CNC tool life prediction system

Abstract

The present invention relates to a CNC tool life prediction system including: a vibration sensor for sensing vibrations that a tool generates during CNC machining and generating vibration data; a state determination unit for determining a tool blade wear state and a machining state for a specific period through the vibration data; a database in which is stored a tool life including a normal time during which the tool operates normally and a dangerous time during which the tool becomes worn and operates abnormally; and a life calculation unit for re-calculating the tool life by comparing the use time of the tool and the tool life when the operation state of the tool is determined to be abnormal by the state determination unit.

Description

CNC tool life prediction system

[0001] The present invention relates to a system for predicting the life of a CNC tool, and more specifically, to a CNC tool life prediction system that compares and analyzes the vibration magnitude generated from a spindle and a tool blade from vibration data generated during processing to determine the condition of the tool and predicts the time until the tool breaks.

[0002] In general, for milling machines that perform cutting operations using tools, in order to maintain the quality of the workpiece, the cutting tool is used a certain number of times and then replaced with a new tool even if it is not broken.

[0003] This means that if a tool breaks during cutting and the cutting process continues without being recognized, the quality of the workpiece will deteriorate, the workpiece material will be wasted, and various problems such as damage to the machine tool due to abnormal vibration will occur.

[0004] In addition, because of these problems, replacing cutting tools that have been used a certain number of times also results in the replacement of cutting tools that are capable of normal processing, which leads to the problem of tool waste and reduced efficiency.

[0005] Therefore, in order to solve these problems, in the past, when an abnormal signal was generated from the sensor, the operator directly judged and replaced the tool, but it was difficult for the operator to accurately judge this point in time, and since one breakage detection setting value was set for each process performed with one tool, there was a problem of false detection in response to momentary size changes unrelated to breakage occurring during processing.

[0006] Furthermore, if the operator arbitrarily inputs breakage detection settings based on reference data, reliability may be low, leading to problems such as recognizing a normal tool as broken or failing to recognize a broken tool even when it is in a broken state. Furthermore, since the magnitude of the vibration acceleration signal varies depending on the processing conditions and environment, the operator must manually set the detection area reference value based on reference data each time before processing, which is a repetitive task that reduces productivity and accessibility.

[0007] Korean Patent No. 10-2580409 is a method for detecting wear or breakage of a tool in real time by converting the vibration acceleration signal of a rotating tool for cutting work. The vibration acceleration signal of the tool is received, a fast Fourier transform is performed to derive a frequency signal, and if a frequency greater than a reference value is detected, an abnormality of the tool is determined. However, the standard is unclear and it is difficult to accurately determine the problem.

[0008] Japanese Patent No. 5543890 sets a threshold by adding a preset coefficient to the maximum value of a frequency analysis waveform, and determines that an abnormality has occurred during processing if the frequency analysis waveform generated during processing is larger than the preset threshold value. However, there is a problem in that it is difficult to accurately determine the condition of the tool simply by using only the threshold value.

[0009] The purpose of the present invention is to provide a tool life prediction system that analyzes vibration data generated during processing in CNC cutting processing equipment to check the condition of the tool blade, thereby enabling efficient use of the tool blade and predicting the life of the tool to minimize damage to the workpiece.

[0010] The present invention may include a vibration sensor that detects the vibration of a tool occurring during CNC machining and generates vibration data, a status judgment module that judges the wear condition of a tool blade and the machining condition at a specific time period through the vibration data, a database that stores the tool life, which includes a normal time when the tool operates normally and a dangerous time when the tool is worn and operates abnormally, and a life calculation unit that compares the usage time of the tool with the tool life and recalculates the tool life when the status judgment unit judges that the operating condition of the tool is abnormal.

[0011] The above life calculation unit may reduce the tool life by the difference between the usage time and the normal time when the tool has an abnormality and the usage time at the abnormal time is shorter than the normal time.

[0012] The above life calculation unit can reduce the risk time in proportion to the difference between the usage time and the normal time.

