JP4358137B2 - Abnormal vibration diagnosis method and abnormal vibration diagnosis system during cutting - Google Patents

Description

  The present invention relates to an abnormal vibration diagnosis method and an abnormal vibration diagnosis system during cutting, and more particularly, to a diagnosis method and a diagnosis system for determining whether or not a tool has a cause of abnormal vibration that occurs in cutting such as end milling. .

  In cutting, vibration is generated at a processing point more or less. Along with this, a sound is generated from the machining point, and this is called a cutting sound. In particular, it is well known that a large cutting sound is generated in the state of chatter vibration generated due to intermittent cutting or insufficient rigidity of a tool or a work material. Such chatter vibration is liable to have adverse effects such as cutting noise, deterioration of the finished surface, and acceleration of damage to the tool edge.

  The chatter vibration as described above is empirically found to occur when the tool system has high rigidity and the work material system has low rigidity, and conversely, when the tool system has low rigidity and the work material system has high rigidity. Therefore, the side with low rigidity vibrates greatly. For this reason, in order to prevent chatter vibration, it is necessary to adjust the mechanical characteristics of either the work material system or the tool system or both in addition to the adjustment of the cutting conditions.

As the adjustment of the mechanical characteristics related to the tool system, a vibration-proof tool having characteristics such as improving the damping property of the tool system or improving the rigidity by using a cemented carbide is often used. Anti-vibration tools are more expensive than ordinary tools, and are expected to be effective when used, but there are many cases where the effect does not actually appear. One of the main causes is a case where the work material side is vibrated greatly. In this case, it is difficult to obtain an effect by measures on the tool side such as using a vibration-proof tool. Therefore, before using the vibration-proof tool, it is important to identify the cause of vibration in advance and determine the possibility of the effect.
Japanese Patent No. 3249111 JP 2002-139377 A

  As described above, the cutting sound appears as a result of vibration and reflects the state of vibration during cutting. Therefore, it is considered that sound analysis is effective in evaluating vibration. Regarding the evaluation of cutting sound, many researches and inventions have been made so far. For example, in Japanese Patent No. 3249111, a plurality of microphones (microphone arrays) are used to eliminate environmental sound components, and actual cutting is performed. A method is disclosed in which only the sound is extracted and the progress of tool wear is estimated from changes over time. However, simply analyzing the cutting sound cannot identify which part is causing the abnormal vibration.

  On the other hand, the analysis for specifying the vibration location is also effective other than the cutting work, and has been tried before. For example, in Japanese Patent Laid-Open No. 2002-139377, a plurality of sound sensors are attached to an evaluation target, the frequency of abnormal sound of the device at the evaluation point is specified, and the energy ratio of the plurality of sound sensors at that frequency The method of identifying the site where the abnormal sound is generated by obtaining the contribution ratio to the abnormal sound is presented.

  However, the above method is too complicated and large to carry out the evaluation at the processing site, and a simple method is required in actual use. Further, the tool and the work material are in contact with each other during the cutting process, and even if a plurality of microphones are used, it is difficult to extract the respective cutting sounds.

  The present invention has been made in order to solve the above-described problems, and identifies a system that causes abnormal vibration during machining such as cutting, and determines the possibility of the effect of the vibration-proof tool. It is an object of the present invention to provide an abnormal vibration diagnosis method and an abnormal vibration diagnosis system at the time of cutting that can be performed.

  The abnormal vibration diagnosis method at the time of cutting according to the present invention includes a step of analyzing a frequency of a cutting sound generated during cutting and identifying a main vibration frequency of the cutting sound, and measuring an acceleration or displacement of the tool during vibration. Analyzing the frequency of the tool to identify the main vibration frequency of the tool, measuring the acceleration or displacement of the work piece during vibration and analyzing the frequency to determine the main vibration frequency of the work material, Determining at least one of the main vibration frequencies of the work material and the main vibration frequency of the cutting sound to determine whether the cause of the cutting sound is in the tool, the work material, or other than these. . It is desirable to compare the main vibration frequency of the tool and the work material with the main vibration frequency of the cutting sound. Further, the frequency analysis of the cutting sound may be performed by recording the cutting sound. Further, measurement of acceleration and displacement of the tool or work material may be performed during cutting, or may be performed by vibrating the tool or work material with a hammer or the like.

  Further, the step of specifying the main vibration frequency divides the analysis frequency band into a plurality of bands, and the evaluation value (component value: sound component value or vibration component value) obtained by the frequency analysis in each band is obtained. A step of selecting the maximum band as the main vibration frequency band may be included. Here, “the band where the evaluation value is maximized” refers to the band where the integral value of the evaluation value is maximized.

