RU2561236C2 - Method for diagnosis of cyclic machines - metal-cutting machines using phase-chronometric method - Google Patents

Abstract

FIELD: physics, measurement.

SUBSTANCE: invention relates to diagnosis of the technical state of machines and mechanisms, and can be used, for example, to evaluate the technical state of metal-cutting machines and structural components thereof. The method includes determining a list of diagnosed parameters and possible defects of machines, determining the values of said diagnosed parameters and defects, installing chronometric sensors of operating phases of the machines on parts of the machines in order to take measurements, and recording readings in a single metrological field, analysing sensor readings and refining values of the diagnosed parameters using mathematical models. The method also includes monitoring the state of components and parts of the machines, taking into account intactness of machines and external operating conditions in the form of temperature and humidity.

EFFECT: high accuracy of measurement and diagnosis.

1 tbl, 18 dwg

Description

Technical field

The invention relates to the field of diagnostics of the technical condition of machines and mechanisms and can be used, for example, to assess the technical condition of metal-cutting machines and their structural elements.

State of the art

The object relates to the field of mechanical engineering devices that measure by determining the time required to go through the phase position to indicate or measure the cutting conditions, cutting ability, tool load, which indicate wear and damage to the machine during processing.

First, information about analogues from the prior art of traditional methods for diagnosing metal cutting machines. As a rule, analogues from traditional methods are methods based on vibroacoustic measurements (vibrodiagnostics) of physical quantities with insufficient metrological accuracy. The disadvantage is the complex process of identifying a defect and the inability to determine the true cause of deviations or breakdowns during operation, which does not allow using them with the required accuracy and reliability as diagnostic methods for metal cutting machines.

In RF patent No. 2363936 METHOD FOR VIBRODIAGNOSTICS OF OBJECTS (IPC G01M 7/02, published: 08/10/2009) it is proposed to construct a vibration spectrum in the frequency domain, linearize the step of arrangement of informative components by non-linear frequency scale conversion, highlight important components, determine the frequencies of significant defects that will be used to assess the technical condition of the facility. This method can be used to diagnose the technical condition of machines and mechanisms.

The disadvantage of the analogue is that the method is based on the method of vibration diagnostics of the technical condition of the object, which consists in the fact that the vibration of the diagnosed object is measured at an informative point, a vibration cepstrum is obtained in the time domain, the amplitudes and highs of the informative components of the cepstrum corresponding to defects of the object are estimated, that the cepstrum of vibration is built in the frequency domain, linearize the step of the location of informative components by non-linear transformation of the frequency scale, determine the hour the totals of significant defects in terms of the value of essential cepstral components, which assess the state of the object. The main disadvantage of this analogue is the lower accuracy of the measurements: the measurement error of vibration is 0.01 ... 5%.

In RF patent No. 2332652 METHOD FOR DIAGNOSTIC AND EVALUATION OF VIBROACTIVITY OF MACHINES OPERATING WITH BLADE TOOLS (IPC G01M 7/00, published: August 27, 2008) it is proposed to measure the amplitudes of vibration velocity and vibration acceleration at a local energy point of the maximum operating temperature of the maximum workstation of the maximum defined from dependencies. The dependencies take into account that the amplitude values of the vibration velocity determine the degree of influence on the vibration of each component of the characteristic coordinate displacement of the axis of rotation of the spindle, and the amplitude values of vibration acceleration indicate the occurrence of dynamic loads in the spindle assemblies. The main disadvantage of this analogue is also a lower measurement accuracy, the measurement error of 0.01 ... 5%.

On the other hand, the general phase-chronometric method (FHM) of the authors from MSTU im. N.E. Bauman (see, for example, "Information and metrological support of the life cycle of machines and mechanisms based on a precision chronometric analysis of the phase of the working cycle" (abstract of the dissertation of V. Pronyakin for the degree of Doctor of Technical Sciences, MSTU named after N.E.Bauman, 2010, Internet address: http://oldvak.ed.gov.ru/en/announcements_1/technikal_sciences/index.php?id4=2458&from4=3).

The phase-chronometric method in the General case includes:

1) a preliminary definition and a list of diagnosed parameters and possible machine defects and structural breakdown of the machine into parts that are critical for diagnosing parameters and possible defects,

2) dividing the working cycle of the machine and its parts into separate phases;

3) compilation with the degree of detail necessary for the precise determination of the values of diagnosed parameters and possible defects, mathematical models of the working cycle of machine parts and their interaction in a phase-chronometric information representation for the relationship of measurement results with the corresponding processes (cycle phases) in the working parts of the machine,

4) the installation of precision (with a relative error of no more than 10 ^-4 %) chronometric sensors of the working cycle phases in the machine parts, the outputs of the sensors are connected to the processing unit for their measurement signals, the block also contains work programs for mathematical models of the working cycle of machine parts and their interaction for subsequent processing of the measurement results, while the location of the sensors in the machine is determined by the design of the parts of the cyclically operating machine, and the installation locations of the sensors are determined from the point of view of obtaining the most olnoy information about the parts of the machine;

5) precision measurements by the indicated sensors of the time intervals of the phases of the working cycles of machine parts and their interaction with the presentation of the processed measurement information in a single metrological format at all stages of the life cycle of the machine and in mathematical modeling of the working cycles of machine parts and their interaction, namely: obtaining data arrays, formed by a series of measured in sequence (without gaps) series of time intervals of phases in a single reference time;

6) during the processing of the measurement results, the values of the parameters included in the mathematical models are refined to correspond to the current technical condition of the machine, and then the values of the diagnosed parameters and possible defects of the machine are determined by simulation results using the updated models and subsequent mathematical processing, according to which evaluate the current technical condition of the machine.

