machine tool control device

Abstract

Machine tool control (1, 1A) for controlling a machine tool performing a machining operation while a tool and a workpiece oscillate relative to each other, wherein the machine tool control (1, 1A) comprises: an oscillation instruction generation unit (13) that generates an oscillation instruction based on oscillation conditions; an oscillation command compensation unit (14) that compensates the oscillation command such that spindle phases do not coincide at any given oscillation phase; and a control unit (18) that causes the tool and the workpiece to oscillate relative to each other, based on a superposition command generated by superimposing the oscillation command compensated by the oscillation command compensation unit (14) with a motion command.

Description

Technical field

[0001] The present disclosure relates to a machine tool control system. State of the art

[0002] Traditionally, oscillating cutting was sometimes used as a countermeasure against chip formation during drilling and turning. When oscillating cutting is applied, the degree of deterioration within a single rotation of a workpiece varies under specific oscillation conditions, and therefore the machining accuracy of the workpiece can be significantly degraded, and the roundness of the workpiece can also be severely affected.

[0003] Therefore, a machine tool control system was proposed that not only sequentially and reliably cuts the chips produced by the workpiece, but also reduces the deterioration of machining accuracy (see, for example, patent document 1). In such a machine tool control system, an oscillation frequency is set for reciprocating motion per relative rotation of the workpiece and tool such that the intersection points of the oscillation paths are distributed. In this way, the intersection points of the cutting tool trajectories are distributed in a relative direction of rotation, resulting in small irregularities on a workpiece's machined surface being evenly distributed in the relative direction of rotation. This is considered suitable for reducing the deterioration of the workpiece's machining accuracy.

[0004] Patent document 1: Japanese patent no. JP 6 470 085 B2.

[0005] DE 10 2018 005 754 A1 discloses a control device for a machine tool for performing vibratory cutting operations. The control device comprises a unit for detecting a time interval of a command block in order to detect any time interval between adjacent command blocks based on a machining program of a machine tool comprising a plurality of command blocks. A feed axis control unit comprises a learning controller and a determination unit that determines whether a current time lies within the arbitrary time interval between the adjacent command blocks and stops the vibration of at least one feed axis based on this determination. Disclosure of the invention Problems to be solved by the invention

[0006] However, in the control system disclosed in patent specification 1, the overall oscillation frequency is altered, preventing the achievement of a desired chip length. Consequently, machining errors, brief downtimes, and machine failures caused by a cutting tool jamming with continuously generated chips may not be rectified.

[0007] Therefore, it is desirable to provide a machine tool control that is capable of achieving a desired chip length while simultaneously reducing the deterioration of machining accuracy.

[0008] The problem is solved by a machine tool control system with the features of claim 1. Means to solve the problems

[0009] One aspect of the present disclosure relates to a machine tool control for controlling a machine tool performing a machining operation while a tool and a workpiece oscillate relative to each other. The machine tool control comprises: an oscillation command generation unit that generates an oscillation command based on oscillation conditions; an oscillation command compensation unit that compensates the oscillation command so that the spindle phases do not coincide at any given oscillation phase; and a control unit that causes the tool and the workpiece to oscillate relative to each other based on a superposition command generated by superimposing the oscillation command compensated by the oscillation command compensation unit with a motion command. Effects of the invention

[0010] According to the aspect of the present disclosure, it is possible to provide a machine tool control that is capable of achieving a desired chip length while simultaneously reducing the deterioration of machining accuracy. Brief description of the characters Fig. 1 is a diagram showing a configuration of a machine tool control according to a first embodiment of the present disclosure; Fig. Figure 2 is a diagram showing the trajectory of a cutting tool on the surface of a workpiece during non-oscillating cutting and conventional oscillating cutting, where the multiplication factor of the oscillation frequency is 1.5 times; Fig. Figure 3 is a diagram that schematically shows the surface irregularities of the workpiece during non-oscillating cutting; Fig. Figure 4 is a diagram that schematically shows the surface irregularities of the workpiece during conventional oscillation cutting; Fig. Figure 5 is a diagram showing a trajectory of a cutting tool on a surface of a workpiece during oscillation cutting according to the first embodiment of the present disclosure; Fig. Figure 6 is a diagram showing a trajectory of a cutting tool on a surface of a workpiece during oscillation cutting according to a second embodiment of the present disclosure, in which the oscillation frequency multiplication factor is 1.35 times; Fig. Figure 7 is a diagram showing a trajectory of a cutting tool on a surface of a workpiece during oscillation cutting according to the second embodiment of the present disclosure, in which the oscillation frequency multiplication factor is 1.65 times; Fig. Figure 8 is a diagram showing a trajectory of a cutting tool on a surface of a workpiece during oscillation cutting according to a third embodiment of the present disclosure, in which the displacement amount of a spindle phase is 10°; Fig. Figure 9 is a diagram showing a trajectory of a cutting tool on a surface of a workpiece during oscillation cutting according to the third embodiment of the present disclosure, in which the displacement amount of the spindle phase is 50°; Fig. Figure 10 is a diagram showing a trajectory of a cutting tool on the surface of a workpiece during oscillation cutting according to a fourth embodiment of the present disclosure, in which the oscillation frequency multiplication factor is 1.5 times; and Fig. Figure 11 is a diagram showing a configuration of a machine tool control according to a fifth embodiment of the present disclosure. Preferred embodiment of the invention

