CN112974871B - Ultrasonic amplitude transformer numerical control correction structure considering local structure and correction method thereof - Google Patents

Abstract

An ultrasonic amplitude transformer numerical control correction structure considering a local structure and a correction method thereof are provided, the numerical control correction structure is suitable for a numerical control lathe and comprises an acoustic vibration component, a special fixture, a conductive slip ring, an impedance analyzer and a PC end, the acoustic vibration component is fixed on a three-jaw chuck through the special fixture, the conductive slip ring is arranged on a left end hollow main shaft of the numerical control lathe, the impedance analyzer is connected with an ultrasonic transducer through the conductive slip ring, the PC end is connected with the impedance analyzer and a numerical control system of the numerical control lathe, the disassembly-free correction of the acoustic vibration component is realized by clamping a flange of the ultrasonic transducer for fixing, the acoustic performance parameters are detected in real time through the use of the conductive slip ring, the influence of the local structure is considered, the precision of a correction model is greatly improved, the correction size calculated by the correction model is corrected, not only the resonance frequency is corrected, but also a displacement node is corrected, not only can independently correct the ultrasonic horn, but also is applicable to the ultrasonic horn with a tool head.

Description

A Numerically Controlled Correction Structure of Ultrasonic Amplifier Considering Local Structure and Its Correction Method

technical field

The invention belongs to the technical field of ultrasonic machining, and in particular relates to an ultrasonic horn numerically controlled correction structure and a correction method thereof considering local structures.

Background technique

Nomex honeycomb composite material is an important material in the fields of aviation, aerospace and missile manufacturing. It has the characteristics of light weight, low density, high specific strength, good self-extinguishing property, excellent insulating properties and chemical properties. The traditional processing method makes the honeycomb of NOMEX honeycomb have quality defects such as deformation, collapse, tearing and pulling. In view of the many problems existing in the traditional processing of Nomex honeycomb, an ultrasonic-assisted cutting technology that integrates ultrasonic machining technology and CNC machining technology emerges. It perfectly solves these problems.

Ultrasonic machining systems generally consist of ultrasonic generators and acoustic vibration components (transducers, horns, tool heads). In the whole ultrasonic machining system, the ultrasonic power supply provides high-frequency electrical energy, which is converted into high-frequency mechanical vibration by the transducer and transmitted to the horn to amplify the amplitude, and the large-amplitude tool head processes the material. In practical applications, due to the influence of assembly, local structure, material inhomogeneity and Poisson effect, the actual resonant frequency of the theoretically designed ultrasonic horn is much lower than the working frequency, and the displacement nodes deviate from the flange, resulting in power mismatch, method The vibration of the flange is too large, and the amplitude of the tool head does not meet the requirements. In order to make the performance parameters of the manufactured ultrasonic horn meet the design requirements, the structural dimensions of the ultrasonic horn are generally revised.

The traditional ultrasonic horn correction method is corrected by the trial repair method, which requires multiple clamping to realize the processing of the front and rear ends of the ultrasonic horn, and requires many trial cuts and inspections to meet the design requirements. During the trial repair process, it is necessary to continuously install and disassemble the ultrasonic horn for processing and testing, the correction efficiency is low, and the accuracy is low. The nodes are deviated and the vibration at the flange is too large.

SUMMARY OF THE INVENTION

In view of the above deficiencies, the technical problem to be solved by the present invention is to provide an ultrasonic horn numerically controlled correction structure and its correction method considering the local structure, which are used to solve the large error between the resonance frequency of the ultrasonic horn and the design value, and the displacement node deviation method. Blue position, and the resulting acoustic vibration components can not work properly. A numerically controlled correction method for ultrasonic horns considering the local structure is proposed, which can not only correct the resonance frequency but also correct the position of the flange node.

In order to solve the above technical problems, the technical scheme adopted in the present invention is,

An ultrasonic horn numerical control correction structure considering the local structure, the numerical control correction structure is suitable for numerical control lathes, and includes an acoustic vibration component, a special fixture, a conductive slip ring, an impedance analyzer and a PC terminal, and the acoustic vibration component is fixed by a special fixture On the three-jaw chuck of the CNC lathe, the conductive slip ring is installed on the hollow spindle at the left end of the CNC lathe, the impedance analyzer is connected to the ultrasonic transducer through the conductive slip ring, and the PC end is connected to the impedance analyzer and the CNC system of the CNC lathe.

