JP2020160830A - Numerical control device, machine tool, control program, and storage medium - Google Patents

Abstract

To provide a numerical control device capable of detecting chatter vibration without adding a new configuration, a machine tool having the numerical control device, a control program for detecting chatter vibration, and a storage medium storing the control program.SOLUTION: A numerical control device specifies a relative moving direction of an industrial tool with respect to a work body (P5). The numerical control device specifies a plurality of cutting edge positions that are positions of cutting edges of the industrial tools with respect to the work body (P4). The numerical control device specifies a plurality of cutting positions at which a blade cuts the work body in the moving direction based on the plurality of specified cutting edge positions (P6). The numerical control device specifies distance between the plurality of specified cutting positions as cutting amount (P7). The numerical control device determines whether chatter vibration has occurred based on the specified cutting amount (P8). The numerical control device notifies when determining that chatter vibration has occurred (P9).SELECTED DRAWING: Figure 3

Description

The present invention relates to a numerical control device, a machine tool provided with the numerical control device, a control program, and a storage medium for storing the control program.

There are various methods for detecting chatter vibration generated in a machine tool. Patent Document 1 discloses a vibration information display device that displays a detection result of chatter vibration on a monitor. The device acquires vibration values in the X-axis, Y-axis, and Z-axis directions from three vibration sensors provided in the spindle housing. The device calculates the rate of change of vibration per unit time based on the result of comparison between the acquired vibration value and a predetermined threshold value. Further, when the rate of change exceeds a set value, the device displays a vibration value or the like as vibration information of chatter vibration on a monitor.

JP-A-2016-224695

In this method, it is necessary to provide a vibration sensor in the spindle housing in order to detect chatter vibration. On the other hand, from the viewpoint of cost reduction and space saving, it is preferable that chatter vibration can be detected without adding a new detector such as a vibration sensor to the machine tool.

An object of the present invention is to store a numerical control device capable of detecting chatter vibration without adding a new configuration, a machine tool equipped with the numerical control device, a control program for detecting chatter vibration, and the control program. It is the provision of the storage medium.

The numerical control device according to the first aspect of the present invention includes a spindle for rotating the tool, a first detector for detecting the rotation of the spindle, and a feed for moving the tool relative to the work piece. A numerical control device that controls a machine tool including a mechanism and a second detector that detects the relative movement of the tool by the feed mechanism, and cuts the work piece by the tool. First specification that specifies the relative movement direction of the tool with respect to the work piece based on the storage unit that stores the tool information including at least the number and diameter of the tool blades and the detection result of the second detector. A plurality of cutting edge positions, which are positions of the cutting edge of the tool with respect to the work piece, are specified based on the unit, the tool information stored in the storage unit, and the detection results of the first detector and the second detector. (Ii) Based on the specified portion and the plurality of cutting edge positions specified by the second specified portion, a plurality of cut positions where the blade cuts the work piece in the moving direction specified by the first specified portion are specified. The fourth specific part that specifies the distance between the third specific part and the plurality of cut positions specified by the third specific part as the cut amount, and the cut amount specified by the fourth specific part. Based on the above, a determination unit for determining whether or not chatter vibration has occurred and a notification unit for notifying when it is determined by the determination unit that chatter vibration has occurred are provided.

The numerical control device specifies the depth of cut in which the work piece is cut by the tool blade based on the detection results of the first detector and the second detector. The numerical control device detects the occurrence of chatter vibration based on the specified depth of cut and notifies the operator. Therefore, the numerical control device can determine the presence or absence of chatter vibration by using the first detector and the second detector usually provided in the machine tool. Therefore, the numerical control device can detect chatter vibration without adding a new detector such as a vibration sensor to the machine tool.

In the first aspect, the first specific unit specifies a plurality of relative positions of the tool with respect to the work piece based on the detection result of the second detector, and a direction extending along the specified relative positions. The moving direction may be specified based on the moving average of. At that time, the numerical control device can accurately identify the relative movement direction of the tool with respect to the work piece by a simple method.

In the first aspect, the second specific unit includes the rotation center of the tool determined based on the detection result of the second detector, the rotation angle of the tool determined based on the detection result of the first detector, and the said. A plurality of the blade edge positions may be specified based on the number of blades and the diameter stored as the tool information in the storage unit. At that time, the numerical control device can accurately identify the cutting edge position.

In the first aspect, the third specific portion is different from the first movement locus, which is the movement locus of the cutting edge, and the first movement locus, based on the plurality of the cutting edge positions specified by the second specific portion. (Ii) The movement locus is specified, and the intersection of the virtual vector extending from the rotation center of the tool in the movement direction specified by the first specific portion and the specified first movement locus and the second movement locus is defined. , The fourth specific part specifies the distance between the first total cut position and the second cut position specified by the third specific part. It may be specified as the cut amount. At this time, the numerical control device can accurately specify the depth of cut, so that the occurrence of chatter vibration can be accurately detected and notified.

In the first aspect, the third specific unit may specify a plurality of arcs passing through the positions of the plurality of cutting edge positions as the movement locus. At this time, the numerical control device can accurately estimate the movement locus of the cutting edge, so that the accuracy of the cutting position can be improved.

In the first aspect, the second specifying portion may specify the cutting edge position of the first blade of the tool and the cutting edge position of the second blade different from the first blade. At that time, the numerical control device can quickly detect and notify the occurrence of chatter vibration in a short time.

In the first aspect, the notification unit may display a locus image including at least the movement locus specified by the third specific unit on the display unit. The operator can grasp not only the presence or absence of chatter vibration but also the degree of chatter vibration.

The machine tool according to the second aspect of the present invention is characterized by including the numerical control device according to the first aspect. According to the second aspect, the same effect as that of the first aspect can be obtained.

The control program according to the third aspect of the present invention includes a spindle for rotating the tool, a first detector for detecting the rotation of the spindle, and a feed mechanism for moving the tool relative to the work piece. And a second detector that detects the relative movement of the tool by the feed mechanism, and a computer that controls the machine tool and cuts the work piece with the tool, Based on the detection result, the first specific step of specifying the relative movement direction of the tool with respect to the work piece, the tool information stored in the storage unit including at least the number and diameter of the blades of the tool, and the first item. A second specific step of specifying a plurality of cutting edge positions of the tool with respect to the work piece based on the detection results of the detector and the second detector, and a plurality of specified steps specified by the second specific step. Based on the cutting edge position, a third specific step for specifying a plurality of cutting positions where the blade cuts the work piece in the moving direction specified by the first specific step, and a plurality of specified steps specified by the third specific step. Judgment as to whether or not chatter vibration has occurred based on the fourth specific step of specifying the distance between the cut positions as the cut amount and the cut amount specified by the fourth specific step. The step and the notification step of notifying when it is determined that chatter vibration has occurred by the determination step are executed. According to the third aspect, the same effect as that of the first aspect can be obtained.

