Control devices, machine tools, control methods, and computer programs

Abstract

The present invention provides a control device, machine tool, control method, and computer program that facilitate the breaking of chips even when using a smoothing filter. [Solution] The control device includes a control unit that controls a machine tool which performs a movement process to move the tool or the workpiece so that the relative position between the tool and the workpiece becomes a target position, and an oscillation process to perform a relative oscillation between the tool and the workpiece while the tool or the workpiece is moving. The control unit generates a first velocity in the movement process, generates an oscillation velocity in the oscillation process, corrects the oscillation velocity to generate a second velocity so that the first trajectory of the tool and the second trajectory of the tool formed after the first trajectory overlap, and performs a smoothing process on the first velocity and the second velocity.

Description

Technical Field

[0001] The present technology relates to a control device, a machine tool, a control method, and a computer program for controlling a moving object including a spindle or a workpiece holding part.

Background Art

[0002] There is a processing machine that performs turning processing by rotating a workpiece, for example, a tool and moving it in the rotational axis direction, and swinging the workpiece in the rotational axis direction. The locus of the tool on the surface of the workpiece is spiral and wavy. By controlling the positions of the tool and the workpiece so that the tops of the waves in the locus overlap, the chips can be broken (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A smoothing filter, for example, a moving average filter may be used to control a motor that drives a tool or a workpiece. However, when a smoothing filter is used, the amplitude of the wavy locus becomes small, the tops of the waves do not overlap, and there is a risk that the chips cannot be broken.

[0005] The present disclosure has been made in view of such circumstances, and provides a control device, a machine tool, a control method, and a computer program that facilitate chip breaking even when a smoothing process is performed.

Means for Solving the Problems

[0006] A control device according to one embodiment of the present disclosure includes a control unit that controls a machine tool which performs a movement process for moving the tool or the workpiece so that the relative position between the tool and the workpiece becomes a target position, and an oscillation process for causing relative oscillation between the tool and the workpiece during the movement of the tool or the workpiece. The control unit generates a first velocity in the movement process, generates an oscillation velocity in the oscillation process, corrects the oscillation velocity to generate a second velocity so that the first trajectory of the tool and the second trajectory of the tool formed after the first trajectory overlap, and performs a smoothing process on the first velocity and the second velocity.

[0007] In this disclosure, the oscillation speed is corrected so that the first and second trajectories of the tool overlap.

[0008] A control device according to one embodiment of the present disclosure calculates the frequency of the oscillation, and in the correction of the oscillation speed, calculates a correction amount corresponding to the gain of the smoothing process with respect to the frequency, and calculates the amplitude of the oscillation based on the correction amount.

[0009] In this disclosure, a correction amount for the gain of the smoothing filter is calculated, and the amplitude of the oscillation in the tool or workpiece is calculated based on the correction amount.

[0010] In one embodiment of the present disclosure, the control device rotates relative to the tool and the workpiece, and the control unit calculates the frequency based on the number of rotations of the relative rotation between the tool and the workpiece.

[0011] In this disclosure, the oscillation frequency is calculated based on the rotational speed of the tool or workpiece.

[0012] In one embodiment of the present disclosure, the control unit calculates the correction amount based on the frequency and the time constant of the smoothing process.

[0013] In this disclosure, the correction amount is calculated based on the frequency and the time constant.

[0014] In one embodiment of the present disclosure, the control device includes a moving average process as part of the smoothing process.

[0015] In this disclosure, moving average processing is performed.

[0016] In one embodiment of the present disclosure, the control unit determines whether the gain corresponding to the calculated frequency is greater than or equal to a threshold determined based on the relative speed between the tool and the workpiece. If it is determined that the gain is not greater than or equal to the threshold, it determines whether an alternative frequency different from the calculated frequency exists. If it is determined that an alternative frequency exists, it outputs a signal to indicate the alternative frequency.

[0017] In this disclosure, if the gain is not above a threshold, it is determined whether or not an alternative frequency exists. If an alternative frequency exists, the alternative frequency is indicated. For example, it may be displayed on a display unit.

[0018] In one embodiment of the present disclosure, the control unit determines the order in which the multiple alternative frequencies are shown, according to the magnitude of the corresponding gains, when multiple alternative frequencies exist.

[0019] In this disclosure, when multiple alternative frequencies exist, the order in which the multiple alternative frequencies are displayed is determined according to the magnitude of the corresponding gains. For example, alternative frequencies with higher gains are displayed with higher priority than alternative frequencies with lower gains.

[0020] In one embodiment of the present disclosure, the control unit determines whether the gain corresponding to the calculated frequency is greater than or equal to a threshold determined based on the relative speed between the tool and the workpiece. If it determines that the gain is not greater than or equal to the threshold, it determines whether an alternative frequency different from the calculated frequency exists. If it determines that no alternative frequency exists, it outputs a signal to indicate a suggestion to change the rotational speed.

[0021] In the present disclosure, when it is determined that the gain is not greater than or equal to the threshold, it is determined whether there is an alternative frequency different from the calculated frequency. If there is no alternative frequency, a proposal for changing the rotational speed is made.

[0022] A machine tool according to an embodiment of the present disclosure includes a control unit that executes a movement process for moving the tool or the workpiece so that the relative position between the tool and the workpiece becomes a target position, and a swing process for performing relative swinging between the tool and the workpiece during the movement of the tool or the workpiece. The control unit generates a first speed in the movement process, generates a swing speed in the swing process, corrects the swing speed to generate a second speed so that a first locus of the tool and a second locus of the tool formed after the first locus overlap, and performs a smoothing process on the first speed and the second speed.

