CNC cutter life prediction system

Abstract

The present invention relates to a CNC cutter life prediction system, comprising: a vibration sensor for sensing cutter vibration generated during CNC processing and generating vibration data; the state determining module is used for determining the abrasion state and the machining state of the cutter blade in a specific time period according to the vibration data; the database is used for storing the service life of the cutter, and the service life of the cutter comprises normal time when the cutter works normally and dangerous time when the cutter is abraded and works abnormally; and the service life calculation unit is used for recalculating the service life of the cutter by comparing the service time of the cutter with the service life of the cutter when the state determination module determines that the working state of the cutter is abnormal.

Description

Technical Field

[0001] The present invention relates to a CNC tool life prediction system, and more specifically, to a CNC tool life prediction system that compares and analyzes the vibration magnitudes generated by a spindle and a tool blade from vibration data generated during machining, determines the state of the tool, and predicts the time until the tool breaks. Background Art

[0002] Generally, for a milling machine that uses a cutting tool for cutting, in order to maintain a certain quality of the processed product, even if the cutting tool is not damaged, it will be replaced with a new tool after being used a predetermined number of times.

[0003] This is because when the tool is broken during cutting but it is not discovered and the broken tool continues to be used for cutting, it will lead to many problems such as deterioration of the quality of the processed product, waste of processing materials, damage to the machine tool due to abnormal vibration, etc.

[0004] Furthermore, based on these problems, if a cutting tool that has been used a predetermined number of times is replaced, a cutting tool that can normally perform machining will be replaced, thereby causing problems of tool waste and reduced efficiency.

[0005] Therefore, in order to solve these problems, the current practice is that the operator replaces the tool as soon as the sensor sends an abnormal signal. However, it is difficult for the operator to accurately determine the time point, and different damage sensing setting values ​​are set for each processing of a tool. This leads to reactions to instantaneous size changes that are unrelated to the damage occurring during processing, causing false sensing problems.

[0006] Furthermore, if the operator inputs arbitrary damage detection settings based on reference data, the system can be unreliable, leading to problems such as a tool being detected as damaged even though it's functioning properly, or failing to detect damage even though it's actually damaged. Furthermore, because the magnitude of the vibration acceleration signal varies depending on machining conditions and the environment, the operator must directly set the baseline value for the sensing area based on the reference data before each machining operation. This repetitive operation reduces production efficiency and operability.

[0007] Korean authorized patent No. 102580409 is a method for converting the vibration acceleration signal of a rotating cutting tool and sensing the wear or damage of the tool in real time. The method receives the vibration acceleration signal of the tool, performs a fast Fourier transform, and derives a frequency signal. When the frequency detected is greater than the reference frequency, it is determined that the tool is abnormal. However, there is a problem that the reference is unclear and difficult to accurately grasp.

[0008] Japanese authorized patent No. 5543890 adds a preset coefficient to the maximum value of the frequency analysis waveform and sets a critical value. When the frequency analysis waveform generated during processing is greater than the set critical value, it is determined that an abnormality has occurred during processing. However, it is difficult to accurately determine the status of the tool using only the critical value. Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The purpose of the present invention is to provide a tool life prediction system that can confirm the status of the tool blade by analyzing the vibration data generated by the CNC cutting processing device during processing, so that the tool blade can be used effectively. By predicting the tool life, damage to the processed product can be minimized.

[0011] Means used to solve problems

[0012] The CNC tool life prediction system of the present invention includes: a vibration sensor for sensing tool vibration generated during CNC machining and generating vibration data; a state determination module for determining the wear state and machining state of the tool blade in a specific time period through the vibration data; a database for storing tool life, wherein the tool life includes normal time when the tool is working normally and dangerous time when the tool is worn and working abnormally; and a life calculation unit for recalculating the tool life by comparing the tool usage time with the tool life when the state determination module determines that the working state of the tool is abnormal.

[0013] The life calculation unit may be configured to subtract a difference between the usage time and the normal time from the tool life when the usage time at the abnormal time point when the tool is abnormal is less than the normal time.

[0014] The life calculation unit may be configured to subtract the dangerous time in proportion to a difference between the usage time and the normal time.

