JP2013039645A - Rotation speed display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotation speed display device allowing an operator to easily recognize change of machining efficiency when changing machining conditions, and reducing the burden on the operator when preventing chatter vibration.SOLUTION: When the generation of chatter vibration is detected, stable rotation speed is calculated, and an assumed machining time when performing the machining at the current rotation speed and an assumed machining time when performing the machining at the stable rotation speed are calculated, respectively, on the basis of a machining program. Further, it is calculated how the machining efficiency changes when the rotation speed of a rotary shaft 3 is changed to the stable rotation speed, and is displayed, together with the stable rotation speed, on a monitor 15. Accordingly, the operator can easily understand the change of the machining efficiency with the change of the rotation speed on the basis of the display on the monitor 15, and the machining efficiency is thereby improved.

Description

  The present invention relates to a rotation speed display device for displaying a rotation speed of a rotary shaft capable of suppressing chatter vibration generated during machining in a machine tool that performs machining while rotating a tool or a workpiece.

  In a machine tool that performs processing by rotating a rotating shaft, so-called chatter vibration may occur during processing due to factors such as inadequate processing conditions such as the amount of cutting and the rotational speed of the rotating shaft. When chatter vibration occurs, problems such as deterioration of the finished surface finish accuracy and damage to the tool occur, and thus suppression of chatter vibration is required.

  As a technique for suppressing such chatter vibration, a technique described in Non-Patent Document 1, that is, a technique using the theory of the stability limit diagram is known. And as a vibration suppression method using this technique, for example, as described in Patent Document 1, a vibration detection means is attached in the vicinity of the rotating shaft of a machine tool, and the chatter frequency is measured. A value obtained by multiplying by 60 and dividing by the number of tool blades and a predetermined integer is set as a stable rotation speed, and the rotating shaft is rotated at the stable rotation speed.

JP 2007-44852 A

2001 Japan Society of Mechanical Engineers workshop materials "Basic knowledge of cutting and chatter vibration"

  According to the vibration suppression method described in Patent Document 1 described above, chatter vibration is suppressed only by changing the rotation speed. However, in actuality, not only the rotation speed but also, for example, the feed speed of the main shaft (rotary shaft) It may be necessary to change the processing conditions such as the loading amount. If such processing conditions are easily changed, not only can the processing efficiency not be improved so much, but there is also a risk that the processing efficiency may deteriorate. Therefore, the worker must change the machining conditions while calculating the improvement ratio of the machining efficiency one by one when suppressing chatter vibration, and there is a problem that a great burden is placed on the worker.

  Therefore, the present invention has been made in view of the above problems, and the operator can easily grasp the change in the machining efficiency when the machining conditions are changed, and the operator's in suppressing chatter vibrations. An object of the present invention is to provide a rotation speed display device capable of reducing the burden.

尚、上記式中のｘ_０、ｙ_０、ｚ_０は夫々現在位置座標であり、ｘ_１、ｙ_１、ｚ_１は夫々目標位置座標である。また、Ｒは円弧半径である。
請求項３に記載の発明は、請求項１又は２に記載の発明において、前記演算手段は、前記加工プログラムをもとに、前記回転速度に加えて他の加工条件についても変更前と変更後とで夫々想定加工時間を算出するととともに、変更前後での想定加工時間をもとに、前記他の加工条件を変更することによる加工能率の変化を算出し、前記表示手段に前記加工能率の変化を表示することを特徴とする。
請求項４に記載の発明は、請求項１〜３の何れかに記載の発明において、前記演算手段は、下記式（１）〜（５）を用いて安定回転速度を算出することを特徴とする。
安定回転速度＝係数×６０×びびり周波数／（任意の整数×工具刃数） ・・・（１）
係数＝ａ−ｂ×ｋ値＋ｃ×位相情報 ・・・（２）
ｋ’値＝６０×びびり周波数／（工具刃数×回転速度） ・・・（３）
ｋ値＝ｋ’値の整数部 ・・・（４）
位相情報＝ｋ’値−ｋ値 ・・・（５）
なお、式（２）におけるａ、ｂ、ｃは予め定められた定数である。 In order to achieve the above object, the invention described in claim 1 of the present invention includes a rotating shaft for rotating a tool or a workpiece, and performs processing while relatively feeding the tool and / or the workpiece in a predetermined direction. In the machine tool, vibration detecting means for detecting vibration information generated when chatter vibration occurs on the rotating shaft, and calculation for calculating a stable rotation speed capable of suppressing the chatter vibration when the occurrence of the chatter vibration is detected. A rotation speed display device comprising: a display means for displaying the stable rotation speed; and a storage means for storing a machining program, wherein the calculation means is configured to detect the chatter vibration based on the machining program. Calculating a first assumed machining time when machining is performed at the rotation speed at the time of occurrence and a second assumed machining time when machining is performed by changing the rotation speed to the stable rotation speed. Then, based on the first assumed machining time and the second assumed machining time, a change in machining efficiency due to changing the rotation speed to the stable rotation speed is calculated, and the machining efficiency is displayed on the display means. It is characterized by displaying the change of.
According to a second aspect of the present invention, in the first aspect of the present invention, the computing means calculates the respective movement distances L in the straight line command and the circle command based on the coordinate values in the machining program by the following equations. In addition, the accumulated value is set as a movement distance Lc, and the first assumed machining time and the second assumed machining time are obtained by dividing the movement distance Lc by a feed speed F.

