JP6701142B2 - Machine tools, machining methods, and machining programs - Google Patents

Description

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

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

  Chatter vibration includes forced chatter vibration and replay chatter vibration. The forced chatter vibration is a vibration generated by intermittent cutting and occurs when the vibration frequency of the tool becomes equal to the natural frequency of the tool. Reproduction chatter vibration is vibration that occurs when the relationship between the vibration frequency of the tool and the cutting depth of the work by the tool satisfies a predetermined condition. The reproduction chatter vibration is also called self-excited chatter vibration.

  As a technique for suppressing reproduction chatter vibration, Japanese Patent Laid-Open No. 2010-105160 (Patent Document 1) discloses a machining device for controlling the rotation speed of a tool based on the following formula (1). ..

_{n = 60 · f c / {} (k + 1) · N} ··· (1)
“N” shown in the above equation (1) represents a rotation 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 blades of the cutting tool. "K" _represents the integer portion of _{60f c / (n 0 N)} . “N ₀ ”represents the current value of the number of revolutions per minute of the cutting tool or the work member.

The above formula (1) is a modification of the Tobias formula. The above formula (1) the _{"f c"} and the natural frequency of the tool, in the case where the natural number "k + 1", the above formula (1) is the expression of Tobias. That is, the machining device disclosed in Patent Document 1 determines the rotation speed of the tool by regarding the vibration frequency detected for the tool as the natural vibration frequency of the tool and substituting it into the equation of Tobias.

JP, 2010-105160, A

  The vibration frequency of the reproduction chatter vibration shows a value slightly different from 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 rotation speed of the tool is determined according to the equation (1). Therefore, a technique for more surely suppressing the reproduction chatter vibration is desired.

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

  According to one aspect, a machine tool generates a spindle for rotating a work or a tool, a sensor for detecting a vibration frequency of the spindle or the tool, and a spindle for the tool or the tool based on the vibration frequency. A vibration detection unit for detecting the reproduction chatter vibration that is present and an adjustment unit for adjusting the rotational speed of the main shaft are provided. When the reproduction chatter vibration is detected by the vibration detection unit, the adjusting unit adjusts the rotation speed of the spindle from the first rotation speed, which is the current setting value, to the second rotation speed according to a predetermined calculation formula. When the reproduction chatter vibration is detected by the vibration detection unit after the adjustment to the second rotation speed, the rotation speed of the spindle is changed to the reproduction chatter by the adjustment from the first rotation speed to the second rotation speed. It is determined whether or not the stable range in which vibration does not occur is exceeded, and whether to increase or decrease the rotation speed according to the determination result is changed, while the reproduction chatter vibration is detected by the vibration detection unit, The rotation speed of the spindle is adjusted from the second rotation speed by a predetermined value, and based on the satisfaction of a predetermined condition indicating that the rotation speed of the spindle is likely to reach the first rotation speed, The adjustment amount of the rotation speed is made smaller than the predetermined value.

  Preferably, the adjustment unit calculates how many times the main shaft rotation speed reaches the first rotation speed by adjusting the predetermined value after reversing the increase or decrease in the main shaft rotation speed, When the calculated number of times is less than or equal to the predetermined number of times, it is determined that the predetermined condition is satisfied.

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

  Preferably, the adjusting unit, when determining that the rotation speed of the spindle does not exceed the stable range, reduces the rotation speed of the spindle by a predetermined first value so that the rotation speed of the spindle falls within the stable range. When it is determined that the rotation speed has been exceeded, the rotation speed 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 or not the rotation speed of the spindle exceeds the stable range based on the comparison result of the vibration frequencies before and after the adjustment of the rotation speed of the spindle.

  Preferably, in the machine tool, machining caused by vibration of the spindle or the tool between the first blade of the tool coming into contact with the work and the second blade of the tool coming into contact with the work. Calculate the wave number of a surface. The adjusting unit determines whether or not the rotational speed of the main spindle exceeds the stable range based on whether or not the integer part of the wave number has changed before and after the adjustment of the rotational speed of the main spindle.

  Preferably, the adjusting unit sequentially performs the adjusting process of the rotation speed of the spindle while the reproduction chatter vibration is detected by the vibration detecting unit, and the vibration detecting unit causes the spindle or the tool to be adjusted. At the time when the reproduction chattering vibration that occurs in 1) is no longer detected, the rotation speed adjustment processing ends.

  Preferably, when the reproduction chatter vibration is detected by the vibration detection unit after the adjustment of the rotation speed of the spindle is performed a predetermined number of times, the adjustment unit sets the rotation speed of the spindle to be higher than the first rotation speed. increase.

  Preferably, when the reproduction chatter vibration is detected by the vibration detection unit after the adjustment of the rotation speed of the spindle is performed a predetermined number of times, the adjustment unit sets the cutting depth of the work by the tool to be greater than the present depth. Make it shallow.

  Preferably, when the reproduction chatter vibration is detected by the vibration detection unit after the second value becomes equal to or less than a predetermined threshold value, the adjustment unit determines the depth of cut of the workpiece by the tool from the present. Also make shallow.

  Preferably, the vibration detection unit further detects forced chatter vibration occurring in the spindle or the tool based on the vibration frequency. In the case where the reproduction chatter vibration is not detected by adjusting the number of revolutions of the main shaft, the adjustment unit is more than the adjustment amount for suppressing the reproduction chatter vibration when the forced chatter vibration is detected. Readjust 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 work or a tool, and a sensor for detecting a vibration frequency of the spindle or the tool. The machining method is based on the vibration frequency, a step of detecting a regenerative chatter vibration occurring in the spindle or the tool, and a predetermined calculation formula when the replay chatter vibration is detected in the detecting step. According to the above, the reproduction chatter vibration is detected in the step of adjusting the rotation speed of the main spindle from the current setting value of the first rotation speed to the second rotation speed, and in the detecting step after the adjustment to the second rotation speed. In this case, it is judged whether or not the rotation speed of the spindle exceeds the stable range in which the reproduction chatter vibration does not occur by adjusting the first rotation speed to the second rotation speed, and the rotation speed is changed according to the judgment result. The number of rotations of the spindle is adjusted from the second number of revolutions by a predetermined value while the reproduction chatter vibration is detected in the step of changing the number of rotations from the second rotation speed. And a step of reducing the adjustment amount of the rotational speed of the spindle below the predetermined value based on the satisfaction of a predetermined condition indicating that the rotational speed is likely to reach the first rotational speed.

