105 results about "Chatter vibration" patented technology

A chatter vibration detection method includes acquiring vibration data of a tool (4) at a time of machining a workpiece at a predetermined sampling period (Δt), calculating an autocorrelation coefficient (Rxx′) corresponding to a time required for a cutting edge (4a, 4b) to contact the workpiece (W) several times based on acquired time series vibration data and calculating a period (Tx) of characteristics of the calculated autocorrelation coefficient (Rxx′), and deciding that chatter vibration occurs when a contact period (T1) at which the cutting edge (4a, 4b) contacts the workpiece (W) is not an integral multiple of the calculated period (Tx).

A vibration suppressing method and a vibration suppressing device are disclosed. After a tool is attached to a main spindle, a modal parameter of the tool or a workpiece is computed. Thereafter, a relation between chatter frequency and phase difference is calculated as an approximation formula based on the obtained modal parameter and machining conditions. If chatter vibration occurs after initiation of the machining, a chatter frequency corresponding to a target phase difference is obtained using the approximation formula, and based on the obtained chatter frequency, the number of tool flutes and the main spindle rotation speed, the optimum rotation speed is calculated. The rotation speed of the main spindle is then changed in accordance with the obtained optimum rotation speed.

A vibration suppressing device and a vibration suppressing method that are capable of obtaining an accurate optimum rotation speed and shortening a time period from generation of chatter vibration to calculation of the optimum rotation speed are provided. The vibration suppressing device 10 includes: vibration sensors 2a to 2c for detecting time-domain vibrational accelerations of a rotary shaft 3 in rotation; and a control device 5 for calculating a chatter frequency and a frequency-domain vibrational acceleration of the rotary shaft 3 at the chatter frequency on the basis of the time-domain vibrational accelerations detected by the vibration sensors 2a to 2c, and when the calculated frequency-domain vibrational acceleration exceeds a predetermined threshold value, calculating an optimum rotation speed on the basis of a predetermined parameter, and rotating the rotary shaft 3 at the calculated optimum rotation speed.

A vibration suppressing device and a vibration suppressing method that are capable of obtaining an accurate optimum rotation speed and shortening a time period from generation of chatter vibration to calculation of the optimum rotation speed are provided. The vibration suppressing device 10 includes: vibration sensors 2a to 2c for detecting time-domain vibrational accelerations of a rotary shaft 3 in rotation; and a control device 5 for calculating a chatter frequency and a frequency-domain vibrational acceleration of the rotary shaft 3 at the chatter frequency on the basis of the time-domain vibrational accelerations detected by the vibration sensors 2a to 2c, and when the calculated frequency-domain vibrational acceleration exceeds a predetermined threshold value, calculating an optimum rotation speed on the basis of a predetermined parameter, and rotating the rotary shaft 3 at the calculated optimum rotation speed.

A stable rotation speed is acquired by finely changing a rotation speed of a rotary shaft 3 based on an expected stable rotation speed, and calculating an amount of change of a k′ number, and the like. Therefore, a more accurate rotation speed can be acquired, and “chatter vibration” generated during machining can be suppressed more effectively than a conventional method. As a result, a quality of a workpiece surface can be improved, and a tool wear and the like can be suppressed.

In a machine tool having a rotary shaft for use in rotating a tool or a workpiece, a plurality of stable rotation speeds at which the chatter vibrations are expected to be suppressed, and at least one switching rotation speed across which a dynamic characteristic of a rotary shaft system changes are stored. The plurality of stable rotation speeds may be determined from chatter vibrations detected using a vibration detection unit. Optimum rotation speed that is a rotation speed to which a rotation speed of the rotary shaft is changeable without crossing the switching rotation speed is selected from the plurality of stable rotation speeds, and the rotation speed of the rotary shaft is changed to the optimum rotation speed. Thus, chatter vibrations generated during rotation of the rotary shaft can be suppressed effectively.

A tool path generation device that calculates a tool path to be used by a machine tool device, and that provides a high machining efficiency with suppressed occurrence of chatter vibration by calculating machining conditions in consideration of a chatter vibration increase and decrease affecting value that affects increase and decrease in chatter vibration.

