Zirconia ceramic microwave single-die-cavity rapid sintering system and intelligent temperature control method

Abstract

The invention relates to the technical field of zirconia ceramic sintering, and discloses a zirconia ceramic microwave single-die-cavity rapid sintering system and an intelligent temperature control method.The system comprises a high-temperature-resistant metal cavity, a microwave generation unit, a temperature detection and control unit, a coil base assembly and an auxiliary structure, and centralized control is achieved through an intelligent touch control computer. A microwave single-mode resonance mode is adopted, a silicon carbide wave absorbing layer is used for enhancing microwave absorption, materials are evenly heated from inside to outside, an intelligent temperature control method is used for monitoring the temperature in real time based on a short-wave infrared thermometer, a PI D control algorithm is combined, the power of a magnetron is dynamically adjusted through an adjustable power source, the temperature control precision reaches + / -2 DEG C, and the temperature control precision reaches + / -2 DEG C; the problems of non-uniform temperature, high energy consumption, high rejection rate, long sintering time and the like in a traditional zirconia ceramic sintering process are effectively solved, the production efficiency can be greatly improved, the cost is reduced, the product quality is improved, the equipment also supports multiple process modes, and diversified production requirements are met.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic material processing, specifically to a rapid sintering system for zirconia ceramics in a microwave single-mode cavity and an intelligent temperature control method, which are applicable to the high-efficiency sintering of dental restorations (such as all-ceramic crowns, inlays, etc.). Background Art

[0002] The production cycle of the processing of all-ceramic restoration products such as zirconia all-ceramics, veneers, and inlays is relatively long, requiring long-time sintering waiting. Moreover, the temperature distribution in the furnace chamber is uneven during the sintering process. The product is heated by radiation from the outside to the inside by means of resistance heating. For products with a large pontic thickness, it is easy to cause incomplete crystallization and insufficient sintering inside the product, which easily affects the strength and quality of the sintered product.

[0003] The processing process of zirconia ceramics is relatively complex. Conventional microwave muffle furnaces generally use a multi-mode cavity sintering method, with uneven product temperature and insufficient temperature control accuracy. A sintering device with a highly stable heat source that is not easily exhausted is required, and the technical requirements are relatively high. The existing process can only be sintered through traditional silicon carbide rods or silicon molybdenum rod traditional sintering furnaces. If rapid sintering is carried out, it may accelerate the rapid attenuation of the heating rods. The sintering time of the processed zirconia products is relatively long, and a slight instability factor will cause deviation in the target color. Moreover, rapid heating or cooling is likely to cause cracking. Since the price of zirconia materials is relatively high, the processing technology is complex, the energy consumption is high, the time used is long, and the longer the processing time, the higher the management cost. Therefore, the manufacturing cost of zirconia all-ceramic teeth is also relatively high. Zirconia materials have high hardness but poor plasticity and are not easily adjusted and repaired after crystallization. Once a problem occurs, it may be necessary to re-cut and sinter for production. Summary of the Invention

[0004] (I) Technical Problem

[0005] The present invention provides a rapid sintering system for zirconia ceramics in a microwave single-mode cavity and an intelligent temperature control method. It can directly perform rapid sintering on the green body ceramic restorations of zirconia all-ceramic single crowns, multi-unit bridge crowns, inlays, veneers, etc. after cutting. After sintering, there is no deformation or hidden crack, and it does not affect the target color and product strength of material crystallization.

[0006] (II) Technical Content

[0007] To solve the above technical problems, the technical solution of the present invention is: A rapid sintering system for zirconia ceramics in a microwave single-mode cavity, including the following structures:

[0008] A high-temperature resistant metal cavity, which is a cylindrical double-layer hollow structure, with a silicon carbide absorbing layer embedded in the inner wall, a temperature measuring hole provided at the top, and a metal cover that can be opened and closed through a hinge at the bottom, used to seal the cavity and prevent microwave leakage;

[0009] The microwave generating unit includes a magnetron, a waveguide, and an adjustable power supply. The magnetron is connected to the slit on the side wall of the cavity through the waveguide and is used to transmit 2.45 GHz microwaves into the cavity.

