CONTROL DEVICE FOR MACHINE TOOL

Abstract

A control device (20) of a machine tool (10) which, while relatively oscillating a workpiece (W) and a tool (11), machines the workpiece (W) to cut chips generated during machining, the control device (20) comprising: a position command calculation unit (22) that calculates a position command for relatively moving the workpiece (W) and the tool (11); a vibration operation execution determination unit (24) that analyzes a machining program for machining the workpiece (W) and determines whether or not a vibration operation of relatively vibratingly moving the workpiece (W) and the tool (11) is performed in a machining block of the machining program; an intermittent vibration operation execution determination unit (25) which, when the vibration operation execution determination unit (24) determines that the vibration operation is being performed, determines whether the vibration operation is enabled or disabled in the machining block of the machining program based on a state of the machine tool (10) to determine whether the vibration operation is being performed intermittently or not; a vibration command calculation unit (23) which, when the intermittent vibration operation execution determination unit (25) determines that the vibration operation is enabled, calculates a vibration command for relatively vibrating the workpiece (W) and the tool (11); and an adder (26a) which adds the position command and the oscillation command.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a control device of a machine tool that performs vibration machining. Related prior art

[0002] When a workpiece is machined with a tool on a machine tool, chips may be continuously generated, causing them to become trapped in the tool. In such a case, it is necessary to stop the machine tool to remove the chips from the tool, which is time-consuming and results in reduced production efficiency. Furthermore, chips may damage the workpiece, thus reducing the quality of the workpiece.

[0003] In this context, for example, vibration machining is known, in which the tool and the workpiece are relatively vibrated in the machining direction (vibration operation), thus breaking up the chips (see, for example, Patent Documents 1 and 2). The control device of the machine tool performing vibration machining (vibration operation) provides a sinusoidal (or cosine wave) feed command to a servo motor for a feed axis that feeds the tool or the workpiece in the machining direction, thus moving the tool and the workpiece relatively vibrating in the machining direction. Patent No. 1: Japanese Patent Application Laid-Open No. JP 2017 - 56 515 A. Patent Document 2: PCT International Publication No. WO 2017 / 051 745 A1.

[0004] DE 10 2018 002 959 A1 discloses a control device comprising a position command generation part, an oscillation command generation part, and a storage part for storing machine operating conditions and servo control conditions. The oscillation command generation part includes an estimation part that estimates an oscillation amplitude and an oscillation frequency of an oscillation command based on a rotational speed of a workpiece and a position command generated by the position command generation part, and a determination part that determines whether the estimated oscillation frequency is an optimal value based on the machine operating conditions and the servo control conditions. SUMMARY OF THE INVENTION

[0005] In the oscillation operation described above, for example, a sinusoidal (or cosine wave) oscillation command is superimposed on a position command, thus generating a fluctuation in acceleration, resulting in an increase in the load on the machine tool. In this regard, it can be considered that in the oscillation operation, the number of times oscillation is performed is reduced.

[0006] The setting for enabling / disabling a vibration operation with a machining program command is made in blocks of a machining program. For example, if the machining program includes a machining block (e.g., a cutting block) and a non-machining block (e.g., a rapid traverse block), the vibration operation is set to enable in the machining block, and the vibration operation is set to disable in the non-machining block. In other words, the activation / deactivation (on / off) of the vibration operation cannot be switched during the machining block.

[0007] Thus, in a control device for a machine tool, it is desirable to switch the activation / deactivation of a vibration operation in a machining block of a machining program in order to reduce the number of times vibration is performed.

[0008] The problem is solved by a control device of a machine tool having the features of patent claim 1.

[0009] A control device of a machine tool according to the present disclosure, which, while relatively oscillating a workpiece and a tool, machines the workpiece to cut chips generated during machining, comprises: a position command calculation unit that calculates a position command for relatively moving the workpiece and the tool; a vibration operation execution determination unit that analyzes a machining program for machining the workpiece and determines whether or not to perform a vibration operation of relatively oscillating the workpiece and the tool in a machining block of the machining program;An intermittent vibration operation execution determination unit that, when the vibration operation execution determination unit determines that the vibration operation is being performed, determines whether the vibration operation is enabled or disabled in the machining block of the machining program based on the state of the machine tool to determine whether the vibration operation is being performed intermittently; A vibration command calculation unit that, when the intermittent vibration operation execution determination unit determines that the vibration operation is enabled, calculates a vibration command for relatively vibrating the workpiece and the tool; and An adder that adds the position command and the vibration command.

