Machine tool control device

Abstract

The present invention is to provide a control device for a machine tool that performs oscillating cutting and that enables loads on a machine tool to be versatilely reduced without depending on the configuration of the machine tool. The present invention provides a control device 1 for a machine tool that performs oscillating cutting by causing a tool T and a workpiece W to oscillate relative to each other, the control device 1 including a cutting edge angle acquiring unit 12 that acquires a cutting edge angle θ1 of the machine tool T, an oscillating amplitude calculating unit 13 that calculates an oscillating amplitude required for chipping in any oscillating direction on the basis of the cutting edge angle θ1 of the tool T, an oscillating direction determining unit 14 that determines an oscillating direction on the basis of a calculation result from the oscillating amplitude calculating unit 13, and an oscillating operation control unit 15 that controls, on the basis of machining conditions, an oscillating operation in the oscillating direction determined by the oscillating direction determining unit 14.

Description

[Technical field]

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

[0002] Conventionally, when cutting a workpiece using a cutting tool, it is known that chips generated continuously become entangled in the cutting tool, causing processing defects and machine tool failures. In response to this, a method called oscillating cutting has been proposed in which the cutting tool and the workpiece are oscillated relative to each other while cutting the workpiece, thereby shredding the chips. In oscillating cutting, the cutting tool and the workpiece are usually oscillated relative to each other in a direction along the machining path.

[0003] For example, when the workpiece has a tapered or arcuate shape, there are multiple feed axes (e.g., Z-axis and X-axis) for feeding the cutting tool or workpiece in the direction along the machining path. In this case, the load on the machine tool increases because multiple axes are oscillated simultaneously. Therefore, a technology has been proposed that can reduce the load on the machine tool while still achieving chip shredding by changing the oscillating direction from the direction along the machining path to a direction different from the direction along the machining path in the tapered portion of the workpiece, etc. (see, for example, Patent Document 1).

[0004] FIG. 7 is a diagram showing an example of conventional oscillating cutting. In this example, cutting is performed by moving a tool T by a feed axis in a feed direction along the generatrix of the outer peripheral surface of a workpiece W rotated by a main shaft S. When cutting a tapered portion W1 of a workpiece W by a tool T as shown in FIG. 7, the oscillating direction of a current pass is changed from a direction along the machining path to a direction different from the previous pass. For example, the oscillating direction is changed from a direction along the machining path indicated by a black arrow in FIG. 7 to a direction indicated by a white arrow, in which the oscillation component in the Z-axis direction increases while the vibration component in the X-axis direction decreases. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6763917 Summary of the Invention [Problem to be solved by the invention]

[0006] 7, however, the swing component in the Z-axis direction increases while the swing component in the X-axis direction decreases due to the change in the swing direction, and the load on the machine tool can be sufficiently reduced only when the inertia of the machine tool in the X-axis direction is much greater than the inertia in the Z-axis direction. That is, in the above-mentioned conventional swing cutting, the effect of reducing the load on the machine tool depends on the configuration of the machine tool.

[0007] Therefore, in a control device for a machine tool that performs swing cutting, there is a demand for a technique that can generally reduce the load on the machine tool, regardless of the configuration of the machine tool. [Means for solving the problem]

[0008] One aspect of the present disclosure is a control device for a machine tool that performs swing cutting by swinging a tool and a workpiece relative to one another, the control device for a machine tool comprising: a cutting angle acquisition unit that acquires a cutting angle of the tool; a swing amplitude calculation unit that calculates the swing amplitude required to shred chips in any swing direction based on the cutting angle of the tool; a swing direction determination unit that determines the swing direction based on a calculation result of the swing amplitude calculation unit; and a swing operation control unit that controls the swing operation in the swing direction determined by the swing direction determination unit based on machining conditions. Effect of the Invention

