Control device for machine tool
阅读说明:本技术 机床的控制装置 (Control device for machine tool ) 是由 山本健太 安田将司 于 2019-07-08 设计创作,主要内容包括:本发明提供一种减少由摆动切削引起的机床的负荷的增加的机床的控制装置。一种机床的控制装置,所述机床具备进给工具的多个进给轴,所述机床一边使工具摆动一边对工件进行加工,所述机床的控制装置具备:摆动指令制作部,其基于加工条件制作摆动指令;以及控制部,其基于摆动指令和移动指令来一边使工具摆动一边对工件进行加工,其中,在加工条件表示通过多个进给轴中的一个进给轴的插补动作进行的加工的情况下,摆动指令制作部制作摆动指令,使得工具沿着沿加工路径的方向摆动,在加工条件表示通过多个进给轴的同时插补动作进行的加工的情况下,摆动指令制作部变更摆动指令,使得相对于加工路径变更摆动方向。(The invention provides a control device for a machine tool, which reduces the increase of the load of the machine tool caused by swing cutting. A control device for a machine tool that is provided with a plurality of feed axes for feeding a tool and that machines a workpiece while swinging the tool, the control device comprising: a swing command generating unit that generates a swing command based on the machining condition; and a control unit that performs machining on the workpiece while swinging the tool based on a swing command and a movement command, wherein the swing command creating unit creates the swing command so that the tool swings in a direction along the machining path when the machining condition indicates machining performed by interpolation operation of one of the plurality of feed shafts, and the swing command creating unit changes the swing command so that the swing direction is changed with respect to the machining path when the machining condition indicates machining performed by simultaneous interpolation operation of the plurality of feed shafts.)
1. A control device for a machine tool including a main shaft that rotates a workpiece and a tool relative to each other and a plurality of feed shafts that feed the workpiece and the tool relative to each other, the machine tool machining the workpiece while relatively swinging the tool and the workpiece by a coordinated operation between the main shaft and the feed shafts, and cutting chips generated by the machining, the control device comprising:
a swing command generating unit that generates a swing command based on the machining condition; and
a control unit that processes the workpiece while relatively swinging the tool and the workpiece based on the swing command and the movement command,
wherein, when the machining condition indicates machining by interpolation operation of one of the plurality of feed axes, the swing command creating unit creates the swing command such that the tool and the workpiece swing relative to each other in a direction along a machining path,
when the machining condition indicates machining by simultaneous interpolation operation of the plurality of feed axes, the swing command creating unit changes the swing command so that the swing direction is changed with respect to the machining path.
2. The control device of a machine tool according to claim 1,
the swing command generating unit includes:
a swing amplitude calculation unit that calculates a swing amplitude based on a swing amplitude magnification and the movement command; and
a swing command calculation unit that calculates the swing command based on the swing amplitude.
3. The control device of a machine tool according to claim 2,
the swing amplitude calculating unit calculates the swing amplitude magnification based on the machining condition and the mechanical condition.
4. The control device of a machine tool according to claim 3,
the machining condition includes information indicating machining performed by interpolation operation of the plurality of feed axes for a cone or a circular arc of the workpiece and a cone angle of the workpiece,
the mechanical condition includes an angle of the tool.
5. The control device of a machine tool according to claim 2,
the workpiece machining device further includes a storage unit that stores in advance information in which a plurality of swing amplitude magnifications are associated with a plurality of taper angles of the workpiece,
the swing amplitude calculation unit acquires the swing amplitude magnification corresponding to the taper angle of the workpiece in the information.
6. The control device for a machine tool according to any one of claims 1 to 5,
when the machining condition indicates machining by simultaneous interpolation operation of the plurality of feed axes, the swing command creating unit changes the swing command so that the tool and the workpiece swing relative to each other in a feed direction of one of the plurality of feed axes.
