JP2019069490A - Machine tool, machining method, and machining program - Google Patents

Abstract

To provide a machine tool capable of more surely suppressing regenerated chattering vibrations.SOLUTION: A machine tool includes: a main shaft which rotates a workpiece or a tool; a sensor which detects a vibration frequency of the main shaft or the tool; a vibration detection section which detects regenerated chattering vibrations generated in the machine tool on the basis of the vibration frequency; and an adjustment section which adjusts the number of rotation of the main shaft. When the regenerated chattering vibrations are detected by the vibration detection section, the adjustment section adjusts the number of rotation of the main shaft from the number of rotation "r0" to be a present set value to the number of rotation "r1" in accordance with a prescribed calculation expression. When the regenerated chattering vibrations are detected after the adjustment, whether the number of rotation is increased or decreased is changed according to whether or not the number of rotation exceeds a stable range A. While the regenerated chattering vibrations are detected, the number of rotation of the main shaft is adjusted by a prescribed value from the number of rotation "r1". Adjustment amount of the number of rotation is made smaller than the prescribed value on the basis of the satisfaction of a prescribed condition indicating that the number of rotation of the main shaft may reach the number of rotation "r0".SELECTED DRAWING: Figure 5

Description

  The present disclosure relates to a technique for suppressing regenerative chatter vibration that occurs in a machine tool.

  When machining a workpiece with a machine tool, the cutting edge of the tool may minutely vibrate. Such vibration is called chatter vibration. If chatter vibration occurs, the processing accuracy of the workpiece is reduced.

  Chatter vibration includes forced chatter vibration and regenerative chatter vibration. Forced chatter vibration is vibration generated by intermittent cutting and occurs when the vibration frequency of the tool becomes equal to the natural frequency of the tool. Regeneration chatter vibration is vibration that occurs when the relationship between the vibration frequency of the tool and the depth of cut of the workpiece by the tool satisfies a predetermined condition. Regeneration chatter is also called self-oscillation.

  As a technique for suppressing regeneration chatter vibration, JP-A-2010-105160 (patent document 1) discloses a machining apparatus for controlling the number of rotations of a tool based on the following equation (1) .

n = 60 · f _c / {(k + 1) · N} (1)
“N” shown in the above equation (1) represents the rotational speed calculation value per minute of the cutting tool or the work member. "F _c " represents the frequency of chatter vibration. “N” represents the number of cutting tools. “K” represents the integer part of 60 f _c / (n ₀ N). “N ₀ ” represents the current rotation number per minute of the cutting tool or the work member.

The above equation (1) is a modified example of the Tobias equation. Assuming that “f _c ” in the above equation (1) is the natural frequency of the tool and “k + 1” is a natural number, the above equation (1) is a Tobias equation. That is, the machining device disclosed in Patent Document 1 determines the number of rotations of the tool by considering the vibration frequency detected for the tool as the natural vibration frequency of the tool and substituting it in the Tobias equation.

JP, 2010-105160, A

  The vibration frequency of the regenerative chatter vibration has a slightly different value with respect to the natural frequency of the tool. Therefore, the machining device disclosed in Patent Document 1 may not be able to suppress the regenerative chatter vibration even if the number of rotations of the tool is determined according to the equation (1). Therefore, a technique for more reliably suppressing regenerative chatter is desired.

  The present disclosure has been made to solve the problems as described above, and an object in one aspect is to provide a machine tool capable of more reliably suppressing regenerative chatter vibration. An object in another aspect is to provide a processing method capable of suppressing regeneration chatter vibration more reliably. An object in another aspect is to provide a processing program capable of more reliably suppressing regenerative chatter vibration.

  According to an aspect, a machine tool is generated on the spindle or the tool based on the spindle for rotating the workpiece or the tool, a sensor for detecting the vibration frequency of the spindle or the tool, and the vibration frequency. A vibration detection unit for detecting regenerative chatter vibration, and an adjustment unit for adjusting the number of revolutions of the spindle. The adjusting unit adjusts the number of rotations of the spindle from the first number of rotations, which is the current setting value, to the second number of rotations according to a predetermined calculation formula when the regenerative chatter vibration is detected by the vibration detecting unit. When the regenerative chatter vibration is detected by the vibration detection unit after the adjustment to the second rotational speed, the rotational speed of the main spindle is the regenerative chatter by adjusting the first rotational speed to the second rotational speed. It is judged whether it has exceeded the stable range in which vibration does not occur, and whether to increase or decrease the rotation speed is changed according to the judgment result, while the regenerative chatter vibration is detected by the vibration detection unit, The spindle speed of the spindle is adjusted based on the satisfaction of a predetermined condition indicating that the spindle speed of the spindle is adjusted by a predetermined value from the second speed and the spindle speed of the spindle is likely to reach the first speed. Adjustment amount of rotation speed Smaller than the predetermined value.

  Preferably, the adjustment unit calculates how many times the number of revolutions of the main spindle reaches the first number of revolutions by performing the adjustment by each predetermined value after reversing the increase and decrease of the number of revolutions of the main spindle. When the calculated number of times is equal to or less than a predetermined number, it is determined that the predetermined condition is satisfied.

  Preferably, the adjustment unit determines that the predetermined condition is satisfied when the number of adjustments by the predetermined value after reversing the increase and decrease of the rotation speed of the spindle exceeds the predetermined number.

  Preferably, when it is determined that the number of revolutions of the spindle does not exceed the stable range, the adjusting unit decreases the number of revolutions of the spindle by a predetermined first value, and the number of revolutions of the spindle is in the stable range. If it is determined that it has exceeded, the number of revolutions of the spindle is increased by a predetermined second value. The second value is smaller than the first value.

  Preferably, the adjusting unit determines whether the number of revolutions of the main shaft exceeds the stable range based on the comparison result of the vibration frequency before and after adjustment of the number of revolutions of the main shaft.

  Preferably, in the machine tool, machining is performed by vibration of the spindle or the tool after the first blade of the tool contacts the workpiece and the second blade of the tool contacts the workpiece. Calculate the wave number of the surface. The adjusting unit determines whether or not the number of revolutions of the main shaft has exceeded the stable range, based on whether or not the integer part of the wave number has changed before and after adjustment of the number of revolutions of the main spindle.

  Preferably, the adjustment unit sequentially executes adjustment processing of the number of revolutions of the spindle while the vibration detection unit detects the regenerative chatter vibration, and the vibration detection unit performs the spindle or the tool. The adjustment process of the rotational speed ends when the above-mentioned regenerative chatter vibration is not detected.

  Preferably, the adjustment unit is configured to adjust the number of rotations of the main spindle more than the first number of rotations when the vibration detection unit detects the regenerative chatter vibration after performing the adjustment of the number of rotations of the main spindle a predetermined number of times increase.

  Preferably, the adjustment unit is configured to adjust the cutting depth of the work by the tool more than the current when the vibration detection unit detects the chatter vibration after the adjustment unit performs the rotation number adjustment of the spindle a predetermined number of times. Make it shallow.

  Preferably, the adjusting unit is configured to adjust the depth of cut of the workpiece by the tool when the regenerated vibration is detected by the vibration detecting unit after the second value becomes equal to or less than a predetermined threshold. Make it shallow too.

  Preferably, the vibration detection unit further detects forced chatter vibration occurring in the spindle or the tool based on the vibration frequency. When the forced chatter vibration is detected when the regenerative chatter vibration is not detected by the adjustment of the number of revolutions of the spindle, the adjusting unit is more than the adjustment amount for suppressing the regenerative chatter vibration when the forced chatter vibration is detected. Re-adjust the rotation speed with a small adjustment amount.

  According to another aspect, a machining method by a machine tool is provided. The machine tool includes a spindle for rotating a workpiece or a tool, and a sensor for detecting the vibration frequency of the spindle or the tool. The processing method is a step of detecting the regenerative chatter vibration occurring in the spindle or the tool based on the vibration frequency, and a predetermined calculation formula when the regenerative chatter vibration is detected in the detecting step. The regeneration chatter vibration is detected in the steps of adjusting the rotation number of the spindle from the first rotation number to the second rotation number, which is the current setting value, and the detection step after adjustment to the second rotation number according to In this case, it is determined whether or not the number of revolutions of the main spindle exceeds the stable range in which the regenerative chatter vibration does not occur by adjustment from the first number of revolutions to the second number of revolutions. While the regeneration chatter vibration is detected in the step of changing whether to increase or decrease the number, and the step of detecting, the number of revolutions of the main spindle is increased by a predetermined value from the second number of revolutions. Adjusting the amount of adjustment of the number of revolutions of the main spindle to be smaller than the predetermined value on the basis that the predetermined condition indicating that the number of revolutions of the main spindle is likely to reach the first number of revolutions is satisfied. Equipped with

  According to another aspect, a machining program by a machine tool is provided. The machine tool includes a spindle for rotating a workpiece or a tool, and a sensor for detecting the vibration frequency of the spindle or the tool. The machining program includes the steps of: detecting, on the machine tool, the regenerative chatter vibration occurring in the spindle or the tool on the basis of the vibration frequency; and detecting the regenerative chatter vibration in the detecting step. Adjusting the rotation number of the spindle from the first rotation number to the second rotation number, which is the current setting value, according to a predetermined calculation formula, and the above detection step after the adjustment to the second rotation number. When chattering vibration is detected, it is determined whether the number of rotations of the spindle exceeds the stable range where the regenerative chattering vibration does not occur by adjusting the first number of rotations to the second number of rotations, and the judgment result According to the step of changing whether to increase or decrease the number of rotations, and while the regeneration chatter vibration is detected in the step of detecting, the number of rotations of the main spindle is set to The adjustment amount of the number of revolutions of the main spindle is set to the predetermined value based on the fact that the predetermined condition indicating that the number of revolutions of the main spindle is likely to reach the first number of revolutions is satisfied. And making the step smaller.

