Method for obtaining the vibration modes of a machining system in the machining process of a workpie

专利摘要:
Method for obtaining the vibration modes of a machining system (100) in the machining process of a workpiece (10), wherein the machining system (100) is a set formed by a machine tool (20), comprising at least one rotating spindle (21) for rotating a cutting tool (22) or the workpiece (10), the workpiece (10), and the machining process of the workpiece (10), the method comprising an excitation step of the machine tool (20) which is carried out with the spindle (21) rotating. The excitation is carried out by machining the workpiece (10) to obtain the vibration modes of the machining system (100), by varying at least one cutting parameter Cp of the machining process, which generates a variation in the cutting forces Fc on the workpiece (10), in a controlled manner. (Machine-translation by Google Translate, not legally binding)
公开号:ES2711000A1
申请号:ES201731254
申请日:2017-10-24
公开日:2019-04-29
发明作者:Aiestaran Xabier Badiola；Arriola Pedro José Arrazola；Iregui Aitzol Iturrospe
申请人:Mondragon Goi Eskola Politeknikoa Jose Maria Arizmendiarrieta Scoop；
IPC主号:

专利说明:

[0001]
[0002] Method for obtaining the vibration modes of a machining system in the machining process of a workpiece
[0003]
[0004] TECHNICAL SECTOR
[0005]
[0006] The present invention relates to methods for obtaining the vibration modes of a machining system in the machining process of a workpiece.
[0007]
[0008] PRIOR STATE OF THE TECHNIQUE
[0009]
[0010] Known methods are implemented in machining systems, which are assemblies formed by a machine tool, the workpiece to be machined and the machining process of the workpiece, whose objective is to reduce the vibrations produced in the system. One type of method is the so-called "on line" method, because the corrective measures are taken at the moment of detecting a deviation.In these methods, in successive moments of the machining process the speed of rotation of a rotating spindle of a cutting tool or a workpiece to be machined from the machine tool, and also the acceleration of the vibration existing in the machining system is detected.It is determined if the spindle speed has changed with respect to the speed in a previous stage, and it is determined if a maximum acceleration value of the vibration of the system exceeds a predefined threshold value In the event that a deviation of the acceleration of the vibration occurs, a modification of the rotational speed of the rotary spindle is made.
[0011]
[0012] Another type of method used in machine tools is known, which allows to obtain the vibration modes of the machine tool prior to machining the work piece, and in this way obtain a stable machining process. In these methods a stability lobe diagram is defined, where the cutting depths are defined for each speed of the rotating spindle, the process being stable machining. These methods are characterized in that an excitation is applied to the machine tool, in order to obtain the frequency response of said machine tool, and thereby define the modes of vibration thereof. The vibration modes of the system being known, by means of known methods, the lobe stability diagram of the machine tool can be obtained.
[0013]
[0014] One way to apply the excitation is through an impact made with a hammer. In this method, the machine tool is static, without machining the work piece, and the hammer hits the cutting tool.
[0015]
[0016] Another way to apply the excitation in these methods of obtaining the modes of vibration of the machine tool, is with an actuator that applies the excitation in the cutting tool of the machine tool, said machine tool being static or with the rotating spindle rotating , but without machining the work piece. US2004 / 0236529A1 describes a device for obtaining the dynamic response of a cutting tool located in a machine tool, said device executing steps to obtain the vibration modes of the machine tool, the steps that the device executes an excitation step of the machine. the machine tool that is made with the spindle rotating, without machining the work piece. The actuator used is an electromagnet that induces a force in the cutting tool without contact, the force being controlled by the electric current supplied to the electromagnet.
[0017]
[0018] EXHIBITION OF THE INVENTION
[0019]
[0020] The object of the invention is to provide a method for obtaining the vibration modes of a machining system in the machining process of a workpiece, as defined in the claims.
[0021]
[0022] In the method of the invention, the machining system is a set formed by a machine tool comprising at least one rotating spindle for rotating a cutting tool or the workpiece, the workpiece and the machining process of the workpiece, the method comprising a step of excitation of the machine tool that is performed with the spindle rotating. The excitation is carried out by the machining process of the work piece to obtain the vibration modes of the machining system, varying at least one cutting parameter of the machining process, which generates a variation in the cutting forces on the work piece. work, in a controlled manner.
