Numerical controller, machine tool, control method, and storage medium

Abstract

The invention provides a numerical controller, a machine tool, a control method, and a storage medium, capable of monitoring a machining load acquired during a desired period during machining of a workpiece. A numerical controller for controlling a machine tool for machining a workpiece using a tool on the basis of an NC program includes: a reading unit for reading, from among commands of the NC program, a first command indicating an acquisition start time at which acquisition of a machining load during machining of the workpiece is started, and a second command indicating an acquisition start time at which acquisition of the machining load during machining of the workpiece is started; the second command indicates an acquisition end time at which the acquisition of the processing load is ended; a first load acquisition unit configured to acquire the processing load during a period from reading of the first command from the reading unit to reading of the second command by the reading unit; and a monitoring unit that performs monitoring on the basis of the machining load acquired by the first load acquisition unit.

Description

Technical Field

[0001] The present invention relates to a numerical control device, a machine tool, a control method, a program, and a storage medium. Background Art

[0002] The detection device described in Patent Document 1 is used to monitor the machining load of a tool. The detection device includes an actual machining load amount acquisition unit and a detection unit. The actual machining load amount acquisition unit acquires the load amount of the tool during an air feed operation and an actual machining operation as the machining load. The air feed operation is an operation mode in which the tool does not machine the workpiece. The actual machining operation is an operation mode in which the tool machines the workpiece. When the air feed operation is executed, the detection unit detects whether the machining load exceeds an air feed threshold. When the actual machining operation is executed, the detection unit detects whether the machining load exceeds an actual machining threshold.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-64128 Summary of the Invention

[0004] In the above detection device, during the actual machining operation, the tool performs a cutting feed, but during this cutting feed, there is a time difference before the tool contacts the workpiece. In this case, the detection device cannot monitor the machining load only for the period when the tool contacts the workpiece during the cutting feed of the actual machining operation.

[0005] An object of the present invention is to provide a numerical control device, a machine tool, a control method, a program, and a storage medium that can monitor the machining load obtained during a desired period during the machining of a workpiece.

[0006] To achieve the above object, the present invention provides a numerical control device for controlling a machine tool that uses a tool to machine a workpiece based on an NC program, including: a reading unit for reading a first command and a second command in the commands of the NC program, the first command indicating a start acquisition time for starting to acquire the machining load during the machining of the workpiece, and the second command indicating an end acquisition time for ending the acquisition of the machining load; a first load acquisition unit for acquiring the machining load during the period from when the reading unit reads the first command to when the reading unit reads the second command; and a monitoring unit for performing monitoring based on the machining load acquired by the first load acquisition unit.

[0007] The above numerical control device designates the start acquisition time and the end acquisition time of the machining load through the first command and the second command of the NC program. Therefore, the numerical control device can monitor the machining load obtained during a desired period.

[0008] The numerical control device of the present invention further includes: a second load acquisition unit configured to acquire a reference machining load as a monitoring reference during the period from when the first command is read by the reading unit to when the second command is read by the reading unit; and a storage control unit configured to store the reference machining load acquired by the second load acquisition unit. The monitoring unit monitors the machining load acquired by the first load acquisition unit based on the reference machining load stored by the storage control unit. The numerical control device can monitor the machining load based on the reference machining load.

[0009] The numerical control device of the present invention further includes: a first setting unit configured to set a monitoring start time at which the monitoring unit starts monitoring the machining load during the period from when the first command is read to when the second command is read, based on the reference machining load stored by the storage control unit; and a second setting unit configured to set a monitoring end time at which the monitoring unit ends monitoring the machining load during the period from when the first command is read to when the second command is read, based on the reference machining load stored by the storage control unit. The monitoring unit monitors the machining load acquired by the first load acquisition unit during the period from the monitoring start time set by the first setting unit to the monitoring end time set by the second setting unit. The numerical control device can perform monitoring of the machining load by taking the monitoring from the monitoring start time to the monitoring end time in the acquired machining load as a required period.

[0010] The numerical control device of the present invention further includes: a third setting unit configured to set an upper limit load based on the reference machining load stored by the storage control unit; and a fourth setting unit configured to set a lower limit load based on the reference machining load stored by the storage control unit. The monitoring unit monitors the machining load acquired by the first load acquisition unit based on the upper limit load set by the third setting unit and the lower limit load set by the fourth setting unit. The numerical control device can monitor the machining load according to the upper limit load and the lower limit load based on the reference machining load.

[0011] In the numerical control device of the present invention, the monitoring unit includes: a first notification control unit configured to notify an abnormality of the machining load when it is determined that the machining load acquired by the first load acquisition unit is greater than the upper limit load set by the third setting unit; and a second notification control unit configured to notify an abnormality of the machining load when it is determined that the machining load acquired by the first load acquisition unit is lower than the lower limit load set by the fourth setting unit. The user of the numerical control device can identify an abnormality of the machining load.

[0012] The numerical control device of the present invention further includes a third setting unit configured to set an upper limit load based on the reference processing load stored in the storage control unit. The monitoring unit includes a first notification control unit configured to notify an abnormality of the processing load when it is determined that the processing load obtained by the first load acquisition unit is greater than the upper limit load set by the third setting unit. The user of the numerical control device can identify the abnormality of the processing load.

[0013] The numerical control device of the present invention further includes a fourth setting unit configured to set a lower limit load based on the reference processing load stored in the storage control unit. The monitoring unit includes a second notification control unit configured to notify an abnormality of the processing load when it is determined that the processing load obtained by the first load acquisition unit is lower than the lower limit load set by the fourth setting unit. The user of the numerical control device can identify the abnormality of the processing load.

[0014] The numerical control device of the present invention further includes a display control unit configured to overlap and display the reference processing load stored in the storage control unit, the upper limit load set by the third setting unit, the lower limit load set by the fourth setting unit, and the processing load obtained by the first load acquisition unit on a display unit. In the numerical control device, the user can visually confirm the processing load.

[0015] In the numerical control device of the present invention, the upper limit load is obtained by adding an upper limit processing load as a specified offset amount to the reference processing load, and the lower limit load is obtained by subtracting a lower limit processing load as a specified offset amount from the reference processing load. The numerical control device further includes: a first correction unit configured to correct the upper limit processing load based on a change amount of the reference processing load with respect to a sampling time of the reference processing load; and a second correction unit configured to correct the lower limit processing load based on the change amount. The third setting unit sets, as the upper limit load, a value obtained by adding the corrected upper limit processing load to the reference processing load, and the fourth setting unit sets, as the lower limit load, a value obtained by subtracting the corrected lower limit processing load from the reference processing load. The numerical control device can appropriately correct the upper limit processing load and the lower limit processing load according to the magnitude of the change amount of the reference processing load.

