JP7010261B2 - Numerical control device and control method - Google Patents

Description

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

Patent Document 1 discloses a method of monitoring a cutting load based on a load current value of a servomotor or a spindle motor of a feed shaft of a cutting machine. In this method, in order not to be affected by the torque due to acceleration / deceleration, the value obtained by subtracting the current value required for acceleration / deceleration of the motor from the detected value of the motor current is corrected and calculated, and the corrected current value is used as the cutting load. To be monitored by.

Japanese Unexamined Patent Publication No. 7-24694

The load current value required for acceleration / deceleration of the motor changes depending on various factors such as aging of the machine, temperature, load weight, and the like. Therefore, in the method described in Patent Document 1, it is difficult to completely remove the current value required for acceleration / deceleration from the detected value of the motor current, and an error may occur.

An object of the present invention is to provide a numerical control device and a control method capable of accurately monitoring the machining load of a spindle motor.

The numerical control device according to claim 1 is a numerical control device capable of monitoring the machining load in the machining of the work material based on the load current value of the spindle motor of the machine tool, from the start of rotation of the spindle motor in the machining. The measuring unit that measures the load current value during the drive period until the rotation stops, the machining load calculation unit that calculates the machining load based on the load current value measured by the measurement unit, and the machining load calculation unit calculate. A determination unit for determining whether the machining load is equal to or greater than the threshold value and an output unit for outputting an alarm when the determination unit determines that the machining load is equal to or greater than the threshold value are provided. The processing load calculation unit includes an acceleration section for accelerating to a constant speed and a deceleration section for decelerating and stopping the spindle motor from the constant speed, and the machining load calculation unit has the constant speed between the acceleration section and the deceleration section. When the constant speed section determination unit for determining whether or not there is a constant speed section which is a section and the constant speed section determination unit determine that the constant speed section exists between the acceleration section and the deceleration section. The first calculation unit that calculates the peak value of the load current value in the constant speed section as the machining load and the constant speed section determination unit do not have the constant speed section between the acceleration section and the deceleration section. When it is determined that the processing load is determined to be, it is characterized by including a second calculation unit that calculates the average value of the load current values in the drive period as the machining load. When there is a constant speed section between the acceleration section and the deceleration section, the numerical control device calculates the peak value of the load current value in the constant speed section as the machining load. Therefore, the numerical control device can monitor the machining load without being affected by the torque due to acceleration / deceleration. Both a momentary change in the machining load generated in a constant speed section and a gradual change in the machining load can be detected. For example, when there is no constant speed section between the acceleration section and the deceleration section as in short tap machining, the numerical control device calculates the average value of the load current values in the drive period as the machining load. The load current value corresponds to the torque of the spindle motor. By calculating the average value of the load current values during the drive period, the acceleration torque and the deceleration torque cancel each other out, so that the numerical control device can monitor the machining torque. Therefore, the numerical control device can accurately monitor the machining load regardless of whether or not there is a constant speed section in the drive period of cutting. "There is no constant speed section" means not only that there is no constant speed section between the acceleration section and the deceleration section, but also that the ratio of the constant speed section to the drive period is small and the constant speed section is short. good.

The constant speed section determination unit of the numerical control device according to claim 2 includes an acceleration / deceleration section calculation unit that calculates an acceleration / deceleration distance or an acceleration / deceleration time required for the acceleration section and the deceleration section, and a distance required for the drive period. Alternatively, the ratio determination unit for determining whether or not the ratio of the acceleration / deceleration distance or the acceleration / deceleration time calculated by the acceleration / deceleration section calculation unit to the time is equal to or less than a predetermined value is provided, and the ratio determination unit determines the ratio. If it is determined that there is a constant speed section or less, and if the ratio determination unit determines that the ratio exceeds the predetermined value, it may be determined that there is no constant speed section. The numerical control device determines the presence or absence of a constant speed section based on whether or not the ratio of the acceleration / deceleration distance or the acceleration / deceleration time to the distance or time required for the drive period is equal to or less than a predetermined value. Since the numerical control device can determine the presence or absence of the constant speed section based on the length of the constant speed section, the machining load calculation method can be appropriately selected.

The cutting process of the numerical control device according to claim 3 is tap processing, and is among three feed motors capable of moving the spindle of the machine tool in three axial directions relatively orthogonal to the work material. A torque monitoring unit for monitoring the torque of a moving motor that moves the spindle toward the work material during tapping is provided, and the constant speed section determination unit is provided with the moving motor starting to drive and monitoring the torque. When the torque monitored by the unit exceeds a certain value, an acceleration completion determination unit for determining whether or not the acceleration section is completed is provided, and the acceleration completion determination unit determines that the acceleration section is completed. In this case, if it is determined that the constant speed section exists and the acceleration completion determination unit determines that the acceleration section has not been completed, it may be determined that the constant speed section does not exist. Cutting is tapping. The numerical control device monitors the torque of the moving motor during tapping. When the torque of the moving motor exceeds a certain value, the numerical control device can determine that the tool has come into contact with the work material and machining has started. If the acceleration section is completed at the start of machining, the numerical control device determines that there is a constant speed section. If the acceleration section is not completed at the start of machining, the numerical control device determines that there is no constant speed section. Therefore, the numerical control device can appropriately select the processing load calculation method according to the presence or absence of a constant speed section.

