold of the crystal.

[0049] Once the power decays to 0, the system continues to circulate cooling water until the furnace temperature drops to room temperature, and finally shuts down the cooling system, completing the automated control of the entire production cycle.

[0050] The industrial bus communication protocol and servo motor motion control algorithm involved in the above process are mature technologies in the field of industrial automation. Those skilled in the art can implement them according to the on-site hardware configuration, and will not be elaborated here.

Claims

1. A smart control system for the large-scale production and molding of cubic zirconia materials, characterized in that, include: The partitioned cooling data monitoring module is connected to the sensor ports of the side wall cooling circuit and the bottom cooling circuit of the cold crucible, respectively. It is used to independently collect the fluid thermal parameters of the side wall water circuit and the bottom water circuit, and output the side wall heat loss power and bottom heat loss power calculated based on the thermodynamic energy conservation principle. The contact thermal resistance liquid level analysis module is connected to the partitioned cooling data monitoring module. It is used to receive the sidewall heat loss power data and, based on the physical difference between liquid and solid zirconium oxide in heat conduction efficiency to the inner wall of the cold crucible, invert the real-time height of the melt level relative to the bottom of the crucible. The vertical temperature gradient construction module is connected to the flow regulation actuator of the cold crucible cooling water circuit. It is used to execute the fluid dynamics regulation strategy, and constructs a vertical heat flow channel by controlling the sensible heat exchange of the side wall cooling water to the limit and maintaining a high turbulent flow velocity of the bottom cooling water. The inductive energy dynamic matching module is connected to the contact thermal resistance liquid level analysis module and the control circuit of the radio frequency power supply, respectively. It is used to map the volume of the remaining liquid phase melt according to the real-time height and dynamically adjust the output parameters of the radio frequency power supply according to the linear attenuation algorithm. The central collaborative control module is connected to the partitioned cooling data monitoring module, the contact thermal resistance liquid level analysis module, the vertical temperature gradient construction module, and the induction energy dynamic matching module, respectively. It is used to coordinate the control of the entire production cycle and coordinate the execution of phased control strategies by each module according to the thermodynamic characteristics of different stages of crystal growth.

2. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 1, characterized in that, The partitioned cooling data monitoring module includes physically isolated sidewall cooling circuits and bottom cooling circuits; temperature sensors and flow transmitters are respectively installed at the inlet and outlet of the sidewall cooling circuit and the bottom cooling circuit. The partitioned cooling data monitoring module calculates the sidewall heat loss power and bottom heat loss power in real time by multiplying the specific heat capacity of water, the density-corrected mass flow rate, and the temperature difference between the outlet and the inlet, and simultaneously collects the total input energy reference of the radio frequency power supply.

3. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 1, characterized in that, The specific method by which the contact thermal resistance level analysis module calculates the real-time height of the melt surface is as follows: Establish a full-load liquid phase thermal power benchmark and an all-solid background thermal power benchmark. The full-load liquid phase thermal power benchmark is the stable thermal power of the sidewall water channel when the raw material is completely melted and the liquid level reaches its maximum value. The all-solid background thermal power benchmark is the stable thermal power of the sidewall water channel when the material is completely solidified. Based on the real-time acquired sidewall heat loss power, the liquid level height is calculated using a normalized power attenuation model. This liquid level height is proportional to the difference between the real-time sidewall heat loss power and the all-solid background heat power reference, and inversely proportional to the difference between the full-load liquid phase heat power reference and the all-solid background heat power reference. The final real-time melt surface height is obtained by combining the crucible shape correction coefficient.

4. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 1, characterized in that, The vertical temperature gradient construction module implements a differentiated cooling strategy during the crystal growth stage: The bottom water channel is controlled to maintain a high turbulent flow rate, so that the bottom copper wall is kept at a low temperature close to the inlet water temperature, forming a low interface thermal resistance heat dissipation channel. At the same time, closed-loop control is performed based on the real-time temperature difference of the side wall water circuit. The valve opening of the side wall water circuit is reduced to reduce the flow rate, and the side wall outlet water temperature is raised to the target set value close to the boiling state. A high thermal resistance boundary layer is formed on the inner wall of the side wall copper pipe using a high-temperature water film. By utilizing the thermal resistance difference between the sidewalls and the bottom, the heat flow vector inside the melt is redirected to a vertical direction from the center of the high-temperature melt to the bottom of the low-temperature crucible.

5. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 1, characterized in that, The inductive energy dynamic matching module is equipped with a constant power density control model. The model calculates the volume of the remaining liquid phase melt based on the real-time melt level and the cross-sectional area of ​​the crucible's inner diameter. The inductive energy dynamic matching module calculates the target output power of the RF power supply based on the linear attenuation algorithm, so that the target output power is equal to the sum of the base loss power and the power required by the liquid phase, wherein the power required by the liquid phase is the product of the optimal unit volume melt power density constant, the effective cross-sectional area inside the cold crucible, and the real-time melt liquid level height.

6. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 1, characterized in that, The inductive energy dynamic matching module also integrates an automatic frequency tracking subroutine; The automatic frequency tracking subroutine is configured to monitor the phase difference of the oscillation circuit in real time during crystal growth. When phase lock-out or increased reflection power is detected, the driving frequency of the oscillation circuit is automatically adjusted to compensate for the load impedance drift caused by the reduction of conductive liquid phase and the increase of insulating solid phase in the crucible.

7. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 1, characterized in that, The central collaborative control module is equipped with thermal balance determination logic; During the raw material melting stage, the rate of change of sidewall heat loss power is continuously monitored; when the absolute value of the rate of change is less than the preset stability threshold within multiple consecutive sampling periods, it is determined that the raw material has completely melted and the melt flow field has reached a steady state, and then the contact thermal resistance level analysis module is triggered to execute the benchmark sampling program to lock the full load heat power.

8. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 1, characterized in that, The central collaborative control module is configured to execute a parallel control process during the crystal growth stage to achieve dynamic matching between the solid-liquid interface propulsion speed and the mechanical motion speed. Specifically, the central collaborative control module is configured to: calculate the liquid level descent speed derived from the liquid level height change rate, and calculate the deviation between the liquid level descent speed and the mechanical descent speed of the servo mechanism. When the liquid level drop rate is less than the mechanical drop rate, the system is configured to send commands to reduce the mechanical drop rate or fine-tune to increase the cooling intensity of the vertical temperature gradient building module. When the liquid level drops faster than the mechanical descent speed, the system is configured to send a command to increase the mechanical descent speed.

9. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 4, characterized in that, The vertical temperature gradient construction module is also configured with vaporization safety threshold monitoring logic. During the implementation of high-temperature throttling control on the sidewall, the pressure drop and temperature fluctuation of the water flow on the sidewall are continuously monitored. Once the outlet water temperature exceeds the preset safety alarm value or the flow rate shows fluctuations with gas-liquid two-phase flow characteristics, the opening of the sidewall water circuit valve is immediately forced to increase.

10. The intelligent control system for large-scale production and molding of cubic zirconia material according to claim 1, characterized in that, The central collaborative control module executes an exponential power decay strategy during the annealing stage after crystal growth is completed. The power attenuation strategy is as follows: the output power of the RF power supply is controlled to decrease exponentially over time, and the attenuation rate is determined by the annealing time constant, which is related to the thermal expansion coefficient and thermal conductivity of the crystal, so as to control the cooling rate to not exceed the critical thermal shock threshold of the crystal.

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