[0023] In the present disclosure, the swing speed is corrected so that the first locus and the second locus of the tool overlap.

[0024] [[ID=?]]

[0025] In the present disclosure, the swing speed is corrected so that the first locus and the second locus of the tool overlap.

[0026] It should be noted that there seems to be a formatting issue with the "ID=?" in the original text which is translated as " " as per the instruction to preserve the 7-digit tags exactly. If this is not correct, please check and correct the original text.A computer program according to one embodiment of the present disclosure is a computer program executable in the control unit of a machine tool that performs a movement process for moving the tool or the workpiece so that the relative position between the tool and the workpiece becomes a target position, and an oscillation process for causing relative oscillation between the tool and the workpiece during the movement of the tool or the workpiece, wherein the control unit is instructed to generate a first velocity in the movement process, generate an oscillation velocity in the oscillation process, correct the oscillation velocity to generate a second velocity so that the first trajectory of the tool and the second trajectory of the tool formed after the first trajectory overlap, and perform a smoothing process on the first velocity and the second velocity.

[0027] In this disclosure, the oscillation speed is corrected so that the first and second trajectories of the tool overlap. [Effects of the Invention]

[0028] In a control device, machine tool, control method, and computer program according to one embodiment of the present disclosure, the amplitude of oscillation in the tool or workpiece is calculated based on a correction amount for the gain of the smoothing filter. By using the calculated amplitude, the peaks of the waveforms tend to overlap, making it easier to break up the chips. [Brief explanation of the drawing]

[0029] [Figure 1] This is a perspective view showing a machine tool. [Figure 2] This is a block diagram illustrating the configuration of the control device. [Figure 3] This is an explanatory diagram illustrating the turning process of a workpiece using a tool. [Figure 4] This is a block diagram illustrating the preprocessing steps for feedback control of the Y-axis motor. [Figure 5] This is a schematic graph showing the relationship between the presence or absence of a moving average filter and the command speed. [Figure 6] This is an unfolded diagram showing an example of the waveform trajectory when a moving average filter is used. [Figure 7]This is an unfolded diagram showing an example of the waveform trajectory when motion processing is performed without oscillation processing. [Figure 8] This is an unfolded diagram showing examples of waveform trajectories for the cases ks=1 / 2, ks=3 / 2, and ks=5 / 2. [Figure 9] This is an explanatory diagram illustrating the amount of movement, the air cut length, and the oscillation amplitude. [Figure 10] This graph shows an example of the relationship between gain characteristics and angular frequency ω. [Figure 11] This is an enlarged diagram showing a comparative example of the waveform trajectory when no correction magnification is used and when a correction magnification is used. [Figure 12] This graph shows an example of the relationship between the threshold and the gain characteristics. [Figure 13] This graph shows an example of the relationship between gain characteristics and angular frequency when no alternative frequency is available. [Figure 14] This is a flowchart illustrating the preprocessing of feedback control by the control unit. [Modes for carrying out the invention]

[0030] The present invention will be described below based on drawings showing a machine tool according to an embodiment. In the following description, the directions up, down, front, back, left, and right in the figures will be used. Up, down, front, back, left, and right in the figures are examples of directional indications, and the directional indications are not limited to these. Figure 1 is a schematic perspective view of a machine tool. Note that the tool magazine for storing replacement tools is not shown in Figure 1.

[0031] The machine tool has a rectangular base 1 that extends front to back. A support device 3 for supporting the workpiece is provided on the front side of the upper part of the base 1. The support device 3 comprises a base 3a, an A-axis motor 3b, a C-axis motor 3c, and two support plates 3d. The two support plates 3d are positioned on the left and right sides of the base 1. Base 3a is positioned between the two support plates 3d and is connected to the support plates 3d so as to be rotatable around the A-axis. The A-axis extends in the left-right direction. Driven by the A-axis motor 3b, base 3a rotates around the A-axis.

[0032] The base 3a has a support surface 3e for supporting the workpiece, and a C-axis motor 3c is provided on the opposite side of the support surface 3e. The support surface 3e is parallel to the A-axis. The C-axis extends in a direction perpendicular to the support surface 3e. The support surface 3e rotates around the C-axis when driven by the C-axis motor 3c.

[0033] A support base 2 for supporting the vertical column 4, which will be described later, is provided on the rear side of the upper part of the base 1. A Y-axis movement mechanism 10 that moves in the front-to-back direction is provided on the upper part of the support base 2. The Y-axis movement mechanism 10 comprises two tracks 11 extending in the front-to-back direction, a Y-axis screw shaft 12, a Y-axis motor 13, and a bearing 14.

[0034] Tracks 11 are provided on the left and right sides of the upper part of the support base 2. The Y-axis screw shaft 12 extends front to back and is provided between the two tracks 11. Bearings 14 are provided at the front end and in the middle of the Y-axis screw shaft 12. The bearing in the middle is not shown in the illustration. The Y-axis motor 13 is connected to the rear end of the Y-axis screw shaft 12.

[0035] A nut (not shown) is screwed onto the Y-axis screw shaft 12. Multiple sliders 15 are slidably mounted on each track 11. A movable plate 16 is connected to the top of the nut and sliders 15. The movable plate 16 extends horizontally. The rotation of the Y-axis motor 13 causes the Y-axis screw shaft 12 to rotate, the nut to move in the front-back direction, and the movable plate 16 to move in the front-back direction.

