Grinding machining method of single crystal silicon carbide mold pressing mold and position control-force control cooperative control high-temperature mold pressing method

Abstract

The invention belongs to the field of die pressing forming of optical glass elements, and relates to a grinding machining method of a single crystal silicon carbide die pressing die and a position control-force control cooperative control high-temperature die pressing method. Single crystal silicon carbide is machined through an ultrasonic vibration auxiliary chemical mechanical grinding method, and an aspheric die with the roughness smaller than 2 nm and the surface shape precision smaller than 0.3 micron is obtained. When the single crystal silicon carbide die is used for high-temperature die forming of optical glass, when the die pressure increasing rate of the lower die exceeds a preset threshold value, the die pressing assembly controls the upper die to reduce the moving rate, and when the die pressure increasing rate of the lower die is smaller than a set value, the die pressing assembly controls the upper die to increase the moving rate. And finally, high-temperature die forming of position control-force control cooperative control is achieved. According to the invention, the service life of the mold is prolonged, meanwhile, the deformation quantity and the deformation rate of the high-temperature glass melt can be accurately controlled, and the problems of surface defects of optical glass elements and service performance failure caused by stress concentration or non-uniform distribution are reduced.

Description

Technical Field

[0001] The present invention relates to the field of technical equipment for forming optical glass elements, and particularly relates to a grinding method for a single crystal silicon carbide molding die and a position control-force control collaborative control high-temperature molding method. Background Art

[0002] Complex curved surface optical glass elements such as aspherical surfaces, free-form surfaces, and lens arrays are core components of high-end optical systems and are widely used in industrial and consumer fields such as lasers, imaging, lighting, security, and medical. However, the traditional grinding, polishing, and lapping processes are complex, inefficient, and costly, and can no longer meet the market's demand for mass production of high-quality, high-precision, and miniaturized optical elements. In view of this, scholars from various countries have proposed directly molding optical glass at high temperature and high pressure to achieve mass production of high-quality and high-precision optical elements. This glass high-temperature molding technology not only simplifies the manufacturing process but also can precisely control the curvature radius, thickness, and surface finish of the lens, meeting the service requirements of high-precision optical systems. In particular, the optical elements produced by this technology do not require grinding and polishing, greatly shortening the production cycle and reducing the manufacturing cost.

[0003] However, due to the harsh high-temperature working environment of the high-temperature molding technology for optical elements, core requirements are imposed on the mold material for high-temperature resistance, low thermal expansion coefficient, thermal fatigue resistance, and nanoscale surface quality. At present, nickel-based alloys and tungsten carbide are mainly used as molding die materials, and surface coatings are used to improve the high-temperature wear resistance of the die, but there are many drawbacks. The oxidation layer of nickel-based alloys thickens at high temperatures, resulting in poor surface shape accuracy of the molded glass. Tungsten carbide has a high edge chipping rate (exceeding 15%) during the molding of complex curved surfaces due to its low fracture toughness material properties, resulting in a short service life of the die.

[0004] Single crystal silicon carbide has extremely high hardness, extremely low thermal expansion coefficient, excellent chemical inertness, and high thermal conductivity, and thus is expected to improve the problems faced by traditional high-temperature molding dies.

[0005] At present, there are few reports on the technology of processing single crystal silicon carbide into high-quality molding dies for high-temperature molding of optical glass. In particular, the unique crystal structure of single crystal silicon carbide can be divided into carbon surface and silicon surface-single crystal silicon carbide according to the surface termination atomic layer. At high temperatures, both the carbon surface and the silicon surface-single crystal silicon carbide have excellent oxidation resistance, creep resistance, and extremely high hardness, and show low reactivity with molten glass. In single crystal silicon carbide, the binding strength of the C-Si bond is higher than that of the Si-Si bond. Therefore, the surface energy of the carbon surface is lower than that of the silicon surface and the chemical inertness is stronger, and the reaction rate with environmental substances such as oxygen is lower. In addition, the grinding force during the grinding process of the carbon surface single crystal silicon carbide is smaller, the surface damage is lower, and it has a lower surface roughness after polishing, making it more suitable for molding optical glass.

[0006] Although single-crystal silicon carbide molding dies can effectively solve the problems faced by traditional dies, silicon carbide dies still face challenges such as wear between the surface and optical glass and brittle machining damage under high-temperature cyclic service, as well as the existing molding process relying on single-pressure control, making it difficult to synchronously coordinate the uniformity of glass melt flow and the accuracy of die movement trajectory, resulting in edge wrinkles, surface shape fluctuations, and low yield of optical glass molded components.

[0007] Therefore, it is urgent to break through the technical bottleneck of ultra-precision grinding of hard and brittle silicon carbide aspheres, develop a position-control - force-control collaborative molding method, and achieve nano-level surface quality and sub-micron-level surface shape accuracy of optical components by precisely regulating the deformation amount and pressure gradient, so as to promote the batch and large-scale manufacturing of high-value-added optical components. Summary of the Invention

[0008] In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a grinding processing method for single-crystal silicon carbide molding dies and a position-control - force-control collaborative control high-temperature molding method, to solve the technical bottleneck of ultra-precision grinding of high-hard and high-brittle silicon carbide aspheres, achieve nano-level surface quality and sub-micron-level surface shape accuracy of optical components, and promote the batch and large-scale manufacturing of high-value-added optical components.

[0009] To achieve the above purpose, the technical solutions adopted by the present invention are as follows:

[0010] In the first aspect, the present invention provides an ultra-precision grinding processing method for single-crystal silicon carbide molding dies, as follows:

[0011] S1. Treat the surface of the single-crystal silicon carbide die;

[0012] S2. Determine the crystal planes of single-crystal silicon carbide, and at the same time mark the C plane and the Si plane as two processing reference directions, then fix the die on a low thermal expansion coefficient fixture and vacuum adsorb it to the workpiece rotating spindle;

[0013] S3. Detect the vibration of the workpiece spindle to ensure that the radial runout of the spindle is less than the set value;

[0014] S4. Select and fix a metal-bonded diamond grinding wheel, adjust the dynamic balance of the grinding wheel to ensure that the unbalance degree at the edge of the grinding wheel is less than the set value;

[0015] S5. Set the rough grinding process parameters, and use a coarse-grained diamond grinding wheel to perform rough grinding on the C-plane and Si-plane single-crystal silicon carbide to pre-form the aspherical contour of the die, with the surface roughness Ra less than 200 nm and a 100-μm allowance reserved;

[0016] S6. Replace the diamond grinding wheel with a finer grain size, set the precision grinding process parameters, and form the aspherical profiles of the C-plane and Si-plane single-crystal silicon carbide molds. The surface form accuracy PV is less than 2 μm, and the surface roughness Ra is less than 20 nm.

