CONTROL SYSTEM

Abstract

Tax system that includes: a machine tool (2) for performing cutting work while moving a tool (25) relative to a workpiece (24); a numerical control device (1B) for controlling the machine tool (2); and a display device (4), wherein the numerical control device (1B) includes: a vibration condition input unit (10) into which a vibration condition is input, the vibration condition being intended to cause the tool (25) to vibrate with respect to the workpiece (24) along a movement path of the tool (25) with respect to the workpiece (24); and an intermittent cutting detection unit (18) for detecting, based on the vibration condition, whether cutting accompanied by vibration under the vibration condition corresponds to intermittent cutting in which the workpiece (24) is cut intermittently and fine chips are generated from the workpiece (24), and the display device (4) includes: a detection information display unit (41) for displaying a detection result from the interrupted cutting detection unit (18); a change input unit (43) into which a changeable condition is input, the changeable condition being determined as a condition from the vibration condition that is changeable; and an interrupted cutting condition calculation unit (40) for calculating a range of the variable condition under which the interrupted cutting is possible.

Description

Area

[0001] The present disclosure relates to a control system for controlling a machine tool that performs cutting work. background

[0002] A machine tool is known that performs cutting work on a workpiece by moving a tool relative to the workpiece. In such a machine tool, in order to prevent chips generated by cutting work from becoming caught on the workpiece or the tool, a method of causing the tool to vibrate with respect to the workpiece can be used to generate fine chips. Since the chips are prevented from becoming caught on the workpiece or the tool, it is possible to reduce the workload for removing chips from the workpiece or the tool. Furthermore, scratching of the workpiece by caught chips is prevented, leading to an improvement in machining quality.

[0003] Patent Literature 1 relates to a control device that moves a tool in at least two axial directions with respect to a workpiece while rotating the workpiece by rotating a spindle, and discloses that the tool is vibrated along the movement path of the tool with respect to the workpiece. The control device according to Patent Literature 1 generates a vibration command for vibrating the tool based on a position command for moving the tool with respect to the workpiece and the rotation angle of the spindle. The control device according to Patent Literature 1 also corrects the vibration command based on a position deviation obtained from the position command and a feedback value indicating the position of the tool or the workpiece.

[0004] The control device according to Patent Literature 1 does not require a table that registers specific data for vibrating the tool, such as the amount of forward movement and the amount of reverse movement of the tool, the speed of forward movement and the speed of reverse movement. The control device according to Patent Literature 1 can eliminate the trouble of creating a table corresponding to various machining conditions in cutting work. The control device according to Patent Literature 1 can cope with changes in the machining conditions of the machine tool by easily changing the command for vibrating the tool to one that corresponds to the changed machining conditions. List of citationsPatent literature

[0005] Patent literature 1: JP 2017 - 182 336 A Brief descriptionTechnical task

[0006] In the conventional technique described in Patent Literature 1, it is not determined whether the generated vibration command will cause fine chips. In the case of the control device according to the conventional technique, it is not possible to determine whether the generated vibration command can ensure the generation of fine chips unless test machining is performed, because the feedback value is required when correcting the vibration command. Therefore, the control device according to the conventional technique is problematic in that it requires time and effort to enable control for generating fine chips.

[0007] The present disclosure has been made in view of the foregoing, and an object thereof is to provide a control system capable of easily implementing control for generating fine chips in cutting work. Solution to the task

[0008] The objects described above are achieved by a control system having the features of patent claim 1. Advantageous effects of the invention

[0009] The control system according to the present disclosure can achieve the effect of easily implementing control for generating fine chips in cutting work. Short description of the drawings Fig. 1 is a diagram illustrating a control system including a numerical control device according to a first embodiment. Fig. 2 is a diagram for explaining the cutting work by a machine tool used in the Fig. 1 illustrated tax system. Fig. 3 is a graphical representation for explaining a vibration of a tool in the machine tool shown in Fig. 1 illustrated tax system. Fig. 4 is a flowchart illustrating a procedure for operating the numerical control device according to the first embodiment. Fig. 5 is a diagram for explaining the detection in an interrupted cutting detection unit provided in the numerical control device according to the first embodiment. Fig. 6 is a flowchart illustrating a procedure for processing by a vibration condition correction unit provided in the numerical control device according to the first embodiment. Fig. 7 is a diagram illustrating a control system including a numerical control device according to a second embodiment. Fig. 8 is a graph illustrating an example of dynamic rigidity information held in the numerical control apparatus according to the second embodiment. Fig. 9 is a flowchart illustrating a procedure for processing by a vibration condition correcting unit provided in the numerical control device according to the second embodiment. Fig. 10 is a diagram illustrating a control system using a numerical control device according to a third embodiment. Fig. 11 is a diagram illustrating an example of a display on a display device used in the Fig. 10 illustrated control system. Fig. 12 is a diagram illustrating a control system including a numerical control device according to a fourth embodiment. Fig. 13 is a diagram illustrating an exemplary hardware configuration provided in the numerical control device according to any one of the first to fourth embodiments. Description of embodiments

[0010] Hereinafter, a control system according to embodiments will be described in detail with reference to the drawings. First embodiment.

[0011] Fig. 1 is a diagram illustrating a control system incorporating a numerical control device according to a first embodiment. The control system includes a numerical control device 1 according to the first embodiment, a machine tool 2 that performs cutting work, and a drive unit 3 that drives the machine tool 2. The numerical control device 1 controls the machine tool 2 by executing a machining program 50. The machine tool 2 cuts a workpiece 24 while moving a cutting tool 25 relative to the workpiece 24.

[0012] The numerical control device 1 includes a vibration condition input unit 10 to which vibration conditions are input, a machining program input unit 11 to which the machining program 50 is input, an intermittent cutting determination unit 12 to determine whether intermittent cutting is being performed, a vibration condition correction unit 13 to correct the vibration conditions input to the vibration condition input unit 10, and a command value generation unit 14 to generate a command value. Interrupted cutting will be described later.

[0013] The vibration condition input unit 10 receives an input of vibration conditions for causing the tool 25 to vibrate with respect to the workpiece 24 along the movement path of the tool 25 with respect to the workpiece 24. The vibration condition input unit 10 outputs vibration condition information 51 representing the input vibration conditions to the interrupted cutting detection unit 12 and the vibration condition correction unit 13.

[0014] The machining program input unit 11 outputs the input machining program 50 to the interrupted cutting detection unit 12 and the target value generation unit 14.

[0015] The interrupted cutting determination unit 12 determines whether cutting accompanied by vibration under the vibration conditions corresponds to interrupted cutting based on the vibration conditions. Interrupted cutting is cutting in which the workpiece 24 is cut intermittently and fine chips are generated from the workpiece 24. The interrupted cutting determination unit 12 outputs determination information 52 representing the determination result to the vibration condition correction unit 13.

[0016] When the determination information 52 indicating that cutting accompanied by vibration does not correspond to intermittent cutting is input to the vibration condition correction unit 13, the vibration condition correction unit 13 finds vibration conditions under which cutting accompanied by vibration work is intermittent cutting. The vibration condition correction unit 13 corrects the vibration condition information 51 based on the result of finding the vibration conditions. In response to the vibration condition correction unit 13 correcting the vibration condition information 51, the vibration condition correction unit 13 outputs vibration condition information 53, which is the corrected vibration condition information 51, to the target value generation unit 14.

[0017] On the other hand, when the determination information 52 indicating that cutting accompanied by vibration corresponds to intermittent cutting is input to the vibration condition correction unit 13, the vibration condition correction unit 13 skips the correction of the vibration condition information 51. In response to skipping the correction of the vibration condition information 51, the vibration condition correction unit 13 outputs the vibration condition information 53, which is the uncorrected vibration condition information 51, to the target value generation unit 14.

[0018] The command value generation unit 14 generates an axis command value 54 based on the machining program 50 and the vibration condition information 53. The axis command value 54 is a command for controlling a spindle motor 22 and a servo motor 23. The command value generation unit 14 outputs the generated axis command value 54 to the drive unit 3.

