WO2025099821A1 - Numerical value control device and numerical value control method - Google Patents

Abstract

A numerical value control device (1) comprises: a servo motor control unit (50) that controls a main spindle motor (71) of a machine tool (2) that performs a drilling process on a workpiece by regularly rotating an implement, and removes chips that have clung onto the implement from the implement by reversely rotating the implement; a current load determination unit (31) that compares the magnitude between a current feedback value of the main spindle motor (71) corresponding to a load applied to the main spindle motor (71) and a reference value, and determines whether to change the acceleration of the rotation of the main spindle motor (71) on the basis of the result of the comparison; and an acceleration change unit that changes the acceleration on the basis of the result of the determination.

Description

Numerical control device and numerical control method

This disclosure relates to a numerical control device and a numerical control method for controlling a machine tool.

One type of machine tool is one that rotates a tool to drill holes in a workpiece. This machine tool generates chips when drilling holes, and the chips can get tangled around the tool. If the machine tool continues to drill holes in the workpiece with chips tangled around the tool, the machining accuracy deteriorates. For this reason, it is desirable to remove the chips tangled around the tool from the tool. If the chips tangled around the tool are removed manually, it is necessary to stop the machine tool before removing the chips from the tool, which reduces the machining efficiency of the drilling process.

The numerical control device described in Patent Document 1 reverses the rotation of a tool in a machine tool that performs drilling after the tool has cut a workpiece, and removes chips by terminating the reverse rotation when a specific time has elapsed.

International Publication No. 2021/141016

However, the technology in Patent Document 1 above reverses the rotation of the tool without taking into account the mechanical characteristics, which causes a problem in that excessive load may be placed on the spindle motor that rotates the tool when reversing the rotation direction of the tool.

The present disclosure has been made in consideration of the above, and aims to provide a numerical control device that can prevent an overload from being applied to the spindle motor that rotates the tool when reversing the rotation direction of the tool.

In order to solve the above problems and achieve the object, the numerical control device disclosed herein includes a servo motor control unit that controls a spindle motor of a machine tool that rotates a tool in the forward direction to drill a hole in a workpiece and rotates the tool in the reverse direction to remove chips entangled in the tool from the tool. The numerical control device disclosed herein also includes a current load determination unit that compares the magnitude of a current feedback value of the spindle motor, which corresponds to the load on the spindle motor, with a preset reference value, and determines whether or not to change the acceleration of the rotation of the spindle motor based on the comparison result, and an acceleration change unit that changes the acceleration based on the result of the determination.

The numerical control device disclosed herein has the effect of preventing an overload from being applied to the spindle motor that rotates the tool when reversing the rotation direction of the tool.

FIG. 1 is a diagram showing a configuration of a numerical control device according to an embodiment; 1 is a flowchart showing a procedure of processing executed by a numerical control device according to an embodiment; FIG. 1 is a diagram for explaining a procedure of a drilling process executed by a machine tool controlled by a numerical control device according to an embodiment; FIG. 1 is a diagram for explaining an example of a spindle rotation speed and an acceleration of a spindle motor when a numerical control device according to an embodiment controls a machine tool; FIG. 1 is a diagram showing an example of a hardware configuration for implementing a numerical control device according to an embodiment;

The numerical control device and numerical control method according to the embodiments of the present disclosure are described in detail below with reference to the drawings.

Embodiment
1 is a diagram showing the configuration of a numerical control device according to an embodiment. The numerical control device 1 is connected to a machine tool 2 and controls the machine tool 2. The machine tool 2 performs machining such as drilling a hole on a workpiece by rotating a tool (not shown) in the normal direction. The machine tool 2 is equipped with a servo motor 70.

The servo motor 70 has a spindle motor (spindle servo motor) 71 and a feed axis motor (feed axis servo motor) 72. Note that in FIG. 1, a case is described in which the machine tool 2 has one feed axis motor 72 and the tool or workpiece is moved in one direction by the one feed axis motor 72, but the machine tool 2 may have multiple feed axis motors 72. In this case, the machine tool 2 moves the tool or workpiece in multiple directions by the multiple feed axis motors 72. For example, when moving a tool in three axial directions, the machine tool 2 has three feed axis motors 72. The machine tool 2 may also have multiple servo motors 70.

A tool is attached to the spindle motor 71. The spindle motor 71 rotates the tool by rotating the rotating shaft. The feed axis motor 72 moves the tool or the workpiece in a specific direction, thereby moving the tool and the workpiece relatively in a specific direction. Below, a case where the feed axis motor 72 moves the tool in a specific direction is described, but the feed axis motor 72 may also move the workpiece in a specific direction.

The machine tool 2 also has a detector (not shown) that detects the rotational position and rotational speed of the rotating shaft mounted on the spindle motor 71. The machine tool 2 also has a detector (not shown) that detects the rotational position and rotational speed of the rotating shaft mounted on the feed shaft motor 72. The rotational position and rotational speed detected by these detectors are sent to the numerical control device 1.

The numerical control device 1 is a computer that controls the spindle motor 71 and the feed shaft motor 72. The numerical control device 1 feedback controls the spindle motor 71 based on the rotational position and rotational speed of the rotating shaft of the spindle motor 71 detected by a detector. The numerical control device 1 also feedback controls the feed shaft motor 72 based on the rotational position and rotational speed of the rotating shaft of the feed shaft motor 72 detected by a detector.

