JP7035875B2 - Numerical control device, numerical control method, and numerical control program - Google Patents

Description

The present invention relates to a numerical control device, a numerical control method, and a numerical control program.

Numerical control devices that detect abnormalities in tools based on the current value of the motor that drives the tools are known. Patent Document 1 discloses a numerical control device having a function of detecting a blade spill of a tool. The numerical control device compares the current value acquired from the servo driver for the spindle with the reference value of the cutting load. The current value represents the load torque of the spindle servo. Therefore, the numerical control device determines that an excessive load torque has acted on the spindle servo when the current value is larger than the reference value. At this time, the numerical control device outputs an abnormality detection signal indicating that the blade of the tool has spilled.

Japanese Patent Application Laid-Open No. 2003-326439

When the motor rotates while accelerating or decelerating, the current value is more likely to fluctuate due to factors other than the load torque, as compared with the case where the motor rotates at a constant speed. Therefore, when the numerical control device detects an abnormality of the tool based on the current value acquired during acceleration or deceleration of the motor, the possibility of erroneous detection increases. Therefore, it is preferable that the numerical control device does not detect the abnormality of the tool when the motor rotates while accelerating or decelerating, and inspects the abnormality of the tool when the motor rotates at a constant speed.

An object of the present invention is to provide a numerical control device, a numerical control method, and a numerical control program capable of appropriately determining when a motor rotates while accelerating or decelerating and preventing detection of a tool abnormality at that time. That is.

The numerical control device according to the first aspect of the present invention is NC for a mechanical device provided with a motor and a drive circuit for relatively rotating and moving the tool for processing the work material and the work material. A numerical control device capable of executing speed control that periodically outputs a speed command based on a speed command included in the program to the drive circuit and position control that periodically outputs a position command based on the position command to the drive circuit. In the first determination means for determining whether the command of the NC program is the speed control or the position control, and when the first determination means determines the position control, the position command based on the position command is second-order differentiated. When the calculation means for calculating the acceleration information and the absolute value of the acceleration information calculated by the calculation means are larger than a predetermined threshold value, it is determined that the motor is accelerating or decelerating, and the absolute value of the acceleration information is When the speed is equal to or less than the predetermined threshold, the second determination means for determining that the motor is in constant speed, and when the first determination means determines the speed control, the speed command based on the speed command and the motor. A third determination means for determining whether or not the measurement information obtained by measuring the rotation speed of the vehicle is the same, a speed storage means for storing the speed command as a storage command when the first determination means determines the speed control, and a speed storage means. The speed command and the measurement information are determined to be the same by the fourth determination means for determining whether or not the storage command previously stored by the speed storage means and the speed command are the same, and the third determination means. Then, until it is determined by the fourth determination means that the storage command and the speed command are not the same, it is determined that the motor is in constant speed, and the storage command is determined by the fourth determination means. It is determined that the motor is accelerating or decelerating from the determination that the speed command is not the same to the determination by the third determination means that the speed command and the measurement information are the same. When the fifth determination means, the detection means for detecting the current flowing through the motor, and the second determination means or the fifth determination means determine that the motor is in a constant speed, the detection means detects it. A sixth determination means for determining the presence or absence of an abnormality in the tool based on the current is provided, and the sixth determination means is accelerating or decelerating the motor by the second determination means or the fifth determination means. When it is determined that the above is true, the presence or absence of the above-mentioned abnormality is not determined.

The numerical control device determines whether or not an abnormality has occurred in the tool when it is determined that the motor is in constant speed, and does not determine whether or not an abnormality has occurred in the tool when it is determined that the motor is accelerating or decelerating. Therefore, when the current fluctuates due to a factor other than the occurrence of the tool abnormality during acceleration / deceleration of the motor, the occurrence of the tool abnormality is not erroneously determined. The numerical control device determines whether the motor is in acceleration / deceleration or constant speed based on different determination methods when the motor is controlled by position control and when the motor is controlled by speed control. Therefore, the numerical control device can appropriately determine whether the motor is in acceleration / deceleration or constant speed by an appropriate determination method according to each control method. Therefore, the numerical control device can improve the accuracy of the occurrence of the abnormality of the tool.

In the first aspect, the mechanical device is for moving the tool relative to the work material and the first motor for rotating the tool relative to the work material. When the second motor is provided and the position control is performed, the first motor rotates in synchronization with the second motor, and when the first determination means determines that the position control is performed, the calculation means is said. The acceleration information is calculated by second-order differentiating the position command for the second motor, and the second determination means means that the first motor is accelerating or decelerating based on the relationship between the acceleration information and the predetermined threshold value. It is determined whether the speed is constant, and the sixth determination means may determine whether or not an abnormality has occurred in the tool based on the current of the first motor. The numerical control device determines whether the first motor is in acceleration / deceleration or constant speed without being affected by the noise mixed in by synchronizing the first motor with the second motor when performing position control. Can be done. Therefore, since the numerical control device can appropriately determine whether acceleration / deceleration is in progress or constant speed, the accuracy of determination of the presence / absence of abnormality can be improved.

In the first aspect, the mechanical device is for moving the tool relative to the work material and the first motor for rotating the tool relative to the work material. When the second motor is provided and the position control is performed, the second motor rotates in synchronization with the first motor, and the calculation means second-orders the position command for the first motor to accelerate the acceleration. The information is calculated, the second determination means determines whether the second motor is in acceleration / deceleration or constant speed based on the relationship between the acceleration information and the predetermined threshold value, and the sixth determination means determines. Based on the current of the second motor, it may be determined whether or not the abnormality has occurred in the tool. The numerical control device determines whether the second motor is in acceleration / deceleration or constant speed without being affected by the noise mixed in by synchronizing the second motor with the first motor when performing the position control. It can be determined. Therefore, since the numerical control device can appropriately determine whether acceleration / deceleration is in progress or constant speed, the accuracy of determination of the presence / absence of abnormality can be improved.

In the first aspect, the presence / absence of the abnormality is not determined before the first storage unit that stores information indicating whether or not the presence / absence of the abnormality has occurred and the first determination by the sixth determination means. By the first storage control means for storing the determination stop information indicating the above in the first storage unit and the second determination means or the fifth determination means in a state where the determination stop information is stored in the first storage unit. When the motor determines that the speed is constant, the second storage control means for storing the determination information indicating that the presence or absence of the abnormality has occurred is stored in the first storage unit, and the determination is in progress in the first storage unit. With the third storage control means for storing the determination stop information in the first storage unit when the motor is determined to be accelerating or decelerating by the second determination means or the fifth determination means in the state where the information is stored. The sixth determination means determines whether or not the abnormality has occurred when the first storage unit stores the determination information, and the first storage unit stores the determination stop information. At that time, it is not necessary to determine whether or not the abnormality has occurred. At that time, it is possible to appropriately determine whether or not an abnormality has occurred depending on whether the motor is in acceleration / deceleration or in constant speed.

In the first aspect, the NC program has a start command indicating to start the determination of the presence / absence of the abnormality and an end command indicating to end the determination of the presence / absence of the abnormality. The determination means determines whether or not an abnormality has occurred in the tool between the time when the start command is read from the second storage unit and the time when the end command is read next, and the determination means issues the end command from the second storage unit. It is not necessary to determine whether or not the abnormality has occurred in the tool between the time of reading and the next time the start command is read. At this time, the numerical control device can specify the determination period for the presence or absence of an abnormality based on the start command and the end command stored in the second storage unit together with the control command of the motor.

