Numerical control device and numerical control method

Abstract

To provide a numerical control device that is able to grasp a state of deterioration of a drive mechanism resulting from vibration cutting in the drive mechanism of a machine tool that performs machining including the vibration cutting.SOLUTION: A numerical control device 1 includes an estimation unit 482 that estimates a remaining life of a mechanical component constituting a drive mechanism based on an execution time of vibration cutting. The drive mechanism is capable of vibrating a to-be-driven body at each of a plurality of positions in a direction of a center line, or a rotation center, of a ball screw. The estimation unit 482 obtains, as the remaining life of the mechanical component, a period in which vibration of the to-be-driven body at the current position can be continued based on a continuation value that is the execution time for the vibration cutting performed by continuing vibration of the to-be-driven body at a predetermined position.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a numerical control device and a numerical control method for controlling a machine tool.

Background Art

[0002] A machine tool that performs cutting operations cuts a workpiece by causing relative movement between the tool and the workpiece while bringing the tool into contact with the workpiece. In cutting operations for machining the surface of a workpiece, vibration cutting may be performed in which cutting is performed while vibrating the tool at a low frequency. According to vibration cutting, by causing a section that interrupts the cutting of the workpiece by the tool to occur in the movement path of the tool, it becomes possible to cut the workpiece while dividing the chips. By shortening and dividing the chips, it is possible to prevent a decrease in machining accuracy due to the chips getting entangled with the workpiece or the tool. In addition, by shortening and dividing the chips, it is possible to reduce damage to the workpiece caused by the chips coming into contact with the workpiece.

[0003] Regarding a machine tool that performs cutting operations, it is desirable to be able to grasp the deterioration status of the drive mechanism in order to plan maintenance such as component replacement before the operation of the drive mechanism for moving the tool or the workpiece becomes difficult.

[0004] Patent Document 1 discloses an apparatus for displaying the operating state of a drive mechanism that linearly moves a moving body via a ball screw, and classifying and displaying information about the movement of the moving body in the ball screw for each type of axis operation. According to the apparatus disclosed in Patent Document 1, by classifying the axis operations into cutting feed for moving the moving body while cutting the workpiece and rapid feed for moving the moving body other than when cutting the workpiece and displaying the operating state, it becomes possible to grasp the deterioration status due to wear of the ball screw.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In vibration cutting, cutting is performed while vibrating the driven body. Therefore, the operation of the driven body in the case of performing vibration cutting is different from that in normal cutting other than vibration cutting. For this reason, when performing vibration cutting, the mode of deterioration of the mechanical components constituting the drive mechanism is different from that in the case of normal cutting. In the technology of Patent Document 1 above, it is possible to grasp the deterioration situation in the case of normal cutting such as cutting feed and rapid feed, but the influence on the deterioration due to vibration cutting is not considered. Therefore, the technology of Patent Document 1 above has a problem that it is impossible to grasp the deterioration situation of the drive mechanism caused by vibration cutting for the drive mechanism of a machine tool that performs machining including vibration cutting.

[0007] The present disclosure has been made in view of the above, and an object thereof is to obtain a numerical control device capable of grasping the deterioration situation of a drive mechanism caused by vibration cutting for a drive mechanism of a machine tool that performs machining including vibration cutting. MEANS FOR SOLVING THE PROBLEMS

[0008] In order to solve the above-described problems and achieve the object, a numerical control device according to the present disclosure is a numerical control device that controls a machine tool that performs machining including vibration cutting by a drive mechanism. The numerical control device according to the present disclosure includes an estimation unit that estimates the remaining life of mechanical components constituting the drive mechanism based on the execution time of vibration cutting. The drive mechanism can vibrate the driven body at each of a plurality of positions in the direction of the center line that is the rotation center of the ball screw. The estimation unit obtains, as the remaining life of the mechanical component, a period during which the vibration of the driven body at the current position can be continued based on a continuous value that is the execution time of vibration cutting by continuing the vibration of the driven body at a predetermined position. EFFECTS OF THE INVENTION

[0009] According to the numerical control device according to the present disclosure, regarding the drive mechanism of a machine tool that performs machining including vibration cutting, there is an effect that it becomes possible to grasp the deterioration status of the drive mechanism caused by vibration cutting.

Brief Description of the Drawings

[0010]

Figure 1

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Mode for Carrying Out the Invention

[0011] Hereinafter, the numerical control device and the numerical control method according to the embodiment will be described in detail with reference to the drawings.

[0012] Embodiment 1. FIG. 1 is a diagram showing a configuration example of a numerical control device 1 according to Embodiment 1. The numerical control (NC) device 1 is a computer that controls a machine tool for performing machining. The machine tool that is the object of control by the numerical control device 1 performs machining including vibration cutting. The machine tool performs vibration cutting by vibrating a driven body by a drive mechanism.

[0013] The numerical control device 1 includes an input operation unit 2, an output unit 3, and a control arithmetic unit 4. FIG. 1 shows the numerical control device 1 and a drive unit 7 which is a component of the machine tool. The drive unit 7 is connected to the control arithmetic unit 4. The numerical control device 1 generates various commands according to a machining program. The numerical control device 1 controls the machine tool by outputting the generated various commands to the drive unit 7. Note that the drive unit 7 may be an element independent of the machine tool.

[0014] The machine tool is an NC machine tool. The machine tool cuts the workpiece by causing relative movement between the tool and the workpiece while bringing the tool into contact with the workpiece. The machine tool processes the workpiece into the desired shape by removing unnecessary portions from the workpiece by cutting. In Embodiment 1, the machine tool processes the workpiece while relatively moving the tool and the workpiece by two or more drive axes and using the tool. In Embodiment 1, the machine tool processes the workpiece, for example, by rotating the workpiece by the drive unit 7 and moving the tool in two directions, the X-axis direction and the Z-axis direction, by the drive unit 7. The X-axis is, for example, a vertical axis. The Z-axis is, for example, an axis parallel to the horizontal plane. The X-axis and the Z-axis are perpendicular to each other. Note that the X-axis is not limited to a vertical axis, and the Z-axis is not limited to an axis parallel to the horizontal plane. The X-axis and the Z-axis can be appropriately set according to the configuration of the machine tool.

[0015] The drive unit 7 includes a servo motor 71x, a detector 72x, and a servo control unit 73x. The servo motor 71x constitutes an X-axis drive mechanism. The X-axis drive mechanism is a drive mechanism that drives the tool for cutting the workpiece or the workpiece in the X-axis direction. In Embodiment 1, the X-axis drive mechanism is a drive mechanism that drives the tool in the X-axis direction. The servo motor 71x is a power source of the X-axis drive mechanism. The detector 72x detects the rotational position and the rotational speed of the servo motor 71x. The detector 72x outputs position information indicating the rotational position of the servo motor 71x and speed information indicating the rotational speed of the servo motor 71x to the servo control unit 73x.

[0016] The numerical control device 1 outputs a command for driving a tool in the X-axis direction to the servo control unit 73x. The servo control unit 73x performs feedback (FB) control of the servo motor 71x based on the command from the numerical control device 1, the position information, and the speed information from the detector 72x. The drive unit 7 operates the tool in the X-axis direction by the FB control of the servo motor 71x. Further, the drive unit 7 outputs information indicating the vibration movement amount in the X-axis direction to the numerical control device 1 by outputting the position information detected by the detector 72x during vibration cutting to the numerical control device 1. The vibration movement amount is the movement amount of the tool with respect to the workpiece in vibration cutting. Hereinafter, the information on the vibration movement amount output from the drive unit 7 to the numerical control device 1 is referred to as the FB vibration movement amount. That is, the drive unit 7 outputs the FB vibration movement amount in the X-axis direction to the numerical control device 1.

[0017] The drive unit 7 includes a servo motor 71z, a detector 72z, and a servo control unit 73z. The servo motor 71z constitutes a Z-axis drive mechanism. The Z-axis drive mechanism is a drive mechanism that drives a tool for cutting a workpiece or the workpiece in the Z-axis direction. In the first embodiment, the Z-axis drive mechanism is a drive mechanism that drives a tool in the Z-axis direction. The servo motor 71z is a power source of the Z-axis drive mechanism. The detector 72z detects the rotational position and the rotational speed of the servo motor 71z. The detector 72z outputs position information indicating the rotational position of the servo motor 71z and speed information indicating the rotational speed of the servo motor 71z to the servo control unit 73z.

[0018] The numerical control device 1 outputs a command for driving a tool in the Z-axis direction to the servo control unit 73z. The servo control unit 73z performs FB control of the servo motor 71z based on the command from the numerical control device 1, the position information, and the speed information from the detector 72z. The drive unit 7 operates the tool in the Z-axis direction by the FB control of the servo motor 71z. Further, the drive unit 7 outputs the FB vibration movement amount in the Z-axis direction to the numerical control device 1 by outputting the position information detected by the detector 72z during vibration cutting to the numerical control device 1.

[0019] The machine tool is provided with one or more tool carriers. The drive mechanism drives the tool carrier and the tool. The tool carrier and the tool are driven bodies driven by the drive mechanism. The tool is attached to the tool carrier. The drive unit 7 is provided with a set of a servo motor 71x, 71z, a detector 72x, 72z, and a servo control unit 73x, 73z for each tool carrier.

[0020] The drive unit 7 includes a spindle motor 71s, a detector 72s, and a spindle control unit 73s. The spindle motor 71s rotates the spindle. The spindle is an axis for rotating the workpiece. The detector 72s detects the rotational position and the rotational speed of the spindle motor 71s. The detector 72s outputs position information indicating the rotational position of the spindle motor 71s and speed information indicating the rotational speed of the spindle motor 71s to the spindle control unit 73s.

[0021] The numerical control device 1 outputs a command for rotating the spindle to the spindle control unit 73s. The spindle control unit 73s performs FB control of the spindle motor 71s based on the command from the numerical control device 1 and the position information and speed information from the detector 72s. The drive unit 7 rotates the workpiece by the FB control of the spindle motor 71s.

[0022] The machine tool may be one for processing one workpiece or one for processing two or more workpieces simultaneously. When the machine tool is one for processing two or more workpieces simultaneously, the drive unit 7 is provided with two or more sets of a spindle motor 71s, a detector 72s, and a spindle control unit 73s. When the machine tool is one for processing two or more workpieces simultaneously, the machine tool is provided with, for example, two or more tool carriers.

[0023] The input operation unit 2 is an input means for inputting information to the control arithmetic unit 4. The input operation unit 2 includes devices such as a keyboard, a touch panel, buttons, or a mouse, for example. The input operation unit 2 is operated by, for example, an operator of the machine tool or a maintenance worker of the machine tool. The input operation unit 2 receives information such as commands, machining program numbers, or parameters related to vibration cutting, and inputs the received information to the control arithmetic unit 4.