[0036] An X-axis movement mechanism 20 that moves in the left-right direction is provided on the upper surface of the movable plate 16. The X-axis movement mechanism 20 comprises two tracks 21 extending to the left and right, an X-axis screw shaft 22, and an X-axis motor 23 (see Figure 2).

[0037] Tracks 21 are provided on the front and rear of the upper surface of the movable plate 16. The X-axis screw shaft 22 extends to the left and right and is provided between the two tracks 21. The left end and the middle section of the X-axis screw shaft 22 are supported by bearings 24. The bearings 24 are fixed to the movable plate 16.

[0038] A nut (not shown) is connected to the X-axis screw shaft 22. Multiple sliders 26 are slidably mounted on each track 21. A vertical column 4 is connected to the upper part of the nut and sliders 26. The vertical column 4 is columnar in shape. The rotation of the X-axis motor 23 causes the X-axis screw shaft 22 to rotate, the nut to move left and right, and the vertical column 4 to move left and right.

[0039] A Z-axis movement mechanism 30 that moves vertically is provided on the front of the vertical column 4. The Z-axis movement mechanism 30 comprises two vertically extending tracks 31, a Z-axis screw shaft 32, a Z-axis motor 33, and a bearing 34.

[0040] Tracks 31 are provided on the left and right sides of the front of the vertical column 4. The Z-axis screw shaft 32 extends vertically and is located between the two tracks 31. Bearings 34 are provided at the lower end and in the middle of the Z-axis screw shaft 32. The bearing in the middle is not shown in the diagram. The Z-axis motor 33 is connected to the upper end of the Z-axis screw shaft 32.

[0041] A nut (not shown) is screwed onto the Z-axis screw shaft 32. Multiple sliders 35 are slidably mounted on each track 31. The spindle head 5 is connected to the front of the nut and sliders 35. The rotation of the Z-axis motor 33 causes the Z-axis screw shaft 32 to rotate, the nut to move vertically, and the spindle head 5 to move vertically.

[0042] A spindle 5a extending vertically is installed inside the spindle head 5. The spindle 5a rotates around its axis. A spindle motor 6 is installed at the upper end of the spindle head 5. A tool is attached to the lower end of the spindle 5a. The rotation of the spindle motor 6 causes the spindle 5a to rotate, and the tool to rotate as well. The rotated tool processes the workpiece supported by the support device 3.

[0043] The machine tool is equipped with a tool changer (not shown) for changing tools. The tool changer exchanges the tool stored in the tool magazine (not shown) with the tool mounted on the spindle 5a.

[0044] Figure 2 is a block diagram illustrating the configuration of the control device 50. The control device 50 comprises a control unit 51, a main memory unit 52, an auxiliary memory unit 53, and an input / output interface 54. The control unit 51 includes, for example, a processor or logic circuit. The processor includes, for example, a CPU, MPU, or GPU. The logic circuit includes, for example, an FPGA or ASIC. The main memory unit 52 includes RAM. When an operator operates the operation unit 7, a signal is input from the operation unit 7 to the input / output interface 54. The operation unit 7 is, for example, a keyboard, buttons, a touch panel, etc. The input / output interface 54 outputs a signal to the display unit 8. The display unit 8 displays characters, figures, symbols, etc. The display unit 8 is, for example, a liquid crystal display or an organic EL display.

[0045] The auxiliary storage unit 53 includes a rewritable storage device, such as an EEPROM, flash ROM, or hard disk. The auxiliary storage unit 53 stores a control program. The control program includes a machining program, a program for executing movement processing and oscillation processing, etc. The machining program, which includes the rotational speed n, movement amount f, command path, etc. (described later), is stored in a storage medium 65, such as an optical disc, flash memory, or hard disk, and may be downloaded from the storage medium 65 to the auxiliary storage unit 53. Alternatively, it may be downloaded from an external server to the auxiliary storage unit 53 via a network connected to the machine tool. The control unit 51 reads the control program from the auxiliary storage unit 53 to the main storage unit 52 and controls the drive of each motor. The processing by the control program may be implemented, for example, by an external server or external terminal via a network, or by distributed processing by an external server and devices other than the external server, such as an external terminal and control device 50, or by a quantum computer.

[0046] The control device 50 includes a Y-axis control circuit 56 that corresponds to the Y-axis motor 13. The Y-axis motor 13 is equipped with an encoder 13a. Based on a command from the control unit 51, the Y-axis control circuit 56 outputs a command indicating the amount of current to the Y-axis motor 13. The Y-axis motor 13 is driven. The encoder 13a outputs a position feedback signal to the Y-axis control circuit 56. Based on the position feedback signal, the Y-axis control circuit 56 performs feedback control.

[0047] The control device 50 includes an X-axis control circuit 55 that corresponds to the X-axis motor 23. The X-axis motor 23 is equipped with an encoder 23a. The X-axis control circuit 55, X-axis motor 23, and encoder 23a are the same as those for the Y-axis, so their explanation is omitted.

[0048] The control device 50 includes a Z-axis control circuit 57 that corresponds to the Z-axis motor 33. The Z-axis motor 33 is equipped with an encoder 33a. The Z-axis control circuit 57, Z-axis motor 33, and encoder 33a are the same as those for the Y-axis, so their explanation is omitted.

[0049] The control device 50 includes an A-axis control circuit 58 corresponding to the A-axis motor 3b. The A-axis motor 3b is equipped with an encoder 3ba. The A-axis control circuit 58, A-axis motor 3b, and encoder 3ba are the same as those for the Y-axis, and their description is omitted.

