Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23B—TURNING; BORING
  • B23B1/00—Methods for turning or working essentially requiring the use of turning-machines; Use of auxiliary equipment in connection with such methods
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B19/00—Program-control systems
  • G05B19/02—Program-control systems electric
  • G05B19/18—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form
  • G05B19/4093—Numerical control [NC], i.e. automatically operating machines, in particular machine tools, e.g. in a manufacturing environment, so as to execute positioning, movement or co-ordinated operations by means of program data in numerical form characterised by part programming, e.g. entry of geometrical information as taken from a technical drawing, combining this with machining and material information to obtain control information, named part program, for the NC machine

Definitions

• This disclosure relates to a numerical control device, a numerical control program, and a numerical control method for controlling a machine tool.
• Vibration cutting is known, in which a tool is vibrated relative to the workpiece to cut it and thereby break up chips.
• the tool In vibration cutting, the tool is moved forward in the machining direction, which is the direction in which the machining proceeds, and then moved backward in the opposite direction to the machining direction, are alternately repeated.
• Vibration cutting makes it possible to cut the workpiece while breaking up chips by creating sections in which cutting of the workpiece by the tool is interrupted. Breaking up chips into short pieces prevents a decrease in machining accuracy due to chips becoming tangled around the workpiece or tool. Breaking up chips into short pieces also reduces damage to the workpiece caused by chips coming into contact with the workpiece.
• Patent Document 1 discloses a machine tool control device that calculates the amplitude required to break chips during vibration cutting and determines the vibration direction of the tool based on the calculated amplitude, thereby reducing the mechanical load on the machine tool.
• the control device disclosed in Patent Document 1 increases or decreases the vibration component for each feed axis, thereby changing the vibration direction to a direction different from the machining direction.
• the amplitude calculation method disclosed in Patent Document 1 assumes the use of a tool with a sharp cutting edge, and is not compatible with tools with rounded cutting edges that are commonly used in cutting processes. Specifically, when a tool with a rounded cutting edge is used, the amplitude calculation method disclosed in Patent Document 1 calculates the amplitude based on, for example, the tip of the rounded cutting edge, which can result in the calculated amplitude being greater than the amplitude necessary to break up the chips. If vibration cutting is performed based on this calculated excessive amplitude, the feed axis will be forced to retract excessively when the tool is retracted, leading to an increase in the machine load.
• the taper of the workpiece being cut can be either an uphill taper, which widens away from the center of rotation of the spindle as it progresses in the machining direction, or a downhill taper, which narrows toward the center of rotation of the spindle as it progresses in the machining direction.
• the taper is a downhill taper, determining the amplitude and vibration direction using the technology disclosed in Patent Document 1 results in excessive cutting away from the desired machining shape. Therefore, the technology disclosed in Patent Document 1 poses the problem of being unable to avoid machining defects caused by excessive cutting away, depending on the machining shape.
• the present disclosure has been made in consideration of the above circumstances, and aims to provide a numerical control device that reduces the mechanical load on machine tools when performing vibration cutting, while making it possible to avoid machining defects regardless of the machining shape.
• the numerical control device disclosed herein is a numerical control device that controls vibration cutting, which cuts a workpiece by vibrating a tool relative to the workpiece.
• the numerical control device disclosed herein includes a vibration waveform generation unit that calculates the tool amplitude that can break up chips generated during vibration cutting and the vibration direction, which is the direction in which the tool moves relative to the workpiece when vibrating the tool at the amplitude, based on tool information that indicates the shape and dimensions of the tool and machining shape information that indicates the shape of the workpiece, and generates a vibration waveform that represents the trajectory of the tool vibration.
• the numerical control device disclosed herein 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.
• FIG. 1 is a diagram showing an example of the configuration of a numerical control device according to an embodiment
• 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
• FIG. 1 is a first diagram for explaining the position of a tool in vibration cutting by a machine tool controlled by a numerical control device according to an embodiment.