[0024] The output unit 3 is an output means for outputting the information processed by the control arithmetic unit 4. The output unit 3 includes display means such as a liquid crystal display device, for example. The output unit 3 displays the information processed by the control arithmetic unit 4 on the screen. Note that the output unit 3 is not limited to those having display means. The output unit 3 may have an audio device such as a speaker. Also, the output unit 3 may output information to a device external to the numerical control device 1. For example, it is also possible that the numerical control device 1 is connected to a network, and the output unit 3 transmits information via the network to a display device connected to the network or a computer connected to the network.

[0025] The control arithmetic unit 4 includes an input control unit 41, a data setting unit 42, a storage unit 43, an output control unit 44, an analysis processing unit 45, a control signal processing unit 46, a PLC (Programmable Logic Controller) circuit unit 47, an interpolation processing unit 48, a acceleration / deceleration processing unit 49, an axis data input / output unit 50, and a data management unit 51. In the configuration shown in FIG. 1, the PLC circuit unit 47 is arranged inside the control arithmetic unit 4, but the PLC circuit unit 47 may be arranged outside the control arithmetic unit 4.

[0026] The input control unit 41 receives the information input from the input operation unit 2 and outputs the received information to the data setting unit 42. The data setting unit 42 stores the information from the input control unit 41 in the storage unit 43. That is, the input information received by the input operation unit 2 is written into the storage unit 43 via the input control unit 41 and the data setting unit 42.

[0027] The storage unit 43 is a device for storing data, such as a non-volatile memory or a hard disk. The storage unit 43 includes a parameter storage area 431, a processing program storage area 432, a display data storage area 433, and a shared area 434.

[0028] Various parameters used in the processing of the control arithmetic unit 4 are stored in the parameter storage area 431. Specifically, the parameter storage area 431 stores control parameters for operating the numerical control device 1, servo parameters, tool data, and parameters related to vibration cutting.

[0029] The processing program storage area 432 stores a processing program, which is an NC program used for machining a workpiece. The processing program stored in the processing program storage area 432 includes one or more blocks. In the first embodiment, the processing program includes commands such as a movement command for moving a tool and a rotation command for rotating a spindle.

[0030] The display data storage area 433 stores screen display data, which is the data of the screen displayed by the output unit 3. The shared area 434 stores data temporarily used when the control arithmetic unit 4 executes each process. For example, the processing program number received by the input operation unit 2 is written into the shared area 434 of the storage unit 43 via the input control unit 41 and the data setting unit 42.

[0031] The output control unit 44 causes the output unit 3 to display the screen display data stored in the display data storage area 433 of the storage unit 43.

[0032] In the control arithmetic unit 4, an analysis processing unit 45, a control signal processing unit 46, and an interpolation processing unit 48 are connected to each other via the storage unit 43, and writing and reading of information are performed via the storage unit 43. Hereinafter, the description of the writing and reading of information between the analysis processing unit 45, the control signal processing unit 46, and the interpolation processing unit 48 via the storage unit 43 may be omitted.

[0033] The analysis processing unit 45 is connected to the storage unit 43. The analysis processing unit 45 refers to the processed program number written in the shared area 434. When the analysis processing unit 45 receives the processed program number selected from within the shared area 434 from the shared area 434, it reads out the processed program indicated by the selected processed program number from within the processed program storage area 432, and performs analysis processing on each block of the processed program, that is, each line of the processed program. The analysis processing unit 45 analyzes various codes such as the S code which is a command for the rotational speed of the main shaft motor 71s, the G code which is a command regarding axis movement such as the movement of the tool, and the M code which is a machine operation command. When the analysis processing unit 45 finishes the analysis processing of each line of the processed program, it writes the analysis results of the various codes to the shared area 434.

[0034] When the processed program contains an S code, the analysis processing unit 45 obtains the rotational speed of the main shaft by analyzing the S code contained in the processed program. The analysis processing unit 45 writes the obtained rotational speed to the shared area 434.

[0035] When the processed program contains a G code, the analysis processing unit 45 obtains the movement conditions which are the conditions for tool feed by analyzing the G code contained in the processed program. Such movement conditions include the speed at which the tool rest is moved in each of the X-axis direction and the Z-axis direction, and the position of the movement destination of the tool rest in each of the X-axis direction and the Z-axis direction, etc. The analysis processing unit 45 writes the obtained movement conditions to the shared area 434.

[0036] Further, when a G-code for vibration cutting is included in the machining program, the analysis processing unit 45 obtains vibration conditions, which are conditions for vibration in vibration cutting, by analyzing the G-code included in the machining program. The vibration conditions include a vibration frequency, which is the frequency at which the tool is vibrated in vibration cutting, and an amplitude at which the tool is vibrated in vibration cutting. The analysis processing unit 45 writes the obtained vibration conditions into the shared area 434.

[0037] The control signal processing unit 46 is connected to the PLC circuit unit 47 and receives signal information such as relays for operating the machine tool from the PLC circuit unit 47. The control signal processing unit 46 writes the received signal information into the shared area 434. The interpolation processing unit 48 refers to the signal information written in the shared area 434 during machining operation. Further, when an auxiliary command is output to the shared area 434 by the analysis processing unit 45, the control signal processing unit 46 reads the auxiliary command from the shared area 434 and sends the auxiliary command to the PLC circuit unit 47. The auxiliary command is a command other than a command for operating a drive axis, which is a numerically controlled axis. The auxiliary command is, for example, an M-code or a T-code.

[0038] The interpolation processing unit 48 is connected to the storage unit 43, the acceleration / deceleration processing unit 49, and the data management unit 51. When the movement conditions and the vibration conditions are written into the shared area 434, the interpolation processing unit 48 reads the movement conditions and the vibration conditions from the shared area 434. Based on the read movement conditions and the read vibration conditions, the interpolation processing unit 48 generates an X-axis commanded vibration movement amount, which is a command for the vibration movement amount in the X-axis direction, and a Z-axis commanded vibration movement amount, which is a command for the vibration movement amount in the Z-axis direction. Hereinafter, the X-axis commanded vibration movement amount and the Z-axis commanded vibration movement amount are collectively referred to as the commanded vibration movement amount. The interpolation processing unit 48 writes the generated commanded vibration movement amount into the shared area 434 and outputs the generated commanded vibration movement amount to the acceleration / deceleration processing unit 49.

[0039] The acceleration / deceleration processing unit 49 is connected to the interpolation processing unit 48 and the axis data input / output unit 50. The acceleration / deceleration processing unit 49 acquires the commanded vibration movement amount from the interpolation processing unit 48, and converts the commanded vibration movement amount into a movement command per unit time with acceleration / deceleration considered according to a previously specified acceleration / deceleration pattern. The acceleration / deceleration processing unit 49 outputs the movement command per unit time to the axis data input / output unit 50.

[0040] The axis data input / output unit 50 is connected to the acceleration / deceleration processing unit 49 and the drive unit 7. The axis data input / output unit 50 acquires the movement command per unit time from the acceleration / deceleration processing unit 49, and outputs the movement command per unit time to the drive unit 7. Also, the axis data input / output unit 50 acquires the FB vibration movement amount from the drive unit 7, and outputs the FB vibration movement amount to the acceleration / deceleration processing unit 49. The acceleration / deceleration processing unit 49 acquires the FB vibration movement amount from the axis data input / output unit 50, and outputs the FB vibration movement amount to the interpolation processing unit 48.

[0041] The interpolation processing unit 48 includes a measurement unit 481, an estimation unit 482, a vibration condition changing unit 483, a waveform generation unit 484, a vibration movement amount generation unit 485, a machining program changing unit 487, and a stroke operation execution unit 488.

[0042] The measurement unit 481 measures the execution time during which vibration cutting is performed. The estimation unit 482 estimates the remaining life of the mechanical components constituting the drive mechanism based on the execution time of vibration cutting and the operation coefficient based on the vibration conditions of vibration cutting. Alternatively, the estimation unit 482 estimates the remaining life of the mechanical components constituting the drive mechanism based on the number of vibrations of the minute vibrations accompanying vibration cutting. The numerical control device 1 estimates the deterioration status of the drive mechanism caused by vibration cutting by estimating the remaining life of the mechanical components in the estimation unit 482. Note that the minute vibrations accompanying vibration cutting are vibrations based on the vibration conditions for vibrating the tool in vibration cutting, for example, vibrations transmitted to the mechanical components constituting the drive mechanism while vibration cutting is being performed. The transmission of the minute vibrations accompanying vibration cutting to the mechanical components constituting the drive mechanism is a factor that has a great influence on the deterioration of the mechanical components constituting the drive mechanism.

[0043] The vibration condition changing unit 483, which is the first changing unit, changes the vibration conditions of vibration cutting. The vibration condition changing unit 483 proposes a change in the vibration conditions based on the remaining life estimated by the estimation unit 482, accepts an instruction to change the vibration conditions, and changes the vibration conditions according to the change instruction.

[0044] The waveform generation unit 484 acquires the vibration conditions from the analysis processing unit 45 and generates a vibration waveform, which is the basic waveform of vibration, based on the acquired vibration conditions. When the vibration conditions are changed by the vibration condition changing unit 483, the waveform generation unit 484 generates a vibration waveform based on the changed vibration conditions.

[0045] The vibration movement amount generation unit 485 obtains, for example, the vibration movement amount in the Z-axis direction based on the vibration waveform generated by the waveform generation unit 484 and the movement path of the tool. Specifically, the vibration movement amount generation unit 485 generates the vibration movement amount of the Z-axis by obtaining the vibration forward position and the vibration backward position for each vibration. The vibration forward position is a position advanced by a distance corresponding to the amplitude shown in the vibration waveform from the position on the movement path of the tool. The vibration backward position is a position retreated by a distance corresponding to the amplitude shown in the vibration waveform from the position on the movement path of the tool. The vibration movement amount generation unit 485 generates a commanded vibration movement amount by obtaining the vibration movement amount.

[0046] The commanded vibration movement amount generated by the vibration movement amount generation unit 485 is sent to the drive unit 7 via the acceleration / deceleration processing unit 49 and the axis data input / output unit 50. The drive unit 7 performs vibration cutting based on the commanded vibration movement amount sent from the vibration movement amount generation unit 485. The drive unit 7 performs vibration cutting, for example, by controlling the servo motor 71z based on the Z-axis commanded vibration movement amount.

[0047] The machining program changing unit 487, which is the second changing unit, changes the machining program. Details of the change in the machining program by the machining program changing unit 487 will be described later. The stroke operation execution unit 488 causes the drive mechanism to execute a stroke operation for rotating the bearing.