[0010] The temperature detection and control unit includes a short-wave infrared thermometer, which extends into the high-temperature resistant metal cavity through a temperature measurement hole and is arranged facing the surface of the material.

[0011] The furnace platform assembly includes an alumina heat-insulating furnace platform and a lifting device driven by a servo motor. The alumina heat-insulating furnace platform is fixed on the lifting device and is used to carry the material crucible and adjust its height through the lifting device.

[0012] The auxiliary structure includes an alumina heat-insulating layer coated on the outside of the high-temperature resistant metal cavity; a water cooling system connected to the double-layer hollow structure of the high-temperature resistant metal cavity through a pipeline; a powerful fan installed on the outside of the top of the high-temperature resistant metal cavity for blowing away dust and smoke.

[0013] Further, an electromagnetic locking device is provided between the metal cover and the bottom of the high-temperature resistant metal cavity. When the alumina heat-insulating furnace platform rises to the closed position, the magnetron is triggered to work electrified.

[0014] Further, the waveguide is a rectangular copper waveguide, one end of which is welded to the microwave output port of the magnetron, and the other end is fixed to the slit on the side wall of the high-temperature resistant metal cavity through a flange.

[0015] Further, the lifting device includes a lead screw transmission mechanism and a guiding slide rail. The servo motor is connected to the lead screw through a coupling and drives the alumina heat-insulating furnace platform to lift in the vertical direction.

[0016] Further, the water cooling system includes a circulating water pump, a radiator, and a cooling water tank, and its water inlet and outlet are respectively connected to the double-layer hollow interlayer of the high-temperature resistant metal cavity through hoses.

[0017] Further, it further includes an intelligent touch computer, which is respectively connected to the servo motor, the magnetron, the short-wave infrared thermometer, and the adjustable power supply through data lines and is used to centrally control the operation parameters of the equipment.

[0018] On the other hand, the present invention provides an intelligent temperature control method for rapid sintering of a zirconia ceramic microwave single-mode cavity, including the following steps:

[0019] S1. Real-time temperature monitoring: Detect the surface temperature of the sintered material through the temperature measurement hole of the high-temperature resistant metal cavity by the short-wave infrared thermometer.

[0020] S2. Temperature error calculation: Compare the real-time temperature detected in step S1 with the target temperature in the preset temperature curve to generate a temperature error value e(t).

[0021] S3. Dynamic power regulation: Based on the PID control algorithm, calculate the real-time output power P(t) of the magnetron according to the error value e(t), proportional coefficient Kp, integral coefficient Ki, and differential coefficient Kd. The system quickly corrects the current deviation based on the error value e(t) and the proportional coefficient Kp, the integral coefficient Ki eliminates the historical cumulative error, and the differential coefficient Kd predicts the temperature change trend to suppress overshoot. Finally, the output magnetron power P(t) is composed of the weighted sum of these three parts;

[0022] S4. Closed-loop temperature control execution: Dynamically adjust the magnetron power through an adjustable power supply to make the actual temperature strictly follow the preset curve, with a deviation not exceeding ±2°C;

[0023] S5. Safe cooling control: After sintering is completed, start the water cooling system to circulate and cool the high-temperature resistant metal cavity, cool it below 850°C within 2 minutes, and at the same time control the furnace platform lifting device to descend step by step through the servo motor. After taking out the material, cool the material to room temperature through air cooling.

[0024] Further, the parameters of the PID control algorithm described in step S3 are set as: Kp = 0.8 - 1.2, Ki = 0.05 - 0.15, Kd = 0.1 - 0.3.

[0025] Further, the preset temperature curve described in step S4 includes the following modes:

[0026] Glazing mode: Keep the temperature at 800°C for 10 minutes, microwave power 30%;

[0027] Degreasing mode: Gradually increase the temperature to 600°C at a rate of 5°C / min, microwave power 50%;

[0028] High-density sintering mode: Keep the temperature at 1500°C for 20 minutes, microwave power 100%.

