JP6605926B2 - Machine tool control apparatus and control method for controlling synchronous operation of main shaft and feed shaft - Google Patents

Description

  The present invention relates to a machine tool control device that controls synchronous operation of a main shaft and a feed shaft. The present invention also relates to a machine tool control method for controlling synchronous operation of a main shaft and a feed shaft.

  In a machine tool that performs tapping by synchronous operation of a main shaft and a feed shaft, various configurations for improving machining accuracy and shortening cycle time have been proposed. For example, Patent Document 1 is a screw machining device that performs tapping while the feed shaft follows the rotation of the main shaft, and calculates a feed command value for the feed shaft from the rotation speed and rotational acceleration of the main shaft and the screw pitch. In addition, a screw machining apparatus is disclosed in which the feed command value is corrected in accordance with the actual rotational position of the spindle, thereby improving the accuracy of tapping. Patent Document 2 discloses a spindle motor acceleration / deceleration control method for a numerical controller that performs synchronous control of a spindle and a feed axis for tapping, where the numerical controller is an acceleration / deceleration command corresponding to the output characteristics of the spindle. A spindle motor acceleration / deceleration control method is disclosed in which the response of the spindle is improved by controlling the spindle in accordance with this acceleration / deceleration command, and as a result, the cycle time can be shortened.

Japanese Patent No. 2629729 Japanese Patent No. 3553741

  In a machine tool that performs tapping by synchronous operation of the main shaft and the feed shaft, the cycle time is generally determined depending on the acceleration capability of the main shaft. With a simpler configuration, the numerical control device can perform the spindle operation without performing preliminary work that requires advanced technology, such as parameter settings and adjustments required for creating acceleration / deceleration commands corresponding to the output characteristics of the spindle. It is desired that the cycle time can be shortened by performing control to maximize the acceleration capability.

  One aspect of the present invention is a machine tool control device that controls synchronous operation of a spindle and a feed axis, a numerical control unit that creates a spindle command and a feed axis command based on a tap machining program, and a spindle according to the spindle command A spindle control unit that controls the rotation operation of the spindle, a rotation detection unit that detects the rotation position of the spindle, and a feed axis control unit that controls the feed operation of the feed axis based on the rotation position according to the feed axis command. The control unit acquires the total rotation amount and the maximum rotation speed of the main shaft from the start position to the target position from the tapping program, and sends the total rotation amount and the maximum rotation speed to the main shaft control unit as a main shaft command. A command output unit is provided, and the spindle control unit rotates between the initial operation control unit that accelerates and rotates the spindle at the maximum capacity from the start position by speed control with the maximum rotation speed as the target value, and the acceleration rotation at the maximum capacity. Based on the rotation amount detection unit for detecting the rotation amount per unit time of the spindle based on the position, the rotation amount storage unit for storing the detected rotation amount per unit time, the total rotation amount and the rotation position, The remaining rotation amount detection unit that detects the remaining amount of rotation of the main spindle from the current position to the target position, and after accelerating rotation at the maximum capacity, the main shaft is decelerated based on the rotation amount per unit time and the remaining rotation amount And a positioning operation control unit that executes position control for rotating and stopping at a target position.

  Another aspect of the present invention is a machine tool control method for controlling the synchronous operation of a main shaft and a feed shaft, wherein the control device has a total rotation amount and a maximum rotation speed of the main shaft from the start position to the target position. The rotation position of the spindle between the step of acquiring from the tapping program, the step of accelerating and rotating the spindle from the starting position at the maximum capacity by speed control with the maximum rotation speed as the target value, and the acceleration rotation at the maximum capacity The step of detecting and storing the rotation amount of the spindle per unit time based on the feedback value, and the remaining rotation amount of the spindle from the current position to the target position based on the total rotation amount and the rotation position feedback value After detecting acceleration and accelerating rotation at maximum capacity, position control is performed to decelerate the spindle and stop it at the target position based on the rotation amount per unit time and the remaining rotation amount A step that is a control method comprising a.

  According to the control device according to one aspect, when causing the spindle to rotate from the start position to the target position, the numerical control unit determines only the total rotation amount and the maximum rotation speed of the spindle relative to the spindle control unit. Command, and the spindle control unit executes the rotation operation by accelerating the spindle with the maximum output that uses the maximum allowable current with the maximum rotation speed as the target according to this spindle command, and the spindle unit stored during that time Based on the amount of rotation per hour and the remaining amount of rotation of the main shaft, the main shaft is decelerated and stopped at the target position. In order to create an acceleration / deceleration command corresponding to the output characteristics of the main shaft to the numerical controller It is not necessary to set or adjust the parameters, and it is possible to reduce the tapping cycle time by performing acceleration / deceleration control that maximizes the acceleration capability of the spindle with a simpler configuration. Moreover, the spindle control unit can create a position control command value for decelerating rotation using the rotation amount of the spindle per unit time stored during acceleration rotation at the maximum output, so that position control can be performed easily and quickly. Can be executed to stop the spindle at the target position.

  According to the control method according to another aspect, an effect equivalent to the effect of the control device described above is exhibited.

It is a functional block diagram which shows the structure of 1st Embodiment of a machine tool control apparatus. It is a flowchart which shows the structure of 1st Embodiment of the machine tool control method. It is a figure which shows an example of operation | movement of the main axis | shaft in embodiment of FIG. It is a figure which shows the other example of operation | movement of the main axis | shaft in embodiment of FIG. It is a functional block diagram which shows the structure of 2nd Embodiment of a machine tool control apparatus. It is a flowchart which shows the structure of 2nd Embodiment of the machine tool control method. It is a figure which shows an example of operation | movement of the main axis | shaft in embodiment of FIG.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Corresponding components are denoted by common reference symbols throughout the drawings.

  FIG. 1 is a functional block diagram showing the configuration of a machine tool control apparatus 10 according to the first embodiment. In a machine tool (for example, a lathe, a drilling machine, a machining center, etc.) that performs tapping by synchronous operation of the main shaft 12 and the feeding shaft 14, the control device 10 considers the screw pitch specified by the tapping program P. On the other hand, synchronous operation (so-called master-slave synchronization method) that operates so as to follow the rotational operation of the main shaft 12 is controlled. Although not shown, the spindle 12 is a control axis set in a drive device such as a spindle motor that rotates a gripping part that grips a workpiece or a tool at a speed necessary for machining. Although not shown, the feed shaft 14 is a control shaft set in a drive device such as a servo motor that feeds and moves a support portion that supports a workpiece or a tool at a speed necessary for machining. For example, in a lathe, a tool can be linearly fed with a feed shaft 14 to a workpiece rotating on the main shaft 12, or a work rotated with the main shaft 12 can be linearly fed to the tool with a feed shaft 14. In the drilling machine, the tool rotating on the main shaft 12 can be linearly fed to the workpiece by the feed shaft 14, or the workpiece can be linearly fed by the feed shaft 14 to the tool rotating on the main shaft 12. In either case, the feed shaft 14 having a relatively large margin for operating acceleration / deceleration torque operates so as to follow the spindle 12 having a relatively small margin for operating acceleration / deceleration torque, thereby reducing synchronization errors. Thus, processing accuracy can be improved. In the present invention, the configuration of the machine tool is not particularly limited.

