A mold wear monitoring and positioning device and method based on multi-channel acoustic emission

Abstract

The present invention discloses a mold wear monitoring and positioning device and method based on multi-channel acoustic emission, which relates to the technical field of stamping mold detection. The monitoring device includes a host computer and acoustic emission sensors connected to the host computer in data communication. The positioning method includes the steps of positioning the die installation line, positioning the punch installation line, installing the acoustic emission sensor, decomposing the stamping stage, judging the degree of wear, and positioning the signal source. The present invention establishes a mapping relationship between mold wear and multi-channel acoustic emission signals in a real stamping process, and through the mapping and data interaction between the stamping mold and the acoustic emission, monitors and locates the wear points of the stamping mold in real time, realizes the prediction and alarm of the maintenance time and area of ​​the stamping mold, effectively avoids the problems of high defective rate and long downtime caused by the lag of mold status monitoring and the lack of timeliness of the mold replacement and repair strategy, is conducive to the control of production costs, and provides the necessary technical foundation for the future intelligent stamping workshop.

Description

Technical Field

[0001] The present invention relates to the technical field of stamping die detection, and particularly relates to a device for monitoring die wear and a method for positioning die wear. Background Art

[0002] Metal forming technology is an important part of modern industry. In recent years, metal forming processes have been continuously improved, greatly improving the production efficiency and precision of parts.

[0003] The high-power complex-curved surface stamping process is one of the most commonly used metal forming methods in large-scale metal forming production. However, mass production inevitably causes rapid wear of the die. In actual production, the die used for stamping will exhibit four main failure modes after a certain period of operation, namely plastic deformation, cracking, chipping, and wear. Among them, the wear failure mode is the most common. Die wear will lead to a rapid decline in product quality. However, its development is slow and difficult to detect in the initial stage of wear, which is extremely likely to result in a large number of unqualified products produced by the automated production line. This not only reduces the yield rate, increases the rework rate, is not conducive to the control of production costs, but may even cause damage to the equipment on the production line, resulting in significant economic losses.

[0004] Monitoring the wear state of the die can effectively avoid the above problems and is of great significance to the production of the automated production line. However, during stamping, the upper and lower dies are completely engaged, which hinders the direct measurement and monitoring of die wear by the monitoring device during the stamping process, resulting in the monitoring of die wear in production can only be achieved by indirect measurement.

[0005] Through the retrieval of the prior art, the following known technical solutions exist:

[0006] Prior Art 1:

[0007] From the current patent disclosures and literature, some scholars have studied the die state during the stamping process. Huang et al. used vibration acceleration signals, and Ubhayaratne et al. used audio signals, etc. to monitor the stamping process, thereby detecting die failures during the stamping process.

[0008] However, this prior art is mainly used to achieve discrete detection of die failure states, and cannot achieve continuous monitoring of die wear states, let alone meet the requirements of high timeliness for die wear monitoring in actual production, and cannot provide timely and effective guidance for the decision-making and adjustment of actual production.

[0009] Prior Art 2:

[0010] Shanbhag, V.V.; Rolfe, B.F.; Pereira, M.P. Investigation of Galling Wear Using Acoustic Emission Frequency Characteristics. Lubricants 2020, 8, 25. https: / / doi.org / 10.3390 / lubricants8030025.

[0011] However, the research of the existing technology mainly focuses on die parts with single features such as square boxes and with rotational symmetry. In actual production, the dies in stamping workshops mostly have complex curved surface structures, with many features and large differences. The wear points are often not single, and the positions of each wear point are discrete and the wear states are inconsistent. The research of the existing technology is obviously divorced from the actual production needs and cannot effectively guide the actual production.

[0012] Therefore, although the existing technology can detect the working state of stamping dies to a certain extent, it can only detect the obvious deformation faults with sudden changes of stamping dies, and it is difficult to detect the wear states with continuous small changes of stamping dies; moreover, the existing technology is mostly applicable to dies with single features and simple structures, and it is difficult to locate the wear points of complex curved surface stamping dies and detect the wear conditions of each wear point; in addition, the die fault detection in the existing technology lacks timeliness and has little practical guiding significance for actual production.

[0013] Through the above retrieval, it is found that the above technical solutions do not affect the novelty of the present invention; and the mutual combination of the above existing technologies does not destroy the creativity of the present invention. Summary of the Invention

[0014] The present invention precisely aims to avoid the deficiencies of the above existing technologies, and provides a die wear monitoring and positioning device and method based on multi-channel acoustic emission.

[0015] The present invention adopts the following technical solutions to solve the technical problems. A die wear monitoring and positioning method based on multi-channel acoustic emission includes the following steps:

[0016] The first step is to locate the die installation line.

[0017] When the die is located above or below the punch, the forming base surface at the top or bottom of the die is taken as the die installation surface respectively, and the intersection line of the die installation surface and the outer side surface of the die is taken as the die installation line.

[0018] The second step is to locate the punch installation line.

[0019] When the punch is located below or above the die, the forming base surface at the bottom or top of the punch is used as the punch mounting surface respectively:

[0020] If the outer edge of the forming structure inside the punch completely falls inside the outer edge of the forming structure inside the die, the intersection line between the punch mounting surface and the outer side surface of the punch is used as the punch mounting line;

[0021] If a part of the outer edge of the forming structure inside the punch falls outside the outer edge of the forming structure inside the die, the intersection line between the punch mounting surface and the outer side surface of the die is used as the punch mounting line;

[0022] Step 3: Install acoustic emission sensors

[0023] At least three points are taken on the die mounting line and the punch mounting line respectively in a non - collinear manner to install acoustic emission sensors;

[0024] Step 4: Decompose the stamping stage

[0025] Stamping is carried out. During the process, each of the acoustic emission sensors collects non - stationary acoustic emission signals and transmits the signals to the data acquisition card. Each acoustic emission sensor forms an amplitude waveform A 0 (t) whose amplitude varies with time;

