CN104318007A - Modal-analysis-based ultrasonic cutting tool design method - Google Patents

Abstract

The invention discloses a modal-analysis-based ultrasonic cutting tool design method, and is used for solving the technical problem of poor using safety of a conventional ultrasonic cutting tool. According to the technical scheme, the method comprises the following steps of determining the resonant frequency of a system, then determining size variables of the tool curing design, and performing optimization to obtain optimal tool size results with the goal of obtaining maximum amplitude by modal analysis by adopting a genetic algorithm. According to the method, variable parameters of the tool are changed to be matched with the working frequency of the ultrasonic vibration cutting system to obtain the maximum amplitude in an ultrasonic machining process; meanwhile, in the machining process, tools selected for the tool replacement of every time are optimal tools obtained by numerical value optimization calculation, and the positions of the top ends of the tools to be selected are not required to be re-positioned and re-measured every time, so that the tools can be automatically replaced in a machining center, the machining efficiency is improved, the machining safety is ensured, and the method is suitable to be popularized and used on a large scale in a factory.

Description

Based on the supersonic cutting tool method for designing of model analysis

Technical field

The present invention relates to a kind of supersonic cutting tool method for designing, particularly relate to a kind of supersonic cutting tool method for designing based on model analysis.

Background technology

Document " UVC Tool Design, machine design and manufacture, 2012, Vol02, p242-244 " discloses a kind of supersonic cutting tool method for designing.The method, to expand for the purpose of cutter tip vibration, is first analyzed the motion state of cutting system, is calculated vibration wavelength, then determines the size of ultrasonic transformer, and aligned cutting tool end points is in the quarter-wave strong point of whole wavelength, to reach peak swing.According to fluctuation composition principle, when system is in resonance state, only by nodal point plane, contrary from the particle displacement equal and opposite in direction direction that unidirectional incident wave and reciprocal reflection wave cause, resultant displacement is always zero.Therefore, the point of fixity that luffing is caught up with is selected, by nodal point place, to increase gradually, arriving cutter top and again occurring the antinodal point that amplitude is maximum, reaching the object expanding amplitude by extending amplitude by nodal point to two ends.Peak swing can be reached to make to add man-hour cutter at every turn, author designed goes out positioned tool post, regulate the size that cutter is fixed at collet chuck, add the peak swing place that cutter in man-hour top is all in wavelength to meet at every turn, solve preferably in UVC, design cutter reaches the object of peak swing.The practical application of method described in the document is not strong, and each tool changing all needs to reorientate the position measuring cutter, reduces working (machining) efficiency; Meanwhile, if some tool length size is shorter, and required position length is longer, cutter may be made to clamp and loosely lean on, easily make cutter come off, have an accident in vibrocutting.In technological design, the length of collet chuck clamp-on tool at least should reach more than 1/3rd of whole tool length.

Summary of the invention

In order to overcome the deficiency of existing supersonic cutting tool safety in utilization difference, the invention provides a kind of supersonic cutting tool method for designing based on model analysis.The resonant frequency of the method first certainty annuity, then the size variable that cutter can be changed when designing is determined, adopt genetic algorithm optimization, target is to the maximum with the amplitude drawn through model analysis, draw the result of tool dimension optimum, the cutter that the cutter of this size uses as this machining can be selected, the UVC system be made up of cutter and ultrasonic handle of a knife is worked under resonance state, thus improve performance and the effect of UVC, only need tool changing, measurement is reorientated without the need to adding man-hour at every turn, improve working (machining) efficiency and the safety coefficient adding man-hour.

The technical solution adopted for the present invention to solve the technical problems is: a kind of supersonic cutting tool method for designing based on model analysis, is characterized in adopting following steps:

Step one, characteristic according to UVC system, carry out model analysis, certainty annuity frequency of operation f before processing ₀.

Step 2, according to tool type and structure, ensure processing request prerequisite under, determine cutter parameters variable to be optimized, setting initial parameter value.If processing is excision material, setting variable element is the thickness of three length of sides and cutting knife; If processing is hole, bit diameter remains unchanged, and setting variable element has the diameter of the length of drill bit, spiral fluted length and handle of a knife.

Step 3, employing genetic algorithm are optimized computing to the variable element in step 2, and the cutter variable element result after optimization is for step 4.

Step 4, draw the cutter variable element after optimization according to step 3, model analysis carried out to UVC system, namely obtain the first natural frequency f and the amplitude of the required vibration shape, and verify the matching degree of target variable a:

$\left\{\begin{array}{c}a=\min |f-f_0|\\ b=\max \left(M\right)\end{array}\right.$

In formula, a represents the difference between the frequency of operation of the first natural frequency and UVC system; B represents the maximal value of tool tip displacement equations multiple; M represents the enlargement factor of tool tip displacement.

Step 5, arithmetic operation repeatedly through step 3 and step 4, draw the result meeting designing requirement most, exports the cutter parameters after optimizing.

The invention has the beneficial effects as follows: the resonant frequency of the method first certainty annuity, then the size variable that cutter can be changed when designing is determined, adopt genetic algorithm optimization, target is to the maximum with the amplitude drawn through model analysis, draw the result of tool dimension optimum, the cutter that the cutter of this size uses as this machining can be selected, the UVC system be made up of cutter and ultrasonic handle of a knife is worked under resonance state, thus improves performance and the effect of UVC.Owing to adopting the method changing cutter variable element, to mate the frequency of operation of UVC system, make obtain maximum amplitude in Ultrasonic machining process.Simultaneously, in process, cutter selected by each tool changing is all through the optimum cutter that numerical optimization calculates, do not need all to reorientate the position measured and select cutter top at every turn, therefore automatic tool changer can be used in the heart by work in-process, improve working (machining) efficiency, ensure the security of processing, be suitable for factory's large-scale promotion and use.