7. A control device for a machine tool including a main shaft that rotates a workpiece and a tool relative to each other and a plurality of feed shafts that feed the workpiece and the tool relative to each other, the machine tool machining the workpiece while relatively swinging the tool and the workpiece by a coordinated operation between the main shaft and the feed shafts, and cutting chips generated by the machining, the control device comprising:
a swing command generating unit that generates a swing command based on the machining condition;
a control unit that performs machining on the workpiece while relatively swinging the tool and the workpiece based on the swing command and the movement command,
wherein, when the machining condition indicates machining by interpolation operation of one of the plurality of feed axes, the swing command creating unit creates the swing command such that the tool and the workpiece swing relative to each other in a direction along a machining path,
when the machining condition indicates machining by simultaneous interpolation operation of the plurality of feed axes, the swing command creating unit changes the swing command so that the swing is stopped.
Technical Field
The present invention relates to a control device for a machine tool that performs swing cutting.
Background
When a workpiece is machined by a cutting tool of a machine tool, chips are continuously generated and sometimes the chips are entangled in the cutting tool. In such a case, it is necessary to stop the machine tool to remove chips from the cutting tool, which takes time, resulting in a reduction in production efficiency. Further, the workpiece may be damaged by the chips, which may result in a reduction in the quality of the workpiece.
In order to avoid such a drawback, there is known swing cutting in which chips are cut by relatively swinging a cutting tool and a workpiece in a machine direction (see, for example, patent documents 1 to 3). A control device for a machine tool that performs swing cutting is configured to provide a sinusoidal feed command to a servomotor that feeds a feed shaft of a cutting tool or a workpiece in a machining direction, thereby swinging the cutting tool and the workpiece relative to each other in the machining direction.
Disclosure of Invention
Problems to be solved by the invention
For example, in the case where the desired workpiece machining shape is a cylindrical or columnar shape, the feed axis for feeding the cutting tool or the workpiece in the machining direction is only 1 axis (for example, Z axis described later). On the other hand, for example, when the desired workpiece machining shape is a conical shape or a truncated cone shape (i.e., a tapered shape), or when the desired workpiece machining shape includes an arc shape, the feed axes for feeding the cutting tool or the workpiece in the machining direction are a plurality of axes (for example, a Z axis and an X axis described later). In this case, the load on the machine tool increases due to simultaneous oscillation of the plurality of axes, and if a machine capable of withstanding the load is used, there is a problem of an increase in cost.
The invention aims to provide a control device of a machine tool, which reduces the increase of the load of the machine tool caused by swing cutting.
Means for solving the problems
(1) The present invention relates to a control device for a machine tool (for example, a control device 20 for a machine tool described later) including a spindle (for example, a spindle M0 described later) that relatively rotates a workpiece (for example, a workpiece W described later) and a tool (for example, a tool 11 described later) and a plurality of feed axes (for example, feed axes M1 and M2 described later) that relatively feeds the workpiece and the tool, the machine tool machining the workpiece while relatively swinging the tool and the workpiece by a coordinated operation between the spindle and the feed axes, and cutting chips generated by the machining, the control device for a machine tool including: a swing command generating unit (for example, a swing
(2) In the control device for a machine tool according to (1), the swing command creating unit may include: a swing amplitude calculation unit (for example, a swing amplitude calculation unit 231 described later) that calculates a swing amplitude based on the swing amplitude magnification and the movement command; and a swing command calculation unit (for example, a swing command calculation unit 233 described later) that calculates the swing command based on the swing amplitude.
(3) In the control device for a machine tool recited in (2), the swing amplitude calculation unit may calculate the swing amplitude magnification based on the machining condition and the mechanical condition.
(4) In the control device for a machine tool recited in (3), the machining condition may include information indicating machining performed by an interpolation operation of the plurality of feed axes for a cone or a circular arc of the workpiece and a cone angle of the workpiece, and the machine condition may include an angle of the tool.
(5) The control device for a machine tool according to (2) may further include a storage unit that stores in advance information in which a plurality of the swing amplitude magnifications are associated with a plurality of taper angles of the workpiece, wherein the swing amplitude calculation unit may acquire the swing amplitude magnification corresponding to a taper angle of the workpiece in the information.
(6) In the control device for a machine tool according to any one of (1) to (5), when the machining condition indicates machining by simultaneous interpolation operation of the plurality of feed axes, the swing command creating unit may change the swing command so that the tool and the workpiece swing relative to each other in a feed direction of one of the plurality of feed axes.