[0016] The numerical control device of the present invention, wherein the second load acquisition unit acquires the reference machining load for each of the tools used in the machining of the workpiece based on the NC program, the storage control unit stores the reference machining loads acquired by the second load acquisition unit for each of the tools in association with the corresponding tools respectively, the first load acquisition unit acquires the machining load when machining the workpiece using any one of the specific tools among the tools, and the monitoring unit monitors the machining load acquired by the first load acquisition unit based on the reference machining load associated with the specific tool among the reference machining loads stored by the storage control unit in association with each tool. The numerical control device can monitor the machining load according to the reference machining load associated with each tool.

[0017] The numerical control device of the present invention further includes: a fifth setting unit for setting an upper limit value, which is the upper limit value of the machining load; and a sixth setting unit for setting a lower limit value, which is the lower limit value of the machining load, and the monitoring unit monitors the machining load acquired by the first load acquisition unit based on the upper limit value set by the fifth setting unit and the lower limit value set by the sixth setting unit. The numerical control device can monitor the machining load according to the upper limit value and the lower limit value.

[0018] The numerical control device of the present invention, the monitoring unit includes: a third notification control unit for notifying an abnormality of the machining load when it is determined that the machining load acquired by the first load acquisition unit is greater than the upper limit value set by the fifth setting unit; and a fourth notification control unit for notifying an abnormality of the machining load when it is determined that the machining load acquired by the first load acquisition unit is lower than the lower limit value set by the sixth setting unit. The user of the numerical control device can identify an abnormality of the machining load.

[0019] The numerical control device of the present invention further includes a fifth setting unit for setting an upper limit value, which is the upper limit value of the machining load, and the monitoring unit includes a third notification control unit for notifying an abnormality of the machining load when it is determined that the machining load acquired by the first load acquisition unit is greater than the upper limit value set by the fifth setting unit. The numerical control device enables the user to identify an abnormality of the machining load.

[0020] The numerical control device of the present invention further includes a sixth setting unit for setting a lower limit value, which is the lower limit value of the machining load. The monitoring unit includes a fourth notification control unit for notifying an abnormality of the machining load when it is determined that the machining load obtained by the first load acquisition unit is lower than the lower limit value set by the sixth setting unit. The user of the numerical control device can identify the abnormality of the machining load.

[0021] The present invention also provides a machine tool for machining a workpiece using a tool based on an NC program, including: a reading unit for reading a first command and a second command in the commands of the NC program, the first command indicating a start acquisition time for starting to acquire the machining load during the machining of the workpiece, and the second command indicating an acquisition end time for ending the acquisition of the machining load; a first load acquisition unit for acquiring the machining load during the period from when the first command is read by the reading unit to when the second command is read by the reading unit; and a monitoring unit for performing monitoring based on the machining load acquired by the first load acquisition unit.

[0022] The above-mentioned machine tool has the same effect as the above-mentioned numerical control device.

[0023] The present invention also provides a control method for a numerical control device, which is used to control a machine tool for machining a workpiece using a tool based on an NC program. The control method includes: a reading step for reading a first command and a second command in the commands of the NC program, the first command indicating a start acquisition time for starting to acquire the machining load during the machining of the workpiece, and the second command indicating an acquisition end time for ending the acquisition of the machining load; a first load acquisition step for acquiring the machining load during the period from when the first command is read in the reading step to when the second command is read in the reading step; and a monitoring step for performing monitoring based on the machining load acquired in the first load acquisition step.

[0024] The above-mentioned control method has the same effect as the above-mentioned numerical control device.

[0025] The present invention also provides a program for causing a computer of a numerical control device to execute the following steps. The numerical control device is used to control a machine tool that processes a workpiece using a tool based on an NC program. The steps include: a reading step for reading a first command and a second command in the commands of the NC program. The first command represents the acquisition start time for starting to acquire the machining load during the machining of the workpiece, and the second command represents the acquisition end time for ending the acquisition of the machining load; a first load acquisition step for acquiring the machining load during the period from the reading step reading the first command to the reading step reading the second command; and a monitoring step for performing monitoring based on the machining load acquired in the first load acquisition step.

[0026] The above program has the same effect as the above numerical control device.

[0027] The present invention also provides a storage medium storing a program for causing a computer of a numerical control device to execute the following steps. The numerical control device is used to control a machine tool that processes a workpiece using a tool based on an NC program. The steps include: a reading step for reading a first command and a second command in the commands of the NC program. The first command represents the acquisition start time for starting to acquire the machining load during the machining of the workpiece, and the second command represents the acquisition end time for ending the acquisition of the machining load; a first load acquisition step for acquiring the machining load during the period from the reading step reading the first command to the reading step reading the second command; and a monitoring step for performing monitoring based on the machining load acquired in the first load acquisition step.

[0028] The above storage medium has the same effect as the above numerical control device. Description of the Drawings

[0029] Figure 1 is the front view of the machine tool 1.

[0030] Figure 2 is a block diagram showing the electrical structure of the machine tool 1.

[0031] Figure 3 is a flowchart of the trial machining process.

[0032] Figure 4 is a diagram showing an example of the code of the NC program.

[0033] Figure 5 is a diagram showing the waveforms of the machining load F and the reference machining load Fr.

[0034] Figure 6 is a diagram showing an example of the code of the NC program.

[0035] Figure 7 It is a diagram showing waveforms of the machining load F and the reference machining load Fr.

[0036] Figure 8 It is a flowchart of the main process.

[0037] Figure 9 It is a flowchart of the absolute monitoring process.

[0038] Figure 10 It is a flowchart of the relative monitoring process.

[0039] Figure 11 It is a diagram showing the change amount of the reference machining load Fr with respect to the sampling time.

[0040] Figure 12 It is a diagram showing the relationship between the upper limit load Fh and the lower limit load Fl before correction and the reference machining load Fr.

[0041] Figure 13 It is a diagram showing the relationship between the upper limit load Fh and the lower limit load Fl after correction and the reference machining load Fr. Detailed implementation mode

[0042] Refer to Figure 1 、 Figure 2 to describe the machine tool 1 of the present invention. Define the upper side, lower side, left side, right side, front side, and depth side of Figure 1 as the upper side, lower side, left side, right side, front side, and back side of the machine tool 1 respectively. Figure 1 The machine tool 1 shown is a machine tool that rotates a cutting tool to perform cutting on a workpiece.

[0043] Figure 1 、 Figure 2 The machine tool 1 shown is a vertical machine tool in which a spindle (not shown) extends in the Z-axis direction. The machine tool 1 includes a base portion 2, a machine tool body 3, and a cover 5. The base portion 2 is an iron base. The machine tool body 3 is provided on the upper part of the base portion 2. The machine tool body 3 performs cutting on a workpiece (not shown) fixed on the upper surface of a worktable (not shown). The worktable is provided on the upper surface of the base portion 2. The cover 5 is fixed to the upper part of the base portion 2 and surrounds the periphery of the machine tool body 3. The operation of the machine tool 1 is controlled by a numerical control device 30 (refer to Figure 2 ).