Note that x ₀ , y ₀ , and z ₀ in the above formulas are current position coordinates, respectively, and x ₁ , y ₁ , and z ₁ are target position coordinates, respectively. R is an arc radius.
According to a third aspect of the present invention, in the first or second aspect of the present invention, the calculation means is configured so that, based on the machining program, other machining conditions in addition to the rotation speed are also changed before and after the change. And calculating the change in machining efficiency by changing the other machining conditions based on the assumed machining time before and after the change, and changing the machining efficiency on the display means. Is displayed.
According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the calculating means calculates a stable rotational speed using the following formulas (1) to (5). To do.
Stable rotational speed = coefficient × 60 × chat frequency / (arbitrary integer × number of tool blades) (1)
Coefficient = a−b × k value + c × phase information (2)
k ′ value = 60 × chat frequency / (number of tool blades × rotational speed) (3)
k value = integer part of k ′ value (4)
Phase information = k ′ value−k value (5)
Note that a, b, and c in Equation (2) are predetermined constants.

According to the present invention, when occurrence of chatter vibration is detected, a stable rotational speed is calculated, and when the rotational speed of the rotary shaft is changed to the stable rotational speed, how the machining efficiency changes before the change. Is calculated and displayed on the display means. Therefore, the operator can easily grasp the change in the machining efficiency due to the change in the rotation speed based on the display on the display means, and thus can improve the machining efficiency.
According to the third aspect of the present invention, not only the rotation speed of the rotary shaft but also other machining conditions (for example, feed speed) are changed. The operator can easily figure out how the machining efficiency will change if other machining conditions are changed based on the display on the display means. can do. Therefore, there is no fear that the machining efficiency is not only improved but deteriorated, and the machining efficiency can be improved extremely easily and reliably.

It is explanatory drawing which showed the block structure of the vibration suppression apparatus. It is explanatory drawing which showed the rotating shaft housing used as the object of vibration suppression from the side. It is explanatory drawing which showed the rotating shaft housing from the axial direction. It is explanatory drawing which showed the display aspect of the stability limit diagram in a monitor. It is an example of the display screen which sorts and displays the processing conditions, the estimated processing time, and the ratio of processing efficiency, and is an explanatory diagram showing a state before display. It is an example of the display screen which sorts and displays the processing conditions, the estimated processing time, and the ratio of processing efficiency, and is an explanatory diagram showing a state after display.

  Hereinafter, a vibration suppression device including a rotation speed display device according to an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an explanatory diagram showing a block configuration of the vibration suppressing device 10. FIG. 2 is an explanatory view showing the rotary shaft housing 1 to be subjected to vibration suppression from the side, and FIG. 3 is an explanatory view showing the rotary shaft housing 1 from the axial direction.
The vibration suppressing device 10 is for suppressing chatter vibration generated in the rotating shaft 3 provided in the rotating shaft housing 1 so as to be rotatable around the C axis, and has characteristics associated with vibration generated in the rotating rotating shaft 3. Vibration sensors 2a to 2c for detecting vibration acceleration in the time domain (meaning vibration acceleration on the time axis), and the presence or absence of chatter vibration by analyzing the detection values by the vibration sensors 2a to 2c And a control device 5 that calculates and displays a stable rotation speed capable of suppressing chatter vibration based on the determination result, and controls the rotation speed of the rotary shaft 3. The rotary shaft housing 1 is slidable in a predetermined direction, and the workpiece is machined while a tool (not shown) that is mounted on the rotary shaft 3 and rotates is sent in a predetermined direction. .

  The vibration sensors 2a to 2c are attached to the rotary shaft housing 1 as shown in FIGS. 2 and 3, and one vibration sensor detects vibration acceleration in the time domain in a direction perpendicular to the other vibration sensors. (For example, the vibration sensors 2a to 2c are attached so as to detect vibration acceleration in the time domain in the X-axis, Y-axis, and Z-axis directions orthogonal to each other).