The storage medium according to the fourth aspect of the present invention includes a spindle for rotating the tool, a first detector for detecting the rotation of the spindle, and a feed mechanism for moving the tool relative to the work piece. And a second detector that detects the relative movement of the tool by the feed mechanism, and a computer that controls the machine tool and cuts the work piece with the tool, Based on the detection result, the first specific step of specifying the relative movement direction of the tool with respect to the work piece, the tool information stored in the storage unit including at least the number and diameter of the blades of the tool, and the first item. A second specific step of specifying a plurality of cutting edge positions of the tool with respect to the work piece based on the detection results of the detector and the second detector, and a plurality of specified steps specified by the second specific step. Based on the cutting edge position, a third specific step for specifying a plurality of cutting positions where the blade cuts the work piece in the moving direction specified by the first specific step, and a plurality of specified steps specified by the third specific step. Judgment as to whether or not chatter vibration has occurred based on the fourth specific step of specifying the distance between the cut positions as the cut amount and the cut amount specified by the fourth specific step. A control program for executing the step and the notification step of notifying when it is determined that chatter vibration has occurred due to the determination step is stored. According to the fourth aspect, the same effect as that of the first aspect can be obtained.

A perspective view of the machine tool 1. The block diagram which shows the electrical structure of the machine tool 1 and the numerical control device 30. Explanatory drawing explaining the detection method of chatter vibration. Explanatory drawing explaining the method of specifying the cutting edge position U ₁ (i), U ₂ (i). Explanatory drawing explaining the method of specifying the moving angle W (i). The figure which shows the 1st movement locus T ₁ and the 2nd movement locus T ₂ . Explanatory drawing explaining the method of specifying the _first insertion position C ₁ (k). Flow diagram of main processing. Flow chart of cut position identification process. Flow chart of cut amount identification processing. An example of a trajectory image displayed on the display unit 17. A surface photograph of the work piece 3 when chatter vibration does not occur. A surface photograph of the work piece 3 when chatter vibration occurs.

An embodiment of the present invention will be described. In the following description, the left and right, front and back, and top and bottom indicated by arrows in the figure are used. The horizontal direction, the front-rear direction, and the vertical direction of the machine tool 1 are the X-axis direction, the Y-axis direction, and the Z-axis direction of the machine tool 1, respectively. The right, backward, and upward directions are the positive directions of the corresponding axes, respectively. The left, front, and down directions are the negative directions of the corresponding axes, respectively. The machine tool 1 shown in FIG. 1 is a machine that rotates a tool 4 mounted on a spindle 9 and cuts a work piece 3 held on the upper surface of a table 13. The numerical control device 30 (see FIG. 2) controls the operation of the machine tool 1.

<Structure of machine tool 1>
The structure of the machine tool 1 will be described with reference to FIG. The machine tool 1 includes a base 2, a column 5, a spindle head 7, a spindle 9, a table device 10, a tool changing device 20, a control box 6, an operation panel 15 (see FIG. 2), and the like. The base 2 is a metal base having a substantially rectangular parallelepiped shape. The column 5 is erected behind the upper part of the base 2. The spindle head 7 is provided so as to be movable in the Z-axis direction along the front surface of the column 5. The spindle head 7 rotatably supports the spindle 9 inside. The spindle 9 has a mounting hole (not shown) at the bottom of the spindle head 7. The spindle 9 mounts the tool 4 in the mounting hole and rotates by driving the spindle motor 52 (see FIG. 2). The spindle motor 52 is provided on the spindle head 7. The spindle head 7 moves in the Z-axis direction by a Z-axis moving mechanism (not shown) provided on the front surface of the column 5. The Z-axis moving mechanism includes a Z-axis motor 51 (see FIG. 2) and the like. The numerical control device 30 controls the movement of the spindle head 7 in the Z-axis direction by controlling the drive of the Z-axis motor 51 (see FIG. 2).

The table device 10 includes a Y-axis moving mechanism (not shown), a Y-axis table 12, an X-axis moving mechanism (not shown), a table 13, and the like. The Y-axis moving mechanism is provided on the front side of the upper surface of the base 2, and includes a pair of Y-axis rails, a Y-axis ball screw, a Y-axis motor 54 (see FIG. 2), and the like. The pair of Y-axis rails and Y-axis ball screws extend in the Y-axis direction. The pair of Y-axis rails guide the Y-axis table 12 on the upper surface in the Y-axis direction. The Y-axis table 12 is formed in a substantially rectangular parallelepiped shape, and has a nut (not shown) on the outer surface of the bottom. The nut is screwed into the Y-axis ball screw. When the Y-axis motor 54 rotates the Y-axis ball screw, the Y-axis table 12 moves along with the nut along the pair of Y-axis rails. Therefore, the Y-axis moving mechanism supports the Y-axis table 12 so as to be movable in the Y-axis direction.

The X-axis moving mechanism is provided on the upper surface of the Y-axis table 12, and includes a pair of X-axis rails (not shown), an X-axis ball screw (not shown), an X-axis motor 53 (see FIG. 2), and the like. The X-axis rail and the X-axis ball screw extend in the X-axis direction. The table 13 is formed in a rectangular plate shape in a plan view and is provided on the upper surface of the Y-axis table 12. The table 13 is provided with a nut (not shown) at the bottom. The nut is screwed into the X-axis ball screw. When the X-axis motor 53 rotates the X-axis ball screw, the table 13 moves along the pair of X-axis rails together with the nut. Therefore, the X-axis moving mechanism supports the table 13 so as to be movable in the X-axis direction. Therefore, the table 13 can be moved in the X-axis direction and the Y-axis direction on the base 2 by the Y-axis moving mechanism, the Y-axis table 12, and the X-axis moving mechanism.

The tool changer 20 is provided on the front side of the spindle head 7, and includes a disk-shaped tool magazine 21, a magazine motor 55 (see FIG. 2), and the like. The tool magazine 21 holds a plurality of tools (not shown) radially on the outer circumference, and positions the tool instructed by the tool change command at the tool change position. The tool change command is given by the NC program. The tool change position is the lowest position of the tool magazine 21. The tool changer 20 drives the magazine motor 55 to move the tool 4 mounted on the spindle 9 and the tool attached to the tool magazine 21 to a series of ascending of the spindle head 7, rotation of the tool magazine 21, and descending of the spindle head 7. Replace and replace depending on the operation.

The control box 6 stores the numerical control device 30 (see FIG. 2). The numerical control device 30 controls the Z-axis motor 51, the spindle motor 52, the X-axis motor 53, the Y-axis motor 54, and the magazine motor 55 (see FIG. 2) provided in the machine tool 1, and holds them on the table 13. Various processes are performed on the work piece 3 by moving the tool 4 mounted on the spindle 9 relative to the work piece 3. The various types of processing include, for example, drilling using a drill, tap, etc., side surface processing using an end mill, milling cutter, and the like.

The operation panel 15 is provided, for example, on the outer wall of a cover (not shown) that covers the machine tool 1. The operation panel 15 includes an operation unit 16 and a display unit 17 (see FIG. 2). The operation unit 16 receives inputs such as various information and operation instructions, and outputs them to the numerical control device 30 described later. The display unit 17 displays various screens based on a command from the numerical control device 30 described later.

<Electrical configuration>
The electrical configuration of the numerical control device 30 and the machine tool 1 will be described with reference to FIG. The numerical control device 30 and the machine tool 1 include a CPU 31, ROM 32, RAM 33, a storage device 34, an external interface 35, an input / output unit 36, drive circuits 51A to 55A, encoders 51B to 55B, and the like. The ROM 32 stores various parameters. The RAM 33 temporarily stores various types of information. The storage device 34 is non-volatile and stores various information including a main processing program, an NC program, and tool information described later. The NC program is composed of a plurality of lines including various control commands, and controls various operations including axis movement and tool change of the machine tool 1 in line units. The CPU 31 reads the NC program commands one by one and executes various operations. The tool information is information about a tool 4 that can be attached to the spindle 9 of the machine tool 1. The tool information is associated with the number of blades and the radius for each type of tool 4. The number of blades is the number of blades of the tool 4. The radius is the distance from the center of rotation of the tool 4 to the cutting edge of the blade, and is associated with each cutting edge. The external interface 35 reads out the information stored in the storage medium 35A. For example, the CPU 31 reads the program stored in the storage medium 35A by the external interface 35 and stores it in the storage device 34.