[0044] As Figure 1 、 Figure 2As shown, the machine tool 1 also includes an operation panel 13. The operation panel 13 is provided at the right part of the front surface 5B of the cover 5. The operation panel 13 includes a display unit 15 and an operation unit 24. The display unit 15 displays various setting screens for selecting various programs, setting machining conditions of an NC (Numerical Control) program, etc. In addition, the display unit 15 displays the waveform of the machining load F (refer to Figure 5 , Figure 7 ), etc.

[0045] The operator uses the operation unit 24 to input settings of various operations, etc. into the machine tool 1. The operator sets various operations of the machine tool 1, machining conditions of the workpiece to be machined, etc. by operating the operation unit 24 while confirming the display unit 15. The operator selects and executes an NC program through the operation unit 24.

[0046] Refer to Figure 2 to describe the electrical structure of the machine tool 1. The machine tool 1 includes a numerical control device 30, an operation panel 13, drive circuits 201 to 204, an X-axis motor 51, a Y-axis motor 52, a Z-axis motor 53, a spindle motor 54, etc. The numerical control device 30 includes a CPU 31, a ROM 32, a RAM 33, a timer 23, a storage device 29, an interference estimation unit 25, and interfaces 34, 35.

[0047] The CPU 31 comprehensively controls the operation of the machine tool 1. The ROM 32 stores various programs such as a trial machining program and a monitoring program. The trial machining program executes the trial machining process described later (refer to Figure 3 ). The monitoring program executes the main process described later (refer to Figure 8 ). The RAM 33 temporarily stores various data, etc.

[0048] The storage device 29 is non-volatile and stores a plurality of NC programs for machining various workpieces to be machined. The NC program is a program executed for machining the workpiece to be machined. The storage device 29 also stores the reference machining load Fr described later. The machining conditions of the workpiece to be machined can be set in detail by the operator's operation on the operation panel 13.

[0049] The disturbance estimation unit 25 estimates, for example, the estimated disturbance force of the spindle motor 54. This estimation can use known methods. For example, it can be estimated based on information such as torque, inertia, angular acceleration, viscosity, speed, and friction. Hereinafter, the estimated disturbance force of the spindle motor 54 is referred to as "processing load F". As the processing load F, the forces applied to the X-axis, Y-axis, and Z-axis of the workpiece measured by a force sensor can also be used. In addition, as the processing load F, the torque around the spindle applied to the workpiece measured by a torque sensor can also be used. In addition, as the processing load F, the vibration amplitude and vibration work of the vibration of the workpiece in the X-axis, Y-axis, and Z-axis directions measured by an acceleration sensor, or the vibration amplitude and vibration work of the vibration of the spindle head in the X-axis, Y-axis, and Z-axis directions can also be used. The timer 23 measures, for example, the elapsed time from the acquisition to the end of the processing load F.

[0050] The display unit 15 and the operation unit 24 are connected to the CPU 31 via the interface 34. The CPU 31 controls the drive circuits 201 to 204 via the interface 35. Each of the drive circuits 201 to 204 controls the X-axis motor 51, Y-axis motor 52, Z-axis motor 53, spindle motor 54, etc. respectively. Each of the encoders 51a to 54a detects the position information of the rotational positions of the X-axis motor 51, Y-axis motor 52, Z-axis motor 53, spindle motor 54, etc. Each of the drive circuits 201 to 204 sends the detection results of the position information, etc. to the CPU 31 via the interface 35. The CPU 31 controls each of the drive circuits 201 to 204 based on this position information to perform the machining of the workpiece.

[0051] Refer to Figure 3 , and the trial machining process will be described. The operator sets the machine tool 1 to trial machining operation. The operator installs the tool on the spindle and places the workpiece on the worktable. The operator operates the operation unit 24 to select and execute the NC program. The CPU 31 reads the trial machining program stored in the ROM 32 and starts the trial machining process. When the trial machining process starts, the CPU 31 performs the machining of the workpiece based on the selected NC program (S1).

[0052] An example of the machining based on the NC program (refer to Figure 4 ) will be described. For example, the CPU 31 is based on Figure 4Command execution processing of each code shown. The processing is threading hole machining with a drill. The height of the workpiece to be machined is assumed to be, for example, the Z-axis position of 145 mm. For example, the spindle quickly moves to the Z-axis position of 200 mm (refer to the code G 90G00 Z 200.M03S 3000). In addition, the spindle performs cutting feed from the Z-axis height of 200 mm to the Z-axis height of 100 mm (refer to the code G01 Z 100.F1000). Then, the spindle rises from the Z-axis position of 100 mm to 150 mm (refer to the code G01 Z 150.F2000). The spindle quickly moves from the Z-axis position of 150 mm to the Z-axis position of 200 mm (refer to the code G00 Z 200.).

[0053] An example of the processing based on the NC program (refer to Figure 6 ) is described. For example, the CPU 31 executes the processing based on the commands of each code shown in Figure 6 . The processing is tapping with a tap. The height of the workpiece to be machined is assumed to be, for example, the Z-axis position of 145 mm. The spindle quickly moves to the Z-axis position of 200 mm (refer to the code G 90G00 Z 200.M03 S 3000). The cutting feed is executed from the Z-axis height of 200 mm to 100 mm, and the spindle rises from the Z-axis position of 100 to 150 mm (refer to the code G84 Z100.R150.F 6000S 6000). The spindle quickly moves from the Z-axis position of 150 mm to the Z-axis position of 200 mm (refer to the code G00 Z200.).

[0054] Refer to Figure 4 and Figure 6 to describe the M code. The M code includes M341 and M340. M341 indicates the start time of obtaining the machining load F during the machining of the workpiece. That is, the CPU 31 starts obtaining the machining load F when M341 is read. M340 indicates the end time of obtaining the machining load F. That is, the CPU 31 ends obtaining the machining load F when the command of M340 is read. Therefore, the operator can set the acquisition period of the machining load F through the NC program. Figure 4 and Figure 6 The example of the M code shown is only for the interval of performing the cutting feed of the workpiece.

[0055] The CPU 31 obtains the machining load F output from the disturbance estimation unit 25 as the reference machining load Fr (S 3). The period of obtaining the reference machining load Fr is from when the M code 341 is read to when the M code 340 is read. The reference machining load Fr is obtained at a specified sampling time. The sampling time can be set appropriately. After the acquisition of the reference machining load Fr is completed, the CPU 31 will obtain the waveform of the obtained reference machining load Fr (refer toFigure 5 , Figure 7 ) is displayed on the display unit 15 (S5). For example, the operator confirms the waveform of the machining load F displayed on the display unit 15 and presses the registration button ("Set as reference") (refer to Figure 5 , Figure 7 ). Thereby, the CPU 31 stores the reference machining load Fr in the storage device 29 (S7). The reference machining load Fr is stored in association with, for example, the NC program number of the NC program, the machining conditions of the workpiece to be machined (type of tool, tool number), etc. The reference machining load Fr becomes the reference for monitoring the machining load F. The NC program number is identification information assigned to identify the NC program.

