Supercritical CO2 / ultrasonic composite machining system and its control method, machine tool

Abstract

This application discloses a supercritical CO2-ultrasonic composite machining system, a control method thereof, and a machine tool. The system includes a supercritical CO2 supply unit, a control module, and an ultrasonic machining apparatus. The control module is electrically connected to the supercritical CO2 supply unit and to the ultrasonic machining apparatus. The control module is configured to control the supercritical CO2 process parameters such that the supercritical CO2 process parameters are dynamically adjusted within a predetermined range according to the ultrasonic parameters, based on a correspondence between the supercritical CO2 process parameters and ultrasonic parameters. The supercritical CO2 process parameters include supercritical CO2 pressure P, and the ultrasonic parameters include ultrasonic amplitude A and ultrasonic vibration frequency f. By controlling the supercritical CO2 pressure so that it is dynamically adjusted according to the ultrasonic parameters, the supercritical CO2 injection effect is enhanced, thereby ensuring machining effect and quality, improving machining efficiency and precision, and effectively reducing costs.

Description

Technical Field

[0001] This application relates to the technical field of cutting, and particularly to a supercritical CO2·ultrasonic composite machining system and its control method, and a machine tool.

Background Art

[0002] Difficult-to-machine materials such as high-strength steel, heat-resistant alloys, and titanium alloys usually have advantages such as high strength, high corrosion resistance, high oxidation resistance, and excellent high-temperature properties, and are widely used in major equipment in important fields such as aerospace, nuclear power, and military industries. However, while meeting the requirements of high performance, the processing of materials is difficult, and the control effect of conventional cutting devices is low, resulting in serious wear of tools, reduction of life, and temperature rise in the cutting area. As a result, the processing effect and quality are reduced. Even if cutting fluid is injected and processed as in the past, these problems cannot be solved. In addition, cutting fluid contains mineral oil and various chemical additives, and if used in large quantities, it will have an adverse impact on the environment and the health of workers, and the production cost may increase due to the treatment of its waste liquid. Supercritical CO2 is environmentally friendly and non-toxic, so in recent years, it is widely used not only in the field of extraction but also in the field of machining. To ensure the cooling effect, a large amount of supercritical CO2 is consumed, resulting in a certain degree of waste and low cooling efficiency.

[0003] Ultrasonic machining technology is widely used because it can not only improve the roughness of the cutting surface, improve the machining accuracy, but also reduce the cutting resistance and extend the life of the tool.

Summary of the Invention

Problems to be Solved by the Invention

[0004] This application provides a supercritical CO2·ultrasonic composite machining system and its control method, and a machine tool for improving the machining effect and quality of difficult-to-machine materials.

Means for Solving the Problems

[0005] According to one aspect of this application, It includes a supercritical CO2 supply unit, a control module, and an ultrasonic processing device. The control module is electrically connected to the supercritical CO2 supply unit, and the control module is further electrically connected to the ultrasonic processing device. The control module is configured to control the process parameters of the supercritical CO2 so that the process parameters of the supercritical CO2 are dynamically adjusted within a predetermined range according to the ultrasonic parameters based on the correspondence between the process parameters of the supercritical CO2 and the ultrasonic parameters. The process parameters of the supercritical CO2 include the supercritical CO2 pressure P, and the ultrasonic parameters include the ultrasonic amplitude A and the ultrasonic vibration frequency f of the ultrasonic processing device, providing a supercritical CO2-ultrasonic composite processing system.

[0006] Optionally, the correspondence between the supercritical CO2 pressure P and the ultrasonic vibration frequency f is such that when the ultrasonic vibration frequency f is within the first predetermined ultrasonic vibration frequency range, the ultrasonic vibration frequency f shows a negative correlation with the supercritical CO2 pressure P, and when the ultrasonic vibration frequency f is within the second predetermined ultrasonic vibration frequency range, the ultrasonic vibration frequency f shows a positive correlation with the supercritical CO2 pressure P, and any value within the first predetermined ultrasonic vibration frequency range is smaller than any value within the second predetermined ultrasonic vibration frequency range.

[0007] Optionally, the first predetermined ultrasonic vibration frequency range is 16KHz ≦ f < 30KHz, and the second predetermined ultrasonic vibration frequency range is 30KHz ≦ f ≦ 50KHz.

[0008] Optionally, when 16KHz ≦ f < 30KHz, 8MPa < P ≦ 15MPa, and f shows a negative correlation with P, and when 30KHz ≦ f ≦ 50KHz, P ≧ 8MPa, and f shows a positive correlation with P.

[0009] Optionally, the correspondence between the supercritical CO2 pressure P and the ultrasonic amplitude A is such that when the ultrasonic amplitude A is within the first predetermined ultrasonic amplitude range, the ultrasonic amplitude A shows a negative correlation with the supercritical CO2 pressure P, and when the ultrasonic amplitude A is within the second predetermined ultrasonic amplitude range, the ultrasonic amplitude A shows a positive correlation with the supercritical CO2 pressure P, and any value within the first predetermined ultrasonic amplitude range is smaller than any value within the second predetermined ultrasonic amplitude range.

[0010] Optionally, the first predetermined ultrasonic amplitude range is 0.5μm ≦ A < 10μm, and the second predetermined ultrasonic amplitude range is A ≧ 10μm.

[0011] Optionally, when 0.5μm ≦ A < 10μm, 8MPa < P ≦ 15MPa, and A shows a negative correlation with P, and when A ≧ 10μm, P ≧ 8MPa, and A shows a positive correlation with P.

[0012] Optionally, the control module is configured to control the supercritical CO2 pressure within a predetermined pressure range, the ultrasonic amplitude within a predetermined ultrasonic amplitude range, and the ultrasonic vibration frequency within a predetermined ultrasonic vibration frequency range. The predetermined pressure range is P ≧ 8MPa, the predetermined ultrasonic amplitude range is A ≧ 0.5μm, and the predetermined ultrasonic vibration frequency is 16KHz ≦ f ≦ 50KHz.

[0013] Optionally, in order to mix the lubricating oil supplied from the micro-lubricating oil supply unit and the supercritical CO2 supplied from the supercritical CO2 supply unit, it further includes a micro-lubricating oil supply unit connected to the discharge pipeline of the supercritical CO2 supply unit and further electrically connected to the control module. The control module is further configured to control the pressure of the lubricating oil discharged from the micro-lubricating oil supply unit to be higher than the supercritical CO2 pressure. [[ID=rg=19]]

[0014] The system optionally further includes a micro-lubricating oil supply unit and a mixing module, both of which are connected to the mixing module to supply lubricating oil and supercritical CO2 to the mixing module, and the micro-lubricating oil supply unit is further electrically connected to the control module.

[0015] Optionally, the system further includes a trace lubricating oil supply unit, the supercritical CO2 supply unit being connected to the discharge pipeline of the trace lubricating oil supply unit for mixing the lubricating oil supplied from the trace lubricating oil supply unit with the supercritical CO2 supplied from the supercritical CO2 supply unit, and the trace lubricating oil supply unit being further electrically connected to the control module. The control module is further configured to control the pressure of the lubricating oil discharged from the trace lubricating oil supply unit so that it is lower than the supercritical CO2 pressure.

[0016] Optionally, the end of the discharge pipeline of the supercritical CO2 supply unit is connected to the ultrasonic processing device.

[0017] According to another aspect of the present application, a control method is provided for a supercritical CO2-ultrasonic composite processing system described in the first aspect, comprising the step of controlling the supercritical process parameters such that the supercritical process parameters are dynamically adjusted within a predetermined range in accordance with the ultrasonic parameters, based on a correspondence between the supercritical CO2 process parameters and ultrasonic parameters, wherein the supercritical CO2 process parameters include supercritical CO2 pressure and the ultrasonic parameters include ultrasonic amplitude and ultrasonic vibration frequency.

[0018] According to another aspect of the present application, a machine tool is provided that includes the supercritical CO2-ultrasonic composite machining system described in the first aspect. [Effects of the Invention]

[0019] The technical solutions of embodiments of the present application provide a supercritical CO2-ultrasonic composite machining system and a control method thereof, and a machine tool, the supercritical CO2-ultrasonic composite machining system comprising a supercritical CO2 supply unit, a control module, and an ultrasonic machining apparatus, wherein the control module is electrically connected to the supercritical CO2 supply unit and controls the process parameters of the supercritical CO2 of the supercritical CO2 supply unit and controls the supercritical CO2 supply unit to supply supercritical CO2 to a machining area, the control module is electrically connected to the ultrasonic machining apparatus and controls the ultrasonic machining apparatus to generate ultrasonic vibrations and acquire ultrasonic parameters of the ultrasonic machining apparatus. The control module is configured to control the process parameters of supercritical CO2 such that the process parameters of supercritical CO2 are dynamically adjusted according to the ultrasonic parameters based on the correspondence between the process parameters of supercritical CO2 and ultrasonic parameters, the process parameters of supercritical CO2 include supercritical CO2 pressure, and the ultrasonic parameters include ultrasonic amplitude and ultrasonic vibration frequency. Based on the above, combining supercritical CO2 and ultrasound enables environmentally friendly machining of difficult-to-process materials. Furthermore, by controlling the process parameters of supercritical CO2 so that they are dynamically adjusted according to the ultrasound parameters based on the correspondence between the process parameters of supercritical CO2 and the ultrasound parameters, the injection effect of supercritical CO2 is enhanced, thereby ensuring machining effectiveness and quality, improving machining efficiency and precision, and effectively reducing costs. In addition, the use of supercritical CO2 is environmentally friendly, pollution-free, has a high cooling effect, and can effectively lower the temperature of the cutting area. Furthermore, ultrasonic machining can improve the roughness of the machined surface and mitigate the problem of machining burrs.