The numerical control method according to the second aspect of the present invention is included in the NC program, and is a machine provided with a motor and a drive circuit for relatively rotating and moving the tool for processing the work material and the work material. First determination for determining whether the speed control for periodically outputting the speed command based on the speed command to the drive circuit or the position control for periodically outputting the position command based on the position command to the drive circuit. When the position control is determined by the step, the first determination step, the calculation step of calculating the acceleration information by second-order differentiation of the position command based on the position command, and the absolute of the acceleration information calculated by the calculation step. A second determination step of determining that the motor is accelerating or decelerating when the value is larger than the predetermined threshold, and determining that the motor is in constant speed when the absolute value of the acceleration information is equal to or less than the predetermined threshold. When the speed control is determined by the first determination step, the third determination step of determining whether or not the speed command based on the speed command and the measurement information measured by the rotational speed of the motor are the same. When the speed control is determined by the first determination step, it is determined whether or not the speed storage step of storing the speed command as a storage command, the storage command previously stored by the speed storage process, and the speed command are the same. After determining that the speed command and the measurement information are the same by the fourth determination step and the third determination step, the storage command and the speed command are not the same by the fourth determination step. Until the determination, it is determined that the motor is in constant speed, the storage command and the speed command are determined not to be the same by the fourth determination step, and then the speed is determined by the third determination step. The fifth determination step of determining that the motor is accelerating or decelerating, the detection step of detecting the current flowing through the motor, and the second determination until it is determined that the command and the measurement information are the same. When it is determined by the step or the fifth determination step that the motor is in constant speed, the sixth determination step of determining whether or not an abnormality has occurred in the tool based on the current detected by the detection step. The sixth determination step is characterized in that, when it is determined by the second determination step or the fifth determination step that the motor is accelerating or decelerating, the presence or absence of the abnormality is not determined. According to the second aspect, the same effect as that of the first aspect can be obtained.

The numerical control program according to the third aspect of the present invention is included in the NC program, and is a machine provided with a motor and a drive circuit for relatively rotating and moving the tool for processing the work material and the work material. First determination for determining whether the speed control for periodically outputting the speed command based on the speed command to the drive circuit or the position control for periodically outputting the position command based on the position command to the drive circuit. When the position control is determined by the step, the first determination step, the calculation step of calculating the acceleration information by second-order differentiation of the position command based on the position command, and the absolute of the acceleration information calculated by the calculation step. A second determination step of determining that the motor is accelerating or decelerating when the value is larger than the predetermined threshold, and determining that the motor is in constant speed when the absolute value of the acceleration information is equal to or less than the predetermined threshold. When the speed control is determined by the first determination step, the third determination step of determining whether or not the speed command based on the speed command and the measurement information measured by the rotational speed of the motor are the same. When the speed control is determined by the first determination step, it is determined whether or not the speed storage step of storing the speed command as a storage command, the storage command previously stored by the speed storage process, and the speed command are the same. After determining that the speed command and the measurement information are the same by the fourth determination step and the third determination step, the storage command and the speed command are not the same by the fourth determination step. Until the determination, it is determined that the motor is in constant speed, the storage command and the speed command are determined not to be the same by the fourth determination step, and then the speed is determined by the third determination step. The fifth determination step of determining that the motor is accelerating or decelerating, the detection step of detecting the current flowing through the motor, and the second determination until it is determined that the command and the measurement information are the same. When it is determined by the step or the fifth determination step that the motor is in constant speed, the sixth determination step of determining whether or not an abnormality has occurred in the tool based on the current detected by the detection step. It is a numerical control prompt for causing a computer to execute, and in the sixth determination step, when it is determined by the second determination step or the fifth determination step that the motor is accelerating or decelerating, the abnormality occurs. It is characterized in that the presence or absence is not determined. According to the third 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 electric composition of the machine tool 1 and the numerical control device 30. The figure which shows an example of NC program. The figure which shows the detail of the drive circuit 51A, 52A. A graph showing position information, velocity information, and acceleration information in the case of position control. Graph showing speed information, measurement information, speed information / measurement information in the case of speed control. Flow chart of the main process. Flow chart of abnormality judgment processing. The flow chart of the first judgment process. The flow chart of the second judgment process.

<Overview of Machine Tool 1>
An embodiment of the present invention will be described. In the following description, left and right, front and back, and up and down indicated by arrows in the figure are used. The left-right direction, the front-back direction, and the up-down 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 machine tool 1 shown in FIG. 1 rotates a tool 4 mounted on a spindle 9 and moves a table 13 holding a work material 3 on the upper surface. The machine tool 1 relatively rotates or moves the tool 4 and the work material 3, and the work material 3 is cut by the tool 4. The numerical control device 30 (see FIG. 2) controls the operation of the 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). At this time, the tool 4 rotates relative to the work material 3. 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 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.

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 is provided with 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 the pair of Y-axis rails together with the nut. 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 the shape of a rectangular plate 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. 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 on the base 2 in the X-axis direction and the Y-axis direction by the Y-axis moving mechanism, the Y-axis table 12, and the X-axis moving mechanism. When the table 13 moves in the X-axis direction and the Y-axis direction, the work material 3 moves relative to the tool 4 in the X-axis direction and the Y-axis direction.

The tool changer 20 is provided on the front side of the spindle head 7 and includes a disk-shaped tool magazine 21. The tool magazine 21 holds a plurality of tools (not shown) radially on the outer periphery, and positions the tool instructed by the tool change command at the tool change position. Tool change instructions are given by the NC program. The tool change position is the lowest position of the tool magazine 21. The tool changing device 20 replaces and replaces the tool 4 mounted on the spindle 9 and the tool attached to the tool magazine 21 by a series of operations of raising the spindle head 7, rotating the tool magazine 21, and lowering the spindle head 7.

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, and the Y-axis motor 54 (see FIG. 2) provided in the machine tool 1, respectively, and holds the work material 3 on the table 13. Various processing is performed on the work material 3 by relatively moving the tool 4 mounted on the spindle 9 and the spindle 9. The various types of processing include, for example, drilling using a drill or the like, screw hole processing using a tap or the like, side surface processing using an end mill, a milling cutter or 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 input unit 16 and a display unit 17 (see FIG. 2). The input 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>
With reference to FIG. 2, the electrical configuration of the numerical control device 30 and the machine tool 1 will be described. The numerical control device 30 and the machine tool 1 include a CPU 31, ROM 32, RAM 33, a storage device 34, an input / output unit 35, drive circuits 51A to 55A, and the like. The CPU 31 controls the numerical control device 30 in an integrated manner. The ROM 32 stores the main program and the like. The CPU 31 executes the main process (see FIG. 7) by reading and executing the main program. The main process reads the instructions of the NC program line by line and executes the corresponding various operations. The NC program consists of multiple lines including various instructions (speed instruction, position instruction, valid instruction, invalid instruction). The NC program controls various operations of the machine tool 1 on a line-by-line basis. The RAM 33 temporarily stores various types of information including the first flag information, the second flag information, and the comparison speed information, which will be described later. The storage device 34 is non-volatile and stores NC programs and various information. In addition to the NC program input by the operator in the input unit 16 of the operation panel 15, the CPU 31 can store the NC program or the like read by the external input in the storage device 34.

The drive circuit 51A is connected to the Z-axis motor 51, the encoder 51B, the current detector 51C, and the speed detector 51D. The drive circuit 52A is connected to the spindle motor 52, the encoder 52B, the current detector 52C, and the speed detector 52D. The drive circuit 53A is connected to the X-axis motor 53, the encoder 53B, and the current detector 53C. The drive circuit 54A is connected to the Y-axis motor 54, the encoder 54B, and the current detector 54C. The drive circuit 55A is connected to the magazine motor 55, the encoder 55B, and the current detector 55C that drive the tool magazine 21. 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. When 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 not distinguished, they are collectively referred to as "motor 50". The drive circuits 51A to 55A receive a command to be periodically output by the CPU 31 and output a drive current to the corresponding motor 50. The encoders 51B to 55B detect the rotation angle of the corresponding motor 50. The encoders 51B to 55B output pulse signals corresponding to the detected rotation angles to the corresponding drive circuits 51A to 55A. The drive circuits 51A to 55A receive the signals output by the encoders 51B to 55B and output them to the CPU 31. The current detectors 51C to 55C detect the current flowing through the corresponding motor 50. The current detectors 51C to 55C output a signal indicating the detected current to the corresponding drive circuits 51A to 55A. The drive circuits 51A to 55A receive the signals output by the current detectors 51C to 55C and output them to the CPU 31. The speed detectors 51D and 52D detect the rotational speed of the corresponding motor 50. The speed detectors 51D and 52D output a signal indicating the detected rotation speed to the corresponding drive circuits 51A and 52A. The drive circuits 51A to 55A receive the signals output by the speed detectors 51D to 55D and output them to the CPU 31. The input / output unit 35 is connected to the input unit 16 and the display unit 17 of the operation panel 15, respectively.