[0015] The state determination module may include: a spindle vibration extraction unit, which extracts the vibration magnitude of the corresponding spindle frequency band, i.e., the spindle vibration value, by analyzing the vibration data; a tool blade vibration extraction unit, which extracts the vibration magnitude of the corresponding tool blade frequency band, i.e., the tool blade vibration value, by analyzing the vibration data; an other frequency vibration extraction unit, which extracts the vibration magnitude of frequency bands other than the frequency bands corresponding to the spindle and tool blade from the vibration data, i.e., other frequency vibration values; a database, which saves the tool blade vibration value generated when the tool blade is in a normal state as a vibration reference value; and a tool state determination unit, which determines the state of the tool blade by analyzing the spindle vibration value, the tool blade vibration value, the other frequency vibration values, and the vibration reference value.

[0016] The tool state determination unit is used to determine the vibration magnitude when the tool blade and the machining state are normal and the tool is operating normally, which is calculated by the following [Formula 1]:

[0017] [Formula 1]

[0018] Vibration value of other frequencies < spindle vibration value < tool blade vibration value = vibration reference value z,

[0019] Where, the vibration reference value z: the error range of the vibration reference value at a 95% confidence level.

[0020] The tool state determination unit is used to determine the vibration magnitude when the tool blade is partially worn and the machining state is normal and the tool is operating normally, which is calculated by the following [Formula 2]:

[0021] [Formula 2]

[0022] Vibration value of other frequencies < spindle vibration value < vibration reference value < tool blade vibration value.

[0023] The tool state determination unit is used to determine the vibration magnitude when the tool blade is worn and the machining state is intermittently poor and the tool is not operating normally, which is calculated by the following [Formula 3]:

[0024] [Formula 3]

[0025] (Vibration reference value < vibration value of other frequencies) AND (tool blade vibration value < vibration value of other frequencies).

[0026] The tool state determination unit is used to determine the vibration magnitude when the tool blade is worn and the machining state is poor and the tool is not operating normally, which is calculated by the following [Formula 4] and [Formula 5]:

[0027] [Formula 4]

[0028] Tool blade vibration value ≤ spindle vibration value,

[0029] [Formula 5]

[0030] dev vibration reference value < dev(A) tool blade vibration value < dev(B) tool blade vibration value,

[0031] Where, dev vibration reference value: the variation range of the tool blade band vibration magnitude calculated when the tool blade is normal and the machining state is normal, dev(A) tool blade vibration value: the variation range of the tool blade band vibration magnitude calculated when the tool blade is partially damaged and the machining state is normal, dev(B) tool blade vibration value: the variation range of the current tool blade band vibration magnitude.

[0032] The tool state determination unit is used to determine the vibration magnitude when the tool blade is damaged, which is calculated by the following [Formula 6] and [Formula 7]:

[0033] [Formula 6]

[0034] (Other frequency vibration values ​​and tool blade vibration values) ≤ spindle vibration value,

[0035] [Formula 7]

[0036] Det_n=Round(Tol / f_z), the number of consecutive tool breakage diagnosis is greater than Det_n,

[0037] Where, Det_n: the number of times the tool is sensed to be abnormal, Tol: tolerance, f_z: the feed rate per unit tool blade, and Round: the rounded integer.

[0038] Effects of the Invention

[0039] The present invention can accurately grasp the state of the tool blade by comparing and analyzing the vibration magnitudes based on different frequencies generated during processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 4 is a structural block diagram of a system for diagnosing and predicting the status of a CNC machining tool according to an embodiment of the present invention.

[0041] Figure 2 FIG. 1 is a diagram illustrating a method for predicting the life of a tool blade of a region setting portion according to an embodiment of the present invention.

[0042] Figure 3 FIG. 4 is a graph showing vibration data when the blade of the tool according to the embodiment of the present invention is normal.

[0043] Figure 4 is a graph illustrating vibration data of an abnormal tool blade according to an embodiment of the present invention.

[0044] Figure 5 4 is a flow chart of a system for diagnosing and predicting the status of a CNC machining tool according to an embodiment of the present invention.

[0045] Description of Reference Signs

[0046] 100: Vibration sensor 200: Spindle vibration detection unit

[0047] 300: Tool blade vibration extraction unit 400: Other frequency vibration extraction unit

[0048] 500: Database 600: Tool status determination unit

[0049] 700: Life calculation unit

[0050] S10: Vibration data generation step S20: Spindle vibration extraction step

[0051] S30: Tool blade vibration extraction step S40: Other frequency vibration extraction step

[0052] S50: Vibration reference storage step S60: Tool state determination step DETAILED DESCRIPTION

[0053] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0054] The advantages and features of the present invention and methods for achieving them will become more apparent from the embodiments described in detail below with reference to the accompanying drawings.