[0011] Embodiments of the present disclosure are described in detail below with reference to the drawings. When describing a second and further embodiment, configurations and effects that are identical to those of the first embodiment are not described, but only configurations and effects that differ from those of the first embodiment. [First embodiment]

[0012] Fig. Figure 1 is a functional block diagram of a machine tool control 1 according to a first embodiment of the present disclosure. As in Fig. As shown in Figure 1, the machine tool control 1 according to the present embodiment comprises a servo controller 10 and controls the drive of a motor 30 which drives a feed axis.

[0013] As in Fig. As shown in Figure 1, the machine tool control 1 according to the present embodiment comprises a first adder 11, an integrator 12, an oscillation command generation unit 13, an oscillation command compensation unit 14, a second adder 15, a lemending control unit 16, a third adder 17 and a position / speed control unit 18.

[0014] In the machine tool control 1 according to the present embodiment, a position command generation unit 20 generates a position command for the motor 30 based on the machining conditions. As in Fig. As shown in Figure 1, the generated position command is entered into the first adder 11 of the servo controller 10, which is described below.

[0015] The first adder 11 calculates a position deviation. In particular, the first adder 11 calculates a position deviation that is a difference between a position feedback, based on the position detection by an encoder provided in the motor 30 on the feed axis, and the position command.

[0016] Integrator 12 calculates an integrated value of the position deviation. In particular, integrator 12 calculates the integrated value of the position deviation by integrating the position deviation calculated by the first adder 11.

[0017] The oscillation command generation unit 13 calculates an oscillation command based on oscillation conditions. The oscillation command generation unit 13 can determine the oscillation command from oscillation conditions, such as an oscillation amplitude multiplication factor and an oscillation frequency multiplication factor, and processing conditions, or it can determine the oscillation command from oscillation conditions, such as an oscillation amplitude and an oscillation frequency. In the present embodiment, for example, the oscillation command is calculated from the oscillation conditions and the processing conditions, but it can also be calculated without using the processing conditions, even considering the application to a case where an oscillation axis is stopped when an oscillation amplitude and an oscillation frequency are set without changing the oscillation conditions.

[0018] The oscillation command compensation unit 14 compensates the oscillation command generated by the oscillation command generation unit 13 according to the oscillation conditions. In particular, the oscillation command compensation unit 14 modifies a procedure for advancing an oscillation phase with respect to the oscillation command generated by the oscillation command generation unit 13 in an oscillation immediately before the spindle phases coincide. The compensation of the oscillation command by the oscillation command compensation unit 14 is described in detail below.

[0019] The second adder 15 generates a superposition instruction. Specifically, the second adder 15 generates a superposition instruction by superimposing the oscillation instruction compensated by the oscillation instruction compensation unit 14 onto an integrated value of the position deviation calculated by the integrator 12. The second adder 15 can be configured to add the oscillation instruction compensated by the oscillation instruction compensation unit 14 to the position instruction. Alternatively, the second adder 15 can be configured to add the oscillation instruction compensated by the oscillation instruction compensation unit 14 to a velocity instruction.

