JP2018065199A - Machine tool - Google Patents

Abstract

A machine tool capable of obtaining highly accurate measurement results at low cost without performing sampling at a very short period as in the past, regarding changes in phenomena occurring in a rotating shaft device. . The measurement of the driving load of the main shaft and the correlation of the rotational phase of the main shaft at the time of measurement of the measured value are continued over a plurality of revolutions of the main shaft, and by obtaining the measured values at various rotational phases, the final The change in the driving force in one rotation of the main shaft is obtained in general. In addition, among the measured values, the measured values whose rotation phase matches the extracted phase are extracted and arranged, or the driving load of the main shaft at a predetermined extracted phase is interpolated, and the measured values over multiple cycles are combined and superimposed. After creating an approximation waveform, the interpolated drive load of the main shaft is interpolated to create changes in the drive load of the main shaft for one cycle. [Selection drawing] Fig. 2

Description

  The present invention relates to a machine tool provided with a rotary shaft device for processing while rotating a tool or a workpiece, for example.

  Conventionally, in a machine tool that performs machining while rotating the rotating shaft, when performing state diagnosis or machining diagnosis of the machine tool itself, vibration and driving force during operation are measured, and diagnosis is performed based on the measurement result. It has become common. For example, when a tool is mounted on a rotating shaft and cutting is performed on a workpiece, the cutting amount is identified or the state of the cutting tool is detected by measuring the driving force of the rotating shaft during cutting. Can be.

Further, in the invention described in Patent Document 1, the driving force generated during cutting is calculated based on the cutting volume obtained from the shape data of the processing object and the processing path and the material of the workpiece, and the calculated driving force and the actual measurement are calculated. Abnormal machining is detected by comparing with the driving force.
Furthermore, in the invention described in Patent Document 2, in the case of performing repetitive machining, an abnormal machining is performed by comparing the driving force when the previous normal machining is performed with the driving force actually measured in the current machining. Is supposed to be detected.
In addition, in recent years, in addition to the driving force of the rotating shaft, vibration sensors and AE sensors are attached to each part of the machine tool, and displacement sensors are used to measure the phenomenon that occurs on the machine tool more clearly. Attempts have been made to try.

JP 2004-126956 A JP 2012-254499 A

However, in the conventional method, in order to detect a change in a desired phenomenon such as a period of driving or cutting of the rotating shaft, a vibration period unique to the bearing or the guide component, it is necessary to measure with a very short sampling period. . For example, when it is attempted to measure a change in driving force for each blade during cutting using a rotary tool having six cutting blades, when the rotational speed is 10,000 min ⁻¹ , the cutting cycle is 100 μsec. Therefore, in order to sample 10 points for each cutting blade, the sampling period must be faster than 10 μsec. When such high-speed sampling is required, there is a problem that measurement and analysis are costly.

  Therefore, the present invention has been made in view of the above problems, and it is possible to reduce the cost and the accuracy without changing the phenomenon occurring in the rotary shaft device without sampling at a very short period as in the prior art. It is an object of the present invention to provide a machine tool capable of obtaining good measurement results.

In order to achieve the above object, the invention according to claim 1 of the present invention is a rotary shaft device provided with a rotary shaft, and is attached to the rotary shaft device, and the rotation is synchronized with the rotation of the rotary shaft. A sensor that acquires information related to a phenomenon that occurs periodically in the shaft device; and a control device that controls the operation of the rotary shaft device and acquires the information via the sensor. Acquiring the information via the sensor at a predetermined sampling period, associating the acquired information with a rotation phase of the rotating shaft, and based on the information acquired over a plurality of rotations of the rotating shaft. A machine tool for creating a change for one cycle of the phenomenon, an extraction sampling cycle which is a sampling cycle for creating the change for the one cycle is set in the control device, When assuming that the change of the phenomenon is sampled in the extraction sampling period, the control device calculates an extraction phase that is a phase at the time of each sampling, and the rotation phase of the information matches the extraction phase. By extracting a thing, the change for the one period is created.
Moreover, in order to achieve the said objective, invention of Claim 2 among this invention is attached to the rotating shaft apparatus provided with the rotating shaft, and the said rotating shaft apparatus, and synchronizes with rotation of the said rotating shaft. A sensor that acquires information related to a phenomenon that occurs periodically in the rotary shaft device; and a control device that controls the operation of the rotary shaft device and acquires the information via the sensor, The control device acquires the information via the sensor at a predetermined sampling period, associates the acquired information with the rotation phase of the rotating shaft, and acquires the information acquired over a plurality of rotations of the rotating shaft. A machine tool that creates a change for one cycle of the phenomenon, and an extraction sampling cycle that is a sampling cycle for creating the change for the one cycle is set in the control device. Thus, when assuming that the change of the phenomenon is sampled at the extraction sampling period, the control device calculates an extraction phase that is a phase at each sampling, and uses the information to calculate the phenomenon at the extraction phase. The information obtained over a plurality of rotations of the rotation axis is overlaid to create an approximate waveform of the change for one period of the phenomenon, and the calculated value of the phenomenon is By inserting, a change for one cycle of the phenomenon is created.
According to a third aspect of the present invention, in using the information for calculating the value of the phenomenon in the extraction phase according to the second aspect of the invention, the rotation phase and the extraction phase associated with the information are used. It is characterized in that it is used when the difference between is less than a predetermined threshold value.
According to a fourth aspect of the present invention, in using the information A for calculating the value of the phenomenon in the extraction phase according to the second aspect of the invention, the rotational phase A associated with the information A, When the change for one period of the phenomenon is created, the information indicating that the phase difference between the rotational phase A and the rotational phase B associated with the closest information B is equal to or less than a predetermined threshold value. A is used.

