Method for regulating and controlling resonant frequency of workpiece under machining condition

Abstract

The invention discloses a method for regulating and controlling the resonant frequency of a workpiece under a machining condition, which comprises the following steps of: detachably mounting a clamp on a working table of a machine tool through a cylindrical supporting tube, and enabling the resonant frequency of a clamping device consisting of the clamp and the cylindrical supporting tube to be within a preset range by replacing the cylindrical supporting tubes with different specifications; the resonant frequency of the clamping device is roughly adjusted, then the input current of an electromagnet coil in the electromagnetic damping device installed between the clamp and the working table is regulated and controlled, the magnetic flux of the electromagnetic damping device is changed, the resonant frequency of the clamping device is adjusted to a preset value, and fine adjustment of the resonant frequency of the clamping device is achieved. According to the invention, fine adjustment of the resonant frequency of the clamping device is realized in a mode of combining coarse adjustment and fine adjustment of the resonant frequency of the clamping device, so that fine adjustment of the resonant frequency of the workpiece is realized, and corresponding resonant frequency conditions can be provided for exploring machining conditions of the workpiece under different resonant frequencies; and the new progress of machining research is promoted.

Description

Technical Field

[0001] The present invention belongs to the field of precision automated machining, and in particular relates to a method for regulating the resonance frequency of a workpiece during machining. Background Art

[0002] Resonance is a hot topic in current machining research. Studying the impact of resonant frequency on machining and optimizing the system's dynamic response has become a key issue. Existing methods for regulating the resonant frequency of machine tools rely primarily on a single damping control technology. While this technology can control the resonant frequency to a certain extent, it suffers from limited adjustment range and slow response speed. Furthermore, existing research on the resonant frequency of machine tools primarily focuses on the resonant frequency of the machine tool spindle, lacking research on the resonant frequency of the workpiece on the machine tool fixture. However, regulating the resonant frequency of the workpiece is crucial in studying the impact of resonant frequency on machining and optimizing the system's dynamic response. Therefore, designing a method for regulating the resonant frequency of the workpiece during machining is essential. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a method for regulating the resonant frequency of a workpiece during machining.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] The present invention provides a method for regulating the resonant frequency of a workpiece during machining, which is specifically as follows:

[0006] Step 1: The fixture is detachably mounted on the work surface of the machine tool through two cylindrical support tubes arranged vertically and spaced apart. The temperature correction coefficient τ is introduced to obtain the resonant frequency of the clamping device consisting of the fixture and the two cylindrical support tubes without eddy current damping after temperature correction:

[0007]

[0008] Where E is the Young's modulus of the cylindrical support tube material, L is the length of the cylindrical support tube, D is the outer diameter of the cylindrical support tube, d is the inner diameter of the cylindrical support tube, ρ is the density of the cylindrical support tube material, and M 夹具 is the mass of the fixture, and n is the number of cylindrical support tubes.

[0009] Among them, the cylindrical support tube is provided with multiple specifications with different inner diameters, different outer diameters, different lengths and different materials. The specifications of the cylindrical support tube are changed before processing, and the resonant frequency of the clamping device is roughly adjusted so that the resonant frequency of the clamping device after temperature correction is within a preset range in the absence of eddy current damping.

[0010] Step 2: Install two vertical and spaced electromagnets on the fixture, and install two vertical and spaced metal tubes on the workbench. Each metal tube is placed on the outside of a long electromagnet to form an electromagnetic damping device with the corresponding long electromagnet. After temperature correction, the resonant frequency f of the clamping device with eddy current damping is fixed for

[0011]

[0012] Where λ is the proportional constant, φ is the magnetic flux, μ is the magnetic permeability of the electromagnet core material, N is the number of turns of the electromagnet coil, A is the effective cross-sectional area of ​​the electromagnet core, L is the length of the electromagnet coil wound on the electromagnet core, and I is the input current of the electromagnet coil.

[0013] By changing the input current of the electromagnet coil and thereby changing the magnetic flux of the electromagnetic damping device, the resonant frequency of the clamping device is finely regulated so that the resonant frequency of the clamping device with eddy current damping after temperature correction is adjusted to a preset value.