[0010] According to the present disclosure, in a control device for a machine tool, it is possible to switch the activation / deactivation of a vibration operation in a machining block of a machining program to reduce the number of times vibration is performed. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram schematically showing the structure of a machining system including a control device of a machine tool according to the present embodiment; Fig. 2 is a diagram showing the structure of the control device of the machine tool according to the present embodiment; Fig. 3 is a diagram showing a relationship between a feed amount and a rotation angle in an oscillation operation; Fig. 4 is a diagram illustrating conventional drilling; Fig. 5 is a diagram showing a cycle time in conventional drilling; Fig. Fig. 6 is a diagram for illustrating drilling (including an intermittent vibration operation) using the control device of the machine tool according to the present embodiment; and Fig. 7 is a diagram showing a cycle time of drilling (including the intermittent vibration operation) using the control device of the machine tool according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Examples of embodiments of the present invention will be described below with reference to the accompanying drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals. (First embodiment)

[0012] Fig. 1 is a diagram schematically showing the structure of a machining system including a control device of a machine tool according to a first embodiment, and Fig. Figure 2 is a diagram showing the structure of the control device of the machine tool according to the first embodiment. Fig. 1 only main sections of the control device of the machine tool are shown, which in Fig. 2. The Fig. The machining system 1 shown in Fig. 1 comprises the machine tool 10 and the control device 20 which controls the machine tool 10.

[0013] The machine tool 10 comprises a tool 11. The tool 11 performs a turning operation on a workpiece W, which has, for example, a tubular shape, a cylindrical shape, a conical shape, or a truncated cone shape. In the example of the Fig. 1, the tool 11 performs a turning operation on the outer peripheral surface of the workpiece W. In the example of Fig. 1, it is assumed that the center axis line of the workpiece serving as the rotation axis of the workpiece W is a Z axis, and that an axis line perpendicular to the Z axis is an X axis.

[0014] The machine tool 10 can machine not only a workpiece whose shape is linear in a direction along the Z-axis, but also a workpiece whose shape is arcuate in that direction. The machine tool 10 can machine not only the outer peripheral surface of a workpiece, but also the inner peripheral surface of a tubular workpiece. The machine tool 10 can perform not only turning but also machining such as cutting, grinding, or polishing.

[0015] The machine tool 10 includes a spindle M0 and two feed axes M1 and M2 that perform coordinated operations with the spindle M0. The spindle M0 includes a spindle motor, and the feed axes M1 and M2 include a servomotor. The spindle M0 and the feed axes M1 and M2 are controlled by the controller 20.

[0016] The spindle M0 rotates the workpiece W around the workpiece's central axis (Z-axis). The feed axis M1 can both feed the tool 11 in the Z-axis direction (first direction) and reciprocate the tool 11 in the Z-axis direction, i.e., oscillate the tool 11. The feed axis M2 can both feed the tool 11 in the X-axis direction (second direction) and reciprocate the tool 11 in the X-axis direction, i.e., oscillate the tool 11.

[0017] When turning is performed on the workpiece having a cylindrical shape or a tubular shape, the workpiece W is rotated around the center axis line (Z axis) of the workpiece, and the tool 11 is fed only in the direction of the Z axis (in this case, the direction of machining) along the generatrix of the outer peripheral surface of the workpiece.

[0018] On the other hand, when turning is performed on a workpiece such as a workpiece having a conical shape, a truncated cone shape, or an arc shape whose outer diameter varies in the Z-axis direction, the workpiece W is rotated around the center axis line (Z-axis) of the workpiece, and the tool 11 is fed in an oblique direction (combined direction of the Z-axis direction and the X-axis direction) (in this case, the machining direction) along the generatrix of the outer peripheral surface of the workpiece. Since the tool 11 is fed in the oblique direction along the generatrix of the outer peripheral surface of the workpiece W, at least two feed axes M1 and M2 are required in this case. Both the feed axes M1 and M2 are controlled, and the tool 11 is thus fed in the oblique direction along the generatrix of the outer peripheral surface of the workpiece W.

