JP2018161716A - Machine tool, tool slewing gear thereof and method for correction of spindle thermal displacement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for effectively preventing that an oscillation component due to oscillation which is intentionally provided in a machine tool or a tool slewing gear thereof even if a tool rotation becomes a slow speed.SOLUTION: A machine tool comprises: a tool slewing gear having a rotary shaft, and a tool which is fitted to the rotary shaft and is rotated by the rotary shaft; and a displacement meter which detects an axial displacement of the rotary shaft in the tool slewing gear in a non-contact manner. The machine tool is so configured as to estimate displacement due to the tool slewing gear by combination of a prescribed primary delay element with respect to an output of the displacement meter, and has: a target part which is provided with a hole which is easy to be intentionally oscillated and to which a probe of the displacement meter is opposite; an analog-digital converter which converts the output of the displacement meter; and a digital low-pass filter. In the tool machine, a cut-off frequency of a low-pass filter on a side of reading a value of a sensor is changed according to a cut-off frequency.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a machine tool, a tool rotation device thereof, and a spindle thermal displacement correction method, and more particularly, to an apparatus for correcting thermal displacement in the rotation axis direction of a tool rotation shaft in a machine tool that performs cutting, grinding, and polishing using a rotary tool. And a method. The rotation axis direction or the turning axis direction is defined so as to call the axis as the rotation axis direction when the object rotates around a certain linear axis.

  In general, in a machine tool that performs cutting using a rotating tool, when the operating state such as the rotation speed of the tool is changed, the heat generation state of the rotary motor and the bearing that freely supports the rotating body and the contact angle of the bearing change. Then, the cutting edge position of the tool is displaced. Of these, especially for changes in the heat generation state, since the settling time from the change tends to be as long as several hours to several hours, generally, it takes time from the change of the tool rotation state to the start of machining. Measures are taken such as performing a so-called warm-up operation, or making the rotational speeds of roughing and finishing close to each other so that the influence of displacement is reduced in the finishing.

  On the other hand, when time such as warm-up operation cannot be allowed, a method of suppressing displacement by correction is adopted. For example, the temperature of a plurality of parts of a machine tool and the machining dimensions of a workpiece are measured, and the measured parts The correlation between the change in the temperature of the workpiece and the change in the machining dimension of the workpiece is obtained by multiple regression analysis, the part of the machine tool whose correlation value obtained by this multiple regression analysis is higher than the predetermined value is selected, and the selected machine tool is selected. A relational expression between the change in the temperature of the machine part and the change in the machining dimension of the workpiece is obtained from the multiple regression analysis, and the machining dimension of the workpiece is predicted from this relational expression, and the machining is performed based on the predicted machining dimension of the workpiece. Although the feed amount of the machine is corrected, there is a problem that in reality, there is a case where elements other than heat may be displaced and the displacement components are not dealt with. In addition, non-contact displacement meters built into the tool shaft and measuring the displacement of the rotating body are also available on the market, and depending on the machine tool, the function of automatically offset and compensate the displacement based on the output of such a displacement meter. Some have However, for example, even in a tool axis rotating device with a built-in displacement meter, depending on the position in which the displacement is built-in, for example, the displacement of the rotating body based on the position of the head can only be grasped and processed. When a displacement is also generated in such a mechanism that supports the head, it is difficult to accurately grasp the displacement around the spindle of the machine tool and correct the correction. In view of this, the present inventor has proposed the technique described in Patent Document 1 as having a higher performance displacement compensation function that enables accurate grasping and correction processing of the displacement around the machine tool spindle. In the machine tool described in Patent Document 1, a tool rotating device having a rotating shaft and a tool attached to the rotating shaft and rotated by the rotating shaft, and non-axial displacement of the rotating shaft in the tool rotating device are not detected. A displacement meter that detects by contact is provided, and the displacement caused by the tool rotating device is estimated with respect to the output of the displacement meter by a combination of predetermined first-order lag elements (Patent Document 1 claim) Item 1), an analog-to-digital converter for intentionally providing a deflection or a hole in the portion of the target that is the measurement target of the displacement meter, where the probe of the displacement meter is opposed, A low-pass filter is added (claim 2 of Patent Document 1).