[0013] The above-mentioned state judgment module may include a spindle vibration extraction unit that analyzes the vibration data to extract a spindle vibration value, which is a vibration magnitude in a frequency band corresponding to a spindle, a tool blade vibration extraction unit that analyzes the vibration data to extract a tool blade vibration value, which is a vibration magnitude in a frequency band corresponding to a tool blade, an other-frequency vibration extraction unit that extracts an other-frequency vibration value, which is a vibration magnitude in a frequency band excluding the frequency bands corresponding to the spindle and the tool blade from the vibration data, a database that stores the tool blade vibration value that occurs when the tool blade is in a normal state as a vibration reference value, and a tool state judgment unit that analyzes the spindle vibration value, the tool blade vibration value, the other-frequency vibration value, and the vibration reference value to determine the state of the tool blade.

[0014] The vibration magnitude at which the tool blade and processing status are judged to be normal and the tool is operating normally in the above tool condition judgment unit can be calculated using the following [Formula 1].

[0015] [Formula 1]

[0016] Frequency vibration value < Spindle vibration value < Tool blade vibration value = Vibration reference value z

[0017] (Here, vibration reference value z: error range of vibration reference value at 95% confidence level)

[0018] The vibration magnitude at which the tool condition judgment unit determines that a part of the tool blade is worn and the machining condition is normal and the tool is operating normally can be calculated using the following [Formula 2].

[0019] [Formula 2]

[0020] Frequency vibration value < Spindle vibration value < Vibration reference value < Tool blade vibration value

[0021] The vibration magnitude at which the tool condition judgment unit determines that the tool blade is worn and the machining condition is poor and the tool is operating abnormally can be calculated using the following [Formula 3].

[0022] [Formula 3]

[0023] (Vibration reference value < other frequency vibration value) AND (tool blade vibration value < other frequency vibration value)

[0024] The vibration magnitude at which the tool condition judgment unit determines that the tool is operating abnormally due to wear of the tool blade and poor machining condition can be calculated using the following [Equation 4] and [Equation 5].

[0025] [Formula 4]

[0026] Tool blade vibration value ≤ spindle vibration value

[0027] [Formula 5]

[0028] dev vibration standard value < dev(A) tool blade vibration value < dev(B) tool blade vibration value

[0029] (Here, dev vibration reference value: tool blade frequency band vibration size fluctuation range calculated when the tool is normal and machining is normal, dev(A) tool blade vibration value: tool blade frequency band vibration size fluctuation range calculated when a part of the tool blade is worn and machining is normal, dev(B) tool blade vibration value: current tool blade frequency band vibration size fluctuation range)

[0030] The vibration magnitude for determining whether the tool blade is damaged in the above tool condition judgment unit can be calculated using the following [Equation 6] and [Equation 7].

[0031] [Formula 6]

[0032] (Other frequency vibration value AND tool blade vibration value) ≤ spindle vibration value

[0033] [Formula 7]

[0034] Det_n=Round(Tol / f_z), the number of consecutive tool breakage diagnoses exceeds Det_n.

[0035] (Here, Det_n: number of times tool defects are detected, Tol: tolerance, f_z: feed per tool blade, Round: rounded integer)

[0036] The present invention has the effect of accurately identifying the condition of a tool blade by comparing and analyzing the vibration size by frequency that occurs during processing.

[0037] Figure 1 is a block diagram of a CNC machining tool status diagnosis and prediction system according to an embodiment of the present invention.

[0038] FIG. 2 is a drawing showing a method for predicting the tool blade life of an area setting unit according to an embodiment of the present invention.

[0039] Figure 3 is a drawing showing normal vibration data of a tool blade according to an embodiment of the present invention.

[0040] Figure 4 is a diagram showing vibration data caused by an abnormal tool blade according to an embodiment of the present invention.

[0041] Figure 5 is a flowchart of a CNC machining tool status diagnosis and prediction system according to an embodiment of the present invention.

[0042]

[0043] 100: Vibration sensor 200: Spindle vibration extraction unit

[0044] 300: Tool blade vibration extraction unit 400: Other frequency vibration extraction unit

[0045] 500: Database 600: Tool status judgment unit

[0046] 700: Life expectancy calculation department

[0047] S10: Vibration data generation step S20: Spindle vibration extraction step

[0048] S30: Tool blade vibration extraction stage S40: Other frequency vibration extraction stage

[0049] S50: Vibration standard storage stage S60: Tool status judgment stage

[0050] Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the attached drawings.