(7) The present invention relates to another control device for a machine tool (for example, a control device 20 for a machine tool described later) including a spindle (for example, a spindle M0 described later) that relatively rotates a workpiece (for example, a workpiece W described later) and a tool (for example, a tool 11 described later) and a plurality of feed axes (for example, feed axes M1 and M2 described later) that relatively feeds the workpiece and the tool, the machine tool machining the workpiece while relatively swinging the tool and the workpiece by a coordinated operation between the spindle and the feed axes, and cutting chips generated by the machining, the control device for a machine tool including: a swing command generating unit (for example, a swing
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, it is possible to provide a control device for a machine tool that reduces an increase in load on the machine tool due to wobbling cutting.
Drawings
Fig. 1 is a diagram showing a machining system including a control device according to the present embodiment.
Fig. 2 is a block diagram showing a more specific configuration example of the control device according to the present embodiment, particularly of the weaving command generating unit and the control unit.
Fig. 3 is a diagram showing a relationship between the feed amount and the rotation angle.
Fig. 4 is a diagram for explaining a method of calculating the swing amplitude magnification of the feed axis (Z axis) when the workpiece machining shape is a conical shape, a truncated cone shape (cone), or when the workpiece machining shape includes a circular arc shape and the workpiece machining shape is swung only in the Z direction which is not the machining direction.
Fig. 5 is a diagram for comparing the swing width of each feed axis (Z axis, X axis) in the case of swinging only in the Z direction, which is not the machining direction, of fig. 4 with the swing width of each feed axis (Z axis, X axis) in the case of swinging in the machining direction.
Fig. 6 is a diagram for explaining a method of calculating the swing amplitude magnification of each feed axis (Z axis, X axis) when the workpiece machining shape is a conical shape, a truncated cone shape (cone), or a circular arc shape, and when the workpiece is swung in a direction slightly inclined from the Z axis direction and not the machining direction.
Fig. 7 is a diagram for comparing the swing width of each feed axis (Z axis, X axis) in the case of swinging in a direction slightly inclined from the Z axis direction and not the machining direction of fig. 6 with the swing width of each feed axis (Z axis, X axis) in the case of swinging in the machining direction.
Description of the reference numerals
1: a processing system; 10: a machine tool; 11: a tool; 20: a control device; 22: a position command making unit; 23: a swing command generating unit; 231: a swing amplitude calculation unit; 232: a swing frequency calculation unit; 233: a swing command calculation unit; 24: an addition operator; 25: a subtraction operator; 26: a control unit; 27: a learning controller; 28: a position and speed controller; 29: a storage unit; m0: a main shaft; m1, M2: a feed shaft; w: and (5) a workpiece.
Detailed Description
An example of an embodiment of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals.
Fig. 1 is a diagram showing a machining system including a control device according to the present embodiment. The machining system 1 shown in fig. 1 includes a
The
The
The
The main shaft M0 rotates the workpiece W around the central axis (Z axis) of the workpiece. The feed shaft M1 is capable of both feeding the tool 11 in the Z-axis direction (first direction) and reciprocating, i.e., swinging, the tool 11 in the Z-axis direction. The feed shaft M2 is capable of both feeding the tool 11 in the X-axis direction (second direction) and reciprocating, i.e., swinging, the tool 11 in the X-direction.
In the case of turning a cylindrical or cylindrical workpiece, the workpiece W is rotated about its central axis (Z-axis), and the tool 11 is fed only in the Z-axis direction (the machining direction in this case) along the generatrix of the outer peripheral surface of the workpiece.
On the other hand, when turning a workpiece having a different outer diameter in the Z-axis direction, such as a workpiece having a conical shape, a truncated cone shape, or an arc shape, the tool 11 is fed in an oblique direction (a direction in which the Z-axis direction and the X-axis direction are combined) along a generatrix of the outer peripheral surface of the workpiece while rotating the workpiece W around the central axis (Z-axis) of the workpiece. In this case, in order to feed the tool 11 in the oblique direction along the generatrix of the outer peripheral surface of the workpiece W, at least 2 feed shafts M1, M2 are required. By controlling both the feed shaft M1 and the feed shaft M2, the tool 11 is fed in the direction inclined along the generatrix of the outer peripheral surface of the workpiece W.