[0023]
[0024] An advantage of this method of the invention is that it allows to obtain the vibration modes of the machining system while the machining process is carried out, reducing the time of obtaining said modes with respect to known methods that apply the impact with the static machine tool. Another advantage is that the vibration modes of the machining system and not only of the machine tool are obtained, so that, if the stability lobes diagram is subsequently obtained, the parameters of the cutting depth and the related rotary spindle speeds will be more precise. Another added advantage is that the implementation of the method is simple and of low cost, because it is not necessary to add any element to apply the excitation to the machine tool. It is the machining process itself that produces the excitation.
[0025]
[0026] These and other advantages and features of the invention will become apparent in view of the figures and the detailed description of the invention.
[0027]
[0028] DESCRIPTION OF THE DRAWINGS
[0029]
[0030] Figure 1 shows a schematic representation of the relative movement between a cutting tool and an orthogonal cutting workpiece, in a turning machining process.
[0031]
[0032] Figure 2 shows a partial diagram of a realization of a machining system comprising a machine tool that is a lathe, a workpiece to be machined, and a machining process for machining the workpiece, which is a turning process .
[0033] Figure 3 shows a partial diagram of a second realization of a machining system, comprising a machine tool that is a milling machine, a work piece to be machined, and a machining process for machining the work piece, which is a process of milling
[0034]
[0035] Figure 4 partially shows a cylindrical workpiece where the original geometry Go of said work piece is indicated, and the geometry intermediate Gi machined with a wavy shape.
[0036]
[0037] Figure 5 shows a schematic of a control unit of the machining system of Figure 2.
[0038]
[0039] Figure 6 shows a stability lobe diagram of a machining system.
[0040]
[0041] DETAILED EXHIBITION OF THE INVENTION
[0042]
[0043] During the machining of a workpiece, it is sought to achieve a final shape of the piece with a previously defined specific geometry, and that meets a series of requirements, such as the dimensional and geometrical tolerances, and / or the surface integrity of the piece. To obtain that definitive geometry with these requirements, the stability of the machining process is a very important factor.
[0044]
[0045] It is known the "chatter" as one of the causes that generate instability of the cutting processes in the machining, being a dynamic problem that results in the appearance of vibrations, either of the machine used in the machining process, or of the assembly tool-cutter-toolholder-rotary spindle, either the work piece, or the entire machining system. The chatter produces a poor surface finish of the workpiece, breakage of the cutting tool and wear of the components of the rotating spindle or the machine tool, or tears of the work pieces with thin walls.
[0046]
[0047] In particular, it is called regenerative chatter to a self-excited vibration typical of the machining processes in which the cutting edge of the cutting tool goes through a Previously machined surface. It can be found in machining processes such as turning, milling, drilling, boring, etc. causing the cutting tool to vibrate. As a result, said cutting tool does not leave a smooth surface, but is wavy. Therefore, the next tooth of the cutting tool that enters to cut, in the case of a milling process, or in the next pass of the cutting tool, in a turning process, is a variable surface, with the that the cutting force varies due to the ripple.
[0048]
[0049] The variations of forces produced excite modes of vibration of the machine, of the tool-holder-spindle or piece assembly, appearing a vibration at said modal frequencies, or frequencies of the dominant mode.
[0050]
[0051] Vibration mode or normal mode of an oscillatory system, is the frequency at which the deformable structure will oscillate free when disturbed. Normal modes are also called natural frequencies or resonant frequencies. For each structure there is a set of these frequencies that is unique. When the frequency of the wave-emitting source that produces the disturbance coincides with the natural frequency of the resonator (oscillating structure), a condition known as resonance is reached, in which the structure tends to oscillate with a greater amplitude at the frequencies natural
[0052]