[0048] The data management unit 51 manages data for estimating the deterioration status of the drive mechanism. The data management unit 51 includes a ball screw data management unit 511 that manages data for estimating the deterioration status of the ball screw, and a bearing data management unit 512 that manages data for estimating the deterioration status of the bearing.

[0049] Next, a configuration example of the drive mechanism will be described. FIG. 2 is a diagram showing a configuration example of a drive mechanism provided in a machine tool controlled by the numerical control device 1 according to the first embodiment. FIG. 2 shows a configuration example of a drive mechanism 8z that is a Z-axis drive mechanism. The X-axis drive mechanism has the same configuration as the drive mechanism 8z.

[0050] The drive mechanism 8z includes a servo motor 71z, a ball screw 81z, a table 82z that is a tool post, and support mechanisms 83z1 and 83z2. The drive mechanism 8z is a mechanism that converts the rotational motion of the ball screw 81z, which is a mechanical component that rotates receiving the power of the servo motor 71z, into the linear motion of the table 82z. The tool is attached to the table 82z. In FIG. 2, the illustration of the tool is omitted. The drive mechanism 8z moves the tool in the Z-axis direction together with the table 82z.

[0051] The shaft 711z of the servo motor 71z and the ball screw 81z are connected via a coupling 84z. The power of the servo motor 71z is transmitted to the ball screw 81z via the coupling 84z. The ball screw 81z rotates receiving the power of the servo motor 71z. The center line that is the rotation center of the shaft 711z and the center line that is the rotation center of the ball screw 81z coincide with each other. The center line of the shaft 711z and the center line of the ball screw 81z are parallel to the Z-axis. The support mechanism 83z1 rotatably supports one end of the ball screw 81z. The support mechanism 83z2 rotatably supports the other end of the ball screw 81z.

[0052] Table 82z moves in a linear direction by the rotation of the ball screw 81z in the nut 85z. The drive mechanism 8z converts the rotational motion of the servo motor 71z into a linear motion by means of the ball screw 81z and the nut 85z. A plurality of balls 86z, which are rolling elements, are placed between the thread groove of the ball screw 81z and the thread groove of the nut 85z. By the rotation of the balls 86z between the thread groove of the ball screw 81z and the thread groove of the nut 85z, the ball screw 81z can rotate smoothly with respect to the nut 85z. The double arrow 87 shown in FIG. 2 indicates that the table 82z can move in the Z-axis direction. The tool moves in the Z-axis direction together with the table 82z.

[0053] The support mechanism 83z1 incorporates a bearing for smoothly rotating the ball screw 81z with respect to the support mechanism 83z1. The support mechanism 83z2 incorporates a bearing for smoothly rotating the ball screw 81z with respect to the support mechanism 83z2. Inside the servo motor 71z, two bearings for smoothly rotating the shaft 711z are incorporated.

[0054] FIG. 3 is a diagram showing a configuration example of the bearings provided in the drive mechanism shown in FIG. 2. FIG. 3 shows a configuration example of the bearing 712z, which is a bearing inside the servo motor 71z. The bearing 712z, which is a bearing inside the servo motor 71z, the bearing inside the support mechanism 83z1, and the bearing inside the support mechanism 83z2 have the same configuration as each other. FIG. 3 shows a cross section perpendicular to the center line of the shaft 711z.

[0055] The bearing 712z includes an outer ring 713z and an inner ring 714z. The inner ring 714z is fixed to the shaft 711z. The inner ring 714z rotates together with the shaft 711z. A plurality of balls 715z, which are rolling elements, are mounted between the outer ring 713z and the inner ring 714z. When the balls 715z rotate between the outer ring 713z and the inner ring 714z, the inner ring 714z and the shaft 711z can rotate smoothly with respect to the outer ring 713z. The double arrows 716 shown in FIG. 3 indicate that the shaft 711z can rotate. The double arrows 717 shown in FIG. 3 indicate that the balls 715z can rotate.

[0056] When the drive mechanism 8z is operated for a long time, the ball screw 81z may deteriorate due to the influence of the load received when operating the drive mechanism 8z. The deterioration of the ball screw 81z means, for example, that so-called flaking where the surface peels off occurs in the thread groove of the ball screw 81z. The flaking of the ball screw 81z can be a factor that deteriorates the positioning accuracy of the driven body by the drive mechanism 8z. Further, when the deterioration progresses, the life comes to an end and the ball screw 81z needs to be replaced. Also, when performing vibration cutting, if there is a bias in the position of the ball screw 81z that vibrates the driven body, so-called uneven wear where the ball screw 81z is partially worn may occur. When performing vibration cutting, the life of the ball screw 81z may be shortened due to uneven wear.

[0057] Hereinafter, taking vibration cutting that vibrates the driven body in the Z-axis direction as an example, the processing executed by the numerical control device 1 will be described. In the first embodiment, the numerical control device 1 estimates the remaining life of the ball screw 81z, which is a mechanical component, by the estimation unit 482. The numerical control device 1 estimates the deterioration of the ball screw 81z by estimating the remaining life of the ball screw 81z. The remaining life is defined as the remaining period until the end of the life.

[0058] Next, the details of the method for estimating the remaining life of the ball screw 81z in Embodiment 1 will be described. Here, an example will be described in which the estimation unit 482 estimates the remaining life of the ball screw 81z, which is a mechanical component, based on the operation time of vibration cutting and the operation coefficient based on the vibration conditions of vibration cutting.

[0059] The estimation unit 482 estimates the remaining life based on the vibration frequency and the operation time measured by the measurement unit 481. The estimation unit 482 refers to the relationship between the life of the ball screw 81z and the operation coefficient representing the operation mode of the drive mechanism 8z in vibration cutting, and based on the cumulative value, which is the result of accumulating the operation time, and the effective operation coefficient, which is the operation coefficient obtained from the vibration conditions, which are the conditions for vibration in vibration cutting, estimates the remaining life of the ball screw 81z. The operation coefficient in the present disclosure is a coefficient related to, for example, the frequency of minute vibrations and the magnitude of vibrations accompanying vibration cutting. In the following description, the cumulative value, which is the result of accumulating the operation time, is also referred to as the cumulative time. Here, the cumulative time for the ball screw 81z is defined as the cumulative time since the start of use of the currently used ball screw 81z.

[0060] FIG. 4 is a diagram for explaining the relationship between the operation coefficient and the life in the estimation unit 482 of the numerical control device 1 according to Embodiment 1. FIG. 4 shows an example of a graph representing the relationship between the operation coefficient of the ball screw 81z and the life of the ball screw 81z. In FIG. 4, the vertical axis represents the life, and the horizontal axis represents the operation coefficient. The unit of life is "hours (h)".

[0061] For a generally used ball screw, the relationship between the operation coefficient and the life is expressed by the following formula (1).

[0062]

Equation

[0063] In formula (1), L is the life (h), N m is the average rotational speed (min -1 ), C is the basic dynamic rated load (N), F mHere, \(F\) represents the axial average load (N), and \(\alpha\) represents the operation coefficient. For example, when a ball screw is used for a quiet operation without impact, the operation coefficient is set to a value within the range of 1.0 to 1.2. When a ball screw is used for normal operation, the operation coefficient is set to a value within the range of 1.2 to 1.5. When a ball screw is used for an operation with impact, the operation coefficient is set to a value within the range of 1.5 to 2.0. The operation coefficient of the ball screw used in a machine tool is set to a value within the range of 1.2 to 2.0, although it depends on the operating conditions of the machine tool. However, in the case of the ball screw 81z in the first embodiment, the operation coefficient will change according to the vibration conditions of vibration cutting.

[0064] The graph shown in FIG. 4 shows the case where \(C = 4400\) (N), \(F\) m = 270 (N), and \(N\) m = 2100 (min -1 ), and represents the result of obtaining the life of the ball screw 81z when the operation coefficient is changed in the range from 1.2 to 2.0. As shown in FIG. 4, the greater the operation coefficient, the shorter the life of the ball screw 81z. Note that the values of \(C\), \(F\) m , and \(N\) m vary depending on the configuration of the machine tool or the usage conditions of the machine tool. Therefore, the graph shown in FIG. 4 varies depending on the configuration of the machine tool or the usage conditions of the machine tool. The data representing the relationship between the operation coefficient of the ball screw 81z and the life of the ball screw 81z is registered in advance in the parameter storage area 431.

[0065] FIG. 5 is a diagram for explaining the relationship between the vibration conditions and the operation coefficient in the estimation unit 482 of the numerical control device 1 according to the first embodiment. FIG. 5 shows a table representing the relationship between the amplitude for vibrating the driven body in vibration cutting and the vibration frequency in vibration cutting, and the operation coefficient of the ball screw 81z. In FIG. 5, the unit of the amplitude is “μm” and the unit of the vibration frequency is “Hz”.

[0066] As shown in FIG. 5, the larger the amplitude, the larger the operation coefficient. Also, the larger the vibration frequency, the larger the operation coefficient. Each value of the operation coefficient shown in FIG. 5 is calculated in advance, for example, by actually operating a machine tool. Data representing the relationship between the amplitude and vibration frequency and the operation coefficient of the ball screw 81z is registered in advance in the parameter storage area 431.

[0067] The estimation unit 482 estimates the remaining life of the ball screw 81z with reference to the relationship between the amplitude and vibration frequency as shown in FIG. 5 and the operation coefficient of the ball screw 81z. Note that the relationship between the amplitude and vibration frequency shown in FIG. 5 and the operation coefficient of the ball screw 81z is taken as an example. That is, the value of the operation coefficient of the ball screw 81z with respect to the amplitude and vibration frequency is not limited to the values shown in FIG. 5.

[0068] The drive mechanism 8z can vibrate the driven body at each of a plurality of positions in the direction of the center line of the ball screw 81z. The interval between each position of the ball screw 81z is, for example, equal to the screw pitch of the ball screw 81z. That is, the interval between each position of the ball screw 81z is equal to the amount of movement of the driven body when the ball screw 81z is rotated 360 degrees. Here, it is assumed that the interval between each position of the ball screw 81z is, for example, 6 mm. The interval between each position of the ball screw 81z may be different from the screw pitch of the ball screw 81z and may be set arbitrarily. However, the interval between each position of the ball screw 81z is preferably finer.

[0069] The measurement unit 481 measures the execution time of vibration cutting at each position of the ball screw 81z. The interpolation processing unit 48 sends the measurement result by the measurement unit 481 to the data management unit 51. The ball screw data management unit 511 calculates the cumulative time of vibration cutting for each position of the ball screw 81z by aggregating the execution time of vibration cutting for each position of the ball screw 81z. In this way, the ball screw data management unit 511 calculates the cumulative time of vibration cutting due to the vibration of the driven body at each of a plurality of positions on the ball screw 81z.