[0009] According to the present disclosure, in a control device for a machine tool that performs swing cutting, the load on the machine tool can be generally reduced, regardless of the configuration of the machine tool. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a control device for a machine tool according to an embodiment of the present disclosure. [Diagram 2] FIG. 4 is a diagram showing the cutting angle of a tool. [Diagram 3] FIG. 11 is a diagram illustrating a method for calculating oscillation amplitude. [Figure 4] 4A to 4C are diagrams showing a first example of orbital cutting according to the present embodiment. [Diagram 5] 11A to 11C are diagrams illustrating a second example of orbital cutting according to the present embodiment. [Figure 6] 11A to 11C are diagrams illustrating a third example of orbital cutting according to the present embodiment. [Figure 7] FIG. 1 is a diagram showing an example of conventional orbital cutting. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0012] Fig. 1 is a diagram showing a machine tool control device 1 according to this embodiment. The machine tool control device 1 according to this embodiment cuts a workpiece with a cutting tool (hereinafter, referred to as tool) by operating at least one spindle that rotates the tool and the workpiece relatively, and at least one feed axis that moves the tool relative to the workpiece. For convenience, Fig. 1 shows only a motor 3 that drives one feed axis.

[0013] The control device 1 of the machine tool according to this embodiment performs oscillating cutting by operating the spindle and the feed axis. That is, the control device 1 of the machine tool rotates the tool and the workpiece relatively and performs cutting while oscillating the tool and the workpiece relatively. The tool path, which is the trajectory of the tool, is set so that the current path partially overlaps the previous path, and the part that has been machined on the previous path is included in the current path. Therefore, an air cut occurs in which the cutting edge of the tool separates from the surface of the workpiece, and chips that are continuously generated by cutting are reliably chopped.

[0014] The control device 1 of the machine tool is configured using a computer including memories such as a read only memory (ROM) and a random access memory (RAM), a control processing unit (CPU), and a communication control unit, which are connected to each other via a bus, for example. As shown in Fig. 1, the control device 1 of the machine tool includes a first storage unit 11, a cutting angle acquisition unit 12, a swing amplitude calculation unit 13, a swing direction determination unit 14, a swing operation control unit 15, and a second storage unit 16, and the functions and operations of each of these units can be achieved by cooperation between the CPU and memory mounted on the computer, and the control program stored in the memory.

[0015] A host computer (not shown), such as a CNC (Computer Numerical Controller) or a PLC (Programmable Logic Controller), is connected to the machine tool control device 1. From these host computers, machining conditions such as rotation speed and feed rate, and oscillation conditions such as oscillation frequency, in addition to machining programs, are input to the machine tool control device 1.

[0016] The first storage unit 11 stores the cutting angle of the tool. Here, FIG. 2 is a diagram showing the cutting angle θ1 of the tool T. Note that FIG. 2 to FIG. 6, which will be described later, all show an example in which the tool T is moved by the feed axis in the feed direction along the generatrix of the outer peripheral surface of the workpiece W rotated by the spindle S, to perform cutting processing. However, this embodiment is not limited to such outer diameter processing, and can also be applied to inner diameter processing. In addition, this embodiment can also be applied to a configuration in which the tool T rotates around the central axis of the workpiece W and the workpiece W moves in the feed direction relative to the tool T. Note that in FIG. 2 to FIG. 7, the central axis of the workpiece W is the Z axis, and the direction perpendicular to the Z axis is the X axis.

[0017] As shown in FIG. 2, the cutting angle θ1 of the tool T means the angle from the Z-axis direction, which is the central axis direction of the workpiece W, to the flank T1 of the tool T. The flank T1 of the tool T means the surface of the cutting edge of the tool T that faces the workpiece W and is also the surface on the machining direction side (see the black arrow in FIG. 2). This cutting angle θ1 is set to a desired angle in advance for each of the multiple tools T, and does not depend on the taper angle of the machining surface. More specifically, the cutting angle θ1 set in advance for each tool T is stored in the first storage unit in association with each tool T.

[0018] The cutting edge angle acquisition unit 12 acquires the cutting edge angle θ1 of the tool T. Specifically, the cutting edge angle acquisition unit 12 reads and acquires the cutting edge angle θ1 corresponding to the tool from the first storage unit 11 based on tool data acquired from a machining program input to the control device 1 of the machine tool. The acquired cutting edge angle θ1 of the tool T is output to the swing amplitude calculation unit 13, which will be described later.