[0055] However, the embodiments disclosed below are not intended to limit the present invention, but are intended to implement the present invention in various different forms to make the disclosure of the present invention clearer and more complete. They are provided to enable those skilled in the art with general knowledge in the technical field to which the present invention belongs to fully understand the scope of the present invention. The present invention is determined based on the scope of the claims.

[0056] Furthermore, in the process of describing the present invention, if it is determined that related known technologies may obscure the gist of the present invention, their detailed description may be omitted.

[0057] Figure 1 is a structural block diagram of a CNC tool status diagnosis and prediction system according to an embodiment of the present invention, Figure 2 is a diagram illustrating a method for predicting the life of a tool blade of a region setting portion according to an embodiment of the present invention, Figure 3 is a diagram showing vibration data of a normal blade of a tool according to an embodiment of the present invention, Figure 4 is a graph showing vibration data as a tool blade wears according to an embodiment of the present invention.

[0058] like Figure 1 As shown, the system may include a vibration sensor 100 , a state determination module 20 , a database 500 , and a life calculation unit 700 .

[0059] The vibration sensor 100 is mounted on a CNC machining device and can generate vibration data by sensing vibration generated during cutting.

[0060] The vibration data may be a graph representing the magnitude of vibration sensed at each frequency.

[0061] The database 500 may store the tool life ( t1 ), which is calculated by the state determination module 20 by predicting the life of the tool blade.

[0062] Specifically, the tool life can be defined as the average time from replacement to breakage of a plurality of tool inserts used in cutting.

[0063] The tool life (t1) may vary depending on the size, shape, material, etc. of the tool blade.

[0064] like Figure 2 As shown, the life calculation unit 700 may set a normal time (t2), a dangerous time (t3), and a dangerous time point (w1) in the tool life (t1).

[0065] Figure 2 (a) in the figure shows the tool life of a general tool blade. Figure 2 (b) in the figure shows the normal time, the dangerous time and the wear time point of a general tool blade, Figure 2 (c) in FIG. 1 illustrates the tool life, the normal area, and the danger area of ​​a defective tool insert.

[0066] The normal time (t2) may be the time when the wear state of the tool blade and the processing state of the cut material in the state determination module 20 are normal and the tool operates normally.

[0067] The specific instructions are as follows: Figure 2 As shown, the time during which the wear of the tool blade is not serious and the cutting process of the cut material does not suffer from defects in the tool life (t1) of the tool blade is extracted from the multiple tool lives, and the average time can be set as the normal time (t2).

[0068] The dangerous time (t3) may be the time when the tool blade wear state and the processing state of the cut material are poor in the state determination module 20 and the tool is not working properly.

[0069] The specific instructions are as follows: Figure 2 As shown, the time from the time when the tool operates abnormally to the time when the tool is damaged can be set as the dangerous time (t3).

[0070] During the dangerous time (t3), the tool blade is severely worn and the defect of the cut material increases during cutting, which may lead to an increased probability of breakage of the tool blade.

[0071] The dividing point between the normal time (t2) and the dangerous time (t3) in the tool life can be set as the dangerous time point (w1).

[0072] When the usage time of the tool at the abnormal time point (w2) when the abnormality occurs is less than the normal time (t2), the life calculation unit 700 can subtract the difference between the usage time at the abnormal time point (w2) and the normal time (t2) from the tool life (t1).

[0073] Specifically, when a defective tool blade is used instead of a normal tool blade in a cutting operation, the special normal time (t'2) of the defective tool blade is less than the normal normal time (t2) of the normal tool blade, and the time point when the abnormality occurs in the defective tool blade can be set as the abnormal time point (w2).

[0074] Therefore, the interval between the general normal time (t2) and the special normal area (t'2, t2>t'2), ie, the time from the dangerous time point (w1) to the abnormal time point (w2), ie, the correction time (t4), can be calculated.

[0075] The life calculation unit 700 calculates the ratio of the correction time ( t4 ) to the normal time ( t2 ), and subtracts the portion of the correction time ( t3 , t3 > t′3 ) from the dangerous time ( t3 ).