[0070] In addition, the ball screw data management unit 511 calculates the effective operation coefficient for each position of the ball screw 81z. The ball screw data management unit 511 calculates the effective operation coefficient for each of the plurality of positions based on the accumulated time calculated for each of the plurality of positions and the vibration conditions when the driven body is vibrated at each of the plurality of positions.

[0071] Here, let the plurality of positions on the ball screw 81z be n positions from P x1 to P xn . Let n be an integer of 2 or more. For each position from P x1 to P xn , the value of the accumulated time and the effective operation coefficient for each position from P x1 to P xn are stored in the shared area 434.

[0072] For example, when vibration cutting due to vibration of the driven body at P x1 is executed, the value of the execution time measured for vibration cutting due to vibration of the driven body at P x1 is added to the value of the accumulated time stored for P x1 . Thereby, the ball screw data management unit 511 updates the accumulated time for P x1 . In the following description, vibration cutting due to vibration of the driven body at P x1 is referred to as the vibration cutting of P x1 . Each time the vibration cutting of P x1 is executed, the ball screw data management unit 511 updates the accumulated time for P x1 .

[0073] The ball screw data management unit 511 obtains the operation coefficient of the ball screw 81z when the vibration cutting of P x1 is executed, based on the amplitude and vibration frequency, which are the vibration conditions in the vibration cutting of P x1 . The ball screw data management unit 511 refers to the relationship between the amplitude and vibration frequency as shown in FIG. 5 and the operation coefficient of the ball screw 81z, and thus P x1Obtain the operation coefficient for vibration cutting. The ball screw data management unit 511 obtains the values of the amplitude and the vibration frequency, for example, by reading the vibration conditions written in the shared area 434 by the analysis processing unit 45 from the shared area 434 via the interpolation processing unit 48. When the vibration frequency and the amplitude are measured by the measurement unit 481, the ball screw data management unit 511 may obtain the values of the vibration frequency and the amplitude from the measurement unit 481.

[0074] The ball screw data management unit 511 calculates the weighted average of the operation coefficients obtained each time the vibration cutting of P x1 is performed, thereby calculating the effective operation coefficient for P x1 . For example, assuming that the vibration cutting of P x1 has been performed k times since the start of use of the currently used ball screw 81z, the ball screw data management unit 511 calculates the effective operation coefficient for P x1 using the following formula (2). Let k be an integer of 2 or more. P x1 Effective operation coefficient for P ={(Execution time of the first vibration cutting of P x1 ×Operation coefficient for the first vibration cutting of P x1 ) + ··· + (Execution time of the k-th vibration cutting of P x1 ×Operation coefficient for the k-th vibration cutting of P x1 )} / (Cumulative time for P x1 ) ··· (2)

[0075] The ball screw data management unit 511 updates the effective operation coefficient for P x1 each time the vibration cutting of P x1 is performed. The ball screw data management unit 511 calculates the cumulative time and the effective operation coefficient in the same manner as in the case of P x1 for each position other than P x1 among the plurality of positions of the ball screw 81z. In this way, the ball screw data management unit 511 calculates the cumulative time for each of the plurality of positions of the ball screw 81z and the effective operation coefficient for each of the plurality of positions of the ball screw 81z.

[0076] In the above description, the effective operating coefficient was calculated by referring to the relationship between the amplitude and vibration frequency and the operating coefficient of the ball screw 81z. However, the method for calculating the effective operating coefficient is not limited to this.

[0077] FIG. 6 is a diagram showing an example of the calculation results of the cumulative time and the effective operating coefficient by the numerical control device 1 according to the first embodiment. FIG. 6 shows a bar graph representing the cumulative time for each of a plurality of positions in the ball screw 81z. The numerical values shown above each bar graph represent the effective operating coefficient for each of the plurality of positions. The ball screw position is represented by the distance from the reference position of the ball screw 81z for each of the plurality of positions in the ball screw 81z. In FIG. 6, the vertical axis represents the cumulative time of vibration cutting, and the horizontal axis represents the ball screw position. In FIG. 6, the unit of the cumulative time is "hour (h)", and the unit of the ball screw position is "mm".

[0078] In FIG. 6, the vibration cutting at the ball screw position of 120 mm is case (A), the vibration cutting at the ball screw position of 126 mm is case (B), and the vibration cutting at the ball screw position of 132 mm is case (C). In the example shown in FIG. 6, in case (A), the cumulative time is 4300 hours and the effective operating coefficient is 1.6. In case (B), the cumulative time is 4800 hours and the effective operating coefficient is 1.56. In case (C), the cumulative time is 4500 hours and the effective operating coefficient is 1.65. In FIG. 6, the notations "(A)", "(B)", and "(C)" represent case (A), case (B), and case (C), respectively.

[0079] The estimation unit 482 estimates the life of each of the plurality of positions in the ball screw 81z based on the effective operating coefficient for each of the plurality of positions in the ball screw 81z. The estimation unit 482 estimates the life of each of the plurality of positions in the ball screw 81z by referring to the relationship between the operating coefficient of the ball screw 81z and the life of the ball screw 81z as shown in FIG. 4.

[0080] For each position of the ball screw 81z, the estimation unit 482 estimates the remaining life at each of the plurality of positions of the ball screw 81z by subtracting the cumulative time calculated by the ball screw data management unit 511 from the time that is the estimation result of the life. In this way, the estimation unit 482 refers to the relationship between the operation coefficient of the ball screw 81z and the life of the ball screw 81z, and estimates the remaining life of the ball screw 81z based on the cumulative time and the effective operation coefficient. The estimation unit 482 estimates the remaining life based on the effective operation coefficient obtained based on the vibration frequency and amplitude and the cumulative time that is the result of accumulating the execution time.

[0081] The estimation unit 482 compares the remaining life estimated for each of the plurality of positions with a preset first threshold value. The first threshold value is a threshold value for determining whether the ball screw 81z needs to be replaced. When the remaining life that is less than or equal to the first threshold value is included in the remaining life estimated for each of the plurality of positions, the interpolation processing unit 48 instructs the output control unit 44 via the storage unit 43 to output a warning that the ball screw 81z needs to be replaced. When receiving the instruction from the interpolation processing unit 48, the output control unit 44 reads out the screen display data for displaying a warning that the ball screw 81z needs to be replaced from the display data storage area 433, and outputs the read screen display data to the output unit 3. The output unit 3 displays the warning indicated in the screen display data. In this way, when the remaining life that is less than or equal to the first threshold value is included in the remaining life estimated for, for example, a predetermined one of the plurality of positions, the numerical control device 1 outputs a warning indicating that the ball screw 81z needs to be replaced. Thereby, the numerical control device 1 can notify the operator or the maintenance staff of the machine tool that the time has come to replace the ball screw 81z.

[0082] The estimation unit 482 compares the remaining life estimated for each of a plurality of positions with a preset second threshold value. The second threshold value is a threshold value for determining whether to propose a change in the vibration conditions in vibration cutting. When the remaining life estimated for each of the plurality of positions includes a remaining life equal to or less than the second threshold value, the estimation unit 482 instructs the vibration condition change unit 483 to calculate an extended life condition. The extended life condition is a vibration condition in which the life of the ball screw 81z is expected to be extended compared to the case where future vibration cutting is performed under the current vibration conditions.

[0083] The vibration condition change unit 483 calculates an extended life condition according to an instruction from the estimation unit 482. Further, the vibration condition change unit 483 instructs the output control unit 44 via the storage unit 43 to propose a change in the vibration condition to the calculated extended life condition. When receiving an instruction from the vibration condition change unit 483, the output control unit 44 reads out screen display data for displaying a message prompting a change in the vibration condition from the display data storage area 433, and outputs the read screen display data to the output unit 3. The output unit 3 displays a message prompting a change in the vibration condition according to the screen display data. In this way, the vibration condition change unit 483 proposes a change in the vibration condition of vibration cutting based on the remaining life estimated by the estimation unit 482.

[0084] The numerical control device 1 receives an instruction to change to the proposed vibration condition on the screen displayed on the output unit 3. The operator inputs an instruction to change the vibration condition to the numerical control device 1 by operating the input operation unit 2. The input control unit 41 sends an instruction to change the vibration condition to the interpolation processing unit 48 via the data setting unit 42 and the storage unit 43. The vibration condition change unit 483 changes the vibration condition according to the instruction to change the vibration condition. The numerical control device 1 causes the machine tool to perform vibration cutting under the changed vibration conditions. The numerical control device 1 can take measures to extend the life of the ball screw 81z by changing the vibration condition to the calculated extended life condition.

[0085] Next, the procedure of the process executed by the numerical control device 1 according to the first embodiment will be described. FIG. 7 is a flowchart showing an example of the procedure of the process executed by the numerical control device 1 according to the first embodiment. Here, an example of the process executed by the numerical control device 1 when vibration cutting by a machine tool is executed will be described. In the following description, it is assumed that the vibration frequency before the vibration conditions are changed is, for example, 90.9 Hz. Further, the numerical control device 1 appropriately calculates the effective operation coefficient for each of a plurality of positions in the ball screw 81z from the vibration conditions of the executed vibration cutting, that is, the vibration frequency, the vibration amplitude, and the like.

[0086] When vibration cutting by the machine tool is started, in step S1, the measurement unit 481 measures the execution time of the vibration cutting. The machine tool executes vibration cutting when the vibration cutting mode, which is one of the operation modes of the machine tool, is on. For example, when the measurement unit 481 receives a cutting start command when the vibration cutting mode is on, the measurement unit 481 starts measuring the execution time of the vibration cutting. When the vibration cutting by the machine tool ends, the measurement unit 481 ends the measurement of the execution time of the vibration cutting. For example, when the measurement unit 481 receives a cutting end command when the vibration cutting mode is on, the measurement unit 481 ends the measurement of the execution time of the vibration cutting.

[0087] The measurement unit 481 measures the execution time of the vibration cutting at each of a plurality of positions in the ball screw 81z. The value of the execution time measured by the measurement unit 481 is sent to the data management unit 51. The ball screw data management unit 511 reads out the value of the accumulated time stored for each of the plurality of positions from the shared area 434, and adds the value of the execution time measured in step S1 to the read value of the accumulated time. The ball screw data management unit 511 stores the value of the accumulated time added with the value of the execution time in the shared area 434. As a result, the value of the accumulated time stored in the shared area 434 is updated.

