A damping and vibration reduction device for machine tool turning tools

Abstract

This invention provides a damping and vibration reduction device for a machine tool turning tool. The device includes: a permanent magnet, a magnetostrictive rod, an energized coil, a fixing element, a connecting tripod, a turning tool, and a turning tool arm. The magnetostrictive rod is fixed to a base plate by the fixing element. The permanent magnet is fixedly mounted on the upper and lower sides of the magnetostrictive rod. The energized coil is wound in a ring around the magnetostrictive rod. Connecting tripods are provided at both ends of the magnetostrictive rod. The base plate is fixed to the turning tool arm by connecting rods. The turning tool is fixed to the turning tool arm by connecting rods. When a damping and vibration reduction current signal is applied to the energized coil, the magnetostrictive rod vibrates, causing the connecting tripod to vibrate at the same frequency on both sides. This vibrates the connecting tube at the junction of the turning tool and causes damping suppression at the tool tip, thereby achieving a damping and vibration reduction effect and reducing the impact of tool chatter on the workpiece machining quality.

Description

Technical Field

[0001] This invention relates to the field of turning technology, and in particular to a damping and vibration reduction device for machine tool turning tools. Background Technology

[0002] In turning, the lathe tool, as the primary cutting tool, is one of the most widely used cutting tools. When a machine tool is machining a workpiece, especially when machining deep holes, the insert mounted on the tool holder's head will experience chatter due to the long tool holder and large tool head. This can lead to accuracy deviations in the machined workpiece, and chatter can also cause tool wear, thus reducing tool life.

[0003] Existing vibration reduction methods are mostly mechanical. Mechanical vibration reduction methods simply use mechanical structures to reinforce the tool holder, preventing vibration caused by excessive tool extension. However, mechanical vibration reduction is too passive in the process, and its effect is singular and difficult to be effectively targeted.

[0004] To address the aforementioned technical problems, this invention proposes a damping and vibration reduction device for machine tool turning tools. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for damping and reducing vibration of machine tool turning tools, to solve the problem described in the background art that existing mechanical vibration reduction methods offer only a single effect and are difficult to achieve effective and targeted results. The specific technical solution is as follows:

[0006] A damping and vibration reduction device for a machine tool turning tool, the device comprising: a permanent magnet, a magnetostrictive rod, an energized coil, a fixing element, a connecting tripod, a turning tool, and a turning tool arm;

[0007] The magnetostrictive rod is fixed to the base plate by the fixing element. The permanent magnet is fixedly installed on the upper and lower sides of the magnetostrictive rod. The energized coil is wound around the magnetostrictive rod in a ring. The two ends of the magnetostrictive rod are provided with connecting tripods. The base plate is fixed to the cutting tool arm by the connecting rod. The cutting tool is fixed to the cutting tool arm by the connecting rod.

[0008] Preferably, the device further includes: a crossbar, an L-bar, an upper fixed bar, and a lower fixed bar;

[0009] One end of the crossbar is fixed to the tool arm, and the other end is fixed to the tool. One end of the L-bar is fixed to the tool arm, and the other end is movably connected to the crossbar. The upper end of the base plate is fixed to the tool arm via the upper fixing rod, and the lower end of the base plate is fixed to the tool arm via the lower fixing rod. The upper fixing rod is close to the crossbar, the lower fixing rod is close to the lower end of the L-bar, and the base plate is close to the upper end of the L-bar. When the magnetostrictive rod vibrates, it drives the base plate to vibrate, and the vibration is transmitted to the crossbar via the upper fixing rod and to the L-bar via the lower fixing rod, thus realizing the transmission of vibration.

[0010] Preferably, the device further includes a base plate that is rhomboid in shape.

[0011] Preferably, the material of the energized coil is copper.

[0012] Preferably, the permanent magnet is made of neodymium iron boron.

[0013] Preferably, two permanent magnets are provided.

[0014] Preferably, the magnetostrictive rod is made of an iron-gallium alloy.

[0015] Preferably, the device further includes: a Hall sensor; the Hall sensor is disposed within the energized coil and is used to detect the magnetic induction intensity within the energized coil.