The drive circuit 51A is connected to the Z-axis motor 51 and the encoder 51B. The drive circuit 52A is connected to the spindle motor 52 and the encoder 52B. The drive circuit 53A is connected to the X-axis motor 53 and the encoder 53B. The drive circuit 54A is connected to the Y-axis motor 54 and the encoder 54B. The drive circuit 55A is connected to the magazine motor 55 that drives the tool magazine 21 and the encoder 55B. The Z-axis motor 51, the spindle motor 52, the X-axis motor 53, the Y-axis motor 54, and the magazine motor 55 are all servo motors (hereinafter, collectively referred to as "motors").

The drive circuits 51A to 55A receive commands from the CPU 31 and output drive currents to the corresponding motors 51 to 55, respectively. The encoders 51B to 55B detect the rotation position of the rotation shaft of each of the corresponding motors 51 to 55, and output a signal indicating the detection result to the drive circuits 51A to 55A. The drive circuits 51A to 55A output the signals received from the encoders 51B to 55B to the CPU 31. Further, the drive circuits 51A to 55A receive signals from the encoders 51B to 55B and perform feedback control of the rotation position and speed of each of the motors 51 to 55. The input / output unit 36 is connected to the operation unit 16 and the display unit 17 of the operation panel 15, respectively.

<Detection method of chatter vibration>
A method of detecting the rattle vibration generated in the machine tool 1 by the numerical control device 30 will be described with reference to FIGS. 3 to 7. Chatter vibration is a general term for unnecessary vibration generated during cutting by the machine tool 1. Chatter vibration is not preferable because it may cause deterioration of the quality of the finished surface of the work piece 3 and abnormal wear of the tool 4. Therefore, the numerical control device 30 detects the chatter vibration by the method shown below and notifies the operator. At this time, since the operator can deal with the chatter vibration at an early stage, the influence of the above-mentioned trouble can be minimized.

In the following description, an example will be given when the machine tool 1 performs a cutting operation using a tool 4 having a total of m (m is an integer of 1 or more) blades. Each of the m blades is referred to as an nth blade (n is an integer from 1 to m). The distance between the center of rotation and the cutting edge of the nth blade in the radial direction extending from the center of rotation of the tool 4 is referred to as a radius R _n . Said time, the storage device 34 stores the number of teeth m and the radius _R 1 · · · _{R m} as the tool information. The angle in the radial direction extending from the center of rotation of the tool 4 through the cutting edge of the nth blade is referred to as a rotation angle θ _n (rad). The reference direction of the rotation angle θ _n is a direction extending from the rotation center of the tool 4 in a predetermined direction (for example, a positive direction (right direction) of the X axis). Hereinafter, this direction is referred to as a reference direction. The position of the rotation shaft of the spindle motor 52 in a state where the direction extending from the rotation center of the tool 4 through the cutting edge of the first blade (n = 1) faces the reference direction is referred to as a spindle reference position. The CPU 31 of the numerical control device 30 can derive the rotation angle θ _n of the nth blade by the following equation (1) when the rotation axis of the spindle motor 52 is at the spindle reference position.
θn = 2π / m × (n-1) (1)

A predetermined origin position (0,0) in the X-axis-Y-axis direction is defined. The position of each rotation axis of the X-axis motor 53 and the Y-axis motor 54 when the rotation center of the tool 4 is arranged at the origin position is set as the feed axis reference position.

The flow of the process for detecting the chatter vibration will be described with reference to FIG. The CPU 31 of the numerical control device 30 acquires the signal output by the encoder 53B via the drive circuit 53A. The CPU 31 specifies the amount of rotation of the rotation axis of the X-axis motor 53 from the feed axis reference position based on the acquired signal. The CPU 31 specifies the position X _FB of the rotation center of the tool 4 in the X-axis direction based on the specified rotation amount (P1). The CPU 31 acquires the signal output by the encoder 54B via the drive circuit 54A. The CPU 31 specifies the amount of rotation of the rotation axis of the Y-axis motor 54 from the feed axis reference position based on the acquired signal. The CPU 31 specifies the position _YFB of the rotation center of the tool 4 in the Y-axis direction based on the specified rotation amount (P2).

CPU31 by the procedure P1, P2, the position of the X-axis -Y-axis direction of the center of rotation of the tool 4, is identified as the feed axis position _{Q FB.} The coordinates indicated by the feed axis position Q _FB are (X _FB , Y _FB ). CPU31 repeats the identification process of the feed axis position _{Q FB} in a predetermined cycle. Hereinafter, the feed axis position Q _FB specified at the i (i is an integer) th position is referred to as a feed axis position Q _FB (i). The coordinates indicated by the feed axis position Q _FB (i) are referred to as (X _FB (i), Y _FB (i)) (see FIG. 4).

The CPU 31 acquires the signal output by the encoder 52B via the drive circuit 52A. The CPU 31 specifies the rotation angle of the rotation shaft of the spindle motor 52 from the spindle reference position based on the acquired signal (P3). The rotation angle identified, referred to as a main shaft angle S _FB. The CPU 31 repeats the process of specifying the spindle angle S _{FB in} the same cycle as the process of specifying the feed axis position Q _FB . Hereinafter, the i-th specified spindle angle S _FB will be referred to as a spindle angle S _FB (i) (see FIG. 4).

CPU31, based on the particular result by the procedure P1 to P3, (referred to as edge positions U _1.) Position of the cutting edge of the first blade of the tool 4 with respect to the Kezukarada 3 and second differs from the first blade with respect to the Kezukarada 3 The position of the cutting edge of the two blades (referred to as the cutting edge position U ₂ ) is specified (P4). The first blade and the second blade may be adjacent to each other, or another blade may be interposed between the first blade and the second blade.

As shown in FIG. 4, the procedure P1, the feed shaft position identified by P2 _Q FB (i), and the cutting edge position _{U 1} and edge position U be identified based on the main shaft angle _S FB identified by the procedure P3 (i) ₂ are referred to as cutting edge positions U ₁ (i) and U ₂ (i), respectively. The coordinates indicated by the cutting edge position U ₁ (i) are referred to as (X ₁ (i), Y ₁ (i)). The coordinates indicated by the cutting edge position U ₂ (i) are referred to as (X ₂ (i), Y ₂ (i)). The CPU 31 has a feed shaft position Q _FB (i) (coordinates (X _FB (i), Y _FB (i)), a spindle angle S _FB (i), and tool information (number of blades m, radius R) stored in the storage device 34. ₁ ... R _m ) and the cutting edge positions U ₁ (i) and U ₂ (i) are specified by applying the following equation (2) based on the rotation angle θ _n calculated by the equation (1). To do.
X ₁ (i) = X _FB (i) + R ₁ cos (S _FB (i) + θ ₁ ) (However, when the first blade, θ ₁ = 0)
Y ₁ (i) = Y _FB (i) + R ₁ sin (S _FB (i) + θ ₁ ) (However, when the first blade, θ ₁ = 0)
X ₂ (i) = X _FB (i) + R ₂ cos (S _FB (i) + θ ₂ )
Y ₂ (i) = Y _FB (i) + R ₂ sin (S _FB (i) + θ ₂ ) (2)