[0053] If that vibration does not decay enough between two consecutive passes of the edge of the cutting tool, it is amplified indefinitely by the successive impacts until reaching a point of saturation. It is said that the process has become unstable. The regenerative chatter can be of three different types:
[0054] - machine tool chatter,
[0055] - tool chatter, or
[0056] - chatter of workpiece to be machined.
[0057]
[0058] The excitation of this vibration mode causes a relative movement between the machine tool and the work piece.
[0059]
[0060] Figure 1 shows a schematic representation of the relative movement between a cutting tool 22 and a workpiece 10 in orthogonal cut in a process of machining of turning, wherein the workpiece 10 is rotating, and chip 11 is pulled from said workpiece 10. The chip 11 is represented with a chip section defined by its width ac and its length aw. The cutting tool 22 as a dynamic model of a degree of freedom, can be represented by its modal parameters mt, kt, ct, which are the mass, the stiffness and the damping coefficient, respectively. Cs is the cutting speed of the workpiece 10. X (t) is the cutting edge position of the cutting tool 22, and T is the time it takes to revolutionize the workpiece 10. 0 d is the phase delay between revolutions of the workpiece 10, and if it appears, it determines the appearance of chatter in the turning process. If there is no phase delay, 0d equal to zero, the chip thickness remains constant and the cutting process remains stable. However, when a phase delay, 0d other than zero, occurs, the chip thickness 11 constantly varies resulting in an unstable cutting process.
[0061]
[0062] They are defined as cutting parameters Cp of a machining process with chip removal, such as a turning process or a milling process:
[0063] - Cutting speed Cs: which is the relative speed between the work piece and the cutting tool. More specifically, it is the relative speed between the cutting edge of the tool and the surface to be machined of the part.
[0064] - Advance Av: which is the length traveled by the tool on the surface to be machined in the piece in a given time.
[0065] - Depth of cut Cd: that is the distance that the tool penetrates in the piece in each of the passes of the machining process.
[0066]
[0067] When chatter occurs in the machining process, vibration marks are formed on the surface of the part, which negatively affect the precision and surface finish of the part. Due to the chatter there are variations in the cutting force Fc, which is the force that the cutting tool performs on the workpiece, and this entails causing damage to the tool and reducing its useful life. The chatter is often a limiting factor in the productivity of the machine tool.
[0068]
[0069] Modal analysis is a process by which a structure or system is described in terms of its dynamic properties or modal parameters. It allows to understand how structures behave under the action of dynamic forces that produce a disturbance. All structures have natural frequencies and modes of vibration, which depend basically on the mass and rigidity of the structure. To identify stable machining zones, it is necessary to identify these frequencies and to know how they affect the response of the structure when the cutting forces act on it. Modal analysis is a tool that allows to describe, understand and model the dynamic behavior of structures or systems.
[0070]
[0071] An altered structure of its rest position through an excitation tends to vibrate at natural or resonant frequencies. For each natural frequency, the structure acquires a certain form called modal form. The modal analysis allows to calculate the natural frequencies and the associated modal forms. The structure is studied when it is subjected to a known excitation, with the aim of obtaining a mathematical model of the dynamic behavior of the structure. The procedure to carry out the experimental modal analysis consists of:
[0072]
[0073] - excite the system or structure,
[0074] - Acquire and analyze data, and
[0075] - determine the modal parameters of the structure.
[0076]
[0077] In a dynamic test a dynamic load is applied to the structure. Said load has components in a certain range of frequencies and the structure responds to all frequencies, but will come into resonance when the components coincide with the natural frequencies of the structure.
[0078]
[0079] The excitation technique for the best-known modal analysis is impact, using a hammer-type exciter. In this technique, the machine tool is static, without machining the work piece, and the hammer is struck against the cutting tool. The duration of the impact is usually very short in comparison with the time that the response has to be measured.
[0080]
[0081] Another exciting technique is that described in document US2004 / 0236529A1, in which an actuator applies the excitation to the cutting tool of the machine tool, without contact, said machine tool being static or with the rotating spindle. rotating, but without machining the work piece.