[0016] Preferably, the device further includes a processor; the processor is used to generate an alternating current based on the detected machine tool chatter information, the alternating current being used to control the extension and retraction of the magnetostrictive rod.

[0017] Preferably, the device is further provided with an optical detection device; the optical detection device is used to detect the chatter information of the cutting tool.

[0018] The beneficial effects of this invention are as follows:

[0019] This invention provides a damping and vibration reduction device for a machine tool turning tool. The device includes: a permanent magnet, a magnetostrictive rod, an energized coil, a fixing element, a connecting tripod, a turning tool, and a turning tool arm. The magnetostrictive rod is fixed to a base plate by the fixing element. The permanent magnet is fixedly mounted on the upper and lower sides of the magnetostrictive rod. The energized coil is wound in a ring around the magnetostrictive rod. Connecting tripods are provided at both ends of the magnetostrictive rod. The base plate is fixed to the turning tool arm by connecting rods. The turning tool is fixed to the turning tool arm by connecting rods. When a damping current signal is applied to the electromagnetic induction coil, the alternating periodically changing current induces a magnetic field around the permanent magnet with the same amplitude but opposite direction to the tool chatter signal. Under the clamping effect of the fixed element, the hysteresis telescopic tube vibrates at twice the vibration frequency, and the tripod also vibrates at the same frequency on both sides, squeezing the connecting tube at the tool joint. This causes damping suppression at the tool tip, thereby achieving a damping effect and reducing the impact of tool chatter on the workpiece machining quality. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of a machine tool cutting tool damping and vibration reduction device according to the present invention;

[0021] Figure 2 This is a partial enlarged view of the cutting tool portion of a machine tool cutting tool damping and vibration reduction device according to the present invention;

[0022] Figure 3 This is a partial enlarged view of the tool arm portion of a machine tool cutting tool damping and vibration reduction device according to the present invention;

[0023] Figure 4 This is a schematic diagram of the signal generation of a machine tool cutting tool damping and vibration reduction device according to the present invention;

[0024] Figure 5 This is a three-dimensional structural schematic diagram of a machine tool turning tool damping and vibration reduction device according to the present invention;

[0025] Among them, 1. permanent magnet; 2. magnetostrictive rod; 3. energized coil; 4. fixing element; 5. connecting tripod; 6. lathe tool; 7. lathe tool arm; 8. cutting end face; 9. cross bar; 10. L-bar; 11. upper fixing rod; 12. lower fixing rod. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this specification clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments in this specification, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this document.

[0027] The following combination Figure 1-5 This specification provides a detailed description of the technical solutions provided in each embodiment. Specific Implementation Example 1:

[0029] The purpose of this invention is to provide a method and system for damping and reducing vibration of machine tool turning tools, to solve the problem described in the background art that existing mechanical vibration reduction methods offer only a single effect and are difficult to achieve effective and targeted results. The specific technical solution is as follows:

[0030] A damping and vibration reduction device for a machine tool turning tool, the device comprising: a permanent magnet, a magnetostrictive rod, an energized coil, a fixing element, a connecting tripod, a turning tool, and a turning tool arm;

[0031] The magnetostrictive rod is fixed to the base plate by the fixing element. The permanent magnet is fixedly installed on the upper and lower sides of the magnetostrictive rod. The energized coil is wound around the magnetostrictive rod in a ring. The two ends of the magnetostrictive rod are provided with connecting tripods. The base plate is fixed to the cutting tool arm by the connecting rod. The cutting tool is fixed to the cutting tool arm by the connecting rod.

[0032] Preferably, the device further includes: a crossbar, an L-bar, an upper fixed bar, and a lower fixed bar;

[0033] One end of the crossbar is fixed to the tool arm, and the other end is fixed to the tool. One end of the L-bar is fixed to the tool arm, and the other end is movably connected to the crossbar. The upper end of the base plate is fixed to the tool arm via the upper fixing rod, and the lower end of the base plate is fixed to the tool arm via the lower fixing rod. The upper fixing rod is close to the crossbar, the lower fixing rod is close to the lower end of the L-bar, and the base plate is close to the upper end of the L-bar. When the magnetostrictive rod vibrates, it drives the base plate to vibrate, and the vibration is transmitted to the crossbar via the upper fixing rod and to the L-bar via the lower fixing rod, thus realizing the transmission of vibration.