[0056] The operator removes the workpiece to be machined and places a new workpiece on the worktable. The operator selects and executes again the NC program executed in S1. When the NC program is executed, the CPU 31 performs machining of the workpiece to be machined (S9). The CPU 31 acquires the machining load F during machining of the workpiece to be machined from the disturbance estimation unit 25 (S11). The acquisition period of the machining load F is the same as in the case of S3, which is the period from the start of reading M341 to the end of reading M340. The CPU 31 displays the acquired machining load F on the display unit 15 (S13). In this case, the display unit 15 overlays and displays the machining load F acquired in S11 and the reference machining load Fr (refer to Figure 5 , Figure 7 ).

[0057] The CPU 31 sets the time constant of the LPF (Low Pass Filter) (S15). The operator confirms the waveform of the machining load F on the display unit 15 and adjusts the time constant of the LPF. By performing the LPF process, the waveforms of the machining load F and the reference machining load Fr can be smoothly adjusted. Therefore, by appropriately adjusting the time constant of the LPF, the CPU 31 can reduce the influence of the deviation of the machining load F on the monitoring.

[0058] The CPU 31 sets the monitoring start time ts (S17). The monitoring start time ts is the time at which the machining load F starts to be monitored during the period from the start of reading the M code 341 to the end of reading the M code 340. The operator confirms the reference machining load Fr and the machining load F on the display unit 15 and inputs the desired time t in the "Monitoring start time" column (refer to Figure 5 , Figure 7 ). For example, the monitoring start time ts is 1000 msec after the start of acquisition of the machining load F (refer to Figure 5 , Figure 7 ).

[0059] The CPU 31 sets the monitoring end time te (S19). The monitoring end time te is the time when the monitoring of the machining load F ends during the period from when the M code 341 is read until the M code 340 is read. The operator confirms the reference machining load Fr and the machining load F displayed on the display unit 15, and inputs the desired time t in the "Monitoring End Time" column (refer to Figure 5 , Figure 7 ). For example, the monitoring end time te is 2000 ms ec after the start of acquisition of the machining load F. For example, in Figure 5 , the operator can specify only the period during which the machining load F is stable during the cutting feed.

[0060] The CPU 31 determines whether to set the absolute monitoring mode or the relative monitoring mode (S21). Each monitoring mode is an example of a method for monitoring the machining load F. The absolute monitoring mode is, for example, a method suitable for the case where the change amount of the machining load F is small. The case where the change amount of the machining load F is small means, for example, the case of the waveform of the machining load F shown in Figure 5 . On the other hand, the relative monitoring mode is a method suitable for, for example, the case where the change amount of the machining load F is large. The case where the change amount of the machining load F is large means, for example, the case of the waveform of the machining load F shown in Figure 7 . For example, the operator selects "Absolute" or "Relative" in the "Judgment Method" of the display unit 15 (refer to Figure 5 , Figure 7 ). "Absolute" corresponds to the absolute monitoring mode, and "Relative" corresponds to the relative monitoring mode.

[0061] In the case where it is determined to be the absolute monitoring mode (S21: Yes), the CPU 31 can set the upper limit value of the machining load F, that is, the upper limit value Fmax (S23). For example, the operator operates the operation panel 13 to set the upper limit value Fmax of the display unit 15 to "9.1" (refer to Figure 5 ). The CPU 31 can set the lower limit value of the machining load F, that is, the lower limit value Fmim (S25). For example, the operator operates the operation panel 13 to set the lower limit value Fmim of the display unit 15 to "7.0" (refer to Figure 5 ). These set values are used in the absolute monitoring process described later. The CPU 31 ends the trial machining process.

[0062] On the other hand, in the case where it is determined to be the relative monitoring mode (S21: No), the CPU 31 can set the upper machining load A (S27). The upper machining load A represents the offset amount upward from the waveform of the reference machining load Fr (refer to Figure 7 ). The CPU 31 can set the lower machining load B (S29). The lower machining load B represents the offset amount downward from the waveform of the reference machining load Fr (refer to Figure 7)。The offset between the upper limit machining load A and the lower limit machining load B can be the same or different. For example, the operator operates the operation unit 24 to set the upper limit machining load A and the lower limit machining load B. These set values are used in the relative monitoring process described later. The CPU 31 ends the trial machining process.

[0063] The operator performs the above trial machining process for each NC program. For each NC program, the machining conditions of the workpiece to be machined are different. Therefore, the numerical control device 30 can obtain the reference machining load Fr for each machining condition of the NC program, for example, for each tool used.

[0064] Refer to Figure 8 An explanation of the main process is given. The operator sets the machine tool 1 to the monitoring operation. The operator operates the operation unit 24 to select and execute an NC program. The CPU 31 reads the monitoring program stored in the ROM 32 and starts the main process.

[0065] When starting the main process, the CPU 31 reads in one block of the NC program (S101). The CPU 31 determines whether the M341 indicating the acquisition of the start time is read in the commands of the NC program (S103). When it is determined that it is not M341 indicating the acquisition of the start time (S103: No), the CPU 31 determines whether the M340 indicating the acquisition of the end time is read (S105). When it is determined that it is not M340 indicating the acquisition of the end time (S105: No), the CPU 31 executes the command represented by the code of one block (S107). For example, the CPU 31 executes the rapid feed of the spindle.

[0066] The CPU 31 determines whether the monitoring mode is set to ON (S115). When it is determined that the monitoring mode is set to OFF (S115: No), the CPU 31 makes the process enter S129. In the initial setting, the monitoring mode is set to OFF.

[0067] On the other hand, when it is determined that the M341 indicating the acquisition of the start time is read (S103: Yes), the CPU 31 sets the monitoring mode to ON (S111). The CPU 31 initializes the time t of the timer 23 to 0 (S113). The CPU 31 makes the process enter S115.

[0068] On the other hand, when the monitoring mode is set to ON (S115: Yes), the CPU 31 determines whether it is the absolute monitoring mode (S117). When it is determined that it is the absolute monitoring mode (S117: Yes), the CPU 31 executes Figure 9 the absolute monitoring process shown (S123).

[0069] When executingFigure 9 When performing the absolute monitoring process shown, the CPU 31 obtains the processing load F from the interference estimation unit 25 (S201). The CPU 31 performs LPF processing on the obtained processing load F according to the time constant set in the trial processing (S203). The CPU 31 determines whether the time t shown by the timer 23 has reached the monitoring start time ts set in the trial processing (S205). If it is determined that the time t shown by the timer 23 has not reached the monitoring start time ts (S205: No), the CPU 31 ends the absolute monitoring process and returns the process to the main process.