The present invention relates to a method and a device for suppressing vibration generated during machining in a machine tool for performing machining while rotating a tool or a work. A stable rotation speed is acquired by finely changing a rotation speed of a rotary shaft 3 based on an expected stable rotation speed, and calculating an amount of change of a k' number, and the like. Therefore, a more accurate rotation speed can be acquired, and 'chatter vibration' generated during machining can be suppressed more effectively than a conventional method. As a result, a quality of a workpiece surface can be improved, and a tool wear and the like can be suppressed.

A vibration suppressing method and a vibration suppressing device are disclosed. After detection of chatter vibration using at least one vibration detecting device, a stable rotation speed for suppressing the chatter vibration is calculated using a stable rotation speed calculating device. A determination device then compares a detection value detected by the vibration detecting device, a predetermined setting value, and / or a current value that is calculated based on at least one of the detection value and the setting value, to a predetermined determination reference value that is previously set. Thereafter, the determination device determines whether or not the stable rotation speed is adopted in accordance with the comparison result, and changes rotation speed of the rotary shaft to the stable rotation speed if the stable rotation speed is adopted.

When generation of a chatter vibration is detected, a parameter calculation device calculates a first frequency range and a second frequency range. A determination validity is calculated in consideration of a rotation speed detection resolution and a frequency resolution, and based on a ratio of a frequency range of rotational-period forced chatter vibration to a frequency range of regenerative chatter vibration. It is determined based on the determination validity whether the generated chatter vibration is regenerative chatter vibration, rotational-period forced chatter vibration, or flute-passage-period forced chatter vibration.

Methods of and apparatuses for mitigating chatter vibrations in machine tools or components thereof. Chatter therein is suppressed by periodically or continuously varying the stiffness of the cutting tool (or some component of the cutting tool), and hence the resonant frequency of the cutting tool (or some component thereof). The varying of resonant frequency of the cutting tool can be accomplished by modulating the stiffness of the cutting tool, the cutting tool holder, or any other component of the support for the cutting tool. By periodically altering the impedance of the cutting tool assembly, chatter is mitigated. In one embodiment, a cyclic electric (or magnetic) field is applied to the spindle quill which contains an electro-rheological (or magneto-rheological) fluid. The variable yield stress in the fluid affects the coupling of the spindle to the machine tool structure, changing the natural frequency of oscillation. Altering the modal characteristics in this fashion disrupts the modulation of current tool vibrations with previous tool vibrations recorded on the workpiece surface.

In a vibration suppressing device provided in a machine tool having a rotary shaft for use in rotating a tool or a workpiece, for suppressing chatter vibrations generated during rotation of the rotary shaft, an arithmetical unit performs an analysis on a vibration of the rotary shaft detected by a detector (vibrations sensors) whenever the vibration is detected and a computation based on a result of the analysis. An operator, while checking results of the analysis and / or the computation displayed in real time in a display unit, manipulates a manipulation element to enter a command to change a rotation speed of the rotary shaft into a rotation speed control unit (NC unit) which controls the rotation speed according to the command entered by the operator through the manipulation element.

A calculating member carries out Fourier analysis of a vibrational acceleration to calculate a maximum acceleration and frequency thereof. The calculating member then compares the maximum acceleration with a threshold value, and when the acceleration exceeds the threshold value, the calculating member calculates a k-value and phase information, and stores each calculated value. When retrying is selected, the calculating member determines a type of a current chatter vibration from the phase information, determines the existence of a chatter vibration which is different from the determined chatter vibration, and calculates each new phase information according to the determined chatter vibration and an existence of a different chatter vibration which had been generated before generation of the current vibration. The calculating member then calculates a k1-value from new phase information, calculates the optimum rotation speed by using the k1-value, and changes the rotation speed to the optimum rotation speed.

The present invention aims to provide a vibration suppressing method and a vibration suppressing device in which an adequate stable rotation speed can be selected from the obtained stable rotation speeds without changing the dynamic characteristics so that chatter vibrations can be suppressed without fail. With the vibration suppressing method and vibration suppressing device as described above, a maximum rotation speed of the main spindle (3) and a switching rotation speed across which a dynamic characteristic of the main spindle (3) system changes are stored, then an optimum rotation speed that is a rotation speed which is not higher than the maximum rotation speed of the main spindle (3) and to which the rotation of speed of the main spindle (3) is changeable without crossing the switching rotation speed is selected from the stable rotation speeds, and the rotation speed of the main spindle (3) is changed to the optimum rotation speed selected. Accordingly, the possibilities of changing the rotation speed of the main spindle (3) to a rotation speed which cannot be attained or a rotation speed such that change of the rotation speed to that speed changes the dynamic characteristic of the main spindle (3) and thus makes it impossible to suppress ''chatter vibrations'' can be eliminated, so that the ''chatter vibrations'' can be suppressed more effectively than any existing methods.