  Preferably, the step of identifying the main vibration frequency of the cutting sound includes a step of removing a sound component other than the cutting sound by measuring a sound near the processing point at the time of non-cutting during frequency analysis of the cutting sound. . To remove sound components other than the cutting sound, for example, measure the sound near the processing point at the time of cutting and non-cutting, perform frequency analysis respectively, and perform non-cutting from the evaluation value (component value) at each frequency at the time of cutting The evaluation value (component value) at each frequency at the time may be subtracted.

A principal vibration frequency above SL tool, Ru with different criteria cause the cutting sound depending on the value of the ratio of the principal vibration frequency of the work material. For example, in the main vibration frequency of the tool and the main vibration frequency of the work material, the side where the value of the main vibration frequency is large is divided by the side where the value of the main vibration frequency is small (the main vibration frequency / value on the side where the value is large is It is conceivable that the criterion for determining the cause of the generation of the cutting sound is made different depending on the value of this ratio on the smaller main vibration frequency).

  The abnormal vibration diagnostic system at the time of cutting according to the present invention is a data input / output unit for registering cutting sound data generated during cutting and vibration data of a vibrating tool and workpiece and outputting a diagnosis result; Frequency analysis unit that performs frequency analysis of vibration data of cutting sound, tool, and work material, and main frequency extraction that extracts main vibration frequency of cutting sound, tool, and work material from the data output from the frequency analysis unit The main vibration frequency of the cutting part and the cutting sound and the main vibration frequency of at least one of the tool and the work material are compared. And a comparison unit for determining whether or not

  The cutting sound data is specifically digital data of time series of sound pressure, the vibration data is digital data of time series of acceleration or displacement, and these time series data and sampling frequency are the data input / output unit. Shall be entered. The main frequency extraction unit may divide the analysis frequency band into a plurality of bands, and specify the center value of the band in which the cutting sound component is maximum in each band as the main vibration frequency of the cutting sound. Good.

  According to the present invention, it is determined from the cutting sound emitted from the machining point and the vibration state of at least one of the tool and the work material whether the main subject of vibration during machining is the tool, the work material, or any other material. can do. Therefore, it is easy to take measures for suppressing vibration during processing, and for example, it can be easily determined whether or not an expensive vibration-proof tool should be introduced, and wasteful investment can be effectively suppressed. .

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

(Embodiment 1)
FIG. 1 is a diagram showing a flow procedure of an abnormal vibration diagnosis method during cutting according to Embodiment 1 of the present invention.

  As shown in FIG. 1, first, cutting sound measurement, tool vibration measurement, and workpiece vibration measurement are performed. These measurements may be performed simultaneously or individually. When the cutting sound measurement, the tool vibration measurement, and the work piece vibration measurement are separately performed, any of them may be measured first.

  Cutting sound is measured by installing a microphone near the cutting point. Then, the cutting sound is recorded using the microphone. For example, by recording the cutting sound by connecting the above microphone to a personal computer, it is possible to easily capture the cutting sound data as a WAVE file. The cutting sound data obtained in this way is registered as time-series sound pressure data.

  In addition, since the frequency of chatter vibration is at a level of several kHz when it is high, it is desirable to use a microphone that can record sound up to about 10 kHz.

  Further, when measuring the cutting sound, the sound emitted from the motor of the machine tool and the noise from the surrounding environment are recorded at the same time. When high-frequency chatter vibration is occurring, the frequency band is generally very different from other sounds and the sound level is very high. It is possible to measure However, when the vibration level is relatively low or the ambient noise is large, it is difficult to separate the sound other than the cutting sound from the cutting sound. Therefore, in such a case, the sound near the machining point at the time of non-cutting is measured, and the frequency analysis result is subtracted from the frequency analysis result at the time of machining, thereby removing sound components other than the cutting sound. What should I do? Thereby, it is possible to remove and evaluate the sound component other than the cutting sound such as the motor sound of the machine tool, and it is possible to evaluate the cutting sound component more accurately.

  The vibration of the tool can be measured by attaching an acceleration pickup to the tool tip. For example, by applying a pulse-like force to the tool with a hammer or the like in an unprocessed state, the signal output from the acceleration pickup is amplified by an amplifier and registered in the recorder as time-series voltage data (acceleration data). . On the other hand, in order to measure vibration during processing, there is a method of measuring with a displacement meter such as a laser type.

