Numerical control device and control method for numerical control device

Abstract

To provide a numerical control device capable of temporarily continuing the operation of a machine tool even if there is an increase in leak current, and a method of controlling a numerical control device.SOLUTION: A numerical control device comprises an air cylinder that performs driving based on a drive signal, a proximity sensor that detects that the air cylinder performed driving, and a CPU that determines a driving situation of the air cylinder based on a relationship between an output voltage V and a threshold Vth (S3) so that the CPU, when determined that the air cylinder has not performed driving after an output of a drive signal, reduces the level of output voltage V so as to be lower than a threshold Vth (S23).SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a numerical control device and a control method for a numerical control device. [Background technology]

[0002] Patent Document 1 discloses a door opening and closing device and a machine tool. The door opening and closing device moves along a travel axis. The door opening and closing device is equipped with a proximity sensor. The proximity sensor detects a position detection dog provided on the door of the machine tool. When the proximity sensor detects the position detection dog, the door opening and closing device drives a coupling mechanism to couple with the door. In this state, the door of the machine tool opens and closes as the door opening and closing device moves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-032506 Summary of the Invention [Problem to be solved by the invention]

[0004] Even when the proximity sensor is off, a small amount of current flows through it as leakage current. When the proximity sensor deteriorates due to factors such as coolant, the leakage current increases. In this case, the proximity sensor is no longer able to properly detect the position detection dog. This can lead to the door opening / closing device being unable to connect to the machine tool door, making it impossible to open or close the door.

[0005] An object of the present invention is to provide a numerical control device and a control method for a numerical control device that can temporarily continue the operation of a machine tool even when leakage current increases. [Means for solving the problem]

[0006] The numerical control device of claim 1 is a numerical control device for a machine tool that includes a drive signal output unit that outputs a drive signal, a drive mechanism that drives based on the drive signal, and a detection unit that detects that the drive mechanism has driven, wherein the detection unit outputs an electrical signal when it detects that the drive mechanism is being driven, and includes a judgment unit that judges the driving status of the drive mechanism based on the relationship between the electrical signal output by the detection unit and a threshold value, and a signal control unit that reduces the level of the electrical signal to below the threshold value when the judgment unit judges that the drive mechanism is not being driven after the drive signal output unit outputs the drive signal.

[0007] If the numerical controller determines that the drive mechanism is not operating after outputting the drive signal, it reduces the level of the electrical signal to a value lower than the threshold value. This allows the numerical controller to recognize that the drive mechanism is operating. Therefore, the numerical controller does not need to recognize a malfunction and stop the machine tool. Therefore, the numerical controller can temporarily continue operating the machine tool even if the leakage current increases.

[0008] In the numerical control device of claim 2, the signal control unit may include a resistor having a predetermined resistance value and a transistor connected in series to the resistor, and the level of the electrical signal may be reduced to below the threshold by turning on the transistor. The numerical control device can reduce the level of the electrical signal to below the threshold by simply turning on the transistor.

[0009] The numerical control device of claim 3 may further include a notification unit that notifies a user of an abnormality in the detection unit when the determination unit determines that the drive mechanism is not operating after the drive signal output unit outputs the drive signal that drives the drive mechanism. By notifying a user of an abnormality in the detection unit, the numerical control device can urge the user to replace the detection unit.

[0010] In the numerical control device of claim 4, the detection unit may be a proximity sensor. The numerical control device can temporarily continue the operation of the machine tool even if the leakage current of the proximity sensor increases.

[0011] In the numerical control device of claim 5, the drive mechanism may be an air cylinder. The numerical control device can temporarily continue driving the air cylinder 17 even if the leakage current of the proximity sensor increases.

[0012] In the numerical control device of claim 6, the signal control unit may reduce the level of the electric signal below the threshold when the determination unit determines that the drive mechanism is not operating after a predetermined time has elapsed after the drive signal output unit outputs the drive signal. The numerical control device can detect an abnormality in the detection unit when it determines that the drive mechanism is not operating after a predetermined time has elapsed after the drive signal output unit outputs the drive signal.