The numerical control device 1 controls the machine tool 2 to rotate the tool attached to the machine tool 2 in the forward direction, thereby causing the machine tool 2 to perform drilling on the workpiece. The numerical control device 1 also controls the machine tool 2 to rotate the tool attached to the machine tool 2 in the reverse direction, thereby causing the machine tool 2 to remove chips entangled in the tool.

When rotating the tool, the numerical control device 1 rotates the spindle of the spindle motor 71 at an acceleration (spindle rotation acceleration) corresponding to the current load based on the current load of the spindle motor 71. When reversing the rotation direction from forward rotation to reverse rotation, the numerical control device 1 rotates the spindle of the spindle motor 71 at an acceleration corresponding to the current load. Also, when reversing the rotation direction from reverse rotation to forward rotation, the numerical control device 1 rotates the spindle of the spindle motor 71 at an acceleration corresponding to the current load.

The numerical control device 1 includes a memory unit 10, a machining operation generation unit 20, a chip removal operation generation unit 30, an interpolation unit 40, a servo motor control unit 50, and a motor FB (Feedback) information acquisition unit 60.

The memory unit 10 stores a machining program and various data (not shown). The machining program is a program for causing the machine tool 2 to perform drilling. The machining program includes a canned cycle. The canned cycle is a command (G code) set so that a frequently used machining operation, such as a drilling operation, can be executed in one block. In a canned cycle, multiple blocks of commands are written in one block. The various data stored in the memory unit 10 includes data used when the machining operation generation unit 20 and the chip removal operation generation unit 30 operate.

The machining operation generating unit 20 generates operation commands for the machine tool 2 to execute drilling based on the analysis results of the machining program. The machining operation generating unit 20 operates while using the storage unit 10 as a temporary memory.

The machining operation generation unit 20 has a program analysis unit 21 and a cycle generation unit 22. The program analysis unit 21 reads out the machining program from the storage unit 10. The program analysis unit 21 analyzes the machining program and calculates information on the operation commands described in the machining program.

The information on the operation commands described in the machining program is information used by the cycle generation unit 22 when generating the operation commands. The information used when generating the operation commands includes, for example, the coordinate values of the start and end points (start and end points) that define the relative movement path between the tool and the workpiece, the interpolation method (linear interpolation, circular interpolation, etc.) of the movement path connecting the start and end points, the feed speed when the tool moves, the rotation speed of the spindle motor 71, and the rotation direction of the spindle motor 71. The program analysis unit 21 transmits the information on the operation commands described in the machining program as the analysis result to the cycle generation unit 22 and the chip removal operation generation unit 30.

The cycle generation unit 22 generates a drilling cycle command based on the analysis results sent from the program analysis unit 21. The cycle generation unit 22 transmits the generated drilling cycle command to the interpolation unit 40.

The motor feedback information acquisition unit 60 acquires a current feedback value (current feedback value) corresponding to the current load on the spindle motor 71, i.e., load information. The current feedback value is the current value required to drive the spindle motor 71, and is used for feedback control of the spindle motor 71. The motor feedback information acquisition unit 60 acquires the current feedback value of the spindle motor 71 from the machine tool 2, and transmits it to the chip removal operation generation unit 30. The motor feedback information acquisition unit 60 continuously acquires the current feedback value of the spindle motor 71 and constantly monitors it.

In addition, the motor feedback information acquisition unit 60 constantly monitors the spindle speed of the spindle motor 71. The motor feedback information acquisition unit 60 acquires the spindle speed of the spindle motor 71 from the machine tool 2 and transmits it to the chip removal operation generation unit 30.

The motor FB information acquisition unit 60 also constantly monitors the position of the tool. The motor FB information acquisition unit 60 acquires the FB position, which is the position of the tool, from the machine tool 2 and transmits it to the chip removal operation generation unit 30. The motor FB information acquisition unit 60 may also calculate the position of the tool based on a position command transmitted to the servo motor 70 by the servo motor control unit 50.

The chip removal operation generation unit 30 generates operation commands for the machine tool 2 to remove chips based on the analysis results sent from the program analysis unit 21. The chip removal operation generation unit 30 operates while using the storage unit 10 as temporary memory. The chip removal operation generation unit 30 has a current load determination unit 31, an acceleration control unit 32, and a rotation direction change unit 33.

The rotation direction change unit 33 receives the FB position indicating the position of the tool from the motor FB information acquisition unit 60. When the FB position returns to a specific position (the return point described below), the rotation direction change unit 33 outputs a command (reverse command) to change the rotation direction of the spindle motor 71 to the interpolation unit 40. Specifically, when the FB position returns to the return point, the rotation direction change unit 33 outputs a command to the interpolation unit 40 to reverse the rotation direction of the spindle motor 71 from forward rotation to reverse rotation, and then outputs a command to the interpolation unit 40 to reverse from reverse rotation to forward rotation. As a result, the rotation direction change unit 33 changes the rotation direction of the tool.

The rotation direction change unit 33 rotates the tool (spindle) in the reverse direction when removing chips. The rotation direction change unit 33 also rotates the spindle in the forward direction when the machine tool 2 performs the next drilling operation.

The rotation direction change unit 33 changes the rotation direction of the spindle motor 71 to reverse rotation, for example, when the tool completes a drilling operation and moves to the initial point (point I), which is the return point (the position where the fixed cycle begins).

In addition, the rotation direction change unit 33 may change the rotation direction of the spindle motor 71 to reverse rotation when the tool moves to a reference point (the position where the cutting feed starts) after the tool has completed one drilling operation.