[0019] The control device 20 is configured with a computer including a memory such as a ROM (Read Only Memory) and a RAM (Random Access Memory), a CPU (Central Processing Unit), and a communication control unit connected to each other by a bus. The control device 20 further includes: a position command calculation unit 22, a vibration command calculation unit 23; a control unit 26 (including an adder 26a); and a storage unit 29. The functions or operations of the individual units thereof can be achieved by coordinating the CPU and memory built into the computer and a control program stored in the memory.

[0020] The storage unit 29 stores machining conditions for the workpiece W and the like. The machining conditions for the workpiece W include: the relative rotational speeds of the workpiece W and the tool 11 around the center axis of the workpiece; the relative feed rates of the tool 11 and the workpiece W; and position commands for the feed axes M1 and M2.

[0021] A host computer (not shown), such as a CNC (Computer Numerical Controller) or a PLC (Programmable Logic Controller), is connected to the controller 20, and the rotational speeds, feed rates, and the like described above can be input from the host computer into the storage unit 29. The storage unit 29 or the position command calculation unit 22 may be included in the host computer rather than the controller 20.

[0022] The storage unit 29 can store a machining program executed by the machine tool 10, and the CPU (not shown) within the controller 20 can read out the above-described rotational speeds and feed rates as the machining conditions from the machining program to output them to the position command calculation unit 22, the vibration command calculation unit 23, or the control unit 26.

[0023] The position command calculation unit 22 calculates a position command that relatively moves the workpiece W and the tool 11. Specifically, the position command calculation unit 22 has the function of calculating position commands (movement commands) for the feed axes M1 and M2 based on the relative rotational speeds of the workpiece W and the tool 11 about the center axis of the workpiece and the relative feed rates of the tool 11 and the workpiece W. The position commands indicate to the control unit 26 a target position when the tool 11 and the workpiece W are relatively fed in a direction (machining direction) along the generatrix of the outer peripheral surface of the workpiece W.

[0024] The vibration command calculation unit 23 calculates a vibration command for relatively oscillating the workpiece W and the tool 11. More specifically, based on the above-described rotational speed and feed rate, the vibration command calculation unit 23 calculates the vibration command for the feed axis M1 such that a vibration frequency is a positive non-integer multiple of the above-described rotational speed, and so that the tool 11 performs intermittent cutting on the workpiece W. The vibration command is a periodic command calculated to be asynchronous with the rotational speed around the above-described central axis line, and includes the vibration frequency and a vibration amplitude. The value of the term S / 60 × I in the formula (1) for the vibration command, which will be described later, corresponds to the vibration frequency, and the value of the term K × F / 2 in the formula (1) corresponds to the vibration amplitude.The details of the vibration command calculation unit 23 will be described later.

[0025] The intermittent cutting described above means that a turning operation is performed on the workpiece W while the tool 11 is periodically brought into contact with and separated from the workpiece W, and is also called oscillation cutting or vibration cutting. Although in Fig. 1 the workpiece W is rotated and at the same time the tool 11 swings with respect to the workpiece W, the tool 11 can be rotated about the center axis line of the workpiece W, and at the same time the workpiece W can swing with respect to the tool 11. Although in Fig. 1 Each of the feed axes M1 and M2 performs both the feed operation and the oscillation operation on the workpiece W, the feed operation and the oscillation operation on the workpiece W can each be performed with separate feed axes.

[0026] The control unit 26 includes the adder 26a for adding the position command and the vibration command. Specifically, the control unit 26 has the function of controlling the feed axes M1 and M2 by calculating a torque command based on a combined command (e.g., a position command value) obtained by adding the above-described vibration command to a position error, which is a difference between the above-described position commands and the actual positions of the feed axes M1 and M2. The actual positions of the feed axes M1 and M2 correspond to position feedback values ​​obtained by position detection units (not shown), such as encoders, built into the feed axes M1 and M2.