[0051] The advantages and features of the present invention and the method for achieving them will become clear with reference to the embodiments described in detail below together with the attached drawings.

[0052] However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and the present embodiments are provided only to make the disclosure of the present invention complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims.

[0053] In addition, when describing the present invention, if it is determined that related known technologies or the like may obscure the gist of the present invention, a detailed description thereof will be omitted.

[0054] FIG. 1 is a block diagram of a CNC tool condition diagnosis and prediction system according to an embodiment of the present invention, FIG. 2 is a diagram showing a method for predicting the tool blade life of an area setting unit according to an embodiment of the present invention, FIG. 3 is a diagram showing vibration data of a normal tool blade according to an embodiment of the present invention, and FIG. 4 is a diagram showing vibration data of a worn tool blade according to an embodiment of the present invention.

[0055] As shown in Fig. 1, it may include a vibration sensor (100), a state judgment module (20), a database (500), and a life calculation unit (700).

[0056] The above vibration sensor (100) can be installed in a CNC machining device to detect vibrations generated during cutting processing and generate vibration data.

[0057] The above vibration data may be a graph showing the magnitude of vibration detected at each frequency.

[0058] The above database (500) can store the tool life (t1) calculated by predicting the life of the tool blade through the status judgment module (20).

[0059] To explain in detail, the average time until multiple tool blades used in cutting processing are replaced and broken can be set as the tool life.

[0060] The above tool life (t1) may vary depending on the size, shape, material, etc. of the tool blade.

[0061] As shown in Fig. 2, the life calculation unit (700) can set the normal time (t2), the dangerous time (t3), and the dangerous time point (w1) in the tool life (t1).

[0062] Figure 2 shows the tool life of a general tool blade (a), the normal time, the risk time and the wear point of a general tool blade (b), and the tool life, the normal area and the risk area (c) of a defective tool blade.

[0063] The above normal time (t2) may be the time during which the tool operates normally with the wear condition of the tool blade and the processing condition of the workpiece determined to be normal by the above condition judgment module (20).

[0064] To explain in detail, as shown in Fig. 2, the tool life (t1) of the tool blade is a time during which the tool blade is not severely worn and no defects occur in the cutting process of the workpiece, and the average time can be extracted from a number of tool lives and set as the normal time (t2).

[0065] The above risk time (t3) may be a time when the tool operates abnormally due to poor wear of the tool blade and poor machining condition of the workpiece in the above condition judgment module (20).

[0066] To explain in detail, as shown in Fig. 2, the time from the time the tool starts to operate abnormally until the tool breaks can be set as the risk time (t3).

[0067] This means that during the above-mentioned risk time (t3), the wear of the tool blade is severe and the defects of the workpiece during cutting processing increase, which may increase the probability of the tool blade being broken.

[0068] The above-mentioned risk time (w1) can be set as the boundary point between the normal time (t2) and the risk time (t3) in the above-mentioned tool life.

[0069] The above life calculation unit (700) can reduce the tool life (t1) by the difference between the use time at the abnormal time (w2) and the normal time (t2) when the tool usage time at the abnormal time (w2) when an abnormality occurs in the tool is shorter than the normal time (t2).

[0070] To explain in detail, when a defective tool blade is used for cutting work rather than a normal tool blade, 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 point in time when an abnormality occurs in the defective tool blade can be set as the abnormal time (w2).

[0071] Accordingly, the correction time (t4), which is the interval between the general normal time (t2) and the special normal area (t'2, t2 > t'2), that is, the time from the above-mentioned dangerous point (w1) to the above-mentioned abnormal point (w2), can be calculated.

[0072] The above life calculation unit (700) can calculate the ratio of the correction time (t4) to the general normal time (t2) and apply the ratio to the risk time (t3, t3 > t'3) to reduce it.

[0073] To explain in detail, a defective tool blade has a tool life shorter than the predicted tool life (t1), and the tool life (t1) can be reduced by applying the proportion of the compensation time (t4) to the risk time (t3) to predict a reduced tool life (t'2, t'3).

[0074] For example, when 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 (w2) occurs at 60 hours due to a tool defect, the difference of 20 hours between the normal time (t2) and the time at which the abnormal time (w2) occurs can be excluded from the tool life (t1) to reset the tool life to 80 hours.