The cutting process of the numerical control device according to claim 4 is tap processing, and is among three feed motors capable of moving the spindle of the machine tool in three axial directions relatively orthogonal to the work material. A torque monitoring unit that monitors the torque of a stationary motor that is stationary during tapping is provided, and the constant speed section determination unit completes the acceleration section when the torque monitored by the torque monitoring unit exceeds a certain value. The acceleration completion determination unit is provided with an acceleration completion determination unit for determining whether or not the acceleration is performed, and when the acceleration completion determination unit determines that the acceleration section is completed, the acceleration completion determination unit determines that there is a constant speed section. If it is determined that the acceleration section has not been completed, it may be determined that the constant speed section does not exist. Cutting is tapping. The numerical control device monitors the torque of the stationary motor during tapping. When the torque of the stationary motor exceeds a certain value, the numerical control device can determine that the tool has come into contact with the work material and machining has started. If the acceleration section has already been completed at the start of machining, the numerical control device determines that there is a constant speed section. If the acceleration section is not completed at the start of machining, the numerical control device determines that there is no constant speed section. Therefore, the numerical control device can appropriately select the processing load calculation method according to the presence or absence of a constant speed section.

The numerical control device according to claim 5 includes a lower limit determination unit that determines whether the machining load calculated by the machining load calculation unit is equal to or less than the lower limit threshold value lower than the threshold value, and the lower limit determination unit determines that the machining load is equal to or less than the lower limit threshold value. If it is determined that the cutting process is performed for the second time or later, it is preferable to provide a notification unit for notifying that the cutting process is the second or subsequent process. The second and subsequent processing means processing when the worker forgets to replace the work material and processes again even though the processing is completed. In the case of the second and subsequent machining, there is almost no machining load. When the machining load is equal to or less than the lower limit threshold value, the numerical control device notifies that the machining is performed for the second time or later, so that the operator can quickly respond by exchanging the work material.

The control method according to claim 6 is a control method of a numerical control device capable of monitoring a machining load in a machining of a work material based on a load current value of a spindle motor of a machine tool, in which the rotation of the spindle motor in the machining is performed. A measurement step for measuring the load current value during the drive period from the start to the stop of rotation, a machining load calculation step for calculating the machining load based on the load current value measured in the measurement step, and a machining load calculation step. A determination step for determining whether the machining load calculated in the above is equal to or greater than the threshold value and an output step for outputting an alarm when the machining load is determined to be equal to or greater than the threshold value in the determination step are provided, and the drive period is at least the spindle. An acceleration section for accelerating the motor to a constant speed and a deceleration section for decelerating and stopping the spindle motor from the constant speed are provided, and the machining load calculation step is the constant between the acceleration section and the deceleration section. In the constant speed section determination step for determining whether or not there is a constant speed section which is a speed section, and the constant speed section determination step, it is determined that the constant speed section exists between the acceleration section and the deceleration section. In the case, in the first calculation step of calculating the peak value of the load current value in the constant speed section as the machining load and the constant speed section determination step, the constant speed section is between the acceleration section and the deceleration section. When it is determined that there is no such thing, it is characterized by including a second calculation step of calculating the average value of the load current values in the drive period as the machining load. Therefore, the numerical control device can obtain the effect according to claim 1.

A perspective view of the machine tool 1. The block diagram which shows the electric composition of a numerical control device 30 and a machine tool 1. The figure which shows the method of tap processing. Waveform diagram of motor current value (torque) for tapping. The figure which shows the method of short tap processing. Waveform diagram of motor current value (torque) for short tap processing. Flow chart of machining control processing. Flow chart of machining control processing (first modification). Flow chart of machining control processing (second modification). Flow chart of machining control processing (third modification).

An embodiment of the present invention will be described. The following description uses left and right, front and back, and up and down indicated by arrows in the figure. The left-right direction, the front-back direction, and the up-down direction of the machine tool 1 are the X-axis direction, the Y-axis direction, and the Z-axis direction of the machine tool 1, respectively. The machine tool 1 shown in FIG. 1 is a machine that rotates a tool 4 mounted on a spindle 9 and cuts a work material 3 held on the upper surface of a workbench 13. The numerical control device 30 (see FIG. 2) controls the operation of the machine tool 1.

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

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

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

The tool changer 20 is provided on the front side of the spindle head 7 and includes a disk-shaped tool magazine 21. The tool magazine 21 holds a plurality of tools (omitted in FIG. 1) radially on the outer periphery, and positions the tool specified by the tool change command at the tool change position. The tool change command is commanded by the NC program. The tool change position is the lowest position of the tool magazine 21. The tool changing device 20 replaces and replaces the tool 4 mounted on the spindle 9 with the tool at the tool changing position.

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

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

With reference to FIG. 2, the electrical configuration of the numerical control device 30 and the machine tool 1 will be described. The numerical control device 30 and the machine tool 1 include a CPU 31, ROM 32, RAM 33, a storage device 34, an input / output unit 35, drive circuits 51A to 55A, and the like. The CPU 31 controls the numerical control device 30 in an integrated manner. The ROM 32 stores various programs including a machining control program. The machining control program executes machining control processing (see FIG. 7). The machining control process is a process that can accurately measure the machining load during cutting while interpreting the NC program line by line and executing various operations. The NC program is composed of a plurality of lines including various control commands, and the numerical control device 30 controls various operations including axis movement and tool change of the machine tool 1 on a line-by-line basis based on the NC program. The RAM 33 temporarily stores various information. The storage device 34 is non-volatile and stores NC programs and various information. In addition to the NC program input by the operator in the input unit 16 of the operation panel 15, the CPU 31 can store the NC program or the like read by the external input in the storage device 34.

