Numerical control device, numerical control program, and numerical control method

Abstract

The numerical control device (1) controls vibration cutting in which a tool is vibrated relative to a workpiece to cut the workpiece. The numerical control device (1) includes a vibration waveform generating unit (13) that calculates a tool amplitude capable of breaking up chips generated in vibration cutting and a vibration direction that is a direction in which the tool is moved relative to the workpiece when vibrating the tool with the amplitude, based on tool information indicating the shape and dimensions of the tool and machining shape information indicating the shape of the workpiece, and generates a vibration waveform that represents a trajectory of the tool vibration.

Description

[Technical field]

[0001] The present disclosure relates to a numerical control device for controlling a machine tool, a numerical control program, and a numerical control method. [Background technology]

[0002] Vibration cutting is known, which cuts the workpiece by vibrating a tool relative to the workpiece to break up the chips. In vibration cutting, the action of moving the tool forward in the machining direction, which is the direction in which machining is carried out, and the action of moving the tool backward in the opposite direction to the machining direction are alternately repeated. Vibration cutting makes it possible to cut the workpiece while breaking up the chips by creating a section in which the cutting of the workpiece by the tool is interrupted. By breaking up the chips into short pieces, it is possible to prevent a decrease in machining accuracy due to the chips becoming entangled in the workpiece or the tool. In addition, by breaking up the chips into short pieces, it is possible to reduce damage to the workpiece caused by the chips coming into contact with the workpiece.

[0003] Patent Document 1 discloses a control device for a machine tool that calculates the amplitude required to break chips in vibration cutting and determines the vibration direction in which the tool is vibrated based on the calculated amplitude, thereby reducing the mechanical load on the machine tool. When machining a tapered workpiece by vibrating the tool with each of a plurality of feed axes, the control device disclosed in Patent Document 1 changes the vibration direction to a direction different from the machining direction by increasing or decreasing the vibration component for each feed axis. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 269751 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of calculating the amplitude disclosed in Patent Document 1 is premised on the use of a tool with a sharp cutting edge, and cannot be applied to tools with rounded cutting edges that are commonly used in cutting. Specifically, when a tool with a rounded cutting edge is used, the method of calculating the amplitude disclosed in Patent Document 1 calculates the amplitude based on the tip of the rounded cutting edge, for example, and may calculate an amplitude that is greater than the amplitude required to break the chips. If vibration cutting is performed based on the calculated excessive amplitude, the feed axis is excessively retracted when the tool is retracted, which leads to an increase in the machine load.

[0006] In addition, the taper of the workpiece to be cut can be either an uphill taper, which is a shape that widens away from the rotation center of the spindle as it advances in the machining direction, or a downhill taper, which is a shape that narrows toward the rotation center of the spindle as it advances in the machining direction. In the case where the taper is a downhill taper, if the amplitude and vibration direction are determined by the technology disclosed in Patent Document 1, excessive cutting occurs with respect to the desired machining shape. For this reason, the technology disclosed in Patent Document 1 has a problem in that machining defects due to excessive cutting cannot be avoided depending on the machining shape.

[0007] The present disclosure has been made in consideration of the above-mentioned circumstances, and aims to obtain a numerical control device that can reduce the mechanical load on a machine tool due to the execution of vibration cutting, while avoiding machining defects regardless of the machining shape. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, a numerical control device according to the present disclosure is a numerical control device that controls vibration cutting in which a tool is vibrated relative to a workpiece to cut the workpiece. Has a circular cutting edge Information indicating the shape and dimensions of the tool, ,bladeThe vibration waveform generating unit calculates the tool amplitude capable of breaking up chips generated in vibration cutting and the vibration direction in which the tool is moved relative to the workpiece when vibrating the tool with the amplitude based on tool information including at least information indicating the roundness of the tip and machining shape information indicating the shape of the workpiece, and generates a vibration waveform representing the trajectory of the tool vibration. A point on the circle of the cutting edge or on the cutting face of the tool at a second time point that is a time period that is a time period for a spindle that rotates a workpiece relative to the tool to rotate once from a first time point when the pull-out operation of the tool is started, Of the workpiece's machining surface At the second point Calculate the cutting incomplete point, which indicates the position where cutting is incomplete, and move the tool to the cutting incomplete point. Tip position of The amplitude and vibration direction for performing the pulling operation to move the Effect of the Invention

[0009] The numerical control device according to the present disclosure has the advantage of being able to reduce the mechanical load on the machine tool caused by performing vibration cutting while avoiding machining defects regardless of the machining shape. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing an example of the configuration of a numerical control device according to an embodiment; [Diagram 2] 4A and 4B are diagrams showing examples of vibration waveforms generated by a vibration waveform generating unit of the numerical control device according to the embodiment; [Diagram 3] FIG. 2 is a first diagram for explaining a position of a tool in vibration cutting by a machine tool controlled by a numerical control device according to an embodiment. [Figure 4] FIG. 2 is a second diagram for explaining the position of the tool in vibration cutting by the machine tool controlled by the numerical control device according to the embodiment. [Diagram 5] 5A and 5B are diagrams for explaining amplitudes calculated by a vibration waveform generating unit of the numerical control device according to the embodiment. [Figure 6] 10A and 10B are diagrams for explaining a case where vibration cutting of an upwardly tapered groove is controlled by the numerical control device according to the embodiment. [Figure 7] 11A and 11B are diagrams for explaining a case where vibration cutting of a downward taper is controlled by the numerical control device according to the embodiment. [Figure 8] 5 is a diagram for explaining a vibration direction calculated by a vibration waveform generating unit of the numerical control device according to the embodiment. FIG. [Figure 9] FIG. 4 is a first diagram for explaining a pulling-out operation controlled by the numerical control device according to the embodiment. [Figure 10] FIG. 2 is a second diagram for explaining the pulling-out operation controlled by the numerical control device according to the embodiment. [Figure 11] FIG. 4 is a first diagram for explaining a method for calculating an incomplete cutting point by the vibration waveform generating unit of the numerical control device according to the embodiment. [Figure 12] 11 is a second diagram for explaining a method for calculating an incomplete cutting point by the vibration waveform generating unit of the numerical control device according to the embodiment. FIG. [Figure 13] 5A and 5B are diagrams for explaining vibration cutting based on a cutting incomplete point calculated by a vibration waveform generating unit of the numerical control device according to the embodiment. [Figure 14] 4 is a flowchart showing an example of an operation procedure of the numerical control device according to the embodiment. [Figure 15] FIG. 2 is a diagram illustrating an example of a configuration of a control circuit according to an embodiment. [Figure 16] FIG. 2 is a diagram showing an example of the configuration of a dedicated hardware circuit according to the embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A numerical control device, a numerical control program, and a numerical control method according to embodiments will be described in detail below with reference to the drawings.