[0075] In addition, the difference between the normal time (t2) and the time at which the abnormal time (w2) occurred, which is 20 hours, is applied to the risk time (t3) by 25%, which is the ratio of the normal time (t2), so that the risk time (t'3) due to tool defect can be predicted to be 15 hours, and the tool life can be reset to 75 hours.

[0076] This allows for accurate prediction of the tool life by reducing both the normal time (t2) and the risk time (t3), since the time until the tool breaks is also reduced when the normal usable time is reduced due to a tool defect.

[0077] Therefore, the life of the tool blade can be accurately predicted by predicting changes in the normal time (t2), the dangerous time (t3), and the abnormal time (w2) depending on the defective condition of the tool blade.

[0078] If it is included in the above risk time (t3), the user can be guided to replace the tool blade.

[0079] The above-mentioned status judgment module (20) may include a spindle vibration extraction unit (200), a tool blade vibration extraction unit (300), a frequency vibration extraction unit (400), and a tool status judgment unit (600).

[0080] The above spindle vibration extraction unit (200) can extract the vibration size of the frequency band corresponding to the spindle from the vibration data generated through the vibration sensor (100).

[0081] To explain in detail, the frequency of vibration occurring in the spindle during processing appears at a specific frequency, that is, in the spindle frequency band, so the spindle vibration extraction unit (200) can extract the spindle vibration value, which is the vibration magnitude corresponding to the spindle frequency band, from the vibration data.

[0082] The tool blade vibration extraction unit (300) can extract the vibration size of the frequency band corresponding to the tool blade from the vibration data generated through the vibration sensor (100).

[0083] To explain in detail, the frequency of vibration generated from the tool blade during processing appears in a specific frequency, that is, a tool blade frequency band, so the tool blade vibration extraction unit (300) can extract a tool blade vibration value, which is a vibration magnitude corresponding to the tool blade frequency band, from the vibration data.

[0084] In addition, the tool blade frequency band changes depending on the number of tool blades, so the tool blade vibration extraction unit (300) can set the tool blade frequency band by inputting the number of tool blades to be used in advance.

[0085] The above-mentioned frequency vibration extraction unit (400) can extract the vibration magnitude of a frequency band excluding the spindle frequency band and the tool blade frequency band.

[0086] That is, the above-mentioned frequency vibration extraction unit (400) can detect the vibration size that occurs when the tool processes the workpiece due to factors other than cutting by rotation of the tool blade due to severe wear of the tool blade and the vibration frequency of a number of parts such as a CNC tool equipment case.

[0087] In cases where cutting is not caused by the rotation of the tool blade, the vibration size can be detected in relation to the chatter phenomenon, which is a phenomenon in which the tool body or tool blade vibrates when subjected to a large external force.

[0088] The above database (500) can store the tool blade vibration value that occurs when the tool blade is in a normal state as a vibration reference value.

[0089] To explain in detail, the method of setting a reference value for determining an abnormal state of a tool blade from the vibration data detected through the detection sensor can be such that the vibration data detected when a workpiece is processed through a normal tool blade and high-quality processing is in progress can be set as a vibration reference value.

[0090] The above tool condition judgment unit (600) can judge the condition of the tool blade by comparing and analyzing the spindle vibration value, the tool blade vibration value, the other frequency vibration value, and the vibration reference value.

[0091] To explain in detail, it is possible to determine which vibration value is larger among the spindle vibration value, the tool blade vibration value, the other frequency vibration value, and the vibration reference value.

[0092] The above tool condition judgment unit (600) can determine that the condition of the tool blade is normal and that high-quality processing is in progress when the following [Formula 1] is satisfied.

[0093] [Formula 1]

[0094] Frequency vibration value < Spindle vibration value < Tool blade vibration value = Vibration reference value z

[0095] Here, the vibration reference value z may fall within the error range occurring at a 95% confidence level from the vibration reference value.

[0096] That is, when looking at the vibration data detected under the CNC machining process conditions according to the embodiment of the present invention as illustrated in FIG. 3, the frequency generated when the tool blade cuts the workpiece (material or product) is 200 Hz, and the largest vibration size can occur in that frequency band.