[0017] S7. Replace the diamond grinding wheel with an ultra-fine grain size, set the ultra-precision grinding process parameters, turn on the minimum quantity lubrication spray device equipped with a thermally activated grinding fluid and the ultrasonic vibration generating device to assist in reducing the hardness of the workpiece surface layer material and the grinding force during the grinding process, and complete the high-efficiency machining of the single-crystal silicon carbide mold with a super-smooth surface. The surface form accuracy is less than 0.5 μm, and the surface roughness is less than 5 nm.

[0018] S8. Scan the mold surface with a white light interferometer to generate a surface form error map, then construct a free-form surface compensation file based on the error map, generate a tool radius compensation path, and through machining compensation, ultra-precisely grind the surface of the silicon carbide mold again. If the surface form accuracy does not meet the requirements, steps S6 and S7 need to be repeated again.

[0019] As a further technical solution, in step S5, the diamond grinding wheel used for rough machining on the ultra-precision grinder has an abrasive particle size of 40 - 50 μm, the binder is a bronze-based alloy containing 80% Cu, 15% Sn, and 5% Ni, and the concentration of diamond abrasive is 100%.

[0020] In step S6, the diamond grinding wheel used for finish machining on the ultra-precision grinder has an abrasive particle size of 10 - 20 μm, the binder is a nickel-based alloy containing 85% Ni, 10% Co, and 5% Cr, and the concentration of diamond abrasive is 75%.

[0021] In step S7, the diamond grinding wheel used for ultra-precision machining on the ultra-precision grinder has an abrasive particle size of 0.5 - 2 μm, the binder is an Fe-Co-Ni alloy ultra-fine cermet, and the concentration of diamond abrasive is 50%.

[0022] As a further technical solution, the thermally activated grinding fluid described in step S7 contains 50 - 70 wt.% of a fully synthetic grinding fluid, 25 - 40 wt.% of polyethylene glycol, 2 - 5 wt.% of an azo compound, and 3 - 5 wt.% of an organic peroxide compound. The minimum quantity lubrication device can control the thermally activated grinding fluid to be atomized into high-speed small droplets at an atomizing air pressure of 0.3 - 0.6 MPa and a flow rate of 10 - 200 mL / h and act on the contact interface between the grinding wheel and the workpiece.

[0023] As a further technical solution, the ultrasonic vibration generating device described in step S7 is directly fixed to the grinding wheel through a magnetic coupling type quick-change fixture base. The fixture base is internally provided with a micro piezoelectric transducer and a stepped titanium alloy horn, and is rigidly connected to the grinding wheel base through conical surface positioning, and can realize axial, radial, or axial-radial simultaneous vibration of the grinding wheel.

[0024] As a further technical solution, the grinding parameters in the step S5 involve a spindle speed of 15,000 - 20,000 rpm, a feed rate of 50 - 80 mm / min, a cutting depth of 5 - 10 μm, and the lubrication and cooling method is to use a water-based emulsion with a pressure of 5 MPa, a flow rate of 20 L / min, and a temperature of 15 ± 2 °C for pouring lubrication and cooling.

[0025] As a further technical solution, the grinding parameters in the step S6 involve a spindle speed of 25,000 - 30,000 rpm, a feed rate of 20 - 30 mm / min, a cutting depth of 1 - 3 μm, and the lubrication and cooling method is to use a water-based emulsion with a pressure of 5 MPa, a flow rate of 20 L / min, and a temperature of 15 ± 2 °C for pouring lubrication and cooling.

[0026] As a further technical solution, the grinding parameters in the step S7 involve a spindle speed of 35,000 - 40,000 rpm, a feed rate of 1 - 3 mm / min, a cutting depth of 0.1 - 0.5 μm, and the lubrication and cooling method is to use a thermally active grinding fluid for chemical modification, lubrication, and cooling of the workpiece surface layer material.

[0027] In a second aspect, the present invention also proposes a position-control - force-control collaborative control high-temperature molding method using the single-crystal silicon carbide molding die obtained by the grinding processing method of the single-crystal silicon carbide molding die, as follows:

[0028] S9. Respectively place the processed single-crystal silicon carbide molding dies with different crystal planes into the molding components in the position-control - force-control collaborative control high-temperature molding device;

[0029] S10. Perform surface pretreatment on the optical glass block to be high-temperature molded, place the processed optical glass block in the inner cavity of the single-crystal silicon carbide mold, and seal the upper end cover at the same time;

[0030] S11. Start the vacuum pump to ensure that the heating cavity is at the set vacuum degree, then close the vacuum pump and turn on the nitrogen gas charging device to ensure that the heating cavity is in a pure nitrogen protection atmosphere;

[0031] S12. Set the initial threshold value of the force control module in the molding component to the set value, turn on the molding component to drive the upper mold to move quickly towards the lower mold, when the contact force measured by the force control module reaches the threshold value, the upper mold stops advancing, and set the initial position value of the upper mold in the position control module to 0 μm;

[0032] S13. In the position control module, set the upper mold to perform die pressing at a certain rate. At the same time, in the force control module, set the threshold value of the increasing rate of the die pressing force of the lower mold. Start the position-control and force-control collaborative control of high-temperature ultra-precision die pressing forming of optical glass. When the increasing rate of the die pressing force exceeds the threshold value, the die pressing assembly controls the upper mold to reduce the die pressing rate. When the increasing rate of the die pressing force is less than the set value, the die pressing assembly controls the upper mold to increase the die pressing rate;

[0033] S14. Set the heat preservation time. After die pressing is completed, when the heating cavity cools down to room temperature, open the upper cover plate of the heating cavity and take out the die-pressed quartz glass optical element;

[0034] S15. Use a complex surface optical profiler, a white light interferometer, and a field emission scanning electron microscope to measure and analyze the surface shape, surface roughness of the die-pressed quartz glass optical element, and the surface wear of the single-crystal silicon carbide mold.

[0035] As a further technical solution, the single-crystal silicon carbide die pressing mold in step S9 is divided into an upper mold and a lower mold, and the shape and size of the mold determine the shape of the high-temperature die-pressed glass optical element;

[0036] The die pressing assembly in step S9 simultaneously includes a pressure sensor with an accuracy of 0.1 N and a displacement sensor with an accuracy of 0.5 μm.

[0037] As a further technical solution, the heating temperature of the heating cavity in step S12 is in the range of 25 - 1600 °C;

[0038] The die pressing rate of the upper mold in step S13 is 1 - 150 μm / s for die pressing. The threshold value of the increasing rate of the die pressing force of the lower mold is 2.0 N / s, and the increasing rate of the die pressing force is 0.2 - 2.0 N / s.