Japanese Patent Laid-Open No. 2006-175167

  However, for example, in a machine tool such as that described in claim 2 of Patent Document 1 described above, there is a problem in that a shake component is superimposed on a correction command even when the tool rotation is intentionally performed when the tool rotation speed is low. In addition, in machine tools that aim for higher accuracy, there is a desire to suppress the superimposition of components such as noise as much as possible. Thus, there has been a strong demand for the development of a technique for effectively preventing the shake component due to the intentionally provided runout from being superimposed on the correction command even when the tool rotation is slow.

  The present invention has been made under the circumstances as described above, and its purpose is to correct a vibration component due to intentionally provided vibration even when the tool rotation speed is low in a tool rotation device for machine tools. An object of the present invention is to provide a technique capable of effectively preventing superposition on a command.

  As a result of earnest research from various viewpoints about the possibility of the technology that can achieve the above-described object, the present inventor has intentionally provided a machine tool having the following configuration even when the tool rotation is slow. It has been found that the shake component due to shake can be effectively prevented from being superimposed on the correction command.

  That is, in the present invention, a tool rotating device having a rotating shaft and a tool attached to the rotating shaft and rotated by the rotating shaft, and axial displacement of the rotating shaft in the tool rotating device are detected without contact. A displacement meter, configured to estimate a displacement caused by the tool rotation device by a combination of predetermined first-order lag elements with respect to the output of the displacement meter, and the probe of the displacement meter is intentionally opposed In a machine tool having a target part provided with a hole that easily swings, an analog-digital converter that converts the output of the displacement meter, and a digital low-pass filter, the cut-off frequency of the low-pass filter on the sensor value reading side is set to the number of revolutions. Accordingly, a machine tool can be obtained which is changed in response, that is, adjusted so that the time constant of the low-pass filter is inversely proportional to the rotational speed.

As described above, if the time constant is completely proportional to the rotation speed, the sensor output will not be read at all when the rotation is completely stopped. To avoid this, the sum of a small constant and the rotation speed is the time constant. A machine tool characterized by processing the correction command so as to be proportional to the reciprocal of the above may be used.

In the case described above, since the sensor value is read even during stoppage, a slight deviation of the superimposed amount occurs in the long term. Therefore, a device that reads the current direction of the rotating body is installed in the rotating device, and a map of compensation information of the direction of the rotating body and the intentionally provided shake component is held in the form of a mathematical formula or table so that the rotation can be performed completely. The machine tool may be configured to read out the shake compensation information from the direction information of the rotating body when it stops and compensate the correction command.

  In the case described above, when the digital filter is configured using an integer or a fixed-point type, the reciprocal of the time constant cannot be less than the minimum representation unit. In this case, it is preferable that the machine tool is configured so that the processing can extend the time constant to the above upper limit or more by switching the sampling interval.

  ADVANTAGE OF THE INVENTION According to this invention, in the tool rotation apparatus of a machine tool, the axial displacement after a rotation state change can be correct | amended more precisely or at low cost. Also, by providing an intentional vibration component and a hole in the target component of the displacement meter and providing a digital low-pass filter for the digital output signal after input to the analog-digital converter, the resolution of the analog-digital converter can be reduced. In addition to being able to reduce the impact on the displacement compensation due to the shortage, it is possible to effectively prevent the runout component due to the intentionally runout from being superimposed on the correction command even when the tool rotation is slow. Is possible.

2 is a functional block diagram of a machine tool common to an embodiment of the present invention and an invention described in Patent Document 1. FIG. It is a figure which shows the basic composition of the machine tool common to embodiment of this invention, and invention of patent document 1. FIG. It is the example of a processing of the displacement meter target and the example of displacement meter installation which the embodiment of this invention and a part of invention of patent document 1 have in common. In the invention described in Patent Document 1, it is a diagram showing an example of a shake component intentionally provided. In the invention described in Patent Document 1, it is a diagram illustrating an example in which the image is superposed but removed to some extent by a filter. In the invention of patent document 1, it is a figure which shows the example which overlaps. In invention of patent document 1, it is a figure which shows the case where it rotates by hand as a 2nd example to overlap. It is a block diagram showing the signal processing performed to the displacement signal which concerns on the 1st Embodiment of this invention, and is an embodiment which improved the same structure in the invention of patent document 1. FIG. It is a block diagram showing the signal processing performed to the displacement signal which concerns on the 1st Embodiment of this invention, and is input as a modification of embodiment shown in FIG. 8 which improved the same structure in invention of patent document 1 The example which can also be put in other than the 1st step | paragraph of the side is shown. It is the example of a process of the displacement meter target which concerns on the 3rd Embodiment of this invention, and the example of displacement meter installation.