  The control device 10 includes a numerical control unit 16 that generates a spindle command CS and a feed axis command CF based on the tap machining program P, a spindle control unit 18 that controls the rotation operation of the spindle 12 according to the spindle command CS, and the rotation of the spindle 12. A rotation detection unit 20 that detects the position, and a feed axis control unit 22 that controls the feed operation of the feed shaft 14 based on the rotation position detected by the rotation detection unit 20 in accordance with the feed axis command CF. The numerical control unit 16 includes a program interpretation unit 24 that interprets the tap machining program P, a spindle command CS that generates a spindle command CS according to the interpretation of the program interpretation unit 24, and a spindle command output unit 26 that sends the spindle command CS to the spindle control unit 18. And a feed axis command output unit 28 that generates a feed axis command CF according to the interpretation of the program interpretation unit 24 and sends the feed axis command CF to the feed axis control unit 22. The numerical control unit 16 can have a hardware configuration of a known CNC device.

  Prior to the start of tapping, the main spindle command output unit 26 determines the main shaft 12 from the starting position (rotational position) to the target position (rotational position) from the command value of the tap machining program P interpreted by the program interpretation unit 24. The total rotation amount S0 and the maximum rotation speed V0 are acquired, and the total rotation amount S0 and the maximum rotation speed V0 are sent to the spindle control unit 18 as a spindle command CS. For example, the tapping program P includes a command for machining a female screw having a screw pitch of 1.25 mm and a screw depth of 30 mm, assuming that the maximum rotation speed (in this example, the maximum rotation speed per minute) V0 of the spindle 12 is 3000 rev / min. In this case, since the total rotation amount S0 of the spindle 12 from the machining start position as the start position to the target screw depth as the target position is 30 ÷ 1.25 = 24 (rev), the spindle command output unit 26 Notifies the spindle controller 18 of V0 = 3000 (rev / min) and S0 = 24 (rev). Thus, the spindle command CS does not include a position command or an acceleration / deceleration command for rotating the spindle 12 to the target position (target screw depth).

  The main shaft control unit 18 controls the rotation operation of the main shaft 12 by general feedback control using the rotation position FBS (that is, feedback value) of the main shaft 12 detected by the rotation detection unit 20. In addition to the feedback value of the feed position of the feed shaft 14, the feed shaft control unit 22 uses the rotational position FBS of the main shaft 12 to control the feed operation of the feed shaft 14 that follows the operation of the main shaft 12 by feedback control. The rotation detection unit 20 can acquire the rotation position FBS from the output of a position detector (not shown) such as an encoder that detects the operating position of the drive device of the main shaft 12.

  The spindle control unit 18 includes an initial operation control unit 30 for accelerating and rotating the spindle 12 at the maximum capacity from the starting position by speed control with the maximum rotation speed V0 sent from the spindle command output unit 26 as a target value. A rotation amount detection unit 32 that detects a rotation amount Sd per unit time t of the spindle 12 based on the rotation position FBS during acceleration rotation, and a rotation amount that stores the rotation amount Sd detected per unit time t. Based on the total rotation amount S0 and the rotation position FBS sent from the storage unit 34 and the spindle command output unit 26, the remaining rotation amount Sr for detecting the remaining rotation amount Sr of the spindle 12 from the current position (rotation position) to the target position is detected. Based on the rotation amount detection unit 36 and the rotation amount Sd per unit time t stored in the rotation amount storage unit 34 and the remaining rotation amount Sr detected by the remaining rotation amount detection unit 36 after the acceleration rotation with the maximum capacity, Spindle 12 is decelerated and rotated And a positioning operation control unit 38 to perform position control for stopping at the target position Te.

  The unit time t, which is the detection time of the rotation amount Sd, is, for example, the time required for the initial motion control unit 30 to reach the maximum rotational speed V0 from the stopped state (that is, accelerated rotation at the maximum capacity). Total time) T0 can be set as a time divided by an arbitrary divisor. For example, the unit time t can be 1/50 or more of T0, and can be 1/10 or less of T0. The unit time t can be set to be the same as, for example, the operation control period (generally several ms) of the spindle 12. As the unit time t is shorter, the positioning accuracy of the position control executed by the positioning operation control unit 38 can be improved. As the unit time t is longer, the calculation load of the command value in the positioning operation control unit 38 can be reduced, and the storage capacity of the rotation amount storage unit 34 can be reduced. The preset unit time t can be stored as one of the control parameters in a memory (not shown) of the control device 10, for example.

  The control device 10 can control a rotation operation (referred to as a cutting operation in the present application) of the spindle 12 for cutting a prepared hole of a workpiece to a target screw depth with a tool in tapping using a machine tool. Further, the control device 10 controls the rotation operation (referred to as return operation in the present application) of the spindle 12 for pulling out the tool from the workpiece after cutting the pilot hole of the workpiece to the target screw depth in tapping using a machine tool. can do. In the control of the cutting operation, the “starting position” corresponds to the “machining start position” of tapping, and the “target position” corresponds to the “target screw depth” of tapping. In the control of the return operation, the “starting position” corresponds to the “target screw depth” for tapping, and the “target position” corresponds to the “return completion position” for tapping.

  FIG. 2 shows a first embodiment of a machine tool control method executed by the control device 10. 3 and 4 show two different examples of the operation of the spindle 12 realized by the control method of FIG. The control method according to this embodiment can control both the cutting operation and the return operation of the spindle 12 in tapping. In the following explanation, to help understanding, terms related to the control of the cutting operation are “total rotation amount”, “maximum rotation speed”, “acceleration rotation”, “rotation amount per unit time”, “remaining rotation amount”, While "current speed" and "decelerated rotation" are used, the terms of the return operation are substantially synonymous terms corresponding to "total return rotation amount", "maximum return rotation speed", "acceleration reverse rotation", "unit" “Return amount per time”, “Remaining return amount”, “Current speed of reverse rotation” and “Deceleration reverse rotation” are used.

  First, with reference to the flowchart of FIG. 2 together with FIG. In Step U1, the numerical control unit 16 (spindle command output unit 26) changes from the machining start position (starting position) to the target screw depth (target position) from the command value of the tap machining program P interpreted by the program interpretation unit 24. The total rotation amount S0 and the maximum rotation speed V0 of the main shaft 12 are acquired, and the total rotation amount S0 and the maximum rotation speed V0 are commanded to the main spindle control unit 18. In step U2, the spindle control unit 18 (initial motion control unit 30) performs maximum control using the allowable current of the drive source from the machining start position to the maximum by speed control with the maximum rotational speed V0 as the target speed. The cutting operation is executed by accelerating rotation with the ability. In Step U3, the spindle control unit 18 (residual rotation amount detection unit 36) sequentially detects the remaining rotation amount Sr from the current position during the acceleration rotation. The spindle control unit 18 notifies the numerical control unit 16 of the detected remaining rotation amount Sr each time it is detected. In Step U4, the spindle control unit 18 (the rotation amount detection unit 32, the rotation amount storage unit 34) calculates the rotation amount Sd of the main shaft 12 per unit time t based on the rotation position FBS during the acceleration rotation with the maximum capacity. Sequentially detect and store. The spindle control unit 18 can simultaneously perform steps U2 to U4.

  Next, in Step U5, the spindle control unit 18 (positioning operation control unit 38) determines whether or not the remaining rotation amount Sr is equal to or less than ½ of the total rotation amount S0. When Sr is ½ or less of S0, in Step U6, the spindle control unit 18 (positioning operation control unit 38) determines the spindle 12 based on the rotation amount Sd and the remaining rotation amount Sr per unit time t. Is rotated at a reduced speed to continue the cutting operation and stop at the target screw depth. If Sr is not less than 1/2 of S0, the process returns to step U4.