[0026] The upper computer performs time - frequency analysis on any amplitude waveform A(t) transmitted to the data acquisition card by the variational mode method, decomposes the amplitude waveform A 0 (t) into amplitude region waveforms A(t) scaled by time t. Each amplitude region waveform A(t) corresponds to a stage of the corresponding stamping process. Subsequently, the amplitude region waveform A(t) corresponding to the slow - down pressing stage is taken for die wear monitoring and positioning;

[0027] Step 5: Judge the wear degree of the acoustic emission signal source

[0028] Based on the amplitude region waveform A(t) in the slow - down pressing stage, judge the wear degree of the acoustic emission signal source:

[0029] If the acoustic emission signal source is not worn, step 4 is executed again to continue the monitoring of die wear;

[0030] If the acoustic emission signal is worn, judge the wear state of the acoustic emission signal source according to the method in step 6;

[0031] Step 6: Locate the acoustic emission signal source

[0032] Based on the amplitude region waveform A(t) in the slow - down pressing stage, judge the wear state of the wear point:

[0033] If the wear state of the wear point is normal wear, in any two planes corresponding to the positioning female die installation line or the positioning male die installation line, perform two-dimensional plane positioning by the acoustic emission adaptive positioning method, obtain and record the spatial positioning of the acoustic emission signal source, that is, the most severely worn area on the mold, which is the wear point, and then execute the fourth step again;

[0034] If the state of the wear point is severe wear, perform three-dimensional spatial positioning by the acoustic emission adaptive positioning method, obtain the spatial positioning of the acoustic emission signal source, that is, the most severely worn area on the mold, which is the wear point, repair the wear point or replace the mold according to actual needs, and then execute the fourth step.

[0035] Preferably, in the fourth step, the stamping stage is decomposed in the following manner:

[0036] Divide the entire time domain T with the time nodes corresponding to the amplitudes A = 0 and A = 3.5 as the segmentation points, and successively obtain t 1 、t 2 ……t 7 Seven time zones and seven amplitude region waveforms A(t) corresponding to t 1 、t 2 ……t 7 The relationship between the amplitude region waveform A(t) and the time t satisfies the following formula (1):

[0037]

[0038] Then the signal in the time zone t 2 is the signal of the slow decline suppression stage.

[0039] Preferably, the signals in the time zones t 1 、t 3 、t 4 、t 5 、t 6 and t 7 are the signals of the fast decline stage, the pressure holding stage, the unloading stage, the fast return stage, the slow return stage and the standby stage respectively.

[0040] Preferably, in the fifth step, the judgment of the wear degree of the acoustic emission signal source is carried out in the following manner:

[0041] Analyze the amplitude region waveform A(t) of the slow decline suppression stage, obtain the root mean square change amplitude R of the acoustic emission data and the maximum value M of the acoustic emission data, and then judge the root mean square change amplitude R of the acoustic emission data and the maximum value M of the acoustic emission data:

[0042] If R < 10% and / or M < 1, the acoustic emission signal source is not worn;

[0043] If R ≥ 10% and M ≥ 1, the acoustic emission signal source is worn out.

[0044] Preferably, in the sixth step, the wear state of the acoustic emission signal source is judged as follows:

[0045] Continue to judge the maximum value M of the acoustic emission data:

[0046] If 1 ≤ M < 2.4, the wear state of the acoustic emission signal source is normal wear;

[0047] If M ≥ 2.4, the wear state of the acoustic emission signal source is severe wear.

[0048] Preferably, after the acoustic emission sensor collects the signal, the signal is filtered and denoised, and then the signal is transmitted to the data acquisition card.

[0049] A mold wear monitoring and positioning device based on multi-channel acoustic emission. The female mold, the suction cup and the male mold of the stamping equipment are sequentially installed and fixed on the rack from top to bottom or from bottom to top, and includes a host computer and acoustic emission sensors respectively in data communication with the host computer;

[0050] When the female mold is located above or below the male mold, the plane at the top or bottom of the forming structure inside the female mold is respectively used as the installation surface of the female mold, and the intersection line of the installation surface of the female mold and the outer side surface of the female mold is used as the installation line of the female mold;

[0051] When the male mold is located below or above the female mold, the plane at the bottom or top of the forming structure inside the male mold is respectively used as the installation surface of the male mold:

[0052] If the outer edge of the forming structure inside the male mold completely falls inside the outer edge of the forming structure inside the female mold, the intersection line of the installation surface of the male mold and the outer side surface of the male mold is used as the installation line of the male mold;

[0053] If part of the outer edge of the forming structure inside the male mold falls outside the outer edge of the forming structure inside the female mold, the intersection line of the installation surface of the male mold and the outer side surface of the female mold is used as the installation line of the male mold;

[0054] At least three acoustic emission sensors are arranged on the installation line of the female mold and the installation line of the male mold in a non-collinear manner.

[0055] Preferably, when the intersection line of the installation surface of the male mold and the outer side surface of the male mold is used as the installation line of the male mold, acoustic emission sensors are additionally arranged between the installation line of the female mold and the installation line of the male mold on the outer side surfaces of the female mold and the male mold;

[0056] When the intersection line of the installation surface of the male mold and the outer side surface of the female mold is used as the installation line of the male mold, acoustic emission sensors are additionally arranged between the installation line of the female mold and the installation line of the male mold on the outer side surface of the female mold.

[0057] Preferably, each of the acoustic emission sensors is in data communication with the data acquisition card of the host computer, and a signal amplifier is also in data communication between the acoustic emission sensor and the data acquisition card.

[0058] Preferably, the acoustic emission sensor, the signal amplifier and the host computer are in data communication with each other through low-noise signal lines.