[0020] It should be understood that the contents described in this section are not intended to represent the main or important features of the embodiments of this application, nor are they intended to limit the scope of this application. Other features of this application will be readily apparent from the following specification. [Brief explanation of the drawing]

[0021] To more clearly explain the technical solution in the embodiments of this application, the drawings necessary for the description of the embodiments will be briefly described below. However, the drawings in the following description are only some embodiments of this application, and it is obvious to those skilled in the art that based on these drawings, other drawings can be obtained without creative efforts. [Figure 1] It is a block diagram of the principle and structure of a supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 2] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 3] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 4] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 5] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 6] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 7] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 8] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 9] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 10] It is a block diagram of the principle and structure of another supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 11] It is a flowchart of the control method of a supercritical CO2·ultrasonic composite processing system according to an embodiment of this application. [Figure 12]This is a schematic diagram of the overall flow of a supercritical CO2-ultrasonic composite processing system according to an embodiment of the present invention. [Modes for carrying out the invention]

[0022] To enable those skilled in the art to better understand the technical solutions of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings of the embodiments, although it will be clear that the embodiments described are only a part of the embodiments of the present application and not all of them. All other embodiments that can be obtained by those skilled in the art without creative effort based on the embodiments of the present application should fall within the scope of protection of the present application.

[0023] Furthermore, terms such as “First,” “Second,” etc., in the specification and claims of this application, as well as in the drawings, are for distinguishing similar subjects and are not intended to indicate a specific order or priority. It should be understood that the numbers used in this manner are interchangeable where appropriate, so that the embodiments of this application described herein may be carried out in an order other than those illustrated or described herein. Moreover, the terms “includes” and “having,” and any variations thereof, are intended to mean “includes” in a non-exclusive sense. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units expressly listed, and may include other steps or units that are not expressly listed or are specific to these processes, methods, products, or apparatus.

[0024] Figure 1 is a block diagram of the principle and structure of a supercritical CO2-ultrasonic composite processing system according to an embodiment of the present application. As shown in Figure 1, the supercritical CO2-ultrasonic composite processing system includes a supercritical CO2 supply unit 10, a control module 20, and an ultrasonic processing apparatus 30. The control module 20 is electrically connected to the supercritical CO2 supply unit and controls the supercritical CO2 supply unit to supply supercritical CO2 to the processing area, as well as controlling the process parameters of the supercritical CO2 in the supercritical CO2 supply unit. The control module is also electrically connected to the ultrasonic processing apparatus and acquires the ultrasonic parameters of the ultrasonic processing apparatus, and further controls the ultrasonic processing apparatus to generate ultrasonic vibrations. Furthermore, the control module 20 is configured to control the supercritical CO2 process parameters so that the supercritical CO2 process parameters are dynamically adjusted within a predetermined range according to the ultrasonic parameters, based on the correspondence between the supercritical CO2 process parameters and ultrasonic parameters, the supercritical CO2 process parameters include the supercritical CO2 pressure P, and the ultrasonic parameters include the ultrasonic amplitude A and the ultrasonic vibration frequency f.

[0025] The end of the discharge pipe of the supercritical CO2 supply unit 10 may be connected to the ultrasonic processing apparatus 30 to supply supercritical CO2 to the processing area through the internal cooling passage of the ultrasonic processing apparatus 30. Specifically, the supercritical CO2 passes through the internal cooling passage of the ultrasonic processing apparatus, then through the cooling passages in the internal cooling holder and internal cooling tool, and is finally supplied to the processing area, thus performing internal cooling. Of course, the supercritical CO2 supply unit may also supply supercritical CO2 to the processing area by directly communicating with a nozzle provided separately, thus performing external cooling. In the case of external cooling, that is, in the case of external cooling, the supercritical CO2 does not pass through the cooling passage of the ultrasonic processing apparatus. This point is the same as in the prior art, so a detailed explanation will be omitted. In the following, unless otherwise specified, the explanation will use internal cooling as an example.

[0026] As an example, the ultrasonic machining apparatus 30 generates ultrasonic vibrations and combines supercritical CO2 supplied from the supercritical CO2 supply unit 10 with ultrasonic waves to perform cutting on a workpiece. Here, the workpiece may be difficult-to-machine materials such as high-tensile steel, heat-resistant alloys, and titanium alloys. The ultrasonic machining apparatus 30 may include a spindle, an ultrasonic generator, a transmitting unit, and an ultrasonic holder and tool provided on the spindle (the transducer part may be mounted inside the spindle and connected to the spindle by a precision holder). Furthermore, the transmitting unit may be mounted inside the spindle, or directly attached to the tip of the spindle, or of course, attached to the spindle housing by a hoop, i.e., provided separately from the spindle housing. When the ultrasonic transmitting unit receives an ultrasonic signal from the ultrasonic generator, it transmits it to the receiving unit of the ultrasonic holder by wired or wireless means, thereby enabling the transmission of ultrasonic signals. These ultrasonic signals can generate ultrasonic vibrations in the ultrasonic holder, thereby performing ultrasonic machining on the workpiece.

[0027] The supercritical CO2 supply unit 10 supplies supercritical CO2. Specifically, the discharge of supercritical CO2 by the supercritical CO2 supply unit 10 may be obtained by heating and pressurizing low-temperature, low-pressure CO2, which then becomes supercritical due to the heating and pressurization.

[0028] The control module 20 may be a controller such as a numerical control system or a PLC, and is not particularly limited to it, as it can be configured according to the actual situation.

[0029] The supercritical CO2 pressure may be obtained by installing a pressure detection unit in the pipeline between the supercritical CO2 supply unit and the ultrasonic processing apparatus. The control module 20 obtains ultrasonic parameters from the ultrasonic processing apparatus 30 and then controls the supercritical CO2 process parameters of the supercritical CO2 supply unit 10 based on these ultrasonic parameters. Specifically, these ultrasonic parameters include the ultrasonic vibration frequency that the ultrasonic generator feeds back to the control module 20, and also include the ultrasonic amplitude detected by a tool parameter monitoring unit installed on the tool side.

[0030] For example, the control module is electrically connected to the ultrasonic generator and the tool parameter monitoring unit. The ultrasonic generator and the tool parameter monitoring unit feed back ultrasonic parameters to the control module, which then adjusts the supercritical CO2 pressure of the supercritical CO2 supply unit based on the correspondence between the supercritical CO2 process parameters and the ultrasonic parameters. Furthermore, the control module is electrically connected to the ultrasonic generator and controls whether or not the ultrasonic generator outputs an ultrasonic signal to the transmitting unit by controlling the starting and stopping of the ultrasonic generator.

[0031] Furthermore, the control module 20 controls the adjustment of the ultrasonic parameters of the ultrasonic processing apparatus 30 so that the ultrasonic parameters are within a predetermined range.

[0032] Furthermore, the control module 20 is electrically connected to the ultrasonic processing device 30 and controls the starting and stopping of the ultrasonic processing device 30, as well as controlling air blowing and tool changes.

[0033] Regarding the correspondence between supercritical process parameters and ultrasonic parameters, in ultrasonic-assisted machining, acoustic resistance exists between the tool and the workpiece, generating a large amount of heat during ultrasonic vibration. On the other hand, in ultrasonic-assisted machining, the tool and chips separate periodically, and heat is removed by this periodic separation. Therefore, when the amplitude is constant, initially, as the ultrasonic vibration frequency increases, the tool and workpiece separate periodically, and the amount of heat removed by this periodic separation is greater than the amount of heat generated by the ultrasonic waves and the acoustic resistance of the tool and workpiece. This contributes to a reduction in the amount of carbon dioxide injected, meaning that the cooling needs can be met even without high supercritical CO2 pressure. However, as the ultrasonic vibration frequency continues to increase, the amount of heat generated by the ultrasonic waves and the acoustic resistance of the tool and workpiece increases rapidly, exceeding the amount of heat removed by periodic separation. In this case, it becomes necessary to increase the amount of carbon dioxide injected, meaning that high supercritical CO2 pressure is required to meet the cooling needs and ensure the stability of ultrasonic machining.

