JP2017209767A - Method for determining contact of cutting tool, method for deciding cutting range and cutting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for determining contact of a cutting tool that can provide a further exact cutting range with respect to a workpiece.SOLUTION: A method for determining contact of a cutting tool 11 includes: a step of inputting a signal indicating vibration of a workpiece 30 into a frequency filter 15; and a step of determining contact when output from the frequency filter 15 satisfies a prescribed criterion. A method for deciding a cutting range includes a step of deciding an action range of the cutting tool 11 based on a position where the contact is determined.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a cutting tool contact determination method, a cutting range determination method, and a cutting apparatus.

  2. Description of the Related Art As a cutting device that performs cutting processing on a material, a device provided with a cutting tool is well known. Such a cutting apparatus is described in Patent Document 1.

JP 2003-117701 A

  When automating cutting, it is important to set a cutting range for a workpiece. Conventionally, in order to set a cutting range, a reference position of a cutting tool (for example, a position assumed to contact a workpiece) is previously measured with a contact sensor or the like and set in the apparatus, and the reference position is set as a starting point. As a technique, a method in which a predetermined range is set as a cutting range has been employed.

  FIG. 8 shows an example of the cutting operation using such a conventional technique. This figure represents the operation | movement which performs the cutting process on the workpiece 130 using the cutting tool 111 (a drill blade etc.) of length 20mm. In this example, the reference position P and the workpiece 130 are separated by 30 mm.

  This example shows a case where the cutting range by the cutting tool 111 is set as “a range of 15 mm from the reference position P as a starting point”. As shown in FIG. 8A, when the cutting tool 111 is at the fixed operation start position, the cutting tool 111 and the workpiece 130 do not contact each other. Next, when the cutting tool 111 starts the cutting operation and moves toward the workpiece 130, as shown in FIG. 8B, the workpiece is moved when the cutting tool 111 moves by 10 mm from the reference position P as shown in FIG. 130. At this point, a cutting action is generated on the workpiece 130, and the operation continues until the cutting tool 111 moves by 15 mm from the reference position P as shown in FIG. As a result, as shown in FIG. 8C, the workpiece 130 is cut by 5 mm. At this point, the cutting operation by the cutting tool 111 ends.

  However, the actual cutting action range may fluctuate regardless of the fixed reference position, and this may cause an error.

  FIG. 9 shows an example of the cause of such an error. FIG. 9 is an example in which an error occurs due to wear of the cutting tool 111 or positional deviation when the cutting tool is attached. In this example, as shown in FIG. 9A, the cutting tool 111 is worn by 3 mm and has a length of 17 mm. For this reason, as shown in FIG.9 (b), when the cutting tool 111 moves 10 mm from the reference position P, it does not contact the process target 130, but generation | occurrence | production of a cutting action becomes slower. As a result, as shown in FIG. 9C, even when the cutting tool 111 moves by 15 mm from the reference position P, the workpiece 130 can only be cut by 2 mm. Thus, an error of −3 mm occurs in the processing depth (that is, the processing depth becomes shallower by 3 mm).

  FIG. 10 shows another example of the cause of such an error. FIG. 10 is an example in which an error occurs due to a change in the arrangement of the workpiece 130. In this example, as shown to Fig.10 (a), the arrangement | positioning precision of the process target object 130 is bad, and it has arrange | positioned in the position away from the reference position P by 32 mm. For this reason, as shown in FIG.10 (b), when the cutting tool 111 moves 10 mm from the reference position P, the cutting tool 111 does not contact the process target object 130, but generation | occurrence | production of a cutting action becomes slower. As a result, as shown in FIG. 10C, even when the cutting tool 111 moves by 15 mm from the reference position P, the workpiece 130 can only be cut by 3 mm.

  In the example of FIG. 10, the workpiece 130 is arranged at a position 32 mm away from the reference position P, and this is a position that is 2 mm away from the accurate value 30 mm. (That is, the processing depth becomes shallower by 2 mm). If the workpiece 130 is arranged at a position 31 mm away from the reference position P, an error of −1 mm will occur in the machining depth, and the workpiece 130 is 28 mm away from the reference position P. If it is arranged in the above, an error of +2 mm occurs in the processing depth.