The drive circuit 51A is connected to the Z-axis motor 51 and the encoder 51B. The drive circuit 52A is connected to the spindle motor 52 and the encoder 52B. The drive circuit 53A is connected to the X-axis motor 53 and the encoder 53B. The drive circuit 54A is connected to the Y-axis motor 54 and the encoder 54B. The drive circuit 55A is connected to the magazine motor 55 that drives the tool magazine 21 and the encoder 55B. The Z-axis motor 51, the spindle motor 52, the X-axis motor 53, the Y-axis motor 54, and the magazine motor 55 are all servo motors (hereinafter, collectively referred to as motors). The drive circuits 51A to 55A receive commands from the CPU 31 and output drive currents to the corresponding motors 51 to 55, respectively. The drive current is the load current of the motor and corresponds to the torque applied to the motor. The drive circuits 51A to 55A receive feedback signals from the encoders 51B to 55B and perform feedback control of position and speed. The input / output unit 35 is connected to the operation panel 15.

A general tapping process will be described with reference to FIG. The tapping process is, for example, a process of forming a tap hole H1 in the work material 3. In tapping, the numerical control device 30 descends in the Z-axis direction while rotating the spindle 9 equipped with the tool T, and cuts the work material 3 to the bottom of the hole. The tool T is a tap. The drive period of the spindle motor 52 in tapping includes an acceleration section, a constant speed section, and a deceleration section. The drive period is a drive period from the start of rotation of the spindle motor 52 to the stop of rotation. The acceleration section is a section for accelerating from the start of rotation of the spindle motor 52 to a constant speed. The constant speed section is a section for maintaining the rotational speed of the spindle motor 52 at a constant speed. The deceleration section is a section from a constant speed to decelerating the rotation speed of the spindle motor 52 to stop. The moving distance of the main shaft 9 in the Z-axis direction required for each of the acceleration section and the deceleration section is the acceleration / deceleration distance and is the same as each other. The acceleration / deceleration distance may be calculated from, for example, the feed rate and the time constant during tapping.

With reference to FIG. 4, the time change of the motor current value at the time of tapping and the method of measuring the machining load will be described. The motor current value is a drive current value output by the drive circuit 52A to the spindle motor 52. The motor current value increases from the constant value M1 to the positive side at t1, decreases after reaching the peak value on the positive side, and returns to the constant value M1 at t2. t1 to t2 are acceleration sections, and the waveform of the motor current value changes in an inverted V shape. After the acceleration section, the motor current value maintains a constant value M1 from t2 to t3. t2 to t3 are constant speed sections. After the constant speed section, the motor current value increases from the constant value M1 to the minus side at t3, decreases after reaching the peak value on the minus side, and returns to the constant value M1 at t4. t3 to t4 are deceleration sections, and the waveform of the motor current value changes in a V shape.

The waveform of the motor current value in the acceleration section and the waveform of the motor current value in the deceleration section have substantially the same shape in which plus and minus are reversed with respect to the constant value M1. The integrated value of the motor current value in the acceleration section corresponds to the area A1 of the triangle of the torque waveform. The integrated value of the motor current value in the deceleration section corresponds to the area A2 of the inverted triangle of the torque waveform. The area ratio of A1 and A2 is 1: 1. If the torque due to acceleration / deceleration is larger than the torque due to machining, it is difficult to directly measure the machining load. Since the area ratio of the areas A1 and A2 is 1: 1, when the motor current values during the driving period are averaged, the acceleration torque in the acceleration section and the deceleration torque in the deceleration section cancel each other out. Therefore, the numerical control device 30 can significantly reduce the influence of the acceleration / deceleration torque by averaging the motor current values during the drive period, so that the machining torque during the drive period can be measured accurately.

As will be described later, in the present embodiment, when the constant speed section is long during the drive period, the numerical control device 30 instead of calculating the average value of the motor current value, the peak of the motor current value in the constant speed section. Detect the value. By detecting and monitoring the peak value in the constant speed section, it is possible to detect both a gradual change and a momentary change in the machining load generated in the constant speed section. As an example of the momentary change, for example, the momentary change of the torque due to chipping of the tool T corresponds to. As an example of a gradual change in machining load, for example, tool wear corresponds to it. The determination of the length of the constant speed section will be described later.

The short tap processing will be described with reference to FIG. The short tap processing is a tap processing in which there is no constant speed section or a constant speed section is short in the above tap processing, and a tap hole H2 having a shallow bottom is formed in the work material 3. The drive period of the spindle motor 52 in the short tap processing includes an acceleration section and a deceleration section, and there is no constant speed section between the acceleration section and the deceleration section, or a short constant speed section is provided.