  The vibration of the work material can also be measured by the same method as that for the tool. Specifically, for example, an acceleration pickup is attached to a work material, and acceleration data at the time of vibration is measured. In the case of cutting, since the work material does not rotate, in addition to vibration by a hammer, vibration during cutting may be directly measured. Also in this case, the signal output from the acceleration pickup is amplified by an amplifier and registered in the recorder as time-series voltage data (acceleration data).

  After the time-series sound pressure data and the time-series acceleration data for the tool and the work material are registered as described above, frequency analysis is performed.

  The frequency analysis of sound pressure data can be performed on a computer using a calculation method such as FFT (Fourier Fast Transform). By performing frequency analysis of sound pressure data in this way, a cutting sound spectrum can be obtained. For example, when frequency analysis is performed using the FFT calculation method, a spectrum as shown in FIG. 2A can be obtained.

  The frequency analysis of the acceleration data can be performed on the computer as in the case of the sound pressure data. An acceleration spectrum can be obtained by frequency analysis of the acceleration data. Note that the frequency analysis result may be obtained directly by inputting the signal from the amplifier to the FFT analyzer. Further, the frequency analysis result may be directly obtained for the cutting sound by using a sound level meter having a frequency analysis function.

  Next, the main vibration frequency is specified. That is, the main vibration frequency of the cutting noise and the vibration of the tool and the work material is specified. Simply, the frequency at which the evaluation value (component value: audio component value or vibration component value) becomes the maximum value in the analysis target frequency band may be obtained. For example, in the spectrum as shown in FIG. 2A, the peak frequency is considered to be the main vibration frequency of the target cutting process. By suppressing the vibration at this vibration frequency, it is possible to suppress abnormal cutting noise during machining, improve the cutting finish surface, and further suppress tool damage.

  However, as shown in FIG. 2 (b), when the pinpoint becomes a high value at a specific frequency, the main vibration frequency cannot be specified simply by obtaining the frequency having the maximum value. In other words, the frequency having the maximum value may not necessarily be the main frequency of vibration.

  Therefore, in such a case, the main frequency of vibration can be specified by performing the following processing. That is, as shown in FIG. 2C, the frequency band to be analyzed is divided into a plurality. Then, an integrated value of evaluation values (component values: audio component values and vibration component values) for each frequency band is obtained, and the band having the largest value is specified as the main vibration frequency band. For example, when a tool such as an end mill is attached to the machining center spindle, the natural frequency of the tool spindle system is often at the level of several hundred Hz. For example, the band may be divided into about 5 to 50 Hz. desirable. If the main vibration frequency band is obtained in this way, for example, the center value is set as each main vibration frequency. Such processing is advantageous when the evaluation process is automated.

  Next, the main vibration frequency of the cutting sound, the main vibration frequency of the tool, and the main vibration frequency of the work material obtained by the above method are compared. In the case of cutting, unlike turning, cases where the natural frequencies of the tool system and the work material system are close to each other are likely to occur. For this reason, there is a case where a reliable determination cannot be made even if the values are compared. Therefore, in the present embodiment, based on the rules shown in FIG. 3, when the lower side of the main vibration frequency of the tool system and the work material system is X (Hz) and the larger side is Y (Hz), 1) Y /X>1.5, 2) 1.2 <Y / X ≦ 1.5, 3) Judgment is made in three cases: 1 ≦ Y / X ≦ 1.2.

  First, in the case of 1), the main vibration frequency of the cutting sound is compared with the main vibration frequency of the tool or the work material, and if it is within ± 20% of either of the main vibration frequencies of the tool or the work material, The corresponding side is determined to be the cause of abnormal vibration, and a diagnosis result to that effect is output. If none of the main vibration frequencies is applicable, it is determined that the disturbance is abnormal vibration caused by a machine tool or external vibration, and a diagnosis result to that effect is output.

  In the case of 2), when the main vibration frequency of the cutting sound is in the middle of X and Y, it is within a range of ± 20% from the main vibration frequency of both the tool and the work material. Therefore, when the main vibration frequency of the cutting sound is Z (Hz), if 0.8X ≦ Z ≦ X or Y ≦ Z ≦ 1.2Y, the corresponding main vibration frequency side is abnormal. It is determined as a factor of vibration, and a diagnosis result to that effect is output. On the other hand, when X <Z <Y, it is difficult to determine either one, so it is determined that either the tool or the work material may be the cause of abnormal vibration, and the diagnosis result to that effect Is output. In other cases, it is determined that the disturbance is abnormal vibration.

