A vertical ultrasonic broaching machine and an assembling and debugging method thereof

Abstract

The present application belongs to the technical field of machining, and particularly relates to a vertical ultrasonic broaching machine and an assembling and debugging method thereof. The broaching machine comprises an ultrasonic auxiliary device, and the ultrasonic auxiliary device comprises an ultrasonic vibration mechanism. The ultrasonic vibration mechanism comprises an ultrasonic vibration amplitude transformer, a cylinder, a limiting block, a gasket, a gasket, a piezoelectric actuator and an ultrasonic power supply. A step protrusion is arranged at the middle part of the ultrasonic vibration amplitude transformer. The connecting part of the step protrusion and the cylinder is provided with the limiting block. The input end of the ultrasonic vibration amplitude transformer and the fixed plate are provided with the gasket. The piezoelectric actuator and the gasket are provided with the gasket. The thickness of the gasket and the gasket and the position of the limiting block can be comprehensively adjusted, so that the problem that the piezoelectric actuator is burned out due to the excessive pre-tightening force of the piezoelectric actuator is avoided, and the problem that the amplitude and the frequency of the piezoelectric actuator are small due to the excessive pressure at the connecting part of the ultrasonic vibration amplitude transformer and the piezoelectric actuator is solved.

Description

Technical Field

[0001] This invention relates to the field of machining technology, specifically to a vertical ultrasonic broaching machine and its assembly and debugging method. Background Technology

[0002] Broaching machines, as a common type of metal cutting machine tool, can be used to machine the internal surfaces of workpieces (such as creating round holes, square holes, spline holes, etc.) and external surfaces (such as planes, shaped surfaces, grooves, etc.). The basic working principle of a broaching machine is that the broach moves linearly to cut (broach) the surface of the workpiece to achieve subtractive machining. Furthermore, some broaching machines can perform multiple cuts on the workpiece in a single stroke, thus generally offering high machining efficiency and accuracy, making them particularly suitable for mass production of parts. However, broaching machines suffer from insufficient thermal management energy during the broaching process, which can easily lead to problems such as excessive tool wear and cutting deformation, significantly limiting the machining performance of the broaching machine.

[0003] With the development of technology, ultrasonic-assisted technology has been widely applied in the field of machine tool processing, leading to the emergence of specialized ultrasonic machine tools. As the name suggests, ultrasonic machine tools are devices that utilize ultrasonic vibration energy for precision machining. They are particularly suitable for machining hard and brittle materials and difficult-to-machine metals, showing significant advantages in machining materials such as titanium alloys, high-temperature alloys, engineering ceramics, and ceramic matrix composites. Ultrasonic machine tools use high-frequency vibration to generate micro-impacts between the tool and the workpiece, effectively reducing cutting forces and temperatures, minimizing tool wear and burrs, thereby improving the overall machining accuracy of the machine tool and the surface finish of the workpiece.

[0004] While the integration of ultrasonic-assisted technology brings numerous advantages to machine tool processing, the high load during broaching also has adverse effects on related components. The core components of an ultrasonic-assisted vibration system mainly include ultrasonic amplitude transformers and piezoelectric actuators. During high-load broaching operations, the performance of the piezoelectric actuators and amplitude transformers is significantly limited, and the piezoelectric actuators may even burn out, thereby reducing the machining accuracy and stability of the broaching machine. Therefore, this application aims to provide a vertical ultrasonic broaching machine and its adjustment method, which can meet the requirements for stable amplitude under high loads, avoid damage to the piezoelectric ceramics, and ensure the machining accuracy and efficiency of the entire ultrasonic broaching machine. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a vertical ultrasonic broaching machine and its assembly and debugging method. This broaching machine and its debugging method can ensure that the piezoelectric ceramic is not damaged, while providing a stable output amplitude, significantly improving the accuracy and efficiency of processing.

[0006] The technical solution of this invention is:

[0007] The present invention first provides a vertical ultrasonic broaching machine, including a machine tool body and an ultrasonic auxiliary device. The ultrasonic auxiliary device includes a fixed plate, on which an ultrasonic vibration mechanism is provided. The ultrasonic vibration mechanism includes an ultrasonic vibration amplitude transformer, a cylinder, a limiting block, a washer, a gasket, a piezoelectric actuator, and an ultrasonic power supply.