With reference to FIG. 6, the time change of the motor current during short tap machining and the method of measuring the machining load will be described. The chart of FIG. 6 (1) is a waveform diagram of the motor current value during idle operation in short tap machining. The idle operation means an operation in which the operation of short tap processing is executed without processing the work material 3. In idle operation, the motor current value increases from the constant value M1 to the plus side at t11, decreases after reaching the peak value on the plus side, and returns to the constant value M1 at t12. t11 to t12 are acceleration sections, and the waveform of the motor current value changes in an inverted V shape. After the acceleration section, the motor current value increases from the constant value M1 to the minus side at t12, decreases after reaching the peak value on the minus side, and returns to the constant value M1 at t13. t12 to t13 are deceleration sections, and the waveform of the motor current value changes in a V shape.

The waveform of the motor current value in the acceleration section and the waveform of the motor current value in the deceleration section have substantially the same shape in which plus and minus are reversed with respect to the constant value M1. The integrated value of the motor current value in the acceleration section corresponds to the area B1 of the triangle of the torque waveform. The integrated value of the motor current value in the deceleration section corresponds to the area B2 of the inverted triangle of the torque waveform. During idle operation, machining torque is not applied during the drive period, only acceleration / deceleration torque is applied, so the area ratio of B1 and B2 is 1: 1.

The chart of FIG. 6 (2) is a waveform diagram of the motor current during machining in short tap machining. “During machining” means that the tool T is in contact with the work material 3 and there is a state in which the work material 3 is being machined. During machining, the motor current increases from the constant value M1 to the plus side at t14, decreases after reaching the peak value on the plus side, and returns to the constant value M1 at t15, as in the case of idle operation. t14 to t15 are acceleration sections, and the waveform of the motor current value changes in an inverted V shape. After the acceleration section, the motor current value increases from the constant value M1 to the minus side at t15, decreases after reaching the peak value on the minus side, and returns to the constant value M1 at t16. t15 to t16 are deceleration sections, and the waveform of the motor current value changes in a V shape. In short tap machining, the acceleration / deceleration torque is larger than the machining torque, so the waveform of the motor current during idle operation and the waveform of the motor current during machining have substantially the same shape.

There is a possibility that the peak value of the motor current value will differ between idle operation and machining. For example, the peak value on the positive side of the acceleration section during machining is slightly higher than the peak value on the positive side of the acceleration section during idle operation. The peak value on the negative side of the deceleration section during machining is slightly lower than the peak value on the negative side of the deceleration section during idle operation. However, the peak value portion in short tap processing is easily affected by noise. The peak value portion may not cut the work material. Therefore, it is difficult to stably measure the machining load from the peak value of the motor waveform.

During machining, the integrated value of the motor current value in the acceleration section corresponds to the area C1 of the triangle of the torque waveform. The integrated value of the motor current value in the deceleration section corresponds to the area C2 of the inverted triangle of the torque waveform. The area ratio of C1 and C2 is not 1: 1 and the area of C2 is slightly smaller than that of C1. Therefore, the difference in area between C1 and C2 appears as the average value of the motor current values. Differences in parts other than the peak value also appear as the average value of the motor current value. As described above, the numerical control device 30 is less susceptible to noise and can stably measure the machining load by averaging the motor current values during the drive period. By executing the machining control process (see FIG. 8) described later, the numerical control device 30 stabilizes the machining load according to the length of the constant speed section during the drive period of the spindle motor 52 during tap machining. Can be measured.

The machining control process will be described with reference to FIG. 7. For example, when tapping the work material 3 with the machine tool 1, the operator inputs the identification number of the NC program for tapping by the input unit 16 of the operation panel 15. When the CPU 31 receives the NC program identification number on the operation panel 15, the CPU 31 reads out the NC program of the identification number input from the storage device 34 and displays it on the display unit 17, for example. The operator confirms the NC program displayed on the display unit 17, and inputs the execution operation on the input unit 16. When the input of the execution operation is received, the CPU 31 reads the machining control program from the ROM 32 and executes this process.

The CPU 31 interprets the NC program in one line (S11). It is determined whether or not the interpreted control command of one line is a tap command (S12). In the case of a control command other than the tap command (S12: NO), the CPU 31 executes the control command (S13). The control commands other than the tap command are, for example, a positioning command, a drill command, a tool change command, and the like. The CPU 31 determines whether or not the program has ended (S14). When the next block is an end command, the NC program ends (S14: YES), so the CPU 31 ends this process. If the next line is not an end command, the NC program continues (S14: NO), so the CPU 31 returns to S11 and repeats the process for the next line.

When the interpreted one-line control command is a tap command (S12: YES), the CPU 31 calculates the acceleration / deceleration distance based on the time constant and the feed rate of the spindle 9 (S15). The time constant is set in advance. The feed rate of the spindle 9 is set by the NC program. The CPU 31 temporarily stores the calculated acceleration / deceleration distance in the RAM 33. The CPU 31 calculates the drive distance required for tap processing based on the start position and end position of tap processing (S16). The start position and end position are set by the NC program. The CPU 31 temporarily stores the calculated drive distance in the RAM 33. The CPU 31 calculates the acceleration / deceleration ratio based on the drive distance and the acceleration / deceleration distance stored in the RAM 33 (S17). The CPU 31 determines whether or not the acceleration / deceleration ratio is equal to or less than a predetermined value (S18). The acceleration / deceleration ratio is the ratio of the acceleration / deceleration distance to the drive distance.