This is a sequence of general methods of FHM actions that must be creatively applied each time with individual nuances of implementation for diagnosing specific types of cyclic machines.

It is also advisable to mention the utility model RU 131167 of the authors of the FHM from MSTU. N.E. Bauman “Measuring unit” (IPC G01M 13/04, published: 08/10/2013) for processing sensor signals used in the framework of the general FHM. This measuring unit is designed to measure time intervals corresponding to a repeated predetermined movement of an element or elements of the mechanism, including a sensor for moving an element or elements of the mechanism and a means of measuring time intervals between pulses from the sensor when the element of the mechanism passes in front of it. The block additionally includes a reference channel sensor, and the means for measuring the time intervals between pulses contains a total count timer that starts a sequence of counting pulses, a counting pulse generator, a counter and a circuit that includes a counter for a time determined by the total count timer using the signals of the reference sensor. The unit also further includes a memory and means for generating and recording the measured time intervals in the memory and communication means for transmitting the measurement results to the mathematical processing means. This utility model is a universal device for the primary processing of sensor signals used in the PCM.

Disclosure of invention

The objective of the invention is the creative implementation of the general provisions of the phase-chronometric method (FHM) with additional new individual features of the inventive step for diagnosing both individual cyclically moving units and elements of metal cutting machines, and machine tools in general, to increase the accuracy of diagnosis up to 10 ^-4 %.

A method for diagnosing cyclic machines - metal-cutting machines by the phase-chronometric method includes:

1) a preliminary definition and a list of diagnosed parameters and possible machine defects and structural breakdown of the machine into parts that are critical for diagnosing parameters and possible defects,

2) dividing the working cycle of the machine and its parts into separate phases;

3) compilation with the degree of detail necessary for the precise determination of the values of diagnosed parameters and possible defects, mathematical models of the working cycle of machine parts and their interaction in a phase-chronometric information representation for the relationship of measurement results with the corresponding processes (cycle phases) in the working parts of the machine,

4) the installation of precision (with a relative error of no more than 10 ^-4 %) chronometric sensors of the working cycle phases in the machine parts, the outputs of the sensors are connected to the processing unit for their measurement signals, the block also contains work programs for mathematical models of the working cycle of machine parts and their interaction for subsequent processing of the measurement results, while the location of the sensors in the machine is determined by the design of the parts of the cyclically operating machine, and the installation locations of the sensors are determined from the point of view of obtaining the most olnoy information about the parts of the machine;

5) precision measurements by the indicated sensors of the time intervals of the phases of the working cycles of machine parts and their interaction with the presentation of the processed measurement information in a single metrological format at all stages of the life cycle of the machine and in mathematical modeling of the working cycles of machine parts and their interaction, namely: obtaining data arrays, formed by a series of measured in sequence (without gaps) series of time intervals of phases in a single reference time;

6) during the processing of the measurement results, the values of the parameters included in the mathematical models are refined to correspond to the current technical condition of the machine, and then the values of the diagnosed parameters and possible defects of the machine are determined by simulation results using the updated models and subsequent mathematical processing, according to which evaluate the current technical condition of the machine.

In the course of processing the measurement results, the values of the parameters included in the mathematical models are refined to correspond to the current technical condition of the machine, and then the values of the diagnosed parameters and possible defects of the machine are determined by the results of simulation using the specified models and subsequent mathematical processing, according to which the current technical condition of the machine; primary analysis of the series of sensor signals consists in the construction and comparison of arrays of series of precision time intervals at different time intervals; secondary analysis - statistical mathematical processing by methods recognized as optimal for processing signals of precision time intervals, taking into account the nuances of the corresponding class of diagnosed cyclic machines: correlation analysis of rotation chronograms; spectral analysis of rotation chronograms; cross-spectral analysis; Fourier transform; and / or trend analysis; regimen and “seasonal” analysis (depending on equipment loading, complexity of processing materials, working hours); simulation chronograms and frequency spectra derived from them, obtained as a result of a computational experiment, are compared with experimental graphs; The criteria for comparing experimental and simulation graphs are primarily mathematical (spread of the range of value, trend of deceleration or acceleration, exit at a steady state beyond the limits of pore values).

The data of experimental chronograms are primarily used to refine the parameters of the used mathematical models of the diagnosed cyclic machine and further approximate the simulation results.

Moreover, in metal-cutting machines, the list of diagnosed parameters and possible defects of the machine includes:

- manufacturing defects of the machine and its elements;

- assembly defects after repair or installation of individual elements;

- worn, broken, poorly fixed parts and elements of the machine;

- determination and measurement of unbalance in the machine;

- dynamic parameters and geometric characteristics of the machine;

- physical and mechanical properties of machine elements (for example, rigidity);

- characteristics of devices for fixing parts and tools;

- processing parameters (cutting speed, feed, cutting depth);

- identification of the output and input control of the machine by comparing the results of the PCM measurement on a particular machine during the presentation tests of the finished product (at the manufacturer) and input control (at the consumer of the product).