As shown in FIG. 3, CPU 31, based on the procedures P1, P2 by a plurality of feed shaft position Q _FB specified in a predetermined period, referred to as angle (moving angle W indicating the direction of movement of the tool 4 with respect to the Kezukarada 3. ) Is specified (P5). Specifically, it is as follows. As shown in FIG. 5, CPU 31, when specifying the feed shaft position _Q FB (i), the feed shaft position _Q FB (i) N-number of identified before the feed shaft position _Q FB _(Q FB _(i -N)), Q _FB (i- (N-1)) ... Acquire Q _FB (i-1). The CPU 31 specifies a line segment connecting adjacent feed shaft positions Q _FB for each of the feed shaft positions Q _FB (i-N) to Q _FB (i). The CPU 31 specifies the angle formed between the specified line segment and the reference direction at the feed axis position _QFB as the traveling direction angle α (rad). The CPU 31 has travel direction angles α (j) (j are from i-N to i-1) corresponding to each of the N feed axis positions Q _FB (i-N) to Q _FB (i-1). (Integer) is specified by the following equation (3).
α (j) = tan ^-1 ((Y _FB (j + 1)-(Y _FB (j)) / (X _FB (j + 1)-(X _FB (j))))
(3)

The CPU 31 calculates the average value of the traveling direction angle α (j) based on the following equation (4), and specifies it as the moving angle W (i) (rad) indicating the moving direction of the tool 4 with respect to the work piece 3. ..
The CPU 31 updates i by repeating steps P1 and P2 (see FIG. 3) to newly specify the feed shaft position Q _FB (i), and each time the CPU 31 newly specifies the feed shaft position Q _FB (i), N feed shaft positions Q _FB to be calculated. (I-N) to Q _FB (i-1) are also updated, and the average value of the traveling direction angle α is calculated based on the equation (4) to specify the moving angle W (i). Here, the traveling direction angle α indicates an angle with respect to the reference direction of each line extending along the N feed axis positions Q _FB (i-N) to Q _FB (i-1). Therefore, the CPU 31 determines the moving average of the traveling direction angle α, in other words, the moving average of the angles of each line extending along the N feed axis positions Q _FB (i-N) to Q _FB (i-1). It is specified as a moving angle W.

FIG. 6 shows an example of a graph showing the relationship between the plurality of cutting edge positions U ₁ (first blade) and U ₂ (second blade) specified by the procedure P4 and the moving angle W specified by the procedure P5. For the sake of simplification of the explanation, it is assumed that the moving angle W does not fluctuate at 0 (rad) and the moving direction of the tool 4 always faces the positive direction of the X-axis. That is, the machine tool 1 executes the cutting process by moving the tool 4 with respect to the work piece 3 in the positive direction of the X-axis.

As shown in FIG. 6, the first movement locus T ₁ , which is the movement locus of the cutting edge position U ₁ , is arranged along a circle having a radius R ₁ whose center moves in the direction of the movement angle W. The second movement locus T ₂ , which is the movement locus of the cutting edge position U ₂ , is arranged along a circle having a radius R ₂ whose center moves in the direction of the movement angle W. The second movement locus T ₂ is adjacent to the first movement locus T ₁ on the movement direction side (right side) of the tool 4. The centers of the circles with radii R ₁ and R ₂ correspond to the center of rotation of the tool 4 and are located at the feed shaft position Q _FB specified by the processing of P1 and P2 (see FIG. 3). In the case of FIG. 6, the feed axis position Q _FB moves in the positive direction along the X axis.

A virtual vector V extending from the feed axis position Q _{FB in} the direction of the movement angle W is defined. In FIG. 6, the virtual vector V points in the positive direction along the X axis. At the intersection of the first movement locus T ₁ and the second movement locus T ₂ and the virtual vector V, the first blade and the second blade cut into the work body 3 during the cutting process of the work body 3 by the tool 4. Corresponds to the insertion position (called the cut position). The intersection of the first movement locus T ₁ and the virtual vector V is referred to as the _first insertion position C ₁ . The intersection of the second movement locus T ₂ and the virtual vector V is referred to as the second cut position C ₂ . The distance in the direction of the moving angle W between the _first cutting position C ₁ and the second cutting position C ₂ is referred to as the cutting amount D. When a plurality of the _first cutting position C ₁ and the second cutting position C ₂ are specified, the cutting amount D is referred to as the cutting amount D (k) (k is an integer). When chatter vibration does not occur, the amount of fluctuation of each of the cut amounts D (k-1), D (k), D (k + 1) ... Is small. On the other hand, when chatter vibration occurs, the amount of cut D (k-1), D (k), D (k + 1) ...

Therefore, as shown in FIG. 3, the CPU 31 has the _first total insertion position C ₁ and the second cut based on the cutting edge positions U ₁ and U ₂ specified by the procedure P4 and the moving angle W specified by the procedure P5. The position C ₂ is specified (P6). Next, the CPU 31 specifies the cutting amount D (k) based on the specified _first cutting position C ₁ and the second cutting position C ₂ (P7). The CPU 31 determines whether or not chatter vibration is generated based on the specified depth of cut D (k) (P8).

With reference to FIG. 7, a method of specifying the _first cutting position C ₁ and the second cutting position C ₂ (see FIG. 6) according to the procedure P6 (see FIG. 3) will be described. Since the method of specifying the _first completely cut position C ₁ and the second cut position C ₂ are the same, the method of specifying the first completely cut position C ₁ will be described below, and the second cut position C ₂ will be described. The explanation of the specific method of is simplified.

When the cutting edge position U ₁ is specified by the procedures P1 to P4 (see FIG. 3), the CPU 31 specifies the angle β between the direction extending from the feed shaft position Q _FB toward the cutting edge position U ₁ and the reference direction. Hereinafter, the angle β corresponding to the cutting edge position U ₁ (i) specified by the procedure P4 is referred to as an angle β (i). The angle β (i) can be calculated by the following equation (5).
β (i) = S _FB (i) + θ ₁ (5)

The CPU 31 compares the specified angle β (i) with the moving angle W (i) specified by the procedures P1, P2, and P5 (see FIG. 3). The CPU 31 updates i in steps P1 to P5 until the angle β (i-1) is larger than the moving angle W (i) and the angle β (i) is smaller than the moving angle W (i). repeat. For example, as shown in FIG. 7, it is assumed that the angle β (i-1) is larger than the moving angle W (i) and the angle β (i) is smaller than the moving angle W (i). At this time, while the cutting edge of the first blade of the tool 4 moves from the cutting edge position U ₁ (i-1) to the cutting edge position U ₁ (i), the moving angle W () passes through the feed shaft position Q _FB (i). It crosses the virtual vector V extending in the direction of i). Therefore, the CPU 31 specifies the arc passing through the cutting edge positions U ₁ (i-2), U ₁ (i-1), and U ₁ (i) as the first movement locus T ₁ of the first blade. The CPU 31 specifies the intersection of the virtual vector V and the first movement locus T ₁ as the _first insertion position C ₁ (k). The coordinates indicating the specified _first inclusion position C ₁ (k) are referred to as (X _1D (k), Y _1D (k)).

