JP2021133474A - Cutting device - Google Patents

Abstract

To provide a cutting device which can improve productivity while suppressing an amount of vibration of an object to be cut.SOLUTION: A cutting device for cutting an object W to be cut by use of a tool T comprises: a rotary shaft 10 for rotating the tool T; a moving unit 20 having a feed mechanism 21 for moving at least one of the object W to be cut and the tool T; and a control part 30 for controlling a rotation speed of the rotary shaft 10 and a movement speed of the feed mechanism 21. If a size of surface roughness of the object W to be cut, when cutting the object W to be cut while rotating the rotary shaft 10 at the same rotation speed as a natural frequency of the object W to be cut calculated in advance and moving the feed mechanism 21 at a prescribed reference speed, is so made as to be a reference roughness, the control part 30 rotates the rotary shaft 10 at a rotation speed different from the natural frequency, and so makes the movement speed of the feed mechanism 21 as to be faster than the reference speed within a range, in which a size of the surface roughness of the object W to be cut after cutting does not exceed the reference roughness, when cutting the object W to be cut.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a cutting device.

Conventionally, a vibration suppression device for a machine tool provided with a rotating shaft for rotating a tool or a workpiece is known (see, for example, Patent Document 1). When the vibration suppression device of this machine tool detects the forced chatter vibration of the rotating shaft (hereinafter, also referred to as forced vibration), it changes the rotation speed of the rotating shaft and suppresses the vibration amount of the forced vibration of the rotating shaft. Suppresses deterioration of processing accuracy.

Japanese Unexamined Patent Publication No. 2012-115963

By the way, among the machine tools described in Patent Document 1, in the cutting device, when the work is cut by rotating the tool, the work may vibrate forcibly. Hereinafter, the work is also referred to as an object to be cut.

However, Patent Document 1 only describes countermeasures for forced vibration of the rotating shaft, and does not consider forced vibration of the object to be cut. Therefore, the vibration suppression device described in Patent Document 1 cannot suppress the forced vibration of the work piece. Forced vibration generated in the work piece is not preferable because it causes deterioration of productivity when the work piece is manufactured by using the cutting device. The work piece is obtained by cutting the work piece by a cutting device.

An object of the present disclosure is to provide a cutting apparatus capable of improving productivity while suppressing the amount of vibration of a work piece.

The invention according to claim 1
A cutting device that cuts an object to be cut (W) using a tool (T).
The rotating shaft (10) that rotates the tool and
A moving device (20) having a feed mechanism for moving at least one of a work piece and a tool,
It is equipped with a control unit (30) that controls the rotation speed of the rotating shaft and the moving speed of the feed mechanism.
The surface roughness of the work piece when the work piece is cut while moving the feed mechanism at a predetermined reference speed while rotating the rotation axis at the same rotation speed as the natural frequency of the work piece calculated in advance. When the size is used as the reference roughness,
When cutting a work piece, the control unit rotates the rotation axis at a rotation speed different from the natural frequency, and the surface roughness of the work piece after cutting does not exceed the standard roughness. , Make the moving speed of the feed mechanism larger than the reference speed.

According to this, when cutting an object to be cut, the rotating shaft is rotated at a rotation speed different from the natural frequency of the object to be cut, and the object to be cut and the tool resonate to increase the size of the object to be cut. Forced vibration can be suppressed. In addition, since the moving speed of the feed mechanism is increased within the range where the surface roughness of the work piece after cutting does not exceed the standard roughness, cutting is performed without deteriorating the surface roughness of the work piece. Productivity can be improved by shortening the time required for completion.

The reference reference numerals in parentheses attached to each component or the like indicate an example of the correspondence between the component or the like and the specific component or the like described in the embodiment described later.

It is a schematic block diagram of the cutting apparatus which concerns on one Embodiment. It is explanatory drawing for demonstrating the operation of the cutting apparatus at the time of detecting the natural frequency of the object to be cut. It is a figure which shows the process at the time of manufacturing the cut work piece which concerns on one Embodiment. It is a figure which shows the relationship between the vibration amount of the object to be cut, and the magnitude of the cutting resistance of a tool. It is a figure which shows the relationship between the surface roughness of the object to be cut, and the moving speed of a feed mechanism. It is a figure which shows the process to carry out in the preparation process which concerns on one Embodiment. It is a figure which shows an example of the vibration waveform which is difficult to detect a natural frequency. It is a figure which shows an example of the vibration waveform which is easy to detect a natural frequency. It is a flowchart which shows an example of the control process which a control part executes in a vibration | vibration process. It is a figure which shows an example of the result of the frequency analysis performed by the natural vibration calculation unit. It is a flowchart which shows an example of the control process which a control part executes in a reference roughness detection process. It is a schematic diagram which shows an example of the forced vibration model of a one-degree-of-freedom damping system. It is a figure which shows an example of the resonance curve of a forced vibration model. It is a flowchart which shows an example of the control process which a control part executes in a cutting process. It is explanatory drawing for demonstrating the surface roughness at the time of cutting a work piece by using the cutting apparatus which concerns on one Embodiment.

An embodiment of the present disclosure will be described with reference to FIGS. 1 to 15. In the present embodiment, the work piece can be obtained by cutting the work piece W with the tool T by the cutting machine 1 according to a program stored in advance in the cutting device 1 which is a machining center. As shown in FIG. 1, the cutting device 1 moves a stage 2 on which an object W to be cut is installed, a rotating shaft 10 to which a tool T is attached, a spindle head 11 for rotating the rotating shaft 10, and a rotating shaft 10. It has a moving device 20 having a feeding mechanism 21. Further, the cutting device 1 has a vibration detection unit 40 that detects the vibration of the work piece W and a natural vibration calculation unit that calculates the natural frequency ω1 of the work piece W based on the detection value detected by the vibration detection unit 40. 50 and a tool changing device (not shown) for replacing the tool T attached to the rotating shaft 10 are provided. The cutting device 1 has a control unit 30 that controls various devices constituting the cutting device 1, and the control unit 30 controls the operation of the various devices.

The stage 2 is an installation table for the work piece W on which the work piece W is installed on the upper side of the stage 2 in the vertical direction. The stage 2 is immovably provided on the base portion 3 forming the base of the cutting device 1. Further, the stage 2 has a fixing jig (not shown) for fixing the installation position of the installed object W, and when the installed object W is cut, the installation position of the object W is set. Fix it.

In the present embodiment, the object W to be cut is made of die-cast aluminum, and as shown in FIG. 2, it is made of a rectangular plate-shaped member. The object to be cut W has a surface to be cut W1 on the upper side in the vertical direction. The surface to be cut W1 is a portion of the object to be cut W to be cut. Further, the workpiece W is provided with openings W2 having different sizes and shapes penetrating in the plate thickness direction. The spindle head 11 and the rotating shaft 10 are arranged on the upper side of the work piece W installed on the stage 2 in the vertical direction.

The spindle head 11 is a driving device that rotates the rotating shaft 10. The spindle head 11 rotatably supports the rotating shaft 10, and the rotating shaft 10 is rotated by the rotation of the motor contained therein. The spindle head 11 is connected to the control unit 30, and the rotation shaft 10 is controlled from the control unit 30 by controlling the rotation speed of the motor based on the rotation speed information of the rotation shaft 10 transmitted from the control unit 30. Rotate so as to approach the transmitted rotation speed. Further, a vibration detection unit 40 is attached to the spindle head 11.

The spindle head 11 is connected to the feed mechanism 21, and is configured to be movable integrally with the rotation shaft 10 and the vibration detection unit 40 as the feed mechanism 21 moves.

The rotating shaft 10 is a rotating member that gives a turning motion to the tool T attached to the rotating shaft 10 by being rotated by the spindle head 11. The rotary shaft 10 has a grip portion (not shown) that grips the tool T, and the attached tool T is detachable. A tool T is attached to the rotating shaft 10, and the rotating shaft 10 rotates integrally with the tool T. In the present embodiment, a face mill T1 formed of cemented carbide and having a blade Tb on the outer peripheral portion is attached to the rotating shaft 10 as a tool T. The face mill T1 attached to the rotating shaft 10 can be replaced by a tool changing device (not shown).

The tool changing device accommodates a plurality of cutting tools (not shown), and is a device for exchanging the tool T attached to the rotating shaft 10 with the accommodating cutting tool. The tool changer accommodates cutting tools required for each machining performed by the cutting device 1. Further, the tool changing device is connected to the control unit 30, and based on the signal transmitted from the control unit 30, the tool changing device is replaced with a cutting tool accommodating the tool T attached to the rotating shaft 10.

The moving device 20 moves the feeding mechanism 21 to move the spindle head 11 connected to the feeding mechanism 21 in the horizontal direction and the vertical direction. The moving device 20 moves the feed mechanism 21 to change the relative position between the tool T attached to the rotating shaft 10 and the object W fixed to the stage 2.