[0019] The machine tool 2 includes a spindle 20, a drive shaft 21, the spindle motor 22, and the servo motor 23. The spindle 20 rotates by receiving the driving force generated by the spindle motor 22. The workpiece 24 rotates together with the spindle 20. The drive shaft 21 linearly drives the tool 25 by receiving the driving force generated by the servo motor 23.

[0020] The drive unit 3 includes a spindle servo control unit 30, which is a servo amplifier that controls the spindle motor 22, and a drive shaft servo control unit 31, which is a servo amplifier that controls the servo motor 23. The spindle servo control unit 30 outputs a spindle motor current 55 based on the axis command value 54 to the spindle motor 22. The spindle motor 22 drives the spindle 20 according to the spindle motor current 55. The drive shaft servo control unit 31 outputs a servo motor current 56 based on the axis command value 54 to the servo motor 23. The servo motor 23 drives the drive shaft 21 according to the servo motor current 56.

[0021] The machine tool 2 rotates the workpiece 24 with the drive force generated by the spindle motor 22 and moves the tool 25 with the drive force generated by the servo motor 23. The machine tool 2 cuts the workpiece 24 by rotating the workpiece 24 and moving the tool 25 according to the machining program 50.

[0022] In the first embodiment, the movement of the tool 25 with respect to the workpiece 24 refers to the relative movement of the tool 25 with respect to the workpiece 24. The machine tool 2 moves the tool 25 with respect to the workpiece 24 by moving the workpiece 24 and / or the tool 25. That is, the machine tool 2 can move the tool 25 without moving the workpiece 24, or can move the workpiece 24 without moving the tool 25. The machine tool 2 can move both the workpiece 24 and the tool 25. The machine tool 2 can include the drive shaft 21 for linearly driving the workpiece 24. The machine tool 2 can cut the workpiece 24 by rotating the tool 25. The machine tool 2 can perform cutting work with a rotating tool, such as drilling or milling.

[0023] Fig. 2 is a graphic representation for explaining the cutting work by the machine tool used in the Fig. 1. The X-axis and the Z-axis are mutually perpendicular axes. A centerline 26 of the workpiece 24 coincides with the rotational axis of the spindle 20. The direction of the Z-axis is the same as the direction of the centerline 26. The tool 25 cuts the surface of the rotating workpiece 24 while moving relative to the workpiece 24 in the ZX plane. The Fig. The dashed arrow illustrated in Figure 2 represents the path of movement of the tool 25 with respect to the workpiece 24.

[0024] The machine tool 2 causes the tool 25 to vibrate along the movement path of the tool 25. Vibrating along the movement path means a back and forth movement in a section within the movement path. In a straight section of the movement path, the tool 25 moves back and forth along the straight line. In a curved section of the movement path, the tool 25 moves back and forth along the curve. The machine tool 2 causes the tool 25 to vibrate with the drive force generated by the servo motor 23. The machine tool 2 moves the tool 25 along the movement path while vibrating the tool 25. The Fig. The double arrows illustrated in Figure 2 represent directions in which the tool 25 is set into vibration.

[0025] In the first embodiment, the vibration of the tool 25 with respect to the workpiece 24 refers to the relative vibration of the tool 25 with respect to the workpiece 24. The machine tool 2 vibrates the tool 25 relative to the workpiece 24 by vibrating the workpiece 24 and / or the tool 25. That is, the machine tool 2 can vibrate the tool 25 without vibrating the workpiece 24, or can vibrate the workpiece 24 without vibrating the tool 25. The machine tool 2 can vibrate both the workpiece 24 and the tool 25.

[0026] Fig. 3 is a graphical representation for explaining a vibration of the tool in the machine tool shown in Fig. 1 illustrated tax system. In the Fig. 3, the horizontal axis represents the angle of rotation of the spindle 20. The vertical axis represents the Z-axial position of the tool 25 on the workpiece 24. The Fig. The white arrow illustrated in Figure 3 represents the feed direction of the tool 25. The feed direction is the direction in which the tool 25 moves with respect to the workpiece 24 and is the direction of the Z-axis.

[0027] The tool 25 vibrates along the trajectory while moving in the feed direction. When the tool 25 vibrates along the trajectory and the workpiece 24 rotates, the tool 25 moves by drawing a sinusoidal trajectory on the surface of the workpiece 24. In the following description, such a trajectory is referred to as a vibration trajectory. The vibration trajectory can be determined by the Fig. 3 illustrated graphic representation. Fig. 3 shows the vibration trajectory in the case that the tool 25 vibrates 1.5 times during one revolution of the spindle 20.

[0028] The vibration trajectory is determined by the rotational speed "S" of the spindle 20, the feed rate "F" of the tool 25, the amplitude "A" of the vibration, and the angular frequency "ω" of the vibration. The rotational speed "S" is the number of revolutions of the spindle 20 per unit of time. The unit of the rotational speed "S" is, for example, "rpm." The feed rate "F" is the feed rate of the tool 25 with respect to the workpiece 24 during one revolution of the spindle 20. The unit of the feed rate "F" is, for example, "mm / rev." In the following description, the feed rate "F" can be referred to as the feed rate "F." The amplitude "A" represents the amplitude with which the tool 25 vibrates with respect to the workpiece 24. The unit of the amplitude "A" is, for example, "mm." The angular frequency "ω" is the angular frequency of vibration of the tool 25 with respect to the workpiece 24. The unit of the angular frequency "ω" is, for example, "rad / s".

[0029] As in Fig. 3, it is assumed that the angle of rotation of the spindle 20 is zero degrees at time "t(n)". The time "t(n)" is when a certain period of time "n" has elapsed from a reference time. The reference time is any specified time, for example, when cutting work on the workpiece 24 is started. The spindle 20 rotates from time "t(n)" to time "t(n+1)". A vibration trajectory 60 is a vibration trajectory representing the movement of the tool 25 from time "e(n)" to time "t(n+1)".

[0030] The rotation angle of spindle 20 returns to zero degrees at time "t(n+1)". Spindle 20 rotates from time "t(n+1)" to time "t(n+2)". A vibration trajectory 61 is a

[0031] Vibration trajectory representing the movement of the tool 25 from the time “t(n+1)” to the time “t(n+2)”.

[0032] While the tool 25 moves along the vibration trajectory 61, the tool 25 cuts the workpiece 24 when the position on the vibration trajectory 61 advances from the position on the vibration trajectory 60 in the feed direction. At this point, the position of the tool 25 at the reference time is set as the reference position, the distance between the reference position and the position on the vibration trajectory 61 is indicated by a distance "d(n+1)", and the distance between the reference position and the position on the vibration trajectory 60 is indicated by a distance "d(n)". The state where the position on the vibration trajectory 61 advances from the position on the vibration trajectory 60 in the feed direction means that "d(n+1)-d(n)", which is the difference between the distance "d(n+1)" and the distance "d(n)", is a positive value.The machine tool 2 cuts the workpiece 24 when “d(n+1)-d(n)” is a positive value.

[0033] "d(n+1)-d(n)" corresponds to the thickness of the chips generated by cutting. In the following description, the chip thickness "D" represents the thickness in the feed direction of chips generated by cutting work from the workpiece 24.

[0034] If "d(n+1)-d(n)" is a negative value, the tool 25 passes through an area in which cutting was performed when the tool 25 passed through the vibration trajectory 60. If "d(n+1)-d(n)" is a negative value, the cutting of the workpiece 24 is interrupted. Fig. 3, hatched areas represent areas where "d(n+1)-d(n)" has a negative value. Machine tool 2 performs interrupted cutting by repeating cutting where "d(n+1)-d(n)" has a positive value and interrupted cutting where "d(n+1)-d(n)" has a negative value. Machine tool 2 separates chips when "d(n+1)-d(n)" has a negative value, thereby generating fine chips.