  In the case of 3), it can be said that the main vibration frequencies of the tool and the work material are almost the same. Therefore, in the case of 0.8X ≦ Z ≦ 1.2Y, it is determined that both the tool and the work material may be the cause of abnormal vibration, and in other cases, disturbance-type abnormal vibration is caused. It is determined that there is, and a diagnosis result to that effect is output.

  In response to this diagnosis result, if the tool is the cause, vibration generation is suppressed by using, for example, an anti-vibration tool, and if the work material side is the cause, the work material is chucked. It is effective to take measures such as improving the rigidity on the work material side by changing.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described with reference to FIG. FIG. 4 is a diagram showing an example of an abnormal vibration diagnosis system at the time of cutting capable of implementing the above-described abnormal vibration diagnosis method.

  As shown in FIG. 4, the abnormal vibration diagnosis system 10 according to the second embodiment includes a data input / output unit 11, a main body system unit 12, and a frequency analysis unit 13.

  The data input / output unit 11 includes a data input unit that receives information input from a system user, an information format inspection unit that performs an inspection of the input information format, and a data output unit that outputs a diagnosis result. Have.

  The input items are a WAVE format electronic file of cutting sound, an electronic file of time series acceleration or displacement data of the tool 15 and the work material 16, and a sampling frequency thereof. For the measurement of the cutting sound, a microphone 14 connected to a personal computer is used as shown in FIG. The acceleration data of the tool 15 is measured by attaching an acceleration pickup 18 to the tool 15 and applying a pulse force to the tool 15 with a hammer 17. The acceleration data of the work material 16 is also measured by attaching an acceleration pickup 18 to the work material 16 and applying a pulse-like force to the work material 16 with the hammer 17.

  The main body system unit 12 includes a main frequency extraction unit, a comparison unit, and a control unit. The main frequency extraction unit extracts the cutting noise, the main vibration frequency of the tool 15 and the work material 16, and inputs them to the comparison unit. The main frequency extraction unit preferably divides the analysis frequency band into a plurality of bands, and specifies the center value of the band in which the integrated value of the cutting sound component is maximum in each band as the main vibration frequency of the cutting sound. Then, the center value of the band in which the integrated value of the vibration component of the tool 15 is maximum in each band is specified as the main vibration frequency of the tool vibration, and the integrated value of the vibration component of the work material 16 is determined in each band. The center value of the maximum band is specified as the main vibration frequency of the workpiece vibration.

  The comparison unit compares the main vibration frequency of each of the tool 15 and the work material 16 with the main vibration frequency of the cutting sound, and determines whether any of them matches. Specifically, the comparison unit sets a certain frequency band around the main vibration frequency of the tool 15 and the work material 16, and whether or not the main vibration frequency of the cutting sound exists in each frequency band. Judging.

  The control unit inputs the time-series sound pressure data, the time-series acceleration data, and the sampling frequency that have been subjected to the information format inspection by the information format inspection unit to the frequency analysis unit 13, and the cutting obtained by the frequency analysis unit 13 A sound spectrum, a tool vibration spectrum, and a workpiece vibration spectrum are input to the main frequency extraction unit.

  Further, the control unit sends the comparison result by the comparison unit to the output unit. In the output unit, for example, in the comparison unit, each main vibration frequency is compared, and if the result that the main vibration frequency of the tool 15 matches the main vibration frequency of the cutting sound is obtained, the cause of the abnormal vibration is on the tool 15 side. To the system user.

  The frequency analysis unit 13 performs frequency analysis by a technique such as FFT based on time-series sound pressure data, time-series acceleration data, and sampling frequency, and outputs a cutting sound spectrum, a tool vibration spectrum, and a workpiece vibration spectrum.

  Next, examples of the present invention will be described.

  A large cutting noise was generated in the side machining by end milling of SCM steel, and chatter marks were seen on the finished surface. Therefore, the cause was investigated using the above-described diagnostic method.

