Method for machining ceramic materials through numerical control machine tool of machining center

Abstract

The invention discloses a method for machining a ceramic material through a numerical control machine tool of a machining center, and relates to the technical field of precision machining.According to the method, the machining process is divided into multiple process categories according to the theoretical material removal rate, and when the numerical control machine tool conducts material removal machining on the ceramic workpiece, ion flow is applied between a tool and the ceramic workpiece; and according to the design that the corresponding ionization current values and the coverage forms are distributed according to the process types, and the ionization current values corresponding to the process types are updated to enable the predicted frequency offset to approach to zero, the peak voltage on the surface of the ceramic workpiece generated by processing of the process types is suppressed. Immediate damage to the ceramic workpiece caused by electrostatic stress in the machining process is effectively relieved, potential performance decay and delayed cracking of the ceramic workpiece caused by electrostatic accumulation in the machining process are inhibited, and the stability and safety of the generated ceramic workpiece are improved.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology, and in particular to a method for machining ceramic materials using a CNC machining center. Background Technology

[0002] When high-insulation ceramic materials such as alumina and aluminum nitride are machined on CNC machining centers using high-speed dry or micro-lubrication processes, intense friction generates and accumulates a large amount of electrostatic charge on the workpiece surface. For workpieces with thin walls and sharp angles, this accumulated charge generates significant local electrostatic forces, forming continuous tensile stress. This stress can exacerbate the formation of subsurface microcracks during machining and, after machining, becomes a potential driving force for the slow, age-related propagation of cracks. This can lead to delayed cracking of ceramic workpieces without warning during storage or subsequent gentle handling, causing serious quality risks.

[0003] Currently, a separate ion fan station is typically set up after the processing steps for static electricity removal. This method has two problems: first, it is a passive post-processing measure and cannot alleviate the immediate damage to ceramic workpieces caused by electrostatic stress during processing; second, for complex cavities or residual attached charges, the neutralization effect of external ion fan is limited. Summary of the Invention

[0004] To address the technical problems existing in the background art, the present invention proposes a method for machining ceramic materials using a CNC machining center.

[0005] This invention proposes a method for machining ceramic materials using a CNC machining center, comprising the following steps: S1. Obtain the theoretical material removal rate of the CNC machine tool; For clarity, the theoretical material removal rate is the volume of material removed per unit time under ideal conditions, as defined by the machining program itself in the CNC machine tool, rather than a value measured by sensors; the unit of the theoretical material removal rate is mm³ / s. Based on the theoretical material removal rate, the machining process of CNC machine tools is divided into several process categories; S2. When performing material removal processing on ceramic workpieces on a CNC machine tool, an ion flow is applied between the CNC machine tool's cutting tool and the ceramic workpiece; According to the process category, the ionization current value and coverage pattern of the ion current are assigned; the ionization current value includes the first ionization current value, the second ionization current value, and the third ionization current value; the coverage pattern includes the first coverage pattern, the second coverage pattern, and the third coverage pattern. S3. After the CNC machine tool completes all the processing of the ceramic workpiece, it applies a micro-amplitude sweep frequency mechanical excitation to the ceramic workpiece. The micro-amplitude sweep frequency mechanical excitation is used to make the ceramic workpiece generate a vibration response signal. S4. Based on the feature point selection rules of ceramic workpieces, obtain several feature points on the ceramic workpieces; The vibration response signal at the characteristic point is measured by a laser vibrometer, and the measured value of the first-order bending natural frequency is generated based on the vibration response signal. Obtain the standard value of the first-order bending natural frequency; As an explanation, the standard value of the first-order bending natural frequency is the first-order bending natural frequency value measured from an isomorphic stress-free reference workpiece. The absolute value of the difference between the measured value of the first-order bending natural frequency and the standard value of the first-order bending natural frequency is used as the frequency offset. S5. Obtain the frequency offset obtained after processing each ceramic workpiece, the ionization current value used for the corresponding process category during processing of each ceramic workpiece, and update the ionization current value corresponding to each process category. For illustration, the processing of a single ceramic workpiece typically includes three process categories: roughing, semi-finishing, and finishing.