[0027] The details of the vibration command calculation unit 23 are described below. Fig. 3 is a diagram showing a relationship between a feed amount and a rotation angle. In Fig. 3, a horizontal axis represents the rotation angle of the workpiece W, and a vertical axis represents the feed amount of the tool 11 in the direction of machining (that is, a direction along the generatrix of the outer peripheral surface of the workpiece W in Fig. 1). In Fig. 3 shows a plurality of linear broken lines C1, C2, C3, ... running obliquely. As can be seen from Fig. 3, the vertical axis coordinates of an intersection point between the broken line C1 and the vertical axis correspond to the vertical axis coordinates at the starting point of the subsequent broken line C2. Likewise, the vertical axis coordinates of an intersection point between the broken line C2 and the vertical axis correspond to the vertical axis coordinates at the starting point of the subsequent broken line C3. These linear broken lines C1, C2, C3, ... indicate the path of the tool 11 in the workpiece W when the vibration command is not present. On the other hand, curves A1, A2 and A3, ..., which are shown in Fig. 3 indicate the path of the tool 11 on the workpiece W when the vibration command is applied. In other words, it is assumed that the broken lines C1, C2, C3, and the like indicate only the position commands (original command values) before the addition of the vibration command, and that the curves A1, A2, A3, and the like indicate the position commands after the addition of the vibration command. Thus, the curves A1, A2, and A3 indicate commands obtained by adding the cosine-wave vibration command to each of the position commands indicated by the broken lines C1, C2, and C3.

[0028] Curve A1 is the path of the tool 11 during the first revolution of the workpiece W, curve A2 is the path of the tool 11 during the second revolution of the workpiece W, and curve A3 is the path of the tool 11 during the third revolution of the workpiece W. For simplicity, the paths of the tool 11 in the fourth and subsequent revolutions of the workpiece W are not shown.

[0029] The vibration command calculation unit 23 calculates vibration commands as follows. The vibration command calculation unit 23 determines a cosine wave vibration frequency to calculate commands such as curves A1, A2, and A3, where the broken lines C1, C2, and C3, which are the position commands for the feed axes M1 and M2 calculated by the position command calculation unit 22, are reference axis lines, respectively. The value of the term S / 60 × I in formula (1), which will be described later, is the vibration frequency.

[0030] When the vibration frequency described above is determined as in Fig. As shown in Figure 3, the initial phase of the cosine wave curve A2, in which a certain broken line, for example, the broken line C2, is the reference axis line, is preferentially shifted by half a period relative to the cosine wave curve A1 in which the preceding broken line, for example, the broken line C1, is the reference axis line. This is because by shifting the reference axis line by half a period, the vibration amplitude of the vibration command can be minimized, and consequently, it is possible to cut chips most efficiently.

[0031] The vibration command calculation unit 23 determines the vibration amplitude of the vibration command described above to calculate the commands, such as curves A1, A2, and A3, in which the broken lines C1, C2, and C3 are reference axis lines, respectively. The value of the term K × F / 2 in formula (1), which will be described later, is the vibration amplitude. The curves A1 and A2 shown in Fig. 3 overlap each other in a part B1, where the angle of rotation is approximately 0 degrees, and in a part B2, where the angle of rotation is approximately 240 degrees. As can be seen from Fig. 3, in parts B1 and B2, the maximum value of curve A1 with respect to the broken line C1 is greater than the minimum value of curve A2 with respect to the broken line C2. In other words, the vibration command calculation unit 23 preferably determines the vibration amplitude such that the preceding curve A1 and the following curve A2 partially overlap each other. For curves A1, A2, and A3, the feed rates are constant, and thus the vibration amplitudes of the vibration commands are all the same.

[0032] In the overlapping parts B1 and B2, the workpiece W is separated when the tool 11 performs machining on the path of the curve A2, and thus the workpiece W is prevented from being machined. In the present embodiment, the overlapping parts B1 and B2 as described above are periodically generated, and thus it is possible to perform so-called intermittent cutting. In an example shown in Fig. As shown in Figure 3, one chip is generated in each of the parts B1 and B2 by an operation corresponding to curve A2. In other words, two chips are generated in curve A2 of the second revolution. The intermittent cutting as described above is performed periodically, and thus vibration cutting can be performed.

[0033] Furthermore, curve A3, formed with respect to the broken line C3, has the same shape as curve A1. Curve A2 and curve A3 overlap each other in a part B3 where the rotation angle is approximately 120°, and in a part B4 where the rotation angle is approximately 360°. A chip is generated in each of parts B3 and B4 by an operation corresponding to curve A3. In other words, two chips are generated in curve A3 of the third revolution. Thereafter, two chips are generated per revolution of the workpiece. However, no chip is generated in the first revolution.