The CPU 31 specifies the second cutting position C ₂ (k) by the same method as described above. Specifically, it is as follows. When the cutting edge position U ₂ is specified by the procedures P1 to P4 (see FIG. 3), the CPU 31 specifies the angle β between the direction extending from the feed shaft position _QFB toward the cutting edge position U ₂ and the reference direction. The CPU 31 compares the specified angle β (i') with the moving angle W (i'). The CPU 31 updates i'until the angle β (i'-1) is larger than the movement angle W (i') and the angle β (i') is smaller than the movement angle W (i'). While repeating steps P1 to P5. When the angle β (i'-1) is larger than the moving angle W (i') and the angle β (i') is smaller than the moving angle W (i'), the CPU 31 moves the cutting edge position U ₂ The arc passing through (i'-2), U ₂ (i'-1), and U ₂ (i') is specified as the second movement locus T ₂ of the second blade. The CPU 31 sets the intersection of the virtual vector V'extending in the direction of the movement angle W (i') through the feed axis position Q _FB (i') and the second movement locus T _{2 at} the second cutting position C ₂ ( Specify as k). The coordinates indicating the specified second cutting position C ₂ (k) are referred to as (X _2D (k), Y _2D (k)). There are times when the time when the cutting edge of the first blade crosses the virtual vector V and the time when the cutting edge of the second blade crosses the virtual vector V are different. Therefore, there are times when i when determining the _first total insertion position C ₁ (k) and i'when determining the second cut position C ₂ (k) are different.

As shown in FIG. 3, after the procedure P6, the CPU 31 sets the distance between the specified _first cutting position C ₁ (k) and the second cutting position C ₂ (k) as the cutting amount D ( It is specified as k) (P7). The CPU 31 has the coordinates (X _1D (k), Y _1D (k)) of the _first insertion position C ₁ (k) and the coordinates (X _2D (k), Y) of the second insertion position C ₂ (k). _The depth of cut D (k) is specified by applying _2D (k)) to the following equation (6).
D (k) = √ ((X _1D (k) -X _2D (k)) ² + (Y _1D (k) -Y _2D (k)) ² ) (6)

By repeating steps P1 to P7, the CPU 31 identifies a plurality of cutting amounts D (k) and stores them in the storage device 34. When the cut amount D (k) is specified, the CPU 31 calculates the difference between the previously specified cut amount D (k-1) and the cut amount D (k) as the fluctuation amount. The CPU 31 compares the specified fluctuation amount with a predetermined threshold value (P8). When the amount of fluctuation is equal to or less than a predetermined threshold value, the CPU 31 determines that chatter vibration has not occurred (P8). On the other hand, the CPU 31 determines that chatter vibration has occurred when the fluctuation amount is larger than a predetermined threshold value (P8). When the CPU 31 determines that the chatter vibration has occurred, the CPU 31 notifies the operator via the display unit 17 (P9).

<Main processing>
The main process will be described with reference to FIGS. 8 to 10. When the CPU 31 of the numerical control device 30 starts the cutting operation by the machine tool 1, the CPU 31 starts the main process by reading and executing the program stored in the storage device 34. The CPU 31 initializes the variables i, k ₁ , and k ₂ stored in the RAM 33 by setting them to 1 (S1).

The CPU 31 acquires the signals output by the encoders 53B and 54B. Based on the acquired signal, the CPU 31 specifies the amount of rotation of the rotation axes of the X-axis motor 53 and the Y-axis motor 54 from the feed axis reference position. Based on the specified rotation amount, the CPU 31 specifies the position of the rotation center of the tool 4 in the X-axis-Y-axis direction as the feed axis position _QFB (i) (see FIG. 4) (S3). The process corresponds to procedures P1 and P2 in FIG. The CPU 31 acquires a signal output by the encoder 52B. Based on the acquired signal, the CPU 31 specifies the rotation angle of the rotation shaft of the spindle motor 52 from the spindle reference position as the spindle angle _SFB (i) (see FIG. 4) (S3). The process corresponds to procedure P3 in FIG. The CPU 31 stores the specified feed shaft position Q _FB (i) and spindle angle S _FB (i) in the storage device 34.

Based on the feed shaft position Q _FB (i) and spindle angle S _FB (i) specified by the process of S3 and the tool information stored in the storage device 34, the CPU 31 of the first blade of the tool 4 with respect to the work piece 3 The cutting edge position U ₁ (i) (see FIG. 4) of the cutting edge is specified (S5). The CPU 31 specifies the cutting edge position U ₂ (i) (see FIG. 4) of the cutting edge of the second blade of the tool 4 with respect to the work piece 3 (S7). The process corresponds to P4 in FIG. The CPU 31 stores the specified cutting edge positions U ₁ (i) and U ₂ (i) in the storage device 34.

Or CPU31 sends axis position _{Q FB} stored in the storage device 34, shaft angle _{S FB,} based on the edge position _U 1, _{U 2,} first change write position _{C 1} and the second cutting position _{C 2} to be identified Judgment (S9). As shown in FIG. 7, the _first cutting position C ₁ and the second cutting position C ₂ are specified by storing three or more cutting edge positions U ₁ and U _{2 in the} storage device 34, respectively. , It is premised that the identification of the movement angle W (i) is completed. Further, as shown in FIG. 5, in order to specify the movement angle W (i), it is premised that N + 1 or more feed shaft positions _QFB are stored in the storage device 34. Therefore, the CPU 31 stores (a) three or more cutting edge positions U ₁ and U _{2 in the} storage device 34, respectively, and (b) stores N + 1 or more feed shaft positions Q _{FB in the} storage device 34. It is determined whether the first total insertion position C ₁ and the second cut position C ₂ can be specified depending on whether or not there is any (S9).

CPU31 determines that (a) (b) when not satisfied at least one of the requirements can not first change identify write position _{C 1} and the second cutting position _{C 2} (S9: NO). At this time, the CPU 31 advances the process to S23 after a predetermined time has elapsed after specifying the feed shaft position Q _FB (i) and the spindle angle S _FB (i) by the process of S3. The CPU 31 adds 1 to the variable i and updates it (S23). The CPU 31 returns the process to S3. The CPU 31 repeats the processes of S3 to S9 in a predetermined cycle based on the updated variable i.

When all of the requirements (a) and (b) are satisfied, the CPU 31 determines that the first cutting position C ₁ and the second cutting position C ₂ can be specified (S9: YES). At this time, the CPU 31 advances the traveling direction angle α (j) (see FIG. 5) based on the N + 1 feed axis positions Q _FB (i-N)) to Q _FB (i) stored in the storage device 34 in a predetermined cycle. To identify. Further, the CPU 31 calculates the moving average value of the specified traveling direction angle α (j), and specifies the moving angle W (i) (see FIG. 5) indicating the moving direction of the tool 4 with respect to the work piece 3 (S11). .. The process corresponds to procedure P5 in FIG.

The CPU 31 acquires a plurality of cutting edge positions U ₁ of the first blade specified by the process of S5 and a moving angle W (i) specified by the process of S11 from the storage device 34. The CPU 31 executes a cut position specifying process (see FIG. 9) in order to specify the _first insertion position C ₁ (see FIG. 7) (S13). The cutting position specifying process will be described with reference to FIG. The CPU 31 calculates the angle β (i-1) (see FIG. 7) in the direction extending from the feed shaft position Q _FB (i-1) toward the cutting edge position U ₁ (i-1), and the feed shaft position Q _FB. The angle β (i) (see FIG. 7) in the direction extending from (i) toward the cutting edge position U ₁ (i) is calculated. The CPU 31 determines whether (c) the angle β (i-1) is larger than the moving angle W (i) and (d) the angle β (i) is smaller than the moving angle W (i) (S31). .. When the CPU 31 does not satisfy at least one of the requirements (c) and (d) (S31: NO), the CPU 31 ends the cutting position specifying process and returns the process to the main process (see FIG. 8).

