Machine tool control device

Abstract

The present invention provides a control device for a machine tool, which can reliably cut and discharge chips and can suppress damage to the tool by reducing the impact when the tool cuts into a workpiece. The control device (100) of the machine tool controls a spindle that rotates a tool (T) and a workpiece (W) relative to each other, and controls a feed axis that moves while swinging the tool (T) and the workpiece (W) relative to each other in a feed direction, thereby performing cutting processing. The control device (100) of the machine tool includes: a swing instruction generating unit (16) that generates a swing instruction based on a predetermined swing condition; and a position speed control unit (15) that controls a motor (30) that drives the feed axis based on an overlap instruction generated by overlapping the swing instruction generated by the swing instruction generating unit (16) with a position instruction or a position deviation. The swing instruction generating unit (16) changes at least one of the phase advancement mode and the amplitude of the swing instruction based on time or the swing phase calculated based on the predetermined swing condition.

Description

Technical Field

[0001] The present disclosure relates to a control device for a machine tool. Background Art

[0002] Conventional drilling processes using a drill as a cutting tool (hereinafter referred to as a tool) are known. In this drilling process, non-stepping drilling, which involves drilling a hole in a single pass, is known to easily cause chips to entangle with the drill and clog the machined hole. Therefore, measures have been proposed to cut and remove chips using stepping feed and pecking (returning motion). However, these methods generate a significant impact when the tool penetrates the workpiece, potentially damaging the cutting edge.

[0003] Therefore, there are known technologies for cutting a workpiece while vibrating the tool at a low frequency in the feed direction (for example, see Patent Documents 1 to 3). According to these technologies, cutting can be performed while cutting off the chips generated by the cutting process, which can improve processing accuracy, workability, and tool life.

[0004] However, while Patent Document 1 describes changing the feed rate of the position command, it does not consider reducing the impact during cutting. Similarly, while Patent Document 2 describes changing the speed by swinging back and forth, it only switches the reciprocating motion at a predetermined spindle angle and does not consider reducing the impact during cutting.

[0005] In contrast, Patent Document 3 describes increasing or decreasing the feed rate within a range where the tool does not retract, thereby reducing the impact during cutting. However, without retracting the tool, it is difficult to remove chips, and chips may become entangled in the tool, resulting in machining defects.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. 2015-162739

[0009] Patent Document 2: Japanese Patent Application Publication No. 2018-126863

[0010] Patent Document 3: Japanese Patent No. 5631467 Summary of the Invention

[0011] Problems to be solved by the invention

[0012] Therefore, it is desirable to provide a control device for a machine tool that can reliably cut and discharge chips and suppress damage to the tool by reducing the impact when the tool cuts into a workpiece.

[0013] Means for solving problems

[0014] One method disclosed herein is a control device for a machine tool, which controls a spindle that rotates a cutting tool relative to a workpiece, and controls a feed axis that moves while causing the cutting tool and the workpiece to swing relative to each other in a feed direction, thereby performing cutting processing. The control device for the machine tool comprises: a swing instruction generating unit that generates a swing instruction that causes the cutting tool and the workpiece to swing relative to each other in a feed direction according to predetermined swing conditions; and a control unit that controls a motor that drives the feed axis according to an overlapping instruction generated by overlapping the swing instruction generated by the swing instruction generating unit with a position instruction or the difference between the position instruction and position feedback, that is, a position deviation. The swing instruction generating unit changes at least one of the advancing mode of the phase of the swing instruction and the amplitude of the swing instruction according to time or the swing phase calculated according to the predetermined swing condition.

[0015] Effects of the Invention

[0016] According to the present disclosure, it is possible to provide a control device for a machine tool that can reliably cut and discharge chips and suppress damage to the tool by reducing the impact when the tool cuts into a workpiece. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a diagram showing a drilling process according to one embodiment of the present disclosure.

[0018] Figure 2 This is a diagram showing the operation of a tool in conventional drilling processing.

[0019] Figure 3 It is a diagram showing the operation of a tool during drilling according to one embodiment of the present disclosure.