In the present invention, the control device acquires information via a sensor at a predetermined sampling period, associates the acquired information with the rotation phase of the rotating shaft, and based on the information acquired over a plurality of rotations of the rotating shaft. A change for one period of the phenomenon is created. In the first aspect of the present invention, an extraction sampling period, which is a sampling period for creating a change for one period, is set in the control apparatus, and the control apparatus samples a change in the phenomenon at the extraction sampling period. Assuming that, an extraction phase that is a phase at the time of each sampling is calculated, and a change corresponding to one cycle is created by extracting information whose rotation phase matches the extraction phase. On the other hand, in the invention according to claim 2, an extraction sampling period which is a sampling period related to creation of a change for one period is set in the control apparatus, and the control apparatus samples a change in phenomenon at the extraction sampling period. Assuming that, the extraction phase, which is the phase at the time of each sampling, is calculated, the value of the phenomenon in the extraction phase is calculated using the information, and the information acquired over multiple rotations of the rotation axis is overlaid. In addition, an approximate waveform of the change for one period of the phenomenon is created, and then the change for the one period of the phenomenon is created by interpolating the calculated value of the phenomenon.
Therefore, for a phenomenon that changes at a high speed, for example, a change in the driving load of the main shaft, a useful measurement result can be obtained in spite of measurement with a longer sampling period than in the past, and cost can be reduced. It is also possible to measure a phenomenon that has been technically difficult due to the change period being too fast. Furthermore, since it is possible to create a change as if it was measured at a fixed period such as an extraction sampling period, it is possible to obtain easy-to-use data such as easy frequency decomposition compared to data with unequal measurement periods. it can.
According to the third and fourth aspects of the present invention, since various threshold values are set for the information used for calculating the value of the phenomenon, data with higher accuracy can be obtained.

It is explanatory drawing which showed the machine tool. It is the flowchart figure shown about the control which concerns on the measurement of the phenomenon which generate | occur | produces in a main shaft apparatus. It is explanatory drawing which showed the change for 1 period of the driving force of the main axis | shaft obtained when measurement conditions are satisfied. It is explanatory drawing which showed the change for 1 period of the driving force of the main axis | shaft obtained when measurement conditions are not satisfied.

  Hereinafter, a machine tool according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory view showing a machine tool 20.
The machine tool 20 is a so-called machining center and includes a spindle device 11 and a control device 12. The spindle head 3 of the spindle device 11 is provided with a spindle 2 serving as a rotating shaft, a drive device (not shown) for rotating the spindle 2, and the like, and a tool is provided at the tip of the spindle 2 The tool holder 1 can be mounted. Further, in main components of the spindle device 11 including the spindle head 3, a sensor for measuring the driving force of the spindle 2 (for example, a sensor for measuring the required power of the driving device) and the spindle device 11 are generated. A sensor or the like for measuring vibration is attached. On the other hand, the control device 12 is for controlling the operation of the spindle 2 and diagnosing the state of the spindle device 11 and machining in the spindle device 11, and is connected to the various sensors described above. A measurement recording unit 4 that measures and records the information, a setting unit 5 that sets a threshold value for the measurement data recorded in the measurement recording unit 4, and a calculation unit 6 that performs various calculation processes.