  First, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a functional block diagram of a machine tool common to the embodiment of the present invention and the invention described in Patent Document 1. FIG. 2 is a basic configuration of a machine tool common to the embodiment of the present invention and the invention described in Patent Document 1. FIGS. 3A and 3B are a working example of a displacement meter target and an example of displacement meter installation in which the embodiment of the present invention and a part of the invention described in Patent Document 1 are common. As shown in FIG. 1, the machine tool 100 according to the present embodiment includes motor drivers 101, 102, 103, 104, and 105 that control driving of each axis, and drivers for these motor drivers 101, 102, 103, 104, and 105. A CNC (computer numerical control) device 107 is provided for controlling each of the axes and numerically controlling the rotational speed, feed rate, etc. of each axis. The CNC (computer numerical control) device 107 includes data for numerical control ( A machining program capable of inputting the specifications of the workpiece in, for example, an interactive format is incorporated. That is, as shown in FIG. 2, the machine tool 100 of the present embodiment has five axes composed of three axes of linear motion XYZ and two (axis) directions (not shown) of rotations A and C. A motor driver 101 that drives the head 122, to which the tool rotating device 121 is fixed, in the X-axis direction, a motor driver 102 that drives in the Y-axis direction, a motor driver 102 that rotates in the A-axis direction, A motor driver 103 that drives the work table 112 in the Z-axis direction, a motor driver 104 that rotates in the A-axis (around the X-axis), a motor driver 105 that rotates in the C-axis (around the Z-axis), and a CNC (computer numerical value) Control) device 107, and CNC (computer numerical control) device 107 controls driving of motor drivers 101-105 in each axial direction according to a predetermined machining program. By Rukoto like, the workpiece W can be processed into a desired shape. Needless to say, the CNC (computer numerical control) device 107 can also control the rotational speed of the tool.

The machine tool 100 has a structure as shown in FIG. 2, for example, and is configured such that the tool rotation axis 201 and the Z-axis direction 202 are parallel to each other. Each motor driver is connected to an X-axis motor 111, a Y-axis motor 112, a Z-axis motor 113, an A-axis motor 114, and a C-axis motor 115. Each motor is provided with a detector (not shown) for detecting rotation, and an angle and displacement detector (not shown) is provided for each axis according to the required accuracy to perform servo control. Be able to. As described above, the machine tool 100 having the above configuration further includes the tool rotation shaft 201 and the probe 301 that can detect the displacement in the rotation axis direction in a non-contact manner with respect to the tool rotation device 121 (see FIG. 3). The displacement caused by the tool rotating device 121 can be estimated by a combination of first-order lag elements shown in FIGS. 8 and 9 to be described later with respect to the output of the displacement meter. In the example of FIG. 2, a grindstone 209 is provided as a tool. Although a single sensor is used in the figure, it goes without saying that a configuration in which a plurality of sensors are used, the processing blocks shown in FIGS. .

  The tool rotating device 121 incorporates a probe 301 of a displacement measuring device (displacement meter) shown in FIG. 3, and the signal is converted to a voltage by a controller 302 (see FIG. 3) that outputs a signal detected by the probe as a voltage. After the conversion, the analog input module 303 converts it into a digital signal. The digital signal is subjected to a digital filter and signal processing by a program of the programmable controller 304. Then, the value up to the signal processing by the programmable controller 304 is transferred to the CNC 107, and an offset is automatically given in the Z-axis direction shown in FIG. 2 without notifying or notifying the operator (not shown). Thereby, the correction for the displacement in the Z-axis direction is completed. Although the programmable controller 304 is drawn as a separate block from the CNC 107 for convenience, it is needless to say that the CNC 107 can be configured so that functions performed by the programmable controller 304 are built in as a software program.