[0020] Figure 4 This is a functional block diagram of a control device for a machine tool according to one embodiment of the present disclosure.

[0021] Figure 5 This is a diagram showing the rate of change of the oscillation phase during drilling according to one embodiment of the present disclosure.

[0022] Figure 6 This is a diagram showing the oscillation phase of drilling according to one embodiment of the present disclosure.

[0023] Figure 7 This is a diagram showing a swing instruction for drilling according to one embodiment of the present disclosure.

[0024] Figure 8 This is a diagram showing an overlap command for drilling according to one embodiment of the present disclosure.

[0025] Figure 9This is a diagram showing an overlap command that can reduce the impact during cutting.

[0026] Figure 10 This diagram shows an overlap command that cannot reduce the impact during cutting.

[0027] Figure 11 This is a diagram showing the trajectory of each cutting edge when the tool has two cutting edges.

[0028] Figure 12 This is a diagram showing the trajectory of each cutting edge when the tool has three cutting edges.

[0029] Figure 13 This is a flowchart showing a drilling process according to one embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] Below, with reference to the attached Figure 1 An embodiment of the present disclosure will be described in detail.

[0031] Figure 1 : is a diagram showing a drilling process according to an embodiment of the present disclosure. Figure 1 As shown, the drilling process of this embodiment uses a drill as a tool T to drill a hole in a workpiece W. More specifically, the drilling process of this embodiment performs drilling while rotating the tool T relative to the workpiece W and swinging the tool T relative to the workpiece W in the feed direction, thereby cutting off chips. The following describes an example of machining in which the workpiece W is fixed, the tool T is rotated by the spindle, and the tool T is moved by the feed axis.

[0032] Here, Figure 2 FIG is a diagram showing the movement of a tool in a conventional drilling process. Figure 2 As shown, in the conventional drilling process with a return action, the tool T moves in a direction temporarily away from the bottom surface of the hole being processed (hereinafter referred to as the workpiece bottom surface) by the return action in the feed direction. At this time, the chips are cut off. Then, the tool T contacts the bottom surface of the workpiece by the cutting action of moving again in the direction close to the workpiece W, and starts cutting again. At this time, an impact is generated due to the contact between the tool T and the bottom surface of the workpiece. In the past, no consideration was given to reducing this impact, such as Figure 2 As shown, the speed (slope) of the tool is constant, therefore, a large impact is produced.

[0033] In contrast, Figure 3 1 is a diagram showing the movement of the tool T in the drilling process of this embodiment. Figure 3As shown, in the drilling process of the present embodiment, as described in detail in the latter section, the tool T moves according to the overlapping instruction generated by adding (hereinafter referred to as overlapping) a sinusoidal swing instruction to the position instruction. Specifically, the tool T swings in the feed direction, and therefore, by the backward movement in the feed direction (hereinafter also referred to as the return movement), the tool T moves in the direction temporarily away from the bottom surface of the workpiece. At this time, the chips are cut off. Then, by the forward movement in the feed direction (hereinafter also referred to as the forward movement), it contacts the bottom surface of the workpiece again and starts cutting again. At this time, in the drilling process of the present embodiment, as described in detail in the latter section, the sinusoidal swing phase and / or swing amplitude are changed in the forward movement and the return movement, and therefore, as shown in FIG. Figure 3 As shown in FIG. 1 , the speed (slope) of the tool can be changed. Therefore, the speed of the tool during cutting can be slowed down, and the impact during cutting can be reduced.

[0034] Next, refer to Figure 4 The structure of the control device for a machine tool that performs the drilling process according to this embodiment will be described in detail. The control device 100 of the machine tool according to this embodiment controls a spindle motor (not shown) that rotates the tool T relative to the workpiece W, and controls a feed axis motor 30 that moves the tool T and the workpiece W while simultaneously swinging in the feed direction relative to each other, thereby performing the drilling process. The control device 100 of the machine tool according to this embodiment is implemented, for example, by having a computer having a CPU, memory, etc. read a program that executes the drilling process according to this embodiment.