The control device 20 is configured using a computer including memories such as a ROM (read only memory) and a RAM (random access memory), a CPU (central processing unit), and a communication control unit, which are connected to each other via a bus. The control device 20 includes a position
The
The control device 20 may be connected to a higher-level Computer (not shown) such as a CNC (Computer Numerical Controller) or a PLC (Programmable Logic Controller), and the above-described rotation speed, feed speed, and the like may be input from the higher-level Computer to the
The
The position
The swing
The intermittent cutting is a cutting process performed on the workpiece W while the tool 11 is periodically brought into contact with and separated from the workpiece W, and is also referred to as swing cutting or vibration cutting. In fig. 1, the workpiece W is rotated and the tool 11 is swung with respect to the workpiece W, but the tool 11 may be rotated around the central axis of the workpiece W and the workpiece W may be swung with respect to the tool 11. In fig. 1, the feeding operation and the swing operation of the workpiece W are performed by 1 feed shaft M1 or M2, but the feeding operation and the swing operation of the workpiece W may be performed by different feed shafts.
The
The swing
In addition, a curve a1 is a trajectory of the tool 11 in the first rotation of the workpiece W, a curve a2 is a trajectory of the tool 11 in the second rotation of the workpiece W, and a curve A3 is a trajectory of the tool 11 in the third rotation of the workpiece W. For the sake of brevity, the trajectory of the tool 11 in the rotation after the fourth rotation of the workpiece W is omitted from illustration.
The swing
When the above-described wobble frequency is determined, it is preferable that the initial phase of a cosine wave-shaped curve a2 having a broken line, for example, a broken line C2, as a reference axis is shifted by half a cycle from a cosine wave-shaped curve a1 having a broken line, for example, a broken line C1, as a reference axis, as shown in fig. 3. This is because, when the displacement is a half cycle, the oscillation amplitude of the oscillation command can be minimized, and as a result, the chips can be cut up most efficiently.
The swing
At the overlapping positions B1 and B2, the tool 11 is separated from the workpiece W when machining is performed on the trajectory of the curve a2, and therefore the workpiece W is not machined. In the present embodiment, since the overlapping positions B1 and B2 are periodically generated, so-called intermittent cutting can be performed. In the example shown in fig. 3, chips are generated at positions B1 and B2 by the action according to the curve a 2. In other words, two chips are generated in the curve a2 of the second rotation. Since such intermittent cutting is periodically performed, vibration cutting can be performed.
The shape of the curve A3 formed with respect to the broken line C3 is the same as the shape of the curve a 1. Curve a2 coincides with curve A3 at a position B3 rotated by an angle of about 120 ° and a position B4 rotated by an angle of about 360 °. By following the action of curve a3, chips are produced at positions B3, B4, respectively. In other words, two chips are generated in the curve a3 of the third rotation. Thereafter, two chips are generated per rotation of the workpiece. However, no chips are generated in the first revolution.
By determining the wobble frequency and the wobble amplitude in this manner, the wobble
For example, the swing command is expressed by the following expression (1).
[ numerical formula 1]
In the formula (1), K is a swing amplitude magnification, and F is a movement amount of the tool 11 per rotation of the workpiece W, i.e., a feed amount per rotation [ mm/rev ]]And S is a rotation speed [ min ] around the central axis of the workpiece W-1]Or [ rpm ]]And I is the swing frequency multiplying power. Here, the wobble frequency corresponds to the term of S/60 × I in equation (1), and the wobble amplitude corresponds to the term of K × F/2 in equation (1). Here, the wobble amplitude magnification K is a number of 1 or more, and the wobble frequency magnification I is a non-integer larger 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, …). The wobble amplitude magnification K and the wobble frequency magnification I are constants (I is 1.5 in the example of fig. 3).
The reason why the oscillation frequency magnification I is not an integer is that when the oscillation frequency is exactly the same as the rotation speed around the central axis of the workpiece W, the aforementioned overlapping positions B1, B2, B3, B4, etc. cannot be generated, and the effect of cutting chips by the oscillation cutting cannot be obtained.