  FIG. 11 shows still another example of the cause of such an error. FIG. 11 is an example in which an error occurs due to a change in the dimension of the workpiece. The workpiece 130a shown in FIG. 11A has standard dimensions, and an accurate machining depth can be realized. However, the workpiece 130b shown in FIG. 11B has a dimension that is smaller by 1 mm than the standard, and therefore the machining depth is shallower by 1 mm. Moreover, the processing object 130c shown in FIG.11 (c) is a dimension larger by 2 mm than a standard, Therefore The processing depth becomes deep by 2 mm.

  In order to stabilize the cutting accuracy against such tool length variation error, workpiece dimension variation error, and workpiece reference layout variation error, the tool tip is detected and contacted with the workpiece. It is conceivable to determine the processing range based on the position.

  However, the conventional method has a problem that the contact between the workpiece and the tool tip cannot be accurately detected.

  For example, the vibration of the cutting device itself generated with the operation of the cutting tool is relatively detected as the vibration of the workpiece, and it may be erroneously determined that the tool has come into contact. In addition, disturbance vibration generated by an apparatus other than the cutting apparatus may be detected as the vibration of the object to be processed, and it may be erroneously determined that the tool has come into contact.

  This invention was made in order to solve such a problem, and it aims at providing the technique which can detect correctly the contact with a workpiece and a tool front-end | tip.

  For example, in the vibration contact detection operation of the tool tip that always stabilizes the cutting accuracy against the error due to tool length wear or misalignment at the time of tool installation, the workpiece dimension variation error, the workpiece reference layout variation error, further disturbance vibration It is possible to solve the erroneous detection error due to.

In order to solve the above-mentioned problems, a contact determination method for a cutting tool according to the present invention is as follows:
Inputting a signal representing the vibration of the workpiece into the frequency filter;
Determining that the cutting tool has contacted the workpiece when the output of the frequency filter satisfies a predetermined criterion.
In certain embodiments,
The frequency filter is a bandpass filter, a highpass filter or a lowpass filter,
The criterion is
-The acceleration associated with the vibration of the workpiece exceeds a predetermined value;
-The amplitude exceeds a predetermined value, or-vibration is detected by a vibration sensor,
At least one of them.
Moreover, the cutting range determination method according to the present invention is:
Performing the method described above;
Determining a working range of the cutting tool on the basis of a position where it is determined that the cutting tool has contacted the workpiece.
Moreover, the cutting device according to the present invention comprises:
Cutting tools,
A frequency filter for filtering the vibration of the workpiece;
And a control device that determines that the cutting tool has contacted the workpiece when the output of the frequency filter satisfies a predetermined criterion.

  According to the present invention, since contact determination is performed based on a specific frequency component of the vibration of the workpiece, it is possible to detect that the cutting tool has actually contacted the workpiece and to realize the cutting range more accurately. can do.

It is a figure which shows the example of a structure of the cutting apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the state by which the process target object has been arrange | positioned at the cutting apparatus of FIG. It is a figure which shows the state at the time of the start of cutting operation. It is a figure which shows the state at the time of cutting tool moving only 5 mm from the reference position. It is a figure which shows the state at the time of cutting tool moving only 10 mm from the reference position. It is a figure which shows the state at the time of cutting tool moving only 13 mm from the reference position. It is a figure which shows the state at the time of the cutting operation by a cutting tool ending. It is a figure which shows the example of the cutting operation using a prior art. It is a figure which shows an example of the cause which an error generate | occur | produces in a prior art. It is a figure which shows another example of the cause which an error generate | occur | produces in a prior art. It is a figure which shows another example of the cause which an error generate | occur | produces in a prior art.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows a configuration of a cutting apparatus 10 according to the present invention. The cutting apparatus 10 includes a cutting tool 11, a drive mechanism 12, a fixed positioning mechanism 13, a vibration detection device 14, a frequency filter 15, and a control device 20. As will be described below, the cutting apparatus 10 cuts a workpiece using the method according to the present invention.

  The cutting tool 11 is a tool that exerts a physical cutting action on a workpiece by performing a cutting operation. The cutting operation may be rotation or rotation of the cutting tool 11, may be linear motion, may be other motion, or may be a combination of these. Further, the cutting operation may be rotation or rotation of the workpiece, may be linear motion, may be other motion, or may be a combination of these. Although the shape of the cutting tool 11 is shown as an elongated rectangle in FIG. 1, this shape is not strict and does not need to be an elongated shape. The cutting tool 11 can be realized as, for example, an end mill, a drill blade, a grindstone, a cutter, a reamer, a tap, a cutting tool, or the like.