[0050] The control device 50 includes a C-axis control circuit 59 that corresponds to the C-axis motor 3c. The C-axis motor 3c is equipped with an encoder 3ca. The C-axis control circuit 59, C-axis motor 3c, and encoder 3ca are the same as those for the Y-axis, so their description is omitted. The control device 50 also performs the same feedback control on the spindle motor 6 as on the Y-axis motor 13.

[0051] Figure 3 is an explanatory diagram illustrating the turning process of a workpiece 61 using a tool 60. For example, the spindle 5a is fitted with the tool 60. The workpiece 61 is supported on a support surface 3e. The support surface 3e faces backward. That is, the support surface 3e is perpendicular to the Y-axis. The workpiece 61 rotates around the C-axis, i.e., around the Y-axis. The Y-axis control circuit 56 performs a movement process in which the spindle 5a moves to a target position, and an oscillation process in which the spindle 5a oscillates while moving to the target position. The movement process is a process of moving from front to back. Driven by the Y-axis motor 13, the tool 60 moves to the target position. That is, the control unit 51 performs a movement process in which the tool 60 moves so that the relative position between the tool 60 and the workpiece 61 becomes the target position.

[0052] The oscillating process is a process of oscillating in the forward and backward direction. Driven by the Y-axis motor 13, the tool 60 moves from front to back while oscillating back and forth. That is, the control unit 51 performs an oscillating process that causes relative oscillating between the tool 60 and the workpiece 61 while the tool 60 is moving. The trajectory of the tool 60 on the surface of the workpiece 61 is helical and wavy. The Y-axis control circuit 56 can break up the chips by controlling the positions of the tool and the workpiece so that the peaks of the waveforms in the trajectory overlap. Hereinafter, the region where the peaks of the waveforms overlap will also be referred to as air cut.

[0053] Figure 4 is a block diagram illustrating the preprocessing of feedback control for the Y-axis motor 13. The control unit 51 includes a movement processing unit 51a, an oscillation processing unit 51b, a correction unit 51c, a moving average filter 51d, an integrator 51e, and an adder 51f. The movement processing unit 51a obtains the target position from the machining program, differentiates the target position to generate the first velocity, and outputs it to the adder 51f. The oscillation processing unit 51b obtains the rotational speed n of the workpiece 61, the oscillation magnification ks, the amount of movement f, and the air cut length α, etc., which will be described later, and generates the oscillation speed, etc., and outputs it to the correction unit 51c. Details of the processing in the oscillation processing unit 51b will be described later.

[0054] The correction unit 51c performs a correction process on the oscillation speed to generate a second speed and outputs it to the adder 51f. Details of the correction process will be described later. The adder 51f adds the first speed and the second speed, in other words, superimposes the first speed and the second speed, and outputs the superimposed speed (hereinafter referred to as the third speed) to the moving average filter 51d.

[0055] The moving average filter 51d performs a moving average operation on the third velocity and outputs the result to the integrator 51e. The integrator 51e integrates the third velocity after the moving average operation and outputs the integrated result, i.e., the position command, to the Y-axis control circuit 56. Based on the integrated result, the Y-axis control circuit 56 outputs a command indicating the amount of current to the Y-axis motor 13. The control of the X-axis motor 23 and Z-axis motor 33 is the same as the control of the Y-axis motor 13 described above, and a detailed explanation thereof is omitted.

[0056] (Need for correction) The necessity of correction will be explained below. The following explanation of the necessity of correction applies when the control unit 51 does not have a correction unit 51c. Figure 5 is a schematic graph showing the relationship between the presence or absence of the moving average filter 51d and the command speed. As shown in the upper part of Figure 5, when the moving average filter 51d is absent, the target speed V0 is input at time t1, and the input of the target speed V0 continues until time t2. At time t2, a speed of 0 is input.

[0057] As shown in the lower part of Figure 5, when a moving average filter 51d is present, a speed smaller than the target speed V0 is input at time t1, the speed gradually increases, and the target speed V0 is input at time t1'. The input of the target speed V0 continues until time t2. From time t2 to time t2', a speed smaller than the target speed V0 is input, and the speed gradually decreases. At time t2', a speed of 0 is input. The moving average filter 51d can suppress the acceleration of the Y-axis motor 13 and suppress the resonant frequency component, for example.

[0058] For example, if the filter length of the moving average filter 51d is k and the sampling period is T, the gain characteristics of the moving average filter 51d are given by the following equation (1). Herein, ω is the angular frequency of the tool 60 at the speed input to the moving average filter 51d. The speed input to the moving average filter 51d includes the oscillation speed generated by the oscillation processing unit 51b. The oscillation speed is the speed when oscillating in a predetermined direction; for example, in the case of controlling the Y-axis motor 13, it is the speed when oscillating in the forward and backward direction. |G(e jωt )|=(1 / k)|sin(ωkT / 2) / sin(ωT / 2)|···(1) In other words, the gain of the angular frequency ω component of the velocity input to the moving average filter 51d is multiplied by (1 / k)|sin(ωkT / 2) / sin(ωT / 2)|. |G(e jωt Since || is less than 1, the gain of the angular frequency ω component of the velocity output from the moving average filter 51d is smaller than that at the input. The time constant Tc of the moving average filter 51d is, for example, Tc = kT. The auxiliary storage unit 53 stores the filter length k and the sampling period T in advance. The control unit 51 can calculate the time constant Tc from the filter length k and the sampling period T. The auxiliary storage unit 53 may also store the time constant Tc in advance. When the sampling period T is sufficiently small, the gain characteristics can be expressed by the following equation (1-2). |G(e jωt )|=|sin(ωTc / 2)| / (ωTc / 2)···(1-2)

[0059] Figure 6 is an unfolded diagram showing an example of the waveform trajectory when using the moving average filter 51d. In Figure 6, the Y-axis indicates the position in the front-back direction. The positive side of the Y-axis indicates the front, and the negative side indicates the rear. The feed direction of the tool 60 is towards the negative side of the Y-axis. The θ-axis indicates the rotation angle of the workpiece 61, i.e., the rotation angle around the C-axis. As shown by the waveform trajectory Pa in Figure 6, when the moving average filter 51d is used, the gain of the angular frequency ω component of the command speed becomes small, so the amplitude of the waveform trajectory becomes small, the peaks of the waveforms do not overlap, and there is a risk that the chips cannot be separated. Therefore, the machine tool according to the embodiment performs a correction.

