Machine tool control device

Abstract

The present invention provides a control device for a machine tool that can suppress the deterioration of machining accuracy and achieve the desired chip length. The control device (1) for a machine tool that performs machining while oscillating the tool relative to the workpiece includes: an oscillation command generation unit (13) that generates an oscillation command based on oscillation conditions; an oscillation command correction unit (14) that corrects the oscillation command so that the spindle phases of any oscillation phases are different; and a position and speed control unit (18) that oscillates the tool relative to the workpiece based on an overlap command generated by superimposing the oscillation command corrected by the oscillation command correction unit (14) on a movement command.

Description

Technical Field

[0001] This invention relates to a control device for machine tools. Background Technology

[0002] In the past, oscillating cutting was sometimes used as a chip countermeasure in machining processes such as hole drilling and turning. When oscillating cutting is used, under specific oscillation conditions, the degree of deterioration varies within one revolution of the workpiece, thus particularly deteriorating the machining accuracy of the workpiece and having a significant impact on the roundness of the workpiece.

[0003] Therefore, a control device for a machine tool is proposed that reduces the deterioration of workpiece machining accuracy while reliably cutting off chips generated from the workpiece sequentially (for example, see Patent Document 1). In this machine tool control device, the reciprocating vibration frequency of the workpiece and tool for each relative rotation is set in such a way that the intersection points of the oscillating trajectories are dispersed. As a result, the intersection portions of the cutting tool's trajectory are dispersed in the relative rotation direction, and consequently, the minute irregularities of the workpiece's machined surface are uniformly dispersed in the relative rotation direction, thus reducing the deterioration of workpiece machining accuracy.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 6470085 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, in the control device of Patent Document 1, the desired chip length cannot be achieved because the vibration frequency of the oscillation is changed as a whole. Therefore, it is sometimes impossible to solve problems such as poor machining, short machine stops, and mechanical failures caused by the continuous generation of chips entangled with the cutting tool.

[0009] Therefore, there is a need for a machine tool control device that can achieve the desired chip length while suppressing the deterioration of machining accuracy.

[0010] Methods for solving problems

[0011] One aspect of this disclosure is a control device for a machine tool that performs machining while oscillating the tool relative to the workpiece. The control device includes: an oscillation command generation unit that generates an oscillation command based on oscillation conditions; an oscillation command correction unit that corrects the oscillation command so that the spindle phases of any oscillation phases are different; and a control unit that oscillates the tool relative to the workpiece based on an overlap command generated by superimposing the oscillation command corrected by the oscillation command correction unit onto a movement command.

[0012] Invention Effects

[0013] According to one aspect of this disclosure, a control device for a machine tool can be provided that can suppress the deterioration of machining accuracy and achieve the desired chip length. Attached Figure Description

[0014] Figure 1 This is a diagram showing the structure of the control device for a machine tool according to the first embodiment of the present invention.

[0015] Figure 2 It is a graph showing the trajectory of the cutting tool on the workpiece surface during non-oscillating cutting and previous oscillating cutting, and it is a graph when the oscillation frequency is 1.5 times.

[0016] Figure 3 It is a schematic diagram showing the unevenness of the workpiece surface during non-oscillating cutting.

[0017] Figure 4 It is a schematic diagram showing the unevenness of the workpiece surface during traditional oscillating cutting.

[0018] Figure 5 This is a diagram showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the first embodiment of this disclosure.

[0019] Figure 6 This is a graph showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the second embodiment of this disclosure, and it is a graph when the oscillation frequency is 1.35 times.

[0020] Figure 7 This is a graph showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the second embodiment of this disclosure, and it is a graph when the oscillation frequency is 1.65 times.

[0021] Figure 8 This is a diagram showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the third embodiment of this disclosure, and it is a diagram when the spindle phase offset is 10°.

[0022] Figure 9 This is a diagram showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the third embodiment of this disclosure, and it is a diagram when the spindle phase offset is 50°.

[0023] Figure 10 This is a graph showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the fourth embodiment of this disclosure, and it is a graph when the oscillation frequency is 1.5 times.