Below in conjunction with the drawings and specific embodiments, the present invention is elaborated.

Accompanying drawing explanation

Fig. 1 is the supersonic cutting tool schematic diagram adopting the inventive method design.

Fig. 2 is the vertical view of Fig. 1.

Embodiment

With reference to Fig. 1-2.The supersonic cutting tool method for designing concrete steps that the present invention is based on model analysis are as follows:

One. certainty annuity frequency of operation.

According to cut requirement, certainty annuity frequency of operation f ₀, the natural frequency of the UVC system namely expected.Generally by transducer and ultrasonic transformer in UVC system integrally, model analysis software is used to try to achieve its natural frequency f ₀, acceleration transducer also can be used to measure its vibration data, draw natural frequency f ₀.When the excitation frequency of the ultrasonic-frequency power supply applied is consistent with the natural frequency of UVC system, system resonance, thus make the amplitude on cutter top reach maximum, improve processing effect.

Two. based on cutter structure and the dimensional parameters optimization of genetic algorithm.

The present invention adopts the non-dominated sorted genetic algorithm based on elitism strategy to carry out cutter structure and dimensional parameters optimization.Detailed process is as follows.

1) coding of cutter optimized Genetic Algorithm is determined.

1. according to type and the structure of cutter, parametric variable is determined.For ultrasonic cutter shown in accompanying drawing 1, setting cutting knife dimensional parameters variable, is respectively AB=l ₁, BC=l ₂, AD=l ₃, thickness is set to h.

2. the span of given parameters.Usually, according to part processing request, determine cutter parameters initial design values, then with designed cutter parameters design load for intermediate value, determine the concrete span of each parameter.Such as, l is got ₁∈ { 5 ± Δ L ₁, l ₂∈ { 25 ± Δ L ₂, l ₃∈ { 12 ± Δ L ₃, h ∈ { 12 ± Δ h} (unit: millimeter).

3. coding strategy is determined.Based on binary coding, each variable can get 16 values, and therefore each variable is tetrad coding.As variable l ₂tetrad be encoded to 0000-1111, at [25-Δ L ₂, 25+ Δ L ₂] between get 16 values.

2) fitness function of cutter optimized Genetic Algorithm is determined.

Using optimization aim as fitness function, F _n=min|f-f ₀|.F ₀for the system operating frequency expected, f is the actual natural frequency of the UVC system (ultrasonic handle of a knife and cutter) after tool dimension changes, and is obtained by model analysis.

3) selection opertor of cutter optimized Genetic Algorithm is determined.

Calculate the desired number N that in colony, each individuality is survived the next generation _i:

$N_i=\frac{F_i}{F_{\mathrm{avg}}}$

Wherein, F _avgrepresent the average of F.

If certain is individual selected and require participate in pairing and intersect, then its existence desired number in the next generation deducts 0.5; If do not participate in pairing and intersect, then the desired number of this individuality deducts 1.0.Along with the carrying out of selection course, if the expectation value of certain individuality is less than zero, then this individuality would not be selected again.

4) crossover operator of cutter optimized Genetic Algorithm is determined.

Gene between two point of crossing is exchanged.

5) mutation operator of cutter optimized Genetic Algorithm is determined.

The substance of mutation operator changes the genic value on some gene location of the individual UVR exposure string in colony.Another genic value different from initial value is replaced by by the genic value on specified change point.As 0000 parameter makes a variation to second, then the parameter after variation is 0010.

6) genetic algorithm is adopted to carry out computing.

Three. model analysis.

The first natural frequency f and the tool nose's amplitude enlargement factor M of longitudinal vibration shape of the UVC system be made up of designed cutter and ultrasonic handle of a knife is obtained by model analysis.The concrete steps of model analysis are:

1. the three-dimensional model of ultrasonic handle of a knife and cutter is set

2. model analysis item and boundary condition is set up

3. grid division

4. solving model, draws the eigenfrequncies and vibration models of tooling system

5. optimization object function is compared

$\left\{\begin{array}{c}a=\min |f-f_0|\\ b=\max \left(M\right)\end{array}\right.$

Four. determine optimized parameter.

By the cutter parameters be optimized through genetic algorithm and model analysis, namely obtain the cutter physical dimension (or cutter structure) of optimization.Cutter material: wimet.Range of application: the cutting of cellular composite material and the material such as fiber, leather.

Claims (1)

1., based on a supersonic cutting tool method for designing for model analysis, it is characterized in that comprising the following steps:

Step one, characteristic according to UVC system, carry out model analysis, certainty annuity frequency of operation f before processing ₀;

Step 2, according to tool type and structure, ensure processing request prerequisite under, determine cutter parameters variable to be optimized, setting initial parameter value; If processing is excision material, setting variable element is the thickness of three length of sides and cutting knife; If processing is hole, bit diameter remains unchanged, and setting variable element has the diameter of the length of drill bit, spiral fluted length and handle of a knife;

Step 3, employing genetic algorithm are optimized computing to the variable element in step 2, and the cutter variable element result after optimization is for step 4;

Step 4, draw the cutter variable element after optimization according to step 3, model analysis carried out to UVC system, namely obtain the first natural frequency f and the amplitude of the required vibration shape, and verify the matching degree of target variable a:

$\left\{\begin{array}{c}a=\min |f-f_0|\\ b=\max \left(M\right)\end{array}\right.$

In formula, a represents the difference between the frequency of operation of the first natural frequency and UVC system; B represents the maximal value of tool tip displacement equations multiple; M represents the enlargement factor of tool tip displacement;

Step 5, arithmetic operation repeatedly through step 3 and step 4, draw the result meeting designing requirement most, exports the cutter parameters after optimizing.