[0035] The numerical control device 1 implements intermittent cutting by generating a phase difference between the vibration trajectory 60 and the vibration trajectory 61. Note that when the vibration trajectory 60 and the vibration trajectory 61 are in phase with each other, "d(n+1)-d(n)" is always constant. In this case, chips are not separated, and the workpiece 24 is cut continuously.

[0036] By generating fine chips, the machine tool 2 prevents chips from becoming trapped on the workpiece 24 or the tool 25. The machine tool 2 can reduce the effort required to remove chips from the workpiece 24 or the tool 25 by preventing them from becoming trapped. Furthermore, scratching of the workpiece 24 by trapped chips is prevented, leading to an improvement in the machining quality of the machine tool 2.

[0037] Next, the operation of the numerical control device 1 will be described. Fig. 4 is a flowchart illustrating a procedure for operating the numerical control device 1 according to the first embodiment.

[0038] An operator using the machine tool 2 inputs vibration conditions to the vibration condition input unit 10. Values ​​of the amplitude "A", the angular frequency "ω", the rotational speed "S", and the feed rate "F" are input to the vibration condition input unit 10 as vibration conditions. Subsequently, the numerical controller 1 acquires vibration condition data in step S1. The vibration condition data are values ​​of the amplitude "A", the angular frequency "ω", the rotational speed "S", and the feed rate "F". The vibration condition input unit 10 outputs the vibration condition information 51 including the input vibration condition data to the interrupted cutting determination unit 12 and the vibration condition correction unit 13.It should be noted that in the first embodiment, the data of vibration conditions acquired by the numerical control device 1 only includes at least one of the amplitude “A”, angular frequency “ω”, rotational speed “S”, and feed amount. must include "F". Vibration condition data may also include other values.

[0039] In step S2, the numerical control device 1 determines whether cutting accompanied by vibration under the vibration conditions corresponds to intermittent cutting. The intermittent cutting determination unit 12 determines whether intermittent cutting is performed based on the vibration condition information 51.

[0040] Here, processing by the interrupted cutting detection unit 12 is described in more detail. The chip thickness "D" is represented by the following formula (1). [Formula 1] D=F+Asin(ωt)−Asin(ωt−ω1)

[0041] F+Asin(ωt) represents the vibration trajectory 61. Asin(ωt-ω1) represents the vibration trajectory 60. Asin(ωt) and Asin(ωt-ω1) are functions that repeat increase and decrease at a constant amplitude and a constant period. According to formula (1), the chip thickness "D" is calculated by subtracting the vibration trajectory 60 from the vibration trajectory 61. "t" represents any specified time. "ω1" represents the phase difference between the vibration trajectory 60 and the vibration trajectory 61. In this way, the interrupted cutting detection unit 12 calculates the chip thickness "D" using formula (1) including the functions representing the vibration trajectories 60 and 61 of the tool 25.

[0042] The phase difference “ω1” is represented by the following formula (2). [Formula 2] ω1=60ωS

[0043] The interrupted cutting determination unit 12 calculates the chip thickness "D" based on the vibration condition information 51. If the minimum value in the calculation result of the chip thickness "D" is less than zero, the interrupted cutting determination unit 12 determines that chip separation is occurring, that is, interrupted cutting is being performed. If the minimum value in the calculation result of the chip thickness "D" is greater than or equal to zero, the interrupted cutting determination unit 12 determines that chip separation is not occurring, that is, interrupted cutting is not being performed. In this way, if the calculation result of the thickness is less than zero, the interrupted cutting determination unit 12 determines that cutting accompanied by vibration corresponds to interrupted cutting.

[0044] Here, a method for finding the minimum value of chip thickness "D" is described. The following formula (3) is obtained based on formula (1) and formulas for converting sums to products in trigonometry. [Formula 3] D=F+2Acos(2ωt−ω12)sin(ω12)

[0045] In formula (3), the value of cos{(2ωt-ω1) / 2} is "1" or "-1" when the chip thickness "D" is the minimum value. Therefore, the intermittent cutting detection unit 12 can determine whether intermittent cutting is being performed depending on whether the phase difference "ω1" satisfying formula (4) or (5) below exists. Formula (4) represents a case where cos{(2ωt-ω1) / 2}=1. Formula (5) represents a case where cos{(2ωt-ω1) / 2}=-1. [Formula 4] D=F+2Asin(ω12)<0sin(ω12)<−F2A [Formula 5] D=F−2Asin(ω12)<0sin(ω12)>F2A

[0046] Substituting formula (2) into formula (4) yields the following formula (6). Substituting formula (2) into formula (5) yields the following formula (7). [Formula 6] sin(30ωS)<−F2A [Formula 7] sin(30ωS)>F2A

[0047] Whether formula (6) is satisfied or whether formula (7) is satisfied or not can be determined, for example, using the geometric solution described below. Fig. 5 is a diagram for explaining the detection in the interrupted cutting detection unit provided in the numerical control device according to the first embodiment.

[0048] In the Fig. The circle illustrated in Figure 5 is a unit circle, that is, a set of points (cos(30ω / S), sin(30ω / S)). Since the angle "30ω / S" satisfying formula (7) is a first solution, the range "R1" is the angular range where the first solution exists. Since the angle "30ω / S" satisfying formula (6) is a second solution, the range "R2" is the angular range where the second solution exists. Note that the amplitude "A" and the feed amount "F" are generally greater than or equal to zero; therefore, it is not necessary to consider a case where the amplitude "A" or the feed amount "F" is a negative value.

[0049] The interrupted cutting determination unit 12 determines whether cutting accompanied by vibration under the vibration condition information 51 corresponds to interrupted cutting based on formulas (6) and (7). The interrupted cutting determination unit 12 outputs the determination information 52 indicating the determination result to the vibration condition correction unit 13.

[0050] According to formula (1), the interrupted cutting detection unit 12 calculates the chip thickness "D" by calculating the addition or subtraction of a function and a constant. The function is a function that repeats increase and decrease at a constant amplitude and a constant period. The constant amplitude detection condition includes the vibration amplitude "A." The constant period detection condition includes the vibration angular frequency "ω." The constant detection condition includes the feed rate "F."

[0051] According to formula (1), when calculating the chip thickness “D”, the vibration is represented as a sine wave.

[0052] The interrupted cutting detection unit 12 can represent the vibration as a cosine wave to calculate the chip thickness "D." The interrupted cutting detection unit 12 can convert a trigonometric function into a complex number using Euler's formula and calculate the chip thickness "D" through a calculation using the complex number.

[0053] In response to a determination that cutting accompanied by vibration corresponds to uninterrupted cutting (step S2: No), the numerical controller 1 proceeds to step S3. In step S3, the numerical controller 1 corrects the vibration conditions. After inputting the determination information 52 indicating that cutting accompanied by vibration corresponds to uninterrupted cutting to the vibration condition correction unit 13, the vibration condition correction unit 13 corrects the vibration condition information 51. In this case, the vibration condition correction unit 13 outputs the vibration condition information 53, which is the corrected vibration condition information 51, to the command value generation unit 14. Thereafter, the numerical controller 1 proceeds to step S4, which will be described later.

[0054] On the other hand, in response to a determination that cutting accompanied by vibration corresponds to intermittent cutting (step S2: Yes), the numerical control device 1 proceeds to step S4. After inputting the determination information 52 indicating that cutting accompanied by vibration corresponds to intermittent cutting to the vibration condition correction unit 13, the vibration condition correction unit 13 skips the correction of the vibration condition information 51. In this case, the vibration condition correction unit 13 outputs the vibration condition information 53, which is the uncorrected vibration condition information 51, to the target value generation unit 14.

[0055] At this point, processing by the unit 13 for correcting vibration conditions is described in more detail. Fig. 6 is a flowchart illustrating a procedure for processing by the vibration condition correcting unit provided in the numerical control device according to the first embodiment.

[0056] In step S11, the vibration condition correcting unit 13 determines whether the amplitude value "A" and the feed amount value "F," which are values ​​included in the vibration condition information 51, satisfy F / 2A > 1. Formulas (6) and (7) have no real number solution when F / 2A > 1; therefore, the vibration condition correcting unit 13 makes such a determination when correcting the vibration conditions.