  According to another aspect, a machining program by a machine tool is provided. The machine tool includes a spindle for rotating a work or a tool, and a sensor for detecting a vibration frequency of the spindle or the tool. The machining program, in the machine tool, based on the vibration frequency, a step of detecting a regenerative chatter vibration generated in the spindle or the tool, and when the replay chatter vibration is detected in the detecting step. , The reproduction in the step of adjusting the rotational speed of the spindle from the current setting value of the first rotational speed to the second rotational speed according to a predetermined calculation formula, and in the detecting step after the adjustment to the second rotational speed When chatter vibration is detected, it is determined by adjusting the first rotation speed to the second rotation speed whether or not the rotation speed of the spindle exceeds a stable range in which the regenerative chatter vibration does not occur, and the result of the judgment. The rotation speed of the main shaft is adjusted by a predetermined value from the second rotation speed while the reproduction chatter vibration is detected in the detecting step and in the detecting step. Then, on the basis of satisfying a predetermined condition indicating that the rotation speed of the spindle is likely to reach the first rotation speed, a step of reducing the adjustment amount of the rotation speed of the spindle below the predetermined value. Let it run.

In a certain aspect, reproduction chatter vibration 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 invention, which is understood in connection with the accompanying drawings.

It is a figure which shows the machine tool according to 1st Embodiment. It is a figure which shows the processing conditions in which reproduction chattering vibration is easy to occur. It is a figure which shows the processing conditions which reproduction chattering vibration does not generate easily. It is a figure showing the processing mode of work W. It is a figure which shows the range which reproduction|regeneration chatter vibration generate|occur|produces and the range which does not generate|occur|produce in the relationship between the rotation speed of a spindle, and the cutting depth of a workpiece|work. FIG. 6 is a diagram for explaining a fine adjustment process of a spindle rotation speed based on a fine adjustment condition 1. FIG. 6 is a diagram for explaining a fine adjustment process of a spindle rotational speed based on a 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 frequency decomposition by an FFT (Fast Fourier Transform) part. It is a figure for explaining an example of a judgment method of excessive adjustment by an 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 determination part. 5 is a flowchart showing a spindle rotation speed adjustment process based on a fine adjustment condition 1. 6 is a flowchart showing a spindle rotation speed adjustment process based on a fine adjustment condition 2. It is a block diagram which shows the main hardware constitutions of the machine tool according to 1st Embodiment. It is a figure for explaining processing of suppressing forced chatter vibration.

  Each embodiment according to the present invention will be described below with reference to the drawings. In the following description, the same parts and components are designated by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. In addition, each embodiment and each modification described below may be appropriately combined selectively.

<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 diagram illustrating an example of the machine tool 100.

  FIG. 1 shows a machine tool 100 as a machining center. The machine tool 100 as a machining center will be described below, but the machine tool 100 is not limited to a machining center. For example, the machine tool 100 may be a lathe, or may be another 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 an installation surface such as a factory.

  A column 21 is attached to the bed 12. The column 21 is fixed to the bed 12. The column 21 as a whole has a gate shape that is erected on the upper surface of the bed 12.

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

  The machine configuration of the machine tool 100 basically has a bilaterally symmetrical structure with respect to the center in the X-axis direction. In the present embodiment, the structures with reference numerals "s" and "t" are a pair of parts that are symmetrical to each other.

  A saddle 18 is attached to the bed 12. The saddle 18 is provided so as to be slidable 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 a space surrounded by the side portion 22s, the top portion 23, the side portion 22t, and the bed 12. The spindle head 41 is parallel to the horizontal direction and is provided so as to be slidable 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 is rotatably provided by a motor drive about a central axis AX1 parallel to the Z-axis direction. At this time, the housing 43 does not rotate. A tool for processing a work to be processed is attached to the spindle 42. With the rotation of the main shaft 42, the 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 42. In this case, the work mounted on the spindle 42 rotates as the spindle 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 vibration of the main shaft 42 in different directions (for example, X, Y, Z directions). 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 serve as a feed mechanism, a guide mechanism, and a drive source for enabling the sliding movement of the saddle 18 in the X-axis direction and the sliding movement of the spindle head 41 in the Z-axis direction. A servo motor or the like is provided as appropriate.

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

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

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

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

  The machining position of the workpiece by the tool mounted on the spindle 42 is obtained by combining the sliding movement of the saddle 18 in the X-axis direction, the sliding movement of the spindle head 41 in the Z-axis direction, and the sliding movement of the table 26 in the Y-axis direction. Moves three-dimensionally.

  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 a replacement tool 32 mounted on the spindle 42. The automatic tool changing device 36 is a device for changing tools between the spindle 42 and the magazine 30.

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

  The magazine body 31 has a plurality of tool holders 34 and a sprocket 35. The tool holding unit 34 is configured to hold the tool 32. The plurality of tool holding portions 34 are annularly arranged around the sprocket 35. The sprocket 35 is provided rotatably about a central axis AX3 parallel to the Y axis by being driven by a motor. With the rotation of the sprocket 35, the plurality of tool holding portions 34 rotate about the central axis AX3.

  The magazine body 31 is supported by the pillar members 14 and 16 and the base member 33 at a position spaced vertically upward from the bed 12.

  With the rotation of the sprocket 35, the tool holding portion 34 holding the specific tool 32 is indexed to a predetermined position in front of the machine. The specific tool 32 is transferred in the Z-axis direction by a tool transfer device (not shown) and moves to the tool exchange position. When the double arm 37 included in the automatic tool changing device 36 rotates, the specific tool 32 conveyed to the tool changing position and the tool attached to the spindle 42 are changed. 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 reproduction chatter vibration]
When machining a workpiece with a machine tool, chatter vibration may occur in which the cutting edge of the tool 32 slightly vibrates. Chatter vibration includes forced chatter vibration and replay chatter vibration. The forced chatter vibration is a vibration generated by a 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. The reproduction chatter vibration is vibration that occurs when the relationship between the vibration frequency of the tool 32 and the depth of cut of the work by the tool 32 satisfies a predetermined condition.

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

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

  The tool 32 processes the work by repeatedly cutting the work while rotating. The tool 32 vibrates during processing of the work, and as shown in FIG. 2A, the cutting surface of the work is uneven.

  When the tool 32 cuts the work next time, the cutting trace at the time of the previous cutting and the vibration frequency of the tool 32 at the time of this cutting may deviate from each other. When this deviation is represented by "φ", the deviation φ is π/4 (=90 degrees) in the examples of FIGS. 2A and 2B. When such a deviation occurs, the cutting thickness of the work changes depending on the cutting position. FIG. 2C shows the variation of the cutting thickness when the deviation of φ=π/4 occurs. When the cutting thickness changes, the force that the tool 32 receives from the work during cutting changes, and reproduction chatter vibration is likely to occur. In particular, reproduction chatter vibration is most likely to occur when φ=π/4.

  FIG. 3 is a diagram showing an example of processing conditions in which reproduction chatter vibration is unlikely to occur. More specifically, FIG. 3(A) shows a cutting trace on the work during the previous cutting. FIG. 3B shows the vibration frequency of the tool 32 during the cutting this time. FIG. 3C shows the cutting thickness of the work by the tool 32 at the time of this cutting.

