Machine tool control device

Abstract

To provide a control apparatus of a machine tool that enables a threading process while reducing a load on the machine tool due to an oscillation motion without extending a cycle time, and that can reliably shred chips when performing a no-oscillation motion in a current path after the oscillation motion in a previous path.SOLUTION: A control apparatus 100 of a machine tool includes an oscillation motion performance determination unit 102 that determines whether or not to perform an oscillation motion causing a cutting tool 16 to oscillate in a radial direction of a work 14, and an oscillation instruction generation unit 106 that generates an oscillation instruction of the oscillation motion based on a determination result of the oscillation motion performance determination unit 102. The oscillation motion performance determination unit 102 determines to intermittently perform cutting by the oscillation motion and then perform cutting without the oscillation motion in a subsequent path. The oscillation instruction generation unit 106 generates the cutting without oscillation motion such that a cutting amount thereof is the same as a cutting amount of a no-oscillation portion of a path in which the cutting by the oscillation motion is intermittently performed.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a control device for a machine tool. [Background technology]

[0002] Conventionally, there are known techniques for performing thread cutting while shredding chips. For example, a technique is disclosed in which a workpiece and a cutting tool are reciprocally vibrated during a predetermined number of cuts, and the vibration pattern during each cut accompanied by the reciprocating vibration is set so that the cut portion during a predetermined cut includes a portion that has already been cut by another cut (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 056526 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology of Patent Document 1, the workpiece and the cutting tool constantly vibrate back and forth (hereinafter also referred to as oscillating motion) during thread cutting, which places a large burden on the machine tool due to the reciprocating vibration. Therefore, there is a demand for a machine tool control device that can perform thread cutting while reducing the burden on the machine tool due to the oscillating motion, without extending the cycle time that is important in machining by the machine tool.

[0005] Furthermore, in the technology of Patent Document 1, during swing operation, the position deviation, which is the deviation between the position command and the actual position, is large due to reasons such as response delay, which causes uncut portions (see FIG. 7 described later). Therefore, it is currently difficult to realize chipping in the finish machining of the final pass, and there is a demand for a control device for a machine tool that can reliably chop chips when executing a non-rocking operation of the current pass after the swing operation of the previous pass, such as in the finish machining of the final pass of thread cutting. [Means for solving the problem]

[0006] One aspect of the present disclosure is a control device for a machine tool that coordinates the operation of at least one spindle that rotates a cutting tool and a workpiece relatively to one another, and at least one feed axis that moves the cutting tool relatively to the workpiece to perform thread cutting while making multiple radial cuts into the workpiece with the cutting tool, the control device for the machine tool comprising: a swing operation execution determination unit that determines whether to perform a swing operation to swing the cutting tool in the radial direction of the workpiece, and a swing command generation unit that generates a swing command for the swing operation based on a result of the determination by the swing operation execution determination unit, wherein the swing operation execution determination unit determines that after intermittently performing cutting using a swing operation, a cut without a swing operation should be performed in the subsequent pass, and the swing command generation unit generates the cut without a swing operation so that the amount of cut is the same as the amount of cut of a non-swing portion of the pass in which cutting using the swing operation is intermittently performed. Effect of the Invention

[0007] According to the present disclosure, it is possible to provide a control device for a machine tool capable of performing thread cutting while reducing the burden on the machine tool due to swing motion without extending the cycle time. It is also possible to provide a control device for a machine tool capable of reliably shredding chips when performing a non-swing operation in a current pass after a swing operation in a previous pass, such as in finish processing in the final pass of thread cutting. [Brief description of the drawings]

[0008] [Figure 1]1 is a functional block diagram showing a configuration of a control device for a machine tool according to one embodiment of the present disclosure. [Diagram 2] FIG. 1 is a diagram showing a screw created by thread cutting. [Diagram 3] FIG. 1 is a diagram showing a workpiece being threaded; [Figure 4] 11A to 11C are diagrams for explaining the operation of thread cutting by a machine tool control device according to one embodiment of the present disclosure. [Diagram 5] 11A to 11C are diagrams for explaining the operation of thread cutting by a machine tool control device according to one embodiment of the present disclosure. [Figure 6] 11A to 11C are diagrams for explaining the operation of thread cutting by a machine tool control device according to one embodiment of the present disclosure. [Figure 7] FIG. 1 is a diagram showing a finish machining in the final pass of conventional thread cutting. [Figure 8] FIG. 13 is a diagram showing a finish machining in a final pass of thread cutting by a machine tool control device according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, one embodiment of the present disclosure will be described in detail with reference to the drawings.