<Outline of abnormality judgment processing>
The CPU 31 of the numerical control device 30 acquires the current flowing through the spindle motor 52 during the cutting operation of the work material 3 by the tool 4 via the corresponding current detector 52C and the drive circuit 52A. When the current acquired by the CPU 31 exceeds a predetermined second threshold value, there is a possibility that an excessive load is acting on the tool 4. Therefore, the CPU 31 determines that an abnormality has occurred in the tool 4 when the acquired current exceeds the second threshold value.

When the rotational speed of the spindle motor 52 accelerates or decelerates, the machine tool 1 tends to vibrate. The vibration may cause an error in the current acquired during the cutting operation of the work material 3. Therefore, the CPU 31 does not determine whether or not an abnormality has occurred in the tool 4 based on the current when the rotational speed of the spindle motor 52 accelerates or decelerates. On the other hand, the CPU 31 determines whether or not an abnormality has occurred in the tool 4 based on the current when the spindle motor 52 rotates at a constant speed. Hereinafter, the process is referred to as "abnormality determination process". When the rotational speed of the spindle motor 52 accelerates or decelerates, it is paraphrased as "the spindle motor 52 is accelerating or decelerating". When the spindle motor 52 rotates at a constant speed, it is paraphrased as "the spindle motor 52 is in a constant speed".

<Specific examples of NC programs (position control and speed control)>
FIG. 3A shows a specific example of the NC program stored in the storage device 34. An NC program contains a plurality of instructions arranged in a predetermined order. FIG. 3B shows the contents of each instruction.

"N02" and "N06" include a tool change command "M06" for changing the tool 4 used for the cutting operation. The tool change order specifies the tool 4 after the change. When the tool change command is read, the CPU 31 controls the drive circuit 51A and the drive circuit 55A to drive the Z-axis motor 51 and the magazine motor 55. At this time, the tool changing device 20 replaces the tool 4. “N03” and “N07” include an instruction “G00” for executing positioning of the tool 4 with respect to the work material 3. The command defines at least one of the position information of the tool 4 in the X-axis direction, the Y-axis direction, and the Z-axis direction. When the CPU 31 reads the command, the CPU 31 calculates a position command based on the command and periodically outputs the position command to the drive circuits 53A, 54A, 51A. At this time, the drive circuits 51A, 53A, and 54A output drive currents to the X-axis motor 53, the Y-axis motor 54, and the Z-axis motor 51, respectively, and drive the X-axis motor 53, the Y-axis motor 54, and the Z-axis motor 51, respectively. do. At this time, the table 13 moves in the X-axis direction and the Y-axis direction by the X-axis movement mechanism and the Y-axis movement mechanism. Further, the spindle head 7 moves in the Z-axis direction.

"N08" uses a tap as a tool 4 and commands "G84" (hereinafter, "tap cutting") for executing a cutting operation (hereinafter, referred to as "tap cutting") for forming a female thread inside a hole. It is called "command"). The tap cutting command at least defines the position information "Z-10" in the Z-axis direction of the tool 4, the movement speed information "F200" in the Z-axis direction of the tool 4, and the rotation speed information "S200" of the spindle 9. When the CPU 31 reads the tap cutting command "G84", it calculates a position command in the Z-axis direction (hereinafter referred to as "Z-axis position command") based on the command, and issues a Z-axis position command to the drive circuit 51A. Output periodically. The drive circuit 51A drives the Z-axis motor 51. At this time, the spindle head 7 moves in the Z-axis direction at "200 mm / min" (movement speed information) up to "Z-10" (position information) by the Z-axis movement mechanism. At the same time, the correction calculator 36B (see FIG. 4), which will be described later, calculates the position command of the spindle 9 synchronized with the Z-axis position command (hereinafter referred to as “spindle position command”), and the spindle position command is given to the drive circuit 52A. Is output periodically. The drive circuit 52A drives the spindle motor 52 in synchronization with the Z-axis motor 51. At this time, the spindle 9 rotates at "200 rpm" (rotational speed information) in synchronization with the movement of the spindle head 7. Hereinafter, the control method of the Z-axis motor 51 and the spindle motor 52 for executing tap cutting is referred to as "position control". Of the tap cutting commands "G84", the commands for calculating the Z-axis position command and the spindle position command are referred to as "position commands", respectively.

With reference to FIG. 4, the position control when the tap cutting is executed will be described in detail. The CPU 31 periodically outputs a Z-axis position command to the calculator 36A. The arithmetic unit 36A outputs the input Z-axis position command to the deviation counter 37B. The encoder 51B provided in the Z-axis motor 51 outputs a pulse signal corresponding to the rotation angle of the Z-axis motor 51 to the deviation counter 37B. The deviation counter 37B calculates the deviation between the input Z-axis position command and the pulse signal. The deviation counter 37B outputs the calculated deviation to the servo amplifier 38B. The speed detector 51D detects the rotation speed of the Z-axis motor 51 based on the pulse signal output by the encoder 51B, and outputs a signal indicating the rotation speed to the servo amplifier 38B. The servo amplifier 38B uses a signal indicating the rotation speed input from the speed detector 51D as a feedback signal, and corrects the deviation input from the deviation counter 37B. The servo amplifier 38B outputs a drive current to the Z-axis motor 51 based on the corrected deviation. The Z-axis motor 51 rotates based on the Z-axis position command corrected according to the current rotation speed. At this time, the spindle head 7 moves in the Z-axis direction.

Further, the arithmetic unit 36A outputs the input Z-axis position command to the correction arithmetic unit 36B. The encoder 51B outputs a pulse signal corresponding to the rotation angle of the Z-axis motor 51 to the correction calculator 36B. The correction calculator 36B uses the pulse signal input from the encoder 51B as a feedback signal to correct the Z-axis position command input from the calculator 36A. The correction calculator 36B calculates a spindle position command from the corrected command and outputs it to the deviation counter 37A. The encoder 52B provided on the spindle motor 52 outputs a pulse signal corresponding to the rotation angle of the spindle motor 52 to the deviation counter 37A. The deviation counter 37A calculates the deviation between the input spindle position command and the pulse signal. The deviation counter 37A outputs the calculated deviation to the servo amplifier 38A. The speed detector 52D detects the rotation speed of the spindle motor 52 based on the pulse signal output by the encoder 52B, and outputs a signal indicating the rotation speed to the servo amplifier 38A. The servo amplifier 38A uses a signal indicating the rotation speed input from the speed detector 52D as a feedback signal, and corrects the deviation input from the deviation counter 37A. The servo amplifier 38A outputs a drive current to the spindle motor 52 based on the corrected deviation. The spindle motor 52 rotates based on the spindle position command corrected according to the current rotation speed. At this time, the spindle head 7 rotates in synchronization with the movement in the Z-axis direction. Therefore, the spindle position command is synchronized with the Z-axis position command.

In the case of position control, the deviation counter 37B and the servo amplifier 38B in FIG. 4 correspond to the drive circuit 51A in FIG. In the case of position control, the deviation counter 37A and the servo amplifier 38A in FIG. 4 correspond to the drive circuit 52A in FIG.