[0097] This is because when the tool blade is in a normal state, cutting is performed using only the tool blade when cutting the workpiece, so the vibration level is the largest in the frequency band corresponding to the vibration generated from the tool blade.

[0098] Therefore, since only the tool blade is involved in cutting, the load on the spindle does not increase, and the CNC machining equipment only generates general vibrations, so it can have a vibration level lower than the tool blade vibration value.

[0099] And the above-mentioned frequency vibration value may be less than the size of the spindle vibration value generated from the above-mentioned spindle.

[0100] In addition, in order to determine the normal state of the tool blade, it is possible to determine whether the tool blade vibration value of the current cutting process is similar to the vibration reference value.

[0101] If the above tool blade vibration value differs from the above vibration standard value by a preset value or more, it can be determined that there is a change in the tool blade.

[0102] The above tool condition judgment unit (600) can determine that a part of the tool blade is worn but quality processing is in progress when the following [Formula 2] is satisfied.

[0103] [Formula 2]

[0104] Frequency vibration value < Spindle vibration value < Vibration reference value < Tool blade vibration value

[0105] To explain in detail, when looking at the vibration data above under CNC machining process conditions, the tool blade is worn more than in the normal state, but the frequency generated when cutting the workpiece is maintained at 200 Hz, and the vibration size in that frequency band can be the largest.

[0106] In addition, the vibration magnitude when the tool blade is in a worn state increases compared to when the tool blade is in a normal state, so the tool blade vibration value may have a value greater than the vibration reference value.

[0107] The above tool condition judgment unit (600) can determine that the tool blade is worn and a poor processing condition is occurring intermittently when the following [Formula 3] is satisfied.

[0108] [Formula 3]

[0109] (Vibration reference value < other frequency vibration value) OR (Tool blade vibration value < other frequency vibration value)

[0110] In this state, the tool blade may be significantly worn and the tool blade vibration value of the tool blade performing cutting may be large, and the highest value may occur in the other frequency vibration value due to abnormal cutting.

[0111] To explain in detail, as shown in Fig. 3, when looking at the vibration data under CNC machining process conditions, the wear of the tool blade becomes severe, and there may be cases where the tool processes the workpiece due to factors other than cutting by rotation of the tool blade.

[0112] For example, the vibration size of other frequency bands may increase due to chatter, which is a phenomenon in which the tool body or tool blade vibrates when subjected to a large external force.

[0113] Therefore, as can be seen in Fig. 4, the vibration reference value, which is the vibration size of the frequency corresponding to the tool blade, and the other frequency vibration value are greater than the tool blade vibration value at 700 Hz, and it can be determined that the tool blade is significantly worn.

[0114] If the above formula is satisfied, it can be determined that the tool has been used for the above-mentioned dangerous time (t3), and it can be determined that it is still at a warning level requiring the operator's attention.

[0115] The above tool condition judgment unit (600) can determine that the tool blade is partially damaged and a major defect in the processing condition occurs when the following [Formula 4] and [Formula 5] are satisfied.

[0116] [Formula 4]

[0117] Tool blade vibration value ≤ spindle vibration value

[0118] [Formula 5]

[0119] dev vibration standard value < dev(A) tool blade vibration value < dev(B) tool blade vibration value

[0120] Here, the dev vibration reference value can represent the range of variation in which the vibration reference value changes when the tool blade is normal and quality processing is in progress.

[0121] The dev(A) tool blade vibration value can indicate the range of variation in which the tool blade vibration value changes when a part of the tool blade is worn and processing is normal.

[0122] The dev(B) tool blade vibration value can indicate the range of variation in which the tool blade vibration value changes when the tool blade is severely worn and processing is abnormal.

[0123] To explain in detail, when the machining process continues while the tool blade is severely worn, cases where the spindle vibration value is greater than the tool blade vibration value and cases where the tool blade vibration value is the greatest may coexist.

[0124] For example, when the tool blade is partially broken, that is, when one of the two tool blades is broken and the other is in a normal tool state, the frequency band of the tool blade and the frequency band of the spindle are the same, so the spindle vibration value corresponding to the spindle frequency band may have the largest value.