[0029] (3) Technical effects

[0030] The advantages of the present invention compared with the prior art are as follows:

[0031] 1. Improve production efficiency: Adopt the microwave single-mode TM 010 resonant mode, the energy utilization rate is increased by 40%, the sintering time is greatly shortened from 3 - 4 hours of the traditional process to 45 minutes, and even one-key start automatic sintering can be realized, greatly improving the production efficiency and reducing the labor cost.

[0032] 2. Improve product quality: By focusing microwave energy in a single-mode cavity, combined with a short-wave infrared thermometer (accuracy ±2°C) and a closed-loop control algorithm (based on the PID adjustment mechanism), uniform heating from the inside out is achieved, with a temperature control accuracy of ±2°C. This ensures that the actual temperature during the sintering process strictly follows the preset curve, with a deviation of no more than ±2°C. This effectively solves the problem of uneven temperature in traditional processes, avoids the situation of incomplete crystallization and insufficient sintering inside the product, makes the product density uniform, and there is no deformation or hidden crack after sintering, without affecting the target color of material crystallization and product strength.

[0033] 3. Multifunctional integration: The equipment supports various processes such as glazing, crystallization of glass ceramics, and debinding of 3D printed zirconia. Different temperature curves can be preset through an intelligent touch computer to meet diverse needs.

[0034] 4. Reduce production costs: The shortened sintering time reduces energy consumption and management costs; the high finished product rate reduces the cost waste caused by defective products; the stable microwave single-mode cavity reduces equipment maintenance costs. Overall, it effectively reduces the production cost of zirconia ceramic products. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic three-dimensional structure of the rapid sintering system of the microwave single-mode cavity for zirconia ceramics of the present invention Figure 1 .

[0036] Figure 2 is a schematic three-dimensional structure of the rapid sintering system of the microwave single-mode cavity for zirconia ceramics of the present invention Figure 2 .

[0037] Figure 3 is a flowchart of the intelligent temperature control method for rapid sintering of the microwave single-mode cavity of zirconia ceramics of the present invention.

[0038] As shown in the figure: 1. High-temperature resistant metal cavity; 2. Alumina insulation layer; 3. Silicon carbide wave-absorbing layer; 4. Alumina insulation furnace table; 5. Metal cover; 6. Intelligent touch computer; 7. Temperature measurement hole; 8. Power cord; 9. Adjustable power supply; 10. Magnetron; 11. Waveguide; 12. Short-wave infrared thermometer; 13. Lifting device; 14. Strong fan; 15. Servo motor; 16. Water cooling system. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The present invention will be further described in detail below with reference to the accompanying drawings.

[0040] Combined with the attached Figure 1 to the attached Figure 3 , the rapid sintering system of the microwave single-mode cavity for zirconia ceramics includes the following structures:

[0041] The high-temperature resistant metal cavity 1 is of a cylindrical double-layer hollow structure, with a silicon carbide wave-absorbing layer 3 embedded in the inner wall, a temperature measurement hole 7 provided at the top, and a metal cover 5 that can be opened and closed through a hinge at the bottom, which is used to seal the cavity and prevent microwave leakage.

[0042] The microwave generating unit includes a magnetron 10, a waveguide 11, and an adjustable power supply 9. The magnetron 10 is connected to the slit on the side wall of the cavity 1 through the waveguide 11, and is used to transmit 2.45 GHz microwaves into the cavity.

[0043] The temperature detection and control unit includes a short-wave infrared thermometer 12, which extends into the high-temperature resistant metal cavity 1 through the temperature measurement hole 7 and is arranged facing the surface of the material.

[0044] The furnace platform assembly includes an alumina heat-insulating furnace platform 4 and a lifting device 13 driven by a servo motor 15. The alumina heat-insulating furnace platform 4 is fixed on the lifting device 13 and is used to carry the material crucible and adjust its height through the lifting device 13.

[0045] The auxiliary structure includes an alumina heat-insulating layer 2 wrapped outside the high-temperature resistant metal cavity 1; a water cooling system 16 connected to the double-layer hollow structure of the high-temperature resistant metal cavity 1 through a pipeline; and a powerful fan 14 installed outside the top of the high-temperature resistant metal cavity 1 for blowing away dust.