"N02" includes a command "M03" for rotating the spindle 9 in the positive direction at a constant speed. The instruction at least defines the rotational speed information "S2000" of the spindle 9. The rotation speed information of the spindle 9 after "N05" is specified in "S1000" in the command of "N05". The correction calculator 36B (see FIG. 4) calculates the speed command of the spindle 9 based on the command (hereinafter referred to as “spindle speed command”), and periodically outputs the spindle speed command to the drive circuit 52A. .. The drive circuit 52A drives the spindle motor 52. At this time, the spindle 9 rotates at "2000 rpm". Hereinafter, the control method of the spindle motor 52 for executing the command "M03" is referred to as "speed control". The command "M03" is referred to as a "speed command".

"N04" and "N05" include a command "G01" (hereinafter referred to as "normal cutting command") for executing a normal cutting operation (hereinafter referred to as "normal cutting") other than tap cutting. .. The instruction at least defines the position information "Z-10 / Z-15" in the Z-axis direction of the tool 4 and the movement speed information "F500 / F250" in the Z-axis direction of the tool 4. When the CPU 31 reads the command "G01" of "N04", it calculates a Z-axis position command based on the command and periodically outputs the Z-axis position command to the drive circuit 51A. The drive circuit 51A drives the Z-axis motor 51. At this time, the spindle head 7 moves in the Z-axis direction at "500 mm / min" (movement speed information) up to "Z-10" (position information) by the Z-axis movement mechanism. At the same time, the CPU 31 periodically outputs a spindle speed command based on the "speed command" of "N02" to the drive circuit 52A, asynchronously with the control of the drive circuit 51A. The drive circuit 52A drives the spindle motor 52 independently of the control of the drive circuit 51A. At this time, the spindle 9 rotates at "2000 rpm" (rotational speed information (in the case of "N04")).

The control method of the spindle motor 52 for executing normal cutting corresponds to "speed control". The control method of the Z-axis motor 51 for executing normal cutting corresponds to "position control". The command for calculating the Z-axis position command in "G01" corresponds to the "position command". The command for calculating the spindle speed command in "G01" corresponds to the "speed command". The command for executing tap cutting (N08) and the command for executing normal cutting (N04, N05) are collectively referred to as a cutting command.

With reference to FIG. 4, speed control in the case of performing normal cutting will be described in detail. The difference from the position control in the case of tap cutting is that in tap cutting, the spindle position command is generated based on the Z-axis position command, whereas in normal cutting, the CPU 31 issues the spindle speed command to the calculator 36A. The point is that the arithmetic unit 36A outputs a spindle speed command to the servo amplifier 38A by bypassing the correction arithmetic unit 36B and the deviation counter 37A. At this time, the spindle head 7 rotates asynchronously with the movement in the Z-axis direction. Therefore, the spindle speed command is not synchronized with the Z-axis position command.

"N01" includes an instruction (referred to as a start instruction) "M901" for indicating to start the abnormality determination process. When the CPU 31 reads the start command, the CPU 31 can execute the abnormality determination process until the next end command described later is read. "N09" includes an instruction (referred to as an end instruction) "M902" for indicating that the abnormality determination process is terminated. When the CPU 31 reads the end instruction, the abnormality determination process cannot be executed until the next valid instruction is read.

<Judgment method during acceleration / deceleration / constant speed>
FIG. 5 shows a case where the CPU 31 controls the Z-axis motor 51 and the spindle motor 52 by position control in response to the tap cutting command “G84” of “N08” (see FIG. 3). As shown in FIG. 5 (a-1), the CPU 31 responds to the position command of the tap cutting command “G84” and performs the position information “Z-10” and the movement speed information “F200” during the time t1 to t2. The Z-axis position command p at times t1 to t2 is calculated and periodically output to the drive circuit 51A. The drive circuit 51A drives the Z-axis motor 51 based on the Z-axis position command p. At this time, since the rotation speed of the Z-axis motor 51 suddenly accelerates or decelerates at the timings of time t1 and t2, the acceleration / deceleration speed becomes large at the timing. Therefore, it is preferable that the CPU 31 does not determine the occurrence of an abnormality based on the current flowing through the Z-axis motor 51 in the vicinity of the timings of the times t1 and t2.

In the present embodiment, the CPU 31 differentiates the time change of the Z-axis position command p that is periodically output, and calculates the velocity information shown in FIG. 5 (a-2). Further, the CPU 31 differentiates the time change of the calculated velocity information and calculates the acceleration information shown in FIG. 5A-3. That is, the CPU 31 secondarily differentiates the time change of the Z-axis position command p (Z-10) that is periodically output to the drive circuit 51A, and calculates the acceleration information. The CPU 31 determines that the Z-axis motor 51 is accelerating or decelerating during the periods d21 and d22 in which the absolute value of the calculated acceleration information is larger than the predetermined first threshold value Th1. Further, as described above, at the time of tap cutting, the spindle position information command q is calculated from the Z-axis position command p and the rotation speed information "S200", and is periodically output to the drive circuit 52A. At this time, the relationship of "q = p × movement speed information ÷ rotation speed information" is satisfied. That is, the spindle motor 52 is driven in synchronization with the Z-axis motor 51. Therefore, the CPU 41 does not determine the occurrence of an abnormality based on the current flowing through the spindle motor 52 during the periods d21 and d22. On the other hand, the CPU 31 determines that the spindle motor 52 is in constant speed during the periods d11, d12, and d13 in which the absolute value of the calculated acceleration information is equal to or less than the first threshold value Th1. During this period, the CPU 31 determines the occurrence of an abnormality based on the current flowing through the spindle motor 52.

FIG. 6 shows a case where the CPU 31 controls the spindle motor 52 by speed control in response to the speed command “M03” of “N02” (see FIG. 3). As shown in FIG. 6 (b-1), the CPU 31 periodically outputs the spindle speed command v indicating the speed information “S2000” to the drive circuit 52A during the time t3 to t4. The drive circuit 52A drives the spindle motor 52 based on the spindle speed command v. FIG. 6 (b-2) shows the temporal change of the information indicating the rotation speed of the spindle motor 52 (hereinafter referred to as “measurement information”) measured by the speed detector 52D connected to the spindle motor 52. The rotational speed of the spindle motor 52 does not increase to 2000 rpm (speed information) at the same time as the timing of the time t3, but gradually increases in the period d41 of the time t3 to t31. Further, the rotation speed of the spindle motor 52 does not decrease to 0 rpm at the same time as the timing of the time t4, but gradually decreases in the period d42 of the time t4 to t41. During the periods d41 and d42, the acceleration / deceleration of the rotational speed of the spindle motor 52 increases. Therefore, it is preferable that the CPU 31 does not determine the occurrence of an abnormality based on the current flowing through the spindle motor 52 during the periods d41 and d42.

As shown in FIG. 6 (b-3), in the present embodiment, the CPU 31 does not determine the occurrence of an abnormality based on the current flowing through the spindle motor 52 during the periods d31 and d33 when the speed information is 0. The CPU 31 determines that the speed information (hereinafter referred to as "mth speed information") indicated by the mth (m is an integer of 1 or more) th speed command is not the same as the m + 1 speed information, and then determines that the speed information is not the same. It is determined that the spindle motor 52 is accelerating / decelerating during the period d41 until it is determined that the speed information and the measurement information are the same. During this period, the CPU 31 does not determine the occurrence of an abnormality based on the current flowing through the spindle motor 52. During the period d32 from the determination that the speed information and the measurement information are the same to the determination that the nth (n is an integer of 1 or more) speed information and the n + 1 speed information are not the same, the CPU 31 determines. It is determined that the spindle motor 52 is in constant speed. During this period, the CPU 31 determines the occurrence of an abnormality based on the current flowing through the spindle motor 52. During the period d42 from the determination that the nth velocity information and the n + 1th velocity information are not the same to the determination that the velocity information and the measurement information are the same, the CPU 31 states that the spindle motor 52 is accelerating or decelerating. judge. During this period, the CPU 31 does not determine the occurrence of an abnormality based on the current flowing through the spindle motor 52.