One of the important advantages of using FHM in the diagnosis of machine tools is to increase the accuracy of metrological information about the measured variables of the cyclic motion of individual critical machine nodes in any cyclic modes of its operation up to 10% due to the use of precision chronometric sensors and a measuring unit for primary processing of sensor signals for FHM .

The following are the critical structural units of a metal cutting machine:

1) a machine with a horizontal axis of rotation of the spindle - a lathe consisting of the following parts: asynchronous motor with gearbox speed of the machine; spindle unit of the machine with the workpiece in the spindle chuck; tailstock of the machine; a support with a cutting tool (if a gear motor is used in the machine, the gear motor replaces the asynchronous motor with the gearbox of the machine).

2) a machine with a vertical axis of rotation of the spindle - a drilling or milling machine, consisting of the following parts: asynchronous motor with gearbox speed of the machine; spindle unit of the machine with a cutting tool in the spindle chuck; the workpiece in a vice on the work table of the machine (in case of using a gear motor in the machine, the gear motor replaces the asynchronous motor with the gearbox of the machine).

The installation locations in the metal-cutting machine of sensors for FHM are determined from the point of view of obtaining the most complete information about the operation of the basic nodes of the machine and the design of the machine, namely:

- measurement of rotation parameters of an induction motor or gearmotor (installation from the motor side);

- measurement of rotation parameters of the machine gearbox (sensors on the input and output shaft);

- measurement of gear box gear wear (sensors on each gear in the gear box);

- measuring the parameters of the spindle rotation (the sensor at the output of the spindle, most often in the places of fixing the cutting tool or workpiece - three-jaw chucks, collet chucks, etc.);

- measurement of parameters and study of the cutting process (sensors from the tailstock side);

- measurement of the processing parameters of the workpiece and the wear of the cutting tool (sensors in the corresponding sections of the workpiece).

Features of the installation of measuring sensors on machines with vertical and horizontal spindle layout are associated with the features of the cutting process, structural elements of machines, differences in rigidity and geometry.

Machines with a horizontal axis of rotation have a tailstock for preloading the part during processing. The cutting forces acting on the workpiece are directed in a horizontal plane perpendicular to the direction of rotation of the workpiece.

A feature of machines with a vertical axis of rotation of the spindle is the rotation of the cutting tool, not the workpiece, as well as the absence of a tailstock.

Features of mathematical models of machines with vertical and horizontal spindle layout are expressed in the recording of the initial equations of the system, associated primarily with the influence of gravity and a change in the direction of flexural-torsional vibrations of the system.

Mathematical models of machine nodes and node interactions for each cyclic phase are presented in the form of systems of nonlinear differential equations containing, in the form of coefficients, concentrated or distributed system parameters, such as moments of inertia, stiffness, internal and external friction coefficients, geometry and material of the cutting tool, material and blank shape, external conditions (temperature, humidity), characteristics of an induction motor, gear ratios, etc.

Consider the following sequence of cyclic operation of the machine with chronometric sensors and a measuring unit for their primary processing in the following optimal modes for diagnosing parameters and possible defects in the main phases of machine cycles:

- turning on / starting the machine;

- machine operation in idle mode at different speeds of rotation;

- cutting tool cutting into the workpiece material;

- the process of processing parts (cutting) in different modes (depth, feed, spindle speed);

- cutting the workpiece with a cutting tool;

- critical wear of the cutting tool (when approaching the maximum standard operating time of the cutting tool or accelerated wear);

- exit of the tool from the workpiece;

- machine stop.

List of figures

Figure 1 - diagram of the main components of the machine with a horizontal axis of rotation of the spindle of a lathe having a gearbox with the installation of chronometric sensors and a measuring unit for the primary processing of sensor signals for FHM diagnostics;

Figure 2 - diagram of the main components of the machine with a horizontal axis of rotation of the spindle of a lathe with a gear motor, with the installation of chronometric sensors and a measuring unit for the primary processing of sensor signals for FHM diagnostics;

Figure 3 - diagram of the main components of the machine with a vertical axis of rotation of the spindle of a drilling or milling machine having a gearbox, with the installation of chronometric sensors and a measuring unit for the primary processing of sensor signals for FHM diagnostics;

Figure 4 - diagram of the main components of the machine with a vertical axis of rotation of the spindle of a drilling or milling machine with a gear motor, with the installation of chronometric sensors and a measuring unit for the primary processing of sensor signals for FHM diagnostics;

Figure 5 is a structural diagram of a lathe system UT16P with FHM diagnostics (corresponds to the case of figures 1, 2);

6 is a dynamic diagram of a gearbox with an electric motor of a lathe UT16P;

7 is a schematic diagram of a sensor measuring signal for transmission to the measuring unit of the primary processing of sensor signals for the PCM;

8, 9 - experimental and computer simulation chronograms in polar coordinates of the rotation of the spindle of the lathe UT16P with cutting, rotation speed 315 rpm, s = 0.045 mm / rev, t = 0.5 mm, workpiece material ШХ15, cutting plate from alloy T15K6;

Figure 10, 11 - experimental and computer simulation chronograms in linear coordinates;

12, 13 - experimental and computer simulation spectra of the rotational frequencies of the spindle of the machine after processing its chronograms;

Fig - defective tooth in the gear wheel of the gearbox of the machine;

Fig - graph of fluctuations of the shoulder forces against time in gear engagement of the machine;

Fig - the implementation of the measurement due to the inconsistency of the "phase" of the gear;

Fig. 17 is a chronogram in linear coordinates of rotation of a gear tooth showing a rotation trend;

Fig. 18 is a difference chronogram between the chronogram of Fig. 17 and its trend.