• 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.
• 5A and 5B are diagrams for explaining amplitudes calculated by a vibration waveform generating unit of the numerical control device according to the embodiment.
• FIGS. 10A and 10B are diagrams for explaining a case where vibration cutting of an uphill taper is controlled by the numerical control device according to the embodiment.
• 10A and 10B are diagrams for explaining a case where vibration cutting of a downward tapered shape is controlled by the numerical control device according to the embodiment.
• 5A and 5B are diagrams for explaining a vibration direction calculated by a vibration waveform generating unit of the numerical control device according to the embodiment.
• FIG. 10 is a first diagram for explaining a pulling-out operation controlled by the numerical control device according to the embodiment.
• FIG. 10 is a second diagram for explaining the extraction operation controlled by the numerical control device according to the embodiment.
• FIG. 10 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.
• 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.
• the machining program includes information indicating the feed rate of the tool relative to the workpiece, the rotational speed of the spindle, the rotation direction of the spindle, machining shape information, tool information, etc.
• Machining shape information is information that indicates the machining shape, which is the shape of the workpiece.
• Tool information is information that indicates the shape and dimensions of the tool.
• the program analysis unit 10 analyzes the machining program and generates the information necessary to generate operation commands.
• the information necessary to generate operation commands includes, for example, information on the movement path for moving the tool relative to the workpiece, or information on the method of interpolating the movement path.
• the method of interpolating the movement path includes linear interpolation or circular interpolation, etc.
• the program analysis unit 10 outputs the information necessary to generate operation commands 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 that described here, and some of the information described here may be omitted.
• the program analysis unit 10 also outputs the machining
• the machining program is, for example, a program consisting of character strings in EIA (Electronic Industries Alliance)/ISO (International Organization for Standardization) format.
• the machining program may be a program called an interactive program that includes information on the workpiece shape, machining shape, and machining dimensions.
• the program analysis unit 10 may output machining shape information calculated from the interactive machining program to the vibration waveform generation unit 13.
• the command generation unit 11 generates operation commands based on information input to the command generation unit 11.
• the command generation unit 11 outputs the generated operation commands to the machine tool 2.
• the vibration condition setting unit 12 sets the vibration conditions for vibration cutting and outputs vibration condition information to the vibration waveform generating unit 13.
• the vibration conditions include the vibration frequency and vibration amplitude.
• the vibration condition setting unit 12 outputs vibration condition information including the set values for 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 also include information on the shape of the vibration waveform.
• the vibration amplitude may be simply referred to as the amplitude.
• 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 on 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 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 on the machine tool 2. If the feed rate is low, the vibration amplitude will be small 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.
• the vibration waveform generation unit 13 generates a vibration waveform that represents the trajectory of the tool vibration during vibration cutting. Based on the tool information and machining shape information, the vibration waveform generation unit 13 calculates the tool amplitude that will enable chips generated during vibration cutting to be broken up, and the vibration direction that is the direction in which the tool moves relative to the workpiece when vibrating the tool at that amplitude, and generates a vibration waveform. The vibration waveform generation unit 13 outputs information indicative of the vibration waveform to the command generation unit 11.
• the command generation unit 11 reflects the vibration waveform generated by the vibration waveform generation unit 13 in the operation command for vibration cutting. In other words, the command generation unit 11 generates an operation command to move the tool along a path on which the vibration waveform generated by the vibration waveform generation unit 13 is superimposed.
• the vibration waveform generator 13 determines a vibration waveform based on the tool information and vibration condition information, thereby determining the tool movement path that minimizes the amount of tool movement during the tool extraction operation. Furthermore, the vibration waveform generated by the vibration waveform generator 13 is a vibration waveform that leaves no uncut portion of the workpiece and enables chips to be broken.
• 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.
• the vertical axis represents the rotation angle of the spindle.
• the horizontal axis represents the position of the tool in the machining direction.