[0034] Preferably, the device further includes a base plate that is rhomboid in shape.

[0035] Preferably, the material of the energized coil is copper.

[0036] Preferably, the permanent magnet is made of neodymium iron boron.

[0037] Preferably, two permanent magnets are provided.

[0038] Preferably, the magnetostrictive rod is made of an iron-gallium alloy.

[0039] Preferably, the device further includes: a Hall sensor; the Hall sensor is disposed within the energized coil and is used to detect the magnetic induction intensity within the energized coil.

[0040] Preferably, the device further includes a processor; the processor is used to generate an alternating current based on the detected machine tool chatter information, the alternating current being used to control the extension and retraction of the magnetostrictive rod.

[0041] Preferably, the device is further provided with an optical detection device; the optical detection device is used to detect the chatter information of the cutting tool. Specific Implementation Example 2:

[0043] To overcome the aforementioned shortcomings of existing technologies, this invention proposes a damping and vibration reduction method for machine tool turning tools. This method utilizes rectification and inversion to control the amplitude and frequency of the output current, and leverages the response of magnetostrictive materials to magnetic field strength to achieve semi-active vibration control. This allows for timely adjustment of machine tool turning tool machining parameters and reduces chatter between the tool and workpiece, thereby improving machining efficiency and quality. This is the content that needs to be explained in this invention. The technical solution adopted by this invention to achieve its objective is as follows:

[0044] The main objective of this invention is to reduce chatter and optimize noise during CNC machine tool turning. It proposes a method for damping and reducing vibration of machine tool turning tools based on magnetostriction, which improves tool life and product quality.

[0045] A method for damping and reducing vibration of machine tool turning tools. This method is based on the shape change of magnetostrictive materials under the influence of a magnetic field. Electromagnetism has established a one-to-one correspondence between the magnetic field and the magnetostriction of magnetostrictive materials. By changing the magnitude and frequency of the magnetic field strength and magnetic induction intensity, the magnitude and frequency of the magnetostrictive deformation of the material are controlled, thereby reducing chatter generated during machine tool turning tool machining and compensating for the chatter phenomenon. The specific implementation steps are as follows:

[0046] S1. Detect chatter information of machine tool cutting tools.

[0047] During turning, the optically detected vibration signal is used as the input. This input is periodically changing, so much so that in the event of a "malfunction," it causes a periodic length change in the ferromagnetic material of the device, producing a "damping effect" that reduces the impact of chatter on the quality of the machined workpiece. During turning, the chatter damping signal of the cutting tool is equal in magnitude but opposite in direction to the periodic signal that generates chatter; its current vector... Figure 4 The damper undergoes length and volume changes under the influence of this signal to suppress tool chatter.

[0048] When chatter occurs in the cutting tool, the amplitude change of the current signal obtained using optical detection is shown in the chatter amplitude signal diagram. Since the chatter signal is weak, a periodically varying sinusoidal signal is superimposed to obtain a chatter amplitude sequence superimposed with a periodic signal diagram. If the chatter occurrence time is 0 to 0.5 seconds, the current signal of the damper is input in reverse to the energized induction coil to obtain a lateral frequency-doubled mechanical vibration, causing deformation of the magnetostrictive material and damping suppression at the cutting tool tip. When the chatter occurrence time is 0.5 to 1 second, a damping effect in the opposite direction is produced. The change in the signal quantity given by the damper is shown in the damper damping signal diagram.

[0049] S2. Calculate the amount of expansion and contraction that needs to be compensated when the cutting tool experiences chatter.

[0050] Based on the signal detected in the previous step, determine whether the cutting tool is chattering, and determine the extension / retraction amount based on the chatter amplitude. The specific formula for determining the extension / retraction amount is shown in formula (23). The specific process is explained in detail in the modeling section below.