In this embodiment, the rotation direction change unit 33 changes the rotation direction of the spindle motor 71 to reverse rotation when the tool moves to the return point after completing one drilling operation.

After the tool moves to the return point and the spindle is rotated in reverse, the rotation direction change unit 33 continues to rotate the spindle motor 71 in reverse until the spindle speed, which is the rotational speed of the spindle motor 71, reaches the command speed included in the analysis result of the machining program. When the spindle speed reaches the command speed, the rotation direction change unit 33 changes the rotation direction of the spindle motor 71 to forward rotation.

The current load determination unit 31 compares the current FB value received from the motor FB information acquisition unit 60 during the spindle reversal operation with a preset reference value of the current load. The spindle reversal operation is an operation in which the machine tool 2 rotates the tool in the opposite direction from the current rotation direction. Spindle reversal operations include an operation to change the rotation direction of the spindle motor 71 from forward rotation to reverse rotation, and an operation to change the rotation direction of the spindle motor 71 from reverse rotation to forward rotation. The reference value of the current load in the spindle motor 71 is a value smaller than the allowable value of the current load in the spindle motor 71.

The current load determination unit 31 compares the current FB value with the reference value and determines whether the current FB value is greater than the reference value, whether the current FB value is smaller than the reference value, or whether the current FB value is the same as the reference value. In this way, the current load determination unit 31 determines which is greater: the reference value of the current load or the current current FB value.

The current load determination unit 31 determines whether or not to change the acceleration of the rotation of the spindle motor 71 based on the result of comparing the magnitude of the current FB value with the reference value. Specifically, when the current FB value of the spindle motor 71 is greater than the reference value, the current load determination unit 31 determines that the spindle motor 71 should be operated at a lower acceleration than the current one. On the other hand, when the current FB value is smaller than the reference value, the current load determination unit 31 determines that the spindle motor 71 should be operated at a higher acceleration than the current one.

In the embodiment, the acceleration is the absolute value of the acceleration. Therefore, a low acceleration in the embodiment is an acceleration whose absolute value is smaller than the absolute value of the current acceleration. Also, a high acceleration in the embodiment is an acceleration whose absolute value is larger than the absolute value of the current acceleration.

If the current load determination unit 31 determines that the spindle motor 71 should be operated at a slower acceleration than the current acceleration, it sends a command to the acceleration control unit 32 to operate the spindle motor 71 at a slower acceleration than the current acceleration (hereinafter, sometimes referred to as a low acceleration command).

On the other hand, if the current load determination unit 31 determines that the spindle motor 71 should be operated at a higher acceleration than the current speed, it sends a command to the acceleration control unit 32 to operate the spindle motor 71 at a higher acceleration than the current speed (hereinafter, sometimes referred to as a high acceleration command).

The current load determination unit 31 may also calculate the difference between the current FB value and the reference value (hereinafter, sometimes referred to as the current difference value). In this case, the current load determination unit 31 calculates the amount of change (amount of increase or decrease) in acceleration that corresponds to the magnitude of the current difference value.

The current load determination unit 31 generates an acceleration command (low acceleration command or high acceleration command) that changes the acceleration by a larger amount of increase or decrease as the current difference value increases. In other words, when the current FB value is greater than the reference value, the current load determination unit 31 generates a low acceleration command that decreases the acceleration by a larger amount as the current difference value increases.

In addition, when the current FB value is smaller than the reference value, the current load determination unit 31 generates a high acceleration command that increases the acceleration more as the current difference value increases. When the current FB value and the reference value are the same value, the current load determination unit 31 does not generate an acceleration command. Note that the current load determination unit 31 does not need to generate an acceleration command when the current difference value is smaller than a specific value.

The reference value used by the current load determination unit 31 may be in a specific range. That is, the reference value to be compared with the current FB value may be within the allowable range of the current FB value. In this case, the current load determination unit 31 determines whether the current FB value is smaller than the minimum value of the allowable range, whether the current FB value is larger than the maximum value of the allowable range, or whether the current FB value is within the allowable range.

When the current FB value is smaller than the minimum value of the allowable range, the current load determination unit 31 sends a high acceleration command to the acceleration control unit 32. When the current FB value is larger than the maximum value of the allowable range, the current load determination unit 31 sends a low acceleration command to the acceleration control unit 32.

When the current FB value is smaller than the minimum value of the allowable range, the current load determination unit 31 may calculate the difference between the current FB value and the minimum value of the allowable range as the current difference value. Also, when the current FB value is larger than the maximum value of the allowable range, the current load determination unit 31 may calculate the difference between the current FB value and the maximum value of the allowable range as the current difference value. In these cases as well, the current load determination unit 31 calculates the amount of change in acceleration that corresponds to the magnitude of the current difference value.

The acceleration control unit 32 changes the acceleration of the spindle motor 71 (the acceleration of the rotational operation) based on the result of the judgment performed by the current load judgment unit 31. For example, the acceleration control unit 32 generates an operation command for controlling the acceleration of the spindle motor 71 based on the acceleration command received from the current load judgment unit 31 during the spindle reversal operation (while removing chips entangled in the tool).

When the acceleration control unit 32 receives a low acceleration command, it generates an operation command to decrease the acceleration of the spindle motor 71. On the other hand, when the acceleration control unit 32 receives a high acceleration command, it generates an operation command to increase the acceleration of the spindle motor 71.

If the acceleration is a positive value, the acceleration control unit 32 generates an operation command to change the acceleration to a positive value, and if the acceleration is a negative value, the acceleration control unit 32 generates an operation command to change the acceleration to a negative value.