<First flag information, second flag information>
The first flag information is flag information for switching whether or not to execute the abnormality determination process based on the NC program start command (“M901”, see FIG. 3) and the end command (“M902”, see FIG. 3). .. When the start instruction is read from the NC program, the CPU 31 stores the start flag as the first flag information (S17 (see FIG. 7)). When the end instruction is read from the NC program, the CPU 31 stores the end flag as the first flag information (S21 (see FIG. 7)). Therefore, the first flag information becomes the start flag from the time when the start instruction is read until the next time when the end instruction is read. The first flag information becomes the end flag from the time when the end instruction is read until the next time when the start instruction is read. The CPU 31 is capable of executing the abnormality determination process while storing the start flag as the first flag information (S45: YES (see FIG. 8)). The CPU 31 makes the abnormality determination process unexecutable while storing the end flag as the first flag information (S45: NO (see FIG. 8)).

The second flag information is flag information for switching whether or not to determine whether or not an abnormality has occurred based on the current flowing through the motor 50 in the abnormality determination process. When the spindle motor 52 determines that acceleration / deceleration is in progress, the CPU 31 stores the determination stop flag as the second flag information (S81 (see FIG. 9), S103 (see FIG. 10)). When the speed information is 0 when the speed control is executed, the CPU 31 stores the determination stop flag as the second flag information (S93 (see FIG. 10)). The determination stop flag indicates that the presence or absence of an abnormality is not determined. When the spindle motor 52 determines that the speed is constant, the CPU 31 stores the determination flag as the second flag information (S77 (see FIG. 9), S99 (see FIG. 10)). The determination flag indicates that the presence or absence of an abnormality is determined. While the determination flag is stored as the second flag information (S53: YES (see FIG. 8)), the CPU 31 determines an abnormality of the tool 4 based on the current flowing through the spindle motor 52 (S57 (see FIG. 8)).

<Main processing>
The main process will be described with reference to FIGS. 7 to 10. The CPU 31 stores the end flag in the RAM 33 as the first flag information, and stores the determination stop flag in the RAM 33 as the second flag information (S11). The CPU 31 reads one instruction of the NC program stored in the storage device 34 in order (S13). The CPU 31 determines whether the read instruction is a start instruction (S15). When the CPU 31 determines that the read instruction is a start instruction (S15: YES), the CPU 31 stores the start flag in the RAM 33 as the first flag information (S17). The CPU 31 returns the process to S13. When the CPU 31 determines that the read instruction is not a start instruction (S15: NO), the CPU 31 determines whether the read instruction is an end instruction (S19). When the CPU 31 determines that the read instruction is an end instruction (S19: YES), the CPU 31 stores the end flag in the RAM 33 as the first flag information (S21). The CPU 31 returns the process to S13.

When the CPU 31 determines that the read instruction is not an end instruction (S19: NO), the CPU 31 determines whether the read instruction is a cutting instruction (position instruction or speed instruction) (S23). When the CPU 31 determines that the read instruction is not a cutting instruction (S23: NO), the CPU 31 determines whether the read instruction is a completion instruction indicating the completion of the NC program (S29). When the CPU 31 determines that the read instruction is not a completion instruction (S29: NO), the CPU 31 executes a process based on the read instruction (S31). After the processing is completed, the CPU 31 advances the processing to S13. The CPU 31 reads one instruction next to the NC program (S13), and repeats the processes of S15 to S31.

When the CPU 31 determines that the command read in S13 is a cutting command (S23: YES), the CPU 31 executes an abnormality determination process (see FIG. 8) (S25). As shown in FIG. 8, the CPU 31 initializes the comparison speed information stored in the RAM 33 (S41). The CPU 31 starts a cutting process (normal cutting or tap cutting) according to a cutting command (S43). The CPU 31 determines whether or not the start flag is stored as the first flag information (S45). When the CPU 31 determines that the end flag is stored as the first flag (S45: NO), the processing proceeds to S59. When the CPU 31 determines that the start flag is stored as the first flag information (S45: YES), the CPU 31 advances the process to S47.

The CPU 31 determines whether the control method for controlling the spindle motor 52 is position control in response to the command read in S13 (see FIG. 7) (S47). When the CPU 31 reads out a tap cutting command for executing tap cutting, it determines that the control method of the spindle motor 52 is position control (S47: YES). At this time, the CPU 31 executes the first determination process (see FIG. 9) (S49). When the CPU 31 reads out a normal cutting command for executing normal cutting, it determines that the control method of the spindle motor 52 is speed control (S47: NO). At this time, the CPU 31 executes the second determination process (see FIG. 10) (S51). After the first determination process or the second determination process is completed, the CPU 31 advances the process to S53.

The first determination process will be described with reference to FIG. The CPU 31 secondarily differentiates the time change of the Z-axis position command that is periodically output to the drive circuit 51A, and calculates the acceleration information (S71). The CPU 31 determines whether or not the determination stop flag is stored as the second flag information (S73). When the CPU 31 determines that the determination stop flag is stored as the second flag information (S73: YES), the CPU 31 determines whether the acceleration information is equal to or less than a predetermined first threshold value (S75). When the CPU 31 determines that the acceleration information is equal to or less than the first threshold value (S75: YES), the CPU 31 determines that the spindle motor 52 that operates in synchronization with the Z-axis motor 51 is in constant speed. The CPU 31 stores the determination flag as the second flag information in the RAM 33 (S77). The CPU 31 ends the first determination process and returns the process to the abnormality determination process (see FIG. 8). When the CPU 31 determines that the acceleration information is larger than the first threshold value (S75: NO), the CPU 31 determines that the spindle motor 52 operating in synchronization with the Z-axis motor 51 is accelerating or decelerating. The CPU 31 ends the first determination process and returns the process to the abnormality determination process (see FIG. 8). At this time, the state in which the determination stop flag is stored as the second flag information continues.

When the CPU 31 determines that the determination flag is stored as the second flag information (S73: NO), the CPU 31 determines whether the acceleration information is larger than the first threshold value (S79). When the CPU 31 determines that the acceleration information is larger than the first threshold value (S79: YES), the CPU 31 determines that the spindle motor 52 operating in synchronization with the Z-axis motor 51 is accelerating or decelerating. The CPU 31 stores the determination stop flag in the RAM 33 as the second flag information (S81). The CPU 31 ends the first determination process and returns the process to the abnormality determination process (see FIG. 8). When the CPU 31 determines that the acceleration information is equal to or less than the first threshold value (S79: NO), the CPU 31 determines that the spindle motor 52 that operates in synchronization with the Z-axis motor 51 is in constant speed. The CPU 31 ends the first determination process and returns the process to the abnormality determination process (see FIG. 8). At this time, the state in which the determination flag is stored as the second flag information continues.

The second determination process will be described with reference to FIG. The CPU 31 acquires the speed information indicated by the spindle speed command periodically output to the drive circuit 52A. The CPU 31 determines whether the acquired speed information is 0 (S91). When the CPU 31 determines that the speed information is 0 (S91: YES), the CPU 31 stores the determination stop flag as the second flag information (S93). The CPU 31 advances the process to S105. When the CPU 31 determines that the speed information is not 0 (S91: NO), the CPU 31 advances the process to S95.