[0008] The ultrasonic vibration amplitude transformer has a stepped protrusion in the middle, with the input end and output end on both sides of the stepped protrusion. The input end of the ultrasonic vibration amplitude transformer extends into the cylinder, and the fixing bolt passes through the stepped protrusion and the cylinder and is fixedly connected to the fixing plate.

[0009] A limiting block is provided at the connection between the stepped protrusion and the cylinder, and the limiting block is used to adjust the contact pressure between the stepped protrusion and the end face of the cylinder.

[0010] A gasket is provided between the input end of the ultrasonic vibration amplitude transformer and the fixed plate; a piezoelectric actuator is provided inside the cylinder, the piezoelectric actuator is connected to the ultrasonic power supply, and the piezoelectric actuator is ring-shaped and sleeved on the outside of the input end of the ultrasonic vibration amplitude transformer; a washer is provided between the piezoelectric actuator and the gasket.

[0011] Furthermore, the machine tool body includes a base, a bed, a lead screw, a worktable, a tool clamping system, a broach, and a clamping device. The bed is mounted on the base, the lower end of the lead screw is connected to the base, and one end of the lead screw is connected to a motor arranged inside the bed. A worktable is mounted on the lead screw; when the motor drives the lead screw to rotate, it can drive the worktable to move up and down. The worktable is used to fix and mount the workpiece to be processed.

[0012] Furthermore, a support frame is provided on the bed, and a tool clamping system is installed on the support frame; the upper end of the pull cutter is movably connected to the tool clamping system, and the lower end of the pull cutter passes through the worktable and is connected to the clamping device below; one end of the ultrasonic auxiliary device is connected to the clamping device, and the other end of the ultrasonic auxiliary device is connected to the base.

[0013] Furthermore, the base is equipped with three sets of ultrasonic auxiliary devices, which are arranged in an equilateral triangle on the base.

[0014] Furthermore, the axis of the ultrasonic vibration amplitude transformer in all three ultrasonic-assisted devices is located at the vertex of an equilateral triangle.

[0015] Furthermore, the output end of the ultrasonic vibration amplitude transformer is connected to the vibration plate, which is connected to the resonance plate. The vibration plate transmits the vibration of the ultrasonic vibration amplitude transformer to the resonance plate, causing the resonance plate to generate stable axial vibration.

[0016] Furthermore, the gasket is cylindrical and can be made of brass. The contact pressure between the ultrasonic vibration amplitude rod and the fixed plate can be adjusted by selecting and installing gaskets of different thicknesses.

[0017] Furthermore, the inner diameter of the washer is adapted to the diameter of the input end of the ultrasonic vibration amplitude transformer, and the outer diameter is the same as the outer diameter of the gasket. The washer can adopt a stacked structure of rubber and high manganese steel.

[0018] Furthermore, the total length of the washer, gasket, and input end of the ultrasonic vibration amplitude transformer is adapted to the length of the cylinder; preferably, during initial assembly, the total length of the washer, gasket, and input end of the ultrasonic vibration amplitude transformer is kept equal to the length of the cylinder to facilitate subsequent adjustment of the thickness of the washer and gasket.

[0019] Furthermore, the limiting block can be a nut, and mounting holes that mate with fixing bolts are provided on the stepped protrusions of the cylinder and the ultrasonic vibration amplitude transformer. The fixing bolt passes through the mounting holes on the stepped protrusions, the limiting block, and the mounting holes on the cylinder in sequence and is connected to the fixing plate. The limiting block can rotate on the fixing bolt to change its position. When the limiting block moves away from the fixing plate, the limiting block can bear more pressure from the ultrasonic vibration amplitude transformer, thereby reducing the pressure exerted by the stepped protrusions of the ultrasonic vibration amplitude transformer on the cylinder.

[0020] Furthermore, the ultrasonic vibration amplitude transformer is a one-dimensional axial vibration amplitude transformer. The output end is the peak position of the ultrasonic vibration amplitude transformer. The output end is conical to meet the high bending moment stiffness requirements and is used to amplify the ultrasonic vibration amplitude and vibration velocity. The stepped protrusion of the ultrasonic vibration amplitude transformer is the mode node of the ultrasonic vibration amplitude transformer, and its vibration amplitude is 0, so as to avoid the ultrasonic vibration being transmitted to the machine tool and reduce the loss of ultrasonic energy.