[0088] In step S2, the estimation unit 482 estimates the remaining life at each of a plurality of positions of the ball screw 81z. The estimation unit 482 reads out the effective operation coefficient for each of the plurality of positions in the ball screw 81z from the shared area 434, and estimates the life at each of the plurality of positions of the ball screw 81z based on the effective operation coefficient. The estimation unit 482 reads out the value of the cumulative time for each of the plurality of positions in the ball screw 81z from the shared area 434, and estimates the remaining life at each of the plurality of positions of the ball screw 81z by subtracting the cumulative time from the estimated life.

[0089] The estimation unit 482 stores the estimation result of the remaining life at each of the plurality of positions of the ball screw 81z in the shared area 434. The output control unit 44 reads out the estimation result of the remaining life at each of the plurality of positions of the ball screw 81z from the shared area 434. Further, the output control unit 44 reads out the screen display data for displaying the remaining life at each of the plurality of positions of the ball screw 81z from the display data storage area 433. The output control unit 44 outputs the screen display data in which the estimation result of the remaining life is reflected to the output unit 3. The output unit 3 displays the remaining life according to the screen display data. A specific example of the display of the remaining life will be described later.

[0090] In step S3, the estimation unit 482 determines whether or not the remaining life estimated in step S2 is equal to or less than a first threshold value. The first threshold value is, for example, 0 hours. When the first threshold value is 0 hours, the remaining life being equal to or less than the first threshold value means that the estimated life has been exceeded. Note that the first threshold value is not limited to 0 hours and may be a value greater than 0 hours.

[0091] When the remaining life for at least one of a plurality of positions is equal to or less than a first threshold value (step S3, Yes), in step S4, the output unit 3 outputs a warning indicating that it is necessary to replace the ball screw 81z. For example, the output unit 3 displays a warning screen including a message warning that it is necessary to replace the ball screw 81z. A specific example of the warning screen will be described later. By finishing step S4, the numerical control device 1 finishes the processing according to the procedure shown in FIG. 7.

[0092] When the remaining life is not equal to or less than the first threshold value for any of the plurality of positions (step S3, No), in step S5, the estimation unit 482 determines whether the remaining life estimated in step S2 is equal to or less than a second threshold value. The second threshold value is, for example, 3000 hours. The second threshold value is not limited to 3000 hours and may be a value greater than 3000 hours or a value less than 3000 hours.

[0093] When the remaining life for at least one of the plurality of positions is equal to or less than the second threshold value (step S5, Yes), the estimation unit 482 instructs the vibration condition changing unit 483 to calculate an extension condition. In step S6, the vibration condition changing unit 483 calculates the extension condition. Details of the method for calculating the extension condition will be described later. Further, the vibration condition changing unit 483 proposes a change of the vibration condition to the calculated extension condition.

[0094] Here, assume that the numerical control device 1 receives an instruction to change to the proposed vibration condition. By the numerical control device 1 receiving the instruction to change to the proposed vibration condition, in step S7, the vibration condition changing unit 483 changes the vibration condition according to the instruction to change the vibration condition. By finishing step S7, the numerical control device 1 finishes the processing according to the procedure shown in FIG. 7.

[0095] If the remaining life is not less than the second threshold value for any of the plurality of positions (step S5, No), the numerical control device 1 ends the process according to the procedure shown in FIG. 7. If the proposed vibration condition is not changed, the numerical control device 1 ends the process according to the procedure shown in FIG. 7 without changing the vibration condition. If the numerical control device 1 neither issues a warning nor changes the vibration condition, after ending the process according to the procedure shown in FIG. 7, the numerical control device 1 executes the process according to the procedure shown in FIG. 7 again.

[0096] FIG. 8 is a diagram showing an example of display of the remaining life estimated by the numerical control device 1 according to the first embodiment. FIG. 8 shows a state in which a bar graph representing the remaining life is displayed on the screen displayed by the output unit 3. In the example shown in FIG. 8, together with the bar graph representing the remaining life, a curve graph representing the relationship between the operation coefficient of the ball screw 81z and the life of the ball screw 81z is displayed. Such a curve graph is the same as the graph shown in FIG. 4. FIG. 8 shows three bar graphs representing the remaining life for the above cases (A), (B), and (C) as examples of the display of the remaining life. In FIG. 8, the notations “(A)”, “(B)”, and “(C)” represent case (A), case (B), and case (C), respectively, and are attached for the purpose of explanation. The notations “(A)”, “(B)”, and “(C)” in FIG. 8 are not included in the screen display.

[0097] The bar graph for Case (A) is shown at a position centered on "1.6" in the horizontal axis direction. "1.6" is the effective operation coefficient for Case (A). "120" shown in the bar graph for Case (A) represents that the ball screw position of Case (A) is 120 mm. The toned part of the bar graph for Case (A) represents the cumulative time of vibration cutting at the ball screw position of 120 mm up to now. The dashed line part of the bar graph for Case (A) represents the time during which vibration cutting is possible at the ball screw position of 120 mm from now on, that is, the remaining life of the ball screw position of 120 mm. "3700" shown in the bar graph for Case (A) represents that the remaining life is 3700 hours.

[0098] The bar graph for Case (B) is shown at a position centered on "1.56" in the horizontal axis direction. "1.56" is the effective operation coefficient for Case (B). "126" shown in the bar graph for Case (B) represents that the ball screw position of Case (B) is 126 mm. The toned part of the bar graph for Case (B) represents the cumulative time of vibration cutting at the ball screw position of 126 mm up to now. The dashed line part of the bar graph for Case (B) represents the time during which vibration cutting is possible at the ball screw position of 126 mm from now on, that is, the remaining life of the ball screw position of 126 mm. "4300" shown in the bar graph for Case (B) represents that the remaining life is 4300 hours.

[0099] The bar graph for case (C) is shown at a position centered on "1.65" in the horizontal axis direction. "1.65" is the effective operating coefficient for case (C). "132" shown in the bar graph for case (C) represents that the ball screw position of case (C) is 132 mm. The shaded part of the bar graph for case (C) represents the cumulative time of vibration cutting at the ball screw position of 132 mm up to now. The dashed line part of the bar graph for case (C) represents the time during which vibration cutting is possible at the ball screw position of 132 mm from now on, that is, the remaining life of the ball screw position of 132 mm. "3000" shown in the bar graph for case (C) represents that the remaining life is 3000 hours.

[0100] In the example shown in FIG. 8, among case (A), case (B), and case (C), only case (C) satisfies the requirement that the remaining life is 3000 hours or less which is the second threshold value.

[0101] In the example shown in FIG. 8, a mark 31 indicating that the remaining life is equal to or less than the second threshold value is displayed on the bar graph for case (C). The mark 31 shown in FIG. 8 is a star-shaped mark. The shape of the mark 31 is not limited to a star shape and is arbitrary. The output unit 3 may also indicate that the remaining life is equal to or less than the second threshold value by means other than the display of the mark 31. The display that the remaining life is equal to or less than the second threshold value may be such that the operator or maintenance staff can recognize that the remaining life is equal to or less than the second threshold value.

[0102] Note that in the example shown in FIG. 8, the remaining life for each position of the ball screw 81z is shown by a bar graph and a numerical value indicating the time of the remaining life, but the display mode of the remaining life is not limited to that shown in FIG. 8. The display of the remaining life may be such that the operator or maintenance staff can recognize the remaining life for each position of the ball screw 81z. For example, the output unit 3 may also display the remaining life only by a numerical value indicating the time of the remaining life.

[0103] The vibration condition changing unit 483 calculates an extended life condition for the case (C). The method for calculating the extended life condition will be described later. In the example shown in FIG. 8, the output unit 3 displays a message 32 including a statement prompting a change in the vibration condition on the screen. In the example shown in FIG. 8, it is assumed that by changing the vibration condition to the calculated extended life condition, the remaining life is estimated to extend from 3000 hours to 3270 hours. The message 32 includes a statement about being able to extend the life of the ball screw 81z from 3000 hours to 3270 hours. Further, the message 32 includes a statement prompting the prior arrangement of the ball screw 81z.

[0104] By the message 32 being displayed on the screen, the operator or maintenance staff can recognize the necessity of changing the vibration condition of the vibration cutting. The operator or maintenance staff can judge whether to change the vibration condition while considering the necessity of changing the vibration condition.

[0105] Furthermore, in the example shown in FIG. 8, the output unit 3 displays a button 33 for selecting a change in the vibration condition and a button 34 for selecting not to change the vibration condition on the screen. When the button 33 is pressed by the operator or maintenance staff, information indicating that a change in the vibration condition has been selected, that is, a vibration condition change instruction, is sent to the interpolation processing unit 48 via the input control unit 41, the data setting unit 42, and the storage unit 43. When a vibration condition change instruction is input, the vibration condition changing unit 483 changes the vibration condition from the current vibration condition to the extended life condition. On the other hand, when the button 34 is pressed by the operator or maintenance staff, information indicating that not changing the vibration condition has been selected is sent to the interpolation processing unit 48 via the input control unit 41, the data setting unit 42, and the storage unit 43. When the said information is input to the vibration condition changing unit 483, the current vibration condition is maintained without being changed.

[0106] Message 32 and buttons 33 and 34 are displayed when the remaining life estimated for each of a plurality of positions includes a remaining life equal to or less than a second threshold value. Note that the layout of the screen on which the remaining life is displayed is not limited to that shown in FIG. 8. For each of the display of the remaining life, message 32, and buttons 33 and 34, the position or size on the screen is arbitrary.

[0107] FIG. 9 is a diagram showing an example of warning display in the numerical control device 1 according to the first embodiment. FIG. 9 shows a state in which a message 36 which is a warning is displayed on the warning screen displayed by the output unit 3. The message 36 includes a statement prompting replacement of the ball screw 81z. The warning screen is displayed when the remaining life estimated for each of a plurality of positions includes a remaining life equal to or less than a first threshold value.

[0108] In the example shown in FIG. 9, a curve graph showing the relationship between the operation coefficient of the ball screw 81z and the life of the ball screw 81z is displayed on the warning screen. Such a curve graph is the same as the graph shown in FIG. 4. Further, in the example shown in FIG. 9, a bar graph representing the cumulative time for each of a plurality of positions in the ball screw 81z is displayed together with the curve graph. FIG. 9 shows three bar graphs representing the cumulative time for three cases as examples of the display of the cumulative time. Here, the three cases are referred to as case (A'), case (B'), and case (C'). Note that in FIG. 9, the notations "(A')", "(B')", and "(C')" represent case (A'), case (B'), and case (C'), respectively, and are added for the purpose of explanation. The notations "(A')", "(B')", and "(C')" in FIG. 9 are not included in the screen display.