[0076] Specifically, the tool life of the defective tool blade is less than the predicted tool life (t1). In order to predict the reduced tool life (t'2, t'3), a time equivalent to the proportion of the correction time (t4) is applied to the dangerous time (t3), which can reduce the tool life (t1).

[0077] For example, assuming that the tool life (t1) is 100 hours, the normal time (t2) is 80 hours, and the dangerous time (t3) is 20 hours, if the abnormal time point (w2) occurs at 60 hours due to tool failure, the difference between the normal time (t2) and the time when the abnormal time point (w2) occurs, that is, 20 hours, is removed from the tool life (t1), so that the tool life can be reset to 80 hours.

[0078] In addition, the difference between the normal time (t2) and the time when the abnormal time point (w2) occurs is 20 hours, which accounts for 25% of the normal time (t2). This proportion is applied to the dangerous time (t3), so that the dangerous time (t'3) caused by tool failure is predicted to be 15 hours, and the tool life is reset to 75 hours.

[0079] This is because if a tool defect causes a reduction in the time during which normal use can be performed, the time until the tool breaks will also be reduced. Therefore, by reducing both the normal time (t2) and the dangerous time (t3), the tool life can be accurately predicted.

[0080] Therefore, according to the bad state of the tool blade, the changes of the normal time (t2), the dangerous time (t3), and the abnormal time point (w2) are predicted, so that the life of the tool blade can be accurately predicted.

[0081] If it is during the dangerous time (t3), the user will be prompted to replace the knife blade.

[0082] The state determination module 20 may include a spindle vibration extraction unit 200 , a tool blade vibration extraction unit 300 , other frequency vibration extraction unit 400 , and a tool state determination unit 600 .

[0083] The main shaft vibration extraction unit 200 extracts the vibration magnitude of the main shaft frequency band from the vibration data generated by the vibration sensor 100 .

[0084] Specifically, the vibration frequency of the spindle during machining will appear in a specific frequency, namely, the spindle frequency band. The spindle vibration extraction unit 200 can extract the vibration magnitude corresponding to the spindle frequency band, namely, the spindle vibration value, from the vibration data.

[0085] The tool blade vibration extraction unit 300 may extract the vibration magnitude of the corresponding tool blade frequency band from the vibration data generated by the vibration sensor 100 .

[0086] The specific description is as follows: the frequency of the tool blade vibration during processing appears in a specific frequency, that is, the tool blade frequency band. The tool blade vibration extraction unit 300 can extract the vibration size corresponding to the tool blade frequency band from the vibration data, that is, the tool blade vibration value.

[0087] In addition, the frequency band of the tool blades may be different depending on the number of tool blades. The tool blade vibration extraction unit 300 may input the number of tool blades in use in advance to set the frequency band of the tool blades.

[0088] The other-frequency vibration extraction unit 400 may extract vibration magnitudes of frequency bands other than the spindle frequency band and the tool blade frequency band.

[0089] That is, the other frequency vibration extraction unit 400 can sense the vibration number of most parts such as the CNC tool equipment housing, as well as the vibration size generated when the tool processes the cut material due to other reasons other than the vibration generated by the severe wear of the tool blade and the rotation cutting of the tool blade.

[0090] It can also sense vibrations related to chattering, which is when the tool body or tool blade is subjected to strong external forces and vibrates in addition to the rotational cutting of the tool blade.

[0091] The database 500 may store the vibration value of the tool blade generated when the tool blade is in a normal state as a vibration reference value.

[0092] The specific description is as follows: a method for setting a reference value for determining the abnormal state of a tool blade from the vibration data sensed by the sensing sensor, wherein the vibration data sensed when the tool blade in a normal state processes the cut material and high-quality processing is in progress can be set as a vibration reference value.

[0093] The tool state determination unit 600 may determine the state of the tool blade by comparing and analyzing the spindle vibration value and the tool blade vibration value, and other frequency vibration values ​​and the vibration reference value.

[0094] Specifically, the determination can be made by checking which vibration value is greater among the spindle vibration value, the tool blade vibration value, the vibration value of another frequency, and the vibration reference value.

[0095] When the following [Formula 1] is satisfied, the tool state determination unit 600 may determine that the tool blade state is normal and high-quality machining is being performed.

[0096] [Formula 1]

[0097] Other frequency vibration value < spindle vibration value < tool blade vibration value = vibration reference value z,

[0098] The vibration reference value z may be generated within an error range of the vibration reference value at a 95% confidence level.