[0059] The present invention provides a die wear monitoring and positioning device and method based on multi-channel acoustic emission, having the following beneficial effects:

[0060] 1. The present invention establishes a mapping relationship between die wear and multi-channel acoustic emission signals during the actual stamping process, and through the mapping and data interaction between the stamping die and the acoustic emission, the wear points of the stamping die are monitored and positioned in real time, realizing the prediction and alarm of the maintenance time and area of the stamping die, effectively avoiding the problems of high defective product rate and long downtime caused by the lag of die state monitoring and the lack of timeliness of die replacement and repair strategies, which is beneficial to the control of production costs;

[0061] 2. The present invention improves the use efficiency of the stamping die, and improves the consistency, safety, reliability and profit rate of the stamping products, realizing the efficient and dynamic control of the complex product stamping workshop, providing the necessary technical basis for the future intelligent stamping workshop;

[0062] 3. The structure of the present invention is simple, convenient to install and use, and has good practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 is a flowchart of the die wear positioning method of the present invention;

[0064] Figure 2 is a schematic structural diagram of the die wear monitoring device of the present invention;

[0065] Figure 3 is a top view schematic diagram of the arrangement position of the acoustic emission sensors in the embodiment of the present invention;

[0066] Figure 4 is the amplitude waveform A 0 (t) of the 200th stamping cycle in the embodiment of the present invention;

[0067] Figure 5a is a maximum value-time curve graph of the acoustic emission data obtained by the 2# acoustic emission sensor in the embodiment of the present invention;

[0068] Figure 5b is a maximum value-time curve graph of the acoustic emission data obtained by the 5# acoustic emission sensor in the embodiment of the present invention;

[0069] Figure 6This is the root mean square-time curve graph of the acoustic emission data in the embodiments of the present invention.

[0070] In the figure:

[0071] 1. Stamping equipment, 11. Female die, 12. Suction cup, 13. Male die; 2. Acoustic emission sensor; 3. Signal amplifier, 4. Host computer, 41. Data acquisition card. Detailed implementation manners

[0072] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0073] As Figure 2 shown, a method for monitoring and positioning die wear based on multi-channel acoustic emission includes the following steps:

[0074] The first step is to locate the female die installation line

[0075] When the female die 11 is above or below the male die 13, the forming base surface at the top or bottom of the female die 11 is respectively used as the female die installation surface, and the intersection line of the female die installation surface and the outer side surface of the female die 11 is taken as the female die installation line;

[0076] The second step is to locate the male die installation line

[0077] When the male die 13 is below or above the female die 11, the forming base surface at the bottom or top of the male die 13 is respectively used as the male die installation surface:

[0078] During actual stamping, the die design must make the forming structure have a flat forming base surface at the top and bottom plane positions, so that after the forming structure is removed from the die, the edge can be conveniently trimmed; the plane where the forming base surface is located at the top or bottom is the female die installation surface or the male die installation surface;

[0079] If the outer edge of the forming structure in the male die 13 completely falls inside the outer edge of the forming structure in the female die 11, the intersection line of the male die installation surface and the outer side surface of the male die 13 is taken as the male die installation line;

[0080] If part of the outer edge of the forming structure in the male die 13 falls outside the outer edge of the forming structure in the female die 11, the intersection line of the male die installation surface and the outer side surface of the female die 11 is taken as the male die installation line;

[0081] The third step is to install the acoustic emission sensor

[0082] At least three acoustic emission sensors are installed on the female die installation line and the male die installation line in a non-collinear manner respectively;

[0083] Fourth step, decompose the stamping stage

[0084] Perform stamping processing. During the process, each acoustic emission sensor 2 collects non-stationary acoustic emission signals and transmits the signals to the data acquisition card 41. Each acoustic emission sensor 2 forms an amplitude waveform A 0 (t) that varies with time;

[0085] The upper computer 4 performs time-frequency analysis on any amplitude waveform A(t) transmitted to the data acquisition card 41 by the variational mode method, and decomposes the amplitude waveform A 0 (t) into amplitude region waveforms A(t) scaled by time t. Each amplitude region waveform A(t) corresponds to a stage of the corresponding stamping processing. Subsequently, the amplitude region waveform A(t) corresponding to the slow-down pressing stage is taken for mold wear monitoring and positioning;

[0086] During actual monitoring, although each acoustic emission sensor 2 can independently obtain a maximum acoustic emission data value M and form an amplitude waveform A 0 (t), since the objects monitored by each acoustic emission sensor 2 are the points with the most severe wear on the stamping die, the maximum acoustic emission data value M obtained by each acoustic emission sensor 2 and the formed amplitude waveform A 0 (t) tend to be infinitely consistent. Therefore, any amplitude waveform A(t) can be taken for analysis. If necessary, each amplitude waveform A(t) can also be analyzed to eliminate a small amount of measurement errors caused by environmental factors by combining statistical methods;

[0087] Fifth step, judge the wear degree of the acoustic emission signal source

[0088] Based on the amplitude region waveform A(t) in the slow-down pressing stage, judge the wear degree of the acoustic emission signal source:

[0089] If the acoustic emission signal source is not worn, then step four is executed again to continue monitoring the mold wear;

[0090] If the acoustic emission signal is worn, then judge the wear state of the acoustic emission signal source according to the method in the sixth step;

[0091] Sixth step, locate the acoustic emission signal source

[0092] Based on the amplitude region waveform A(t) in the slow-down pressing stage, judge the wear state of the worn point:

[0093] If the wear state of the wear point is normal wear, in any two planes corresponding to the positioning female die installation line or the positioning male die installation line, perform two-dimensional plane positioning using the acoustic emission adaptive positioning method, obtain and record the acoustic emission signal source, that is, the spatial positioning of the most severely worn area on the mold, which is the wear point, and then execute the fourth step again;

[0094] If the state of the wear point is severe wear, perform three-dimensional space positioning using the acoustic emission adaptive positioning method, obtain the acoustic emission signal source, that is, the spatial positioning of the most severely worn area on the mold, which is the wear point, repair the wear point or replace the mold according to actual needs, and then execute the fourth step.

[0095] The above positioning method locates the wear point in a two-dimensional plane or three-dimensional space according to the actual situation of the wear point. Compared with the prior art that can only perform two-dimensional plane positioning with three sensors or three-dimensional space positioning with six or more sensors, it saves computing power as much as possible and improves the positioning efficiency on the premise of ensuring the realization of wear point positioning.

[0096] The acoustic emission adaptive positioning method can refer to:

[0097] Madhav Baral,Ali Al-Jewad,Alexander Breunig,Peter Groche,Jinjin Ha,Yannis P.Ko rkolis,Brad L.Kinsey,Acoustic emission monitoring for necking insheet metal forming,Jour nal of Materials Processing Technology,Volume 310,2022,117758,ISSN0924-0136,https: / / doi.or g / 10.1016 / j.jmatprotec.2022.117758.