  Referring now to FIG. 3, when the remaining rotational speed Sr becomes 1/2 of the total rotational speed S0 before the current speed of the spindle 12 reaches the maximum rotational speed V0 (when the determination in step U5 is YES). An example of the cutting operation of the main shaft 12 is shown by a speed-time curve (curve on the upper side of the time axis). In FIG. 3, Vb is preset in the spindle 12 as a rotational speed (for example, the base speed of the spindle motor) that can be accelerated with a constant torque (ie, constant acceleration) from the start to the speed Vb, For example, it can be stored as one of the control parameters in a memory (not shown) of the control device 10. In practice, the speed Vb may be equal to or less than the base speed of the spindle motor (a speed in consideration of the reduction ratio when a reduction ratio exists between the spindle motor and the spindle 12).

The maximum capacity acceleration rotation (speed control) of the main spindle 12 in step U2 is executed at times T1 and T2 in FIG. Time T1 is a time of constant acceleration (maximum acceleration) from the start at the machining start position until reaching the speed Vb, and time T2 exceeds the speed Vb and the acceleration is automatically increased from the maximum acceleration due to the characteristics of the spindle motor. Time to gradually decrease. At these times T1 and T2 (that is, the acceleration rotation total time T0), the detection and storage of the rotation amount Sd of the spindle 12 per unit time t in step U4 is executed. Assuming that the unit time t is 1 / n of the speed control time (T1 + T2) (n is an integer equal to or greater than 2), the rotation amount detection unit 32 determines the rotation amount Sd ₁ from the start to the time point when the unit time t _{1 has} elapsed, t ₁ unit from the elapsed time period _{t 2} until the elapsed time amount of rotation Sd _2, ......, the unit time _{t (n-1)} sequentially detects in real time the rotation amount Sd _n from the elapsed time to time the unit time _{t n} passed . The rotation amount storage unit 34, all of the rotation amount Sd ₁ to SD _n the rotation amount detection unit 32 has detected is stored each time of the detection. The rotation amount Sd is detected and stored until the remaining rotation amount Sr becomes 1/2 of the total rotation amount S0 (that is, the rotation amount from the machining start position becomes 1/2 of the total rotation amount S0). In this configuration, ΣSd _i = Sd ₁ + Sd ₂ +... + Sd _n = S0 / 2.

  The speed control of the spindle 12 by the initial motion control unit 30 at the time point A (hereinafter, the intermediate point A) when the remaining rotation amount Sr becomes ½ of the total rotation amount S0 (when the determination at step U5 is YES). The positioning operation control unit 38 starts position control of the spindle 12. With the switching from speed control to position control, the operation of the main shaft 12 changes from accelerated rotation to decelerated rotation, and the decelerated rotation of the main shaft 12 in step U6 is executed at times T3 and T4. The remaining rotation amount detection unit 36 sequentially detects the remaining rotation amount Sr from the current position of the spindle 12 during the deceleration rotation.

In step U6, the positioning operation control unit 38 monitors the remaining rotation amount Sr that is sequentially detected, and the rotation amount Sd of the spindle 12 per unit time t stored during the speed control (that is, Sd _{1 to} Sd _n ). Is associated with the remaining rotation amount Sr, and a position control command value representing the position after the unit time t has elapsed from the current position is created. Specifically, the main shaft 12, the midpoint A (i.e. Sr = S0 / 2) Sr = from after the unit time t elapses (S0 / 2-Sd _n) command value to reach the position of, Sr = (S0 / 2 −Sd _n ) command value to reach the position of Sr = (S0 / 2−Sd _n −Sd _(n−1) ) after elapse of the unit time t, and Sr = (S0 / 2−Sd _{n -Sd (n-1) - ......} -Sd 2 Sr = after unit time t elapses from the _{position) (S0 / 2-Sd n} -Sd (n-1) - ...... -Sd 2 -Sd 1) = 0 A command value for reaching the position (namely, the target screw depth) is created. The spindle 12 operates in accordance with the position control command value created in this way, so that the negative acceleration represented by the speed-time curve obtained by inverting the speed-time curve during acceleration rotation when the intermediate point A is reached is a boundary. While it occurs, it rotates at a reduced speed from the intermediate point A toward the target screw depth. As can be seen from FIG. 3, time T3 corresponds to time to decelerate to velocity Vb with a gradually increasing negative acceleration, and time T4 reaches from velocity Vb to zero velocity with constant acceleration (negative maximum acceleration). Is equivalent to By such position control by the positioning operation control unit 38, the spindle 12 stops rotating when it reaches the target screw depth (Sr = 0).

  In the machine tool control method shown in FIG. 2, while the main shaft 12 is operated from the start position to the target position, the main shaft 12 is accelerated and rotated at the maximum capacity of the driving source in the speed control, and is acquired during the speed control in the position control. Since the main shaft 12 is decelerated and rotated using the rotation amount Sd per unit time t, it is not necessary to monitor the current speed of the main shaft 12 except during execution of the speed control loop. In this configuration, an example of the operation of the spindle 12 when the current speed of the spindle 12 reaches the maximum rotation speed V0 before the remaining rotation amount Sr becomes 1/2 of the total rotation amount S0 will be described with reference to FIG. To do.

FIG. 4 shows an example of a cutting operation of the main shaft 12 when the current speed of the main shaft 12 reaches the maximum rotational speed V0 before the main shaft 12 reaches the intermediate point A. Curve). Accelerated rotation (speed control) of the maximum capacity of the main shaft 12 in step U2 in FIG. 2 is executed at times T1 and T2 in FIG. At time T1, the spindle 12 is accelerated at a constant acceleration (maximum acceleration) from the start at the machining start position until reaching the speed Vb, and at time T2, the acceleration gradually decreases from the maximum acceleration beyond the speed Vb due to the characteristics of the spindle motor. . At time T2, when the current speed of the main shaft 12 reaches the maximum rotational speed V0 by the speed control loop before the main shaft 12 reaches the intermediate point A, the main shaft 12 thereafter reaches a time T5 until it reaches the intermediate point A. The cutting operation is continued by rotating at a constant speed V0 (that is, no acceleration). The detection and storage of the rotation amount Sd of the spindle 12 per unit time t in step U4 in FIG. 2 is executed at times T1 and T2 (that is, the total time T0 of acceleration rotation) and time T5. During the speed control of the times T1, T2 and T5, as with operation example of FIG. 3, all the rotational amount Sd ₁ to SD _n the rotation amount detection unit 32 has detected is stored in the rotation amount storage unit 34. The rotation amount Sd is detected and stored until the remaining rotation amount Sr becomes 1/2 of the total rotation amount S0. In this configuration, ΣSd _i = Sd ₁ + Sd ₂ +... + Sd _n = S0 / 2.

At the time point A (intermediate point A) when the remaining rotation amount Sr becomes ½ of the total rotation amount S0, the speed control of the main shaft 12 by the initial operation control unit 30 ends, and the positioning operation control unit 38 detects the position of the main shaft 12. Start control. With the switching from speed control to position control, the operation of the main shaft 12 changes from acceleration rotation to deceleration rotation, and at time T3 and T4, the main shaft 12 is decelerated and rotated at step U6 in FIG. In step U6, as in the operation example of FIG. 3, the positioning operation control unit 38 monitors the remaining rotation amount Sr that is sequentially detected, and the rotation amount per unit time t of the spindle 12 stored during the speed control. Sd (that is, Sd _{1 to} Sd _n ) is associated with the remaining rotation amount Sr, and a position control command value representing a position after the unit time t has elapsed from the current position is created. The spindle 12 operates in accordance with the position control command value created in this way, so that the negative acceleration represented by the speed-time curve obtained by inverting the speed-time curve during acceleration rotation when the intermediate point A is reached is a boundary. While it occurs, it rotates at a reduced speed from the intermediate point A toward the target screw depth. As understood from FIG. 4, the time T3 corresponds to a time for decelerating to the speed Vb with a negative acceleration that gradually increases through a constant speed rotation at the maximum rotational speed V0, and the time T4 is a constant acceleration ( This corresponds to the time until the speed reaches zero at (negative maximum acceleration). By such position control by the positioning operation control unit 38, the spindle 12 stops rotating when it reaches the target screw depth (Sr = 0).