[0057] In response to determining that F / 2A > 1 is satisfied (step S11: Yes), the vibration condition correcting unit 13 proceeds to step S12. On the other hand, in response to determining that F / 2A > 1 is not satisfied (step S11: No), the vibration condition correcting unit 13 proceeds to step S13, which will be described later.

[0058] In step S12, the vibration condition correcting unit 13 changes the vibration conditions so that F / 2A < 1 is satisfied. The vibration condition correcting unit 13 increases the value of the amplitude "A" to a value that can satisfy F / 2A < 1. Alternatively, the vibration condition correcting unit 13 reduces the value of the feed amount "F" to a value that can satisfy F / 2A < 1. In step S12, the change in the vibration conditions is a change that increases the value of the amplitude "A" or a change that reduces the value of the feed amount "F". The vibration condition correcting unit 13 can change the amplitude "A" and the feed amount "F". After changing the amplitude "A" and / or the feed amount "F", the vibration condition correcting unit 13 proceeds to step S13.

[0059] In step S13, the vibration condition correcting unit 13 determines whether the amplitude value "A", the angular frequency value "ω", the rotational speed value "S", and the feed rate value "F" satisfy formula (6) or formula (7). In response to determining that neither formula (6) nor formula (7) is satisfied (step S13: No), the vibration condition correcting unit 13 proceeds to step S14. On the other hand, in response to determining that formula (6) and / or formula (7) is satisfied (step S13: Yes), the vibration condition correcting unit 13 proceeds to step S17, which will be described later.

[0060] In step S14, the vibration condition correction unit 13 determines whether the value of the angular frequency "ω" and the value of the rotational speed "S" satisfy 30ω / S≥0. In response to determining that 30ω / S≥0 is satisfied (step S14: Yes), the vibration condition correction unit 13 changes the vibration conditions in step S15 so that the following formula (8) is satisfied. The vibration condition correction unit 13 changes the angular frequency "ω" and / or the rotational speed "S" so that formula (8) is satisfied. [Formula 8] sin(30ωS)=1

[0061] In response to determining that 30ω / S ≥ 0 is not satisfied (step S14: No), the vibration condition correction unit 13 changes the vibration conditions in step S16 so that the following formula (9) is satisfied. The vibration condition correction unit 13 changes the angular frequency "ω" and / or the rotational speed "S" so that formula (9) is satisfied. [Formula 9] sin(30ωS)=−1

[0062] In steps S15 and S16, the change in the vibration conditions is a change in the angular frequency "ω" and / or the rotational speed "S." After changing the angular frequency "ω" and / or the rotational speed "S" in step S15 or step S16, the vibration condition correction unit 13 proceeds to step S17.

[0063] The vibration condition correction unit 13 corrects the vibration condition information 51 so that the calculation result of the chip thickness "D" becomes less than zero by changing the vibration conditions in steps S11 to S16 as described above. In step S17, the vibration condition correction unit 13 outputs the vibration condition information 53, which is the corrected vibration condition information 51, to the target value generation unit 14. Then, the vibration condition correction unit 13 completes the processing performed by the Fig. 6 illustrated process.

[0064] In step S4, which is Fig. 4, the numerical control device 1 generates the axis command value 54. The command value generation unit 14 receives an input of the machining program 50 and the vibration condition information 53. The command value generation unit 14 generates the axis command value 54 based on the machining program 50 and the vibration condition information 53.

[0065] The axis command value 54 includes a command for controlling the spindle motor 22 and a command for controlling the servo motor 23. The command for controlling the spindle motor 22 is an angle command or a speed command. The command for controlling the servo motor 23 is a position command or a speed command. The command value generation unit 14 outputs the generated axis command value 54 to the drive unit 3. The axis command value 54 output based on the vibration condition information 53 only needs to include a command for controlling the spindle motor 22 and / or a command for controlling the servo motor 23.

[0066] The numerical control device 1 outputs the axis command value 54 to terminate the operation caused by the Fig. 4 illustrated process.

[0067] In the numerical control device 1, the rotational speed "S" and the feed rate "F" are not limited to those detected by inputting them to the vibration condition input unit 10. The rotational speed "S" and the feed rate "F" may be included in the machining conditions described in the machining program 50. In this case, the interrupted cutting detection unit 12 may detect the rotational speed "S" and / or the feed rate Read "F" from the machining program 50. That is, the interrupted cutting determination unit 12 determines whether interrupted cutting is performed based on a machining condition, which is the rotational speed "S" and / or the feed rate "F", and the input vibration conditions.

[0068] According to the first embodiment, the numerical controller 1 receives input of vibration conditions and determines, based on the vibration conditions, whether cutting accompanied by vibration under the vibration conditions corresponds to intermittent cutting. The numerical controller 1 does not need to prepare a table in advance in which specific data for causing the tool 25 to vibrate is registered. The numerical controller 1 can eliminate the trouble of preparing a table corresponding to various machining conditions. The numerical controller 1 can easily cope with a change in machining conditions by changing the axis command value 54 to an axis command value corresponding to the changed machining conditions.Furthermore, the numerical control device 1 can determine whether interrupted cutting is possible without using a feedback value acquired during machining. No test machining is required to determine whether interrupted cutting is possible. Thus, the numerical control device 1 can achieve the effect of easily implementing control for generating fine chips in cutting work.

[0069] The first embodiment assumes that the mechanism that transmits the driving force generated by the servo motor 23 to the tool 25 does not experience a decrease in gain when the tool 25 is vibrated. That is, in the first embodiment, the numerical control device 1 determines whether intermittent cutting is being performed by considering the mechanism from the servo motor 23 to the tool 25 as a rigid body. In a second embodiment to be described next, it is determined whether intermittent cutting is being performed by considering a decrease in gain in the mechanism from the servo motor 23 to the tool 25. Second embodiment.

[0070] Fig. 7 is a diagram illustrating a control system including a numerical control device according to the second embodiment. In the second embodiment, the same components as in the first embodiment are denoted by the same reference numerals, and configuration differences from the first embodiment will be mainly described. The control system includes a numerical control device 1A according to the second embodiment, the machine tool 2 that performs cutting work, and the drive unit 3 that drives the machine tool 2.

[0071] The numerical control device 1A includes a dynamic rigidity obtaining unit 15 that obtains dynamic rigidity information 57. The numerical control device 1A also includes the vibration condition input unit 10, the machining program input unit 11, the command value generation unit 14, an interrupted cutting detection unit 16, and a vibration condition correction unit 17. Processing by the interrupted cutting detection unit 16 is different from the processing by the interrupted cutting detection unit 12 according to the first embodiment. Processing by the vibration condition correction unit 17 is different from the processing by the vibration condition correction unit 13 according to the first embodiment.

[0072] The dynamic stiffness information 57 is information representing the dynamic stiffness of a mechanism including the servo motor 23, that is, a motor for driving the tool 25, and the tool 25. The dynamic stiffness of the mechanism including the servo motor 23 and the tool 25 is measured in advance, and the dynamic stiffness information 57 is stored in the dynamic stiffness storage unit 15.

[0073] The dynamic stiffness holding unit 15 stores a transfer function representing the dynamic stiffness of the drive shaft. The transfer function "FRF1(s)" is obtained using a relational formula of FRF1(s)=Xt(s) / Xs(s). "Xs(s)" represents the position of the servo motor 23. "Xt(s)" represents the position of the tool 25. "s" is the Laplace operator. The dynamic stiffness of the drive shaft can be represented by a discrete frequency transfer function. For example, the servo motor current 56 is applied to the servo motor 23 to sweep excite the servo motor 23, and the position "Xs(s)" and the position "Xt(s)" at that time are sampled. By comparing the position "Xs(s)" and the position "Xt(s)" in the frequency domain, a discrete frequency transfer function is obtained.