The implementation of the invention

In figure 1 ... 4 in a continuous numbering, the positions indicated: 1 - asynchronous motor; 2 - spindle unit of the machine; 3 - blank in the spindle chuck of a lathe or vice of a drilling / milling machine; 4 - the tailstock of the lathe; 5 - machine gearbox; 6, 7, 8, 9, 10 - chronometric sensors; 11 - measuring unit for the primary processing of sensor signals; 12 - machine gear motor; 13 - a cutting tool in the support of a lathe or in the chuck of the spindle of a drilling / milling machine.

The best options for installing the minimum number of chronometric sensors in the most important nodes of the two types of metal cutting machines were recognized and investigated the following options.

In Fig.1 - a lathe having a gear box, and with FHM diagnostics contains: 1 - asynchronous motor; 5 - a box of speeds of the machine; 2 - spindle unit of the machine; 3 - workpiece in the spindle chuck; 4 - the tailstock of the machine; 13 - a support with a cutting tool; 6, 7, 8, 9, 10 - chronometric sensors, respectively, in the nodes of the machine 4, 1, 2, at the input and output of node 5; and 11 is a measuring unit for primary processing of sensor signals.

In Fig.2 a lathe with a gear motor and with FHM diagnostics contains: 12 - a gear motor of the machine; 2 - spindle unit of the machine; 3 - workpiece in the spindle chuck; 4 - the tailstock of the machine; 13 - a support with a cutting tool; 6, 7, 8 - chronometric sensors, respectively, in the nodes of the machine 4, 12, 2; and 11 is a measuring unit for primary processing of sensor signals.

In Fig.3 a drilling or milling machine having a gearbox and with FHM diagnostics contains: 1 - an asynchronous motor; 5 - a box of speeds of the machine; 2 - spindle unit of the machine; 13 - cutting tool in the spindle chuck. 3 - workpiece in a vice; 7, 8, 9, 10 - chronometric sensors, respectively, in the nodes of the machine 1, 2, at the input and output of node 5; and 11 is a measuring unit for primary processing of sensor signals.

In Fig.4, a drilling or milling machine with a gear motor and with FHM diagnostics contains: 12 - a gear motor; 2 - spindle unit of the machine; 13 - cutting tool in the spindle chuck; 3 - workpiece in a vice; 7, 8 - chronometric sensors, respectively, in the nodes of the machine 12, 2; and 11 is a measuring unit for primary processing of sensor signals.

The differences in the diagnosis of machines with vertical and horizontal spindle axes are in a different description of mathematical models (the influence of the bending and torsional components, gravity).

For example, a system of differential equations describing the simplest operation scheme of a screw-cutting lathe has the following form:

j = 1, 2.

Depending on the direction of the axis of rotation of the spindle (horizontal or vertical) for a vertical arrangement, a term of the form m _j gn _y appears in the first and second equations of the system. In the third and fourth equations of the system of equations (1) (their number may increase depending on the number of elements for splitting the spindle elements) a member of the form m _j gn _{y is} present only for the z axis (vertical axis)

The following notation is used in the system of differential equations:

J ₁ , J ₂ - reduced moments of inertia of the spindle unit and the console with the table;

θ ₁ , θ ₂ - generalized coordinates, angular deviations of the reduced masses from the position of their static equilibrium;

Q ₁ , σ ₂ - generalized forces determined from the work of cutting forces at possible displacements;

q ₁ - coefficient characterizing torsional rigidity;

k ₁₂ is a coefficient characterizing the viscosity;

c ₁ - coefficient of external friction during bending vibrations;

c is the coefficient of internal friction during bending vibrations;

q _1j - bending stiffness of the spindle;

e _2j are eccentricities;

x _j , y _j - coordinates of the centers of mass;

m _j are the corresponding concentrated masses of the spindle sections;

q is the acceleration of gravity;

n _y - normal overload (overload impact of longitudinal component, in this case assumed to be negligible).

Indices: 1 - gearbox with engine, 2 - spindle.

Example 1

A method for diagnosing the parameters of the rotation of the spindle of a lathe UT16P using FHM.

Figure 5 presents a structural diagram of a system of a lathe UT16P with FHM diagnostics (corresponds to the case of figure 1), where LIR 158A angular sensors were used as chronometric sensors (figure 5 shows the spindle rotation sensor of the machine), the measuring unit is designated as FHM system.

Measurements for the PCM were made in the operating conditions of the lathe during the processing of parts in accordance with the dynamic scheme of a three-stage gearbox with an electric motor, where the cutting force is taken into account at the moment of cutting resistance M _C in Fig.6. In the model of FIG. 6, only dynamic components were taken into account - those that are involved in movement, and not in static - therefore, the machine bed was not taken into account.

The assumptions made when compiling the system of differential equations:

- the distributed parameters of the system are replaced by concentrated with masses m _i and moments of inertia J _i ;

- shafts are considered weightless and have stiffness c _i ;

- the deformation in the engagement is not taken into account, since the deformation of the shafts is significantly greater than the deformation of the teeth;

- Friction in gearing is not taken into account.