[0070] On the other hand, if it is determined that the time t shown by the timer 23 has reached the monitoring start time ts (S205: Yes), the CPU 31 determines whether the time t shown by the timer 23 has reached the monitoring end time te (S207). If it is determined that the time t shown by the timer 23 has not reached the monitoring end time te (S207: Yes), the CPU 31 determines whether the processing load F is greater than the upper limit value Fmax (S209).

[0071] If it is determined that the processing load F is below the upper limit value Fmax (S209: No), the CPU 31 determines whether the processing load F is lower than the lower limit value Fmin (S211). If it is determined that the processing load F is above the lower limit value Fmin (S211: No), the CPU 31 considers that the processing load F has no abnormality and returns the process to the main process.

[0072] On the other hand, if it is determined that the processing load F is greater than the upper limit value Fmax (S209: Yes), that is, when it is detected that the obtained processing load F is abnormal, the CPU 31 issues an alarm notification for the case where the upper limit value Fmax is exceeded (S213). The alarm notification can, for example, display a string such as "There is an abnormality in the processing load" on the display unit 15. In addition, the alarm notification can also be given a warning with a buzzer or the like. The CPU 31 stops the drive of the machine tool 1 (S217). The CPU 31 ends the absolute monitoring process and returns the process to the main process.

[0073] On the other hand, if it is determined that the processing load F is lower than the lower limit value Fmin (S211: Yes), that is, when it is detected that the obtained processing load F is abnormal, the CPU 31 issues an alarm notification for the case where the lower limit value Fmim is exceeded (S215). The alarm notification is performed in the same manner as the case where the upper limit value Fmax is exceeded, for example. The CPU 31 stops the drive of the machine tool 1 (S217). The CPU 31 ends the absolute monitoring process and returns the process to the main process.

[0074] On the other hand, when it is determined in S117 of the main process that it is the relative monitoring mode (S117: No), the CPU 31 executes Figure 10 the relative monitoring process (S125) shown.

[0075] When executing Figure 10 the relative monitoring process shown, the CPU 31 acquires the processing load F from the interference estimation unit 25 (S301). The CPU 31 acquires the reference processing load Fr from the storage device 29 (S303). In this case, the CPU 31 acquires the reference processing load Fr acquired at the same time as the time t shown by the timer 23. The CPU 31 performs LPF processing on the processing load F and the reference processing load Fr with the time constant set in the trial machining process (S305).

[0076] The CPU 31 acquires the slope α by referring to the following formula (1) (S307). The CPU 31 divides the absolute value of the difference between the reference processing load Fr at the previous sampling time t - 1 and the reference processing load Fr at the current sampling time t by the sampling time to calculate the slope α per unit time.

[0077] α = |Fr t - Fr t-1 | ÷ sampling time... Formula (1)

[0078] The CPU 31 corrects the upper limit processing load A set in the trial machining process according to the slope α (S309). Here, the following formula (2) is used in the correction of the upper limit processing load A.

[0079] A' = α × tc When α × tc > A,

[0080] A When α × tc ≤ A... Formula (2)

[0081] Here, A' is the corrected upper limit processing load. α is the slope. tc is the allowable time for deviation. The deviation allowable time tc is a parameter determined according to the deviations of the machine tool 1, the machining object, the cutting tool, etc. Therefore, when the slope α is larger than A, the corrected upper limit processing load A' increases proportionally, and when the slope α is less than or equal to A, the corrected upper limit processing load A' is the same as A before correction (refer to Figure 11 ). Similarly, the CPU 31 corrects the lower limit processing load B (S310). In the correction of the lower limit processing load B, the following formula (3) is used.

[0082] B' = α × tc When α × tc > B,

[0083] B When α × tc ≤ B... Formula (3)

[0084] Here, B’ is the corrected lower limit machining load. α is the slope. tc is the allowable time for deviation.

[0085] The CPU 31 sets the upper limit load Fh (S 311). In this case, in principle, the CPU 31 adds the corrected upper limit machining load A’ to the reference machining load Fr (refer to Figure 7 ). The value obtained by the addition is called the “upper limit load Fh”. The upper limit load Fh is a value based on the reference machining load Fr.

[0086] The CPU 31 sets the lower limit load Fl (S 313). In this case, in principle, the CPU 31 subtracts the corrected lower limit machining load B’ from the reference machining load Fr. The value obtained by the subtraction is called the “lower limit load Fl”. The lower limit load Fl is a value based on the reference machining load Fr.

[0087] As Figure 12 shown, without correcting the upper limit machining load A and the lower limit machining load B, the distances among the reference machining load Fr, the upper limit load Fh, and the lower limit load Fl are close. Therefore, when the machining load F deviates in the time axis direction due to deviations of the machine tool 1, the workpiece, the cutting tool, etc., the CPU 31 is likely to erroneously detect an abnormality of the machining load F. On the other hand, as Figure 13 shown, when the upper limit machining load A and the lower limit machining load B are corrected, that is, when the corrected upper limit machining load A’ and the lower limit machining load B’ are used, the distances between the upper limit load Fh and the lower limit load Fl with respect to the reference machining load Fr increase. Therefore, even if the machining load F deviates in the time axis direction due to deviations of the machine tool 1, the workpiece, the cutting tool, etc., the CPU 31 is less likely to erroneously detect an abnormality of the machining load F. In this way, this correction does not affect the detection ability during a period when the change in the machining load F is small, and is not easily affected by deviations of the machine tool 1, the workpiece, the cutting tool, etc. during a period when the change in the machining load F is large.

[0088] The CPU 31 determines whether the time t shown by the timer 23 has reached the monitoring start time ts (S 315). If it is determined that the time t shown by the timer 23 has not reached the monitoring start time ts (S 315: No), the CPU 31 ends the relative monitoring process and returns the process to the main process.

[0089] If it is determined that the time t shown by the timer 23 has reached the monitoring start time ts (S 315: Yes), the CPU 31 determines whether the time t has reached the monitoring end time te (S 317). If it is determined that the time t shown by the timer 23 has exceeded the monitoring end time te (S 317: No), the CPU 31 ends the relative monitoring process and returns the process to the main process.

[0090] On the other hand, when it is determined that the time t shown by the timer 23 has not reached the monitoring end time te (S317: Yes), the CPU 31 determines whether the acquired machining load F is greater than the upper limit load Fh (S319). When it is determined that the machining load F is below the upper limit load Fh (S319: No), the CPU 31 determines whether the machining load F is lower than the lower limit load Fl (S321). When it is determined that the machining load F is above the lower limit load Fl (S321: No), the CPU 31 ends the relative monitoring process and returns the process to the main process.

[0091] On the other hand, when it is determined that the machining load F is greater than the upper limit load Fh (S319: Yes), that is, when an abnormality occurs in the machining load F, the CPU 31 notifies an alarm exceeding the upper limit load Fh in the same manner as in S213 (S323). The CPU 31 stops the drive of the machine tool 1 (S327). In addition, when it is determined that the machining load F is lower than the lower limit load Fl (S321: Yes), the CPU 31 notifies an alarm lower than the lower limit load Fl in the same manner as in S213 (S325). The CPU 31 stops the drive of the machine tool 1 (S327). The CPU 31 ends the relative monitoring process and returns the process to the main process.