[0034] When the ultrasonic vibration frequency is constant, initially, as the ultrasonic amplitude gradually increases, the tool and workpiece periodically separate. The amount of heat removed by this periodic separation is greater than the amount of heat generated by the acoustic resistance between the ultrasonic waves and the tool or workpiece, contributing to a reduction in the amount of carbon dioxide injected. In other words, the cooling needs can be met even without high supercritical CO2 pressure. However, as the ultrasonic amplitude continues to increase, the amount of heat generated by the acoustic resistance between the ultrasonic waves and the tool or workpiece increases rapidly and becomes greater than the amount of heat removed by the periodic separation. In this case, it becomes necessary to increase the amount of carbon dioxide injected. In other words, high supercritical CO2 pressure is required to meet the cooling needs and ensure the stability of ultrasonic machining.

[0035] Optionally, when the control module 20 further controls the ultrasonic amplitude A to be constant, when the ultrasonic vibration frequency f is within the first predetermined ultrasonic vibration frequency range, the ultrasonic vibration frequency f shows a negative correlation with the supercritical CO2 pressure P, and when the ultrasonic vibration frequency f is within the second predetermined ultrasonic vibration frequency range, the ultrasonic vibration frequency f shows a positive correlation with the supercritical CO2 pressure P, and any value within the first predetermined ultrasonic vibration frequency range is configured to be smaller than any value within the second predetermined ultrasonic vibration frequency range.

[0036] Here, the first predetermined ultrasonic vibration frequency range is 16KHz ≤ f < 30KHz, and the second predetermined ultrasonic vibration frequency range is 30KHz ≤ f ≤ 50KHz.

[0037] Furthermore, when 16KHz ≤ f < 30KHz, 8MPa < P ≤ 15MPa, and f shows a negative correlation with P, and when 30KHz ≤ f ≤ 50KHz, P ≥ 8MPa, and f shows a positive correlation with P.

[0038] Optionally, the control module further controls the ultrasonic amplitude A to be constant, and sets the ultrasonic vibration frequency to the first predetermined ultrasonic vibration frequency f1 and the supercritical CO2 pressure to the first predetermined pressure P1, and the first predetermined ultrasonic vibration frequency is configured to show a negative correlation with the first predetermined pressure.

[0039] Here, the first predetermined ultrasonic vibration frequency f1 satisfies 16 ≤ f1 < 30KHz, and the first predetermined pressure P1 satisfies 8MPa < P1 ≤ 15MPa. The values of the first predetermined ultrasonic vibration frequency and the first predetermined pressure may be specifically set according to the actual situation and are not particularly limited here.

[0040] Optionally, the control module further controls the ultrasonic amplitude A to be constant, and sets the ultrasonic vibration frequency to the second predetermined ultrasonic vibration frequency f2 and the supercritical CO2 pressure to the second predetermined pressure P2, and the second predetermined ultrasonic vibration frequency is configured to show a positive correlation with the second predetermined pressure.

[0041] Here, the second predetermined ultrasonic vibration frequency f2 satisfies 30 KHz ≤ f2 ≤ 50 KHz, and the second predetermined pressure P2 satisfies P2 ≥ 8 MPa. Note that the values of the second predetermined ultrasonic vibration frequency and the second predetermined pressure may specifically be set according to the actual situation and are not particularly limited here.

[0042] Optionally, when the control module 20 further controls the ultrasonic vibration frequency f to be constant, when the ultrasonic amplitude A is within the first predetermined ultrasonic amplitude range, the ultrasonic amplitude A shows a negative correlation with the supercritical CO2 pressure P; when the ultrasonic amplitude A is within the second predetermined ultrasonic amplitude range, the ultrasonic amplitude A shows a positive correlation with the supercritical CO2 pressure P, and it is configured such that any value within the first predetermined ultrasonic amplitude range is smaller than any value within the second predetermined ultrasonic amplitude range.

[0043] Here, the first predetermined ultrasonic amplitude range is 0.5 - 10 μm, and the second predetermined ultrasonic amplitude range is greater than 10 μm.

[0044] Furthermore, when 0.5 μm ≤ A < 10 μm, 8 MPa < P ≤ 15 MPa, and A shows a negative correlation with P; when A ≥ 10 μm, P ≥ 8 MPa, and A shows a positive correlation with P.

[0045] Optionally, the control module controls the ultrasonic vibration frequency f to be constant, and sets the ultrasonic amplitude as the first predetermined ultrasonic amplitude A1 and the supercritical CO2 pressure as the first predetermined pressure P1, and is configured such that the first predetermined ultrasonic amplitude A1 shows a negative correlation with the first predetermined pressure P1.

[0046] Here, the first predetermined ultrasonic amplitude A1 satisfies 0.5 μm ≤ A1 < 10 μm, and the first predetermined pressure P1 satisfies 8 MPa < P1 ≤ 15 MPa. Note that the values of the first predetermined ultrasonic amplitude and the first predetermined pressure may specifically be set according to the actual situation and are not particularly limited here.

[0047] Optionally, the control module is configured to control the ultrasonic vibration frequency f to a constant value, and to set the ultrasonic amplitude to a second predetermined ultrasonic amplitude A2 and the supercritical CO2 pressure to a second predetermined pressure P2, such that the second predetermined ultrasonic amplitude A2 shows a positive correlation with the first predetermined pressure P2.

[0048] Here, the second predetermined ultrasonic amplitude A2 satisfies A2 ≥ 10 μm, and the second predetermined pressure P2 satisfies P2 ≥ 8 MPa. Note that the values ​​of the second predetermined ultrasonic amplitude and the second predetermined pressure are not particularly limited here and can be set according to the actual situation.

[0049] Note that the ranges for the first predetermined ultrasonic vibration frequency, the second predetermined ultrasonic vibration frequency, the first predetermined ultrasonic amplitude, the second predetermined ultrasonic amplitude, the first predetermined pressure, and the second predetermined pressure are merely examples and may be set according to the actual situation; they are not particularly limited here. They may be set to other numerical ranges. For example, when the ultrasonic amplitude A is controlled to be constant, the ranges for the ultrasonic vibration frequency f and the corresponding supercritical CO2 pressure P may be set as shown in Table 1, or when the ultrasonic vibration frequency f is controlled to be constant, the ranges for the ultrasonic amplitude A and the corresponding supercritical CO2 pressure P may be set as shown in Table 2.

[0050] [Table 1] Values ​​of ultrasonic vibration frequency f and supercritical CO2 pressure P JPEG2026527424000002.jpg26169 [Table 2] Values ​​of ultrasonic amplitude A and supercritical CO2 pressure P JPEG2026527424000003.jpg26169Optionally, the control module is configured to further control the supercritical CO2 pressure P within a predetermined pressure range, the ultrasonic amplitude A within a predetermined amplitude range, and the ultrasonic vibration frequency f within a predetermined vibration frequency range.

[0051] For example, the specified pressure range may be 8 MPa or higher, the specified amplitude range may be 0.5 μm or higher, and the specified vibration frequency range may be 16 to 50 kHz. The lower limit of the pressure of supercritical CO2 is 7.31 MPa, and a certain amount of loss occurs when it flows through a pipeline, so in this application, the lower limit of the specified pressure range is limited to be slightly higher than the lower limit of supercriticality.

[0052] In the technical solution of this embodiment, the supercritical CO2-ultrasonic composite machining system is realized as follows. Referring to Figure 1, when it is necessary to cut a workpiece, the workpiece is fixed in the machining area. The control module 20 controls the supercritical CO2 supply unit 10 to supply supercritical CO2 to the machining area and controls the ultrasonic machining apparatus 30 to start ultrasonic machining. The control module 20 obtains the ultrasonic amplitude from the ultrasonic machining apparatus 30 and dynamically adjusts the supercritical CO2 pressure of the supercritical CO2 supply unit 10 based on the correspondence between the process parameters of supercritical CO2 and the ultrasonic parameters, thereby dynamically adjusting the supercritical CO2 pressure according to the ultrasonic parameters.

[0053] By using supercritical CO2 and ultrasound in combination, environmentally friendly machining of difficult-to-process materials becomes possible. Initially, as the ultrasonic parameters increase, the tool and chips are periodically separated by ultrasonic vibrations, and at this time, most of the heat is removed, allowing for a reduction in the amount of supercritical CO2 injected. As the ultrasonic parameters continue to increase, the amount of heat removed by periodic separation becomes smaller than the amount of heat generated by acoustic resistance, in which case it becomes necessary to increase the amount of supercritical CO2 injected. Therefore, there is a correlation between ultrasonic parameters and supercritical parameters, and by rationally adjusting the supercritical parameters based on this relationship, the effect of supercritical CO2 injection is improved, ensuring machining effectiveness and quality, increasing machining efficiency and precision, and effectively reducing costs. Furthermore, using supercritical CO2 is environmentally friendly, pollution-free, has a high cooling effect, and can effectively lower the temperature of the cutting area. In addition, ultrasonic machining can improve the roughness of the machined surface and alleviate the problem of machining burrs.