For example, when the acceleration control unit 32 receives a low acceleration command, it generates an operation command to decrease the acceleration of the spindle motor 71 by a constant value. Also, when the acceleration control unit 32 receives a high acceleration command, it generates an operation command to increase the acceleration of the spindle motor 71 by a constant value.

The amount of increase (constant value) when increasing the acceleration and the amount of decrease (constant value) when decreasing the acceleration may be set by the user using parameters, for example, or may be preregistered in the numerical control device 1.

When the acceleration command (low acceleration command or high acceleration command) includes a change amount (increase or decrease amount) in acceleration, the acceleration control unit 32 generates an operation command corresponding to this change amount. In other words, when the received low acceleration command includes a change amount in acceleration, the acceleration control unit 32 generates an operation command to decrease the acceleration by this change amount. When the received high acceleration command includes a change amount in acceleration, the acceleration control unit 32 generates an operation command to increase the acceleration by this change amount.

The current load determination unit 31 may determine the amount of change in acceleration so that the current FB value does not exceed the reference value. In other words, even if the current FB value is smaller than the reference value, if the current load determination unit 31 determines that increasing the acceleration by a certain value will cause the current FB value to become larger than the reference value, the current load determination unit 31 may not need to increase the acceleration. In other words, the current load determination unit 31 may determine the amount of increase or decrease in acceleration so that the acceleration of the spindle motor 71 becomes smaller than the reference value and approaches the reference value.

When the current load determination unit 31 generates an acceleration command based on the allowable range of the current FB value, upon receiving an acceleration command from the current load determination unit 31, the acceleration control unit 32 generates an operation command that brings the current FB value into the allowable range.

Specifically, when the acceleration control unit 32 receives a high acceleration command from the current load determination unit 31, it generates an operation command to increase the acceleration so that the current FB value is within the allowable range. As a result, if the current FB value is smaller than the minimum value of the allowable range, the current FB value is brought within the allowable range by increasing the acceleration.

Furthermore, when the acceleration control unit 32 receives a low acceleration command from the current load determination unit 31, it generates an operation command to bring the current FB value within the allowable range by lowering the acceleration. As a result, when the current FB value is greater than the maximum value of the allowable range, the current FB value is brought within the allowable range by lowering the acceleration.

In this way, the acceleration control unit 32 decreases the acceleration when the current load determination unit 31 determines that the spindle motor 71 should be operated at a lower acceleration than the current acceleration. Also, the acceleration control unit 32 increases the acceleration when the current load determination unit 31 determines that the spindle motor 71 should be operated at a higher acceleration than the current acceleration. That is, the acceleration control unit 32 determines the acceleration of the spindle motor 71 based on the determination result (acceleration command) of the current load determination unit 31. The acceleration control unit 32 generates an operation command corresponding to the determined acceleration of the spindle motor 71 and transmits the generated operation command to the interpolation unit 40. The acceleration control unit 32 generates an operation command to change the acceleration for each control cycle or each specific period (for example, 10 msec) and transmits it to the interpolation unit 40.

The interpolation unit 40 receives a drilling cycle command from the cycle generation unit 22. The interpolation unit 40 also receives a command to change the rotation direction of the spindle motor 71 from the rotation direction change unit 33. The interpolation unit 40 also receives an acceleration operation command from the acceleration control unit 32.

The interpolation unit 40 generates a control command (movement command) for the servo motor 70 based on the command received from the cycle generation unit 22 and the command received from the chip removal operation generation unit 30. Specifically, based on the command for the drilling cycle, it generates a control command for the spindle motor 71 and a control command for the feed axis motor 72 to perform drilling. In addition, based on a command to change the rotation direction of the spindle motor 71, the interpolation unit 40 generates a control command for the spindle motor 71 to change the rotation direction of the spindle motor 71. In addition, the interpolation unit 40 generates a control command for the spindle motor 71 to rotate the spindle at an acceleration corresponding to the acceleration operation command. The interpolation unit 40 transmits the generated control commands to the servo motor control unit 50.

The servo motor control unit 50 generates a position command according to the control command received from the interpolation unit 40, and controls the servo motor 70 using the position command. The servo motor control unit 50 may also generate a speed command according to the control command received from the interpolation unit 40, and control the servo motor 70 using the speed command.

Next, the processing procedure of the process executed by the numerical control device 1 will be described. FIG. 2 is a flowchart showing the processing procedure of the process executed by the numerical control device according to the embodiment. When the numerical control device 1 starts controlling the drilling process, the motor feedback information acquisition unit 60 acquires the current feedback value of the spindle motor 71 from the machine tool 2 (step S10) and transmits it to the chip removal operation generation unit 30.

The current load determination unit 31 of the chip removal operation generation unit 30 compares the current FB value received from the motor FB information acquisition unit 60 with a preset reference value of the current load. That is, the current load determination unit 31 determines whether the current FB value is greater than the reference value (step S20).

The current load determination unit 31, for example, determines whether the current FB value is greater than a reference value during a spindle reversal operation. That is, the current load determination unit 31 determines whether the current FB value is greater than a reference value when the rotation direction of the spindle motor 71 is reversed from forward rotation to reverse rotation. The current load determination unit 31 also determines whether the current FB value is greater than a reference value when the rotation direction of the spindle motor 71 is reversed from reverse rotation to forward rotation.