[0098] Preferably, in the fourth step, the stamping stage is decomposed as follows:

[0099] Use the time nodes corresponding to the amplitudes A = 0 and A = 3.5 as the segmentation points to segment the entire time domain T, and sequentially obtain t 1 、t 2 ……t 7 Seven time zones and the seven amplitude region waveforms A(t) corresponding to t 1 、t 2 ……t 7 Seven amplitude region waveforms A(t), and the relationship between the amplitude region waveform A(t) and the time t satisfies the following formula (1):

[0100]

[0101] Then the signal within time zone t 2 is the signal in the slow descent and suppression stage, and the determination of die wear positioning and wear degree is analyzed based on the signal in the slow descent and suppression stage.

[0102] Preferably, the signal within time zone t 1 、t 3 、t 4 、t 5 、t 6 and t 7 are respectively the signals in the fast descent stage, pressure holding stage, unloading stage, fast return stage, slow return stage and standby stage; although the signals in the fast descent stage, pressure holding stage, unloading stage, fast return stage, slow return stage and standby stage have little significance for die wear positioning and wear degree monitoring, they can be used for on-line monitoring of the stamping production process and provide guidance for the arrangement and adjustment of other work in production.

[0103] Preferably, in the fifth step, the determination of the wear degree of the acoustic emission signal source is carried out as follows:

[0104] Analyze the waveform A(t) of the amplitude region in the slow descent and suppression stage to obtain the root mean square change amplitude R of the acoustic emission data and the maximum value M of the acoustic emission data, and then determine the root mean square change amplitude R of the acoustic emission data and the maximum value M of the acoustic emission data:

[0105] If R < 10% and / or M < 1, the acoustic emission signal source is not worn;

[0106] If R ≥ 10% and M ≥ 1, the acoustic emission signal source is worn.

[0107] During actual monitoring, this method can be combined with the time-delay neural network processing and multi-scale convolutional attention network method to jointly realize the determination of the wear degree of the acoustic emission signal source. Compared with the existing technology that needs to classify and identify the data in the stamping cycle according to the neural network algorithm after a complete stamping cycle, the timeliness of die wear monitoring is significantly improved.

[0108] Preferably, in the sixth step, the determination of the wear state of the acoustic emission signal source is carried out as follows:

[0109] Continue to determine the maximum value M of the acoustic emission data:

[0110] If 1 ≤ M < 2.4, the wear state of the acoustic emission signal source is normal wear;

[0111] If M ≥ 2.4, the wear state of the acoustic emission signal source is severe wear.

[0112] Preferably, after the acoustic emission sensor 2 collects the signal, it filters and denoises the signal, and then transmits the signal to the data acquisition card 41.

[0113] A device for monitoring and positioning die wear by the above method, its structural characteristics are: the female die 11, the suction cup 12 and the male die 13 of the stamping equipment 1 are sequentially installed and fixed to the frame 14 from top to bottom or from bottom to top, including a host computer 4 and acoustic emission sensors 2 each in data communication with the host computer 4;

[0114] When the female die 11 is above or below the male die 13, the forming base surface of the top or bottom of the female die 11 is respectively taken as the female die installation surface, and the intersection line of the female die installation surface and the outer side surface of the female die 11 is taken as the female die installation line;

[0115] When the male die 13 is below or above the female die 11, the forming base surface of the bottom or top of the male die 13 is respectively taken as the male die installation surface:

[0116] If the outer edge of the formed structure in the male die 13 completely falls inside the outer edge of the formed structure in the female die 11, the intersection line of the male die installation surface and the outer side surface of the male die 13 is taken as the male die installation line;

[0117] If part of the outer edge of the formed structure in the male die 13 falls outside the outer edge of the formed structure in the female die 11, the intersection line of the male die installation surface and the outer side surface of the female die 11 is taken as the male die installation line;

[0118] At least three acoustic emission sensors are arranged on the female die installation line and the male die installation line in a non - collinear manner.

[0119] Preferably, when the intersection line of the male die installation surface and the outer side surface of the male die 13 is the male die installation line, additional acoustic emission sensors 2 are also arranged between the female die installation line and the male die installation line on the outer side surfaces of the female die 11 and the male die 13;

[0120] When the intersection line of the male die installation surface and the outer side surface of the female die 11 is the male die installation line, additional acoustic emission sensors 2 are also arranged between the female die installation line and the male die installation line on the outer side surface of the female die 11;

[0121] Increasing the number of acoustic emission sensors 2 is beneficial to improving the die wear positioning and monitoring accuracy.

[0122] Preferably, each acoustic emission sensor 2 is in data communication with the data acquisition card 41 of the host computer 4, and a signal amplifier 3 is also in data communication between the acoustic emission sensor 2 and the data acquisition card 41;

[0123] In actual setting, the host computer can be FieldGo M9 ATX, the signal amplifier can be PXPA3, the acoustic emission sensor can be PXR15, and the data acquisition card can be NI PCI - 6713.

[0124] Preferably, the acoustic emission sensor 2, the signal amplifier 3 and the host computer 4 are connected by a low-noise signal line, that is, a cable whose self-generated pulse signal is less than 5 mV.

[0125] Embodiment 1

[0126] Taking a certain type of stamping die for a car door part as an example, the working principle and characteristics of the present invention will be further described below. In this embodiment, the planar dimensions of the stamping die, that is, the female die 11 and the male die 13, are 600 mm * 600 mm. The outer edge of the formed structure inside the male die 13 completely falls inside the outer edge of the formed structure inside the female die 11. When the dies are engaged, the distance between the forming base surface of the female die and the forming base surface of the male die is 200 mm.

[0127] As Figure 1 shown, the female die 11, the suction cup 12 and the male die 13 are sequentially installed and fixed to the frame 14 from top to bottom. Wear monitoring and positioning of the above stamping die include the following steps:

[0128] The first step is to position the installation line of the female die

[0129] Taking the plane at the top of the formed structure inside the female die 11 as the installation surface of the female die, and taking the intersection line of the installation surface of the female die and the outer side surface of the female die 11 as the installation line of the female die.