The feed mechanism 21 includes a movable portion (not shown) that moves in the horizontal direction and the vertical direction together with the spindle head 11. The moving device 20 has a motor for driving the movable portion, and by rotating the motor, the feed mechanism 21 is moved in the horizontal direction and the vertical direction.

The moving device 20 is connected to the control unit 30, and controls the rotation position of the motor based on the trajectory information of the feed mechanism 21 transmitted from the control unit 30, so that the trajectory of the trajectory transmitted from the control unit 30 is controlled. The feed mechanism 21 is moved according to the information. Further, the moving device 20 controls the rotation speed of the motor based on the information on the moving speed of the feeding mechanism 21 transmitted from the control unit 30, so that the feeding mechanism 21 approaches the moving speed transmitted from the control unit 30. Move it like this. Here, the moving speed of the feed mechanism 21 is the moving distance of the movable portion in the horizontal direction per unit time.

The moving device 20 is provided with a position sensor (not shown) that detects the rotational position of the motor. The position sensor detects the position of the feed mechanism 21 by detecting the rotational position of the motor, and transmits the detected position information of the feed mechanism 21 to the control unit 30.

The vibration detection unit 40 is a vibration sensor that detects the vibration of the work piece W in a non-contact manner with the work piece W. The vibration detection unit 40 is attached to the spindle head 11 via a sensor support portion 41 formed by extending from the spindle head 11 toward the tip of the face mill T1. The vibration detection unit 40 of the present embodiment is composed of a sound wave detection microphone that detects a sound wave generated when the object W to be cut is cut as a sound pressure signal. The vibration detection unit 40 transmits information on the magnitude and frequency of the sound pressure signal to be detected to the natural vibration calculation unit 50 as information on the vibration of the object W to be cut.

The natural vibration calculation unit 50 is a calculation unit that calculates the natural frequency ω1 of the work piece W based on the vibration information detected by the vibration detection unit 40. The natural vibration calculation unit 50 calculates the natural frequency ω1 of the work piece W by performing frequency analysis on the vibration information of the work piece W detected by the vibration detection unit 40. The natural vibration calculation unit 50 performs frequency decomposition by performing a fast Fourier transform on the vibration frequency of the object W to be cut, and calculates the vibration amount for each frequency. Further, the natural vibration calculation unit 50 sets the frequency at which the vibration amount protrudes as compared with the vibration amount of another frequency from the calculated vibration amount information for each frequency of the work piece W, which is the natural frequency of the work piece W. Calculated as ω1. The natural vibration calculation unit 50 is connected to the control unit 30 and transmits the calculated information on the natural frequency ω1 to the control unit 30. The details of the operation of the cutting device 1 when the natural vibration calculation unit 50 calculates the natural frequency ω1 will be described later.

The control unit 30 is composed of a microcomputer including a processor, a memory, and the like and peripheral circuits thereof, and is a control device that controls the operation of various devices constituting the cutting device 1. The control unit 30 is pre-programmed with the operations of various devices constituting the cutting device 1, and performs various calculations and processes based on the programs.

The control unit 30 has an input unit (not shown) for an operator to input parameter information necessary for operating various devices, an operation start signal of the cutting device 1, an operation end signal, and the like to the control unit 30. Further, the control unit 30 stores the parameter information input by the operation of the input unit, the position information of the feed mechanism 21 transmitted from the position sensor, the information of the natural frequency ω1 transmitted from the natural vibration calculation unit 50, and the like. Remember in. Further, the control unit 30 stores the information on the rotation speed of the rotation shaft 10 and the information on the movement speed of the feed mechanism 21 calculated in the preparation step described later in the memory.

Subsequently, an outline of a method for manufacturing a machined product will be described with reference to FIG. As shown in FIG. 3, the method for manufacturing a work piece includes a preparatory step before cutting the work piece W and a cutting step for cutting the work piece W. In the preparatory step, the target rotation speed n, which is the target rotation speed of the rotary shaft 10 in the cutting process, and the target speed Vf1, which is the target moving speed of the feed mechanism 21 in the cutting process, are set. A work piece is manufactured by cutting the work piece W.

By the way, when the cutting device 1 cuts the work piece W, if the blade Tb of the face mill T1 that rotates with the rotation of the rotating shaft 10 and the work surface W1 repeatedly collide with each other, the work piece W and the face mill T1 Forced vibration occurs between and. Forced vibration is vibration generated by force disturbance or displacement disturbance caused by a forced vibration source. In the present embodiment, the face mill T1 that repeatedly collides with the machined surface W1 in a rotated state serves as a vibration source, and forced vibration is generated between the machined object W and the face mill T1.

The workpiece W of the present embodiment is made of die-cast aluminum and has lower rigidity than the face mill T1 and the rotating shaft 10 made of cemented carbide. Therefore, when the object W to be cut is machined using the face mill T1, forced vibration is more likely to occur as compared with the face mill T1 and the rotating shaft 10. The forced vibration generated in the object W to be cut increases the cutting resistance applied to the face mill T1 when cutting the object W to be cut, and causes an increase in wear and breakage of the face mill T1. Further, the forced vibration generated in the work piece W becomes a factor that increases the size of the surface roughness of the work piece W after cutting the work piece W. The magnitude of the surface roughness in the description of the present embodiment is the maximum value of the peak height of the contour curve and the maximum valley depth of the contour curve at a predetermined reference length in the contour curve of the cross section of the surface to be cut W1. Use the maximum height obtained by the sum of the values.

As for the forced vibration generated in the object W to be cut, the larger the vibration amount, the larger the cutting resistance applied to the face mill T1 and the larger the surface roughness. Further, when the object W to be machined vibrates forcibly, the rotation speed of the rotating shaft 10 and the natural frequency ω1 overlap, and when the object W to be machined and the face mill T1 resonate, the vibration amount is compared with the case where the object W does not resonate. Becomes larger.

The relationship between the amount of vibration of the work piece W when the work piece W is forcibly vibrated and the magnitude of the cutting resistance applied to the face mill T1 will be described with reference to FIG. As shown in FIG. 4, the magnitude of the cutting resistance applied to the face mill T1 tends to increase as the amount of vibration of the work piece W increases when the work piece W vibrates forcibly. The target rotation speed n is set to a rotation speed different from the natural frequency ω1 in order to suppress the vibration amount of the work piece W and suppress the expansion of wear and the occurrence of breakage of the face mill T1. The details of the target rotation speed n will be described later.

Subsequently, the relationship between the magnitude of the surface roughness after cutting the object W to be cut and the magnitude of the moving speed of the feed mechanism 21 will be described with reference to FIG. FIG. 5 is a diagram showing the measurement result of the surface roughness of the work piece W after cutting the work piece W, and is a feed mechanism among various parameters for cutting the work piece W. The change of the measurement result when only the moving speed of 21 is changed is shown.

The black circles in FIG. 5 indicate the magnitude of the theoretical surface roughness of the work piece W when the work piece W is cut by moving the feed mechanism 21 at different moving speeds. Here, the size of the theoretical surface roughness is the size of the surface roughness when it is assumed that neither the tool T nor the work piece W vibrates when the work piece W is cut, and the blade It is a theoretical value determined by the feed rate per blade of Tb and the radius of the cutting edge of the blade Tb.

Further, the white circles in FIG. 5 indicate the magnitude of the surface roughness of the work piece W when the work piece W is cut by moving the feed mechanism 21 at different moving speeds. Further, at each movement speed shown in FIG. 5, the difference between the size of the surface roughness indicated by the black circle and the size of the surface roughness indicated by the white circle is the difference between the size of the surface roughness indicated by the white circle and the size of the surface roughness generated when the work piece W is cut. Indicates the magnitude of surface roughness that increases due to vibration. The magnitude of the surface roughness that increases due to the vibration of the work piece W varies depending on various factors such as the moving speed of the feed mechanism 21, the rotation speed of the rotating shaft 10, the rigidity of the work piece W and the tool T, and the like. It is a value to be used. The size of the surface roughness when the work piece W is cut is the sum of the size of the theoretical surface roughness and the size of the surface roughness that increases due to the vibration of the work piece W.

As shown in FIG. 5, the magnitude of the theoretical surface roughness and the magnitude of the surface roughness that increases due to the vibration of the work piece W are each determined by the feed mechanism 21 when cutting the work piece W. The higher the movement speed, the larger the movement speed. Therefore, as the target speed Vf1 increases, the machining accuracy of the workpiece W deteriorates. The details of the target speed Vf1 will be described later.

Subsequently, the details of the manufacturing method of the machined product will be described with reference to FIG. 6 and the like. As shown in FIG. 6, in the preparatory step, the work piece W is vibrated, and the vibration step of detecting the vibration of the vibrated work piece W and the detection value of the vibration detected in the vibration step are used. It has a natural vibration calculation step of calculating the natural frequency ω1 based on the natural vibration. Further, the preparatory step includes a reference roughness detecting step for detecting the magnitude of the surface roughness which is a reference for setting the target surface roughness in the cutting step.