[0024] Figure 11 This is a diagram showing the structure of the control device for the machine tool according to the fifth embodiment of this disclosure. Detailed Implementation

[0025] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Furthermore, in the descriptions following the second embodiment, descriptions of structures and effects identical to those of the first embodiment will be omitted; only structures and effects different from those of the first embodiment will be described.

[0026] [First Implementation Method]

[0027] Figure 1 This is a functional block diagram of the control device 1 of the machine tool according to the first embodiment of this disclosure. Figure 1 As shown, the control device 1 of the machine tool in this embodiment is configured to include a servo control device 10 to drive and control the motor 30 that drives the feed axis.

[0028] like Figure 1 As shown, the control device 1 of the machine tool in this embodiment includes a first adder 11, an integrator 12, a swing command generation unit 13, a swing command correction unit 14, a second adder 15, a learning controller 16, a third adder 17, and a position and speed control unit 18.

[0029] In this embodiment, the machine tool control device 1 generates position commands for the motor 30 based on machining conditions via a position command generation unit 20. For example... Figure 1 As shown, the generated position command is input to the first adder 11 of the servo control device 10, which will be described later.

[0030] The first adder 11 calculates the position deviation. Specifically, the first adder 11 calculates the position deviation, which is the difference between the position feedback based on the position detection performed by the encoder of the feed axis motor 30 and the position command.

[0031] Integrator 12 calculates the cumulative value of the position deviation. Specifically, integrator 12 calculates the cumulative value of the position deviation by accumulating the position deviation calculated by the first adder 11.

[0032] The swing command generation unit 13 generates swing commands based on swing conditions. The swing command generation unit 13 can calculate swing commands based on swing conditions such as swing amplitude ratio and swing frequency ratio, as well as machining conditions. Alternatively, it can calculate swing commands based on swing conditions such as swing amplitude and swing frequency. For example, in this embodiment, the swing command is calculated based on the swing conditions and machining conditions. However, considering applications such as when the swing axis stops, if the swing amplitude and swing frequency are directly set under the swing conditions, calculation can be performed without using machining conditions.

[0033] The swing command correction unit 14 corrects the swing command generated by the swing command generation unit 13 according to the swing conditions. Specifically, the swing command correction unit 14 changes the advance mode of the swing phase in the previous swing before the swing command generated by the swing command generation unit 13 is the same as the spindle phase. The correction of the swing command performed by the swing command correction unit 14 will be described in detail later.

[0034] The second adder 15 generates an overlap command. Specifically, the second adder 15 overlaps the accumulated value of the position deviation calculated by the integrator 12 with the oscillation command corrected by the oscillation command correction unit 14, thereby generating an overlap command. Alternatively, the second adder 15 may be configured to add the oscillation command corrected by the oscillation command correction unit 14 to the position command. Or, the second adder 15 may be configured to add the oscillation command corrected by the oscillation command correction unit 14 to the velocity command.

[0035] The learning controller 16 calculates a correction amount for the overlapping command based on the superposition command, and adds the calculated correction amount to the superposition command via the third adder 17, thereby correcting the superposition command. The learning controller 16 has a memory that stores the oscillation phase and the superposition command in association within one or more oscillation cycles. At a timing that compensates for the phase delay of the oscillation action corresponding to the responsiveness of the motor 30, the superposition command stored in the memory is read out as a correction amount and output to the third adder 17. Generally, the higher the oscillation frequency, the greater the deviation (overlap command) relative to the oscillation command. Therefore, through the correction by the learning controller 16, the tracking accuracy for periodic oscillation commands can be improved. As a result, the tracking accuracy for overlapping commands can be improved, the deterioration of machining accuracy can be suppressed, and the desired chip length can be easily achieved.

[0036] The position and speed control unit 18 generates a torque command for the motor 30 driving the feed axis based on the superposition command after the correction amounts are added, and controls the motor 30 according to the generated torque command. As a result, machining is performed while the tool and the workpiece are oscillating relative to each other.

[0037] Next, the correction of the swing command of the swing command correction unit 14 will be explained in detail.