[0054] Figure 2 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite machining system according to an embodiment of the present invention. Based on the above embodiment, the ultrasonic machining apparatus may include a spindle 31 and an ultrasonic generator 32, and the supercritical CO2 supply unit 10 is connected to the spindle 31 of the ultrasonic machining apparatus and performs cooling by ejecting supercritical CO2 through the cooling passage of the spindle 31. In the technical solution of this embodiment, the supercritical CO2-ultrasonic composite machining system is realized as follows. Referring to Figure 2, when it is necessary to cut a workpiece, the workpiece is fixed in the machining area. The control module 20 controls the supercritical CO2 supply unit 10 to supply supercritical CO2 to the machining area via the spindle 31 and controls the ultrasonic generator 32 to supply an ultrasonic signal to the transmitting unit of the spindle 31. The control module 20 acquires the ultrasonic vibration frequency from the ultrasonic generator 32 and the ultrasonic amplitude from the tool parameter monitoring unit. Based on the correspondence between the process parameters of supercritical CO2 and the ultrasonic parameters, it dynamically adjusts the supercritical CO2 pressure of the supercritical CO2 supply unit 10. This dynamically adjusts the supercritical CO2 pressure according to the ultrasonic parameters, contributing to an enhanced supercritical CO2 injection effect, thereby ensuring processing effectiveness and quality, improving processing efficiency and precision, and effectively reducing costs.

[0055] Figure 3 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite processing system according to an embodiment of the present invention. Based on the above embodiment, as shown in Figure 3, the control module 20 may include a supercritical CO2 control module 22 and an ultrasonic processing control module 21, the supercritical CO2 control module 21 being electrically connected to the supercritical CO2 supply unit 10 and controlling the process parameters of supercritical CO2, the ultrasonic processing control module 20 including an ultrasonic control module 211, the ultrasonic control module 211 being electrically connected to the ultrasonic processing apparatus 20 and acquiring ultrasonic parameters, the ultrasonic control module 211 being further electrically connected to the supercritical CO2 control module 22 and controlling the process parameters of supercritical CO2 such that the process parameters of the supercritical CO2 supply unit are dynamically adjusted within a predetermined range according to the ultrasonic parameters, based on the correspondence between the process parameters of supercritical CO2 and the ultrasonic parameters of the ultrasonic processing apparatus. The process parameters for supercritical CO2 include the supercritical CO2 pressure, and the ultrasonic parameters include the ultrasonic amplitude and ultrasonic vibration frequency.

[0056] By combining supercritical CO2 and ultrasound, environmentally friendly machining of difficult-to-process materials becomes possible. The use of supercritical CO2 is environmentally friendly, pollution-free, provides high cooling efficiency, and effectively reduces the temperature of the cutting area. Furthermore, ultrasonic machining improves surface roughness and reduces the problem of burrs. Additionally, by controlling the supercritical CO2 process parameters so that they are dynamically adjusted according to the ultrasonic parameters based on the correspondence between the supercritical CO2 process parameters and the ultrasonic parameters, the supercritical CO2 injection effect is enhanced. As a result, machining effectiveness and quality are ensured, machining efficiency and precision are increased, and costs are effectively reduced. Furthermore, communication between each control module enables the automation of the supercritical CO2-ultrasonic composite machining system.

[0057] Here, the supercritical CO2 control module 22 and the ultrasonic machining control module 21 may be controllers such as single-chip microcontrollers, and are not particularly limited to them as they can be set according to the actual situation. The ultrasonic machining control module further includes other modules, such as the spindle control module described later, which will be described in detail below.

[0058] Figure 4 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite machining system according to an embodiment of the present invention. Based on the embodiment in Figure 3, as shown in Figure 4, the supercritical CO2 supply unit may be connected to a third control valve 40 before discharging supercritical CO2 into the machining area, and a supercritical CO2 control module may also be electrically connected to the third control valve 40 and control the discharge of supercritical CO2 from the supercritical CO2 supply unit to the machining area by opening and closing the third control valve 40. Furthermore, the supercritical CO2 supply unit 10 may also be connected to an ultrasonic machining apparatus via the third control valve 40, which injects supercritical CO2 into the cutting area through its cooling passage, i.e., internal cooling is performed. Of course, the third control valve 40 may also be opened and closed by other modules, such as the spindle control module of the ultrasonic machining control system 21. When supercritical CO2 is required, the spindle control module controls the third control valve to open, and the supercritical CO2 supply unit supplies supercritical CO2 to the ultrasonic machining apparatus through the third control valve, thereby cooling the machining area. The following explanation will use the case where the supercritical CO2 control module is electrically connected to the third control valve 40 as an example. Here, the third control valve 40 is a switching control valve.

[0059] Figure 5 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite processing system according to an embodiment of the present invention (in this figure, electrical connections are represented by dashed lines to distinguish them from connections by piping). Based on the above embodiment, optionally, as shown in Figure 5, the supercritical CO2 supply unit 10 includes a CO2 supply unit 11, a pressure boosting heating unit 12, a third temperature monitoring unit 14, a first temperature monitoring unit 16, a third pressure monitoring unit 15, and a first pressure monitoring unit 17, wherein the third temperature monitoring unit 14 and the third pressure monitoring unit 15 are connected to the CO2 supply unit 11, respectively, and monitor the temperature and pressure of the CO2 in the CO2 supply unit 11, respectively, and the pressure boosting heating unit 12 is connected to the CO2 supply unit 11. The first temperature monitoring unit 16 and the first pressure monitoring unit 17 are connected to the pressurizing and heating unit 12 and the third control valve 40, and monitor the temperature and pressure of the pressurized and heated supercritical CO2, respectively. Furthermore, the pressurizing and heating unit 12, the first temperature monitoring unit 16, the first pressure monitoring unit 17, the second temperature monitoring unit 14, and the second pressure monitoring unit 15 are all electrically connected to the supercritical CO2 control module 22 and control the process parameters of the discharged supercritical CO2. Of these, the third temperature monitoring unit 14 and the third pressure monitoring unit 15 may be omitted.

[0060] The pressurizing and heating unit 12 includes a first pressurizing unit 121 and a heating unit 122. The CO2 supply unit 11 supplies low-temperature, low-pressure CO2 to the first pressurizing unit 121. The CO2 supply unit 11 is connected to the first pressurizing unit 121, and the pressurizing by the first pressurizing unit 121 pressurizes the low-temperature, low-pressure CO2 to a certain pressure value (e.g., 7.31 MPa or higher), obtaining high-pressure CO2, which is then sent to the heating unit 122 via a pipeline for heating. The heating unit 122 heats the low-temperature, high-pressure CO2 to a certain temperature (e.g., 31.7°C or higher). That is, by pressurizing and heating, the low-pressure CO2 becomes supercritical, thereby obtaining supercritical CO2, which is sent to the ultrasonic processing apparatus 30 via the third control valve 40. Of course, as long as the supercritical CO2 discharged from the supercritical CO2 supply unit meets the specified requirements, the order of the first pressure boosting unit and the heating unit can be reversed; that is, heating can be performed after pressure boosting, or pressure boosting can be performed after heating, or both can be performed simultaneously.

[0061] The supercritical CO2 control module 22 controls the process parameters of the supercritical CO2 discharged from the supercritical CO2 supply unit 10. Specifically, the third temperature monitoring unit 14 and the third pressure monitoring unit 15 are connected to the CO2 supply unit 11, respectively, and monitor the temperature and pressure of the low-temperature, low-pressure CO2 inside the CO2 supply unit 11, and transmit the detection information to the supercritical CO2 control module 22. The first temperature monitoring unit 16 and the first pressure monitoring unit 17 are installed in the pipeline connecting the heating unit 122 and the third control valve 40, respectively, and monitor the pressure and temperature after the pressure is increased by the first pressure boosting unit 121 and the heating is performed by the heating unit 122, and transmit this monitoring information to the supercritical CO2 control module 22. The supercritical CO2 control module 22 monitors the temperature and pressure of the CO2 in the CO2 supply unit 11 in real time based on the temperature and pressure data transmitted by the third temperature monitoring unit 14 and the third pressure monitoring unit 15, respectively. It also monitors the temperature and pressure of the supercritical CO2 after the pressure is increased by the first pressure boosting unit and the heating unit 122 is heated, based on the temperature and pressure data transmitted by the first temperature monitoring unit 16 and the first pressure monitoring unit 17, respectively. When the pressure and temperature of the CO2 heated by the heating unit 122 reach the set target pressure and target temperature, the supercritical CO2 control module 22 controls the operation of the first pressure boosting unit 121 and the heating unit 122 to stop.

[0062] Here, the supercritical CO2 control module 22 is connected sequentially to the first pressure boosting unit 121 and the heating unit 122 in order to control the starting and stopping of the first pressure boosting unit 121 and the heating unit 122.

[0063] Optionally, referring to Figure 5, the supercritical CO2-ultrasonic composite machining system further includes a compressed air supply unit 61, which is connected to a first pressure boosting unit 121 via a first control valve 64, and by supplying compressed air to the first pressure boosting unit 121, drives the first pressure boosting unit 121 to boost the low-temperature, low-pressure CO2 discharged from the CO2 supply unit. The compressed air supply unit 61 is further connected to the ultrasonic machining apparatus 30 via a second control valve 62 and a check valve 63, the second control valve 62 is further electrically connected to a supercritical CO2 control module 22, the ultrasonic machining control module 21 further includes a spindle control module 212, which is electrically connected to the spindle 31 of the ultrasonic machining apparatus 30 and also electrically connected to the supercritical CO2 control module 22.