In the preparatory step, the vibration step is first carried out. In the vibration step, the work piece W and the face mill T1 collide with each other, and the work piece W is vibrated by the impact when the work piece W and the face mill T1 collide with each other, and the vibrated work piece is vibrated. This is a step in which the vibration detection unit 40 detects the vibration of W.

In the vibration step, the operator first installs the workpiece W on the stage 2. The object W to be cut is fixed at a predetermined installation position by using a fixing jig of the stage 2 so that the installed position is not changed at the time of cutting. Subsequently, the cutting device 1 moves the feed mechanism 21 while rotating the rotating shaft 10 based on the information of various parameters determined in advance in the control unit 30, and collides the rotating face mill T1 with the object W to be cut. Let me. Further, the vibration detection unit 40 detects the vibration of the object to be cut W when the face mill T1 and the surface to be cut W1 collide with each other while moving integrally with the spindle head 11 as the feed mechanism 21 moves. .. Further, the vibration detection unit 40 transmits the vibration information of the object W to be detected to the natural vibration calculation unit 50.

The operation of the cutting device 1 during the vibration step is controlled by the control unit 30. In the memory of the control unit 30, information on the rotation speed of the rotating shaft 10, information on the moving speed of the feed mechanism 21, and information on the trajectory of the feed mechanism 21 are set in advance as parameters for executing the vibration step. .. Each parameter set in the control unit 30 is set, for example, by inputting an operator's operation into the input unit. The control unit 30 stores in the memory a control map in which each parameter in the vibration step is defined.

Here, in order to increase the collision interval between the blade Tb and the surface to be cut W1 in the vibration step, the number of rotations of the rotary shaft 10 in the vibration step is higher than the number of rotations of the rotary shaft 10 in the cutting process in the control unit 30. Set small.

If the rotation speed of the rotating shaft 10 in the vibration step is larger than the rotation speed of the rotating shaft 10 in the cutting process, the collision interval between the blade Tb and the surface to be cut W1 tends to be small. The smaller the collision interval between the blade Tb and the surface to be cut W1, the smaller the period of vibration of the object to be cut W, which is repeatedly vibrated by the collision between the blade Tb and the surface to be cut W1. Further, the smaller the vibration cycle of the work piece W, the sufficient time is secured from the collision between the blade Tb and the work piece W until the next collision between the blade Tb and the work piece W. Becomes difficult.

When the time until the blade Tb and the object W to collide cannot be sufficiently secured, as shown in FIG. 7, the amplitude indicating the vibration of each vibration of the object W cannot be sufficiently attenuated. As a result, it becomes difficult to detect the start timing and the end timing of each of the repeatedly generated vibrations, so that it is difficult to calculate the natural frequency ω1 in the natural vibration calculation step described later.

On the other hand, when the rotation speed of the rotating shaft 10 in the vibration step is smaller than the rotation speed of the rotating shaft 10 in the cutting process, the collision interval between the blade Tb and the surface to be cut W1 tends to be large. Further, the larger the collision interval between the blade Tb and the surface to be cut W1, the larger the period of vibration of the object to be cut W, which is repeatedly vibrated by the collision between the blade Tb and the surface to be cut W1. As a result, it is possible to secure a sufficient time from the collision between the blade Tb and the work piece W until the next collision between the blade Tb and the work piece W.

In the present embodiment, the face mill T1 attached to the rotary shaft 10 in the vibration step uses the same face mill T1 as the face mill T1 attached to the rotary shaft 10 in the cutting step, thereby performing the vibration step and the cutting step. Match the tools T used for each of.

In this case, as shown in FIG. 8, when the work piece W is repeatedly vibrated, the amplitude indicating the vibration of each vibration of the work piece W can be sufficiently attenuated, so that each of the repeatedly generated vibrations can be sufficiently damped. The start timing and end timing of are easily detected. Therefore, the natural frequency ω1 can be stably calculated in the natural vibration calculation step described later.

Further, the control unit 30 is set so that the information on the trajectory of the feed mechanism 21 in the vibration step passes through at least a part of the trajectory in the cutting process. In the present embodiment, the trajectory of the feed mechanism 21 in the vibration step is the same trajectory as the trajectory of the feed mechanism 21 in the cutting process, and the face mill T1 is defined to move along the machined surface W1. .. Further, the trajectory of the feed mechanism 21 in the vibration step is defined so that the blade Tb comes into contact with the surface to be cut W1 when the feed mechanism 21 moves the face mill T1 along the trajectory.

Further, the control unit 30 is set so that the moving speed of the feed mechanism 21 in the vibration step is such that the surface to be cut W1 and the blade Tb collide with each other at a plurality of points. The vibration detection unit 40 detects the vibration of the work piece W at a plurality of places where the surface W1 to be cut and the blade Tb collide, and uniquely provides information on the vibration of the work piece W at the detected plurality of places. It is transmitted to the vibration calculation unit 50.

Subsequently, an example of the control process executed by the control unit 30 in the vibration excitation step will be described with reference to the flowchart shown in FIG. The control process shown in FIG. 9 is executed when the start signal of the vibration step is input to the control unit 30.

When the start signal of the vibration process is input, the control unit 30 refers to the control map stored in the memory of the control unit 30 in step S10, and each parameter in the vibration process defined in the control map. Get information about.

Subsequently, in step S11, the control unit 30 rotates the face mill T1 by rotating the rotation shaft 10 according to the information on the rotation speed of the rotation shaft 10 in the vibration step. Then, in step S12, the control unit 30 moves the feed mechanism 21 according to the information on the moving speed of the feed mechanism 21 in the vibration step and the information on the trajectory in the cutting step, thereby moving the face mill T1 to the surface to be cut W1. Move along.

As a result, the cutting device 1 repeatedly vibrates the object to be cut W by colliding the rotating face mill T1 with a plurality of different points on the surface to be cut W1. When the blade Tb repeatedly collides with the surface to be cut W1, the object to be cut W is cut by the surface W1 to be cut and is forcibly vibrated by the impact when the blade Tb collides with the surface W1 to be cut.

Returning to FIG. 6, the natural vibration calculation step is performed after the vibration step. The natural vibration calculation step is a step of calculating the natural frequency ω1 based on the detected value of the vibration of the work piece W detected in the vibration step.

The natural vibration calculation unit 50 performs frequency analysis on the vibration information of each of the plurality of locations on the machined surface W1 transmitted from the vibration detection unit 40. FIG. 10 shows an example of the result of frequency analysis performed by the natural vibration calculation unit 50 for the vibration at a predetermined location detected by the vibration detection unit 40. FIG. 10 shows a frequency spectrum for each component of the vibration amount of the work piece W at the predetermined location. In the frequency spectrum shown in FIG. 10, in the frequency region having a vibration component, there are a plurality of frequencies in which the vibration amount is prominently large as compared with the vibration amount of the surrounding frequency.

Specifically, there are frequencies ν1, ν2, ν3, ν4, and ν5 as frequency values in which the vibration amount is prominently larger than the vibration amount of the surrounding frequency. The natural vibration calculation unit 50 calculates each of the frequencies ν1 to ν5 as the natural frequency ω1 at a predetermined position. Further, the natural vibration calculation unit 50 transmits the calculated information on the natural frequency ω1 to the control unit 30. When the control unit 30 acquires the information of the natural frequency ω1 from the natural vibration calculation unit 50, the control unit 30 acquires the position information of the feed mechanism 21 when the vibration detection unit 40 detects the vibration of the work piece W from the position sensor. do.

The control unit 30 associates the information of the natural frequency ω1 transmitted from the natural vibration calculation unit 50 with the position information of the feed mechanism 21 when the information of the natural frequency ω1 is received. Further, the control unit 30 determines, based on the linked natural frequency ω1 information and the position information of the feed mechanism 21, a part of the part to be cut of the object W to be cut and a part showing the position information of the feed mechanism 21. The correspondence relationship with the natural frequency ω1 in the relevant part is stored in the memory.

Further, the control unit 30 provides information on each natural frequency ω1 calculated by the natural vibration calculation unit 50 with respect to the vibration detected by the vibration detection unit 40 at a plurality of locations on the surface W1 to be cut, and each natural frequency. The position information of the feed mechanism 21 when the information of ω1 is received is associated with it. The control unit 30 stores in the memory the correspondence between each portion of the surface to be cut W1 from which the natural frequency ω1 is calculated and the natural frequency ω1 at the portion.

In this way, in the vibration excitation step and the natural vibration calculation step, by using the cutting device 1, the natural frequency ω1 of the part to be cut in the work piece W is calculated before the work piece W is cut.

By the way, the object W to be cut in the present embodiment is provided with a plurality of openings W2 having different shapes, and the natural frequency ω1 tends to differ depending on the portion where the face mill T1 and the surface W1 to be cut collide with each other. On the other hand, the cutting device 1 is based on the detection value detected by the vibration detection unit 40 of the vibration when the face mill T1 and the surface to be cut W1 collide with each other and vibrate. The natural frequency ω1 of each of a plurality of locations can be calculated.