[0092] When the CPU 31 ends the absolute monitoring process or the relative monitoring process, it determines whether the machine tool has stopped (S127). When it is determined that the machine tool has stopped (S127: Yes), the CPU 31 ends the process. When it is determined that the machine tool has not stopped (S127: No), the CPU 31 advances the process to S129.

[0093] On the other hand, in S129, it is determined whether the read code is M30 (S129). When it is determined that the read code is not M30 (S129: No), the CPU 31 increments the time t shown by the timer 23 (S131). The CPU 31 returns the process to S101.

[0094] In this way, the CPU 31 acquires the machining load F at each sampling time from the monitoring start time ts to the monitoring end time te. When it is determined that the M code 340 indicating the acquisition end time has been read (S105: Yes), the monitoring mode is set to OFF (S109). The CPU 31 advances the process to S115.

[0095] On the other hand, when it is determined that the read code is M30 (S129: Yes), the CPU 31 displays the machining load F on the display unit 15 (S133). In the case of the absolute monitoring mode, for example, the display unit 15 only displays Figure 5The machining load F therein. In the case of the relative monitoring mode, the display unit 15 overlays and displays the reference machining load Fr, the upper limit load Fh, and the lower limit load Fl on the machining load F as shown in Figure 7 . In the case of the absolute monitoring mode, when there is a reference machining load Fr, it can also be overlaid and displayed with the machining load F.

[0096] As described above, the CPU 31 reads the M code 341 indicating the acquisition start time of the machining load F during the machining of the workpiece to be machined and the M code 340 indicating the acquisition end time of the machining load F from the commands in the NC program. The CPU 31 acquires the machining load F during the period from reading the M code 341 to reading the M code 340. The CPU 31 performs monitoring based on the acquired machining load F.

[0097] The above numerical control device 30 designates the acquisition start time and the acquisition end time of the machining load F using the M code 341 and the M code 340 of the NC program. Therefore, the numerical control device 30 can monitor the machining load F acquired during the desired period.

[0098] The CPU 31 acquires the reference machining load Fr serving as the monitoring reference during the period from reading the M code 341 to reading the M code 340. The CPU 31 stores the acquired reference machining load Fr. The CPU 31 monitors the acquired machining load F based on the stored reference machining load Fr. The numerical control device 30 can monitor the machining load F based on the reference machining load Fr.

[0099] The CPU 31 sets the monitoring start time ts for starting to monitor the machining load F during the period from reading the M code 341 to reading the M code 340 based on the stored reference machining load Fr. The CPU 31 sets the monitoring end time te for ending the monitoring of the machining load F during the period from reading the M code 341 to reading the M code 340 based on the stored reference machining load Fr. The CPU 31 monitors the acquired machining load F during the period from the set monitoring start time ts to the set monitoring end time te. The numerical control device 30 can perform the monitoring of the machining load F by taking the monitoring from the monitoring start time ts to the monitoring end time te in the acquired machining load F as the required period.

[0100] The CPU 31 sets an upper limit load Fh based on the stored reference machining load Fr. The CPU 31 sets a lower limit load Fl based on the stored reference machining load Fr. The CPU 31 monitors the machining load F according to the set upper limit load Fh and the set lower limit load Fl. The numerical control device 30 can monitor the machining load F based on the upper limit load Fh and the lower limit load Fl based on the reference machining load Fr. For example, the numerical control device 30 can appropriately perform monitoring even when the change in the reference machining load Fr is large.

[0101] When the CPU 31 determines that the obtained machining load F is greater than the set upper limit load Fh, it notifies an abnormality of the machining load F. When the CPU 31 determines that the obtained machining load F is lower than the set lower limit load Fl, it notifies an abnormality of the machining load F. The user of the numerical control device 30 can identify an abnormality of the machining load F.

[0102] The CPU 31 overlays and displays the stored reference machining load Fr, the set upper limit load Fh, the set lower limit load Fl, and the obtained machining load F on the display unit 15. In the numerical control device 30, the user can visually confirm the machining load F.

[0103] The upper limit load Fh is obtained by adding a prescribed offset, i.e., an upper limit machining load A, to the reference machining load Fr. The lower limit load Fl is obtained by subtracting a prescribed offset, i.e., a lower limit machining load B, from the reference machining load Fr. The CPU 31 corrects the set upper limit machining load A according to the change amount of the reference machining load Fr with respect to the sampling time of the reference machining load Fr. The CPU 31 corrects the set lower limit machining load B according to the change amount. The numerical control device 30 can appropriately correct the upper limit machining load A and the lower limit machining load B according to the magnitude of the change amount of the reference machining load Fr.

[0104] The CPU 31 obtains the reference machining load Fr for each tool used in machining the workpiece based on the NC program. The CPU 31 stores the obtained reference machining load Fr for each tool in association with the respective tool. The CPU 31 obtains the machining load F when machining the workpiece with any one of the used tools. The CPU 31 monitors the obtained machining load F based on the reference machining load Fr associated with the current tool among the reference machining loads Fr stored in association with each tool. The numerical control device 30 can monitor the machining load F based on the reference machining load Fr associated with each tool.

[0105] The CPU 31 sets the upper limit value of the machining load F, i.e., the upper limit value Fmax. The CPU 31 sets the lower limit value of the machining load F, i.e., the lower limit value Fmin. The CPU 31 monitors the acquired machining load F based on the set upper limit value Fmax and the set lower limit value Fmin. The numerical control device 30 can monitor the machining load F based on the upper limit value Fmax and the lower limit value Fmin. The numerical control device 30 can monitor the machining load F, for example, for a stable period with little variation in the reference machining load Fr.

[0106] When the CPU 31 determines that the acquired machining load F is greater than the set upper limit value Fmax, it notifies an abnormality of the machining load F. When the CPU 31 determines that the acquired machining load F is lower than the set lower limit value Fmin, it notifies an abnormality of the machining load F. The user of the numerical control device 30 can identify the abnormality of the machining load F.