  3 and 4, while the spindle control unit 18 controls the rotation operation (cutting operation) from the machining start position of the spindle 12 to the target screw depth, the feed shaft control unit 22 (FIG. 1). Uses the rotational position FBS of the main shaft 12 to control the feed shaft 14 so as to follow the operation of the main shaft 12 to perform the feed operation. The numerical control unit 16 monitors the remaining rotation amount Sr notified from the spindle control unit 18 while the main shaft control unit 18 executes the processes of Step U2 to Step U6, and the remaining rotation amount Sr is a first predetermined value. When the value becomes (minimum value close to zero) or less, it is determined that tapping has reached the target thread depth.

  As described above, when the controller 10 causes the spindle 12 to perform a cutting operation from the machining start position to the target screw depth, the numerical controller 16 controls the spindle controller 18 with respect to the total rotation amount S0 of the spindle 12. Only the maximum rotation speed V0 is notified as the spindle command CS, and the spindle control unit 18 accelerates the spindle 12 with the maximum output using the maximum allowable current for the maximum rotation speed V0 in accordance with the spindle command CS. Based on the rotation amount Sd of the main shaft 12 per unit time t stored during the operation and the remaining rotation amount Sr of the main shaft 12 detected sequentially, the cutting operation to the target screw depth is performed while rotating the main shaft 12 at a reduced speed. Is continuously executed and stopped at the target screw depth. Therefore, according to the control device 10, it is not necessary to set or adjust parameters for creating an acceleration / deceleration command corresponding to the output characteristics of the spindle 12 with respect to the numerical controller 16, and the spindle 12 can be configured with a simpler configuration. Acceleration / deceleration control that maximizes the acceleration capability of the tapping process can be performed to shorten the tapping cycle time.

  In addition, according to the control device 10, the spindle control unit 18 uses the rotation amount Sd of the spindle 12 for each unit time t stored during the acceleration rotation at the maximum output to obtain a command value for position control for the deceleration rotation. Therefore, the main shaft 12 can be stopped at the target screw depth by executing the position control easily and quickly.

  In the embodiment shown in FIGS. 1 and 2, the control device 10 can perform the same control as the above-described cutting operation control from the machining start position to the target screw depth when the main shaft 12 is returned as described above. 3 and 4 show the return operation of the main shaft 12 corresponding to the cutting operation in addition to the above-described cutting operation of the main shaft 12 by a speed-time curve (curve on the lower side of the time axis). Hereinafter, with reference to FIG. 1 to FIG. 4, a method for controlling the return motion of the spindle 12 executed by the control device 10 will be described.

  After determining that the tapping has reached the target thread depth, the numerical control unit 16 (spindle command output unit 26) determines the target screw from the command value of the tapping program P interpreted by the program interpretation unit 24 in step U1. The total return rotation amount S0 and the maximum return rotation speed V0 of the spindle 12 from the depth (starting position) to the return completion position (target position) are acquired, and the total return rotation amount S0 and the maximum return rotation amount V0 are acquired by the spindle control unit 18. Command the return rotational speed V0. The spindle command CS for the return operation also does not include a position command or an acceleration / deceleration command for rotating the spindle 12 to the return completion position. Next, in Step U2, the spindle control unit 18 (initial motion control unit 30) maximizes the allowable current of the drive source for the spindle 12 from the target screw depth by speed control with the maximum return rotational speed V0 as the target speed. Execute the return motion by accelerating reverse rotation with the maximum capacity used for. In step U3, the spindle control unit 18 (remaining rotation amount detection unit 36) sequentially detects the remaining return rotation amount Sr from the current position during the reverse acceleration rotation. The spindle control unit 18 notifies the numerical control unit 16 of the detected return rotation amount Sr each time it is detected. In step U4, the spindle control unit 18 (rotation amount detection unit 32, rotation amount storage unit 34) returns the amount of return rotation per unit time t of the spindle 12 based on the rotational position FBS during acceleration reverse rotation with the maximum capacity. Sd is sequentially detected and stored. The spindle control unit 18 can simultaneously perform steps U2 to U4.

  Next, in Step U5, the spindle control unit 18 determines whether or not the remaining return rotation amount Sr is equal to or less than ½ of the total return rotation amount S0. When Sr is ½ or less of S0, in Step U6, the spindle control unit 18 (positioning operation control unit 38), based on the return rotation amount Sd and the remaining return rotation amount Sr per unit time t, The spindle 12 is decelerated and reversely rotated to continue the return operation and stop at the return completion position. If Sr is not less than 1/2 of S0, the process returns to step U4.

Referring to FIG. 3, when the remaining return rotation amount Sr becomes 1/2 of the total return rotation amount S0 before the current speed of the reverse rotation of the main shaft 12 reaches the maximum return rotation speed V0 (determination in step U5 is YES). An example of the return operation of the main shaft 12 in the case of (1) is shown by a speed-time curve (curve below the time axis). The acceleration reverse rotation (speed control) of the maximum capacity of the main shaft 12 in step U2 is executed at times T6 and T7 in FIG. Time T6 is a time of constant acceleration (maximum acceleration) from the start at the target screw depth until reaching the speed Vb, and time T7 exceeds the speed Vb, and the acceleration is automatically accelerated according to the characteristics of the spindle motor. It is time to gradually decrease from. At these times T6 and T7 (that is, the entire acceleration rotation time T0), the return rotation amount Sd per unit time t of the spindle 12 in step U4 is detected in the same manner as the processing at the times T1 and T2 of the cutting operation described above. storing is executed, all of the return rotation amount Sd ₁ to SD _n the rotation amount detection unit 32 has detected is stored in the rotation amount storage unit 34. In the detection and storage of the return rotation amount Sd, the remaining return rotation amount Sr becomes 1/2 of the total return rotation amount S0 (that is, the return rotation amount from the target screw depth becomes 1/2 of the total return rotation amount S0). ) Is done. In this configuration, ΣSd _i = Sd ₁ + Sd ₂ +... + Sd _n = S0 / 2.

  At the time point A (intermediate point A) when the remaining return rotation amount Sr becomes ½ of the total return rotation amount S0 (when the determination at step U5 is YES), the speed control of the spindle 12 by the initial motion control unit 30 is performed. The positioning operation control unit 38 starts position control of the spindle 12. As the speed control is switched to the position control, the operation of the main shaft 12 is changed from the reverse acceleration to the reverse rotation. At times T8 and T9, the reverse rotation of the main shaft 12 in step U6 is executed. The remaining rotation amount detection unit 36 sequentially detects the remaining return rotation amount Sr from the current position of the main shaft 12 even during the reverse deceleration rotation.

In Step U6, the positioning operation control unit 38 monitors the remaining return rotation amount Sr detected sequentially and stores it during the speed control in the same manner as the processing at the times T3 and T4 of the cutting operation described above. return rotation amount per unit time t of Sd (i.e. _Sd 1 ~Sd _n) in correspondence with the remaining return rotation amount Sr, and creates a command value of the position control which represents the position after the unit time t elapses from the current position. The spindle 12 operates in accordance with the position control command value created in this way, so that a negative acceleration represented by a speed-time curve obtained by inverting the speed-time curve during acceleration reverse rotation when the intermediate point A is reached is a boundary. , Decelerate and reversely rotate from the intermediate point A toward the return completion position. As can be seen from FIG. 3, time T8 corresponds to time to decelerate to speed Vb with a gradually increasing negative acceleration, and time T9 extends from speed Vb to zero speed with constant acceleration (negative maximum acceleration). Is equivalent to By such position control by the positioning operation control unit 38, the spindle 12 stops rotating when it reaches the return completion position (Sr = 0).