If the current FB value is greater than the reference value (step S20, Yes), the current load determination unit 31 determines that the spindle motor 71 should be rotated at a lower acceleration than the current acceleration (step S30). In this case, the current load determination unit 31 transmits a low acceleration command to the acceleration control unit 32 to operate the spindle motor 71 at a lower acceleration than the current acceleration.

On the other hand, if the current FB value is smaller than the reference value (step S20, No), the current load determination unit 31 determines that the spindle motor 71 should be rotated at a higher acceleration than the current acceleration (step S40). In this case, the current load determination unit 31 transmits a high acceleration command to the acceleration control unit 32 to operate the spindle motor 71 at a higher acceleration than the current acceleration. The current load determination unit 31 does not generate an acceleration command if the current FB value and the reference value are the same value.

The acceleration control unit 32 determines the acceleration of the spindle motor 71 based on the acceleration command from the current load determination unit 31 (step S50). The acceleration control unit 32 generates an operation command corresponding to the determined acceleration of the spindle motor 71, and transmits the generated operation command to the interpolation unit 40.

The interpolation unit 40 generates a control command for the servo motor 70 based on the command received from the cycle generation unit 22 and the command received from the chip removal operation generation unit 30, and transmits the control command to the servo motor control unit 50. The servo motor control unit 50 generates a position command according to the control command received from the interpolation unit 40, and controls the servo motor 70 according to the position command.

As a result, when changing the rotation direction of the spindle motor 71, if the current FB value (current load) of the spindle motor 71 is greater than the reference value, the numerical control device 1 reduces the acceleration of the spindle motor 71, thereby making it possible to suppress overload on the spindle motor 71.

In addition, when changing the rotation direction of the spindle motor 71, if the current FB value of the spindle motor 71 is smaller than a reference value, the numerical control device 1 increases the acceleration of the spindle motor 71, making it possible to change the rotation direction of the spindle motor 71 in a short time.

Next, the processing procedure of the hole drilling process executed by the machine tool 2 controlled by the numerical control device 1 will be described. FIG. 3 is a diagram for explaining the processing procedure of the hole drilling process executed by the machine tool controlled by the numerical control device according to the embodiment. In FIG. 3, two axes in a plane parallel to the top surface of the workpiece 81 and perpendicular to each other are defined as the X-axis and the Y-axis. The axis perpendicular to the X-axis and the Y-axis is defined as the Z-axis. Here, a case will be described in which the numerical control device 1 controls the first hole drilling process H1 and then controls the second hole drilling process H2.

When the numerical control device 1 starts drilling, it starts controlling the machine tool 2. As a result, the tool 80 attached to the machine tool 2 is moved by the feed axis motor 72. In addition, the motor feedback information acquisition unit 60 acquires the current feedback value, spindle speed, and feedback position of the spindle motor 71 from the machine tool 2 and transmits them to the chip removal operation generation unit 30.

The numerical control device 1 starts moving the tool 80 from position P1, which is the initial position on the workpiece 81. At this point, the tool 80 has not yet rotated. Position P1 is a position that is higher than the top surface of the workpiece 81 by a height Z1.

The numerical control device 1 moves the tool 80 from position P1 in a plane parallel to the XY plane to position P2. Position P2 is the return point where the fixed cycle begins for the first machining hole. The Z-direction position of the return point, position P2, is the position where the fixed cycle is commanded, and the XY-direction position of the return point is the position on the machining hole where drilling will now take place.

The numerical control device 1 moves the tool 80 downward in the Z direction using the feed axis motor 72, thereby moving the tool 80 from position P2, which is the return point, to position P3, which is the reference point (point R). This causes the tool 80 to move in a direction parallel to the Z direction from position P2 to position P3. Position P3 is lower in the Z direction than position P2, and is closer to the workpiece 81 than position P2.

When the tool 80 reaches position P3, the numerical control device 1 accelerates the rotation of the spindle motor 71 to rotate the tool 80 in the forward direction (st1). The numerical control device 1 increases the rotation speed of the spindle motor 71 to the machining speed. The numerical control device 1 also moves the tool 80 from position P3 to position P4, which is the bottom surface position of the machined hole, by the feed axis motor 72. Position P4 is a position within the workpiece 81 and is a position lower in the Z direction than the top surface of the workpiece 81. By the numerical control device 1 moving the tool 80 from position P3 to position P4, the tool 80 starts drilling a hole from the top surface of the workpiece 81 and reaches position P4. Note that in FIG. 3, two positions P4 are shown for convenience of explanation, but the two positions P4 are the same position.

Then, the numerical control device 1 moves the tool 80 upward in the Z direction by the feed axis motor 72, thereby moving the tool 80 from position P4 to position P5 (st2). Position P5 is the same position as position P2. In other words, position P5 is the return point where the fixed cycle was started.

When the tool 80 reaches position P5, the numerical control device 1 reverses the rotation of the spindle motor 71 to change the rotation of the tool 80 from forward to reverse (st3). Specifically, when the FB position of the tool 80 reaches position P5, which is the return point, the rotation direction change unit 33 changes the rotation direction of the spindle motor 71 from forward to reverse.

After reversing the spindle motor 71, the numerical control device 1 accelerates the spindle motor 71 until the spindle speed of the spindle motor 71 reaches the commanded speed (st4). When the spindle speed of the spindle motor 71 reaches the commanded speed, the rotation direction change unit 33 reverses the spindle motor 71 again to change the tool 80 from reverse rotation to forward rotation in order to perform the next drilling process (st5).