[0006] Preferably, in S1, based on the theoretical material removal rate, the machining process of the CNC machine tool is divided into several process categories, as follows: If the theoretical material removal rate is greater than 50 mm³ / s, then the process category is roughing. If the theoretical material removal rate is greater than or equal to 5 mm³ / s and less than or equal to 50 mm³ / s, then the process category is semi-finishing. If the theoretical material removal rate is less than 5 mm³ / s, then the process category is finishing.

[0007] Preferably, in S2, the ion current is pulsed direct current ionization.

[0008] Preferably, in S2, the ionization current value and coverage pattern of the ion flow are allocated according to the process type, as follows: Obtain the cutting width of the CNC machine tool; For illustrative purposes, the cutting width is the cutting contact width of the tool during one cutting stroke, which is parallel to the workpiece surface and perpendicular to the feed direction.

[0009] The contact zone formed by the contact between the cutting edge of the tool and the surface of the ceramic workpiece is taken as the linear contact zone; a strip-shaped area is formed by extending 0.1 mm to 0.5 mm on both sides of the linear contact zone, which is taken as the contact line area; When the process category is rough machining, a first ionization current value is adopted, the value of which ranges from 1.8mA to 2.2mA, and a first coverage pattern is adopted. The first coverage pattern is: the ion flow covers a fan-shaped area on the ceramic workpiece with the tool tip as the vertex and an angle of not less than 90 degrees. When the process category is semi-finishing, a second ionization current value is adopted, the value of which ranges from 0.9mA to 1.1mA, and a second coverage pattern is adopted. The second coverage pattern is: the ion flow is concentrated to cover a strip-shaped area on the ceramic workpiece with the cutting edge of the tool as the axis, and the width of the strip-shaped area is 1.5 to 2.5 times the cutting width. When the process category is finishing, a third ionization current value is used, with the value ranging from 0.45mA to 0.55mA, and a third coverage pattern is adopted; the third coverage pattern is: the ion current covers a contact line area on the ceramic workpiece; As an explanation, in actual use, by measuring the peak voltage on the surface of the ceramic workpiece in the unsuppressed state during processing of different process categories, and testing the suppression effect curves under different ionization current values, it is determined that the above-mentioned current ranges can suppress the peak voltage on the surface of the ceramic workpiece generated by the corresponding process category to below the safe threshold of ±200V; the first coverage mode, the second coverage mode, and the third coverage mode are achieved by adjusting the installation position of the ionization device relative to the tool, the spray direction, and the distance between it and the surface of the ceramic workpiece.

[0010] Preferably, in S3, a micro-amplitude sweep frequency mechanical excitation is applied to the ceramic workpiece as follows: The surface of the ceramic workpiece used for positioning and clamping on the CNC machine tool is used as the machining reference surface; all surfaces of the ceramic workpiece other than the machining reference surface are used as non-machining reference surfaces. A piezoelectric actuator applies mechanical force to a non-machined reference surface of a ceramic workpiece through point contact. The frequency range of the piezoelectric actuator is 1 kHz to 50 kHz. The frequency sweep method of the piezoelectric actuator is a sweep method in which the frequency increases or decreases uniformly with time at a constant frequency change rate within the frequency range of 1 kHz to 50 kHz. The output displacement amplitude of the piezoelectric actuator is no greater than 5 μm, and the amplitude of the mechanical force applied by the piezoelectric actuator to the ceramic workpiece is no greater than 10 mN. For clarification, the frequency sweep method of a piezoelectric actuator refers to the output frequency control method of the piezoelectric actuator.

[0011] Preferably, in S4, the selection rules for feature points of the ceramic workpiece are as follows: On ceramic workpieces, thin-walled areas with a thickness of less than 1 mm are designated as sensitive areas; Obtain the geometric center of the sensitive region as the feature point; If there is no sensitive area on the ceramic workpiece, obtain the acute angle with a radius of curvature of less than 0.5 mm on the ceramic workpiece, and use the vertex of the acute angle as the feature point.