• the numerical control device 1 moves the tool by a fixed feed amount for each rotation of the spindle, and vibrates the tool.
• Curve 42 represents the position of the tool during one spindle rotation 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 spindle rotation 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 spindle rotation 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 generator 13 generates vibration waveforms represented by curves 41, 42, and 43.
• the hatched area 44 represents an idle area.
• An idle area is an area where cutting is interrupted when the tool temporarily separates from the workpiece, i.e., an area where the tool idles.
• the tool passes through an area that was machined in the previous machining operation, and this area becomes an idle area.
• the tool passes through an area that was machined in the current machining operation, and this area becomes an idle area.
• Chips that have been generated up until the time the tool reaches the idle area are broken up in the idle area.
• the vibration waveform generator 13 generates a vibration waveform that creates such an idle area. In this way, the vibration waveform generator 13 generates a vibration waveform that leaves no uncut material on the workpiece and enables chips to be broken up.
• vibration conditions are set by the vibration condition setting unit 12, and that 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 this. If information such as vibration frequency and vibration amplitude is included in the machining program, this 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 rotational speed of the spindle.
• the method of setting vibration condition information is arbitrary.
• the tool information includes information indicating the tool length and information indicating the tool diameter.
• the tool information for a tool with a rounded cutting edge includes information indicating the radius of the cutting edge.
• the tool information also includes information indicating the amount of wear on the tool.
• the tool information included in the machining program is input to the vibration waveform generator 13.
• tool information that has been set in advance in the numerical control device 1 may also be input to the vibration waveform generator 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 amount of wear on a tool changes depending on the length of time the tool is in use.
• the information indicating the amount of wear included in the tool information is updated depending on the length of time the tool is in use.
• the tool information may also include information indicating the amount of wear measured using a measurement function.
• the method of setting the tool information is arbitrary.
• the vibration waveform generator 13 calculates amplitude.
• the workpiece on which vibration cutting is performed is a tapered workpiece.
• the coordinate system used as the reference for tool operation is an orthogonal machine coordinate system of the X, Y, and Z axes.
• the machine tool 2 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 orientation of the taper. For this reason, in the embodiment, there are no particular limitations on the direction in which the tool is withdrawn when vibration cutting of a taper.
• the tool is withdrawn in 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.
• 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 tapered workpieces, the vibration waveform generating unit 13 calculates the taper angle, which is the angle of the taper relative 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 through calculations that incorporate the cutting thickness value, taper angle value, and tool information.
• FIG. 3 is a first diagram for explaining the position of the tool during vibration cutting by a machine tool 2 controlled by a numerical control device 1 according to an embodiment.
• FIG. 4 is a second diagram for explaining the position of the tool during vibration cutting by a machine tool 2 controlled by a numerical control device 1 according to an embodiment.
• T,” “W,” and “h” shown in FIGS. 3 and 4 represent the tool, workpiece, and cutting thickness, respectively.
• Arrow 21 shown in FIG. 3 represents the machining direction. In FIG. 4, the machining direction is assumed to be the same direction as the direction indicated by arrow 21 in FIG. 3.
• Straight line 22 represents the surface of the workpiece before vibration cutting. Hereinafter, this surface will be referred to as the machined surface.
• "R” shown in FIG. 4 represents the radius of the cutting edge.
• ⁇ shown in FIG. 4 represents the taper angle.
• Arrow 23 shown in FIG. 4 represents the amplitude calculated by the vibration waveform generating unit 13.
• the up-down direction in each of FIGS. 3 and 4 is the X-axis direction, and the left-right direction in each of FIGS. 3 and 4 is the Z-axis direction.
• the X-axis is the vertical axis that is perpendicular to the horizontal direction
• the Z-axis is the horizontal axis that is in the horizontal direction.
• the Z-axis is an axis parallel to the central axis of the workpiece.
• the taper angle is an angle based on the Z-axis.