The numerical control device 1 rotates the tool 80 in the forward direction by accelerating the spindle motor 71. The numerical control device 1 increases the rotation speed of the spindle motor 71 to the processing speed.

The numerical control device 1 moves the tool 80 from position P5 in a plane parallel to the XY plane to position P6 (st6). Position P6 is the return point where the fixed cycle begins for the second machining hole. The Z-direction position of the return point, position P6, is the position where the fixed cycle is commanded, and the XY-direction position of the return point is the position on the machining hole where drilling will now take place.

The numerical control device 1 moves the tool 80 downward in the Z direction by the feed axis motor 72 (st7). As a result, the numerical control device 1 moves the tool 80 from position P6, which is the return point, through position P7, which is the reference point, to position P8, which is the bottom position of the machined hole. Position P8 is a position within the workpiece 81, and is a position lower in the Z direction than the top surface of the workpiece 81. By the numerical control device 1 moving the tool 80 from position P7 to position P8, the tool 80 starts drilling a hole from the top surface of the workpiece 81 and reaches position P8. Note that, for ease of explanation, two positions P8 are shown in FIG. 3, but the two positions P8 are the same position.

Then, the numerical control device 1 moves the tool 80 upward in the Z direction by the feed axis motor 72, thereby moving the tool 80 from position P8 to position P9 (st8). Position P9 is the same position as position P6. In other words, position P9 is the return point where the fixed cycle was started.

After the tool 80 reaches position P9, the numerical control device 1 executes the same processes as steps st3 to st5 described above, and then executes the same processes as steps st6 to st8 described above. Thereafter, the numerical control device 1 repeats the same processes as steps st3 to st8 for the other machined holes.

In the embodiment of the numerical control device 1, when the rotation direction of the spindle motor 71 is changed from forward to reverse at positions P5 and P9, the current load determination unit 31 compares the current FB value received from the motor FB information acquisition unit 60 during the spindle reversal operation with a preset reference value of the current load. Then, the current load determination unit 31 determines whether the current FB value is greater than the reference value, whether the current FB value is less than the reference value, or whether the current FB value is the same as the reference value.

If the current FB value is greater than the reference value, the current load determination unit 31 determines that the spindle motor 71 should be operated at a lower acceleration than the current acceleration, and transmits a low acceleration command to the acceleration control unit 32 to operate the spindle motor 71 at a lower acceleration than the current acceleration.

On the other hand, if the current FB value is smaller than the reference value, the current load determination unit 31 determines that the spindle motor 71 should be operated at a higher acceleration than the current value, and transmits a high acceleration command to the acceleration control unit 32 to operate the spindle motor 71 at a higher acceleration than the current value.

In addition, when changing the rotation direction of the spindle motor 71 from reverse rotation to forward rotation at positions P5 and P9, the numerical control device 1 of the embodiment compares the current FB value with the reference value of the current load, just as when changing the rotation direction from forward rotation to reverse rotation. Then, if the current FB value is greater than the reference value, the current load determination unit 31 sends a low acceleration command to the acceleration control unit 32, and if the current FB value is less than the reference value, it sends a high acceleration command to the acceleration control unit 32.

In addition, the numerical control device 1 may set the magnitude of the absolute value of the acceleration of the spindle motor 71 when the rotation direction of the spindle motor 71 is changed from reverse rotation to forward rotation to be the same as the magnitude of the absolute value of the acceleration calculated when the rotation direction is changed from forward rotation to reverse rotation.

The numerical control device 1 may also control the spindle motor 71 so that the acceleration of the spindle motor 71 at position P9 is the acceleration used at position P5. In other words, after the second or subsequent hole drilling is completed, the numerical control device 1 may rotate the spindle motor 71 at the acceleration used after the first hole drilling is completed. In this case, at position P9, the current load determination unit 31 does not need to compare the current FB value with the reference value.

Note that while FIG. 3 illustrates a case in which the machine tool 2 performs multiple drilling operations on the workpiece 81, the machine tool 2 may perform only one drilling operation on the workpiece 81. In this case, the numerical control device 1 performs processes st1 to st5, and then replaces the tool 80 with another tool. This allows the numerical control device 1 to perform drilling operations using the tool 80 without any cutting chips attached the next time the tool 80 is used.

Here, we will explain the rotation speed (spindle rotation speed) and acceleration of the spindle motor 71 when the numerical control device 1 controls the machine tool 2. Figure 4 is a diagram for explaining an example of the spindle rotation speed and acceleration of the spindle motor when the numerical control device according to the embodiment controls the machine tool. The horizontal axis in Figure 4 is time. The vertical axis of the upper graph in Figure 4 is the spindle rotation speed of the spindle motor 71, and the vertical axis of the lower graph is the acceleration of the spindle motor 71.

The spindle rotation speed is the machining speed, which is a constant speed VX (>0), from when the tool 80 starts drilling until it reaches position P5, which is the return point. Also, the rotation acceleration of the spindle motor 71 is acceleration AX = 0 from when the tool 80 starts drilling until it reaches position P5, which is the return point.

When the tool 80 reaches position P5, the numerical control device 1 reverses the rotation of the spindle motor 71, causing the tool 80 to rotate in the reverse direction instead of forward. As a result, the spindle rotation speed drops from speed VX, and after the spindle rotation speed becomes 0, it becomes a negative value.