[0046] An electromagnetic locking device is provided between the metal cover 5 and the bottom of the high-temperature resistant metal cavity 1. When the alumina heat-insulating furnace platform 4 rises to the closed position, it triggers the magnetron 10 to work energized. The waveguide 11 is a rectangular copper waveguide, one end of which is welded to the microwave output port of the magnetron 10, and the other end is fixed to the slit on the side wall of the high-temperature resistant metal cavity 1 through a flange. The lifting device 13 includes a lead screw transmission mechanism and a guiding slide rail. The servo motor 15 is connected to the lead screw through a coupling to drive the alumina heat-insulating furnace platform 4 to lift in the vertical direction. The water cooling system 16 includes a circulating water pump, a radiator, and a cooling water tank, and its water inlet and outlet are respectively connected to the double-layer hollow interlayer of the high-temperature resistant metal cavity 1 through hoses.

[0047] The zirconia ceramic microwave single-mode cavity rapid sintering system further includes an intelligent touch computer 6. The intelligent touch computer 6 is respectively connected to the servo motor 15, the magnetron 10, the short-wave infrared thermometer 12, and the adjustable power supply 9 through data lines, and is used to centrally control the operation parameters of the equipment.

[0048] On the other hand, the present invention provides an intelligent temperature control method for rapid sintering of a zirconia ceramic microwave single-mode cavity, including the following steps:

[0049] S1. Real-time temperature monitoring: Detect the surface temperature of the sintered material through the short-wave infrared thermometer 12 from the temperature measurement hole 7 of the high-temperature resistant metal cavity 1;

[0050] S2. Temperature error calculation: Compare the real-time temperature detected in step S1 with the target temperature in the preset temperature curve to generate a temperature error value e(t).

[0051] S3. Dynamic power regulation: Based on the PID control algorithm, calculate the real-time output power P(t) of the magnetron 10 according to the error value e(t), proportional coefficient Kp, integral coefficient Ki, and differential coefficient Kd. The system quickly corrects the current deviation based on the error value e(t) in combination with the proportional coefficient Kp. The integral coefficient Ki eliminates the historical cumulative error, and the differential coefficient Kd predicts the temperature change trend to suppress overshoot. The finally output magnetron power P(t) is composed of the weighted sum of these three parts. The parameters of the PID control algorithm are set as: Kp = 0.8 - 1.2, Ki = 0.05 - 0.15, Kd = 0.1 - 0.3.

[0052] S4. Closed-loop temperature control execution: Dynamically adjust the power of the magnetron 10 through the adjustable power supply 9 to make the actual temperature strictly follow the preset curve, with a deviation not exceeding ±2°C. The preset temperature curve includes the following modes:

[0053] Glazing mode: Keep warm at 800°C for 10 minutes, microwave power 30%.

[0054] Degreasing mode: Gradually heat up to 600°C at a rate of 5°C / min, microwave power 50%.

[0055] High-density sintering mode: Keep warm at 1500°C for 20 minutes, microwave power 100%.

[0056] S5. Safe cooling control: After sintering is completed, start the water cooling system 16 to circulate and cool the high-temperature resistant metal cavity 1, and cool it below 850°C within 2 minutes to prevent the cavity from deforming or overheating. At the same time, control the furnace table lifting device 13 to descend step by step through the servo motor 15, and take out the material and cool it to room temperature through air cooling.

[0057] The working principle of the present invention is: The device adopts the microwave single-mode TM 010 resonant mode, and enhances the microwave absorption efficiency through the silicon carbide absorbing layer 3 embedded in the high-temperature resistant metal cavity 1. The magnetron 10 of the microwave generating unit generates 2.45 GHz microwave, which is transmitted to the cavity through the waveguide 11, enabling the material to preferentially absorb energy inside, realizing uniform heating from the inside out, and avoiding the hot spot problem of traditional multi-mode cavities. The temperature detection and control unit uses the short-wave infrared thermometer 12 to detect the surface temperature of the material in real time and feeds the data back to the intelligent touch computer 6. The powerful fan 14 is to prevent smoke and dust from running out to interfere with the temperature measurement effect when the cavity is at high temperature. The intelligent touch computer 6 dynamically adjusts the power of the magnetron 10 through the adjustable power supply 9 based on the PID control algorithm, making the actual temperature strictly follow the preset curve, and the temperature control accuracy reaches ±2°C.