  The drive mechanism 12 generates a cutting action on the workpiece by moving the cutting tool 11. For example, when the cutting tool 11 rotates, the drive mechanism 12 may include a motor. The drive mechanism 12 generates a cutting action in a specific cutting range by moving the cutting tool 11 with respect to the workpiece. For example, when the cutting tool 11 is a drill blade, the drive mechanism 12 moves the cutting tool 11 in the direction of the rotation axis and causes the workpiece to be indented by a predetermined depth. Generate cutting action. As a result, cutting machining with a predetermined depth is formed on the workpiece.

  The fixed positioning mechanism 13 fixes and positions the workpiece. The fixed positioning mechanism 13 may be any structure as long as it can fix the workpiece, but can be realized as a chuck mechanism, for example. Further, any mechanism for positioning or fixing the workpiece can be used in place of the fixed positioning mechanism 13. Furthermore, instead of the fixed positioning mechanism 13, any mechanism for rotating, rotating, linearly moving the workpiece can be used. Note that the method of positioning or fixing the workpiece may be a gripping method, a pressing method, or another method.

  The vibration detection device 14 is attached to the fixed positioning mechanism 13 and detects the vibration of the workpiece. In the example of FIG. 1, vibration transmitted from the processing object via the fixed positioning mechanism 13 is detected, but the vibration is transmitted directly from the processing object (for example, by being in direct contact with the processing object). ) Vibration may be detected. For example, when the fixed positioning mechanism 13 includes a pin or the like for fixing the workpiece, the vibration detection device 14 may be disposed in contact with the pin or the like. The vibration detection device 14 can be realized as a sensor that converts position displacement or pressure displacement into an electric displacement signal, for example.

  The frequency filter 15 is connected to the vibration detection device 14 and filters vibration (or a signal representing vibration) transmitted from the vibration detection device 14. For example, a signal representing vibration is received as an electrical signal, which is filtered to block a specific frequency component or allow only a specific frequency component to pass. The frequency filter 15 can be configured as a bandpass filter, for example. Specifically, a bandpass filter that transmits a frequency component around 5 kHz (for example, a frequency band of 4 kHz to 6 kHz) can be used.

  The control device 20 controls the operation of the entire cutting device 10. For example, as shown in the figure, the control device 20 is electrically connected to the drive mechanism 12, and controls the operation of the cutting tool 11 by controlling the operation of the drive mechanism 12. As a result, the cutting action range for the workpiece is determined. Control. The control device 20 is electrically connected to the frequency filter 15 and receives a signal output from the frequency filter 15. In particular, as will be described later, the control device 20 determines whether or not the cutting tool 11 has contacted the workpiece based on a signal from the frequency filter 15.

  FIG. 2 shows a state in which a workpiece 30 (also called a workpiece or the like) is arranged in the cutting apparatus 10. The workpiece 30 is fixed and positioned by the fixed positioning mechanism 13. The workpiece 30 is made of, for example, a metal, but may be of any shape or material as long as it includes a workpiece material that generates vibration upon contact with the cutting tool 11.

  An example of the cutting operation by the cutting apparatus 10 according to the present invention will be described with reference to FIGS. In this example, description will be made using a configuration in which the workpiece 30 is fixed and the cutting tool 11 is driven. However, a configuration in which the cutting tool is fixed and the workpiece is driven may be employed. Further, in this example, a state is considered in which the cutting tool 11 having a length of 20 mm at the time of manufacture is worn or displaced to a length of 17 mm with use or when the cutting tool is attached.

  FIG. 3 shows a state at the start of the cutting operation. Under the control of the control device 20, the cutting device 10 places the cutting tool 11 at a predetermined cutting operation start initial position (reference position P) as shown in FIG. 3A, and starts the cutting operation there. The reference position P may be an initial position of the cutting tool 11 when the cutting apparatus 10 is powered on.

  In the present embodiment, the position of the cutting tool 11 is represented as the position of the drive mechanism 12 side end as shown in FIG. 3A, but any position as long as the position is fixed with respect to the cutting tool 11. Can be expressed as

  For example, when the cutting tool 11 is a drill blade, the control device 20 starts the rotation operation of the cutting tool 11 at the reference position P. In this example, the reference position P is separated from the workpiece 30 by 30 mm.