[0012] Preferably, in step S4, the measured value of the first-order bending natural frequency is generated based on the vibration response signal, as follows: All vibration response signals are acquired to form a vibration response signal set; Based on the vibration response signal set, the modal parameters of the ceramic workpiece are identified by frequency domain decomposition. Modal parameters are a set of orders ordered from smallest to largest natural frequency. Each order includes natural frequency, damping ratio, and displacement response amplitude at multiple characteristic points. From the modal parameters, the displacement response amplitudes of multiple feature points corresponding to each order are extracted sequentially to form a sequence of displacement response amplitudes of multiple feature points. In the multi-feature point displacement response amplitude sequence, the first multi-feature point displacement response amplitude that is not equal to 0 is selected as the target multi-feature point displacement response amplitude. The order of the target is taken as the order of the displacement response amplitude of the target's multiple feature points. The natural frequency corresponding to the target order is obtained as the measured value of the first-order bending natural frequency of the ceramic workpiece after processing.

[0013] Preferably, in S5, the ionization current values ​​corresponding to each process category are updated as follows: The frequency offset corresponding to the same ceramic workpiece is associated with the ionization current value used in the corresponding process category during processing to form a historical process record. Multiple historical process records form a collection of historical process records; Based on the historical process record set, the recursive least squares method is used to update the ionization current value corresponding to each process category with the goal of making the predicted frequency offset approach zero.

[0014] As an explanation, the purpose is to use an updated ionization current value when processing the same type of ceramic workpiece again, in order to alleviate the immediate damage to the ceramic workpiece caused by electrostatic stress during the processing.

[0015] The method for machining ceramic materials using a CNC machining center proposed in this invention has the following beneficial technical effects: This application first divides the machining process into multiple process categories based on the theoretical material removal rate of CNC machine tools. Then, during the material removal machining of ceramic workpieces on CNC machine tools, an ion current is applied between the tool and the ceramic workpiece, and corresponding ionization current values ​​and coverage patterns are assigned according to the process category. After machining, a piezoelectric actuator applies micro-amplitude sweep frequency mechanical excitation to the non-machining reference surface of the ceramic workpiece in a point-contact manner to generate a vibration response signal. Then, feature points are obtained according to the feature point selection rules of the ceramic workpiece. After measuring the vibration response signal at the feature point using a laser vibrometer, the modal parameters are identified using the frequency domain decomposition method. From the modal parameters sorted by natural frequency from smallest to largest, the target corresponding to the first non-zero multi-feature point displacement response amplitude is selected. The design employs a method that uses the natural frequency corresponding to the target order as the measured value of the first-order bending natural frequency and the absolute value of the difference between the standard values ​​of the first-order bending natural frequencies as the frequency offset. Finally, it associates the frequency offset of each ceramic workpiece with the ionization current value used in the corresponding process category to form a historical process record set. The design uses a recursive least squares method to update the ionization current value corresponding to each process category so that the predicted frequency offset approaches zero. This design achieves the suppression of the peak voltage on the surface of the ceramic workpiece generated by each process category, effectively alleviates the immediate damage to the ceramic workpiece caused by electrostatic stress during processing, suppresses the potential performance degradation and delayed cracking of the ceramic workpiece caused by electrostatic accumulation during processing, and improves the stability and safety of the ceramic workpiece after it is generated. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating a method for machining ceramic materials using a CNC machine tool according to the present invention; Figure 2 A comparison chart showing the rate of delayed cracking of ceramic workpieces under different processes. Detailed Implementation