In one aspect, regenerative chatter can be suppressed more reliably.
The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention taken in conjunction with the accompanying drawings.

FIG. 1 is a view showing a machine tool according to a first embodiment. It is a figure which shows the process conditions which a reproduction | regeneration chatter vibration tends to produce. It is a figure which shows the processing conditions which a reproduction | regeneration chatter vibration does not produce easily. It is a figure which shows the processing aspect of the workpiece | work. It is a figure which shows the range which a reproduction | regeneration chatter vibration produces, and the range which does not produce in the relationship between the rotation speed of a main axis | shaft, and the cutting depth of a workpiece | work. FIG. 6 is a diagram for describing a fine adjustment process of a spindle rotational speed based on a fine adjustment condition 1; FIG. 10 is a diagram for describing a fine adjustment process of the spindle rotational speed based on the fine adjustment condition 2. It is a figure showing an example of functional composition of a machine tool according to a 1st embodiment. It is a figure which shows an example of the result of the frequency decomposition by a FFT (Fast Fourier Transform) part. It is a figure for demonstrating an example of the determination method of the excessive adjustment by the excessive adjustment judgment part. It is a figure for demonstrating the other example of the determination method of the excessive adjustment by the excessive adjustment judgment part. 10 is a flowchart illustrating adjustment processing of a spindle rotational speed based on a fine adjustment condition 1; 10 is a flowchart showing adjustment processing of the spindle rotational speed based on the fine adjustment condition 2. FIG. It is a block diagram showing the main hardware constitutions of the machine tool according to a 1st embodiment. It is a figure for demonstrating the suppression process of forced chatter vibration.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description of these will not be repeated. In addition, each embodiment and each modification which are explained below may be combined suitably suitably.

First Embodiment
[A. Configuration of machine tool 100]
The configuration of the machine tool 100 will be described with reference to FIG. FIG. 1 is a view showing an example of a machine tool 100. As shown in FIG.

  A machine tool 100 as a machining center is shown in FIG. Although the machine tool 100 as a machining center will be described below, the machine tool 100 is not limited to the machining center. For example, the machine tool 100 may be a lathe or any other cutting machine or grinding machine.

  As shown in FIG. 1, the machine tool 100 has a bed 12, a saddle 18, a column 21, a spindle head 41, and a table 26 as main components.

  The bed 12 is a base member for mounting the saddle 18, the column 21 and the like, and is installed on a mounting surface of a factory or the like.

  A column 21 is attached to the bed 12. The column 21 is fixed to the bed 12. The column 21 generally has a gate-like shape standing on the upper surface of the bed 12.

  More specifically, the column 21 has side portions 22 (22s, 22t) and a top 23 as its component parts. The side portion 22 is provided to rise vertically upward from the upper surface of the bed 12. The side 22s and the side 22t are spaced apart in the X axis direction parallel to the horizontal direction. The top 23 extends from the side 22s to the side 22t along the X-axis direction.

  The machine configuration of the machine tool 100 basically has a left-right symmetric structure with respect to the center in the X-axis direction. In the present embodiment, the configurations in which “s” and “t” are attached to reference numbers are a pair of parts corresponding to the left-right symmetry.

  A saddle 18 is attached to the bed 12. The saddle 18 is provided slidably in the X axis direction with respect to the bed 12. A spindle head 41 is attached to the saddle 18. The spindle head 41 extends toward the table 26 through the space surrounded by the side 22s, the top 23, the side 22t and the bed 12. The spindle head 41 is parallel to the horizontal direction, and is provided slidably in the Z-axis direction orthogonal to the X-axis direction.

  The spindle head 41 has a spindle 42 and a housing 43. The main shaft 42 is disposed inside the housing 43, and rotatably provided by motor drive around a central axis AX1 parallel to the Z-axis direction. At this time, the housing 43 does not rotate. On the spindle 42, a tool for processing a workpiece to be processed is mounted. As the main shaft 42 rotates, a tool mounted on the main shaft 42 rotates about the central axis AX1. When the machine tool 100 is a lathe, a work is mounted on the spindle. In this case, as the main shaft 42 rotates, the work mounted on the main shaft 42 rotates.

  The housing 43 is provided with an acceleration sensor 110 for detecting the vibration frequency of the spindle 42 or the tool. Preferably, a plurality of acceleration sensors 110 are provided in the housing 43, and each acceleration sensor 110 detects vibrations in different directions (for example, X, Y, Z directions) of the main shaft 42. The sensor for detecting the vibration frequency of the main shaft 42 is not limited to the acceleration sensor 110, and any sensor capable of detecting the vibration frequency of the main shaft 42 may be used.

  The bed 12, the saddle 18, and the spindle head 41 are used as a feed mechanism, a guiding mechanism, and a drive source to enable sliding movement of the saddle 18 in the X axis direction and sliding movement of the spindle head 41 in the Z axis direction. A servomotor etc. are suitably provided.

  A table 26 is attached to the column 21. The table 26 is provided parallel to the column 21 so as to be slidable in the Y-axis direction orthogonal to the X-axis direction and the Z-axis direction with respect to the column 21.

  The table 26 is a device for fixing a work, and has a pallet 27 and rotation mechanisms 29 (29s, 29t).

  The pallet 27 is a metal base and works are attached using various clamp mechanisms. The pallet 27 is provided so as to be pivotable about a central axis AX2 parallel to the X-axis by the rotation mechanism unit 29 (a-axis pivoting). The rotation mechanism portion 29s and the rotation mechanism portion 29t are disposed at an interval in the X-axis direction. The pallet 27 is mounted between the rotation mechanism 29s and the rotation mechanism 29t. The pallet 27 may be further provided so as to be pivotable about a central axis orthogonal to the main surface of the pallet 27 (b-axis pivoting).

  The column 21 and the table 26 are appropriately provided with a feed mechanism and a guide mechanism for enabling the slide movement of the table 26 in the Y-axis direction, a servomotor as a drive source, and the like.

  The slide movement of the saddle 18 in the X-axis direction, the slide movement of the spindle head 41 in the Z-axis direction, and the slide movement of the table 26 in the Y-axis direction combine to form the machining position of the workpiece by the tool mounted on the spindle 42 Move in three dimensions.

  The machine tool 100 further includes a magazine 30 and an automatic tool changer (ATC: Automatic Tool Changer) 36. The magazine 30 is a device for accommodating the replacement tool 32 mounted on the main shaft 42. The automatic tool changer 36 is a device for changing tools between the main shaft 42 and the magazine 30.

  The magazine 30 has a magazine body 31, column members 14 and 16, and a base member 33.

  The magazine body 31 has a plurality of tool holders 34 and sprockets 35. The tool holder 34 is configured to be able to hold the tool 32. The plurality of tool holders 34 are annularly arranged around the sprocket 35. The sprocket 35 is rotatably provided about a central axis AX3 parallel to the Y axis by motor drive. Along with the rotation of the sprocket 35, the plurality of tool holding portions 34 rotate about the central axis AX3.

  The magazine body portion 31 is supported by the column members 14 and 16 and the base member 33 at a position where the distance from the bed 12 in the vertically upward direction is provided.

  As the sprocket 35 rotates, a tool holder 34 for holding a specific tool 32 is indexed to a predetermined position in front of the machine. The specific tool 32 is transported in the Z-axis direction by a tool transport device (not shown) and moved to the tool replacement position. By pivoting the double arm 37 of the automatic tool changer 36, the specific tool 32 transported to the tool change position and the tool mounted on the spindle 42 are exchanged. The tool 32 that can be mounted on the spindle 42 includes, for example, a milling cutter such as an end mill.

[B. Principle of regeneration chatter]
When processing a workpiece with a machine tool, chatter vibration may occur in which the tip of the tool 32 slightly vibrates. Chatter vibration includes forced chatter vibration and regenerative chatter vibration. Forced chatter vibration is vibration generated by the machine tool as a vibration source and occurs when the vibration frequency of the tool 32 becomes equal to the natural frequency of the tool 32. Regeneration chatter vibration is vibration that occurs when the relationship between the vibration frequency of the tool 32 and the depth of cut of the workpiece by the tool 32 satisfies a predetermined condition.

  Machine tool 100 according to the present embodiment suppresses regenerative chatter vibration by sequentially adjusting the number of rotations of main shaft 42. In order to facilitate understanding of this adjustment process, the principle of the occurrence of regenerative chatter will be described first with reference to FIGS.

  FIG. 2 is a diagram showing an example of processing conditions in which regenerative chatter vibration is likely to occur. More specifically, FIG. 2A shows a cutting trace on the workpiece at the time of the previous cutting. The vibration frequency of the tool 32 at the time of cutting this time is shown by FIG. 2 (B). FIG. 2C shows the cutting thickness of the work by the tool 32 at the time of cutting this time.