[0012] Embodiment 1 is a diagram showing an example of the configuration of a numerical control device 1 according to an embodiment. The numerical control (Numerical Control: NC) device 1 is a computer that controls a machine tool 2. The machine tool 2, which is the object of control by the numerical control device 1, performs machining including vibration cutting. The machine tool 2 has a spindle that rotates a workpiece relative to a tool, and multiple feed axes that move the tool relative to the workpiece. The numerical control device 1 controls vibration cutting, which cuts the workpiece by vibrating the tool relative to the workpiece.

[0013] The numerical control device 1 includes a program analysis unit 10, a command generation unit 11, a vibration condition setting unit 12, and a vibration waveform generation unit 13. The numerical control device 1 generates operation commands in accordance with a machining program input to the numerical control device 1. The numerical control device 1 controls the machine tool 2 by outputting operation commands to the machine tool 2.

[0014] The machining program includes the feed rate of the tool relative to the workpiece, the rotation speed of the spindle, information indicating the rotation direction of the spindle, machining shape information, tool information, etc. The machining shape information is information indicating the machining shape, which is the shape of the workpiece. The tool information is information indicating the shape of the tool and the dimensions of the tool. The program analysis unit 10 analyzes the machining program and generates information necessary for generating an operation command. The information necessary for generating an operation command is, for example, information on a moving path for moving the tool relative to the workpiece, or information on an interpolation method for the moving path. The interpolation method for the moving path is linear interpolation, circular interpolation, etc. The program analysis unit 10 outputs information necessary for generating an operation command to the command generation unit 11. The information output from the program analysis unit 10 to the command generation unit 11 may include information other than the information described here, and some of the information described here may be omitted. The program analysis unit 10 also outputs the machining shape information and the tool information to the vibration waveform generation unit 13.

[0015] The machining program is, for example, a program consisting of character strings in the EIA (Electronic Industries Alliance) / ISO (International Organization for Standardization) format. Alternatively, the machining program may be a program called an interactive program, which includes information on the shape of the workpiece, the machining shape, and the machining dimensions. The program analysis unit 10 may output the machining shape information calculated from the interactive machining program to the vibration waveform generation unit 13.

[0016] The command generating unit 11 generates an operation command based on information input to the command generating unit 11. The command generating unit 11 outputs the generated operation command to the machine tool 2.

[0017] The vibration condition setting unit 12 sets vibration conditions for vibration cutting, and outputs vibration condition information to the vibration waveform generating unit 13. The vibration conditions include vibration frequency and vibration amplitude. The vibration condition setting unit 12 outputs vibration condition information including the set values ​​of the vibration frequency and vibration amplitude to the vibration waveform generating unit 13. The numerical control device 1 adjusts the vibration amplitude set in the vibration condition setting unit 12 by calculating the vibration amplitude in the vibration waveform generating unit 13. The vibration condition information may include information on the shape of the vibration waveform. Hereinafter, the vibration amplitude may be simply referred to as the amplitude.

[0018] The vibration frequency included in the vibration conditions is the number of vibrations per rotation of the spindle. The magnitude of the vibration frequency affects the mechanical load of the machine tool 2. The vibration amplitude included in the vibration conditions represents the amount of movement before and after the tool pull-out operation. The pull-out operation is defined as the operation of moving the tool in the direction away from the workpiece. The magnitude of the vibration amplitude is related to the machining shape and feed rate, and affects the mechanical load of the machine tool 2. If the feed rate is small, the vibration amplitude becomes smaller and the mechanical load can be reduced, but the machining time will be longer. The numerical control device 1 needs to operate the machine tool 2 at an appropriate feed rate.

[0019] The vibration waveform generating unit 13 generates a vibration waveform that represents a trajectory along which the tool is vibrated in vibration cutting. Based on the tool information and the machining shape information, the vibration waveform generating unit 13 calculates the tool amplitude that can break chips generated in vibration cutting and the vibration direction that is the direction in which the tool is moved relative to the workpiece when the tool is vibrated with the amplitude, and generates a vibration waveform. The vibration waveform generating unit 13 outputs information indicating the vibration waveform to the command generating unit 11.

[0020] The command generating unit 11 reflects the vibration waveform generated by the vibration waveform generating unit 13 in the operation command for vibration cutting. In other words, the command generating unit 11 generates an operation command for moving a tool along a path on which the vibration waveform generated by the vibration waveform generating unit 13 is superimposed.

[0021] The vibration waveform generating unit 13 obtains a vibration waveform based on the tool information and the vibration condition information, thereby obtaining a tool movement path that minimizes the amount of tool movement during the tool extraction operation. The vibration waveform generated by the vibration waveform generating unit 13 is a vibration waveform that leaves no uncut portions of the workpiece and enables chips to be broken.

[0022] Here, the vibration waveform generated by the vibration waveform generating unit 13 will be described. Fig. 2 is a diagram showing an example of a vibration waveform generated by the vibration waveform generating unit 13 of the numerical control device 1 according to the embodiment. In the graph shown in Fig. 2, the vertical axis represents the rotation angle of the spindle, and the horizontal axis represents the position of the tool in the machining direction. The numerical control device 1 moves the tool at a constant feed amount for each rotation of the spindle, and vibrates the tool.