[0019] The swing amplitude calculation unit 13 calculates the swing amplitude required to chop chips in any swing direction based on the cutting angle θ1 of the tool T acquired by the cutting angle acquisition unit 12. The calculated swing amplitude in each swing direction is output to a swing direction determination unit 14 and a swing operation control unit 15, which will be described later. Note that the swing amplitude in this embodiment includes not only the swing amplitude itself but also the swing amplitude magnification.

[0020] 3 is a diagram showing a method of calculating the oscillation amplitude in the oscillation amplitude calculation unit 13. In FIG. 3, for convenience of explanation, the mode of oscillation in the direction along the conventional machining path is referred to as "before change", and the mode of oscillation in an arbitrary oscillation direction different from the direction along the machining path is referred to as "after change" (similar to FIGS. 4 to 7). As shown in FIG. 3, the oscillation amplitude A' required for shredding the chips in the oscillation direction after the oscillation direction change is calculated by the following formula (1) using the oscillation amplitude A required for shredding the chips in the oscillation direction along the conventional machining path before the change, the shift angle θ of the oscillation direction before and after the change, the cutting angle θ1 of the tool T, and the angle θ2 between the oscillation direction along the conventional machining path before the change and the Z-axis direction. [Number 1] A'=A×(cosθ-sinθ / tan(θ+θ1-θ2)) Formula (1)

[0021] In this embodiment, the oscillation amplitude refers to a composite oscillation amplitude of a Z-axis oscillation amplitude component and an X-axis oscillation amplitude component. That is, the oscillation amplitude in this embodiment is a composite oscillation amplitude calculated by the following formula (2). [Number 2] Composite oscillation amplitude = (Z-axis amplitude) 2 +(X-axis amplitude) 2 ) 1 / 2 Formula (2)

[0022] Returning to Fig. 1, the swing direction determination unit 14 determines the swing direction based on the swing amplitude calculated by the swing amplitude calculation unit 13. Preferably, the swing direction determination unit 14 determines a swing direction that results in a swing amplitude A' that is smaller than the swing amplitude A of the swing operation in the direction along the machining path, within the range of swing directions in which chips can be chopped. This generally reduces the load on the machine tool due to the swing operation.

[0023] More specifically, as shown in FIG. 3, the oscillation direction determination unit 14 determines, as the oscillation direction, a direction in which the composite oscillation amplitude of the oscillation amplitude component in the Z-axis direction and the oscillation amplitude component in the X-axis direction becomes smaller.

[0024] More preferably, the swing direction determination unit 14 determines, as the swing direction, a direction perpendicular to the flank T1 of the tool T. In this case, the swing amplitude can be set to the minimum value capable of shredding the chips, and the load on the machine tool is minimized while shredding the chips.

[0025] The second storage unit 16 stores machining conditions for the workpiece W, etc. The machining conditions for the workpiece W include the relative rotation speed of the workpiece W and the tool T about the central axis of the workpiece W, the relative feed speed of the tool T and the workpiece W, and a position command for the feed axis. The second storage unit 16 may be configured to store a machining program to be executed by the machine tool, and a CPU in the control device 1 of the machine tool reads out the rotation speed and feed speed from the machining program as machining conditions and outputs them to the swing motion control unit 15. The second storage unit 16 and a position command creation unit in the swing motion control unit 15 described later may be provided in the above-mentioned higher-level computer.

[0026] The swing operation control unit 15 controls the swing operation in the swing direction determined by the swing direction determination unit 14 based on the machining conditions. In order to control the swing operation, the swing operation control unit 15 includes various functional units (none of which are shown) such as a position command generation unit, a swing command generation unit, a superposition command generation unit, a learning control unit, and a position and speed control unit.

[0027] The position command generating unit reads out the machining conditions stored in the second storage unit 16, and generates a position command as a movement command for the motor 3 based on the machining conditions. Specifically, the position command creating unit generates a position command (movement command) for each feed axis based on the relative rotation speed of the workpiece W and the tool T about the central axis of the workpiece W and the relative feed speed of the tool T and the workpiece W.

[0028] The swing command generating unit generates a swing command. The swing command generating unit may generate a swing command from swing conditions, such as a swing amplitude magnification and a swing frequency magnification, and processing conditions, or may generate a swing command from swing conditions, such as a swing amplitude and a swing frequency. Specifically, the swing command generating unit generates a swing command based on the swing amplitude calculated by the swing amplitude calculating unit 13 and swing conditions, such as a swing frequency input from a host computer and stored in the second storage unit.