Further, the acoustic vibration component includes an ultrasonic transducer and an ultrasonic horn, the ultrasonic horn is installed on the ultrasonic transducer, and the conductive slip ring is installed on the hollow spindle at the left end of the CNC lathe, so that the impedance analyzer passes through the conductive slip ring. Obtain the resonant frequency of the ultrasonic horn.

Further, the ultrasonic horn includes a horn main body, a connecting screw and a tool head, and the connecting screw and the tool head are respectively fixed and connected on both side end surfaces of the horn main body.

The above-mentioned correction method for the numerical control correction structure of the ultrasonic horn considering the local structure includes the following steps:

(1) Assemble the acoustic vibration components;

(2) Fix the acoustic vibration component on the three-jaw chuck of the CNC lathe through a special fixture;

(3) Install the conductive slip ring, and connect the impedance analyzer to the ultrasonic transducer through the conductive slip ring;

(4) The PC-side controlled impedance analyzer realizes the measurement of the resonant frequency, calculates the correction margin according to the obtained measurement value and generates the correction program;

(5) The PC terminal transmits the numerical control programming to the numerical control system of the numerical control lathe to realize the correction of the allowance.

Further, step (4) includes a correction method without a tool head and a correction method with a tool head.

Further, the toolless head correction method includes the following steps,

(4.1.1) Effectively connect the ultrasonic horn without the tool head to the ultrasonic transducer, obtain the resonance frequency of the ultrasonic horn through the impedance analyzer, and calculate the actual equivalent sound speed through the frequency equation of the horn. model, obtain the equivalent sound speed, and correct the sound speed;

(4.1.2) Substitute the equivalent sound speed into the performance parameter calculation model, establish a correction model, take the constant magnification as the objective function, and take the target resonant frequency and node position as the constraints, and determine the modified geometric size through the SQP optimization algorithm;

(4.1.3) Carry out numerical control programming and import it into the numerical control machine tool, carry out allowance processing, and realize the correction of the performance parameters of the horn.

Further, the tool head correction method includes the following steps,

(4.2.1) First measure the resonant frequency without the tool head installed, record the resonant frequency 1, then obtain the equivalent sound speed to correct the sound speed; then connect the tool head, measure the resonant frequency 2, and compare the resonant frequency 2 with the equivalent sound speed The sound velocity is substituted into the resonance frequency equation of the tool head to determine the equivalent radius of the tool head;

(4.2.2) Substitute the equivalent sound velocity and the equivalent radius of the tool head into the mechanical four-terminal network model, determine the performance parameter calculation model, and establish a correction model. The midpoint of the blue is a constraint, and the trimming geometric size is determined by the SQP optimization algorithm;

(4.2.3) Remove the tool head, carry out numerical control programming and import it into the numerical control machine tool, realize the machining of allowances, and realize the correction of the performance parameters of the horn.

Further, the SQP optimization algorithm is established by using the calculation model of the ultrasonic horn. The objective function is to take the minimum difference before and after the magnification correction as the objective function, the resonant frequency as the target frequency, and the displacement node at the midpoint of the flange as the constraint condition.

Further, the parameter calculation model of the ultrasonic horn is:

Further, the target frequency F is substituted into:

Objective function:

Restrictions:

The beneficial effects of the present invention are that (1) by clamping the flange of the ultrasonic transducer to fix it, the disassembly-free correction of the acoustic vibration component is realized.

(2) Real-time detection of acoustic performance parameters is realized through the use of conductive slip rings.

(3) Considering the influence of local structure, the accuracy of the correction model is greatly improved.

(4) The corrected size calculated by the corrected model, not only the resonant frequency but also the displacement node is corrected.

(5) Not only can the ultrasonic horn be corrected alone, but also applicable to the ultrasonic horn with a tool head.

(6) Using the SQP optimization algorithm, the calculation speed and accuracy of the calculation model are greatly improved.

Description of drawings

Fig. 1 is a block diagram of the numerical control correction system of the ultrasonic horn of the present invention.