[0039] The present invention uses an ultrasonic vibration-assisted chemical mechanical grinding method to process single-crystal silicon carbide to obtain an aspherical mold with a surface roughness less than 2 nm and a surface shape accuracy less than 0.3 μm. Then, when using the single-crystal silicon carbide mold for high-temperature die pressing forming of optical glass, when the increasing rate of the die pressing force of the lower mold exceeds the preset threshold value, the die pressing assembly controls the upper mold to reduce the moving rate. When the increasing rate of the die pressing force of the lower mold is less than the set value, the die pressing assembly controls the upper mold to increase the moving rate, and finally realizes the high-temperature die pressing forming with position-control and force-control collaborative control. The present invention can eliminate the material adhesion on the surface of the mold, improve the service life of the mold, and at the same time can accurately control the deformation amount and deformation rate of the high-temperature glass melt, reduce the surface defects of the optical glass element, and the problem of service performance failure caused by stress concentration or uneven distribution.

[0040] The beneficial effects of the present invention are as follows:

[0041] Based on the low surface energy and ultra-high hardness of the carbon surface of the single-crystal silicon carbide mold, after ultrasonic vibration-assisted chemical mechanical grinding, the surface roughness is less than 2 nm, and the aspherical profile form accuracy PV is less than 0.3 μm. This greatly improves the mold's ability to resist material adhesion at high temperatures, eliminates the adhesion of glass materials on the mold surface, and increases the service life of the mold. The position-control and force-control collaborative control molding system realizes precise control of the deformation amount and deformation rate of high-temperature glass melt through sub-micron displacement feedback and dynamic pressure regulation, reducing the surface defects of optical glass components and the problem of service performance failure caused by stress concentration or uneven distribution.

[0042] The present invention can eliminate the material adhesion on the mold surface, increase the service life of the mold, and at the same time can precisely control the deformation amount and deformation rate of high-temperature glass melt, reducing the surface defects of optical glass components and the problem of service performance failure caused by stress concentration or uneven distribution.

[0043] By integrating the optimization of single-crystal silicon carbide mold materials, aspherical ultrasonic vibration-assisted ultra-precision grinding technology, and position-control and force-control collaborative molding methods, the present invention has achieved an all-round breakthrough in high-temperature glass molding technology: Brief Description of the Drawings

[0044] The specification drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0045] Figure 1 It is a schematic diagram of the processing technology and molding process of the single-crystal silicon carbide mold of the present invention;

[0046] Figures 2(a) and 2(b) are atomic force micrographs of the carbon surface-single-crystal silicon carbide and silicon surface-single-crystal silicon carbide mold surfaces obtained by the grinding process of the present invention;

[0047] Figures 3(a), 3(b), and 3(c) are SEM micrographs of the surfaces of the carbon surface-single-crystal silicon carbide mold and silicon surface single-crystal silicon carbide mold after high-temperature molding of glass in the grinding process of the present invention: They are the abrasive wear characteristics of the carbon surface mold, the adhesive wear characteristics of the silicon surface mold, and the corresponding O element EDS energy spectrum diagrams;

[0048] Figures 4(a) and 4(b) are the surface wear characteristics of the carbon surface-single-crystal silicon carbide mold after position-control and force-control collaborative molding and single position-control molding: They are the abrasive wear characteristics induced by plastic deformation and the micro-fracture wear induced by brittle fracture, respectively. Detailed Embodiments

[0049] As explained in the background art, silicon carbide molds still face the challenges of abrasive or adhesive wear and brittle processing damage on the surface when serving under high-temperature cycles with optical glass. The existing molding process relies on single pressure control and it is difficult to synergistically control the uniformity of glass melt flow and the accuracy of mold movement trajectory, resulting in wrinkles at the edges of components, surface shape fluctuations, and low product yields. To solve the above problems and machine an aspherical mold with a roughness less than 2 nm and a surface shape accuracy less than 0.3 μm, the present invention proposes an ultrasonic vibration-assisted chemical mechanical grinding method. By means of diamond grinding wheel grinding, rough grinding, ultrasonic vibration-assisted fine grinding, and thermally activated grinding fluid chemical mechanical ultra-precision grinding are carried out in sequence, and an on-line surface shape detection and closed-loop compensation strategy is constructed. Finally, the ultra-precision machining of the aspherical profile of single-crystal silicon carbide is realized. The position control-force control synergy control method proposed in combination with the present invention can better control the shape and size of optical components during the high-temperature molding process by precisely controlling the pressure and movement trajectory of the mold at the same time, providing an effective solution for the requirements of modern optical systems for high-precision components.

[0050] The words expressing position and direction described in the present invention are all illustrated by taking the drawings as examples, but can be changed according to needs, and all changes made are included in the protection scope of the present invention.

[0051] This Example 1

[0052] This embodiment provides a grinding method for a single-crystal silicon carbide molding mold; it includes the following steps:

[0053] S1. Ultrasonically clean the single-crystal silicon carbide mold in sequence with acetone, ethanol, and deionized water, set the frequency to 40 kHz, and the time for each is 15 min to remove surface oil stains and particulate contaminants. Then blow dry with clean and dry compressed air, and treat with a plasma cleaner to enhance surface activity;

[0054] S2. Determine the (0001) crystal plane of single-crystal silicon carbide through an X-ray diffractometer, and at the same time mark the C plane and the Si plane as two processing reference directions. Then fix the mold to a low thermal expansion coefficient fixture with hydrolytic glue and vacuum adsorb it to the spindle of the workpiece rotating machine tool. The hydrolytic glue is epoxy resin-based, the curing temperature is 80 °C, and the machine tool is Chengying UPC-200;

[0055] S3. Detect the vibration of the workpiece spindle with the built-in dynamic balancer of the grinding machine to ensure that the radial runout of the spindle is less than 1 nm;

[0056] S4. Select a metal-bonded diamond grinding wheel, fix it through a conical surface positioning and hydraulic locking mechanism, and adjust the dynamic balance of the grinding wheel with a laser dynamic balancer to ensure that the unbalance degree at the edge of the grinding wheel is less than 0.2 g·mm;

[0057] S5. Set the rough grinding process parameters, and use a coarse-grained diamond grinding wheel to rough grind the C-plane and Si-plane single-crystal silicon carbide to pre-form the aspherical contour of the mold. The roughness Ra is less than 200 nm, and a margin of 100 μm is reserved. The large spacing between the coarse-grained abrasive grains and the sufficient chip space are suitable for rapid removal with a large cutting amount. If a fine-grained grinding wheel is directly used, the abrasive grains are easily passivated quickly by the high hardness of SiC, and the efficiency drops by more than 80%.