[0010] A control device for a machine tool according to one embodiment of the present disclosure coordinates at least one spindle which rotates the cutting tool and workpiece relative to one another, and at least one feed axis which moves the cutting tool relative to the workpiece, to perform thread cutting while making multiple radial cuts into the workpiece with the cutting tool.

[0011] Fig. 1 is a functional block diagram showing a configuration of a control device 100 for a machine tool according to one embodiment of the present disclosure. As shown in Fig. 1, the control device 100 outputs drive commands to a motor 120 that drives at least one spindle that rotates a cutting tool and a workpiece relatively and at least one feed axis that moves the cutting tool relative to the workpiece, for cooperative operation of these axes.

[0012] Before describing the configuration of the control device 100, thread cutting will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a diagram showing a screw 12 created by thread cutting. Fig. 3 is a diagram showing a workpiece 14 being thread cut.

[0013] 2, a screw 12 created by thread cutting has a sufficiently deep screw groove 10 formed in a spiral shape on its outer circumferential surface. A machine tool control device 100 according to one embodiment of the present disclosure forms this screw groove 10 by cutting the workpiece by rotating the cutting tool and the workpiece relatively and moving the cutting tool relative to the workpiece.

[0014] As indicated by arrow P in Figure 3, cutting of the thread groove 10 on the workpiece 14 is performed multiple times by a cutting tool 16 along a predetermined trajectory 10a (i.e., the position of the thread groove 10) on the workpiece 14. The trajectory 10a exists in a spiral shape around the entire circumference of the outer circumferential surface of the workpiece 14. Figure 3 shows the state just after cutting has started, and the depth of the thread groove 10 is still shallow. By repeating the cutting process multiple times, a deep thread groove 10 as shown in Figure 2 is formed, and the final screw 12 is completed.

[0015] 3, the workpiece 14 is attached to a spindle 18 and is controlled to rotate in the direction indicated by an arrow C. The rotation coordinate axis indicated by the arrow C is called the C-axis. In other words, the C-axis is an angular coordinate that represents an angle around the spindle 18.

[0016] The cutting tool 16 moves on a trajectory 10a on the surface of the rotating workpiece 14 to cut the thread groove 10. To this end, the cutting tool 16 is controlled to move along the Z-axis, which is the coordinate axis in the longitudinal direction of the workpiece 14, in synchronization with the rotation of the workpiece 14 in the C-axis direction.

[0017] Furthermore, the cutting tool 16 gradually moves in the X-axis direction, which is a coordinate axis perpendicular to the surface of the workpiece 14, i.e., in the radial direction, for each cutting operation. Therefore, the cutting tool 16 is controlled to perform cutting at gradually deeper positions in the workpiece 14.

[0018] Next, a configuration of a control device 100 for a machine tool according to one embodiment of the present disclosure will be described. As shown in Fig. 1, the control device 100 includes a swing operation execution determination unit 102, a swing condition calculation unit 104, a swing command generation unit 106, an adder 108, and a control unit 110.

[0019] For example, a numerical control device is used as the control device 100. The control device 100 is realized by causing a computer having, for example, a CPU, a memory, etc. to load a program according to this embodiment.

[0020] The swing operation execution determination unit 102 determines whether or not to execute a swing operation that swings the cutting tool 16 in the radial direction (X-axis direction) of the workpiece 14. This determination is made based on a machining program input from the outside. The swing operation execution determination unit 102 according to one aspect of the present disclosure is characterized in that it determines to execute the swing operation intermittently. That is, the swing operation execution determination unit 102 determines to execute an intermittent swing operation so that a swing operation that relatively vibrates the cutting tool 16 and the workpiece 14 back and forth and a non-swing operation that does not vibrate back and forth are alternately repeated. As a result, the swing operation and the non-swing operation are alternately and repeatedly executed within the same machining path.