Then, the control related to the measurement of the phenomenon occurring in the spindle device 11 which is the main part of the present invention will be described with reference to the flowchart of FIG. It should be noted that when machining is performed at the rotational speed of the main shaft 2 (drive cycle to be measured) R _spd = 600 min ⁻¹ , the change in the drive load of the main shaft 2 is measured at the sampling cycle S _T = 82 msec. .
In measuring the change in the driving load of the main shaft 2, the control device 12 first sets the extraction sampling period S _Tgt (S1). The extraction sampling period, the measured value measured at a sampling period S _T In preparing waveform based on a period of the extraction of the measured value. That is, when the rotational speed R _spd of the main shaft 2 is 600 min ⁻¹ , the driving load of the main shaft 2 appears as 10 Hz vibration (10 cycles in 1 sec), so that a waveform that is sampled at 10 points per cycle is created. _Therefore , the extraction sampling period S _Tgt = 10 msec is set.

Next, measurement of the driving load of the main shaft 2 at the sampling period S _T (for example, 30 msec) is started, and the measured value is associated with the rotational phase of the main shaft 2 at the time of measurement and sequentially recorded in the measurement recording unit 4 ( S2). In addition, when the control apparatus 12 does not acquire the rotation phase of the main shaft 2 from the main shaft apparatus 11, the rotation period R _T = 100 msec is obtained by the following formula 1, and the elapsed time from the start of measurement and the rotation period R _T are calculated. The rotational phase of the main shaft 2 may be calculated from the remainder.

Further, when the measurement value is accumulated, a measurement condition (here, measurement time) which is a condition related to waveform creation is calculated (S3). That is, as shown by the following formula 2, the least common multiple of the sampling period _{S T} and extracted sampling period _{S Tgt,} rotation period _{R T,} and extracting a sampling period _{S Tgt} than the measurement time _{M Time} (time measurement in this case _{M Time} = 4.1 sec.). Then, it is determined whether or not the calculated measurement condition is satisfied, that is, whether or not a change in the driving load of the main shaft 2 is steadily generated over a time equal to or longer than the measurement time M _Time (S4).

If it is determined that the change in the driving load of the main shaft 2 is constantly occurring over the measurement time M _Time (YES in S4), all the measurement values necessary for waveform creation are recorded. Therefore, by arranging the measurement values recorded in the measurement recording unit 4 along the phase information, it relates to the change in the driving load of the main shaft 2 for one cycle as shown in FIG. A waveform is created (S6). It should be noted that, instead of simply arranging the measured values along the phase information, assuming that the change in the driving load of the spindle 2 for one period is sampled in the extraction sampling period _STgt , the phase of the change at each sampling time The extracted phase is calculated by the following equation 5, and among the measurement values recorded in the measurement recording unit 4, the measurement values whose rotation phase matches the extraction phase are extracted and arranged, and the data of the equal sampling interval It is preferable.

On the other hand, if it is determined that the change in the driving load of the main shaft 2 has not steadily occurred over the measurement time M _Time or longer (determined as NO in S4), the driving of the main shaft 2 is not stable or is driven. Since the measurement time required for waveform creation is insufficient due to the short time, it is necessary to interpolate the measurement values by executing interpolation processing when creating the waveform. Therefore, a threshold value used for extraction of measurement values used for such interpolation is set (S5). As this threshold value, the phase information related to the measured value and the phase difference between the extracted phase when creating the waveform, the phase information A related to the measured value A, and the waveform are created. When superimposing the measurement values over a plurality of periods, the phase difference between the phase information A and the phase information B related to the measurement value B (the measurement value B having a phase closer to the phase information A) whose phase is before and after. There is something against. Then, the threshold value may be set by an operator using an input device or the like according to the required accuracy, or may be calculated by the control device 12 from various conditions.

As a specific example, it is conceivable to set a threshold value equal to or less than the extraction sampling period S _Tgt for the difference between the phase information associated with the measurement value and the extraction phase when the waveform is created. By setting such a threshold value, when creating a waveform, interpolation processing may be performed without a measurement value having appropriate phase information between plots at the extraction sampling period _STgt. Since it can be avoided, the disappearance of the peak of the waveform can be avoided. Further, the phase difference between the phase information A and the phase information B, and is considered to be set as a threshold the accuracy more than the value of the sampling period S _T of the sensor. By setting such a threshold value, interpolation processing can be executed in consideration of the change of rotational phase and uncertainty in waveform creation.

この最大周波数成分ｆ_ｍａｘは、アンチエリアシングフィルタのカットオフ周波数であってもよいし、回転検出器の刃数等のセンサの固有値（所謂測定器の時間精度）であってもよい。また、エンドミルやフライスカッターを用いた加工であれば、駆動周期Ｒ_ｓｐｄ、工具刃数Ｚと、切れ刃１枚あたりに検出したい分割数ｐとをもとに下記式４から算出してもよい。他にも軸受けの転動体の通過周波数等も考えられる。

Further, the threshold value may be obtained by the following expression 3 based on the maximum frequency component f _max in the assumed input component (here, change in the driving load of the main shaft 2).