The CPU 31 determines whether or not the determination stop flag is stored as the second flag information (S95). When the CPU 31 determines that the determination stop flag is stored as the second flag information (S95: YES), the CPU 31 advances the process to S97. The CPU 31 acquires measurement information obtained by measuring the rotation speed of the spindle motor 52 based on the signal output by the speed detector 52D connected to the spindle motor 52. The CPU 31 determines whether or not the measurement information and the speed information are the same (S97). When the CPU 31 determines that the measurement information and the speed information are the same (S97: YES), the CPU 31 determines that the spindle motor 52 is in constant speed. The CPU 31 stores the determination flag as the second flag information (S99). The CPU 31 advances the process to S105. When the CPU 31 determines that the measurement information and the speed information are not the same (S97: NO), the CPU 31 advances the process to S105. At this time, the state in which the determination stop flag is stored as the second flag information continues.

When the CPU 31 determines that the determination flag is stored as the second flag information (S95: NO), the CPU 31 determines whether or not the comparative speed information stored in the RAM 33 and the speed information are the same (S101). As a result, the CPU 31 determines whether or not the two speed information indicated by the two speed commands continuously output by the drive circuit 52A to the spindle motor 52 are the same. When the CPU 31 determines that the comparative speed information and the speed information are not the same (S101: NO), the CPU 31 determines that the spindle motor 52 is accelerating or decelerating. The CPU 31 stores the determination stop flag as the second flag information (S103). The CPU 31 advances the process to S105. When the CPU 31 determines that the comparative speed information and the speed information are the same (S101: YES), the CPU 31 advances the process to S105. At this time, the state in which the determination flag is stored as the second flag information continues.

The CPU 31 stores the speed information as the comparison speed information and updates the comparison speed information (S105). The CPU 31 ends the second determination process and returns the process to the abnormality determination process (see FIG. 8).

As shown in FIG. 8, after the end of the first determination process (S49) or the second determination process (S51), the CPU 31 determines whether or not the determination flag is stored as the second flag information (S53). When the CPU 31 determines that the determination stop flag is stored as the second flag information (S53: NO), the CPU 31 does not determine whether or not the tool 4 has an abnormality. At this time, the CPU 31 advances the process to S59. When the CPU 31 determines that the determination flag is stored as the second flag information (S53: YES), the CPU 31 determines whether or not an abnormality has occurred in the tool 4 as follows.

The CPU 31 acquires the current detected by the current detector 52C from the drive circuit 52A as the current flowing through the spindle motor 52 (S55). The CPU 31 determines whether the detected current is equal to or less than a predetermined second threshold value (S57). When the CPU 31 determines that the detected current is larger than the second threshold value (S57: NO), the CPU 31 determines that an abnormality has occurred in the tool 4. The CPU 31 displays a warning on the display unit 17 (see FIG. 2) (S61). The CPU 31 ends the abnormality determination process and returns the process to the main process (see FIG. 7). When the CPU 31 determines that the detected current is equal to or less than the second threshold value (S57: YES), the CPU 31 advances the process to S59. The CPU 31 determines whether or not the cutting process corresponding to the cutting command read in S13 (see FIG. 7) is completed (S59). When the CPU 31 determines that the cutting process has not been completed (S59: NO), the CPU 31 returns the process to S45. The CPU 31 ends the abnormality determination process when it is determined that the cutting process is completed (S59: YES), and returns the process to the main process (see FIG. 7).

As shown in FIG. 7, the CPU 31 determines whether or not a warning has been displayed on the display unit 17 after the abnormality determination process (S25) is completed (S27). When the warning is displayed on the display unit 17 (S27: YES), the CPU 31 ends the main process because an abnormality has occurred in the tool 4. When the warning is not displayed on the display unit 17 (S27: NO), the CPU 31 returns the process to S13. The CPU 31 reads one instruction next to the NC program (S13), and repeats the processes of S15 to S31. When the CPU 31 determines that the read instruction is a completion instruction (S29: YES), the CPU 31 ends the main process.

<Action and effect of this embodiment>
The machine tool 1 includes a Z-axis motor 51, a spindle motor 52, and drive circuits 51A and 52A for driving each. When the numerical control device 30 executes the speed control of the spindle motor 52, the numerical control device 30 periodically outputs a spindle speed command based on the speed command to the drive circuit 52A (deviation counter 37A and servo amplifier 38A) via the arithmetic unit 36A. .. When the numerical control device 30 executes the position control of each of the spindle motor 52 and the Z-axis motor 51, the numerical control device 30 issues a Z-axis position command based on the position command to the drive circuit 51A (deviation counter 37B and servo amplifier) via the arithmetic unit 36A. 38B) is periodically output, and the spindle position command is periodically output to the drive circuit 52A (deviation counter 37A and servo amplifier 38A) via the arithmetic unit 36A and the correction arithmetic unit 36B. When the numerical control device 30 determines that the spindle motor 52 is in constant speed (S53: YES), the numerical control device 30 determines whether or not an abnormality has occurred in the tool 4. When the numerical control device 30 determines that the spindle motor 52 is accelerating / decelerating (S53: NO), the numerical control device 30 does not determine whether or not an abnormality has occurred in the tool 4. Therefore, when the current flowing through the spindle motor 52 fluctuates due to a factor other than the occurrence of the abnormality of the tool 4 while the spindle motor 52 is accelerating or decelerating, the possibility of erroneously determining the occurrence of the abnormality of the tool 4 can be reduced. .. The numerical control device 30 is based on a determination method different between when the spindle motor 52 is controlled by position control (during tap cutting) and when the spindle motor 52 is controlled by speed control (during normal cutting). Determine whether acceleration / deceleration is in progress or constant speed is in progress. Therefore, the numerical control device 30 can appropriately determine whether the spindle motor 52 is in acceleration / deceleration or in constant speed by an appropriate determination method according to each control method. Therefore, the numerical control device 30 can improve the accuracy of the occurrence of the abnormality of the tool 4.

The machine tool 1 includes a spindle motor 52 for rotating the tool 4 relative to the work material 3 and a Z-axis motor 51 for moving the tool 4 relative to the work material 3. When the numerical control device 30 performs tap cutting, the spindle motor 52 rotates in synchronization with the Z-axis motor 51. At this time, the control method of the spindle motor 52 is position control. When the spindle motor 52 determines the position control (see FIG. 9), the numerical control device 30 second-orders the Z-axis position command output to the Z-axis motor 51 to calculate the acceleration information (S71). The numerical control device 30 determines whether the spindle motor 52, which operates in synchronization with the Z-axis motor 51, is in acceleration / deceleration or in constant speed, according to the relationship between the acceleration information and the first threshold value. On the other hand, when the numerical control device 30 performs normal cutting, the spindle motor 52 rotates asynchronously with the Z-axis motor 51. At this time, the control method of the spindle motor 52 is speed control. When the numerical control device 30 determines that the spindle motor 52 determines the speed control (see FIG. 10), the speed information indicated by the spindle speed command output to the spindle motor 52 and the measurement information measured by the rotation speed of the spindle motor 52 are displayed. It is determined whether the spindle motor 52 is in acceleration / deceleration or in constant speed depending on whether they are the same (S97). When the numerical control device 30 determines that the speed control is performed (see FIG. 10), the spindle motor 52 is added depending on whether or not the two speed information indicated by the two speed commands continuously output to the spindle motor 52 are the same. It is determined whether deceleration is in progress or constant speed is in progress (S101). At this time, the numerical control device 30 can appropriately determine whether the spindle motor 52 is in acceleration / deceleration or constant speed, so that the accuracy of determining whether or not an abnormality has occurred can be improved.