  Next, an embodiment of the present invention will be described. The embodiment of the present invention also has the configuration described above, that is, the same configuration as the machine tool according to claim 2 of Patent Document 1 described above. However, with such a configuration alone, when the rotation of the tool (grinding stone) 209 becomes low speed, there may be a problem that a shake component is superimposed on the correction command even if the shake is intentionally provided. Therefore, first, with reference to FIG. 4 to FIG. 7, a mechanism in which such a defect occurs in the machine tool according to claim 2 of Patent Document 1 will be described. FIG. 4 is a diagram (graph) showing an example of the intentionally provided runout component in the same configuration as the machine tool of claim 2 of Patent Document 1, and the horizontal axis of the graph is the machine tool shown in FIG. The rotational position of the spindle (tool rotation axis 201) and the vertical axis represent the deflection component. FIG. 5 shows a configuration similar to that of the machine tool of claim 2 of Patent Document 1, since the rotation of the tool (grinding stone) 209 is not slow, the intentionally provided runout component is superimposed on the correction command. It is a figure which shows the example removed to some extent by the filter process of the patent document 1 mentioned above, (a) is 0-360 the vertical position shows the rotational position of the spindle (tool rotating shaft 201) of the machine tool shown in FIG. It shows within the range of °, and the horizontal axis shows the elapsed time (second). (b) is a signal in which the vertical axis is a signal obtained by converting the sensor signal (displacement signal) of the machine tool displacement measuring device (displacement meter) shown in FIG. (Abbreviated as sensor signal), a signal obtained by converting the sensor signal into a digital signal by the analog input module 303 (hereinafter abbreviated as A / D conversion), and the digital signal (after A / D conversion) The digital filter and the signal processed by the program (hereinafter abbreviated as “after passing through the filter”), the respective outputs (μm), and the horizontal axis indicates the elapsed time (seconds). In the machine tool according to claim 2 of Patent Document 1 described above, even when a runout component as shown in FIG. 4 is intentionally added and added, a tool (grinding stone) 209 as shown in FIG. 5 is repeated at a constant speed and not at a low speed, as shown in FIG. 5B, although the intentionally provided shake component is superimposed on the correction command, the above-described filter of Patent Document 1 is used. Since it is removed to some extent by processing, there are few problems. FIG. 6 is a diagram showing an example in which the intentionally provided runout component is superimposed on the correction command because the rotation of the tool (grinding stone) 209 has become slow in the same configuration as the machine tool of claim 2 of Patent Document 1. In (a), the vertical axis indicates the rotation position of the spindle (tool rotation axis 201) in the range of 0 to 360 °, and the horizontal axis indicates the elapsed time (seconds) in the same manner as described above. In (b), the vertical axis indicates the output (μm) after the sensor signal, A / D conversion and after passing through the filter in the same manner as described above, and the horizontal axis indicates the elapsed time (seconds). As shown in FIG. 6 (a), when the rotation of the tool (grinding stone) 209 becomes low speed, as shown in FIG. 6 (b), there is a problem that the intentionally provided shake component is superimposed on the correction command. Arise. FIG. 7 is a diagram showing a case where a tool is turned by hand as another example of superposition in the same configuration as the machine tool of claim 2 of Patent Document 1, and (a) is similar to the above in the vertical axis. The rotation position of the spindle (tool rotation shaft 201) is shown in the range of 0 to 360 °, and the horizontal axis shows the elapsed time (seconds). In (b), the vertical axis indicates the output (μm) after the sensor signal, A / D conversion and after passing through the filter in the same manner as described above, and the horizontal axis indicates the elapsed time (seconds). In the example shown in FIG. 7A, the tool (grinding stone) 209 is slowly turned to a little less than 2 seconds by hand, then quickly turned to 2 turns, and then stopped (illustrated in FIG. 2). However, it is also assumed that a mechanism for manually rotating the tool (spindle) is also provided. Even in such a case, as shown in FIG. 7B, the problem that the intentionally provided shake component is superimposed on the correction command is the same.