[0020] The learning control unit 16 calculates a compensation amount for the superimposition command based on the superimposition command and then causes the third adder 17 to add the calculated compensation amount to the superimposition command in order to compensate for the superimposition command. The learning control unit 16 contains a memory that allows the memory to store the oscillation phase and the superimposition command together in one or a plurality of oscillation cycles. At a time when a phase delay of an oscillation process can be compensated according to the responsiveness of the motor 30, the learning control unit reads the superimposition command stored in the memory and outputs the superimposition command as a compensation amount to the third adder 17.Generally, the higher the oscillation frequency, the greater the deviation (superimposition command) from the oscillation command. This makes it possible to improve the tracking of a cyclic oscillation command through compensation by the learning control unit 16. This improves the compliance of the superimposition command and makes it easier to achieve a desired chip length, while reducing the deterioration in machining accuracy.

[0021] The position / speed control unit 18 generates a torque command for motor 30, which drives the feed axis, based on the superposition command and after adding the compensation amount, and controls motor 30 with the generated torque command. Machining is thus carried out while the tool and the workpiece oscillate relative to each other.

[0022] The following section describes in detail the compensation of the oscillation command by the oscillation command compensation unit 14. Fig. Figure 2 is a diagram showing the trajectory of a cutting tool on a workpiece surface during non-oscillating cutting and conventional oscillating cutting. Fig. 2 represents a horizontal axis and a spindle phase (0° to 360°), and a vertical axis represents a feed rate (mm) in the direction of the feed axis. Fig. Figure 2 shows several dashed straight lines representing the path of the cutting tool on the workpiece surface during non-oscillating cutting, and several curved thick solid lines representing the path of the cutting tool on the workpiece surface during conventional oscillating cutting. In the tool trajectory during conventional oscillating cutting, indicated by the thick solid line, air cutting (C) occurs at a point where a previous path and a current path intersect, and the chips are crushed during air cutting (C).

[0023] Fig. Figure 2 shows a case where the feed rate of the cutting tool per revolution of spindle 1 is constant. Therefore, in Fig. 2 a distance D0 between adjacent dashed lines in the direction of the feed axis, i.e. the distance D0 between the previous path and the current path during non-oscillating cutting, constant.

[0024] In contrast, it can be seen that the distance between adjacent curved thick solid lines in the direction of the feed axis, i.e., the distance between the previous path and the current path during conventional oscillation cutting, depends strongly on the spindle phase. This is particularly true at a position where the spindle phase is 180°, indicated by an alternating long and short dashed line. Fig. When position 2 is displayed, the distance D1 between the previous path and the current path is constant during conventional oscillation cutting and is the same as the distance D0 between the previous path and the current path during non-oscillating cutting. At a position where the spindle phase is 240°, which in Fig. While 2 is indicated by an alternating long and short dashed line, a distance D2 between the previous path and the current pass is repeated during conventional oscillation cutting, as is a distance D3 in a direction opposite to the feed direction. Distance D2 is larger than distance D0 and distance D1. As can be seen, in conventional oscillation cutting, the feed rate per spindle revolution is not constant depending on the spindle phase, and the feed rate varies considerably depending on the spindle phase.

[0025] Fig. Figure 3 is a diagram that schematically shows the surface irregularities of a workpiece during oscillation-free cutting. Fig. 3 denotes N1 to N6 the positions of the cutting tool on the respective paths during non-oscillating cutting and corresponds to the paths N1 to N6 in Fig. 2. In Fig. 3. A thick, solid line represents a surface irregularity of the workpiece. As in Fig. As shown in Figure 3, during non-oscillating cutting the feed rate per revolution of the spindle is constant, and the feed rate of the cutting tool in the direction of the feed axis is constant, thus keeping the surface roughness of the workpiece constant due to a tool nose radius in the cutting tool, which always has a corner section at a tool nose.

[0026] Fig. Figure 4 is a diagram that schematically shows the surface irregularities of a workpiece during conventional oscillating cutting. More precisely, it is Fig. 4 A diagram schematically showing the surface irregularities of the workpiece during conventional oscillation cutting at the position where the spindle phase is 240°, indicated by the alternating long and short dashed line in Fig. 2 is displayed. Fig. Figure 4 shows positions O1 to O6 as the positions of the cutting tool in the paths during conventional oscillation cutting and corresponds to paths O1 to O6 in Fig. 2. In Fig. Figure 4 shows a thick solid line indicating surface irregularities of the workpiece. As described above, in the position where the spindle phase is in Fig. Since the angle is 4240°, the feed rate per spindle revolution is represented by repeating D2 in the direction of the feed axis and D3 in the direction opposite to the feed axis. For this reason, the cutting tool moves as shown in Fig. As shown in Figure 4, the spindle moves forward by D2 in the direction of the feed axis and then back by D3 in the opposite direction, increasing the surface unevenness of the workpiece due to the tool nose radius of the cutting tool. With increasing unevenness, the surface roughness deteriorates. However, since, as described above, the feed per spindle revolution is constant at the position where the spindle phase is 180°, indicated by the alternating long and short dashed lines, the surface unevenness (roughness) of the workpiece is the same as in non-oscillating cutting. Fig. 3. Constant. Since, as described above, the degree of surface unevenness of the workpiece varies depending on the spindle phase during conventional oscillation cutting, the degree of surface roughness deterioration can also vary. This can also adversely affect the roundness of the workpiece.