[0035] Figure 4 FIG. 1 is a functional block diagram of the control device 100 of the machine tool according to the present embodiment. Figure 4 As shown, the control device 100 of the machine tool of this embodiment includes: a position command preparation unit 21, a storage unit 22, a servo control device 10, adders 11 and 13, an accumulator 12, a learning control unit 14, a position and speed control unit 15, a swing command generation unit 16 and a load acquisition unit 17.

[0036] The position command generating unit 21 generates a position command. Specifically, the position command generating unit 21 generates a position command for the motor 30 of the feed axis by analyzing a machining program stored in a storage unit 22 to be described later.

[0037] The adder 11 calculates the position deviation. Specifically, the adder 11 calculates the position deviation, which is the difference between the position feedback detected by the encoder (not shown) provided on the motor 30 of the feed shaft and the position instruction of the feed shaft generated by the above-mentioned position instruction generating unit 21.

[0038] The accumulator 12 calculates an accumulated value of the position deviation. Specifically, the accumulator 12 calculates an accumulated value of the position deviation by accumulating the position deviation calculated by the adder 11.

[0039] The adder 13 calculates the overlap command. Specifically, the adder 13 generates the overlap command by adding (overlapping) the swing command generated by the swing command generating unit 16 described later to the accumulated value of the position deviation calculated by the accumulator 12. The method of generating the overlap command will be described in detail later.

[0040] The learning control unit 14 calculates a correction amount for the overlap command based on the position deviation and adds the calculated correction amount to the overlap command to correct the overlap command. More specifically, the learning control unit 14 repeatedly calculates a periodic correction amount based on the periodic overlap command. Specifically, the learning control unit 14 includes a memory that stores the deviation between the ideal position and the actual position of the motor 30, which can define a certain period. The learning control unit 14 periodically reads the stored deviation from the memory to calculate a correction amount to bring the deviation close to zero. The calculated correction amount is then superimposed on the overlap command to perform correction. The overlap command of this embodiment includes an oscillation command, which can easily cause position deviation. However, the correction performed by the learning control unit 14 improves the ability to follow the periodic oscillation command.

[0041] Furthermore, the learning control unit 14 preferably stores the phases of the overlap command and the swing command in correspondence in a memory, and calculates the correction amount of the overlap command based on the stored correspondence between the phases of the overlap command and the swing command. This further improves the ability to follow the periodic swing command.

[0042] The position and speed control unit 15 generates a torque command for the feed shaft driving motor 30 based on the corrected overlap command, and controls the motor 30 with the generated torque command. As a result, the feed shaft driving motor 30 reaches the command position while oscillating.

[0043] The swing command generating unit 16 generates a swing command for swinging the tool T and the workpiece W relative to each other in the feed direction according to a predetermined swing condition. Figure 4As shown, the swing command generation unit 16 includes a swing phase calculation unit 163, a swing amplitude calculation unit 161, and a swing command calculation unit 162. The swing phase calculation unit 163 calculates a reference phase (not shown) based on predetermined swing conditions and multiplies time or the reference phase by a rate of change based on the predetermined swing conditions to calculate the swing phase. The swing amplitude calculation unit 161 calculates the swing amplitude based on the predetermined swing conditions. The swing command calculation unit 162 calculates a swing command based on the swing phase calculated by the swing phase calculation unit 163 and the swing amplitude calculated by the swing amplitude calculation unit 161. The predetermined swing conditions include swing phase information, swing amplitude information, time, and the relative rotation speed of the tool T and workpiece W, which can be obtained from a machining program stored in the storage unit 22 (described later). The swing command generation unit 16 generates a swing command based on this swing phase information and swing amplitude information.

[0044] The oscillation phase calculation unit 163 preferably changes the rate of change of the oscillation phase calculated based on predetermined oscillation conditions to reduce the machining load on the tool T obtained by the load acquisition unit 17, which will be described later. Similarly, the oscillation amplitude calculation unit 161 preferably changes the oscillation amplitude calculated based on predetermined oscillation conditions to reduce the machining load on the tool T obtained by the load acquisition unit 17, which will be described later. Thus, the oscillation phase and amplitude can be changed according to the increase or decrease in the machining load, further reducing the impact during cutting.