In addition, according to equation (1), the weaving command is a command obtained by subtracting a term of (K × F/2) as an offset value from a cosine wave having the broken lines C1, C2, and C3 indicating the position command as a reference axis. Therefore, the position trajectory of the tool 11 based on the combined command value obtained by adding the swing command to the position command can be controlled with the position based on the position command as the upper limit in the machining direction of the tool 11. Therefore, the curves a1, a2, A3, and the like of fig. 3 do not exceed the broken lines C1, C2, C3, and the like in the + direction (i.e., the machine direction of the tool 11).
By setting the swing command as expressed by the equation (1), it is understood from the curve a1 in fig. 3 that a large swing is not generated in the feed direction of the tool 11 from the beginning at the machining start point (the position of 0 ° on the horizontal axis) of the tool 11.
The initial values of the parameters (K, I in expression (1)) adjusted when determining the oscillation frequency and the oscillation amplitude are stored in the
Fig. 2 is a block diagram showing a more specific configuration example of the control device 20, particularly the weaving
The swing
In general, when the workpiece machining shape is a cylindrical or cylindrical shape, the workpiece is oscillated in a machining direction along a feed axis M1(Z axis) direction which is a generatrix along the outer peripheral surface of the workpiece W.
On the other hand, when the workpiece machining shape is a cone shape, a truncated cone shape (cone), or a circular arc shape, in general, the workpiece machining shape is oscillated in a machining direction which is a direction in which a generatrix along the outer peripheral surface of the workpiece W is inclined, that is, a direction in which the feed axis M1(Z axis) and the feed axis M2(X axis) are combined. In this case, the feed shafts M1 and M2 are simultaneously swung, and the load on the machine tool increases.
Therefore, in the present embodiment, when the workpiece machining shape is a cylindrical shape or a cylindrical shape, that is, when the machining condition indicates machining by interpolation operation of only one feed shaft M1 of the plurality of feed shafts M1 and M2, the swing
On the other hand, when the workpiece machining shape is a conical shape or a truncated cone shape (cone), or when the workpiece machining shape includes an arc shape, that is, when the machining condition indicates machining by simultaneous interpolation operation of the plurality of feed shafts M1 and M2, the swing
The wobble
The swing amplitude calculation unit 231 calculates a swing amplitude magnification K of each of the feed axes M1 and M2(Z axis and X axis) based on the machining conditions and the machine conditions, and calculates a swing amplitude K × F/2 of each of the feed axes M1 and M2(Z axis and X axis) based on the swing amplitude magnification K and the movement command.
Here, the machining conditions include information indicating machining performed by interpolation operations of the plurality of feed axes M1 and M2 for a cone or an arc of the workpiece W, and a cone angle θ 1 of the workpiece W (see fig. 4 and 6). The mechanical condition includes an
Specifically, when the workpiece machining shape is a cylindrical shape or a cylindrical shape, that is, when the machining condition indicates machining by interpolation operation of only one feed shaft M1 of the plurality of feed shafts M1 and M2, the swing amplitude calculation unit 231 calculates only the swing amplitude magnification K of the feed shaft M1 (Z-axis), and calculates only the swing amplitude K × F/2 of the feed shaft M1 (Z-axis) based on the swing amplitude magnification K, so that the tool 11 and the workpiece W swing relative to each other in the direction along the machining path, that is, in the machining direction (the Z-axis direction along the generatrix of the outer peripheral surface of the workpiece). More specifically, the wobble amplitude calculation unit 231 calculates the wobble amplitude K × F/2 based on a predetermined wobble amplitude magnification K.
On the other hand, when the workpiece machining shape is a cone shape, a truncated cone shape (cone), or a shape including an arc shape, that is, when the machining condition indicates machining by simultaneous interpolation operation of the plurality of feed shafts M1, M2, the swing amplitude calculation unit 231 calculates a swing amplitude magnification K of each of the feed shafts M1, M2 (Z-axis, X-axis), and calculates a swing amplitude K × F/2 of each of the feed shafts M1, M2 (Z-axis, X-axis) based on the swing amplitude magnification K so that the swing direction is changed with respect to the machining path even if the tool 11 and the workpiece W swing relatively in a direction other than the machining direction (a direction in which the Z-axis direction along the generatrix of the outer peripheral surface of the workpiece and the X-axis direction are combined).