[0021] Furthermore, the piezoelectric actuator uses piezoelectric ceramics, and the ultrasonic power supply can convert industrial electricity (220V) into ultrasonic frequency power. Under the action of the ultrasonic power supply, the piezoelectric actuator will generate reciprocating periodic vibration, which in turn excites the ultrasonic vibration amplitude transformer to vibrate.

[0022] This invention also provides a specific debugging method for the aforementioned vertical ultrasonic broaching machine, which includes the following steps:

[0023] S1. Calculate the critical strain value of the piezoelectric actuator.

[0024] A strain monitoring system is installed at the input end of the ultrasonic vibration amplitude transformer. The strain monitoring system includes a strain gauge, a charge amplifier, data acquisition and analysis software, and a computer. The strain acquired by the strain monitoring system is denoted as ε. x Then, calculate according to the following formula:

[0025] σ x =Eεx (1)

[0026] Where σ x The stress is at the vertical cross section, and E is the elastic modulus, which is determined by the physical properties of the material (it can be directly looked up or obtained through measurement experiments, for example, the elastic modulus of stainless steel is 200 GPa).

[0027] F x =σ x A, (2)

[0028] Where F x Let ε be the preload of the piezoelectric actuator, and A be the cross-sectional area of ​​the piezoelectric actuator. The preload of the piezoelectric actuator is adjusted by successively increasing the thickness of the washers until the critical strain value at which the piezoelectric actuator burns out is obtained, denoted as ε. max At the same time, the value of the critical preload is also obtained.

[0029] S2, Preliminary assembly and debugging

[0030] First, install the ultrasonic vibration mechanism according to standard dimensions, i.e., the sum of the lengths of the washers, gaskets, and the input end of the ultrasonic vibration amplitude transformer is the same as the length of the cylinder. Apply a specific pressure load to the output end of the ultrasonic vibration amplitude transformer, and place strain gauges at the center of the washers, gaskets, and the input end of the ultrasonic vibration amplitude transformer. Record the measured strains as ε1, ε2, and ε3, respectively. To avoid excessive preload of the piezoelectric actuator, it is necessary to ensure that the values ​​of ε1, ε2, and ε3 are all less than the ε obtained in step S1. max The value of .

[0031] The values ​​of ε1, ε2, and ε3 can be adjusted using one or more of the following methods:

[0032] 1) Adjust the position of the limiting block. Adjusting the limiting block upwards can transfer the pressure load to the fixing bolt; reduce the preload at the input end of the ultrasonic vibration amplitude transformer, thereby reducing the corresponding strain value; conversely, adjusting it downwards will increase the corresponding strain value.

[0033] 2) Reducing the shim thickness will reduce the preload between the piezoelectric actuator, the amplitude transformer, and the washer, thereby reducing the corresponding strain value; conversely, reducing the shim thickness will increase the preload, thereby increasing the corresponding strain value.

[0034] 3) Reducing the thickness of the gasket will reduce the preload between the piezoelectric actuator, the amplitude transformer, and the gasket, thereby reducing the corresponding strain value; conversely, it will increase the preload, thereby increasing the corresponding strain value.

[0035] S3, Test

[0036] Start the ultrasonic vibration mechanism and measure the vibration amplitude and frequency at the output end of the ultrasonic vibration amplifier using a Doppler laser vibrometer. Adjust the mechanism based on the measurement results.

[0037] 1) If the vibration amplitude already meets the pre-designed parameter requirements, no adjustment is needed;

[0038] 2) If the vibration amplitude does not meet the pre-designed parameter requirements, the vibration amplitude can be adjusted to meet the design requirements by adjusting the position of the limit block or the thickness of the shim.

[0039] Furthermore, in step S3, if the vibration amplitude does not meet the pre-designed parameter requirements and the vibration amplitude is less than 20% of the target vibration amplitude, the limiting block is first moved upward to transfer the load to the fixing bolt so that the ultrasonic vibration amplitude is not less than 80% of the design value; then the thickness of the shim is adjusted to make the vibration amplitude meet the design requirements.