[0017] Embodiments of the present invention are described in detail below. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar symbols denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0018] like Figure 1 A method for machining ceramic materials using a CNC machining center, as shown, includes the following steps: S1. Obtain the theoretical material removal rate of the CNC machine tool; For clarity, the theoretical material removal rate is the volume of material removed per unit time under ideal conditions, as defined by the machining program itself in the CNC machine tool, rather than a value measured by sensors; the unit of the theoretical material removal rate is mm³ / s. Based on the theoretical material removal rate, the machining process of CNC machine tools is divided into several process categories; In an optional embodiment, in S1, the machining process of the CNC machine tool is divided into several process categories based on the theoretical material removal rate, as follows: If the theoretical material removal rate is greater than 50 mm³ / s, then the process category is roughing. If the theoretical material removal rate is greater than or equal to 5 mm³ / s and less than or equal to 50 mm³ / s, then the process category is semi-finishing. If the theoretical material removal rate is less than 5 mm³ / s, then the process category is finishing. In an optional embodiment, in S1, the CNC machine tool processing is divided into multiple process categories based on the theoretical material removal rate. This is a specific and directly implementable optional embodiment, not the only classification scheme. In the field of precision machining technology, considering the processing characteristics of ceramic materials, in addition to the theoretical material removal rate, process categories can also be classified based on the following factors. As long as the process can adapt to the process category and adjust the ionization current value of the ion flow, the purpose of mitigating electrostatic damage and improving workpiece stability can be achieved. The specific factors are as follows: Machining accuracy, ceramic material properties, tool machining parameters, and machining process objectives; among which, machining process objectives refer to the division of machining tasks according to each machining stage, which is more suitable for machining complex cavity ceramic workpieces; S2. When performing material removal processing on ceramic workpieces on a CNC machine tool, an ion flow is applied between the CNC machine tool's cutting tool and the ceramic workpiece; In an optional embodiment, in S2, the ion flow is pulsed DC ionization; According to the process category, the ionization current value and coverage pattern of the ion current are assigned; the ionization current value includes the first ionization current value, the second ionization current value, and the third ionization current value; the coverage pattern includes the first coverage pattern, the second coverage pattern, and the third coverage pattern. In an optional embodiment, in S2, the ionization current value and coverage pattern of the ion flow are assigned according to the process type, as follows: Obtain the cutting width of the CNC machine tool; For illustrative purposes, the cutting width is the cutting contact width of the tool during one cutting stroke, which is parallel to the workpiece surface and perpendicular to the feed direction.

[0019] The contact zone formed by the contact between the cutting edge of the tool and the surface of the ceramic workpiece is taken as the linear contact zone; a strip-shaped area is formed by extending 0.1 mm to 0.5 mm on both sides of the linear contact zone, which is taken as the contact line area; 0.1mm to 0.5mm refers to 0.1 millimeters to 0.5 millimeters; When the process category is rough machining, a first ionization current value is adopted, the value of which ranges from 1.8mA to 2.2mA, and a first coverage pattern is adopted. The first coverage pattern is: the ion flow covers a fan-shaped area on the ceramic workpiece with the tool tip as the vertex and an angle of not less than 90 degrees. When the process category is semi-finishing, a second ionization current value is adopted, the value of which ranges from 0.9mA to 1.1mA, and a second coverage pattern is adopted. The second coverage pattern is: the ion flow is concentrated to cover a strip-shaped area on the ceramic workpiece with the cutting edge of the tool as the axis, and the width of the strip-shaped area is 1.5 to 2.5 times the cutting width. When the process category is finishing, a third ionization current value is used, with the value ranging from 0.45mA to 0.55mA, and a third coverage pattern is adopted; the third coverage pattern is: the ion current covers a contact line area on the ceramic workpiece; As an explanation, in actual use, by measuring the peak voltage on the surface of ceramic workpieces in the unsuppressed state during processing under different process categories, and testing the suppression effect curves under different ionization current values, it was determined that all the aforementioned current ranges could suppress the peak voltage on the surface of ceramic workpieces generated by the corresponding process categories. The first coverage mode, the second coverage mode, and the third coverage mode are achieved by adjusting the installation position of the ionization device relative to the tool, the spray direction, and its distance from the surface of the ceramic workpiece. The ionization device refers to existing equipment that applies an ion flow.

[0020] S3. After the CNC machine tool completes all the machining of the ceramic workpiece, it applies a micro-amplitude sweep frequency mechanical excitation to the ceramic workpiece. In an optional embodiment, in S3, a micro-amplitude sweep frequency mechanical excitation is applied to the ceramic workpiece as follows: The surface of the ceramic workpiece used for positioning and clamping on the CNC machine tool is used as the machining reference surface; all surfaces of the ceramic workpiece other than the machining reference surface are used as non-machining reference surfaces. A piezoelectric actuator applies mechanical force to a non-machined reference surface of a ceramic workpiece through point contact. The frequency range of the piezoelectric actuator is 1 kHz to 50 kHz. The frequency sweep method of the piezoelectric actuator is a sweep method in which the frequency increases or decreases uniformly with time at a constant frequency change rate within the frequency range of 1 kHz to 50 kHz. The output displacement amplitude of the piezoelectric actuator is no greater than 5 μm, and the amplitude of the mechanical force applied by the piezoelectric actuator to the ceramic workpiece is no greater than 10 mN. For clarification, the frequency sweep method of a piezoelectric actuator refers to the output frequency control method of the piezoelectric actuator.