[0013] The control method for a numerical control device of claim 7 is a control method for a numerical control device of a machine tool having a drive signal output unit that outputs a drive signal, a drive mechanism that drives based on the drive signal, and a detection unit that detects that the drive mechanism has driven, wherein the detection unit outputs an electrical signal when it detects that the drive mechanism is being driven, and the control method further comprises a judgment step that judges the driving status of the drive mechanism based on the relationship between the electrical signal output by the detection unit and a threshold value, and a signal control step that reduces the level of the electrical signal to below the threshold value when the judgment step judges that the drive mechanism is not being driven after the drive signal output unit outputs the drive signal.

[0014] The numerical control device achieves the same effect as in claim 1 by performing control using the above control method. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the machine tool 1. [Figure 3] FIG. [Figure 4] 3A and 3B are diagrams showing a state in which the air cylinder 17 is not driven and a state in which the air cylinder 17 is driven. [Figure 5]1 is a diagram showing the relationship between a drive signal S, an output current I, and an output voltage V. FIG. [Figure 6] 1 is a diagram showing the relationship between the drive signal S, the output current I, and the output voltage V when the leakage current increases. [Figure 7] 1 is a flowchart of the main process. DETAILED DESCRIPTION OF THE INVENTION

[0016] A machine tool 1 according to the present invention will be described with reference to Figures 1 and 2. The upper, lower, left, right, front, and rear sides of Figure 1 are defined as the upper, lower, left, right, front, and rear sides of the machine tool 1, respectively. The left-right direction, front-rear direction, and up-down direction of the machine tool 1 are the X-axis direction, Y-axis direction, and Z-axis direction of the machine tool 1, respectively.

[0017] The machine tool 1 is a vertical machine tool with a main spindle (not shown) extending in the Z-axis direction. The machine tool 1 comprises a base 2, a machine body 3, a cover 5, a display 15, an operation unit 24, and a proximity sensor 23. The base 2 is an iron base. The machine body 3 is provided on top of the base 2. The machine body 3 performs cutting processes on a workpiece (not shown) fixed to the top surface of a table (not shown). The table is rotatably installed on the top surface of the base 2. The cover 5 is fixed to the top of the base 2 and surrounds the machine body 3.

[0018] Display unit 15 is provided on the front of cover 5 and displays a setting screen for making various settings. Operation unit 24 is provided on the front of cover 5 and can input settings for various operations into machine tool 1. The user operates operation unit 24 while checking display unit 15, and sets various operations of machine tool 1, processing conditions for workpieces, etc.

[0019] When setting the machining conditions for a workpiece and cutting the workpiece, the table is fixed so that it cannot rotate by a clamping mechanism (not shown). The drive mechanism for the clamping mechanism includes, for example, an air cylinder 17. When the air cylinder 17 is driven, the table cannot rotate. When the air cylinder 17 is not driven, the table can rotate.

[0020] The proximity sensor 23 is fixed inside the machine tool 1 and in the vicinity of the air cylinder 17. The proximity sensor 23 detects the driving status of the air cylinder 17. The proximity sensor 23 is, for example, an induction type or a capacitance type sensor.

[0021] The electrical configuration of machine tool 1 will be described with reference to Fig. 2. As shown in Fig. 2, machine tool 1 includes numerical control device 29, display unit 15, operation unit 24, drive circuits 201-205, X-axis motor 51, Y-axis motor 52, Z-axis motor 53, spindle motor 54, magazine motor 55, air cylinder 17, and proximity sensor 23.

[0022] The numerical control device 29 comprises a CPU 31, a ROM 32, a RAM 33, a control circuit 41, and interfaces 34 and 35. The CPU 31 controls the machine tool 1. The ROM 32 stores a program that performs main processing, which will be described later. The RAM 33 temporarily stores various data. The control circuit 41 will be described later.