Referring to FIG. 4, an example of the return operation of the main shaft 12 when the current speed of the reverse rotation of the main shaft 12 reaches the maximum return rotation speed V0 before the main shaft 12 reaches the intermediate point A is a speed-time curve. (Curve below the time axis). The maximum reverse acceleration (speed control) of the main shaft 12 in step U2 in FIG. 2 is executed at times T6 and T7 in FIG. At time T6, the spindle 12 is accelerated at a constant acceleration (maximum acceleration) from the start at the target screw depth until reaching the speed Vb, and at time T7, the acceleration gradually decreases from the maximum acceleration beyond the speed Vb due to the characteristics of the spindle motor. To do. At time T7, when the current speed of the reverse rotation of the main shaft 12 reaches the maximum return rotational speed V0 by the speed control loop before the main shaft 12 reaches the intermediate point A, the main shaft 12 reaches the intermediate point A thereafter. The motor returns at a constant speed V0 (that is, zero acceleration) for a period of time T10 until the return operation continues. The detection and storage of the return rotation amount Sd of the main spindle 12 per unit time t in step U4 in FIG. 2 is executed at times T6 and T7 (that is, the total acceleration rotation time T0) and at time T10. During the speed control time T6, T7 and T10, similarly to the operation example of FIG. 3, all return rotation amount Sd ₁ to SD _n the rotation amount detection unit 32 has detected is stored in the rotation amount storage unit 34 . The detection and storage of the return rotation amount Sd is performed until the remaining return rotation amount Sr becomes 1/2 of the total return rotation amount S0. In this configuration, ΣSd _i = Sd ₁ + Sd ₂ +... + Sd _n = S0 / 2.

At the time point A (intermediate point A) when the remaining return rotation amount Sr becomes ½ of the total return rotation amount S0, the speed control of the main shaft 12 by the initial operation control unit 30 ends, and the positioning operation control unit 38 performs the main shaft 12 operation. Start position control. With the switching from speed control to position control, the operation of the spindle 12 changes from acceleration reverse rotation to deceleration reverse rotation, and at times T8 and T9, deceleration reverse rotation of the spindle 12 in step U6 in FIG. 2 is executed. In step U6, as in the operation example of FIG. 3, the positioning operation control unit 38 monitors the remaining return rotation amount Sr detected sequentially, and returns the main shaft 12 for each unit time t stored during the speed control. rotation amount Sd (that Sd 1 _{to SD n)} in correspondence with the remaining return rotation amount Sr, creates a command value of the position control which represents the position after the unit time t elapses from the current position. The spindle 12 operates in accordance with the position control command value created in this way, so that a negative acceleration represented by a speed-time curve obtained by inverting the speed-time curve during acceleration reverse rotation when the intermediate point A is reached is a boundary. , Decelerate and reversely rotate from the intermediate point A toward the return completion position. As understood from FIG. 4, the time T8 corresponds to the time for decelerating to the speed Vb with a negative acceleration that gradually increases through constant speed rotation at the maximum return rotational speed V0, and the time T9 is a constant acceleration from the speed Vb. This corresponds to the time until the speed reaches zero at (negative maximum acceleration). By such position control by the positioning operation control unit 38, the spindle 12 stops rotating when it reaches the return completion position (Sr = 0).

  3 and 4, while the main shaft control unit 18 controls the reverse rotation operation (return operation) from the target screw depth of the main shaft 12 to the return completion position, the feed shaft control unit 22 (see FIG. 3). 1) uses the rotational position FBS of the main shaft 12 to control the feed shaft 14 so as to follow the operation of the main shaft 12 to perform a reverse feed operation. The numerical control unit 16 monitors the remaining rotation amount Sr notified from the main shaft control unit 18 while the main shaft control unit 18 executes the processes of Step U2 to Step U6, and the remaining rotation amount Sr is the second amount. When the value is equal to or less than a predetermined value (minimum value close to zero), it is determined that the return operation is completed and the tool is pulled out from the workpiece.

  As described above, when the control device 10 causes the main shaft 12 to perform a return operation from the target screw depth to the return completion position, the numerical control unit 16 makes a total return rotation of the main shaft 12 with respect to the main shaft control unit 18. Only the amount S0 and the maximum return rotational speed V0 are notified as the spindle command CS, and the spindle control unit 18 follows the main spindle command CS and outputs the spindle 12 with the maximum output using the maximum allowable current with the maximum return rotational speed V0 as a target. While performing the return operation by accelerating, the main shaft 12 is decelerated and reversely rotated based on the return rotation amount Sd of the main shaft 12 stored per unit time t and the remaining return rotation amount Sr of the main shaft 12 detected sequentially. A return operation up to the return completion position is continuously executed and stopped at the return completion position. Therefore, according to the control device 10, it is not necessary to set or adjust parameters for creating an acceleration / deceleration command corresponding to the output characteristics of the spindle 12 with respect to the numerical controller 16, and the spindle 12 can be configured with a simpler configuration. Acceleration / deceleration control that maximizes the acceleration capability of the tapping process can be performed to shorten the tapping cycle time.

  In addition, according to the control device 10, the spindle control unit 18 uses the return rotation amount Sd of the spindle 12 for each unit time t stored during acceleration reverse rotation at the maximum output to perform position control for decelerating reverse rotation. Since the command value can be created, the position control can be executed easily and quickly and the spindle 12 can be stopped at the return completion position.

  FIG. 5 is a functional block diagram showing the configuration of the machine tool control apparatus 40 according to the second embodiment. The control device 40 has the same configuration as that of the control device 10 shown in FIG. 1 except that the control device 40 has a configuration for monitoring the current speed of the spindle 12 not only during execution of the speed control loop. Corresponding components are denoted by common reference numerals, and detailed description thereof is omitted as appropriate.

  The control device 40 includes a numerical control unit 16, a spindle control unit 18, a rotation detection unit 20, and a feed axis control unit 22. The spindle control unit 18 includes an initial operation control unit 30, a rotation amount detection unit 32, a rotation amount storage unit 34, a remaining rotation amount detection unit 36, and a positioning operation control unit 38. The spindle control unit 18 further includes a current speed detection unit 42 that detects the current speed Vc of the spindle 12 based on the rotational position FBS. The positioning operation control unit 38 performs position control for decelerating and rotating the spindle 12 at the target position based on the rotation amount Sd, the remaining rotation amount Sr, and the current speed Vc per unit time t.

  Similar to the control device 10, the control device 40 can control both the cutting operation and the return operation of the spindle 12. FIG. 6 shows a second embodiment of the machine tool control method executed by the control device 40. FIG. 7 shows an example of the operation of the spindle 12 realized by the control method of FIG. Hereinafter, with reference to FIGS. 5 to 7, a control method for the cutting operation and the return operation of the main shaft 12 performed by the control device 40 will be described.