Fig. 2 is a flow chart of the correction system of the ultrasonic horn of the present invention.

FIG. 3 is a schematic diagram of a conical ultrasonic horn with a tool head considering the local structure of the present invention.

FIG. 4 is a model diagram of the equivalent sound velocity and the resonant frequency when the ultrasonic horn is removed from the tool head.

FIG. 5 is a model diagram of the equivalent radius and resonance frequency of the tool head when the ultrasonic horn is installed with the tool head.

Figure 6 is a model diagram of displacement nodes and magnifications of the present invention.

FIG. 7 is a partial cutaway view of FIG. 6 .

Detailed ways

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

As shown in FIG. 1 , a numerical control correction structure of ultrasonic horn considering the local structure, the numerical control correction structure is suitable for numerical control lathe 3, including acoustic vibration component 1, special fixture 2, conductive slip ring 4, impedance analyzer 5 and PC terminal 6, the acoustic vibration component 1 is fixed on the three-jaw chuck 9 of the CNC lathe through the special fixture 2, the conductive slip ring 4 is installed on the hollow spindle at the left end of the CNC lathe 3, and the impedance analyzer 5 is connected to the ultrasonic through the conductive slip ring 4. The transducer 8 and the PC terminal 6 are connected to the impedance analyzer 5 and the numerical control system 10 of the numerical control lathe.

The acoustic vibration assembly 1 includes an ultrasonic transducer 8 and an ultrasonic horn 7, the ultrasonic horn 7 is installed on the ultrasonic transducer 8, and the special fixture 2 clamps the acoustic vibration assembly 1 and is fixed on the three-jaw chuck of the CNC lathe 9, the conductive slip ring 4 is installed on the hollow spindle at the left end of the CNC lathe 3. Preferably, the conductive slip ring 4 is connected to the ultrasonic transducer 8 and the impedance analyzer 5, so that the impedance analyzer 5 obtains the ultrasonic transformer through the conductive slip ring 4. The resonant frequency of the horn 7.

As shown in FIG. 3 , the ultrasonic horn 7 includes a horn body 11 , a connecting screw 12 and a tool head 13 .

The above-mentioned correction method for the numerical control correction structure of the ultrasonic horn considering the local structure includes the following steps:

(1) Assemble the acoustic vibration components;

(2) Fix the acoustic vibration component on the three-jaw chuck of the CNC lathe through a special fixture;

(3) Install the conductive slip ring, and connect the impedance analyzer to the ultrasonic transducer through the conductive slip ring;

(4) The PC-side controlled impedance analyzer realizes the measurement of the resonant frequency, calculates the correction margin according to the obtained measurement value and generates the correction program;

(5) The PC terminal transmits the numerical control programming to the numerical control lathe system to realize the correction of the allowance.

Step (4) includes the correction method without the tool head and the correction method with the tool head.

As shown in Figure 2, the toolless head correction method includes the following steps,

(4.1.1) Effectively connect the ultrasonic horn without the tool head to the ultrasonic transducer, obtain the resonance frequency of the ultrasonic horn through the impedance analyzer, and calculate the actual equivalent sound speed through the frequency equation of the horn. model, obtain the equivalent sound speed, and correct the sound speed;

(4.1.2) Substitute the equivalent sound speed into the performance parameter calculation model, establish a correction model, take the constant magnification as the objective function, and take the target resonant frequency and node position as the constraints, and determine the modified geometric size through the SQP optimization algorithm;

(4.1.3) Carry out numerical control programming and import it into the numerical control machine tool, carry out allowance processing, and realize the correction of the performance parameters of the horn.

As shown in Figure 2, the tool head correction method includes the following steps:

(4.2.1) First measure the resonant frequency without the tool head installed, and after recording the resonant frequency 1, obtain the equivalent sound speed to correct the sound speed; then install the tool head, measure the resonant frequency 2, and compare the resonant frequency 2 with the equivalent sound speed. The sound velocity is substituted into the resonance frequency equation of the tool head to determine the equivalent radius of the tool head;

(4.2.2) Substitute the equivalent sound velocity and the equivalent radius of the tool head into the mechanical four-terminal network model, determine the performance parameter calculation model, and establish a correction model. The midpoint of the blue is a constraint, and the trimming geometric size is determined by the SQP optimization algorithm;

(4.2.3) Remove the tool head, carry out numerical control programming and import it into the numerical control machine tool, realize the machining of allowances, and realize the correction of the performance parameters of the horn.