  On the other hand, the control device 5 includes an FFT calculation device 11 that performs analysis based on vibration acceleration in the time domain detected from the vibration sensors 2a to 2c, and various values (the occurrence of chatter vibration) input to the operator. A value used when determining or calculating a stable rotation speed), a storage device 13 for storing a machining program, etc., whether or not chatter vibration is occurring, and as described later. An arithmetic device 12 for calculating machining efficiency and calculating a stable rotational speed and an NC device 14 for controlling the rotational speed of the rotary shaft 3 are provided. The NC device 14 includes a machining program and a current position of the machine. In addition, a monitor 15 is provided for displaying the calculation results of the calculation device 12 such as machining efficiency and stable rotation speed.

The vibration suppression control of “chatter vibration” by the vibration suppression device 10 will be described.
First, before starting machining, a machining program, tool information such as the number of tool blades, a threshold value for determining occurrence of chatter vibration, and the like are input and stored in the storage device 13 in advance. When processing is started, the control device 5 monitors whether chatter vibration is occurring in the rotary shaft housing 1 based on the vibration information obtained by the vibration sensors 2a to 2c. That is, the vibration acceleration in the time domain in the rotary shaft housing 1 is always detected by the vibration sensors 2a to 2c, the Fourier calculation of the vibration acceleration in the time domain is performed in the FFT arithmetic unit 11, and the vibration acceleration in the frequency domain as vibration information is detected. The maximum value (maximum acceleration) and its frequency (chatter frequency) are acquired. Further, in the arithmetic device 12, the acquired maximum acceleration is compared with the threshold value stored in the storage device 13. When the maximum acceleration exceeds the threshold value, chatter vibration to be suppressed is generated in the rotary shaft housing 1. The stable rotational speed is calculated by the following formulas (1) to (5). Then, the calculated stable rotational speed is displayed on the monitor 15 together with a stability limit diagram obtained as described later (displayed in a manner as shown in FIG. 4), and an instruction to change the rotational speed is input to the operator. Encourage you to.

Stable rotational speed = coefficient × 60 × chat frequency / (arbitrary integer × number of tool blades) (1)
Coefficient = a−b × k value + c × phase information (2)
k ′ value = 60 × chat frequency / (number of tool blades × rotational speed) (3)
k value = integer part of k ′ value (4)
Phase information = k ′ value−k value (5)
Note that a, b, and c in Equation (2) are predetermined constants and are stored in the storage device 13.

  Therefore, the vibration speed of the rotary shaft 3 is changed to a stable rotational speed by the operator, and chatter vibration is suppressed by changing processing conditions such as the feed speed of the rotary shaft 3 as necessary. However, the calculation device 12 calculates the change in machining efficiency when each parameter (rotation speed, feed rate, etc.) is changed as follows, and displays it on the monitor 15 together with the stable rotation speed as shown in FIG. indicate.

Here, the calculation and display mode of the machining efficiency, which is the main part of the present invention, will be described in detail with reference to FIGS.
First, in the current machining program, the type of tool to be used (stored in association with the tool number), the rotation speed of the rotary shaft 3 (rotation speed before changing to a stable rotation speed), the feed speed, and the machining program From the moving distance of the cutting feed calculated from the coordinates, an assumed machining time (first assumed machining time) when machining under the condition (initial condition before change) is calculated, and an initial condition column (in FIG. 5) In the left column). Next, the assumed machining time (second assumed machining time) when the rotation speed is changed to the stable rotation speed is the same as the stable rotation speed and the feed speed (including both cases of changing and not changing). It calculates using the moving distance of the cutting feed for each combination and displays it in the final condition column (right column in FIG. 5). In each case, a machining efficiency ratio (change in machining efficiency) indicating how much the machining time is shortened from the assumed machining time in the initial condition is calculated and displayed in the machining efficiency ratio column. When the pre-change condition and the post-change conditions are selected, the arithmetic unit 12 displays the stability limit diagram and the ratio of machining efficiency on the monitor 15 in the manner shown in FIG.

  FIG. 5 is a screen before the estimated machining time and the like are displayed. When the estimated machining time and the like are displayed, for example, a screen as shown in FIG. 6 is displayed. In the example shown in FIG. 6, the process in the first line is the same, but the process time, rotational speed, feed speed, etc. are different in the processes in the second to fourth lines, and the processing conditions are shown as the final conditions. It can be seen that efficient machining can be expected by changing to the conditions described above. In particular, in the processes in the third and fourth lines, the rotation speed described in the left column (for example, the rotation speed set by the machining program) is changed to the rotation speed described in the right column (stable rotation speed). Even if it does, it turns out that processing time is shortened and processing efficiency improves.