The RAM 33 stores the second flag information indicating whether or not to determine whether or not an abnormality has occurred. The numerical control device 30 uses the determination stop flag indicating that the presence or absence of an abnormality has not been determined as the second flag information in the RAM 33 before first determining whether the motor 50 is in acceleration / deceleration or constant speed (SS57). It is stored in (S11). When the spindle motor 52 determines that the speed is constant (S75: YES, S97: YES) in a state where the determination stop flag is stored as the second flag information, the numerical control device 30 determines whether or not an abnormality has occurred. The indicating determination flag is stored in the RAM 33 as the second flag information (S77, S99). When the spindle motor 52 determines that acceleration / deceleration is in progress (S79: NO, S101: NO) in a state where the determination flag is stored as the second flag information, the numerical control device 30 uses the determination stop flag as the second flag information. It is stored in the RAM 33 (S81, S103). The numerical control device 30 determines whether or not an abnormality has occurred (S55, S57) when the determination flag is stored as the second flag information (S53: YES). The numerical control device 30 does not determine whether or not an abnormality has occurred when the determination stop flag is stored as the second flag information (S53: NO). Therefore, the numerical control device 30 can appropriately determine whether or not to determine whether or not an abnormality has occurred, depending on the state of the spindle motor 52.

The NC program stored in the storage device 34 includes a start command indicating to start the determination of the presence / absence of an abnormality and an end command indicating to end the determination of the presence / absence of an abnormality. The numerical control device 30 stores the start flag as the first flag information (S17) from the time when the start instruction is read (S15: YES) to the time when the end instruction is read (S19: YES). At that time, the numerical control device 30 determines whether or not an abnormality has occurred in the tool 4. The numerical control device 30 stores the end flag as the first flag information (S21) from the time when the end command is read (S19: YES) to the time when the start command is read (S15: YES). At this time, the numerical control device 30 does not determine whether or not the tool 4 has an abnormality. At this time, the numerical control device 30 can specify a determination body for the presence or absence of an abnormality based on the start command and the end command that the NC program has together with the control command of the motor 50.

<Modification example>
The present invention is not limited to the above embodiment. When executing the process of S97, the CPU 31 does not have to determine whether the speed information and the measurement information are completely the same. For example, the CPU 31 may determine that the speed information and the measurement information are the same when the measurement information is included in the predetermined range with respect to the speed information. When executing the process of S101, the CPU 31 does not have to determine whether the comparative speed information and the speed information are completely the same. For example, the CPU 31 may determine that the comparative speed information and the speed information are the same when the speed information is included in the predetermined range with respect to the comparative speed information.

The machine tool 1 may include a motor for rotating the table 13 that holds the work material 3. The machine tool 1 may execute cutting by rotating the work material 3 relative to the tool 4 by the rotation of the motor. At that time, when the CPU 31 determines that the speed control is performed (see FIG. 10), the CPU 31 determines whether or not the speed information indicated by the speed command output to the motor is the same as the measurement information measured by the rotation speed of the motor. May be good. Further, when the CPU 31 determines that the speed control is performed, the CPU 31 may determine whether or not the two speed information indicated by the two speed commands continuously output to the motor are the same.

The CPU 31 may periodically output a spindle position command to the drive circuit 52A when performing tap cutting. As a result, the drive circuit 52A may drive the spindle motor 52. At the same time, the Z-axis position command may be periodically output to the drive circuit 51A in synchronization with the control of the drive circuit 52A. As a result, the drive circuit 51A may drive the Z-axis motor 51 in synchronization with the spindle motor 52. The CPU 31 may calculate the acceleration information by second-order differentializing the spindle position command periodically output to the drive circuit 52A of the spindle motor 52 (S71). The CPU 31 may determine whether the Z-axis motor 51 operating in synchronization with the spindle motor 52 is in acceleration / deceleration or in constant speed based on the relationship between the calculated acceleration information and the first threshold value (S75, S79). ). The CPU 31 may determine whether or not an abnormality has occurred in the tool 4 based on the current of the Z-axis motor 51 (S57).

The CPU 31 may secondarily differentiate the position commands (Z-axis position command and spindle position command) output to the Z-axis motor 51 and the spindle motor 52, respectively, and calculate the respective acceleration information when tap cutting is performed. The CPU 31 may determine whether either the Z-axis motor 51 or the spindle motor 52 is in acceleration / deceleration or in constant speed based on the relationship between the calculated acceleration information and the first threshold value (S75, S79). .. When the CPU 31 determines that either the Z-axis motor 51 or the spindle motor 52 is in constant speed, the CPU 31 determines whether or not an abnormality has occurred in the tool 4 based on the current flowing through either the Z-axis motor 51 or the spindle motor 52. You may judge.

When the read command is a normal cutting command, the CPU 31 determines that the control method of the spindle motor 52 is speed control (S47: YES). When the read command is a tap cutting command, the CPU 31 determines that the control method of the spindle motor 52 is position control (S47: NO). The CPU 31 may determine whether it is speed control or position control by a method different from the above. For example, the NC program may include flag information indicating whether it is speed control or position control. The CPU 31 may determine whether to control the speed or the position based on the flag information. The NC program may not include a start instruction and an end instruction. The CPU 31 is not limited to the flag stored as the first flag information, and may always determine whether or not an abnormality has occurred in the tool 4.

<Others>
The machine tool 1 is an example of the "mechanical device" of the present invention. The CPU 31 that performs the processing of S47 is an example of the "first determination means" of the present invention. The CPU 31 that performs the processing of S71 is an example of the "calculation means" of the present invention. The CPU 31 that performs the processing of S75, S77, S79, and S81 is an example of the "second determination means" of the present invention. The CPU 31 that performs the processing of S95 is an example of the "third determination means" of the present invention. The CPU 31 that performs the processing of S105 is an example of the "speed storage means" of the present invention. The CPU 31 that performs the processing of S101 is an example of the "fourth determination means" of the present invention. The CPU 31 that performs the processes of S99 and S103 is an example of the "fifth determination means" of the present invention. The CPU 31 that performs the processing of S55 is an example of the "detection means" of the present invention. The CPU 31 that performs the processes of S57 and S61 is an example of the "sixth determination means" of the present invention. The spindle motor 52 is an example of the "first motor" of the present invention. The Z-axis motor 51 is an example of the "second motor" of the present invention. The RAM 33 that stores the second flag information is an example of the "first storage unit" of the present invention. The CPU 31 that performs the processing of S11 is an example of the "first storage control means" of the present invention. The determination stop flag is an example of the "determination stop information" of the present invention. The constant flag is an example of the "determining information" of the present invention. The CPU 31 that performs the processing of S77 and S99 is an example of the "second storage control means" of the present invention. The CPU 31 that performs the processing of S81 and S103 is an example of the "third storage control means" of the present invention. The storage device 34 is an example of the "second storage unit" of the present invention.

The treatment of S47 is an example of the "first determination step" of the present invention. The process of S71 is an example of the "calculation step" of the present invention. The processing of S75, S77, S79, and S81 is an example of the "second determination step" of the present invention. The treatment of S95 is an example of the "third determination step" of the present invention. The process of S105 is an example of the "speed storage step" of the present invention. The process of S101 is an example of the "fourth determination step" of the present invention. The processing of S99 and S103 is an example of the "fifth determination step" of the present invention. The treatment of S55 is an example of the "detection step" of the present invention. The processing of S57 and S61 is an example of the "sixth determination step" of the present invention.