[0130] The second step is to position the installation line of the male die

[0131] Taking the plane at the bottom of the formed structure inside the male die 13 as the installation surface of the male die:

[0132] If the outer edge of the formed structure inside the male die 13 completely falls inside the outer edge of the formed structure inside the female die 11, then taking the intersection line of the installation surface of the male die and the outer side surface of the male die 13 as the installation line of the male die;

[0133] If a part of the outer edge of the formed structure inside the male die 13 extends outside the outer edge of the formed structure inside the female die 11, then taking the intersection line of the installation surface of the male die and the outer side surface of the female die 11 as the installation line of the male die.

[0134] The third step is to install the acoustic emission sensor

[0135] As Figures 2 to 3 shown, install the 1# to 3# acoustic emission sensors 2 on the installation line of the female die. The 1# acoustic emission sensor 2 is located 200 mm from the front side on the left side surface of the female die 11, the 2# acoustic emission sensor 2 is located 200 mm from the front side on the right side surface of the female die 11, and the 3# acoustic emission sensor 2 is located on the midline of the rear side surface of the female die 11;

[0136] Install AE sensors 2 from No. 4 to No. 6 on the punch installation line. The No. 4 AE sensor 2 is located at 200 mm from the front side on the left side of the punch 13. The No. 5 AE sensor 2 is located at 200 mm from the front side on the right side of the punch 13. The No. 6 AE sensor 2 is located on the midline of the rear side of the punch 13.

[0137] The resonance frequency of each AE sensor 2 is 150 KHz, and the sampling accuracy is 24 bit.

[0138] Step 4: Decompose the stamping stage

[0139] Perform stamping processing. During the process, each AE sensor 2 collects non-stationary AE signals and transmits the signals to the data acquisition card 41. Each AE sensor 2 forms an amplitude waveform A 0 (t) whose amplitude changes with time. The host computer 4 performs time-frequency analysis on any amplitude waveform A 0 (t) transmitted to the data acquisition card 41 by the variational mode method. Using the time nodes corresponding to the amplitudes A = 0 and A = 3.5 as the segmentation points, the entire time domain T is segmented, and t 1 , t 2 ……t 7 Seven time zones and seven amplitude region waveforms A(t) corresponding to t 1 , t 2 ……t 7 are obtained in sequence.

[0140] As Figure 4 shown, Figure 4 is the amplitude waveform A 0 (t) of a complete stamping work cycle. The time domain T ranges from 0 s to 2 s. The time domain T is segmented using the time nodes corresponding to the amplitudes A = 0 and A = 3.5, and t 1 , t 2 ……t 7 Seven time zones are obtained, corresponding to the fast descent stage, slow descent pressing stage, pressure holding stage, unloading stage, fast return stage, slow return stage, and standby stage within a stamping work cycle of stamping production respectively.

[0141] Step 5: Judge the wear degree of the AE signal source

[0142] Analyze the amplitude region waveform A(t) in the slow descent pressing stage, that is, the amplitude region waveform A(t) corresponding to the time zone of t 2 to obtain the root mean square change amplitude R of the AE data and the maximum value M of the AE data. Then judge the root mean square change amplitude R of the AE data and the maximum value M of the AE data:

[0143] If R < 10% and / or M < 1, the acoustic emission signal source is not worn. Perform step four again and continue to monitor the die wear.

[0144] If R ≥ 10% and M ≥ 1, the acoustic emission signal source is worn. Judge the wear state of the acoustic emission signal source according to the method in step six.

[0145] As Figure 4 shown, further analyze the waveform A(t) of the amplitude region corresponding to the slow descent suppression stage, i.e., the t 2 time zone. The t 2 time zone ranges from 0.78 s to 9 s. The maximum value M of the acoustic emission data in this time zone is 0.97, and the root mean square change amplitude R of the acoustic emission data is 8%.

[0146] It can be seen that the acoustic emission signal source is not worn at this time, and step four should be performed again.

[0147] Step six, acoustic emission signal source positioning

[0148] Based on the amplitude region waveform A(t) of the slow descent suppression stage, i.e., the amplitude region waveform A(t) corresponding to the t 2 time zone, judge the wear state of the wear point, and continue to judge the maximum value M of the acoustic emission data:

[0149] If 1 ≤ M < 2.4, the wear state of the acoustic emission signal source is normal wear. In any of the two planes corresponding to the positioning die installation line or the positioning punch installation line, perform two-dimensional plane positioning using the acoustic emission adaptive positioning method, obtain and record the spatial positioning of the acoustic emission signal source, i.e., the most severely worn area on the die, i.e., the wear point, and then perform step four again.

[0150] If M ≥ 2.4, the wear state of the acoustic emission signal source is severe wear. Perform three-dimensional spatial positioning using the acoustic emission adaptive positioning method to obtain the spatial positioning of the acoustic emission signal source, i.e., the most severely worn area on the die, i.e., the wear point. Repair the wear point or replace the die according to actual needs, and then perform step four.

[0151] As Figure 5a 、 Figure 5b and Figure 6 shown, merge the amplitude region waveforms A(t) corresponding to the slow descent suppression stage in 600 complete stamping work beats, and analyze and process the merged amplitude region waveform A(t).

[0152] Figure 5a and Figure 5b are respectively the maximum value - time curves of the acoustic emission data obtained by analyzing and processing the signals collected by the 2# acoustic emission sensor 2 and the 5# acoustic emission sensor 2 in 600 slow descent suppression stages.

[0153] FromFigure 5a It can be known that:

[0154] In AE sensor 2, before the 220th stamping cycle, the maximum value M of AE data is less than 1; from the 220th stamping cycle to before the 420th stamping cycle, the maximum value M of AE data satisfies 1 ≤ M < 2.4, where the maximum value M of AE data at the 220th stamping cycle is 1.34; starting from the 420th stamping cycle, the maximum value M of AE data is greater than or equal to 2.4, where the maximum value M of AE data at the 420th stamping cycle is 3.17.

