CN111390306A - Electric spark machining state detection method based on acoustic emission technology - Google Patents
Electric spark machining state detection method based on acoustic emission technology Download PDFInfo
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- CN111390306A CN111390306A CN202010324320.8A CN202010324320A CN111390306A CN 111390306 A CN111390306 A CN 111390306A CN 202010324320 A CN202010324320 A CN 202010324320A CN 111390306 A CN111390306 A CN 111390306A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H1/00—Electrical discharge machining, i.e. removing metal with a series of rapidly recurring electrical discharges between an electrode and a workpiece in the presence of a fluid dielectric
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
- B23H11/00—Auxiliary apparatus or details, not otherwise provided for
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
Abstract
The invention discloses an electric spark machining state detection method based on an acoustic emission technology, belongs to the technical field of electric spark machining, and aims to solve the problem that the electric spark machining state cannot be effectively judged in the prior art. The detection method comprises the following steps: an acoustic emission sensor is placed in the working liquid, and acoustic emission wave signals between electrodes are collected in real time; acquiring the intensity of a sound wave signal and the duration of the sound wave; judging the processing state according to the intensity of the sound wave signal and the duration of the sound wave: when the intensity of the sound wave signal and the duration time of the sound wave are both zero, the machining state is invalid; when the intensity of the sound wave signal is greater than or equal to the intensity threshold value of the sound wave signal and the duration time of the sound wave is greater than or equal to the duration time threshold value of the sound wave, the machining state is an effective machining state; and when the intensity of the sound wave signal is smaller than the intensity threshold value of the sound wave signal, or the duration of the sound wave is smaller than the duration threshold value of the sound wave, the dangerous processing state is established. The invention is used for electric spark machining.
Description
Technical Field
The invention relates to a method for detecting an electric spark machining state, and belongs to the technical field of electric spark machining.
Background
A large amount of high-strength difficult-to-machine materials exist in the fields of aerospace and die machining, and the materials are machined by adopting a traditional cutting means, so that the problems of low machining efficiency and high cutter cost exist. The electric spark processing is to utilize the energy generated by the discharge between the positive electrode and the negative electrode to melt the surface material of the workpiece, so as to achieve the purpose of material processing. Compared with the traditional cutting machining method, the machining cost can be obviously reduced by adopting electric spark machining. The control of the discharge state in the electric discharge machining process directly determines the quality of the surface quality of the machined part, so that the discharge state is reliably controlled according to the requirement on the quality of the machined surface in the electric discharge machining process.
The discharge state of the electric discharge machining is mainly divided into five states of open circuit, spark discharge, unstable arc discharge, stable arc discharge and short circuit. The two states of spark discharge and unstable arc discharge can realize effective material erosion, and the discharge is maintained in the two discharge states in the machining process; the stable arc discharge and the short circuit state easily ablate the workpiece, so that the product is scrapped and is avoided in processing. Therefore, in the electric discharge machining process, reliable control of the machining state is a key to achieving stable machining.
At present, the control of the machining state is mainly realized based on the monitoring of the discharge voltage between electrodes, and when the average discharge voltage between electrodes is higher, the discharge between electrodes is insufficient, and the electrode feeding speed needs to be improved; when the average discharge voltage between electrodes is too low, the discharge between electrodes is unstable, and the feeding needs to be reduced; when the average discharge voltage between the electrodes is lower than a set threshold value, the short circuit between the electrodes is indicated, and the short circuit needs to be stopped through the cutter lifting action. The main problem of this machining state control method is that the difference between the discharge voltage between the unstable arc discharge and the stable arc discharge is small, and therefore it is difficult to distinguish the discharge voltage from the voltage detection result, and erroneous judgment of the machining state is likely to occur, resulting in low machining efficiency or burning of the workpiece.
Therefore, it is necessary to develop a detection method capable of reliably distinguishing different processing states, so as to provide a more reliable basis for controlling the processing states and effectively improve the processing stability.
Disclosure of Invention
The invention aims to solve the problem that the prior art cannot effectively judge the electric spark machining state, and provides an electric spark machining state detection method based on an acoustic emission technology.
The invention relates to an electric spark machining state detection method based on an acoustic emission technology, which comprises the following specific processes:
s1, placing an acoustic emission sensor in the working solution, and collecting an acoustic emission wave signal between electrodes in real time by adopting the acoustic emission sensor;
s2, acquiring the intensity and the duration of the sound wave according to the sound emission wave signal acquired in the S1;
s3, judging the processing state according to the intensity and the duration of the sound wave signal acquired in the S2:
when the intensity of the sound wave signal and the duration time of the sound wave are both zero, the machining state is invalid;
when the intensity of the sound wave signal is greater than or equal to the intensity threshold value of the sound wave signal and the duration time of the sound wave is greater than or equal to the duration time threshold value of the sound wave, the machining state is an effective machining state;
and when the intensity of the sound wave signal is smaller than the intensity threshold value of the sound wave signal, or the duration of the sound wave is smaller than the duration threshold value of the sound wave, the dangerous processing state is established.