[0034] In this way, the vibration frequency and vibration amplitude are determined, and thus the vibration command calculation unit 23 within the control unit 26 calculates the vibration command. For example, the vibration command is indicated by the formula (1) below. [Math 1]. OSCILLATION COMMAND=K×F2cos(2π×S60×l×t)−K×F2

[0035] In formula (1), K represents a vibration amplitude magnification, F represents the amount of movement of the tool 11 per revolution of the workpiece W, that is, a feed rate per revolution [mm / rev], S represents the rotational speed of the workpiece W around the central axis line [min-1] or [rpm], and I represents a vibration frequency magnification. Here, the vibration frequency described above corresponds to the term S / 60 × I in formula (1), and the vibration amplitude described above corresponds to the term K × F / 2 in formula (1). However, the vibration amplitude magnification K is a number greater than or equal to one, and the vibration frequency magnification I is a non-integer greater than zero (for example, a positive non-integer such as 0.5, 0.8, 1.2, 1.5, 1.9, 2.3, or 2.5, 1 / 4). The oscillation amplitude magnification K and the oscillation frequency magnification I are constants (in the Fig. 3 shown example is I 1.5).

[0036] The reason why the vibration frequency magnification I is not set to an integer is that in the case of a vibration frequency exactly equal to the number of revolutions of the workpiece around the central axis line, the overlapping parts B1, B2, B3, B4 and the like described above cannot be generated, and thus it is impossible to achieve the effect of crushing chips by vibration cutting.

[0037] In formula (1), the vibration command is a command in which the term (K × F / 2) is subtracted as an offset value with respect to a cosine wave, where each of the broken lines C1, C2, and C3 indicating the position command is the reference axis line. Therefore, the position path of the tool 11, which is based on a combined command value obtained by adding the vibration command to the position command, can be controlled under the assumption that the position of the tool 11 in the machining direction is an upper limit by the position command. Therefore, the curves A1, A2, A3, and the like are prevented from Fig. 3 exceed the broken lines C1, C2, C3 and the like in a positive direction (that is, in the direction of machining of the tool 11).

[0038] Furthermore, the vibration command as indicated by the formula (1) is provided, and thus, as can be seen from the curved line A1 in Fig. 3 that a large vibration is generated at the machining start point (position 0° in the horizontal axis) of the tool 11 in the direction of feed of the tool 11 from the beginning.

[0039] It is assumed that the initial values ​​of each parameter (K ​​and I in formula (1)) set when determining the vibration frequency and vibration amplitude are stored in the storage device 29 before the operation of the machine tool 10. The rotational speed (S) of the workpiece W is previously stored in the storage unit 29 as the machining condition. The feed rate per revolution F is calculated from the rotational speed (S) and the position command calculated by the position command calculation unit 22.

[0040] For example, when a workpiece machining shape is tubular or cylindrical, oscillation is performed along the machining direction, which is the direction of the feed axis M1 (Z axis) along the generatrix of the outer peripheral surface of the workpiece W. On the other hand, for example, when the workpiece machining shape is conical or truncated cone (tapered), or when it includes an arc shape, oscillation is performed along an oblique direction along the generatrix of the outer peripheral surface of the workpiece W, that is, the machining direction, which is the combined direction of the direction of the feed axis M1 (Z axis) and the direction of the feed axis M2 (X axis).

[0041] As in Fig. 2, the control device 20 further includes a vibration operation execution determination unit 24 and an intermittent vibration operation execution determination unit 25.

[0042] The vibration operation execution determination unit 24 analyzes the machining program to determine whether or not the vibration operation described above is performed in a machining block of the machining program. For example, the machining program commands the vibration operation in respective blocks. For example, the machining program commands the vibration operation in a cutting block and does not command the vibration operation in a non-cutting block, such as rapid traverse. In other words, the vibration operation execution determination unit 24 determines whether or not the vibration operation described above is performed in each of the blocks of the machining program.