[0058] The working process of the present invention is as follows:

[0059] 1. Equipment preparation: Connect the power supply of the equipment, and the intelligent touch computer 6 automatically starts the safety detection program. Place the crucible containing the zirconia ceramic green body on the alumina insulation furnace table 4, and the servo motor 15 drives the lifting device 13 to raise the alumina insulation furnace table 4. When the metal cover 5 is tightly closed with the bottom of the high-temperature resistant metal cavity 1, the electromagnetic locking device is triggered, and at the same time, the magnetron 10 is triggered to be powered on and work.

[0060] 2. Microwave heating: The magnetron 10 generates microwaves of 2.45 GHz, which are transmitted through the waveguide 11 and enter the cavity through the slit on the side wall of the high-temperature resistant metal cavity 1. The microwave energy is absorbed by the silicon carbide wave-absorbing layer 3 and converted into heat energy to heat the material. The powerful fan 14 starts to blow away the smoke and dust to avoid interfering with the temperature measurement effect.

[0061] 3. Temperature control: The short-wave infrared thermometer 12 detects the surface temperature of the sintered material through the temperature measurement hole 7 and transmits the temperature data to the intelligent touch computer 6. The intelligent touch computer 6 compares the real-time temperature with the target temperature in the preset temperature curve to generate a temperature error value e(t). Based on the PID control algorithm, the real-time output power P(t) of the magnetron 10 is calculated according to the error value e(t), the proportional coefficient Kp, the integral coefficient Ki, and the differential coefficient Kd. The power of the magnetron 10 is dynamically adjusted through the adjustable power supply 9 to make the actual temperature strictly follow the preset curve, and the deviation does not exceed ±2°C. There are various modes for the preset temperature curve, such as the glazing mode (holding at 800°C for 10 minutes, microwave power 30%), the debinding mode (heating up to 600°C at a gradient rate of 5°C / min, microwave power 50%), and the high-density sintering mode (holding at 1500°C for 20 minutes, microwave power 100%).

[0062] 4. Sintering completion and cooling: When the sintering is completed, start the water cooling system 16 to circulate and cool the high-temperature resistant metal cavity 1. At the same time, the servo motor 15 controls the furnace table lifting device 13 to descend step by step to take out the material, and then the material is cooled to room temperature through air cooling to obtain the sintered product.

[0063] The above describes the present invention and its implementation manners. This description is not restrictive, and what is shown in the drawings is only one of the implementation manners of the present invention. The actual structure is not limited to this. Generally speaking, if those of ordinary skill in the art are inspired by it and design similar structural manners and embodiments without creative work without departing from the spirit of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. Zirconia ceramic microwave single-mode cavity rapid sintering system, characterized by: Includes the following structures: The high temperature resistant metal cavity (1) is a cylindrical double-layer hollow structure, the inner wall of which is embedded with a silicon carbide absorbing layer (3), the top is provided with a temperature measuring hole (7), and the bottom is connected to an openable and closable metal cover (5) via a hinge, which is used to seal the cavity and prevent microwave leakage; A microwave generating unit comprises a magnetron (10), a waveguide (11) and an adjustable power supply (9); the magnetron (10) is connected to a slit on a side wall of a cavity (1) via the waveguide (11) and is used to transmit 2.45 GHz microwaves into the cavity; A temperature detection and control unit, comprising a short-wave infrared thermometer (12), which extends through a temperature measuring hole (7) into the interior of the high-temperature resistant metal cavity (1) and is arranged toward the surface of the material; A furnace table assembly, comprising an alumina heat-insulating furnace table (4) and a lifting device (13) driven by a servo motor (15); the alumina heat-insulating furnace table (4) is fixed on the lifting device (13) and is used to carry a material crucible and adjust its height through the lifting device (13); The auxiliary structure includes an aluminum oxide insulation layer (2) coated on the outside of the high-temperature resistant metal cavity (1); a water cooling system (16) connected to the double-layer hollow structure of the high-temperature resistant metal cavity (1) through a pipeline; and a powerful fan (14) installed on the outside of the top of the high-temperature resistant metal cavity (1) for blowing away smoke and dust.