This maximum frequency component f _max may be a cut-off frequency of the anti-aliasing filter, or may be a characteristic value of the sensor such as the number of blades of the rotation detector (so-called measuring device time accuracy). Further, in the case of machining using an end mill or a milling cutter, it may be calculated from the following formula 4 based on the driving cycle R _spd , the number of tool edges Z, and the number of divisions p to be detected per cutting edge. . In addition, the passing frequency of the rolling elements of the bearing can be considered.

When the setting of the threshold value is completed, the extraction phase is calculated by the following formula 5, and a waveform relating to the change in the driving load of the spindle 2 for one cycle is created while performing the interpolation process (S6). In performing this interpolation process, a measured value associated with the smallest rotation phase than the calculated extracted phase SP _n, and a measurement value associated with the highest rotational phase does not exceed the calculated extracted phase SP _n Extract. Then, _assuming that the interpolation condition is satisfied when the difference from the extracted phase SP _n is equal to or less than the threshold value set in S5, linear interpolation is performed using those measured values, and the main axis 2 in the extracted phase SP _n The driving load is calculated. This process is performed in a range of n = 1, 2,... | S _T / S _Tgt ”( _where “ | ”also indicates a floor function), and the driving load of the spindle 2 in the extraction sampling period S _Tgt is calculated. Then, after approximating the measured values over a plurality of cycles and superimposing them together to create an approximate waveform, by interpolating the interpolated driving load of the main shaft 2, the main shaft 2 for one cycle as shown in FIG. 4 is interpolated. It is possible to obtain a waveform related to a change in driving load (this is also data at equal sampling intervals), that is, a waveform substantially equivalent to the waveform shown in FIG. In addition, when the waveform shown in FIG. 3 is a waveform at the measurement time M _Time = 4.1 sec, the waveform shown in FIG. 4 is a waveform at the measurement time M _Time = 2.05 sec. Here, it is determined whether the interpolation condition is satisfied by using the phase difference between the phase information (that is, the rotational phase) associated with the measurement value and the extracted phase as a threshold value. As described above, the phase difference between the phase information A and the phase information B may be compared with a threshold value to determine whether or not the interpolation condition is satisfied.

  According to the machine tool 20 having the above-described configuration, the measurement of the driving load of the main shaft 2 and the association of the rotation phase of the main shaft 2 at the time of measurement of the measurement value are continued over a plurality of rotations of the main shaft 2. By obtaining measured values at various rotational phases, the change in driving force in one revolution of the main shaft 2 is finally obtained. Therefore, for a phenomenon that changes at a high speed, such as a change in the driving load of the main shaft 2, a useful measurement result can be obtained in spite of measurement with a longer sampling period than before, and cost can be reduced. It is also possible to measure a phenomenon that has been technically difficult due to the change period being too fast.

Further, when it is assumed that the change in the driving load of the spindle 2 for one cycle is sampled at the extraction sampling cycle S _Tgt , the extraction phase that is the phase of the change at each sampling is calculated and recorded in the measurement recording unit 4. Among the measured values, the measured values whose rotational phase matches the extracted phase are extracted and arranged, the driving load of the spindle 2 at the predetermined extracted phase is interpolated, and the measured values over a plurality of cycles are combined with the cycle. Since an approximate waveform is created by superimposing, the interpolated driving load of the main shaft 2 is interpolated to create a change in the driving load of the main shaft 2 for one cycle, so that data of equal sampling intervals is obtained. Therefore, it is possible to obtain data that is easy to use, such as being easy to perform frequency decomposition as compared with data having unequal measurement cycles.

In addition, the threshold for the difference between the phase information associated with the measured value and the extracted phase when creating the waveform, and the threshold for the phase difference between phase information A and phase information B are set. Since the measurement values used for interpolation of the driving load of the spindle 2 are discarded based on the threshold values, more accurate data can be obtained.
In addition, or calculate the threshold based on the maximum frequency component f _max in the input component to be assumed, the maximum frequency component f _max, the anti-aliasing filter cut-off frequency and the measurement instrument and the time precision Extraction of measurement values used for interpolation is performed more effectively by using any one or a combination thereof, or by calculating using the product of the drive period R _spd of the measurement target and the division number p to be detected. And data with extremely high accuracy can be obtained.