[0043] When the vibration operation execution determination unit 24 determines that the vibration operation is being performed, the intermittent vibration operation execution determination unit 25 determines whether the vibration operation is enabled or disabled in, for example, the cutting block based on the state of the machine tool 10 to determine whether the vibration operation is being performed intermittently. In this way, the intermittent vibration operation execution determination unit 25 determines the start / completion of the vibration operation in the cutting block. In other words, the intermittent vibration operation execution determination unit 25 switches the activation / deactivation (on / off) of the vibration operation in the cutting block.

[0044] When the state of the machine tool is abnormal due to chips generated during machining, for example, when chips continuously become trapped in the tool and thus normal turning is not performed, the intermittent vibration operation execution determination unit 25 determines that the vibration operation is enabled. On the other hand, when the state of the machine tool is normal, the intermittent vibration operation execution determination unit 25 determines that the vibration operation is disabled.

[0045] For example, the intermittent vibration operation execution determination unit 25 determines the state of the machine tool 10 based on the feedback information of the servo motor or the spindle motor in the machine tool 10, on the feedback information (detection vibration) of a vibration sensor S1 that detects the vibration of the machine tool 10, or on the feedback information (detection noise) of a noise sensor S2 that detects noise of the machine tool 10.

[0046] For example, if chips are continuously caught in the tool, the following is assessed: · the operation of the servo motor is restricted, and thus a position error between the position command and the position feedback of the servo motor is increased; · the operation of the spindle motor is restricted, and thus the load or drive current of the spindle motor is increased; · the vibration of the machine tool is increased; · the noise of the machine tool is increased; or · the operation of the machine tool is restricted, and thus the noise of the machine tool is reduced.

[0047] In this way, for example, the intermittent vibration operation execution determination unit 25 determines that the state of the machine tool is not in a normal state due to chips generated during machining: · when the position error between the position command and the position feedback of the servo motor exceeds a specified threshold; · when the load or drive current of the spindle motor exceeds a specified threshold; · if the detection vibration of the vibration sensor S1 exceeds a predetermined threshold value; or · when the detection noise of the noise sensor S2 falls outside a specified range.

[0048] These predetermined threshold values ​​can be stored in advance in the storage unit 29.

[0049] Alternatively, if it is judged that the state of the machine tool is abnormal due to chips generated during machining, for example, if it is judged that chips are continuously caught in the tool and thus normal turning is not performed, the intermittent vibration operation execution determination unit 25 determines that the vibration operation is enabled. On the other hand, if it is judged that the state of the machine tool is normal, the intermittent vibration operation execution determination unit 25 determines that the vibration operation is disabled.

[0050] For example, the intermittent vibration operation execution determination unit 25 estimates the state of the machine tool based on execution information of the machining program.

[0051] For example: · when the relative machining distance between the workpiece and the tool is increased; · if the machining time of the workpiece is increased; or · When the amount of machining of the workpiece is increased, it is estimated that chips are continuously caught in the tool.

[0052] In this way, for example, the intermittent vibration operation execution determination unit 25 determines that the state of the machine tool 10 is abnormal due to chips generated during machining: · when the relative machining distance between the workpiece and the tool exceeds a specified threshold; if the machining time of the workpiece exceeds a specified threshold; or · if the amount of machining of the workpiece exceeds a specified threshold.

[0053] These predetermined threshold values ​​can be stored in advance in the storage unit. The machining distance, machining time, and machining amount can be initialized to zero when vibration occurs. The machining distance, machining time, and machining amount can be set to a total amount, and thus, at threshold intervals, it can be estimated that the condition of the machine tool 10 is abnormal.

[0054] If the intermittent vibration operation execution determination unit 25 determines that the vibration operation is enabled, the above-described vibration command calculation unit 23 calculates the above-described vibration command. If the intermittent vibration operation execution determination unit 25 determines that the vibration operation is disabled, the vibration command calculation unit 23 does not calculate the above-described vibration command. The above-described control unit 26 includes the adder 26a for adding the position command and the vibration command.

[0055] As described above, in the control device 20 of the machine tool according to the first embodiment, since it is possible to perform the vibration operation intermittently even in the machining block of the machining program, that is, since it is possible to switch the activation / deactivation (on / off) of the vibration operation, the number of times the vibration is performed can be reduced, with the result that it is possible to reduce the load on the machine tool 10.