[0021] Micro-amplitude sweep frequency mechanical excitation is used to induce vibration response signals in ceramic workpieces; S4. Based on the feature point selection rules of ceramic workpieces, obtain several feature points on the ceramic workpieces; In an optional embodiment, in S4, the feature point selection rules for the ceramic workpiece are as follows: On ceramic workpieces, thin-walled areas with a thickness of less than 1 mm are designated as sensitive areas; Obtain the geometric center of the sensitive region as the feature point; If there is no sensitive area on the ceramic workpiece, obtain the acute angle with a radius of curvature of less than 0.5 mm on the ceramic workpiece, and use the vertex of the acute angle as the feature point; The vibration response signal at the characteristic point is measured by a laser vibrometer, and the measured value of the first-order bending natural frequency is generated based on the vibration response signal. In an optional embodiment, in S4, the measured value of the first-order bending natural frequency is generated based on the vibration response signal, as follows: All vibration response signals are acquired to form a vibration response signal set; Based on the vibration response signal set, the modal parameters of the ceramic workpiece are identified by frequency domain decomposition. Modal parameters are a set of orders ordered from smallest to largest natural frequency. Each order includes natural frequency, damping ratio, and displacement response amplitude at multiple characteristic points. From the modal parameters, the displacement response amplitudes of multiple feature points corresponding to each order are extracted sequentially to form a sequence of displacement response amplitudes of multiple feature points. In the multi-feature point displacement response amplitude sequence, the first multi-feature point displacement response amplitude that is not equal to 0 is selected as the target multi-feature point displacement response amplitude. The order of the target is taken as the order of the displacement response amplitude of the target's multiple feature points. The natural frequency corresponding to the target order is obtained as the measured value of the first-order bending natural frequency of the ceramic workpiece after processing. Obtain the standard value of the first-order bending natural frequency; As an explanation, the standard value of the first-order bending natural frequency is the first-order bending natural frequency value measured from an isomorphic stress-free reference workpiece. The absolute value of the difference between the measured value of the first-order bending natural frequency and the standard value of the first-order bending natural frequency is used as the frequency offset. S5. Obtain the frequency offset obtained after processing each ceramic workpiece, the ionization current value used for the corresponding process category during processing of each ceramic workpiece, and update the ionization current value corresponding to each process category. As an explanation, the processing of a single ceramic workpiece typically includes three process categories: roughing, semi-finishing, and finishing. In an optional embodiment, in S5, the ionization current value corresponding to each process category is updated as follows: The frequency offset corresponding to the same ceramic workpiece is associated with the ionization current value used in the corresponding process category during processing to form a historical process record. Multiple historical process records form a collection of historical process records; Based on the historical process record set, the recursive least squares method is used to update the ionization current value corresponding to each process category with the goal of making the predicted frequency offset approach zero.

[0022] As an explanation, the purpose is to use an updated ionization current value when processing the same type of ceramic workpiece again, so as to alleviate the immediate damage to the ceramic workpiece caused by electrostatic stress during the processing. This application first divides the machining process into multiple process categories based on the theoretical material removal rate of CNC machine tools. Then, during the material removal machining of ceramic workpieces on CNC machine tools, an ion current is applied between the tool and the ceramic workpiece, and corresponding ionization current values ​​and coverage patterns are assigned according to the process category. After machining, a piezoelectric actuator applies micro-amplitude sweep frequency mechanical excitation to the non-machining reference surface of the ceramic workpiece in a point-contact manner to generate a vibration response signal. Then, feature points are obtained according to the feature point selection rules of the ceramic workpiece. After measuring the vibration response signal at the feature point using a laser vibrometer, the modal parameters are identified using the frequency domain decomposition method. From the modal parameters sorted by natural frequency from smallest to largest, the target corresponding to the first non-zero multi-feature point displacement response amplitude is selected. The design employs a method that uses the natural frequency corresponding to the target order as the measured value of the first-order bending natural frequency and the absolute value of the difference between the standard values ​​of the first-order bending natural frequencies as the frequency offset. Finally, it associates the frequency offset of each ceramic workpiece with the ionization current value used in the corresponding process category to form a historical process record set. The design uses a recursive least squares method to update the ionization current value corresponding to each process category so that the predicted frequency offset approaches zero. This design achieves the suppression of the peak voltage on the surface of the ceramic workpiece generated by each process category, effectively alleviates the immediate damage to the ceramic workpiece caused by electrostatic stress during processing, suppresses the potential performance degradation and delayed cracking of the ceramic workpiece caused by electrostatic accumulation during processing, and improves the stability and safety of the ceramic workpiece after it is generated.