[0060] The machine tool according to this embodiment is equipped with a correction unit 51c, and when a moving average filter 51d is used, the correction unit 51c performs a correction process. The correction process calculates a correction amount corresponding to the gain of the moving average filter 51d with respect to the oscillation speed. Based on the correction amount, the correction unit 51c calculates the amplitude of the oscillation of the spindle 5a so that the peaks of the waveforms overlap, that is, so that air cut occurs and the chips are divided. The correction process will be described below.

[0061] Figure 7 is an unfolded diagram showing an example of the waveform trajectory when movement processing is performed without oscillation processing. The control unit 51 of the machine tool obtains the rotational speed of the support surface 3e around the C axis, i.e., the rotational speed of the workpiece 61 n [min-1], and the amount of movement per revolution of the tool 60 f [mm / rev] from the machining program. Note that the machine tool according to this embodiment performs oscillation processing. Figure 7 is shown for convenience to facilitate understanding of the rotational speed n and the amount of movement f.

[0062] For example, the operator operates the control unit 7 and inputs the oscillation magnification ks. The oscillation processing unit 51b obtains the oscillation magnification ks. The oscillation processing unit 51b calculates the angular frequency ω of the oscillation from the rotational speed n and the oscillation magnification ks. The angular frequency ω is calculated using the following equation 2. ω=2πnks / 60(ks=1 / 2, 3 / 2, 5 / 2,...)...(2) The operator sets ks such that, for example, the phase of the tool 60's oscillation at the p-th rotation (where p is a natural number) of the workpiece 61 is in opposite phase to the phase of the tool 60's oscillation at the p+1-th rotation of the workpiece 61. By setting them in opposite phase, the peaks of the waveform at the p-th rotation and the peaks of the waveform at the p+1-th rotation come closer together and are more likely to overlap. In other words, air cut is more likely to occur. The operator operates the control unit 7 and inputs the desired ks.

[0063] Figure 8 is an unfolded diagram showing examples of waveform trajectories for the cases ks=1 / 2, ks=3 / 2, and ks=5 / 2. The top diagram in Figure 8 shows the case ks=1 / 2, the middle diagram shows the case ks=3 / 2, and the bottom diagram shows the case ks=5 / 2. As shown in the top diagram of Figure 8, when ks=1 / 2, the vicinity of the peak of the waveform at the p-th cycle and the vicinity of the peak of the waveform at the p+1-th cycle overlap at one point. That is, an air cut occurs at one point. As shown in the middle diagram of Figure 8, when ks=3 / 2, the vicinity of the peak of the waveform at the p-th cycle and the vicinity of the peak of the waveform at the p+1-th cycle overlap at three points. That is, an air cut occurs at three points. As shown in the bottom diagram of Figure 8, when ks=5 / 2, the vicinity of the peak of the waveform at the p-th cycle and the vicinity of the peak of the waveform at the p+1-th cycle overlap at five points. That is, an air cut occurs at five points. The waveform at the p-th lap constitutes the first trajectory of the tool, and the waveform at the p+1-th lap constitutes the second trajectory of the tool.

[0064] The operator sets ks according to the diameter of the workpiece 61, for example, around the C-axis. If the diameter of the workpiece 61 is small, the length of the chips generated in one rotation of the workpiece 61 will be small. Therefore, fewer air cut points are needed. If the diameter of the workpiece 61 is large, the length of the chips generated in one rotation of the workpiece 61 will also be large. Therefore, more air cut points are desirable. The operator inputs the oscillation ratio ks so that the number of air cut points reaches the desired number.

[0065] Figure 9 is an explanatory diagram illustrating the movement amount f, air cut length α, and oscillation amplitude A. For example, the operator inputs the air cut length α by operating the control unit 7. As shown in Figure 9, the air cut length α is the distance between the peak of the waveform at the p-th cycle and the peak of the waveform at the p+1-th cycle. When α is positive, the waveform at the p-th cycle and the waveform at the p+1-th cycle overlap, and chip cutting occurs. When α is negative, the waveform at the p-th cycle and the waveform at the p+1-th cycle do not overlap, and chip cutting does not occur. Depending on the material of the workpiece 61, the chips may become thin, and the chips may break apart naturally without cutting. In such cases, α may be negative. The oscillation processing unit 51b calculates the oscillation amplitude A from the movement amount f and the air cut length α. The oscillation amplitude A is obtained by the following equation 3. A = (f + α) / 2 ... (3)

[0066] Figure 10 is a graph showing an example of the relationship between the gain characteristic |G| and the angular frequency ω. Note that the gain characteristic |G| is the gain characteristic |G(e jωt The correction unit 51c determines the correction factor, i.e., the correction amount, from the angular frequency ω obtained by the oscillation processing unit 51b using the above-mentioned equation (2). Specifically, the correction unit 51c determines the reciprocal of the gain characteristic |G| in equation (1) or equation (1-2). That is, the correction factor for the gain characteristic |G| is k|sin(ωT / 2) / sin(ωkT / 2)| or (ωTc / 2) / |sin(ωTc / 2)|.