[0155] From Figure 5b it can be known that:

[0156] In AE sensor 5, before the 223rd stamping cycle, the maximum value M of AE data is less than 1; from the 223rd stamping cycle to before the 419th stamping cycle, the maximum value M of AE data satisfies 1 ≤ M < 2.4, where the maximum value M of AE data at the 220th stamping cycle is 1.3; starting from the 419th stamping cycle, the maximum value M of AE data is greater than or equal to 2.4, where the maximum value M of AE data at the 419th stamping cycle is 2.43.

[0157] There are slight errors in the results obtained from AE sensor 2 and AE sensor 5 because there is a very small delay due to the non - coplanarity of the two sensors, which is within a reasonable range and will not affect the accuracy of the determination.

[0158] Figure 6 It is the root - mean - square change - time curve of AE data obtained by analyzing and processing the signals collected by AE sensor 2 and AE sensor 5 during 600 slow - down pressing stages. The root - mean - square change amplitude R of AE data refers to the change amplitude of the root - mean - square of AE data in each slow - down pressing stage compared to the root - mean - square of AE data in the previous slow - down pressing stage during 600 slow - down pressing stages. From Figure 6 it can be known that:

[0159] In AE sensor 2, before the 160th stamping cycle, the root - mean - square change amplitude R of AE data is less than 10%; starting from the 160th stamping cycle, the root - mean - square change amplitude R of AE data is greater than 10%, where the root - mean - square change amplitude R of AE data at the 160th stamping cycle is 11.37%.

[0160] In 5# acoustic emission sensor 2, before the 209th stamping working cycle, the root mean square change amplitude of the acoustic emission data R<10%; from the 209th stamping working cycle, the root mean square change amplitude of the acoustic emission data R>10%, among which the root mean square change amplitude of the acoustic emission data of the 209th stamping working cycle R=10.43%.

[0161] In this embodiment, 1# to 3# acoustic emission sensors 2 are all installed on the concave mold 11, and the signals collected by the three tend to be consistent. Similarly, 4# to 6# acoustic emission sensors 2 are all installed on the convex mold 13, and the signals collected by the three tend to be consistent. Therefore, the signals collected by 2# and 5# acoustic emission sensors 2 are taken for display; from Figure 5 to Figure 6 It can also be seen that even for the 2# and 5# acoustic emission sensors 2, whose collected signals are relatively different among the 1# to 6# acoustic emission sensors 2, the root mean square change trends obtained by analyzing the collected signals are very similar, and the change amplitude gradually increases. This is consistent with the situation in actual production where the root mean square change amplitude of the acoustic emission data first increases when the stamping die begins to wear.

[0162] right Figure 5a , Figure 5b and Figure 6 The maximum value-time curve of acoustic emission data and the root mean square-time curve of acoustic emission data are further analyzed:

[0163] Based on the collected signal of 2# acoustic emission sensor 2:

[0164] 1) Before the 160th stamping cycle, R < 10% and M < 1; at this time, the acoustic emission signal source is not worn, and the next stamping cycle can be carried out directly;

[0165] 2) From the 160th stamping cycle to the 220th stamping cycle, R>10% and M<1; at this time, the acoustic emission signal source is not worn and the next stamping cycle can be carried out directly;

[0166] 3) From the 220th stamping cycle to before the 420th stamping cycle, R>10% and 1≤M<2.4; at this time, the acoustic emission signal source has been worn and the wear state is normal wear, and the two-dimensional plane positioning of the acoustic emission signal source should be performed using the acoustic emission adaptive positioning method.

[0167] Taking the plane corresponding to the installation line of the positioning die as an example, the two-dimensional plane positioning of the acoustic emission signal source is performed using the acoustic emission adaptive positioning method:

[0168] Take the location of 1# acoustic emission sensor 2 as the coordinate origin O, the horizontal right as the positive direction of the x-axis, and the horizontal backward as the positive direction of the y-axis to establish a two-dimensional rectangular coordinate system. The plane positioning coordinates of 1# to 3# acoustic emission sensors 2 in the plane corresponding to the die installation line are as follows:

[0169] AE sensor 1: (0, 0), AE sensor 2: (300, 400), AE sensor 3: (600, 0);

[0170] Assume the planar coordinates of the AE signal source P are (x, y), establish the following set of equations, and obtain and record the planar positioning of the AE signal source, i.e., the most severely worn area on the mold, i.e., the worn point:

[0171]

[0172] where v = 340 m / s, which is the propagation speed of the AE signal, s 1 、s 2 and s 3 are the distances between AE sensors 1 - 3 and the AE signal source respectively, t 1# 、t 2# and t 3# are the times when AE sensors 1 - 3 receive the AE signal respectively, (x 1 , y 1 ), (x 1 , y 1 ) and (x 1 , y 1 ) correspond to the planar coordinates of AE sensors 1 - 3 respectively;

[0173] In this embodiment, the time difference (t 1# - t 2# ) between AE sensors 1 and 2 receiving the AE signal is 27.48 ms, and the time difference (t 1# - t 3# ) between AE sensors 1 and 3 receiving the AE signal is 0.05 ms. Solving gives the planar coordinates of the AE signal source P(x, y) as (289, 163), which is in precise agreement with the actual position of the worn point.

[0174] Although the acquisition and recording of the worn point positioning do not involve the immediate adjustment and replacement of the mold, it can be used as a guiding basis for related work such as mold processing adjustment and stamping process optimization, with the aim of adjusting and improving the existing stamping molds, devices, and processes, delaying the wear of the vulnerable points of the mold, reducing the maintenance and replacement frequency of the mold, and extending the service life of the mold.

[0175] 4) Starting from the 420th stamping work cycle, R > 10% and M ≥ 2.4; at this time, the AE signal source has been worn and the wear state is severe wear. The three - dimensional space positioning of the AE signal source should be carried out by the AE adaptive positioning method, and the AE signal source, i.e., the worn point, should be repaired or the mold should be replaced according to actual needs.