A vibration damping tool having the following structure is provided. In the vibration damping tool, a hollow portion is formed in the interior of the distal end portion of a tool body and one end of a weight member is connected to the inner wall surface of the distal end side of this hollow portion. A gap created between the outer peripheral surface of the weight member and the inner wall surface of the hollow portion is filled with a visco-elastic body. The one end of the weight member is formed as a narrow diameter shaft portion. The tool body can be divided into two and freely removed from and reattached at a dividing surface located on the base end side of the hollow portion. A hole portion is formed inside the other end of the weight member by hollowing out the interior thereof. Chatter vibration is thus absorbed using a simple structure without there being any effects from heat generated during cutting processing.

In suppressing chatter vibration of a rotary shaft in a machine tool by fluctuating rotation speed of the rotary shaft, easy setting of a fluctuation parameter is realized. In a monitor apparatus of the machine tool, a graph showing a fluctuation amplitude of the rotation speed is displayed. On this graph, a current fluctuation position (first point) is indicated by a black circle marker, and also, a power limit line L of a motor fluctuation period is depicted based on a predetermined equation. In an area not exceeding the power limit line L, a new fluctuation position (second point) having a larger fluctuation amplitude and a shorter fluctuation period than the current fluctuation position is calculated and indicated with an arrow A guiding this new point from the current fluctuation position.

The invention discloses an active control method of milling chatter vibration based on an electric spindle of a magnetic suspension bearing. The method comprises the following steps: collecting a current displacement signal generated when the electric spindle has the milling chatter vibration; obtaining a state vector Q(t) formed by the displacement of the electric spindle and the speed; obtaining harmonic displacement which is shown as the formula in the description according to the electric spindle displacement [Fx Fy]T and a trigonometric function column vector phi(t); obtaining a first self-adaptive weight coefficient which is shown as the formula in the description and a second self-adaptive weight coefficient which is shown as the formula in the description; obtaining a first self-adaptive rate K1 and a second self-adaptive rate K2 according to the harmonic displacement h(t), the first self-adaptive weight coefficient lambda1 and a second self-adaptive weight coefficient lambda2; obtaining self-adaptive control current which is shown as the formula in the description according to the first self-adaptive rate K1, the second self-adaptive rate K2 and the harmonic displacement h(t); and applying the self-adaptive control current Qc(t) on a radial magnetic suspension bearing and generating corresponding magnetic field force so as to restrain the chatter vibration of the spindle. Through the active control method, the chatter vibration in the milling process is eliminated, thereby ensuring the processing quality and improving the processing efficiency.

The vibration suppressing device includes vibration sensors, a FFT calculating unit, a store device, a calculating unit, and a NC device. The vibration sensors detect a time-domain vibrational acceleration of a rotary shaft during rotating. The FFT calculating unit calculates a frequency of chatter vibration and a frequency-domain vibrational acceleration in the frequency of chatter vibration on the basis of the detected time-domain vibrational acceleration. The store device stores the frequency-domain vibrational acceleration, the frequency of chatter vibration and the like as machining information. When the calculated maximum frequency-domain acceleration exceeds a predetermined threshold value, the calculating unit stores the maximum acceleration, the frequency of chatter vibration, and the like as current machining information in the store device, and calculates an optimal rotation speed of the rotary shaft, by which the chatter vibration can be suppressed, based on the current machining information and previous machining information stored in the store device. The NC device rotates the rotary shaft at the optimal rotation speed.