As shown in FIGS. 4 and 5 , the model diagrams of the equivalent sound velocity, the equivalent tool radius and the resonant frequency provided by this embodiment. The connecting screw is regarded as a mass block, and it is equivalent to a small circle with the same diameter as the large end of the horn, and the mass remains unchanged before and after the equivalence; the part of the threaded hole is regarded as the end of the hollow section; Flanges will make the structure abrupt discontinuity, stress concentration, etc., which will make the theoretical calculation resonance frequency high, which can be ignored; the tool head is equivalent to a cylinder (the length is equal to the size of the tool head, and the diameter is obtained by the calculation model).

For the calculation of the equivalent sound speed of the horn, from the model diagram in Figure 4 and the structural dimensions of the ultrasonic horn, the four-terminal network and matrix transfer method can be used to write the expression of the resonant frequency 1 and the equivalent sound speed without the tool head installed , which is the value of the circular wave number. The equivalent sound speed can be calculated by _measuring the resonant frequency 1(f) with an impedance analyzer.

Four-terminal network and matrix transfer method:

In the formula: F ₁ and F ₂ are the forces at the beginning and end of the horn respectively; V ₁ and V ₂ are the velocities of the particles at the beginning and end of the horn respectively; A' is the network parameter matrix of the four ends of the horn in Fig. 4; A _i is the four-terminal network parameter matrix of each section of the horn in Fig. 4; .

Figure 4 Model circular wave number:

In the formula: r is all the radial dimensions of the horn in Figure 4; l is all the length dimensions of the horn in Figure 4.

Equivalent sound speed:

For the calculation of the equivalent radius of the tool head, from the model diagram in Figure 5 and the structure size of the ultrasonic horn, the four-terminal network and matrix transfer method can be used to write the expression of the resonant frequency 2 with the tool head and the equivalent radius of the tool head. The equivalent radius of the tool head can be calculated by _measuring the resonant frequency 2 (f') with an impedance analyzer.

Four-terminal network and matrix transfer method:

Figure 5 Model circular wave number:

Tool head equivalent radius:

At the same time, the expression of the resonance frequency of the ultrasonic horn can be obtained from Figure 5:

A ₁₂ (k ₁ ,r,l,x)=0

As shown in FIGS. 6 and 7 , the model diagrams of the displacement nodes and magnifications of the ultrasonic horn provided in this embodiment. The addition of the flange makes the theoretical value of the resonance frequency higher, but makes the displacement node closer to the actual value; the influence of the flange on the magnification is very small and can be ignored. During transmission, only half of the screws in the horn vibrate together with the horn, and the other half vibrate together with the transducer, so only half of the equivalent screw length is considered.

The calculation of the displacement node of the horn can be obtained from the model diagrams in Figures 6 and 7 and the structural dimensions of the ultrasonic horn using the four-terminal network and matrix transfer method. Because the displacement node is the point on the horn where the displacement or velocity is zero, it is generally taken in the flange section, so this embodiment takes the node in the flange section as an example for sampling calculation, so the thickness value on the flange is set as Object X is sampled from big endian to little endian.

Figure 6 Model circular wave number:

In the formula: B is the four-terminal network parameter matrix of the horn in Figure 6.

Since the displacement node is the point where the displacement is zero in the model diagram of Fig. 6, the model diagram shown in Fig. 7 is intercepted to calculate the displacement node.

Displacement node:

The magnification can be obtained by using the four-terminal network and matrix transfer method from the model diagram in Figure 6 and the structural dimensions of the ultrasonic horn.

gain:

The parameter calculation model of the solid ultrasonic horn is:

The establishment of the SQP correction model is based on the above-mentioned calculation model of the ultrasonic horn, and the objective function is to take the minimum difference before and after the magnification correction as the objective function, the resonant frequency as the target frequency, and the displacement node at the midpoint of the flange as the constraint. Substitute the target frequency into the resonance frequency equation to realize the resonance frequency constraint, and quantify the flange dimension X as L/2 to realize the node constraint. For the selection of the variable size of the horn, in order to realize the modification of the horn without dismantling, the variable size of the selected horn must satisfy the distance from the transducer on the right side of the flange to remain unchanged. For the right side of the flange, there is only a single shape In this example, the large end radius can be selected, and the left side length and small end radius can be selected in this example on the left side of the flange.