[0023] Curve 42 represents the position of the tool during one rotation of the spindle from a certain point in time. Machining performed by moving the tool along the trajectory represented by curve 42 is referred to as the current machining. Curve 41 represents the position of the tool during one rotation of the spindle immediately before the current machining. Machining performed by moving the tool along the trajectory represented by curve 41 is referred to as the previous machining. Curve 43 represents the position of the tool during one rotation of the spindle immediately after the current machining. Machining performed by moving the tool along the trajectory represented by curve 43 is referred to as the next machining. The vibration waveform generating unit 13 generates vibration waveforms represented by the curves 41, 42, and 43.

[0024] In the graph shown in FIG. 2, the hatched area 44 represents an idle area. The idle area is an area where cutting is interrupted by the tool being temporarily separated from the workpiece, that is, an area where the tool idles. In the current machining, the tool passes through a portion machined in the previous machining, and the portion becomes an idle area. In the next machining, the tool passes through a portion machined in the current machining, and the portion becomes an idle area. The chips generated before the tool reaches the idle area are cut in the idle area. The vibration waveform generating unit 13 generates a vibration waveform that generates such an idle area. In this way, the vibration waveform generating unit 13 generates a vibration waveform that does not leave any cutting residue on the workpiece and can cut the chips.

[0025] In the above, the vibration conditions are set by the vibration condition setting unit 12, and the vibration condition information is output from the vibration condition setting unit 12 to the vibration waveform generating unit 13, but this is not limited to the above. When information such as the vibration frequency and vibration amplitude is included in the machining program, the information included in the machining program may be input to the vibration waveform generating unit 13. The vibration frequency may be calculated based on the information set in the vibration condition setting unit 12 and the rotation speed of the spindle. In the embodiment, the method of setting the vibration condition information is arbitrary.

[0026] The tool information includes information indicating the tool length and information indicating the tool diameter. The tool information of a tool having a rounded cutting edge includes information indicating the radius of the cutting edge. The tool information also includes information indicating the wear amount of the tool. In the above, the tool information included in the machining program is input to the vibration waveform generating unit 13, but the tool information previously set in the numerical control device 1 may be input to the vibration waveform generating unit 13. The tool information may be stored in advance in the numerical control device 1. The tool information may also be set in the numerical control device 1 when various correction amounts are set before machining. The wear amount of the tool changes depending on the usage time of the tool. Therefore, the information indicating the wear amount included in the tool information is updated depending on the usage time of the tool. The tool information may include information indicating the wear amount measured using a measurement function. In the embodiment, the method of setting the tool information is arbitrary.

[0027] Next, a method for calculating the amplitude by the vibration waveform generating unit 13 will be described. In the following description, the workpiece on which vibration cutting is performed is assumed to be a tapered workpiece. The coordinate system based on which the tool operates is assumed to be an orthogonal machine coordinate system of the X-axis, Y-axis, and Z-axis.

[0028] When performing vibration cutting of a taper, the machine tool 2 needs to withdraw the tool in two directions simultaneously. The direction in which the tool is withdrawn varies depending on the configuration of the machine tool 2 and the direction of the taper. For this reason, in the embodiment, the direction in which the tool is withdrawn during vibration cutting of a taper is not particularly limited. In the following description, the directions in which the tool is withdrawn are the X-axis direction and the Z-axis direction. The machine tool 2 performs vibration cutting by driving a feed axis that moves the tool in the X-axis direction and a feed axis that moves the tool in the Z-axis direction.

[0029] The vibration waveform generating unit 13 calculates the cutting thickness, which is the thickness of the portion cut from the workpiece by vibration cutting, based on the machining shape information. For a tapered workpiece, the vibration waveform generating unit 13 calculates the taper angle, which is the angle of the taper with respect to the central axis of the workpiece. The central axis of the workpiece is the center of rotation when the workpiece is rotated relative to the tool. The vibration waveform generating unit 13 calculates the amplitude and vibration direction in vibration cutting by a calculation that incorporates the cutting thickness value, the taper angle value, and tool information.

[0030] FIG. 3 is a first diagram for explaining the position of the tool in vibration cutting of the machine tool 2 controlled by the numerical control device 1 according to the embodiment. FIG. 4 is a second diagram for explaining the position of the tool in vibration cutting of the machine tool 2 controlled by the numerical control device 1 according to the embodiment. "T", "W", and "h" shown in FIG. 3 and FIG. 4 respectively represent the tool, the workpiece, and the cutting thickness. The arrow 21 shown in FIG. 3 represents the machining direction. In FIG. 4, the machining direction is also assumed to be the same direction as the direction indicated by the arrow 21 in FIG. 3. The straight line 22 represents the surface of the workpiece before vibration cutting is performed. Hereinafter, such a surface is referred to as the machined surface. "R" shown in FIG. 4 represents the radius of the cutting edge. "θ" shown in FIG. 4 represents the taper angle. The arrow 23 shown in FIG. 4 represents the amplitude calculated by the vibration waveform generating unit 13. The vertical direction in each of FIG. 3 and FIG. 4 is assumed to be the X-axis direction, and the horizontal direction in each of FIG. 3 and FIG. 4 is assumed to be the Z-axis direction. The X-axis is a vertical axis perpendicular to the horizontal direction, and the Z-axis is a horizontal axis parallel to the central axis of the workpiece. In the embodiment, the taper angle is an angle based on the Z-axis.

[0031] Here, the cutting thickness will be described. The vibration waveform generating unit 13 calculates the cutting thickness based on the moving path and the processing shape generated according to the processing program. The calculation method of the cutting thickness by the vibration waveform generating unit 13 is not limited to the calculation method based on the moving path and the processing shape, but may be any method.