  The cutting device 10 causes the frequency filter 15 to input a signal representing the vibration of the workpiece 30. The signal representing the vibration of the workpiece 30 has a spectrum shown in FIG. 3B, for example. The horizontal axis of FIG.3 (b) represents a frequency and a vertical axis | shaft represents the magnitude | size of a vibration. In the example of FIG. 3B, the magnitude of the vibration is represented by the acceleration associated with the vibration of the workpiece 30. Alternatively, the magnitude of the vibration may be represented by the amplitude of the vibration of the workpiece 30.

  This vibration includes, for example, vibrations of the cutting apparatus 10 itself that occur with the operation of the cutting tool 11 and vibrations of the drive mechanism 12 that are relatively detected as vibrations of the workpiece 30. . Further, this vibration may include disturbance vibration. The disturbance vibration means, for example, vibration generated by an apparatus other than the cutting apparatus 10. Due to these factors, even if the cutting tool 11 and the workpiece 30 are not in contact, vibration of the workpiece 30 as shown in FIG. 3B may be detected.

  In this example, the magnitude of the vibration of the workpiece 30 shows a peak at the frequency f1, and exceeds a predetermined threshold value TH in the frequency band before and after that. This threshold value TH may be a predetermined value stored in advance by the control device 20.

  The frequency filter 15 filters the input signal (for example, the signal shown in FIG. 3B) and outputs the result. For example, the output signal has a spectrum shown in FIG. The vertical axis and horizontal axis in FIG. 3C are the same as those in FIG.

  In this example, the frequency filter 15 is a band-pass filter, which transmits a frequency component included in a predetermined frequency band B and blocks or attenuates a frequency component in another frequency band. Here, the frequency band B can be arbitrarily designed. For example, the frequency band B is a band including a frequency of a characteristic vibration generated in the workpiece 30 when the cutting tool 11 and the workpiece 30 are in contact with each other. Can do. In this example, the components around the frequency f1 are blocked, and there are no components exceeding the threshold TH.

  Based on the output of the frequency filter 15, the control device 20 determines whether or not the cutting tool 11 and the workpiece 30 are in contact with each other. For example, the control device 20 determines that the cutting tool 11 has contacted the workpiece 30 when the output of the frequency filter 15 satisfies a predetermined determination criterion. The criterion is, for example, that the acceleration related to the vibration of the workpiece 30 exceeds the threshold value TH in the output of the frequency filter 15. More precisely, among the frequency components included in the vibration of the workpiece 30, there are those whose acceleration exceeds the threshold value TH. Thus, it can be said that one aspect of the present invention includes a contact determination method for the cutting tool 11.

  In the example of FIG. 3C, the acceleration does not exceed the threshold value TH in the output signal of the frequency filter 15 (more strictly speaking, there is no frequency component whose acceleration exceeds the threshold value TH). It is determined that 11 is not in contact with the workpiece 30. In this case, the control device 20 brings the cutting tool 11 closer to the workpiece 30. For example, when the cutting tool 11 is a drill blade, the cutting tool 11 is moved in a specific direction in the rotation axis direction.

  FIG. 4 shows a state when the cutting tool 11 has moved from the reference position P by 5 mm. FIG. 4A shows the position of the cutting tool 11. At this position, the cutting tool 11 has not yet contacted the workpiece 30, but vibrations accompanying the operation of the drive mechanism 12 occur. Due to this vibration, a new vibration is applied to the workpiece 30, and this new vibration is detected by the vibration detection device 14.

  The signal representing the vibration of the workpiece 30 including this new vibration has a spectrum shown in FIG. 4B, for example. In FIG. 4B, in addition to the peak at the frequency f1, a new peak at the frequency f2 appears as the drive mechanism 12 operates.

  The magnitude of the vibration of the workpiece 30 exceeds a predetermined threshold value TH in a frequency band extending before and after the frequency f1 and a frequency band extending before and after the frequency f2 (these frequency bands may be separated from each other). And some or all may overlap, or one may be included in the other). However, since the acceleration does not exceed the threshold value TH in the output signal of the frequency filter 15, the control device 20 determines that the cutting tool 11 is not in contact with the processing object 30, and further adds the cutting tool 11 to the processing object 30. Move closer.