[0029] The superimposition command generator calculates a position deviation, which is the difference between the position feedback based on the position detection by the encoder of the feed axis motor 3 and the position command, and generates a superimposition command by superimposing the swing command generated by the swing command generator on the calculated position deviation. Alternatively, the swing command may be superimposed on the position command instead of the position deviation.

[0030] The learning control unit calculates a correction amount of the superimposition command based on the superimposition command, and corrects the superimposition command by adding the calculated correction amount to the superimposition command. The learning control unit has a memory, correlates the oscillation phase and the correction amount within one or multiple oscillation periods, and stores them in the memory. The learning control unit reads out the superimposition command stored in the memory at a timing when the phase delay of the oscillation operation according to the responsiveness of the motor 3 can be compensated for, and outputs the superimposition command as a correction amount. If the oscillation phase for which the correction amount is output does not exist in the oscillation phases stored in the memory, the correction amount to be output may be calculated from a correction amount close to the oscillation phase. Generally, the higher the oscillation frequency, the larger the position deviation with respect to the oscillation command, so by performing this correction by the learning control unit, it is possible to improve the followability to the periodic oscillation command.

[0031] The position and speed control unit generates a torque command for the motor 3 that drives the feed axis based on the superimposed command after the correction amount is added, and controls the motor 3 by the generated torque command. As a result, machining is performed while the tool T and the workpiece W are oscillated relatively to each other.

[0032] Next, the swing cutting executed by the control device 1 of the machine tool according to this embodiment will be described in more detail with a specific example.

[0033] 4 is a diagram showing a first example of swing cutting according to this embodiment. This first example is an example when a swing direction is determined to have a swing amplitude A' smaller than the swing amplitude A of the swing operation in the direction along the machining path within the range of swing directions capable of shredding chips. As is clear from FIG. 4, the swing amplitude A' capable of shredding chips in the changed swing direction is smaller than the swing amplitude A of the swing operation in the direction along the machining path, so that the load on the machine tool can be reduced.

[0034] 5 is a diagram showing a second example of swing cutting according to this embodiment. This second example is an example in which the direction perpendicular to the flank T1 of the tool T is determined as the swing direction within the range of swing directions in which chips can be chopped. As is clear from FIG. 5, the swing amplitude A' capable of chip chopping when the direction perpendicular to the flank T1 of the tool T is determined as the swing direction is significantly smaller than the swing amplitude A of the swing operation in the direction along the machining path, making it possible to minimize the load on the machine tool.

[0035] 6 is a diagram showing a third example of the swing cutting according to this embodiment. In this third example, a cylindrical or cylindrical workpiece W is used, and the direction perpendicular to the flank T1 of the tool T is determined as the swing direction within the range of swing directions in which chips can be chopped. As is clear from FIG. 6, even when the shape of the workpiece W does not have a tapered portion or an arc-shaped portion, and the feed axis is a specific axis (Z axis in FIG. 6), the swing amplitude A' capable of chopping chips when the direction perpendicular to the flank T1 of the tool T is set as the swing direction is much smaller than the swing amplitude A of the swing operation in the direction along the machining path, and the load on the machine tool can be minimized.

[0036] Thus, in the swing cutting according to this embodiment, the shape of the workpiece W is not limited. That is, it is applicable even when the workpiece W has a tapered portion or an arc-shaped portion on the machining surface, which requires multiple feed axes (Z axis and X axis), or when the workpiece W is columnar or cylindrical and only one specific axis (Z axis) is sufficient as the feed axis. Therefore, the swing operation control unit 15 according to this embodiment is configured to change from a swing operation that swings multiple feed axes, or from a swing operation that swings only one specific axis among the multiple feed axes, to a swing operation in the swing direction determined by the swing direction determination unit 14.

[0037] According to this embodiment, the following effects are achieved.