[0074] The dynamic stiffness information 57 includes at least one gain "G(f)" in the transfer function "FRF1(s)" associated with each frequency. "f" represents the vibration frequency represented by the axis setpoint 54. The dynamic stiffness information 57 is read out to the interrupted cutting detection unit 16 and the vibration condition correction unit 17. The gain "G(f)" is the ratio between the actual vibration amplitude of the tool 25 and the vibration amplitude represented by the axis setpoint 54. The value of the gain "G(f)" varies depending on the frequency "f".

[0075] Fig. 8 is a graph illustrating an example of dynamic rigidity information held in the numerical control device according to the second embodiment. The dynamic rigidity information 57 is a table in which frequency "f" data and gain "G(f)" data are stored. The first column of the table stores values ​​of frequency "f" in 1 Hz increments from 1 Hz to 100 Hz. The second column of the table stores values ​​of gain "G(f)" corresponding to the respective values ​​of frequency "f". The gain "G(f)" is read out from the dynamic rigidity holding unit 15 in the form of such a table.

[0076] Here, processing by the intermittent cutting determination unit 16 will be described in detail. The intermittent cutting determination unit 16 determines whether intermittent cutting is performed based on the vibration condition information 51 and the dynamic stiffness information 57.

[0077] The chip thickness “D” is represented by the following formula (10). [Formula 10] D=F+G(ƒ)Asin(ωt)−G(ƒ)Asin(ωt−ω1)

[0078] F+G(f)Asin(ωt) represents the vibration trajectory 61. G(f)Asin(ωt-ω1) represents the vibration trajectory 60. According to formula (10), the chip thickness "D" is calculated by subtracting the vibration trajectory 60 from the vibration trajectory 61. In formula (10), each of the vibration trajectory 61 and the vibration trajectory 60 is multiplied by the gain "G(f)". As a result, the interrupted cutting detection unit 16 can accurately calculate the vibration of the tool 25 caused by the drive of the servo motor 23 based on the axis command value 54.

[0079] The phase difference “ω1”, which is the phase difference between the vibration trajectory 60 and the vibration trajectory 61, is represented by the following formula (11). [Formula 11] ω1=60ωS

[0080] The interrupted cutting determination unit 16 calculates the chip thickness "D" based on the vibration condition information 51 and the dynamic stiffness information 57. If the minimum value of the chip thickness "D" is less than zero, the interrupted cutting determination unit 16 determines that chip separation is occurring, that is, interrupted cutting is being performed. If the minimum value of the chip thickness "D" is greater than or equal to zero, the interrupted cutting determination unit 16 determines that chip separation is not occurring, that is, interrupted cutting is not being performed.

[0081] Here, a method for finding the minimum value of chip thickness "D" is described. The following formula (12) is obtained based on formula (10) and formulas for converting sums to products in trigonometry. [Formula 12] D=F+2G(ƒ)Acos(2ωt−ω12)sin(ω12)

[0082] In formula (12), the value of cos{(2ωt-ω1) / 2} is "1" or "-1" when the chip thickness "D" is the minimum value. Therefore, the intermittent cutting determination unit 16 can determine whether intermittent cutting is being performed depending on whether the phase difference "ω1" exists, which corresponds to formula (13) or (14) below. Formula (13) represents a case where cos{(2ωt-ω1) / 2}=1. Formula (14) represents a case where cos{(2wt-w1) / 2}=-1. [Formula 13] D=F+2G(ƒ)Asin(ω12)<0 sin(ω12)<−F2G(f)A [Formula 14] D=F−2G(f)Asin(ω12)<0sin(ω12)>F2G(f)A

[0083] In the second embodiment, the interrupted cutting detection unit 16 detects, from the dynamic rigidity information 57 for the tool 25 vibrating at the angular frequency "ω", the value of the gain "G(f)" corresponding to the angular frequency "ω". The frequency "f" and the angular frequency "ω" are related by the following formula (15). [Formula 15] f=ω2π

[0084] By substituting formula (11) and formula (15) into formula (13), the following formula (16) is obtained. By substituting formula (11) and formula (15) into formula (14), the following formula (17) is obtained. Note that the intermittent cutting detection unit 16 calculates the gain “G(f)” corresponding to the frequency “f” by referring to the table shown in Fig. 8 is illustrated. [Formula 16] G(ω2π)sin(30ωS)<−F2A [Formula 17] G(ω2π)sin(30ωS)>F2A

[0085] The interrupted cutting determination unit 16 determines whether cutting accompanied by vibration corresponds to interrupted cutting under the vibration condition information 51. The interrupted cutting determination unit 16 outputs the determination information 52 indicating the determination result to the vibration condition correction unit 17.

[0086] According to formula (10), the interrupted cutting detection unit 16 calculates the chip thickness "D" by calculating the addition or subtraction of a function and a constant. The function is a function that repeats increase and decrease at a constant amplitude and a constant period. The constant amplitude detection condition includes the vibration amplitude "A" and the gain "G(f)." The constant period detection condition includes the vibration angular frequency "ω." The constant detection condition includes the feed rate "F."

[0087] Next, processing by the vibration condition correction unit 17 will be described in detail. After the determination information 52 indicating that cutting accompanied by vibration corresponds to uninterrupted cutting is input to the vibration condition correction unit 17, the vibration condition correction unit 17 corrects the vibration condition information 51. In this case, the vibration condition correction unit 17 outputs the vibration condition information 53, which is the corrected vibration condition information 51, to the target value generation unit 14.

[0088] On the other hand, after inputting the determination information 52 indicating that cutting accompanied by vibration corresponds to intermittent cutting to the vibration condition correcting unit 17, the vibration condition correcting unit 17 skips the correction of the vibration condition information 51. In this case, the vibration condition correcting unit 17 outputs the vibration condition information 53, which is the uncorrected vibration condition information 51, to the target value generating unit 14.

[0089] Fig. 9 is a flowchart illustrating a procedure for processing by the vibration condition correcting unit provided in the numerical control device according to the second embodiment. In step S21, the vibration condition correcting unit 17 determines whether the value of the amplitude "A" and the value of the feed amount "F", which are values ​​included in the vibration condition information 51, satisfy F / 2A>1. Formulas (16) and (17) have no real number solution when F / 2A>1; therefore, the vibration condition correcting unit 17 makes such a determination when correcting the vibration conditions.

[0090] In response to determining that F / 2A > 1 is satisfied (step S21: Yes), the vibration condition correcting unit 17 proceeds to step S22. On the other hand, in response to determining that F / 2A > 1 is not satisfied (step S21: No), the vibration condition correcting unit 17 proceeds to step S23, which will be described later.

[0091] In step S22, the vibration condition correction unit 17 changes the vibration conditions so that F / 2A < 1 is satisfied. The vibration condition correction unit 17 increases the value of the amplitude "A" to a value that can satisfy F / 2A < 1. Alternatively, the vibration condition correction unit 17 reduces the value of the feed amount "F" to a value that can satisfy F / 2A < 1. In step S22, the change in the vibration conditions consists of increasing the value of the amplitude "A" or reducing the value of the feed amount "F". The vibration condition correction unit 17 can change the amplitude "A" and the feed amount "F". After changing the amplitude "A" and / or the feed amount "F", the vibration condition correction unit 17 proceeds to step S23.

[0092] In step S23, the vibration condition correcting unit 17 determines whether the amplitude value "A", the angular frequency value "ω", the rotational speed value "S", and the feed amount value "F" satisfy formula (16) or formula (17). In response to determining that neither formula (16) nor formula (17) is satisfied (step S23: No), the vibration condition correcting unit 17 proceeds to step S24. On the other hand, in response to determining that formula (16) and / or formula (17) is satisfied (step S23: Yes), the vibration condition correcting unit 17 proceeds to step S25, which will be described later.