  FIG. 5 shows a state when the cutting tool 11 has moved from the reference position P by 10 mm. FIG. 5A shows the position of the cutting tool 11. This position is a position that should be in contact with the workpiece 30 if it is a cutting tool 11 (20 mm in length) immediately after manufacture, but the cutting tool 11 is shortened due to wear as described above. It does not contact the workpiece 30. For this reason, as shown in FIGS. 5B and 5C, there is no substantial change in the signal representing the vibration of the workpiece 30 and the output signal of the frequency filter 15.

  In the example of FIG. 5C, since the acceleration does not exceed the threshold value TH in the output signal of the frequency filter 15, the control device 20 determines that the cutting tool 11 is not in contact with the workpiece 30. In this case, the control device 20 brings the cutting tool 11 closer to the workpiece 30.

  FIG. 6 shows a state when the cutting tool 11 has moved from the reference position P by 13 mm. FIG. 6A shows the position of the cutting tool 11. At this point, the cutting tool 11 contacts the workpiece 30. Due to this contact, a new vibration is applied to the workpiece 30, and this new vibration is detected by the vibration detection device 14.

  The signal representing the vibration of the workpiece 30 including this new vibration has a spectrum shown in FIG. 6B, for example. In addition to the peaks at frequencies f1 and f2 shown in FIG. 4B, a new peak at frequency f3 appears. The magnitude of the vibration of the workpiece 30 exceeds a predetermined threshold TH in a frequency band extending around the frequency f3.

  This frequency f3 is assumed to be included in the frequency band B. In this case, as shown in FIG. 6C, the output signal of the frequency filter 15 includes a frequency component whose acceleration exceeds the threshold value TH. In this case, since the output of the frequency filter 15 satisfies the criterion (that is, the acceleration related to the vibration of the workpiece 30 exceeds a predetermined value), the control device 20 causes the cutting tool 11 to be processed by the workpiece 30. It is determined that the contact has been made.

  Thus, due to the action of the frequency filter 15, among the vibrations representing the vibration of the workpiece 30, disturbances, vibrations by the cutting tool 11 (for example, components having a peak at the frequency f 1), and vibrations by the drive mechanism 12 (for example, frequency f 2) Component having a peak in FIG. 5) and vibration due to contact with the cutting tool 11 (component having a peak at frequency f3) are separated, so that vibration due to contact with the cutting tool 11 is appropriately detected and determined. It is possible.

  When it is determined that the cutting tool 11 has contacted the workpiece 30, the control device 20 determines the operating range of the cutting tool 11 using the determined position as a reference position. The action range can be determined as a range of a predetermined distance in the direction in which cutting proceeds from the reference position, for example. Specifically, when it is required to cut by a depth of 5 mm, the range from the reference position to the feed processing by 5 mm in the axial direction is the working range of the cutting tool 11. Further, the difference between the actual contact time and the contact detection time after the communication time (in this embodiment, the communication time from the vibration detection device 14 via the frequency filter 15 to the control device 20) is appropriately offset. If the value is set, the accuracy may be further improved. Thus, it can be said that one aspect of the present invention includes a method for determining a cutting range of the cutting tool 11.

  After determining the action range, the control device 20 causes the cutting tool 11 to act within the action range, thereby realizing cutting on the workpiece 30. Thus, it can be said that one aspect of the present invention includes a cutting method using the cutting tool 11.

  FIG. 7 shows a state at the time when the cutting operation by the cutting tool 11 ends. In this example, the cutting tool 11 has moved by 18 mm from the reference position P, and the machining object 30 is formed with a cutting machine work having a depth of 5 mm. At this point, the control device 20 ends the cutting operation of the cutting tool 11.

  In addition, although the action range is defined as a length range in a specific direction in the example of FIG. 7, it may be defined as a range having an area or a volume. In addition, the working range is defined only by the linear motion of the cutting tool 11 in the example of FIG. 7, but instead of or in addition to this, rotation or other motion of the cutting tool 11 or other cutting tools. May be defined. Further, the range of action may be defined by a linear motion, rotation, or other motion of the workpiece 30.