[0032] In vibration cutting, the tool only needs to be pulled out from the workpiece by a distance equivalent to the cutting thickness. For this reason, the numerical control device 1 can reduce the movement amount of the tool from the workpiece by incorporating the value of the cutting thickness into the calculation of the amplitude and the vibration direction. In addition, the numerical control device 1 can calculate the minimum movement amount that can completely separate the chip from the workpiece by incorporating the value of the cutting thickness into the calculation of the amplitude and the vibration direction. If the amplitude is smaller than the calculated cutting thickness, the workpiece may remain uncut. If the amplitude is larger than the calculated cutting thickness, the amplitude in vibration cutting becomes larger than the amplitude required to separate the chip. In this case, for example, the feed axis is excessively retracted when the tool is retracted, and the machine load of the machine tool 2 becomes excessive.

[0033] Next, the tool information will be described. Since the machining characteristics change depending on the shape and dimensions of the cutting edge, an appropriate tool is selected depending on the machining performed by the machine tool 2. Here, the tool used in vibration cutting is assumed to be a tool having a cutting edge with a rounded shape. The tool information incorporated in the calculation of the amplitude and vibration direction is assumed to be information representing the shape and dimensions of the cutting edge. The information representing the shape and dimensions of the cutting edge is, for example, information indicating the radius of the cutting edge.

[0034] The tool information incorporated in the calculation of the amplitude and the vibration direction only needs to include at least information representing the shape and dimensions of the cutting edge. The vibration waveform generating unit 13 can calculate the amplitude and the vibration direction based on the information representing the shape and dimensions of the cutting edge even when the cutting edge of the tool has a shape other than rounded. The numerical control device 1 can calculate the amplitude required to break up the chips regardless of the shape of the cutting edge by incorporating information representing the shape and dimensions of the cutting edge, i.e., the tool information, into the calculation of the amplitude and the vibration direction. The numerical control device 1 can calculate the amplitude required to break up the chips when a tool having a cutting edge with a rounded shape is used by incorporating information indicating the radius of the cutting edge into the calculation.

[0035] Each of Fig. 3 and Fig. 4 shows two figures representing a portion of a tool including a cutting edge. In Fig. 3, one of the two figures shown forward in the machining direction represents the position of the tool at a first time point, which is the present time. The other of the two figures represents the position of the tool at a second time point that is a time period that goes back from the first time point by one rotation of the spindle. In Fig. 4, one of the two figures shown forward in the machining direction represents the position of the tool at the first time point. The other of the two figures represents the position of the tool at a third time point after the tool has been removed from the first time point. In Fig. 4, the figure representing the position of the tool at the second time point is shown by a dashed line.

[0036] In vibration cutting, after the tool is pulled out, the uncut portion during one revolution must be cut. The position of the uncut portion can be calculated based on the shape and dimensions of the cutting edge and the cutting thickness. In order to make the machine tool 2 perform vibration cutting without leaving any uncut portions, the numerical control device 1 moves the tool in a direction perpendicular to the machining surface of the workpiece after the pull-out operation to cut the portion corresponding to the cutting thickness. When cutting the portion corresponding to the cutting thickness, the tool is moved in a direction perpendicular to the machining surface of the workpiece, taking into account the shape and dimensions of the cutting edge. The amplitude indicated by the arrow 23 in FIG. 4 is the amplitude in the pull-out direction of the tool in vibration cutting. By moving the tool in a direction perpendicular to the machining surface after the pull-out operation, the uncut portion can be cut by moving the tool with the minimum amount of movement.

[0037] Next, the taper angle will be described. The taper angle can be obtained from the machining direction. The vibration waveform generating unit 13 can calculate the taper angle based on the start point and end point of the tool in each of the X-axis direction and the Z-axis direction. The direction from the start point to the end point is the machining direction. The vibration waveform generating unit 13 calculates the taper angle based on the movement amount of the tool in each of the X-axis direction and the Z-axis direction and the machining direction, and can distinguish between an uphill taper and a downhill taper from the calculation result of the taper angle. If the taper angle is a positive value, the taper is an uphill taper, and if the taper angle is a negative value, the taper is a downhill taper. Note that the taper of the workpiece shown in FIG. 3 and FIG. 4 is an uphill taper. The numerical control device 1 can generate a vibration waveform that does not cause excessive cutting, regardless of whether the taper is an uphill taper or a downhill taper, by incorporating the taper angle into the calculation of the amplitude and the vibration direction.

[0038] FIG. 5 is a diagram for explaining the amplitude calculated by the vibration waveform generating unit 13 of the numerical control device 1 according to the embodiment. The vibration waveform generating unit 13 calculates the amplitude, which is the amount of tool withdrawal, from the tool withdrawal direction in vibration cutting and the amount of feed axis movement during one rotation of the spindle. An arrow 24 shown in FIG. 5 indicates the amount of feed axis movement. The amount of feed axis movement is specified based on information included in the machining program, for example. Alternatively, when the amount of feed axis movement is set in the vibration condition setting unit 12, the set value in the vibration condition setting unit 12 may be used for the amount of feed axis movement.

[0039] A vector representing the amplitude, which is the amount of tool withdrawal, and the direction in which the tool is withdrawn is called a withdrawal vector. The arrow 23 shown in FIG. 4 and FIG. 5 represents the amplitude in the withdrawal direction. That is, the arrow 23 represents the withdrawal vector. Here, before explaining the calculation of the withdrawal vector, the movement amount corresponding to the part to be machined before the spindle rotates once will be explained. In FIG. 5, the arrow 25 represents such a movement amount. Such a movement amount is the movement amount in the direction of the taper angle, that is, the movement amount in the direction parallel to the taper. By calculating the amplitude by incorporating such a movement amount of the tool in the direction parallel to the taper per one rotation of the spindle, it becomes possible to cut only by the movement amount corresponding to the part to be machined, and for example, it becomes possible to perform machining without leaving any uncut parts while preventing unnecessary retreat of the feed axis. Considering the shape and dimensions of the cutting edge, it is possible to machine a part corresponding to R from the position where the previous machining was performed. Furthermore, by considering the cutting thickness, it is possible to calculate the part machined during the previous spindle rotation. The arrow 26 shown in FIG. 5 represents the part machined during the previous spindle rotation.