[0093] In step S24, the vibration condition correction unit 17 changes the vibration conditions so that the following formula (18) is satisfied. The vibration condition correction unit 17 searches for the value of the angular frequency "ω" and the value of the rotational speed "S" that satisfy formula (18). Subsequently, the vibration condition correction unit 17 changes the angular frequency "ω" and / or the rotational speed "S" so that formula (18) is satisfied. In step S24, the change in the vibration conditions is a change in the angular frequency "ω" and / or the rotational speed "S". [Formula 18] G(ω2π)sin(30ωS)<1

[0094] Since in the second embodiment, the value of the gain “G(ω / 2π)” is determined with reference to the Fig. 8, the gain "G(ω / 2π)" is a nonlinear and discontinuous element. Therefore, the angular frequency "ω" and the rotational speed "S" cannot be resolved using differentiation. Subsequently, the vibration condition correction unit 17 changes the angular frequency "ω" and / or the rotational speed "S" using a search method such as the simplex algorithm. After changing the angular frequency "ω" and / or the rotational speed "S", the vibration condition correction unit 17 proceeds to step S25.

[0095] The vibration condition correction unit 17 corrects the vibration condition information 51 so that the calculation result of the chip thickness "D" becomes less than zero by changing the vibration conditions in steps S21 to S24 as described above. In step S25, the vibration condition correction unit 17 outputs the vibration condition information 53, which is the corrected vibration condition information 51, to the target value generation unit 14. Then, the vibration condition correction unit 17 completes the processing performed by the Fig. The process illustrated in Figure 9 is shown.

[0096] The vibration condition correction unit 17 corrects the vibration condition information 51 so that the calculation result of the chip thickness "D" becomes less than zero by taking into account the decrease in the gain "G(f)" due to the influence of the dynamic rigidity in the mechanism from the servo motor 23 to the tool 25. The vibration condition correction unit 17 can correct the vibration conditions to enable intermittent cutting by taking into account the decrease in the gain "G(f)".

[0097] According to the second embodiment, the numerical control device 1A includes the dynamic rigidity obtaining unit 15 that obtains the dynamic rigidity information 57. The intermittent cutting determining unit 16 can determine whether intermittent cutting is being performed by considering the decrease in the gain "G(f)" due to the influence of the dynamic rigidity in the mechanism from the servo motor 23 to the tool 25. The numerical control device 1A can accurately determine whether intermittent cutting is being performed even if the mechanism from the servo motor 23 to the tool 25 is not a rigid body and the gain "G(f)" decreases. Third embodiment.

[0098] In the first embodiment, the numerical control device 1 corrects the vibration conditions in the vibration condition correcting unit 13 based on the determination information 52. A third embodiment describes a case where the range of vibration conditions under which intermittent cutting is possible is displayed on a display device, and the operator selects vibration conditions to correct the vibration conditions.

[0099] Fig. 10 is a diagram illustrating a control system including a numerical control device according to the third embodiment. In the third embodiment, the same components as those in the first or second embodiment are denoted by the same reference numerals, and configuration differences from the first or second embodiment will be mainly described. The control system includes a numerical control device 1B according to the third embodiment, the machine tool 2 that performs cutting work, the drive unit 3 that drives the machine tool 2, and a display device 4.

[0100] The numerical control device 1B includes the vibration condition input unit 10, the machining program input unit 11, an interrupted cutting detection unit 18, and a target value generation unit 19. Processing by the interrupted cutting detection unit 18 is different from both the processing by the interrupted cutting detection unit 12 according to the first embodiment and the processing by the interrupted cutting detection unit 16 according to the second embodiment. Processing by the target value generation unit 19 is different from the processing by the target value generation unit 14 according to the first or second embodiment.

[0101] The display device 4 includes an intermittent cutting condition calculation unit 40 that calculates the range of changeable conditions under which intermittent cutting is possible, a determination information display unit 41 that displays a determination result from the intermittent cutting determination unit 18, an intermittent cutting condition display unit 42 that displays information indicating the range calculated by the intermittent cutting condition calculation unit 40, a change input unit 43 into which changeable conditions are input, and a correction condition input unit 44 into which corrected conditions are input. Changeable conditions are described below.

[0102] After determining that cutting accompanied by vibration corresponds to non-interrupted cutting, the intermittent cutting determination unit 18 outputs the determination information 52 indicating that cutting accompanied by vibration corresponds to non-interrupted cutting to the determination information display unit 41. The intermittent cutting determination unit 18 outputs the vibration condition information 51 to the set value generation unit 19. The determination information display unit 41 displays a message indicating that intermittent cutting cannot be performed under the vibration conditions input to the vibration condition input unit 10.

[0103] After checking the display of the detection information display unit 41, the operator inputs a changeable condition from among the input vibration conditions to the change input unit 43. The operator determines a condition from among the amplitude "A", angular frequency "ω", rotational speed "S", and feed rate "F" that he or she considers changeable by inputting it to the change input unit 43. In the third embodiment, a changeable condition is a condition determined by the operator as a changeable condition from among the vibration conditions.

[0104] Here, processing by the display device 4 will be described on the assumption that the changeable condition input to the change input unit 43 is the amplitude "A". The change input unit 43 outputs change condition information 70 representing the changeable condition input by the operator to the intermittent cutting condition calculation unit 40. The intermittent cutting condition calculation unit 40 calculates the range of solutions of the amplitude "A" that satisfy formulas (6) and (7). In this example, where the changeable condition is the amplitude "A", the following formula (19) representing the range of solutions of the amplitude "A" is obtained based on formula (6). Furthermore, the following formula (20) representing the range of solutions of the amplitude "A" is obtained based on formula (7).It should be noted that the amplitude “A” cannot be a negative value and thus the range of solutions is limited to A>0. [Formula 19] A>F2G(ω2π)sin(30ωS)where A>0 [Formula 20] A>F2sin(30ωS)where A>0

[0105] The interrupted cutting condition calculation unit 40 outputs cutting condition information 71 representing the range of amplitudes "A" satisfying formula (19) or (20) to the interrupted cutting condition display unit 42. Based on the cutting condition information 71, the interrupted cutting condition display unit 42 displays the range of solutions of amplitude "A" that enable interrupted cutting. Since, in this example, the range of solutions to be displayed is the range related to a variable, the interrupted cutting condition display unit 42 displays the range of solutions using specific numerical values.

[0106] After checking the display of the interrupted cutting condition display unit 42, the operator determines the value of the amplitude "A" from the displayed range of solutions and inputs the determined value to the correction condition input unit 44. Thus, the value of the corrected amplitude "A" is input to the correction condition input unit 44. The correction condition input unit 44 outputs the vibration condition information 72, which includes the value of the corrected amplitude "A," to the command value generation unit 19. The vibration condition information 72 represents the corrected vibration conditions. The command value generation unit 19 generates the axis command value 54 based on the machining program 50, the vibration condition information 51, and the vibration condition information 72.

[0107] The above description is an example of a case where one variable condition is input to the change input unit 43. There may be two variable conditions input to the change input unit 43. Here, a case will be described where the variable conditions input to the change input unit 43 are the rotational speed "S" and the amplitude "A."

[0108] The interrupted cutting condition calculation unit 40 calculates the range of rotational speeds "S" and the range of amplitudes "A" that satisfy formula (19) or (20). The interrupted cutting condition calculation unit 40 outputs the cutting condition information 71 representing the range of rotational speeds "S" and the range of amplitudes "A" to the interrupted cutting condition display unit 42.

[0109] The interrupted cutting condition display unit 42 displays the range of solutions of the rotational speed "S" and the range of solutions of the amplitude "A" that enable interrupted cutting based on the cutting condition information 71. In this example, since the range of solutions to be displayed is the range related to two variables, the interrupted cutting condition display unit 42 displays the range of solutions with a two-dimensional plane.