[0082]
[0083] However, these excitation techniques of experimental modal analysis present some disadvantages. It is necessary to understand that the vibrations that produce the chatter originate when the piece of work is being machined in a machining system. A machining system is defined as a set formed by a machine tool, the workpiece to be machined, and the machining process used to machine the workpiece, the machine tool comprising at least one rotating spindle for rotating a cutting tool or the work piece, depending on the machining process carried out, whether it is turning, milling, etc.
[0084]
[0085] In the aforementioned excitation techniques of the state of the art, the excitation of the system is performed at a standstill, since, although the spindle of the cutting tool or of the workpiece is rotating, the machining system is not mechanizing the part of work. Therefore, the machining system is decoupled, since the cutting tool is not in contact with the part. The machining system changes dynamically during machining because the vibration modes are different, which can lead to erroneous conclusions.
[0086]
[0087] The method of the invention is described below, which allows to excite the machine tool during the machining of the work piece, to obtain the vibration modes of the machining system. Figure 2 shows a partial diagram of a realization of a machining system 100, comprising a machine tool 20, which in this embodiment is a lathe, a workpiece 10 to be machined, which in this
[0088] embodiment is a metal cylinder, and a machining process used to machine the workpiece 10, which in this embodiment is a turning process. The machine tool 20 comprises in this embodiment a rotating spindle 21 for rotating the workpiece 10, and a tailstock 26 where the workpiece 10 rests in its turn.
[0089]
[0090] The machine tool 20 also comprises a turret 25 for fixing a cutting tool 22 used to machine the workpiece 10, and a sensor 23 which measures the vibrations or displacements of the machining system 100, in response to said machining system 100 to the applied excitation, the sensor 23 being in this embodiment an accelerometer, but in other embodiments, an optical or capacitive displacement sensor can be used in the machining system 100. The sensor 23 is fixed in this embodiment in the turret 25 of the cutting tool 22.
[0091]
[0092] The machine tool 20 also comprises a control system 24, which allows the introduction of the machining parameters necessary for machining the workpiece 10, the control of the evolution of the machining process until its completion and obtaining the desired final geometry Gd of the workpiece 10, starting from an original geometry Go of said workpiece 10, but also allows the acquisition and analysis of the vibration data of the machining system 100, and the determination of the modal parameters of said machining system 100
[0093]
[0094] The method comprises an excitation step of the machine tool 20 carried out with the spindle 21 rotating, and machining the workpiece 10 with the machining process of turning. With this excitation, the vibration modes of the machining system 100 are obtained, as will be described below, by varying in a controlled manner during the machining process, one or more of the cutting parameters Cp of said machining process, such as depth of cutting Cd, the advance Av, or the cutting speed Vc. This variation of the cutting parameters Cp generates a variation in the cutting forces Fc on the workpiece 10. In the turning process of Figure 1, the workpiece 10 is rotating with a speed Vc that in a process of turning is the cutting speed, the cutting tool 22 advances with an offset Av, and the cutting tool 22 penetrates the workpiece at a distance that is the cutting depth Cd.
[0095]
[0096] Figure 3 shows a partial diagram of a second embodiment of a machining system 100, comprising a machine tool 20, which in this embodiment is a milling machine, a workpiece 10 to be machined, which in this embodiment is a cubic piece of rectangular metal base, and a machining process used to machine the workpiece 10, which in this embodiment is a milling process. The machine tool 20 comprises in this embodiment a rotating spindle 21 for rotating the cutting tool 10 in both directions, and which can also be moved axially. The machine tool 20 also comprises a turret 25 for fixing the cutting tool 22, and a sensor 23 that measures the vibrations or displacements of the machining system 100, the sensor 23 being in this embodiment also an accelerometer. The sensor 23 is fixed in the turret 25 of the cutting tool 22.
[0097]
[0098] The machine tool 20 also comprises a control system 24, with the same characteristics of data introduction, acquisition and analysis of data related to the vibrations of the system 100, and determination of the modal parameters of said system 100, as described for the first embodiment of the machining system 100.