  8 and 9 are each a block diagram showing signal processing applied to the displacement signal in the machine tool according to the first embodiment of the present invention, and an embodiment in which the same configuration in the invention described in Patent Document 1 is improved. It is. That is, the machine tool according to the first embodiment of the present invention performs the signal processing shown in FIGS. 8 and 9 instead of the signal processing described in FIG. First, as in the invention described in Patent Document 1, the present invention uses the fact that the portion of heat in the displacement acts like a serial combination of first-order lag elements. By performing signal processing using such serial coupling of first-order lag elements (shown in the block diagram of FIG. 1 of Patent Document 1 and shown in FIGS. 8 and 9 of the present application), high-performance axial displacement correction can be performed. It is possible to make it possible. 8 and 9 are also block diagrams showing signal processing that is a feature of the present invention, that is, signal processing using a serial combination of first-order lag elements performed on a signal representing displacement. In the present invention, the signal ΔZsense (t) representing the displacement is subjected to signal processing using a serial combination of first-order lag elements to obtain an output signal ΔZest (t) representing the processing result. The coefficients K1, K2, K3, and K4 in FIGS. 8 and 9 are correction coefficients for thermal displacement, and some of these K1, K2, K3, and K4 can be set to zero. Further, in the example shown in FIGS. 8 and 9, a four-stage signal processing system is configured, but it may be configured in more stages. Further, the correction coefficient need not be a positive value. First, FIG. 8 is a block diagram showing signal processing applied to the displacement signal according to the first embodiment of the present invention, which is an embodiment in which a similar configuration in the invention described in Patent Document 1 is improved. That is, the machine tool according to the first embodiment of the present invention performs the signal processing shown in FIG. 8 instead of the signal processing shown in FIG. That is, as shown in FIG. 8, by filtering the reference numeral 00 in the first stage on the input side, the cut-off frequency of the low-pass filter on the reading side of the sensor value is changed according to the rotational speed, The time constant is adjusted to be inversely proportional to the rotation speed of the low-pass filter. As shown in FIG. 9, as an embodiment in which a similar configuration in the invention described in Patent Document 1 is improved, the first stage on the input side can be omitted. FIG. 9 is a block diagram showing signal processing applied to a displacement signal according to a modification of the first embodiment of the present invention, and is another modification in which the same configuration in the invention described in Patent Document 1 is improved. The example which can also be put in other than the 1st step | paragraph on the input side is shown. That is, as shown in FIG. 9, filtering of reference numeral 00 is inserted in the first stage on the input side, but here, all signal components may be processed only partially without filtering. As shown in FIGS. 8 and 9, the machine tool according to the first embodiment of the present invention includes a rotating shaft and a tool rotating device that is attached to the rotating shaft and rotated by the rotating shaft, A displacement meter that detects the axial displacement of the rotating shaft in the tool rotating device in a non-contact manner, and a displacement caused by the tool rotating device is combined with a predetermined first-order lag element with respect to the output of the displacement meter. In a machine tool including a target unit that is configured to estimate and has a hole that is intentionally easy to swing, facing the probe of the displacement meter, an analog-to-digital converter that converts the output of the displacement meter, and a digital low-pass filter The cutoff frequency of the low-pass filter on the reading side of the sensor value is changed according to the rotation speed, that is, adjusted so that the time constant is inversely proportional to the rotation speed of the low-pass filter. It is characterized in Rukoto.

The filtering of the reference numeral 00 in FIG. 8 to the update of the output of the first-order lag element of the designated portion in FIG.

Next, signal processing applied to the displacement signal according to the second embodiment of the present invention will be described. In the first embodiment described above, that is, in the processing shown in FIGS. 8 and 9 and the processing according to the equations (1), (2), and (3), the time constant is completely set to the rotational speed of the tool (spindle) as described above. If it is proportional to, the output of the sensor will not be read at all when the rotation is completely stopped. Therefore, in order to avoid this problem, the correction command is processed so that the sum of the minute constant and the rotational speed is proportional to the reciprocal of the time constant (the first example as an improvement of the first embodiment described above). 2) is preferred. The update process of the output signal applied to the displacement signal according to the second embodiment is executed by the following equations (4), (5), and (6).