The system of differential equations of a three-speed gearbox with an electric motor of a lathe cutting machine, taking into account the above assumptions, has the form:

where Ψ _X (t) and Ψ _x (t) are the projection values of the flux link vectors onto the X axis of the stator and rotor, respectively;

Ψ _Y (t) and Ψ _y (t) are the projection values of the flux link vectors onto the Y axis of the stator and rotor, respectively;

R _S , L _S , l _S - active resistance, inductance of self-induction and stator phase inductance, respectively;

R _r , L _r , l _r - resistance, self-induction inductance and rotor phase leakage inductance, respectively;

E _f is the effective phase voltage;

M is the magnitude of the mutual induction between the phases of the stator and rotor;

σ is the total scattering coefficient;

ω _C is the angular velocity of rotation of the field;

p is the number of pole pairs;

J ₁ , J ₂ , J ₃ , J ₄ , J ₅ , J ₆ , J ₇ , J ₈ - moments of inertia of the rotor of the electric motor, gears of the 1st stage, wheels of the 1st stage, gears of the 2nd stage, wheels 2- 1st stage, 3rd stage gears, 3rd stage wheels, spindle, respectively;

c ₁ , c ₂ , c ₃ , c ₄ - torsional stiffness of the shafts;

φ ₁ (t), φ ₂ (t), φ ₃ (t), φ ₄ (t), φ ₅ (t), φ ₆ (t), φ ₇ (t), φ ₈ (t) - rotation angles rotor of an electric motor, gears of the 1st stage, wheels of the 1st stage, gears of the 2nd stage, wheels of the 2nd stage, gears of the 3rd stage, wheels of the 3rd stage, spindle, respectively;

P ₁ (t), P ₂ (t), P ₃ (t) - dynamic forces in gearing of the 1st, 2nd and 3rd steps, respectively;

M _G1 , M _G2 , M _G3 , M _G4 , M _G5 , M _G6 - moments due to the eccentricity of the shafts of the gears of the 1st stage, wheels of the 1st stage, gears of the 2nd stage, wheels of the 2nd stage, gears 3rd stage, wheels of the 3rd stage, spindle, respectively;

r _1b (t), r _2b (t), r _3b (t), r _4b (t), r _5b (t), r _6b (t) are the radii of the initial circumferences of the gears (shoulders of forces P ₁ (t), P ₂ (t), P ₃ (t)).

M _D - the electromagnetic moment developed by the engine;

M _With - moment of resistance to the load.

The moment of resistance at the load is nothing more than the moment of resistance by cutting.

The moments of inertia and torsional stiffness of the shafts are determined based on the design features of the gearbox.

Partitioning the engine-gearbox system.

Part of the system (1) describes the electric motor:

The other part is the gearbox equations:

является общим для привода (электродвигателя вместе с коробкой передач).The equation $$\begin{array}{l}J\cdot \frac{d^2}{\mathrm{<figure-callout\; id="2"\; label="d\; t"\; filenames="00000024.png,00000026.png"\; state="\{\{state\}\}">d\; </figure-callout>}{t}^{}{}^2}{\varphi }_{\mathrm{one}}(t)+c_{\mathrm{one}}\cdot ({\varphi }_{\mathrm{one}}(t)-{\varphi }_2(t))-\frac{3}{2}\cdot \frac{p\cdot M}{\sigma \cdot ((L_S+l_S)\cdot (L_r+l_r))}\times \\ \times ({\Psi }_Y(t)\cdot {\Psi }_x(t)-{\Psi }_y(t)\cdot {\Psi }_X(t))=0\end{array}$$

is common to the drive (electric motor with gearbox).

The result of the simulation solution of the system of differential equations in computer simulation using the appropriate application software are simulation chronograms, the analogs of which are also obtained after processing the real signals of the chronometric sensors in the measuring unit. Next, rotation chronograms for all the masses obtained from the experiment using chronometric sensors (the principle of operation of a typical chronometric phase sensor is shown in Fig. 7, where the number of pulsed precision measurements of time intervals corresponds to the number of precision information marks or slots uniformly distributed over the rotation angle of the sensor disk , and determine the completeness and accuracy of the information in Figs. 8 and 9; 10 and 11, the width of the natural frequency spectra of Figs. 12 and 13, and this number also determines EU ETS phase and phase sequence numbers 8 ... 11). The signals from the outputs of the chronometric sensors enter the measuring unit (according to the above utility model RU 131167), where they are processed for subsequent transmission to a computer for generating chronometric charts in polar and / or linear coordinates and secondary processing for comparison with simulation chronograms as in polar (Fig. 8, 9), and in linear coordinates - (Fig. 10, 11). In polar coordinates, the phase numbers change in a circle from 0 to a maximum per 1 revolution of the controlled coordinate, for example, the spindle rotation angle, and along the radii of the polar grid graphs of precision measurements of the time intervals measured by the sensor variable in rows for the required operating time interval or linear number grid phases are located on the horizontal abscissa axis, and the obtained time intervals for the corresponding phase numbers are located on the vertical ordinate axis.

Simulated chronograms and frequency spectra derived from them (Figs. 12, 13) obtained as a result of a computational experiment are compared with experimental graphs. The criteria for comparing experimental and simulation graphs are primarily mathematical (spread of a range of values, a trend of deceleration or acceleration, exit at a steady state beyond the limits of pore values. Expert evaluation is also allowed). These methods are: trend analysis; regimen and “seasonal” analysis (depending on the equipment load, complexity of processing materials, working hours, etc. - for primary processing of chronograms of different types of representation (in polar and linear coordinates). The data of experimental chronograms are primarily used to refine the parameters (moments of inertia, stiffness, viscosities, etc.) used mathematical models of machines and further approximation of simulation results.