[0040] The principle of debugging in this invention is as follows: Since the stepped protrusion of the ultrasonic vibration amplitude transformer is located at the node of the ultrasonic vibration amplitude transformer's vibration mode, its vibration amplitude is very small under the excitation of the piezoelectric actuator. Adjusting the position of the limiting block between the stepped protrusion and the cylinder can adjust the contact pressure between the stepped protrusion of the ultrasonic vibration amplitude transformer and the cylinder. Specifically, adjusting the limiting block upwards (away from the cylinder) can transfer the pressure load to the fixing bolt, thereby reducing the squeezing force of the ultrasonic vibration amplitude transformer on the gasket, washer, and piezoelectric actuator in the cylinder. Reducing the thickness of the gasket will reduce the preload between the piezoelectric actuator, ultrasonic vibration amplitude transformer, and washer; conversely, it will increase the preload. Reducing the thickness of the washer will also reduce the preload between the piezoelectric actuator, amplitude transformer, and washer; conversely, it will increase the preload.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: The vertical ultrasonic broaching machine of the present invention can avoid the piezoelectric actuator from being burned out due to excessive preload by comprehensively adjusting the thickness of the washers and shims as well as the position of the limiting block. It also solves the problem that excessive pressure at the connection between the ultrasonic vibration amplitude rod and the piezoelectric actuator leads to a small amplitude and frequency of piezoelectric actuator excitation. Attached Figure Description

[0042] Figure 1 This is a three-dimensional schematic diagram of the ultrasound-assisted device in Embodiment 1 of the present invention;

[0043] Figure 2 This is a side view of the ultrasound-assisted device in Embodiment 1 of the present invention;

[0044] Figure 3 This is a cross-sectional view of the ultrasound-assisted device in Embodiment 1 of the present invention;

[0045] Figure 4This is a three-dimensional schematic diagram of the ultrasonic vibration amplitude transformer in Embodiment 1 of the present invention;

[0046] Figure 5 This is a cross-sectional view of the ultrasonic vibration amplitude transformer in Embodiment 1 of the present invention;

[0047] Figure 6 This is an overall exploded view of the ultrasonic-assisted device in Embodiment 1 of the present invention;

[0048] Figure 7 This is a schematic diagram of the assembly of the ultrasonic-assisted device on the broaching machine in Embodiment 1 of the present invention;

[0049] In the diagram: 1-fixed plate, 2-ultrasonic vibration amplitude rod, 21-step protrusion, 22-input end, 23-output end, 24-mounting hole, 3-cylinder, 4-shim, 5-washer, 6-piezoelectric actuator, 7-limit block, 8-fixing bolt, 9-base, 10-vibration plate. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below in conjunction with the accompanying drawings and specific embodiments. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. The structures, proportions, sizes, etc., illustrated in the accompanying drawings are only for illustrative purposes and to enable those skilled in the art to understand and read the invention; they are not intended to limit the conditions under which the invention can be implemented and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts in this invention.

[0051] Example 1

[0052] like Figure 1-7As shown, the vertical ultrasonic broaching machine in this embodiment includes a machine body and an ultrasonic auxiliary device. The ultrasonic auxiliary device includes a fixed plate 1, on which an ultrasonic vibration mechanism is mounted. The ultrasonic vibration mechanism includes an ultrasonic vibration amplitude transformer 2, a cylinder 3, a limiting block 7, a washer 5, a gasket 4, a piezoelectric actuator 6, and an ultrasonic power supply. A stepped protrusion 21 is provided in the middle of the ultrasonic vibration amplitude transformer 2. The two sides of the stepped protrusion 21 are an input end 22 and an output end 23, respectively. The input end 22 of the ultrasonic vibration amplitude transformer 2 extends into the cylinder 3, and the fixing bolt 8 passes through the stepped protrusion. The protrusion 21 and the cylinder 3 are then fixedly connected to the fixing plate 1; a limiting block 7 is provided at the connection between the stepped protrusion 21 and the cylinder 3, and the limiting block 7 is used to adjust the contact pressure between the stepped protrusion 21 and the end face of the cylinder 3; a gasket 4 is provided between the input end 22 of the ultrasonic vibration amplitude rod 2 and the fixing plate 1; a piezoelectric actuator 6 is provided inside the cylinder 3, the piezoelectric actuator 6 is connected to the ultrasonic power supply, and the piezoelectric actuator 6 is annular and sleeved on the outside of the input end 22 of the ultrasonic vibration amplitude rod 2; a washer 5 is provided between the piezoelectric actuator 6 and the gasket 4.