[0051] S3. Apply the corresponding current to the energized coil according to the amount of expansion and contraction.

[0052] A non-magnetic screw is placed in the middle of the damping device, and a current-carrying solenoid made of magnetostrictive material is placed at its upper and lower ends. The amplitude and frequency of the output current are changed by means of rectification, DC-DC conversion and inversion, so that the current coil generates a corresponding magnetic field and changes the amount of expansion and contraction of the magnetostrictive material.

[0053] S4. Measure the magnetic flux density of the magnetostrictive material using a Hall sensor.

[0054] This analysis examines the relationship between the expansion and contraction of magnetostrictive materials and the magnetic field strength based on magnetic polarization intensity. Magnetic polarization intensity J directly reflects the relationship between the magnetic and mechanical properties of a magnetic medium within a magnetic field. Since magnetic polarization intensity is difficult to measure, magnetic induction intensity is used as a substitute. A Hall effect sensor is used to measure the magnetic induction intensity of the magnetostrictive material. This magnetic induction intensity data is then used as feedback to adjust the current, thereby ensuring that the expansion and contraction of the magnetostrictive rod reaches a preset value, thus improving the vibration damping effect.

[0055] S5. Obtain the machining texture information of the workpiece to compensate for the alternating current.

[0056] After the workpiece is machined, its texture is analyzed. Based on the actual machining conditions, chatter, and the chatter compensation method, the actual machining effect is observed. Corresponding compensation parameters are set based on the machining effect and applied to the next machining cycle. This process continues until the machined product meets production requirements.

[0057] The modeling process of the quantitative relationships in this invention is as follows:

[0058] A non-magnetic screw is placed in the middle of the damping device, and a current-carrying solenoid made of magnetostrictive material is placed at its upper and lower ends. The amplitude and frequency of the output current are changed by means of rectification, DC-DC conversion and inversion, so that the current coil generates a corresponding magnetic field and changes the amount of expansion and contraction of the magnetostrictive material.

[0059] After rectification and inversion, the required AC sinusoidal voltage is generated. By adding a variable load, a variable AC sinusoidal current is generated. The power supply control circuit adopts a three-stage design: the front stage is a three-phase bridge uncontrolled rectifier, the middle stage uses a Buck converter, and the rear stage uses an LCL full-bridge inverter. The control strategy is a constant current SPWM, and the current is controlled by PI control in the dq coordinate system. This generates an output alternating current I with controllable amplitude and frequency. After being passed through an N-turn energized coil, it generates the magnetic field strength H and changing frequency required by the magnetostrictive material.

[0060] (1)

[0061] The relationship between the stretching and contraction of magnetostrictive materials and the magnetic field strength is analyzed based on the magnetic polarization intensity. The magnetic polarization intensity J directly reflects the relationship between the magnetism and mechanics of the magnetic medium in the magnetic field. Since the magnetic polarization intensity is difficult to measure, the magnetic induction intensity is used instead of the magnetic polarization intensity. The magnetic induction intensity of the magnetostrictive material is measured by a Hall sensor.

[0062] The magnetostrictive effect of a magnetostrictive rod is mainly related to the strength of the applied excitation magnetic field. When working under vibration, if an alternating current is input into the energized coil, the magnetostrictive rod is excited by the alternating magnetic field, and its output frequency is twice that of the applied excitation magnetic field, i.e., a frequency doubling effect occurs.

[0063] To avoid the frequency doubling effect of the material, a common method is to apply a suitable bias magnetic field in addition to the external excitation magnetic field, so that the output frequency of the magnetostrictive rod matches the input frequency. A permanent magnet circuit is used to add the bias magnetic field; the bias magnetic field generated by the permanent magnet is provided by the permanent magnet itself. In this method, the magnetic circuit is generally closed. Because cylindrical permanent magnets produce a more uniform bias magnetic field than disk-shaped permanent magnets, cylindrical permanent magnets are chosen. Ti:FeB is selected as the permanent magnet material. This material has strong magnetic properties, high remanence, high coercivity, high energy product, and a high performance-to-price ratio, and its processing cost is very low. Symmetrical placement of the permanent magnets will result in a uniform bias magnetic field.