For example, the experimental polar chronograms of Fig. 8 are converted into rotation angles φ ₁ (t), φ ₂ (t), φ ₃ (t), φ ₄ (t), φ ₅ (t) (depending on the number of installed sensors, each value φ _i (t) corresponds to the angle of rotation of the element at the installation site of the measuring sensor (transducer) and is substituted into the system of equations (1), the solution of which gives an updated value of the model parameters, for example, stiffnesses from ₁ , ₂ , ₃ , ₄

Then a frequency spectrum is constructed — from chronograms or separately by one of 4 methods: correlation analysis of rotation chronograms; spectral analysis of rotation chronograms; cross-spectral analysis; Fourier transform; or their combination (through expert assessments).

Figures 8, 9 respectively show the experimental and simulation chronograms of the spindle rotation of the UT16P machine in polar coordinates in the cutting mode of the workpiece at a rotation speed of 315 rpm, feed s = 0.045 mm / rev, cutting depth t = 0.5 mm, workpiece material ШХ15, cutting insert from T15K6 alloy cutter.

A comparative analysis of Fig. 8 and Fig. 9 shows the equally "torn" nature of the processing of this material ШХ15 with a T15K6 cutting insert. The difference in the results of mathematical modeling and experiment is related to the difference in real measurement conditions and mathematical modeling. Based on the measurement results (Fig. 8), the parameters of the mathematical model are refined in different operating modes. A comparative analysis of the chronograms in the linear coordinates of FIG. 10 and 11 also shows that the scatter of values (the amplitude of the values on the chronograms) differs in the experiment and in computer mathematical modeling, which also requires refinement of the parameters of the mathematical model.

When analyzing the chronometric measurement information in the example, the following results were obtained: variations of time intervals corresponding to fractions of a revolution for rotation speeds of 315 rpm - no more than 5.5 μs, 400 rpm - no more than 3 μs, 1000 rpm - not more than 1.0 μs, 2000 rpm - not more than 0.5 μs. The analysis of experimental chronograms shows that the UT16P lathe has deviations of the rotation period from the nominal value during operation. The value is from 0.5 to 8 μs, depending on the operating mode. In this case, the average value of the period varies in the range up to 5 μs, which corresponds to a value from 5 to 26 μm in circular coordinates.

To evaluate the diagnostic parameters of the machine and linking to system elements, a spectral analysis of chronograms was performed. Spectral analysis of a series of time intervals showed the presence of a frequency region in the range from 0.5 to 18 Hz, as well as the presence of a stable frequency peak in the region of 200 Hz.

The presence of spindle shaft swing frequencies independent of cutting conditions and environmental parameters indicates the presence of stable signs of machine operation, which can be used as diagnostic ones.

On Fig, 13 shows the spectra of the natural frequencies of the swing of the spindle shaft of the machine UT16P obtained by spectral analysis of rotation chronograms after applying the autocorrelation function, the spindle rotation speed of 315 rpm, S = 0,045 mm / rev. t = 0.5 mm. When constructing the chronogram spectrum of the refined mathematical model in the process of work, the deviation (deviation) of the frequency of the natural frequencies in the process of work was evaluated, which is used to judge changes in the metal cutting machine. A comparative analysis of the experimental and simulation frequency spectra of Figs. 12, 13 shows the presence of close frequencies, respectively: 4.241 Hz (experiment) and 4.67 Hz (simulation), 8.482 Hz (experiment) and 8.82 Hz (simulation). A comparative analysis of the torsional vibration frequencies of the UT16P lathe is given in table 1. The results show the presence of frequencies in the region of 4 Hz, 6 Hz, 9 Hz, 12 Hz, and 15 Hz.

Table 1 The values of the natural frequencies of the oscillations of the lathe UT16P under different processing conditions, the processing material is steel ШХ15 Rotational speed 315 rpm; s = 0.045 mm / rev; t = 0.4 mm Rotational speed 315 rpm; s = 0.045 mm / rev; t = 0.5 mm Rotational speed 315 rpm; s = 0.064 mm / rev; t = 0.4 mm Intermittent cutting, rotation speed 315 rpm; s = 0.045 mm / rev; t = 0.4 mm Carbide treatment, rotation speed 400 rpm; s = 0.109 mm / rev; t = 0.2 mm + insert.

- - 1.343 Hz 1.309 Hz 1,660 Hz 4.241 Hz 4.170 Hz - 4.583 Hz 4.160 Hz 6.362 Hz 6.255 Hz 6.042 Hz 5.892 Hz 5.824 Hz 8.482 Hz 9.035 Hz 9.398 Hz 9.166 Hz 7.488 Hz 9.896 Hz 12.510 Hz - 12,440 Hz - 13.430 Hz 15,990 Hz - 13.750 Hz - 17.670 Hz 207,100 Hz - 15.710 Hz - Note: “plunge” - cutting the tool into the workpiece, t - cutting depth, s - feed.

The low-frequency components of the spectrum of the natural frequencies of oscillations of the machine are determined primarily by the first forms of vibration of the main body parts and vibrations of heavy nodes with non-rigid joints.