[0064] Here, the second control valve 62 is connected to the compressed air supply unit 61 and the check valve 63, respectively, and the check valve 63 is connected to the ultrasonic machining apparatus 30. The second control valve 62 controls whether or not the compressed air supply unit 61 introduces compressed air into the ultrasonic machining apparatus 30. The check valve plays a role in preventing supercritical CO2 in the connecting pipeline from entering the pipeline containing compressed air. Specifically, in a machining machine tool, if it is necessary to clean foreign matter inside the spindle, the spindle control module 212 sends a signal to the supercritical CO2 control module 22, which controls the opening of the third control valve to clean the spindle with compressed air, and after the work is completed, closes the third control valve to stop the introduction of gas from the compressed air supply unit to the spindle.

[0065] The supercritical CO2 control module 22 is electrically connected to the second control valve 62 and controls the opening and closing of the second control valve 62. Of course, the second control valve 62 may also be directly electrically connected to the spindle control module 212 of the ultrasonic machining control module 21 to directly control the opening and closing of the second control valve 62. Here, the second control valve 62 and the first control valve 64 may be switching control valves.

[0066] Optionally, referring to Figure 5, the ultrasonic machining apparatus 30 includes a tool parameter monitoring unit 33, a spindle 31, an ultrasonic generator 32, a transmitting unit 35, an ultrasonic holder 36, and a tool 34. The tool parameter monitoring unit 33 and the ultrasonic generator 32 are electrically connected to an ultrasonic control module 211, which feeds back ultrasonic parameters. Furthermore, the ultrasonic control module 211 is electrically connected to a supercritical CO2 control module 22, which controls the process parameters of the supercritical CO2 in the supercritical CO2 supply unit 10 so that the process parameters of the supercritical CO2 are dynamically adjusted according to the ultrasonic parameters of the ultrasonic machining apparatus 30, based on the correspondence between the process parameters of the supercritical CO2 and the ultrasonic parameters of the ultrasonic machining apparatus. Furthermore, the spindle control module 212 is electrically connected to the spindle 31 and controls tool changes on the spindle 31. The ultrasonic generator 32 outputs a voltage or current signal to the transmission unit 35 according to the command of the ultrasonic control module 211. The transmission unit 35 is fixed to the tip of the spindle 31 and transmits wirelessly to the receiving unit of the ultrasonic holder 36. The tool 34 is connected to the spindle 31 via the ultrasonic holder 36. The spindle 31 is connected to the third control valve 40, which transports supercritical CO2 discharged from the supercritical CO2 supply unit to the cutting area via the cooling passage of the spindle 31.

[0067] The third control valve 40 is connected to the spindle 31 and supplies supercritical CO2 to the spindle 31. The supercritical CO2 is injected onto the cutting edge of the tool 34 through the internal cooling passage of the spindle 31 and the ejection holes in the ultrasonic holder 36, providing cooling during the cutting process.

[0068] The ultrasonic generator 32 and the tool parameter monitoring unit 33 are electrically connected to the ultrasonic control module 211 and feed back ultrasonic parameters to the ultrasonic control module 211. Specifically, the tool parameter monitoring unit 33 feeds back ultrasonic amplitude information to the ultrasonic control module 211, and the ultrasonic generator 32 feeds back ultrasonic vibration frequency information to the ultrasonic control module 211.

[0069] The ultrasonic control module 211 is electrically connected to the ultrasonic generator 32 and controls the adjustment of the ultrasonic parameters of the ultrasonic generator 32 to control ultrasonic parameters such as ultrasonic vibration frequency within a predetermined range. The tool parameter monitoring unit 33 is electrically connected to the ultrasonic control module 211 and compares the actual ultrasonic amplitude of the tool 34 with a pre-stored tool ultrasonic amplitude. If the two do not match, it controls the ultrasonic generator 32 to output an adjustment signal. The ultrasonic generator 32 outputs a new voltage or current signal to the transmission unit 33 based on the adjustment signal, thereby adjusting the actual ultrasonic amplitude of the tool 36 to match the pre-stored tool ultrasonic amplitude.

[0070] Optionally, referring to Figure 5, the supercritical CO2-ultrasonic composite processing system further includes a second temperature monitoring unit 91, which is installed in a conduit connecting the third control valve 40 and the ultrasonic processing apparatus 30, and monitors the temperature of the conduit. The second temperature monitoring unit 91 is also electrically connected to a supercritical CO2 control module 22.

[0071] As an example, as shown in Figure 5, the second temperature monitoring unit 91 is installed in the pipeline connecting the third control valve 40 and the spindle 31, and the second temperature monitoring unit 91 is further electrically connected to the supercritical CO2 control module 22 to monitor the temperature of the pipeline and transmit the monitored temperature to the supercritical CO2 control module 22. When the second temperature monitoring unit 91 is installed between the third control valve 40 and the spindle 31, the cooling effect of supercritical CO2 is good when using supercritical CO2, so if a leak occurs, the temperature in the transport passage will drop significantly. To avoid such a situation affecting machining, the second temperature monitoring unit 91 is installed between the third control valve 40 and the spindle 31 to monitor the temperature in real time, and if a low temperature is detected, the device will automatically stop, the supply of supercritical CO2 will also stop, and troubleshooting will be easier.

[0072] Optionally, referring to Figure 5, the supercritical CO2-ultrasonic composite machining system further includes a pressure relief valve 92 and a fourth pressure monitoring unit 93, both of which are located in the pipeline connecting the third control valve 40 and the ultrasonic machining apparatus 30, i.e., connected to the ultrasonic machining apparatus 30, and both are electrically connected to the supercritical CO2 control module 22, and of course, may be directly electrically connected to the spindle control module 212.

[0073] Because supercritical CO2 is present under high pressure within the spindle's cooling passage, if a tool needs to be changed at the spindle tip, the pressure inside the spindle must be quickly released before the tool is changed. Therefore, the supercritical CO2-ultrasonic composite machining system is also provided with a pressure relief element, which further includes a pressure relief valve 92 and a fourth pressure monitoring unit 93. The pressure relief valve 92 and the fourth pressure monitoring unit 93 are located between the third control valve 40 and the spindle 31, respectively. The fourth pressure monitoring unit 93 monitors the internal pressure of the spindle 31 in real time and performs the tool change operation only when the internal pressure of the spindle is zero. The pressure relief valve 92 plays the role of quickly releasing the high-pressure CO2 gas inside the spindle and quickly reducing the pressure to zero. When a tool needs to be changed, the spindle control module 212 sends a relevant signal to the supercritical CO2 control module 22, which controls the pressure relief valve 92 to open and performs the tool change operation when the fourth pressure monitoring unit 93 receives feedback that the pressure is 0.

[0074] In this supercritical CO2-ultrasonic composite machining system, temperature and pressure monitoring is primarily performed by temperature and pressure monitoring devices installed after the pressure boosting unit (e.g., a first temperature monitoring unit and a first pressure monitoring unit), and temperature and pressure monitoring devices installed before the material enters the spindle (e.g., a second temperature monitoring unit and a fourth pressure monitoring unit). A certain transport distance exists between the supercritical CO2 supply unit and the spindle, resulting in certain pressure and temperature losses. However, the pressure and temperature at the injection end of the ultrasonic holder 36 must exceed certain set values ​​(for example, the pressure must exceed 7.31 MPa to ensure a supercritical state), and if a tool needs to be changed, the pressure must be released beforehand. The tool can only be changed when the pressure is zero, and the temperature within the system must be monitored to prevent leakage. Therefore, pressure and temperature monitoring is necessary.

[0075] For example, the first temperature monitoring unit, the second temperature monitoring unit, and the third temperature monitoring unit may be temperature sensors. The first pressure monitoring unit, the second pressure monitoring unit, the third pressure monitoring unit, and the fourth pressure monitoring unit may be pressure sensors.

[0076] In the technical solution of this embodiment, the supercritical CO2-ultrasonic composite machining system is realized as follows. Referring to Figure 5, when cutting is required, the workpiece is mounted at the machining position. The CO2 supply unit 11 supplies low-temperature, low-pressure CO2 to the first pressure boosting unit 121. The compressed air supply unit 61 is connected to the first pressure boosting unit 121 and supplies compressed air to the first pressure boosting unit 121, driving the pressure boosting by the first pressure boosting unit 121. The first pressure boosting unit 121 pressurizes the low-temperature, low-pressure CO2 to a certain pressure value (7.31 MPa or higher), obtains high-pressure CO2, and then sends it to the heating unit 122 for heating. The heating unit 122 heats the low-temperature, high-pressure CO2 to convert it into high-temperature, high-pressure supercritical CO2. Furthermore, a first temperature monitoring unit 16 and a first pressure monitoring unit 17 are provided in the pipeline connecting the heating unit 122 and the third control valve 40, respectively, to monitor the temperature and pressure of the supercritical CO2 at the outlet of the heating unit 122 in real time, thereby ensuring that the temperature and pressure of the CO2 reach the set temperature and set pressure, respectively (the set values ​​are slightly above the lower limits of temperature and pressure in the supercritical state, and are set according to the actual situation). After pressurization and heating, the low-temperature, low-pressure CO2 becomes supercritical, and supercritical CO2 is obtained, which is then sent to the spindle 31 via the third control valve 40. The spindle control module 212 controls the spindle 31 so that the supercritical CO2 passes through the spindle 31 and is ejected into the machining area, and the ultrasonic control module 211 controls the ultrasonic generator 32 to transmit ultrasonic signals, thereby achieving cutting by combining supercritical CO2 and ultrasonic waves. Furthermore, the ultrasonic control module 211 is electrically connected to the ultrasonic generator 32 and the tool parameter monitoring unit 33 to acquire ultrasonic vibration frequency and ultrasonic amplitude. The ultrasonic control module 211 is also electrically connected to the supercritical CO2 control module 22 and controls the supercritical CO2 pressure so that the supercritical CO2 pressure is dynamically adjusted according to the ultrasonic parameters based on the correspondence between the supercritical CO2 process parameters and the ultrasonic parameters. This enhances the injection effect of supercritical CO2, ensures processing effect and processing quality, improves processing efficiency and precision, and effectively reduces costs.