• the vibration waveform generating unit 13 calculates the cutting thickness based on the movement path and machining shape generated in accordance with the machining program.
• the method of calculating the cutting thickness by the vibration waveform generating unit 13 is not limited to a calculation method based on the movement path and machining shape, and may be any method.
• the numerical control device 1 can reduce the amount of movement of the tool from the workpiece by incorporating the value of the cutting thickness into its calculations of the amplitude and vibration direction. Furthermore, by incorporating the value of the cutting thickness into its calculations of the amplitude and vibration direction, the numerical control device 1 can calculate the minimum amount of movement necessary to completely separate the chip from the workpiece. Note that if the amplitude is smaller than the calculated cutting thickness, some of the workpiece may remain uncut. If the amplitude is larger than the calculated cutting thickness, the amplitude in vibration cutting will be larger than the amplitude necessary to separate the chip. In this case, for example, the feed axis may be moved back too far when the tool is retracted, resulting in excessive mechanical load on the machine tool 2.
• the tool information incorporated into the calculation of amplitude and vibration direction is information representing the shape and dimensions of the cutting edge.
• Information representing the shape and dimensions of the cutting edge is, for example, information indicating the radius of the cutting edge.
• the tool information incorporated into the calculation of amplitude and vibration direction only needs to include information representing the shape and dimensions of the cutting edge.
• the vibration waveform generator 13 can calculate the amplitude and vibration direction based on the information representing the shape and dimensions of the cutting edge, even if the cutting edge of the tool is not rounded.
• the numerical control device 1 can calculate the amplitude required to break chips regardless of the shape of the cutting edge.
• the numerical control device 1 can calculate the amplitude required to break chips when a tool with a rounded cutting edge is used.
• FIGs 3 and 4 show two figures representing the portion of the tool that includes the cutting edge.
• one of the two figures, shown forward in the machining direction represents the position of the tool at the first time point, which is the present.
• the other of the two figures represents the position of the tool at a second time point, which is the time it takes for the spindle to rotate once from the first time point.
• 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 withdrawn from the first time point.
• the figure representing the position of the tool at the second time point is shown by a dashed line.
• the uncut portion In vibration cutting, after the tool is withdrawn, the uncut portion must be cut during one rotation.
• the position of the uncut portion can be calculated based on the shape and dimensions of the cutting edge, as well as the cut thickness.
• the numerical control device 1 moves the tool in a direction perpendicular to the workpiece's machining surface after the withdrawal operation to cut a portion equivalent to the cut thickness.
• the tool is moved in a direction perpendicular to the workpiece's machining surface, taking into account the shape and dimensions of the cutting edge.
• the amplitude indicated by arrow 23 in Figure 4 is the amplitude in the tool withdrawal direction during vibration cutting.
• the taper angle can be determined from the machining direction.
• the vibration waveform generation unit 13 can calculate the taper angle based on the start and end points of the tool in each of the X-axis and Z-axis directions. The direction from the start point to the end point is the machining direction.
• the vibration waveform generation unit 13 calculates the taper angle based on the tool movement amount and machining direction in each of the X-axis and Z-axis directions, and can distinguish between an uphill taper and a downhill taper from the taper angle calculation result. 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.
• the taper of the workpiece shown in Figures 3 and 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.
• 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 during vibration cutting and the amount of feed axis movement during one rotation of the spindle.
• the arrow 24 shown in FIG. 5 represents the amount of feed axis movement.
• the amount of feed axis movement is specified, for example, based on information included in the machining program. Alternatively, if 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.
• the vector representing the amplitude, which is the amount of tool pull-out, and the pull-out direction of the tool is called the pull-out vector.
• Arrow 23 in Figures 4 and 5 represents the amplitude in the pull-out direction. That is, arrow 23 represents the pull-out vector.
• arrow 25 represents this movement amount. This movement amount is the movement amount in the direction of the taper angle, i.e., the movement amount in the direction parallel to the taper.