[0023] Display unit 15 and operation unit 24 are connected to CPU 31 via interface 34. CPU 31 is connected to drive circuits 201-205 via interface 35. Drive circuits 201-205 are connected to control targets: X-axis motor 51, Y-axis motor 52, Z-axis motor 53, spindle motor 54, and magazine motor 55. X-axis motor 51, Y-axis motor 52, Z-axis motor 53, spindle motor 54, and magazine motor 55 are equipped with encoders 51a-55a.

[0024] Encoders 51a to 55a detect the rotational positions and the like of the drive shafts of X-axis motor 51, Y-axis motor 52, Z-axis motor 53, spindle motor 54, and magazine motor 55, and output the detection results to drive circuits 201 to 205. CPU 31 can detect the X-, Y-, and Z-axis coordinate values ​​of X-axis motor 51, Y-axis motor 52, and Z-axis motor 53 based on the detection results of the rotational positions of encoders 51a to 53a by drive circuits 201 to 203. The X-, Y-, and Z-axis coordinate values ​​are position information of the spindle.

[0025] The control circuit 41 is connected to the air cylinder 17 and the proximity sensor 23. The control circuit 41 controls, for example, an air valve (not shown) to drive the air cylinder 17. The proximity sensor 23 outputs the detection result of the drive state of the air cylinder 17 to the control circuit 41.

[0026] The control circuit 41 of the numerical control device 29 will be described with reference to FIG. 3. The control circuit 41 converts the output current I of the proximity sensor 23 into an output voltage V. The control circuit 41 includes an FPGA 45, a power supply IC 38, resistors R1 and R2, and a transistor Tr. The FPGA 45 controls the control circuit 41 under the control of the CPU 31. For example, the FPGA 45 controls an air valve (not shown) to drive the air cylinder 17. The power supply IC 38 is connected to the proximity sensor 23 via a wire L1. The power supply IC 38 supplies a DC voltage of 24 V to the proximity sensor 23. The proximity sensor 23 is connected to the FPGA 45 via a wire L2.

[0027] One end of resistor R1 is connected to wiring L2 and the other end is connected to ground GND. Resistor R1 has a predetermined resistance value. The predetermined resistance value is, for example, 4.4 kΩ. Resistor R2 has one end connected to wiring L2 and the other end connected to the collector of transistor Tr. Resistor R2 has a predetermined resistance value. The predetermined resistance value is, for example, 1.1 kΩ. The emitter of transistor Tr is connected to ground GND. In other words, transistor Tr is connected in series to resistor R2. The base of transistor Tr is connected to FPGA 45. The on / off of transistor Tr is controlled by FPGA 45.

[0028] Normally, the transistor Tr is off. When the transistor Tr is off, the resistor R1 converts the output current I of the proximity sensor 23 into an output voltage V. On the other hand, when the transistor Tr is on, the resistors R1 and R2 convert the output current I of the proximity sensor 23 into an output voltage V.

[0029] 4 and 5, the relationship between the driving state of the air cylinder 17 and the output current I and output voltage V of the proximity sensor 23 will be described. In the following description, it is assumed that the transistor Tr is in an off state.

[0030] When the drive signal S is low (see FIG. 5(A)), the air cylinder 17 is not driven (see FIG. 4(A)). In this case, the proximity sensor 23 is in an ON state. The proximity sensor 23 outputs an output current I of, for example, 5.6 mA (see FIG. 5(B)). The resistor R1 converts the output current I of 5.6 mA into an output voltage V of 24.6 V (see FIG. 5(C)). Therefore, the FPGA 45 detects a voltage of 24.6 V. The FPGA 45 transmits the detection result to the CPU 31.

[0031] When the drive signal S is high (see FIG. 5A), the air cylinder 17 is in a driven state (see FIG. 4B). In this case, the proximity sensor 23 turns off after a predetermined time t1 has elapsed since the rising edge of the drive signal S. The predetermined time t1 is, for example, 500 msec. In this case, the proximity sensor 23 outputs a current equal to the leakage current as the output current I. The leakage current is, for example, 0.8 mA (see FIG. 5B). The resistor R1 converts the 0.8 mA leakage current into a 3.5 V output voltage V (see FIG. 5C). Therefore, the FPGA 45 detects a voltage of 3.5 V. The FPGA 45 transmits the detection result to the CPU 31.