[0027] To overcome the aforementioned disadvantages, the machine tool control 1 according to the present embodiment can reduce the deterioration in the machining accuracy of a workpiece by reducing the variation in the surface unevenness of the workpiece described above. In particular, the machine tool control 1 according to the present embodiment compensates the oscillation command by causing the oscillation command compensation unit 14 to compensate the oscillation command in such a way that the spindle phases do not coincide at any given oscillation phase, thereby shifting the oscillation phase in which the air cut C occurs and reducing variations in the surface unevenness of the workpiece.

[0028] Preferably, the oscillation command compensation unit 14 modifies, by compensating the oscillation command, a method for advancing an oscillation phase during a backward movement in an oscillation immediately before the spindle phases coincide in the oscillation phase in which the oscillation command becomes 0, because it is necessary to effect air cutting C with the previous path during a forward movement in the oscillation, and it may be difficult to effect air cutting C if the method for advancing an oscillation phase is changed during the forward movement.

[0029] Therefore, the oscillation command compensation unit 14 of the present embodiment calculates, based on the oscillation conditions, the number of oscillations required to return to the same spindle phase. Furthermore, the oscillation command compensation unit 14 counts the number of oscillations and changes the method for advancing the oscillation phase upon reaching the specified number of oscillations required to return to the same spindle phase.

[0030] Here, the number of oscillations required to return to the same spindle phase depends on an oscillation frequency multiplication factor (the number of oscillations per spindle revolution) I. As a calculation example: If the greatest common divisor for the oscillation frequency multiplication factor I is calculated with a weight of 0.001 times 1000, then I × 1000 / greatest common divisor is the number of oscillations required to return to the same spindle phase, and thus the oscillation command compensation unit 14 calculates the number of oscillations according to this formula. For example, if the multiplication factor of the oscillation frequency is 1.5 times, since the greatest common divisor of I×1000 (= 1500 and 1000) is 500, then 1500 / 500 = 3 times, and the number of oscillations until returning to the same oscillation phase is calculated as 3 times.A method for calculating the number of oscillations until returning to the same oscillation phase is not limited to the above calculation method, but may also include other calculation methods.

[0031] Fig. Figure 5 is a diagram showing a trajectory of the cutting tool on the surface of the workpiece during oscillation cutting according to the first embodiment of the present disclosure. The diagram in Fig. Example 5 shows the trajectory of the cutting tool on the workpiece surface when the oscillation frequency is multiplied by 1.5. As described above, the spindle phase returns to its original state after three oscillations when the oscillation frequency is multiplied by 1.5. When the oscillation frequency is multiplied by 1.5, air cut C typically occurs when the spindle phases are 0°, 120°, and 240°.

[0032] Here, as in Fig. 5, if a single oscillation (one oscillation) advances the spindle phase by θ (an alternating long- and short-dash line L1 to an alternating long- and short-dash line L2 and an alternating long- and short-dash line L2 to an alternating long- and short-dash line L3), the oscillation phase is shifted by α relative to the spindle phase, if the oscillation phase is advanced by θ + α in a third oscillation immediately before the spindle phase returns to the original spindle phase (alternating long- and short-dash line L3 to alternating long- and short-dash line L4). As from Fig. As can be seen in Figure 5, the spindle phase (its center), in which the air cutting C takes place, can be shifted by α. In the present embodiment, as described above, the air cutting phase (the phase in which the air cutting takes place) is shifted, thereby distributing the surface irregularities of the workpiece and reducing the deterioration of surface roughness due to oscillation cutting in only a specific spindle phase.