• the vibration waveform generator 13 calculates the amplitude and vibration direction in vibration cutting by a calculation that incorporates 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.
• the amount of movement represented by the pull-out vector is a combination of the amount of movement in the X-axis direction and the amount of movement in the Z-axis direction.
• the vibration waveform generator 13 decomposes the amount of movement represented by the pull-out vector into the amount of movement in the X-axis direction and the amount of movement in the Z-axis direction.
• the combination of feed axes to achieve the amount of movement 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 is arbitrary.
• 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 equation (3). Note that in equation (3), when “ ⁇ " is greater than or equal to 0 degrees and less than 90 degrees, the taper is an uphill taper. When “ ⁇ " is greater than -90 degrees and less than 0 degrees, the taper is a downhill taper.
• the vibration waveform generator 13 calculates the amplitude in each direction of the multiple feed axes through calculations that incorporate the taper angle value.
• FIG. 6 is a diagram illustrating a case where vibration cutting of an uphill taper is controlled by a numerical control device 1 according to an embodiment.
• FIG. 7 is a diagram illustrating a case where vibration cutting of a downhill taper is controlled by a numerical control device 1 according to an embodiment.
• Arrow 27 shown in FIGS. 6 and 7 represents the amount of movement in the Z-axis direction.
• Arrow 28 represents the amount of movement in the X-axis direction.
• the pulling direction calculated by the vibration waveform generating unit 13 is switched depending on 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 equations (1) to (3).
• Figure 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.
• " ⁇ " shown in Figure 8 represents the angle representing the vibration direction.
• Arrow 29 shown in Figure 8 represents the amount of movement of the tool in the XZ plane.
• " ⁇ " represents the angle between arrows 27 and 29.
• FIG. 9 is the first diagram illustrating the pulling-out 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 also holds in FIGS. 3 to 8.
• " ⁇ " in FIG. 9 represents the clearance angle of the tool. The clearance angle is intended to avoid contact between the tool and the workpiece, for example.
• " ⁇ " 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 referred to as the angle of the corner portion of the tool.
• the angle of the cutting edge of the tool will be referred to as the corner angle.
• Point 30 in FIG. 9 represents the incomplete cutting point, which will be described below.
• the tool information may also include information indicating the corner angle of the tool.
• Figure 9 shows a diagram representing the position of the tool at a second point in time, which is the time it takes for the spindle to rotate once from the first point in time.
• the angle representing the vibration direction can be calculated using equation (4).
• the incomplete cutting point which represents the position on the tapered machining surface where cutting is incomplete, is a point on the circle representing the cutting edge at the second point in time. In vibration cutting, the tool is withdrawn to this incomplete cutting point, which allows the tool to be pulled out with minimal amplitude, without leaving any uncut material, and to break up the chips.
• FIG. 10 is a second diagram illustrating 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.
• Figure 11 is the first diagram for explaining how the incomplete cutting point is calculated by the vibration waveform generating unit 13 of the numerical control device 1 according to the embodiment.
• the tool's rake face is the surface of the tool that comes into contact with the workpiece.
• the angle between the rake face and the horizontal axis can be calculated from the tool's clearance angle and corner angle, as described below. If information indicating the tool's corner angle is included in the tool information, the vibration waveform generator 13 can calculate the angle between the rake face and the horizontal axis by referencing the information indicating the corner angle, making it possible, for example, to prevent the feed axis from being retracted excessively when the tool is retracted.
• the center of the circle representing the cutting edge at the second point in time is defined as "O," the origin of the XZ plane.
• 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.
• the cutting face is represented by a tangent to the circle representing the cutting edge.
• Point 33 shown in Figure 11 represents the point of contact between the cutting face and the circle representing the cutting edge.
• Equation (5) can be changed to the following equation (6), which is a linear function on the XZ plane.
• the rake face is inclined relative 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.