[0058] S6. Replace the grinding wheel with a fine-grained diamond grinding wheel, and dress the grinding wheel by means of electrical discharge dressing. Set the fine grinding process parameters to form the aspherical contour of the C-plane and Si-plane single-crystal silicon carbide mold. The surface form accuracy PV is less than 2 μm, and the roughness Ra is less than 20 nm. Using a finer particle size for fine grinding will repair the cracks generated in the rough grinding stage; the increase in the density of finer abrasive grains can reduce the load on a single abrasive grain, promote the removal in the plastic region, and converge the crack depth to the sub-micron level. If this process is skipped, the deep cracks left by rough grinding will cause the ultra-precision grinding wheel to be blocked, greatly reducing the processing efficiency.

[0059] S7. Replace the grinding wheel with an ultra-fine-grained diamond grinding wheel, set the ultra-precision grinding process parameters, and turn on the minimum quantity lubrication spray device equipped with a thermally activated grinding fluid and the ultrasonic vibration generating device to assist in reducing the hardness of the workpiece surface material and the grinding force during the grinding process, and complete the efficient processing of the single-crystal silicon carbide mold with a super-smooth surface. The surface form accuracy is less than 0.5 μm, and the roughness is less than 5 nm. Using ultra-fine abrasive grains to form a continuous cutting edge to achieve nano-level material removal;

[0060] S8. Use a white light interferometer to scan the surface of the mold to generate a surface form error map, then construct a free-form surface compensation file based on the error map, generate a tool radius compensation path using the B-spline interpolation algorithm, and through machining compensation, ultra-precision grind the surface of the silicon carbide mold again. If the surface form accuracy does not meet the requirements, steps S6 and S7 need to be repeated again. At this time, the surface form accuracy PV of the silicon carbide surface is 0.3 μm, and the surface roughness Ra is 2 nm. The surface of the single-crystal silicon carbide is shown in Figure 2;

[0061] In this embodiment, the mold material is single-crystal silicon carbide, the aspherical contour surface of the mold is the carbon surface and the silicon surface of the single-crystal silicon carbide (0001) crystal plane, and the surface quality of the mold is nano-level roughness and sub-micron-level surface form accuracy.

[0062] In this embodiment, the diamond grinding wheel used in the rough machining of the ultra-precision grinding machine in step S5 has an abrasive particle size of 40-50 μm. The binder is a bronze-based alloy containing 80% Cu, 15% Sn, and 5% Ni. The concentration of diamond abrasive is 100%. The processing parameters are as follows: spindle speed of 15,000-20,000 rpm, feed rate of 50-80 mm / min, and cutting depth of 5-10 μm. The lubrication and cooling method is to use a water-based emulsion with a pressure of 5 MPa, a flow rate of 20 L / min, and a temperature of 15±2°C for pouring lubrication and cooling. The spindle speed of 20,000 rpm represents an 80% increase compared to the traditional mold processing parameters, enabling efficient removal through brittle fracture by kinetic impact. The water-based emulsion cooling method matches the high thermal conductivity of SiC, avoiding wheel dulling caused by heat accumulation. The present invention converges the crack depth to 5-8 μm through high-speed rotation and high-pressure cooling, balancing the contradiction between the high hardness and brittleness of silicon carbide and laying a foundation for subsequent repair.

[0063] In this embodiment, the diamond grinding wheel used in the finish machining of the ultra-precision grinding machine in step S6 has an abrasive particle size of 10-20 μm. The binder is a nickel-based alloy containing 85% Ni, 10% Co, and 5% Cr. The concentration of diamond abrasive is 75%. The dressing of the grinding wheel is carried out by electric discharge dressing with a voltage of 60 V and a pulse width of 3 μs. The processing parameters are as follows: spindle speed of 25,000-30,000 rpm, feed rate of 20-30 mm / min, and cutting depth of 1-3 μm. The lubrication and cooling method is to use a water-based emulsion with a pressure of 5 MPa, a flow rate of 20 L / min, and a temperature of 15±2°C for pouring lubrication and cooling. The dressing of the grinding wheel is carried out by laser dressing with a wavelength of 1064 nm, a power of 50 W, and a scanning speed of 10 mm / s. By matching different grit sizes of the grinding wheel with the feed rate, the maximum undeformed chip thickness is reduced from 5-10 μm in the rough grinding stage to 0.5-1 μm in the finish grinding stage, promoting the transition of the material removal mechanism from brittle fracture to the quasi-plastic domain.

[0064] In this embodiment, in the ultra-precision machining of the ultra-precision grinding machine in step S7, the diamond grinding wheel abrasive has a particle size of 0.5 - 2 μm, the binder is an Fe-Co-Ni alloy ultrafine cermet, and the concentration of the diamond abrasive is 50%. The dressing of the grinding wheel is carried out by laser dressing with a wavelength of 1064 nm, a power of 50 W, and a scanning speed of 10 mm / s; the machining parameters are a spindle speed of 35000 - 40000 rpm, a feed rate of 1 - 3 mm / min, a cutting depth of 0.1 - 0.5 μm, and the lubrication and cooling method is to use a thermally active grinding fluid to chemically modify, lubricate, and cool the surface layer material of the workpiece. The 50% concentration diamond abrasive balances the abrasive grain density and chip space, increases the porosity of the binder, and improves the penetration efficiency of the grinding fluid by 3 times; ultra-high-speed grinding increases the linear speed of the grinding wheel and increases the kinetic energy impact to further promote the brittle-ductile transition; a cutting depth of 0.1 - 0.5 μm is close to the critical value of the plastic region of SiC, and combined with ultrasonic vibration, the maximum undeformed chip thickness is pressed to 0.05 - 0.1 μm;

[0065] In this embodiment, the thermally active grinding fluid described in step S7 contains 50 - 70 wt.% of a fully synthetic grinding fluid, 25 - 40 wt.% of polyethylene glycol, 2 - 5 wt.% of an azo compound, and 3 - 5 wt.% of an organic peroxide. The minimum quantity lubrication device can control the thermally active grinding fluid to be atomized into high-speed small droplets at an atomizing air pressure of 0.3 - 0.6 MPa and a flow rate of 10 - 200 mL / h and act on the contact interface between the grinding wheel and the workpiece. The thermally active grinding fluid can soften the SiC surface through chemical adsorption to generate a Si-OH weakening layer, reducing the grinding force by 20%, and the SiC surface undergoes selective etching in an alkaline environment to preferentially remove surface defects. The reaction formula is: SiC + 4OH - →SiO4 4- +CH4↑.