[0099] That is, Figure 3 As shown, the vibration data sensed under the CNC machining process according to an embodiment of the present invention are observed as follows: the frequency generated when the tool blade cuts the material to be cut (material or product) is 200 Hz, and the maximum vibration magnitude can occur in this frequency band.

[0100] This is because when the tool blade is in a normal state and is cutting the material, only the tool blade is used for cutting processing, so the vibration generated by the tool blade has the largest vibration magnitude in the frequency band corresponding to the vibration.

[0101] Therefore, since only the tool blade is involved in the cutting process, the load on the spindle does not increase, and the CNC processing equipment only generates general vibrations having a vibration magnitude smaller than the vibration value of the tool blade.

[0102] In addition, the vibration value of the other frequencies may be smaller than the main shaft vibration value generated by the main shaft.

[0103] In addition, in order to determine the normal state of the tool blade, it can be determined whether the vibration value of the tool blade during the current cutting process is close to the vibration reference value.

[0104] When the difference between the vibration value of the tool blade and the vibration reference value is greater than or equal to a preset value, it can be determined that the tool blade has changed.

[0105] When the following [Formula 2] is satisfied, the tool state determination unit 600 may determine that the tool blade is partially worn but high-quality machining is being performed.

[0106] [Formula 2]

[0107] Other frequency vibration values ​​< spindle vibration value < vibration reference value < tool blade vibration value.

[0108] The specific description is as follows. The vibration data under the CNC machining process conditions are as follows. Compared with the normal state, although the tool blade is worn, the frequency generated when cutting the cut material is maintained at 200 Hz. The vibration magnitude in this frequency band will produce the maximum vibration magnitude.

[0109] In addition, compared with when the tool blade is in a normal state, the vibration magnitude increases when the tool blade is in a worn state, and the tool blade vibration value may be greater than the vibration reference value.

[0110] When the following [Formula 3] is satisfied, the tool state determination unit 600 may determine that the tool blade is worn and the machining state is intermittently poor.

[0111] [Formula 3]

[0112] (Vibration reference value < other frequency vibration value) OR (Tool blade vibration value < other frequency vibration value).

[0113] In this state, there is a mixture of a case where the tool blade vibration value is large when cutting is performed in a state where the tool blade is significantly worn, and a case where the maximum value occurs in the other frequency vibration values ​​during abnormal cutting.

[0114] The specific instructions are as follows: Figure 3 As shown, observing the vibration data under the CNC machining process conditions is as follows. In addition to the cutting based on the rotation of the tool blade when the tool blade is severely worn, there may be a situation where the tool processes the cut material due to other reasons.

[0115] For example, chatter is a phenomenon in which a tool body or a tool blade vibrates under a strong external force. This phenomenon can cause the magnitude of vibration in other frequency bands to increase.

[0116] Therefore, if Figure 4As shown, at 700 hz, the vibration value of the other frequency is shown to be greater than the vibration magnitude corresponding to the frequency of the tool blade, that is, the vibration reference value and the vibration value of the tool blade, so that it can be determined that the tool blade is worn more.

[0117] When this formula is satisfied, it can be determined that the tool has been used for a time equivalent to the dangerous time (t3), is at the warning level, and is a stage that requires the operator's attention.

[0118] When the following [Formula 4] and [Formula 5] are satisfied, the tool state determination unit 600 can determine that the tool blade is partially damaged and the machining state has deteriorated significantly.

[0119] [Formula 4]

[0120] Vibration value of the tool blade ≤ Vibration value of the spindle

[0121] [Formula 5]

[0122] dev vibration reference value < dev(A) vibration value of the tool blade < dev(B) vibration value of the tool blade

[0123] Among them, the dev vibration reference value can represent the variation range of the vibration reference value when the normal state of normal and high-quality machining of the tool blade is in progress.

[0124] The dev(A) vibration value of the tool blade can represent the variation range of the vibration value of the tool blade when the tool blade is partially worn and the machining is normal.

[0125] The dev(B) vibration value of the tool blade can represent the variation range of the vibration value of the tool blade when the tool blade is severely worn and the machining is abnormal.

[0126] Specifically, when the machining process is continued in the state where the tool blade is severely worn, the situation where the vibration value of the spindle is greater than the vibration value of the tool blade and the situation where the vibration value of the tool blade is the largest will occur mixedly.