[0045] In this embodiment, the swing command generator 16 features a method of changing at least one of the swing command phase progression or amplitude based on time or a reference phase calculated based on predetermined swing conditions. This change in the swing command phase progression includes at least a change in the swing phase change rate and may also include a change in the swing amplitude. By changing the swing command phase progression and amplitude, the impact during cutting can be reduced, as will be described in detail later.

[0046] In addition, the swing instruction generating unit 16 preferably changes at least one of the advancing mode of the phase of the swing instruction and the amplitude of the swing instruction according to the tool information. The tool information is stored in the storage unit 22 described later. As tool information, the specifications of the tool T including the number of blades of the tool T, the diameter of the tool T, etc. are included. For example, when the ratio of the machining depth to the tool diameter is greater than a predetermined value, the chip discharge performance can be improved by increasing the rate of change of the swing phase. Moreover, for example, the more blades the tool T has, the easier it is for the trajectories of the blades to overlap and to produce idle swing (backlash). Therefore, even if the rate of change of the swing phase is increased or the swing amplitude is reduced, the chips can be cut off. The relationship between the number of blades of the tool T and the swing instruction will be described in detail in the latter section.

[0047] Furthermore, the swing command generator 16 preferably synchronizes the phase of the swing command with the phase of the spindle that rotates the tool T and workpiece W relative to each other. For example, if the tool T has many blades, the spacing between the blades is narrow, resulting in poor chip removal. However, synchronizing the phase of the swing command with the phase of the spindle can improve chip removal. The synchronization of the phase of the swing command with the phase of the spindle will be described in detail later.

[0048] The storage unit 22 stores tool information related to the tool T (specifications of the tool T including the number of blades of the tool T, the diameter of the tool T, etc.), a machining program, oscillation phase information (such as the rate of change of the oscillation phase) and oscillation amplitude information (such as the oscillation amplitude magnification) that can be obtained from the machining program, time, the relative rotation speed of the tool T and the workpiece W (spindle speed), and other information.

[0049] The load acquisition unit 17 acquires the machining load applied to the tool T during cutting. Specifically, the load acquisition unit 17 acquires the machining load applied to the tool T during cutting based on an overlap command or a current value or a torque command of the motor 30 .

[0050] Next, refer to Figures 5 to 8 The method for generating the overlap command of this embodiment in which the phase of the swing command is changed according to time is described in detail. Figure 5 This is a diagram showing the rate of change of the oscillation phase during drilling according to the present embodiment. Figure 6 It is a diagram showing the oscillation phase of the drilling process according to this embodiment. Figure 7 This is a diagram showing the swing command for drilling according to the present embodiment. Figure 8 It is a diagram showing the overlapping command of drilling processing according to this embodiment.

[0051] First, without synchronizing the oscillation phase with the phase of the main shaft rotation, the oscillation command is calculated using the following formula (1).

[0052] [Mathematical formula 1]

[0053] Swing command = (K×F / 2)×cos(2π×I×t)-(K×F / 2)…(1)

[0054] In the above formula (1), K is the ratio of the oscillation amplitude to the tool movement amount, F is the tool movement amount, that is, the feed rate per revolution [mm / spindle revolution], I is the rate of change of the oscillation phase per unit time, and t is the time [s]. In addition, (K×F / 2) represents the oscillation amplitude, (2π×I×t) represents the oscillation phase, and -(K×F / 2) represents the offset to prevent unnecessary cutting relative to the command position during normal cutting without oscillation.

[0055] Here, when the wobble phase change rate I is changed by using the time t1 when the wobble phase is π and the time t2 when the wobble phase is 2π as thresholds, as shown in FIG. Figures 5 to 8 At this time, I1 and I2 can be directly specified from the predetermined frequency, or I1 can be specified as 1 and I2 as a multiplication factor of the predetermined frequency.