[0038] Figure 2 It is a diagram showing the trajectory of the cutting tool on the workpiece surface during non-oscillating cutting and traditional oscillating cutting. Figure 2 The horizontal axis represents the spindle phase (0°~360°), and the vertical axis represents the feed rate (mm) in the feed axis direction. Figure 2In the diagram, the dashed lines represent the tool path on the workpiece surface during non-oscillating cutting, while the thick solid lines represent the tool path on the workpiece surface during conventional oscillating cutting. Furthermore, in the conventional oscillating cutting tool path shown by the thick solid lines, an oxy-fuel cutting C is generated at the intersection of the previous path and the current path, where the chips are shredded.

[0039] Figure 2 This indicates the case where the feed rate of the cutting tool is constant per revolution of the spindle. Therefore, in Figure 2 In the diagram, the distance D0 between adjacent straight lines shown by the dashed lines in the feed axis direction, i.e. the distance D0 between the previous path and the current path when there is no oscillation cutting, is fixed.

[0040] In contrast, it can be seen that the interval between adjacent curves shown by the thick solid line in the feed axis direction, that is, the interval between the previous path and the current path during previous oscillating cutting, varies greatly depending on the spindle phase. Specifically, in Figure 2 In the conventional oscillating cut, at the position of 180° spindle phase (shown by the dashed line), the interval between the previous path and the current path during oscillating cut is fixed at D1, while the interval between the previous path and the current path during non-oscillating cut is the same at D0. On the other hand, at the position of 240° spindle phase (shown by the dashed line), the interval between the previous path and the current path during oscillating cut repeats as an interval D2 larger than both D0 and D1, and an interval D3 in the opposite direction to the feed direction. Thus, in conventional oscillating cut, the feed rate per spindle rotation is not fixed depending on the spindle phase; the feed rate varies considerably depending on the spindle phase.

[0041] Here, Figure 3 This is a schematic diagram illustrating the surface roughness of a workpiece during non-oscillating cutting. Figure 3 In the diagram, N1 to N6 represent the positions of the cutting tool in each path during non-oscillating cutting, and are related to... Figure 2 The paths N1 to N6 correspond to this. Additionally, in Figure 3 In the diagram, thick solid lines represent the unevenness of the workpiece surface. For example... Figure 3 As shown, in non-oscillating cutting, the feed rate per spindle rotation is fixed, and the forward movement of the cutting tool in the feed axis direction is fixed. Therefore, in cutting tools where the tool tip must have an angle, the unevenness of the workpiece surface caused by the radius of the tool tip arc is fixed.

[0042] In contrast, Figure 4 This is a schematic diagram illustrating the unevenness of the workpiece surface during traditional oscillating cutting. More specifically, it schematically illustrates... Figure 2 The image shows the surface roughness of the workpiece during conventional oscillating cutting, indicated by the dashed line at a spindle phase of 240°. Figure 4In the diagram, O1 to O6 represent the positions of the cutting tool in each path during traditional oscillating cutting, and... Figure 2 The paths O1 to O6 correspond to this. Additionally, in... Figure 4 In the diagram, the thick solid lines represent the unevenness of the workpiece surface. As mentioned above, in Figure 4 The spindle is shown at a phase of 240°. The feed rate per spindle rotation is repeatedly defined as D2 in the feed axis direction and D3 in the opposite direction. Therefore, as... Figure 4 As shown, after the cutting tool advances by D2 along the feed axis, it retreats by D3, thus increasing the surface roughness of the workpiece due to the radius of the tool tip. This increased roughness results in a worse surface roughness. On the other hand, as mentioned above, at the position where the spindle phase is 180° (represented by the dashed line), the feed rate per spindle rotation is fixed; therefore, the surface roughness (roughness) of the workpiece is related to... Figure 3 The non-oscillating cutting shown is identical and fixed. In contrast, in conventional oscillating cutting, the surface roughness of the workpiece varies with the spindle phase, resulting in variations in the degree of surface roughness deterioration. This could potentially also negatively affect the roundness of the workpiece.