For example, when the acceleration / deceleration ratio exceeds a predetermined value (S18: NO), the ratio of the constant speed section during the drive period is small, so the CPU 31 determines that there is no constant speed section, and the average value of the motor current values during the drive period. Is set as a monitoring target (S19). For example, this corresponds to short tap machining (see FIG. 5) in which the tool T continues to accelerate even when the work material 3 starts to be scraped. On the other hand, when the acceleration / deceleration ratio is equal to or less than a predetermined value (S17: YES), the ratio of the constant speed section during the drive period is large, so the CPU 31 determines that there is a constant speed section and monitors the peak value of the constant speed section. (S20). For example, this corresponds to machining (see FIG. 4) in which the acceleration section ends before the tool T starts cutting the work material 3.

The CPU 31 executes a tap command while measuring the motor current value output by the drive circuit 52A to the spindle motor 52 (S21). The measured motor current value is stored in the RAM 33. The CPU 31 determines whether or not the tap processing is completed (S22). Until the tap processing is completed (S22: NO), the CPU 31 returns to S22 and subsequently executes the tap processing while measuring the motor current value. When the tapping process is completed (S22: YES), the CPU 31 determines whether or not the peak value or the average value to be monitored is equal to or greater than the threshold value based on the motor current value stored in the RAM 33 (S23).

When the monitoring target is set to the peak value in the constant speed section, the CPU 31 detects the peak value from the time change of the motor current value in the constant speed section. The peak value is, for example, the maximum value or the minimum value of the motor current value. The CPU 31 determines whether or not the detected peak value is equal to or greater than the threshold value (S23). The threshold value is a threshold value for determining the peak value, and is a determination value as to whether or not a large processing load is generated. When the detected peak value is less than the threshold value (S23: NO), the spindle motor 52 does not have a large machining load, so the CPU 31 returns to S11 and repeats the process for the next line.

When the detected peak value is equal to or higher than the threshold value (S23: YES), a large machining load is generated on the spindle motor 52, so the CPU 31 outputs an alarm (S24) and forcibly terminates the execution of the NC program. .. Therefore, the numerical control device 30 can prevent the machining of the work material from being continued in a state where a large machining load is generated on the spindle motor 52. As an example of the alarm, for example, a message, a figure, or the like for notifying an abnormality may be displayed on the display unit 17 of the operation panel 15, or the alarm may be notified by a buzzer, a voice, or the like, and the alarm information is output to an external device or the like. You may do it. From the output of the alarm, the operator can recognize that a large machining load has been generated on the spindle motor 52, and thus can quickly respond to the abnormality of the machine tool 1.

Since the monitoring target is set to the peak value in the constant speed section, the CPU 31 can easily detect the chipping of the tool T in the constant speed section, for example. Chipping is a momentary change, but it can be easily detected by monitoring it in a constant speed section. The CPU 31 can detect not only a momentary change in the machining load generated in a constant speed section but also a gradual change in the machining load.

When the monitoring target is set to the average value during the drive period, the CPU 31 calculates the average value of the motor current values during the drive period. The CPU 31 determines whether or not the calculated average value is equal to or greater than the threshold value (S23). The threshold value is a threshold value for determining the average value, and is a threshold value different from the threshold value of the peak value. The threshold value is a determination value as to whether or not a large machining load is generated on the spindle motor 52. When the detected average value is less than the threshold value (S23: NO), the spindle motor 52 does not have a large machining load, so the CPU 31 returns to S11 and repeats the process for the next line.

When the detected peak value is equal to or higher than the threshold value (S23: YES), a large machining load is generated on the spindle motor 52. Therefore, the CPU 31 outputs an alarm (S24) and executes the NC program in the same manner as described above. Forced to terminate. Therefore, the numerical control device 30 can prevent the machining of the work material from being continued even in the short tap machining in a state where a large machining load is generated on the spindle motor 52. Since the monitoring target is set to the average value of the motor current values during the drive period, the CPU 31 can accurately measure the machining load even if there is no constant speed section or the constant speed section is short during the drive period.

As described above, the numerical control device 30 of the present embodiment can monitor the machining load in the cutting of the work material 3 based on the load current value of the spindle motor 52 of the machine tool 1. The CPU 31 of the numerical control device 30 measures, for example, the load current value of the drive period from the start of rotation to the stop of rotation of the spindle motor 52 in tapping. The CPU 31 calculates the machining load based on the measured load current value, and determines whether the calculated machining load is equal to or greater than the threshold value. When it is determined that the machining load is equal to or higher than the threshold value, the CPU 31 outputs an alarm. The drive period includes at least an acceleration section and a deceleration section. The acceleration section is a section for accelerating the spindle motor 52 to a constant speed. The deceleration section is a section in which the spindle motor 52 is decelerated from a constant speed and stopped. The CPU 31 determines whether or not there is a constant speed section between the acceleration section and the deceleration section. The constant speed section is a section in which the spindle motor 52 has a constant speed. When it is determined that there is a constant speed section between the acceleration section and the deceleration section, the CPU 31 calculates the peak value of the load current value in the constant speed section as the machining load. Therefore, the numerical control device 30 can detect both a momentary change in the machining load and a gradual change in the machining load that occur in a constant speed section. When it is determined that there is no constant speed section between the acceleration section and the deceleration section, the CPU 31 calculates the average value of the load current values in the drive period as the machining load. The load current value corresponds to the torque of the spindle motor 52. Since the acceleration torque and the deceleration torque cancel each other out, the numerical control device 30 can accurately monitor the machining torque. Therefore, the numerical control device 30 can accurately monitor the machining load regardless of whether or not there is a constant speed section during the drive period during tap machining.