[0056] First, if Figure 5 As shown in FIG. 1 , during the period from t1 to t2, the rate of change of the swing phase changes from I1 to a larger I2. Figure 6 As shown in the figure, it can be seen that the change rate (frequency) of the swing phase is larger than that of other times from t1 to t2, and the slope of the swing phase becomes larger. In addition, the swing command generated at this time is Figure 7 As shown in FIG, the sine wave swing command is shown. From this figure, it can be seen that the change rate (frequency) of the swing phase is large during the period from t1 to t2. Figure 7 The overlapping instruction obtained by overlapping the swing instruction and the position instruction (no swing) is Figure 8 The superposition command is a sine wave-shaped command as shown. As described above, the superposition command is generated.

[0057] Next, refer to Figure 9 and Figure 10 While the impact reduction method during cutting in the drilling process of this embodiment is described in detail. Figure 9 It is a diagram showing an overlap instruction that can reduce the impact when cutting in. Figure 10 This diagram shows an overlap command that cannot reduce the impact during cutting.

[0058] exist Figure 9 and Figure 10 In the figure, one cycle of a certain oscillation is shown. Figure 9 as well as Figure 10 In the example, t0 represents the moment when the swing phase is 0 (I×t0=0), t1 represents the moment when the swing phase is π (I×t1=0.5), t2 represents the moment when the swing phase is 2π (I×t2=1), and t i Indicates the moment when the tool T comes into contact with the workpiece W.

[0059] Figure 9 Indicates the superposition instruction when the shock reduction condition is set according to the speed. At t1 when the swing phase is π, the speed of the superposition instruction is the same as the position instruction (excluding the swing instruction). Figure 9The slope of the curve of the overlap instruction at t1 is used to express it. If expressed in terms of a formula, when the swing phase is π, the term containing sin in the formula of the overlap instruction speed, that is, the following formula (5), is 0. The speed at this time is shown in the following formula (3), which is the same as the speed of normal cutting. In addition, it can be seen that at the moment t when the tool T contacts the bottom surface of the workpiece i , in order to satisfy 0<I×t i When I is changed in a manner of <0.5, the slope of the overlap command is smaller than the slope of t1, and the impact of the collision moment can be reduced compared with the normal cutting without swinging. Figure 10 It can be seen that when 0<I×t is not satisfied i When I is changed to a value less than 0.5, the speed at the moment of collision is higher than that of normal cutting. In this case, it can be said that the impact reduction effect cannot be achieved.

[0060] Therefore, if the slope of the overlap command at the moment tool T contacts the workpiece bottom surface is lower than that during normal cutting, it can be said that compared to conventional step-by-step machining, the impact can be reduced, thereby improving tool life. Furthermore, to further improve tool life, it is desirable to adjust the oscillation amplitude so that the sign of the overlap command slope reverses midway. Specifically, it is preferable to temporarily remove tool T from the workpiece bottom surface to supply coolant to the bottom surface. This prevents the deposition of chips due to frictional heat and cutting heat, and is expected to improve the surface quality of the machined surface and tool life.

[0061] Next, a shock reduction method based on acceleration and jerk will be described below.

[0062] In the case of normal cutting without weaving, the command position is expressed by the following formula (2) using the spindle speed S per minute, and the speed is expressed by the following formula (3).

[0063] [Mathematical formula 2]

[0064] Command position = F [mm / spindle revolution] × S [spindle revolution / minute] × t [seconds] / 60…(2)

[0065] Command speed = F × S / 60…(3)

[0066] In contrast, in the case of an overlapping swing command, the command position based on the overlapping command is expressed by the following formula (4), and the speed, acceleration, and jerk are expressed by the following formulas (5), (6), and (7), respectively.

[0067] [Mathematical formula 3]

[0068] Command position = F × S × t / 60 + (K × F / 2) × cos (2π × I × t) - (K × F / 2)…(4)

[0069] Command speed = F × S / 60 - (π × I × K × F) × sin (2π × I × t)… (5)

[0070] Command acceleration = -2π 2 ×I 2 ×K×F×cos(2π×I×t)…(6)

[0071] Command jerk = 4π 3 ×I 3 ×K×F×sin(2π×I×t)…(7)

[0072] As mentioned above, if the slope of the overlap command is less than or equal to the slope of normal cutting, F×S / 60 [mm / second], the impact during cutting can be reduced. Therefore, when setting the impact reduction condition based on the speed at which the tool T collides with the bottom surface of the workpiece, the following equation can be satisfied: F×S / 60 > F×S / 60 - (π×I×K×F) × sin(2π×I×t). If 0 < I×t < 0.5, the term containing sin becomes negative, resulting in a slower speed than normal cutting.