When all of the requirements (c) and (d) are satisfied (S31: YES), the CPU 31 makes an arc passing through the cutting edge positions U ₁ (i-2), U ₁ (i-1), and U ₁ (i). It is specified as the first movement locus T ₁ (see FIG. 7) of the first blade (S33). The CPU 31 identifies a virtual vector V (see FIG. 7) extending in the direction of the moving angle W (i) through the feed axis position _QFB (i). The CPU 31 specifies the intersection of the specified virtual vector V and the first movement locus T ₁ as the _first insertion position C ₁ (k ₁ ) (see FIG. 7) (S35). The process corresponds to procedure P6 of FIG. The CPU 31 stores the specified _first insertion position C ₁ (k ₁ ) in the storage device 34 (S37), and the CPU 31 adds ₁ to the variable k ₁ and updates it (S39). The CPU 31 ends the cutting position specifying process and returns the process to the main process (see FIG. 8).

As shown in FIG. 8, the CPU 31 identifies the _first insertion position C1 by the first blade (see S13), and then proceeds to the process in S15. The CPU 31 acquires a plurality of cutting edge positions U ₂ of the second blade specified by the process of S7 and a movement angle W (i) specified by the process of S11 from the storage device 34. The CPU 31 executes a cut position specifying process (see FIG. 9) in order to specify the second cut position C ₂ (S15). Since the cut position specifying process is the same as the cut position specifying process executed in the process of S13 in order to specify the _first cutting position C ₁ , the description is simplified. As shown in FIG. 9, when the CPU 31 satisfies all of the requirements (c) and (d) (S31: YES), the cutting edge positions U ₂ (i-2), U ₂ (i-1), and U ₂ ( an arc through i), is identified as the second movement track _{T 2} of the second blade (S33). The CPU 31 identifies a virtual vector V extending in the direction of the movement angle W (i) through the feed axis position Q _FB (i). The CPU 31 specifies the intersection of the specified virtual vector V and the second movement locus T ₂ as the second cutting position C ₂ (k ₂ ) (S35). The CPU 31 stores the specified second cut position C ₂ (k ₂ ) in the storage device 34 (S37), and the CPU 31 adds 1 to the variable k ₂ and updates it (S39).

As shown in FIG. 8, the CPU 31 executes a cut amount specifying process (see FIG. 10) in order to specify the cut amount D (k) (S17). The cutting amount specifying process will be described with reference to FIG. The CPU 31 newly stores at least _one of the first cutting position C ₁ (k ₁ ) and the second cutting position C ₂ (k ₂ ) in the storage device 34 by the processing of S13 and S15 (see FIG. 8). Is determined (S41). When the CPU 31 determines that neither the _first cutting position C ₁ (k ₁ ) nor the second cutting position C ₂ (k ₂ ) is newly stored in the storage device 34 (S41: NO), the CPU 31 is turned off. The filling amount specifying process is completed, and the process is returned to the main process (see FIG. 8).

When the CPU 31 determines that at least _{one of the first} total insertion position C ₁ (k ₁ ) and the second cut position C ₂ (k ₂ ) is newly stored in the storage device 34 (S41: YES), the processing is performed. To S43. The CPU 31 extracts the first cutting position C ₁ (k) and the second cutting position C ₂ (k) where the elements k ₁ and k ₂ match, and sets the distance between the respective positions as the cutting amount D ( It is specified as k) (S43). The process corresponds to procedure P7 in FIG. The CPU 31 stores the specified depth of cut D (k) in the storage device 34 (S45). The CPU 31 ends the cutting amount specifying process and returns the process to the main process (see FIG. 8).

As shown in FIG. 8, the CPU 31 acquires the cut amounts D (k-1) and D (k) stored in the storage device 34 after the cut amount specifying process (S17) is completed. The CPU 31 calculates the difference between the acquired cut amounts D (k-1) and D (k) as the fluctuation amount. The CPU 31 determines whether or not chatter vibration is generated based on the specified fluctuation amount (S19). When the amount of fluctuation is equal to or less than a predetermined threshold value, the CPU 31 determines that chatter vibration has not occurred (S19: NO). At this time, the CPU 31 advances the process to S23 after a predetermined time has elapsed after specifying the feed shaft position Q _FB (i) and the spindle angle S _FB (i) by the process of S3. The CPU 31 adds 1 to the variable i and updates it (S23). The CPU 31 returns the process to S3. The CPU 31 determines that chatter vibration has occurred when the amount of fluctuation is larger than a predetermined threshold value (S19: YES). At this time, the CPU 31 advances the process to S21. The process corresponds to procedure P8 of FIG.

The CPU 31 notifies the operator of the occurrence of chatter vibration by displaying the locus image on the display unit 17 (S21). The process corresponds to procedure P9 in FIG. FIG. 11 shows an example of a locus image displayed on the display unit 17. Locus image, S3 the edge position U ₁ identified by the process (see FIG. 8), connected by a circle of radius R ₁ centered on the feed shaft position Q _FB, and the particular by the process of S3 (see FIG. 8) It is formed by connecting the sharpened cutting edge positions U ₂ with a circle having a radius R ₂ centered on the feed shaft position Q _FB . Therefore, the locus image includes at least the first movement locus T ₁ and the second movement locus T ₂ specified by the processing of S33 (see FIG. 9). In the enlarged view 171 in which the region 17A is enlarged, the movement loci are arranged at substantially equal intervals, and a state in which chatter vibration is not generated is shown (see FIG. 12). The enlarged view 172, which is an enlarged view of the region 17B, shows a state in which the interval of the movement locus fluctuates and chatter vibration occurs (see FIG. 13).

As shown in FIG. 8, the CPU 31 ends the main process after notifying the occurrence of chatter vibration.

<Action and effect of this embodiment>
The CPU 31 of the numerical control device 30 specifies the depth of cut D when cutting the work piece 3 with the blade of the tool 4 based on the signals output by the encoders 52B, 53B, 54B of the machine tool 1 (S17). .. The CPU 31 detects the occurrence of chatter vibration based on the specified depth of cut D (S19) and notifies the operator (S21). Therefore, the numerical control device 30 can determine the presence or absence of the occurrence of chatter vibration by using the encoders 52B to 54B that the machine tool 1 normally provides to control the motors 52 to 54. Therefore, the numerical control device 30 can detect chatter vibration without adding a new detector such as a vibration sensor to the machine tool 1. The numerical control device 30 can detect not only chatter vibration but also when some trouble occurs that hinders the movement of the tool 4 with respect to the work piece 3.

The CPU 31 specifies the traveling direction angle α based on the N + 1 feed axis positions _QFB stored in the storage device 34 at a predetermined cycle. Further, the CPU 31 calculates the moving average value of the specified traveling direction angle α, and specifies the moving angle W (see FIG. 5) indicating the moving direction of the tool 4 with respect to the work piece 3 (S11). Therefore, the numerical control device 30 can accurately identify the relative movement direction of the tool 4 with respect to the work piece 3 by a simple method. Further, the numerical control device 30 can suppress an increase in the load on the CPU 31 by limiting the number of traveling direction angles α when calculating the average value to N.