Example 2

Method for diagnosing small parts of a machine tool using the PCM using the example of gear teeth of a gearbox of a UT16P lathe gear.

FHM also allows, with the appropriate details of mathematical models of machine parts, to reach the diagnosis of the smallest parts of the machine, for example, determining the wear of gear wheels of a gearbox and then determining the residual life, for example, for a UT16P lathe.

1) Processing the measurement results of the PCM system, i.e. translation of the rotation chronogram into the functions φ ₁ (t), φ ₂ (t), φ ₃ (t), φ ₄ (t), φ ₅ (t), φ ₆ (t), φ ₇ (t), φ ₈ ( t), and the definition of gear ratios:

2) Substitution of the real functions of the rotation angles into the system and determination of the force factors M _D , M _C , P ₁ (t), P ₂ (t), P ₃ (t), as well as the shoulders of the reaction forces in the links r _1b (t), r _2b (t), r _3b (t), r _4b (t), r _5b (t), r _6b (t), as functions of time.

The values of r _1b (t), r _2b (t), r _3b (t), r _4b (t), r _5b (t), r _6b (t) are connected to each other through gear ratios of the steps:

3) Analysis of the functions r _1b (t), r _2b (t), r _3b (t), r _4b (t), r _5b (t), r _6b (t).

Due to the fact that the reaction forces in the links are vectors and are directed along the line of engagement perpendicular to the contacting involutes, when the working profiles are mowed and worn, these vectors will experience fluctuations in the direction relative to the line of engagement. Thus, the shoulders of the forces r _1b (t), r _2b (t), r _3b (t), r _4b (t), r _5b (t), r _6b (t) will also experience oscillations.

On Fig shows a defective tooth gear and thin lines show the normal to the surface in various parts of the painted area. The dash-dotted line shows the normal to the involute, h is the amount of wear. On Fig shows an example of a graph of fluctuations in time and shoulder forces in engagement, r _b0 is the nominal value of the force in engagement. In the period of time when the contact occurs on the painted surface, r _b begins to experience fluctuations, the amplitude Δ of which will be proportional to the amount of wear, i.e.:

Δ = k

4) Finding the proportionality coefficient k.

5) Determination of wear h and residual gear life.

Mathematical modeling, determination of wear and residual gear life.

The given equation of gear dynamics for the purposes of FHM diagnostics looks like:

here J ₁ and J ₂ are the moments of inertia of the gears and wheels, respectively, including the moments of inertia of the shafts and the rotor of the drive;

M ₁ - moment on the drive;

M ₂ - moment of resistance on the actuator;

M _G1 - moment, due to eccentricity (displacement of the center of mass relative to the axis of rotation) of the gear shaft;

M _G2 - moment, due to the eccentricity of the wheel shaft;

φ ₁ and φ ₂ are the angles of rotation of the gear and wheel, respectively;

u (t) is the gear ratio of the gearbox (from the wheel to the gear).

The result of solving equation (10) is the angle of rotation of the gear φ ₁ .

With a uniform rotation of the gear, the change in the width of the tooth due to wear on the pitch diameter can be determined from the ratio:

here h is the wear of the tooth along the pitch circle;

ω ₀ - constant angular speed of rotation of the gear;

r ₁ is the radius of the pitch circle of the gear;

Δt is the deviation of the duration of the passage of half the angular step from the nominal due to wear of the tooth profile.

On Fig presents the implementation of the measurement due to the inconsistency of the "phase" of the gear wheel and dashed lines conventionally shows a worn tooth profile. To simplify, wear is shown uniform over the entire height of the tooth, although in reality this is not so because of the variable sliding speed. Ф ₀ is the nominal value of half the angular step (“phase”), and Δφ ₁ , Δφ ₂ , ..., Δφ _n is the wear of the working tooth profiles along the pitch circle in angular units. It is assumed that the gear rotates always in one direction, so the working profiles are on one side.

On Fig presents an experimental chronogram in the linear coordinates of the rotation of the tooth of the gear wheel showing the rotation trend, and Fig. 18 is a difference chronogram between the chronogram of Fig. 17 and its trend (to determine the wear of the nth tooth, it is necessary to take the difference of two graphs by n m step). Having excluded from consideration the influence of the gear ratio, it is necessary to use formula (11) to determine the wear. For example, the wear of the third gear tooth will be equal to:

h ₃ = ω ₀ · r ₁ · Δt ₃ = 32.97 · 38.75 · 6 · 10 ^-3 = 7.6 μm

For the lathe UT16P we consider a gear wheel No. 11 according to the passport of the machine: Z = 31, m = 2.5 mm. Then the width of the tooth along the pitch circle is h = m / 2. Those. in our case, h = 1.25 mm. According to the requirements of regulatory documents, depending on the type of gear transmission, wear is allowed from 5 to 15% of the nominal size. Imagine the toughest option, then the maximum allowable wear is Δh = 62.5 μm. With a wear of 7.6 μm, real wear is 12.5% of the possible maximum wear. Thus, in the case of uniform wear of the teeth during operation of the machine (no breakage and fatigue chipping (partial surface destruction of the tooth)), the remaining gear life is 87.5%.

The two specific examples of the implementation of the diagnostic method show the wide functionality and high accuracy of diagnosis using the phase-chronometric method of the class of cyclic machines - metal-cutting machines.