[0110] Fig. 11 is a diagram illustrating an example of a display on the display device used in the Fig. 10 illustrated control system. Fig. 11 shows an example of a screen displayed on the intermittent cutting condition display unit 42 to show an example of how the range related to two changeable conditions is displayed. The screen includes a display area 80 that displays the range of solutions related to the two variables. The horizontal axis in the display area 80 represents the rotational speed "S," which is the first variable. The vertical axis in the display area 80 represents the amplitude "A," which is the second variable. Hatched areas in the display area 80 represent the range of rotational speeds "S" and amplitudes "A" in which intermittent cutting is possible. White areas in the display area 80 represent the range of rotational speeds "S" and amplitudes "A" in which intermittent cutting is not possible.

[0111] In addition, the screen includes a field 81 for displaying the content of the vibration conditions before correction and a field 82 for displaying the content of the vibration conditions after correction. Field 81 displays the content of the vibration condition information 51 input to the vibration condition input unit 10. Field 82 displays the content of the vibration condition information 72 input to the correction condition input unit 44 for the amplitude "A" and the rotational speed "S", which are the corrected vibration conditions.

[0112] The field 82 also shows the content of the vibration condition information 51 for the angular frequency “ω” and the feed amount “F”, which are the uncorrected vibration conditions.

[0113] First, the intermittent cutting condition display unit 42 displays, in the display area 80, a mark 83 representing each value of the rotational speed "S" and the amplitude "A" included in the vibration condition information 51. After checking the display area 80, the operator inputs specified values ​​of the rotational speed "S" and the amplitude "A" from the range of rotational speeds "S" and the amplitudes "A" at which intermittent cutting is possible to the correction condition input unit 44.

[0114] For example, the pointer in the display area 80 is moved by operating the pointing device and the pointing device is clicked, whereby the values ​​of the rotational speed "S" and the amplitude "A" are input into the correction condition input unit 44. The interrupted cutting condition display unit 42 displays a mark 84 in the display area 80 representing each value of the rotational speed "S" and the amplitude "A" input into the correction condition input unit 44. It should be noted that each value of the rotational speed "S" and the amplitude "A" can be manually input into the correction condition input unit 44. The correction of the vibration conditions in the Fig. The example illustrated in Figure 11 is a correction that reduces the amplitude “A” from “0.15” to “0.1” and increases the speed “S” from “650” to “900”.

[0115] The correction condition input unit 44 outputs the vibration condition information 72, including the corrected speed value "S" and the corrected amplitude value "A," to the setpoint generation unit 19. Thus, when two variable conditions are input to the change input unit 43, the display device 4 can display the range related to the two variable conditions in an easily understandable manner.

[0116] According to the third embodiment, the control system can show the operator whether intermittent cutting is possible by displaying the determination information 52 on the display device 4. The display device 4 calculates the range of changeable conditions under which intermittent cutting is possible and displays information representing the calculated range. If intermittent cutting is not possible under the vibration conditions input to the vibration condition input unit 10, the control system can show the operator the vibration conditions under which intermittent cutting is possible. The operator can cause the machine tool 2 to perform intermittent cutting without searching for vibration conditions by trial and error. The operator can make preparations for machining efficiently. Fourth embodiment.

[0117] Fig. 12 is a diagram illustrating a control system including a numerical control device according to a fourth embodiment. In the fourth embodiment, the control system includes the same components as in the third embodiment and the dynamic rigidity providing unit 15 according to the second embodiment. In the fourth embodiment, the same components as in the first to third embodiments are denoted by the same reference numerals, and configuration differences from the first to third embodiments will be mainly described.

[0118] A numerical control device 1C according to the fourth embodiment includes the vibration condition input unit 10, the machining program input unit 11, the dynamic rigidity readiness unit 15, the interrupted cutting detection unit 18, and the command value generation unit 19. Processing by the interrupted cutting detection unit 18 is different from that by the interrupted cutting detection unit 18 according to the third embodiment. Processing by the interrupted cutting condition calculation unit 40 is different from that by the interrupted cutting condition calculation unit 40 according to the third embodiment.

[0119] The intermittent cutting determination unit 18 determines whether intermittent cutting is being performed based on the vibration condition information 51 and the dynamic rigidity information 57. Processing by the intermittent cutting determination unit 18 is similar to the processing by the intermittent cutting determination unit 16 according to the second embodiment. When formula (16) or (17) is satisfied, the intermittent cutting determination unit 18 determines that cutting accompanied by vibration corresponds to intermittent cutting.

[0120] After determining that cutting accompanied by vibration corresponds to non-interrupted cutting, the intermittent cutting determination unit 18 outputs the determination information 52 indicating that cutting accompanied by vibration corresponds to non-interrupted cutting to the determination information display unit 41. The intermittent cutting determination unit 18 outputs the vibration condition information 51 to the set value generation unit 19. The determination information display unit 41 displays a message indicating that intermittent cutting cannot be performed under the vibration conditions input to the vibration condition input unit 10.

[0121] As in the third embodiment, after checking the display of the detection information display unit 41, the operator inputs a condition from among the input vibration conditions that is changeable to the change input unit 43. The operator determines a condition from among the conditions of the amplitude "A", the angular frequency "ω", the rotational speed "S", and the feed amount "F" that he considers changeable by inputting it to the change input unit 43.

[0122] Here, processing by the display device 4 will be described assuming that the changeable condition input to the change input unit 43 is the amplitude "A". The change input unit 43 outputs the change condition information 70 representing the changeable condition input by the operator to the interrupted cutting condition calculation unit 40.

[0123] The interrupted cutting condition calculation unit 40 calculates the range of solutions of amplitude "A" satisfying formula (16) or (17), which is obtained based on the vibration condition information 51 and the dynamic stiffness information 57. In this example, where the variable condition is amplitude "A", formula (21) below, which represents the range of solutions of amplitude "A", is obtained based on formula (16). In addition, formula (22) below, which represents the range of solutions of amplitude "A", is obtained based on formula (17). Note that amplitude "A" cannot be a negative value, and thus the range of solutions is limited to A>0. [Formula 21] A>−F2G(ω2π)sin(30ωS)where A>0 [Formula 22] A>−F2G(ω2π)sin(30ωS)where A>0

[0124] The interrupted cutting condition calculation unit 40 outputs the cutting condition information 71 representing the range of amplitudes "A" satisfying formula (21) or (22) to the interrupted cutting condition display unit 42. Based on the cutting condition information 71, the interrupted cutting condition display unit 42 displays the range of solutions of amplitude "A" that enable interrupted cutting. As in the third embodiment, the interrupted cutting condition display unit 42 can also display the range of solutions that enable interrupted cutting for two changeable conditions.

[0125] According to the fourth embodiment, the numerical control device 1C can obtain similar effects to those in the third embodiment. As in the case of the second embodiment, the numerical control device 1C can accurately determine whether intermittent cutting is being performed even when the mechanism from the servo motor 23 to the tool 25 is not a rigid body and the gain decreases. If intermittent cutting is not possible under the vibration conditions input to the vibration condition input unit 10, the control system can show the operator the vibration conditions under which intermittent cutting is possible.

[0126] Next, a hardware configuration for the numerical control devices 1, 1A, 1B and 1C according to the first to fourth embodiments will be described.

[0127] Fig. 13 is a diagram illustrating an exemplary hardware configuration provided in the numerical control device according to any one of the first to fourth embodiments. Fig. 13 illustrates a hardware configuration in which the functions of the numerical control device 1, 1A, 1B or 1C are implemented using hardware that executes a program.

[0128] The numerical control device 1, 1A, 1B, or 1C is a computer system in which a control program, which is a program for controlling the machine tool 2 according to the machining program 50, is installed. The numerical control device 1, 1A, 1B, or 1C includes a processor 91 that executes various processes, a memory 92 that is a built-in memory, an interface circuit 93 for inputting information to and outputting information from the numerical control device 1, 1A, 1B, or 1C, a storage device 94 that stores information, and an input device 95 into which information is input.

[0129] The processor 91 is a central processing unit (CPU). The processor 91 may be a processing device, a computing device, a microprocessor, a microcomputer, or a digital signal processor (DSP). The memory 92 is a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM, registered trademark).