  First, with reference to the flowchart of FIG. 6 together with FIG. In step Q1, the numerical control unit 16 (spindle command output unit 26) uses the command value of the tap machining program P interpreted by the program interpretation unit 24, from the machining start position (starting position) to the target screw depth (target position). The total rotation amount S0 and the maximum rotation speed V0 of the main shaft 12 are acquired, and the total rotation amount S0 and the maximum rotation speed V0 are commanded to the main spindle control unit 18. In step Q2, the spindle control unit 18 (initial motion control unit 30) performs maximum control using the allowable current of the drive source from the machining start position to the maximum by speed control with the maximum rotational speed V0 as the target speed. The cutting operation is executed by accelerating rotation with the ability. In step Q3, the spindle control unit 18 (residual rotation amount detection unit 36, current speed detection unit 42) sequentially detects the remaining rotation amount Sr and the current speed Vc from the current position during the acceleration rotation. The spindle control unit 18 notifies the numerical control unit 16 of the detected remaining rotation amount Sr each time it is detected. In step Q4, the spindle control unit 18 (rotation amount detection unit 32, rotation amount storage unit 34) calculates the rotation amount Sd of the spindle 12 per unit time t based on the rotation position FBS during the acceleration rotation with the maximum capacity. Sequentially detect and store. The spindle control unit 18 can simultaneously perform steps Q2 to Q4.

  Next, at Step Q5, the spindle control unit 18 (positioning operation control unit 38) determines whether or not the current speed Vc during the acceleration rotation has reached the maximum rotation speed V0. When Vc has not reached V0, in Step Q6, the spindle control unit 18 (positioning operation control unit 38) determines whether or not the remaining rotation amount Sr is equal to or less than ½ of the total rotation amount S0. When Sr is ½ or less of S0, in Step Q7, the spindle control unit 18 (positioning operation control unit 38) determines the spindle 12 based on the rotation amount Sd and the remaining rotation amount Sr per unit time t. Is rotated at a reduced speed to continue the cutting operation and stop at the target screw depth. If Sr is not less than 1/2 of S0, the process returns to step Q4.

  If it is determined in step Q5 that the current speed Vc during acceleration rotation has not reached the maximum rotation speed V0, and it is determined in step Q6 that the remaining rotation amount Sr is less than or equal to ½ of the total rotation amount S0, The processes in steps Q1 to Q7 are substantially the same as the processes in steps U1 to U6 in FIG. 2 except for the processes related to the current speed Vc. Therefore, in this case, the main shaft 12 can perform the same cutting operation as the cutting operation shown in FIG.

On the other hand, when it is determined in step Q5 that the current speed Vc during the acceleration rotation has reached the maximum rotation speed V0, the spindle control unit 18 performs the determination of the spindle 12 in step Q8 instead of performing the determination in step Q6. The total rotation ΣSd _i (that is, Sd ₁ + Sd ₂ +... + Sd) of the rotation amount Sd per unit time t detected and stored until the current rotation speed Vc reaches the maximum rotation speed V0. _n ) It is determined whether or not the following is true. If Sr is equal to or less than ΣSd _i , the process proceeds to step Q7, where the spindle control unit 18 (positioning operation control unit 38) rotates the spindle 12 at a reduced speed and stops it at the target screw depth. Sr is If it is not less ΣSd _i, Sr repeats determination at step Q8 until the following ΣSd _i. The spindle 12 passes through the intermediate point A during the determination of step Q8.

FIG. 7 shows an example of the cutting operation of the spindle 12 when the spindle 12 passes the intermediate point A after the current speed Vc reaches the maximum rotational speed V0 (when the determination at step Q5 is YES). A curve (upper curve on the time axis) is shown. The acceleration rotation (speed control) of the maximum capacity of the main shaft 12 in step Q2 in FIG. 6 is executed at times T1 and T2 in FIG. At time T1, the spindle 12 is accelerated at a constant acceleration (maximum acceleration) from the start at the machining start position until reaching the speed Vb, and at time T2, the acceleration gradually decreases from the maximum acceleration over the speed Vb due to the characteristics of the spindle motor. . The detection and storage of the amount of rotation Sd of the main shaft 12 per unit time t in step Q4 in FIG. During the speed control of the time T1 and T2, similarly to the operation example of FIG. 3, all the rotational amount Sd ₁ to SD _n the rotation amount detection unit 32 has detected is stored in the rotation amount storage unit 34.

When the current speed Vc of the main shaft 12 reaches the maximum rotational speed V0 at time T2, the processing of the main shaft control unit 18 proceeds from step Q5 to step Q8 as described above, so whether the main shaft 12 has reached the intermediate point A or not. Is not determined (therefore, the rotation amount Sd is not detected and stored in step Q4 thereafter), and the spindle 12 rotates at a constant speed V0 (that is, acceleration is zero) over time T11 and continues the cutting operation. To do. From time T11 when the current speed Vc of the main shaft 12 reaches the maximum rotation speed V0, the remaining rotation amount Sr of the main shaft 12 becomes equal to the sum ΣSd _i of the rotation amounts Sd per unit time t stored during acceleration rotation. It corresponds to the time until. At time T11, the spindle 12 performs a cutting operation under speed control executed by the initial operation control unit 30. In this configuration, ΣSd _i = Sd ₁ + Sd ₂ +... + Sd _n ≠ S0 / 2.

At the time B when the remaining rotation amount Sr becomes equal to the total amount ΣSd _i of the rotation amount Sd, the speed control of the main shaft 12 by the initial operation control unit 30 ends, and the positioning operation control unit 38 starts position control of the main shaft 12. With the switching from speed control to position control, the operation of the main shaft 12 changes from acceleration rotation to deceleration rotation, and at time T3 and T4, the main shaft 12 is decelerated and rotated at step Q7 in FIG. In step Q7, as in the operation example of FIG. 3, the positioning operation control unit 38 monitors the remaining rotation amount Sr that is sequentially detected, and the rotation amount per unit time t of the spindle 12 stored during the speed control. Sd (that is, Sd _{1 to} Sd _n ) is associated with the remaining rotation amount Sr, and a position control command value representing a position after the unit time t has elapsed from the current position is created. The spindle 12 operates in accordance with the position control command value created in this way, so that the negative acceleration represented by the speed-time curve obtained by inverting the speed-time curve during acceleration rotation when the intermediate point A is reached is a boundary. As it occurs, it rotates at a reduced speed from the point B toward the target screw depth. As understood from FIG. 7, the time T3 corresponds to the time to decelerate to the speed Vb with the gradually increasing negative acceleration, and the time T4 reaches from the speed Vb to the speed zero with the constant acceleration (negative maximum acceleration). Is equivalent to By such position control by the positioning operation control unit 38, the spindle 12 stops rotating when it reaches the target screw depth (Sr = 0).

  In the operation example of FIG. 7, while the main shaft control unit 18 controls the rotation operation (cutting operation) from the machining start position of the main shaft 12 to the target screw depth, the feed shaft control unit 22 (FIG. 5) rotates the main shaft 12. Using the position FBS, the feed shaft 14 is controlled so as to follow the motion of the main shaft 12 to perform the feed operation. The numerical control unit 16 monitors the remaining rotation amount Sr notified from the spindle control unit 18 while the main shaft control unit 18 executes the processes of Step Q2 to Step Q8, and the remaining rotation amount Sr is a first predetermined value. When the value becomes (minimum value close to zero) or less, it is determined that tapping has reached the target thread depth.

  In the embodiment shown in FIGS. 5 and 6, the control device 40 can perform the same control as the above-described cutting operation control from the machining start position to the target screw depth when the spindle 12 returns. FIG. 7 shows a return operation of the main shaft 12 corresponding to the cutting operation in addition to the above-described cutting operation of the main shaft 12 by a speed-time curve (curve on the lower side of the time axis). Hereinafter, with reference to FIG. 5 to FIG. 7, a method for controlling the return motion of the spindle 12 executed by the control device 10 will be described.