[0127] For example, when the tool blade is in a state of partial damage, that is, when one of the two tool blades is broken and the other is normal, the frequency band of the tool blade is the same as that of the spindle, and the vibration value corresponding to the spindle frequency band can be the maximum value.

[0128] Or when both tool blades are severely worn, the size and shape of the tool blade are severely damaged, and even if the tool blade participates in the cutting process, the change in the vibration magnitude of the vibration value of the tool blade will be very obvious.

[0129] Therefore, compared with the variation range of the tool blade vibration value when the tool blade is in a normal state or a slightly worn state, the variation range of the tool blade vibration value when the wear state is serious will be very obvious.

[0130] When this formula is satisfied, it can be determined that the tool has been used for a time equivalent to the dangerous time (t3), and is at a dangerous level where the tool may break at any time, requiring the operator to quickly replace the tool.

[0131] When the following [Formula 6] and [Formula 7] are satisfied, the tool state determination unit 600 may determine that the tool is completely broken.

[0132] [Formula 6]

[0133] (Other frequency vibration values ​​and tool blade vibration values) ≤ spindle vibration value,

[0134] [Formula 7]

[0135] Det_n=Round(To l / f_z), the number of consecutive tool breakage diagnosis is greater than Det_n,

[0136] Where Det_n is the number of times the tool is sensed to be defective, Tol is the tolerance, f_z is the feed rate per unit tool blade, and Round is the rounded integer.

[0137] The specific description is as follows: considering the feed rate of the unit tool blade, when abnormal cutting of the tool occurs continuously and causes the product to exceed the allowable tolerance range, it can be determined that the tool is in a bad state.

[0138] For example, when the tolerance of the cut material (To l) = ±0.1, the spindle RPM (rotations per minute) = 6000 RPM, and the feed rate of the unit tool blade (f_z) = 0.05, when the number of abnormal tool blade processing times sensed is more than two consecutive times, it can be determined that the condition is poor.

[0139] In addition, since the tool cannot cut the material when it is damaged, the tool blade vibration value and the other frequency vibration values ​​may be less than or equal to the spindle vibration value.

[0140] Figure 5 4 is a flow chart of a system for diagnosing and predicting the status of a CNC machining tool according to an embodiment of the present invention.

[0141] like Figure 5 As shown, the sequence of the diagnostic method for CNC machining tool status may include a vibration data generating step S10, a spindle vibration extracting step S20, a tool blade vibration extracting step S30, other frequency vibration extracting step S40, a vibration reference storing step S50 and a tool status determining step S60.

[0142] The vibration data generating step S10 uses the vibration sensor 100 to sense tool vibration generated during CNC machining and generates vibration data.

[0143] The vibration data may be a graph representing the magnitude of vibration sensed at each frequency.

[0144] The spindle vibration extraction step S20 can extract the vibration magnitude of the corresponding spindle frequency band, ie, the spindle vibration value, by analyzing the vibration data.

[0145] Specifically, the vibration generated by the spindle during machining occurs in a specific frequency, namely, a spindle frequency band. The spindle vibration extraction step S20 can extract the vibration magnitude corresponding to the spindle frequency band, namely, the spindle vibration value, from the vibration data.

[0146] The tool blade vibration extraction step S30 can extract the vibration magnitude corresponding to the tool blade frequency band, ie, the tool blade vibration value, by analyzing the vibration data.

[0147] The specific description is as follows: the vibration frequency generated by the tool blade during processing appears in a specific frequency, namely, the tool blade frequency band. The tool blade vibration extraction step S30 can extract the vibration magnitude corresponding to the tool blade frequency band, namely, the tool blade vibration value, from the vibration data.

[0148] The other frequency vibration extraction step S40 may extract vibration magnitudes of frequency bands other than the frequency bands corresponding to the spindle and the tool blade, ie, other frequency vibration values, from the vibration data.

[0149] That is, the other frequency vibration extraction step S40 can sense the vibration number of most parts such as the CNC equipment housing and the vibration size generated when the tool processes the cut material due to other reasons except the rotary cutting of the tool blade when the tool blade is severely worn.

[0150] It can also sense vibrations related to chattering, which is the vibration of the tool body or tool blade due to a strong external force other than the rotary cutting of the tool blade.

[0151] The vibration reference storing step S50 may store the vibration value of the tool blade generated when the tool blade is in a normal state as a vibration reference value.