[0032] Here, the CPU 31 compares the level of the output voltage V transmitted by the FPGA 45 with a threshold value Vth. The threshold value Vth is, for example, 12 V. When the air cylinder 17 is not being driven (see FIG. 4(A)), the level of the output voltage V (24.6 V) is equal to or greater than the threshold value Vth (12 V). In this case, the CPU 31 determines that the air cylinder 17 is not being driven.

[0033] On the other hand, when the air cylinder 17 is driven (see FIG. 4B), the level of the output voltage V (3.5 V) is less than the threshold value Vth (12 V). In this case, the CPU 31 determines that the air cylinder 17 is in a driven state. In this way, the CPU 31 detects the driving state of the air cylinder 17 based on the detection result of the proximity sensor 23.

[0034] A case where the leakage current of the proximity sensor 23 increases will be described with reference to Figure 6. For example, since the proximity sensor 23 is used inside the machine tool 1, it may deteriorate due to the influence of coolant, etc. In this case, the leakage current from the proximity sensor 23 increases (see arrow A1 in Figure 6(B)). The leakage current increases from 0.8 mA to 5.0 mA, for example.

[0035] When the drive signal S is low (see FIG. 6(A)), the air cylinder 17 is not driven. In this case, as in the case shown in FIG. 5, the output current I of the proximity sensor 23 is 5.6 mA (see FIG. 6(B)). Therefore, the level of the output voltage V is 24.6 V (see FIG. 6(C)).

[0036] Here, when the drive signal S is switched from low to high to drive the air cylinder 17, the proximity sensor 23 outputs a leakage current of 5.0 mA after a predetermined time t1 has elapsed since the rising edge of the drive signal S. The resistor R1 converts the leakage current (5.0 mA) of the proximity sensor 23 into an output voltage V level of 22 V (see FIG. 6(C)). The FPGA 45 transmits the detection result to the CPU 31.

[0037] In this case, the level of the output voltage V is 22 V, which is equal to or greater than the threshold value Vth (12 V). Therefore, the CPU 31 determines that the air cylinder 17 is not being driven, even after the drive signal S has been output. In this case, the CPU 31 recognizes that an abnormality has occurred in the machine tool 1, and stops the operation of the machine tool 1.

[0038] To avoid this situation, the CPU 31 controls the FPGA 45 to turn on the transistor Tr. In this case, the resistor R2 is connected in parallel to the resistor R1. As a result, the combined resistance value of the resistors R1 and R2 becomes 0.88 kΩ.

[0039] Because the leakage current is 5.0 mA, the level of the output voltage V converted by resistors R1 and R2 becomes 4.4 V (see FIG. 6(D)). That is, by turning on transistor Tr, the level of output voltage V changes from 22 V to 4.4 V, which becomes less than threshold value Vth (see arrow A2 in FIG. 6(D)). In this case, CPU 31 determines that air cylinder 17 has been driven. That is, CPU 31 can avoid determining that air cylinder 17 is not being driven even after drive signal S has been output. This eliminates the need for CPU 31 to stop machine tool 1.

[0040] The main processing will be described with reference to Figure 7. When the user turns on the power, the CPU 31 reads and executes a program stored in the ROM 32. When the program is executed, the CPU 31 executes the main processing. Note that, in the initial setting, the transistor Tr is in the off state.

[0041] The CPU 31 determines whether or not it has received a drive signal S for driving the air cylinder 17 (S1). If it determines that it has not received the drive signal S (S1: NO), the CPU 31 returns the process to S1 and waits. If it determines that it has received the drive signal S (S1: YES), the CPU 31 determines whether or not the level of the output voltage V is equal to or greater than the threshold value Vth (S3). If it determines that the level of the output voltage V is equal to or greater than the threshold value Vth (S3: YES), the CPU 31 detects that the air cylinder 17 is not being driven (see FIG. 4A) (S5). The CPU 31 proceeds to S9.