[0040] If the amount of movement in the taper angle direction is "B" and the amount of movement of the feed axis per rotation of the main shaft is "mv", then "B" is expressed by the following formula (1).

[0041]

number

[0042] If the extraction vector is “P”, “P” is expressed by the following equation (2).

[0043]

number

[0044] In this way, the vibration waveform generating unit 13 calculates the amplitude and vibration direction in vibration cutting by calculation incorporating the cutting thickness value, the radius value indicated in the tool information, and the amount of tool movement in the direction parallel to the taper.

[0045] The movement amount represented by the pull-out vector is a combination of the movement amount in the X-axis direction and the movement amount in the Z-axis direction. The vibration waveform generating unit 13 breaks down the movement amount represented by the pull-out vector into the movement amount in the X-axis direction and the movement amount in the Z-axis direction. The combination of feed axes for realizing the movement amount represented by the pull-out vector is not limited to the combination of a feed axis that moves the tool in the X-axis direction and a feed axis that moves the tool in the Z-axis direction, and may be any combination.

[0046] The amount of movement in the X-axis direction and the amount of movement in the Z-axis direction can be calculated using the taper angle, which represents the shape of the taper. If the amount of movement in the X-axis direction is "Xd" and the amount of movement in the Z-axis direction is "Zd", then "Xd" and "Zd" are each expressed by the following formula (3). In formula (3), when "θ" is equal to or greater than 0 degrees and less than 90 degrees, the taper is an uphill taper. In formula (3), when "θ" is greater than -90 degrees and less than 0 degrees, the taper is a downhill taper.

[0047]

number

[0048] In this way, the vibration waveform generating unit 13 calculates the amplitude in each direction of the multiple feed axes through a calculation that incorporates the value of the taper angle.

[0049] Fig. 6 is a diagram for explaining a case where vibration cutting of an uphill taper is controlled by the numerical control device 1 according to the embodiment. Fig. 7 is a diagram for explaining a case where vibration cutting of a downhill taper is controlled by the numerical control device 1 according to the embodiment. Arrow 27 shown in Fig. 6 and Fig. 7 indicates the amount of movement in the Z-axis direction. Arrow 28 indicates the amount of movement in the X-axis direction.

[0050] The extraction direction calculated by the vibration waveform generating unit 13 is switched according to the taper angle. Regardless of whether the taper is an uphill taper or a downhill taper, the vibration waveform generating unit 13 can calculate the amplitude and vibration direction using formulas (1) to (3).

[0051] Next, the angle representing the vibration direction in vibration cutting will be described. Fig. 8 is a diagram for explaining the vibration direction calculated by the vibration waveform generating unit 13 of the numerical control device 1 according to the embodiment. "ω" shown in Fig. 8 represents the angle representing the vibration direction. Arrow 29 shown in Fig. 8 represents the amount of movement of the tool on the XZ plane. "ω" represents the angle of the angle between arrows 27 and 29.

[0052] Using inverse trigonometric functions, “ω” is expressed by the following equation (4).

[0053]

number

[0054] FIG. 9 is a first diagram for explaining the pulling operation controlled by the numerical control device 1 according to the embodiment. FIG. 9 shows a case where R>h holds. Note that R>h holds in FIG. 3 to FIG. 8 as well. "φ" shown in FIG. 9 represents the clearance angle of the tool. The clearance angle is for avoiding contact between the tool and the workpiece, for example. "ψ" shown in FIG. 9 represents the angle of the cutting edge of the tool. The angle of the cutting edge of the tool can also be said to be the angle of the corner portion of the tool. Hereinafter, the angle of the cutting edge of the tool will be referred to as the corner angle. Point 30 shown in FIG. 9 represents an incomplete cutting point described below. The tool information may include information indicating the corner angle of the tool.

[0055] FIG. 9 shows a figure representing the position of the tool at a second point traced back from a first point for the time when the main shaft makes one revolution. When the cutting thickness is smaller than the radius of the cutting edge, cutting is performed by the circular cutting edge. The angle representing the vibration direction can be calculated by Equation (4). In FIG. 9, the uncompleted cutting point representing the position where cutting is incomplete on the tapered machining surface is a point on the circle representing the cutting edge at the second point. In vibration cutting, by pulling out the tool up to this uncompleted cutting point, it is possible to generate no residue and to break the chips with a minimum amplitude.

[0056] FIG. 10 is a second diagram for explaining the pulling-out operation controlled by the numerical control device 1 according to the embodiment. FIG. 10 shows the case where R < h holds. The straight line 31 shown in FIG. 10 represents the rake face of the tool.

[0057] When the radius of the cutting edge is smaller than the cutting thickness, cutting is performed by the circular cutting edge and the portion of the tool other than the cutting edge. In FIG. 10, the uncompleted cutting point is not on the circle representing the cutting edge at the second point but is located on the machining surface away from the circle. In vibration cutting when R > h holds, by pulling out the tool up to this uncompleted cutting point, it is possible to generate no residue and to break the chips.

[0058] Here, a method for calculating the uncompleted cutting point when R < h holds will be described. FIG. 11 is a first diagram for explaining the method for calculating the uncompleted cutting point by the vibration waveform generation unit 13 of the numerical control device 1 according to the embodiment.

[0059] When cutting is performed by the tool, the rake face of the tool is the surface of the tool that contacts the workpiece. The angle formed by the rake face and the horizontal axis can be calculated by the clearance angle and the corner angle of the tool, as will be described later. When information indicating the corner angle of the tool is included in the tool information, the vibration waveform generation unit 13 can calculate the angle formed by the rake face and the horizontal axis with reference to the information indicating the corner angle, and for example, it is possible to prevent the feed axis from being excessively retracted when the tool is retracted.