  In the example of FIG. 3A and FIG. 3B, the vibration frequency of the tool 32 overlaps with the cutting trace during the previous cutting. In this case, the deviation “φ” becomes 0 and the cutting thickness of the work becomes constant. Therefore, the force that the tool 32 receives from the work during cutting becomes constant, and regenerative chatter vibration hardly occurs.

  Therefore, when the rotational speed of the main shaft 42 is adjusted so that the deviation “φ” approaches 0, reproduction 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, reproduction chatter vibration is likely to occur.

  Typically, when “k” shown in the following formula (2) becomes an integer, the deviation “φ” becomes 0.

_{k = 60 · f c / (} n 0 · N) ··· (2)
“K” shown in the equation (2) is the wave number of the machining surface generated by the vibration of the tool 32 from the time when the first blade of the tool 32 contacts the work to the time when the second blade contacts the work. Represent. “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 rotation speed of the spindle 42. The rotational speed as used herein means the rotational speed of the spindle 42 per unit time (for example, per minute) and is synonymous with the rotational speed. Since the tool 32 is interlocked with the spindle 42, the rotation speed of the spindle 42 is equal to the rotation speed of the tool 32. Therefore, the rotation speed of the spindle 42 is synonymous with the rotation speed of the tool 32.

  FIG. 4 is a diagram showing a processing mode of the work W in the case where “k” is an integer. FIG. 4 shows aspects of the tool 32 and the work W when viewed from the axial direction of the spindle 42.

  FIG. 4A shows a processing mode of the work W when “k” is 1. As shown in FIG. 4A, when “k” is 1, the tool 32 is between the blade 32A of the tool 32 and the workpiece W and the blade 32B of the tool 32 is in contact with the workpiece W. The number of waves on the machined surface caused by the vibration is 1.

  FIG. 4B shows a processing mode of the work W when “k” is 2. The rotation speed of the tool 32 in the machining mode of FIG. 4B corresponds to 1/2 of the rotation speed of the tool 32 in the machining mode of FIG. 4A. As shown in FIG. 4B, when “k” is 2, the wave number on the processed surface of the work W is 2.

  FIG. 4C shows a processing mode of the work W when “k” is 3. The rotation speed of the tool 32 in the machining mode of FIG. 4(C) corresponds to 1/3 of the rotation speed of the tool 32 in the machining mode of FIG. 4(A). As shown in FIG. 4C, when “k” is 3, the wave number on the processed surface of the work W is 3.

  In the processing modes shown in FIGS. 4A to 4C, since the deviation “φ” is 0, reproduction chatter vibration is unlikely to occur.

  FIG. 5 is a diagram showing a range where the reproduction chatter vibration occurs and a range where the reproduction chatter vibration does not occur in the relationship between the rotation speed of the main shaft 42 and the cutting depth of the work W. The horizontal axis of the graph shown in FIG. 5 represents the rotation speed of the main shaft 42. The vertical axis of the graph shown in FIG. 5 represents the cutting depth of the work. The depth of cut referred to here means the length of the contact portion between the tool 32 and the work W in the axial direction of the main shaft 42.

  A range in which the depth of cut of the work is smaller than the boundary line 50 represents a processing condition in which reproduction chatter vibration is unlikely to occur. Hereinafter, this range is also referred to as a stable range A.

  A range where the depth of cut of the work is larger than the boundary line 50 is a processing condition in which reproduction chatter vibration is likely to occur. Hereinafter, the range is also referred to as an unstable range B.

[C. Adjustment processing of the rotation speed of the 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.

  Machine tool 100 according to the present embodiment sequentially adjusts the rotation speed of spindle 42, and when the rotation speed of spindle 42 falls within stable range A, the adjustment processing of the rotation speed of spindle 42 ends. More specifically, until the rotation speed of the spindle 42 exceeds the stable range A, the machine tool 100 reduces the rotation speed of the spindle 42 by a predetermined amount. When the rotation speed of the spindle 42 exceeds the stable range A, the machine tool 100 reverses the increase/decrease in the rotation speed of the spindle 42 from the previous adjustment, and reduces the adjustment amount of this time from the adjustment amount of the previous time. As a result, the rotation speed of the spindle 42 falls within the stable range A, and the machine tool 100 can suppress regenerative chatter vibration.

  FIG. 5 shows a state in which the rotation speed of the spindle 42 is contained in the lobe A2 of the stable range A by sequentially executing the adjustment processing of steps S1 to S4. In the following, an example of processing in which the rotation speed of the main shaft 42 is contained in the lobe A2 of the stable range A will be described.

  When the machining of the work is started, the machine tool 100 sets the rotation speed of the spindle 42 to the initial value "r0". After that, the machine tool 100 calculates the vibration frequency of the spindle 42 from the output signal of the acceleration sensor 110 (see FIG. 1), and determines whether or not the regenerative chatter vibration is occurring in the tool 32 based on the vibration frequency. .. Details of the method for detecting the reproduction chatter vibration will be described later.

  When the reproduction chatter vibration occurs at the rotation speed “r0”, the machine tool 100 calculates the rotation speed of the spindle 42 according to a predetermined calculation formula. As an example, the machine tool 100 calculates the new rotation speed of the 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 spindle 42 that is set next. “F _C ”represents the vibration frequency of the main shaft 42. “[K]” represents an integer obtained by adding 1 to the integer part of “k” calculated by the above formula (2). “N” represents the number of blades of the tool mounted on the spindle 42.

  The machine tool 100 substitutes the vibration frequency of the spindle 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, the machine tool 100 adjusts the rotational speed of the spindle 42 from the rotational speed "r0" (first rotational speed) to the rotational speed "r1" (second rotational speed) in step S1. After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that reproduction chatter vibration continues to occur. Next, the machine tool 100 determines whether or not the rotation speed of the spindle 42 exceeds the stable range A by the adjustment processing in step S1, and increases or decreases the rotation speed of the spindle 42 according to the determination result. Change something. Since the boundary line 50 is unknown, it is necessary to somehow determine whether or not the rotation speed of the spindle 42 exceeds the stable range A. The details of this determination method will be described later.

  When the machine tool 100 determines that the rotation speed of the spindle 42 does not exceed the stable range A, the machine tool 100 reduces the rotation speed of the spindle 42 by a predetermined value. On the other hand, when the machine tool 100 determines that the rotation speed of the spindle 42 exceeds the stable range A, the machine tool 100 increases the rotation speed of the spindle 42 by a predetermined value.

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

  After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that reproduction chatter vibration continues to occur. Next, the machine tool 100 determines whether or not the rotation speed of the spindle 42 exceeds the stable range A by the adjustment processing in step S2, and increases or decreases the rotation speed of the spindle 42 according to the determination result. Change something. In the example of FIG. 5, since the rotation speed of the spindle 42 does not exceed the stable range A in the adjustment processing of step S2, in step S3, the machine tool 100 changes the rotation speed of the spindle 42 by the same amount as the previous adjustment ( That is, Δr1) is decreased.