  After determining that the tapping has reached the target thread depth, the numerical control unit 16 (spindle command output unit 26) determines the target screw from the command value of the tapping program P interpreted by the program interpretation unit 24 in step Q1. The total return rotation amount S0 and the maximum return rotation speed V0 of the spindle 12 from the depth (starting position) to the return completion position (target position) are acquired, and the total return rotation amount S0 and the maximum return rotation amount V0 are acquired by the spindle control unit 18. Command the return rotational speed V0. The spindle command CS for the return operation also does not include a position command or an acceleration / deceleration command for rotating the spindle 12 to the return completion position. Next, in Step Q2, the spindle control unit 18 (initial motion control unit 30) maximizes the allowable current of the drive source for the spindle 12 from the target screw depth by speed control with the maximum return rotational speed V0 as the target speed. Execute the return motion by accelerating reverse rotation with the maximum capacity used for. In step Q3, the spindle control unit 18 (remaining rotation amount detection unit 36, current speed detection unit 42) sequentially detects the remaining rotation amount Sr and the current speed Vc from the current position during the reverse acceleration rotation. The spindle control unit 18 notifies the numerical control unit 16 of the detected return rotation amount Sr each time it is detected. In step Q4, the spindle control unit 18 (rotation amount detection unit 32, rotation amount storage unit 34) returns the amount of return rotation per unit time t of the spindle 12 based on the rotation position FBS during acceleration reverse rotation with the maximum capacity. Sd is sequentially detected and stored. The spindle control unit 18 can simultaneously perform steps Q2 to Q4.

  Next, in Step Q5, the spindle control unit 18 (positioning operation control unit 38) determines whether or not the current speed Vc during the reverse acceleration rotation has reached the maximum return rotation speed V0. If Vc has not reached V0, in Step Q6, the spindle control unit 18 (positioning operation control unit 38) determines whether or not the remaining return rotation amount Sr is ½ or less of the total return rotation amount S0. To do. When Sr is less than or equal to 1/2 of S0, in Step Q7, the spindle control unit 18 (positioning operation control unit 38), based on the return rotation amount Sd and the remaining return rotation amount Sr per unit time t, The spindle 12 is decelerated and reversely rotated to continue the return operation and stop at the return completion position. If Sr is not less than 1/2 of S0, the process returns to step Q4.

  In step Q5, it is determined that the current speed Vc during acceleration reverse rotation has not reached the maximum return rotation speed V0, and in step Q6, it is determined that the remaining return rotation amount Sr is ½ or less of the total return rotation amount S0. In this case, the processes in steps Q1 to Q7 described above are substantially the same as the processes in steps U1 to U6 in FIG. 2 except for the processes related to the current speed Vc. Therefore, in this case, the main shaft 12 can perform a return operation similar to the return operation shown in FIG.

On the other hand, when it is determined in step Q5 that the current speed Vc during the reverse acceleration rotation has reached the maximum return rotation speed V0, the main spindle control unit 18 performs the main spindle in step Q8 instead of performing the determination in step Q6. The total return ΣSd _i of the return rotation amount Sd per unit time t detected and stored until the current reverse rotation current velocity Vc reaches the maximum return rotation velocity V0. Sd ₁ + Sd ₂ +... + Sd _n ) or less is determined. When Sr is equal to or less than ΣSd _i , the process proceeds to step Q7, and the main shaft control unit 18 (positioning operation control unit 38) rotates the main shaft 12 at a reverse speed and stops at the return completion position. Sr is If it is not less ΣSd _i, Sr repeats determination at step Q8 until the following ΣSd _i. The spindle 12 passes through the intermediate point A during the determination of step Q8.

Referring to FIG. 7, when the main shaft 12 passes the intermediate point A after the current speed Vc of the reverse rotation reaches the maximum return rotational speed V0 (when the determination in step Q5 is YES), the return operation of the main shaft 12 is performed. An example is shown in the speed-time curve (the curve below the time axis). The acceleration reverse rotation (speed control) of the maximum capacity of the main shaft 12 in step Q2 in FIG. 6 is executed at times T6 and T7 in FIG. At time T6, the spindle 12 is accelerated at a constant acceleration (maximum acceleration) from the start at the target screw depth until reaching the speed Vb, and at time T7, the acceleration gradually decreases from the maximum acceleration beyond the speed Vb due to the characteristics of the spindle motor. To do. The detection and storage of the return rotation amount Sd of the main shaft 12 per unit time t in step Q4 of FIG. 6 is executed at times T6 and T7 (that is, the total acceleration reverse rotation time T0). During the speed control time T6 and T7, as with operation example of FIG. 3, all the rotational amount Sd ₁ to SD _n the rotation amount detection unit 32 has detected is stored in the rotation amount storage unit 34.

At time T7, when the current speed Vc of the reverse rotation of the spindle 12 reaches the maximum return rotation speed V0, the process of the spindle control unit 18 proceeds from step Q5 to step Q8 as described above. Without determining whether or not it has been reached (therefore, the return rotation amount Sd in step Q4 is not detected and stored thereafter), the spindle 12 rotates at a constant speed V0 (that is, zero acceleration) over time T12. And return to continue. From time T12 when the current speed Vc of the reverse rotation of the main shaft 12 reaches the maximum return rotation speed V0, the return rotation amount Sd per unit time t stored during the acceleration reverse rotation is stored as the remaining return rotation amount Sr of the main shaft 12. This corresponds to the time until it becomes equal to the sum ΣSd _i of. At time T <b> 12, the spindle 12 moves back under speed control executed by the initial motion control unit 30. In this configuration, ΣSd _i = Sd ₁ + Sd ₂ +... + Sd _n ≠ S0 / 2.

At the time point B when the remaining return rotation amount Sr becomes equal to the sum ΣSd _i of the return rotation amounts Sd, the speed control of the main shaft 12 by the initial operation control unit 30 ends, and the positioning operation control unit 38 starts position control of the main shaft 12. To do. With the switching from speed control to position control, the operation of the spindle 12 changes from acceleration reverse rotation to deceleration reverse rotation, and at times T8 and T9, deceleration reverse rotation of the spindle 12 in step Q7 of FIG. 6 is executed. In step Q7, as in the operation example of FIG. 3, the positioning operation control unit 38 monitors the remaining return rotation amount Sr detected sequentially, and returns the main shaft 12 for each unit time t stored during the speed control. rotation amount Sd (that Sd 1 _{to SD n)} in correspondence with the remaining return rotation amount Sr, creates a command value of the position control which represents the position after the unit time t elapses from the current position. The spindle 12 operates in accordance with the position control command value created in this way, so that a negative acceleration represented by a speed-time curve obtained by inverting the speed-time curve during acceleration reverse rotation when the intermediate point A is reached is a boundary. , Decelerate and reversely rotate from point B toward the return completion position. As understood from FIG. 7, the time T8 corresponds to a time for decelerating to the speed Vb with a negative acceleration that gradually increases through a constant speed rotation at the maximum return rotational speed V0, and the time T9 is a constant acceleration from the speed Vb. This corresponds to the time until the speed reaches zero at (negative maximum acceleration). By such position control by the positioning operation control unit 38, the spindle 12 stops rotating when it reaches the return completion position (Sr = 0).

  In the operation example of FIG. 7, while the main shaft control unit 18 controls the reverse rotation operation (return operation) from the target screw depth of the main shaft 12 to the return completion position, the feed shaft control unit 22 (FIG. 5) Using the rotational position FBS, the feed shaft 14 is controlled so as to follow the operation of the main shaft 12 to perform the reverse feed operation. The numerical control unit 16 monitors the remaining rotation amount Sr notified from the main shaft control unit 18 while the main shaft control unit 18 executes the processing of Step Q2 to Step Q8, and the remaining rotation amount Sr is the second amount. When the value is equal to or less than a predetermined value (minimum value close to zero), it is determined that the return operation is completed and the tool is pulled out from the workpiece.