[0042] If it is determined that the level of the output voltage V is less than the threshold value Vth (S3: NO), the CPU 31 detects that the air cylinder 17 is in a driven state (see FIG. 4B) (S7). The CPU 31 proceeds to S9.

[0043] In the process of S9, the CPU 31 determines whether the proximity sensor 23 was activated within a predetermined time t1 (S9). If it is determined that the proximity sensor 23 was activated within the predetermined time t1 (S9: YES), the CPU 31 returns the process to S1. If it is determined that the proximity sensor 23 was not activated within the predetermined time t1 (S9: NO), the CPU 31 determines that an abnormality has occurred around the air cylinder 17 and stops the machine tool 1 (S11). The CPU 31 notifies the user that a malfunction has occurred around the air cylinder 17 (S13). In this case, the CPU 31 displays, for example, "There is an abnormality around the air cylinder" on the display unit 15. Therefore, the user checks whether there is an abnormality around the air cylinder 17. If there is a malfunction around the air cylinder 17, the user resolves the malfunction by, for example, servicing the machine tool 1.

[0044] The CPU 31 determines whether or not there was a malfunction in the vicinity of the air cylinder 17 (S15). If there is a malfunction in the machinery around the air cylinder 17, the user operates the operation unit 24 to input to the CPU 31 that there was a malfunction in the machinery around the air cylinder 17 (S15: YES). Since the malfunction has been resolved by the user, the CPU 31 returns the process to S1.

[0045] On the other hand, if the user operates the operation unit 24 to input that there is no malfunction in the vicinity of the air cylinder 17 (S15: NO), the CPU 31 determines whether the number of times that the proximity sensor 23 has not been activated within a predetermined time t1 after the output of the drive signal S is less than a specified number of times (S17). The specified number of times is, for example, three times. The number of times that the proximity sensor 23 has not been activated is stored in the RAM 33.

[0046] If it is determined that the number of times that the proximity sensor 23 has not been activated within the predetermined time t1 is less than the specified number of times (S17: YES), the CPU 31 determines that there is no abnormality in the proximity sensor 23, and cancels the stop of the machine tool 1 performed in S11 (S19).The CPU 31 returns the process to S1.

[0047] On the other hand, if it is determined that the number of times that the proximity sensor 23 has not been actuated within the predetermined time t1 is equal to or greater than the specified number of times (S17: NO), the CPU 31 notifies the user of a sensor abnormality in the proximity sensor 23 (S21). That is, if the CPU 31 determines that the air cylinder 17 is not actuated after outputting the drive signal S that drives the air cylinder 17, it notifies the user of a sensor abnormality in the proximity sensor 23. The sensor abnormality is, for example, an increase in leakage current due to deterioration. For example, the CPU 31 displays on the display unit 15, "The proximity sensor 23 has deteriorated; please replace it." This allows the user to, for example, request a replacement of the proximity sensor 23 from the manufacturer.

[0048] Thereafter, the CPU 31 controls the FPGA 45 to turn on the transistor Tr (S23). This reduces the resistance value of the control circuit 41 from 4.4 kΩ to 0.88 kΩ. Therefore, the level of the output voltage V becomes less than the threshold value Vth, for example, 4.4 V. That is, if the CPU 31 determines that the air cylinder 17 is not being driven after the drive signal S is output and a predetermined time t1 has elapsed, the CPU 31 reduces the level of the output voltage V to less than the threshold value Vth (see arrow A2 in FIG. 6(D)). This allows the CPU 31 to recognize that the air cylinder 17 has been driven after the drive signal S is output.

[0049] Since there is no longer any need to continue stopping machine tool 1, CPU 31 cancels the stop of machine tool 1 that was stopped in the processing of S11 (S25). Therefore, the user can provisionally use machine tool 1 until proximity sensor 23 is replaced. CPU 31 returns the processing to S1.

[0050] As described above, when the CPU 31 determines that the air cylinder 17 is not being driven after outputting the drive signal S, it reduces the level of the output voltage V to below the threshold value Vth.