[0125] Or, if both tool blades are severely worn, the size and shape of the tool blade may be seriously damaged, so that even if the tool blade participates in the cutting process, the vibration magnitude of the tool blade vibration value may vary greatly.

[0126] Accordingly, the range of variation of the tool blade vibration value when the tool blade is in a serious state of wear may be greater than the range of variation of the tool blade vibration value when the tool blade is in a normal state or when the wear state is less.

[0127] If the equation is satisfied, the tool has been used for the above-mentioned risk time (t3), and it can be judged that the tool has been used at a risk level where it is not known when the tool will break, and the worker must quickly replace the tool.

[0128] The above tool condition judgment unit (600) can determine that the tool is completely broken if the following [Formula 6] and [Formula 7] are satisfied.

[0129] [Formula 6]

[0130] (Other frequency vibration value AND tool blade vibration value) ≤ spindle vibration value

[0131] [Formula 7]

[0132] Det_n=Round(Tol / f_z), the number of consecutive tool breakage diagnoses exceeds Det_n.

[0133] Here, Det_n is the number of times tool defects are detected, Tol is the allowable tolerance, f_z is the feed per tool edge, and Round can be a rounded integer.

[0134] To elaborate, when abnormal cutting of the tool occurs continuously by considering the feed per tool blade and the product goes beyond the allowable tolerance range, the tool can be judged to be defective.

[0135] For example, if the allowable tolerance of the workpiece (Tol) = ±0.1, the spindle RPM (revolutions per minute) = 6000 RPM, and the feed per tool edge (f_z) = 0.05, if an abnormal number of tool edge processing operations is detected twice or more consecutively, it can be judged as a defective state.

[0136] In addition, if the tool is broken, the cutting of the workpiece does not proceed, so the tool blade vibration value and the other frequency vibration value may be lower than the spindle vibration value.

[0137] Figure 5 is a flowchart of a CNC machining tool status diagnosis and prediction system according to an embodiment of the present invention.

[0138] As illustrated in Fig. 5, the sequence of a method for diagnosing the status of a CNC machining tool may include a vibration data generation step (S10), a spindle vibration extraction step (S20), a tool blade vibration extraction step (S30), a different frequency vibration extraction step (S40), a vibration reference storage step (S50), and a tool status judgment step (S60).

[0139] The above vibration data generation step (S10) can generate vibration data by detecting tool vibration occurring during CNC machining using a vibration sensor (100).

[0140] The above vibration data may be a graph showing the magnitude of vibration detected at each frequency.

[0141] The above spindle vibration extraction step (S20) can analyze the vibration data to extract the spindle vibration value, which is the vibration magnitude of the frequency band corresponding to the spindle.

[0142] To explain in detail, since the vibration occurring in the spindle during processing appears at a specific frequency, i.e., in the spindle frequency band, the spindle vibration extraction step (S20) can extract the spindle vibration value, which is the vibration size corresponding to the spindle frequency band, from the vibration data.

[0143] The above tool blade vibration extraction step (S30) can analyze the vibration data to extract the tool blade vibration value, which is the vibration magnitude of the frequency band corresponding to the tool blade.

[0144] To explain in detail, since it appears in the tool blade frequency band, which is a specific frequency of vibration generated from the tool blade during processing, the tool blade vibration extraction step (S30) can extract the tool blade vibration value, which is the vibration magnitude corresponding to the tool blade frequency band, from the vibration data.

[0145] The above-mentioned off-frequency vibration extraction step (S40) can extract an off-frequency vibration value, which is a vibration magnitude of a frequency band excluding a frequency band corresponding to the spindle and the tool blade, from the vibration data.

[0146] That is, the above-mentioned frequency vibration extraction step (S40) can detect the vibration size that occurs when the tool processes the workpiece due to factors other than cutting by rotation of the tool blade due to severe wear of the tool blade and the vibration frequency of multiple parts such as the CNC equipment case.

[0147] In cases where cutting is not caused by the rotation of the tool blade, the vibration size can be detected in relation to the chatter phenomenon, which is a phenomenon in which the tool body or tool blade vibrates when subjected to a large external force.

[0148] The above vibration standard storage step (S50) can store the tool blade vibration value that occurs when the tool blade is in a normal state as a vibration standard value.