  After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that reproduction chatter vibration continues to occur. Next, the machine tool 100 determines whether or not the rotation speed of the spindle 42 exceeds the stable range A by the adjustment processing in step S3, and increases or decreases the rotation speed of the spindle 42 according to the determination result. Change something. In the example of FIG. 5, the rotation speed of the spindle 42 exceeds the stable range A in the adjustment process of step S3, so in step S4, the machine tool 100 sets the rotation speed of the spindle 42 to a predetermined value (for example, Δr2). )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 an example, the adjustment amount “Δr2” is a quarter of the adjustment amount “Δr1”. As described above, the machine tool 100 switches the rotation speed of the main spindle 42 by changing the increase or decrease of the rotation speed of the main spindle 42 based on the rotation speed of the main spindle 42 exceeding the stable range, and makes the adjustment amount of the main spindle 42 smaller than the previous adjustment amount. To do. As a result, the machine tool 100 can surely keep the rotation speed of the spindle 42 within the stable range A in a short time, and suppress reproduction chatter vibration at an early stage.

  In the above description, an example in which the rotation speed is adjusted to decrease the rotation speed of the main shaft 42 so that the rotation speed of the main shaft 42 is contained in the lobe A2 of the stable range A has been described. The rotation speed may be adjusted to increase. By adjusting the rotation speed so as to decrease, the machine tool 100 can prevent the tool 32 from being worn. 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 adjusts the rotation speed of the spindle 42 so that the rotation speed of the spindle 42 is stable. The area A can be reliably accommodated.

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

  By performing such fine adjustment processing, the machine tool 100 can reliably keep the rotation speed of the spindle 42 within the stable range A. Further, since the rotation speed of the spindle 42 is roughly adjusted in the initial stage of the adjustment, the time required for the adjustment process is shortened, and the machine tool 100 can suppress the regenerative chatter vibration earlier. Further, the machine tool 100 can prevent the rotation speed of the spindle 42 from being adjusted to the first rotation speed before the adjustment in which the reproduction chatter vibration was generated.

  Various conditions may be adopted as the fine adjustment conditions. Below, the adjustment processing of the spindle rotational speed based on the fine adjustment conditions 1 and 2 will be described.

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

  In this specific example, the machine tool 100 determines how many times the spindle rotation speed reaches the pre-adjustment first rotation speed by adjusting the predetermined value “Δr2” after the increase and decrease of the spindle rotation speed is reversed. When the calculated number of times (hereinafter, also referred to as “adjustable number of times”) is less than or equal to a predetermined threshold number of times (predetermined number of times), it is determined that the spindle rotation speed is likely to reach the first rotation 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 hereinafter, the fine adjustment process based on the fine adjustment condition 1 will be described on the assumption that the threshold number of times is set to "1".

  Referring to FIG. 6, it is assumed that reproduction chatter vibration is occurring at the rotation speed “r5” of main shaft 42. As a result, the machine tool 100 stores the current rotation speed “r5” (first rotation speed) and executes the adjustment process in step S5. The machine tool 100 determines whether or not the rotational speed of the spindle 42 exceeds the stable range A by the adjustment processing in step S5, and if it determines that the rotational speed exceeds the stable range A, the increase or decrease of the spindle rotational speed is set to the previous value. And reverse. In the example of FIG. 6, since the spindle rotational speed exceeds the stable range A in the adjustment processing in step S5, the increase/decrease in the spindle rotational speed is reversed from the previous time. Further, the machine tool 100 reduces the adjustment amount of the spindle 42 from “Δ1” to “Δr2”.

  Further, 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 speed “r6” from the rotation speed “r5” and divides the difference result by the adjustment amount “Δr2” to calculate the result as the adjustable number of times. In the example of FIG. 6, “3 times” is calculated as the adjustable number of times from the rotation speed “r6”. Since the adjustable number of times is larger than the threshold number of times “1”, 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 by “Δr2”. As a result, as shown in step S6, the spindle rotational speed is adjusted from "r6" to "r7".

  After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that reproduction chatter vibration continues to occur. The machine tool 100 determines whether or not the spindle rotation speed exceeds the stable range A by the adjustment processing in step S6, and increases or decreases the spindle rotation speed in reverse 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 processing in step S6, the increase/decrease in the spindle rotational speed is not reversed.

  Further, the machine tool 100 calculates the adjustable number of times from the spindle rotational speed “r7”. In the example of FIG. 6, “2 times” is calculated as the adjustable number of times from the spindle rotational speed “r7”. Since the adjustable number of times is larger than the threshold number of times “1”, 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 by “Δr2”. As a result, as shown in step S7, the spindle speed is adjusted from "r7" to "r8".

  After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that reproduction chatter vibration continues to occur. The machine tool 100 determines whether or not the spindle rotation speed exceeds the stable range A by the adjustment processing in step S7, and increases or decreases the spindle rotation speed in reverse 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 processing in step S7, the increase/decrease in the spindle rotational speed is not reversed.

  Further, the machine tool 100 calculates the adjustable number of times from the current rotation speed “r8”. In the example of FIG. 6, “1 time” is calculated as the adjustable number of times from the spindle rotation speed “r8”. Since the adjustable number of times is equal to or less than the threshold number of times “1”, 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 an example, “Δr3” is 1/2 (=0.5) times of “Δr2”. As a result, as shown in step S8, the rotation speed of the main shaft 42 is adjusted from "r8" to "r9".

  After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that the reproduction chatter vibration has subsided. As a result, the machine tool 100 ends the spindle rotation speed adjustment processing.

  As described above, the machine tool 100 adjusts the spindle rotational speed by the predetermined adjustment amount “Δr2” while the spindle rotational speed does not exceed the stable range A when the reproduction chatter vibration is generated. In the adjustment process, the machine tool 100 determines that the fine adjustment condition is satisfied based on that the remaining adjustable number of times becomes equal to or less than the predetermined threshold number of times, and determines the adjustment amount of the spindle rotational speed from “Δr2”. Lower to “Δr3”. By performing such fine adjustment processing, the machine tool 100 can surely and early set the spindle rotational speed within the stable range A.

  When the spindle rotational speed again exceeds the stable range A in the adjustment process of the adjustment amount “Δr2”, the machine tool 100 reverses the increase/decrease in the spindle rotational speed from the previous adjustment, and the spindle rotational speed. The adjustment amount of is reduced from “Δr2” to “Δr3”. After that, when the reproduction 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, and further reduces the adjustment amount from “Δr3” based on the remaining adjustable number of times being equal to or less than the predetermined threshold number.