[0051] This allows the numerical control device 29 to recognize that the air cylinder 17 is in operation. Therefore, the numerical control device 29 does not need to recognize a malfunction and stop the machine tool 1. Therefore, the numerical control device 29 can temporarily continue the operation of the machine tool 1 even if the leakage current increases.

[0052] The control circuit 41 includes a resistor R2 having a predetermined resistance value and a transistor Tr connected in series to the resistor R2. The CPU 31 turns on the transistor Tr to reduce the level of the output voltage V to less than the threshold value Vth. The numerical control device 29 can reduce the level of the output voltage V to less than the threshold value Vth simply by turning on the transistor Tr.

[0053] If the CPU 31 determines that the air cylinder 17 is not being driven after outputting the drive signal S that drives the air cylinder 17, the CPU 31 notifies the user of an abnormality in the proximity sensor 23. By notifying the user of an abnormality in the proximity sensor 23, the numerical control device 29 can urge the user to replace the proximity sensor 23.

[0054] Machine tool 1 is equipped with proximity sensor 23. Numerical control device 29 can temporarily continue the operation of machine tool 1 even if the leakage current of proximity sensor 23 increases.

[0055] The driving mechanism is an air cylinder 17. The numerical control device 29 can temporarily continue driving the air cylinder 17 even if the leakage current of the proximity sensor 23 increases.

[0056] If the CPU 31 determines that the air cylinder 17 is not being driven after the drive signal S is output and the predetermined time t1 has elapsed, the CPU 31 reduces the level of the output voltage V to below the threshold value Vth. If the CPU 31 determines that the air cylinder 17 is not being driven after the drive signal S is output and the predetermined time t1 has elapsed, the numerical control device 29 can detect an abnormality in the proximity sensor 23.

[0057] In the above description, CPU 31 is an example of a "drive signal output unit" of the present invention. Air cylinder 17 is an example of a "drive mechanism" of the present invention. Proximity sensor 23 is an example of a "detection unit" of the present invention. Output voltage V is an example of an "electrical signal" of the present invention. Resistor R2 is an example of a "resistance" of the present invention. 1.1 kΩ of resistor R2 is an example of a "predetermined resistance value" of the present invention. CPU 31 that processes S3 is an example of a "determination unit" of the present invention. CPU 31 that processes S23 is an example of a "signal control unit" of the present invention. CPU 31 that processes S21 is an example of an "alert unit" of the present invention.

[0058] The present invention is not limited to the above embodiment and can be modified in various ways. The machine tool 1 in the above embodiment is a vertical machine tool whose main spindle extends in the Z-axis direction, but the present invention can also be applied to a horizontal machine tool whose main spindle extends horizontally.

[0059] The drive mechanism is the air cylinder 17 inside the machine tool 1, but is not limited to this. The drive mechanism may also be provided outside the machine tool 1. The air cylinder 17 may be a hydraulic cylinder. The drive mechanism may also be another mechanism of the machine tool 1 other than the clamp mechanism. A sensor for detecting the drive of the other mechanism may be used.

[0060] The proximity sensor 23 may be a semiconductor sensor other than a proximity sensor. For example, a photoelectric sensor, a reflective sensor, a transmission sensor, or the like may be used depending on the mechanism to be detected.

[0061] The output current I of the proximity sensor 23 is 5.6 mA and 0.8 mA, but is not limited to these. The output current I may be changed depending on the specifications of the proximity sensor 23. Resistors R1 and R2 of the control circuit 41 may be changed accordingly.

[0062] The leakage current when the proximity sensor 23 is deteriorated is 5.0 mA, but this is not limited to this. If the leakage current changes in accordance with the degree of deterioration, the values ​​of the resistors R1 and R2 may be changed appropriately.

[0063] The control circuit 41 is configured with resistors R1 and R2 and a transistor Tr, but is not limited to this. For example, a variable resistor may be used instead of these components. The resistance value of the variable resistor may be changed by the CPU 31 or the FPGA 45.