[0099]
[0100] As already indicated, the excitation of the machining system 100 is performed by and during the machining of the workpiece 10, so that a first determination of the vibration modes of the machining system 100 is not necessary, before proceeding to the machining of the workpiece 10. The workpiece 10 to be machined has an original geometry Go, which in the case of the cylindrical workpiece shown in Figure 2 comprises a smooth lateral surface. Prior to the machining of the part 10, the final or final geometry Gf to be obtained is defined, and also a geometry intermediate Gi specific to be machined before machining the final geometry Gf, but performing it in the same machining process.
[0101]
[0102] The prior definition of the intermediate geometry Gi depends on the machine tool 20, in this embodiment a lathe, but also depending on the type of lathe used, and the range of Fex frequencies to be excited, which has to do with the resonance frequencies or natural machining system 100. The excitation of the machining system 100 in which a dynamic load is applied, can be carried out when generating, machining, the geometry intermediate Gi specific in the workpiece 10, when removing, machining , the intermediate geometry Gi in the workpiece 10, or when generating and then eliminating, by machining, the intermediate geometry Gi. It must be taken into account that the generation of the final geometry Gf of the workpiece 10 is carried out after generating the intermediate geometry Gi, and always supposes the elimination of this intermediate geometry Gi.
[0103]
[0104] The Fex excitation frequencies to be applied to the machining system 100 by machining the intermediate geometry Gi specifics, is related to said geometry intermediate Gi. These Fex excitation frequencies are calculated with the formula:
[0105]
[0106]
[0107]
[0108] where,
[0109] - Av1 is the advance when it is generated by machining the intermediate geometry Gi, - Cs1 is the cutting speed when it is generated by machining the intermediate geometry Gi,
[0110] - f is the oscillation frequency of the cutting tool 22 on the cutting depth axis Cd,
[0111] - Av2 is the advance when it is eliminated by machining the intermediate geometry Gi, and - Cs2 is the cutting speed when it is eliminated by machining the intermediate geometry Gi.
[0112]
[0113] Figure 4 partially shows a workpiece 10 cylindrical of radius R and length L, where the original geometry Go of said work piece is indicated, and the geometry intermediate Gi machined with a wavy shape. In this generated geometry Gi, the wavy shape is defined by an amplitude a and a space s between waves. With this wavy shape of the intermediate geometry Gi, determined Fex frequencies are defined to be applied as a dynamic load to the machining system 100. The diameter of the workpiece 10 varies along its length L, and depending on the amplitude a of variation of the diameter of the part 10, the space s between each undulation, and the advance Av employed by the cutting tool 22, the excitation of the machining system 100 is controlled.
[0114]
[0115] Another embodiment of intermediate geometry Gi to excite the machining system in a turning process, is a cylindrical part with the offset axis. In this piece a variation of the cutting depth Cd is generated, and the system is excited as a function of the speed of rotation or cutting Cs of said piece. In this embodiment of the intermediate geometry Gi, the excitation frequency Fex is limited by the rotational speed of the spindle.
[0116]
[0117] To perform the excitation with several Fex excitation frequencies, a sweep of frequencies. To obtain said range of excitation frequencies Fex, one way is to vary the oscillation frequency f of the cutting tool 22 progressively along the workpiece 10, when generating, machining, the intermediate geometry Gi in said piece 10. In this way, the Fex excitation frequency increases as the workpiece 10 is machined, covering a range of specific Fex excitation frequencies.
[0118]
[0119] Another way to obtain a range of excitation frequencies Fex is to vary the cutting speed Cs2, which is the speed of rotation of the spindle 21 in the turning process, while eliminating, by machining, the intermediate geometry Gi. The progressive increase in the speed of rotation of the spindle 21 during the machining of the workpiece 10 allows covering a wide range of excitation frequencies Fex. These forms of obtaining a range of excitation frequencies Fex can be transferred to the milling process.
[0120]
[0121] As already described above, the excitation of the machining system 100 is carried out by means of and during the machining of the workpiece 10, so that a first determination of the vibration modes of the machining system 100 is not necessary beforehand. of proceeding to the machining of the workpiece 10. Another way to perform the excitation of the machining system 100 is by means of an actuator during the machining process.