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

  As described above, machine tool 100 according to the present embodiment adjusts the rotation speed of spindle 42 by a predetermined value “Δr2” while the reproduction chatter vibration is detected. At this time, the machine tool 100 determines that the number of adjustments at the predetermined value “Δr2” after reversing the increase/decrease in the rotation speed of the spindle 42 has exceeded the predetermined number (for example, 3 times), and the fine adjustment condition Judge that is satisfied. Based on this determination result, the machine tool 100 reduces the adjustment amount of the rotation speed of the spindle 42 to be smaller than the predetermined value “Δr2”. By performing such a fine adjustment process, the machine tool 100 can reliably and early set the rotational speed of the spindle 42 within the stable range A.

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

  After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that reproduction chatter vibration continues to occur. As a result, in step S12, the machine tool 100 increases the rotation speed of the spindle 42 by the same amount as the previous adjustment amount (that is, Δr2). As a result, the rotation speed of the main shaft 42 is adjusted from "r12" to "r13".

  After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that reproduction chatter vibration continues to occur. As a result, in step S13, the machine tool 100 increases the rotation speed of the spindle 42 by the same amount as the previous adjustment amount (that is, Δr2). As a result, the rotation speed of the main shaft 42 is adjusted from "r13" to "r14".

  After that, the machine tool 100 determines again whether or not reproduction chatter vibration is occurring. As a result, it is assumed that reproduction chatter vibration continues to occur. At this time, the machine tool 100 determines that the adjustment with the adjustment amount “Δr2” has exceeded the predetermined number of times (for example, three times), and determines that the fine adjustment condition is satisfied. Based on this determination result, the machine tool 100 lowers the adjustment amount of the rotation speed of the spindle 42 below the previous adjustment amount "r2". In the example of FIG. 7, the adjustment amount of the rotation speed of the main shaft 42 is lowered from “Δr2” to “Δr3” in step S14. As a result, the rotation speed of the main shaft 42 is adjusted from "r14" to "r15".

  As described above, in the machine tool 100, when the reproduction chatter vibration is generated, as long as the rotation speed of the spindle 42 does not exceed the stable range A, the rotation speed of the spindle 42 is the same as the previous time (that is, Δr2). Keep increasing or decreasing. After that, the machine tool 100 reduces the adjustment amount from “Δr2” to “Δr3” based on the number of adjustments with “Δr2” exceeding the predetermined number (for example, three times). By performing such a fine adjustment process, the machine tool 100 can reliably and early set the rotational speed of the spindle 42 within the stable range A.

[E. Functional configuration of machine tool 100]
Functions of the machine tool 100 will be described with reference to FIGS. 8 to 11. FIG. 8 is a diagram showing an example of the functional configuration of the machine tool 100.

  The machine tool 100 includes a control device 101. The control device 101 is, for example, an NC control device capable of executing an NC (Numerical Control) program. The NC controller is composed of at least one integrated circuit. The integrated circuit includes, for example, at least one CPU (Central Processing Unit), at least one ASIC (Application Specific Integrated Circuit), at least one FPGA (Field Programmable Gate Array), 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 rotation speed of the spindle 42. The functions of the vibration detection unit 150 and the adjustment unit 160 will be sequentially described below.

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

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

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

  The reproduction chatter vibration detection unit 154 extracts, as the vibration frequency, the frequency of the signal component having the maximum signal strength among the signal components in the spectrum 70. After that, the reproduction chatter vibration detection unit 154 detects the reproduction chatter vibration when the vibration frequency exceeds the predetermined threshold th. When the reproduction chatter vibration detection unit 154 detects the reproduction chatter vibration, it outputs the fact to the adjustment unit 160.

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

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

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

  The second adjuster 164 adjusts the rotation speed of the spindle 42 from the second time onward. More specifically, the second adjustment unit 164 readjusts the rotation speed of the main shaft 42 when the reproduction chatter vibration continues to occur after the rotation speed is adjusted by the first adjustment unit 162. At this time, the second adjusting unit 164 changes whether to increase or decrease the rotation speed of the main shaft 42, depending on whether or not the excessive adjustment has been performed in the previous adjustment. More specifically, when excessive adjustment is performed in the previous adjustment, the second adjustment unit 164 reverses the increase and decrease in the rotation speed of the main shaft 42 from the previous adjustment, and adjusts the rotation amount more than the previous adjustment amount. Reduce the adjustment amount this time. On the other hand, when the excessive adjustment is not performed in the previous adjustment, the second adjustment unit 164 adjusts the rotation speed of the spindle 42 in the same manner as the previous adjustment.

  The second adjusting unit 164 outputs the determined rotation speed as the target rotation speed to the servo driver 106 (see FIG. 14) described later. The servo driver 106 controls a later-described servo motor 107 (see FIG. 14) that drives the spindle 42 so that the spindle 42 rotates at the determined target rotation speed.

  The second adjusting unit 164 sequentially executes the adjustment processing of the rotational speed of the spindle 42 while the reproduction chatter vibration detection unit 154 detects the reproduction chatter vibration, and the reproduction chatter generated in the tool 32 or the spindle 42. When the vibration is no longer detected, the rotation speed adjustment process ends.

  Preferably, the second adjusting unit 164 reduces the rotation speed of the main shaft 42 when the reproduction chatter vibration is still occurring after the rotation speed of the main shaft 42 is adjusted a predetermined number of times (for example, 10 times). It is determined that there is no stable range A lobe in the direction, and a stable range A lobe is searched for in the direction in which the rotation speed of the main shaft 42 is increased. Therefore, in this case, the second adjusting unit 164 increases the rotation speed of the spindle 42 above the initial value. As a result, the second adjusting unit 164 can search for a lobe in the stable range A in a direction larger than the initial value.

  In another aspect, when the reproduction chatter vibration is still occurring after the adjustment of the rotation speed of the spindle 42 is performed a predetermined number of times (for example, 10 times), the second adjustment unit 164 determines the cutting depth of the spindle 42 at the present time. Shallower than. In the example of FIG. 5, the second adjusting unit 164 lowers the cutting depth of the spindle 42 below the initial value “h”. This increases the possibility that the rotation speed of the main shaft 42 falls within the stable range.

  The second adjusting unit 164 determines that the lobe of the stable range A does not exist in the direction of decreasing the rotation speed of the main shaft 42 when the adjustment amount of the rotation amount of the main shaft 42 becomes equal to or less than the predetermined threshold value. Good. In such a case, the second adjusting unit 164 may search for a lobe in the stable range A in the direction of increasing the rotation speed of the main shaft 42, or set the cutting depth of the main shaft 42 to “h” which is the initial value. May be lower than.

  The excessive adjustment determination unit 166 determines whether the excessive adjustment of the rotation speed is performed by the first adjustment unit 162 or the second adjustment unit 164. More specifically, the over-adjustment determination unit 166 determines that the over-adjustment has been performed when the rotation speed of the spindle 42 exceeds the above-described stable range A (see FIG. 5) due to the previous adjustment. Whether or not the rotation speed of the main shaft 42 exceeds the stable range A is determined by various methods. Hereinafter, a method of determining excessive adjustment will be described with reference to FIGS. 10 and 11.