[0060] Here, the center of the circle representing the cutting edge at the second time point is defined as "O", which is the origin of the XZ plane. In Fig. 11, the direction of the arrow indicating the X-axis is the positive X direction, and the opposite side of the positive X direction is the negative X direction. The direction of the arrow indicating the Z-axis is the positive Z direction, and the opposite side of the positive Z direction is the negative Z direction.

[0061] In Figure 11, the cutting face is represented by a tangent to the circle representing the cutting edge. Point 33 shown in Figure 11 represents the tangency point between the cutting face and the circle representing the cutting edge.

[0062] If the point of contact between the cutting face and the circle representing the cutting edge is (a, b), the following equation (5) holds true.

[0063]

number

[0064] Equation (5) can be changed to the following equation (6), which is a linear function on the XZ plane.

[0065]

number

[0066] The rake face is inclined to the horizontal axis by an angle equal to the sum of the tool's clearance angle and the tool's corner angle. Since the inclination of the rake face is expressed as "-(b / a)", the following equation (7) holds true.

[0067]

number

[0068] Furthermore, since the tangency point (a, b) is a point on a circle with radius R, the following equation (8) holds.

[0069]

number

[0070] By substituting equation (7) into equation (8), we obtain the following equation (9). The coordinate of the tangent point, "b", is calculated using equation (9). Furthermore, by substituting the calculated "b" into equation (7) or equation (8), the coordinate of the tangent point, "a", is calculated. This determines the coordinate of the tangent point, (a,b).

[0071]

number

[0072] By finding the coordinates of the tangent point (a, b), the linear equation that represents the rake face can be found from equation (6). The following equation (10) is the linear equation that represents the rake face. Here, for ease of explanation and calculation, "b" is assumed to be a positive value.

[0073]

number

[0074] FIG. 12 is a second diagram for explaining a method for calculating an incomplete cutting point by the vibration waveform generating unit 13 of the numerical control device 1 according to the embodiment. Here, an equation expressing the machining surface of the taper is obtained. Point 32 shown in FIG. 11 and FIG. 12 represents the intersection point between the straight line 22 expressing the machining surface and the straight line of Z=0. The value of X at this intersection point is taken as "d". Line 35 shown in FIG. 12 represents the surface of the taper after machining by vibration cutting. Point 34 shown in FIG. 12 represents the intersection point between the straight line 35 and the straight line of Z=0. The value of X at this intersection point is taken as "e".

[0075] The shift amount, which is the distance between the lines 22 and 35 in the vertical axis direction, is represented as "ed." "ed" satisfies the following equation (11).

[0076]

number

[0077] The straight line 35 is a tangent line to the circle representing the cutting edge. Using equations from (5) to (9), the following equation (12) is derived. Equation (12) is a linear equation representing the straight line 35.

[0078]

Number

[0079] Since the straight line 22 is obtained by shifting the straight line 35 in the direction of the vertical axis, using equations (11) and (12), the following equation (13) is derived.

[0080]

Number

[0081] The uncompleted cutting point is the intersection of the straight line 22 and the straight line 35. Assuming the uncompleted cutting point is (x, z) = (γ, δ), the coordinates of (γ, δ) which is the uncompleted cutting point can be obtained by the following equation (14).

[0082]

Number

[0083] In vibration cutting when R < h holds, by pulling out the tool up to this uncompleted cutting point, with a minimum amplitude, no uncut residue is generated and the chips can be segmented.

[0084] FIG. 13 is a diagram for explaining vibration cutting based on an unfinished cutting point calculated by a vibration waveform generation unit 13 of a numerical control device 1 according to an embodiment. A point 37 shown in FIG. 13 represents the tip position of a tool at a first time point. A point 38 shown in FIG. 13 represents the tip position of the tool at a second time point. An arrow 39 shown in FIG. 13 represents the movement amount of the tool from the point 37, which is the tip position of the tool at the first time point, to the point 30, which is an unfinished cutting point. That is, the arrow 39 represents the amplitude in the pulling-out direction of the tool in vibration cutting. An arrow 36 shown in FIG. 13 represents the movement amount of the tool from the point 38, which is the tip position of the tool at the second time point, to the point 30, which is an unfinished cutting point. "ε" represents the angle between an arrow 24 representing the movement amount "mv" of the feed axis and the arrow 39 representing the movement amount of the tool. That is, "ε" represents the angle of the vibration direction with respect to the machining direction.

[0085] The point 38, which is the tip position of the tool at the second time point, is a point on a circle with a radius of R and is also a point on a straight line 35. The straight line 35 represents the tapered surface after machining by vibration cutting. The angle between the surface and the horizontal axis is "θ". The coordinates of the point 38 are represented by the following equation (15).

[0086]

Number

[0087] The coordinates of the point 37, which is the tip position of the tool at the first time point, are represented by the following equation (16).

[0088]

Number

[0089] Let the amplitude represented by the arrow 39 be "S". "S" is the amplitude in vibration cutting when R < h holds. From equations (14) and (16), S = (Xs, Zs) is represented by the following equation (17).

[0090]

Number

[0091] Furthermore, "ε" is expressed by the following equation (18): This determines "ε", which is the angle of the vibration direction with respect to the machining direction.

[0092]

number

[0093] Next, an operation procedure of the numerical control device 1 according to the embodiment will be described below. Fig. 14 is a flowchart showing an example of the operation procedure of the numerical control device 1 according to the embodiment.

[0094] In step S1, the program analysis unit 10 analyzes the machining program. The program analysis unit 10 generates information necessary for generating an operation command by analyzing the machining program. In addition, the program analysis unit 10 outputs machining shape information and tool information to the vibration waveform generation unit 13.