[0043] Therefore, the control device 1 of the machine tool in this embodiment can reduce the deterioration of the workpiece's machining accuracy by suppressing the unevenness of the workpiece surface. Specifically, the control device 1 of the machine tool in this embodiment corrects the oscillation command by the oscillation command correction unit 14, so that the spindle phases of any oscillation phases are different, thereby causing the oscillation phases that generate gas cutting C to be staggered, thus suppressing the unevenness of the workpiece surface.

[0044] Furthermore, more preferably, the oscillation command correction unit 14 corrects the oscillation command by changing the advance mode of the oscillation phase during the re-motion of the oscillation before it becomes the same spindle phase in the oscillation phase where the oscillation command becomes 0. This is because the previous path and gas cutting C need to be generated during the forward motion of the oscillation; therefore, if the advance mode of the oscillation phase is changed during the forward motion, it may be difficult to generate gas cutting C.

[0045] Therefore, the swing command correction unit 14 in this embodiment calculates the number of swings required to return to the same spindle phase based on the swing conditions. Furthermore, the swing command correction unit 14 counts the number of swings, and if it reaches the number of swings required to return to the same spindle phase, it changes the forward movement of the swing phase.

[0046] Here, the number of swings required to return to the same spindle phase depends on the swing frequency multiplier (the number of swings per spindle rotation) I. As an example of calculation, if the greatest common divisor is found between the swing frequency multiplier I (with a weight of 0.001) and 1000, then I × 1000 / the greatest common divisor becomes the number of swings required to return to the same spindle phase. Therefore, the swing command correction unit 14 calculates the number of swings according to this formula. For example, when the swing frequency multiplier is 1.5, since I × 1000 = 1500 and the greatest common divisor of 1000 is 500, 1500 / 500 = 3 times, and the number of swings required to return to the same swing phase is calculated as 3 times. Furthermore, the method for calculating the number of swings required to return to the same spindle phase is not limited to the above calculation method and other calculation methods may also be used.

[0047] Figure 5 This is a diagram showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the first embodiment of this disclosure. Figure 5 The example shown illustrates the cutting tool trajectory on the workpiece surface when the oscillation frequency is multiplied by 1.5. As mentioned above, with an oscillation frequency multiplied by 1.5, if the oscillation occurs 3 times, the spindle phase returns to the same position as the original spindle phase. Furthermore, with an oscillation frequency multiplied by 1.5, gas cutting C is typically achieved at spindle phases of 0°, 120°, and 240°.

[0048] Here, as Figure 5 As shown, if the principal axis phase advances only by θ (dotted line L1 to dotted line L2, dotted line L2 to dotted line L3) in one oscillation (one oscillation), then in the third oscillation before returning to the same principal axis phase as before, if the oscillation phase advances by θ+α (dotted line L3 to dotted line L4), the oscillation phase relative to the principal axis phase will be offset by α. Therefore, from... Figure 5 It is known that the spindle phase (center) that generates the air cut C can be offset by α. Thus, in this embodiment, by offsetting the air cutting phase (the phase that generates the air cut), the unevenness of the workpiece surface can be dispersed, and the situation where the surface roughness deteriorates only in a specific spindle phase due to oscillating cutting can be suppressed.

[0049] Next, the changes in the forward movement of the oscillation phase will be explained in detail.

[0050] First, the overlapping command (position command + swing command) of this embodiment is calculated by the following mathematical formula (1).

[0051] [Mathematical Expression 1]

[0052]

[0053] Here, in the above mathematical formula (1), Y represents the overlap command, F represents the feed per revolution [mm / revolution], and S represents the spindle speed [minutes]. -1 In this context, I represents the oscillation frequency multiplier (times), K represents the oscillation amplitude multiplier (times), and t represents time (seconds). Additionally, (K×F) / 2 is the oscillation amplitude (mm), and πSIt / 30 is the oscillation phase (oscillation frequency) (rad). The oscillation amplitude multiplier K and the oscillation frequency multiplier I are constants. The oscillation amplitude multiplier K is a number greater than 1, and the oscillation frequency multiplier I is a non-integer greater than zero (e.g., positive non-integers such as 0.5, 0.8, 1.2, 1.5, 1.9, 2.3, 2.5, etc.). These values ​​of the oscillation amplitude multiplier K and the oscillation frequency multiplier I are pre-stored.