Further, for example, when cutting a work piece W having the same shape and manufacturing the same work piece, the plurality of work pieces W may have the same shape and configuration, respectively. The natural frequency ω1 is substantially the same. Therefore, the vibration excitation step and the natural vibration calculation step are performed on one work piece W out of the plurality of work pieces W even when there are a plurality of work pieces W.

Subsequently, the reference roughness detection step is carried out after the natural vibration calculation step. In the reference roughness detection step, the reference roughness Rz0 is detected by actually cutting the work piece W using the cutting device 1 and measuring the size of the surface roughness of the work piece W after cutting. It is a process to do. Here, the reference roughness Rz0 means that when the predetermined speed of the feed mechanism 21 is set to the reference speed Vf0, the feed mechanism 21 is rotated at the same rotation speed as the natural frequency ω1 and the feed mechanism 21 is set to the reference speed Vf0. It is the magnitude of the surface roughness of the work piece W when the work piece W is cut while being moved.

In the reference roughness detection step, the operator installs the work piece W on the stage 2 as in the vibration step. The object W to be cut is fixed at a predetermined installation position by using the fixing jig of the stage 2. Subsequently, the cutting device 1 moves the feed mechanism 21 while rotating the rotating shaft 10 based on the information of various parameters previously determined in the control unit 30, and cuts the object W to be cut.

The operation of the cutting device 1 in the reference roughness detection step is controlled by the control unit 30. In the memory of the control unit 30, information on the rotation speed of the rotating shaft 10, information on the moving speed of the feed mechanism 21, and information on the trajectory of the feed mechanism 21 are set as parameters for carrying out the reference roughness detection step. ..

The rotation speed of the rotation shaft 10 in the reference roughness detection step is set by, for example, the control unit 30 at the same rotation speed as the natural frequency ω1 calculated in the natural vibration calculation step. Further, the moving speed of the feed mechanism 21 in the reference roughness detection step is set by being input to the input unit by, for example, an operator's operation. Further, the information on the trajectory of the feed mechanism 21 in the reference roughness detection step is set to the same trajectory as the trajectory of the feed mechanism 21 in the vibration excitation process. The control unit 30 stores in the memory a control map in which each parameter in the reference roughness detection step is defined.

An example of the control process executed by the control unit 30 in the reference roughness detection step will be described with reference to the flowchart shown in FIG. The control process shown in FIG. 11 is executed when the start signal of the reference roughness detection step is input to the control unit 30.

When the start signal of the reference roughness detection step is input, the control unit 30 refers to the control map stored in the memory of the control unit 30 in step S20, and the reference roughness detection step defined in the control map. Get the information of each parameter in.

Subsequently, in step S21, the control unit 30 starts the feed mechanism 21 to move at the reference speed Vf0 along the trajectory in the cutting process. Then, in step S22, the control unit 30 rotates the rotation shaft 10 at the same rotation speed as the natural frequency ω1 as the feed mechanism 21 moves. The control unit 30 changes the rotation speed of the rotation shaft 10 to the natural frequency ω1 for each part for which the natural frequency ω1 is calculated when cutting each part for which the natural frequency ω1 is calculated in the natural vibration calculation process. do.

When a plurality of natural frequencies ω1 exist in the portion where the natural frequency ω1 is calculated, the control unit 30 determines the rotation number of the rotation shaft 10 to be unique to any one of the plurality of calculated natural frequencies ω1. Change to frequency ω1.

As a result, the cutting device 1 can cut the object W to be cut by moving the feed mechanism 21 at the reference speed Vf0 while rotating the rotating shaft 10 at the same rotation speed as the natural frequency ω1 calculated in the natural vibration calculation process. .. Further, the reference roughness Rz0 can be detected by the operator measuring the size of the surface roughness of the work piece W cut in the reference roughness detection step using a surface roughness meter or the like.

Subsequently, the control unit 30 sets each parameter for carrying out the cutting step after the reference roughness detection step. Specifically, the control unit 30 sets the target rotation speed n based on the calculation result in the natural vibration calculation process, and sets the target speed Vf1 based on the calculation result in the reference roughness detection process and the set target rotation speed n. do. Further, information on the trajectory of the feed mechanism 21 is preset in the control unit 30. The control unit 30 stores in the memory a control map in which each parameter in the cutting process is defined.

A method of calculating the target rotation speed n will be described with reference to FIGS. 12 and 13. In the present embodiment, the generated state of the forced vibration of the object W to be cut is replaced with the forced vibration model of the one-degree-of-freedom damping system shown in FIG. This forced vibration model is composed of a substance M having a mass m corresponding to a work piece W, a damper Dp having a damping coefficient c, and a spring S having a spring constant k. The substance M is forcibly vibrated by being vibrated from the outside.

In the present embodiment, the forced vibration of the object W to be cut corresponds to the forced vibration of the substance M. Further, the frequency of the forced vibration generated when the cutting device 1 cuts the object W to be cut corresponds to the frequency ω when the substance M is forced to vibrate. Further, the frequency of the forced vibration generated when the cutting device 1 cuts the work piece W is determined by the collision interval when the rotating tool T and the work piece W repeatedly collide with each other. Therefore, the rotation speed of the rotation shaft 10 corresponds to the frequency ω when the substance M is forced to vibrate.

Here, in the forced vibration model shown in FIG. 12, when the substance M is vibrated by applying an external excitation force of Fcosωt to the substance M, the amplitude x at time t of the substance M in the transient state of vibration is as follows. It can be calculated from Equation 1 of.

数式１におけるｘａは、強制振動の振動量の最大値を示す。また、数式１におけるζは、ダンパＤｐの減衰比を示す。また、数式１におけるω０は、物質Ｍの固有振動数を示す。また、数式１におけるωｄは、減衰系の固有振動数を示す。また、数式１におけるφは、強制振動の位相を示す。

Xa in Equation 1 indicates the maximum value of the amount of forced vibration. Further, ζ in Equation 1 indicates the damping ratio of the damper Dp. Further, ω0 in Equation 1 indicates the natural frequency of the substance M. Further, ωd in Equation 1 indicates the natural frequency of the damping system. Further, φ in Equation 1 indicates the phase of forced vibration.

Further, the maximum value xa of the vibration amount of the substance M in the steady state in which a sufficient time has passed from the transient state can be calculated from the following mathematical formula 2.

数式２におけるｘｓは、物質Ｍに静的な力Ｆを加えたときの物質Ｍの静的変位量を示す。なお、物質Ｍに加えられる力Ｆは固定値である。このため、物質Ｍに静的な力Ｆを加えたときの物質Ｍの静的変位量であるｘｓは固定値になる。また、数式２におけるωは、物質Ｍが加振される際の強制振動の振動数ωを示す。

Xs in Equation 2 indicates the amount of static displacement of the substance M when a static force F is applied to the substance M. The force F applied to the substance M is a fixed value. Therefore, xs, which is the amount of static displacement of the substance M when a static force F is applied to the substance M, becomes a fixed value. Further, ω in Equation 2 indicates the frequency ω of forced vibration when the substance M is vibrated.

Further, the phase φ in the steady state can be calculated from the following mathematical formula 3.

また、上述の数式２において、強制振動の振動量の最大値ｘａを静的変位量ｘｓで除した値である振幅倍率と、強制振動の振動数ωを固有振動数ω０で除した値である強制振動の周波数比との相関関係を図１３の共振曲線に示す。なお、図１３に示す共振曲線は、数式２において減衰比ζを０．０２で設定した場合の曲線である。

Further, in the above equation 2, the amplitude magnification which is the value obtained by dividing the maximum value xa of the vibration amount of the forced vibration by the static displacement amount xs and the value obtained by dividing the frequency ω of the forced vibration by the natural frequency ω0. The correlation with the frequency ratio of forced vibration is shown in the resonance curve of FIG. The resonance curve shown in FIG. 13 is a curve when the attenuation ratio ζ is set to 0.02 in Equation 2.

As shown in FIG. 13, the amplitude magnification increases as the frequency ratio of forced vibration approaches 1, and decreases as the frequency ratio of forced vibration increases from 1. That is, the amplitude magnification increases as the frequency ω of the forced vibration when the substance M is vibrated approaches the natural frequency ω 0, and the frequency ω of the forced vibration when the substance M is vibrated becomes the natural vibration. The farther from the number ω0, the smaller it becomes.

Furthermore, as shown in FIG. 13, the reduction rate of the amplitude magnification increases as the frequency ratio of the forced vibration approaches 1, and decreases as the frequency ratio of the forced vibration approaches 1. In particular, when the frequency ratio of forced vibration is 0.8 to 1.2, the reduction rate of the amplitude magnification is when the frequency ratio of forced vibration is smaller than 0.8, or the frequency ratio of forced vibration is 1.2. It is large compared to the reduction rate of the amplitude magnification when it is larger.

In other words, when the forced vibration frequency ω is set so that the forced vibration frequency ratio is between 0.8 and 1.2, the amplitude magnification is such that the forced vibration frequency ratio is 0.8. It is greatly reduced as compared with the case where it is smaller or larger than 1.2.