• equation (7) By substituting equation (7) into equation (8), we obtain the following equation (9).
• the coordinate "b” of the tangent point is calculated using equation (9).
• the coordinate "a” of the tangent point is calculated. This determines the coordinates of the tangent point (a, b).
• the linear equation representing the rake face can be determined from equation (6).
• the following equation (10) is a linear equation representing the rake face.
• "b" is a positive value.
• FIG. 12 is a second diagram illustrating a method for calculating the incomplete cutting point by the vibration waveform generating unit 13 of the numerical control device 1 according to the embodiment.
• an equation representing the tapered machining surface is found.
• Line 35 shown in FIG. 12 represents the tapered surface after machining by vibration cutting.
• Straight line 35 is a tangent to the circle representing the cutting edge.
• equation (12) can be derived.
• Equation (12) is a linear equation representing straight line 35.
• FIG. 13 is a diagram for explaining vibration cutting based on the incomplete cutting point calculated by the vibration waveform generating unit 13 of the numerical control device 1 according to the embodiment.
• Point 37 shown in FIG. 13 represents the tool tip position at a first time point.
• Point 38 shown in FIG. 13 represents the tool tip position at a second time point.
• Arrow 39 shown in FIG. 13 represents the amount of tool movement from point 37, which is the tool tip position at the first time point, to point 30, which is the uncut point.
• arrow 39 represents the amplitude of the tool in the tool pull-out direction during vibration cutting.
• Arrow 36 shown in FIG. 13 represents the amount of tool movement from point 38, which is the tool tip position at the second time point, to point 30, which is the uncut point.
• " ⁇ " represents the angle between arrow 24, which represents the feed axis movement amount "mv,” and arrow 39, which represents the tool movement amount. In other words, " ⁇ ” represents the angle of the vibration direction relative to the cutting direction.
• Point 38 which is the tip position of the tool at the second time point, is a point on a circle with radius R and also on line 35.
• Line 35 represents the tapered surface after machining by vibration cutting. The angle between this surface and the horizontal axis is " ⁇ ".
• the coordinates of point 38 are expressed by the following equation (15).
• ⁇ is expressed by the following equation (18). This determines " ⁇ ", the angle of the vibration direction relative to the machining direction.
• Figure 14 is a flowchart showing an example of the operating procedure of the numerical control device 1 according to the embodiment.
• step S1 the program analysis unit 10 analyzes the machining program. By analyzing the machining program, the program analysis unit 10 generates information necessary for generating operation commands. In addition, the program analysis unit 10 outputs machining shape information and tool information to the vibration waveform generation unit 13.
• step S2 the vibration waveform generation unit 13 generates a vibration waveform. Based on the machining shape information and tool information input to the vibration waveform generation unit 13, the vibration waveform generation unit 13 calculates the tool amplitude that enables chips generated during vibration cutting to be broken up, and the tool vibration direction when the tool is vibrated at that amplitude. The vibration waveform generation unit 13 generates a vibration waveform by calculating the amplitude and vibration direction.
• step S3 the command generation unit 11 generates an operation command based on the information input to the command generation unit 11.
• the command generation unit 11 receives information necessary for generating the operation command, which was generated by analyzing the machining program in step S1.
• the command generation unit 11 also receives information indicating the vibration waveform generated in step S2.
• the command generation 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 generation unit 11 generates an operation command for moving the tool along a path on which the vibration waveform is superimposed.
• step S4 the command generator 11 outputs the operation command generated in step S3 to the machine tool 2.
• the numerical control device 1 then completes the operation according to the procedure shown in FIG. 14.
• 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 it may be a dedicated circuit.
• FIG 15 is a diagram showing an example configuration of the control circuit 50 according to an embodiment.
• the control circuit 50 comprises 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 it to the processor 52.
• the output unit 54 is an interface circuit that sends data from the processor 52 or memory 53 to outside the control circuit 50.
• 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 memory 53.