[0056] Incidentally, the activation / deactivation of the oscillation operation can be set not only by the machining program command described above, but also by the I / O signal of the PLC. However, if the activation / deactivation of the oscillation operation is set by the I / O signal of the PLC, the start / stop of the oscillation operation is delayed only by the processing time of the I / O signal. Furthermore, a significant burden is placed on the preparation of a ladder program and the like in the PLC. In this regard, the control device 20 of the machine tool according to the first embodiment does not depend on the I / O signal of the PLC, and thus the start / stop of the oscillation operation is prevented from being delayed. (Second embodiment)

[0057] Although the first embodiment illustrated the form in which vibration machining is performed in turning, a second embodiment illustrates a form in which vibration machining is performed in drilling.

[0058] Fig. 4 is a diagram illustrating conventional drilling. As shown in Fig. As shown in Figure 4, in conventional drilling, the tool 11 is rotated around the Z-axis by the spindle motor, and the tool 11 is moved in the Z-axis direction (in this case, the machining direction) by the servo motor. In drilling as described above, there is a command called a high-speed deep hole drilling cycle, in which cutting is performed by a certain amount (solid line) and then retraction is performed slightly (broken line).

[0059] Although drilling, which has the high-speed deep hole drilling cycle, can also produce chips, as in Fig. 5, the cycle time is prolonged, and thus the machining time is prolonged. In drilling as described above, the oscillation operation of the present disclosure is used instead of the high-speed deep hole drilling cycle, and thus it is possible to prevent the cycle time from being prolonged.

[0060] The structure of the control device 20 of the machine tool according to a second embodiment is the same as the structure of the control device 20 of the machine tool shown in the Fig. 1 and Fig. 2, and according to the first embodiment. The control device 20 of the machine tool according to a second embodiment differs from the control device 20 of the machine tool according to the first embodiment in that drilling is performed instead of turning. In the position command calculation unit 22, the position command of the conventional drilling without providing the pull-out operation when the high-speed deep hole drilling cycle is performed is calculated. The control device 20 of the machine tool according to a second embodiment differs from the control device 20 of the machine tool according to the first embodiment in the function and operation of the intermittent vibration operation execution determination unit 25.

[0061] The intermittent vibration operation execution determination unit 25 has the function and operation of the above-described intermittent vibration operation execution determination unit 25. Furthermore, the intermittent vibration operation execution determination unit 25 analyzes the machining program and determines that the above-described vibration operation is enabled in a period during which the high-speed deep drilling cycle commands the tool 11 retraction operation in the drilling block of the machining program. On the other hand, in a period other than the period during which the high-speed deep drilling cycle commands the tool 11 retraction operation in the drilling block of the machining program, the intermittent vibration operation execution determination unit 25 determines that the vibration operation is disabled ( Fig. 6). In other words, the intermittent vibration operation execution determination unit 25 determines whether the vibration operation is performed intermittently or not.

[0062] The control device 20 of the machine tool according to a second embodiment also has the same advantage as the control device 20 of the machine tool according to the first embodiment. Specifically, since it is possible to perform the vibration operation intermittently even in the machining block of the machining program, that is, since it is possible to switch the activation / deactivation (on / off) of the vibration operation, the number of times the vibration is performed can be reduced, with the result that it is possible to reduce the load on the machine tool 10. The control device 20 of the machine tool according to the first embodiment does not depend on the I / O signal of the PLC, thus preventing the start / completion of the vibration operation from being delayed.

[0063] Furthermore, in the control device 20 of the machine tool according to a second embodiment, as shown in Fig.7 prevents the cycle time from being extended, and thus prevents the machining time from being extended.

[0064] Although the embodiments of the present invention are described above, the present invention is not limited to the above-described embodiments, and various modifications and variations are possible. For example, although the numerical control device of the machine tool that performs turning or drilling is illustrated in the above-described embodiments, the present disclosure is not limited to this structure and can be applied to control devices of machine tools that perform various types of machining.