[0067] For example, as shown in Figure 10, if ωa is determined as the angular frequency ω, then the gain characteristic |G| is assumed to be |G|a. The correction unit 51c calculates the reciprocal of |G|a, 1 / |G|a, i.e., the correction factor. The correction unit 51c obtains the angular frequency ωa and oscillation speed from the oscillation processing unit 51b, and multiplies the oscillation speed by the correction factor. The value obtained by multiplying the oscillation speed by the correction factor is the second speed. That is, the correction unit 51c generates the second speed. As shown in Figure 4, the adder 51f superimposes the first speed and the second speed and outputs the third speed to the moving average filter 51d. The multiplication by the correction factor in the correction unit 51c suppresses the decrease in the gain of the angular frequency ωa component of the third speed by the moving average filter 51d.

[0068] Figure 11 is an enlarged view showing a comparative example of the waveform trajectory Pa without using a correction factor and the waveform trajectory Pb with a correction factor. The waveform trajectory Pa without a correction factor is the same as the trajectory Pa shown in Figure 6. As shown in Figure 11, multiplying the oscillation speed by a correction factor suppresses the reduction in the amplitude of the waveform trajectory Pb. As a result, the peaks of the waveforms tend to overlap, promoting chip fragmentation.

[0069] Figure 12 is a graph showing an example of the relationship between the threshold S and the gain characteristic |G|. In Figure 12, angular frequency ω1 is the angular frequency when ks = 1 / 2, angular frequency ω3 is the angular frequency when ks = 3 / 2, and angular frequency ω5 is the angular frequency when ks = 5 / 2. The auxiliary storage unit 53 stores the gain threshold S. The threshold S is determined based on the mechanical characteristics. For example, it may be determined based on the maximum speed in movement in the Y-axis direction. The maximum speed in movement in the Y-axis direction is an example of the relative speed between the tool and the workpiece. As the maximum speed increases, the threshold S decreases. The threshold S is, for example, a value less than 0.1. The control unit 51 determines whether the angular frequency ω obtained by equation (2) above is greater than or equal to the threshold S. If the angular frequency ω is not greater than or equal to the threshold S, the correction magnification becomes excessively large. Therefore, if the angular frequency ω is not greater than or equal to the threshold S, the control unit 51 determines whether there is an alternative angular frequency. Hereinafter, the alternative angular frequency will also be referred to as the alternative frequency. If an alternative frequency exists, the control unit 51 notifies the system of the alternative frequency as a candidate. For example, the control unit 51 transmits a signal indicating the alternative frequency to the display unit 8. The display unit 8 then displays the alternative frequency.

[0070] For example, as shown in Figure 12, when the control unit 51 determines the angular frequency ω3, the angular frequency ω3 is less than or equal to the threshold S. The control unit 51 changes the value of ks to a value other than 3 / 2, determines the angular frequency, and determines whether there is an angular frequency greater than or equal to the threshold S. Since angular frequencies ω1 and ω5 are greater than or equal to the threshold S, the control unit 51 determines that there are alternative frequencies. The control unit 51 transmits signals indicating the replaceable angular frequencies ω1 and ω5, i.e., signals indicating the alternative frequencies ω1 and ω5, to the display unit 8. The display unit 8 displays the alternative frequencies ω1 and ω5.

[0071] If there are multiple alternative frequencies, the control unit 51 may determine the order in which to display the multiple alternative frequencies according to the magnitude of their gains. For example, in the case of Figure 12, the gain of alternative frequency ω1 is greater than the gain of alternative frequency ω5, so the control unit 51 places a higher priority on alternative frequency ω1 than on alternative frequency ω5. The control unit 51 places alternative frequency ω1 as rank 1 and alternative frequency ω5 as rank 2, and transmits signals indicating alternative frequencies ω1 and ω5 to the display unit 8, linking the information indicating the ranks. The display unit 8, for example, displays alternative frequency ω1 above alternative frequency ω5.

[0072] Figure 13 is a graph showing an example of the relationship between the gain characteristic |G| and the angular frequency ω when there is no alternative frequency. For example, as shown in Figure 13, if the value of ks is changed to a value other than 3 / 2, but there is no angular frequency above the threshold S, i.e., there is no alternative frequency, the control unit 51 outputs a signal to suggest changing the rotational speed n of the workpiece 61.

[0073] For example, the control unit 51 sends a signal to the display unit 8 to display the message, "No alternative frequency available. Please change the rotation speed of the workpiece." The display unit 8 then displays the message.

[0074] Figure 14 is a flowchart illustrating the preprocessing of feedback control by the control unit 51. The control unit 51 obtains the rotational speed n of the workpiece 61, for example, from the machining program (S1). The control unit 51 obtains the oscillation ratio ks, for example, from the operation unit 7 (S2). The operator operates the operation unit 7 and inputs the oscillation ratio ks.

[0075] The control unit 51 obtains the angular frequency ω (S3). The control unit 51 calculates the angular frequency ω from the rotational speed n and the oscillation magnification ks. The control unit 51 obtains the time constant Tc of the moving average filter 51d (S4). The control unit 51 obtains the time constant Tc by calculation or from the auxiliary storage unit 53. The control unit 51 obtains the correction magnification, i.e., the correction amount, from the angular frequency ω (S5). For example, the control unit 51 finds the reciprocal of the gain characteristic |G| of equation (1) or equation (1-2).