[0095] In step S2, the vibration waveform generating unit 13 generates a vibration waveform. The vibration waveform generating unit 13 calculates the tool amplitude that can break chips generated in vibration cutting and the tool vibration direction when the tool is vibrated at the amplitude, based on the machining shape information and tool information input to the vibration waveform generating unit 13. The vibration waveform generating unit 13 generates a vibration waveform by calculating the amplitude and the vibration direction.

[0096] In step S3, the command generating unit 11 generates an operation command based on the information input to the command generating unit 11. The command generating unit 11 receives information necessary for generating the operation command, which is generated by analyzing the machining program in step S1. The command generating unit 11 also receives information indicating the vibration waveform generated in step S2. The command generating unit 11 generates an operation command for vibration cutting, and reflects the vibration waveform generated in step S2 in the operation command. As a result, the command generating unit 11 generates an operation command for moving a tool along a path on which the vibration waveform is superimposed.

[0097] In step S4, the command generating unit 11 outputs the operation command generated in step S3 to the machine tool 2. With the above, the numerical control device 1 ends the operation according to the procedure shown in FIG.

[0098] Next, a hardware configuration for realizing the numerical control device 1 according to the embodiment will be described. The numerical control device 1 is realized by a processing circuit. The processing circuit may be a circuit in which a processor executes software, or may be a dedicated circuit.

[0099] When the processing circuit is realized by software, the processing circuit is, for example, a control circuit 50 shown in Fig. 15. Fig. 15 is a diagram showing an example of the configuration of the control circuit 50 according to the embodiment. The control circuit 50 includes an input unit 51, a processor 52, a memory 53, and an output unit 54. The input unit 51 is an interface circuit that receives data input from outside the control circuit 50 and provides the data to the processor 52. The output unit 54 is an interface circuit that sends data from the processor 52 or the memory 53 to outside the control circuit 50.

[0100] The numerical control device 1 is realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a program and stored in the memory 53. In the control circuit 50, the processor 52 reads and executes the numerical control program stored in the memory 53, thereby realizing each function of the numerical control device 1. That is, the control circuit 50 includes a memory 53 for storing the numerical control program that results in the processing of the numerical control device 1 being executed. It can also be said that the numerical control program causes the computer to execute the procedures and methods of the numerical control device 1. The memory 53 is also used as a temporary memory when the processor 52 executes various processes.

[0101] The processor 52 is a CPU (Central Processing Unit). The processor 52 may be a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor). The memory 53 may be, for example, a random access memory (RAM), a read only memory (ROM), a flash memory, an erasable programmable read only memory (EPROM), an electrically erasable programmable read only memory (EEPROM (registered trademark)), or other non-volatile or volatile semiconductor memory, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a digital versatile disk (DVD).

[0102] Fig. 15 shows an example of hardware in which the functions of the numerical control device 1 are realized by a general-purpose processor 52 and a memory 53, but the functions of the numerical control device 1 may be realized by a dedicated hardware circuit. Fig. 16 is a diagram showing an example of the configuration of a dedicated hardware circuit 55 according to the embodiment.

[0103] The dedicated hardware circuit 55 includes an input unit 51, an output unit 54, and a processing circuit 56. The processing circuit 56 is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a circuit that combines these. The numerical control device 1 may be realized by the processing circuit 56 on a function-by-function basis, or the functions of the numerical control device 1 may be realized collectively by the processing circuit 56. The numerical control device 1 may be realized by combining the control circuit 50 and the hardware circuit 55.

[0104] The numerical control program according to the embodiment may be provided by being stored in a recording medium such as a CD (Compact Disc)-ROM or a DVD-ROM. The numerical control program according to the embodiment may be provided by being stored in a computer connected to a network such as the Internet and downloaded via the network such as the Internet. The numerical control program according to the embodiment may be provided or distributed via a network such as the Internet.

[0105] According to the embodiment, the numerical control device 1 includes a vibration waveform generating unit 13 that calculates the tool amplitude that can break up chips generated in vibration cutting and the vibration direction in which the tool is moved relative to the workpiece when vibrating the tool at that amplitude based on tool information indicating the shape and dimensions of the tool and machining shape information indicating the shape of the workpiece, and generates a vibration waveform that represents the trajectory of the tool vibration. As a result, even when the cutting edge of the tool has a rounded shape or the shape of the workpiece has a downward taper, the numerical control device 1 calculates the tool amplitude that can break up chips and the vibration direction in which the tool is moved relative to the workpiece when vibrating the tool at that amplitude, taking into account both the shape of the tool and the shape of the workpiece. This makes it possible to prevent an increase in the machine load caused by excessively retracting the feed axis when the tool is retracted. In addition, it is possible to achieve the breaking up of chips while avoiding excessive cutting of the workpiece. As described above, the numerical control device 1 can avoid machining defects regardless of the machining shape while reducing the machine load of the machine tool due to the execution of vibration cutting. Furthermore, by being able to avoid machining defects due to excessive cutting, it is possible to eliminate the need for measures such as remachining a workpiece due to machining defects or discarding a workpiece due to machining defects.

[0106] Furthermore, the vibration waveform generating unit 13 calculates the cutting thickness, which is the thickness of the portion cut from the workpiece by vibration cutting, based on the machining shape information, and calculates the amplitude by a calculation incorporating the value of the cutting thickness. In this way, the numerical control device 1 can obtain the minimum amplitude capable of breaking up the chips by calculating the amplitude taking into account the cutting thickness in vibration cutting. By minimizing the amplitude, the numerical control device 1 can reduce the mechanical load on the machine tool 2.

[0107] Furthermore, for a tapered workpiece, the vibration waveform generating unit 13 calculates the taper angle, which is the angle of the taper with respect to the central axis of the workpiece, and calculates the amplitude by a calculation incorporating the value of the taper angle. This allows the numerical control device 1 to generate a vibration waveform that does not cause excessive cutting, whether the taper is an uphill taper or a downhill taper. The numerical control device 1 can avoid machining defects caused by excessive cutting, regardless of the machining shape.