Substitute the target frequency F into:

Objective function:

Restrictions:

In the formula: r' is the radius size of the horn after correction; l' is the length of the horn after correction.

In NC programming, G73 can be used more widely for wavy lines. The object of the present invention is to correct the horn that is processed, so the required cutting amount is relatively small, and the G73 cycle processing method is adopted to reduce the processing and programming time. At the same time, for the surface of parts with complex functions, the programming method of macro program is used to improve the accuracy of machining allowance.

For the programmed text, DNC online processing can be realized by importing the control system of the numerical control machine tool through the communication software, which greatly improves the production efficiency.

For the ultrasonic horn correction without a tool head, the calculation of the equivalent radius of the tool head can be omitted.

The present invention carries out the correction example to the conical ultrasonic horn with tool head:

(1) Fix the transducer with flange on the special fixture for CNC machine tools, and connect the ultrasonic horn with a preload of 50N.M and lubricate it effectively;

(2) A conductive slip ring is arranged on the back side of the hollow spindle of the CNC machine tool to realize rotating conduction, and the positive and negative electrodes of the transducer are respectively connected with the positive and negative electrodes of the impedance analyzer through the conductive slip ring;

(3) Input the corresponding ultrasonic horn parameters and target frequency values in the correction software. Target frequency: 20000Hz Screw parameters: length 35mm, material 45 steel; tool length: length LD=37mm; ultrasonic horn parameters: material 45 steel, screw hole size: large end hole radius R3 = 6.35mm, large end hole Depth L1=20mm; small end hole radius R8=4.8mm, small end hole depth L4=20mm; flange size: flange radius R=30mm, flange thickness L=4mm; basic size: big end radius R1=25mm, The radius of the small end is R7=15mm; the length of the left end of the flange L1+L2=78.84mm, the length of the right end of the flange L3+L4=71.39mm;

(4) The measured resonant frequency value 1 is 19886Hz; the tool head is connected with a pre-tightening torque of 25N.M, and the resonant frequency 2 of the ultrasonic horn with the tool is tested to be 19369Hz, and the tool is removed afterwards;

(5) The equivalent thickness x of the screw in the calculation model can be determined from the screw size and material parameters; it can be determined from the resonance frequency value 1 and the calculation model of the horn without the tool, and the equivalent sound velocity in the horn can be determined. It is 5.416*10^6mm/s; the equivalent radius of the tool can be determined to be 4.03mm from the resonant frequency value 2 and the horn with the tool head calculation model; according to the target frequency value of 20000Hz and the SQP optimization algorithm, the horn is calculated. correct size;

(6) The built-in G73 programming code is automatically corrected by the corrected size to realize the generation of the numerical control program code for the correction allowance; and it is transmitted to the numerical control machine tool system to realize DNC online processing. After a correction is completed, the software will further detect the resonant frequency of the acoustic vibration component. When the error between the detection result and the target value is greater than 10Hz, the above steps and procedures will be restarted.

(7) The resonant frequency value after correction is 19998.8Hz, which is only 1.2Hz away from the target value of 20000Hz. The results show that the correction system is accurate in correcting the resonant frequency of the horn; applying 15w of power to the acoustic vibration components before and after correction, the tool tip amplitude is around 35μm before and after correction, and the displacement amplitude of the horn flange before correction is close to 3μm; The displacement amplitude of the horn flange is less than 1 μm, and the results show the accuracy of the correction system to correct the displacement nodes.

Dimensional comparison of tapered horn with tool head before and after correction

The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention; thus , the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Although the terms corresponding to the reference numerals in the figures are used more in this paper, the possibility of using other terms is not excluded; these terms are only used to describe and explain the essence of the present invention more conveniently; they are interpreted as any Such additional limitations are contrary to the spirit of the invention.