[0021] Preferably, the swing operation execution determination unit 102 determines the execution of the swing operation so that the swing cutting is performed in a position different from the swing cut portion in the previous cutting operation in the current cutting operation. This makes it possible to more reliably include the previous cut portion in the current cutting operation, more reliably generating so-called misses and more reliably shredding the chips.

[0022] Also, preferably, the swinging operation execution determination unit 102 determines to execute cutting without swinging operation in the next pass after performing the swinging cutting intermittently. This makes it possible to reliably shred chips when, for example, non-swinging cutting is performed in the final pass after swing cutting is performed. This will be described in detail later.

[0023] Also preferably, the swinging operation execution determination unit 102 determines to execute non-rocking cutting in the non-rocking cutting section by intermittent swinging operation until the position deviation, which is the deviation between the position command and the actual position, becomes equal to or less than a predetermined threshold value. This makes it possible to reliably chop chips in the non-rocking cutting section by intermittent swinging operation. This will be described in detail later.

[0024] The swing condition calculation unit 104 calculates the conditions of the swing operation to be output to the swing command generation unit 106 based on at least one of the machining program, machining parameters, and feedback values ​​from the machine tool. For example, as shown in Fig. 1, the swing condition calculation unit 104 calculates conditions such as the interval (the distance between adjacent peaks in a swing waveform as shown in Fig. 4 described later), amplitude, and period of the swing operation based on a machining program input from the outside.

[0025] Preferably, the swing condition calculation unit 104 changes the interval of the swing motion. More specifically, the swing condition calculation unit 104 may change the interval of the swing motion between different machining passes. Also, the swing condition calculation unit 104 may change the interval of the swing motion within the same machining pass. Alternatively, the swing condition calculation unit 104 may change the interval of the swing motion between different machining passes and also change the interval of the swing motion within the same machining pass.

[0026] The oscillation condition calculation unit 104 may also change the interval between oscillation operations depending on the diameter of the workpiece 14. For example, the smaller the diameter of the workpiece 14, i.e., the more cutting operations are performed, the longer the interval between oscillation operations may be. Alternatively, conversely, the smaller the diameter of the workpiece 14, i.e., the more cutting operations are performed, the shorter the interval between oscillation operations may be. The setting of the interval between oscillation operations will be described in detail later.

[0027] The swing command generating unit 106 generates a swing command for the swing operation based on the determination result by the swing operation execution determining unit 102. The swing command generating unit 106 also generates a swing command for the swing operation according to the swing conditions calculated by the swing condition calculating unit 104. The swing command generating unit 106 according to one aspect of the present disclosure generates a swing command such that the non-swing cutting part in the current cutting operation includes the swing cutting part in the previous cutting operation. Alternatively, the swing command generating unit 106 generates a swing command such that the swing cutting part in the current cutting operation includes the non-swing cutting part in the previous cutting operation. This makes it possible to more reliably generate a so-called miss and more reliably shred the chips.

[0028] An adder 108 calculates a position deviation, which is the difference between a position feedback based on position detection by an encoder (not shown) provided on the motor 120 and a position command for the feed shaft. The position command and position deviation for the feed shaft are input to a control unit 110, which will be described later.

[0029] The control unit 110 generates a drive command for the motor 120 that drives the feed axis by superimposing the swing command generated by the swing command generating unit 106 on the position command and position deviation of the feed axis. Note that in one aspect of the present disclosure, the position command of the feed axis is once generated, and the swing command is superimposed on the generated position command, but this is not limiting. The position command of the feed axis may be generated by superimposing the swing command in advance.