The CPU 31 of the present embodiment calculates the acceleration / deceleration distance required for the acceleration section and the deceleration section in determining the presence / absence of the constant speed section. The CPU 31 determines whether or not the ratio of the acceleration / deceleration distance to the drive distance required for the drive period is equal to or less than a predetermined value. When the CPU 31 determines that the ratio is equal to or less than a predetermined value, the ratio of the constant speed section during the drive period is large. Therefore, the CPU 31 determines that there is a constant speed section between the acceleration section and the deceleration section, and calculates the peak value of the load current value in the constant speed section as the machining load. When the CPU 31 determines that the ratio exceeds a predetermined value, the ratio of the constant speed section during the drive period is small. Therefore, the CPU 31 determines that there is no constant speed section between the acceleration section and the deceleration section, and calculates the average value of the load current values in the drive period as the machining load. Therefore, the numerical control device 30 can appropriately determine the length of the constant speed section in the drive period, and can appropriately select the processing load calculation method according to the length of the constant speed section.

In the above description, the CPU 31 that executes the process of S21 is an example of the measuring unit of the present invention. The CPU 31 that executes the process of S23 is an example of the determination unit of the present invention. The CPU 31 that executes the process of S24 is an example of the output unit of the present invention. The CPU 31 that executes the processes of S15 to S18 is an example of the constant speed section determination unit of the present invention. The CPU 31 that executes the process of S20 is an example of the first calculation unit of the present invention. The CPU 31 that executes the process of S19 is an example of the second calculation unit of the present invention. The CPU 31 that executes the process of S15 is an example of the acceleration / deceleration section calculation unit of the present invention. The CPU 31 that executes the process of S18 is an example of the ratio determination unit of the present invention.

The present invention is not limited to the above embodiment and can be modified in various ways. In S17 of the machining control process shown in FIG. 7, the CPU 31 is constant depending on whether or not the ratio of the acceleration / deceleration distance to the drive distance in the Z-axis direction required for the drive period of the spindle motor 52 during tap machining is equal to or less than a predetermined value. The length of the speed section is determined, but the length of the constant speed section may be determined by another method. For example, as a first modification, the torque of the Z-axis motor 51 that moves the spindle 9 toward the work material 3 during tapping is monitored, and when the monitored torque exceeds a certain value, the work material 3 is used. The length of the constant speed section in the drive period may be determined depending on whether or not the acceleration section is completed at that time. As a second modification, the torque of the X-axis motor 53 or the Y-axis motor 54 that stands still during tapping is monitored, and when the monitored torque exceeds a certain value, the work material 3 starts to be scraped. The length of the constant speed section in the driving period may be determined based on whether or not the acceleration section is completed.

A first modification will be described with reference to FIG. The machining control process of the first modification is a modification of a part of the machining control process (see FIG. 7) of the above embodiment. In the machining control process of the first modification, new S31 to S35 are executed instead of S15 to S18 of the machining control process of the above embodiment, and S21 is deleted. The processing common to the processing control processing of the above embodiment is assigned the same step number, and the description thereof is omitted or simplified.

The CPU 31 interprets the NC program on one line (S11), executes the tap command when the interpreted control command on the line is a tap command (S12: YES) (S31), and measures the motor current value of the spindle motor 52. Start (S32). The CPU 31 starts measuring the torque of the Z-axis motor 51 (S33). Here, the torque of the Z-axis motor 51 is a disturbance torque (disturbance force) excluding the effects of acceleration / deceleration, self-weight holding, friction, etc., and corresponds to the disturbance torque output from the drive circuit 51A to the Z-axis motor 51. It is a current value. The measured motor current value of the spindle motor 52 and the torque of the Z-axis motor 51 are temporarily stored in the RAM 33. The CPU 31 determines whether or not the torque of the Z-axis motor 51 exceeds a certain value (S34). When the torque of the Z-axis motor 51 is equal to or less than a certain value (S34: NO), since the tool T is not in contact with the work material 3, the CPU 31 returns to S33 and continues to descend the spindle 9.

When the torque of the Z-axis motor 51 exceeds a certain value (S34: YES), the tool T has come into contact with the work material 3, so that the CPU 31 determines whether or not the acceleration section is completed (S35). When the acceleration section is not completed (S35: NO), the CPU 31 determines that there is no constant speed section or the constant speed section is short during the drive period, and monitors the average value of the motor current during the drive period. Set (S19). On the other hand, when the acceleration section is completed (S35: YES), the CPU 31 determines that the constant speed section is long during the drive period, and sets the peak value of the constant speed section during the drive period as the monitoring target (S20). ). Therefore, in the first modification, the length of the constant speed section can be determined by whether or not the acceleration section is completed when the tool T comes into contact with the work material 3 in the tapping process.