Here, since the static displacement amount xs is a fixed value, the reduction rate of the amplitude magnification corresponds to the reduction rate of the maximum value xa of the vibration amount of the forced vibration. Therefore, the maximum value xa of the vibration amount of the forced vibration is the maximum value xa of the vibration amount of the forced vibration when the frequency ratio of the forced vibration is 1, and the frequency ratio of the forced vibration becomes farther from 1. , It's getting smaller. The reduction rate when the maximum value xa of the vibration amount of the forced vibration becomes small is equal to the reduction rate of the amplitude magnification.

Further, the reduction width when the maximum value xa of the vibration amount of the forced vibration becomes small can be calculated based on the frequency ratio of the forced vibration and the resonance curve shown in FIG. For example, when the frequency ratio of the forced vibration is 0.8 or 1.2, the decrease width of the vibration amount of the forced vibration of the substance M is 1 for the frequency ratio of the forced vibration based on the resonance curve shown in FIG. It is about 80% of the vibration amount of the forced vibration in the case of. In other words, the vibration amount of the forced vibration of the substance M when the frequency ratio of the forced vibration is 0.8 or 1.2 is 20 of the vibration amount of the forced vibration when the frequency ratio of the forced vibration is 1. It becomes%.

Further, as described above, in the present embodiment, the generated state of the forced vibration of the work piece W is replaced with the forced vibration model. Therefore, the frequency ω of the forced vibration of the material M corresponds to the rotation speed of the rotating shaft 10 when cutting the work piece W, and the natural frequency ω0 of the material M is the natural frequency of the work piece W. Corresponds to ω1. Further, corresponds to the amount of vibration when the work piece W is forcibly vibrated, and the static displacement amount xs is the case where a static force is received from the face mill T1 when the work piece W is cut. Corresponds to the amount of static displacement.

Therefore, the amplitude magnification and the ratio of the natural frequency ω1 to the target rotation number n when the object W to be forced vibrates corresponds to the amplitude magnification of the forced vibration model and the frequency ratio of the forced vibration. Therefore, the amplitude magnification when the object W to be forced vibrates increases as the target rotation speed n approaches the natural frequency ω1, and decreases as the target rotation speed n becomes farther from the natural frequency ω1.

The reduction rate of the amplitude magnification when the work piece W is forced to vibrate corresponds to the reduction rate of the vibration amount of the forced vibration of the work piece W. Further, the vibration amount of the forced vibration of the object W to be cut is the natural frequency ω1 and the target rotation speed n, with the vibration amount when the ratio of the natural frequency ω1 and the target rotation speed n is 1 as the maximum value. As the ratio increases from 1, it decreases.

Therefore, the target rotation speed n is set at a rotation speed different from the natural frequency ω1. As a result, the amount of forced vibration of the object to be cut W becomes smaller than when cutting with the rotation shaft 10 set to the same rotation speed as the natural frequency ω1.

Further, in the present embodiment, the amplitude magnification of the forced vibration of the object W to be cut corresponds to the amplitude magnification of the forced vibration model. Therefore, the vibration amount of the work piece W when the rotation shaft 10 is rotated at the target rotation speed n with respect to the vibration amount of the work piece W when the rotation shaft 10 is rotated at the same rotation speed as the natural frequency ω1. The reduction width of can be calculated from the ratio of the natural frequency ω1 and the target rotation speed n.

For example, the rotation speed n1, which is a value obtained by multiplying the natural frequency ω1 by 0.8, is set as the first candidate for the target rotation speed n of the rotation shaft 10. The reduction width of the vibration amount of the work piece W when the rotating shaft 10 is rotated at a rotation speed of n1 or less is set to the natural frequency ω1 based on the resonance curve shown in FIG. It is about 80% or more of the vibration amount of the work piece W when it is rotated and cut at the same rotation speed. In other words, the vibration amount of the work piece W when the rotary shaft 10 is rotated at a rotation speed n1 or less and cut is the cover when the rotary shaft 10 is rotated at the same rotation speed as the natural frequency ω1. It is 20% or less of the vibration amount of the cut object W.

Further, the rotation speed n2, which is a value obtained by multiplying the natural frequency ω1 by 1.2, is set as the second candidate for the target rotation speed n of the rotation shaft 10. Similarly, when the rotary shaft 10 is rotated at a rotation speed of n2 or more for cutting, the reduction width of the vibration amount of the work piece W is such that the rotary shaft 10 is rotated at the same rotation speed as the natural frequency ω1. It is about 80% or more of the vibration amount of the work piece W when it is cut. That is, the vibration amount of the work piece W when the rotary shaft 10 is rotated at a rotation speed of n2 or more and cut is the case where the rotary shaft 10 is rotated at the same rotation speed as the natural frequency ω1 and cut. It is 20% or less of the vibration amount of the work piece W.

Here, the target rotation speed n is determined so that the vibration amount when the rotating shaft 10 is rotated at the target rotation speed n to cut the object W to be cut is equal to or less than the target vibration amount. The target vibration amount is determined so as to be a predetermined ratio with respect to the vibration amount of the work piece W when the rotating shaft 10 is rotated at the same rotation speed as the natural frequency ω1. For example, when the target vibration amount is determined by 20% of the vibration amount of the work piece W when the rotation shaft 10 is rotated at the same rotation speed as the natural frequency ω1, the target rotation speed n is the rotation speed. It is set to a rotation speed of n1 or less or n2 or more.

The magnitude of the predetermined ratio used when determining the target vibration amount corresponds to the predetermined ratio α used when explaining the calculation method of the target speed Vf1 described later. Further, the target vibration amount is not limited to 20% of the vibration amount of the work piece W when the rotation shaft 10 is rotated at the same rotation speed as the natural frequency ω1, and can be set as appropriate.

The control unit 30 sets the target rotation speed n for each part of the information stored in the memory based on the correspondence between each part where the natural frequency ω1 is calculated and the natural frequency ω1 in the part. do. In the present embodiment, the target rotation speed n is set to the rotation speed n1 or the rotation speed n2 for each part where the natural frequency ω1 is calculated.

Further, the magnitude of the surface roughness that increases due to the vibration of the work piece W becomes smaller as the vibration amount of the forced vibration of the work piece W is reduced. Therefore, for example, the magnitude of the surface roughness that increases due to the vibration of the work piece W when the rotating shaft 10 is rotated at the rotation speed n1 or n2 is the same as the natural frequency ω1 of the rotating shaft 10. It is smaller than the magnitude of the surface roughness that increases due to the vibration of the work piece W when it is rotated at the number of rotations. Specifically, the magnitude of the surface roughness that increases due to the vibration of the work piece W when the rotating shaft 10 is rotated at the rotation number n1 or n2 is the same as the rotation of the rotating shaft 10 with the natural frequency ω1. It is about 20% of the magnitude of the surface roughness that increases due to the vibration of the work piece W when it is rotated by a number. Therefore, when the moving speed of the feed mechanism 21 is the reference speed Vf0, the surface roughness increases due to the vibration of the work piece W when the rotating shaft 10 is rotated at the rotation speed n1 or n2 to cut. The size is about 20% of the standard roughness. Further, when the rotating shaft 10 is rotated at the target rotation speed n, the decrease in surface roughness that increases due to the vibration of the work piece W is the case where the rotating shaft 10 is rotated at the target rotation speed n. This is the amount of decrease in the amount of vibration of the work piece W.

Here, a method of setting the target rotation speed n when a plurality of natural frequencies ω1 exist at each calculation site of the natural frequency ω1 in the object W to be cut will be described. When a plurality of natural frequencies ω1 exist in each of the calculation sites of the natural frequency ω1, the control unit 30 sets the target rotation speed n at a rotation speed different from that of each of the plurality of natural frequencies ω1. Further, the control unit 30 extracts one of the plurality of natural frequencies ω1 and targets a value obtained by multiplying the extracted one natural frequency ω1 by 0.8 or 1.2. Set to the number of revolutions n.

Further, the control unit 30 has a plurality of natural frequencies so that the target rotation speed n set at each calculation portion of the object W to be cut becomes a value as close as possible to the target rotation speed n set at each other calculation portion. One natural frequency ω1 is extracted from ω1. In particular, the control unit 30 sets the target rotation speed n set at the calculation sites adjacent to each other on the orbit so as to be as close to each other as possible.

Subsequently, a method of calculating the target speed Vf1 by using an arithmetic formula that associates the size of the surface roughness when cutting the object W to be cut, the rotation speed of the rotating shaft 10, and the moving speed of the feed mechanism 21. An example will be described. Specifically, a calculation method using the reference roughness Rz0 corresponding to the natural frequency ω1 and the reference speed Vf0 and the target roughness Rz1 corresponding to the target rotation speed n and the target speed Vf1 will be described. The size of the theoretical surface roughness when the work piece W is cut by moving the feed mechanism 21 at the reference speed Vf0 while rotating the rotation shaft 10 at the same rotation speed as the natural frequency ω1 is Rh0, and the work piece is to be cut. The magnitude of the surface roughness caused by the vibration of the object W is defined as the surface roughness Rh1 caused by the vibration. In this case, the reference roughness Rz0 is the sum of the theoretical surface roughness Rh0 and the surface roughness Rh1 caused by vibration, and is therefore determined by the following mathematical formula 4.