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

  The upper graph of FIG. 10 shows a range in which the reproduction chatter vibration occurs and a range in which the reproduction chatter vibration does not occur in the relationship between the rotation speed of the spindle 42 and the cutting depth of the work. The lower graph of FIG. 10 shows the relationship between the rotation speed of the spindle 42 and the vibration frequency of the spindle 42.

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

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

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

  As shown in FIG. 11, the integer part (that is, [k]) of “k” in the above equation (2) changes before and after the apices of the lobes A1 to A3 in the stable range A. Below, the integer part of "k" is also called an order. The excessive adjustment determination unit 166 determines whether or not the rotational speed of the main shaft 42 exceeds the stable range A based on whether or not the order changes before and after the 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” by adjusting the rotation speed of the spindle 42 from “r2” to “r3” (m: integer). In this case, the excessive adjustment determination unit 166 determines that the rotation speed of the spindle 42 exceeds the stable range A, and determines that the excessive adjustment has been performed. On the other hand, when the order does not change before and after the adjustment of the rotation speed of the spindle 42, the excessive adjustment determination unit 166 determines that the rotation speed of the spindle 42 does not exceed the stable range A, and the excessive adjustment is performed. Judge that it has not been broken.

[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 fine adjustment condition 1 described above. 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 of FIGS. 12 and 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, the control flow of the adjustment processing based on the fine adjustment condition 1 will be described with reference to FIG.

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

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

  In step S122, the control device 101 calculates the rotation speed “n′” of the spindle 42 according to a predetermined calculation formula as the above-described first adjustment unit 162 (see FIG. 8). As the calculation formula, for example, the Tobias formula of the above formula (3) is adopted.

  "[K]" shown in the above equation (3) may be calculated based on the above equation (2), or may be calculated based on the following equation (4).

_{[K] = [60 · f} c / (n 0 · N)] + dir ··· (4)
“K” shown in the equation (4) represents the wave number of the machining surface generated by the vibration of the tool from the time when the first blade of the tool 32 contacts the work to the time when the second blade contacts the work. .. “F _c ”represents the vibration frequency of the main shaft 42. "N" represents the number of blades of the cutting tool. “N ₀ ”represents the rotation speed of the spindle 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 rotation speed of the main shaft 42, “dir” is set to 0. When lowering the rotation speed of the spindle 42, "dir" is set to 1.

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

  In step S126, the control device 101, as the adjusting unit 160 (see FIG. 8), changes the rotation speed of the spindle 42 from the current setting value of the rotation speed “n” to the rotation speed “n′”.

  In step S130, the control device 101 determines as the above-described excessive adjustment determination unit 166 (see FIG. 8) whether or not the rotational speed of the spindle 42 has exceeded the stable range A (see FIG. 5) due to the previous adjustment. Since the determination method is as described in FIGS. 10 and 11, the description will not be repeated. When the control device 101 determines that the rotation speed of the spindle 42 has exceeded the stable range A due to the previous adjustment (YES in step S130), the control device 101 switches the control to step S132. Otherwise (NO in step S130), the control device 101 switches control to step S136.

  In step S132, the control device 101 calculates the rotation speed "n'" of the spindle 42 based on the following equation (5) as the second adjusting unit 164 (see FIG. 8) described above.

n′=n−Δn·a (5)
“N′” shown in Expression (5) represents the adjusted rotation speed. "N" represents the current rotational speed. “Δn” represents the adjustment amount of the previous rotation speed. “A” is a coefficient larger than 0 and smaller than 1. The coefficient “a” is set small every time the process of step S132 is executed. As an example, at the first time, the coefficient “a” is set to ¼.

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

  In step S135, the control device 101 stores the current rotation speed “n” of the main spindle 42 in the storage device 120 (see FIG. 14) described later as the second adjusting unit 164.

  In step S136, the control device 101, as the second adjusting unit 164 described above, how many times the spindle rotation speed reaches the rotation speed stored in step S135 by performing the sequential adjustment after the increase and decrease of the spindle rotation speed is reversed. To calculate. As an example, the control device 101 subtracts the current rotation speed from the rotation speed stored in step S135, and divides the difference result by the current adjustment amount to calculate the result as the adjustable number of times. 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 second adjusting unit 164 described above, determines whether or not the above-described fine adjustment condition 1 is satisfied. In this example, the control device 101 determines that the fine adjustment condition 1 is satisfied when the adjustable count calculated in step S136 is less than or equal to a predetermined threshold count (for example, once). When the control device 101 determines that the adjustable count calculated in step S136 is less than or equal to the predetermined threshold count (YES in step S137), the control device 101 switches control to step S138. Otherwise (NO in step S137), the control device 101 switches control to step S140.

  In step S138, the control device 101, as the second adjusting unit 164 described above, makes the adjustment amount “Δn” of the rotation speed of the spindle 42 smaller than the previous adjustment amount “Δn”. At this time, the control device 101, as the above-mentioned second adjusting unit 164, initializes the number of adjustments “c” of the rotation speed of the spindle 42. The adjustment count “c” is initialized to “1”, for example. 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 rotational speed. “Δn” on the right side of the equation (6) represents the adjustment amount of the previous rotation speed. “B” is a coefficient greater than 0 and less than 1. As an example, the coefficient “b” is ½ (=0.5).

  In step S140, the control device 101, as the second adjusting unit 164 described above, calculates the rotation speed "n'" of the spindle 42 based on the following equation (7).

n'=n+Δn (7)
“N′” shown in Expression (7) represents the adjusted rotation speed. "N" represents the current rotational speed. “Δn” represents the adjustment amount of the previous rotation speed.

  In step S142, the control device 101, as the second adjusting unit 164 described above, increments the number of adjustments “c” of the rotation speed of the spindle 42.

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

  In step S135A, the control device 101, as the above-mentioned second adjustment unit 164, initializes the number of adjustments “c” of the rotation speed of the spindle 42. The number of adjustments “c” is a variable for counting the number of adjustments of the rotation speed of the spindle 42. The adjustment count “c” is initialized to “1”, for example.

  In step S137A, the control device 101, as the above-described second adjustment unit 164, determines whether or not the above-described fine adjustment condition 2 is satisfied. In this example, the control device 101 determines that the fine adjustment condition 2 is satisfied when the number of adjustments “c” of the spindle rotation speed exceeds a predetermined number (for example, 3 times). When determining that the number of adjustments “c” of the spindle rotation speed has exceeded the predetermined number (YES in step S137A), control device 101 switches the control to step S138. Otherwise (NO in step S137A), the control device 101 switches control to step S140.

  In step S142, the control device 101, as the second adjusting unit 164 described above, increments the number of adjustments “c” of the rotation speed of the spindle 42.

[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 machine tool 100.

  The machine tool 100 includes a spindle 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, an acceleration sensor 110, and And a storage device 120.