[0030] Next, the operation of thread cutting by the control device 100 of the machine tool according to one embodiment of the present disclosure will be described in detail with reference to Figs. 4 to 6. Here, Figs. 4 to 6 are diagrams for explaining the operation of thread cutting by the control device 100 of the machine tool according to one embodiment of the present disclosure. These diagrams correspond to a view of part A in Fig. 3 from the cutting start side in the Z-axis direction. More specifically, Fig. 4 is a diagram showing an example in which the interval between the swinging motions of each machining pass (hereinafter simply referred to as a pass) is constant. Fig. 5 is a diagram showing an example in which the interval between the swinging motions is made longer as the diameter of the workpiece 14 becomes smaller. Fig. 6 is a diagram showing an example in which the swinging motion of each pass is made in a direction away from the workpiece 14 instead of in a direction cutting into the workpiece 14.

[0031] The C-axis, Z-axis, and X-axis in Figures 4 to 6 are defined in the same way as the C-axis, Z-axis, and X-axis in Figure 3. In Figures 4 to 6, the part circled by the dashed line is a part that includes a part that has been cut previously in the current cutting process, and indicates a part where a so-called miss occurs and the chips are chopped.

[0032] In the operation example shown in Fig. 4, the first to fourth passes all involve intermittent oscillating motion, with linear non-oscillating cutting and curved deep-cut oscillating cutting being repeated alternately. Also, the interval L of the oscillating motion shown in Fig. 4 is constant in all of the first to fourth passes. As for the final pass, since it is a finishing process, only non-oscillating cutting is performed, and all cutting is linear.

[0033] Here, the interval L of the oscillation motion, i.e., the distance between adjacent peaks in the oscillation waveform as shown in Fig. 4, can be set in accordance with the allowable chip length. The allowable chip length is set to a length that does not impede the cutting process by causing the chip to become entangled in the cutting tool 16 during cutting. This makes it possible to chop the chips to a length that does not impede the cutting process. The allowable chip length can be specified by a G code, a parameter, or the like, so that the interval L of the intermittent oscillation motion can be specified.

[0034] In the operation example shown in Fig. 5, like the operation example shown in Fig. 4, the first to fourth passes all involve intermittent oscillating motion, with linear non-oscillating cutting and curved deep-cut oscillating cutting being repeated alternately. However, the intervals between the oscillating motions are different between the first to fourth passes, as shown in Fig. 5. As for the final pass, since it is a finishing process, only non-oscillating cutting is performed, and all cutting is linear.

[0035] Specifically, the smaller the diameter of the workpiece 14, i.e., the more cutting processing progresses, the longer the interval between the swinging motions is set. Therefore, as shown in Fig. 5, the interval L2 between the swinging motions in the fourth pass is set longer than the interval L1 between the swinging motions in the first pass. As a result, the circumferential length of the workpiece 14 becomes shorter as the number of cutting processing steps progresses, but by lengthening the interval between the swinging motions, it is possible to keep the length of the chips constant.

[0036] In the operation example shown in Fig. 6, like the operation example shown in Fig. 4, the first to fourth passes all perform intermittent swinging motion, and linear non-swinging cutting and curved swinging cutting are alternately and repeatedly performed. Also, in the first to fourth passes, like the operation example shown in Fig. 4, the swinging motion interval L is constant. However, in the first to fourth passes, the swinging motion is not in the direction cutting into the workpiece 14 but in the direction moving away from it. That is, the swinging direction is reversed compared to the operation examples shown in Figs. 4 and 5.

[0037] Here, when performing a swing operation in the direction cutting into the workpiece 14 as shown in Figures 4 and 5, in order to determine the swing amplitude so that the cutting process of the next pass includes the cut portion of the current pass, it is necessary to read ahead the machining program by the control device 100 such as a numerical control device, since the cutting depth of the next pass depends on the swing amplitude of the current pass. In contrast, by reversing the swing direction as in the operation example shown in Figure 6, the swing amplitude of the next pass does not depend on the swing amplitude of the current pass, so there is no need to read ahead the machining program by the control device 100 such as a numerical control device.