[0033] The modification of the procedure for advancing an oscillation phase is described in detail below. First, the superposition command (position command + oscillation command) of the present embodiment is calculated according to equation (1) below. [Math. 1] Y=FS60t+KF2{cos(πSI30t)−1}

[0034] In equation (1) Y represents a superposition command, F a feed rate per revolution [mm / revolution], and S a spindle speed [min -1 ], I represents a multiplication factor of the oscillation frequency [number], K represents a multiplication factor of the oscillation amplitude [number], and t represents a time [s]. Furthermore, (K×F) / 2 represents an oscillation amplitude [mm] and πSlt / 30 represents an oscillation phase (oscillation frequency) [rad]. The oscillation amplitude multiplication factor K and the oscillation frequency multiplication factor I are constants. The oscillation amplitude multiplication factor K is a number equal to or greater than 1, and the oscillation frequency multiplication factor I is a non-integer greater than zero (e.g., a positive non-integer such as 0.5, 0.8, 1.2, 1.5, 1.9, 2.3, 2.5 ...). The values ​​for the oscillation amplitude multiplication factor K and the oscillation frequency multiplication factor I are stored in advance.

[0035] The oscillation phase is defined as θ, and the oscillation phase θ [rad] described above is calculated according to equation (2) below. [Math. 2] θ=πSI30t=ωt

[0036] The time t1 [s] required for one oscillation is calculated according to equation (3) below. [Math. 3] t1=60SI[s]

[0037] The spindle phase θ1 [rad] progressing by one oscillation is calculated according to the following equation (4). [Math. 4] θ1=πS30⋅60SI=2πI[rad]

[0038] The time Δt [s] required to advance the spindle phase by α [rad] is calculated according to equation (5). [Math. 5] Δt=απs30=30απs[s]

[0039] Therefore, if the procedure for advancing the oscillation phase in the oscillation immediately before the spindle phase returns to the original spindle phase is modified by performing an oscillation, when the oscillation phase θπ to 2π [rad] in the path immediately before the spindle phase returns to the original spindle phase, the oscillation phase can be advanced with an angular velocity ω' calculated according to equations (6) and (7) below. In other words, the oscillation command compensation unit 14 can compensate the oscillation command such that the oscillation phase is advanced with the angular velocity ω' in the oscillation immediately before the spindle phase returns to the original spindle phase by performing the oscillation. [Math. 6] ωt12=ω'(t12+Δt) [Math. 7] ω'=ωt12t12+Δt=πSI30(30SI30SI+30απS)=πSI30⋅ππ+αI

[0040] The following effects can be achieved with the machine tool control 1 according to the present embodiment. The present embodiment comprises the oscillation command generation unit 13, which generates the oscillation command based on the oscillation conditions, and the oscillation command compensation unit 14, which compensates the oscillation command so that the spindle phases do not coincide during any given oscillation phase. This makes it possible to shift the spindle phase in which air cutting C takes place. Therefore, it is possible to distribute the surface irregularities of the workpiece and reduce the deterioration of these irregularities only during a specific spindle phase due to oscillation cutting. Since the overall oscillation frequency remains unchanged, it is also possible to reduce fluctuations in chip length and achieve a desired chip length.Accordingly, according to the present embodiment, it is possible to provide the machine tool control 1 which is capable of achieving a desired chip length while simultaneously reducing the deterioration of machining accuracy.

[0041] The present embodiment is configured such that the oscillation command compensation unit 14 changes the method for advancing an oscillation phase in an oscillation immediately before the spindle phases coincide. More precisely, the present embodiment is configured such that the oscillation command compensation unit 14 changes the method for advancing an oscillation phase during the reverse movement in the immediately preceding oscillation.Since it is necessary to effect the air cutting C with the previous path during the forward movement in the oscillation, it can be difficult to effect the air cutting C if the method for advancing an oscillation phase is changed during the forward movement, whereas according to the present embodiment, in order to change the method for advancing an oscillation phase during the backward movement in the immediately preceding oscillation, it is possible to shift the spindle phase in which the air cutting C occurs and to effect the air cutting C with the previous path more reliably during the forward movement in the immediately preceding oscillation. [Second embodiment]

[0042] In a machine tool control according to a second embodiment, the oscillation command compensation unit 14 determines a direction in which the spindle phase is to be shifted according to the oscillation frequency multiplication factor I. In the present embodiment, therefore, a method for advancing an oscillation phase in the immediately preceding oscillation is modified according to the shifted direction.