[0130] The storage device 94 is a hard disk drive (HDD) or a solid state drive (SSD). A control program for causing the computer to function as the numerical control device 1, 1A, 1B, or 1C is stored on the storage device 94. The processor 91 reads a program stored on the storage device 94 into the memory 92 and executes the program. The input device 95 is an instrument such as a keyboard or a pointing device. The interface circuit 93 communicates with the drive unit 3 and the display device 4.

[0131] The control program may be recorded on a storage medium readable by the computer system. The numerical control device 1, 1A, 1B, or 1C may store the control program recorded on the storage medium on the memory 92. The storage medium may be a portable storage medium such as a floppy disk or a flash memory such as a semiconductor memory. The control program may be installed on the computer system from another computer or a server device via a communication network.

[0132] The functions of the interrupted cutting detection unit 12, 16, or 18, the vibration condition correction unit 13 or 17, and the setpoint generation unit 14 or 19 in the numerical control device 1, 1A, 1B, or 1C are implemented by a combination of the processor 91 and software. These functions may be implemented by a combination of the processor 91 and firmware, or by a combination of the processor 91, software, and firmware. The software or firmware is described in the form of a program and stored in the storage device 94.

[0133] The function of the dynamic stiffness storage unit 15 in the numerical control device 1A or 1C is implemented by using the storage device 94. The functions of the vibration condition input unit 10 and the machining program input unit 11 in the numerical control device 1, 1A, 1B, or 1C are implemented by using the input device 95.

[0134] The function of the display device 4 is achieved by using a hardware configuration similar to the hardware configuration shown in Fig. 13. The display device 4 includes the components shown in Fig.13, and a display that displays information. The function of the intermittent cutting condition calculation unit 40 is implemented by a combination of the processor 91 and software. The function of the intermittent cutting condition calculation unit 40 may be implemented by a combination of the processor 91 and firmware, or by a combination of the processor 91, software, and firmware. The functions of the change input unit 43 and the correction condition input unit 44 are implemented by using the input device 95. The functions of the determination information display unit 41 and the intermittent cutting condition display unit 42 are implemented by using a display.

[0135] The configurations described in the above-mentioned embodiments provide examples of the content of the present disclosure. The configurations of the embodiments can be combined with other well-known techniques. The configurations of the embodiments can be combined with each other as needed. Some of the configurations of the embodiments may be omitted or changed without departing from the gist of the present invention. List of reference symbols

[0136] 1, 1A, 1B, 1C numerical control device; 2 machine tool; 3 drive unit; 4 display device; 10 vibration condition input unit; 11 machining program input unit; 12, 16, 18 interrupted cutting detection unit; 13, 17 vibration condition correction unit; 14, 19 setpoint generation unit; 15 dynamic rigidity holding unit; 20 spindle; 21 drive shaft; 22 spindle motor; 23 servo motor; 24 workpiece; 25 tool; 26 center line; 30 spindle servo control unit; 31 drive shaft servo control unit; 40 interrupted cutting condition calculation unit; 41 detection information display unit; 42 interrupted cutting condition display unit; 43 change input unit; 44 correction condition input unit; 50 machining program; 51, 53, 72 Vibration condition information; 52 Detection information;54 Axis command value; 55 Spindle motor current; 56 Servo motor current; 57 Dynamic stiffness information; 60, 61 Vibration trajectory; 70 Change condition information; 71 Cutting condition information; 80 Display area; 81, 82 Field; 83, 84 Marker; 91 Processor; 92 Memory; 93 Interface circuit; 94 Storage device; 95 Input device.;

Claims

A control system comprising: a machine tool (2) for performing cutting work while moving a tool (25) relative to a workpiece (24); a numerical control device (1B) for controlling the machine tool (2); and a display device (4), wherein the numerical control device (1B) includes: a vibration condition input unit (10) into which a vibration condition is input, the vibration condition being for causing the tool (25) to vibrate with respect to the workpiece (24) along a movement path of the tool (25) with respect to the workpiece (24);andan intermittent cutting determination unit (18) for determining, based on the vibration condition, whether cutting accompanied by vibration under the vibration condition corresponds to intermittent cutting in which the workpiece (24) is cut intermittently and fine chips are generated from the workpiece (24).The display device (4) includes:a determination information display unit (41) for displaying a determination result from the intermittent cutting determination unit (18);a change input unit (43) into which a changeable condition is input, the changeable condition being determined as a condition from the vibration condition that is changeable; andan intermittent cutting condition calculation unit (40) for calculating a range of the changeable condition under which the intermittent cutting is possible. The control system of claim 1, wherein the vibration condition includes at least one of an amplitude of the vibration, a rotational speed of a spindle rotating the workpiece (24), a feed rate of the tool (25), or an angular frequency of the vibration. A control system according to claim 1, wherein the interrupted cutting determination unit (12) determines whether the interrupted cutting is performed based on the vibration condition and a machining condition described in a machining program for controlling the machine tool (2). A control system according to claim 3, wherein the machining condition includes at least one of a rotational speed of a spindle rotating the workpiece (24) or a feed rate of the tool (25). A control system according to any one of claims 1 to 4, wherein the interrupted cutting determining unit (12) calculates, based on the vibration condition, a thickness, in a feed direction of the tool (25), of chips generated from the workpiece (24) by the cutting work, and determines that the vibration-accompanied cutting corresponds to the interrupted cutting when a calculation result of the thickness is less than zero. A control system according to claim 5, wherein the interrupted cutting detection unit (12) calculates the thickness by a calculation using a function that repeats increase and decrease at a constant amplitude and a constant period, a condition for detecting the constant amplitude includes an amplitude of the vibration, and a condition for detecting the constant period includes an angular frequency of the vibration. A control system according to claim 6, wherein the interrupted cutting detection unit (12) calculates the thickness by calculation including addition or subtraction of the function and a constant, and a condition for detecting the constant includes a feed rate of the tool (25). A control system according to any one of claims 1 to 7, wherein the numerical control device (1A; 1C) includes a dynamic rigidity holding unit (15) for holding dynamic rigidity information representing the dynamic rigidity of a mechanism including a motor that drives the tool (25) and the tool (25), and the intermittent cutting determination unit (16; 18) determines whether the intermittent cutting is performed based on the vibration condition and the dynamic rigidity information. A control system according to claim 8, wherein the dynamic stiffness information includes a gain which is a ratio between an amplitude of actual vibration of the tool (25) and an amplitude of vibration represented by a command for controlling the motor, and a value of the gain varies depending on a frequency of the vibration represented by the command. A control system according to claim 9, wherein the interrupted cutting determination unit (16) calculates, based on the vibration condition and the gain, a thickness, in a feed direction, of the tool (25) of chips generated from the workpiece (24) by the cutting work, and determines that the vibration-accompanied cutting corresponds to the interrupted cutting when a calculation result of the thickness is less than zero. A control system according to claim 10, wherein the interrupted cutting detection unit (16) calculates the thickness using a function that repeats increase and decrease at a constant amplitude and a constant period, a condition for detecting the constant amplitude includes an amplitude of the vibration and the gain, and a condition for detecting the constant period includes an angular frequency of the vibration. A control system according to any one of claims 1 to 11, wherein the numerical control device (1; 1A) includes a vibration condition correcting unit (13; 17) for correcting the vibration condition input to the vibration condition input unit (10), and the vibration condition correcting unit (13; 17) corrects, based on a determination result indicating that the cutting accompanied by vibration does not correspond to the intermittent cutting, at least one of an amplitude of the vibration, a rotational speed of a spindle that rotates the workpiece (24), a feed rate of the tool (25), or an angular frequency of the vibration in the vibration condition. A control system according to claim 12, wherein the vibration condition correcting unit (13) corrects the vibration condition so that a calculation result of a thickness, in a feed direction of the tool (25), of chips generated from the workpiece (24) by the cutting work becomes smaller than zero. A control system according to any one of claims 1 to 13, wherein the display device (4) includes an intermittent cutting condition display unit (42) for displaying information representing the area calculated by the intermittent cutting condition calculation unit (40).

Images