[0053] In this embodiment, the machine tool body includes a base 9, a bed, a lead screw, a worktable, a tool clamping system, a broach, and a clamping device. The bed is mounted on the base 9. The lower end of the lead screw is connected to the base 9, and one end of the lead screw is connected to a motor arranged inside the bed. The worktable is mounted on the lead screw. When the motor drives the lead screw to rotate, it can drive the worktable to move up and down. The worktable is used to fix the workpiece to be processed. A bracket is mounted on the bed, and the tool clamping system is mounted on the bracket. The upper end of the broach is movably connected to the tool clamping system, and the lower end of the broach passes through the worktable and is connected to the clamping device below. One end of the ultrasonic auxiliary device is connected to the clamping device, and the other end of the ultrasonic auxiliary device is connected to the base 9.

[0054] In this embodiment, three sets of ultrasonic auxiliary devices are mounted on the base 9, and these three sets of ultrasonic auxiliary devices are arranged in an equilateral triangle on the base 9. The axis of the ultrasonic vibration amplitude transformer 2 in the three sets of ultrasonic auxiliary devices is located at the vertex of the equilateral triangle. The output end 23 of the ultrasonic vibration amplitude transformer 2 is connected to a vibrating plate, which is connected to a resonant plate. The vibrating plate transmits the vibration of the ultrasonic vibration amplitude transformer 2 to the resonant plate, causing the resonant plate to generate stable axial vibration.

[0055] In this embodiment, the limiting block 7 can be a nut. Mounting holes 24 for the fixing bolt 8 are provided on the stepped protrusion 21 of the cylinder 3 and the ultrasonic vibration amplitude transformer 2. The fixing bolt 8 passes through the mounting holes 24 on the stepped protrusion 21, the limiting block 7, and the cylinder 3 in sequence before connecting to the fixing plate 1. The limiting block 7 can rotate on the fixing bolt 8 to change its position. When the limiting block 7 moves away from the fixing plate 1, it can bear more pressure from the ultrasonic vibration amplitude transformer 2, thereby reducing the pressure exerted by the stepped protrusion 21 of the ultrasonic vibration amplitude transformer 2 on the cylinder 3.

[0056] In this embodiment, the gasket 4 is cylindrical and made of brass. The contact pressure between the ultrasonic vibration amplitude rod 2 and the fixed plate 1 can be adjusted by selecting gaskets 4 of different thicknesses. The washer 5 is a stacked structure of rubber and high manganese steel. The inner diameter of the washer 5 is adapted to the diameter of the input end 22 of the ultrasonic vibration amplitude rod 2, and the outer diameter is the same as the outer diameter of the gasket 4.

[0057] In this embodiment, the total length of the washer 5, the gasket 4, and the input end 22 of the ultrasonic vibration amplitude transformer 2 is adapted to the length of the cylinder 3. Specifically, during the initial assembly, the total length of the washer 5, the gasket 4, and the input end 22 of the ultrasonic vibration amplitude transformer 2 is selected to be equal to the length of the cylinder 3, so that the thickness of the washer 5 and the gasket 4 can be adjusted later according to the actual situation.

[0058] In this embodiment, the ultrasonic vibration amplitude transformer 2 is a one-dimensional axial vibration amplitude transformer. The output end 23 is the peak position of the mode shape of the ultrasonic vibration amplitude transformer 2. The output end 23 is conical to meet the high bending moment stiffness requirements and is used to amplify the ultrasonic vibration amplitude and vibration velocity. The step protrusion 21 of the ultrasonic vibration amplitude transformer 2 is the mode shape node of the ultrasonic vibration amplitude transformer 2, and its vibration amplitude is 0, so as to avoid the ultrasonic vibration being transmitted to the machine tool and reduce the loss of ultrasonic energy.

[0059] In this embodiment, the piezoelectric actuator 6 uses piezoelectric ceramics. The ultrasonic power supply can convert industrial electricity (220V) into ultrasonic frequency power. Under the action of the ultrasonic power supply, the piezoelectric actuator 6 will generate reciprocating periodic vibration, which in turn excites the ultrasonic vibration amplitude rod 2 to vibrate.