[0077] Figure 6 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite machining system according to an embodiment of the present invention. Based on the above embodiment, optionally, as shown in Figure 6, the supercritical CO2-ultrasonic composite machining system further includes a trace lubricating oil supply unit 50, which is connected to the discharge pipe of the supercritical CO2 supply unit 10. Thereafter, the lubricating oil supplied from the trace lubricating oil supply unit 50 and the supercritical CO2 supplied from the supercritical CO2 supply unit 10 are mixed in the discharge pipe of the supercritical CO2 supply unit 10, then pass through the internal cooling passage of the main spindle 31 of the ultrasonic machining apparatus, and the mixture of supercritical CO2 and oil mist is injected into the machining area, thereby performing cooling and lubrication functions. Of course, the discharge pipe of the supercritical CO2 supply unit 10 may also be directly connected to a nozzle provided separately, that is, the mixture of supercritical CO2 and oil mist may be injected into the machining area without passing through the internal cooling passage of the ultrasonic machining apparatus. The control module 20 is further configured to control the oil pressure of the oil discharged from the trace lubricating oil supply unit 50 so that it is higher than the supercritical CO2 pressure, and to control the amount of lubricating oil discharged.

[0078] Here, the control module 20 is connected to the micro-lubricating oil supply unit 50 and controls the starting and stopping of the micro-lubricating oil supply unit 50, thereby controlling whether or not the micro-lubricating oil supply unit 50 supplies a small amount of lubricating oil to the discharge pipeline of the supercritical CO2 supply unit.

[0079] As an example, the discharge pipeline of the minute lubrication oil supply unit 50 may be equipped with a lubrication oil quantitative supply device to control the amount of lubrication oil mixed with supercritical CO2. Here, the lubrication oil quantitative supply device may be a mechanical pump or a precision metering pump, and is not particularly limited here, as it can be set according to the actual situation.

[0080] Specifically, when a workpiece needs to be cut, the workpiece is fixed in the machining area. The control module 20 controls the supercritical CO2 supply unit 10 to supply supercritical CO2 and the micro-lubricating oil supply unit 50 to supply lubricating oil. Subsequently, the mixture of lubricating oil and supercritical CO2 is sent to the spindle 31. The control module 20 also controls the ultrasonic generator 32 to output relevant signals to the transmission unit of the spindle 31, and dynamically adjusts the supercritical CO2 pressure of the supercritical CO2 supply unit 10 based on the correspondence between the process parameters of supercritical CO2 and the ultrasonic parameters, according to the feedback ultrasonic vibration frequency and ultrasonic amplitude, and controls the hydraulic pressure of the oil discharged from the micro-lubricating oil supply unit 50 to be higher than the supercritical CO2 pressure. Thus, by jointly controlling micro-lubrication, supercritical CO2, and ultrasound, the process parameters of supercritical CO2, ultrasonic parameters, and lubricating oil pressure can be controlled within a reasonable range, enhancing the injection effect of the cooling lubricating medium, thereby ensuring machining effect and quality, and improving machining efficiency and precision. Furthermore, the high-frequency vibrations of the ultrasound thoroughly mix the supercritical CO2 and lubricating oil. Due to the low solubility of lubricating oil in supercritical CO2, excess oil accumulates in the pipeline and eventually forms oil droplets that are ejected from the spindle nozzle, thus preventing this. This achieves efficient internal injection of lubricating oil and supercritical CO2. Moreover, when supercritical CO2 is ejected from the nozzle of the ultrasonic holder, dry ice may form at the outlet over time, potentially causing blockages. This can affect the direction of supercritical CO2 injection and impact the cooling and lubrication effects on the tool. However, the high-frequency vibrations of the ultrasound effectively prevent dry ice accumulation and inhibit its growth, thereby avoiding any impact on the direction of supercritical CO2 injection. In addition, the use of supercritical CO2 is environmentally friendly, pollution-free, provides high cooling efficiency, effectively lowers the temperature of the cutting area, and, in combination with ultrasound, can improve surface roughness, reduce burr problems, lower processing costs, and improve processing quality and effectiveness.

[0081] Optionally, to allow the lubricating oil to dissolve more effectively into supercritical CO2, the pressure difference between the oil pressure of the oil discharged from the trace lubricating oil supply unit and the supercritical CO2 pressure may be set to a predetermined pressure difference. The predetermined pressure difference may be 0.5 MPa. The predetermined pressure difference may be any other value, and is not particularly limited here, as it should be set according to the actual situation.

[0082] Figure 7 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite machining system according to an embodiment of the present invention. Based on the above embodiment, optionally, as shown in Figure 7, the supercritical CO2-ultrasonic composite machining system further includes a trace lubricating oil supply unit 50, which is electrically connected to a control module 20 to control the supply of lubricating oil from the trace lubricating oil supply unit 50, and a supercritical CO2 supply unit 10 is connected to the discharge pipeline of the trace lubricating oil supply unit 50, thereby mixing the lubricating oil supplied from the trace lubricating oil supply unit 50 and the supercritical CO2 supplied from the supercritical CO2 supply unit 10 in the discharge pipeline of the trace lubricating oil supply unit 50, passing through the internal cooling passage of the spindle 31, and injecting the mixture of supercritical CO2 and oil mist into the machining area to perform cooling and lubrication. The control module 20 is further configured to control the pressure of the lubricating oil discharged from the trace lubricating oil supply unit 50 so that it is lower than the supercritical CO2 pressure, and also to control the amount of lubricating oil discharged, in order to ensure that the supercritical CO2 is well mixed with the lubricating oil.

[0083] Figure 8 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite machining system according to an embodiment of the present invention. Based on the above embodiment, optionally, as shown in Figure 8, the supercritical CO2-ultrasonic composite machining system further includes a micro-lubricating oil supply unit 50 and a mixing module 60, both of which are connected to the mixing module 60. To control the amount of lubricating oil discharged, the micro-lubricating oil supply unit 50 is electrically connected to a control module 20, and the mixing module 60 is further connected to the spindle 31. The micro-lubricating oil supply unit 50 supplies lubricating oil to the mixing module 60, and the supercritical CO2 supply unit 10 supplies supercritical CO2 to the mixing module 60. The mixing module 60 mixes the supercritical CO2 and lubricating oil and then transports it to the spindle 31.

[0084] Here, the control module 20 is connected to the micro-lubricating oil supply unit 50 and controls the starting and stopping of the micro-lubricating oil supply unit 50, controls whether or not the micro-lubricating oil supply unit 50 supplies a small amount of lubricating oil to the mixing module 60, and also controls the amount of lubricating oil discharged.

[0085] Figure 9 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite machining system according to an embodiment of the present invention. Based on the above embodiment, optionally, as shown in Figure 9, the supercritical CO2-ultrasonic composite machining system further includes a minute lubricating oil supply unit 50 and a compressed air supply unit 61, wherein the discharge end of the minute lubricating oil supply unit 50 is connected to a pipeline connecting the supercritical CO2 supply unit 10 and a third control valve 40, that is, it is connected to the discharge pipeline of the supercritical CO2 supply unit 10, and the third control valve 40 is connected to the ultrasonic machining apparatus 30, so that finally, supercritical CO2 and oil mist are ejected from the ultrasonic machining apparatus 30. The minute lubricating oil supply unit 50 is further electrically connected to a supercritical CO2 control module 22. The compressed air supply unit 61 is not only connected to the supercritical CO2 supply unit 10, but also to the micro-lubricating oil supply unit 50, which drives the pressure boosting unit of the micro-lubricating oil supply unit 50, thereby ensuring that the lubricating oil pressure reaches a set value.

[0086] Here, the trace lubricating oil supply unit 50 supplies lubricating oil to the discharge pipeline of the supercritical CO2 supply unit 10, facilitating the mixing of the lubricating oil and supercritical CO2.