[0073] The machine tool control device 100 can identify the machined area based on position feedback from the motor 30. Furthermore, the progression of the swing phase is known, so the moment when the tool T, operating according to the overlap command, collides with the workpiece W can be determined. Therefore, by changing I so that the aforementioned inequality is satisfied at that moment, the impact can be reduced.

[0074] Alternatively, the acceleration -2π can be used as the time zone during which the tool T cuts the workpiece W. 2 ×I 2 By changing the values ​​of I and K so that ×K×F×cos(2π×I×t) is minimized, the acceleration of the tool T during machining is suppressed and the conditions for reducing the impact are set.

[0075] Alternatively, the jerk 4π can be used throughout the swing. 3 ×I 3 The values ​​of I and K are set so that ×K×F×sin(2π×I×t) is minimized, thereby reducing the impact on the entire machine caused by the vibration of the driving unit including the feed axis of the tool T.

[0076] Next, refer to Figure 11 and Figure 12 The synchronization between the swing phase and the main shaft rotation phase is explained. Figure 11 : is a diagram showing the trajectory of each blade when the number of blades of the tool T is 2. Figure 12 1 is a diagram showing the trajectory of each cutting edge when the tool T has three cutting edges.

[0077] First, when synchronizing the oscillation phase with the main shaft rotation, the oscillation command is expressed by the following formula (8).

[0078] [Formula 4]

[0079] Swing command = (K×F / 2)×cos(2π×S×I'×t / 60)-(K×F / 2)…(8)

[0080] In the above formula (8), S is the rotation speed of the main shaft [minutes] -1 ] or [rpm], where I' represents the rate of change of the swing phase per spindle rotation. F, K, and t are the same as those in formula (1) above. Even when synchronizing the swing phase with the spindle rotation phase, an overlap command can be generated in the same manner as described above when the swing phase is not synchronized with the spindle rotation phase.

[0081] from Figure 11 and Figure 12 As can be seen, the greater the number of blades in tool T, the more points at which the paths of the blades overlap, the more likely lost motion (lost motion) occurs, and the easier it is to cut chips. For example, when the number of blades is one, it is preferable to oscillate at a frequency that is not an integral multiple of the spindle's rotation. In contrast, when the number of blades increases, synchronizing with only one spindle rotation allows for efficient chip cutting into a stable size. For example, oscillating once per multiple spindle rotations can also achieve the same effect.

[0082] And, compare Figure 11 and Figure 12 As can be seen, the greater the number of blades in tool T, the smaller the swing amplitude can be used to cut chips. A smaller swing amplitude offers advantages in power consumption. Furthermore, while a tool T with many blades offers high cutting efficiency, the spacing between the blades is narrow, resulting in poor chip removal. However, by synchronizing the swing phase with the spindle phase, chips can be cut more reliably, eliminating this problem. This also offers advantages in terms of machining efficiency.

[0083] Next, refer to Figure 13 The process of drilling performed by the control device 100 of the machine tool of this embodiment will be described. Figure 13 This is a flowchart showing the drilling process of this embodiment when the advancing manner of the oscillation phase is changed based on the reference phase.

[0084] First, in step S1, the position command, oscillation phase information (including frequency information and rates of change I1 and I2), and oscillation amplitude information are obtained from the machining program. Next, in step S2, a reference phase θ is calculated and updated based on the obtained frequency information. Alternatively, the reference phase θ can be calculated synchronously with the spindle phase, rather than using frequency information.

[0085] Next, in step S3, it is determined whether the calculated reference phase θ is equal to or greater than a predetermined threshold. If so, in step S4, the swing phase θ' is calculated (updated) based on the reference phase θ obtained by multiplying the change rate I1. If not, in step S5, the swing phase θ' is calculated (updated) based on the reference phase θ obtained by multiplying the change rate I2.