[0014] Preferably, the f0 expression is constructed by considering the clamping device as a spring oscillator model, wherein E*π(D 2 -d 2 ) / 4 / L is the expression of the equivalent stiffness k of the system in the spring oscillator model, which is derived from the approximate formula of Young's modulus E of the cylindrical support tube material, that is, Approximately take 1, take We get k = E*π(D 2 -d 2 ) / 4 / L.

[0015] Preferably, the temperature correction coefficient is:

[0016] τ=1+α*ΔT+α*(ΔT) 2

[0017] Where α is the thermal expansion coefficient of the cylindrical support tube material, and ΔT is the temperature change relative to the room temperature of 25°C.

[0018] The present invention has the following beneficial effects:

[0019] The present invention can achieve fine adjustment of the resonant frequency of the workpiece; specifically, in the present invention, the clamp is detachably mounted on the machine tool work surface through two cylindrical support tubes, and by replacing cylindrical support tubes of different specifications, the resonant frequency of the clamping device (composed of the clamp and the two cylindrical support tubes) is within a preset range, thereby achieving coarse adjustment of the resonant frequency of the clamping device, and then by regulating the input current of the electromagnet coils in the two electromagnetic damping devices installed between the clamp and the work surface, the magnetic flux of the electromagnetic damping device is changed, so that the resonant frequency of the clamping device is adjusted to a preset value, thereby achieving fine adjustment of the resonant frequency of the clamping device; the present invention achieves fine adjustment of the resonant frequency of the clamping device by combining coarse adjustment and fine adjustment of the resonant frequency of the clamping device, thereby achieving fine adjustment of the resonant frequency of the workpiece, providing corresponding resonant frequency conditions for exploring the machining conditions of the workpiece at different resonant frequencies, and promoting new progress in machining research. Among them, the temperature correction coefficient is also taken into account in the calculation of the resonant frequency of the clamping device, which can more accurately reflect the resonant frequency of the clamping device under actual working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the structure of the clamp and cylindrical support tube in the present invention;

[0021] Figure 2 It is a schematic structural diagram of the clamp, cylindrical support tube and electromagnetic damping device in the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings.

[0023] The present invention provides a method for regulating the resonant frequency of a workpiece during machining, which is specifically as follows:

[0024] Step 1: Figure 1 As shown in the figure, the fixture is detachably mounted on the working table of the machine tool through two cylindrical support tubes arranged vertically and spaced apart. At this time, the resonant frequency f of the clamping device composed of the fixture and the two cylindrical support tubes without eddy current damping is

[0025]

[0026] Where E is the Young's modulus of the cylindrical support tube material, L is the length of the cylindrical support tube, D is the outer diameter of the cylindrical support tube, d is the inner diameter of the cylindrical support tube, ρ is the density of the cylindrical support tube material, and M 夹具 is the mass of the fixture, and n is the number of cylindrical support tubes.

[0027] Formula (1) regards the clamping device as a spring oscillator model, thereby deriving the resonance frequency expression without eddy current damping. Among them, the equivalent stiffness k of the system in the spring oscillator model is derived from the approximate formula of Young's modulus E of the cylindrical support tube material, that is, Approximately take 1, take We get k = E*π(D 2 -d 2 ) / 4 / L.

[0028] Furthermore, considering the influence of ambient temperature changes on the material properties of the cylindrical support tube, a temperature correction coefficient τ is introduced for correction. After correction, the resonant frequency f0 of the clamping device without eddy current damping is

[0029]

[0030] τ=1+α*ΔT+α*(ΔT) 2

[0031] Where α is the thermal expansion coefficient (linear expansion coefficient) of the cylindrical support tube material, and ΔT is the temperature change relative to the room temperature of 25°C.

[0032] The cylindrical support tube is provided with various specifications of different inner diameters, different outer diameters, different lengths and different materials. The specifications of the cylindrical support tube are changed before processing, and the resonant frequency of the clamping device is roughly adjusted so that the resonant frequency of the clamping device after temperature correction is within the preset range without eddy current damping.