[0152] Specifically described below, as a method of setting a reference value for determining the abnormal state of a tool blade from the vibration data sensed by the sensing sensor, the vibration data sensed when the tool blade in a normal state is processing the cut material and high-quality processing is being performed can be set as a vibration reference value.

[0153] The tool state determining step S60 may determine the state of the tool blade by analyzing the spindle vibration value, the tool blade vibration value, the other frequency vibration values, and the vibration reference value.

[0154] Specifically, the determination can be made by checking which vibration value is greater among the spindle vibration value, the tool blade vibration value, the vibration value of another frequency, and the vibration reference value.

[0155] In the tool state determining step S60 , when the spindle vibration value is greater than the other frequency vibration values ​​and the tool blade vibration value is greater than the spindle vibration value, it can be determined that the cutting process is being performed.

[0156] Furthermore, when the tool blade vibration value is within the error range of the vibration reference value at a 95% confidence level, it can be determined that the condition of the tool blade is normal and high-quality machining is being performed.

[0157] This is because when the tool blade is in a normal state and is cutting the material, only the tool blade is used for cutting processing, so the vibration generated by the tool blade can have the maximum vibration magnitude in the frequency band corresponding to the vibration.

[0158] Therefore, since only the tool blade is involved in the cutting process, the load on the spindle does not increase, and the CNC processing equipment only generates general vibrations having a vibration magnitude smaller than the vibration value of the tool blade.

[0159] In the tool state determining step S60 , when the spindle vibration value is greater than the other frequency vibration value, the tool blade vibration value is greater than the spindle vibration value, and the tool blade vibration value is greater than the vibration reference value, it can be determined that wear of the tool blade is occurring.

[0160] This is because the vibration magnitude increases when the tool blade is in a worn state compared to when the tool blade is in a normal state, and thus the tool blade vibration value may be greater than the vibration reference value.

[0161] In the tool state determination step S60 , when the other frequency vibration value is greater than the vibration reference value and the tool blade vibration value, it can be determined that wear of the tool blade is occurring and the machining state is intermittently poor.

[0162] This is because the tool blade vibration value is large when normal cutting is performed when the tool blade is significantly worn, and the maximum value occurs in the other frequency vibration values ​​when abnormal cutting is performed.

[0163] Therefore, the vibration value of the other frequencies may be greater than the vibration reference value and the vibration value of the tool blade in a normal state or a state where partial wear occurs.

[0164] The tool state determination step S60 can determine that the tool blade is worn and the processing state is poor when the spindle vibration value is greater than the tool blade vibration value, and the sensed tool blade vibration value is greater than the variation range of the vibration reference value and the variation range of the tool blade vibration value when the tool blade is partially worn.

[0165] This is because when the machining process is continued in a state where the tool blade is severely worn, there will be a mixture of a situation where the spindle vibration value is greater than the tool blade vibration value and a situation where the tool blade vibration value is the largest.

[0166] Therefore, when the tool blade is severely worn, the size and shape of the tool blade are severely damaged. Even if the tool blade participates in the cutting process, the vibration magnitude of the tool blade vibration value will vary significantly. Therefore, compared with the range of variation of the tool blade vibration value when the tool blade is in a normal state or slightly worn state, the range of variation of the tool blade vibration value when the wear state is severe will be very obvious.

[0167] The tool state determination step S60 determines that the tool state is bad when the spindle vibration value is greater than the other frequency vibration values ​​and the tool blade vibration value, and taking into account the feed rate of the unit tool blade, when abnormal cutting of the tool occurs continuously and causes the product to exceed the allowable tolerance range.

[0168] For example, when the tolerance of the cut material (To l) = ±0.1, the spindle RPM (rotations per minute) = 6000 RPM, and the feed rate of the unit tool blade (f_z) = 0.05, when the number of abnormal tool blade processing times sensed is more than two times in a row, it can be determined that the condition is bad.

[0169] The present invention has been described above with reference to the embodiments shown in the accompanying drawings. However, this is for illustrative purposes only. It is understood that persons skilled in the art will readily appreciate that various modifications may be made based on this description, and that all or part of the embodiments described may be selectively combined. Therefore, the true scope of protection of the present invention shall be determined by the technical principles of the appended claims.

[0170] Industrial Applicability

[0171] The present invention relates to a CNC tool life prediction system. More specifically, by comparing and analyzing the vibration magnitudes generated by the spindle and tool blade from the vibration data generated during machining and determining the condition of the tool, the time until the tool breaks can be predicted. This invention can be regarded as a very beneficial invention in industrial production.