  The configuration related to the machine tool of the present invention is not limited to the above-described embodiment, and the gist of the present invention is not limited to the overall configuration of the machine tool, but also the configuration related to the control related to the measurement of the phenomenon. It can be appropriately changed as necessary without departing from the scope.

For example, although the spindle device of the machining center has been described in the above embodiment, the present invention can be suitably applied to other machine tools and rotary shaft devices such as a lathe spindle device and a feed shaft device.
In the above embodiment, the driving load of the main shaft is cited as a phenomenon that changes periodically. However, the driving load of the other driving shaft such as a feed shaft may be used without limitation thereto. It may be vibration, displacement, temperature, etc. generated in the rotary shaft device. As a specific example, a vibration sensor (sensor) may be attached to the feed shaft (rotary shaft), and the vibration when the moving body is moved by rotating the feed shaft at a constant speed may be measured. By obtaining such measurement results, it is possible to diagnose the state of the bearing and ball screw related to the feed shaft movement.

Furthermore, in the above embodiment, the driving load of the main shaft at the extraction phase is obtained by linear interpolation, but the interpolation method is not limited to linear interpolation, and other approximation methods may be used. Furthermore, although interpolation is performed using two measurement values close to the calculated extraction phase, the number of measurement values used for interpolation may be increased to improve accuracy.
In addition, the extraction phase _SP n _| against the calculation result of _{(n = 1,2 ·· S T /} S Tgt ") relates to the rotational phase of the measurements taken and recorded at a sampling period _{S T,} the rotational phase The measurement time can be determined by verifying whether or not the interpolation condition is satisfied. Therefore, after determining the measurement time required for the measurement of the periodic phenomenon, a waveform for one period calculated by the extraction phase SP _n (n = 1, 2,... | S _T / S _Tgt ) is created. By setting the sampling period S _Tgt so as to satisfy all the extraction phases necessary for the measurement, measurement can be performed in the shortest time, and the influence due to time change can be reduced.

  2 .. Spindle (rotary axis) 4 .. Measurement recording unit 5.. Setting unit 6.. Calculation unit 11.. Spindle unit (rotary axis unit) 12 .. Control device 20. .

Claims (4)

A rotary shaft device provided with a rotary shaft; a sensor attached to the rotary shaft device for acquiring information relating to a phenomenon that occurs periodically in the rotary shaft device in synchronization with the rotation of the rotary shaft; and the rotary shaft A control device that controls the operation of the device and obtains the information via the sensor;
The control device acquires the information via the sensor at a predetermined sampling period, associates the acquired information with the rotation phase of the rotating shaft, and acquires the information over a plurality of rotations of the rotating shaft. A machine tool that creates a change of one cycle of the phenomenon based on
In the control device, an extraction sampling period which is a sampling period related to creation of the change for the one period is set,
When assuming that the change of the phenomenon is sampled in the extraction sampling period, the control device calculates an extraction phase which is a phase at the time of each sampling, and the rotation phase of the information matches the extraction phase. A machine tool characterized by creating a change for one period by extracting a thing. A rotary shaft device provided with a rotary shaft; a sensor attached to the rotary shaft device for acquiring information relating to a phenomenon that occurs periodically in the rotary shaft device in synchronization with the rotation of the rotary shaft; and the rotary shaft A control device that controls the operation of the device and obtains the information via the sensor;
The control device acquires the information via the sensor at a predetermined sampling period, associates the acquired information with the rotation phase of the rotating shaft, and acquires the information over a plurality of rotations of the rotating shaft. A machine tool that creates a change of one cycle of the phenomenon based on
In the control device, an extraction sampling period which is a sampling period related to creation of the change for the one period is set,
When assuming that the change of the phenomenon is sampled in the extraction sampling period, the control device calculates an extraction phase that is a phase at each sampling, and uses the information to calculate the value of the phenomenon in the extraction phase Is calculated,
By superposing the information acquired over a plurality of rotations of the rotation axis to create an approximate waveform of the change for one period of the phenomenon, and interpolating the calculated value of the phenomenon, A machine tool characterized by creating a change for one cycle.   When using the information to calculate the value of the phenomenon in the extraction phase, use the fact that the phase difference between the rotation phase and the extraction phase associated with the information is equal to or less than a predetermined threshold value. The machine tool according to claim 2.   In using the information A to calculate the value of the phenomenon in the extraction phase, the rotational phase A associated with the information A and the rotation phase A and the phase when creating a change for one period of the phenomenon 3. The machine tool according to claim 2, wherein the information A is used when the phase difference from the rotational phase B associated with the information B that is closest to is equal to or less than a predetermined threshold value.

Images