[0023] like Figure 2 As shown, to verify the effectiveness of this method in improving the rate of delayed cracking of ceramic workpieces under roughing, semi-finishing, and finishing conditions, 300 alumina ceramic workpieces were selected. All 300 alumina ceramic workpieces were high-insulation alumina ceramic workpieces with ultra-thin walls and micro-acute angles. Ultra-thin walls refer to walls less than 1 mm thick, and micro-acute angles refer to acute angles with a radius of curvature less than 0.5 mm on the alumina ceramic workpiece. Because these alumina ceramic workpieces have a weak structure and are prone to static electricity accumulation on their surface, static stress during traditional processing can easily exacerbate the propagation of subsurface microcracks, resulting in a significantly higher risk of delayed cracking compared to ordinary ceramic workpieces.

[0024] The alumina ceramic workpieces were divided into three groups: roughing, semi-finishing, and finishing, with 100 pieces in each group. In each group, 50 pieces were processed using the method of this application, and the other 50 pieces were processed using the existing method of conventional ion-free flow processing. After processing, the alumina ceramic workpieces were stored in a constant temperature and humidity environment for 30 days, and the occurrence of delayed cracking was statistically analyzed. The constant temperature environment was 25℃±2℃, and the constant humidity environment was 50%±5%. In the figure, the non-delayed cracking rate under the method of this application is 96% under roughing, 98% under semi-finishing, and 100% under finishing, all of which are greater than the non-delayed cracking rate under traditional ion-free flow processing.

[0025] For clarification, "acquisition" in this application refers to obtaining the required content or data using existing technical means.

[0026] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0027] In the embodiments provided by this invention, it should be understood that the disclosed system or method can be implemented in other ways. For example, the embodiments of the invention described above are merely illustrative; for instance, the division of modules is only a logical functional division, and there may be other division methods in actual implementation.

[0028] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0029] Furthermore, the functional modules in the various embodiments of this invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module. The integrated module can be implemented in hardware or in a combination of hardware and software functional modules.

[0030] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the basic characteristics of the present invention.

[0031] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for machining a ceramic material on a machining center numerical control machine tool, characterized in that, The method comprises the following steps: S1, obtaining a theoretical material removal rate of the numerical control machine tool; and dividing the machining process of the numerical control machine tool into multiple process categories according to the theoretical material removal rate; S2, applying an ion flow between the tool and the ceramic workpiece when the numerical control machine tool removes material from the ceramic workpiece; According to the process category, the ion flow is assigned an ionization current value and a coverage form; the ionization current value includes a first ionization current value, a second ionization current value, and a third ionization current value; the coverage form includes a first coverage form, a second coverage form, and a third coverage form; S3, after the numerical control machine tool completes the entire machining of the ceramic workpiece, applying a micro-sweep frequency mechanical excitation to the ceramic workpiece, which is used to generate a vibration response signal of the ceramic workpiece; S4, obtaining a plurality of characteristic points on the ceramic workpiece according to a characteristic point selection rule; measuring the vibration response signal at the characteristic points by a laser vibration meter, and generating a first-order bending natural frequency measured value according to the vibration response signal; obtaining a first-order bending natural frequency standard value; and taking the absolute value of the difference between the first-order bending natural frequency measured value and the first-order bending natural frequency standard value as a frequency offset; S5, obtaining the frequency offset obtained after machining each ceramic workpiece, the ionization current value used by the corresponding process category during machining of each ceramic workpiece, and updating the ionization current value corresponding to each process category.

2. The method of machining ceramic material according to claim 1, characterized in that, In S1, the machining process of the numerical control machine tool is divided into multiple process categories according to the theoretical material removal rate, as follows: If the theoretical material removal rate is greater than 50 mm³ / s, the process category is rough machining; If the theoretical material removal rate is greater than or equal to 5 mm³ / s and less than or equal to 50 mm³ / s, the process category is semi-finishing; If the theoretical material removal rate is less than 5 mm³ / s, the process category is finishing.