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

  A LAN, an antenna, etc. 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 machining 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 according to a command 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 the input of the target rotation speed from the control device 101, and controls the servo motor 107 so that the spindle 42 rotates at the target rotation speed. More specifically, the servo driver 106 calculates the rotation speed of the spindle 42 from the output signal of the encoder (not shown) of the servo motor 107, and if the rotation speed is smaller than the target rotation speed, the servo motor 107 The rotation speed is increased, and when the rotation speed is higher than the target rotation speed, the rotation speed of the servo motor 107 is decreased. In this way, the servo driver 106 brings the rotation speed of the spindle 42 close to the target rotation speed while sequentially receiving the feedback of the rotation speed of the spindle 42.

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

  The storage device 120 is, for example, a storage medium such as a hard disk or a flash memory. Storage device 120 stores machining program 122 according to the present embodiment, set value 124 referred to by machining program 122 (for example, rotation speed of spindle 42), and the like. The storage locations of the machining program 122 and the set value 124 are not limited to the storage device 120, and are stored in the storage area (for example, cache memory) of the control device 101, the ROM 102, the RAM 103, an external device (for example, a server), or the like. May be.

  The processing program 122 may be provided as a part of an arbitrary program instead of as a stand-alone program. In this case, the control process according to the present embodiment is realized in cooperation with an arbitrary program. Even a program that does not include some of such modules does not depart from the spirit of the machining 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. Further, the machine tool 100 may be configured in a form such as a so-called cloud service in which at least one server executes a part of the processing of the machining program 122.

[H. advantage]
As described above, machine tool 100 according to the present embodiment reduces the rotational speed of main spindle 42 by a predetermined amount until the rotational speed of main spindle 42 exceeds stable range A. When the rotation speed of the spindle 42 exceeds the stable range A, the machine tool 100 reverses the increase/decrease in the rotation speed of the spindle 42 from the previous adjustment, and reduces the adjustment amount of this time from the adjustment amount of the previous time. The machine tool 100 ends the process of adjusting the rotational speed of the spindle 42 when the rotational speed of the spindle 42 falls within the stable range A.

  By sequentially adjusting the rotation speed of the spindle 42 in this manner, the machine tool 100 can reliably keep the rotation speed of the spindle 42 within the stable range A in a short time, and the reproduction chatter vibration in a short time. And it can be suppressed reliably.

<Second Embodiment>
In machine tool 100 according to the first embodiment, the rotational speed of main shaft 42 is adjusted in order to suppress regenerative chatter vibration. On the other hand, machine tool 100 according to the second embodiment adjusts the rotation speed of main shaft 42 in order to suppress both reproduction chattering vibration and forced chattering vibration.

  Other points such as the hardware configuration of machine tool 100 according to the second embodiment are the same as those of machine tool 100 according to the first embodiment, and therefore the description thereof will not be repeated below.

  The frequency of the forced chatter vibration can be calculated based on the number of blades of the tool 32 and the rotation speed of the spindle 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 rotation speed of the spindle 42. “N” represents the number of blades of the tool 32.

  When the vibration frequency of the spindle 42 coincides with an integer multiple of the frequency “f”, the machine tool 100 determines that forced chatter vibration is occurring. On the other hand, when the vibration frequency of the spindle 42 does not match an integral multiple of the frequency “f” under the condition that chatter vibration is occurring, the machine tool 100 determines that the regenerative chatter vibration is occurring.

  In the example of FIG. 9, since the signal strength of the signal component that does not match the integral multiple of the frequency “f” exceeds the threshold th, the machine tool 100 determines that the reproduction chatter vibration is occurring. On the other hand, when the signal strength of the signal component at an integer multiple of the frequency “f” (for example, “m−1” times, “m” times, “m+1” times) exceeds the predetermined threshold, the machine tool 100 Determines that forced chatter vibration 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 rotation speed of the spindle 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 is generated, the machine tool 100 sequentially increases or decreases the rotation speed of the spindle 42. At this time, it is necessary to adjust the rotation speed of the main shaft 42 within the above-mentioned 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 stable range A.

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

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

  However, as described above, when the vibration frequency of the main shaft 42 matches an integral multiple of the frequency “f” shown in the above equation (8), forced chatter vibration is likely to occur. A region in which such forced chatter vibration is likely to occur is shown as an unstable range D in FIG. In the example of FIG. 15, the rotational speed of the spindle 42 belongs to the unstable range D due to the adjustment processing in step S20.

  In step S20, the machine tool 100 re-adjusts the rotation speed of the spindle 42 with the adjustment amount "Δr4" smaller than the rotation speed adjustment amount "Δr3" for suppressing the reproduction chatter vibration. At this time, the machine tool 100 may increase the rotation speed of the spindle 42 by “Δr4” or decrease the rotation speed of the spindle 42 by “Δr4”. In the example of FIG. 15, the machine tool 100 reduces the rotation speed of the spindle 42 by “Δr4”. By setting the adjustment amount “Δr4” to be smaller than the adjustment amount “Δr3”, the machine tool 100 can finely adjust the rotation speed of the spindle 42 within the stable range A, and the forced chatter vibration and reproduction can be performed. Both chatter vibration can be suppressed.

  The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

  12 beds, 14, 16 pillar members, 18 saddles, 21 columns, 22, 22s, 22t side parts, 23 tops, 26 tables, 27 pallets, 29, 29s, 29t rotating mechanism parts, 30 magazines, 31 magazine body parts, 32 Tools, 32A, 32B blades, 33 stand members, 34 tool holders, 35 sprockets, 36 automatic tool changers, 37 double arms, 41 spindle heads, 42 spindles, 43 housings, 50 boundaries, 70 spectra, 100 machine tools, 101 control device, 102 ROM, 103 RAM, 104 communication interface, 105 display interface, 106 servo driver, 107 servo motor, 109 input interface, 110 acceleration sensor, 120 storage device, 122 machining program, 124 set value, 130 display, 131 Input device, 150 vibration detection unit, 152 FFT unit, 154 reproduction chatter vibration detection unit, 160 adjustment unit, 162 first adjustment unit, 164 second adjustment unit, 166 excessive adjustment determination unit.