また、回転体の方向と意図的に設けた振れの成分の補償処理を３２１で実行する場合に、振れ分補償の式の例を以下の数式（７）（８）に示す。

Next, signal processing applied to the displacement signal according to the third embodiment of the present invention will be described. In the second embodiment described above, that is, when the processing according to the formulas (4), (5), and (6) is performed as described above, the sensor value is read even during the stop, so that in the long run, the amount of fluctuation is small. Deviation occurs. Therefore, a device that reads the current direction of the rotating body is installed in the rotating device, and a map of compensation information of the direction of the rotating body and the intentionally provided shake component is maintained in the form of a table or a mathematical expression, so that the rotation is complete. It may be configured to read out the shake compensation information from the direction information of the rotating body when it stops and compensate the correction command. FIG. 10 is an example of such an apparatus or mechanism provided in the machine tool according to the third embodiment of the present invention. As shown in FIG. 10 (a), the machine tool according to the third embodiment of the present invention has a rotating device, that is, a spindle motor 300 (corresponding to the spindle motor 116 in FIG. 1), a rotating body, that is, a tool 311 ( In FIG. 1, a rotary encoder reading head 321 and a rotary encoder rotating side disk 322 are mounted as devices for reading the current direction of a tool (grinding stone) 209). Reference numeral 301 denotes a non-contact displacement meter head, 301 c denotes a cable, and 302 denotes a flow to a non-contact displacement meter amplifier (amplifier). As shown in FIG. 10B, angle information and the like from the rotary encoder rotating side disk 322 and the rotary encoder reading head 321 as a device for reading the current direction of the rotating body are input to the programmable controller 304 by the process of 321. The As shown in FIG. 10B, a signal from the non-contact displacement meter head 301 (corresponding to the probe 301 in FIG. 2) is converted into a voltage by a controller 302 that outputs the signal as a voltage, and then an analog input module 303. To convert it to a digital signal. The digital signal is subjected to signal processing that combines the digital filter and the above-described processing 321 by the program of the programmable controller 304. Then, the value up to the signal processing by the programmable controller 304 is transferred to the CNC 107, and an offset is automatically given in the Z-axis direction shown in FIG. 2 without notifying or notifying the operator (not shown). Thereby, the correction for the displacement in the Z-axis direction is completed. An example of such a table is shown in Table 1 below when a map of compensation information of the direction of the rotating body and the intentionally provided shake component is stored in 321 as a table.

Further, in the case of executing the compensation process of the direction of the rotating body and the intentionally provided shake component at 321, examples of shake compensation formulas are shown in the following formulas (7) and (8).

In the case described above, when the digital filter is configured using an integer or a fixed-point type, the reciprocal of the time constant cannot be less than the minimum expression unit. In this case, it is preferable that the machine tool is configured so that the processing can extend the time constant to the above upper limit or more by switching the sampling interval. That is, it is preferable to perform output update when implemented using an integer type, and the output update is executed by the following formulas (9) and (10). Needless to say, a scan that does not require updating may be selected stochastically using a pseudo-random number sequence or the like.

201 Rotating shaft, 209 Tool (grinding stone), 121 Tool rotating device, 301 Displacement probe, 10, 20, 30 First-order lag element, 100 Machine tool, 300 Target (annular workpiece), 299 hole,
303 Analog-digital converter (analog input module), 304 Programmable controller (digital low-pass filter)

Claims (4)

  A tool rotating device having a rotating shaft and a tool attached to the rotating shaft and rotated by the rotating shaft; and a displacement meter for detecting an axial displacement of the rotating shaft in the tool rotating device in a non-contact manner, It is configured to estimate the displacement caused by the tool rotating device by combining a predetermined first order lag element with respect to the output of the displacement meter. In a machine tool having a target section provided with a portion, an analog-digital converter for converting the output of the displacement meter, and a digital low-pass filter, the cut-off frequency of the low-pass filter on the sensor value reading side is determined according to the number of rotations. A machine tool characterized by changing.   In the machine tool according to claim 1, in order to avoid a situation where the output of the sensor is not read at all when the rotation is completely stopped when the time constant is made completely proportional to the rotation speed, the sum of the minute constant and the rotation speed is avoided. A machine tool characterized by processing a correction command so that is proportional to the inverse of the time constant.   The machine tool according to claim 2, wherein a device for reading the current direction of the rotating body is mounted on the rotating device, and a map of compensation information of the direction of the rotating body and the intentionally provided shake component is expressed in a mathematical expression or a table state. The machine tool is configured to read out the shake compensation information from the direction information of the rotating body and compensate the correction command when the rotation is completely stopped. 4. The machine tool according to claim 3, wherein when the digital filter is configured using an integer or a fixed-point type, the reciprocal of the time constant cannot be less than the minimum expression unit. In this case, the sampling interval is switched. A machine tool configured to be able to perform a process of extending the time constant to the above upper limit or more.

Images