[0086] In step S6, a swing command is generated based on the swing phase θ' and the swing amplitude. In step S7, the swing command is added (superimposed) to the position command to generate a superposition command. The generation method of the swing command and the superposition command is as described above.

[0087] In step S8, the motor 30 driving the feed axis is activated according to the overlap command generated in step S7. In step S8, it is determined whether the motor 30 has reached the command position. If the determination is negative, the process returns to step S2 and the process is executed again. If the determination is positive, the process ends.

[0088] According to this embodiment, the following effects are obtained.

[0089] (1) In this embodiment, a swing instruction generating unit 16 is provided for generating a swing instruction for causing the tool T and the workpiece W to swing relative to each other in the feed direction according to predetermined swing conditions, and at least one of the phase advancement mode of the swing instruction and the amplitude of the swing instruction is changed according to time or the swing phase calculated according to predetermined swing conditions.

[0090] According to this embodiment, the phase advancement mode, i.e., frequency and amplitude, can be changed through forward motion and return motion within one cycle of the swinging action, thereby reliably cutting and discharging chips, and suppressing tool breakage by reducing the impact when the tool T cuts into the workpiece W.

[0091] Specifically, for example, a sinusoidal oscillation command can be superimposed on a constant-speed cutting feed command. During the period from when the tool T retreats in accordance with the superimposed command until it re-contacts the workpiece W, the oscillation phase change rate per unit time is multiplied by a predetermined factor, thereby slowing the phase advance. Alternatively, the machining program can specify first and second frequency information, switching between them during the aforementioned period to slow the phase advance. This reliably reduces the impact during cutting.

[0092] Furthermore, in this embodiment, only the frequency of the oscillation (the way the phase advances) can be changed, while the feed rate of the position command can be maintained unchanged. Therefore, the operation can be performed with the same cycle time as when the oscillation is not performed. Furthermore, the return motion of the oscillation operation can be used to separate the tool T from the bottom surface of the workpiece, thereby suppressing wear of the tool tip and temperature rise at the machining point.

[0093] (2) In the present embodiment, a storage unit 22 is further provided for storing tool information related to the tool T. At least one of the phase advancement method and the amplitude of the swing command is changed based on the tool information.

[0094] According to this embodiment, the phase progression and amplitude of the oscillation command can be modified relative to the overall phase rather than within a cycle, in accordance with tool information related to the number of blades, tool diameter, and other tool information related to the number of tool strands, such as the number of blades in the tool T, based on the timing of tool T replacement. This allows for the generation of optimal oscillation commands and the suppression of tool wear caused by excessive oscillation.

[0095] For example, when the ratio of machining depth to tool diameter is greater than a predetermined value, chip removal can be improved by increasing the oscillation phase (frequency). Furthermore, for example, if the tool T has a greater number of cutting edges, the paths of the cutting edges are more likely to overlap, leading to lost motion. Therefore, even if the oscillation phase (frequency) is increased or the oscillation amplitude is reduced, chips can still be cut.

[0096] (3) In this embodiment, a load acquisition unit is provided for acquiring the load generated on the tool T during cutting processing, and the swing phase calculation unit 163 changes the forward direction of the swing phase calculated according to the predetermined swing condition in a manner that reduces the load, or the swing amplitude calculation unit 161 changes the swing amplitude calculated according to the predetermined swing condition in a manner that reduces the load.

[0097] This allows the advancement pattern and amplitude of the swing phase, which creates a significant impact during cutting, to be altered, thereby more reliably preventing tool breakage from excessive cutting loads. For example, when the load exceeds a predetermined threshold, it is determined that the tool T has engaged the chips, and the swing phase and amplitude are altered to increase the idle swing (backflip) time. This more reliably reduces the impact and further prevents tool T breakage.

[0098] (4) In the present embodiment, a learning control unit 14 is provided that calculates a correction amount for the overlap command based on the positional deviation and adds the calculated correction amount to the overlap command to thereby correct the overlap command.