Preferably, the method for acquiring the intensity of the sound wave signal in S2 includes:
and fitting a waveform chart of the acoustic emission wave signal according to the acoustic emission wave signal, wherein the amplitude of the waveform chart is the intensity of the acoustic wave signal and the unit is V.
Preferably, the method for acquiring the duration of the sound wave in S2 includes:
firstly, acquiring a threshold voltage: 1% of the maximum amplitude of the waveform diagram is the threshold voltage;
then, obtaining the duration of the sound wave according to the threshold voltage: the time interval during which the acoustic emission wave signal crosses the threshold voltage for the first time until it decreases to the threshold voltage is the acoustic duration in mus.
Preferably, the method for selecting the acoustic wave signal intensity threshold and the acoustic wave duration threshold comprises the following steps:
before the machining state is detected, a machining state detection test is firstly carried out, the threshold voltage obtained in the test process is used as an acoustic wave signal intensity threshold value, and the acoustic wave duration time obtained in the test process is used as an acoustic wave duration time threshold value.
The invention has the advantages that: the electric spark machining state detection method based on the acoustic emission technology provided by the invention realizes the distinguishing of the invalid machining state, the effective machining state and the dangerous machining state by utilizing the acoustic emission wave signal generated in the discharge process, and is beneficial to improving the stability of electric discharge machining.
Drawings
FIG. 1 is a schematic illustration of acoustic emission wave signals collected during an electrical discharge machining process in accordance with the present invention;
FIG. 2 is a schematic diagram of acoustic emission wave signals corresponding to different discharge states;
fig. 3 is a schematic diagram of acoustic signal intensity thresholds for distinguishing machining states under different current conditions, wherein the abscissa represents machining current and the ordinate represents acoustic signal intensity thresholds corresponding to effective machining states;
fig. 4 is a schematic diagram of acoustic signal intensity thresholds for distinguishing machining states under different current conditions, wherein the abscissa represents machining current and the ordinate represents acoustic signal intensity thresholds corresponding to effective machining states.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The first embodiment is as follows: the following describes the present embodiment with reference to fig. 1 and fig. 2, and the method for detecting the state of electric discharge machining based on the acoustic emission technology in the present embodiment includes the following specific steps:
s1, placing an acoustic emission sensor in the working solution, and collecting an acoustic emission wave signal between electrodes in real time by adopting the acoustic emission sensor;
s2, acquiring the intensity and the duration of the sound wave according to the sound emission wave signal acquired in the S1;
s3, judging the processing state according to the intensity and the duration of the sound wave signal acquired in the S2:
when the intensity of the sound wave signal and the duration time of the sound wave are both zero, the machining state is invalid;
when the intensity of the sound wave signal is greater than or equal to the intensity threshold value of the sound wave signal and the duration time of the sound wave is greater than or equal to the duration time threshold value of the sound wave, the machining state is an effective machining state;
and when the intensity of the sound wave signal is smaller than the intensity threshold value of the sound wave signal, or the duration of the sound wave is smaller than the duration threshold value of the sound wave, the dangerous processing state is established.
Further, the method for acquiring the intensity of the acoustic wave signal in S2 includes:
and fitting a waveform chart of the acoustic emission wave signal according to the acoustic emission wave signal, wherein the amplitude of the waveform chart is the intensity of the acoustic wave signal and the unit is V.
Still further, the method for acquiring the duration of the sound wave in S2 includes:
firstly, acquiring a threshold voltage: 1% of the maximum amplitude of the waveform diagram is the threshold voltage;
then, obtaining the duration of the sound wave according to the threshold voltage: the time interval during which the acoustic emission wave signal crosses the threshold voltage for the first time until it decreases to the threshold voltage is the acoustic duration in mus.
Still further, the method for selecting the acoustic wave signal intensity threshold and the acoustic wave duration threshold comprises the following steps:
before the machining state is detected, a machining state detection test is firstly carried out, the threshold voltage obtained in the test process is used as an acoustic wave signal intensity threshold value, and the acoustic wave duration time obtained in the test process is used as an acoustic wave duration time threshold value.
In the present embodiment, before the actual machining state is detected, a test for detecting the machining state is first performed, a threshold voltage (1% of the maximum amplitude of the waveform diagram) is selected as an acoustic wave signal intensity threshold value for the actual machining state in the test, and an acoustic wave duration (a time interval during which an acoustic emission wave signal first crosses the threshold voltage and decreases to the threshold voltage) acquired in the test is used as an acoustic wave duration threshold value for the actual machining state detection.
In the present embodiment, the acoustic duration threshold is generally 0.1s to 0.2 s.
The working principle of the invention is as follows: in the process of forming an electric spark machining discharge breakdown plasma channel, the interelectrode can gasify the working solution around the discharge channel due to the instantaneous high temperature effect to form bubbles surrounding the plasma channel, and due to the continuous supply of the viscosity of the working solution and the energy in the discharge process, the volume and the pressure of the bubbles can fluctuate within a certain range, so that an acoustic emission wave is generated.
In different discharge states (spark discharge, unstable arc discharge, stable arc discharge and short-circuit state), the acoustic emission waves generated in the discharge process are obviously different, so that the machining state can be judged according to the difference of the collected acoustic emission wave signals.
In the electric spark machining process, the acoustic emission sensor is arranged in the working fluid, and acoustic emission wave signals released by the discharge channel in the discharging process are collected in real time.
And judging whether the machining state needs to be adjusted or not according to the difference of the intensity and the duration time of the detected acoustic emission wave signals.
The open discharge state is classified as an ineffective machining state in which no discharge occurs and no acoustic emission wave is generated between the electrodes.
The stable arc discharge and short circuit states are classified as dangerous machining states, and the collected acoustic emission wave signals are very weak.
The spark discharge and unstable arc discharge states are classified as effective machining states, in which the intensity of the generated acoustic emission wave signal is high and the duration is long.
In the electric spark machining process, the acoustic emission sensor is fixed in the working solution or on a working table, acoustic emission wave signals generated in the discharging process are collected in real time, the intensity and duration of the collected acoustic emission wave signals are calculated, and the intensity and duration of the acoustic emission wave signals are shown in fig. 1. There are significant differences in the intensity and duration of the acoustic emission wave signals generated by the different discharge states, as shown in fig. 2. When the intensity and the duration time of the detected acoustic emission wave signal are both 0, the fact that the distance between the electrode and the workpiece is large and no discharge occurs indicates that the machining state is invalid. When the detected acoustic emission wave signal intensity and duration are both greater than or equal to the threshold values as shown in fig. 3 and 4, it is indicated that electric discharge machining is in progress, which is an effective machining state. When the intensity and duration of the detected acoustic emission wave signal are greater than 0 and less than the threshold values as shown in fig. 3 and 4, it is indicated that the electric discharge machining is in a stable arc discharge or short circuit state, which is a dangerous machining state.
Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that features described in different dependent claims and herein may be combined in ways different from those described in the original claims. It is also to be understood that features described in connection with individual embodiments may be used in other described embodiments.
Claims (4)
1. An electric spark machining state detection method based on an acoustic emission technology is characterized by comprising the following specific processes:
s1, placing an acoustic emission sensor in the working solution, and collecting an acoustic emission wave signal between electrodes in real time by adopting the acoustic emission sensor;
s2, acquiring the intensity and the duration of the sound wave according to the sound emission wave signal acquired in the S1;
s3, judging the processing state according to the intensity and the duration of the sound wave signal acquired in the S2:
when the intensity of the sound wave signal and the duration time of the sound wave are both zero, the machining state is invalid;
when the intensity of the sound wave signal is greater than or equal to the intensity threshold value of the sound wave signal and the duration time of the sound wave is greater than or equal to the duration time threshold value of the sound wave, the machining state is an effective machining state;
and when the intensity of the sound wave signal is smaller than the intensity threshold value of the sound wave signal, or the duration of the sound wave is smaller than the duration threshold value of the sound wave, the dangerous processing state is established.
2. The method for detecting the electric discharge machining state based on the acoustic emission technology as claimed in claim 1, wherein the method for acquiring the acoustic wave signal intensity of S2 is as follows:
and fitting a waveform chart of the acoustic emission wave signal according to the acoustic emission wave signal, wherein the amplitude of the waveform chart is the intensity of the acoustic wave signal and the unit is V.
3. The method for detecting the electric discharge machining state based on the acoustic emission technology as claimed in claim 2, wherein the method for acquiring the acoustic wave duration in S2 is as follows:
firstly, acquiring a threshold voltage: 1% of the maximum amplitude of the waveform diagram is the threshold voltage;
then, obtaining the duration of the sound wave according to the threshold voltage: the time interval during which the acoustic emission wave signal crosses the threshold voltage for the first time until it decreases to the threshold voltage is the acoustic duration in mus.
4. An electric discharge machining state detection method based on an acoustic emission technology as claimed in claim 3, characterized in that the selection method of the acoustic signal intensity threshold and the acoustic duration threshold is as follows:
before the machining state is detected, a machining state detection test is firstly carried out, the threshold voltage obtained in the test process is used as an acoustic wave signal intensity threshold value, and the acoustic wave duration time obtained in the test process is used as an acoustic wave duration time threshold value.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112692388A (en) * | 2021-01-04 | 2021-04-23 | 张晓民 | Electric spark machining fixture for acoustic emission sensor |
| CN112809113A (en) * | 2021-01-04 | 2021-05-18 | 张晓民 | Mounting method of acoustic emission sensor |
| CN114192911A (en) * | 2021-12-03 | 2022-03-18 | 中国航发北京航空材料研究院 | Turbine blade electric spark drilling penetration detection method |
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Application publication date: 20200710 |