[0076] The control unit 51 determines whether the gain of angular frequency ω is greater than or equal to the threshold S (S6). If it is determined that the gain of angular frequency ω is greater than or equal to the threshold S (S6: YES), the control unit 51 obtains the air cut length α (S7). The control unit 51 obtains the air cut length α from, for example, the operation unit 7. The operator operates the operation unit 7 to input the air cut length α.

[0077] The control unit 51 obtains the amount of movement f (S8). The control unit 51 obtains the amount of movement f from, for example, a machining program. The control unit 51 obtains the oscillation amplitude A (S9). The control unit 51 calculates the oscillation amplitude A from, for example, the amount of movement f and the air cut length α.

[0078] The control unit 51 acquires the target position and generates a first velocity (S10). The control unit 51 acquires the target position from, for example, a machining program. The control unit 51 generates an oscillation velocity (S11). The control unit 51 corrects the oscillation velocity (S12). That is, the control unit 51 generates a second velocity. The control unit 51 superimposes the first and second velocities (S13). That is, the control unit 51 generates a third velocity. The control unit 51 performs a moving average operation on the third velocity (S14).

[0079] The control unit 51 integrates the processing results of the moving average (S15). That is, the control unit 51 generates a position command indicating the target position. The control unit 51 outputs the position command indicating the target position to the Y-axis control circuit 56 (S16), and the process ends.

[0080] In step S6, if it is determined that the gain of the angular frequency ω is not greater than or equal to the threshold S (S6: NO), the control unit 51 determines whether or not there is an alternative frequency (S17). If it is determined that there is an alternative frequency (S17: YES), the control unit 51 notifies the alternative frequency as a candidate (S19) and terminates the process. For example, the control unit 51 transmits a signal indicating the alternative frequency to the display unit 8. The display unit 8 displays the alternative frequency. If there are multiple alternative frequencies, the control unit 51 may determine the order in which to display the multiple alternative frequencies according to the magnitude of the gain. For example, the display unit 8 displays the higher-ranking alternative frequency above the lower-ranking alternative frequency.

[0081] If the operator selects an alternative frequency by operating the control unit 7, the control unit 51 may perform the correction process again. In this case, in step S3, the control unit 51 acquires the selected alternative frequency.

[0082] In step S13, if it is determined that there is no alternative frequency (S17: NO), the control unit 51 outputs a signal to indicate a suggestion to change the rotational speed n of the workpiece 61 (S18). For example, the control unit 51 sends a signal to the display unit 8 to display the message, "There is no alternative frequency. Please change the rotational speed of the workpiece." The display unit 8 displays the message.

[0083] If the operator changes the rotation speed n by operating the control unit 7, the control unit 51 may perform the correction process again. In this case, in step S1, the control unit 51 obtains the changed rotation speed n.

[0084] The movement and oscillation processes for the Z-axis motor 33 and X-axis motor 23 are the same as those for the Y-axis motor 13, and therefore a detailed explanation is omitted.

[0085] The machine tool according to this embodiment is a vertical machine tool in which the spindle extends in the vertical direction, but it may also be a horizontal machine tool in which the spindle extends in the front-rear direction or the left-right direction. Movement processing, oscillation processing and compensation processing can also be applied to horizontal machine tools. In a horizontal machine tool, for example, a workpiece 61 is attached to the spindle, the workpiece 61 rotates, and the tool 60 cuts the workpiece 61 while moving and oscillating in the axial direction of the spindle, i.e., in the front-rear direction or the left-right direction.

[0086] In a horizontal machine tool, for example, the workpiece 61 may be attached to the spindle and the tool 60 fixed. In this case, the workpiece 61 rotates, moves in the axial direction of the spindle, i.e., in the forward / backward or left / right direction, and oscillates, while the tool 60 cuts the workpiece 61. The workpiece 61 moves to the target position by the drive of a motor that moves the spindle in the axial direction. That is, the control unit 51 performs a movement process to move the workpiece 61 so that the relative position between the tool 60 and the workpiece 61 becomes the target position. The control unit 51 performs an oscillating process to oscillate the relative position between the tool 60 and the workpiece 61 while the workpiece 61 is moving.

[0087] In a horizontal machine tool, a tool 60 may be attached to the spindle, and a workpiece 61 extending in the axial direction of the spindle, i.e., in the front-to-back or left-to-right direction, may be fixed. The cutting edge of the tool 60 is positioned radially away from the axis of the spindle. In this case, the tool 60 rotates around the workpiece 61, moves in the axial direction of the spindle, and oscillates to cut the workpiece 61. In this case, the control unit 51 calculates the oscillation frequency based on the rotational speed of the tool 60. The control unit 51 also calculates a correction amount based on the oscillation frequency of the tool 60 and the time constant Tc of the moving average filter 51d.

[0088] In the machine tool according to this embodiment, the amplitude of oscillation in the moving object is calculated based on the correction amount for the gain of the smoothing filter, i.e., the moving average filter 51d. By using the calculated amplitude, the peaks of the waveforms tend to overlap, making it easier to break up the chips. Note that the moving average processing by the moving average filter 51d is one example of smoothing processing. Weighted averaging processing may be performed as the smoothing processing, or simple moving average processing may be performed multiple times.