[0149] To explain in detail, the vibration data detected by the detection sensor is a method of setting a reference value for judging an abnormal state of the tool blade, and the vibration data detected when a workpiece is processed by a normal tool blade and high-quality processing is in progress can be set as a vibration reference value.

[0150] The above tool condition judgment step (S60) can determine the condition of the tool blade by analyzing the spindle vibration value, the tool blade vibration value, the other frequency vibration value, and the vibration reference value.

[0151] To explain in detail, it is possible to determine which vibration value is larger among the spindle vibration value, the tool blade vibration value, the other frequency vibration value, and the vibration reference value.

[0152] The above tool condition judgment step (S60) can determine that cutting is taking place when the spindle vibration value is greater than the other frequency vibration value and the tool blade vibration value is greater than the spindle vibration value.

[0153] In addition, if the tool blade vibration value is within the error range occurring at a 95% confidence level from the vibration reference value, it can be determined that the condition of the tool blade is normal and high-quality processing is in progress.

[0154] This is because when the tool blade is in a normal state, cutting is performed using only the tool blade when cutting the workpiece, so the vibration level can be the largest in the frequency band corresponding to the vibration generated from the tool blade.

[0155] Therefore, since only the tool blade is involved in cutting, the load on the spindle does not increase, and the CNC machining equipment only generates general vibrations, so it can have a vibration level lower than the tool blade vibration value.

[0156] The above tool condition judgment step (S60) can determine that wear of the tool blade is in progress 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.

[0157] This means that the vibration magnitude when the tool blade is in a worn state increases compared to when the tool blade is in a normal state, so the tool blade vibration value may have a value greater than the vibration reference value.

[0158] In the above tool condition judgment step (S60), if the other frequency vibration value is greater than the vibration reference value and the tool blade vibration value, it can be determined that the tool blade is wearing out and the machining condition is poor.

[0159] This may occur in a mixed manner, where the tool blade is significantly worn and the tool blade performs normal cutting, and the tool blade performs abnormal cutting, resulting in the highest value among the above-mentioned non-frequency vibration values.

[0160] Therefore, the above-mentioned frequency vibration value may be greater than the vibration reference value of the tool blade and the tool blade vibration value when in a normal state or a partially worn state.

[0161] In the above tool condition judgment step (S60), if the spindle vibration value is greater than the tool blade vibration value and the vibration reference value fluctuation range and the tool blade wear are partially advanced, and the detected tool blade vibration value is greater than the fluctuation range of the tool blade vibration value, it can be determined that the tool blade is worn and the machining condition is poor.

[0162] This may occur in a mixed manner, where the spindle vibration value is greater than the tool blade vibration value when the machining process continues while the tool blade is severely worn, and where the tool blade vibration value is the greatest.

[0163] Accordingly, when the tool blade is severely worn, the size and shape of the tool blade are seriously damaged, and even if the tool blade participates in the cutting process, the vibration magnitude of the tool blade vibration value varies greatly, so the range of variation of the tool blade vibration value when the tool blade is severely worn may be greater than the range of variation of the tool blade vibration value when the tool blade is in a normal state or when the wear state is slight.

[0164] The above tool condition judgment step (S60) can be used to determine that the tool is defective when the spindle vibration value is greater than the other frequency vibration value and the tool blade vibration value, abnormal cutting of the tool continuously occurs by considering the feed per tool blade, and the tool condition is outside the product's allowable tolerance range.

[0165] For example, if the allowable tolerance of the workpiece (Tol) = ±0.1, the spindle RPM (revolutions per minute) = 6000 RPM, and the feed per tool edge (f_z) = 0.05, if an abnormal number of tool edge processing operations is detected twice or more consecutively, it can be judged as a defective state.

[0166] Although the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary. Those skilled in the art will understand that various modifications may be made therefrom, and that all or part of the described embodiments may be selectively combined and configured. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

[0167] The present invention relates to a system for predicting the life of a CNC tool, and more specifically, it is an invention that is very useful industrially because it enables the condition of a tool to be determined and the time until the tool breaks to be predicted by comparing and analyzing the magnitude of vibration generated from a spindle and a tool blade from vibration data generated during processing.