[0107] In the above description, M code 341 is an example of the first command of the present invention. M code 340 is an example of the second command of the present invention. The slope α is an example of the variation amount of the present invention. The CPU 31 that executes the process of S101 is an example of the reading unit of the present invention. The CPU 31 that executes the processes of S201 and S301 is an example of the first load acquisition unit of the present invention. The CPU 31 that executes the processes of S209, S211, S319, and S321 is an example of the monitoring unit of the present invention. The CPU 31 that executes the process of S3 is an example of the second load acquisition unit of the present invention. The CPU 31 that executes the process of S7 is an example of the storage control unit of the present invention. The CPU 31 that executes the process of S17 is an example of the first setting unit of the present invention. The CPU 31 that executes the process of S19 is an example of the second setting unit of the present invention. The CPU 31 that executes the process of S311 is an example of the third setting unit of the present invention. The CPU 31 that executes the process of S313 is an example of the fourth setting unit of the present invention. The CPU 31 that executes the process of S133 is an example of the display control unit of the present invention. The CPU 31 that executes the process of S309 is an example of the first correction unit of the present invention. The CPU 31 that executes the process of S310 is an example of the second correction unit of the present invention. The CPU 31 that executes the process of S23 is an example of the fifth setting unit of the present invention. The CPU 31 that executes the process of S25 is an example of the sixth setting unit of the present invention. The CPU 31 that executes the process of S323 is an example of the first notification control unit of the present invention. The CPU 31 that executes the process of S325 is an example of the second notification control unit of the present invention. The CPU 31 that executes the process of S213 is an example of the third notification control unit of the present invention. The CPU 31 that executes the process of S215 is an example of the fourth notification control unit of the present invention.

[0108] The present invention is not limited to the above-described embodiments. The machine tool 1 in the above-described embodiment is a vertical machine tool in which the spindle extends in the Z-axis direction. However, the present invention can also be applied to a horizontal machine tool in which the spindle extends in the horizontal direction. In addition, the machine tool 1 can be a table traverse type in which the table moves on the XY plane, or a column traverse type in which the spindle moves on the XY plane.

[0109] In the above-described embodiment, M341 and M340 of the machining program are read during cutting feed, but are not limited thereto. M341 and M340 can also be appropriately specified by the operator.

[0110] In the above-described embodiment, the monitoring start time ts is set to 1000 msec, and the monitoring end time te is set to 2000 msec or 3000 msec, but it is not limited thereto. For example, the monitoring start time ts may also be merged with the time t0, i.e., the machining load acquisition start time. The monitoring start time ts may be appropriately set according to the reference machining load Fr. The same applies to the monitoring end time te.

[0111] In the above-described embodiment, the reference machining load Fr is acquired once, but it is not limited thereto. The reference machining load Fr may also be updated according to the situation.

[0112] In the above-described embodiment, in the absolute monitoring mode, monitoring is performed with the upper limit value Fmax and the lower limit value Fmim, but it is not limited thereto. For example, monitoring may be performed using only either the upper limit value Fmax or the lower limit value Fmin. For example, the CPU 31 may set only the upper limit value of the machining load F, i.e., the upper limit value Fmax. When the CPU 31 determines that the acquired machining load F is greater than the set upper limit value Fmax, it notifies an abnormality of the machining load F. In addition, the CPU 31 may set only the lower limit value of the machining load F, i.e., the lower limit value Fmin. When the CPU 31 determines that the acquired machining load F is lower than the set lower limit value Fmin, it notifies an abnormality of the machining load F. Even in this case, the user of the numerical control device 30 can identify an abnormality of the machining load F. In addition, the machining load F may be monitored by observing the deviation between the reference machining load Fr and the machining load F.

[0113] In the above-described embodiment, in the relative monitoring mode, the upper limit machining load A and the lower limit machining load B are corrected using the slope α, but the correction may not be performed. In order to remove the portion where the slope α is steep, it is only necessary to appropriately set the monitoring start time ts and the monitoring end time te.

[0114] In the above-described embodiment, in the relative monitoring mode, comparison is made with the upper limit load Fh and the lower limit load Fl, but it is not limited thereto. For example, monitoring may be performed using only either the upper limit load Fh or the lower limit load Fl. For example, the CPU 31 may set only the upper limit load Fh based on the stored reference machining load Fr. When the CPU 31 determines that the obtained machining load F is greater than the set upper limit load Fh, it notifies an abnormality of the machining load F. On the other hand, the CPU 31 may set only the lower limit load Fl based on the stored reference machining load Fr. When the CPU 31 determines that the obtained machining load F is lower than the set lower limit load Fl, it notifies an abnormality of the machining load F. Even in such a case, the user of the numerical control device 30 can identify an abnormality of the machining load F. Further, monitoring of the machining load F may be performed by observing the deviation between the reference machining load Fr and the machining load F. For example, as a comparison value, the amount of change of the reference machining load Fr at each sampling time and the amount of change of the machining load F may be compared.

[0115] In the above-described embodiment, in the relative monitoring mode, the upper limit load Fh is calculated by adding the upper limit machining load A as a prescribed offset amount to the reference machining load Fr, and the lower limit load Fl is calculated by subtracting the lower limit machining load B as a prescribed offset amount from the reference machining load Fr, but it is not limited thereto. For example, the upper limit load Fh may also be calculated by multiplying the reference machining load Fr by a prescribed coefficient Ar. Further, the lower limit load Fl may also be calculated by multiplying the reference machining load Fr by a prescribed coefficient Br.

[0116] In the above-described embodiment, in the relative monitoring mode, the reference machining load Fr, the upper limit load Fh, the lower limit load Fl, and the machining load F are overlapped and displayed, but it is not limited thereto. For example, it is sufficient to display at least one of the reference machining load Fr, the upper limit load Fh, the lower limit load Fl, and the machining load F. The displayed waveform can be appropriately set by the operator.

[0117] In the above-described embodiment, the reference machining load Fr is stored in the storage device 29 without being subjected to LPF processing, but it is not limited thereto. The reference machining load Fr may also be stored after being subjected to LPF processing. In this case, for the obtained machining load F, monitoring may also be performed by performing LPF processing using the same time constant.

[0118] Explanation of the reference numerals

[0119] 1: Machine tool

[0120] 15: Display unit

[0121] 29: Storage device

[0122] 30: Numerical control device

[0123] 31: CPU

[0124] M341: M code

[0125] M340: M code

[0126] t s: Monitoring start time

[0127] te: Monitoring end time

[0128] F: Machining load

[0129] Fr: Reference machining load

[0130] A, A’: Upper limit machining load

[0131] B, B’: Lower limit machining load

[0132] Fh: Upper limit load

[0133] Fl: Lower limit load

[0134] Fmax: Upper limit value

[0135] Fmim: Lower limit value

[0136] α: Slope

Claims

1. A numerical control device for controlling a machine tool for machining a workpiece using a tool based on an NC program, comprising: a reading unit configured to read a first command and a second command from among the commands of the NC program, wherein the first command indicates a start time for starting to obtain a machining load in machining the workpiece, and the second command indicates a stop time for ending to obtain the machining load; a first load acquisition unit configured to acquire the processing load during a period from when the reading unit reads the first command to when the reading unit reads the second command; as well as The monitoring unit is configured to perform monitoring based on the machining load acquired by the first load acquisition unit.

2. The numerical control device according to claim 1, characterized in that: Also includes: a second load acquisition unit for acquiring a reference machining load as a monitoring reference during a period from when the reading unit reads the first command to when the reading unit reads the second command; as well as a storage control unit configured to store the reference machining load acquired by the second load acquisition unit, The monitoring unit monitors the machining load acquired by the first load acquisition unit based on the reference machining load stored by the storage control unit.