[0176] The following is an example of three-dimensional spatial positioning of an acoustic emission signal source using an acoustic emission adaptive positioning method:

[0177] Take the location of 4# acoustic emission sensor 2 as the coordinate origin O, horizontal right as the positive direction of x-axis, horizontal backward as the positive direction of y-axis, and vertical upward as the positive direction of z-axis to establish a three-dimensional rectangular coordinate system, then the spatial positioning coordinates of 1#~6# acoustic emission sensors 2 in the mold bite state are as follows:

[0178] 1# acoustic emission sensor 2: (0,0,200), 2# acoustic emission sensor 2: (300,400,200), 3# acoustic emission sensor 2: (600,0,200), 4# acoustic emission sensor 2: (0,0,0), 5# acoustic emission sensor 2: (300,400,0), 6# acoustic emission sensor 2: (600,0,0);

[0179] Assume that the spatial coordinates of the acoustic emission signal source P are (x, y, z), and combine the following two equations to obtain the spatial location of the acoustic emission signal source, that is, the area with the most severe wear on the mold, that is, the wear point:

[0180]

[0181] Among them, s 4 is the distance between 4# acoustic emission sensor 2 and the acoustic emission signal source, t 4# is the time when 4# acoustic emission sensor 2 receives the acoustic emission signal, (x 4 ,y 4 ,z 4 ) is the spatial coordinate of 4# acoustic emission sensor 2;

[0182] In this embodiment, the time difference (t 1# -t 2# ) is 21.63ms, and the time difference (t 1# -t 3# ) is 0.07ms, and the time difference (t 1# -t 4# ) is 11.45ms, and the spatial coordinates of the acoustic emission signal source P(x, y, z) are solved to be (286, 161, 193), which is exactly consistent with the actual wear point position.

[0183] In this embodiment, for the convenience of description and calculation, taking the minimum number of acoustic emission sensors 2 required to achieve three-dimensional space positioning requirements, i.e., four acoustic emission sensors 2 as an example, the acoustic emission adaptive positioning method further includes a specific method for realizing the spatial positioning of the acoustic emission signal source with six or more acoustic emission sensors 2. This method also belongs to the category of the prior art and will not be elaborated here.

[0184] Whether it is two-dimensional plane positioning or three-dimensional space positioning, the selection of the coordinate system should make the positioning calculation as simple as possible, but different selections of the coordinate system will not affect the actual positioning result.

[0185] Based on the acquisition signal of the 5# acoustic emission sensor 2:

[0186] 1) Before the 209th stamping work beat, R < 10% and M < 1; at this time, the acoustic emission signal source is not worn, and the next stamping work beat can be directly carried out;

[0187] 2) From the 209th stamping work beat to before the 223rd stamping work beat, R > 10% and M < 1; at this time, the acoustic emission signal source is not worn, and the next stamping work beat can be directly carried out;

[0188] 3) From the 223rd stamping work beat to before the 419th stamping work beat, R > 10% and 1 ≤ M < 2.4; at this time, the acoustic emission signal source is worn and the wear state is normal wear. The two-dimensional plane positioning of the acoustic emission signal source should be carried out by the acoustic emission adaptive positioning method.

[0189] 4) Starting from the 419th stamping work beat, R > 10% and M ≥ 2.4; at this time, the acoustic emission signal source is worn and the wear state is severe wear. The three-dimensional space positioning of the acoustic emission signal source should be carried out by the acoustic emission adaptive positioning method, and the acoustic emission signal source, i.e., the wear point, should be trimmed or the mold should be replaced according to actual needs.

[0190] It can be seen from this embodiment that the maximum value M of the acoustic emission data obtained based on the acquisition signals of the 2# acoustic emission sensor 2 and the 5# acoustic emission sensor 2 is extremely similar in both the change trend and the critical change point, and the difference is completely within the production allowable error range;

[0191] Meanwhile, since the 2# acoustic emission sensor 2 and the 5# acoustic emission sensor 2 are respectively installed on the female die 11 and the male die 13, the difference in the installation positions results in the same root mean square change trend of the acoustic emission data obtained based on the signals collected by the two sensors, and there is a certain gap in the critical change points of the root mean square change amplitude of the acoustic emission data. However, considering that in actual production, when the stamping die starts to wear, the root mean square change amplitude of the acoustic emission data increases first. The critical point of the root mean square change amplitude of the acoustic emission data usually appears before the maximum value M of the acoustic emission data reaches the first critical point M = 1, and only a very small part appears between M reaching the first critical point and M reaching the second critical point M = 2.4. However, regardless of whether the critical point of the root mean square change amplitude of the acoustic emission data appears before the maximum value M of the acoustic emission data reaches the first critical point M = 1 or between M reaching the first critical point and M reaching the second critical point M = 2.4, it will not affect the judgment of severe wear of the acoustic emission signal source, that is, it will not affect the determination of the wear point of the die or the replacement of the die.

[0192] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the element.

[0193] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for monitoring and locating die wear based on multi-channel acoustic emission, characterized in that, it includes the following steps: The first step is to locate the die installation line When the die (11) is located above or below the punch (13), the die forming base surface at the top or bottom of the die (11) is taken as the die installation surface respectively, and the intersection line of the die installation surface and the outer side surface of the die (11) is taken as the die installation line; The second step is to locate the punch installation line When the punch (13) is located below or above the die (11), the punch forming base surface at the bottom or top of the punch (13) is taken as the punch installation surface respectively: If the outer edge of the inner forming structure of the punch (13) completely falls inside the outer edge of the inner forming structure of the die (11), the intersection line of the punch installation surface and the outer side surface of the punch (13) is taken as the punch installation line; If a part of the outer edge of the inner forming structure of the punch (13) falls outside the outer edge of the inner forming structure of the die (11), the intersection line of the punch installation surface and the outer side surface of the die (11) is taken as the punch installation line; The third step is to install acoustic emission sensors At least three points are taken on the die installation line and the punch installation line respectively in a non-collinear manner to install acoustic emission sensors; The fourth step is to decompose the stamping stage Stamping is carried out. During the process, each of the acoustic emission sensors (2) collects non-stationary acoustic emission signals and transmits the signals to the data acquisition card (41). Each of the acoustic emission sensors (2) forms an amplitude waveform A whose amplitude changes with time 0 (t); The host computer (4) performs time-frequency analysis on any amplitude waveform A(t) transmitted to the data acquisition card (41) by the variational mode method, and decomposes the amplitude waveform A 0 (t) into amplitude region waveforms A(t) scaled by time t. Each amplitude region waveform A(t) corresponds to a stage of the corresponding stamping process. Subsequently, the amplitude region waveform A(t) corresponding to the slow-down pressing stage is taken for die wear monitoring and positioning; The fifth step is to judge the wear degree of the acoustic emission signal source Based on the amplitude region waveform A(t) in the slow descent suppression stage, judge the wear degree of the acoustic emission signal source: If the acoustic emission signal source is not worn, perform step four again to continue monitoring the die wear; If the acoustic emission signal has been worn, judge the wear state of the acoustic emission signal source according to the method in the sixth step; The sixth step is to locate the acoustic emission signal source Based on the amplitude region waveform A(t) in the slow descent suppression stage, judge the wear state of the wear point: If the wear state of the wear point is normal wear, in any of the two planes corresponding to the die installation line or the punch installation line, perform two-dimensional plane positioning by the acoustic emission adaptive positioning method, obtain and record the spatial positioning of the acoustic emission signal source, that is, the most severely worn area on the die, that is, the wear point, and then perform step four again; If the state of the wear point is severe wear, perform three-dimensional spatial positioning by the acoustic emission adaptive positioning method, obtain the spatial positioning of the acoustic emission signal source, that is, the most severely worn area on the die, that is, the wear point, repair the wear point or replace the die according to actual needs, and then perform step four.