The CPU 31 specifies the cutting edge positions U ₁ and U ₂ of the tool 4 with respect to the work piece 3 based on the feed shaft position Q _FB and the spindle angle S _FB specified by the process of S3 and the tool information stored in the storage device 34. (S5, S7). At this time, the numerical control device 30 can easily and accurately identify the cutting edge positions U ₁ and U ₂ of the first blade and the second blade of the tool 4 that move while rotating.

The CPU 31 specifies the intersections of the virtual vector V and the first movement locus T ₁ and the second movement locus T ₂ as the first total insertion position C ₁ and the second cut position C ₂ (S33). The CPU 31 specifies the distance between the specified _first cutting position C ₁ and the second cutting position C ₂ as the cutting amount D. At this time, the numerical control device 30 can accurately specify the cutting positions of the first blade and the second blade, as compared with the case where the cutting positions are directly specified from the cutting edge positions U ₁ and U ₂ . Therefore, the numerical control device 30 can accurately specify the depth of cut D and accurately detect the occurrence of chatter vibration.

The CPU 31 specifies the arc passing through the three cutting edge positions U ₁ as the first movement locus T ₁ and the arc passing through the three cutting edge positions U ₂ as the second moving locus T ₂ . At this time, the numerical control device 30 can accurately estimate the movement locus of the cutting edge by a simple method. Therefore, the numerical control device 30 can improve the accuracy of the _first cutting position C ₁ and the second cutting position C ₂ while suppressing the load increase of the CPU 31.

For example, the CPU 31 can specify the intersections when the movement locus of a specific blade of the tool 4 repeatedly intersects the virtual vector V as the first completely inserted position C ₁ and the second cut position C _2. is there. At that time, the first blade and the second blade are the same. However, in this method, until identify the depth of cut based on the first change identified write position C ₁ and the second cutting position C _2, it takes time to at least the tool 4 makes one rotation. On the other hand, in the present embodiment, the CPU 31 specifies the cutting edge position U ₁ of the first blade of the tool 4 and the cutting edge position U ₂ of the second blade different from the first blade of the tool 4, and the chatter vibration is generated. Determine the presence or absence. Said time, in a shorter time than the tool 4 makes one rotation, can identify the depth of cut based on the first change write position C ₁ and the second cutting position C _2. Therefore, the numerical control device 30 can quickly detect and notify the occurrence of chatter vibration in a short time.

When it is determined that the chatter vibration has occurred (S19: YES), the CPU 31 displays a locus image including at least the first movement locus T ₁ and the second movement locus T ₂ on the display unit 17. The locus image shows that chatter vibration occurs when the interval between the movement loci of the first blade and the second blade fluctuates. Therefore, the operator can sensuously recognize the presence or absence of the occurrence of chatter vibration. Further, the operator can grasp not only the presence or absence of chatter vibration but also the degree of chatter vibration. For example, the operator can recognize the occurrence of chatter vibration that cannot be determined by the appearance of the work piece 3.

<Modification example>
The present invention is not limited to the above embodiment. The machine tool 1 may have an encoder connected to the spindle 9. At this time, the CPU 31 may specify the spindle angle _SFB based on the signal output by the encoder. The machine tool 1 may have a rotation detection sensor that can detect the rotation of the spindle motor 52 by a method different from that of the encoder, instead of the encoders 52B, 53B, 54B. The CPU 31 may specify the spindle angle S _FB and the feed shaft position Q _FB based on the signal output by the rotation detection sensor.

The coordinate system when the CPU 31 specifies the depth of cut D is not limited to the X-axis-Y-axis coordinate system, but the X-axis-Z-axis coordinate system, the Y-axis-Z-axis coordinate system, and the X-axis-Y-axis-Z-axis. It may be a coordinate system. For example, when specifying the depth of cut D based on the X-axis-Y-axis-Z-axis coordinate system, the CPU 31 may specify the coordinates (X _FB , Y _FB , Z _FB ) as the feed axis position Q _FB. .. CPU31 on the basis of the specified feed shaft position _{Q FB} and shaft angle _{S FB,} identifies the coordinates _{(X 1, Y 1, Z} 1) as the edge position _{U 1,} coordinates as the cutting edge position _{U 2 (X 2, Y 2} , Z ₂ ) may be specified. The CPU 31 may specify the moving angle W three-dimensionally based on the specified cutting edge positions U ₁ and U ₂ . The CPU 31 specifies the coordinates (X _1D , Y _1D , Z _1D ) as the _first insertion position C ₁ based on the specified cutting edge positions U ₁ , U ₂ and the moving angle W, and sets the second cutting position C _2. Coordinates (X _2D , Y _2D , Z _2D ) may be specified. The CPU 31 may specify the cutting amount D based on the specified _first cutting position C ₁ and the second cutting position C ₂ . That is, the CPU 31 may three-dimensionally specify the depth of cut D of the tool 4 and determine the presence or absence of the occurrence of chatter vibration.

The CPU 31 determined that chatter vibration occurred when the fluctuation amount of the cutting amount D was larger than a predetermined threshold value. The method for determining whether or not chatter vibration has occurred based on the depth of cut D is not limited to this, and other well-known outlier detection algorithms can be applied. For example, the CPU 31 causes chatter vibration by applying the k-nearest neighbor method, the singular spectrum conversion method, or the like to the depths of cut D (1), D (2) ... D (k) stored in the storage device 34. It may be determined whether or not it has occurred. Further, the CPU 31 may determine whether or not chatter vibration has occurred by applying a well-known statistical method such as standard deviation or dispersion.

The CPU 31 specified the moving average of the angles of each line extending along the N + 1 feed axis positions _QFB as the moving angle W. The method for specifying the moving angle W is not limited to this method. For example, the CPU 31 may calculate an approximate straight line by a well-known approximate calculation such as the least squares method based on N + 1 feed axis positions Q _FB, and specify the slope of the approximate straight line as the movement angle W.

The tool information may have a common radius R instead of the radii R ₁ ... R _m . The tool information may have a central angle of a line extending radially from the center of rotation of the tool 4 toward each cutting edge. The CPU 31 may specify the cutting edge positions U ₁ and U ₂ based on the diameter from the rotation center of the tool 4 to each cutting edge and the center angle.

Of the specified cutting edge positions U ₁ and U ₂ , the CPU 31 may specify the cutting edge position closest to the virtual vector V as the first cutting position C ₁ and the second cutting position C ₂ , respectively. In this case, the CPU 31 does not have to specify the first movement locus T ₁ and the second movement locus T ₂ .

When the angle β (i-1) is larger than the moving angle W (i) and the angle β (i) is smaller than the moving angle W (i), the CPU 31 has a cutting edge position U ₁ (i-1). ), U ₁ (i) may be specified as the first movement locus T ₁ of the first blade. The same applies to the second movement locus T ₂ of the second blade.