[0060] The debugging method of the present invention will be described in detail below.

[0061] The principle of the adjustment is as follows: Since the stepped protrusion of the ultrasonic vibration amplitude transformer is located at the node of the vibration mode, its vibration amplitude is very small under the excitation of the piezoelectric actuator. Adjusting the position of the limiting block between the stepped protrusion and the cylinder can adjust the contact pressure between the stepped protrusion of the ultrasonic vibration amplitude transformer and the cylinder. Specifically, adjusting the limiting block upwards (away from the cylinder) can transfer the pressure load to the fixing bolt, thereby reducing the squeezing force of the ultrasonic vibration amplitude transformer on the gasket, washer, and piezoelectric actuator in the cylinder. Reducing the thickness of the gasket will reduce the preload between the piezoelectric actuator, ultrasonic vibration amplitude transformer, and washer; conversely, it will increase the preload. Reducing the thickness of the washer will also reduce the preload between the piezoelectric actuator, amplitude transformer, and washer; conversely, it will increase the preload.

[0062] Assuming the target broaching machine has a cutting (pressure) load of 20 tons, then each of the three ultrasonic-assisted devices receives a pressure load of one-third of 20 tons, which is 6.67 tons.

[0063] S1. First, calculate the critical strain value when the piezoelectric actuator (piezoelectric ceramic) burns out. This can be obtained through a preload test of the piezoelectric actuator, i.e., conduct experiments on ultrasonic power supply-excited piezoelectric actuators under different preloads. Assume that the piezoelectric actuator mounted on the ultrasonic vibration amplitude transformer has an inner diameter of 30mm, an outer diameter of 60mm, and a thickness of 10mm.

[0064] Considering the impact of the broaching process, the pressure load at the output end of the ultrasonic vibration amplitude transformer will be greater than 6.67 tons. Therefore, a pressure load of 7 tons (70 kN) can be input at the output end of the ultrasonic vibration amplitude transformer. Then, the thickness of the washer is adjusted to change the preload. The preload is identified by a strain monitoring system bonded to the input end of the ultrasonic vibration amplitude transformer. This strain monitoring system can consist of strain gauges, charge amplifiers, Donghua data acquisition and analysis software, and a computer. The strain acquired by the strain monitoring system is denoted as ε. x Then, calculate according to the following formula:

[0065] σ x =Eε x (1)

[0066] Where σ x The stress is the vertical cross-section, and E is the elastic modulus, determined by the material's physical properties (which can be directly looked up or measured; for example, the elastic modulus of stainless steel is 200 GPa, or 2 × 10⁻⁶ GPa). 11 Pa);

[0067] F x =σ x A, (2)

[0068] F xHere, A represents the preload force of the piezoelectric actuator, and A is the annular cross-sectional area of ​​the piezoelectric actuator, which is calculated to be 0.00212 square meters, or 2.12 × 10⁻⁶. -3 m 2 .

[0069] The preload of the piezoelectric actuator can be changed by successively increasing the thickness of the gasket. For example, using a strain monitoring system, experiments can be conducted with preloads of 0.5KN, 1KN, 2KN, 4KN, 8KN, 16KN, 32KN, and 64KN. Ultimately, the critical strain value at which the piezoelectric actuator burns out can be obtained, denoted as ε. max Of course, the value of the critical preload will also be obtained at the same time.

[0070] S2. First, install the ultrasonic vibration mechanism according to the standard dimensions, so that the sum of the lengths of the washer, shim, and input end of the ultrasonic vibration amplitude transformer is the same as the length of the cylinder. For example, set the length (thickness) of the washer to L1, the length (thickness) of the shim to l2, the length of the input end of the ultrasonic vibration amplitude transformer to l3, and the length (height) of the cylinder to L4, then: L4=L1+L2+L3.

[0071] A load of 6.67 tons (66 kN) is applied to the output end of the ultrasonic vibration amplitude transformer. Strain gauges are placed at the center of the washer, gasket, and the input end of the ultrasonic vibration amplitude transformer, and the measured strains are denoted as ε1, ε2, and ε3, respectively. To avoid excessive preload of the piezoelectric actuator, the values ​​of ε1, ε2, and ε3 must all be lower than the critical value ε. max Therefore, the preload can be reduced by decreasing the length (thickness) of the washer, thereby reducing the values ​​of ε1, ε2, and ε3.