  The target end mill is a two-blade φ10 mm blade, and is a brazing end mill in which a cemented carbide blade portion is brazed to a steel shank portion. Attach an acceleration pickup to the tip of the end mill, apply impact in a pulsed manner with a hammer, measure time-series acceleration data, and then attach an acceleration pickup to the work material in the same way, and apply impact in a pulsed manner with a hammer. Time-series acceleration data was measured. Then, cutting was performed using the end mill, and the cutting sound at that time was measured. Then, frequency analysis is performed on the three data of the cutting sound data and the acceleration data of the end mill and the work material, the frequency band to be analyzed (up to 2000 Hz) is divided into 20 Hz units, and the component values in each band are compared. As a result, the main vibration frequency of the tool was 310 Hz, and the main vibration frequency of the work material was 450 Hz. Further, when the cutting sound was analyzed in the same manner, the main vibration frequency of the cutting sound was 290 Hz. Therefore, the frequency ratio between the work material and the tool (the main vibration frequency of the work material / the main vibration frequency of the tool) is about 1.45, which corresponds to the case 2) described above. Further, since the main vibration frequency of the cutting sound is about 93% of the main vibration frequency of the tool, it is smaller than the main vibration frequency of the tool and 80% or more of the main vibration frequency of the tool. From this, it is considered that the vibration of the tool system is a major cause of abnormal cutting noise, that is, abnormal vibration.

  Therefore, when machining was performed using a solid carbide end mill that was actually expensive but had high rigidity and high vibration resistance, abnormal cutting noise was reduced and the finished surface properties were good.

  As described above, according to the diagnosis method of the present embodiment, it is possible to easily diagnose whether the cause of the abnormal cutting sound is in the tool, the work material, or any other than these. Based on this diagnosis result, for example, it is possible to predict in advance whether or not there is an effect by using a vibration isolation tool, and it is possible to make an efficient investment for vibration suppression.

  Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above embodiments and examples.

  The present invention is not limited to the above-described embodiments and examples. The scope of the present invention is defined by the terms of the claims, and includes meanings equivalent to the terms of the claims and all modifications within the scope.

  The present invention is effectively applied to an abnormal vibration diagnosis method and an abnormal vibration diagnosis system during cutting.

It is a figure which shows the flow procedure of the abnormal vibration diagnostic method at the time of the cutting in Embodiment 1 of this invention. (A)-(c) is a figure which shows the example of a spectrum obtained by the frequency analysis. It is explanatory drawing which shows typically the determination method of the abnormal vibration at the time of the cutting in Embodiment 1 of this invention. It is a schematic block diagram of the abnormal vibration diagnostic system at the time of the cutting in Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Abnormal vibration diagnosis system, 11 Data input / output part, 12 Main body system part, 13 Frequency analysis part, 14 Microphone, 15 Tool, 16 Work material, 17 Hammer, 18 Accelerometer.

Claims (4)

Performing a frequency analysis of the cutting sound generated during the cutting process, and identifying a main vibration frequency of the cutting sound;
Measuring the acceleration or displacement of the tool during vibration and performing frequency analysis to identify the main vibration frequency of the tool;
Measuring the acceleration or displacement of the workpiece in vibration and performing a frequency analysis to identify the main vibration frequency of the workpiece;
By comparing at least one of the main vibration frequencies of the tool and the work material and the main vibration frequency of the cutting sound, the cause of the generation of the cutting sound is any of the tool, the work material, and any other than these and a step of determining in,
An abnormal vibration diagnosis method at the time of cutting , in which a criterion for determining the cause of the generation of the cutting sound is made different according to a value of a ratio between the main vibration frequency of the tool and the main vibration frequency of the work material .   The step of identifying the main vibration frequency is a step of dividing the analysis frequency band into a plurality of bands, and selecting a band in which the evaluation value obtained by the frequency analysis is maximum among the bands as the main vibration frequency band. The method for diagnosing abnormal vibration during cutting according to claim 1.   The step of specifying a main vibration frequency of the cutting sound includes a step of removing a sound component other than the cutting sound by measuring a sound near a processing point at the time of non-cutting during frequency analysis of the cutting sound. The method for diagnosing abnormal vibration during cutting according to claim 1 or 2. A data input / output unit for registering cutting sound data generated during cutting and vibration data of a vibrating tool and work material and outputting a diagnosis result;
A frequency analysis unit that performs frequency analysis of vibration data of cutting sound , tools and work materials;
A main frequency extraction unit that extracts the main vibration frequency of the cutting sound, the tool, and the work material from the data output from the frequency analysis unit;
Comparing the main vibration frequency of the cutting sound with the main vibration frequency of at least one of the tool and the work material, the cause of abnormal vibration during cutting is the tool, the work material, and other than these And a comparison unit for determining which of the
An abnormal vibration diagnosis system at the time of cutting , in which a criterion for determining the cause of generation of the cutting sound is made different according to a value of a ratio between a main vibration frequency of the tool and a main vibration frequency of the work material .

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