Claims

1. A CNC tool life prediction system, characterized in that: The CNC tool life prediction system includes: Vibration sensor, used to sense tool vibration generated during CNC machining and generate vibration data; a state determination module for determining the wear state and processing state of the tool blade in a specific time period based on the vibration data; A database for storing tool life, wherein the tool life includes normal time when the tool is working normally and dangerous time when the tool is worn and not working normally; and The life calculation unit recalculates the tool life by comparing the tool usage time with the tool life when the state determination module determines that the working state of the tool is abnormal.

2. The CNC tool life prediction system according to claim 1, characterized in that: The life calculation unit is configured to subtract a difference between the usage time and the normal time from the tool life when the usage time at the abnormal time point when the tool is abnormal is less than the normal time.

3. The CNC tool life prediction system according to claim 2, characterized in that: The life calculation unit is configured to subtract the dangerous time in proportion to the difference between the usage time and the normal time.

4. The CNC tool life prediction system according to claim 1, characterized in that: The state determination module includes: A spindle vibration extraction unit extracts the vibration magnitude corresponding to the spindle frequency band, i.e., the spindle vibration value, by analyzing the vibration data; a tool blade vibration extraction unit, which extracts the vibration magnitude of the frequency band corresponding to the tool blade, namely, the tool blade vibration value, by analyzing the vibration data; Other frequency vibration extraction unit extracts the vibration magnitude of the frequency band other than the frequency band corresponding to the spindle and the tool blade, that is, other frequency vibration values, from the vibration data; A database is used to store the vibration value of the tool blade generated when the tool blade is in a normal state as a vibration reference value; and The tool state determination unit determines the state of the tool blade by analyzing the spindle vibration value, the tool blade vibration value, other frequency vibration values ​​and the vibration reference value.

5. The CNC tool life prediction system according to claim 4, characterized in that: The tool state determination unit is used to determine the vibration magnitude when the tool blade and the machining state are normal and the tool is working normally, and is calculated by the following [Formula 1]: [Formula 1] Other frequency vibration value < spindle vibration value < tool blade vibration value = vibration reference value z, Wherein, vibration reference value z: the error range of the vibration reference value at a 95% confidence level.

6. The CNC tool life prediction system according to claim 4, characterized in that: The tool state determination unit is used to determine the vibration magnitude of the tool when the tool blade is partially worn and the machining state is normal and the tool is working normally, which is calculated by the following [Formula 2]: [Formula 2] Other frequency vibration values ​​< spindle vibration value < vibration reference value < tool blade vibration value.

7. The CNC tool life prediction system according to claim 4, characterized in that: The tool state determination unit is used to determine the vibration magnitude during abnormal operation of the tool when the tool blade is worn and the machining state is intermittently poor, which is calculated by the following [Formula 3]: [Formula 3] (Vibration reference value < other frequency vibration values) OR (Tool blade vibration value < other frequency vibration values).

8. The CNC tool life prediction system according to claim 4, wherein: The tool state determination unit is used to determine the vibration magnitude during abnormal operation of the tool when the tool blade is worn and the machining state is poor, which is calculated by the following [Formula 4] and [Formula 5]: [Formula 4] Tool blade vibration value ≤ spindle vibration value, [Formula 5] dev vibration reference value < dev(A) tool blade vibration value < dev(B) tool blade vibration value, where, dev vibration reference value: the variation range of the tool blade band vibration magnitude calculated when the tool blade is normal and the machining state is normal; dev(A) tool blade vibration value: the variation range of the tool blade band vibration magnitude calculated when the tool blade is partially damaged and the machining state is normal; dev(B) tool blade vibration value: the variation range of the current tool blade band vibration magnitude.

9. The CNC tool life prediction system according to claim 4, wherein: The tool state determination unit is used to determine the vibration magnitude when the tool blade state is damaged, which is calculated by the following [Formula 6] and [Formula 7]: [Formula 6] (Other frequency vibration value and tool blade vibration value) ≤ spindle vibration value, [Formula 7] Det_n = Round(Tol / f_z), the continuous number of times of tool breakage diagnosis is greater than Det_n, where, Det_n: the number of times of sensing whether the tool is defective; Tol: tolerance; f_z: the feed per unit tool blade; Round: the integer after rounding.

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