[0122] A range of excitation frequencies Fex applied to the machining system 100 is obtained by varying the cutting forces Fc by varying at least one cutting parameter Cp of the machining process in a controlled manner. For this purpose, the actuators, which are for example the drive motors, of the axes of the machine tool 20 can be used. An external actuator, such as a piezoelectric actuator, can also be used to vary the cutting conditions of the actuator. controlled form.
[0123]
[0124] After the excitation step in the modal analysis, the method to obtain the vibration modes of a machining system 100 in the machining process of a workpiece 10, comprises a stage of acquisition and analysis of data, and determination of the modal parameters of the machining system 100. In this step the vibrations of the machining system 100 are captured with the sensor 23. The control unit 24 of the machine tool 20 of the machining system 100, as shown in the Figure 5, receives the vibrations captured by the sensor 23 in a vibration acquisition unit 24a, and analyzes said vibrations with the help of an operating program of a program unit 24e, obtaining the frequency response of the machining system 100, and with This defines the vibration modes of said machining system 100, defining the Frequency Response Function FRF as a frequency response to the excitation applied to the machining system 100, in a stability analysis unit 24c. This obtained information is stored in a memory 24b of the control unit 24.
[0125]
[0126] The response of the machining structure or system 100 is a linear superposition of all the vibration modes excited in the machining system 100. An important property of the vibration modes is that any response of the structure can be expressed as a combination of a series of vibration modes. The frequency spectrum of the response of a mechanical system has as many peaks as there are degrees of freedom in the system. For example, we can consider that the turning process is a system that presents a peak in the frequency spectrum of the response. Each peak of the response of a structure can be represented by a physical model of a degree of freedom. This physical model consists of a point mass, supported by a massless spring and connected with a viscous damper. For a structure whose behavior is linear and invariant in time, the equation that defines its movement is:
[0127]
[0128] [M] {x (t)} + [C] {x (t)} [K] {x (t)} = {f (t)}
[0129]
[0130] where [M], [C] and [K] are the modal parameters of the system 100, and are formed by matrices N x N of mass, damping and rigidity of the system, and (x (t)}, {x ' (t}}, {x (t)} and {/ (t)} are vectors N x 1 representing the acceleration, velocity, displacement and excitation force in each of their N degrees of freedom. of control 24 calculates said modal parameters of the machining system 100, taking into account that the natural frequencies fn of a mechanical system, and therefore its modes of vibration, are related to the rigidity K and the mass m with the formula:
[0131]
[0132] fn = (k / m) 1/2
[0133] After the stage of acquisition and analysis of data, and determination of the modal parameters of the machining system 100, and once the vibration modes of said system 100 have been obtained, defining with these modes of vibration the Frequency Response Function FRF in response In frequency to the excitation applied to the machining system 100, the method for obtaining the vibration modes of a machining system 100 comprises a definition stage of the stability lobes diagram 30 of the machining system 100. This is, known behavior dynamic of the machine tool 20 and known the cutting constant of the machine tool 20, which is related to the material of the cutting tool 22, the stability lobes diagram 30 is obtained, as shown in Figure 6.
[0134]
[0135] Stability lobe diagrams are used to identify stable machining zones. The stability lobe diagram varies depending on the machine tool used, the work piece to be machined, and the cutting tool used in the machining process. This diagram 30 is obtained in the control unit 24 in the stability analysis unit 24c, with the data of the analysis and calculation of the modal parameters and vibration modes performed previously, and with the help of an operating program of the unit of analysis. 24e programs This obtained information is stored in a memory 24b of the control unit 24. The stability lobes diagram 30 of the machining system 100 obtained separates a stable zone and an unstable zone from the machining process of said system 100, defining the depths of cutting limit Cd for each speed Ss of the rotary spindle 21 of the machine tool 20, in the stable zone of the machining process.