[0064] Neither current intensity nor magnetic field strength can directly reflect the relationship between the magnetic and mechanical properties of a magnetic medium in a magnetic field. This is a key reason why the magnetostriction of ferromagnetic media is not a single-valued function of magnetic field strength. Therefore, when establishing a control model for magnetostrictive materials, variables directly related to the magnetization state of the magnetic medium should be selected as control quantities to establish a one-to-one correspondence. In electromagnetism, magnetic polarization J directly reflects the relationship between the magnetic and mechanical properties of a magnetic medium in a magnetic field. The following analysis uses the magnetic charge perspective of the magnetization of the magnetic medium to analyze the relationship between the magnetostriction of magnetostrictive materials and magnetic polarization intensity.

[0065] First, two assumptions need to be made: (1) Based on the discretization model, the magnetostrictive material is approximately equivalent to an elastic body on a macroscopic scale, satisfying Hooke's law. (2) The magnetostrictive material and its driving coil are equivalent to an inductor with an iron core, and the internal magnetic field is uniform.

[0066] A cylindrical rod made of magnetostrictive material is placed in a uniform magnetization field H0 generated by a driving current. Equal and reciprocally opposite magnetic charges are generated at both ends of the magnetostrictive cylindrical rod. Let the surface density of the generated magnetic charges be ± The equivalent surface density of the magnetization field is However, during the magnetization process, magnetostrictive materials generate a reverse additional magnetic field, namely a demagnetizing field H′, which weakens the applied magnetic field. Therefore, the relationship between the resultant magnetic field H, the magnetizing field H0, and the demagnetizing field H′ inside the magnetostrictive material is as follows:

[0067] (2)

[0068] (3)

[0069] In the formula, μ0 is the vacuum permeability, μ0 = 4π × 10⁻⁷ H / m.

[0070] From assumption (2) and Gauss's law in a magnetic field, we get:

[0071] (4)

[0072] In the formula, μ is the air permeability.

[0073] By rearranging equations (3) and (4), we get:

[0074] (5)

[0075] Considering the relationship between the magnetostriction coefficient and linear strain at zero prestress:

[0076] (6)

[0077] in For linear strain, The magnetostriction coefficient is 1. It represents the magnetic polarization intensity. It represents the saturation magnetic polarization intensity.

[0078] Under the action of a resultant magnetic field H, the magnetostrictive material is equivalent to a magnetic dipole in the magnetic field, and the force on the magnetic charge in the magnetic field is the product of the magnetic charge and the magnetic field strength. Then the magnetostrictive force F generated by the magnetostrictive material is:

[0079] (7)

[0080] In the formula, K is the elastic coefficient of the magnetostrictive material, and S is the cross-sectional area of ​​the magnetostrictive material.

[0081] According to Hooke's Law based on assumption (1), we can obtain:

[0082] (8)

[0083] In the formula It represents the amount of expansion and contraction of a magnetostrictive material under the influence of a magnetic field.

[0084] From equations (7) and (8), we get:

[0085] (9)

[0086] Unit volume within a magnetic medium In the middle, use Representing the vector sum of magnetic dipoles within a unit volume, the magnetic polarization J can be expressed as:

[0087] (10)

[0088] It can be derived from a similar electric field theory that:

[0089] (11)

[0090] (12)

[0091] In a closed surface, Let n be the algebraic sum of magnetic charges within the end face area, and n be the unit outward normal vector of the magnetic medium surface.

