A method of regulating the resonant frequency of a workpiece under machining conditions

Abstract

The application discloses a kind of methods for regulating workpiece resonance frequency under machining condition, clamp is detachably installed on machine tool workbench by cylindrical support tube, by replacing different specifications of cylindrical support tube, the resonance frequency of clamping device composed of clamp and cylindrical support tube is in preset range, the coarse adjustment of the resonance frequency of clamping device is realized, then by regulating the input current of electromagnet coil in electromagnetic damping device installed between clamp and workbench, the magnetic flux size of electromagnetic damping device is changed, the resonance frequency of clamping device is adjusted to preset value, the fine adjustment of the resonance frequency of clamping device is realized.The application realizes the fine adjustment of the resonance frequency of clamping device by the combination of coarse adjustment and fine adjustment of the resonance frequency of clamping device, and then realizes the fine adjustment of the resonance frequency of workpiece, can provide corresponding resonance frequency condition for exploring the machining condition of workpiece under different resonance frequency, promote the new progress of machining research.

Description

Technical Field

[0001] This invention belongs to the field of precision automated machining, and specifically relates to a method for controlling the resonant frequency of a workpiece during machining. Background Technology

[0002] Resonance is a current hot topic in machining research. Studying the impact of resonant frequency on machining and optimizing the system's dynamic response is crucial. Current methods for controlling machine tool resonant frequency mainly rely on single damping control techniques. While these can control the resonant frequency to some extent, they suffer from limited adjustment range and slow response speed. Furthermore, existing research on machine tool resonant frequency 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. Since controlling the workpiece resonant frequency is essential in studying the impact of resonant frequency on machining and optimizing the system's dynamic response, designing a method for controlling the workpiece resonant frequency during machining is highly necessary. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a method for controlling the resonant frequency of a workpiece during machining.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] The present invention discloses a method for adjusting the resonant frequency of a workpiece during machining, as detailed below:

[0006] Step 1: The fixture is detachably mounted on the machine tool's worktable via two vertically spaced cylindrical support tubes; introducing a temperature correction coefficient τ, the resonant frequency of the clamping device consisting of the fixture and the two cylindrical support tubes after temperature correction is obtained under undamped eddy current conditions:

[0007]

[0008] In the formula, 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 Let n be the mass of the fixture, and n be the number of cylindrical support tubes.

[0009] The cylindrical support tube is available in various specifications with different inner diameters, outer diameters, lengths, and materials. Before processing, the specifications of the cylindrical support tube are changed to coarsely adjust the resonance frequency of the clamping device so that the resonance frequency of the clamping device under no eddy current damping after temperature correction is within a preset range.

[0010] Step 2: Install two vertically spaced, elongated electromagnets on the fixture, and install two vertically spaced, elongated metal tubes on the worktable. Each metal tube is fitted over the outside of one of the elongated electromagnets, forming an electromagnetic damping device with the corresponding elongated electromagnet. After temperature correction, the resonant frequency f of the clamping device under eddy current damping is determined. fixed for

[0011]

[0012] In the formula, λ is the proportionality constant, φ is the magnetic flux, μ is the 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 thus changing the magnetic flux of the electromagnetic damping device, the resonant frequency of the clamping device can be finely controlled, so that the resonant frequency of the clamping device under eddy current damping after temperature correction is adjusted to the preset value.

[0014] Preferably, the f0 expression is constructed by treating the clamping device as a spring oscillator model, where E*π(D 2 -d 2 ) / 4 / L is the expression for the equivalent stiffness k of the system in the spring oscillator model. k is derived from the approximate formula of the 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] In the formula, α is the coefficient of thermal expansion of the cylindrical support tube material, and ΔT is the temperature change relative to room temperature of 25℃.

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

[0019] This invention enables fine adjustment of the workpiece's resonant frequency. Specifically, the fixture is detachably mounted on the machine tool table via two cylindrical support tubes. By replacing the cylindrical support tubes with different specifications, the resonant frequency of the clamping device (consisting of the fixture and the two cylindrical support tubes) is kept within a preset range, achieving coarse adjustment of the clamping device's resonant frequency. Then, by adjusting the input current of the electromagnet coils in the two electromagnetic damping devices installed between the fixture and the worktable, the magnetic flux of the electromagnetic damping devices is changed, adjusting the clamping device's resonant frequency to a preset value, achieving fine adjustment of the clamping device's resonant frequency. This invention achieves fine adjustment of the clamping device's resonant frequency by combining coarse and fine adjustment, thereby achieving fine adjustment of the workpiece's resonant frequency. This provides corresponding resonant frequency conditions for exploring the machining of workpieces at different resonant frequencies, promoting new progress in machining research. Furthermore, the calculation of the clamping device's resonant frequency also considers a temperature correction coefficient, which more accurately reflects the resonant frequency of the clamping device under actual working conditions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the clamp and cylindrical support tube in this invention;

[0021] Figure 2 This is a schematic diagram of the structure of the clamp, cylindrical support tube and electromagnetic damping device in this invention. Detailed Implementation

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

[0023] The present invention discloses a method for adjusting the resonant frequency of a workpiece during machining, as detailed below:

[0024] Step 1, such as Figure 1 As shown, the fixture is detachably mounted on the machine tool's worktable via two vertically arranged, spaced cylindrical support tubes. In this case, the resonant frequency f of the clamping device consisting of the fixture and the two cylindrical support tubes under undamped eddy current conditions is:

[0025]

[0026] In the formula, 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 Let n be the mass of the fixture, and n be the number of cylindrical support tubes.