[0043] Fig. Figure 6 is a diagram showing a trajectory of the cutting tool on the surface of the workpiece during oscillation cutting according to the second embodiment of the present disclosure, where the oscillation frequency multiplication factor is 1.35. Furthermore, Fig. 7 A diagram showing a trajectory of the cutting tool on the surface of the workpiece during oscillation cutting according to the second embodiment of the present disclosure, wherein the oscillation frequency multiplication factor is 1.65. In the Fig. 6 and Fig. 7 represents W1 a peak of the oscillation process, and W2 represents a trough of the oscillation process.

[0044] As from the Fig. 6 and Fig. As can be seen in Figure 7, the positional relationship between the peak W1 and the trough W2 of the oscillation process changes depending on the oscillation frequency multiplication factor I. Since the air cut C occurs at the intersection of the peak W1 and the trough W2 of the oscillation process, the positional relationship between them is highly related to the occurrence of the air cut C. Therefore, the direction in which the spindle phase is shifted is determined by the positional relationship between the peak W1 and the trough W2, specifically whether the air cut C is likely to occur when the spindle phase is shifted. In other words, the direction in which the spindle phase is shifted depends on the multiplication factor I of the oscillation frequency.

[0045] In particular, the oscillation command compensation unit 14 of the present embodiment compensates the oscillation command in a direction in which the spindle phase is delayed when the oscillation frequency multiplication factor I is equal to or less than n.5 times (in the case of Fig. 6) Furthermore, the oscillation command compensation unit 14 of the present embodiment compensates the oscillation command in a direction in which the spindle phase is advanced when the oscillation frequency multiplication factor I exceeds n.5 times (in the case of Fig. 7) where n is an integer of 1 or more.

[0046] If the multiplication factor of the oscillation frequency is 1.35 times, then in Fig. 6 shows that the spindle phase delay facilitates the intersection of the apex W1 and the trough W2 and facilitates the occurrence of air cutting C. Here, the spindle phase delay represents a case where the above in Fig. The α described in section 5 is negative, and the oscillation phase progresses rapidly. In other words, the direction in which the spindle phase is delayed indicates a direction in which the spindle phase progressing in an oscillation decreases.

[0047] If the multiplication factor of the oscillation frequency is 1.65 times, then in Fig. 7 shows that the advance of the spindle phase facilitates the intersection of vertex W1 and trough W2 and facilitates the occurrence of air cutting C. In this case, the advance of the spindle phase means that the top in Fig. The α described in section 5 is positive, and the oscillation phase progresses slowly. In other words, the direction in which the spindle phase is advanced indicates a direction in which the spindle phase advanced in an oscillation increases.

[0048] According to the present embodiment, the following effects can be achieved. The present embodiment has a configuration in which the oscillation command compensation unit 14 determines the direction in which the spindle phase is to be shifted according to the oscillation frequency multiplication factor I, thereby changing the method for advancing the oscillation phase in the immediately preceding oscillation. In this way, it is possible to determine whether the oscillation phase should be advanced quickly or slowly according to the oscillation frequency multiplication factor I, and thus the effects of the first embodiment can be achieved more reliably. [Third embodiment]

[0049] In a machine tool control according to a third embodiment, the oscillation command compensation unit 14 changes the method for advancing an oscillation phase in an oscillation immediately before the spindle phases match each other at any oscillation phase and changes the oscillation amplitude.

[0050] In the machine tool control according to the third embodiment, the oscillation command compensation unit 14 compensates the oscillation command in order to shift the spindle phase into the area where the air cut C occurs.

[0051] If the spindle phase is significantly shifted during oscillation cutting, air cutting C cannot occur unless the oscillation amplitude is also modified. Therefore, in the present embodiment, the oscillation amplitude is compensated depending on the amount of the spindle phase shift. Alternatively, the amount of the spindle phase shift is determined within a range where the oscillation amplitude does not need to be compensated.

[0052] Fig. Figure 8 is a diagram showing a trajectory of the cutting tool on the surface of the workpiece during oscillation cutting according to the third embodiment of the present disclosure, in which the spindle phase advances by 10° when the oscillation frequency multiplication factor is 1.5 times the oscillation frequency multiplication factor. As shown by P1 in Fig. As indicated in Figure 8, it can be seen that the air section C occurs where the peak and trough of the oscillation process overlap, even if the spindle phase advances by 10°.