[0066] In this embodiment, the ultrasonic vibration generating device described in step S7 is directly fixed to the grinding wheel through a magnetic coupling type quick-change fixture base. The fixture base is internally provided with a micro piezoelectric transducer and a stepped titanium alloy horn, and is rigidly connected to the grinding wheel base through conical surface positioning, enabling the grinding wheel to vibrate axially, radially, or axially-radially simultaneously. The power of the ultrasonic vibration generating device is 50 - 300 W, the vibration frequency is 20 - 50 kHz, and the amplitude is 1 - 5 μm. The ultrasonic vibration assistance reduces the effective cutting thickness from 0.1 - 0.5 μm in static grinding to the nanoscale through 30,000 micro-impacts per second, breaking through the 0.1 μm brittle-ductile transition critical value of SiC and enabling the material to be removed by lattice slip rather than brittle fracture. In addition, the ultrasonic vibration decomposes the continuous grinding force into discrete pulse forces, reduces the continuous friction between the abrasive grains and single-crystal SiC, greatly reduces the frictional force, and at the same time, the tangential vibration assists in chip removal, preventing abrasive grain clogging and reducing the clogging rate of the grinding wheel pores.

[0067] Example 2

[0068] Based on the single-crystal silicon carbide molding die obtained in Example 1, this example provides a high-temperature molding method with coordinated position control and force control, which specifically includes the following steps:

[0069] S9. Place the processed single-crystal silicon carbide molding dies with different crystal planes into the molding components of the high-temperature molding device with coordinated position control and force control respectively;

[0070] S10. Perform surface pretreatment on the optical glass block to be high-temperature molded, remove oil stains and contaminants, place the processed optical glass block into the inner cavity of the single-crystal silicon carbide die, and seal the upper end cover at the same time;

[0071] S11. Start the vacuum pump to ensure that the heating cavity has a vacuum degree of 10 -3 Pa, then close the vacuum pump and turn on the nitrogen filling device to ensure that the heating cavity is in a pure nitrogen protection atmosphere;

[0072] S12. Set the initial threshold of the force control module in the molding component to 0.5 N, then start the molding component to drive the upper mold to move rapidly towards the lower mold. When the contact force measured by the force control module reaches the threshold of 0.5 N, the upper mold stops advancing, and set the initial position value of the upper mold in the position control module to 0 μm;

[0073] S13. Set the upper mold in the position control module to perform molding at a certain rate, and at the same time set the threshold of the increasing rate of the molding pressure of the lower mold in the force control module, and start the coordinated position control and force control high-temperature ultra-precision molding of the optical glass. When the increasing rate of the molding pressure exceeds the threshold, the molding component controls the upper mold to reduce the molding rate, and when the increasing rate of the molding pressure is less than the set value, the molding component controls the upper mold to increase the molding rate;

[0074] S14. Set the heat preservation time. After the molding is completed, when the heating cavity cools down to room temperature, open the upper cover of the heating cavity and take out the molded quartz glass optical element;

[0075] S15. Measure and analyze the surface shape, surface roughness of the molded quartz glass optical element and the surface wear of the single-crystal silicon carbide die by using a complex surface optical surface profiler, a white light interferometer, and a field emission scanning electron microscope.

[0076] In this example, the single-crystal silicon carbide molding die described in step S10 is divided into an upper die and a lower die, and the shape and size of the die determine the shape of the high-temperature molded glass optical element.

[0077] In this embodiment, the molding assembly described in step S10 includes both a pressure sensor with an accuracy of 0.1 N and a displacement sensor with an accuracy of 0.5 μm.

[0078] In this embodiment, the heating temperature of the heating chamber described in step S12 is in the range of 25 to 1600 °C.

[0079] In this embodiment, the upper mold molding rate described in step S14 is carried out at 1 to 150 μm / s, the threshold value of the increase rate of the lower mold molding pressure is 2.0 N / s, and the molding pressure increase rate is in the range of 0.2 to 2.0 N / s.

[0080] Example 3

[0081] Based on the method disclosed in Example 2, this example provides a worn surface after multiple high-temperature molding of a silicon carbide mold with different crystal planes, as shown in Figure 3. The specific steps are as follows:

[0082] S1. Ultrasonically clean the single-crystal silicon carbide mold in turn with acetone, ethanol, and deionized water, set the frequency to 40 kHz, and the time to 15 min each to remove surface oil stains and particulate contaminants. Then blow dry with clean and dry compressed air and treat with a plasma cleaner to enhance surface activity.

[0083] S2. Determine the (0001) crystal plane of the single-crystal silicon carbide by means of an X-ray diffractometer, and at the same time mark the C plane and the Si plane as two processing reference directions. Then fix the mold to a low thermal expansion coefficient fixture with a hydrolytic glue and vacuum adsorb it to the spindle of a workpiece rotary machine tool. The hydrolytic glue is epoxy resin-based, the curing temperature is 80 °C, and the machine tool is an ultra-precision turning-grinding-milling composite grinding machine UPC-200.

[0084] S3. Detect the vibration of the workpiece spindle with the built-in dynamic balancer of the grinding machine to ensure that the radial runout of the spindle is less than 1 nm.

[0085] S4. Select a metal-bonded diamond grinding wheel, fix it through a conical surface positioning and hydraulic locking mechanism, and adjust the dynamic balance of the grinding wheel with a laser dynamic balancer to ensure that the unbalance degree at the edge of the grinding wheel is less than 0.2 g·mm.

[0086] S5. Set the rough grinding process parameters, and use a coarse-grained diamond grinding wheel to perform rough grinding on the C plane and the Si plane of the single-crystal silicon carbide respectively to achieve preforming of the aspherical contour of the mold, with a surface roughness Ra less than 200 nm and a remaining allowance of 100 μm. The processing parameters for the carbon surface of the single-crystal silicon carbide are a spindle speed of 18000 rpm, a feed rate of 50 mm / min, and a cutting depth of 5 μm; the processing parameters for the silicon surface are a spindle speed of 15000 rpm, a feed rate of 70 mm / min, and a cutting depth of 7 μm.

[0087] S6. Replace the diamond grinding wheel with a finer grain size, dress the grinding wheel by electrical discharge dressing, and set the precision grinding process parameters to achieve the aspherical profile forming of the single-crystal silicon carbide mold on the C surface and the Si surface. The surface form accuracy PV is less than 2 μm, and the surface roughness Ra is less than 20 nm. Among them, the processing parameters for the carbon surface of single-crystal silicon carbide are a spindle speed of 25000 rpm, a feed rate of 20 mm / min, and a cutting depth of 2 μm; the processing parameters for the silicon surface are a spindle speed of 22000 rpm, a feed rate of 25 mm / min, and a cutting depth of 2.5 μm.