  The tool 32 processes the workpiece by repeatedly cutting the workpiece while rotating. The tool 32 vibrates during processing of the workpiece, and as shown in FIG. 2A, unevenness occurs on the cutting surface of the workpiece.

  When the tool 32 cuts the workpiece next time, there may be a deviation between the cutting trace at the previous cutting and the vibration frequency of the tool 32 at the current cutting. Denoting this deviation by “φ”, in the example of FIGS. 2A and 2B, the deviation φ is π / 4 (= 90 degrees). When such a deviation occurs, the cutting thickness of the workpiece fluctuates according to the cutting position. FIG. 2C shows the variation of the cutting thickness when a shift of φ = π / 4 occurs. If the cutting thickness changes, the force that the tool 32 receives from the workpiece during cutting changes, which makes it more likely that regenerative chatter vibration occurs. In particular, when φ = π / 4, regenerative chatter is most likely to occur.

  FIG. 3 is a diagram showing an example of processing conditions in which regeneration chatter vibration hardly occurs. More specifically, FIG. 3A shows a cutting trace on the workpiece at the time of the previous cutting. The vibration frequency of the tool 32 at the time of cutting this time is shown by FIG. 3 (B). FIG. 3C shows the cutting thickness of the work by the tool 32 at the time of cutting this time.

  In the example of FIG. 3 (A) and FIG. 3 (B), the vibration frequency of the tool 32 has overlapped with the cutting trace at the time of the last cutting. In this case, the deviation “φ” becomes 0, and the cutting thickness of the workpiece becomes constant. Therefore, the force that the tool 32 receives from the work during cutting becomes constant, and it becomes difficult for the regenerative chatter vibration to occur.

  Therefore, when the number of rotations of the main shaft 42 is adjusted so that the deviation “φ” approaches 0, the regenerative chatter vibration is less likely to occur. On the other hand, when the rotational speed of the main shaft 42 is adjusted so that the deviation “φ” approaches π / 4, regenerative chatter vibration is likely to occur.

  Typically, when “k” shown in the following equation (2) is an integer, the shift “φ” is 0.

k = 60 · f _c / (n ₀ · N) (2)
In equation (2), “k” represents the wavenumber of the processing surface generated by the vibration of the tool 32 from the time the first blade of the tool 32 contacts the work to the time the second blade contacts the work Show. “F _c ” represents the vibration frequency of the main shaft 42. “N” represents the number of blades of the tool 32. “N ₀ ” represents the number of revolutions of the main shaft 42. The number of rotations here means the number of rotations of the main shaft 42 per unit time (for example, per one minute), and is synonymous with the rotation speed. Since the tool 32 interlocks with the main shaft 42, the number of rotations of the main shaft 42 is equal to the number of rotations of the tool 32. Therefore, the number of rotations of the spindle 42 is the same as the number of rotations of the tool 32.

  FIG. 4 is a view showing a processing mode of the workpiece W when “k” is an integer. FIG. 4 shows an aspect of the tool 32 and the workpiece W when viewed from the axial direction of the main spindle 42.

  FIG. 4A shows the processing mode of the workpiece W when “k” is 1. As shown in FIG. 4A, when “k” is 1, the tool 32 is in a period from when the blade 32A of the tool 32 contacts the workpiece W to when the blade 32B of the tool 32 contacts the workpiece W. The wave number of the machined surface generated by the vibration of is 1.

  FIG. 4B shows the processing mode of the workpiece W in the case where “k” is two. The rotation speed of the tool 32 in the processing mode of FIG. 4 (B) corresponds to 1⁄2 of the rotation speed of the tool 32 in the processing mode of FIG. 4 (A). As shown in FIG. 4B, when “k” is 2, the wave number on the processing surface of the workpiece W is 2.

  FIG. 4C shows the processing mode of the workpiece W when “k” is three. The rotation speed of the tool 32 in the processing mode of FIG. 4C corresponds to 1⁄3 of the rotation speed of the tool 32 in the processing mode of FIG. 4A. As shown in FIG. 4C, when “k” is 3, the wave number on the processing surface of the workpiece W is 3.

  In the processing modes shown in FIG. 4A to FIG. 4C, since all the displacements “φ” become 0, the reproduction chatter vibration hardly occurs.

  FIG. 5 is a view showing a range in which the regenerative chatter vibration occurs and a range in which the chatter vibration does not occur in the relationship between the rotational speed of the main shaft 42 and the cutting depth of the workpiece W. The horizontal axis of the graph shown in FIG. 5 represents the number of rotations of the main shaft 42. The vertical axis of the graph shown in FIG. 5 represents the cutting depth of the workpiece. The cutting depth referred to here is the length of the contact portion between the tool 32 and the work W in the axial direction of the main spindle 42.

  The range in which the cutting depth of the workpiece is smaller than the boundary line 50 represents the processing conditions in which the regenerative chatter vibration hardly occurs. Hereinafter, the range is also referred to as a stable range A.

  A range in which the cutting depth of the workpiece is larger than the boundary line 50 is a processing condition in which regenerative chatter vibration is likely to occur. Hereinafter, the range is also referred to as unstable range B.

[C. Adjustment processing of rotation speed of main shaft 42]
Continuing to refer to FIG. 5, the process of adjusting the rotational speed of the spindle 42 by the machine tool 100 will be described.

  The machine tool 100 according to the present embodiment sequentially adjusts the number of rotations of the main shaft 42, and ends the adjustment processing of the number of rotations of the main shaft 42 when the number of rotations of the main shaft 42 falls within the stable range A. More specifically, machine tool 100 reduces the number of rotations of main shaft 42 by a predetermined amount until the number of rotations of main shaft 42 exceeds stable range A. When the number of revolutions of the main spindle 42 exceeds the stable range A, the machine tool 100 reverses the increase and decrease of the number of revolutions of the main spindle 42 from the previous adjustment and makes the current adjustment amount smaller than the previous adjustment amount. As a result, the rotational speed of the main spindle 42 falls within the stable range A, and the machine tool 100 can suppress the regenerative chatter vibration.

  FIG. 5 shows that the rotational speed of the main shaft 42 is accommodated in the lobe A2 of the stable range A by sequentially executing the adjustment processes of steps S1 to S4. In the following, a process example in which the rotational speed of the main shaft 42 is contained in the lobe A2 of the stable range A will be described.

  When machining of a workpiece is started, the machine tool 100 sets the number of rotations of the spindle 42 to the initial value “r0”. Thereafter, the machine tool 100 calculates the vibration frequency of the main shaft 42 from the output signal of the acceleration sensor 110 (see FIG. 1), and determines whether the chattering vibration is generated in the tool 32 based on the vibration frequency. . The details of the method of detecting the regenerative chatter vibration will be described later.

  When the regenerative chatter vibration occurs at the rotational speed “r0”, the machine tool 100 calculates the rotational speed of the spindle 42 according to a predetermined calculation formula. As an example, the machine tool 100 calculates the number of rotations of the new main spindle 42 based on the Tobias equation of the following equation (3).

n = 60 · f _C / {[k] · N} (3)
“N” shown in the above equation (3) represents the number of revolutions of the main shaft 42 to be set next. “F _C ” represents the vibration frequency of the main shaft 42. "[K]" represents the integer which added 1 to the integer part of "k" calculated by said Formula (2). “N” represents the number of blades of the tool attached to the spindle 42.

  The machine tool 100 substitutes the vibration frequency of the main shaft 42 calculated from the output signal from the acceleration sensor 110 into the above equation (3). As a result, it is assumed that “n = r1” is calculated. In response to this, in step S1, the machine tool 100 adjusts the number of rotations of the spindle 42 from the number of rotations "r0" (first number of rotations) to the number of rotations "r1" (second number of rotations). Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter vibration is continuously generated. Next, the machine tool 100 determines whether or not the number of rotations of the main shaft 42 exceeds the stable range A by the adjustment process in step S1, and increases or decreases the number of rotations of the main shaft 42 according to the determination result. Change your mind. Since boundary line 50 is unknown, it is necessary to determine whether the rotational speed of main shaft 42 exceeds stable range A by some method. Details of this determination method will be described later.

  When the machine tool 100 determines that the number of revolutions of the spindle 42 does not exceed the stable range A, it reduces the number of revolutions of the spindle 42 by a predetermined value. On the other hand, when the machine tool 100 determines that the number of rotations of the main shaft 42 exceeds the stable range A, it increases the number of rotations of the main shaft 42 by a predetermined value.

  In the example of FIG. 5, since the number of rotations of the spindle 42 does not exceed the stable range A in the adjustment process of step S1, the machine tool 100 reduces the number of rotations of the spindle 42 by a predetermined value in step S2. As an example, the machine tool 100 reduces the rotational speed by the same amount as the adjustment amount at step S1. As a result, the number of rotations of the main shaft 42 is adjusted from the number of rotations "r1" to the number of rotations "r2".

  Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter vibration is continuously generated. Next, the machine tool 100 determines whether or not the number of rotations of the main shaft 42 exceeds the stable range A by the adjustment process in step S2, and increases or decreases the number of rotations of the main shaft 42 according to the determination result. Change your mind. In the example of FIG. 5, since the number of rotations of the main shaft 42 does not exceed the stable range A in the adjustment process of step S2, the machine tool 100 in step S3 rotates the number of rotations of the main shaft 42 by the same amount as the previous adjustment ( That is, Δr1) is decreased.

  Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter vibration is continuously generated. Next, the machine tool 100 determines whether or not the number of revolutions of the main spindle 42 exceeds the stable range A by the adjustment process in step S3, and increases or decreases the number of revolutions of the main spindle 42 according to the determination result. Change your mind. In the example of FIG. 5, since the number of rotations of the main shaft 42 exceeds the stable range A in the adjustment process of step S3, the machine tool 100 sets the number of rotations of the main shaft 42 to a predetermined value (for example, Δr2 in step S4). )increase.

  The adjustment amount “Δr2” after exceeding the stable range A is smaller than the adjustment amount “Δr1” before exceeding the stable range A. As one example, the adjustment amount “Δr2” is a quarter of the adjustment amount “Δr1”. Thus, the machine tool 100 switches the increase and decrease of the rotation speed of the spindle 42 based on the fact that the rotation speed of the spindle 42 exceeds the stable range, and the adjustment amount of the spindle 42 is smaller than the previous adjustment amount. Do. As a result, the machine tool 100 can ensure that the rotational speed of the main spindle 42 falls within the stable range A in a short time and reliably, and can suppress regenerative chatter vibration at an early stage.

  In the above, an example was described in which the number of rotations of the main shaft 42 is contained in the lobe A2 of the stable range A by adjusting the number of rotations to reduce the number of rotations of the main shaft 42. The number of revolutions may be adjusted to increase. The machine tool 100 can prevent the wear of the tool 32 by adjusting the rotational speed to be reduced. On the other hand, since the stable range in the lobe A1 is wider than the stable range in the lobe A2, the machine tool 100 stabilizes the rotational speed of the main shaft 42 by adjusting the rotational speed in the direction of increasing the rotational speed of the main shaft 42. The range A can be reliably contained.

[D. Fine adjustment of the number of revolutions of the main spindle 42]
As described above, when the regenerative chatter vibration occurs, the machine tool 100 calculates the number of rotations of the main shaft 42 from the first number of rotations, which is the current setting value, according to the above equation (3). Change to rotation speed. When the rotation speed of the main spindle 42 exceeds the stable range A by this adjustment, the machine tool 100 reverses the increase / decrease of the rotation speed of the main spindle 42 from the previous adjustment and also adjusts the rotation speed adjustment amount from "Δr1" to " Reduce to Δr 2. Thereafter, the machine tool 100 sequentially adjusts the rotational speed of the main spindle 42 by a predetermined value “Δr2” toward the first rotational speed before adjustment. At this time, based on the satisfaction of a predetermined condition (hereinafter, also referred to as “fine adjustment condition”) indicating that the rotational speed of the main shaft 42 is likely to reach the first rotational speed, the machine tool 100 The adjustment amount of the number of revolutions of is smaller than the predetermined value “Δ2”. That is, the machine tool 100 roughly adjusts the number of rotations of the main spindle 42 until the fine adjustment condition is satisfied, and makes the amount of adjustment of the rotational speed smaller than the previous time based on the fact that the fine adjustment condition is satisfied. .

  By performing such fine adjustment processing, the machine tool 100 can reliably keep the rotational speed of the spindle 42 in the stable range A. In addition, by roughly adjusting the number of rotations of the main shaft 42 in the initial stage of adjustment, the time required for the adjustment process can be shortened, and the machine tool 100 can suppress the regenerative chatter vibration earlier. In addition, the machine tool 100 can prevent the rotational speed of the main spindle 42 from being adjusted to the first rotational speed before adjustment in which the regenerative chatter vibration has occurred.

  Various conditions may be adopted as the above-mentioned fine adjustment condition. The adjustment processing of the spindle rotational speed based on the fine adjustment conditions 1 and 2 will be described below.

(D1. Adjustment process based on fine adjustment condition 1)
FIG. 6 is a diagram for explaining the fine adjustment process of the spindle rotational speed based on the fine adjustment condition 1. As shown in FIG.

  In this specific example, machine tool 100 determines how many times the spindle rotational speed reaches the first rotational speed before adjustment if the adjustment is performed for each predetermined value “Δr2” after reversing the increase and decrease of the spindle rotational speed. When it is calculated and the calculated number of times (hereinafter, also referred to as “adjustable number of times”) is less than or equal to a predetermined threshold number (predetermined number), it is determined that the spindle rotational speed is about to reach the first rotational speed. , It is determined that the fine adjustment condition 1 is satisfied. An arbitrary number of times may be set as the threshold number of times, but in the following, the fine adjustment processing based on the fine adjustment condition 1 will be described on the premise that “one time” is set as the threshold number of times.

  Referring to FIG. 6, it is assumed that the regenerative chatter vibration occurs at the rotational speed "r5" of the main shaft 42. Thereby, the machine tool 100 stores the current rotation number "r5" (first rotation number), and executes the adjustment process in step S5. The machine tool 100 determines whether or not the number of revolutions of the spindle 42 has exceeded the stable range A by the adjustment processing in step S5, and determines that the number of spindle revolutions has increased or decreased last time if it determines that the number of revolutions exceeds the stable range A. And reverse. In the example of FIG. 6, since the spindle rotational speed exceeds the stable range A in the adjustment process of step S5, the increase or decrease of the spindle rotational speed is reversed from the previous one. Further, the machine tool 100 reduces the adjustment amount of the spindle 42 from “Δ1” to “Δr2”.

  Furthermore, the machine tool 100 calculates the adjustable number of times from the spindle rotational speed "r6", and determines whether or not the fine adjustment condition is satisfied based on the adjustable number of times. More specifically, the machine tool 100 subtracts the current rotation number "r6" from the rotation number "r5", and divides the difference result by the adjustment amount "Δr2" to calculate the adjustable number as the number of adjustments. In the example of FIG. 6, “three times” is calculated as the adjustable number of times from the rotation number “r6”. Since the number of adjustable times is larger than “one time” which is the threshold number of times, the machine tool 100 determines that the fine adjustment condition is not satisfied. As a result, the machine tool 100 maintains the current adjustment amount “Δr2” and increases the spindle rotational speed “Δr2”. Thus, as shown in step S6, the spindle rotational speed is adjusted from "r6" to "r7".

  Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter vibration is continuously generated. The machine tool 100 determines whether or not the spindle rotational speed has exceeded the stable range A by the adjustment process in step S6, and reverses the increase and decrease of the spindle rotational speed from the previous time according to the determination result. In the example of FIG. 6, since the spindle rotational speed does not exceed the stable range A in the adjustment process in step S6, the increase or decrease of the spindle rotational speed is not reversed.

  Furthermore, the machine tool 100 calculates the adjustable number of times from the spindle rotational speed "r7". In the example of FIG. 6, "twice" is calculated as the adjustable number of times from the spindle rotational speed "r7". Since the number of adjustable times is larger than “one time” which is the threshold number of times, the machine tool 100 determines that the fine adjustment condition is not satisfied. As a result, the machine tool 100 maintains the current adjustment amount “Δr2” and increases the spindle rotational speed “Δr2”. Thus, as shown in step S7, the spindle rotational speed is adjusted from "r7" to "r8".

  Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter vibration is continuously generated. The machine tool 100 determines whether or not the spindle rotational speed has exceeded the stable range A by the adjustment process in step S7, and reverses the increase and decrease of the spindle rotational speed from the previous time according to the determination result. In the example of FIG. 6, since the spindle rotational speed does not exceed the stable range A in the adjustment process of step S7, the increase or decrease of the spindle rotational speed is not reversed.

  Furthermore, the machine tool 100 calculates the adjustable number of times from the current rotation number "r8". In the example of FIG. 6, "one" is calculated as the adjustable number of times from the spindle rotational speed "r8". Since the adjustable number of times is equal to or less than “one” of the threshold number of times, the machine tool 100 determines that the fine adjustment condition is satisfied. As a result, the machine tool 100 reduces the adjustment amount of the spindle rotational speed from “Δr2” to “Δr3”. As one example, “Δr3” is 1⁄2 (= 0.5) times “Δr2”. As a result, as shown in step S8, the rotational speed of the main shaft 42 is adjusted from "r8" to "r9".

  Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter has been settled. Thus, the machine tool 100 ends the adjustment processing of the spindle rotational speed.

  As described above, when the regenerative chatter vibration occurs, the machine tool 100 adjusts the spindle rotational speed by a predetermined adjustment amount “Δr2” while the spindle rotational speed does not exceed the stable range A. In this adjustment process, the machine tool 100 determines that the fine adjustment condition is satisfied based on the remaining number of times of adjustment becoming equal to or less than the predetermined number of times, and the adjustment amount of the spindle rotational speed is "Δr2". Lower to "Δr3". By performing such fine adjustment processing, the machine tool 100 can ensure that the spindle rotational speed falls within the stable range A reliably and quickly.