[0053] On the other hand, Fig. 9 A diagram showing a trajectory of the cutting tool on the surface of the workpiece during oscillation cutting according to the third embodiment of the present disclosure, in which the spindle phase advances by 50° when the oscillation frequency multiplication factor is 1.5 times. As shown by P2 in Fig. As indicated in Figure 9, it can be seen that the peak and trough of the oscillation process do not overlap and the air section C does not occur when the spindle phase advances by 50°. Therefore, in this case, it can be seen that the oscillation amplitude must be increased.

[0054] According to the present embodiment, the following effects are achieved. The present embodiment has been configured such that the oscillation command compensation unit 14 modifies the method for advancing an oscillation phase in an oscillation immediately before the spindle phases coincide with any oscillation phase and changes the oscillation amplitude. This makes it possible to trigger the air cut C more reliably, even with a significantly shifted spindle phase, by changing the oscillation amplitude.

[0055] Furthermore, the present embodiment was configured such that the oscillation command compensation unit 14 compensates the oscillation command in such a way that the spindle phase is shifted into the region in which the air cut C occurs. This makes it possible to trigger the air cut C more reliably without changing the oscillation amplitude. [Fourth embodiment]

[0056] In a machine tool control according to a fourth embodiment, the oscillation command compensation unit 14 determines the amount by which the spindle phase is advanced based on a distance between the spindle phases in which the air cut C occurs. Thus, in the present embodiment, the oscillation command compensation unit 14 modifies methods for advancing an oscillation phase in an oscillation immediately before the spindle phases coincide in any oscillation phase based on the distance between the spindle phases in which the air cut C occurs.

[0057] Here, the interval between the spindle phases in which the air cut C occurs depends on the number of oscillations required to return to the spindle phase corresponding to the original spindle phase. In other words, the interval between the spindle phases in which the air cut C occurs is calculated according to equation (8) below. [Math. 8] Distance=360 Number of oscillations until return to the original spindle phase [deg]

[0058] Therefore, the oscillation command compensation unit 14 of the present embodiment determines the amount to advance the spindle phase based on the distance between the spindle phases at which air-cutting C occurs, as calculated according to equation (8) above. In particular, the oscillation command compensation unit 14 determines the amount (the α described above) to advance the spindle phase within a range of the distance between the spindle phases at which air-cutting C occurs and changes the method for advancing an oscillation phase in an oscillation immediately before the spindle phases coincide at any given oscillation phase, according to the determined advance amount. The advance amount of the spindle phase can be a fixed value predetermined or it can be determined depending on the oscillation conditions, e.g., the multiplication factor I of the oscillation frequency.

[0059] Fig. Figure 10 is a diagram showing a trajectory of the cutting tool on the surface of the workpiece during oscillation cutting according to the fourth embodiment of the present disclosure, in which the oscillation frequency multiplication factor is 1.5. As shown in Fig. As shown in Figure 10, if the oscillation frequency multiplication factor is 1.5, the number of oscillations required to return to the original spindle phase is three, as described above. Equation (8) shows that the interval between the spindle phases in which the air cut C occurs is 120°, i.e., when the spindle phases are 0°, 120°, and 240°. In this case, the feed rate of the spindle phase is determined by the 120° range of the spindle phase.

[0060] According to the present embodiment, the following effects are achieved. The present embodiment is configured such that the oscillation command compensation unit 14 determines the advance amount of the spindle phase based on the distance between the spindle phases at which the air gap C occurs, and modifies the method for advancing an oscillation phase in an oscillation immediately before the spindle phases align at any given oscillation phase. Since the displacement amount of the spindle phase can be determined, it is thus possible to achieve the effects of the first embodiment more reliably. [Fifth embodiment]

[0061] Fig.Figure 11 is a diagram showing a configuration of a machine tool control 1A according to a fifth embodiment. The machine tool control 1A according to the fifth embodiment further comprises a spindle phase storage unit 19, which stores a spindle phase in any oscillation phase. Furthermore, the oscillation command compensation unit 14 modifies the method for advancing the oscillation phase in the immediately preceding oscillation, such that a subsequent spindle phase in any oscillation phase does not correspond to the spindle phase stored in the spindle phase storage unit 19.

[0062] More precisely, the spindle phase storage unit 19 stores a spindle phase in any oscillation phase of the oscillation instruction generated by the oscillation instruction generation unit 13. The spindle phase stored in the spindle phase storage unit 19 is input into the oscillation instruction compensation unit 14.