[0054] If the swing phase is set as θ, then as described above, the swing phase θ [rad] is calculated by the following mathematical formula (2).

[0055] [Mathematical Expression 2]

[0056]

[0057] The time t1[s] required for one swing is calculated by the following mathematical formula (3).

[0058] [Mathematical Expression 3]

[0059]

[0060] The phase θ1 [rad] of the main axis that advances by one swing is calculated by the following mathematical formula (4).

[0061] [Mathematical Expression 4]

[0062]

[0063] The time Δt [s] required to advance the principal axis phase by α [rad] is calculated by the following mathematical formula (5).

[0064] [Mathematical Expression 5]

[0065]

[0066] Therefore, when the forward movement of the swing phase in a swing that is about to return to the same principal axis phase as the original principal axis phase is changed during the swing, when the swing phase θ is π to 2π [rad], the swing phase can be advanced by using the angular velocity ω' calculated by the following mathematical formulas (6) and (7). That is, the swing command correction unit 14 only needs to correct the swing command so that the swing phase in the swing that is about to return to the same principal axis phase as the original principal axis phase advances with the angular velocity ω'.

[0067] [Mathematical Expression 6]

[0068]

[0069] [Mathematical Expression 7]

[0070]

[0071] The control device 1 for the machine tool according to this embodiment has the following effects.

[0072] In this embodiment, a swing command generation unit 13 is provided, which generates a swing command based on swing conditions; and a swing command correction unit 14, which corrects the swing command so that the principal axis phases of any swing phase are different.

[0073] Therefore, the spindle phases that generate the gas cutting C can be staggered. This disperses the unevenness of the workpiece surface and suppresses surface roughness deterioration only at specific spindle phases due to oscillating cutting. Furthermore, since the oscillation frequency is not changed globally, chip length variation can be suppressed, achieving the desired chip length. Therefore, according to this embodiment, a machine tool control device 1 can be provided that can suppress the deterioration of machining accuracy and achieve the desired chip length.

[0074] Furthermore, in this embodiment, the configuration is a forward movement of the swing phase during a swing before the swing command correction unit 14 changes to the same spindle phase. More specifically, the configuration is a forward movement of the swing phase during the re-motion of a previous swing, where the swing command correction unit 14 changes to the previous swing phase.

[0075] During the swinging motion, the previous path and gas cutting C need to be generated. Therefore, if the forward movement of the swing phase is changed during the swinging motion, it may be difficult to generate gas cutting C. However, according to this embodiment, since the forward movement of the swing phase during the re-motion of the previous swing is changed, the main axis phase for generating gas cutting C can be staggered, and gas cutting C can be generated more reliably between the previous swinging motion and the previous path.

[0076] [Second Implementation]

[0077] In the control device of the machine tool in the second embodiment, the oscillation command correction unit 14 determines the direction in which the spindle phase is offset based on the oscillation frequency multiplier I. Thus, in this embodiment, the forward movement of the oscillation phase in the previous oscillation is changed according to the offset direction.

[0078] Figure 6 This is a graph showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the second embodiment of this disclosure, specifically a graph with an oscillation frequency multiple of 1.35. Additionally, Figure 7 This is a graph showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the second embodiment of this disclosure, specifically a graph with an oscillation frequency multiple of 1.65. Figure 6 and Figure 7 In the diagram, W1 represents the peak of the swing motion, and W2 represents the trough of the swing motion.

[0079] from Figure 6 as well as Figure 7 It is known that the positional relationship between the crests W1 and troughs W2 of the oscillating motion varies according to the oscillation frequency multiplier I. Here, since the gas cutting C is generated by the intersection of the crests W1 and troughs W2 of these oscillating motions, their positional relationship is highly relevant to the generation of gas cutting C. Therefore, the direction in which the main shaft phase is shifted is determined based on the positional relationship between the crests W1 and troughs W2, and on whether gas cutting C is easily generated when the main shaft phase is shifted. That is, the direction in which the main shaft phase is shifted is determined based on the oscillation frequency multiplier I.