• the processor 52 reads and executes the numerical control program stored in memory 53, thereby realizing each function of the numerical control device 1.
• the control circuit 50 is equipped with memory 53 for storing the numerical control program that will result in the processing of the numerical control device 1 being executed.
• This numerical control program can also be said to cause the computer to execute the procedures and methods of the numerical control device 1.
• the memory 53 is also used as temporary memory when the processor 52 executes various processes.
• Processor 52 is a CPU (Central Processing Unit). Processor 52 may also be a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor).
• Memory 53 may be, for example, non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), magnetic disk, flexible disk, optical disk, compact disk, minidisc, or DVD (Digital Versatile Disc).
• Figure 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 memory 53, but the functions of the numerical control device 1 may also be realized by a dedicated hardware circuit.
• Figure 16 is a diagram showing an example configuration of a dedicated hardware circuit 55 according to an embodiment.
• 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 combination of these.
• the numerical control device 1 may be implemented by the processing circuit 56 on a function-by-function basis, or all of the functions of the numerical control device 1 may be implemented by the processing circuit 56.
• the numerical control device 1 may also be implemented by combining the control circuit 50 and the hardware circuit 55.
• the numerical control program according to the embodiment may be provided by being stored on a recording medium such as a CD (Compact Disc)-ROM or DVD-ROM.
• the numerical control program according to the embodiment may also be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network such as the Internet.
• the numerical control program according to the embodiment may also be provided or distributed via a network such as the Internet.
• the numerical control device 1 is equipped with a vibration waveform generation unit 13 that calculates the tool amplitude that enables chip breaking during vibration cutting and the vibration direction in which the tool moves relative to the workpiece when vibrating at that amplitude, based on tool information indicating the tool shape and tool dimensions and machining shape information indicating the shape of the workpiece, and generates a vibration waveform that represents the trajectory of the tool vibration.
• the numerical control device 1 takes into account both the tool shape and the workpiece shape to calculate the tool amplitude that enables chip breaking and the vibration direction in which the tool moves relative to the workpiece when vibrating at that amplitude.
• the numerical control device 1 can reduce the machine load on the machine tool caused by vibration cutting and avoid machining defects regardless of the machining shape. Furthermore, by being able to avoid machining defects caused by excessive cutting, it is possible to eliminate the need for measures such as remachining the workpiece due to machining defects or discarding the workpiece due to machining defects.
• the vibration waveform generator 13 also 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 through a calculation that incorporates the value of the cutting thickness.
• the numerical control device 1 can calculate the amplitude taking into account the cutting thickness in vibration cutting, thereby determining the minimum amplitude that is capable of breaking up the chips. By minimizing the amplitude, the numerical control device 1 can reduce the mechanical load on the machine tool 2.
• the vibration waveform generating unit 13 calculates the taper angle, which is the angle of the taper relative to the central axis of the workpiece, and calculates the amplitude through a calculation that incorporates 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 or downhill taper. The numerical control device 1 can avoid machining defects caused by excessive cutting, regardless of the machining shape.
• the vibration waveform generator 13 calculates the amplitude by a calculation that incorporates the amount of tool movement 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 portion to be machined, preventing unnecessary retraction of the feed axis and enabling machining without leaving any uncut portions.
• the tool information for a tool with a rounded cutting edge includes information indicating the radius of the cutting edge.
• the numerical control device 1 can calculate the amplitude required to break chips when a tool with a rounded cutting edge is used.
• the tool information also includes information indicating the angle of the cutting edge of the tool.
• the numerical control device 1 is able to calculate the angle between the rake face and the horizontal axis.
• the numerical control device 1 can prevent the feed axis from being retracted excessively when the tool is retracted.

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• 2024
  • 2024-03-18 JP JP2024543994A patent/JP7651074B1/ja active Active
  • 2024-03-18 WO PCT/JP2024/010532 patent/WO2025196886A1/ja active Pending

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