Electrochemical discharge machining surface pre-contact detection method and system

Abstract

The invention belongs to the field of non-traditional machining, and particularly provides an electrochemical discharge machining surface pre-contact detection method and system. According to the method, vibration signals are collected through an acceleration sensor installed on a motor main shaft, filtered and then input into a trained mathematical model, and whether the bottom of a tool electrode makes pre-contact with the to-be-machined surface of a workpiece or not is judged. The system comprises an execution system and a detection control system, vibration signals and machining parameters are fused through a neural network model, and interelectrode gap changes are monitored in real time. And when it is detected that the bottom of the tool electrode makes pre-contact with the to-be-machined surface of the workpiece, the feeding rate of the tool electrode is adjusted through a machine tool controller so as to maintain the constant interelectrode gap, bending or breakage of the tool electrode is avoided, and the machining stability and the material removal rate are improved.

Description

Technical Field

[0001] This invention belongs to the field of special processing technology, specifically relating to a method and system for pre-contact detection of electrochemical discharge machining surfaces. Background Technology

[0002] Electrochemical electrical discharge machining (ECDM) is a specialized machining technique used for precision machining of hard, brittle, and non-conductive materials such as glass and ceramics. Its process relies on maintaining a small and stable gap between the tool electrode and the workpiece; the gas film formed within this gap is crucial for initiating discharge and achieving material removal. However, in actual machining, especially during initial tool setting and the machining process, the tool electrode is prone to excessive contact with the workpiece surface, leading to electrode bending and breakage, thus reducing machining quality and efficiency.

[0003] Traditional contact detection methods (such as those based on current or voltage changes) lack sufficient sensitivity and reliability in the complex and variable machining environment of ECDM, making it difficult to accurately identify the pre-contact state between the bottom of the tool electrode and the workpiece surface to be machined. This limits machining efficiency, surface quality, and process stability, becoming a key bottleneck restricting the high-precision and automated application of ECDM technology. Therefore, developing a method and system capable of real-time and accurate detection of the inter-electrode state and maintaining a constant inter-electrode gap after pre-contact occurs is crucial for improving the machining performance, reliability, and automation level of ECDM. Summary of the Invention

[0004] To achieve the above objectives, this invention provides a method and system for detecting pre-contact on the surface of electrochemical discharge machining. Vibration signals are collected by an accelerometer mounted on the motor spindle, filtered, and then input into a trained mathematical model to determine whether pre-contact has occurred between the bottom of the tool electrode and the workpiece surface to be machined. When pre-contact occurs, the machine tool controller adjusts the tool electrode feed rate to maintain a constant inter-electrode gap, preventing the tool electrode from bending or breaking, and improving machining stability and material removal rate.

[0005] A method for pre-contact detection of electrochemical discharge machining surfaces includes the following steps:

[0006] S1. Fix the workpiece in the solution tank and pour in the prepared electrolyte solution until the workpiece is completely submerged;

[0007] S2. Install the accelerometer on the motor spindle, and connect the positive and negative terminals of the DC pulse power supply to the auxiliary electrode and the tool electrode, respectively.

[0008] S3. Turn on the pulsed DC power supply, start the machine tool feed program, and open the acceleration signal acquisition software in the computer to start acquiring the vibration signal of the motor spindle;

[0009] S4, the collected vibration signal is input into the trained mathematical model after filtering processing, the contact state between the tool electrode bottom and the workpiece is judged, when the two occur pre-contact, the feed rate of the tool electrode is adjusted by the machine tool controller to maintain the constant inter-electrode gap.

[0010] Further, in S3, as the tool electrode gradually approaches the workpiece surface to be processed by feeding downward, when the inter-electrode gap is reduced to 10 μm, the gas film at the bottom of the tool electrode will adhere to the surface to be processed of the workpiece, and the working medium between the electrodes changes from gas-liquid-solid phase to gas-solid phase, at this time, the two produce pre-contact.

[0011] Further, the vibration signal collected by the acceleration sensor is composed of two parts, which are the vibration signal generated by the mechanical movement of the motor spindle and the vibration signal generated by the electrochemical discharge around the solution in which the tool electrode is located.

[0012] Further, when the tool electrode bottom and the workpiece surface to be processed occur pre-contact, the vibration signal generated by the mechanical movement of the motor spindle has no obvious change, and the vibration signal generated by the electrochemical discharge is significantly weakened due to insufficient electrolyte supply at the bottom of the tool electrode, so the collected vibration signal will be attenuated to a certain extent.