[0080] Specifically, in this embodiment, the swing command correction unit 14 is used when the swing frequency multiplier I is n.5 times or less ( Figure 6 In cases where the spindle phase is delayed, a directional correction oscillation command is issued. Furthermore, in this embodiment, the oscillation command correction unit 14 corrects for oscillations where the oscillation frequency multiplier I exceeds n.5 times. Figure 7 In the case of ( ), a oscillation command is given to correct the direction of spindle phase advancement. Here, n is an integer greater than or equal to 1.

[0081] like Figure 6 As shown, when the oscillation frequency is 1.35 times the normal frequency, the peak W1 and trough W2 tend to intersect when the spindle phase is delayed, easily resulting in gas cutting C. Here, delaying the spindle phase refers to the aforementioned... Figure 5 When α is negative, it indicates that the oscillation phase advances rapidly. That is, the direction that delays the principal axis phase refers to the direction in which the principal axis phase advances less relative to one oscillation.

[0082] In contrast, such as Figure 7As shown, when the oscillation frequency is 1.65 times the normal frequency, the peak W1 and trough W2 easily intersect when the main spindle phase is advanced, easily causing gas cutting C. Here, advancing the main spindle phase refers to the aforementioned... Figure 5 When α is positive, it indicates that the oscillation phase is delayed. That is, the direction in which the principal axis phase advances is the direction in which the principal axis phase advances more relative to one oscillation.

[0083] According to this embodiment, the following effects are achieved.

[0084] In this embodiment, the swing command correction unit 14 determines the direction of phase shifting of the spindle based on the swing frequency multiplier I, thereby changing the advance mode of the swing phase in the previous swing. Therefore, it is possible to determine whether the swing phase advances quickly or delayed based on the swing frequency multiplier I, thus achieving the effects of the first embodiment more reliably.

[0085] [Third Implementation Method]

[0086] In the control device of the machine tool in the third embodiment, the spindle phase of the change oscillation command correction unit 14 is changed to the same oscillation phase as the previous oscillation in any oscillation phase, and the oscillation amplitude is changed.

[0087] In addition, in the control device of the machine tool in the third embodiment, the swing command correction unit 14 corrects the swing command so that the spindle phase is staggered within the range of generating gas cutting C.

[0088] Here, if the spindle phase is significantly offset during oscillating cutting, gas cutting C may not occur even when the oscillation amplitude remains unchanged. Therefore, in this embodiment, the oscillation amplitude is corrected based on the spindle phase offset. Alternatively, the spindle phase offset is determined within the range where the oscillation amplitude is not corrected.

[0089] Figure 8 This is a diagram showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the third embodiment of this disclosure. It is a diagram showing the case where the spindle phase advances by 10° at a oscillation frequency multiple of 1.5. Figure 8 As shown in section P1, even advancing the main axis phase by 10° produces the gas cutting C with the intersection of the peaks and troughs of the oscillating motion.

[0090] In contrast, Figure 9 This is a diagram showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the third embodiment of this disclosure. It is a diagram showing the case where the spindle phase advances by 50° at a oscillation frequency multiple of 1.5. Figure 9As shown in section P2, if the main shaft phase is advanced by 50°, the peaks and troughs of the oscillation motion will not intersect, and gas cutting C will not occur. Therefore, in this case, it is known that the oscillation amplitude needs to be increased.

[0091] According to this embodiment, the following effects are achieved.

[0092] In this embodiment, the swing command correction unit 14 changes the advance mode of the swing phase in the previous swing, making the principal axis phase the same in any swing phase, and also changes the swing amplitude. Therefore, even when the principal axis phase is significantly misaligned, the generation of gas cutting C can be more reliably achieved by changing the swing amplitude.

[0093] Furthermore, in this embodiment, the oscillation command correction unit 14 is configured to correct the oscillation phase by offsetting the spindle phase within the range of generating gas cutting C. Therefore, even without changing the oscillation amplitude, gas cutting C can be generated more reliably.