[0033] Step 2: Figure 2 As shown, two vertical and spaced-apart long electromagnets are installed on the fixture, and two vertical and spaced-apart metal tubes are installed on the work surface. Each metal tube is placed on the outside of a long electromagnet to form an electromagnetic damping device with the corresponding long electromagnet. The vibration of the fixture drives the electromagnet to vibrate, causing relative movement between the metal tube and the electromagnet, cutting the magnetic flux lines to generate eddy currents. The eddy currents are acted upon by the Ampere force in the magnetic field, forming an eddy current damping force in the opposite direction to the direction of relative movement, thereby achieving a vibration reduction effect. Generally speaking, the presence of eddy current damping force causes the resonant frequency of the clamping device to be lower than the resonant frequency of the clamping device in the absence of eddy current damping, and as the eddy current damping force increases, the resonant frequency of the clamping device will gradually decrease until the eddy current damping force reaches a critical value (after which it will tend to a stable state with very little change), and the resonant frequency of the clamping device reaches a relatively stable state. This stable state depends on the magnetic flux. and the physical characteristics of the clamping device, the resonant frequency f of the clamping device with eddy current damping after temperature correction fixed for

[0034]

[0035] Where λ is a proportional constant, which is related to the characteristics of the electromagnetic damping device and is measured by calibration test (i.e., by multiple sets of f fixed, f0 and φ values ​​are calculated by linear fitting), φ is the magnetic flux, μ is the magnetic permeability of the electromagnet core material, N is the number of turns of the electromagnet coil, A is the effective cross-sectional area of ​​the electromagnet core (i.e., the cross-sectional area), L is the length of the electromagnet coil wound on the electromagnet core (in this embodiment, it is the length of the electromagnet core, i.e., the electromagnet coil is fully wound around the electromagnet core), and I is the input current of the electromagnet coil.

[0036] By changing the input current of the electromagnet coil and thereby changing the magnetic flux of the electromagnetic damping device, the resonant frequency of the clamping device is finely regulated so that the resonant frequency of the clamping device with eddy current damping after temperature correction is adjusted to a preset value.

Claims

1. A method for regulating the resonant frequency of a workpiece during machining, characterized in that: The details are as follows: Step 1: The fixture is detachably mounted on the work surface of the machine tool through two cylindrical support tubes arranged vertically and spaced apart. The temperature correction coefficient τ is introduced to obtain the resonant frequency of the clamping device consisting of the fixture and the two cylindrical support tubes without eddy current damping after temperature correction: Where E is the Young's modulus of the cylindrical support tube material, L is the length of the cylindrical support tube, D is the outer diameter of the cylindrical support tube, d is the inner diameter of the cylindrical support tube, ρ is the density of the cylindrical support tube material, and M 夹具 is the mass of the fixture, n is the number of cylindrical support tubes; The cylindrical support tube is provided with various specifications of different inner diameters, different outer diameters, different lengths and different materials. The specifications of the cylindrical support tube are changed before processing, and the resonant frequency of the clamping device is roughly adjusted so that the resonant frequency of the clamping device after temperature correction without eddy current damping is within a preset range; Step 2: Install two vertical and spaced electromagnets on the fixture, and install two vertical and spaced metal tubes on the workbench. Each metal tube is placed on the outside of a long electromagnet to form an electromagnetic damping device with the corresponding long electromagnet. After temperature correction, the resonant frequency f of the clamping device with eddy current damping is fixed for Where λ is the proportional constant, φ is the magnetic flux, μ is the magnetic permeability of the electromagnet core material, N is the number of turns of the electromagnet coil, A is the effective cross-sectional area of ​​the electromagnet core, L is the length of the electromagnet coil wound on the electromagnet core, and I is the input current of the electromagnet coil; By changing the input current of the electromagnet coil and thereby changing the magnetic flux of the electromagnetic damping device, the resonant frequency of the clamping device is finely regulated so that the resonant frequency of the clamping device with eddy current damping after temperature correction is adjusted to a preset value.

2. The method for regulating the resonant frequency of a workpiece during machining according to claim 1, wherein: The f0 expression is constructed by considering the clamping device as a spring oscillator model, where E*π(D 2 -d 2 ) / 4 / L is the expression of the equivalent stiffness k of the system in the spring oscillator model, which is derived from the approximate formula of Young's modulus E of the cylindrical support tube material, that is, Approximately take 1, take We get k = E*π(D 2 -d 2 ) / 4 / L.

3. The method for regulating the resonant frequency of a workpiece during machining according to claim 1, wherein: The temperature correction factor is: τ=1+α*ΔT+α*(ΔT) 2 Where α is the thermal expansion coefficient of the cylindrical support tube material, and ΔT is the temperature change relative to the room temperature of 25°C.

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