1: Machine tool 4: Tool 30: Numerical control device 31: CPU
34: Storage device 51: Z-axis motor 51A: Drive circuit 51B: Encoder 51C, 52C: Current detector 52: Spindle motor 52A: Drive circuit 52B: Encoder p, q: Position command v: Speed command

Claims (7)

The speed command based on the speed command included in the NC program is driven to the mechanical device provided with the motor and the drive circuit for relatively rotating and moving the tool for processing the work material and the work material. In a numerical control device capable of performing speed control that periodically outputs to a circuit and position control that periodically outputs a position command based on a position command to the drive circuit.
The first determination means for determining whether the instruction of the NC program is the speed control or the position control,
When the position control is determined by the first determination means, the calculation means for calculating the acceleration information by second-order differentializing the position command based on the position command, and
When the absolute value of the acceleration information calculated by the calculation means is larger than the predetermined threshold value, it is determined that the motor is accelerating or decelerating, and when the absolute value of the acceleration information is equal to or less than the predetermined threshold value, the motor is determined. The second judgment means for determining that the vehicle is in speed,
When the speed control is determined by the first determination means, the third determination means for determining whether or not the speed command based on the speed command and the measurement information measured by the rotational speed of the motor are the same.
When the speed control is determined by the first determination means, the speed storage means for storing the speed command as a storage command and the speed storage means.
A fourth determination means for determining whether or not the storage command previously stored by the speed storage means and the speed command are the same.
From the time when the third determination means determines that the speed command and the measurement information are the same until the fourth determination means determines that the storage command and the speed command are not the same, the said After determining that the motor is in constant speed and determining that the storage command and the speed command are not the same by the fourth determination means, the speed command and the measurement information are transmitted by the third determination means. Until it is determined that they are the same, the fifth determination means for determining that the motor is accelerating or decelerating, and
A detection means for detecting the current flowing through the motor and
When the second determination means or the fifth determination means determines that the motor is in constant speed, the sixth determination is to determine whether or not an abnormality has occurred in the tool based on the current detected by the detection means. Means and
Equipped with
The sixth determination means is
A numerical control device, characterized in that, when it is determined by the second determination means or the fifth determination means that the motor is accelerating or decelerating, the presence or absence of the occurrence of the abnormality is not determined. The mechanical device is
A first motor for rotating the tool relative to the work material and a second motor for moving the tool relative to the work material are provided.
When performing the position control, the first motor rotates in synchronization with the second motor, and the first motor rotates in synchronization with the second motor.
When the position control is determined by the first determination means,
The calculation means second-orders the position command for the second motor to calculate the acceleration information.
The second determination means determines whether the first motor is in acceleration / deceleration or constant speed based on the relationship between the acceleration information and the predetermined threshold value.
The numerical control device according to claim 1, wherein the sixth determination means determines whether or not an abnormality has occurred in the tool based on the current of the first motor. The mechanical device is
A first motor for rotating the tool relative to the work material and a second motor for moving the tool relative to the work material are provided.
When performing the position control, the second motor rotates in synchronization with the first motor, and the second motor rotates in synchronization with the first motor.
The calculation means second-orders the position command with respect to the first motor to calculate the acceleration information.
The second determination means determines whether the second motor is in acceleration / deceleration or constant speed based on the relationship between the acceleration information and the predetermined threshold value.
The numerical control device according to claim 1, wherein the sixth determination means determines whether or not the abnormality has occurred in the tool based on the current of the second motor. A first storage unit that stores information indicating whether or not to determine whether or not an abnormality has occurred, and
Prior to the first determination by the sixth determination means, the first storage control means for storing the determination stop information indicating that the presence or absence of the abnormality has not been determined is stored in the first storage unit.
With the determination stop information stored in the first storage unit, when the second determination means or the fifth determination means determines that the motor is in constant speed, it is determined whether or not the abnormality has occurred. A second storage control means for storing the determined information to be shown in the first storage unit,
When the motor is determined to be accelerating or decelerating by the second determination means or the fifth determination means in a state where the determination information is stored in the first storage unit, the determination stop information is stored in the first storage unit. Equipped with a third memory control means to store in
The sixth determination means is
When the first storage unit stores the determination information, it is determined whether or not the abnormality has occurred, and when the first storage unit stores the determination stop information, it is determined whether or not the abnormality has occurred. The numerical control device according to any one of claims 1 to 3, wherein the numerical control device is not provided. The NC program has a start command indicating to start the determination of the presence / absence of the abnormality and an end command indicating to end the determination of the presence / absence of the abnormality.
The sixth determination means is
From the time when the start command is read until the next time when the end command is read, it is determined whether or not the abnormality has occurred in the tool.
The numerical control device according to any one of claims 1 to 4, wherein the presence or absence of the abnormality occurrence of the tool is not determined between the time when the end command is read and the time when the start command is read next. The speed command based on the speed command is given to the mechanical device included in the NC program and equipped with a motor and a drive circuit for relatively rotating and moving the tool for machining the work material and the work material. The first determination step of determining whether the speed control is periodically output to the drive circuit or the position command is periodically output to the drive circuit based on the position command.
When the position control is determined by the first determination step, the calculation step of calculating the acceleration information by second-order differentiating the position command based on the position command, and
When the absolute value of the acceleration information calculated by the calculation step is larger than the predetermined threshold value, it is determined that the motor is accelerating or decelerating, and when the absolute value of the acceleration information is equal to or less than the predetermined threshold value, the motor is determined. The second judgment process to determine that the speed is high, and
When the speed control is determined by the first determination step, the third determination step of determining whether or not the speed command based on the speed command and the measurement information measured by the rotational speed of the motor are the same.
When the speed control is determined by the first determination step, the speed storage step of storing the speed command as a storage command and the speed storage step.
The fourth determination step of determining whether or not the storage command previously stored by the speed storage step and the speed command are the same,
From the determination that the speed command and the measurement information are the same by the third determination step to the determination that the storage command and the speed command are not the same by the fourth determination step, the said After determining that the motor is in constant speed and determining that the storage command and the speed command are not the same by the fourth determination step, the speed command and the measurement information are sent by the third determination step. Until it is determined that they are the same, the fifth determination step of determining that the motor is accelerating or decelerating, and
A detection process for detecting the current flowing through the motor, and
When it is determined by the second determination step or the fifth determination step that the motor is in constant speed, the sixth determination is to determine whether or not an abnormality has occurred in the tool based on the current detected by the detection step. Process and
Equipped with
The sixth determination step is
A numerical control method characterized in that when it is determined by the second determination step or the fifth determination step that the motor is accelerating or decelerating, the presence or absence of the occurrence of the abnormality is not determined. The speed command based on the speed command is given to the mechanical device included in the NC program and equipped with a motor and a drive circuit for relatively rotating and moving the tool for machining the work material and the work material. The first determination step of determining whether the speed control is periodically output to the drive circuit or the position command is periodically output to the drive circuit based on the position command.
When the position control is determined by the first determination step, the calculation step of calculating the acceleration information by second-order differentiating the position command based on the position command, and
When the absolute value of the acceleration information calculated by the calculation step is larger than the predetermined threshold value, it is determined that the motor is accelerating or decelerating, and when the absolute value of the acceleration information is equal to or less than the predetermined threshold value, the motor is determined. The second judgment process to determine that the speed is high, and
When the speed control is determined by the first determination step, the third determination step of determining whether or not the speed command based on the speed command and the measurement information measured by the rotational speed of the motor are the same.
When the speed control is determined by the first determination step, the speed storage step of storing the speed command as a storage command and the speed storage step.
The fourth determination step of determining whether or not the storage command previously stored by the speed storage step and the speed command are the same,
From the determination that the speed command and the measurement information are the same by the third determination step to the determination that the storage command and the speed command are not the same by the fourth determination step, the said After determining that the motor is in constant speed and determining that the storage command and the speed command are not the same by the fourth determination step, the speed command and the measurement information are sent by the third determination step. Until it is determined that they are the same, the fifth determination step of determining that the motor is accelerating or decelerating, and
A detection process for detecting the current flowing through the motor, and
When it is determined by the second determination step or the fifth determination step that the motor is in constant speed, the sixth determination is to determine whether or not an abnormality has occurred in the tool based on the current detected by the detection step. Process and
Is a numerical control program for letting a computer execute
The sixth determination step is
A numerical control program characterized in that when it is determined by the second determination step or the fifth determination step that the motor is accelerating or decelerating, the presence or absence of the occurrence of the abnormality is not determined.

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