[0092] Magnetic induction intensity vector B:

[0093] (13)

[0094] (14)

[0095] in Since is the relative permeability, we have:

[0096] (15)

[0097] From equations (12) and (15), we get:

[0098] (16)

[0099] According to Gauss's law in magnetic fields: the magnetic flux through any closed surface in a magnetic field is always zero, that is:

[0100] (17)

[0101] For a uniformly magnetized magnetic body, the magnetic charge is distributed on the surface of the magnetic body, and the surface charge density on its surface is... It is equal to the projection of the magnetic polarization intensity onto the direction of the outward normal of the surface, therefore we can conclude that:

[0102] (18)

[0103] Since the direction of magnetic polarization of magnetostrictive materials is the same as the direction of the outward normal intensity, that is... Therefore, equation (18) can be simplified to:

[0104] (19)

[0105] From equations (5), (9), and (19), we can obtain:

[0106] (20)

[0107] Since μ0 is 4π×10-7H / m, in practical engineering, µ-µ0 is often replaced by µ, so (20) can be simplified to:

[0108] (twenty one)

[0109] Since magnetostrictive materials are soft magnetic materials, the difference between their magnetic flux density B and magnetic polarization is very small. Therefore, measuring the magnetic flux density within the magnetostrictive rod can be used as an approximation to measure the magnetic polarization, i.e.:

[0110] (twenty two)

[0111] Magnetostriction The relationship with the magnetic flux density B is as follows:

[0112] (twenty three)

[0113] To measure the magnetic flux density, a very small air gap is made at the cross-section where the magnetic conductor contacts the magnetostrictive rod, and a Hall plate is placed tightly against the surface of the magnetostrictive rod. Since the normal component of the magnetic flux density on both sides of the boundary between the magnetostrictive rod and the air gap is continuous, and the dimensions of the Hall plate and the air gap are very small, the magnetic flux density measured by the Hall plate is approximately equal to the magnetic flux density inside the magnetostrictive rod.

[0114] The above description is merely a preferred embodiment of this specification and is not intended to limit this specification. Various modifications and variations can be made to this specification by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.

Claims

1. A damping and vibration reduction device for a machine tool turning tool, characterized in that, The device includes: a permanent magnet, a magnetostrictive rod, an energized coil, a fixing element, a connecting tripod, a cutting tool, a cutting tool arm; a Hall sensor; and a processor. The magnetostrictive rod is fixed to the base plate by the fixing element. The permanent magnet is fixedly installed on the upper and lower sides of the magnetostrictive rod. The energized coil is wound around the magnetostrictive rod in a ring. The two ends of the magnetostrictive rod are provided with connecting tripods. The base plate is fixed to the cutting tool arm by the connecting rod. The cutting tool is fixed to the cutting tool arm by the connecting rod. The connecting rod also includes: a crossbar, an L-bar, an upper fixing rod, and a lower fixing rod. One end of the crossbar is fixed to the tool arm, and the other end is fixed to the tool. One end of the L-shaped rod is fixed to the tool arm, and the other end is movably connected to the crossbar. The upper end of the base plate is fixed to the tool arm via the upper fixing rod, and the lower end of the base plate is fixed to the tool arm via the lower fixing rod. The upper fixing rod is close to the crossbar, the lower fixing rod is close to the lower end of the L-shaped rod, and the base plate is close to the upper end of the L-shaped rod. When the magnetostrictive rod vibrates, it drives the base plate to vibrate, and the vibration is transmitted to the crossbar via the upper fixing rod and to the L-shaped rod via the lower fixing rod, respectively, thus realizing the transmission of vibration. The Hall sensor is set inside the energized coil to detect the magnetic induction intensity inside the energized coil. The processor is used to generate an alternating current based on the detected machine tool chatter information, and the alternating current is used to control the extension and retraction of the magnetostrictive rod.

2. The machine tool turning tool damping and vibration reduction device as described in claim 1, characterized in that, The base plate is rhomboid in shape.

3. The machine tool turning tool damping and vibration reduction device as described in claim 1, characterized in that, The material of the energized coil is copper.

4. The machine tool turning tool damping and vibration reduction device as described in claim 1, characterized in that, The permanent magnet is made of neodymium iron boron.

5. The machine tool turning tool damping and vibration reduction device as described in claim 1, characterized in that, Two permanent magnets are provided.

6. The machine tool turning tool damping and vibration reduction device as described in claim 1, characterized in that, The magnetostrictive rod is made of an iron-gallium alloy.

7. The machine tool turning tool damping and vibration reduction device as described in claim 1, characterized in that, The device is also equipped with an optical detection device; the optical detection device is used to detect the chatter information of the cutting tool.

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