[0099] Thus, for example, even with high-frequency oscillation, the motor 30 can accurately follow the overlap command and efficiently cut chips. Furthermore, even when the cutting load is heavy or the reaction of the oscillating feed shaft is large and the overlap command cannot be followed, the motor 30 can accurately follow the overlap command and efficiently cut chips.

[0100] (5) In the present embodiment, the phase of the swing command is synchronized with the phase of the spindle that rotates the tool T and the workpiece W relative to each other.

[0101] This makes it possible to cut chips more efficiently and to follow high-speed swinging.

[0102] In addition, the present invention is not limited to the above-described embodiment, and modifications and improvements within the scope that can achieve the object of the present invention are also included in the present invention.

[0103] For example, in the above-described embodiment, the present invention is applied to drilling using a drill as a cutting tool, but the present invention is not limited thereto and can be applied to other cutting processes such as turning and thread cutting.

[0104] Explanation of symbols

[0105] 10. Servo control device;

[0106] 11, 13 adders;

[0107] 12 accumulators;

[0108] 14 Learning Control Department;

[0109] 15. Position and speed control unit (control unit);

[0110] 16. Swing command generating unit;

[0111] 17. Load acquisition unit;

[0112] 21 Position Instruction Production Department;

[0113] 22 Storage Department;

[0114] 30 motor (electric motor);

[0115] 100 Machine tool control device;

[0116] 161 Swing amplitude calculation unit;

[0117] 162 swing command calculation unit;

[0118] 163 Swing phase calculation unit.

Claims

1. A control device for a machine tool, which controls a spindle for rotating a cutting tool relative to a workpiece, and controls a feed axis for moving the cutting tool relative to the workpiece while swinging in a feed direction, thereby performing cutting processing, wherein: The control device of the machine tool has: a swing command generating unit for generating a swing command for relatively swinging the cutting tool and the workpiece in a feed direction based on a predetermined swing condition; and a control unit that controls the motor driving the feed axis based on a superimposition command generated by superimposing the swing command generated by the swing command generating unit and a position command or a position deviation that is a difference between the position command and position feedback, The swing command generating unit changes at least one of the phase progression of the swing command and the amplitude of the swing command according to time or the swing phase calculated based on the predetermined swing condition. The control device of the machine tool further includes: a load acquisition unit that acquires a load generated on the cutting tool during the cutting process; The swing instruction generating unit includes: a swing phase calculation unit for calculating the swing phase according to the predetermined swing condition; a swing amplitude calculation unit for calculating the swing amplitude based on the predetermined swing condition; as well as a swing command calculation unit that calculates the swing command based on the swing phase calculated by the swing phase calculation unit and the swing amplitude calculated by the swing amplitude calculation unit, The swing phase calculation unit changes the advancement of the swing phase calculated based on the predetermined swing condition in a manner that reduces the load obtained by the load acquisition unit, or the swing amplitude calculation unit changes the swing amplitude calculated based on the predetermined swing condition in a manner that reduces the load obtained by the load acquisition unit.

2. The machine tool control device according to claim 1, wherein: The control device of the machine tool further includes: a storage unit that stores tool information related to the cutting tool; The swing command generating unit changes at least one of a phase advancement pattern of the swing command and an amplitude of the swing command based on the tool information.

3. The control device for a machine tool according to claim 1, wherein: The machine tool control device further includes a learning control unit that calculates a correction amount for the overlap command for bringing the position deviation close to 0, and corrects the overlap command by adding the calculated correction amount to the overlap command, thereby improving followability to the swing command.

4. The control device for a machine tool according to claim 2, wherein: The machine tool control device further includes a learning control unit that calculates a correction amount for the overlap command for bringing the position deviation close to 0, and corrects the overlap command by adding the calculated correction amount to the overlap command, thereby improving followability to the swing command.

5. The control device for a machine tool according to any one of claims 1 to 4, wherein: The swing command generating unit synchronizes a phase of the swing command with a phase of a spindle that rotates the cutting tool and the workpiece relative to each other.

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