[0109] Case (A’) is vibration cutting at a ball screw position of 120 mm, with an effective operation coefficient of 1.6. Case (A’) shall have the same ball screw position and effective operation coefficient as the above case (A), but the cumulative time shall be different from that of the above case (A). Case (B’) is vibration cutting at a ball screw position of 126 mm, with an effective operation coefficient of 1.56. Case (B’) shall have the same ball screw position and effective operation coefficient as the above case (B), but the cumulative time shall be different from that of the above case (B). Case (C’) is vibration cutting at a ball screw position of 132 mm, with an effective operation coefficient of 1.65. Case (C’) shall have the same ball screw position and effective operation coefficient as the above case (C), but the cumulative time shall be different from that of the above case (C). Here, cases with effective operation coefficients of 1.56, 1.6, and 1.65 have been described, but even when the value of the execution operation coefficient is different from this case, the same determination as this case is possible.

[0110] In FIG. 9, the difference between the life shown by the curve graph, that is, the estimated life, and the cumulative time shown by the bar graph corresponds to the remaining life. In the example shown in FIG. 9, it is assumed that among case (A’), case (B’), and case (C’), only case (A’) satisfies the requirement that the remaining life is 0 hours or less, which is the first threshold value.

[0111] In the example shown in FIG. 9, a mark 35 indicating that the remaining life is less than or equal to the first threshold value is displayed on the bar graph for case (A’). The mark 35 shown in FIG. 9 is a star-shaped mark. The shape of the mark 35 is not limited to a star and shall be arbitrary. The output unit 3 may also indicate that the remaining life is less than or equal to the first threshold value by means other than the display of the mark 35. The display that the remaining life is less than or equal to the first threshold value only needs to be recognizable by the operator or maintenance personnel that the remaining life is less than or equal to the first threshold value.

[0112] When message 36 is displayed on the warning screen, the operator or maintenance staff can recognize that it is time to replace the ball screw 81z. Also, on the warning screen, a graph indicating the remaining life is displayed together with message 36, allowing the operator or maintenance staff to intuitively grasp the deterioration status of the ball screw 81z.

[0113] In the example shown in FIG. 9, a graph indicating the remaining life is displayed together with message 36 on the warning screen. However, the output unit 3 may display only message 36 on the warning screen.

[0114] Next, a method for calculating the life extension condition will be described. Here, an example of calculating the life extension condition will be described by selecting a pattern that can be a life extension condition from among a set of vibration conditions set in advance.

[0115] FIG. 10 is a diagram showing an example of vibration conditions set in advance in the numerical control device 1 according to the first embodiment. FIG. 10 shows examples of vibration conditions that enable vibration cutting, that is, conditions that enable chip breaking. Both the vibration conditions before change and the vibration conditions after change are vibration conditions selected from among a plurality of vibration conditions set in advance as vibration conditions that enable vibration cutting.

[0116] In the example shown in FIG. 10, the vibration conditions set in advance are the number of vibrations per revolution of the spindle, the spindle rotation speed, and the vibration frequency. The set of vibration conditions set in advance is a set of the number of vibrations per revolution of the spindle, the spindle rotation speed, and the vibration frequency. In FIG. 10, the unit of the number of vibrations per revolution of the spindle is "times", the unit of the spindle rotation speed is "r / min", and the unit of the vibration frequency is "Hz". Note that the vibration frequency is uniquely determined from the number of vibrations per revolution of the spindle and the spindle rotation speed.

[0117] The vibration condition changing unit 483 selects one of a plurality of sets of preset vibration conditions as the changed vibration condition, that is, the life extension condition. In the changed vibration condition, at least one of the number of vibrations per revolution of the main shaft, the main shaft rotation speed, and the vibration frequency is changed from the vibration condition before the change.

[0118] From the relationship shown in FIG. 4, by reducing the operation coefficient, the life of the ball screw 81z is extended. Also, from the relationship shown in FIG. 5, by reducing the vibration frequency, the operation coefficient can be reduced. For this reason, the vibration condition changing unit 483 calculates, as the life extension condition, a vibration condition in which at least the vibration frequency is lower than before the change of the vibration condition. Since the vibration frequency is uniquely determined from the number of vibrations per revolution of the main shaft and the main shaft rotation speed, the vibration frequency is changed by changing at least one of the number of vibrations per revolution of the main shaft and the main shaft rotation speed.

[0119] In the example shown in FIG. 10, the vibration condition before the change is the number of vibrations per revolution of the main shaft "1.5 times", the main shaft rotation speed "3636 r / min", and the vibration frequency "90.9 Hz". The vibration condition after the change is the number of vibrations per revolution of the main shaft "1.5 times", the main shaft rotation speed "3333 r / min", and the vibration frequency "83.3 Hz". In this example, the main shaft rotation speed is changed from "3636 r / min" to "3333 r / min", and the vibration frequency is changed from "90.9 Hz" to "83.3 Hz". Since the vibration frequency after the change is lower than the vibration frequency before the change, the life of the ball screw 81z can be extended under the vibration condition after the change.

[0120] Note that the greater the change in the vibration condition, for example, when both the number of vibrations per revolution of the main shaft and the main shaft rotation speed change significantly, the processing condition changes significantly due to the change in the vibration condition. For this reason, in the example shown here, the number of vibrations per revolution of the main shaft is not changed, and only the main shaft rotation speed is changed.

[0121] Also, when it is desired to further extend the lifespan compared to the above example, it is also conceivable to keep the spindle rotation speed substantially the same as before the change and reduce the number of vibrations per spindle rotation. For example, it is conceivable to change the number of vibrations per spindle rotation from "1.5 times" to "0.5 times" and change the spindle rotation speed from "3636 r / min" to "3529 r / min". In this case, since the number of vibrations per spindle rotation decreases, the chip will become longer than in the above example. For example, when the chip becomes longer due to a change in the vibration conditions, the numerical control device 1 may output a warning display for the operator or maintenance personnel using the output unit 3.

[0122] The method for calculating the lifespan extension conditions is not limited to the above method. For example, the vibration condition change unit 483 may change at least one of the number of vibrations per spindle rotation and the spindle rotation speed by inputting a desired lifespan time into the numerical control device 1 and performing a reverse calculation from the input lifespan time.

[0123] Next, the change in the vibration waveform due to the change in the vibration conditions will be described. FIG. 11 is a diagram for explaining the change in the vibration waveform due to the change in the vibration conditions in Embodiment 1. The upper part of FIG. 11 shows an example of the vibration waveform before the change in the vibration conditions. The lower part of FIG. 11 shows an example of the vibration waveform after the change in the vibration conditions. In each of the upper and lower parts of FIG. 11, the vertical axis represents the axis position and the horizontal axis represents time. The axis position is the position of the driven body in the vibration direction.

[0124] In FIG. 11, the vibration frequency before the change is 90.9 Hz and the vibration frequency after the change is 83.3 Hz. CT1 represents the vibration period before the change in the vibration conditions. CT2 represents the vibration period after the change in the vibration conditions. In each of the upper and lower parts of FIG. 11, C is the vibration waveform of the nth cycle n and C is the vibration waveform of the (n + 1)th cycle n+1It is shown as follows. Let n be an arbitrary integer. In each of the upper and lower parts of FIG. 11, S represents an idle area. The idle area is an area in the movement path of the tool where it does not contact the workpiece and no cutting is performed, that is, the area where the tool makes an idle stroke. In the idle area, the chips generated so far are segmented. In each of the upper and lower parts of FIG. 11, the idle area is an area below the vibration waveform of the n-th cycle and above the vibration waveform of the (n + 1)-th cycle.

[0125] By changing the vibration conditions in the vibration condition changing unit 483, as shown in FIG. 11, it is possible to lower the vibration frequency while maintaining the state where an idle area occurs even after the change of the vibration conditions. Thereby, the numerical control device 1 can calculate the vibration conditions that enable the vibration cutting, that is, the conditions that enable cutting while segmenting the chips, and at the same time enable the extension of the life of the mechanical parts. Note that the vibration waveform shown in FIG. 11 may be based on either the vibration waveform based on the command value or the vibration waveform based on the FB value as long as the vibration waveform based on the measured value satisfies the conditions for enabling vibration cutting.

[0126] By lowering the vibration frequency from 90.9 Hz to 83.3 Hz, it can be expected that the remaining life after the change of the vibration conditions will be extended by approximately 1.09 times (= 90.9 Hz / 83.3 Hz) compared to the case where the vibration conditions before the change are maintained. Therefore, in the case (C) shown in FIG. 8, when performing the same processing after the change of the vibration conditions as before the change of the vibration conditions, the remaining life can be extended from 3000 hours to 3270 hours (= 3000 hours × 1.09), an extension of 270 hours. The vibration condition changing unit 483 causes the display unit to display a message 32 including a statement that the life of the ball screw 81z can be extended from 3000 hours to 3270 hours by estimating that the remaining life can be extended from 3000 hours to 3270 hours.

[0127] The numerical control device 1 can take measures to extend the life of the ball screw 81z while enabling vibration cutting by changing the vibration conditions to the life extension conditions calculated based on the estimation result of the remaining life.

[0128] In the above description, the estimation unit 482 estimates the remaining life of the ball screw 81z based on the cumulative time, which is the result of accumulating the execution time of the vibration cutting, and the effective operation coefficient. The estimation unit 482 may estimate the remaining life of the ball screw 81z based on the cumulative number of vibrations, which is the result of accumulating the number of vibrations of the driven body in the vibration cutting, and the effective operation coefficient. That is, the estimation unit 482 estimates the remaining life of the ball screw 81z based on the cumulative value, which is the result of accumulating the execution time or the number of vibrations, and the effective operation coefficient. Here, the cumulative number of vibrations for the ball screw 81z is defined as the cumulative number of vibrations since the start of use of the currently used ball screw 81z.

[0129] The estimation unit 482 obtains the value of the number of vibrations, for example, by multiplying the vibration frequency by the execution time of the vibration cutting. Alternatively, the estimation unit 482 may obtain the value of the number of vibrations by counting the number of vibrations. The estimation unit 482 may count the number of vibrations based on, for example, the vibration waveform, which is the basic waveform of the vibration generated by the waveform generation unit 484.

[0130] By estimating the remaining life of the ball screw 81z based on the cumulative value, which is the result of accumulating the execution time or the number of vibrations, and the effective operation coefficient by the numerical control device 1, the operator or the maintenance staff can grasp the deterioration status of the ball screw 81z caused by the vibration cutting.

[0131] In the above description, the numerical control device 1 calculates the life extension condition by the vibration condition change unit 483 and attempts to extend the life of the ball screw 81z by changing the vibration condition. The numerical control device 1 may also attempt to extend the life of the ball screw 81z by changing the position where the driven body is vibrated in the vibration cutting. The machining program change unit 487 changes the position where the driven body is vibrated in the vibration cutting based on the cumulative value aggregated for each of a plurality of positions in the ball screw 81z.