[0013] Further, the vibration signal generated by the electrochemical discharge has the same frequency as the discharge pulse frequency of the pulse direct current power supply, so the signal can be filtered by a filter to obtain the vibration signal component generated by the electrochemical discharge, which is used to judge the occurrence of pre-contact.

[0014] An electrochemical discharge machining surface pre-contact detection system for realizing the method of claim 1, characterized by comprising an execution system and a detection control system.

[0015] The execution system comprises a solution tank, a glass pad, an electrolyte solution, a workpiece, a fixing device, a tool electrode, a conductive transition device, an electrode spindle, a motor spindle support plate, an auxiliary electrode, and a pulse direct current power supply. The workpiece and the fixing device are immersed in the electrolyte solution, the positive electrode of the pulse direct current power supply is connected to the auxiliary electrode, and the negative electrode is connected to the tool electrode.

[0016] The detection control system comprises a sensor, a data acquisition card, a computer, and a machine tool controller. The computer is connected to the data acquisition card and the machine tool controller, respectively, and controls the feed movement of the tool electrode according to the judgment result of the mathematical model.

[0017] Further, the mathematical model is a double-channel TCN neural network model, one end of the model inputs filtered data, and the other end inputs processing parameters.

[0018] Further, the collected vibration signal is filtered to obtain the vibration signal component generated by the electrochemical discharge, which can reflect the change of the interelectrode gap, thereby accurately locating the position of the workpiece surface to be machined.

[0019] Further, when the tool electrode bottom is detected to be in pre-contact with the workpiece surface to be machined, the machine tool controller adjusts the feed rate of the tool electrode to maintain the interelectrode gap (8-10 μm), which can make the electrochemical discharge better act on the workpiece surface to be machined, thereby improving the material removal rate.

[0020] Further, by maintaining the interelectrode gap, constant gap machining can be achieved, and the tool electrode bending or breaking caused by excessive contact force between the tool electrode bottom and the workpiece surface to be machined can be avoided.

[0021] The present application has the following advantages:

[0022] The present application collects the spindle vibration signal in real time through the acceleration sensor, and uses the trained mathematical model to monitor the interelectrode pre-contact state in real time, thereby realizing online and accurate monitoring of the state of the invisible machining area. When the tool electrode bottom is in pre-contact with the workpiece surface to be machined, the control system adjusts the feed rate to maintain the interelectrode gap constant, thereby fundamentally avoiding the tool electrode bending or breaking caused by excessive contact force, and improving the machining quality and material removal rate. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Fig. 1 is a structure diagram of the pre-contact detection system in the embodiment of the present application;

[0024] Figure 2 Fig. 2 is a diagram of the interelectrode working medium before pre-contact in the embodiment of the present application;

[0025] Figure 3 Fig. 3 is a diagram of the interelectrode working medium after pre-contact in the embodiment of the present application;

[0026] Figure 4 Fig. 4 (a) is the original vibration signal collected in the embodiment of the present application;

[0027] Figure 4 Fig. 4 (b) is the vibration signal after filtering in the embodiment of the present application;

[0028] Fig. 1 is a structure diagram of the pre-contact detection system in the embodiment of the present application; DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of the present application.

[0030] An electrochemical discharge machining surface pre-contact detection method, comprising the following steps:

[0031] S1, fixing a workpiece 4 in a solution tank 1 through a fixing device 5, the workpiece 4 being a zirconia ceramic sheet; adding an electrolyte solution 3 to a liquid level higher than the upper surface of the workpiece by 0.5-2 mm, the electrolyte solution 3 being a NaOH solution with a solubility of 6 mol / L;

[0032] S2, installing an acceleration sensor 8 on a motor main shaft 9, connecting a positive electrode of a direct current pulse power supply 15 with an auxiliary electrode 14, and connecting a negative electrode with a tool electrode 6 through a conductive transition device 7; the auxiliary electrode 14 being a graphite sheet, and the tool electrode 6 being a spiral tool electrode with a diameter of 0.25 mm;

[0033] S3, turning on the pulse direct current power supply 15, setting a discharge pulse frequency to be 760 Hz and a voltage to be 50 V; starting a machine tool feeding program, setting a motor main shaft 9 rotating speed to be 2000 r / min, setting an initial feeding speed of the tool electrode 6 to be 1 μm / s on a machine tool controller 13; opening an acceleration signal acquisition software in a computer 12, setting a sampling rate to be 10000 Hz, and starting to collect vibration signals of the motor main shaft 9;

[0034] S4, designing a passband of a filter in the computer 12 to be 680 Hz-840 Hz, inputting the collected vibration signals after filter processing into a trained mathematical model, and judging a contact state between the bottom of the tool electrode 6 and the workpiece 4; when pre-contact occurs between the two, adjusting a feeding rate of the tool electrode 6 according to a material removal rate, so as to realize constant gap machining.