[0038] Next, the finish machining in the final pass of thread cutting by the machine tool control device 100 according to one embodiment of the present disclosure will be described in detail with reference to Figs. 7 and 8. Here, Fig. 7 is a diagram showing the finish machining in the final pass of conventional thread cutting. Fig. 8 is a diagram showing the finish machining in the final pass of thread cutting by the machine tool control device 100 according to one embodiment of the present disclosure. Note that the C-axis, Z-axis, and X-axis in Figs. 7 and 8 are used with the same definitions as the C-axis, Z-axis, and X-axis in Fig. 3 described above. Also, the part circled by the dashed line in Fig. 8 is a part including the part cut in the previous cutting in the current cutting, and indicates a part where a so-called miss occurs and the chips are chopped.

[0039] In conventional thread cutting, when a cutting operation without oscillation is performed in the final pass after an oscillation-based cutting operation in the pass before the final pass, the chips should be chopped because the processed part in the final pass includes a part that has been machined in the pass before the final pass (i.e., the part where the dashed line 72 and the straight line of the final pass overlap, which is the valley of the dashed line 72 and the so-called idle part), as shown by the dashed line 72 in Fig. 7. However, in reality, as shown by the solid line 71 in Fig. 7, there is no part in the processed part in the final pass that includes a part that has been machined in the pass before the final pass (i.e., the part where the solid line 71 and the straight line of the final pass overlap). This is due to a position deviation, which is the deviation between the position command and the actual position during the oscillation operation.

[0040] In contrast, in one embodiment of the present disclosure, ideally, as shown by dashed line 82 in Fig. 8, there will be a portion where the processed portion in the final pass includes a portion processed in the pass before the final one, and in reality, as shown by solid line 81 and a dashed line surrounded by a circle in Fig. 8, there will be a portion where the processed portion in the final pass includes a portion processed in the pass before the final one, and the chips will be chopped. This is because by providing a swinging motion and a non-swinging motion within the same pass, the position deviation converges during the non-swinging motion. This makes it possible to reliably chop the chips in the final pass.

[0041] The period of the non-oscillating operation can be determined simply by a predetermined value in terms of time or distance, or can be determined based on whether the position deviation is equal to or less than a predetermined threshold value. In the above description, the finishing process in the final pass of the thread cutting process is taken as an example, but the present invention is not limited to this, and the same can be said for all cases in which a cutting operation without oscillation is performed in the next pass after a cutting operation with oscillation.

[0042] In summary, one embodiment of the present disclosure provides the following advantages. (1) In a control device 100 for a machine tool that performs thread cutting while making multiple cuts in the radial direction (X direction) of the workpiece 14 with the cutting tool 16 by cooperatively operating at least one spindle 18 that rotates the cutting tool 16 and the workpiece 14 relatively, and at least one feed axis that moves the cutting tool 16 relatively to the workpiece 14, the control device 100 is provided with a swing operation execution determination unit 102 that determines whether or not to execute a swing operation to swing the cutting tool 16 in the radial direction (X direction) of the workpiece 14, a swing command generation unit 106 that generates a swing command for the swing operation based on a result of the determination by the swing operation execution determination unit 102, and a control unit 110 that generates a drive command for the feed axis by superimposing the swing command on a position command of the feed axis. The swing operation execution determination unit 102 determines to execute the swing operation intermittently, and the swing command generation unit 106 is configured to generate a swing command so that the non-swinging cut portion in the current cutting operation includes the swinging cut portion in the previous cutting operation, or so that the swinging cut portion in the current cutting operation includes the non-swinging cut portion in the previous cutting operation. This allows chips to be shredded reliably without extending the cycle time compared to conventional methods by performing the swing motion intermittently. In addition, the number of swing motions can be reduced, which reduces the burden on the machine tool caused by the swing motion. Furthermore, in the past, large position deviations caused by response delays and the like during oscillating operations could result in leftover cuttings and making it impossible to shred the chips. However, according to the present disclosure, the position deviations converge during non-oscillating operations, so that the chips can be reliably shredded when the non-oscillating operation of the current pass is performed after the oscillating operation of the previous pass.

[0043] (2) The swing operation execution determination unit 102 is configured to determine the execution of a swing operation so that, in the current cutting operation, swing cutting is performed at a position different from the portion that has been swing-cut in the previous cutting operation. This makes it possible to more reliably include the previously cut portion in the current cutting process, thereby more reliably generating a so-called miss and more reliably shredding the chips.