[0087] Specifically, if the system requires oil mixing, the supercritical CO2 control module 22 controls the micro-lubricating oil supply unit 50 to operate. If the system does not require oil mixing, the micro-lubricating oil supply unit 50 does not operate. Whether or not oil mixing is required may be set according to the actual processing requirements; for example, when processing some products for the medical industry, there is a special requirement that oil must not be mixed.

[0088] In the technical solution of this embodiment, the supercritical CO2-ultrasonic combined machining system is realized as follows. Referring to Figure 9, when cutting is required, the workpiece is mounted at the machining position. The supercritical CO2 supply unit 10 supplies supercritical CO2, and the trace lubricating oil supply unit 50 supplies lubricating oil. The supercritical CO2 and lubricating oil are mixed in a pipeline connecting the supercritical CO2 supply unit 10 and the third control valve 40, and then the supercritical CO2 mixed with lubricating oil is supplied to the ultrasonic machining apparatus 30 via the third control valve 40. The ultrasonic machining apparatus 30 sprays this supercritical CO2 mixed with lubricating oil as supercritical CO2 and oil mist through its main spindle into the machining area, thereby performing cooling and lubrication, and also performing cutting on the workpiece by combining it with ultrasound.

[0089] Figure 10 is a block diagram of the principle and structure of another supercritical CO2-ultrasonic composite processing system according to an embodiment of the present invention (in this figure, electrical connections are represented by dashed lines to distinguish them from connections by piping). Based on the above embodiment, optionally, as shown in Figure 10, the micro-lubricating oil supply unit 50 includes a lubricating oil storage tank 51, a second pressure boosting unit 52, and a second pressure monitoring unit 53, wherein the lubricating oil storage tank 51 is connected to the discharge pipeline of the supercritical CO2 supply unit via the second pressure boosting unit 52 and supplies lubricating oil to the discharge pipeline. The second pressure monitoring unit 53 is connected to the discharge pipeline of the second pressure boosting unit 52 and monitors the pressure of the lubricating oil from the second pressure boosting unit 52. Both the second pressure boosting unit 52 and the second pressure monitoring unit 53 are electrically connected to the supercritical CO2 control module 22.

[0090] Here, the compressed air supply unit 61 is also connected to the second pressure boosting unit 52 and supplies compressed air to the second pressure boosting unit 52, driving the pressure boosting by the second pressure boosting unit 52. Of course, a control valve (not shown) is provided between the second pressure boosting unit and the compressed air supply unit, and this control valve is electrically connected to the supercritical CO2 supply unit and has the same function as the second control valve, so a detailed explanation is omitted here. The second pressure boosting unit 52 pressurizes the lubricating oil. The second pressure monitoring unit 53 is connected to the second pressure boosting unit 52 and monitors the pressure of the lubricating oil after pressurization. When the pressure reaches the pressure value set in the system, the second pressure boosting unit 52 stops pressurizing. The lubricating oil pressurized by the second pressure boosting unit 52 is then transported to the discharge pipeline of the supercritical CO2 supply unit and mixed with supercritical CO2.

[0091] When mixing supercritical CO2 with pressurized lubricating oil (i.e., high-pressure lubricating oil), the pressure of the high-pressure lubricating oil must be higher than the pressure of the supercritical CO2. For example, the pressure of the lubricating oil should be 0.5 MPa higher than the pressure of the supercritical CO2, thereby facilitating the dissolution of the lubricating oil into the supercritical CO2.

[0092] As an example, as shown in Figure 10, the compressed air supply unit 61 is connected to the first pressure boosting unit 121 and the second pressure boosting unit 72, respectively, and drives the first pressure boosting unit 121 and the second pressure boosting unit 72, respectively.

[0093] Optionally, referring to Figure 10, the supercritical CO2-ultrasonic composite processing system further includes a lubricating oil quantitative supply unit 80, one end of which is connected to a second pressure boosting unit 72, and the other end of which is connected to a pipeline connecting the supercritical CO2 supply unit 10 and a third control valve 40.

[0094] When lubricating oil is required in the system, the amount used is usually small. Therefore, by installing a lubricating oil quantitative supply unit 80, the amount of lubricating oil supplied can be precisely controlled, and efficient mixing of the lubricating oil and supercritical CO2 can be ensured.

[0095] The lubricating oil quantitative supply unit 80 is electrically connected to the supercritical CO2 control module 22 and limits the amount of lubricating oil mixed with supercritical CO2. Here, the oil volume may be controlled within a range of 0 to 100 ml / h, or within a range of other values, and may be set according to the actual situation, and is not particularly limited here.

[0096] The lubricating oil metering supply unit 80 may be a mechanical pump or a precision metering pump, and is not particularly limited here, as it can be set according to the actual situation.

[0097] In the technical solution of this embodiment, the supercritical CO2-ultrasonic composite machining system is realized as follows. Referring to Figure 10, when machining requires mixing supercritical CO2 with a small amount of lubricating oil, the lubricating oil storage tank 51 is connected to the second pressure boosting unit 52, and the compressed air supply unit 61 is connected to the second pressure boosting unit 52, supplying compressed air to the second pressure boosting unit 52 and driving the pressure boosting by the second pressure boosting unit 52. The second pressure boosting unit 52 pressurizes the lubricating oil by boosting the pressure. The second pressure monitoring unit 53 is connected to the second pressure boosting unit 52 and monitors the pressure of the lubricating oil after pressurization. When the pressure reaches the pressure value set in the system, the second pressure boosting unit 52 stops pressurizing. The lubricating oil pressurized by the second pressure boosting unit 52 is then quantitatively transported by the lubricating oil quantitative supply unit 80 to the discharge end of the supercritical CO2 supply unit 10 and mixed with supercritical CO2. Supercritical CO2 mixed with lubricating oil is transported to the spindle 31 via the third control valve 40. The spindle control module 212 controls the spindle 31 to spray the supercritical CO2 mixed with lubricating oil as supercritical CO2 and oil mist into the machining area through the cooling passage of the spindle 31 for cooling and lubrication. The ultrasonic control module 211 controls the ultrasonic generator 54 to transmit ultrasonic signals, thereby performing cutting in combination with ultrasonic waves using supercritical CO2 mixed with a small amount of lubricating oil.

[0098] Figure 11 is a flowchart of a control method for a supercritical CO2-ultrasonic composite machining system according to an embodiment of the present application. The embodiment of the present application further provides a control method for a supercritical CO2-ultrasonic composite machining system, which, as shown in Figure 11, includes the following step S110.

[0099] S110: Based on the correspondence between the process parameters of supercritical CO2 and the ultrasonic parameters, the process parameters of supercritical CO2 are controlled so that the process parameters of supercritical CO2 are dynamically adjusted within a predetermined range according to the ultrasonic parameters.

[0100] Here, the process parameters for supercritical CO2 include the supercritical CO2 pressure, and the ultrasonic parameters include the ultrasonic amplitude and ultrasonic vibration frequency.

[0101] The control method for the supercritical CO2-ultrasonic composite machining system is applied to the supercritical CO2-ultrasonic composite machining system. The supercritical CO2-ultrasonic composite machining system includes at least a supercritical CO2 supply unit, a control module, and an ultrasonic machining apparatus. Of these, the supercritical CO2 supply unit supplies supercritical CO2 to the machining area. The control module controls the process parameters of the supercritical CO2 so that the process parameters of the supercritical CO2 are dynamically adjusted within a predetermined range according to the ultrasonic parameters, based on the correspondence between the process parameters of the supercritical CO2 and the ultrasonic parameters.

[0102] Furthermore, the control module also controls the process parameters of the supercritical CO2 supply unit and the ultrasonic parameters of the ultrasonic processing device to stabilize within a predetermined range, and controls the starting and stopping of the supercritical CO2 supply unit and the ultrasonic processing device.

[0103] In this embodiment, a technical solution is provided which is a control method for a supercritical CO2-ultrasonic composite processing system, the control method for a supercritical CO2-ultrasonic composite processing system, the control method for a supercritical CO2-ultrasonic composite processing system, the control method for a supercritical CO2 supply unit, and the ultrasonic parameters of an ultrasonic processing apparatus, the control of the supercritical CO2 process parameters, based on the correspondence between the supercritical CO2 process parameters and the ultrasonic parameters, such that the supercritical CO2 process parameters are dynamically adjusted within a predetermined range according to the ultrasonic parameters, the supercritical CO2 process parameters include supercritical CO2 pressure, and the ultrasonic parameters include ultrasonic amplitude and ultrasonic vibration frequency. As can be seen, by combining supercritical CO2 and ultrasound, it is possible to cut difficult-to-machine materials in an environmentally friendly manner. Furthermore, by controlling the supercritical CO2 process parameters so that they are dynamically adjusted according to the ultrasound parameters based on the correspondence between the supercritical CO2 process parameters and the ultrasound parameters, the supercritical CO2 process parameters can be controlled within a reasonable range, thereby ensuring processing effectiveness and quality, improving processing efficiency and precision, and effectively reducing costs. In addition, by using internal injection of supercritical CO2, it is possible to reduce the temperature of the cutting area in an environmentally friendly and pollution-free manner, with a high cooling effect. Furthermore, ultrasonic processing can improve the roughness of the processed surface, improve the problem of burrs, and reduce processing costs.