3. The numerical control device according to claim 2, characterized in that: Also includes: a first setting unit for setting a monitoring start time for starting the monitoring of the machining load by the monitoring unit during a period from reading the first command to reading the second command based on the reference machining load stored in the storage control unit; as well as a second setting unit for setting a monitoring end time for ending the monitoring of the machining load by the monitoring unit during a period from reading the first command to reading the second command based on the reference machining load stored in the storage control unit; The monitoring unit monitors the machining load acquired by the first load acquisition unit during a period from the monitoring start time set by the first setting unit to the monitoring end time set by the second setting unit.

4. The numerical control device according to claim 2, characterized in that: Also includes: a third setting unit for setting an upper limit load based on the reference machining load stored in the storage control unit; as well as a fourth setting unit for setting a lower limit load based on the reference machining load stored in the storage control unit, The monitoring unit monitors the machining load acquired by the first load acquisition unit based on the upper limit load set by the third setting unit and the lower limit load set by the fourth setting unit.

5. The numerical control device according to claim 4, characterized in that: The monitoring unit includes: a first notification control unit configured to notify an abnormality in the machining load when it is determined that the machining load acquired by the first load acquisition unit is greater than the upper limit load set by the third setting unit; and The second notification control unit is configured to notify an abnormality in the machining load when it is determined that the machining load acquired by the first load acquisition unit is lower than the lower limit load set by the fourth setting unit.

6. The numerical control device according to claim 2, characterized in that: further comprising a third setting unit configured to set an upper limit load based on the reference machining load stored in the storage control unit, The monitoring unit includes a first notification control unit configured to notify an abnormality in the machining load when it is determined that the machining load acquired by the first load acquisition unit is greater than the upper limit load set by the third setting unit.

7. The numerical control device according to claim 2, characterized in that: further comprising a fourth setting unit configured to set a lower limit load based on the reference machining load stored in the storage control unit, The monitoring unit includes a second notification control unit configured to notify an abnormality in the machining load when it is determined that the machining load acquired by the first load acquisition unit is lower than the lower limit load set by the fourth setting unit.

8. The numerical control device according to claim 4, characterized in that: It also includes a display control unit, which is used to overlap and display the reference machining load stored by the storage control unit, the upper limit load set by the third setting unit, the lower limit load set by the fourth setting unit, and the machining load obtained by the first load obtaining unit on a display unit.

9. The numerical control device according to claim 4, characterized in that: The upper limit load is obtained by adding the upper limit load as a predetermined offset to the reference machining load. The lower limit load is obtained by subtracting the lower limit machining load as a predetermined offset amount from the reference machining load. The numerical control device also includes: a first correction unit configured to correct the upper limit machining load based on a change amount of the reference machining load relative to a sampling time of the reference machining load; and a second correction unit configured to correct the lower limit machining load based on the change amount; The third setting unit sets a value obtained by adding the corrected upper limit machining load to the reference machining load as the upper limit load, The fourth setting unit sets a value obtained by subtracting the corrected lower limit machining load from the reference machining load as the lower limit load.

10. The numerical control device according to claim 2, characterized in that: The second load acquisition unit acquires the reference machining load for each of the tools used in machining the workpiece based on the NC program. The storage control unit stores the reference machining load acquired by the second load acquisition unit for each of the tools in association with the corresponding tool. The first load acquisition unit acquires the machining load when the workpiece is machined using any specific one of the tools. The monitoring unit monitors the machining load acquired by the first load acquisition unit based on the reference machining load associated with the specific tool among the reference machining loads stored by the storage control unit in association with each tool.

11. The numerical control device according to claim 1 or 3, characterized in that: Also includes: a fifth setting unit, configured to set an upper limit value, wherein the upper limit value is an upper limit value of the machining load; as well as a sixth setting unit, configured to set a lower limit value, wherein the lower limit value is a lower limit value of the machining load, The monitoring unit monitors the machining load acquired by the first load acquisition unit based on the upper limit value set by the fifth setting unit and the lower limit value set by the sixth setting unit.

12. The numerical control device according to claim 11, characterized in that: The monitoring unit includes: a third notification control unit configured to notify an abnormality in the machining load when it is determined that the machining load acquired by the first load acquisition unit is greater than the upper limit value set by the fifth setting unit; and The fourth notification control unit is configured to notify an abnormality in the machining load when it is determined that the machining load acquired by the first load acquisition unit is lower than the lower limit value set by the sixth setting unit.

13. The numerical control device according to claim 1 or 3, characterized in that: The system further includes a fifth setting unit configured to set an upper limit value, wherein the upper limit value is an upper limit value of the machining load. The monitoring unit includes a third notification control unit configured to notify an abnormality in the machining load when it is determined that the machining load acquired by the first load acquisition unit is greater than the upper limit value set by the fifth setting unit.

14. The numerical control device according to claim 1 or 3, characterized in that: The system further includes a sixth setting unit configured to set a lower limit value, wherein the lower limit value is a lower limit value of the machining load. The monitoring unit includes a fourth notification control unit configured to notify an abnormality in the machining load when it is determined that the machining load acquired by the first load acquisition unit is lower than the lower limit value set by the sixth setting unit.

15. A machine tool for machining a workpiece using a tool based on an NC program, comprising: a reading unit configured to read a first command and a second command from among the commands of the NC program, wherein the first command indicates a start time for starting to obtain a machining load in machining the workpiece, and the second command indicates a stop time for ending to obtain the machining load; a first load acquisition unit configured to acquire the processing load during a period from when the reading unit reads the first command to when the reading unit reads the second command; as well as The monitoring unit is configured to perform monitoring based on the machining load acquired by the first load acquisition unit.

16. A control method for a numerical control device, the numerical control device being used to control a machine tool for processing a workpiece using a tool based on an NC program, the control method comprising: A reading step for reading a first command and a second command from among the commands of the NC program, wherein the first command indicates a start time for starting to obtain a machining load in machining the workpiece, and the second command indicates a finish time for finishing obtaining the machining load; A first load acquisition step for acquiring the processing load during a period from when the first command is read in the reading step to when the second command is read in the reading step; as well as A monitoring step is for performing monitoring based on the machining load acquired in the first load acquisition step.

17. A storage medium storing a program for causing a computer of a numerical control device to execute the following steps, wherein the numerical control device is used to control a machine tool for processing a workpiece using a tool based on an NC program, the steps comprising: A reading step for reading a first command and a second command from among the commands of the NC program, wherein the first command indicates a start time for starting to obtain a machining load in machining the workpiece, and the second command indicates a finish time for finishing obtaining the machining load; A first load acquisition step for acquiring the processing load during a period from when the first command is read in the reading step to when the second command is read in the reading step; as well as A monitoring step is for performing monitoring based on the machining load acquired in the first load acquisition step.

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