[0044] (3) There is further provided a swing condition calculation unit 104 that calculates the conditions of the swing operation to be output to the swing command generation unit 106 based on at least one of the machining program, the machining parameters, and the feedback value from the machine tool, and the swing condition calculation unit 104 is configured to change the interval of the swing operation. This makes it possible to calculate conditions such as the interval, amplitude, and cycle of the rocking motion, and therefore the chips can be shredded more reliably. In particular, the length of the chips can be adjusted by changing the interval of the rocking motion.

[0045] (4) The oscillation condition calculation unit 104 is configured to change the oscillation interval between different machining passes. This makes it possible to more reliably chop the chips and adjust the length of the chips.

[0046] (5) The oscillation condition calculation unit 104 is configured to change the interval of the oscillation operation within the same machining path. This makes it possible to more reliably chop the chips and adjust the length of the chips.

[0047] (6) The oscillation condition calculation unit 104 is configured to change the interval of the oscillation operation depending on the diameter of the workpiece 14. As a result, the circumference of the workpiece 14 becomes shorter as the number of cutting processes increases, but by lengthening the interval between swinging operations as the diameter of the workpiece 14 becomes smaller, the length of the cutting chips can be kept constant, resulting in more efficient and smooth thread cutting.

[0048] (7) The rocking motion execution determination unit 102 is configured to intermittently perform cutting using a rocking motion, and then determine to perform cutting without a rocking motion in the next pass. This ensures that chips can be shredded reliably when non-oscillating cutting is performed in the next pass after oscillating cutting has been performed. For example, chips can be shredded reliably even in the finishing process of the final pass.

[0049] (8) The swing operation execution determination unit 102 is configured to determine that non-rocking cutting should be performed in the non-rocking cutting section by intermittent swing operation until the position deviation becomes equal to or less than a predetermined threshold value. This allows chips to be more reliably chopped in non-oscillating cutting areas using intermittent oscillating motion.

[0050] The present invention is not limited to the above-described embodiment, and modifications and improvements within the scope of the present invention that can achieve the object of the present invention are included in the present invention.