  In the machine tool 100, when the spindle rotational speed again exceeds the stable range A in the adjustment process of each adjustment amount “Δr2,” the increase or decrease of the spindle rotational speed is reversed with the previous adjustment and the spindle rotational speed The adjustment amount of is reduced from ".DELTA.r2" to ".DELTA.r3". Thereafter, when the regenerative chatter vibration continues to occur, the machine tool 100 adjusts the spindle rotational speed by a predetermined adjustment amount “Δr3” while the spindle rotational speed does not exceed the stable range A. In the adjustment process, the machine tool 100 determines that the fine adjustment condition is satisfied based on the remaining number of times of adjustment becoming equal to or less than the predetermined number of times, and further decreases the adjustment amount from “Δr3”.

(D2. Fine adjustment processing based on the fine adjustment condition 2)
Next, another example of the fine adjustment process will be described with reference to FIG. FIG. 7 is a diagram for explaining the fine adjustment process of the spindle rotational speed based on the fine adjustment condition 2. As shown in FIG.

  As described above, machine tool 100 according to the present embodiment adjusts the number of rotations of main shaft 42 by a predetermined value “Δr2” while regeneration chatter vibration is detected. At this time, the machine tool 100 performs the fine adjustment condition based on the fact that the number of adjustments at the predetermined value “Δr2” after reversing the increase and decrease of the rotational speed of the spindle 42 exceeds the predetermined number of times (for example, three times). Is judged to be satisfied. Based on the determination result, the machine tool 100 makes the adjustment amount of the number of rotations of the spindle 42 smaller than the predetermined value “Δr2”. By performing such fine adjustment processing, the machine tool 100 can reliably and quickly bring the rotational speed of the main spindle 42 into the stable range A.

  More specifically, referring to FIG. 7, it is assumed that the regenerative chatter vibration occurs at the rotational speed "r10" of the main shaft 42. Thereby, the machine tool 100 executes the adjustment process in step S10. The machine tool 100 determines whether or not the number of revolutions of the main spindle 42 exceeds the stable range A by the adjustment process in step S10, and changes whether to increase or decrease the number of revolutions of the main spindle 42 according to the determination result. In the example of FIG. 7, since the number of rotations of the main shaft 42 exceeds the stable range A in the adjustment process of step S10, the increase and decrease of the number of rotations of the main shaft 42 are reversed. As a result, in step S11, the machine tool 100 increases the number of rotations of the spindle 42 by a predetermined value (for example, Δr2). Thereby, the rotation speed of the main shaft 42 is adjusted from "r11" to "r12".

  Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter vibration is continuously generated. Thus, in step S12, the machine tool 100 increases the number of rotations of the main spindle 42 by the same amount as the previous adjustment amount (ie, Δr2). As a result, the rotational speed of the main shaft 42 is adjusted from "r12" to "r13".

  Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter vibration is continuously generated. Thus, in step S13, the machine tool 100 increases the number of rotations of the main spindle 42 by the same amount as the previous adjustment amount (ie, Δr2). As a result, the number of rotations of the main shaft 42 is adjusted from "r13" to "r14".

  Thereafter, the machine tool 100 determines again whether or not regeneration chatter vibration occurs. As a result, it is assumed that the regenerative chatter vibration is continuously generated. At this time, the machine tool 100 determines that the adjustment at the adjustment amount “Δr2” has exceeded a predetermined number of times (for example, three times), and determines that the fine adjustment condition is satisfied. Based on the determination result, the machine tool 100 lowers the adjustment amount of the rotation speed of the spindle 42 than the previous adjustment amount “r2”. In the example of FIG. 7, in step S14, the adjustment amount of the number of rotations of the main shaft 42 is reduced from “Δr2” to “Δr3”. As a result, the rotational speed of the main shaft 42 is adjusted from "r14" to "r15".

  Thus, in the machine tool 100, when the regenerative chatter vibration occurs, the rotational speed of the main shaft 42 by the same amount as the previous time (that is, Δr2) while the rotational speed of the main shaft 42 does not exceed the stable range A. Continue to increase or decrease. After that, the machine tool 100 reduces the adjustment amount from “Δr2” to “Δr3” based on the fact that the number of adjustments in “Δr2” exceeds a predetermined number of times (for example, three times). By performing such fine adjustment processing, the machine tool 100 can reliably and quickly bring the rotational speed of the main spindle 42 into the stable range A.

[E. Functional configuration of machine tool 100]
The functions of the machine tool 100 will be described with reference to FIGS. FIG. 8 is a diagram showing an example of a functional configuration of the machine tool 100. As shown in FIG.

  The machine tool 100 includes a control device 101. The control device 101 is, for example, an NC control device capable of executing a numerical control (NC) program. The NC controller is configured by at least one integrated circuit. The integrated circuit is configured by, for example, at least one central processing unit (CPU), at least one application specific integrated circuit (ASIC), at least one field programmable gate array (FPGA), or a combination thereof.

  As shown in FIG. 8, the control device 101 includes a vibration detection unit 150 for detecting chatter vibration occurring in the machine tool 100, and an adjustment unit 160 for adjusting the number of rotations of the main shaft 42. Below, the function of the vibration detection part 150 and the adjustment part 160 is demonstrated in order.

(E1. Vibration detection unit 150)
Vibration detection unit 150 includes an FFT unit 152 and a regenerative chatter vibration detection unit 154.

  The FFT unit 152 samples an output signal from the acceleration sensor 110 (see FIG. 1) at a predetermined sampling rate while processing a workpiece, and Fourier-transforms a sampling result for a predetermined time. The result of the frequency decomposition by the FFT unit 152 is output to the regenerative chatter vibration detection unit 154.

  FIG. 9 is a diagram showing an example of the result of frequency decomposition by the FFT unit 152. As shown in FIG. A spectrum 70 is shown in FIG. 9 as an example of the result of frequency decomposition by the FFT unit 152.

  Among the signal components in the spectrum 70, the reproduction chatter vibration detection unit 154 extracts, as a vibration frequency, the frequency of the signal component having the largest signal strength. Thereafter, when the vibration frequency exceeds the predetermined threshold th, the regenerative chatter vibration detection unit 154 detects the regenerative chatter vibration. When the reproduction chatter vibration is detected, the reproduction chatter vibration detection unit 154 outputs the fact to the adjustment unit 160.

  Although the details will be described in the “second embodiment”, the vibration frequency in the predetermined frequency band may be generated due to forced chatter vibration. Therefore, the regenerative chatter vibration detection unit 154 may detect the regenerative chatter vibration after excluding the predetermined frequency band.

(E2. Adjustment unit 160)
Referring back to FIG. 8, the adjustment unit 160 includes a first adjustment unit 162, a second adjustment unit 164, and an excessive adjustment determination unit 166.

  The first adjustment unit 162 performs the first adjustment of the rotation speed of the main shaft 42. More specifically, when the regenerative chatter vibration is detected, the first adjustment unit 162 calculates the number of rotations of the main shaft 42 according to a predetermined calculation formula. For example, the Tobias equation of the above equation (3) is adopted for the calculation equation. The first adjusting unit 162 outputs the rotation speed calculated according to the above equation (3) as a target rotation speed to a servo driver 106 (see FIG. 14) described later. The servo driver 106 controls the servomotor 107 (see FIG. 14) that drives the main shaft 42 so that the main shaft 42 rotates at the target rotational speed.

  The second adjusting unit 164 adjusts the rotational speed of the main shaft 42 for the second time and thereafter. More specifically, the second adjustment unit 164 re-adjusts the rotation speed of the main shaft 42 when the regenerative chatter vibration is continuously generated after the rotation speed is adjusted by the first adjustment unit 162. At this time, the second adjustment unit 164 changes whether to increase or decrease the number of rotations of the main shaft 42 depending on whether or not the excessive adjustment has been performed in the previous adjustment. More specifically, when the excessive adjustment is performed in the previous adjustment, the second adjustment unit 164 reverses the increase / decrease of the rotational speed of the main shaft 42 to the previous adjustment and also makes the adjustment amount more than the previous adjustment amount. Reduce the amount of adjustment this time. On the other hand, when the excessive adjustment is not performed in the previous adjustment, the second adjustment unit 164 adjusts the number of rotations of the main shaft 42 in the same manner as the previous adjustment.

  The second adjustment unit 164 outputs the determined number of rotations as a target number of rotations to a servo driver 106 (see FIG. 14) described later. The servo driver 106 controls a later-described servomotor 107 (see FIG. 14) which drives the main shaft 42 so that the main shaft 42 rotates at the determined target rotational speed.

  While the regenerative chatter vibration detection unit 154 detects the regenerative chatter vibration, the second adjustment unit 164 sequentially executes the process of adjusting the rotational speed of the spindle 42, and the regenerative chatter occurring in the tool 32 or the spindle 42 When the vibration is not detected, the adjustment process of the rotational speed ends.

  Preferably, the second adjusting unit 164 reduces the number of revolutions of the main shaft 42 when the regenerative chatter vibration is still generated after performing the adjustment of the number of revolutions of the main shaft 42 a predetermined number of times (for example, 10 times). It is determined that no lobe of the stable range A exists in the direction, and the lobe of the stable range A is searched in the direction in which the number of rotations of the main shaft 42 is increased. Therefore, in this case, the second adjustment unit 164 raises the number of rotations of the main shaft 42 more than the initial value. Thereby, the second adjustment unit 164 can search for a lobe of the stable range A in a direction larger than the initial value.