[0072] S3. Start the ultrasonic vibration mechanism and measure the vibration amplitude and frequency at the output end of the ultrasonic vibration amplitude transformer using a Doppler laser vibrometer. Adjust the mechanism based on the measurement results.

[0073] 1) If the vibration amplitude already meets the pre-designed parameter requirements, no adjustment is needed;

[0074] 2) If the vibration amplitude does not meet the pre-designed parameter requirements, the vibration amplitude can be adjusted to meet the design requirements by adjusting the position of the limiting block or the thickness of the shim. More specifically, if the vibration amplitude is less than 20% of the target vibration amplitude, the limiting block can be moved upward first to transfer the load to the fixing bolt so that the ultrasonic vibration amplitude is not less than 80% of the design value. Then, the vibration amplitude can be adjusted to meet the design requirements by adjusting the thickness of the shim.

[0075] The above are only some embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various combinations and modifications of the aforementioned technical features. Any improvements, modifications, equivalent substitutions, or applications of the structure or method of the present invention to other fields to achieve the same effect without departing from the spirit and scope of the present invention shall fall within the protection scope of the present invention.

Claims

1. A vertical ultrasonic broaching machine, comprising a machine tool body, characterized in that, It also includes an ultrasonic auxiliary device, which includes a fixing plate and an ultrasonic vibration mechanism is provided on the fixing plate; The ultrasonic vibration mechanism includes an ultrasonic vibration amplitude transformer, a cylinder, a limiting block, a washer, a gasket, a piezoelectric actuator, and an ultrasonic power supply. The ultrasonic vibration amplitude transformer has a stepped protrusion in the middle, with the input end and output end on both sides of the stepped protrusion. The input end of the ultrasonic vibration amplitude transformer extends into the cylinder, and the fixing bolt passes through the stepped protrusion and the cylinder and is fixedly connected to the fixing plate. A limiting block is provided at the connection between the stepped protrusion and the cylinder, and the limiting block is used to adjust the contact pressure between the stepped protrusion and the end face of the cylinder. A gasket is provided between the input end of the ultrasonic vibration amplitude transformer and the fixed plate; A piezoelectric actuator is installed inside the cylinder. The piezoelectric actuator is connected to the ultrasonic power supply and is ring-shaped, and is sleeved on the outside of the input end of the ultrasonic vibration amplitude transformer. A washer is provided between the piezoelectric actuator and the gasket; The machine tool body includes a base, a bed, a lead screw, a worktable, a tool clamping system, a broach, and a clamping device. The bed is mounted on the base. The lower end of the lead screw is connected to the base and to a motor arranged inside the bed. The worktable is mounted on the lead screw. The motor drives the lead screw to rotate, thereby causing the worktable to move up and down. A bracket is mounted on the bed, and the tool clamping system is mounted on the bracket. The upper end of the broach is movably connected to the tool clamping system, and the lower end of the broach passes through the worktable and is connected to the clamping device. One end of the ultrasonic auxiliary device is connected to the clamping device, and the other end of the ultrasonic auxiliary device is connected to the base.

2. The vertical ultrasonic broaching machine according to claim 1, characterized in that: The base is equipped with three sets of ultrasonic auxiliary devices, which are arranged in an equilateral triangle on the base.

3. The vertical ultrasonic broaching machine according to claim 2, characterized in that: The axes of the ultrasonic vibration amplitude transformers in the ultrasonic auxiliary device are all located at the vertices of an equilateral triangle.

4. The vertical ultrasonic broaching machine according to claim 1, characterized in that: The output end of the ultrasonic vibration amplitude transformer is connected to the vibration plate, and the vibration plate is connected to the resonance plate. The vibration plate transmits the vibration of the ultrasonic vibration amplitude transformer to the resonance plate, so that the resonance plate generates stable axial vibration.

5. The vertical ultrasonic stretching bed according to claim 1, characterized in that: The gasket is cylindrical, and the contact pressure between the ultrasonic vibration amplitude transformer and the fixed plate can be adjusted by selecting gaskets of different thicknesses; the inner diameter of the washer is adapted to the diameter of the input end of the ultrasonic vibration amplitude transformer, and the outer diameter is the same as the outer diameter of the gasket; the total length of the washer, the gasket and the input end of the ultrasonic vibration amplitude transformer is adapted to the length of the cylinder.