A vibration information display device includes a monitor, a vibration information acquisition unit, an operating information acquisition unit, a storage unit, and a display control unit. The monitor displays information on the chatter vibrations. The vibration information acquisition unit acquires vibration information when the chatter vibrations are detected. The operating information acquisition unit acquires operating information of the machine tool when the chatter vibrations are detected. The storage unit stores the acquired vibration information and operating information. The display control unit displays the vibration information and the operating information stored in the storage unit on the monitor. Alternatively, the display control unit displays the vibration information stored in the storage unit on the monitor together with trajectory information of a blade edge of the tool included in the operating information.

A chattering vibration inhibiting mechanism capable of inhibiting chattering vibration of a machine tool without increasing weight nor requiring a time-consuming adjustment work is provided. A box-shaped package body 21 attached to a spindle head 6, a supporting member 22 disposed to bridge between front and rear walls 21a, 21b in the box-shaped package body 21, and a damper 23 composed of an elastic member 27 and a weight 26 supported by the supporting member 22 are provided.

In a machine tool which includes a rotary shaft configured to allow a tool or a workpiece to be attached thereto, a driving unit for causing the rotary shaft to rotate is regulated to change a rotation speed of the rotary shaft in such a manner that the rotation speed oscillates with a given amplitude and a given period with respect to a given mean rotation speed, so that chatter vibrations can be suppressed. A parameter display control unit configured to cause a display device to display parameter information related to predetermined parameters for changing at least one of the mean rotation speed, the amplitude and the period is provided so that the parameters can be changed based upon the parameter information displayed in the display device.

Determination of chatter vibration is done for a plurality of peak values that appears when frequency-domain vibrational acceleration is obtained through fast Fourier analysis on time-domain vibrational acceleration. In machining at a low rotation speed and machining using a tool with small flute number in particular, a type of chatter vibration that has occurred can be accurately determined, and “natural vibration type forced chatter vibration” occurring due to friction between a tool and a workpiece and an impact force caused by machining can also be determined.

A chattering vibration inhibiting mechanism capable of inhibiting chattering vibration of a machine tool without increasing weight nor requiring a time-consuming adjustment work is provided. A box-shaped package body 21 attached to a spindle head 6, a supporting member 22 disposed to bridge between front and rear walls 21a, 21b in the box-shaped package body 21, and a damper 23 composed of an elastic member 27 and a weight 26 supported by the supporting member 22 are provided.

The invention discloses a bent actuator-based thin-walled workpiece machining vibration suppressing device. The vibration suppressing device comprises a vibration detection unit, a signal acquisitionunit, a power amplification unit, a control computer, a programmable signal generator and a bent actuator; the bent actuator is used for applying a reverse vibration suppressing force to a thin-walledworkpiece to perform active control over regenerative chatter vibration in a milling process. The invention further discloses an active vibration control method aiming at the vibration suppressing device. The vibration suppressing device disclosed by the invention is capable of realizing real-time detection and feedback control on the vibration of the thin-walled workpiece in the milling processby relatively high precision, is fast in response speed, has a big and accurate output force, also has the advantages of being small in size, low in power consumption, high unit volume strain energy,and the like, and can adapt to the narrow machining space of a thin-walled workpiece complicated in shape and the complexity and the time variation of the dynamic characteristic of a tool-workpiece system in the machining process of the thin-walled workpiece complicated in shape.

In an interference fit type cutting tool according to the present invention, a projection and a fitting projection are formed at the rear end of an edge section and at the leading end of a shank section, respectively. A connecting member is provided with first and second holes that have a predetermined interference with respect to the outer diameters of the projection and the fitting projection. The edge section and the shank section are fixed by interference fitting between the first hole and the projection, and between the second hole and the fitting projection. Chatter vibration is reduced by making the edge section and the shank section of a high-rigidity material having a lower coefficient of thermal expansion than that of the connecting member.

A method is provided to cut a thin-walled member without causing chattering vibration, without using a chattering vibration preventing retainer, that performs the following: (A) preparing a material having much stock for obtaining a thin-walled material, (B) while rotating the material about a center axis, cutting the inner round surface of the material within a predetermined range by feeding a cutting tool relative to material by the desired distance from one end side to the other end side of the material along the center axis, (C) while rotating the material about the center axis, cutting the outer round surface of the material within a predetermined range by feeding the cutting tool relative to the material by the desired distance from the one end side to the other end side of the material along the center axis, and (D) alternately repeating (B) and (C) to finish cutting the material.