[0038] In this embodiment, the control device 1 for the machine tool is configured to include a cutting angle acquisition unit 12 that acquires the cutting angle of the tool T, a swing amplitude calculation unit 13 that calculates the swing amplitude required to shred chips in any swing direction based on the cutting angle of the tool T, a swing direction determination unit 14 that determines the swing direction based on the calculation result of the swing amplitude calculation unit 13, and a swing operation control unit 15 that controls the swing operation in the swing direction determined by the swing direction determination unit 14 based on the machining conditions.

[0039] In conventional swing cutting, the swing amplitude capable of shredding the chips is calculated after the swing direction is determined, whereas in this embodiment, the swing amplitude capable of shredding the chips in any of a plurality of swing directions is calculated, and then the swing direction is determined based on the calculated swing amplitude. Therefore, according to this embodiment, it is possible to select and determine a swing direction that results in a swing amplitude smaller than the swing amplitude of the swing operation in the direction along the machining path, and the load on the machine tool can be reduced. Furthermore, according to this embodiment, the load on the machine tool can be reduced in a general manner without depending on the configuration of the machine tool.

[0040] In the present embodiment, the tool is swung in a direction that has a smaller amplitude than the amplitude of the swing motion along the machining path within the range of swing directions that can shred the chips, which makes it possible to more reliably reduce the load on the machine tool while shredding the chips, compared to conventional swing motion along the machining path.

[0041] In addition, in this embodiment, the tool T is configured to oscillate in a direction perpendicular to the flank T1 of the tool T. This makes it possible to more reliably reduce the load on the machine tool while shredding chips, as compared to a conventional oscillating operation in a direction along the machining path, and thus makes it possible to minimize the load on the machine tool.

[0042] In this embodiment, the swing operation control unit 15 changes the swing operation from swinging only one specific axis among the multiple feed axes to swing operation in the swing direction determined by the swing direction determination unit 14. As described above, this embodiment is applicable not only to cases where the workpiece W has a tapered portion or an arc-shaped portion on the machining surface and thus requires multiple feed axes (Z axis and X axis), but also to cases where the workpiece W is columnar or cylindrical and only one specific axis (Z axis) is sufficient as a feed axis, and can achieve the above-mentioned effects.

[0043] The present disclosure is not limited to the above-described aspects, and modifications and improvements within the scope that can achieve the object of the present disclosure are included in the present disclosure. [Explanation of symbols]

[0044] 1. Machine tool control device 11 1st memory section 12 Cutting angle acquisition section 13 Swing amplitude calculation section 14 Swing direction determination unit 15 Swing motion control section 16 2nd memory section 3 Motor S spindle T-tool Double work W1 Tapered section θ1 Cutting angle

Claims

1. A control device for a machine tool that performs swing cutting by swinging a tool and a workpiece relative to each other, A cutting angle acquisition unit that acquires a cutting angle of the tool; A swing amplitude calculation unit that calculates a swing amplitude required to chop chips in an arbitrary swing direction based on a cutting angle of the tool; a swing direction determination unit that determines a swing direction based on the swing amplitude calculated by the swing amplitude calculation unit; a swing operation control unit that controls the swing operation in the swing direction determined by the swing direction determination unit based on processing conditions, The swing direction determination unit is a control device for a machine tool that determines a swing direction that has a swing amplitude smaller than the swing amplitude of the swing motion in a direction along the machining path, within a range of swing directions in which chips can be shredded.

2. A control device for a machine tool that performs swing cutting by swinging a tool and a workpiece relative to each other, comprising: A cutting angle acquisition unit that acquires a cutting angle of the tool; A swing amplitude calculation unit that calculates a swing amplitude required to chop chips in an arbitrary swing direction based on a cutting angle of the tool; a swing direction determination unit that determines a swing direction based on the swing amplitude calculated by the swing amplitude calculation unit; a swing operation control unit that controls the swing operation in the swing direction determined by the swing direction determination unit based on processing conditions, The control device for a machine tool, wherein the swing direction determination unit determines, as the swing direction, a direction perpendicular to the flank of the tool, which is the surface of the cutting edge of the tool that faces the workpiece and faces in the machining direction.

3. A control device for a machine tool as described in claim 1 or 2, wherein the swing motion control unit changes the swing motion from one that swings only a specific axis among a plurality of feed axes to a swing motion in the swing direction determined by the swing direction determination unit.

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