  In another aspect, the second adjusting unit 164 adjusts the rotational speed of the main shaft 42 a predetermined number of times (for example, 10 times), and if the regenerative chatter vibration is still occurring, the depth of cut of the main shaft 42 is Make it shallower. In the example of FIG. 5, the second adjusting unit 164 lowers the depth of cut of the main shaft 42 than the initial value “h”. This increases the possibility of the rotational speed of the main shaft 42 falling within the stable range.

  When the adjustment amount of the rotation amount of the main shaft 42 becomes equal to or less than the predetermined threshold value, the second adjusting unit 164 determines that no lobe of the stable range A exists in the direction of decreasing the number of rotations of the main shaft 42. It is also good. In such a case, the second adjustment unit 164 may search for a lobe of the stable range A in the direction of increasing the number of rotations of the main shaft 42, and the depth of cut of the main shaft 42 may be an initial value “h”. It may be lower than that.

  The excessive adjustment determination unit 166 determines whether or not the excessive adjustment of the rotational speed has been performed by the first adjustment unit 162 or the second adjustment unit 164. More specifically, the excessive adjustment determination unit 166 determines that the excessive adjustment has been performed when the number of revolutions of the main shaft 42 exceeds the above-described stable range A (see FIG. 5) by the previous adjustment. Whether or not the number of revolutions of the main shaft 42 has exceeded the stable range A may be determined by various methods. Below, with reference to FIG. 10 and FIG. 11, the judgment method of excessive adjustment is demonstrated.

  FIG. 10 is a diagram for explaining an example of the determination method of the excessive adjustment by the excessive adjustment determination unit 166. In FIG.

  The upper graph of FIG. 10 shows the range in which the regenerative chatter vibration occurs and the range in which the chatter vibration does not occur in the relationship between the rotational speed of the main shaft 42 and the cutting depth of the workpiece. The lower graph of FIG. 10 shows the relationship between the number of revolutions of the main shaft 42 and the vibration frequency of the main shaft 42.

  As shown in FIG. 10, the vibration frequency of the main shaft 42 largely changes before and after the apexes of the lobes A1 to A3 of the stable range A. Focusing on this point, the excessive adjustment determination unit 166 determines whether the number of rotations of the main shaft 42 exceeds the stable range A based on the comparison result of the vibration frequency of the main shaft 42 before and after adjustment of the number of rotations of the main shaft 42. to decide.

  In the example of FIG. 10, the vibration frequency of the main shaft 42 is changed by “Δf1” by adjusting the rotational speed of the main shaft 42 from “r2” to “r3”. The excessive adjustment determination unit 166 determines that the number of rotations of the main shaft 42 exceeds the stable range A when the change amount “Δf1” of the vibration frequency of the main shaft 42 is equal to or more than a predetermined threshold, and determines that the excessive adjustment is performed. . On the other hand, the excessive adjustment determination unit 166 determines that the number of revolutions of the main shaft 42 does not exceed the stable range A when the change amount “Δf1” of the vibration frequency of the main shaft 42 is smaller than a predetermined threshold, Judged that it has not been done. In the example of FIG. 10, since the change amount “Δf1” is larger than the threshold value th, the excess adjustment determination unit 166 determines that the excess adjustment has been performed.

  FIG. 11 is a diagram for explaining another example of the determination method of the excessive adjustment by the excessive adjustment determination unit 166. In FIG.

  As shown in FIG. 11, the integer part (that is, [k]) of “k” of the above equation (2) changes before and after the apex of the lobes A1 to A3 of the stable range A. Below, the integer part of "k" is also called order. The excessive adjustment determination unit 166 determines whether or not the rotational speed of the main shaft 42 has exceeded the stable range A, based on whether or not the order has changed before and after adjustment of the rotational speed of the main shaft 42.

  In the example of FIG. 11, the order is changed from “m” to “m + 1” (m: integer) by adjusting the rotation speed of the main shaft 42 from “r2” to “r3”. In this case, the excessive adjustment determination unit 166 determines that the number of rotations of the main shaft 42 has exceeded the stable range A, and determines that excessive adjustment has been performed. On the other hand, when the order does not change before and after the adjustment of the rotational speed of the main spindle 42, the excessive adjustment determination unit 166 determines that the rotational speed of the main spindle 42 does not exceed the stable range A, and excessive adjustment is performed. It is judged that it has not been done.

[F. Control structure of machine tool 100]
The control structure of the machine tool 100 will be described with reference to FIGS. 12 and 13. FIG. 12 is a flowchart showing the adjustment processing of the spindle rotational speed based on the above-mentioned fine adjustment condition 1. FIG. 13 is a flowchart showing the adjustment processing of the spindle rotational speed based on the above-mentioned fine adjustment condition 2. The processes in FIG. 12 and FIG. 13 are realized by the control device 101 of the machine tool 100 executing a program. In other aspects, some or all of the processing may be performed by circuit elements or other hardware.

(F1. Adjustment process based on fine adjustment condition 1)
First, with reference to FIG. 12, a control flow of adjustment processing based on the fine adjustment condition 1 will be described.

  In step S110, the control device 101, as the adjustment unit 160 (see FIG. 8) described above, determines whether or not the regenerative chatter vibration occurs based on the output value of the acceleration sensor 110 (see FIG. 1). The method of detecting the regenerative chatter vibration is as described in FIG. 9, and therefore the description thereof will not be repeated. When it is determined that the regenerative chatter vibration is occurring (YES in step S110), the control device 101 switches the control to step S120. If not (NO in step S110), control device 101 ends the adjustment process shown in FIG.

  In step S120, the control device 101 determines whether it is the first adjustment after the adjustment process shown in FIG. 12 is started. When determining that the adjustment is the first adjustment (YES in step S120), the control device 101 switches the control to step S122. If not (NO in step S120), control device 101 switches control to step S130.

  In step S122, the control device 101, as the above-described first adjustment unit 162 (see FIG. 8), calculates the number of rotations "n '" of the main shaft 42 according to a predetermined calculation formula. For example, the Tobias equation of the above equation (3) is adopted for the calculation equation.

  Although "[k]" shown by the said Formula (3) may be calculated based on the said Formula (2), it may be calculated based on a following formula (4).

[K] = [60 · f _c / (n ₀ · N)] + dir (4)
“K” shown in the equation (4) represents the wave number of the processing surface generated by the vibration of the tool from the time the first blade of the tool 32 contacts the workpiece to the time the second blade contacts the workpiece . “F _c ” represents the vibration frequency of the main shaft 42. “N” represents the number of cutting tools. “N ₀ ” represents the number of revolutions of the main shaft 42. “[60 · f _c / (n ₀ · N)]” represents the integer part of “60 · f _c / (n ₀ · N)”. “Dir” is a value of 0 or 1. When increasing the number of rotations of the main shaft 42, “dir” is set to 0. When decreasing the number of revolutions of the main shaft 42, “dir” is set to 1.

  In step S124, the control device 101 calculates the adjustment amount "Δn" of the rotational speed of the main shaft 42. The adjustment amount “Δn” is calculated by subtracting the current rotation number “n” from the rotation number “n ′” calculated in step S122.

  In step S126, the control device 101 changes the number of rotations of the main shaft 42 from the number of rotations "n", which is the current setting value, to the number of rotations "n '" as the adjusting unit 160 described above (see FIG. 8).

  In step S130, the control device 101 determines, as the above-described excessive adjustment determination unit 166 (see FIG. 8), whether the number of rotations of the main shaft 42 has exceeded the stable range A (see FIG. 5) by the previous adjustment. The determination method is as described with reference to FIGS. 10 and 11, and thus the description thereof will not be repeated. When the control device 101 determines that the number of rotations of the main shaft 42 has exceeded the stable range A by the previous adjustment (YES in step S130), the control is switched to step S132. If not (NO in step S130), control device 101 switches control to step S136.

  In step S132, the control device 101 calculates the number of revolutions "n '" of the main shaft 42 based on the following equation (5) as the above-mentioned second adjustment unit 164 (see FIG. 8).

n ′ = n−Δn · a (5)
"N '" shown by Formula (5) represents the rotation speed after adjustment. "N" represents the current number of revolutions. “Δn” represents the previous adjustment amount of rotational speed. "A" is a factor greater than zero and less than one. The coefficient "a" is set to a smaller value each time the process of step S132 is performed. As an example, at the first time, the coefficient “a” is set to 1⁄4.

  In step S134, the control device 101 calculates the adjustment amount "Δn" of the rotational speed of the main shaft 42. The adjustment amount “Δn” is calculated by subtracting the current rotation number “n” from the rotation number “n ′” calculated in step S132.

  In step S135, the control device 101 stores the current rotational speed "n" of the main spindle 42 in the storage device 120 (see FIG. 14) described later as the above-mentioned second adjustment unit 164.

  In step S136, if the control device 101 performs the sequential adjustment after reversing the increase and decrease of the spindle rotational speed as the second adjustment unit 164 described above, how many times does the spindle rotational speed reach the rotational speed stored in step S135? Calculate As an example, the control device 101 subtracts the current rotation number from the rotation number stored in step S135, and calculates the result of dividing the difference result by the current adjustment amount as the adjustable number. When the adjustable number of times is calculated last time, the control device 101 may calculate the result of subtracting 1 from the previous adjustable number of times as a new adjustable number of times.