2. The zirconia ceramic microwave single-mode cavity rapid sintering system according to claim 1, characterized in that: An electromagnetic locking device is provided between the metal cover (5) and the bottom of the high temperature resistant metal cavity (1); when the alumina heat preservation furnace table (4) rises to a sealing position, the magnetron (10) is triggered to be energized and operated.

3. The zirconia ceramic microwave single-mode cavity rapid sintering system according to claim 1, characterized in that: The waveguide tube (11) is a rectangular copper waveguide, one end of which is welded to the microwave output port of the magnetron (10), and the other end is fixed to the slit on the side wall of the high-temperature resistant metal cavity (1) through a flange.

4. The zirconia ceramic microwave single-mode cavity rapid sintering system according to claim 1, characterized in that: The lifting device (13) comprises a screw transmission mechanism and a guide slide rail, and the servo motor (15) is connected to the screw through a coupling to drive the alumina insulation furnace table (4) to lift and lower in a vertical direction.

5. The zirconia ceramic microwave single-mode cavity rapid sintering system according to claim 1, characterized in that: The water cooling system (16) comprises a circulating water pump, a radiator and a cooling water tank, and its water inlet and outlet are respectively connected to the double-layer hollow interlayer of the high-temperature resistant metal cavity (1) through hoses.

6. The zirconia ceramic microwave single-mode cavity rapid sintering system according to claim 1, characterized in that: It also includes an intelligent touch computer (6), which is connected to the servo motor (15), the magnetron (10), the short-wave infrared thermometer (12) and the adjustable power supply (9) through data cables, and is used to centrally control the operating parameters of the equipment.

7. An intelligent temperature control method for rapid sintering of zirconia ceramics in microwave single-mode cavity, characterized in that: The following steps are involved: S1. Real-time temperature monitoring: using a short-wave infrared thermometer (12) to detect the surface temperature of the sintering material from the temperature measuring hole (7) of the high-temperature resistant metal cavity (1); S2, temperature error calculation: compare the real-time temperature detected in step S1 with the target temperature in the preset temperature curve to generate a temperature error value e(t); S3, dynamic power regulation: based on PID control algorithm, the real-time output power P(t) of the magnetron (10) is calculated according to the error value e(t), proportional coefficient Kp, integral coefficient Ki and differential coefficient Kd. The system quickly corrects the current deviation based on the error value e(t) and the proportional coefficient Kp, the integral coefficient Ki eliminates the historical accumulated error, and the differential coefficient Kd predicts the temperature change trend to suppress overshoot. The final output power P(t) of the magnetron is composed of the weighted sum of these three parts. S4, closed-loop temperature control execution: dynamically adjust the power of the magnetron (10) through the adjustable power supply (9) so that the actual temperature strictly follows the preset curve with a deviation of no more than ±2°C; S5. Safe temperature reduction control: When sintering is completed, the water cooling system (16) is started to circulate and cool the high temperature resistant metal cavity (1), and the temperature is reduced to below 850° C. within 2 minutes. At the same time, the servo motor (15) controls the furnace lifting device (13) to descend in a step-by-step manner. After the material is taken out, it is cooled to room temperature through air cooling.

8. The intelligent temperature control method for rapid sintering of zirconia ceramics by microwave single-mode cavity according to claim 7, characterized in that: The parameters of the PID control algorithm in step S3 are set as follows: Kp=0.8-1.2, Ki=0.05-0.15, Kd=0.1-0.

3.

9. The intelligent temperature control method for rapid sintering of zirconia ceramics by microwave single-mode cavity according to claim 7, characterized in that: The preset temperature curve in step S4 includes the following modes: Glazing mode: 800℃ for 10 minutes, microwave power 30%; Degreasing mode: gradient heating to 600°C, rate 5°C / min, microwave power 50%; High density sintering mode: 1500℃ for 20 minutes, microwave power 100%.

Images