Fig. 4 is a diagram for explaining a calculation method of the swing amplitude magnification K of the feed axis M1(Z axis) when the workpiece machining shape is a conical shape, a truncated cone shape (cone), or when the workpiece machining shape includes an arc shape and the workpiece machining shape is swung only in the Z direction which is not the machining direction. In fig. 4, F is the amount of movement of the tool 11 per rotation of the workpiece W, i.e., the feed amount per rotation [ mm/rev ], θ 1 is the taper angle [ rad ] of the workpiece W,
For example, the swing amplitude magnification K of the arrow portion in fig. 4 is expressed by the following expression (2).
[ numerical formula 2]
In fig. 4 and 5, the margin α is set to 0.
As a result, as shown in fig. 5, the swing width in the Z-axis direction (solid line arrow) is slightly increased as compared with the swing width in the Z-axis direction (broken line arrow) and the swing width in the X-axis direction (broken line arrow) in the case of swinging in the machining direction, but the swing width in the X-axis direction (solid line arrow) is 0, and therefore the total swing width of the plurality of feed axes is reduced. Therefore, the load on the entire machine tool is reduced.
As shown in fig. 4, the swing amplitude magnification K required for cutting chips by 1-axis swing changes depending on the taper angle θ 1 of the workpiece and the
When the workpiece machining shape is an arc, the taper angle θ 1 of the workpiece may be changed according to the cutting angle, and the swing amplitude magnification may be changed.
Fig. 6 is a diagram for explaining a method of calculating the swing amplitude magnification K of each of the feed axes M1 and M2(Z axis and X axis) when the workpiece machining shape is a cone shape, a truncated cone shape (cone), or a circular arc shape, and when the workpiece machining shape is swung in a direction slightly inclined from the Z axis direction and not the machining direction. In fig. 6, Fz and Fx are the amount of movement of the tool 11 on the Z axis or the X axis per rotation of the workpiece W, that is, the feed amount [ mm/rev ] per rotation on the Z axis or the X axis, θ 3 is the inclination angle [ rad ] with respect to the Z axis direction, Kz and Kx are the swing amplitude magnification [ multiple ] of the Z axis or the X axis, and α Z and α X are the margin of the Z axis or the X axis.
For example, the minimum swing amplitude a in the case of the feed amount F per revolution is expressed by the following expression (3).
[ numerical formula 3]
A=Fcos(θ1-θ3)+Fsin(θ1-θ3)×tan(θ2-θ3) …(3)
Thus, for example, the swing amplitude magnifications Kz and Kx of the Z-axis and the X-axis are expressed by the following expressions (4) and (5).
[ numerical formula 4]
[ numerical formula 5]
When θ 3 is 0 in equation (4), the equation becomes the same as equation (2) that oscillates only in the Z-axis direction. In fig. 6 and 7, the margin α z is 0 and the margin α x is 0.
As a result, as shown in fig. 7, the swing width Az (solid line arrow) in the Z-axis direction is slightly increased, but the swing width Ax (solid line arrow) in the X-axis direction is decreased, compared with the swing width Az (broken line arrow) in the Z-axis direction and the swing width Ax (broken line arrow) in the X-axis direction in the case of swinging in the machining direction. When the swing in the X-axis direction has a large influence on the machine, the load on the entire machine tool is reduced.
The oscillation frequency calculation unit 232 calculates the oscillation frequency based on the machining conditions. Specifically, the oscillation frequency calculation unit 232 calculates the oscillation frequency S/60 × I based on the rotation speed S [ min-1] or [ rpm ] around the center axis of the workpiece W and the oscillation frequency magnification I.
The wobble command calculation unit 233 calculates a wobble command by equation (1) based on the wobble amplitude and the wobble frequency.
Next, the
The subtractor 25 obtains a positional deviation which is a difference between the position command (movement command) generated by the position
The learning controller 27 receives the synthesis command immediately after the output from the adder 24, performs learning control so as to reduce the correction amount of the synthesis command, thereby obtaining the correction amount of the synthesis command, and adds the correction amount to the synthesis command immediately before the input to the position/velocity controller 28.