また、送り機構２１が基準速度Ｖｆ０で移動する際において、フェイスミルＴ１が一回転する際の一刃あたりの移動距離を刃当たり送りｆｚ０、刃Ｔｂの刃先の半径をｒとすると、理論表面粗さＲｈ０は、以下の数式５より算出できる。

Further, when the feed mechanism 21 moves at the reference speed Vf0, assuming that the moving distance per blade when the face mill T1 makes one rotation is the feed fz0 per blade and the radius of the cutting edge of the blade Tb is r, the theoretical surface roughness Rh0 can be calculated from the following mathematical formula 5.

これにより、基準粗さＲｚ０は、数式５で示す理論表面粗さＲｈ０および振動に起因する表面粗さＲｈ１に基づいて、以下の数式６より算出できる。

Thereby, the reference roughness Rz0 can be calculated from the following equation 6 based on the theoretical surface roughness Rh0 shown by the equation 5 and the surface roughness Rh1 caused by the vibration.

これに対して、目標回転数ｎで回転軸１０を回転させつつ、目標速度Ｖｆ１で送り機構２１を移動させながら被切削物Ｗを切削した際の被切削物Ｗの表面粗さの大きさを目標粗さＲｚ１とする。また、回転軸１０を目標回転数ｎで回転させつつ、送り機構２１を目標速度Ｖｆ１で移動させて被切削物Ｗを切削した際の理論表面粗さの大きさをＲｈ２、被切削物Ｗの振動に起因して増大する表面粗さの大きさを振動に起因する表面粗さＲｈ３とする。この場合、目標粗さＲｚ１は、理論表面粗さＲｈ２と、振動に起因する表面粗さＲｈ３との合計になるため、以下の数式７より定まる。

On the other hand, the size of the surface roughness of the work piece W when the work piece W is cut while rotating the rotation shaft 10 at the target rotation speed n and moving the feed mechanism 21 at the target speed Vf1 is determined. The target roughness Rz1 is set. Further, while rotating the rotating shaft 10 at the target rotation speed n, the feed mechanism 21 is moved at the target speed Vf1 to cut the work piece W, and the size of the theoretical surface roughness is Rh2 and the work piece W. The magnitude of the surface roughness caused by the vibration is defined as the surface roughness Rh3 caused by the vibration. In this case, the target roughness Rz1 is the sum of the theoretical surface roughness Rh2 and the surface roughness Rh3 caused by vibration, and is therefore determined by the following mathematical formula 7.

また、送り機構２１が目標速度Ｖｆ１で移動する際において、フェイスミルＴ１が一回転する際の一刃あたりの移動距離を刃当たり送りｆｚ１、刃Ｔｂの刃先の半径をｒとすると、理論表面粗さＲｈ２は、以下の数式８より算出できる。

Further, when the feed mechanism 21 moves at the target speed Vf1, assuming that the moving distance per blade when the face mill T1 makes one rotation is the feed fz1 per blade and the radius of the cutting edge of the blade Tb is r, the theoretical surface roughness Rh2 can be calculated from the following equation 8.

ところで、フェイスミルＴ１が一回転する際の一刃あたりの移動距離を刃当たり送りｆｚ０から刃当たり送りｆｚ１に大きくすると、フェイスミルＴ１が被切削物Ｗを切削する際の切削抵抗が増加する。仮に、回転軸１０の回転数が一定の場合、切削抵抗が大きくなるにしたがい、振動に起因する表面粗さは大きくなる。回転軸１０の回転数が一定の場合、送り機構２１の移動速度を刃当たり送りｆｚ１に大きくした際の振動に起因する表面粗さは、振動に起因する表面粗さＲｈ１に刃当たり送りｆｚ１と刃当たり送りｆｚ０との比率を乗じることよって算出できる。

By the way, if the moving distance per blade when the face mill T1 makes one rotation is increased from the blade-per-blade feed fz0 to the blade-per-blade feed fz1, the cutting resistance when the face mill T1 cuts the workpiece W increases. If the rotation speed of the rotating shaft 10 is constant, the surface roughness caused by vibration increases as the cutting resistance increases. When the rotation speed of the rotating shaft 10 is constant, the surface roughness caused by the vibration when the moving speed of the feed mechanism 21 is increased to the blade-per-blade feed fz1 is the surface roughness Rh1 caused by the vibration and the blade-per-blade feed fz1. It can be calculated by multiplying the ratio with the feed per blade fz0.

On the other hand, when the rotation speed of the rotating shaft 10 is changed from the same rotation speed as the natural frequency ω1 to the target rotation speed n, the vibration amount when cutting the workpiece W is suppressed. Therefore, if the moving distance per blade when the face mill T1 makes one rotation is constant, the surface roughness caused by vibration is suppressed. When the movement distance per blade when the face mill T1 makes one rotation is constant, the surface roughness caused by the vibration when the rotation speed of the rotation shaft 10 is changed to the target rotation speed n is the target vibration amount. It can be calculated based on the predetermined ratio α used when determining. The predetermined ratio α is a predetermined value within a range larger than 0 and smaller than 1, and is determined by the ratio of the natural frequency ω1 and the target rotation speed n based on the resonance curve shown in FIG. be.

Therefore, the surface roughness Rh3 caused by vibration is calculated from the following equation 9 based on the surface roughness Rh1 caused by vibration, the ratio of the feed per blade fz1 and the feed fz0 per blade, and a predetermined ratio α. Can be calculated.

本実施形態において、目標回転数ｎは、回転数ｎ１、または、回転数ｎ２に設定される。この場合、被切削物Ｗの振動に起因して増大する表面粗さの大きさは、回転軸１０を固有振動数ω１と同じ回転数で回転させて切削した場合の被切削物Ｗの振動に起因して増大する表面粗さの大きさの約２０％になる。このため、回転軸１０を回転数ｎ１、または、回転数ｎ２で回転させた場合、所定の割合αは、０．２を用いることができる。

In the present embodiment, the target rotation speed n is set to the rotation speed n1 or the rotation speed n2. In this case, the magnitude of the surface roughness that increases due to the vibration of the work piece W is the vibration of the work piece W when the rotating shaft 10 is rotated at the same rotation speed as the natural frequency ω1 and cut. It is about 20% of the magnitude of the surface roughness that results from it. Therefore, when the rotation shaft 10 is rotated at the rotation speed n1 or the rotation speed n2, 0.2 can be used as the predetermined ratio α.

The predetermined ratio α is not limited to 0.2, and can be determined by the ratio of the natural frequency ω1 corresponding to the natural frequency ω0 shown in FIG. 13 and the target rotation speed n corresponding to the frequency ω. .. For example, when the target rotation speed n is set to a rotation speed smaller than the rotation speed n1 or a rotation speed larger than the rotation speed n2, the amplitude magnification of the forced vibration of the workpiece W is such that the target rotation speed n is the rotation speed n1 or It becomes smaller than when it is set to n2. Therefore, a value smaller than 0.2 can be used for the predetermined ratio α. Further, when the target rotation speed n is set to a rotation speed larger than the rotation speed n1 and smaller than the rotation speed n2, the amplitude magnification of the forced vibration of the work piece W is set to the rotation speed n1 or n2. It will be larger than the case. Therefore, a value larger than 0.2 can be used for the predetermined ratio α.

As a result, the target roughness Rz1 can be calculated from the following formula 10 based on the formulas 8 and 9.

そして、上述の数式６および数式１０に基づいて、刃当たり送りｆｚ１は、以下の数式１１を満たす。

Then, based on the above-mentioned formulas 6 and 10, the blade-per-blade feed fz1 satisfies the following formula 11.

数式１１より、目標粗さＲｚ１を予め定めることによって、制御部３０は、刃当たり送りｆｚ１を算出することができる。また、フェイスミルＴ１の移動距離が刃当たり送りｆｚ１である場合の目標速度Ｖｆ１は、フェイスミルＴ１に取り付けられた刃Ｔｂの数をｚとしたとき、刃当たり送りｆｚ１と刃Ｔｂの数ｚと目標回転数ｎとに基づいて、以下の数式１２より算出できる。

By predetermining the target roughness Rz1 from Equation 11, the control unit 30 can calculate the feed per blade fz1. Further, the target speed Vf1 when the moving distance of the face mill T1 is the blade-to-blade feed fz1 is the number z of the blade-to-blade feed fz1 and the blade Tb, where z is the number of blades Tb attached to the face mill T1. It can be calculated from the following formula 12 based on the target rotation speed n.