The CPU 31 may specify the specific blade of the tool 4 as the first blade and the second blade. That is, the first blade and the second blade may be the same blade of the tool 4. The CPU 31 may specify the intersections when the movement locus of the specific blade of the tool 4 repeatedly intersects the virtual vector V as the first total insertion position C ₁ and the second cutting position C ₂ . On the other hand, the CPU 31 has a cutting position (first cutting position, second cutting position) based on the cutting edge positions of three or more blades (for example, the first blade, the second blade, and the third blade) of the tool 4. , Third notch position) may be specified. At that time, for example, the CPU 31 sets the cutting amount between the first cutting position and the second cutting position and the cutting amount between the second cutting position and the third cutting position, respectively. The amount of fluctuation may be calculated. The CPU 31 may determine the presence or absence of the occurrence of chatter vibration by comparing the specified plurality of fluctuation amounts with the threshold value.

The notification mode when notifying the operator when chatter vibration occurs is not limited to the above embodiment. For example, the locus image may be formed by connecting the cutting edge positions U ₁ and U ₂ specified by the process of S3 (see FIG. 8) with straight lines, respectively. For example, the CPU 31 may notify the operator of the occurrence of chatter vibration by outputting a warning sound from a speaker (not shown). Further, the CPU 31 may stop the cutting process by the machine tool 1 when it detects the occurrence of chatter vibration.

<Others>
The encoder 52B is an example of the "first detector" of the present invention. The X-axis motor 53 and the Y-axis motor 54 are examples of the "feed mechanism" of the present invention. The encoders 53B and 54B are examples of the "second detector" of the present invention. The storage device 34 is an example of the "storage unit" of the present invention. The CPU 31 that performs the processing of S11 is an example of the "first specific unit" of the present invention. The CPU 31 that performs the processing of S5 and S7 is an example of the "second specific unit" of the present invention. The CPU 31 that performs the processes of S13, S15, and FIG. 9 is an example of the "third specific unit" of the present invention. The CPU 31 that performs the processing of S17 is an example of the "fourth specific unit" of the present invention. The CPU 31 that performs the processing of S19 is an example of the "determination unit" of the present invention. The CPU 31 that performs the processing of S21 is an example of the "notifying unit" of the present invention. The treatment of S11 is an example of the "first specific step" of the present invention. The treatments of S5 and S7 are an example of the "second specific step" of the present invention. The processes of S13, S15, and FIG. 9 are an example of the "third specific step" of the present invention. The treatment of S17 is an example of the "fourth specific step" of the present invention. The process of S19 is an example of the "determination step" of the present invention. The process of S21 is an example of the "notification step" of the present invention.

1: Machine tool 3: Work piece 4: Tool 9: Spindle 17: Display 30: Numerical control device 31: CPU
34: Storage device 35A: Storage medium 51, 52, 53, 54: Motors 51B, 52B, 53B, 54B: Encoder

Claims (10)

The spindle for rotating the tool and
The first detector that detects the rotation of the spindle and
A feed mechanism for moving the tool relative to the work piece,
A second detector that detects the relative movement of the tool by the feed mechanism,
A numerical control device that controls a machine tool equipped with a machine tool and cuts the work piece with the tool.
A storage unit that stores tool information including at least the number and diameter of the blades of the tool, and
Based on the detection result of the second detector, the first specific part that specifies the relative movement direction of the tool with respect to the work piece, and
A second specifying unit that specifies a plurality of cutting edge positions, which are positions of the cutting edge of the tool with respect to the work piece, based on the tool information stored in the storage unit and the detection results of the first detector and the second detector. When,
Based on the plurality of cutting edge positions specified by the second specific portion, the third specific portion that specifies a plurality of cutting positions in which the blade cuts the work piece in the moving direction specified by the first specific portion. ,
The fourth specific part that specifies the distance between the plurality of cut positions specified by the third specific part as the cut amount, and
A determination unit that determines whether or not chatter vibration has occurred based on the depth of cut specified by the fourth specific unit.
A numerical control device including a notification unit that notifies when it is determined that chatter vibration has occurred by the determination unit. The first specific part is
Based on the detection result of the second detector, a plurality of relative positions of the tool with respect to the work piece are specified, and the moving direction is specified based on the moving average of the directions extending along the specified relative positions. The numerical control device according to claim 1. The second specific part is
The center of rotation of the tool determined based on the detection result of the second detector,
The rotation angle of the tool determined based on the detection result of the first detector, and
The numerical control device according to claim 1 or 2, wherein a plurality of cutting edge positions are specified based on the number of blades and the diameter stored as tool information in the storage unit. The third specific part is
Based on the plurality of cutting edge positions specified by the second specific unit, a first moving locus which is a moving locus of the cutting edge and a second moving locus different from the first moving locus are specified.
The intersections of the virtual vector extending in the moving direction specified by the first specific portion from the center of rotation of the tool and the specified first movement locus and the second movement locus are set at the first insertion position and Specified as the second cut position,
The fourth specific part is
The invention according to any one of claims 1 to 3, wherein the distance between the first cutting position and the second cutting position specified by the third specific part is specified as the cutting amount. Numerical control device. The third specific part is
The numerical control device according to claim 4, wherein a plurality of arcs passing through the positions of the plurality of cutting edge positions are specified as the movement loci. The second specific part is
The numerical control device according to any one of claims 1 to 5, wherein the position of the cutting edge of the first blade of the tool and the position of the cutting edge of a second blade different from the first blade are specified. The notification unit
The numerical control device according to claim 4 or 5, wherein a locus image including at least the movement locus specified by the third specific unit is displayed on the display unit. A machine tool comprising the numerical control device according to any one of claims 1 to 7. The spindle for rotating the tool and
The first detector that detects the rotation of the spindle and
A feed mechanism for moving the tool relative to the work piece,
A second detector that detects the relative movement of the tool by the feed mechanism,
To a computer that controls a machine tool equipped with a tool and cuts the work piece with the tool.
Based on the detection result of the second detector, the first specific step of specifying the relative movement direction of the tool with respect to the work piece, and
At the position of the cutting edge of the tool with respect to the work piece, based on the tool information including at least the number and diameter of the blades of the tool stored in the storage unit and the detection results of the first detector and the second detector. The second specific process to specify multiple cutting edge positions and
Based on the plurality of cutting edge positions specified by the second specific step, the third specific step of specifying a plurality of cutting positions where the blade cuts the work piece in the moving direction specified by the first specific step. ,
The fourth specific step of specifying the distance between the plurality of cut positions specified by the third specific step as the cut amount, and
A determination step of determining whether or not chatter vibration has occurred based on the depth of cut specified by the fourth specific step, and
A control program for executing a notification process for notifying when it is determined that chatter vibration has occurred in the determination process. The spindle for rotating the tool and
The first detector that detects the rotation of the spindle and
A feed mechanism for moving the tool relative to the work piece,
A second detector that detects the relative movement of the tool by the feed mechanism,
To a computer that controls a machine tool equipped with a tool and cuts the work piece with the tool.
Based on the detection result of the second detector, the first specific step of specifying the relative movement direction of the tool with respect to the work piece, and
At the position of the cutting edge of the tool with respect to the work piece, based on the tool information including at least the number and diameter of the blades of the tool stored in the storage unit and the detection results of the first detector and the second detector. The second specific process to specify multiple cutting edge positions and
Based on the plurality of cutting edge positions specified by the second specific step, the third specific step of specifying a plurality of cutting positions where the blade cuts the work piece in the moving direction specified by the first specific step. ,
The fourth specific step of specifying the distance between the plurality of cut positions specified by the third specific step as the cut amount, and
A determination step of determining whether or not chatter vibration has occurred based on the depth of cut specified by the fourth specific step, and
A storage medium that stores a control program for executing a notification step of notifying when it is determined that chatter vibration has occurred by the determination step.