[0035] In the embodiment, the mathematical model adopts a double-channel TCN neural network model, one end of the model inputs filtered data, and the other end inputs machining parameters.

[0036] Referring to Figure 1 The embodiment of the present application provides an electrochemical discharge machining surface pre-contact detection system for realizing the above method, the detection system comprising an execution system and a detection control system.

[0037] The execution system comprises a solution tank 1, a glass pad 2, an electrolyte solution 3, a workpiece 4, a fixing device 5, a tool electrode 6, a conductive transition device 7, an electrode spindle 9, a motor spindle support plate 10, an auxiliary electrode 14, and a pulse direct current power supply 15, wherein the workpiece 4 and the fixing device 5 are immersed in the electrolyte solution 3, the positive electrode of the pulse direct current power supply 15 is connected to the auxiliary electrode 14, and the negative electrode is connected to the tool electrode 6.

[0038] The detection control system comprises a sensor 8, a data acquisition card 11, a computer 12, and a machine tool controller 13, wherein the computer 12 is connected to the data acquisition card 11 and the machine tool controller 13, respectively, and controls the feeding movement of the tool electrode 6 according to the judgment result of the mathematical model.

[0039] Referring to Figure 2 , the tool electrode 6 is gradually approached to the surface to be machined of the workpiece 4 by downward feeding, and before the inter-electrode gap is reduced to 10 μm, the working medium between the electrodes is composed of gas-liquid-solid three phases, and the electrochemical discharge has not yet acted on the surface to be machined of the workpiece 4; referring to Figure 3 , as the tool electrode 6 continues to feed until the inter-electrode gap is reduced to 10 μm, the gas film at the bottom of the tool electrode 6 will adhere to the surface to be machined of the workpiece 4, and the working medium between the electrodes changes from gas-liquid-solid phase to gas-solid phase, at which time the two reach the pre-contact state.

[0040] In this embodiment, when the bottom of the tool electrode 6 and the surface to be machined of the workpiece 4 are in pre-contact, the vibration signal generated by the mechanical movement of the motor spindle 9 in the collected vibration signal has no obvious change, and the vibration signal generated by the electrochemical discharge is obviously weakened due to insufficient electrolyte supply at the bottom of the tool electrode, and the original signal (referring to Figure 4 (a) shown) is subjected to band-pass filtering processing, and the vibration signal component (referring to Figure 4 (b) shown) generated by the electrochemical discharge is retained, which significantly enhances the distinguishing features of the vibration signals before and after the pre-contact occurs, thereby improving the recognition accuracy and efficiency of the network model.

[0041] In this embodiment, through the inter-electrode gap value (8-10 μm) when the bottom of the tool electrode 6 and the surface to be machined of the workpiece 4 are in pre-contact, the relative positions of the two can be accurately located, and the feeding rate of the tool electrode 6 is adjusted to maintain the inter-electrode gap, so that the electrochemical discharge can better act on the surface to be machined of the workpiece 4, the machining quality and material removal rate can be improved, the bending or breaking of the tool electrode 6 caused by excessive contact force between the bottom of the tool electrode 6 and the surface to be machined of the workpiece 4 can be avoided, and the efficiency and stability of the machining can be ensured.

[0042] The above merely describes the preferred embodiments of the present application, and it should be pointed out that those skilled in the art can make several improvements without departing from the principles of the present application, and these improvements should also be considered as the protection scope of the present application.