本実施形態において、目標粗さＲｚ１は、被切削物Ｗの加工精度が基準粗さＲｚ０より悪化することを回避するため、基準粗さＲｚ０を超えない範囲で設定される。すなわち、目標粗さＲｚ１の最大値を基準粗さＲｚ０としている。

In the present embodiment, the target roughness Rz1 is set within a range not exceeding the reference roughness Rz0 in order to prevent the machining accuracy of the workpiece W from becoming worse than the reference roughness Rz0. That is, the maximum value of the target roughness Rz1 is set as the reference roughness Rz0.

Further, it is desirable that the target speed Vf1 is set to a value as large as possible in order to improve productivity when manufacturing a machined product using the cutting device 1. Therefore, in the present embodiment, the target speed Vf1 is set to a value larger than the reference speed Vf0. Further, since the size of the surface roughness of the work piece W increases as the moving speed of the feed mechanism 21 increases, the target speed Vf1 can be set larger as the target roughness Rz1 is set larger.

Here, since the target roughness Rz1 is set within a range that does not exceed the reference roughness Rz0, the target velocity Vf1 becomes the maximum value when the target roughness Rz1 is set with the reference roughness Rz0. Therefore, the target speed Vf1 becomes the allowable maximum speed Vf2 when the target roughness Rz1 becomes the reference roughness Rz0. By setting the target roughness Rz1 to the reference roughness Rz0, the allowable maximum speed Vf2 can be set to the reference roughness Rz0, the radius r of the cutting edge of the blade Tb, the target rotation speed n, and the face mill T1 according to Equations 11 and 12. It can be calculated based on the number z of the attached blades Tb.

Then, the target speed Vf1 is set within the speed range Vfr which is larger than the reference speed Vf0 and equal to or less than the allowable maximum speed Vf2.

From the above, the control unit 30 uses the target rotation speed n and the target rotation speed n and the target rotation speed n by using the equations 11 and 12 in which the target roughness Rz1, the target speed Vf1 set in the speed range Vfr, and the target rotation speed n are associated with each other. The target velocity Vf1 corresponding to the roughness Rz1 can be calculated. Further, the target speed Vf1 is set in the control unit 30 by being input to the input unit by the operation of the operator.

Further, the control unit 30 is set so that the information on the trajectory of the feed mechanism 21 in the cutting process moves the face mill T1 along the machined surface W1 as described above.

Then, returning to FIG. 3, the cutting step is carried out based on the various parameters set in the preparatory step after the preparatory step. The cutting process is a process of cutting the work piece W using the cutting device 1 to manufacture a machined work piece.

In the cutting process, the operator installs the object W to be cut on the stage 2 in the same manner as in the vibration step and the reference roughness detection process. The object W to be cut is fixed at a predetermined installation position by using the fixing jig of the stage 2.

The operation of the cutting device 1 in the cutting process is controlled by the control unit 30. An example of the control process executed by the control unit 30 in the cutting process will be described with reference to the flowchart shown in FIG. The control process shown in FIG. 14 is executed when the start signal of the cutting process is input to the control unit 30.

When the start signal of the cutting process is input, the control unit 30 acquires the parameter information set in the preparation process in step S30.

Subsequently, in step S31, the control unit 30 moves the feed mechanism 21 at the target speed Vf1 set in the preparation step according to the information of the orbit determined in advance.

Then, in step S32, the control unit 30 rotates the rotation shaft 10 at a target rotation speed n, which is a rotation speed different from the natural frequency ω1, as the feed mechanism 21 moves. The control unit 30 rotates the rotation shaft 10 at a target rotation speed n determined based on the correspondence between the portion where the natural frequency ω1 is calculated and the natural frequency ω1 at the portion. Specifically, the control unit 30 determines the rotation speed of the rotation shaft 10 when cutting each of the parts for which the natural frequency ω1 of the object W to be calculated is calculated in the natural vibration calculation step, and the natural frequency for each part. Change to the number of revolutions obtained by multiplying ω1 by 0.8 or 1.2.

As a result, the cutting device 1 can manufacture the machined object while suppressing the vibration amount of the forced vibration of the object to be machined W for each part where the natural frequency ω1 is calculated.

Subsequently, the magnitude of the surface roughness of the work piece W cut in the cutting step will be described with reference to FIG. FIG. 15 shows the machine to be cut when the moving speed of the feed mechanism 21 when the rotating shaft 10 is rotated at the same rotation speed as the natural frequency ω1 or the target rotation speed n is changed from the reference speed A to the allowable maximum speed C. The measurement result of the surface roughness of the thing W is shown.

The black circles in FIG. 15 indicate the magnitude of the theoretical surface roughness of the work piece W. The white circles in FIG. 15 indicate actual measurement results of the surface roughness of the work piece W when the work piece W is cut by rotating the rotation shaft 10 at the same rotation speed as the natural frequency ω1.

Further, the double circle in FIG. 15 indicates an actually measured value of the measurement result of the surface roughness of the work piece W when the rotation shaft 10 is rotated at the target rotation speed n to cut the work piece W. The white circles at the reference speed A are the magnitudes of the reference roughness Rz0.

In the present embodiment, since the rotating shaft 10 is rotated at a target rotation speed n different from the natural frequency ω1, the vibration amount of the work piece W determines the rotating shaft 10 while moving the feed mechanism 21 at the reference speed A. It can be made smaller than the amount of vibration when cutting by rotating at the same rotation speed as the frequency ω1. Further, as shown in FIG. 15, when the target roughness Rz1 is set to be smaller than the reference roughness Rz0, the moving speed of the feed mechanism 21 is increased from the reference speed A to a speed B larger than the reference speed A and smaller than the allowable maximum speed C. can do.

Further, when the target roughness Rz1 is set to be about the same as the reference roughness Rz0, the moving speed of the feed mechanism 21 can be increased from the reference speed A to the allowable maximum speed C.

According to the cutting device 1 of the present embodiment described above, when the object W to be cut is cut, the rotating shaft 10 is rotated at a rotation frequency different from the natural frequency ω1 to obtain forced vibration of the object W to be cut. The amount of surface roughness caused by this can be suppressed. Further, since the moving speed of the feed mechanism 21 is increased within the range where the target roughness Rz1 does not exceed the reference roughness Rz0, the time required to complete the cutting can be reduced without deteriorating the size of the surface roughness of the work piece W. By shortening, productivity can be improved.

Further, the control unit 30 sets the rotation speed of the rotation shaft 10 when cutting each of the parts for which the natural frequency ω1 is calculated to be different from the natural frequency ω1 for each part. Therefore, even if the natural frequency ω1 differs depending on the portion to be cut by the workpiece W, the amount of forced vibration of the workpiece W at each portion to be cut can be suppressed.

Further, since the work piece W can be vibrated by using the rotary shaft 10 and the tool T for cutting the work piece W, the cutting device 1 does not need to be provided with a device for vibrating the work piece W. In both cases, the work piece W can be vibrated.

Further, since the cutting device 1 includes a vibration detecting unit 40 and can detect the vibration of the work piece W by using the cutting device 1, it is necessary to detect the vibration of the work piece W in addition to the cutting device 1. No need for equipment.

Further, since the natural frequency ω1 of the work piece W can be calculated by using the cutting device 1, a device other than the cutting device 1 for calculating the natural frequency ω1 of the work piece W becomes unnecessary.

Further, the cutting device 1 detects the natural frequency ω1 of the work piece W by colliding with the work piece W installed on the stage 2 in a rotated state in the same manner as when performing the cutting process. can do. Therefore, since the cutting device 1 can calculate the natural frequency ω1 of the work piece W in the environment where the work piece W is cut, the influence on the detection of the natural frequency ω1 due to the change in the environment can be suppressed, and the work piece W can be cut. The natural frequency ω1 of the cutting object W can be calculated stably.

Further, the cutting device 1 makes the rotation speed of the rotary shaft 10 in the vibration process smaller than the rotation speed of the rotary shaft 10 in the cutting process, so that the amplitude of each vibration of the work piece W in the vibration process can be sufficiently increased. It can be attenuated. Therefore, it is possible to easily detect the start timing and the end timing of each of the repeatedly generated vibrations, so that the natural frequency ω1 can be calculated stably.

Further, when the control unit 30 sets the target rotation speed n at each of the calculation parts of the natural frequency ω1 in the object W to be cut, the target rotation speed n set at the calculation parts adjacent to each other on the trajectory in the cutting process is set. Set the values so that they are as close as possible to each other. As a result, in the cutting process, when the control unit 30 changes the rotation speed of the rotation shaft 10 to the target rotation speed n determined for each calculation site of the natural frequency ω1, it is changed to each target rotation speed n. The time required can be reduced.

(Other embodiments)
Although the typical embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and can be variously modified as follows, for example.

In the above-described embodiment, an example in which the cutting device 1 is configured by a machining center has been described, but the present invention is not limited to this. For example, the cutting apparatus 1 may be composed of a machining apparatus such as a lathe processing apparatus, a milling apparatus, and an NC machining apparatus.