6. The vertical ultrasonic broaching machine according to claim 1, characterized in that: The ultrasonic vibration amplitude transformer is a one-dimensional axial vibration amplitude transformer. The output end is the peak position of the ultrasonic vibration amplitude transformer. The output end is conical to meet the high bending moment stiffness requirements and is used to amplify the ultrasonic vibration amplitude and vibration velocity. The stepped protrusion of the ultrasonic vibration amplitude transformer is the mode node of the ultrasonic vibration amplitude transformer, and its vibration amplitude is 0 to avoid the ultrasonic vibration being transmitted to the machine tool and reduce ultrasonic energy loss.

7. The vertical ultrasonic broaching machine according to claim 1, characterized in that: The piezoelectric actuator uses piezoelectric ceramics. Under the action of the ultrasonic power supply, the piezoelectric actuator generates high-frequency vibration, which excites the ultrasonic vibration amplitude transformer to generate high-frequency vibration.

8. A method for assembling and debugging a vertical ultrasonic broaching machine, wherein the vertical ultrasonic broaching machine is the broaching machine according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Calculate the critical strain value of the piezoelectric actuator. A strain monitoring system is installed at the input end of the ultrasonic vibration amplitude transformer. The strain monitoring system includes strain gauges, a charge amplifier, data acquisition and analysis software, and a computer. The strain acquired by the strain monitoring system is recorded as... Then, calculate according to the following formula: ， （1） In the formula The stress is at the vertical cross section. It is the elastic modulus, determined by the physical properties of the material; ， （2） In the formula Let A be the preload of the piezoelectric actuator, and A be the annular cross-sectional area of ​​the piezoelectric actuator. The preload of the piezoelectric actuator is adjusted by successively increasing the thickness of the washers, yielding the critical strain value at which the piezoelectric actuator burns out, denoted as […]. At the same time, the value of the critical preload is also obtained; S2, Preliminary assembly and debugging Install the ultrasonic vibration mechanism according to standard dimensions, ensuring the sum of the lengths of the washers, gaskets, and the input end of the ultrasonic vibration amplifier is the same as the length of the cylinder. Apply a pressure load to the output end of the ultrasonic vibration amplifier, and place strain gauges at the center of the washers, gaskets, and the input end of the ultrasonic vibration amplifier. Record the measured strains as follows: , , To avoid excessive preload in the piezoelectric actuator, it is necessary to ensure... , , The values ​​are all less than those obtained in step S1. The value; Adjust using one or more of the following methods: 1) Adjust the position of the limiting block upwards to transfer the pressure load to the fixing bolt; reduce the preload at the input end of the ultrasonic vibration amplitude transformer, thereby reducing the corresponding strain value; conversely, it will increase the corresponding strain value. 2) Reducing the thickness of the gasket will reduce the preload between the piezoelectric actuator, the amplitude transformer, and the washer, thereby reducing the corresponding strain value; conversely, reducing the thickness will increase the preload, thereby increasing the corresponding strain value. 3) Reducing the thickness of the gasket will reduce the preload between the piezoelectric actuator, the amplitude transformer, and the gasket, thereby reducing the corresponding strain value; conversely, it will increase the preload, thereby increasing the corresponding strain value. S3, Test The ultrasonic vibration mechanism is activated, and the vibration amplitude at the output end of the ultrasonic vibration amplitude transformer is measured using a Doppler laser vibrometer. The measurement results are then processed. 1) If the vibration amplitude already meets the pre-designed parameter requirements, no adjustment is needed; 2) If the vibration amplitude does not meet the pre-designed parameter requirements, the vibration amplitude can be adjusted to meet the design requirements by adjusting the position of the limit block or the thickness of the shim.

9. The assembly and debugging method of the vertical ultrasonic broaching machine according to claim 8, characterized in that: In step S3, if the measured vibration amplitude is less than 20% of the target vibration amplitude, the limiting block is first moved upward to transfer the pressure load to the fixing bolt, thereby ensuring that the ultrasonic vibration amplitude is not less than 80% of the design value; then the thickness of the shim is adjusted to ensure that the vibration amplitude meets the design requirements.

Images