In the above description, the CPU 31 that executes the process of S33 is an example of the torque monitoring unit of the present invention. The CPU 31 that executes the processes of S34 and S35 is an example of the acceleration completion determination unit of the present invention.

A second modification will be described with reference to FIG. The machining control process of the second modification is a modification of a part of the machining control process (see FIG. 8) of the first modification. Therefore, the second modification will be described mainly on the portion different from the first modification, and other explanations will be omitted or simplified. In the machining control process of the second modification, new S43 and S44 are executed instead of S33 and S34 of the machining control process of the first modification. The CPU 31 of the second modification starts the measurement of the torque of the X-axis motor 53 (or the Y-axis motor 54) that is stationary at the time of tapping (S43). Here, the torque of the X-axis motor 53 is a disturbance torque (disturbance force) excluding the effects of acceleration / deceleration, friction, etc., and is a motor current value corresponding to the disturbance torque output from the drive circuit 53A to the X-axis motor 53. be. The CPU 31 determines whether or not the torque of the X-axis motor 53 exceeds a certain value (S44).

When the torque of the X-axis motor 53 is equal to or less than a certain value (S44: NO), since the tool T is not in contact with the work material 3, the CPU 31 returns to S44 and continues to descend the spindle 9. When the torque of the X-axis motor 53 exceeds a certain value (S44: YES), the CPU 31 can determine that the tool T has come into contact with the work material 3 as in the first modification, so that the acceleration section of the drive period Is determined to be completed (S35). Therefore, in the second modification, by monitoring the torque of the X-axis motor 53 (or the Y-axis motor 54) that is stationary during tapping, is the tool T in contact with the work material 3 as in the first modification? You can judge whether or not. The processing after S35 is the same as that of the first modification.

In the above description, the CPU 31 that executes the process of S43 is an example of the torque monitoring unit of the present invention. The CPU 31 that executes the processes of S44 and S35 is an example of the acceleration completion determination unit of the present invention.

A third modification will be described with reference to FIG. The machining control process of the third modification determines the double machining of the tap machining, and notifies the operator when it is determined to be the double machining. The double machining means the second and subsequent machining when the worker forgets to replace the work material 3 on the workbench 13 and reworks even though the machining is completed. In the machining control process of the third modification, new S51 and S52 are executed after the determination of S23: NO in the machining control process (see FIG. 7) of the above embodiment. Other processing is common. Therefore, the third modification will be described mainly on the parts different from the above-described embodiment, and the description of the common parts will be omitted or simplified.

After the tap processing is completed (S22: YES), the CPU 31 determines whether or not the processing load to be monitored is equal to or greater than the threshold value (S23). For example, when the monitoring target is the average value of the motor current values during the drive period and the average value is less than the threshold value (S23: NO), the CPU 31 determines whether the average value of the machining load is equal to or less than the lower limit threshold value. Is determined (S51). The lower limit threshold value is a value lower than the threshold value at the time of determination in S23, and may be set to a value close to zero, for example. When the average value exceeds the lower limit threshold value (S51: NO), since an appropriate machining load is applied to the spindle motor 52, the CPU 31 returns to S11 and repeats the process.

When the average value is equal to or less than the lower limit threshold value (S51: YES), there is a possibility of double machining because there is almost no machining load. Therefore, the CPU 31 notifies the double processing on the display unit 17 of the operation panel 15 (S52). For example, the CPU 31 may display a message, a figure, or the like indicating that the processing is performed twice on the display unit 17. The operator can confirm the work material 3 on the workbench 13 by the notification on the display unit 17 and replace it with a new work material 3 and take prompt action. In addition to the display on the display unit 17, the mode of notifying the double processing may be, for example, voice, buzzer, or the like, and the notification of the double processing may be output to an external device or the like.

In the above description, the CPU 31 that executes the process of S51 is an example of the lower limit determination unit of the present invention. The CPU 31 that executes the process of S52 is an example of the notification unit of the present invention.

In addition to the first, second, and third modifications described above, the present invention can be modified in various ways. In the machining control process of the above embodiment (see FIG. 7), it is determined whether or not the ratio of the acceleration / deceleration distance to the drive distance required for the drive period is equal to or less than a predetermined value (see S15 to S17), but it is necessary for the drive period. It may be determined whether or not the ratio of the acceleration / deceleration time to the time is equal to or less than a predetermined value.

The machining control process of the above embodiment (see FIG. 7) monitors the machining load during the drive period of tap machining as an example of cutting, but can also be applied to other machining such as drilling and milling. Is.

In the machine tool 1 of the above embodiment, the spindle 9 on which the tool 4 is mounted is movable in the Z-axis direction, and the workbench 13 is movable in the X-axis and Y-axis directions. The mechanism of the movement mechanism of the spindle that moves relative to the material 3 in the X-axis, Y-axis, and Z-axis directions is not limited to the above embodiment. For example, the spindle is driven by three axes in the X, Y, and Z axis directions, and the workbench may be fixed or rotatable.

The workbench device 10 of the above embodiment is a mechanical device that rotatably supports the workbench 13 in the X-axis direction and the Y-axis direction, but the workbench 13 may be rotatably supported.

The machine tool 1 of the above embodiment is a vertical machine tool whose spindle is parallel to the Z-axis direction, but may be a horizontal machine tool whose spindle extends in the horizontal direction.