Claims

1. A method for pre-contact detection of electrochemical discharge machining surfaces, comprising the following steps: S1. Fix the workpiece (4) in the solution tank (1) and pour in the prepared electrolyte solution (3) until the workpiece (4) is completely submerged. S2. Install the accelerometer (8) on the motor spindle (9), and connect the positive and negative terminals of the DC pulse power supply (15) to the auxiliary electrode (14) and the tool electrode (6) respectively. S3. Connect the pulse DC power supply (15), start the machine tool feed program, and open the acceleration signal acquisition software in the computer (12) to start acquiring the vibration signal of the motor spindle (9); S4. The collected vibration signal is filtered and then input into the trained mathematical model to determine the contact state between the bottom of the tool electrode (6) and the workpiece (4). When the two make pre-contact, the feed rate of the tool electrode (6) is adjusted by the machine tool controller (13) to maintain a constant inter-electrode gap.

2. The method for pre-contact detection of electrochemical discharge machining surfaces according to claim 1, characterized in that: In S3, as the tool electrode (6) feeds downward and gradually approaches the surface to be processed of the workpiece (4), when the gap between the electrodes decreases to 10 μm, the gas film at the bottom of the tool electrode (6) will adhere to the surface to be processed of the workpiece (4). At this time, the working medium between the electrodes changes from gas-liquid-solid phase to gas-solid phase, that is, the two are in pre-contact.

3. The method for pre-contact detection of electrochemical discharge machining surfaces according to claim 1, characterized in that: The vibration signal collected by the accelerometer (8) consists of two parts: the vibration signal generated by the mechanical movement of the motor spindle (9) and the vibration signal generated by the electrochemical discharge around the solution where the tool electrode (6) is located.

4. The method for pre-contact detection of electrochemical discharge machining surfaces according to claim 3, characterized in that: When the bottom of the tool electrode (6) makes pre-contact with the surface to be processed of the workpiece (4), the vibration signal generated by the mechanical movement of the motor spindle (9) does not change significantly. The vibration signal generated by the electrochemical discharge is significantly weakened due to insufficient electrolyte supply at the bottom of the tool electrode (6). Therefore, the collected vibration signal will be attenuated to a certain extent.

5. The method for pre-contact detection of electrochemical discharge machining surfaces according to claim 4, characterized in that: The vibration signal frequency generated by the electrochemical discharge is the same as the discharge pulse frequency of the pulsed DC power supply (15). The vibration signal components generated by the electrochemical discharge can be obtained by designing a filter, and then used to determine the pre-contact between the bottom of the tool electrode (6) and the surface to be processed of the workpiece (4).

6. A pre-contact detection system for electrochemical discharge machining surfaces, used to implement the method of claim 1, characterized in that: Including execution systems and detection and control systems; The execution system includes a solution tank (1), a glass pad (2), an electrolyte solution (3), a workpiece (4), a fixing device (5), a tool electrode (6), a conductive transition device (7), an electrode spindle (9), a motor spindle support plate (10), an auxiliary electrode (14), and a pulsed DC power supply (15). The workpiece (4) and the fixing device (5) are placed in the electrolyte solution (3). The positive terminal of the pulsed DC power supply (15) is connected to the auxiliary electrode (14), and the negative terminal is connected to the tool electrode (6). The detection and control system includes a sensor (8), a data acquisition card (11), a computer (12), and a machine tool controller (13). The computer (12) is connected to the data acquisition card (11) and the machine tool controller (13) respectively, and controls the feed motion of the tool electrode (6) according to the judgment result of the mathematical model.

7. The electrochemical discharge machining surface pre-contact detection system according to claim 6, characterized in that: The mathematical model is a dual-channel TCN neural network model, with one channel receiving filtered data and the other channel receiving processing parameters.

8. The electrochemical discharge machining surface pre-contact detection system according to claim 6, characterized in that: The vibration signal collected by the acceleration sensor (8) is filtered to obtain the vibration signal component generated by electrochemical discharge, which can reflect the change in the inter-electrode gap, thereby accurately locating the position of the workpiece (4) to be processed surface.

9. The electrochemical discharge machining surface pre-contact detection system according to claim 6, characterized in that: When the bottom of the tool electrode (6) is detected to be in pre-contact with the surface to be processed of the workpiece (4), the feed rate of the tool electrode (6) is adjusted by the machine tool controller (13) to maintain the inter-electrode gap (8-10μm), so that the electrochemical discharge can better act on the surface to be processed of the workpiece (4), thereby improving the material removal rate.

10. The electrochemical discharge machining surface pre-contact detection system according to claim 9, characterized in that: By maintaining the inter-electrode gap, constant gap machining can be achieved, avoiding bending or breakage of the tool electrode due to excessive contact force between the bottom of the tool electrode (6) and the workpiece (4) surface to be machined.

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