[0094] [Fourth Implementation Method]

[0095] In the control device of the machine tool in the fourth embodiment, the oscillation command correction unit 14 determines the amount by which the spindle phase advances based on the interval between the spindle phases that generate the gas cutting C. Thus, in this embodiment, based on the interval between the spindle phases that generate the gas cutting C, the spindle phase in any oscillation phase is changed to the same advance mode as the oscillation phase in the previous oscillation.

[0096] Here, the interval of the spindle phase that can be used for gas cutting C depends on the number of swings until it returns to the same spindle phase as the original spindle phase. That is, the interval of the spindle phase that can be used for gas cutting C is calculated by the following mathematical formula (8).

[0097] [Mathematical Expression 8]

[0098]

[0099] Therefore, the swing command correction unit 14 of this embodiment determines the amount by which the spindle phase advances based on the interval of the spindle phase capable of gas cutting C calculated by the mathematical formula (8). Specifically, within the range of the interval of the spindle phase capable of gas cutting C, the swing command correction unit 14 determines the amount (α) by which the spindle phase advances, and changes the advance mode of the spindle phase in any swing phase to the same as the swing phase in the previous swing, based on the determined advance amount. The advance amount of the spindle phase can be a predetermined fixed value, or it can be determined based on swing conditions such as the swing frequency multiple I.

[0100] Figure 10This is a graph showing the trajectory of the cutting tool on the workpiece surface during oscillating cutting according to the fourth embodiment of this disclosure, specifically a graph with an oscillation frequency multiple of 1.5. Figure 10 As shown, with an oscillation frequency multiplier of 1.5, the number of oscillations required to return to the original spindle phase, as described above, is 3. Therefore, according to the mathematical formula (8), the interval between the spindle phases capable of gas cutting C is 120°, specifically, when the spindle phase is 0°, 120°, or 240°. In this case, the advance amount of the spindle phase is determined within the 120° range of the spindle phase.

[0101] According to this embodiment, the following effects are achieved.

[0102] In this embodiment, the oscillation command correction unit 14 determines the amount by which the spindle phase advances based on the interval of the spindle phase generated by the gas cutting C, thereby changing the spindle phase in any oscillation phase to the same advance mode as the oscillation phase in the previous oscillation. Therefore, the amount of spindle phase offset can be determined, and the effects of the first embodiment can be obtained more reliably.

[0103] [Fifth Implementation Method]

[0104] Figure 11 This diagram illustrates the structure of the control device 1A for the machine tool according to the fifth embodiment. The control device 1A for the machine tool in this embodiment further includes a spindle phase storage unit 19 that stores arbitrary swing phases of the spindle phase. Furthermore, the swing command correction unit 14 changes the advance mode of the swing phase during the previous swing, making it inconsistent with the spindle phase stored in the spindle phase storage unit 19.

[0105] More specifically, the spindle phase storage unit 19 stores the spindle phase of any swing phase of the swing command generated by the swing command generation unit 13. The spindle phase stored in the spindle phase storage unit 19 is input to the swing command correction unit 14.

[0106] Not only the previous spindle phase, the swing command correction unit 14 also changes the advance mode of the swing phase in the previous swing so that the past spindle phase stored in the spindle phase storage unit 19 is inconsistent with the next spindle phase under the arbitrary swing phase.

[0107] According to this embodiment, the following effects are achieved.

[0108] In this embodiment, as in the embodiments described above, the spindle phase at any oscillation phase determined by the oscillation conditions is replaced with the spindle phase stored in the spindle phase storage unit 19. Therefore, according to this embodiment, by changing the advance mode of the oscillation phase in the previous oscillation, the spindle phase at any oscillation phase is inconsistent with the past spindle phase stored in the spindle phase storage unit 19. Thus, oscillation can continue even when the spindle phases at any oscillation phase are different. As a result, the deterioration of machining accuracy can be suppressed, and the desired chip length can be achieved.

[0109] Furthermore, this disclosure is not limited to the described method, and variations and improvements within the scope of achieving the purpose of this disclosure are included in this disclosure.