[0065] Although the first embodiment described above illustrates the structure in which the workpiece W is rotated and, at the same time, the workpiece 11 is oscillated along the generatrix of the outer peripheral surface of the workpiece W, the present disclosure is not limited to this structure. The machine tool according to the first embodiment of the present disclosure preferably has a structure in which the machine tool controls the spindle M0 to relatively rotate the workpiece W and the tool 11 around the center axis line of the workpiece and at least one of the feed axes M1 and M2 to relatively feed the workpiece W and the tool 11 in the machining direction along the center axis line, and the like, to machine the workpiece W.For example, a structure in which the tool 11 is rotated around the central axis line of the workpiece W and in which the workpiece W is oscillated with respect to the tool 11, or a structure in which the workpiece W is rotated and in which the workpiece W is oscillated with respect to the tool 11 in a direction along the generatrix of the outer peripheral surface of the workpiece W can be adopted. In the present disclosure, a machining method of cutting the workpiece W by rotating the tool 11 around the central axis line of the workpiece W is also a type of machining. Although the structure in which oscillation is performed during drilling is illustrated in the second embodiment, the present disclosure is not limited to this structure. A structure such as a machining center or a grinder can be selected. EXPLANATION OF REFERENCE SYMBOLS 1 processing system 10 Machine tool 11 Tools 20 Control device 22 Position command calculation unit 23 Vibration command calculation unit 24 Determination unit for vibration operation execution 25 Determination unit for intermittent vibration operation execution 26 Control unit 26a Adder 29 Storage unit M0 spindle (spindle motor) M1, M2 feed axis (servo motor) W workpiece

Claims

[1] A control device (20) of a machine tool (10) which, while relatively oscillating a workpiece (W) and a tool (11), machines the workpiece (W) to cut chips generated during machining, the control device (20) comprising: a position command calculation unit (22) that calculates a position command for relatively moving the workpiece (W) and the tool (11); a vibration operation execution determination unit (24) that analyzes a machining program for machining the workpiece (W) and determines whether or not a vibration operation of relatively vibratingly moving the workpiece (W) and the tool (11) is performed in a machining block of the machining program; an intermittent vibration operation execution determination unit (25) which, when the vibration operation execution determination unit (24) determines that the vibration operation is being performed, determines whether the vibration operation is enabled or disabled in the machining block of the machining program based on a state of the machine tool (10) to determine whether the vibration operation is being performed intermittently or not; a vibration command calculation unit (23) which, when the intermittent vibration operation execution determination unit (25) determines that the vibration operation is enabled, calculates a vibration command for relatively vibrating the workpiece (W) and the tool (11); and an adder (26a) which adds the position command and the oscillation command. [2] The control device (20) of the machine tool (10) according to claim 1, wherein, when the state of the machine tool (10) is abnormal due to chips generated during machining, the intermittent vibration operation execution determination unit (25) determines that the vibration operation is activated. [3] The control device (20) of the machine tool (10) according to claim 2, wherein the intermittent vibration operation execution determination unit (25) determines that the machine tool (10) is not in a normal state due to chips generated during machining based on feedback information of a servo motor (M1, M2) or a spindle motor (M0) in the machine tool (10), on feedback information of a vibration sensor (S1) that detects vibration of the machine tool (10), or on feedback information of a noise sensor (S2) that detects noise of the machine tool (10), if a position error between the position command and the position feedback of the servo motor (M1, M2) exceeds a specified threshold, if a load or drive current of the spindle motor (M0) exceeds a specified threshold value, if a detection vibration of the vibration sensor (S1) exceeds a predetermined threshold value, or when a detection sound of the sound sensor (S2) falls outside a specified range. [4] The control device (20) of the machine tool (10) according to claim 1, wherein, when it is judged that the state of the machine tool (10) is abnormal due to chips generated during machining, the intermittent vibration operation execution determination unit (25) determines that the vibration operation is activated. [5] Control device (20) of the machine tool (10) according to claim 4, wherein, when a relative machining distance between the workpiece (W) and the tool (11) exceeds a predetermined threshold value, if a machining time of the workpiece (W) exceeds a specified threshold value, or if an amount of machining of the workpiece (W) exceeds a predetermined threshold value, the intermittent vibration operation execution determination unit (25) estimates, based on execution information of the machining program, that the state of the machine tool (10) is not normal due to chips generated during machining. [6] The control device (20) of the machine tool (10) according to claim 1, wherein, when a program of drilling to perform a retraction operation is executed, the intermittent vibration operation execution determination unit (25) determines that the vibration operation is enabled without performing the retraction operation.

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