Although the drive circuits 51A to 55A of the above embodiment are provided in the machine tool 1, the drive circuits 51A to 55A may be provided in the numerical control device 30.

1 Machine tool 3 Work material 30 Numerical control device 31 CPU
51 Z-axis motor 52 Spindle motor 53 X-axis motor 54 Y-axis motor T tool

Claims (6)

In a numerical control device that can monitor the machining load in the cutting of the work material based on the load current value of the spindle motor of the machine tool.
A measuring unit that measures the load current value during the drive period from the start of rotation to the stop of rotation of the spindle motor in the cutting process.
A machining load calculation unit that calculates the machining load based on the load current value measured by the measurement unit, and a machining load calculation unit.
A determination unit for determining whether the processing load calculated by the processing load calculation unit is equal to or greater than a threshold value, and a determination unit.
When the determination unit determines that the machining load is equal to or higher than the threshold value, the determination unit includes an output unit that outputs an alarm.
The driving period is at least
An acceleration section that accelerates the spindle motor to a constant speed,
It is provided with a deceleration section in which the spindle motor is decelerated from the constant speed and stopped.
The processing load calculation unit is
A constant speed section determination unit that determines whether or not there is a constant speed section that is a constant speed section between the acceleration section and the deceleration section.
When the constant speed section determination unit determines that the constant speed section exists between the acceleration section and the deceleration section, the peak value of the load current value in the constant speed section is calculated as the processing load. One calculation unit and
When the constant speed section determination unit determines that there is no constant speed section between the acceleration section and the deceleration section, the second is to calculate the average value of the load current values in the drive period as the processing load. A numerical control device characterized by having a calculation unit. The constant speed section determination unit
An acceleration / deceleration section calculation unit that calculates the acceleration / deceleration distance or acceleration / deceleration time required for the acceleration section and the deceleration section, and the acceleration / deceleration section calculation unit.
It is provided with a ratio determination unit for determining whether or not the ratio of the acceleration / deceleration distance or the acceleration / deceleration time calculated by the acceleration / deceleration section calculation unit to the distance or time required for the drive period is equal to or less than a predetermined value.
When the ratio determination unit determines that the ratio is equal to or less than the predetermined value, it is determined that there is the constant speed section.
The numerical control device according to claim 1, wherein when the ratio determination unit determines that the ratio exceeds the predetermined value, it determines that there is no constant speed section. The cutting process is a tap process.
Of the three feed motors that can move the spindle of the machine tool in three axial directions that are relatively orthogonal to the work material, the movement that moves the spindle toward the work material during tapping. Equipped with a torque monitoring unit that monitors the torque of the motor
The constant speed section determination unit
When the moving motor starts driving and the torque monitored by the torque monitoring unit exceeds a certain value, an acceleration completion determination unit for determining whether or not the acceleration section is completed is provided.
When the acceleration completion determination unit determines that the acceleration section has been completed, it determines that the constant speed section exists.
The numerical control device according to claim 1, wherein when the acceleration completion determination unit determines that the acceleration section has not been completed, it determines that the constant speed section does not exist. The cutting process is a tap process.
Of the three feed motors that can move the spindle of the machine tool in three axial directions that are relatively orthogonal to the work material, a torque monitoring unit that monitors the torque of the stationary motor that is stationary during tapping is provided. Prepare,
The constant speed section determination unit
When the torque monitored by the torque monitoring unit exceeds a certain value, the acceleration completion determination unit for determining whether or not the acceleration section is completed is provided.
When the acceleration completion determination unit determines that the acceleration section has been completed, it determines that the constant speed section exists.
The numerical control device according to claim 1, wherein when the acceleration completion determination unit determines that the acceleration section has not been completed, it determines that the constant speed section does not exist. A lower limit determination unit for determining whether the machining load calculated by the machining load calculation unit is equal to or less than the lower limit threshold value lower than the threshold value, and a lower limit determination unit.
4. Numerical control device described in any. In the control method of the numerical control device that can monitor the machining load in the cutting of the work material based on the load current value of the spindle motor of the machine tool.
A measurement step for measuring the load current value during the drive period from the start of rotation to the stop of rotation of the spindle motor in the cutting process, and a measurement step.
A machining load calculation step for calculating the machining load based on the load current value measured in the measurement step, and a machining load calculation step.
A determination step for determining whether the machining load calculated in the machining load calculation step is equal to or higher than the threshold value, and a determination step.
When the processing load is determined to be equal to or higher than the threshold value in the determination step, an output step for outputting an alarm is provided.
The driving period is at least
An acceleration section that accelerates the spindle motor to a constant speed,
It is provided with a deceleration section in which the spindle motor is decelerated from the constant speed and stopped.
The machining load calculation step is
A constant speed section determination step for determining whether or not there is a constant speed section which is a constant speed section between the acceleration section and the deceleration section, and
When it is determined in the constant speed section determination step that the constant speed section exists between the acceleration section and the deceleration section, the peak value of the load current value in the constant speed section is calculated as the processing load. One calculation step and
When it is determined in the constant speed section determination step that there is no constant speed section between the acceleration section and the deceleration section, the average value of the load current values in the drive period is calculated as the processing load. A control method characterized by having a calculation step.

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