Further, when calculating the assumed machining time, for example, it can be calculated as follows. That is, when the machining program is a straight line command and when the machining program is a circle command, the movement distance is calculated by the following equations, and the cumulative value of continuous commands having the same tool, rotation speed, and feed rate is obtained as the movement distance Lc. . Then, the assumed machining time T can be calculated by dividing the obtained movement distance Lc by the feed speed F (assumed machining time T = movement distance Lc / feed speed F). In the expression, x ₀ , y ₀ , and z ₀ are current position coordinates, respectively, and x ₁ , y ₁ , and z ₁ are target position coordinates, respectively. R is an arc radius.

  Therefore, the operator can refer to the display on the monitor 15 to grasp the machining condition that can suppress chatter vibration and achieve the highest machining efficiency, and operates the NC device 14 to rotate the rotary shaft 3. While changing the speed to the stable rotation speed, the feed speed of the rotary shaft 3 may be set to the feed speed at which the machining efficiency is the highest.

  It may be possible to change the machining conditions (for example, in addition to the rotation speed and feed speed, including the type of tool and the cutting depth) in order to improve the machining efficiency regardless of the occurrence of chatter vibration. Therefore, in such a case, by inputting a machining condition and a machining program to be changed, an estimated machining time is calculated for each combination of, for example, a tool, a cutting amount, a rotation speed, and a feed speed by the same method as described above. At the same time, it is possible to calculate the change in machining efficiency from the comparison with the assumed machining time under the initial condition (initial condition) and display it on the monitor 15.

The calculation of the stability limit diagram displayed on the monitor 15 will be described.
When the coefficient matrix determined by the processing conditions is A ₀ and the transfer function of the system is G, the critical condition formula causing chatter vibration is the following formula (6).

尚、式（６）中におけるＦ_０は切削力ベクトル、ａ_ｌｉｍは限界切込量、Ｋ_ｔは比切削抵抗、ω_ｃはびびり周波数、Ｔは切刃通過周期、ｉは虚数単位である。

In Equation (6), F ₀ is a cutting force vector, a _lim is a limit cutting amount, K _t is a specific cutting resistance, ω _c is a chatter frequency, T is a cutting edge passage period, and i is an imaginary unit.

However, in this embodiment, for the sake of simplicity, it is assumed that the modal parameters in the direction orthogonal to the rotation axis of the system are equal, and the transfer function matrix is defined by the following equation (7).

When f _n is the natural frequency of the system, ζ is the damping ratio, and R _max is compliance, the equivalent parameters M, K, and C are expressed by the following formula (8), respectively.

Here, when the inverse of the eigenvalue of the matrix A ₀ · G (iω _c ) is _denoted by Λ, the relationship of the following formula (9) is established.

尚、式（１２）中のｌは任意の整数である。 At this time, the rotational axis rotational speed S corresponding to the limit cut amount a _lim , the phase information ε, and the chatter frequency ω _c is expressed by the following equations (10) to (12), respectively.

In the formula (12), l is an arbitrary integer.

Here, in the stability limit diagram, l in Equation (12) is a k value calculated from the machining result, and the relationship between the rotational shaft rotational speed S around the k value and the limit cut amount a _lim is arranged. A stable rotation speed can be calculated. Since the compliance R _max does not affect the phase information ε from the relational expressions (6) to (11), the natural vibration is obtained by setting R _max to an arbitrary value and performing parameter identification using the phase information ε. Numbers and damping ratios can be obtained.

  According to the vibration suppressing device 10 as described above, when the occurrence of chatter vibration is detected, a stable rotation speed is calculated, and an estimated machining time when machining is performed at the current rotation speed based on a machining program, and stable Calculate the estimated machining time when machining at the rotation speed, and calculate how the machining efficiency will change when the rotation speed of the rotating shaft 3 is changed to the stable rotation speed. At the same time, it is displayed on the monitor 15. Therefore, the operator can easily grasp the change in the machining efficiency due to the change in the rotation speed based on the display on the monitor 15, and can improve the machining efficiency.