[0089] The control unit 51 also calculates the angular frequency of oscillation based on the rotational speed of the tool 60 or workpiece 61. It also calculates a correction amount based on the angular frequency ω and the time constant Tc. If the gain |G| is not greater than or equal to the threshold S, the control unit 51 determines whether an alternative frequency exists. If an alternative frequency exists, it indicates the alternative frequency. For example, it is displayed on the display unit 8.

[0090] When multiple alternative frequencies exist, the control unit 51 determines the order in which to display the multiple alternative frequencies according to the magnitude of the corresponding gain |G|. For example, alternative frequencies with a larger gain |G| are displayed with priority over alternative frequencies with a smaller gain |G|.

[0091] If the control unit 51 determines that the gain |G| is not equal to or greater than the threshold S, it determines whether or not there is an alternative frequency different from the calculated frequency. If no alternative frequency exists, it proposes a change in rotational speed.

[0092] Computer programs (program products) can be deployed to run on a single computer, located in one site, or distributed across multiple sites and interconnected by a communication network.

[0093] The embodiments disclosed herein should be considered illustrative and not restrictive in all respects. The scope of the present invention is intended to include all modifications within the claims and equivalents thereof. The matters described in each embodiment can be combined with one another. Furthermore, the independent and dependent claims described in the claims can be combined with one another in any combination, regardless of the form of reference. In addition, the claims use a multi-claim format in which claims refer to two or more other claims (multi-claim format), but are not limited thereto. They may also be described using a multi-claim format in which at least one multi-claim refers to another multi-claim (multi-multi-claim format). [Explanation of symbols]

[0094] 5. Spindle head 5a main shaft 13a encoder 50 Control device 51 Control Unit 51a Movement Processing Unit 51b Oscillating Processing Unit 51c Correction section 51d Moving Average Filter 51e Calculator 51f Adder 52 Main memory 53 Auxiliary storage 56 Y-axis control circuit 60 Tools 61 Work

Claims

1. The machine tool is equipped with a control unit that controls a machine tool which performs a movement process for moving the tool or the workpiece so that the relative position of the tool and the workpiece becomes a target position, and a swinging process for swinging the relative position of the tool and the workpiece while the tool or the workpiece is moving. The control unit, The first velocity is generated in the aforementioned movement process, The oscillation process generates the oscillation speed, The oscillation speed is corrected to generate a second speed such that the first trajectory of the tool and the second trajectory of the tool formed after the first trajectory overlap. Smoothing is performed on the first speed and the second speed. Control device.

2. The frequency of the oscillation is calculated, In correcting the oscillation speed, For the aforementioned frequency, a correction amount corresponding to the gain of the smoothing process is calculated, The amplitude of the oscillation is calculated based on the correction amount. The control device according to claim 1.

3. The tool and the workpiece rotate relative to each other. The control unit calculates the frequency based on the rotational speed of the relative rotation between the tool and the workpiece. The control device according to claim 2.

4. The control unit calculates the correction amount based on the frequency and the time constant of the smoothing process. The control device according to claim 2 or 3.

5. The smoothing process includes a moving average process. The control device according to claim 2 or 3.

6. The control unit, Determine whether the calculated gain corresponding to the frequency is greater than or equal to a threshold determined based on the relative speed between the tool and the workpiece. If it is determined that the gain is not equal to or greater than the threshold, it is determined whether or not there is an alternative frequency different from the calculated frequency. If it is determined that the aforementioned alternative frequency exists, a signal indicating the aforementioned alternative frequency will be output. The control device according to claim 2 or 3.

7. The control unit, If multiple alternative frequencies exist, the order in which these multiple alternative frequencies are shown is determined according to the magnitude of the corresponding gains. The control device according to claim 6.

8. The control unit, Determine whether the calculated gain corresponding to the frequency is greater than or equal to a threshold determined based on the relative speed between the tool and the workpiece. If it is determined that the gain is not equal to or greater than the threshold, it is determined whether or not there is an alternative frequency different from the calculated frequency. If it is determined that no alternative frequency exists, a signal is output to indicate a proposed change in the rotational speed. The control device according to claim 3.

9. The system includes a control unit that performs a movement process for moving the tool or the workpiece so that the relative position between the tool and the workpiece becomes a target position, and a swinging process for swinging the relative position between the tool and the workpiece while the tool or the workpiece is moving. The control unit, The first velocity is generated in the aforementioned movement process, The oscillation process generates the oscillation speed, The oscillation speed is corrected to generate a second speed such that the first trajectory of the tool and the second trajectory of the tool formed after the first trajectory overlap. Smoothing is performed on the first speed and the second speed. Machine tools.

10. A control method for a machine tool, comprising: a movement process for moving the tool or the workpiece so that the relative position between the tool and the workpiece becomes a target position; and a swinging process for swinging the relative position between the tool and the workpiece during the movement of the tool or the workpiece, The first velocity is generated in the aforementioned movement process, The oscillation process generates the oscillation speed, The oscillation speed is corrected to generate a second speed such that the first trajectory of the tool and the second trajectory of the tool formed after the first trajectory overlap. Smoothing is performed on the first speed and the second speed. Control method.

11. A computer program executable in the control unit of a machine tool, which performs a movement process for moving the tool or the workpiece so that the relative position of the tool and the workpiece becomes a target position, and a swinging process for swinging the relative position of the tool and the workpiece while the tool or the workpiece is moving, The control unit, The first velocity is generated in the aforementioned movement process, The oscillation process generates the oscillation speed, The oscillation speed is corrected to generate a second speed such that the first trajectory of the tool and the second trajectory of the tool formed after the first trajectory overlap. Smoothing is performed on the first speed and the second speed. A computer program that executes a process.

Images