[0088] S7. Replace the diamond grinding wheel with an ultra-fine grain size, set the ultra-precision grinding process parameters, turn on the minimum quantity lubrication spray device equipped with a thermally activated grinding fluid and the ultrasonic vibration generating device to assist in reducing the hardness of the workpiece surface material and the grinding force during the grinding process, and complete the high-efficiency processing of the single-crystal silicon carbide mold with a super-smooth surface. The surface form accuracy is less than 0.5 μm, and the surface roughness is less than 5 nm. Among them, the ultrasonic vibration generating device is directly fixed to the grinding wheel through a magnetic coupling type quick-change fixture base. The power of the ultrasonic vibration generating device is 200 W, the vibration frequency is 35 kHz, and the amplitude is 3 μm; the processing parameters for the carbon surface of single-crystal silicon carbide are a spindle speed of 35000 rpm, a feed rate of 3 mm / min, and a cutting depth of 0.5 μm; the processing parameters for the silicon surface are a spindle speed of 32000 rpm, a feed rate of 3 mm / min, and a cutting depth of 0.6 μm.

[0089] S8. Scan the mold surface with a white light interferometer to generate a surface form error map, then construct a free-form surface compensation file based on the error map, generate a tool radius compensation path using the B-spline interpolation algorithm, and through machining compensation, ultra-precisely grind the surface of the silicon carbide mold again. The surface form accuracy PV of the silicon carbide surface is 0.3 μm, and the surface roughness Ra is 2 nm, obtaining the single-crystal silicon carbide molds for the carbon surface and the silicon surface.

[0090] S9. Place the processed single-crystal silicon carbide molding dies with different crystal planes into the molding components in the high-temperature molding device with position-control and force-control coordinated control.

[0091] S10. Perform surface pretreatment on the optical glass block to be formed at high temperature, remove oil stains and contaminants, place the treated optical glass block into the inner cavity of the single-crystal silicon carbide mold, and seal the upper end cover at the same time.

[0092] S11. Start the vacuum pump to ensure that the heating cavity is at a vacuum degree of 10 -3 Pa, then turn off the vacuum pump and turn on the nitrogen gas filling device to ensure that the heating cavity is in a pure nitrogen protection atmosphere.

[0093] S12. Set the initial threshold of the force control module in the molding assembly to 0.5 N. Then start the molding assembly to drive the upper mold to move rapidly towards the lower mold. When the contact force measured by the force control module reaches the threshold of 0.5 N, the upper mold stops advancing, and set the initial position value of the upper mold in the position control module to 0 μm.

[0094] S13. Set the upper mold to perform molding at a rate of 0.1 mm / min in the position control module. At the same time, set the threshold of the increase rate of the molding pressure of the lower mold in the force control module, and start the position-control - force-control collaborative control high-temperature ultra-precision molding of the optical glass. When the increase rate of the molding pressure exceeds the threshold of 2 N / min, the molding assembly controls the upper mold to reduce the molding rate, and when the increase rate of the molding pressure is less than the set value, the molding assembly controls the upper mold to increase the molding rate.

[0095] S14. Set the heat preservation time. After the molding is completed, when the heating cavity cools down to room temperature, open the upper cover plate of the heating cavity and take out the molded quartz glass optical element.

[0096] S15. Use a complex surface optical profiler, a white light interferometer, and a field emission scanning electron microscope to measure and analyze the surface shape, surface roughness, and surface wear of the molded quartz glass optical element and the single-crystal silicon carbide mold.

[0097] In this embodiment, as shown in Figure 3, after multiple moldings of the silicon carbide mold with different crystal planes with optical glass, the wear conditions are different. After multiple moldings of the carbon-face - single-crystal silicon carbide mold, plastic deformation appears on the surface, without obvious breakage and adhesion, showing the characteristics of abrasive wear; after multiple moldings of the silicon-face - single-crystal silicon carbide mold, breakage appears on the surface. At the same time, EDS analysis of the silicon face shows that there are a large number of oxygen elements from SiO2 in the optical glass on the surface of the silicon-face mold, and a large area of silicon dioxide deposition occurs, indicating that a serious adhesion occurs between the silicon face and the optical glass. Therefore, with the same roughness and surface shape accuracy, the carbon-face - single-crystal silicon carbide as the molding mold can better mold high-quality optical glass.

[0098] In this embodiment, through the integration of single-crystal silicon carbide mold material optimization, aspherical ultrasonic vibration-assisted ultra-precision grinding technology, and position-control-force-control collaborative molding method, all-round breakthroughs in high-temperature glass molding technology have been achieved: Based on the low surface energy and ultra-high hardness of the carbon surface of the single-crystal silicon carbide mold, after ultrasonic vibration-assisted chemical mechanical grinding, the surface roughness is less than 2 nm, and the aspherical profile form accuracy PV is less than 0.3 μm, greatly improving the mold's ability to resist material adhesion at high temperatures, eliminating the adhesion of glass materials on the mold surface, and improving the service life of the mold; The position-control-force-control collaborative control molding system realizes precise control of the deformation amount and deformation rate of the high-temperature glass melt through sub-micron displacement feedback and dynamic pressure regulation, reducing the surface defects of optical glass components and the problem of service performance failure caused by stress concentration or uneven distribution.

[0099] Example 4

[0100] Based on the method disclosed in Example 2, this example provides the worn surfaces of a silicon carbide mold under position-control-force-control collaborative control and single position control after multiple moldings, as shown in Figure 4. The specific steps are as follows:

[0101] S1. Ultrasonically clean the single-crystal silicon carbide mold in sequence with acetone, ethanol, and deionized water, set the frequency to 40 kHz, and the time to 15 min each to remove surface oil stains and particulate contaminants. Then, blow dry with clean and dry compressed air and treat with a plasma cleaner to enhance surface activity;

[0102] S2. Determine the (0001) crystal plane of the single-crystal silicon carbide through an X-ray diffractometer, mark the C plane as the processing reference direction, and then fix the mold to a low thermal expansion coefficient fixture with hydrolytic glue and vacuum adsorb it to the spindle of the workpiece rotary machine tool. The hydrolytic glue is epoxy resin-based, with a curing temperature of 80 °C, and the machine tool is an ultra-precision turning-grinding-milling composite grinding machine UPC-200;

[0103] S3. Detect the vibration of the workpiece spindle with the built-in dynamic balancer of the grinding machine to ensure that the radial runout of the spindle is less than 1 nm;

[0104] S4. Select a metal-bonded diamond grinding wheel, fix it through a conical surface positioning and hydraulic locking mechanism, and adjust the dynamic balance of the grinding wheel with a laser dynamic balancer to ensure that the unbalance degree at the edge of the grinding wheel is less than 0.2 g·mm;

[0105] S5. Set the rough grinding process parameters, and use a coarse-grained diamond grinding wheel to perform rough grinding on the C-plane single-crystal silicon carbide to preform the aspherical profile of the mold, with a roughness Ra less than 200 nm and a remaining allowance of 100 μm. The processing parameters are a spindle speed of 18000 rpm, a feed speed of 50 mm / min, and a cutting depth of 5 μm;

[0106] S6. Replace the diamond grinding wheel with a finer grit size, dress the grinding wheel by means of electrical discharge dressing, set the precision grinding process parameters, and achieve the non-spherical profile forming of the C-plane single-crystal silicon carbide mold. The surface form accuracy PV is less than 2 μm, and the surface roughness Ra is less than 20 nm. Among them, the processing parameters are the spindle speed of 25,000 rpm, the feed rate of 20 mm / min, and the cutting depth of 2 μm.