[0132] Here, a specific example of changing the position where the driven body is vibrated will be described. In step S5 shown in FIG. 7, when the remaining life of at least one of the plurality of positions of the ball screw 81z is equal to or less than the second threshold value, the machining program change unit 487 proposes a change to the machining program based on the cumulative time aggregated for each of the plurality of positions, accepts an instruction to change the machining program, and changes the machining program according to the change instruction. The machining program change unit 487 changes the position where the driven body is vibrated in vibration cutting by changing the machining program.

[0133] Taking a specific example, when the remaining life of at least one of the plurality of positions of the ball screw 81z is equal to or less than the second threshold value, the estimation unit 482 instructs the machining program change unit 487 to select a machining program. The machining program change unit 487 refers to the description of vibration cutting in the machining program stored in the machining program storage area 432, and analyzes the position where the driven body is vibrated. Based on the analysis result, the machining program change unit 487 selects, for example, a machining program that includes vibration cutting at a position where the remaining life of the plurality of positions of the ball screw 81z is greater than the second threshold value. The machining program change unit 487 selects, for example, a machining program to be proposed as the changed machining program from among the machining programs stored in the machining program storage area 432.

[0134] The machining program change unit 487 selects a position among a plurality of positions of the ball screw 81z where the cumulative time does not exceed a preset upper limit time, and selects a machining program for vibrating the driven body at the selected position. For example, assume that the upper limit time is set to 4000 hours and the cumulative time for each ball screw position is calculated as shown in FIG. 6. In this case, a machining program is selected in which the position for vibrating the driven body is a position where the remaining life estimated to be greater than the second threshold value. For example, since the cumulative time exceeds 4000 hours in the range of the ball screw positions from 120 mm to 132 mm, the machining program change unit 487 selects a ball screw position outside the range from 120 mm to 132 mm. The machining program change unit 487 selects a machining program for vibrating the driven body at the selected ball screw position.

[0135] The machining program change unit 487 instructs the output control unit 44 via the storage unit 43 to propose a change to the selected machining program. When receiving an instruction from the machining program change unit 487, the output control unit 44 reads out screen display data for displaying a message prompting the change of the machining program from the display data storage area 433, and outputs the read screen display data to the output unit 3. The output unit 3 displays a message prompting the change of the machining program according to the screen display data. In this way, the machining program change unit 487 proposes a change to the machining program based on the cumulative time aggregated for each of the plurality of positions.

[0136] The numerical control device 1 accepts an instruction to change the proposed machining program on the screen displayed on the output unit 3. The operator inputs an instruction to change the machining program to the numerical control device 1 by operating the input operation unit 2. The input control unit 41 sends an instruction to change the machining program to the interpolation processing unit 48 via the data setting unit 42 and the storage unit 43. The machining program change unit 487 changes the machining program according to the instruction to change the machining program. The numerical control device 1 causes the machine tool to perform vibration cutting according to the changed machining program. The numerical control device 1 can take measures to extend the life of the ball screw 81z by changing the position where the driven body vibrates and performing vibration cutting.

[0137] The numerical control device 1 can effectively reduce the unilateral wear of the ball screw 81z by changing the position where the driven body vibrates. Thereby, the numerical control device 1 can extend the life of the ball screw 81z.

[0138] According to the first embodiment, the estimation unit 482 includes an estimation unit 482 that estimates the remaining life of the mechanical components constituting the drive mechanism based on the execution time during which vibration cutting is performed or the number of vibrations of the driven body in vibration cutting. The operator or maintenance personnel can grasp in advance the replacement timing of the mechanical components by checking the estimation result of the remaining life by the estimation unit 482. For this reason, the operator or maintenance personnel can take appropriate measures to avoid problems before a problem occurs in the drive mechanism. The operator or maintenance personnel can take appropriate measures to avoid failure before the drive mechanism fails.

[0139] In Embodiment 1, it is possible to grasp the deterioration status of the ball screw 81z, which is a mechanical component, due to vibration cutting. An operator or maintenance staff can take appropriate measures corresponding to the deterioration status of the ball screw 81z by being able to grasp the deterioration status of the ball screw 81z. Also, by being able to grasp the deterioration status for each of a plurality of positions in the ball screw 81z, measures can be taken to reduce the unilateral wear of the ball screw 81z caused by vibration cutting. By being able to reduce the unilateral wear of the ball screw 81z, it is possible to avoid shortening the life of the ball screw 81z due to unilateral wear.

[0140] As described above, according to the numerical control device 1 according to Embodiment 1, there is an effect that it becomes possible to grasp the deterioration status of the drive mechanism of a machine tool that performs machining including vibration cutting due to vibration cutting.

[0141] Embodiment 2. In Embodiment 2, an example of estimating the remaining life of at least one of the bearing built in the servo motor and the bearing that rotatably supports the ball screw will be described. The operations described in Embodiment 2 are realized by the numerical control device 1 shown in FIG. 1. In Embodiment 2, as in Embodiment 1, taking vibration cutting that vibrates the driven body in the Z-axis direction as an example, the processes executed by the numerical control device 1 will be described.

[0142] The drive mechanism 8z shown in FIG. 2 vibrates the driven body by operating the shaft 711z and the ball screw 81z from a certain rotational position within a certain angle range or less by means of the servo motor 71z. When continuously vibrating the driven body near the same position, as the time for vibrating the driven body becomes longer, the grease gradually becomes uneven in the bearing 712z inside the servo motor 71z. When the grease does not spread throughout the entire bearing 712z, the wear of the bearing 712z will accelerate. The bearings inside the support mechanisms 83z1 and 83z2 also gradually become uneven in grease and the wear of the bearings accelerates as the time for vibrating the driven body becomes longer, similar to the case of the bearing 712z inside the servo motor 71z. The bearing 712z inside the servo motor 71z and the bearings inside the support mechanisms 83z1 and 83z2 will have their replacement times advanced due to accelerated wear. In vibration cutting, since the vibration of the driven body at a certain position may be continuous, the bearings may experience wear in a manner different from that in normal cutting. Note that the wear due to vibration cutting is the same for the bearing of the nut 85z as for the bearings inside the support mechanisms 83z1 and 83z2 or the bearing 712z inside the servo motor 71z.

[0143] In Embodiment 2, the estimation unit 482 estimates the remaining life of at least one of the mechanical components, which is the bearing 712z inside the servo motor 71z and the bearing that rotatably supports the ball screw 81z. The estimation unit 482 obtains, as the remaining life of the mechanical component, the period during which the vibration of the driven body at the current position can be continued based on a continuous value, which is the execution time or the number of vibrations for vibration cutting by continuously vibrating the driven body at a certain position. The vibration of the driven body at a certain position is assumed to mean vibrating the driven body around a certain position.

[0144] Next, details of a method for estimating the remaining life of a mechanical component, which is at least one of the bearings 712z inside the servo motor 71z and the bearings inside the support mechanisms 83z1 and 83z2 in Embodiment 2, will be described. Here, an example will be described in which the estimation unit 482 estimates the remaining life of the mechanical component based on a continuous value, which is the execution time of vibration cutting by continuously vibrating the driven body at a fixed position. In the following description, the continuous value, which is the execution time of vibration cutting by continuously vibrating the driven body at a fixed position, is also referred to as the continuous time. Also, in the following description, the bearing 712z built into the servo motor 71z and the bearing that rotatably supports the ball screw 81z are simply referred to as bearings without distinction.

[0145] The bearing data management unit 512 sets a life, which is the time during which the vibration of the driven body can be continuously executed at each of a plurality of positions on the ball screw 81z. The life set by the bearing data management unit 512 is the life of the bearing with the shortest life among the bearings mounted on the drive mechanism 8z. The life set in the bearing data management unit 512 is desirably determined, for example, by actually performing vibration cutting with a machine tool. It is also possible that the time specified by the operator is set as the life in the bearing data management unit 512.

[0146] When vibration cutting is started, the measurement unit 481 measures the continuous time of vibration cutting that vibrates the driven body at the current position of the driven body. When the position at which the driven body vibrates in vibration cutting moves, the measurement unit 481 resets the continuous time measured for the position before the movement and measures the continuous time for the position after the movement. The measurement unit 481 measures the continuous time for each of a plurality of positions on the ball screw 81z. The measurement unit 481 sends the measurement result of the continuous time to the bearing data management unit 512.

[0147] The estimation unit 482 estimates the remaining life of the bearing based on the measured continuous time. In Embodiment 2, the remaining life is the time during which vibration cutting for vibrating the driven body can be continued at the current position of the driven body. In Embodiment 2, the estimation unit 482 compares the measured continuous time with a preset reference time. The reference time is, for example, a time corresponding to 80% of the life set by the bearing data management unit 512. When the measured continuous time is equal to or longer than the reference time, the estimation unit 482 estimates that the remaining life of the bearing will soon expire. Note that the reference time may be any time shorter than the life set by the bearing data management unit 512, and is not limited to the time corresponding to 80% of the life.

[0148] When the measured continuous time is equal to or longer than the reference time, the estimation unit 482 instructs the stroke operation unit 488 to perform a stroke operation by rotating the ball screw 81z. When an instruction from the estimation unit 482 is input, the stroke operation unit 488 waits for the machining by the machine tool to end, and outputs a command for the stroke operation during the period until the next machining starts. The command for the stroke operation is output to the drive unit 7 via the acceleration / deceleration processing unit 49 and the axis data input / output unit 50. The drive mechanism 8z executes the stroke operation according to the command for the stroke operation. When the drive mechanism 8z is made to execute the stroke operation, the bearing data management unit 512 resets the measured continuous time for the position of the driven body before the stroke operation. The stroke operation is an operation in which the bearing is rotated by 360 degrees or more and does not involve a large axial movement.

[0149] In this way, the numerical control device 1 causes the drive mechanism 8z to execute a stroke operation before the remaining life of the bearing runs out. By means of the stroke operation, grease can be spread over the entire bearing, so that it is possible to reduce the wear of the bearing. According to the second embodiment, since it is not necessary to periodically perform an operation with a large movement amount, less time for stopping the machining is required. Thereby, it is possible to reduce the wear of the bearing while reducing the efficiency reduction for the entire machining by the machine tool.

[0150] FIG. 12 is a diagram showing an example of the result of measuring the continuous time of vibration cutting by the numerical control device 1 according to the second embodiment. FIG. 12 shows a bar graph representing the continuous time for each position in the ball screw 81z. In FIG. 12, the vertical axis represents the continuous time of vibration cutting. The horizontal axis represents the ball screw position. In FIG. 12, the unit of the continuous time is "hour (h)", and the unit of the ball screw position is "mm".