  As described above, when the control device 40 causes the spindle 12 to perform the cutting operation (or the return operation) from the machining start position (or the target screw depth) to the target screw depth (or the return completion position), numerical values are used. The control unit 16 notifies only the total rotation amount S0 (or total return rotation amount S0) and the maximum rotation speed V0 (or the maximum return rotation speed V0) of the main shaft 12 to the main shaft control unit 18 as the main shaft command CS. In accordance with the spindle command CS, the control unit 18 accelerates the spindle 12 with the maximum output using the maximum allowable current with the maximum rotational speed V0 (or maximum return rotational speed V0) as a target, and performs a cutting operation (or return operation). The rotation amount Sd of the main shaft 12 for each unit time t (or the return rotation amount Sd for each unit time t) and the remaining rotation amount Sr of the main shaft 12 (or the remaining return rotation amount Sr) that are sequentially detected. Based on The cutting operation (or return operation) up to the target screw depth (or return completion position) is continuously executed while the spindle 12 is decelerated (or reversely rotated at a reduced speed) and stopped at the target screw depth (or return completion position). It is configured to let you. Therefore, according to the control device 10, it is not necessary to set or adjust parameters for creating an acceleration / deceleration command corresponding to the output characteristics of the spindle 12 with respect to the numerical controller 16, and the spindle 12 can be configured with a simpler configuration. Acceleration / deceleration control that maximizes the acceleration capability of the tapping process can be performed to shorten the tapping cycle time.

  Moreover, according to the control device 40, the spindle control unit 18 rotates the rotation amount Sd per unit time t of the spindle 12 stored during acceleration rotation (or acceleration reverse rotation) at the maximum output (or return rotation every unit time t). Since the amount Sd) can be used to create a position control command value for decelerating rotation (or decelerating reverse rotation), the position control can be easily and quickly executed to move the spindle 12 to the target screw depth (or return completion position). ) Can be stopped. Further, in the control device 40, the spindle control unit 18 (positioning operation control unit 38) causes the rotation amount Sd of the spindle 12 per unit time t (or the return rotation amount Sd per unit time t) and the remaining rotation amount Sr (or the remaining rotation amount Sr). Since the position control is executed based on the return rotation amount Sr) and the current speed Vc (or the reverse rotation current speed Vc), the spindle 12 operates at the maximum rotation speed V0 (or the maximum return rotation speed V0). Can omit the detection and storage of the rotation amount Sd per unit time t (or the return rotation amount Sd per unit time t), thereby reducing the calculation load of the rotation amount detection unit 32 and the rotation amount. The storage capacity of the storage unit 34 can be reduced.

  The configuration of the control devices 10 and 40 described above can be described as a machine tool control method for controlling the synchronous operation of the main shaft 12 and the feed shaft 14. In this control method, the control devices 10 and 40 obtain the total rotation amount S0 and the maximum rotation speed V0 of the main shaft 12 from the start position to the target position from the tap machining program P, and the maximum rotation speed V0. A predetermined unit time of the main shaft 12 based on the rotational position feedback value FBS of the main shaft 12 between the step of accelerating and rotating the main shaft 12 from the starting position with the maximum capacity by speed control as a target value and the acceleration rotation with the maximum capacity. detecting and storing a rotation amount Sd for each t; detecting a remaining rotation amount Sr of the spindle 12 from the current position to the target position based on the total rotation amount S0 and the rotation position feedback value FBS; After the acceleration rotation at the maximum capacity, the spindle 12 is decelerated and stopped at the target position based on the rotation amount Sd and the remaining rotation amount Sr per unit time t. In which and a step of performing a position control of. This control method can further include a step of detecting the current speed Vc of the spindle 12 based on the rotational position feedback value FBS. In this case, the position control is executed based on the rotation amount Sd, the remaining rotation amount Sr, and the current speed Vc per unit time t. According to this control method, an effect equivalent to the effect of the control devices 10 and 40 described above is exhibited.

DESCRIPTION OF SYMBOLS 10, 40 Control apparatus 12 Spindle 14 Feed axis 16 Numerical control part 18 Spindle control part 20 Rotation detection part 22 Feed axis control part 26 Spindle command output part 28 Feed axis command output part 30 Initial operation control part 32 Rotation amount detection part 34 Rotation Amount storage unit 36 Remaining rotation amount detection unit 38 Positioning operation control unit 42 Current speed detection unit

Claims (8)

A machine tool control device for controlling the synchronous operation of a main shaft and a feed shaft,
A numerical control unit that creates a spindle command and a feed axis command based on a tap machining program;
A spindle control unit for controlling the rotation operation of the spindle according to the spindle command;
A rotation detector for detecting a rotation position of the spindle;
In accordance with the feed axis command, comprising a feed axis control unit for controlling the feed operation of the feed axis based on the rotational position,
The numerical control unit acquires the total rotation amount and the maximum rotation speed of the main shaft from the start position to the target position from the tapping program, and determines the total rotation amount and the maximum rotation speed from the main spindle command. As a spindle command output unit to be sent to the spindle control unit,
The spindle control unit
An initial operation control unit for accelerating and rotating the spindle at a maximum capacity from the starting position by speed control with the maximum rotational speed as a target value;
A rotation amount detection unit for detecting a rotation amount of the spindle per predetermined unit time based on the rotation position during acceleration rotation at the maximum capacity;
A rotation amount storage unit for storing the detected rotation amount per unit time;
A remaining rotation amount detection unit that detects a remaining rotation amount of the spindle from the current position to the target position based on the total rotation amount and the rotation position;
Positioning operation control unit for performing position control for decelerating and rotating the spindle to stop at the target position based on the rotation amount per unit time and the remaining rotation amount after the acceleration rotation with the maximum capacity And comprising
Control device.   A current speed detector for detecting a current speed of the spindle based on the rotational position; and the positioning operation control unit controls the position based on the rotation amount per unit time, the remaining rotation amount, and the current speed. The control device according to claim 1, wherein:   The control device according to claim 1, wherein the start position corresponds to a machining start position of tapping, and the target position corresponds to a target thread depth of tapping.   The control device according to claim 1, wherein the start position corresponds to a target thread depth for tapping, and the target position corresponds to a return completion position for tapping. A machine tool control method for controlling synchronous operation of a spindle and a feed axis,
The control unit
Obtaining a total rotation amount and a maximum rotation speed of the spindle from the start position to the target position from a tapping program;
Accelerating and rotating the spindle at a maximum capacity from the starting position by speed control with the maximum rotational speed as a target value;
Detecting and storing a predetermined amount of rotation of the spindle per unit time based on a rotational position feedback value of the spindle during acceleration rotation at the maximum capacity;
Detecting a remaining rotation amount of the main spindle from a current position to the target position based on the total rotation amount and the rotation position feedback value;
After accelerating rotation at the maximum capacity, performing position control for rotating the spindle at a reduced speed and stopping at the target position based on the rotation amount per unit time and the remaining rotation amount;
A control method comprising:   The step of detecting the current speed of the spindle based on the rotational position feedback value is further included, and the step of executing the position control is based on the rotation amount per unit time, the remaining rotation amount, and the current speed. The control method according to claim 5, wherein control is executed.   The control method according to claim 5 or 6, wherein the start position corresponds to a machining start position of tapping, and the target position corresponds to a target thread depth of tapping.   The control method according to claim 5 or 6, wherein the start position corresponds to a target thread depth for tapping, and the target position corresponds to a return completion position for tapping.

Images