[0107] S7. Replace the diamond grinding wheel with an ultra-fine grit size, set the ultra-precision grinding process parameters, turn on the minimum quantity lubrication spray device equipped with a thermally active grinding fluid and the ultrasonic vibration generating device, and assist in reducing the hardness of the workpiece surface layer material and the grinding force during the grinding process to complete the efficient processing of the ultra-smooth C-plane single-crystal silicon carbide mold. The surface form accuracy is less than 0.5 μm, and the surface roughness is less than 5 nm. Among them, the ultrasonic vibration generating device is directly fixed to the grinding wheel through a magnetic coupling type quick-change fixture base. The power of the ultrasonic vibration generating device is 200 W, the vibration frequency is 35 kHz, and the amplitude is 3 μm. The processing parameters are the spindle speed of 35,000 rpm, the feed rate of 5 mm / min, and the cutting depth of 0.5 μm.

[0108] S8. Scan the surface of the mold with a white light interferometer to generate a surface form error map, then construct a free-form surface compensation file based on the error map, generate a tool radius compensation path using the B-spline interpolation algorithm, and through machining compensation, ultra-precisely grind the surface of the silicon carbide mold again. The surface form accuracy PV of the silicon carbide surface is 0.3 μm, and the surface roughness Ra is 2 nm.

[0109] S9. Place the machined C-plane single-crystal silicon carbide molding die into the molding assembly in the high-temperature molding device with position-control and force-control coordinated control.

[0110] S10. Perform surface pretreatment on the optical glass block to be formed at high temperature, remove oil stains and contaminants, place the treated optical glass block into the inner cavity of the single-crystal silicon carbide mold, and seal the upper cover at the same time.

[0111] S11. Start the vacuum pump to ensure that the heating cavity has a vacuum degree of 10 -3 Pa, then close the vacuum pump and turn on the nitrogen filling device to ensure that the heating cavity is in a pure nitrogen protection atmosphere.

[0112] S12. Set the initial threshold of the force control module in the molding assembly to 0.5 N, then turn on the molding assembly to drive the upper mold to move rapidly towards the lower mold. When the force control module measures that the contact force reaches the threshold of 0.5 N, the upper mold stops advancing, and set the initial value of the position of the upper mold in the position control module to 0 μm.

[0113] S13. Set the upper mold in the position control module to perform die pressing at a rate of 0.1 mm / min, and at the same time, set the threshold value of the increase rate of the die pressing force of the lower mold in the force control module to 2 N / s or turn off the force control module, and perform the position-control - force-control collaborative control or single-position control of the high-temperature ultra-precision die pressing forming of the optical glass element respectively;

[0114] S14. Set the heat preservation time. After the die pressing is completed, when the heating cavity is cooled down to room temperature, open the upper cover plate of the heating cavity and take out the die-pressed quartz glass optical element;

[0115] S15. Use a complex surface optical profiler, a white light interferometer, and a field emission scanning electron microscope to measure and analyze the surface shape, surface roughness, and surface wear of the single-crystal silicon carbide mold of the die-pressed quartz glass optical element.

[0116] In this embodiment, as shown in Fig. 4, when performing position-control - force-control collaborative control die pressing based on a carbon surface - single-crystal silicon carbide mold, it can be found that only some tiny plastic grooves appear on the surface of the silicon carbide after multiple die pressings, without material adhesion and brittle fracture, which can effectively ensure the surface quality of the formed optical element; when performing position control die pressing based on a carbon surface - single-crystal silicon carbide mold, it can be found that although there is no obvious material adhesion, there are some micro-cracks on the surface of the silicon carbide mold. During the die pressing forming process, the micro-cracks will be copied onto the surface of the glass melt, forming surface defects, resulting in a decrease in the light transmittance of the element and an increase in scattered light. In addition, under multiple die pressing cyclic loads, the micro-cracks will rapidly expand, affecting the service life of the mold. It can be seen that the position-control - force-control collaborative control ultra-high temperature die pressing method proposed by the present invention has good adaptability and flexibility, precisely controls the die pressing glass forming process, improves the surface shape accuracy of the glass element, reduces surface unevenness or defects, reduces mold wear, extends the mold life, and improves the yield of die pressing forming.

[0117] In summary, the present invention provides a single-crystal silicon carbide die pressing mold and a position-control - force-control collaborative control high-temperature die pressing method. The aspherical mold with a roughness less than 2 nm and a surface shape accuracy less than 0.3 μm is obtained by using the ultrasonic vibration-assisted chemical mechanical grinding method to efficiently process single-crystal silicon carbide. At the same time, combined with the position-control - force-control collaborative control high-temperature die pressing control strategy, the deformation amount and forming rate of the high-temperature glass melt are precisely controlled, the surface quality and surface shape accuracy of the optical glass element die pressing forming are improved, the die pressing efficiency and yield are increased, providing a reliable technical guarantee for realizing the mass production of high-quality and high-precision optical elements, promoting the development of high-end optical element manufacturing technology, and having broad application prospects.