Claims (1)

A method for diagnosing cyclic machines - metal-cutting machines by the phase-chronometric method, including: preliminary determination of the list of diagnosed parameters and possible defects of the machine and structural breakdown of the machine into parts that are critical for diagnosing parameters and possible defects; dividing the working cycle of the machine and its parts into separate phases; drawing up with the degree of detail necessary for precision determination of the values of diagnosed parameters and possible defects, mathematical models of the working cycle of machine parts and their interaction in a phase-chronometric representation for the relationship of measurement results with the corresponding processes or phases of the cycle in the working parts of the machine; the installation in the machine parts of precision, with a relative error of not more than 10 ^-4 %, chronometric sensors for the phases of the working cycle, the outputs of the sensors are connected to the processing unit for the signals of their measurements, the block also contains work programs for mathematical models of the working cycle of machine parts and their interaction for subsequent processing the measurement results, while the location of the sensors in the machine is determined by the design of the machine parts, and the installation locations of the sensors are determined in terms of obtaining the most complete information about the operation ie parts of the machine; precision measurements by the indicated sensors of the time intervals of the phases of the working cycles of machine parts and their interaction with the presentation of the processed measurement information in a single metrological format at all stages of the life cycle of the machine and in mathematical modeling of the working cycles of machine parts and their interaction, namely: obtaining data arrays formed by series measured sequentially, i.e. without gaps, series of time intervals of phases in a single reference time; in the course of processing the measurement results, the values of the parameters included in the mathematical models are refined to match the current technical condition of the machine, and then the values of the diagnosed parameters and possible defects of the machine are determined by the results of simulation using the updated models and subsequent mathematical processing, according to which the current technical condition of the machine; primary analysis of the series of sensor signals consists in the construction and comparison of arrays of series of precision time intervals at different time intervals; secondary analysis - statistical mathematical processing by methods recognized as optimal for processing signals of precision time intervals, taking into account the nuances of the corresponding class of diagnosed cyclic machines: correlation analysis of rotation chronograms; spectral analysis of rotation chronograms; cross-spectral analysis; Fourier transform and / or trend analysis; regime analysis; simulation chronograms and frequency spectra derived from them, obtained as a result of a computational experiment, are compared with experimental graphs; criteria for comparing experimental and simulation graphs - first of all, the scatter of the range of values, the trend of deceleration or acceleration, the exit at a steady state beyond the threshold values; experimental chronogram data is primarily used to refine the parameters of the mathematical models used in the diagnosed cyclic machine and to further approximate the simulation results, characterized in that in metal-cutting machines the list of diagnosed parameters and possible defects of the machine includes: manufacturing defects of the machine and its elements; assembly defects after repair or installation of individual elements; worn, broken, poorly fixed parts and elements of the machine; determination and measurement of unbalance in the machine; dynamic parameters and geometric characteristics of a metal cutting machine; physical and mechanical properties of machine elements; characteristics of devices for fixing parts and tools; identification of the output and input control of the technological equipment of the machine by comparing the results of measurement with a phase-chronometric system on a particular machine during bearer tests of finished products at the manufacturer and input control at the consumer of the product; at the same time, the following are recognized as critical structural components of the machine: for a machine with a horizontal axis of rotation of the spindle: an asynchronous motor with a gearbox of the machine or a gear motor; spindle unit of the machine with the workpiece in the spindle chuck; tailstock of the machine; caliper with a cutting tool; for a machine with a vertical axis of rotation of the spindle: an induction motor with a gearbox of the machine or a gear motor; spindle unit of the machine; cutting tool in the spindle; workpiece in a vice; installation locations of chronometric sensors are determined from the point of view of obtaining information about the operation of the basic components of the machine and the design of the machine, namely: - to measure the rotation parameters of an induction motor, installation on the motor side is required; - to measure the rotation parameters of the machine speed box, the installation of sensors on the input and output shaft of the box; - to measure the wear of gears in the gearbox, installing sensors on each gear in the gearbox; - to measure the parameters of rotation of the spindle, the installation of the sensor at the output of the spindle, in the places of fixing the cutting tool or workpiece - chucks; - to measure parameters and study the cutting process, the installation of sensors from the tailstock side of the machine; - to measure the processing parameters and wear of the cutting tool, the installation of sensors in the corresponding sections of the workpiece; the features of installing chronometric sensors on machines with vertical and horizontal spindle layout are associated with features of the cutting process, structural elements of machines, differences in rigidity and geometry parameters; the cyclic operation of the machine is divided into the following basic phases of the cycle: turning on / starting the machine; work of the machine in idle mode at different speeds of rotation; cutting tool cutting into the workpiece material; part machining process; cutting the workpiece with a cutting tool; critical wear of the cutting tool when approaching the maximum standard operating time of the cutting tool or accelerated wear; tool exit from the workpiece; machine stop; mathematical models of machine nodes and node interactions for each phase are presented in the form of systems of nonlinear differential equations containing in the form of coefficients concentrated or distributed system parameters, such as moments of inertia, stiffness, internal and external friction coefficients, geometry and material of the cutting tool, material and shape blanks, external conditions temperature and humidity, characteristics of an induction motor, gear ratios of gearboxes; The features of mathematical models of machines with vertical and horizontal spindle layout are expressed in the recording of the initial equations of the system, which are primarily associated with the influence of gravity and a change in the direction of the bending-torsional vibrations of the system.

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