[0063] The oscillation command compensation unit 14 changes the procedure in which not only the immediately preceding spindle phase, but also the past spindle phase stored in the spindle phase storage unit 19 described above and the oscillation phase in the immediately preceding oscillation advance, so that the next spindle phase does not coincide with the arbitrary oscillation phase.

[0064] According to the present embodiment, the following effects are achieved. In this embodiment, the spindle phase, which is any oscillation phase determined from the oscillation conditions in each of the embodiments described above, is replaced by the spindle phase stored in the spindle phase storage unit 19. Therefore, according to the present embodiment, it is possible to continue the oscillation without the spindle phases in the arbitrary oscillation phase coinciding, since the method for advancing the oscillation phase in the immediately preceding oscillation is modified such that the spindle phase in any arbitrary oscillation phase does not coincide with the previous spindle phase stored in the spindle phase storage unit 19. As a result, it is possible to achieve a desired chip length while reducing the deterioration in machining accuracy.

[0065] It should be noted that the present disclosure is not limited to the embodiments described above and includes modifications and improvements within a scope in which the purpose of the present disclosure can be achieved. Explanation of reference symbols 1, 1A Machine tool control 10 servo controllers 11 first adder 12 Integrator 13 Oscillation command generation unit 14 Oscillation command compensation unit 15 second adder 16 Learning control unit (learning control unit) 17 third adder (learning control unit) 18 Position / Speed ​​Control Unit (Control Unit) 19 spindle phase storage unit 20 Position command generation unit 30 engine

Claims

[1] Machine tool control (1, 1A) for controlling a machine tool performing a machining operation while a tool and a workpiece oscillate relative to each other, wherein the machine tool control (1, 1A) comprises: an oscillation instruction generation unit (13) that generates an oscillation instruction based on oscillation conditions; an oscillation command compensation unit (14) that compensates the oscillation command such that spindle phases do not coincide at any given oscillation phase; and a control unit (18) that causes the tool and the workpiece to oscillate relative to each other, based on a superposition command generated by superimposing the oscillation command compensated by the oscillation command compensation unit (14) with a motion command. [2] Machine tool control (1, 1A) according to claim 1, wherein the oscillation command compensation unit (14) is a method for advancing one oscillation phase in one oscillation immediately before the spindle phases match each other. [3] Machine tool control (1, 1A) according to claim 2, wherein the oscillation command compensation unit (14) is a method for advancing an oscillation phase during a backward movement in an oscillation immediately before the spindle phases coincide in the oscillation phase in which the oscillation command becomes 0. [4] Machine tool control (1, 1A) according to claim 2 or 3, wherein the oscillation command compensation unit (14) determines in which direction a spindle phase is to be shifted according to an oscillation frequency multiplication factor, and the method for advancing the oscillation phase in one oscillation immediately before the spindle phases coincide with each other according to the direction. [5] Machine tool control (1, 1A) according to claim 2 or 3 further comprising a spindle phase storage unit (19) which stores a spindle phase in any oscillation phase, wherein The oscillation command compensation unit (14) changes the procedure for advancing the oscillation phase in one oscillation immediately before the spindle phases match each other, so that a subsequent spindle phase in the arbitrary oscillation phase does not match the spindle phase stored in the spindle phase storage unit (19). [6] Machine tool control (1, 1A) according to one of claims 2 to 5, wherein the oscillation command compensation unit (14) changes the method for advancing the oscillation phase in one oscillation immediately before the spindle phases coincide with each other, and changes an oscillation amplitude. [7] Machine tool control (1, 1A) according to one of claims 2 to 5, characterized by, that the oscillation command compensation unit (14) modifies the procedure for advancing the oscillation phase in one oscillation immediately before the spindle phases coincide such that the spindle phase shifts into a region where air cutting occurs. [8] Machine tool control (1, 1A) according to one of claims 2 to 5, wherein the oscillation command compensation unit (14) modifies the method for advancing the oscillation phase in one oscillation immediately before the alignment of the spindle phases in order to shift the spindle phase on the basis of a distance between the spindle phases at which air cutting occurs. [9] Machine tool control (1, 1A) according to one of claims 1 to 8, further comprising a learning control unit (16) which calculates a compensation amount for the superposition command on the basis of the superposition command and compensates the superposition command by adding the calculated compensation amount to the superposition command.

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