  In step S137, the control device 101, as the above-mentioned second adjustment unit 164, determines whether or not the above-mentioned fine adjustment condition 1 is satisfied. In the present example, the control device 101 determines that the fine adjustment condition 1 is satisfied when the adjustable number calculated in step S136 is equal to or less than a predetermined threshold number (for example, one). When the control device 101 determines that the adjustable number calculated in step S136 is equal to or less than the predetermined threshold number (YES in step S137), the control is switched to step S138. If not (NO in step S137), the control device 101 switches the control to step S140.

  In step S138, the control device 101 causes the adjustment amount “Δn” of the rotational speed of the main shaft 42 to be smaller than the previous adjustment amount “Δn” as the above-described second adjustment unit 164. At this time, the control device 101 initializes the number of times of adjustment “c” of the number of rotations of the main shaft 42 as the above-mentioned second adjustment unit 164. The number of times of adjustment “c” is initialized to, for example, “1”. As an example, the control device 101 reduces the adjustment amount “Δn” based on the following equation (6).

Δn = Δn · b (6)
“Δn” on the left side shown in the equation (6) represents the adjustment amount of the present rotation speed. The right side “Δn” shown in the equation (6) represents the previous adjustment amount of the rotational speed. "B" is a factor greater than zero and less than one. As an example, the coefficient "b" is 1/2 (= 0.5).

  In step S140, the control device 101, as the above-mentioned second adjustment unit 164, calculates the number of rotations "n '" of the main shaft 42 based on the following equation (7).

n '= n + Δn (7)
"N '" shown by Formula (7) represents the number of rotations after adjustment. "N" represents the current number of revolutions. “Δn” represents the previous adjustment amount of rotational speed.

  In step S142, the control device 101 increments the number of adjustment times “c” of the number of rotations of the main shaft 42 as the above-described second adjustment unit 164.

(F2. Adjustment process based on fine adjustment condition 2)
Next, with reference to FIG. 13, a control flow of adjustment processing based on the above-described fine adjustment condition 2 will be described. In FIG. 13, the process of steps S135A and 137A is different from that of FIG. 12, the process of step S142 is added from FIG. 12, and the process of step S136 is deleted from FIG. The other processes shown in FIG. 13 are the same as those in FIG. 12, and therefore, the description of the processes other than steps S135A, S137A, and S142 will not be repeated below.

  In step S135A, the control device 101 initializes the number of times of adjustment “c” of the number of rotations of the main shaft 42 as the above-mentioned second adjustment unit 164. The number of times of adjustment "c" is a variable for counting the number of times of adjustment of the number of rotations of the main shaft 42. The number of times of adjustment “c” is initialized to, for example, “1”.

  In step S137A, the control device 101, as the above-described second adjustment unit 164, determines whether the above-described fine adjustment condition 2 is satisfied. In the present embodiment, the control device 101 determines that the fine adjustment condition 2 is satisfied when the number of times of adjustment “c” of the spindle rotational speed exceeds a predetermined number of times (for example, three times). Control device 101 switches control to step S138 when it is determined that the number of times of adjustment “c” of the spindle rotational speed exceeds the predetermined number (YES in step S137A). If not (NO in step S137A), control device 101 switches control to step S140.

  In step S142, the control device 101 increments the number of adjustment times “c” of the number of rotations of the main shaft 42 as the above-described second adjustment unit 164.

[G. Hardware configuration of machine tool 100]
An example of the hardware configuration of the machine tool 100 will be described with reference to FIG. FIG. 14 is a block diagram showing the main hardware configuration of the machine tool 100. As shown in FIG.

  The machine tool 100 includes a main shaft 42, a control device 101, a ROM 102, a RAM 103, a communication interface 104, a display interface 105, a servo driver 106, a servo motor 107, an input interface 109, and an acceleration sensor 110. And a storage device 120.

  The control device 101 controls various operations of the machine tool 100 by executing various programs such as a machining program 122 (NC program) of the machine tool 100. The control device 101 reads the processing program 122 from the storage device 120 to the ROM 102 based on the acceptance of the execution command of the processing program 122. The RAM 103 functions as a working memory, and temporarily stores various data necessary for the execution of the machining program 122.

  A LAN, an antenna, and the like are connected to the communication interface 104. The machine tool 100 exchanges data with an external communication device via the communication interface 104. The external communication device includes, for example, a server and other communication terminals. The machine tool 100 may be configured to be able to download the processing program 122 from the communication terminal.

  The display interface 105 is connected to the display 130, and sends an image signal for displaying an image to the display 130 in accordance with an instruction from the control device 101 or the like. The display 130 is, for example, a liquid crystal display, an organic EL display, or another display device.

  The servo driver 106 receives an input of the target rotational speed from the control device 101, and controls the servomotor 107 so that the main spindle 42 rotates at the target rotational speed. More specifically, the servo driver 106 calculates the number of revolutions of the main shaft 42 from the output signal of the encoder (not shown) of the servomotor 107, and when the number of revolutions is smaller than the target number of revolutions, The rotational speed is increased, and when the rotational speed is larger than the target rotational speed, the rotational speed of the servomotor 107 is decreased. Thus, the servo driver 106 brings the rotation speed of the main shaft 42 close to the target rotation speed while sequentially receiving feedback of the rotation speed of the main shaft 42.

  Input interface 109 may be connected to input device 131. The input device 131 is, for example, a mouse, a keyboard, a touch panel, or any other device capable of accepting user operations.

  The storage device 120 is, for example, a storage medium such as a hard disk or a flash memory. Storage device 120 stores processing program 122 according to the present embodiment, setting value 124 (for example, the number of rotations of main shaft 42) referred to by processing program 122, and the like. The storage location of the processing program 122 and the setting value 124 is not limited to the storage device 120, and is stored in a storage area (for example, cache memory etc.) of the control apparatus 101, ROM 102, RAM 103, external equipment (for example server) etc. May be

  The processing program 122 may be provided as part of any program, not as a single program. In this case, control processing according to the present embodiment is realized in cooperation with an arbitrary program. Even a program that does not include such a part of modules does not deviate from the spirit of the processing program 122 according to the present embodiment. Furthermore, some or all of the functions provided by the processing program 122 may be realized by dedicated hardware. Furthermore, the machine tool 100 may be configured as a so-called cloud service in which at least one server executes a part of the processing of the processing program 122.

[H. advantage]
As described above, machine tool 100 according to the present embodiment reduces the number of revolutions of main shaft 42 by a predetermined amount until the number of revolutions of main shaft 42 exceeds stable range A. When the number of revolutions of the main spindle 42 exceeds the stable range A, the machine tool 100 reverses the increase and decrease of the number of revolutions of the main spindle 42 from the previous adjustment and makes the current adjustment amount smaller than the previous adjustment amount. When the rotation speed of the spindle 42 falls within the stable range A, the machine tool 100 ends the adjustment processing of the rotation speed of the spindle 42.

  The machine tool 100 can adjust the number of rotations of the main shaft 42 in a short time and reliably within the stable range A by sequentially adjusting the number of rotations of the main shaft 42 in this manner, and the regenerative chatter vibration can be reduced in a short time. And it can be suppressed reliably.

Second Embodiment
The machine tool 100 according to the first embodiment adjusts the number of rotations of the main shaft 42 in order to suppress the regenerative chatter vibration. On the other hand, the machine tool 100 according to the second embodiment adjusts the number of rotations of the main shaft 42 in order to suppress both the regenerative chatter vibration and the forced chatter vibration.

  Since the hardware configuration of machine tool 100 according to the second embodiment and the like are otherwise the same as machine tool 100 according to the first embodiment, the description thereof will not be repeated below.

  The frequency of forced chatter vibration can be calculated based on the number of blades of the tool 32 and the number of rotations of the main shaft 42. More specifically, the frequency of forced chatter vibration can be calculated based on the following equation (8).

f = n ₀ · N / 60 (8)
“N ₀ ” shown in the above equation (8) represents the number of rotations of the main shaft 42. “N” represents the number of blades of the tool 32.

  When the vibration frequency of the spindle 42 coincides with an integral multiple of the frequency "f", the machine tool 100 determines that forced chatter vibration is occurring. On the other hand, when chatter vibration is occurring and the vibration frequency of the main shaft 42 does not coincide with an integral multiple of the frequency "f", the machine tool 100 determines that regenerative chatter vibration is occurring.

  In the example of FIG. 9, since the signal strength of the signal component that does not coincide with the integral multiple of the frequency “f” exceeds the threshold th, the machine tool 100 determines that the regenerative chatter vibration is occurring. On the other hand, when the signal strength of the signal component at an integral multiple (for example, “m−1”, “m”, “m + 1”) of frequency “f” exceeds the predetermined threshold, machine tool 100 Determines that forced chatter is occurring.

  The occurrence of forced chatter vibration means that the vibration frequency of the tool 32 matches the natural frequency of the tool 32. When the rotational speed of the main shaft 42 changes, the vibration frequency of the tool 32 changes, and the vibration frequency of the tool 32 does not match the natural frequency of the tool 32. Focusing on this point, when the forced chatter vibration occurs, the machine tool 100 successively increases or decreases the rotational speed of the main shaft 42. At that time, it is necessary to adjust the rotational speed of the main shaft 42 within the range of the above-described stable range A (see FIG. 5). The machine tool 100 can suppress both forced chatter vibration and regenerative chatter vibration by adjusting the rotation speed of the spindle 42 within the range of the stable range A.