权利要求:
Claims (15)
[1]
Method for obtaining the vibration modes of a machining system (100) in the machining process of a workpiece (10), wherein the machining system (100) is a set formed by a machine tool (20) ), comprising at least one rotating spindle (21) for rotating a cutting tool (22) or the workpiece (10), the workpiece (10), and the machining process of the workpiece (10). ), the method comprising a step of excitation of the machine tool (20) that is performed with the spindle (21) rotating, characterized in that the excitation is carried out by machining the workpiece (10) to obtain the vibration modes of the machining system (100), by varying at least one cutting parameter Cp of the machining process, which generates a variation in the cutting forces Fc on the workpiece (10), in a controlled manner.
[2]
Method according to claim 1, wherein the cutting parameter is the cutting depth Cd, the advance Av, or the cutting speed Cs.
[3]
Method according to claim 1 or 2, wherein the excitation of the machining system (100) is carried out by machining in the workpiece (10) of an intermediate geometry Gi specific previously defined, obtaining a range of excitation frequencies Fex applied to the specific machining system (100), related to the geometry intermediate Gi defined.
[4]
Method according to claim 3, wherein the definition of the intermediate geometry Gi depends on the machine tool (20) and the frequency range Fex that it is desired to excite.
[5]
Method according to claim 3 or 4, wherein the excitation of the machining system (100) is carried out when generating the intermediate geometry Gi in the workpiece (10) and / or by removing the intermediate geometry Gi. in the work piece (10).
[6]
The method according to claim 5, wherein the Fex excitation frequencies are calculated with the formula:
Av 2 * Cs 2
Fex - A - v - 1 --- * - C - sl * f
where,
- Av1 is the advance when it is generated by machining the intermediate geometry Gi, - Cs1 is the cutting speed when it is generated by machining the intermediate geometry Gi,
- f is the oscillation frequency of the cutting tool (22) on the cutting depth axis Cd,
- Av2 is the advance when it is eliminated by machining the intermediate geometry Gi, and - Cs2 is the cutting speed when it is eliminated by machining the intermediate geometry Gi.
[7]
Method according to claim 6, wherein a range of excitation frequencies Fex is obtained by varying the oscillation frequency f of the cutting tool (22) when generating the intermediate geometry Gi in the workpiece (10).
[8]
8. Method according to claim 6, wherein a range of excitation frequencies Fex is obtained by varying the cutting speed Cs2 while it is eliminated by machining the intermediate geometry Gi.
[9]
Method according to claim 1 or 2, wherein the excitation of the machining system (100) is performed by means of an actuator, obtaining a range of excitation frequencies Fex applied to the machining system (100) related to the variation of at least a cutting parameter Cp of the machining process in a controlled manner.
[10]
The method according to claim 9, wherein the actuator is the actuator of each drive shaft of the machine tool (20).
[11]
11. Method according to claim 9, wherein the actuator is external.
[12]
Method according to any of claims 1 to 11, wherein the measurement of the vibrations or displacements of the machining system (100) as a response of said machining system (100) to the applied excitation, is performed with at least one sensor (2. 3).
[13]
The method according to claim 12, wherein the sensor (23) is an optical or capacitive displacement sensor, or is an accelerometer.
[14]
14. Method according to claim 12 or 13, comprising:
- a stage of acquisition and analysis of data, and determination of the modal parameters of the machining system (100), after the excitation stage, where the vibrations of the machining system (100) with the sensor (23) are captured, the machine tool (20) comprising a control unit (24) that analyzes the vibrations and calculates the modal parameters M, C and K of the machining system (100), defining the Frequency Response Function FRF as a frequency response to the excitation applied to the machining system (100), and - a definition stage of the stability lobes diagram of the machining system (100), after the acquisition and data analysis stage, and determination of the modal parameters of the machining system (100), wherein the control unit (24), from the modal parameters M, C and K, defines the stability lobe diagram (30) separating a stable zone and an unstable zone from the machining process, defining yourself profu cutting units Cd for different speeds Ss of the rotary spindle (21) in the stable zone of the machining process.
[15]
15. Method according to any of claims 1 to 14, wherein the process of machining the workpiece (10) is a process of machining chip removal.

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Yılmaz2015|Dynamic modelling in micromachining

同族专利:

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公开号 | 公开日

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ES2711000B2|2019-09-10|

引用文献:

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公开号 | 申请日 | 公开日 | 申请人 | 专利标题

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US20090187270A1|2008-01-22|2009-07-23|Valenite, Llc|Method to align characteristic frequency of material removal tool and rotation speed of spindle of machine tool and material removal tool so aligned|

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JP2016005858A|2014-06-20|2016-01-14|株式会社ジェイテクト|Dynamic characteristic calculation device and dynamic characteristic calculation method for machine tool|

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ES201731254A|ES2711000B2|2017-10-24|2017-10-24|Method to obtain the vibration modes of a machining system in the machining process of a workpiece|ES201731254A| ES2711000B2|2017-10-24|2017-10-24|Method to obtain the vibration modes of a machining system in the machining process of a workpiece|