[0064] Although the control circuit 41 converts the output current I into the output voltage V, this is not limiting. For example, the control circuit 41 may directly detect the current of the proximity sensor 23. In this case, the threshold may be set to, for example, 3 mA. The threshold Vth was set to 12 V, but this may be changed as appropriate.

[0065] Although the proximity sensor 23 outputs an output current I of 5.6 mA when the air cylinder 17 is not driven and an output current I of 0.8 mA when the air cylinder 17 is driven, this is not limited to this. For example, the output current I of the proximity sensor 23 may be 0.8 mA when the air cylinder 17 is not driven and 5.6 mA when the air cylinder 17 is driven. In this case, the CPU 31 detects that the air cylinder 17 is driven when the output voltage V is equal to or greater than the threshold value Vth, and detects that the air cylinder 17 is not driven when the output voltage V is less than the threshold value Vth.

[0066] The specified number of times is three in the above example, but is not limited to this. The specified number of times may be changed as appropriate. For example, the user may operate the operation unit 24 to set a desired specified number of times.

[0067] Although an abnormality in proximity sensor 23 is notified by displaying it on display unit 15 of machine tool 1, it may be notified by other methods. For example, CPU 31 may notify an alarm by turning on an LED for error notification, sounding a buzzer, or displaying it on a teaching pendant or the like. [Explanation of symbols]

[0068] 1 Machine tools 17 Air cylinder 23 Proximity Sensor 29 Numerical Control Device 31 CPU 32 ROM 33 RAM 41 Control circuit S drive signal I Output current V output voltage Vth threshold R1, R2 resistance Tr transistor t1 specified time

Claims

1. a drive signal output unit that outputs a drive signal; a drive mechanism that is driven based on the drive signal; a detection unit that detects that the drive mechanism has been driven; In a numerical control device for a machine tool, the detection unit outputs an electrical signal when detecting the driving of the drive mechanism; a first determination unit that determines that the drive mechanism is not operating when the electrical signal output by the detection unit is equal to or greater than a threshold, and that the drive mechanism is operating when the electrical signal output by the detection unit is less than the threshold; a second determination unit that determines whether the drive mechanism has a malfunction based on a user's input when the first determination unit determines that the drive mechanism is not operating after the drive signal output unit outputs the drive signal; a signal control unit that reduces the level of the electrical signal to below the threshold value when the second determination unit determines that there is no malfunction in the drive mechanism; A numerical control device comprising:

2. The signal control unit a resistor having a predetermined resistance value; a transistor connected in series to the resistor; Equipped with 2. The numerical control device according to claim 1, wherein the level of the electrical signal is reduced below the threshold value by turning on the transistor.

3. a notification unit that notifies the abnormality of the detection unit when the second determination unit determines that there is no abnormality in the drive mechanism; 3. The numerical control device according to claim 1, further comprising:

4. 4. The numerical control device according to claim 1, wherein the detection unit is a proximity sensor.

5. 5. The numerical control device according to claim 1, wherein the drive mechanism is an air cylinder.

6. A numerical control device as described in any one of claims 1 to 5, characterized in that the second judgment unit judges whether there is a malfunction in the drive mechanism when the first judgment unit judges that the drive mechanism is not operating after the drive signal output unit outputs the drive signal and a predetermined time has elapsed.

7. a drive signal output unit that outputs a drive signal; a drive mechanism that is driven based on the drive signal; a detection unit that detects that the drive mechanism has been driven; A control method for a numerical control device for a machine tool, comprising: the detection unit outputs an electrical signal when detecting the driving of the drive mechanism; a first determination step of determining that the drive mechanism is not operating when the electrical signal output by the detection unit is equal to or greater than a threshold value, and determining that the drive mechanism is operating when the electrical signal output by the detection unit is less than the threshold value; a second determination step of determining whether the drive mechanism is malfunctioning based on a user's input when the first determination step determines that the drive mechanism is not operating after the drive signal output unit outputs the drive signal; a signal control step of reducing the level of the electrical signal to below the threshold value when it is determined in the second determination step that there is no malfunction in the drive mechanism; A control method for a numerical control device comprising:

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