  As described above, according to the cutting apparatus 10 according to Embodiment 1 of the present invention, the contact determination is performed based on the frequency component included in the frequency band B among the vibrations of the workpiece 30, so that cutting is performed. It can be detected that the tool 11 has actually contacted the workpiece 30, and the cutting range can be realized more accurately.

  For example, accurate contact determination is possible even if the length of the cutting tool 11 varies as described in FIGS. Further, even when the size of the processing object 30 is changed or when the position of the processing object 30 is changed, the same accurate contact determination is possible.

  In particular, since the disturbance can be removed by applying the frequency filter 15, it is possible to suppress erroneous detection and perform accurate contact determination.

  In addition, as a method for detecting that the cutting tool 11 has contacted the workpiece 30, a method based on electrical continuity is also possible, but this method has various technical difficulties. For example, although it can be determined that the cutting tool 11 and the workpiece 30 are in contact with each other due to electrical continuity, in this case, there is a risk of erroneous detection due to lubricating oil, metal powder generated by cutting, or the like. There is. Moreover, the electrical continuity between the cutting tool 11 and the workpiece 30 may not be directly measured due to a request for the insulating structure or grounding structure of the cutting apparatus 10. According to the method according to the present invention, such a difficulty can be avoided, and contact can be determined more accurately in a wider configuration.

  The frequency band B which is the transmission band of the frequency filter 15 is a band including the frequency of characteristic vibration generated in the workpiece 30 when the cutting tool 11 and the workpiece 30 are in contact with each other as described above. . The frequency band B is not limited to the example in the first embodiment, and may be determined appropriately by those skilled in the art.

  For example, it is possible to use a frequency filter that experimentally brings the cutting tool 11 and the workpiece 30 into contact with each other, measures vibration thereof, specifies a frequency band in which a characteristic component appears, and transmits the frequency band. Alternatively, in the actual operating environment of the cutting apparatus 10, it is possible to use a frequency filter that measures vibrations until the cutting tool 11 and the workpiece 30 come into contact with each other, that is, disturbances and blocks the disturbances.

  The frequency filter 15 is a bandpass filter in the first embodiment, but may be another filter. For example, a high pass filter, a low pass filter, or the like may be used.

  In the first embodiment described above, the reference for determining the contact between the cutting tool 11 and the workpiece 30 relates to the acceleration related to the vibration of the workpiece 30, but other criteria may be used. For example, when the amplitude of the output of the frequency filter 15 (more strictly, for example, the one having the maximum amplitude among the frequency components) exceeds a predetermined value, the control device 20 causes the cutting tool 11 to move to the workpiece 30. You may determine with contact.

  Alternatively, the control device 20 may include a known vibration sensor, and may be configured such that an output signal from the frequency filter 15 is input to the vibration sensor. In that case, when the vibration is detected by the vibration sensor, it may be determined that the cutting tool 11 has contacted the workpiece 30. In this way, the method and apparatus of the present invention can be implemented using a commercially available vibration sensor.

Moreover, you may combine a some reference | standard as a determination reference | standard. For example, the criterion is
-The acceleration associated with the vibration of the workpiece exceeds a predetermined value;
-The amplitude exceeds a predetermined value;-the vibration is detected by a vibration sensor;
Any one of these may be satisfied, or any of these may be simultaneously satisfied.

  DESCRIPTION OF SYMBOLS 10 Cutting apparatus, 11 Cutting tool, 15 Frequency filter, 20 Control apparatus, 30 Process target, TH threshold value (predetermined value).

Claims (4)

Inputting a signal representing the vibration of the workpiece into the frequency filter;
And a step of determining that the cutting tool is in contact with the workpiece when the output of the frequency filter satisfies a predetermined criterion. The frequency filter is a bandpass filter, a highpass filter or a lowpass filter,
The criterion is
-The acceleration associated with the vibration of the workpiece exceeds a predetermined value;
-The amplitude exceeds a predetermined value, or-vibration is detected by a vibration sensor,
The method of claim 1, comprising at least one of: Performing the method according to claim 1 or 2;
And a step of determining an operating range of the cutting tool with reference to a position where it is determined that the cutting tool has contacted the workpiece. Cutting tools,
A frequency filter for filtering the vibration of the workpiece;
A cutting apparatus comprising: a control device that determines that the cutting tool has contacted the workpiece when the output of the frequency filter satisfies a predetermined criterion.

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