2. A method for monitoring and locating die wear based on multi-channel acoustic emission according to claim 1, characterized in that, In the fourth step, the stamping stage is decomposed as follows: The entire time domain T is segmented with the time nodes corresponding to amplitudes A = 0 and A = 3.5 as the segmentation points, and t is obtained sequentially 1 , t 2 ……t 7 seven time zones and seven amplitude region waveforms A(t) corresponding to t 1 , t 2 ……t 7 seven amplitude region waveforms, and the relationship between the amplitude region waveform A(t) and time t satisfies the following formula (1): Then time zone t 2 The signal within is the signal in the slow decline suppression stage.

3. A method for monitoring and locating die wear based on multi-channel acoustic emission according to claim 2, characterized in that: Time zone t 1 、t 3 、t 4 、t 5 、t 6 and t 7 The signals within are the signals for the fast descent stage, pressure holding stage, unloading stage, fast return stage, slow return stage, and standby stage respectively.

4. A method for monitoring and locating die wear based on multi-channel acoustic emission according to claim 1, characterized in that, In the fifth step, the judgment of the wear degree of the acoustic emission signal source is carried out as follows: Analyze the amplitude region waveform A(t) in the slow descent suppression stage to obtain the root mean square change amplitude R of the acoustic emission data and the maximum value M of the acoustic emission data, and then judge the root mean square change amplitude R of the acoustic emission data and the maximum value M of the acoustic emission data: If R < 10% and / or M < 1, the acoustic emission signal source is not worn; If R ≥ 10% and M ≥ 1, the acoustic emission signal source is worn.

5. A method for monitoring and positioning die wear based on multi-channel acoustic emission according to claim 4, characterized in that, In the sixth step, the wear state of the acoustic emission signal source is judged as follows: Continue to judge the maximum value M of the acoustic emission data: If 1 ≤ M < 2.4, the wear state of the acoustic emission signal source is normal wear; If M ≥ 2.4, the wear state of the acoustic emission signal source is severe wear.

6. A method for monitoring and positioning die wear based on multi-channel acoustic emission according to any one of claims 1 to 5, characterized in that: The acoustic emission sensor (2) filters and denoises the signal after collecting the signal, and then transmits the signal to the data acquisition card (41).

7. A device for monitoring and positioning die wear based on multi-channel acoustic emission, which is used to monitor and position the wear of a stamping die according to the method for monitoring and positioning die wear based on multi-channel acoustic emission according to any one of claims 1 to 5. The female die (11), the suction cup (12) and the male die (13) of the stamping equipment (1) are sequentially installed and fixed to the frame (14) from top to bottom or from bottom to top, characterized in that: It includes a host computer (4) and acoustic emission sensors (2) each data-connected to the host computer (4); When the female die (11) is above or below the male die (13), the plane at the top or bottom of the forming structure inside the female die (11) is respectively taken as the female die installation surface, and the intersection line of the female die installation surface and the outer side surface of the female die (11) is taken as the female die installation line; When the male die (13) is below or above the female die (11), the plane at the bottom or top of the forming structure inside the male die (13) is respectively taken as the male die installation surface: If the outer edge of the forming structure inside the male die (13) completely falls inside the outer edge of the forming structure inside the female die (11), the intersection line of the male die installation surface and the outer side surface of the male die (13) is taken as the male die installation line; If part of the outer edge of the forming structure inside the male die (13) falls outside the outer edge of the forming structure inside the female die (11), the intersection line of the male die installation surface and the outer side surface of the female die (11) is taken as the male die installation line; At least three acoustic emission sensors are provided on the female die installation line and the male die installation line in a non-collinear manner.

8. A device for monitoring and positioning die wear based on multi-channel acoustic emission according to claim 7, characterized in that: When the intersection line of the male die installation surface and the outer side surface of the male die (13) is the male die installation line, acoustic emission sensors (2) are additionally provided between the female die installation line and the male die installation line on the outer side surfaces of the female die (11) and the male die (13); When the intersection line of the male die installation surface and the outer side surface of the female die (11) is the male die installation line, acoustic emission sensors (2) are additionally provided between the female die installation line and the male die installation line on the outer side surface of the female die (11).

9. A device for monitoring and positioning die wear based on multi-channel acoustic emission according to claim 7 or 8, characterized in that: Each of the acoustic emission sensors (2) is in data communication with a data acquisition card (41) of a host computer (4), and a signal amplifier (3) is also in data communication between the acoustic emission sensor (2) and the data acquisition card (41).

10. A mold wear monitoring and positioning device based on multi-channel acoustic emission according to claim 9, characterized in that: The acoustic emission sensor (2), the signal amplifier (3) and the host computer (4) are in data communication with each other through a low-noise signal line.

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