In addition, when changing not only the rotation speed of the rotary shaft 3 but also the feed speed, the operator calculates whether the machining efficiency changes before and after the change for each feed speed value and displays it on the monitor 15. It is possible to easily grasp how the machining efficiency changes if the feed rate is changed based on the display on the monitor 15. Therefore, there is no fear that the machining efficiency is not only improved but deteriorated, and the machining efficiency can be improved extremely easily and reliably.
Furthermore, even when it is desired to change the machining conditions regardless of the occurrence of chatter vibration, how the machining efficiency changes with the change of the machining conditions is calculated and displayed on the monitor 15, which is extremely convenient.

  The rotational speed display device according to the present invention is not limited to the aspect of the above embodiment, and the configuration relating to vibration detection means, control after detection of chatter vibration, etc. departs from the spirit of the present invention. As long as it is not necessary, it can be changed as needed.

For example, in the above embodiment, the calculated stable rotation speed is only displayed on the monitor 15. However, when the occurrence of chatter vibration is detected, the NC apparatus 14 automatically sets the rotation speed to suppress chatter vibration. It is also possible to configure to change to a stable rotational speed.
In the above embodiment, the vibration acceleration of the rotating shaft is detected by the vibration sensor. However, the displacement and sound pressure of the rotating shaft due to vibration are detected, and the stable rotation speed is determined based on the displacement and sound pressure. Alternatively, a detector that detects the position and rotation of the rotating shaft, and a current measuring device that measures the current of the rotating shaft motor and the feed shaft motor can be used as the vibration detecting means. is there.

Furthermore, there is no problem even if the arithmetic unit 12 and the FFT arithmetic unit 11 are made external computers separate from the NC unit 14 and are connected via a network.
In addition, in the above embodiment, the configuration is such that the vibration on the rotating shaft of the machine tool is detected, but the configuration is such that the vibration on the non-rotating side (fixed side) is detected and the stability limit diagram and forced chatter region are calculated. May be. Moreover, the present invention can be applied not only to a machining center that rotates a tool, but also to a machine tool such as a lathe that rotates a workpiece, and the installation position and number of vibration detection means, the threshold value, etc., the type and size of the machine tool, etc. Needless to say, it may be appropriately changed according to the above.

  Rotating shaft housing, 2a, 2b, 2c, vibration sensor (vibration detecting means), 3, rotating shaft, 5, control device, 10 vibration suppression device (rotation speed display device), 11 FFT computing device (vibration detecting means), 12 .... arithmetic device (vibration detecting means, computing means), 13 .... storage device (memory means), 14 .... NC device, 15 .... monitor (display means).

Claims (4)

In a machine tool that has a rotating shaft for rotating a tool or a workpiece and that processes the tool and / or the workpiece while relatively feeding in a predetermined direction, vibration information generated when chatter vibration is generated on the rotating shaft is detected. Vibration detecting means for detecting the occurrence of chatter vibration, calculating means for calculating a stable rotation speed capable of suppressing the chatter vibration, display means for displaying the stable rotation speed, and storage means for storing a machining program A rotational speed display device comprising:
The arithmetic means is based on the machining program, the first assumed machining time when machining at the rotation speed when chatter vibration occurs, and the machining is performed by changing the rotation speed to the stable rotation speed And calculating the second assumed machining time of
Based on the first assumed machining time and the second assumed machining time, a change in machining efficiency due to changing the rotation speed to the stable rotation speed is calculated, and the change in the machining efficiency is displayed on the display means. Rotation speed display device characterized by displaying. The computing means calculates the respective movement distances L in the straight line command and the circle command based on the coordinate values in the machining program by the following formulas, and sets the accumulated value as the movement distance Lc, and uses the first assumed machining. The rotation speed display device according to claim 1, wherein the time and the second assumed machining time are obtained by dividing the moving distance Lc by a feed speed F.

Note that x ₀ , y ₀ , and z ₀ in the above formulas are current position coordinates, respectively, and x ₁ , y ₁ , and z ₁ are target position coordinates, respectively. R is an arc radius. The calculation means calculates an estimated machining time before and after the change for the other machining conditions in addition to the rotation speed based on the machining program,
The change in machining efficiency due to changing the other machining conditions is calculated based on the assumed machining time before and after the change, and the change in machining efficiency is displayed on the display means. Or the rotational speed display apparatus of 2. The rotational speed display device according to any one of claims 1 to 3, wherein the calculation means calculates a stable rotational speed using the following formulas (1) to (5).
Stable rotational speed = coefficient × 60 × chat frequency / (arbitrary integer × number of tool blades) (1)
Coefficient = a−b × k value + c × phase information (2)
k ′ value = 60 × chat frequency / (number of tool blades × rotational speed) (3)
k value = integer part of k ′ value (4)
Phase information = k ′ value−k value (5)
Note that a, b, and c in Equation (2) are predetermined constants.

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