[0110] Explanation of reference numerals in the attached figures

[0111] 1.1A Machine Tool Control Device

[0112] 10 Servo Control Device

[0113] 11 First Adder

[0114] 12 Integrators

[0115] 13. Swing Command Generation Unit

[0116] 14. Swing Command Correction Unit

[0117] 15 Second Adder

[0118] 16. Learning Controller (Learning Control Unit)

[0119] 17. Third Adder (Learning Control Unit)

[0120] 18. Position and speed control unit (control unit)

[0121] 19 Spindle Phase Storage Unit

[0122] 20 Position Instruction Generation Unit

[0123] 30 Electric motor.

Claims

1. A control device for a machine tool that performs machining while simultaneously oscillating the tool relative to the workpiece, characterized in that, The control device has the following features: The swing command generation unit generates swing commands based on swing conditions. The swing command correction unit corrects the swing command so that the principal axis phases of any swing phase are different; The control unit, based on an overlap command generated by superimposing the oscillation command corrected by the oscillation command correction unit onto the movement command, causes the tool to oscillate relative to the workpiece. The swing command correction unit changes the forward mode of the swing phase in the previous swing to the same spindle phase.

2. The machine tool control device according to claim 1, characterized in that, The swing command correction unit changes the advance mode of the swing phase during the re-motion of the swing phase before the swing phase becomes the same as the main axis phase in the swing phase where the swing command is 0.

3. The machine tool control device according to claim 1, characterized in that, The swing command correction unit determines the direction that causes the spindle phase to shift based on the swing frequency multiple, and changes the forward movement of the swing phase in the previous swing according to the direction.

4. The machine tool control device according to claim 2, characterized in that, The swing command correction unit determines the direction that causes the spindle phase to shift based on the swing frequency multiple, and changes the forward movement of the swing phase in the previous swing according to the direction.

5. The machine tool control device according to claim 1, characterized in that, The control device includes: a spindle phase storage unit that stores the spindle phase of any swing phase. The swing command correction unit changes the forward movement of the swing phase in the previous swing, making it inconsistent with the spindle phase stored in the spindle phase storage unit.

6. The machine tool control device according to claim 2, characterized in that, The control device includes: a spindle phase storage unit that stores the spindle phase of any swing phase. The swing command correction unit changes the forward movement of the swing phase in the previous swing, making it inconsistent with the spindle phase stored in the spindle phase storage unit.

7. The control device for a machine tool according to any one of claims 1 to 6, characterized in that, The swing command correction unit changes the advance mode of the swing phase in the previous swing and changes the swing amplitude.

8. The control device for a machine tool according to any one of claims 1 to 6, characterized in that, The swing command correction unit changes the advance mode of the swing phase in the previous swing, so that the spindle phase is staggered within the range of gas cutting.

9. The control device for a machine tool according to any one of claims 1 to 6, characterized in that, The swing command correction unit changes the advance mode of the swing phase in the previous swing, so that the spindle phase is staggered based on the interval of the spindle phase that generates the gas cutting.

10. The control device for a machine tool according to any one of claims 1 to 6, characterized in that, The control device further includes a learning control unit, which calculates a correction amount for the overlapping instruction based on the overlapping instruction, and adds the calculated correction amount to the overlapping instruction, thereby correcting the overlapping instruction.

11. The machine tool control device according to claim 7, characterized in that, The control device further includes a learning control unit, which calculates a correction amount for the overlapping instruction based on the overlapping instruction, and adds the calculated correction amount to the overlapping instruction, thereby correcting the overlapping instruction.

12. The machine tool control device according to claim 8, characterized in that, The control device further includes a learning control unit, which calculates a correction amount for the overlapping instruction based on the overlapping instruction, and adds the calculated correction amount to the overlapping instruction, thereby correcting the overlapping instruction.

13. The machine tool control device according to claim 9, characterized in that, The control device further includes a learning control unit, which calculates a correction amount for the overlapping instruction based on the overlapping instruction, and adds the calculated correction amount to the overlapping instruction, thereby correcting the overlapping instruction.

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