  In the following, the process of suppressing forced chatter vibration will be described with reference to FIG. FIG. 15 is a diagram for explaining a process of suppressing forced chatter vibration. An enlarged view of the lobe A2 shown in FIG. 5 is shown in FIG.

  In step S20, it is assumed that the machine tool 100 adjusts the rotational speed of the main shaft 42 from "r20" to "r21" in order to suppress the regenerative chatter vibration. Thereby, the rotation speed of the main shaft 42 falls within the stable range A, and the regenerative chatter vibration is suppressed.

  However, as described above, when the vibration frequency of the main shaft 42 coincides with an integral multiple of the frequency "f" shown in the above equation (8), forced chatter vibration is likely to occur. A region where such forced chatter vibration is likely to occur is shown as an unstable range D in FIG. In the example of FIG. 15, the number of rotations of the main shaft 42 belongs to the unstable range D by the adjustment process in step S20.

  In step S20, the machine tool 100 re-adjusts the rotational speed of the main shaft 42 with an adjustment amount "Δr4" which is smaller than the adjustment amount "Δr3" of the rotational speed to suppress the regenerative chatter vibration. At this time, the machine tool 100 may increase the rotational speed of the main shaft 42 by “Δr4” or may decrease the rotational speed of the main shaft 42 by “Δr4”. In the example of FIG. 15, the machine tool 100 reduces the rotational speed of the spindle 42 by “Δr4”. By setting the adjustment amount “Δr4” smaller than the adjustment amount “Δr3”, the machine tool 100 can finely adjust the number of rotations of the main spindle 42 within the stable range A, and forced chatter vibration and regeneration Both chatter vibration can be suppressed.

  It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

  12 bed, 14, 16 pillar member, 18 saddle, 21 column, 22, 22s, 22t side, 23 top, 26 table, 27 pallet, 29, 29s, 29t rotating mechanism part, 30 magazine, 31 magazine body part, 32 Tool, 32A, 32B blade, 33 base member, 34 tool holder, 35 sprocket, 36 automatic tool changer, 37 double arm, 41 spindle head, 42 spindle, 43 housing, 50 boundaries, 70 spectra, 100 machine tools, DESCRIPTION OF SYMBOLS 101 control apparatus, 102 ROM, 103 RAM, 104 communication interface, 105 display interface, 106 servo driver, 107 servo motor, 109 input interface, 110 acceleration sensor, 120 memory | storage device, 122 processing program, 124 setting , 130 display, 131 input device, 150 vibration detection unit, 152 FFT unit, 154 playback chatter vibration detection unit, 160 adjustment section 162 first adjustment unit, 164 second adjustment unit, 166 excessive adjustment determination unit.

Claims (13)

A spindle for rotating the workpiece or tool,
A sensor for detecting the vibration frequency of the spindle or the tool;
A vibration detection unit for detecting a regenerative chatter vibration occurring in the spindle or the tool based on the vibration frequency;
An adjusting unit for adjusting the number of revolutions of the spindle;
The adjustment unit is
When the regenerative chatter vibration is detected by the vibration detection unit, the number of rotations of the main spindle is adjusted from the first number of rotations which is the current setting value to the second number of rotations according to a predetermined calculation formula,
When the regenerative chatter vibration is detected by the vibration detection unit after the adjustment to the second rotational speed, the rotational speed of the main spindle is adjusted to the regenerative chatter vibration by adjusting the first rotational speed to the second rotational speed. It is judged whether or not it has exceeded the stable range in which no rotation occurs, and the rotation speed is changed depending on the judgment result.
While the regenerative chatter vibration is detected by the vibration detection unit, the number of rotations of the main shaft is adjusted by a predetermined value from the second number of rotations, and the number of rotations of the main shaft is likely to reach the first number of rotations A machine tool, wherein the adjustment amount of the number of rotations of the spindle is made smaller than the predetermined value based on satisfaction of a predetermined condition indicating.   The adjustment unit calculates how many times the number of revolutions of the main spindle reaches the first number of revolutions by adjusting how many times each of the predetermined values is adjusted after reversing the increase and decrease of the number of revolutions of the main spindle. The machine tool according to claim 1, wherein if the number of times is equal to or less than a predetermined number of times, it is determined that the predetermined condition is satisfied.   The work according to claim 1, wherein the adjusting unit determines that the predetermined condition is satisfied when the number of times of adjustment by the predetermined value after reversing the increase and decrease of the rotation speed of the spindle exceeds the predetermined number. machine. The adjustment unit is
If it is determined that the number of revolutions of the spindle does not exceed the stable range, the number of revolutions of the spindle is decreased by a first predetermined value,
When it is determined that the number of revolutions of the spindle exceeds the stable range, the number of revolutions of the spindle is increased by a predetermined second value,
The machine tool according to any one of claims 1 to 3, wherein the second value is smaller than the first value.   The said adjustment part judges whether the rotation speed of the said main axis | shaft exceeded the said stable range based on the comparison result of the said vibration frequency before and behind adjustment of the rotation speed of the said main axis. The machine tool according to item 1. In the machine tool, the wave number of the processing surface generated by the vibration of the spindle or the tool after the first blade of the tool contacts the work and the second blade of the tool contacts the work. Calculate
The adjustment unit determines whether or not the number of revolutions of the main shaft has exceeded the stable range based on whether or not the integer part of the wave number has changed before and after adjustment of the number of revolutions of the main spindle. The machine tool according to any one of ~ 4.   The adjustment unit sequentially executes adjustment processing of the rotation speed of the spindle while the vibration detection unit detects the regenerative chatter vibration, and the vibration detection unit generates the spindle or the tool. The machine tool according to any one of claims 1 to 6, wherein the adjustment process of the rotational speed is ended when the regenerative chatter vibration is not detected.   The adjustment unit is configured to increase the number of revolutions of the main spindle more than the first number of revolutions when the vibration detection unit detects the regenerative chatter after the adjustment of the number of revolutions of the main spindle is performed a predetermined number of times. The machine tool according to any one of Items 1 to 7.   The adjustment unit makes the cutting depth of the workpiece by the tool shallower than the present when the regenerative vibration is detected by the vibration detection unit after performing the adjustment of the number of rotations of the spindle a predetermined number of times. The machine tool according to any one of claims 1 to 8.   The adjustment unit makes the cutting depth of the workpiece by the tool shallower than the present when the regenerative vibration is detected by the vibration detection unit after the second value becomes equal to or less than a predetermined threshold. The machine tool according to claim 4. The vibration detection unit further detects forced chatter vibration occurring in the spindle or the tool based on the vibration frequency.
When the forced chatter vibration is detected when the regenerative chatter vibration is not detected due to the adjustment of the number of revolutions of the main shaft, the adjusting unit is more than the adjustment amount for suppressing the regenerative chatter vibration. The machine tool according to any one of claims 1 to 10, wherein the rotational speed is readjusted with a small adjustment amount. The machining method by a machine tool
The machine tool is
A spindle for rotating the workpiece or tool,
A sensor for detecting a vibration frequency of the spindle or the tool;
The processing method is
Detecting a regenerative chatter vibration occurring in the spindle or the tool based on the vibration frequency;
Adjusting the number of rotations of the main spindle from the first number of rotations, which is the current setting value, to the second number of rotations according to a predetermined calculation formula when the regenerative chatter vibration is detected in the detecting step;
When the regenerative chatter vibration is detected in the detecting step after the adjustment to the second rotational speed, the rotational speed of the main spindle is adjusted to the regenerative chatter vibration by adjusting the first rotational speed to the second rotational speed. Determining whether it has exceeded a stable range in which no rotation occurs, and changing whether to increase or decrease the number of revolutions according to the result of the determination;
While the regenerative chatter vibration is detected in the detecting step, the number of rotations of the main shaft is adjusted by a predetermined value from the second number of rotations, and the number of rotations of the main shaft is likely to reach the first number of rotations And D. making the amount of adjustment of the number of rotations of the spindle smaller than the predetermined value based on the satisfaction of the predetermined condition indicating. Machining program by machine tool,
The machine tool is
A spindle for rotating the workpiece or tool,
A sensor for detecting a vibration frequency of the spindle or the tool;
The processing program is for the machine tool
Detecting a regenerative chatter vibration occurring in the spindle or the tool based on the vibration frequency;
Adjusting the number of rotations of the main spindle from the first number of rotations, which is the current setting value, to the second number of rotations according to a predetermined calculation formula when the regenerative chatter vibration is detected in the detecting step;
When the regenerative chatter vibration is detected in the detecting step after the adjustment to the second rotational speed, the rotational speed of the main spindle is adjusted to the regenerative chatter vibration by adjusting the first rotational speed to the second rotational speed. Determining whether it has exceeded a stable range in which no rotation occurs, and changing whether to increase or decrease the number of revolutions according to the result of the determination;
While the regenerative chatter vibration is detected in the detecting step, the number of rotations of the main shaft is adjusted by a predetermined value from the second number of rotations, and the number of rotations of the main shaft is likely to reach the first number of rotations And a step of executing the step of making the amount of adjustment of the number of rotations of the spindle smaller than the predetermined value based on the satisfaction of the predetermined condition indicating.

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