Claims (12)

A spindle for rotating a workpiece or tool,
A sensor for detecting the vibration frequency of the spindle or the tool,
Based on the vibration frequency, a vibration detection unit for detecting reproduction chatter vibration occurring in the spindle or the tool,
An adjusting unit for adjusting the number of revolutions of the main shaft,
The adjustment unit,
When the reproduction chatter vibration is detected by the vibration detection unit, the rotation speed of the spindle is adjusted from the first rotation speed, which is the current setting value, to the second rotation speed according to a predetermined calculation formula,
While the reproduction chatter vibration is being detected by the vibration detection unit, the rotation speed of the spindle is sequentially adjusted by a predetermined value from the second rotation speed,
When the number of revolutions of the main spindle exceeds the stable range in which the reproduction chatter vibration does not occur before and after the adjustment of the number of revolutions of the main spindle, the increase and decrease of the adjustment amount of the number of revolutions of the main spindle is reversed, and the number of revolutions of the main spindle is changed. The adjustment amount is smaller than the predetermined value,
Based on that a predetermined condition indicating that the rotation speed of the spindle is likely to reach the first rotation speed is satisfied, the adjustment amount of the rotation speed of the spindle is made smaller than the predetermined value,
A machine tool , wherein the adjustment processing of the rotational speed of the spindle is ended when the reproduction chatter vibration is no longer detected by the vibration detection unit by the sequential adjustment of the rotational speed of the spindle .   The adjustment unit calculates how many times the main shaft rotation speed reaches the first rotation speed by adjusting the predetermined value after reversing the increase and decrease in the main shaft rotation speed, and the calculation is performed. The machine tool according to claim 1, wherein it is determined that the predetermined condition is satisfied when the number of times is equal to or less than a predetermined number.   The work according to claim 1, wherein the adjusting unit determines that the predetermined condition is satisfied when the number of adjustments by the predetermined value after reversing the increase/decrease in the rotation speed of the spindle exceeds a predetermined number. machine. The adjustment unit,
When it is determined that the rotation speed of the spindle does not exceed the stable range, the rotation speed of the spindle is reduced by a predetermined first value,
When it is determined that the rotation speed of the spindle exceeds the stable range, the rotation speed of the spindle is increased by a predetermined second value,
The machine tool according to claim 1, wherein the second value is smaller than the first value.   The adjusting unit determines whether or not the rotation speed of the spindle exceeds the stable range based on a comparison result of the vibration frequencies before and after the adjustment of the rotation speed of the spindle. The machine tool according to item 1. The adjusting unit, when the reproduction chatter vibration is detected by the vibration detecting unit after performing the adjustment of the rotation speed of the spindle a predetermined number of times, raises the rotation speed of the spindle higher than the first rotation speed. The machine tool according to any one of Items 1 to 5 . When the reproduction chatter vibration is detected by the vibration detection unit after the adjustment of the rotation speed of the spindle is performed a predetermined number of times, the adjustment unit makes the depth of cut of the work by the tool shallower than the present. the machine tool according to any one of claims 1-6. The adjustment unit, when the reproduction chatter vibration is detected by the vibration detection unit after the adjustment amount of the number of rotations of the spindle is equal to or less than a predetermined threshold value, the cutting depth of the work by the tool is currently set. The machine tool according to claim 4, which is shallower than the machine tool. The vibration detection unit further detects, based on the vibration frequency, the forced chatter vibration occurring in the spindle or the tool,
In the case where the reproduction chatter vibration is not detected by adjusting the number of rotations of the main shaft, when the forced chatter vibration is detected, the adjustment unit is more than the adjustment amount for suppressing the reproduction chatter vibration. small amount of adjustment to readjust the rotational speed, the machine tool according to any one of claims 1-8. A spindle for rotating a workpiece or tool,
A sensor for detecting the vibration frequency of the spindle or the tool,
Based on the vibration frequency, a vibration detection unit for detecting reproduction chatter vibration occurring in the spindle or the tool,
An adjusting unit for adjusting the number of revolutions of the main shaft,
The adjustment unit,
When the reproduction chatter vibration is detected by the vibration detection unit, the rotation speed of the spindle is adjusted from the first rotation speed, which is the current setting value, to the second rotation speed according to a predetermined calculation formula,
Calculate the wave number of the machining surface caused by the vibration of the spindle or the tool between the first blade of the tool coming into contact with the work and the second blade of the tool coming into contact with the work,
Based on whether or not the integer part of the wave number has changed before and after the adjustment of the rotational speed of the spindle, it is determined whether the rotational speed of the spindle exceeds a stable range in which the reproduction chatter vibration does not occur, and the determination is made. Depending on the result, change whether to increase or decrease the rotation speed,
While the reproduction chatter vibration is being detected by the vibration detection unit, the rotation speed of the spindle is adjusted from the second rotation speed by a predetermined value, and the rotation speed of the spindle is likely to reach the first rotation speed. A machine tool that reduces the amount of adjustment of the rotational speed of the spindle below the predetermined value based on the satisfaction of a predetermined condition indicating . A method of machining with a machine tool,
The machine tool is
A spindle for rotating a workpiece or tool,
A sensor for detecting the vibration frequency of the spindle or the tool,
The processing method is
Detecting a reproduction chatter vibration occurring in the spindle or the tool based on the vibration frequency;
When the reproduction chatter vibration is detected in the detecting step, adjusting the rotation speed of the spindle according to a predetermined calculation formula from the first rotation speed, which is the current setting value, to the second rotation speed,
While the reproduction chatter vibration is being detected in the detecting step, sequentially adjusting the rotation speed of the spindle from the second rotation speed by a predetermined value,
When the number of revolutions of the main spindle exceeds the stable range in which the reproduction chatter vibration does not occur before and after the adjustment of the number of revolutions of the main spindle, the increase and decrease of the adjustment amount of the number of revolutions of the main spindle are reversed, and the number of revolutions of the main spindle is changed. A step of making the adjustment amount smaller than the predetermined value,
A step of reducing the adjustment amount of the rotation speed of the spindle below the predetermined value based on the satisfaction of a predetermined condition indicating that the rotation speed of the spindle is likely to reach the first rotation speed;
And a step of ending the adjustment processing of the rotational speed of the spindle when the reproduction chatter vibration is no longer detected in the detecting step by adjusting the rotational speed of the spindle in the adjusting step . A machining program using a machine tool,
The machine tool is
A spindle for rotating a workpiece or tool,
A sensor for detecting the vibration frequency of the spindle or the tool,
The machining program, the machine tool,
Detecting a reproduction chatter vibration occurring in the spindle or the tool based on the vibration frequency;
When the reproduction chatter vibration is detected in the detecting step, adjusting the rotation speed of the spindle according to a predetermined calculation formula from the first rotation speed, which is the current setting value, to the second rotation speed,
While the reproduction chatter vibration is being detected in the detecting step, sequentially adjusting the rotation speed of the spindle from the second rotation speed by a predetermined value,
When the number of revolutions of the main spindle exceeds the stable range in which the reproduction chatter vibration does not occur before and after the adjustment of the number of revolutions of the main spindle, the increase and decrease of the adjustment amount of the number of revolutions of the main spindle are reversed, and the number of revolutions of the main spindle is changed. A step of making the adjustment amount smaller than the predetermined value,
A step of reducing the adjustment amount of the rotation speed of the spindle below the predetermined value based on the satisfaction of a predetermined condition indicating that the rotation speed of the spindle is likely to reach the first rotation speed;
And a step of terminating the adjusting process of the rotational speed of the spindle when the reproduction chatter vibration is no longer detected in the detecting step by adjusting the rotational speed of the spindle in the adjusting step .

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