In this case, if the current FB value of the spindle motor 71 is smaller than the reference value, the numerical control device 1 increases the acceleration above the current acceleration, A3. In other words, the numerical control device 1 controls the acceleration to an acceleration with an absolute value greater than that of acceleration A3. Here, the numerical control device 1 controls the acceleration of the spindle motor 71 to be acceleration A1 (>A3) corresponding to the reference value of the current FB value. This increases the slope of the spindle rotation speed.

In FIG. 4, the speed transition when the spindle motor 71 is rotating in reverse and the current FB value is smaller than the reference value is shown as speed transition V3, and the speed transition after the acceleration is increased is shown as speed transition V1.

When the current FB value of the spindle motor 71 is greater than the reference value, the numerical control device 1 decreases the acceleration below the current acceleration, A2. In other words, the numerical control device 1 controls the acceleration to an acceleration with an absolute value smaller than that of acceleration A2. Here, the numerical control device 1 controls the acceleration of the spindle motor 71 to be acceleration A1, which corresponds to the reference value of the current FB value. This reduces the slope of the spindle rotation speed.

In FIG. 4, the speed transition when the spindle motor 71 is rotating in reverse and the current FB value is greater than the reference value is shown as speed transition V2, and the speed transition after the acceleration is decreased is shown as speed transition V1.

After reversing the spindle motor 71, the numerical control device 1 accelerates the spindle motor 71 until the spindle speed of the spindle motor 71 reaches the command speed. The numerical control device 1 of the embodiment sends an acceleration command to the spindle motor 71 while changing the acceleration until the rotation speed of the spindle motor 71 during the spindle reversal reaches the command speed.

When the spindle speed of the spindle motor 71 reaches the command speed, the numerical control device 1 reverses the spindle motor 71 again to change the tool 80 from reverse rotation to forward rotation in order to perform the next drilling process. As a result, the spindle rotation speed increases from a negative value, and after the spindle rotation speed becomes 0, it becomes a positive value.

In this case, if the current FB value of the spindle motor 71 is smaller than the reference value, the numerical control device 1 increases the acceleration above the current acceleration, acceleration A6. In other words, the numerical control device 1 controls the acceleration to an acceleration with an absolute value greater than that of acceleration A6. Here, the numerical control device 1 controls the acceleration of the spindle motor 71 to be acceleration A4 (> A6) corresponding to the reference value of the current FB value. This increases the slope of the spindle rotation speed.

In FIG. 4, the speed transition when the current FB value is smaller than the reference value while the spindle motor 71 is rotating in the forward direction is shown as speed transition V6, and the speed transition after the acceleration is increased is shown as speed transition V4.

If the current FB value of the spindle motor 71 is greater than the reference value, the numerical control device 1 decreases the acceleration below the current acceleration A5. In other words, the numerical control device 1 controls the acceleration to an acceleration with an absolute value smaller than that of acceleration A5. Here, the numerical control device 1 controls the acceleration of the spindle motor 71 to be acceleration A4, which corresponds to the reference value of the current FB value. This reduces the slope of the spindle rotation speed.

In FIG. 4, the speed transition when the current FB value is greater than the reference value while the spindle motor 71 is rotating in the forward direction is shown as speed transition V5, and the speed transition after the acceleration is decreased is shown as speed transition V4.

In this way, the numerical control device 1 monitors the current load of the spindle motor 71 during the reversing operation of the tool 80, and rotates the tool 80 at an appropriate acceleration that takes into account the load on the spindle motor 71, thereby removing chips from the tool 80.

When the machine tool 2 controlled by the numerical control device 1 reverses the rotation of the spindle, the highest load is placed on the spindle motor 71 at the time the spindle reverses direction. For example, if the machine tool 2 is a large machine, performing a reversal operation of the spindle at an acceleration higher than the acceleration corresponding to the allowable value of the current feedback value may cause an excessive load to be placed on the spindle motor 71. Also, if the machine tool 2 is a machine that has gears between the spindle motor 71 and the tool 80, performing a reversal operation of the spindle at an acceleration higher than the acceleration corresponding to the allowable value of the current feedback value may accelerate wear of the gears, etc., and may promote wear of parts.

The numerical control device 1 of the embodiment reduces the acceleration when the acceleration is higher than the acceleration corresponding to the reference value of the current FB value. This allows the numerical control device 1 to prevent an excessive load from being placed on the spindle motor 71 even when the machine tool 2 is a large machine. Furthermore, the numerical control device 1 can slow down gear wear even when the machine tool 2 is a machine in which there is a gear between the spindle motor 71 and the tool 80.

In addition, the numerical control device 1 of the embodiment increases the acceleration when the acceleration is lower than the acceleration corresponding to the reference value of the current FB value. This enables the numerical control device 1 to shorten the processing time of the machine tool 2.

In this way, when a load greater than a reference value is applied to the spindle motor 71, the numerical control device 1 operates the spindle motor 71 at a low acceleration, thereby preventing the occurrence of an excessive load on the spindle motor 71. As a result, the numerical control device 1 can slow down gear wear and therefore suppress wear on parts. Therefore, the numerical control device 1 can extend the mechanical life of the machine tool 2. Furthermore, when a load smaller than a reference value is applied to the spindle motor 71, the numerical control device 1 operates the spindle motor 71 at a higher acceleration than before, thereby shortening the cycle time of the drilling process.

Here, the hardware configuration of the numerical control device 1 will be described. FIG. 5 is a diagram showing an example of a hardware configuration for realizing a numerical control device according to an embodiment. The numerical control device 1 can be realized by an input device 300, a processor 100, a memory 200, and an output device 400. An example of the processor 100 is a CPU (also called a Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, or DSP (Digital Signal Processor)) or a system LSI (Large Scale Integration). An example of the memory 200 is a RAM (Random Access Memory) or a ROM (Read Only Memory).