[0104] Figure 12 is a schematic diagram of the overall flow of the supercritical CO2-ultrasonic composite machining system according to an embodiment of the present invention. As an example, referring to Figure 12, in a normal machining state (automatic mode, started up and program loaded), the flow of related operations of the machining machine tool is as follows: First, the supercritical CO2 supply unit is started, the pressure and heating system (i.e., the first pressure boosting unit and heating unit) increases the pressure and heats it to a reasonable predetermined value, the workpiece is fixed to the machine tool's operating table, the machine tool is started up and prepared for machining, the pressure relief system (i.e., the second pressure monitoring unit) monitors the internal pressure of the spindle, and when the pressure signal becomes zero, the execution of the command for the next step is permitted. If a tool change command exists in the program, the tool change operation is performed. After the tool is ready, (if there is a command in the program) the ultrasonic control module controls the unit to perform amplitude debugging, and then the supercritical CO2 control module controls the supercritical CO2 supply unit to inject supercritical CO2 (the supercritical CO2 control module controls the unit to open the third control valve). Then, machining is performed according to the part machining program, and during machining, a second temperature monitoring unit may monitor the system temperature in real time. During machining, the ultrasonic control module collects monitoring data of the ultrasonic vibration frequency of the ultrasonic generator and the ultrasonic amplitude by the tool parameter monitoring unit, and the supercritical CO2 control module monitors the supercritical CO2 pressure. The ultrasonic control module is electrically connected to the supercritical CO2 control module, and based on the acquired ultrasonic vibration frequency and ultrasonic amplitude, the ultrasonic control module continuously transmits commands to the supercritical CO2 control module to adjust the supercritical CO2 pressure, that is, it controls the process parameters of the supercritical CO2 supply unit to be dynamically adjusted within a predetermined range according to the ultrasonic parameters of the ultrasonic machining apparatus. The above adjustments are repeated during machining.If, after the current tooling process is complete, it is necessary to change the tool for subsequent machining, the ultrasonic control module controls the ultrasonic generator to stop, and at the same time, communicates with the supercritical CO2 control module to control the supercritical CO2 supply unit to stop the injection of supercritical CO2, and activates the pressure relief system (i.e., the fourth pressure monitoring unit and pressure relief valve) so that when the internal pressure of the spindle becomes zero, the tool is changed and subsequent machining is performed until the machining of the part is complete.

[0105] The embodiments of the present application also provide machine tools including a supercritical CO2-ultrasonic composite machining system according to any embodiment of the present application.

[0106] It is understood that the order, additions, or deletions of steps can be made using the various forms of flows described above. For example, each step described in this application may be executed in parallel, sequentially, or in a different order, as long as the technical solution of this application achieves the desired result.

[0107] The specific embodiments described above do not limit the scope of protection of this application. Those skilled in the art should understand that various modifications, combinations, subcombinations, and substitutions are possible depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made without departing from the spirit and principles of this application should be included within the scope of protection.

Claims

1. supercritical CO ２ • An ultrasonic composite machining system, supercritical CO ２ The system includes a supply unit, a control module, and an ultrasonic processing apparatus, wherein the control module is the supercritical CO2 ２ The control module is electrically connected to the supply unit, and is further electrically connected to the ultrasonic processing apparatus. The control module is based on the correspondence between the process parameters of supercritical CO ２ and the ultrasonic parameters, and the process parameters of the supercritical CO ２ are dynamically adjusted within a predetermined range according to the ultrasonic parameters, and the process parameters of the supercritical CO ２ are configured to control the process parameters of the supercritical CO ２ The process parameters of the supercritical CO ２ include the supercritical CO pressure P, and the ultrasonic parameters include the ultrasonic amplitude A and the ultrasonic vibration frequency f of the ultrasonic processing device. A supercritical CO ２ ・ultrasonic composite processing system is characterized by this.

2. The supercritical CO ２ The relationship between pressure P and ultrasonic vibration frequency f is such that when the ultrasonic vibration frequency f is within a first predetermined ultrasonic vibration frequency range, the ultrasonic vibration frequency f is supercritical CO ２ When pressure P shows a negative correlation and the ultrasonic vibration frequency f is within a second predetermined ultrasonic vibration frequency range, the ultrasonic vibration frequency f is supercritical CO ２ The supercritical CO2 according to claim 1, characterized in that it shows a positive correlation with pressure P, and any value within the first predetermined ultrasonic vibration frequency range is smaller than any value within the second predetermined ultrasonic vibration frequency range. ２ • Ultrasonic composite machining system.

3. The supercritical CO2 according to claim 2, characterized in that the first predetermined ultrasonic vibration frequency range is 16 kHz ≤ f < 30 kHz, and the second predetermined ultrasonic vibration frequency range is 30 kHz ≤ f ≤ 50 kHz. ２ • Ultrasonic composite machining system.

4. The supercritical CO2 according to claim 3, characterized in that when 16 kHz ≤ f < 30 kHz, 8 MPa < P ≤ 15 MPa and f shows a negative correlation with P, and when 30 kHz ≤ f ≤ 50 kHz, P ≥ 8 MPa and f shows a positive correlation with P. ２ • Ultrasonic composite machining system.

5. The supercritical CO ２ The relationship between pressure P and ultrasonic amplitude A is such that when ultrasonic amplitude A is within a first predetermined ultrasonic amplitude range, ultrasonic amplitude A is supercritical CO ２ When pressure P shows a negative correlation and ultrasonic amplitude A is within a second predetermined ultrasonic amplitude range, ultrasonic amplitude A is supercritical CO ２ The supercritical CO2 according to claim 1, characterized in that it shows a positive correlation with pressure P, and any value within the first predetermined ultrasonic amplitude range is smaller than any value within the second predetermined ultrasonic amplitude range. ２ • Ultrasonic composite machining system.

6. The supercritical CO2 according to claim 5, characterized in that the first predetermined ultrasonic amplitude range is 0.5 μm ≤ A < 10 μm, and the second predetermined ultrasonic amplitude range is A ≥ 10 μm. ２ • Ultrasonic composite machining system.

7. The supercritical CO2 according to claim 6, characterized in that when 0.5 μm ≤ A < 10 μm, 8 MPa < P ≤ 15 MPa and A shows a negative correlation with P, and when A ≥ 10 μm, P ≥ 8 MPa and A shows a positive correlation with P. ２ • Ultrasonic composite machining system.

8. The control module is the supercritical CO2 ２ The supercritical CO2 device according to claim 1 is configured to control the pressure within a predetermined pressure range, the ultrasonic amplitude within a predetermined ultrasonic amplitude range, and the ultrasonic vibration frequency within a predetermined ultrasonic vibration frequency range, wherein the predetermined pressure range is P ≥ 8 MPa, the predetermined ultrasonic amplitude range is A ≥ 0.5 μm, and the predetermined ultrasonic vibration frequency is 16 kHz ≤ f ≤ 50 kHz. ２ • Ultrasonic composite machining system.

9. The supercritical CO ２ The system further includes a small lubricating oil supply unit that is connected to the discharge pipeline of the supply unit and is electrically connected to the control module, The control module further determines that the pressure of the lubricating oil discharged from the trace lubricating oil supply unit is supercritical CO2 ２ The supercritical CO2 according to claim 1, characterized in that it is configured to be controlled to be higher than the pressure. ２ • Ultrasonic composite machining system.

10. The system further includes a micro-lubricating oil supply unit and a mixing module, and the micro-lubricating oil supply unit and the supercritical CO ２ The supercritical CO2 supply unit according to claim 1 is characterized in that all supply units are connected to the mixing module, and the trace lubricant supply unit is further electrically connected to the control module. ２ • Ultrasonic composite machining system.

11. The system further includes a small lubrication oil supply unit, and the supercritical CO ２ The supply unit is connected to the discharge pipeline of the trace lubricating oil supply unit, and the trace lubricating oil supply unit is further electrically connected to the control module. The control module further determines that the pressure of the lubricating oil discharged from the trace lubricating oil supply unit is the supercritical CO2 pressure. ２ The supercritical CO2 according to claim 1, characterized in that it is configured to be controlled to be lower than the pressure. ２ • Ultrasonic composite machining system.

12. The supercritical CO ２ The supercritical CO2 according to claim 1, characterized in that the end of the discharge pipeline of the supply unit is connected to the ultrasonic processing apparatus. ２ • Ultrasonic composite machining system.

13. Supercritical CO2 according to any one of claims 1 to 12 ２ A control method applied to an ultrasonic composite machining system, supercritical CO ２ Based on the correspondence between the process parameters and ultrasonic parameters, the supercritical CO ２ The process parameters of the supercritical CO2 are dynamically adjusted within a predetermined range according to the ultrasonic parameters. ２ The step includes controlling the process parameters of the supercritical CO ２ The process parameters are supercritical CO ２ A control method characterized in that it includes pressure, and the ultrasonic parameters include ultrasonic amplitude and ultrasonic vibration frequency.

14. It is a machine tool, Supercritical CO2 according to any one of claims 1 to 12 ２ A machine tool characterized by including an ultrasonic composite machining system.

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