[0051] [Note] One aspect of the present disclosure is a control device for a machine tool that coordinates the operation of at least one spindle that rotates a cutting tool and a workpiece relatively to one another, and at least one feed axis that moves the cutting tool relatively to the workpiece, to perform thread cutting on the workpiece while making multiple radial cuts with the cutting tool, the control device comprising: a swing operation execution determination unit that determines whether to perform a swing operation to swing the cutting tool in the radial direction of the workpiece, a swing command generation unit that generates a swing command for the swing operation based on a determination result by the swing operation execution determination unit, and a control unit that generates a drive command for the feed axis by superimposing the swing command on a position command of the feed axis, wherein the swing operation execution determination unit determines to perform the swing operation intermittently, and the swing command generation unit generates a swing command such that a non-swinging cut portion in the current cutting operation includes a swinging cut portion in the previous cutting operation, or such that a swinging cut portion in the current cutting operation includes a non-swinging cut portion in the previous cutting operation. [1] A control device for a machine tool that performs thread cutting by cutting the workpiece radially a plurality of times with the cutting tool by coordinating at least one spindle that rotates a cutting tool and a workpiece relatively and at least one feed axis that moves the cutting tool relative to the workpiece, the control device comprising: a swing operation execution determination unit that determines whether or not to execute a swing operation for swinging the cutting tool in a radial direction of the workpiece based on a machining program supplied from an external source, and determines execution of the swing operation so that swing cutting is performed in a position different from a portion that has been swing-cut in a previous cutting operation in a current cutting operation; a rocking command generating unit that generates a rocking command for the rocking action based on a result of the determination by the rocking action execution determining unit; a control unit that generates a drive command for the feed shaft by superimposing the swing command on a position command for the feed shaft, The rocking motion execution determination unit determines to perform the rocking motion intermittently, A control device for a machine tool, wherein the swing command generating unit generates a swing command so that the non-swinging cutting portion in the current cutting operation includes the swinging cutting portion in the previous cutting operation, or so that the swinging cutting portion in the current cutting operation includes the non-swinging cutting portion in the previous cutting operation. [2] a swing condition calculation unit that calculates swing operation conditions to be output to the swing command generation unit based on at least one of a machining program, a machining parameter, and a feedback value from the machine tool; The control device for a machine tool described in [1], wherein the swing condition calculation unit changes the interval of the swing operation. [3] The control device for a machine tool described in [2], wherein the oscillation condition calculation unit changes the interval of the oscillation motion between different machining paths. [4] The control device for a machine tool described in [2] or [3], wherein the oscillation condition calculation unit changes the interval of the oscillation motion within the same machining path. [5] The control device for a machine tool described in any one of [2] to [4], wherein the swing condition calculation unit changes the interval of the swing operation depending on the diameter of the workpiece. [6] A control device for a machine tool that performs thread cutting by cutting the workpiece radially a plurality of times with the cutting tool by coordinating at least one spindle that rotates a cutting tool and a workpiece relatively and at least one feed axis that moves the cutting tool relative to the workpiece, the control device comprising: a swing operation execution determination unit that determines whether or not to execute a swing operation for swinging the cutting tool in a radial direction of the workpiece, The swing operation execution determination unit determines to perform cutting without swing operation in the next pass after intermittently performing cutting using a swing operation, and determines to perform non-swing cutting processing in the non-swing cutting processing unit using intermittent swing operation until the position deviation becomes equal to or less than a predetermined threshold value.A control device for a machine tool. [7] The control device for a machine tool described in any one of [1] to [5], wherein the oscillating operation execution determination unit determines to perform non-oscillating cutting processing in a non-oscillating cutting processing unit using intermittent oscillating operation until the position deviation becomes equal to or less than a predetermined threshold value. [Explanation of symbols]

[0052] 10 Thread groove 12 Screws 14 Work 16 Cutting tools 18 Spindle 100 Control device 102 Swinging motion execution determination unit 104 Oscillation condition calculation unit 106 Swing command generator 108 Adder 110 Control section 120 Motor XX axis ZZ axis CC axis L, L1, L2 Swing motion interval

Claims

1. A control device for a machine tool that performs thread cutting by cutting the workpiece radially a plurality of times with the cutting tool by coordinating at least one spindle that rotates a cutting tool and a workpiece relatively and at least one feed axis that moves the cutting tool relative to the workpiece, the control device comprising: a swing operation execution determination unit that determines whether or not to execute a swing operation for swinging the cutting tool in a radial direction of the workpiece; a rocking command generating unit that generates a rocking command for a rocking operation based on a result of the determination by the rocking operation execution determining unit; the swinging motion execution determination unit determines to execute a cut without a swinging motion in a subsequent pass after intermittently executing a cut by a swinging motion; A control device for a machine tool, wherein the swing command generating unit generates a cutting depth without a swing motion so that the cutting depth amount is the same as the cutting depth amount of a non-swinging portion of a path that intermittently performs cutting by the swing motion.

2. 2. The control device for a machine tool according to claim 1, wherein the swing command generating unit generates a path that intermittently performs cutting by the swing motion so that the cutting amount of the non-swinging portion is the same as the cutting amount without swing motion in a final pass.

3. a swing condition calculation unit that calculates swing operation conditions to be output to the swing command generation unit based on at least one of a machining program, a machining parameter, and a feedback value from the machine tool; The control device for a machine tool according to claim 1 , wherein the swing condition calculation unit changes an interval of the swing operation.

4. The control device for a machine tool according to claim 3 , wherein the swing condition calculation unit changes an interval of the swing motion between different machining passes.

5. The control device for a machine tool according to claim 3 or 4, wherein the oscillation condition calculation unit changes an interval of the oscillation motion within the same machining path.

6. The control device for a machine tool according to claim 3 , wherein the swing condition calculation unit changes an interval of the swing operation in accordance with a diameter of the workpiece.

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