The numerical control device 1 is realized by the processor 100 reading and executing a control operation program (not shown) that is stored in the memory 200 and can be executed by a computer to execute the operations of the numerical control device 1. The control operation program, which is a program for executing the operations of the numerical control device 1, can also be said to cause a computer to execute the procedures or methods of the numerical control device 1.

The control calculation program executed by the processor 100 has a modular configuration including the numerical control device 1, and these components are loaded onto the main memory device and generated on the main memory device. Specifically, the control calculation program executed by the processor 100 has a modular configuration including a machining operation generation unit 20, a chip removal operation generation unit 30, an interpolation unit 40, a servo motor control unit 50, and a motor FB information acquisition unit 60, and these components are loaded onto the main memory device and generated on the main memory device.

The input device 300 accepts information set by the user and sends it to the processor 100 or the memory 200. The memory 200 stores control calculation programs, machining programs, various data (not shown), etc. The memory 200 is also used as a shared area that is a temporary memory when the processor 100 executes various processes. The output device 400 outputs a position command to the machine tool 2.

The control calculation program and machining program may be provided as a computer program product in the form of an installable or executable file stored on a computer-readable storage medium. The control calculation program and machining program may also be provided to the numerical control device 1 via a network such as the Internet. Note that some of the functions of the numerical control device 1 may be realized by dedicated hardware such as a dedicated circuit, and some by software or firmware.

In this way, when the current FB value of the spindle motor 71 is greater than the reference value, the numerical control device 1 of this embodiment operates the spindle motor 71 at a lower acceleration than at present, making it possible to reduce the load on the spindle motor 71 that rotates the tool 80 when removing chips entangled in the tool 80 from the tool 80.

In addition, when the current FB value of the spindle motor 71 is smaller than the reference value, the spindle motor 71 is operated at a higher acceleration than at present, so that chips entangled in the tool 80 can be removed from the tool 80 in a short time.

The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies. Parts of the configurations may be omitted or modified without departing from the spirit of the invention.

1 Numerical control device, 2 Machine tool, 10 Memory unit, 20 Machining operation generation unit, 21 Program analysis unit, 22 Cycle generation unit, 30 Chip removal operation generation unit, 31 Current load determination unit, 32 Acceleration control unit, 33 Rotation direction change unit, 40 Interpolation unit, 50 Servo motor control unit, 60 Motor FB information acquisition unit, 70 Servo motor, 71 Spindle motor, 72 Feed axis motor, 80 Tool, 81 Workpiece, 100 Processor, 200 Memory, 300 Input device, 400 Output device, A1 to A6, AX Acceleration, P1 to P9 Position.

Claims (8)

a servo motor control unit that controls a spindle motor of a machine tool that rotates a tool in a forward direction to drill a hole in a workpiece and rotates the tool in a reverse direction to remove chips entangled in the tool from the tool;
a current load determination unit that compares a current feedback value of the spindle motor corresponding to a load applied to the spindle motor with a preset reference value, and determines whether or not to change the acceleration of rotation of the spindle motor based on a result of the comparison;
an acceleration change unit that changes the acceleration based on a result of the determination;
Equipped with
A numerical control device comprising: A rotation direction change unit is further provided for outputting a command to reverse the rotation direction of the tool from forward rotation to reverse rotation after the completion of the drilling process.
the current load determination unit determines whether or not to change the acceleration when reversing a rotation direction of the tool from a forward rotation to a reverse rotation.
2. The numerical control device according to claim 1 . the rotation direction changing unit outputs a command to further reverse the rotation direction of the tool from reverse rotation to forward rotation after reversing the rotation direction of the tool from forward rotation to reverse rotation;
the current load determination unit determines whether or not to change the acceleration when reversing a rotation direction of the tool from reverse rotation to forward rotation.
3. The numerical control device according to claim 2 . the current load determination unit determines that the acceleration is to be decreased when the current feedback value is greater than the reference value,
The acceleration change unit decreases the acceleration.
4. The numerical control device according to claim 2 or 3. the current load determination unit determines that the acceleration is to be increased when the current feedback value is smaller than the reference value,
The acceleration change unit increases the acceleration.
4. The numerical control device according to claim 2 or 3. the current load determination unit determines whether or not to change the acceleration each time a plurality of drilling processes are completed when the drilling processes are performed;
The acceleration change unit controls the acceleration based on a result determined each time the drilling process is completed.
6. The numerical control device according to claim 1, wherein the numerical control device is a control device for controlling a control operation of the control unit. the current load determination unit calculates an amount of change in acceleration corresponding to a magnitude of a difference between the current feedback value and the reference value;
The acceleration change unit changes the acceleration using the calculated change amount.
7. The numerical control device according to claim 1, wherein the numerical control device is a control device for controlling a control operation of the control unit. a servo motor control step in which a numerical control device controls a spindle motor of a machine tool that rotates a tool in a forward direction to drill a hole in a workpiece and rotates the tool in a reverse direction to remove chips entangled in the tool from the tool;
a current load determination step in which the numerical control device compares a current feedback value of the spindle motor corresponding to a load applied to the spindle motor with a reference value, and determines whether or not to change the acceleration of rotation of the spindle motor based on a result of the comparison;
an acceleration control step in which the numerical control device controls the acceleration based on a result of the determination;
Including,
A numerical control method comprising:

Images