Claims

1. A vibration sensor that detects tool vibration occurring during CNC machining and generates vibration data; A condition judgment module that judges the tool blade wear condition and processing condition at a specific time period through the above vibration data; A database storing the tool life, including the normal time during which the tool operates normally and the dangerous time during which the tool wears out and operates abnormally; and A CNC tool life prediction system including a life calculation unit that recalculates the tool life by comparing the tool usage time and the tool life when the operation status of the tool is determined to be abnormal in the above-mentioned status judgment module.

2. In paragraph 1, The above life calculation section is, A CNC tool life prediction system, characterized in that when the usage time at an abnormal point in time when an abnormality occurs in the tool is shorter than the normal time, the tool life is reduced by the difference between the usage time and the normal time.

3. In paragraph 2, The above life calculation section is, A CNC tool life prediction system characterized in that the risk time is reduced in proportion to the difference between the above-mentioned usage time and the above-mentioned normal time.

4. In paragraph 1, The above status judgment module is, A spindle vibration extraction unit that analyzes the above vibration data to extract a spindle vibration value, which is a vibration size of a frequency band corresponding to the spindle; A tool blade vibration extraction unit that analyzes the above vibration data and extracts a tool blade vibration value, which is a vibration magnitude of a frequency band corresponding to the tool blade; An off-frequency vibration extraction unit that extracts off-frequency vibration values, which are vibration magnitudes of a frequency band excluding the frequency bands corresponding to the spindle and tool blade, from the above vibration data; A database that stores the tool blade vibration value that occurs when the tool blade is in a normal state as a vibration reference value; and A CNC tool life prediction system including a tool condition judgment unit that analyzes the spindle vibration value, the tool blade vibration value, the other frequency vibration value, and the vibration reference value to judge the condition of the tool blade.

5. In paragraph 4, A CNC tool life prediction system in which the vibration magnitude at which the tool blade and processing status are judged to be normal and the tool is operating normally in the tool condition judgment section is calculated using the following [Formula 1]. [Formula 1] Frequency vibration value < Spindle vibration value < Tool blade vibration value = Vibration reference value z (Here, vibration reference value z: error range of vibration reference value at 95% confidence level) 6. In paragraph 4, A CNC tool life prediction system in which the vibration magnitude at which the tool condition judgment unit determines that a part of the tool blade is worn and the machining condition is normal and the tool is operating normally is calculated using the following [Formula 2]. [Formula 2] Frequency vibration value < Spindle vibration value < Vibration reference value < Tool blade vibration value 7. In paragraph 4, A CNC tool life prediction system in which the vibration magnitude at which the tool condition judgment unit determines that the tool blade is worn and the machining condition is poor and the tool is operating abnormally is calculated using the following [Formula 3]. [Formula 3] (Vibration reference value < other frequency vibration value) OR (tool blade vibration value < other frequency vibration value) 8. In paragraph 4, The vibration magnitude at which the tool condition judgment unit determines that the tool is operating abnormally due to wear of the tool blade and poor machining condition is calculated using the following [Formula 4] and [Formula 5] in the CNC tool life prediction system. [Formula 4] Tool blade vibration value ≤ spindle vibration value [Formula 5] dev vibration standard value < dev(A) tool blade vibration value < dev(B) tool blade vibration value (Here, dev vibration reference value: calculated when the tool is normal and processing is normal. Tool blade frequency band vibration magnitude fluctuation range, dev(A) Tool blade vibration value: Tool blade frequency band vibration magnitude fluctuation range calculated when part of the tool blade is broken and machining is normal, dev(B) Tool blade vibration value: Current tool blade frequency band vibration magnitude fluctuation range) 9. In paragraph 4, The vibration magnitude for determining the condition of a tool blade breakage in the tool condition judgment section above is calculated using the following [Formula 6] and [Formula 7] in the CNC tool life prediction system. [Formula 6] (Other frequency vibration value AND tool blade vibration value) ≤ spindle vibration value [Formula 7] Det_n=Round(Tol / f_z), the number of consecutive tool breakage diagnoses exceeds Det_n (Here, Det_n: the number of times to detect tool defects, Tol: tolerance, f_z: feed per tool edge, Round: rounded integer)

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