The position/speed controller 28 performs position control, speed control, and current control based on the synthesized command corrected by the learning controller 27, and drives and controls the servo motors at the feed axes M1 and M2.
As described above, according to the control device 20 of the machine tool of the present embodiment, when the workpiece machining shape is a conical shape, a truncated cone shape (cone), or a circular arc shape, the swing command is automatically changed so as to swing in a direction other than the machining direction (the direction in which the Z-axis direction and the X-axis direction are combined). This can reduce the total swing width of the plurality of feed axes, reduce the load on the entire machine tool, and reduce the increase in the load on the machine tool due to swing cutting. Further, the swing of the feed shaft with a large load can be reduced, and the increase in the load of the machine tool due to the swing cutting can be reduced.
Further, when the driving mechanism portion of the tool 11 has a backlash (backlash) or when the rigidity of the driving mechanism portion is low, if the control gain is set high in order to improve the responsiveness of the servo, vibration may occur, and the positional accuracy of the tool 11 may be unstable. For example, even if the feed axes M1, M2 are driven based on command values corresponding to the curves a1, a2, A3, etc. shown in fig. 3, the actual position of the tool 11 may not completely follow the curves a1, a2, A3, etc. In this case, if the actual position of the tool 11 does not match the command values such as the curves a1, a2, A3 at the overlap positions B1, B2, B3, B4, etc., intermittent cutting does not occur, and as a result, chips cannot be formed satisfactorily.
Therefore, in the present embodiment, the following ability to the swing command is improved by using the learning control. The learning control is a control method for improving the followability to the "periodic command with a fixed repetition pattern", and is capable of reducing the positional deviation as the period progresses from the 1 st period to the 2 nd period, and from the 2 nd period to the 3 rd period … …. Specifically, the positional deviation corresponding to the predetermined number of vibration cycles of the workpiece W and the tool 11 is learned and used as the correction amount, thereby suppressing an increase in the periodic positional deviation due to the swing command. Further, for example, the cycle of learning can be determined from the wobble frequency of the wobble command of the above equation (1) (for example, 1 wobble cycle is 1/wobble frequency). The
As a result, the actual position of the tool 11 gradually approaches the curves a1, a2, A3, etc. of the command values, and finally matches the curves a1, a2, A3, etc. of the command values. In this case, since the curves a1, a2, A3, and the like of the command values have the aforementioned overlapping positions B1, B2, B3, B4, and the like, intermittent cutting is reliably generated, and the cut chips can be reliably formed.
(modification 1)
In the above-described embodiment, the swing amplitude calculating unit 231 calculates the swing amplitude magnification based on the machining condition and the mechanical condition. However, the present invention is not limited to this, and the control device 20 may store tables or functions (information) in which a plurality of swing amplitude magnifications are associated with a plurality of taper angles of the workpiece in the storage unit in advance, and the swing amplitude calculation unit 231 may acquire the swing amplitude magnifications corresponding to the taper angles of the workpiece in the tables or functions.
(modification 2)
In the above-described embodiment, when the workpiece machining shape is a conical shape, a truncated cone shape (cone), or a circular arc shape, the swing
While the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various changes and modifications can be made. For example, in the above-described embodiment, the structure in which the workpiece W is rotated and the tool 11 is oscillated along the generatrix of the outer peripheral surface of the workpiece W is exemplified, but the present invention is not limited to this structure.
The machine tool related by the invention has the following structure: the workpiece W is machined by controlling a spindle M0 for relatively rotating the workpiece W and the tool 11 about the central axis of the workpiece W, at least two feed shafts M1, M2 for relatively feeding the workpiece W and the tool 11 in a machining direction along the central axis, and the like. For example, the following structure can be conceived: the tool 11 rotates about the central axis of the workpiece W and the workpiece W swings relative to the tool 11; or the workpiece W is rotated and the workpiece W is swung with respect to the tool 11 in a direction along a generatrix of the outer peripheral surface of the workpiece W. In the present invention, a machining method of cutting the workpiece W by rotating the tool 11 around the central axis of the workpiece W is also one type of machining.
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