[0108] Furthermore, the vibration waveform generating unit 13 calculates the amplitude by a calculation that incorporates the amount of movement of the tool in a direction parallel to the taper per rotation of the spindle that rotates the workpiece relative to the tool. This enables the numerical control device 1 to cut the workpiece by the amount of movement corresponding to the part to be machined, and enables machining without leaving any uncut parts while preventing unnecessary retreat of the feed axis.

[0109] Moreover, the tool information of a tool having a rounded cutting edge includes information indicating the radius of the cutting edge. By incorporating the information indicating the radius of the cutting edge into the calculation, the numerical control device 1 can calculate the amplitude required to break the chip when a tool having a rounded cutting edge is used.

[0110] The tool information also includes information indicating the angle of the cutting edge of the tool. The numerical control device 1 can calculate the angle between the rake face and the horizontal axis by incorporating the information indicating the angle of the cutting edge of the tool into the calculation. The numerical control device 1 can control the vibration cutting based on the angle between the rake face and the horizontal axis, thereby making it possible to prevent the feed axis from being excessively retracted when the tool is retracted.

[0111] The configurations shown in the above embodiments are examples of the contents of the present disclosure. The configurations of the embodiments can be combined with other known technologies. Part of the configurations of the embodiments can be omitted or modified without departing from the gist of the present disclosure. [Explanation of symbols]

[0112] 1 numerical control device, 2 machine tool, 10 program analysis unit, 11 command generation unit, 12 vibration condition setting unit, 13 vibration waveform generation unit, 21, 23, 24, 25, 26, 27, 28, 29, 36, 39 arrow, 22, 31, 35 line, 30, 32, 33, 34, 37, 38 point, 41, 42, 43 curve, 44 area, 50 control circuit, 51 input unit, 52 processor, 53 memory, 54 output unit, 55 hardware circuit, 56 processing circuit.

Claims

1. A numerical control device that controls vibration cutting in which a tool is vibrated relative to a workpiece to cut the workpiece, a vibration waveform generating unit that calculates an amplitude of the tool that can break chips generated in the vibration cutting and a vibration direction that is a direction in which the tool is moved relative to the workpiece when the tool is vibrated at the amplitude, based on tool information that indicates the shape and dimensions of the tool having a circular cutting edge, the tool information including at least information indicating the roundness of the cutting edge, and machining shape information that indicates the shape of the workpiece, and generates a vibration waveform that represents a trajectory of the vibration of the tool; The vibration waveform generating unit calculates an incomplete cutting point, which is a point on the circle of the cutting edge or on the rake face of the tool at a second time point preceding a time taken for one rotation of a spindle that rotates the workpiece relatively to the tool from a first time point at which a pull-out operation of the tool is started, and which represents a position on the machined surface of the workpiece where cutting is incomplete at the second time point, and calculates the amplitude and the vibration direction for performing the pull-out operation to move the tip position of the tool to the incomplete cutting point. A numerical control device comprising:

2. The vibration waveform generating unit calculates a cutting thickness, which is the thickness of a portion cut from the workpiece by the vibration cutting, based on the machining shape information, and calculates the amplitude by a calculation that incorporates the value of the cutting thickness.

2. The numerical control device according to claim 1 .

3. The vibration waveform generating unit calculates a taper angle, which is the angle of the taper with respect to the central axis of the workpiece having a taper, and calculates the amplitude by a calculation that incorporates the value of the taper angle.

3. The numerical control device according to claim 1 or 2.

4. The vibration waveform generating unit calculates the amplitude by a calculation that incorporates a movement amount of the tool in a direction parallel to the taper per rotation of a spindle that rotates the workpiece relatively to the tool.

4. The numerical control device according to claim 3 .

5. The tool information includes information indicating the radius of the cutting edge.

3. The numerical control device according to claim 1 or 2.

6. The tool information includes information indicating the angle of the cutting edge.

3. The numerical control device according to claim 1 or 2.

7. In vibration cutting, in which a tool is vibrated relative to a workpiece to cut the workpiece, a computer is caused to execute a step of calculating an amplitude of the tool that can break off chips generated in the vibration cutting and a vibration direction that is a direction in which the tool is moved relative to the workpiece when the tool is vibrated at the amplitude, based on tool information that indicates the shape and dimensions of the tool having a circular cutting edge, the tool information including at least information indicating the roundness of the cutting edge, and machining shape information that indicates the shape of the workpiece, and generating a vibration waveform that indicates a trajectory of the vibration of the tool, In the step, a cutting incomplete point is calculated, which is a point on the circle of the cutting edge or on the rake face of the tool at a second time point preceding a first time point at which a pull-out operation of the tool is started by a time taken for a spindle that rotates the workpiece relatively to the tool to make one rotation, and which represents a position on the machined surface of the workpiece where cutting is incomplete at the second time point, and the amplitude and the vibration direction are calculated for performing the pull-out operation to move the tip position of the tool to the cutting incomplete point. A numerical control program comprising:

8. In vibration cutting, which cuts a workpiece by vibrating a tool relative to the workpiece, the method includes a step of calculating an amplitude of the tool that can break chips generated in the vibration cutting and a vibration direction that is a direction in which the tool is moved relative to the workpiece when vibrating the tool at the amplitude, based on tool information that indicates the shape and dimensions of the tool having a circular cutting edge, the tool information including at least information indicating the roundness of the cutting edge, and machining shape information that indicates the shape of the workpiece, to generate a vibration waveform that indicates a trajectory of the tool vibration, In the step, a cutting incomplete point is calculated, which is a point on the circle of the cutting edge or on the rake face of the tool at a second time point preceding a first time point at which a pull-out operation of the tool is started by a time taken for a spindle that rotates the workpiece relatively to the tool to make one rotation, and which represents a position on the machined surface of the workpiece where cutting is incomplete at the second time point, and the amplitude and the vibration direction are calculated for performing the pull-out operation to move the tip position of the tool to the cutting incomplete point. A numerical control method comprising: