A method for detecting the health status of machine tool processing based on potential difference

Abstract

The present invention discloses a method for detecting the health status of a machine tool processing process based on electric potential difference. The present invention installs detectors 1 and 2 at the lower end of the machine tool spindle, detectors 3 and 4 in the middle, and detector 5 at the upper end. Detectors 6 and 7 are installed on the workpiece surface and the machine tool fixture. Detectors 8, 9, 10, and 11 are installed on the machine tool work table. Each detector converts a vibration signal into a voltage signal through a piezoelectric plate. The present invention calculates the potential difference between the output voltage signals of detectors 1 to 4 and detector 5 in real time through lead formula I, and calculates the potential difference between the output voltage signals of detectors 6 and 7 and detectors 8 to 11 in real time through lead formula II. Finally, the value calculated by the judgment formula is used to determine whether the machine tool processing process is in a healthy state. The present invention uses an analog electrocardiogram method to detect human health to achieve accurate and convenient detection of the health status of the machine tool processing process.

Description

Technical Field

[0001] The present invention belongs to the technical field of machine tool health detection, and in particular relates to a method for detecting the health status of a machine tool machining process based on potential difference. Background Art

[0002] CNC machine tools are widely used in the machining of parts. The health of the machining process plays a crucial role in determining the surface roughness and dimensional tolerances of the finished product. Unhealthy conditions during machining, caused by factors such as tool wear, tool breakage, feed rate variations, and back-cut variations, can directly impact the machine's machining efficiency and the yield rate of finished products. Early detection of unhealthy conditions during machining can extend the machine's service life, thereby improving the company's production efficiency and reducing production costs. Currently, widely used methods for detecting the health of machining processes rely on recording audio or directly collecting vibration signals during operation. However, audio recording suffers from high ambient noise levels that affect data accuracy, while directly collecting vibration signals suffers from large data volumes and cumbersome analysis. Existing methods for collecting vibration signals primarily use accelerometers. The machine tool spindle vibrates in four directions: x, y, -x, and -y. The vibration signal waveforms collected by accelerometers fluctuate in both positive and negative directions, resulting in large amplitude fluctuations and difficulty in observation. Therefore, a method is needed to accurately detect and facilitate observation of the health of the machine tool's machining process. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the existing technology and propose a method for detecting the health status of a machine tool processing process based on potential difference.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for detecting the health status of a machine tool during machining based on potential difference, which is specifically as follows:

[0006] Step 1. Before machine tool processing, install detector 1 and detector 2 at the lowest end of the machine tool spindle, which are flush with each other and arranged vertically, install detector 3 and detector 4 symmetrically in the middle of the machine tool spindle, install detector 5 at the highest end of the machine tool spindle, install detector 6 on the workpiece surface, install detector 7 on the machine tool fixture, and install detector 8, detector 9, detector 10 and detector 11 at the four corners of the machine tool worktable respectively.

[0007] Step 2. During the stable machining process of the machine tool, each detector detects the vibration signal generated at the corresponding installation position in real time, converts the corresponding vibration signal into a voltage signal, and amplifies it. The signal acquisition module converts the amplified voltage signal into a digital signal and transmits it to the host computer. The host computer calculates the potential difference between the voltage signals output by detector one, detector two, detector three and detector four and the voltage signal output by detector five according to the established lead formula I, and calculates the potential difference between the voltage signals output by detector six and detector seven and the voltage signals output by detector eight, detector nine, detector ten and detector eleven according to the established lead formula II.

[0008] Step 3: Determine the health status of the machine tool processing process. The judgment formula is:

[0009]

[0010] Where, P is the health status index of the machine tool processing process, I max is the maximum potential difference calculated by lead formula I during the processing, min is the minimum potential difference calculated by lead formula I during the processing, max is the maximum potential difference calculated by lead formula II during the processing, min is the minimum potential difference calculated by lead formula II during the processing, is the average value of each potential difference calculated by lead formula I during the processing, is the average value of each potential difference calculated by lead formula II during the processing, and n is the number of acquisitions of each detector during the processing;

[0011] If the value calculated by the judgment formula is within the preset value, the machine tool processing state is judged to be a healthy state; otherwise, the machine tool processing state is judged to be an unhealthy state.

[0012] Preferably, the detector includes a protective shell, a piezoelectric sheet and an amplifying module. The bottom plate of the protective shell is fixed at a corresponding installation position on the workpiece surface, machine tool fixture, machine tool spindle or machine tool work table. The piezoelectric sheet and the amplifying module are both fixed in the protective shell, and the piezoelectric sheet is located on the bottom plate of the protective shell; the signal output end of the piezoelectric sheet is connected to the signal input end of the amplifying module; the signal output end of the amplifying module of each detector is connected to the signal input end of the signal acquisition module; the signal output end of the signal acquisition module communicates with the host computer.

[0013] More preferably, the shape of the bottom plate of each protective shell is consistent with the shape of the corresponding installation position.

[0014] Preferably, the protective shell is filled with waterproof rubber.

[0015] Preferably, the piezoelectric plates of detector one and detector two are connected in series, the piezoelectric plates of detector three and detector four are connected in series, and the piezoelectric plates of detector eight, detector nine, detector ten and detector eleven are connected in series.

[0016] More preferably, the lead formula I is

[0017] I=a1(V1+V2)+b1(V3+V4)-cV5

[0018] Lead formula II is

[0019] II=a2(V6+V7)-b2(V8+V9+V 10 +V 11 )

[0020] Where, V1, V2, V3, V4, V5, V6, V7, V8, V9, V 10 and V 11 They are the voltage signal values ​​output by detector 1, detector 2, detector 3, detector 4, detector 5, detector 6, detector 7, detector 8, detector 9, detector 10 and detector 11 respectively.

[0021] Among them, the voltage signal value output by each detector includes the voltage signal converted from the vibration signal generated by the machine tool resonance, and the vibration signals generated by the machine tool resonance detected by each detector at any position on the machine tool are considered to be the same. Then, the voltage signals converted from the vibration signal generated by the machine tool resonance in the voltage signals output by each detector are the same, then let

[0022] a1(V1'+V2')+b1(V3'+V4')-cV5'=0

[0023] a2(V6'+V7')-b2(V8'+V9'+V1'0+V1'1)=0

[0024] Wherein, V1', V2', V3', V4', V5', V6', V7', V8', V9', V1'0 and V1'1 are the voltage signal values ​​converted from the vibration signals generated by the machine tool resonance collected by detector 1, detector 2, detector 3, detector 4, detector 5, detector 6, detector 7, detector 8, detector 9, detector 10 and detector 11 respectively;

[0025] When the machine tool spindle is set vertically and the bottom end is suspended in the air, since the installation positions of detectors 1, 2, 3, 4 and 5 are located at distances from the lower end face of the tool from near to far, the vibration of the tool is gradually weakened during the transmission process.

[0026]

[0027] a1>b1

[0028] In addition, from a2(V6'+V7')-b2(V8'+V9'+V1'0+V1'1)=0, we can get:

[0029]

[0030] The potential differences calculated by the formulas of each lead are all generated by the vibration of the tool.

[0031] The present invention has the following beneficial effects:

[0032] The present invention adopts a method of detecting human health by analogy with electrocardiogram, and can realize the detection of the health status of the machine tool processing process. Specifically, the present invention installs detector 1 and detector 2 at the lower end of the machine tool spindle, detector 3 and detector 4 in the middle, and detector 5 at the upper end, installs detector 6 and detector 7 on the workpiece surface and the machine tool fixture respectively, and installs detector 8, detector 9, detector 10 and detector 11 on the machine tool work table. During the stable processing of the machine tool, the piezoelectric piece in each detector converts the vibration signal at the corresponding installation position into a voltage signal, and calculates the potential difference between the voltage signal output by detector 1, detector 2, detector 3 and detector 4 and the voltage signal output by detector 5 in real time through lead formula I, and calculates the potential difference between the voltage signal output by detector 6 and detector 7 and the voltage signal output by detector 8, detector 9 and detector 11 in real time through lead formula II. The potential difference of the voltage signals output by the detector 10 and the detector 11 is finally determined by the value calculated by the judgment formula to determine whether the machine tool processing process is in a healthy state, thereby realizing the detection of the healthy state of the machine tool processing process; further, the lead formulas established in the present invention eliminate the voltage signal generated by the machine tool resonance during calculation, and minimize the influence of the machine tool resonance on the collected voltage signal generated by the tool vibration. In addition, the waveform of the potential difference calculated by each lead formula is compared with the waveform of the vibration detected by the existing acceleration sensor. The waveform of the potential difference calculated by each lead formula is always in the positive direction and has a small fluctuation amplitude, which is convenient for observing the change of the results, so that whether the machine tool processing process is in a healthy state can be observed intuitively. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the installation positions of all detectors on the machine tool;

[0034] Figure 2 This is a schematic diagram of the installation positions of various detectors on the machine tool spindle;

[0035] Figure 3 Schematic diagram of the installation positions of various detectors on the workpiece surface, machine tool fixture and machine tool work table;

[0036] Figure 4Schematic diagram of the protective shell structure with different shapes of base plates;

[0037] Figure 5 This is the potential difference waveform during the healthy tool machining process;

[0038] Figure 6 The potential difference waveform during the machining process of a broken tool. DETAILED DESCRIPTION

[0039] The present invention will be further described below with reference to the accompanying drawings.

[0040] The present invention provides a method for detecting the health status of a machine tool during machining based on potential difference, which is specifically as follows:

[0041] Step 1: Figure 1 、 Figure 2 and Figure 3 As shown, before the machine tool is processed, detector 1 and detector 2 are installed at the lowest end of the machine tool spindle with the same height and arranged vertically, detector 3 3 and detector 4 4 are installed in the middle of the machine tool spindle with symmetrical arrangement, detector 5 5 is installed at the highest end of the machine tool spindle, detector 6 6 is installed on the workpiece surface, detector 7 7 is installed on the machine tool fixture, and detector 8 8, detector 9 9, detector 10 and detector 11 11 are installed at the four corners of the machine tool worktable respectively; each detector is composed of a protective shell, a piezoelectric piece and an amplifying module, the bottom plate of the protective shell is fixed to the corresponding installation position on the workpiece surface, the machine tool fixture, the machine tool spindle or the machine tool worktable, the piezoelectric piece and the amplifying module are fixed in the protective shell, and the piezoelectric piece is located on the bottom plate of the protective shell, and the vibration signal at the corresponding installation position is converted into a voltage signal through the piezoelectric effect, the signal output end of the piezoelectric piece is connected to the signal input end of the amplifying module, and the piezoelectric piece converts the voltage signal The signal is output to the corresponding amplification module, and the amplification module amplifies the corresponding voltage signal; the signal output end of the amplification module of each detector is connected to the signal input end of the signal acquisition module, and the amplified voltage signal is output to the signal acquisition module; the signal output end of the signal acquisition module communicates with the host computer, converts the amplified voltage signal into a digital signal, and transmits it to the host computer; the protective shell is filled with waterproof rubber to ensure the stable operation of the circuit while preventing foreign matter from affecting the normal operation of the piezoelectric piece; wherein, the amplification module is powered by a 5V DC power supply, and the signal acquisition module is powered by a 12V DC power supply, the piezoelectric pieces of detector 1 and detector 2 are connected in series, the piezoelectric pieces of detector 3 3 and detector 4 4 are connected in series, the piezoelectric pieces of detector 8 8, detector 9 9, detector 10 and detector 11 11 are connected in series, and the shape of the bottom plate of each protective shell is consistent with the shape of the corresponding installation position, such as Figure 4 shown.

[0042] Step 2: During the stable machining process of the machine tool (the machining parameters are constant, excluding the process of starting and ending machining), each detector detects the vibration signal generated at the corresponding installation position in real time, converts the corresponding vibration signal into a voltage signal, and amplifies it. The signal acquisition module converts the amplified voltage signal into a digital signal and transmits it to the host computer. The host computer calculates the potential difference between the voltage signal output by detector 1 1, detector 2 2, detector 3 3 and detector 4 4 and the voltage signal output by detector 5 5 according to the established lead formula I, and calculates the potential difference between the voltage signal output by detector 6 6 and detector 7 and the voltage signal output by detector 8 8, detector 9 9, detector 10 and detector 11 according to the established lead formula II;

[0043] Lead formula I is

[0044] I=a1(V1+V2)+b1(V3+V4)-cV5

[0045] Lead formula II is

[0046] II=a2(V6+V7)-b2(V8+V9+V 10 +V 11 )

[0047] Where, V1, V2, V3, V4, V5, V6, V7, V8, V9, V 10 and V 11 They are the voltage signal values ​​output by detector 1, detector 2, detector 3, detector 4, detector 5, detector 6, detector 7, detector 8, detector 9, detector 10 and detector 11 respectively.

[0048] Among them, the voltage signal value output by each detector includes the voltage signal converted from the vibration signal generated by the machine tool resonance, and the vibration signal generated by the machine tool resonance detected by each detector at any position on the machine tool is considered to be the same, then the voltage signal converted from the vibration signal generated by the machine tool resonance in the voltage signal output by each detector is the same. In order to eliminate the voltage signal converted from the vibration signal generated by the machine tool resonance, all the collected voltage signals are voltage signals converted from the tool vibration (the vibration of the workpiece surface, machine tool fixture, machine tool spindle and machine tool worktable is caused by the machine tool resonance, and the other factors causing vibration are mainly tool vibration), then let

[0049] a1(V1'+V2')+b1(V3'+V4')-cV5'=0

[0050] a2(V6'+V7')-b2(V8'+V9'+V1'0+V1'1)=0

[0051] Wherein, V1', V2', V3', V4', V5', V6', V7', V8', V9', V1'0 and V1'1 are the vibration signals generated by the resonance of the machine tool collected by detector 1, detector 2, detector 3, detector 4, detector 5, detector 6, detector 7, detector 8, detector 9, detector 10 and detector 11, respectively, which are converted into voltage signal values;

[0052] Among them, during milling and drilling processing, the machine tool spindle is set vertically and the bottom end is suspended. At this time, since the installation positions of detectors 1, 2, 3, 4 and 5 are located at distances from the lower end face of the tool from near to far, the vibration of the tool is gradually weakened during the transmission process.

[0053]

[0054] a1>b1

[0055] In addition, from a2(V6'+V7')-b2(V8'+V9'+V1'0+V1'1)=0, we can get:

[0056]

[0057] In this embodiment,

[0058] The potential differences calculated by lead formula I and lead formula II can be considered to be generated by tool vibration.

[0059] Step 3: Determine the health status of the machine tool processing process. The judgment formula is:

[0060]

[0061] Where, P is the health status index of the machine tool processing process, I max is the maximum potential difference calculated by lead formula I during the processing, min is the minimum potential difference calculated by lead formula I during the processing, max is the maximum potential difference calculated by lead formula II during the processing, min is the minimum potential difference calculated by lead formula II during the processing, is the average value of each potential difference calculated by lead formula I during the processing, is the average value of each potential difference calculated by lead formula II during the processing, where n is the number of acquisitions of each detector during the processing.

[0062] Among them, when the health status of the machine tool processing is good (mainly the tool wear is small, the tool damage is small, the feed rate and the back cutting amount cannot be too large), the voltage calculated by the lead formula in real time during the stable processing shows a small fluctuation phenomenon, and the maximum voltage is relatively small. At this time, the P value calculated by the judgment formula is closer to 1 (it may be less than 1 in the case of excellent health status, and the difference with 1 is very small), but it is basically impossible to be 1, because the tool will gradually wear and break during the processing, and the feed rate and back cutting amount cannot be too small (otherwise the processing efficiency is low). The machine tool resonance detected by each detector at any position on the machine tool The vibration signals generated cannot be exactly the same, that is, it is impossible to completely eliminate the influence of machine tool resonance. When the health status of the machine tool processing is poor (mainly due to large tool wear and damage, or too much feed or back cutting), the voltage fluctuation phenomenon calculated by the lead formula in real time during the stable processing will change significantly, and the maximum voltage is relatively large. At this time, the P value calculated by the judgment formula is further away from 1 (and is greater than 1 at this time). In the processing of a machine tool with excellent health (using new tools and small feed and back cutting), the voltage calculated by lead formula I is as follows Figure 5 As shown, during the processing of a machine tool in poor health, the voltage calculated by lead formula I is as follows Figure 6 Therefore, conversely, if the P value calculated by the judgment formula during the smooth processing is within the preset value, the machine tool processing state can be judged to be a healthy state, otherwise, the machine tool processing state can be judged to be an unhealthy state; in this embodiment, the preset value is 1.02.

Claims

1. A method for detecting the health status of a machine tool machining process based on potential difference, characterized in that: The details are as follows: Step 1: Before machining, install detectors 1 and 2 at the bottom of the machine spindle, which are flush and arranged vertically. Install detectors 3 and 4, which are symmetrically arranged, in the middle of the machine spindle. Install detector 5 at the top of the machine spindle. Install detector 6 on the workpiece surface. Install detector 7 on the machine fixture. Install detectors 8, 9, 10, and 11 at the four corners of the machine worktable. Step 2: During the machining process of the machine tool, each detector detects the vibration signal generated at the corresponding installation position in real time, converts the corresponding vibration signal into a voltage signal, and amplifies it. The signal acquisition module converts the amplified voltage signal into a digital signal and transmits it to the host computer. The host computer calculates the potential difference between the voltage signals output by detectors 1, 2, 3, and 4 and the voltage signal output by detector 5 according to the established lead formula I, and calculates the potential difference between the voltage signals output by detectors 6 and 7 and the voltage signals output by detectors 8, 9, 10, and 11 according to the established lead formula II; Step 3: Determine the health status of the machine tool processing process. The judgment formula is: Where, P is the health status index of the machine tool processing process, I max is the maximum potential difference calculated by lead formula I during the processing, min is the minimum potential difference calculated by lead formula I during the processing, max is the maximum potential difference calculated by lead formula II during the processing, min is the minimum potential difference calculated by lead formula II during the processing, is the average value of each potential difference calculated by lead formula I during the processing, is the average value of each potential difference calculated by lead formula II during the processing, and n is the number of acquisitions of each detector during the processing; If the P value calculated by the judgment formula is within the preset value, the machine tool processing state is judged to be a healthy state; otherwise, the machine tool processing state is judged to be an unhealthy state.

2. The method for detecting the health status of a machine tool machining process based on potential difference according to claim 1, characterized in that: The detector includes a protective shell, a piezoelectric piece and an amplifying module. The bottom plate of the protective shell is fixed at a corresponding installation position on the workpiece surface, machine tool fixture, machine tool spindle or machine tool work table. The piezoelectric piece and the amplifying module are both fixed in the protective shell, and the piezoelectric piece is located on the bottom plate of the protective shell; the signal output end of the piezoelectric piece is connected to the signal input end of the amplifying module; the signal output end of the amplifying module of each detector is connected to the signal input end of the signal acquisition module; the signal output end of the signal acquisition module communicates with the host computer.

3. The method for detecting the health status of a machine tool processing process based on potential difference according to claim 2, characterized in that: The shape of the bottom plate of each protective shell is consistent with the shape of the corresponding installation position.

4. The method for detecting the health status of a machine tool processing process based on potential difference according to claim 2, characterized in that: The protective shell is filled with waterproof rubber.

5. The method for detecting the health status of a machine tool machining process based on potential difference according to claim 1, characterized in that: The piezoelectric plates of the detector 1 and the detector 2 are connected in series, the piezoelectric plates of the detector 3 and the detector 4 are connected in series, and the piezoelectric plates of the detector 8, the detector 9, the detector 10 and the detector 11 are connected in series.

6. The method for detecting the health status of a machine tool machining process based on potential difference according to claim 5, characterized in that: The lead formula I is I=a1(V1+V2)+b1(V3+V4)-cV5 Lead formula II is II = a2(V6+V7)-b2(V8+V9+V 10 +V 11 ) Where, V1, V2, V3, V4, V5, V6, V7, V8, V9, V 10 and V 11 are the voltage signal values ​​output by detector 1, detector 2, detector 3, detector 4, detector 5, detector 6, detector 7, detector 8, detector 9, detector 10 and detector 11 respectively; Among them, the voltage signal value output by each detector includes the voltage signal converted from the vibration signal generated by the machine tool resonance, and the vibration signals generated by the machine tool resonance detected by each detector at any position on the machine tool are considered to be the same. Then, the voltage signals converted from the vibration signal generated by the machine tool resonance in the voltage signals output by each detector are the same, then let a1(V1'+V′2)+b1(V′3+V′4)-cV′5=0 a2(V′6+V′7)-b2(V′8+V′9+V′ 10 +V′ 11 )=0 In the formula, V1', V'2, V'3, V'4, V'5, V'6, V'7, V'8, V'9, V' 10 and V′ 11 The vibration signals generated by the resonance of the machine tool collected by detectors 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 are converted into voltage signal values; When the machine tool spindle is set vertically and the bottom end is suspended in the air, since the installation positions of detectors 1, 2, 3, 4 and 5 are located at distances from the lower end face of the tool from near to far, the vibration of the tool is gradually weakened during the transmission process. a1>b1 In addition, by a2(V′6+V′7)-b2(V′8+V′9+V′ 10 +V′ 11 )=0, we get: The potential differences calculated by the formulas of each lead are all generated by the vibration of the tool.

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