Claims

1. A grinding method for a single-crystal silicon carbide molding die, characterized in that, It includes the following steps: S1. Treat the surface of the single-crystal silicon carbide mold; S2. Determine the crystal plane of the single-crystal silicon carbide, and at the same time mark the C plane and the Si plane as two machining reference directions. Then fix the mold on a fixture with a low coefficient of thermal expansion and vacuum adsorb it to the workpiece rotating spindle; S3. Detect the vibration of the workpiece spindle to ensure that the radial runout of the spindle is less than the set value; S4. Select and fix a metal-bonded diamond grinding wheel, adjust the dynamic balance of the grinding wheel to ensure that the unbalance degree at the edge of the grinding wheel is less than the set value; S5. Set the rough grinding process parameters, and use a coarse-grained diamond grinding wheel to rough grind the single-crystal silicon carbide on the C plane and the Si plane to preform the aspherical contour of the mold, with the roughness Ra less than 200 nm and a 100-μm allowance reserved; S6. Replace the diamond grinding wheel with a fine grain size, set the fine grinding process parameters, and form the aspherical contour of the single-crystal silicon carbide mold on the C plane and the Si plane, with the surface form accuracy PV less than 2 μm and the roughness Ra less than 20 nm; S7. Replace the diamond grinding wheel with an ultra-fine grain size, set the ultra-precision grinding process parameters, turn on the minimum quantity lubrication spray device equipped with a thermally activated grinding fluid and the ultrasonic vibration generating device to assist in reducing the hardness of the workpiece surface layer material and the grinding force during the grinding process, and complete the high-efficiency machining of the single-crystal silicon carbide mold with a super-smooth surface, with the surface form accuracy less than 0.5 μm and the roughness less than 5 nm; S8. Use a white light interferometer to scan the surface of the mold to generate a surface form error map, then construct a free-form surface compensation file based on the error map to generate a tool radius compensation path, and through machining compensation, ultra-precisely grind the surface of the silicon carbide mold again. If the surface form accuracy does not meet the requirements, steps S6 and S7 need to be repeated again; 2. The grinding method of the single crystal silicon carbide molding die according to claim 1, characterized in that In step S5, the abrasive grain size of the diamond grinding wheel used for rough machining on the ultra-precision grinding machine is 40-50 μm, the binder is a bronze-based alloy containing 80% Cu, 15% Sn, and 5% Ni, and the concentration of the diamond abrasive is 100%; In step S6, the abrasive grain size of the diamond grinding wheel used for finish machining on the ultra-precision grinding machine is 10-20 μm, the binder is a nickel-based alloy containing 85% Ni, 10% Co, and 5% Cr, and the concentration of the diamond abrasive is 75%; In step S7, the abrasive grain size of the diamond grinding wheel used for ultra-precision machining on the ultra-precision grinding machine is 0.5-2 μm, the binder is an Fe-Co-Ni alloy ultra-fine metal ceramic, and the concentration of the diamond abrasive is 50%.

3. The grinding method of the single crystal silicon carbide molding die according to claim 1, characterized in that, The thermally activated grinding fluid described in step S7 contains 50-70 wt.% of a fully synthetic grinding fluid, 25-40 wt.% of polyethylene glycol, 2-5 wt.% of an azo compound, and 3-5 wt.% of an organic peroxide compound. The minimum quantity lubrication spray device can control the thermally activated grinding fluid to be atomized into high-speed small droplets at an atomizing air pressure of 0.3-0.6 MPa and a flow rate of 10-200 mL / h and act on the contact interface between the grinding wheel and the workpiece; 4. The grinding method of the single crystal silicon carbide molding die according to claim 1, wherein The ultrasonic vibration generating device described in step S7 is directly fixed to the grinding wheel through a magnetic coupling type quick-change fixture base. The fixture base is internally provided with a micro piezoelectric transducer and a stepped titanium alloy horn, and is rigidly connected to the grinding wheel base through conical surface positioning, and can realize axial, radial, or axial-radial simultaneous vibration of the grinding wheel.

5. The grinding method of the single-crystal silicon carbide molding die according to claim 1, characterized in that, In the step S5, the grinding parameters include a spindle speed of 15,000 - 20,000 rpm, a feed rate of 50 - 80 mm / min, a cutting depth of 5 - 10 μm, and the lubrication and cooling method is to use a water-based emulsion with a pressure of 5 MPa, a flow rate of 20 L / min, and a temperature of 15 ± 2 °C for pouring lubrication and cooling.

6. The grinding method of the single crystal silicon carbide molding die according to claim 1, characterized in that, In the step S6, the grinding parameters include a spindle speed of 25,000 - 30,000 rpm, a feed rate of 20 - 30 mm / min, a cutting depth of 1 - 3 μm, and the lubrication and cooling method is to use a water-based emulsion with a pressure of 5 MPa, a flow rate of 20 L / min, and a temperature of 15 ± 2 °C for pouring lubrication and cooling.

7. The grinding method of the single crystal silicon carbide molding die according to claim 1, characterized in that In the step S7, the grinding parameters include a spindle speed of 35,000 - 40,000 rpm, a feed rate of 1 - 3 mm / min, a cutting depth of 0.1 - 0.5 μm, and the lubrication and cooling method is to use a thermally active grinding fluid to chemically modify, lubricate, and cool the surface layer material of the workpiece.

8. A high-temperature die pressing method with coordinated position control and force control using a single-crystalline silicon carbide die pressing mold obtained by the grinding method of the single-crystalline silicon carbide die pressing mold according to any one of claims 1-7, characterized in that, As follows: S9. Respectively place the processed single-crystal silicon carbide molding dies with different crystal planes into the molding components in the high-temperature molding device with position-control and force-control coordinated control. S10. Perform surface pretreatment on the optical glass block to be subjected to high-temperature molding. Place the treated optical glass block into the inner cavity of the single-crystal silicon carbide mold, and at the same time seal the upper end cover. S11. Start the vacuum pump to ensure that the heating cavity is at the set vacuum degree. Then close the vacuum pump and turn on the nitrogen gas filling device to ensure that the heating cavity is in a pure nitrogen protection atmosphere. S12. Set the initial threshold value of the force-control module in the molding component to the set value. Turn on the molding component to drive the upper mold to move rapidly towards the lower mold. When the contact force measured by the force-control module reaches the threshold value, the upper mold stops advancing, and set the initial position value of the upper mold in the position-control module to 0 μm. S13. Set the upper mold in the position-control module to perform molding at a set rate. At the same time, set the threshold value of the increase rate of the molding pressure of the lower mold in the force-control module. Start the position-control and force-control coordinated control high-temperature ultra-precision molding of the optical glass. When the increase rate of the molding pressure exceeds the threshold value, the molding component controls the upper mold to reduce the molding rate. When the increase rate of the molding pressure is less than the set value, the molding component controls the upper mold to increase the molding rate. S14. Set the heat preservation time. After the molding is completed, when the heating cavity cools down to room temperature, open the upper cover of the heating cavity and take out the molded quartz glass optical element. S15. Use a complex surface optical profiler, a white light interferometer, and a field emission scanning electron microscope to measure and analyze the surface shape, surface roughness of the molded quartz glass optical element, and the surface wear condition of the single-crystal silicon carbide mold.

9. The high-temperature die pressing method with coordinated position-control and force-control using the single-crystal silicon carbide die pressing mold obtained by the grinding method according to claim 8, characterized in that, As follows: The single-crystal silicon carbide molding die in the step S9 is divided into an upper mold and a lower mold, and the shape and size of the mold determine the shape of the high-temperature molded glass optical element. The molding component in the step S9 simultaneously includes a pressure sensor with an accuracy of 0.1 N and a displacement sensor with an accuracy of 0.5 μm.

10. The high-temperature die pressing method with coordinated position-force control using the single-crystalline silicon carbide die pressing die obtained by the grinding method according to claim 8, characterized in that : The heating temperature of the heating cavity in the step S12 is in the range of 25 - 1600 °C. The upper die pressing rate in step S13 is carried out at 1 to 150 μm / s, the threshold value of the increasing rate of the lower die pressing force is 2.0 N / s, and the increasing rate of the pressing force is between 0.2 and 2.0 N / s.

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