[0151] For example, assume that the life set in the bearing data management unit 512 is 30 hours. Also, the reference time is 24 hours, which is the time corresponding to 80% of the life set by the bearing data management unit 512. FIG. 12 shows three bar graphs representing the continuous times measured for the ball screw positions of 125.7 mm, 126 mm, and 126.3 mm. The interval between each ball screw position when measuring the continuous time needs to be an interval corresponding to the movement amount of the driven body when the rotation of the ball screw 81z is less than one rotation. In other words, the continuous time is measured with the interval between each ball screw position being an interval corresponding to less than one rotation of the ball screw 81z, that is, an interval corresponding to less than 360 degrees of rotation of the bearing. Here, assume that the continuous time is measured with the interval between each ball screw position being 0.3 mm, which is an interval corresponding to 1 / 20 rotation of the ball screw 81z.

[0152] In the example shown in FIG. 12, assume that the duration for the ball screw position of 126 mm is 25 hours. In the example shown in FIG. 12, for the ball screw position of 126 mm, the measured duration satisfies the requirement that it is equal to or longer than the reference time. Since the duration for the ball screw position of 126 mm is equal to or longer than the reference time, the numerical control device 1 causes the drive mechanism 8z to execute a stroke operation.

[0153] Next, a procedure of processing executed by the numerical control device 1 according to the second embodiment will be described. FIG. 13 is a flowchart showing an example of a procedure of processing executed by the numerical control device 1 according to the second embodiment. Here, an example of processing executed by the numerical control device 1 when vibration cutting by a machine tool is executed will be described. In the numerical control device 1, assume that the vibration frequency of the vibration cutting before the change is 90.9 Hz, which is the same as that in the first embodiment, for example.

[0154] As a premise of the processing according to the procedure shown in FIG. 13, the bearing data management unit 512 sets a life, which is a time during which the vibration of the driven body can be continuously executed, at each of a plurality of positions in the ball screw 81z.

[0155] In step S11, the measurement unit 481 measures the duration of the vibration cutting. When the vibration cutting is started, the measurement unit 481 measures the duration of the vibration cutting that vibrates the driven body at the current position of the driven body. The measurement unit 481 measures the duration for each of a plurality of positions in the ball screw 81z.

[0156] In step S12, the estimation unit 482 determines whether or not the duration measured in step S11 is equal to or longer than the reference time. If the duration is equal to or longer than the reference time (step S12, Yes), in step S13, the estimation unit 482 instructs the stroke operation execution unit 488 to execute a stroke operation. The stroke operation execution unit 488 causes the drive mechanism 8z to execute a stroke operation. Thereby, the numerical control device 1 ends the processing according to the procedure shown in FIG. 13.

[0157] When the continuous time is not longer than the reference time (step S12, No), the numerical control device 1 ends the process according to the procedure shown in FIG. 13. After the numerical control device 1 ends the process according to the procedure shown in FIG. 13, the numerical control device 1 executes the process according to the procedure shown in FIG. 13 again.

[0158] In the above description, the estimation unit 482 is configured to estimate the remaining life of the bearing based on the measured continuous time. The estimation unit 482 may estimate the remaining life of the bearing based on the number of continuous vibrations, which is the number of vibrations in vibration cutting by continuously vibrating the driven body at a certain position. That is, the estimation unit 482 obtains, as the remaining life of the bearing, the period during which the vibration of the driven body at the current position can be continued based on the continuous value, which is the execution time or the number of vibrations in vibration cutting by continuously vibrating the driven body at a predetermined position.

[0159] The estimation unit 482 obtains the value of the number of continuous vibrations, for example, by multiplying the vibration frequency by the continuous time of vibration cutting. Alternatively, the estimation unit 482 may obtain the value of the number of continuous vibrations by counting the number of vibrations. The estimation unit 482 may count the number of continuous vibrations based on, for example, the vibration waveform, which is the basic waveform of the vibration generated by the waveform generation unit 484.

[0160] According to the second embodiment, the estimation unit 482 estimates the remaining life of the bearing, which is a mechanical component constituting the drive mechanism, based on the execution time of vibration cutting. The estimation unit 482 obtains, as the remaining life of the bearing, the time during which vibration cutting for vibrating the driven body at the current position of the driven body can be continued. The numerical control device 1 causes the drive mechanism to execute a stroke operation based on the estimation result of the remaining life of the bearing. Since the numerical control device 1 can execute a stroke operation according to the remaining life of the bearing, it is possible to avoid wear of the bearing due to unevenness of grease. By reducing the wear of the bearing, it is possible to prevent the replacement time of the bearing from being advanced. Therefore, it is possible to delay the deterioration of the drive mechanism caused by vibration cutting.

[0161] As described above, according to the numerical control device 1 according to the second embodiment, it is possible to grasp the deterioration status of the drive mechanism caused by vibration cutting for the drive mechanism of a machine tool that performs machining including vibration cutting, and thus has the effect of achieving this.

[0162] In the second embodiment, based on the remaining life of the bearing estimated by the estimation unit 482, similar to the first embodiment, the vibration condition changing unit 483 may change the vibration conditions so as to extend the remaining life without changing the position where vibration cutting is executed. Specifically, the vibration condition changing unit 483 changes the vibration conditions so that the vibration frequency becomes lower than 90.9 Hz, which is the vibration frequency of the vibration cutting before the change, in order to extend the remaining life.

[0163] In the first and second embodiments, the numerical control device 1 vibrates the tool to execute vibration cutting, but it is not limited to this. The numerical control device 1 may, for example, vibrate the workpiece to execute vibration cutting.

[0164] Next, the hardware configuration of the control arithmetic unit 4 provided in the numerical control device 1 will be described. FIG. 14 is a diagram showing a hardware configuration example of the control arithmetic unit 4 provided in the numerical control device 1 according to the first or second embodiment.

[0165] The control arithmetic unit 4 is realized by a control circuit 100 shown in FIG. 14. The control circuit 100 includes a processor 101 and a memory 102. The control circuit 100 is a circuit in which the processor 101 executes software.

[0166] The control arithmetic unit 4 is implemented by software, firmware, or a combination of software and firmware. The software or firmware is described as a program and stored in the memory 102. In the control circuit 100, the processor 101 reads and executes the program stored in the memory 102, thereby realizing each function of the control arithmetic unit 4. That is, the control circuit 100 includes a memory 102 for storing a program in which the processing of the control arithmetic unit 4 is ultimately executed. This program is a numerical control program that causes a computer to execute the procedures and methods of the control arithmetic unit 4. The memory 102 is also used as a temporary memory when the processor 101 executes various processes.

[0167] The processor 101 is a CPU (Central Processing Unit), a processing device, an arithmetic device, a microprocessor, a microcomputer, a processor, a DSP (Digital Signal Processor), or a system LSI (Large Scale Integration), etc. The memory 102 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), or a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc), etc.

[0168] The program executed by the processor 101 may be a computer program product having a computer-readable and non-transitory recording medium including a plurality of instructions executable by a computer for data processing. The program executed by the processor 101 causes a computer to execute the plurality of instructions for data processing.

[0169] The control arithmetic unit 4 may be implemented by dedicated hardware. Also, a part of the functions of the control arithmetic unit 4 may be implemented by dedicated hardware, and another part of the functions of the control arithmetic unit 4 may be implemented by software or firmware.

[0170] The configurations shown in the above embodiments are examples of the content of the present disclosure. The configurations of each embodiment can be combined with other known technologies. The configurations of each embodiment may be appropriately combined with each other. A part of the configuration of each embodiment can be omitted or changed without departing from the gist of the present disclosure.

Explanation of Reference Numerals

[0171] 1 Numerical control device, 2 Input operation unit, 3 Output unit, 4 Control arithmetic unit, 7 Driving unit, 8z Driving mechanism, 31, 35 Marks, 32, 36 Messages, 33, 34 Buttons, 41 Input control unit, 42 Data setting unit, 43 Storage unit, 44 Output control unit, 45 Analysis processing unit, 46 Control signal processing unit, 47 PLC circuit unit, 48 Interpolation processing unit, 49 Acceleration / deceleration processing unit, 50 Axis data input / output unit, 51 Data management unit, 71s Main spindle motor, 71x, 71z Servo motors, 72s, 72x, 72z Detectors, 73s Main spindle control unit, 73x, 73z Servo control units, 81z Ball screw, 82z Table, 83z1, 83z2 Support mechanisms, 84z Coupling, 85z Nut, 86z, 715z Balls, 87, 716, 717 Double arrows, 100 Control circuit, 101 Processor, 102 Memory, 431 Parameter storage area, 432 Machining program storage area, 433 Display data storage area, 434 Shared area, 481 Measurement unit, 482 Estimation unit, 483 Vibration condition change unit, 484 Waveform generation unit, 485 Vibration movement amount generation unit, 487 Machining program change unit, 488 Stroke operation execution unit, 511 Ball screw data management unit, 512 Bearing data management unit, 711z Shaft, 712z Bearing, 713z Outer ring, 714z Inner ring.

Claims

1. A numerical control device for controlling a machine tool that performs machining including vibration cutting using a drive mechanism, an estimation unit that estimates a remaining life of a mechanical component that constitutes the drive mechanism based on an execution time of the vibration cutting; The drive mechanism is capable of vibrating the driven body at each of a plurality of positions in a direction of a center line which is a rotation center of the ball screw, The numerical control device is characterized in that the estimation unit calculates the period during which vibration of the driven body can be continued at the current position as the remaining life of the mechanical component based on a continuation value, which is the execution time for the vibration cutting by continuing the vibration of the driven body at a specified position.

2. The mechanical components include bearings, The numerical control device according to claim 1 , wherein the estimating unit estimates a remaining life of the bearing.

3. 3. The numerical control device according to claim 1, further comprising a stroke operation execution unit that causes the drive mechanism to execute a stroke operation based on the estimated remaining life of the mechanical component.

4. A numerical control method for controlling a machine tool that performs machining including vibration cutting using a drive mechanism, comprising: a step of estimating a remaining life of a mechanical component constituting the drive mechanism based on an execution time of the vibration cutting; The drive mechanism is capable of vibrating the driven body at each of a plurality of positions in a direction of a center line which is a rotation center of the ball screw, A numerical control method characterized in that in the step of estimating the remaining life, the period during which vibration of the driven body can be continued at the current position is obtained as the remaining life of the mechanical component based on a continuation value, which is the execution time for the vibration cutting by continuing the vibration of the driven body at a specified position.

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