Claims (6)

1. A correction method for an ultrasonic horn numerically controlled correction structure considering a local structure, the numerically controlled correction structure is suitable for a numerically controlled lathe (3), an acoustic vibration assembly (1), a special fixture (2), a conductive slip ring (4) ), impedance analyzer (5) and PC end (6), the acoustic vibration component (1) is fixed on the three-jaw chuck (9) of the CNC lathe by a special fixture (2), and the conductive slip ring (4) is installed on the CNC lathe On the hollow spindle at the left end of the lathe (3), the impedance analyzer (5) is connected to the ultrasonic transducer (8) through the conductive slip ring (4), the PC end (6) is connected to the impedance analyzer (5), and the numerical control system ( 10) connect, it is characterized in that, described correction method comprises the following steps, (1) Assemble the acoustic vibration components; (2) Fix the acoustic vibration component on the three-jaw chuck of the CNC lathe through a special fixture; (3) Install the conductive slip ring, and connect the impedance analyzer to the ultrasonic transducer through the conductive slip ring; (4) The PC-side controlled impedance analyzer realizes the measurement of the resonant frequency, calculates the correction margin according to the obtained measurement value and generates the correction program; (5) The PC terminal transmits the numerical control programming to the numerical control system of the numerical control lathe to realize the correction of the allowance; Step (4) includes the correction method without the tool head and the correction method with the tool head; The toolless head correction method includes the following steps, (4.1.1) Effectively connect the ultrasonic horn without the tool head to the ultrasonic transducer, obtain the resonance frequency of the ultrasonic horn through the impedance analyzer, and calculate the actual equivalent sound speed through the frequency equation of the horn. model, obtain the equivalent sound speed, and correct the sound speed; (4.1.2) Substitute the equivalent sound speed into the performance parameter calculation model, establish a correction model, take the constant magnification as the objective function, and take the target resonant frequency and node position as the constraints, and determine the modified geometric size through the SQP optimization algorithm; (4.1.3) Carry out numerical control programming and import it into the numerical control machine tool, carry out allowance processing, and realize the correction of the performance parameters of the horn. 2. a kind of correction method of the ultrasonic horn numerical control correction structure considering local structure according to claim 1, is characterized in that, acoustic vibration assembly comprises ultrasonic transducer (8) and ultrasonic horn (7), The ultrasonic horn (7) is installed on the ultrasonic transducer (8), and the conductive slip ring (4) is installed on the hollow spindle at the left end of the CNC lathe (3), so that the impedance analyzer (5) passes through the conductive slip ring (4) ) to obtain the resonance frequency of the ultrasonic horn (7). 3. A correction method for ultrasonic horn numerically controlled correction structure considering local structure according to claim 2, characterized in that the ultrasonic horn (7) comprises a horn body (11), a connecting screw (12) ) and a tool head (13), the connecting screws (12) and the tool head (13) are respectively fixedly connected to the end faces on both sides of the horn main body. 4. The correction method of the ultrasonic horn numerically controlled correction structure considering the local structure according to any one of claims 1-3, is characterized in that, the tool head correction method comprises the following steps, (4.2.1) First measure the resonant frequency without the tool head installed, record the resonant frequency 1, then obtain the equivalent sound speed to correct the sound speed; then connect the tool head, measure the resonant frequency 2, and compare the resonant frequency 2 with the equivalent sound speed The sound velocity is substituted into the resonance frequency equation of the tool head to determine the equivalent radius of the tool head; (4.2.2) Substitute the equivalent sound velocity and the equivalent radius of the tool head into the mechanical four-terminal network model, determine the performance parameter calculation model, and establish a correction model. The midpoint of the blue is a constraint, and the trimming geometric size is determined by the SQP optimization algorithm; (4.2.3) Remove the tool head, carry out numerical control programming and import it into the numerical control machine tool, realize the machining of allowances, and realize the correction of the performance parameters of the horn. 5. The correction method of the ultrasonic horn numerically controlled correction structure considering the local structure according to any one of claims 1-3, is characterized in that, The calculation model of the performance parameters of the ultrasonic horn is:

6. The correction method of the ultrasonic horn numerical control correction structure considering the local structure according to any one of claims 1-3, it is characterized in that, Substitute the target frequency F into:

Objective function:

Restrictions:

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