3. The method of machining ceramic material according to claim 1, characterized in that, In S2, the ion flow is pulsed direct current ionization.

4. The method of machining ceramic material according to claim 3, characterized in that, In S2, according to the process category, the ion flow is assigned an ionization current value and a coverage form, as follows: Obtain the cutting width of the numerical control machine tool; Take the contact band formed by the contact between the tool edge and the surface of the ceramic workpiece as a linear contact band; expand 0.1 mm to 0.5 mm to both sides of the linear contact band to form a strip-shaped area as a contact line area; When the process category is rough machining, the first ionization current value is used, the value of the first ionization current value is 1.8 mA to 2.2 mA, and the first coverage form is used; the first coverage form is to make the ion flow cover a fan-shaped area on the ceramic workpiece with the tool endpoint as the vertex and the opening angle not less than 90 degrees; When the process category is semi-finishing, the second ionization current value is used, the value of the second ionization current value is 0.9 mA to 1.1 mA, and the second coverage form is used; the second coverage form is to make the ion flow cover a strip-shaped area on the ceramic workpiece with the tool cutting edge as the axis, and the width of the strip-shaped area is 1.5 to 2.5 times the cutting width; When the process category is finishing, the third ionization current value is used, the value of the third ionization current value is 0.45 mA to 0.55 mA, and the third coverage form is used; the third coverage form is to make the ion flow cover a contact line area on the ceramic workpiece.

5. The method of machining ceramic material according to claim 4, characterized in that, In S3, a micro-sweep mechanical excitation is applied to the ceramic workpiece, as follows: The surface of the ceramic workpiece used for positioning and clamping on the numerical control machine tool is taken as the machining reference surface; all surfaces of the ceramic workpiece except the machining reference surface are taken as non-machining reference surfaces; A mechanical force is applied to the ceramic workpiece by a piezoelectric driver acting on the non-machining reference surface of the ceramic workpiece in a point contact manner; the frequency range of the piezoelectric driver is 1 kHz to 50 kHz; the sweep frequency of the piezoelectric driver is: within the frequency range of 1 kHz to 50 kHz, the frequency uniformly increases or uniformly decreases with a constant frequency change rate over time; the output displacement amplitude of the piezoelectric driver is not greater than 5 μm, and the amplitude of the mechanical force applied to the ceramic workpiece by the piezoelectric driver is not greater than 10 mN.

6. The method of machining ceramic material according to claim 5, characterized in that, In S4, the feature point selection rules of the ceramic workpiece are as follows: On the ceramic workpiece, a thin wall with a thickness less than 1 mm is taken as a sensitive area; The geometric center of the sensitive area is taken as a feature point; If there is no sensitive area on the ceramic workpiece, an acute angle with a curvature radius less than 0.5 mm is taken on the ceramic workpiece, and the vertex of the acute angle is taken as a feature point.

7. The method of machining ceramic material according to claim 6, characterized in that, In S4, the first-order bending natural frequency measured value is generated according to the vibration response signal, as follows: All vibration response signals are obtained to form a vibration response signal set; According to the vibration response signal set, modal parameter identification is performed by using a frequency domain decomposition method to obtain modal parameters of the ceramic workpiece; The modal parameters are an order set sorted in ascending order of natural frequency, and each order includes a natural frequency, a damping ratio, and a multi-feature point displacement response amplitude; From the modal parameters, the multi-feature point displacement response amplitudes corresponding to each order are sequentially extracted to form a multi-feature point displacement response amplitude sequence; In the multi-feature point displacement response amplitude sequence, the first multi-feature point displacement response amplitude not equal to 0 is selected as a target multi-feature point displacement response amplitude; The order corresponding to the target multi-feature point displacement response amplitude is taken as a target order; The natural frequency corresponding to the target order is taken as the first-order bending natural frequency measured value of the ceramic workpiece after machining.

8. Method for machining ceramic materials with a machining center numerical control machine tool according to claim 7, characterized in that, In S5, the ionization current value corresponding to each process category is updated, as follows: The frequency offset corresponding to the same ceramic workpiece is associated with the ionization current value used for the corresponding process category during machining to form a historical process record; A plurality of historical process records form a historical process record set; According to the historical process record set, the ionization current value corresponding to each process category is updated by using a recursive least squares method to make the predicted frequency offset tend to zero.

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