[0027] Equation (1) derives the resonant frequency expression for the undamped condition by treating the clamping device as a spring oscillator model. The equivalent stiffness k of the system in the spring oscillator model is derived from the approximate formula of the Young's modulus E of the cylindrical support tube material. 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 under undamped eddy current conditions is:

[0029]

[0030] τ = 1 + α*ΔT + α*(ΔT) 2

[0031] In the formula, α is the coefficient of thermal expansion (linear expansion coefficient) of the cylindrical support tube material, and ΔT is the temperature change relative to the ambient temperature of 25℃.

[0032] The cylindrical support tube is available in various specifications with different inner diameters, outer diameters, lengths, and materials. Before processing, the cylindrical support tube specifications are changed, and the resonance frequency of the clamping device is coarsely adjusted so that the resonance frequency of the clamping device under the condition of no eddy current damping after temperature correction is within the preset range.

[0033] Step 2, as follows Figure 2 As shown, two vertically spaced, elongated electromagnets are mounted on the clamp, and two vertically spaced, equally spaced metal tubes are mounted on the worktable. Each metal tube is fitted over the outer side of one of the elongated electromagnets, forming an electromagnetic damping device. The clamp's vibration drives the electromagnets to vibrate, causing relative motion between the metal tubes and the electromagnets. This relative motion cuts magnetic field lines, generating eddy currents. These eddy currents are subjected to Ampere's force in the magnetic field, creating an eddy current damping force in the opposite direction to the relative motion, thus achieving vibration reduction. Generally, the presence of eddy current damping force lowers the resonant frequency of the clamping device compared to the case without eddy current damping. Furthermore, as the eddy current damping force increases, the resonant frequency gradually decreases until it reaches a critical value (after which it tends towards a stable state with minimal change). The resonant frequency of the clamping device then reaches a relatively stable state, which depends on the magnetic flux. The physical characteristics of the clamping device, and the resonant frequency f of the clamping device under eddy current damping after temperature correction. fixed for

[0034]

[0035] In the formula, λ is a proportionality constant, which is related to the characteristics of the electromagnetic damping device and is obtained through calibration tests (i.e., through multiple sets of f). fixedThe λ value is obtained by linear fitting of the values ​​of f0 and φ, where φ is the magnetic flux, μ is the 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 (in this embodiment, it is the length of the electromagnet core, i.e., the electromagnet coil is fully wound on the electromagnet core), and I is the input current of the electromagnet coil.

[0036] By changing the input current of the electromagnet coil, and thus changing the magnetic flux of the electromagnetic damping device, the resonant frequency of the clamping device can be finely controlled, so that the resonant frequency of the clamping device under eddy current damping after temperature correction is adjusted to the preset value.

Claims

1. A method for regulating the resonant frequency of a workpiece during machining, characterized in that: Specifically as follows: Step 1: The fixture is detachably mounted on the machine tool's worktable via two vertically spaced cylindrical support tubes; introducing a temperature correction coefficient τ, the resonant frequency of the clamping device consisting of the fixture and the two cylindrical support tubes after temperature correction is obtained under undamped eddy current conditions: In the formula, 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 The mass of the fixture is n, and the number of cylindrical support tubes is n. The cylindrical support tube is available in various specifications with different inner diameters, outer diameters, lengths and materials. Before processing, the cylindrical support tube specifications are changed to coarsely adjust the resonance frequency of the clamping device so that the resonance frequency of the clamping device under no eddy current damping after temperature correction is within the preset range. Step 2: Install two vertically spaced, elongated electromagnets on the fixture, and install two vertically spaced, elongated metal tubes on the worktable. Each metal tube is fitted over the outside of one of the elongated electromagnets, forming an electromagnetic damping device with the corresponding elongated electromagnet. After temperature correction, the resonant frequency f of the clamping device under eddy current damping is determined. fixed for In the formula, λ is the proportionality constant, ϕ is the magnetic flux, μ is the 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 thus changing the magnetic flux of the electromagnetic damping device, the resonant frequency of the clamping device can be finely controlled, so that the resonant frequency of the clamping device under eddy current damping after temperature correction is adjusted to the preset value.

2. The method for adjusting the resonant frequency of a workpiece during machining according to claim 1, characterized in that: The expression for f0 is constructed by treating the clamping device as a spring oscillator model, where... It is the equivalent stiffness of the system in the spring oscillator model. The expression, Young's modulus of cylindrical support tube material It is derived from the approximate formula, that is Approximately take 1, take ,get .

3. The method for adjusting the resonant frequency of a workpiece during machining according to claim 1, characterized in that: The temperature correction factor: In the formula, α is the coefficient of thermal expansion of the cylindrical support tube material, and ΔT is the temperature change relative to room temperature of 25℃.

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