In the above-described embodiment, the example in which the tool T and the rotary shaft 10 are attached to the lower side of the spindle head 11 in the vertical direction has been described, but the present invention is not limited thereto. For example, the tool T and the rotating shaft 10 may be mounted in a direction other than the vertical direction, such as a horizontal direction with respect to the installation position of the spindle head 11.

In the above-described embodiment, an example in which the workpiece W is made of aluminum die-cast has been described, but the present invention is not limited to this. For example, as the workpiece W, various objects other than aluminum, such as iron and copper, can be applied.

In the above-described embodiment, an example in which the feed mechanism 21 moves the tool T has been described, but the present invention is not limited to this. For example, the feed mechanism 21 may be configured to move the workpiece W by moving the stage 2.

In the above-described embodiment, the control unit 30 sets the rotation speed of the rotating shaft 10 in the cutting process to the natural frequency ω1 of each calculated part for each calculation part of the work piece W calculated in the natural vibration calculation step. An example of changing to a different rotation speed has been described, but the present invention is not limited to this. For example, the control unit 30 sets the rotation speed of the rotating shaft 10 in the cutting process to a rotation speed different from all the natural frequencies ω1 of the calculated portion, and does not change the rotation speed of the rotating shaft 10 according to the portion to be cut. It may be a configuration.

In the above-described embodiment, the target rotation speed n is determined so that the vibration amount when cutting the object W to be cut becomes the target vibration amount based on the mathematical formula 2 when the damping ratio is set to 0.02. An example has been described, but the present invention is not limited to this. For example, when the damping ratio is set to a value different from 0.02, the target rotation speed n is the vibration amount at which the work piece W is cut based on the mathematical formula 2 set at that value. It may be set to be a quantity.

In the above-described embodiment, the control unit 30 uses an arithmetic expression that associates the size of the surface roughness of the work piece W, the rotation speed of the rotating shaft 10, and the moving speed of the feed mechanism 21 with the target roughness Rz1 and An example of obtaining the target speed Vf1 corresponding to the target rotation speed n has been described, but the present invention is not limited to this. For example, the control unit 30 uses a control map in which the size of the surface roughness of the work piece W, the rotation speed of the rotating shaft 10, and the moving speed of the feed mechanism 21 are previously associated with each other, and the target roughness Rz1 and the target rotation speed are used. The target speed Vf1 corresponding to n may be obtained. Specifically, the control unit 30 stores in the memory a control map in which the target speed Vf1 corresponding to the target rotation speed n and the target roughness Rz1 is determined in advance, and by referring to the control map, the target speed Vf1 May be sought. Further, the control unit 30 uses another method without using a control map in which the size of the surface roughness of the object W to be cut, the rotation speed of the rotating shaft 10, and the moving speed of the feed mechanism 21 are previously associated with each other. , The target speed Vf1 may be obtained.

In the above-described embodiment, an example in which the cutting device 1 vibrates the work piece W by colliding the tool T with the work piece W has been described, but the present invention is not limited to this. For example, the cutting device 1 is configured to include a vibrating device for vibrating the work piece W, and may be configured to vibrate the work piece W by the vibrating device.

In the above-described embodiment, an example in which the natural vibration calculation unit 50 calculates the natural frequency ω1 based on the detection value of the vibration detection unit 40 when the object W to be cut is vibrated has been described, but the present invention is limited to this. Not done. The cutting device 1 is configured not to include the vibration detection unit 40 and the natural vibration calculation unit 50, and is based on the natural frequency ω1 calculated in advance by using a device other than the cutting device 1, the manufacturing method of the above-described embodiment. It may be configured to perform.

In the above-described embodiment, an example has been described in which the face mill T1 attached to the rotary shaft 10 in the vibration step is the same face mill T1 as the face mill T1 attached to the rotary shaft 10 in the cutting step, but the present invention is not limited thereto. .. For example, the face mill T1 attached to the rotary shaft 10 in the vibration step may have a configuration in which the number of blades Tb attached to the face mill T1 is smaller than that of the face mill T1 attached to the rotary shaft 10 in the cutting step. As the number of blades Tb of the face mill T1 used in the vibration step is smaller, the number of collisions between the blade Tb and the machined surface W1 per rotation of the face mill T1 decreases, so that the blade Tb and the machined surface W1 The collision interval can be increased. Therefore, the smaller the number of blades Tb of the face mill T1 used in the vibration step, the more stable the natural frequency ω1 can be calculated in the natural vibration calculation step.

In the above-described embodiment, the example in which the rotation speed of the rotary shaft 10 in the vibration step is set to be smaller than the rotation speed of the rotary shaft 10 in the cutting step has been described, but the present invention is not limited to this. The rotation speed of the rotating shaft 10 in the vibration step may be set to be the same as the rotation speed of the rotating shaft 10 in the cutting process, or may be set to be larger than the rotation speed of the rotating shaft 10 in the cutting process.

In the above-described embodiment, an example in which the vibration detection unit 40 is composed of a sound wave detection microphone and detects the vibration of the work piece W without contacting the work piece W has been described, but the present invention is not limited to this. For example, the vibration detection unit 40 may be composed of a non-contact type acceleration sensor such as an acceleration sensor that detects vibration by detecting a change in the capacitance of the sensor element. Further, the vibration detection unit 40 may be composed of a contact type acceleration sensor such as an acceleration sensor that detects vibration by detecting the distortion of the piezoelectric element.

Needless to say, in the above-described embodiment, the elements constituting the embodiment are not necessarily essential except when it is clearly stated that they are essential and when they are clearly considered to be essential in principle.

In the above-described embodiment, when numerical values such as the number, numerical value, amount, range, etc. of the components of the embodiment are mentioned, when it is clearly stated that it is particularly essential, and in principle, it is clearly limited to a specific number. Except as the case, it is not limited to the specific number.

In the above-described embodiment, when referring to the shape, positional relationship, etc. of a component or the like, the shape, positional relationship, etc., unless otherwise specified or limited in principle to a specific shape, positional relationship, etc. Etc. are not limited.

10 Rotating shaft 20 Moving device 21 Feeding mechanism 30 Control unit T Tool W Work piece

Claims (7)

A cutting device that cuts an object to be cut (W) using a tool (T).
A rotating shaft (10) for rotating the tool and
A moving device (20) having a feed mechanism for moving at least one of the object to be cut and the tool.
A control unit (30) for controlling the rotation speed of the rotation shaft and the moving speed of the feed mechanism is provided.
The work piece when the work piece is cut while moving the feed mechanism at a predetermined reference speed while rotating the rotation shaft at the same rotation speed as the natural frequency of the work piece calculated in advance. When the size of the surface roughness of
When cutting the work piece, the control unit rotates the rotation axis at a rotation speed different from the natural frequency, and the size of the surface roughness of the work piece after cutting is the reference roughness. A cutting device that increases the moving speed of the feed mechanism above the reference speed within a range not exceeding the above. The control unit
Correspondence relationship between a plurality of different points in the work piece and the natural frequency at the plurality of points is stored.
The cutting device according to claim 1, wherein the rotating shaft is rotated at a rotation speed different from the natural frequency based on the correspondence relationship when cutting the plurality of parts. A vibration detection unit (40) that detects the vibration of the object to be cut, and
The natural frequency of the work piece is calculated based on the detection value of the vibration detection unit when the work piece is vibrated by colliding the tool in the rotating state with the work piece. The cutting apparatus according to claim 1 or 2, further comprising a vibration calculation unit (50). A stage (2) for installing the work piece when cutting the work piece is provided.
The control unit stores in advance information on the trajectory of the feed mechanism when cutting the object to be cut, and when the object to be cut is vibrated, the control unit sets the feed mechanism on the trajectory according to the information on the trajectory. The cutting device according to claim 3, wherein the object to be cut and the tool in a rotating state collide with each other while being moved along at least a part of the cutting device. When the control unit vibrates the work piece, the control unit rotates the rotation shaft at a rotation speed smaller than the rotation speed of the rotation shaft when cutting the work piece, and the blade of the tool and the work piece. The cutting device according to claim 4, wherein the collision interval with a cutting object is increased. The control unit calculates the moving speed of the feed mechanism when the size of the surface roughness of the work piece after cutting becomes the reference roughness as the allowable maximum speed, and when cutting the work piece. The cutting device according to any one of claims 1 to 5, wherein the feed mechanism is moved within a speed range that is greater than the reference speed and equal to or less than the allowable maximum speed. The control unit
The target roughness, which is the size of the surface roughness when cutting the work piece, is set to a size within a range not exceeding the reference roughness.
The target rotation speed of the rotation speed of the rotation shaft when cutting the object to be cut is set to a rotation speed different from the natural frequency.
The target roughness using a calculation formula or a control map that associates the magnitude of the surface roughness when cutting the work piece, the rotation speed of the rotation shaft, and the moving speed of the feed mechanism within the speed range. And the moving speed of the feed mechanism corresponding to the target rotation speed is obtained as the target speed.
The cutting device according to claim 6, wherein when cutting the object to be cut, the feed mechanism is moved at the target speed while rotating the rotation shaft at the target rotation speed.

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