RU2379737C2 - Method of maintaining acceptable technological modes - Google Patents

Abstract

FIELD: physics; control.

SUBSTANCE: invention relates to methods of controlling technological modes, particularly modes for mechanical processing with application of ultrasonic oscillations onto a workpiece and can be used in mechanical engineering for automatic maintenance of acceptable technological processes by changing processing conditions on NC machines. The method of maintaining maximum allowable technological modes on cutting machines with application of ultrasonic oscillations on a workpiece involves measurement of information-bearing parametres of these modes, entering the results into a computer and using the results to determine standardised factors of technological modes which are compared with acceptable values. During cutting, ultrasonic oscillations with amplitude of 4-6 mcm are applied to the workpiece, while measuring the greatest information-bearing parametre at the same time, where the said information-bearing parametre is the value of change in voltage of the piezoelectric transducer of the oscillatory system AU. The correlation relationship between them and surface roughness of the workpiece Ra are determined. Values of critical changes of voltage of the piezoelectric transducer of the oscillatory system are determined and if the value is greater than 35%, the load is reduced, and if less than 10% the load is increased.

EFFECT: wider functional capabilities of maintaining maximum allowable technological modes.

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Description

The invention relates to mechanical engineering and can be used to maintain the maximum permissible technological conditions during machining with superposition of ultrasonic vibrations on the workpiece on CNC machines.

A known method for automatically monitoring the state and conditions of the cutting process and a device for its implementation, containing two piezoelectric transducers to create a probing signal for recording the reflected energy of ultrasonic waves (SU 1380910, IPC B23Q 15/00, 1988).

The disadvantage of this method is the presence of two sensors mounted in the tool body; when replacing the tool, it is necessary to remove the sensors, prepare seats and install sensors, which leads to a loss of accuracy and an increase in the cost of the tool.

Closest to the claimed invention is a method of maintaining the maximum permissible technological modes, comprising measuring devices and a computer, which determines the decrement of oscillations at the natural frequencies of the system, the obtained values are compared with a critical value (RU 2246124, IPC G05B 19/18, B23Q 15/007, 2005 )

The disadvantage of this system is the inability to maintain optimal processing modes in real time, since the change in processing modes occurs only after the end of the processing process and control of the part.

Known methods for the maximum maintenance of the maximum allowable technological regimes have a low technical level, determined by the inability to control the surface roughness of the workpiece in real time, the inability to quickly control the parameters of surface roughness through changes in processing conditions and outdated element base, in this regard, an important task is to create ways to maintain the maximum allowable technological modes adapted to CNC machines.

The technical result of the invention consists in determining the surface roughness of the workpiece during machining with the application of ultrasonic vibrations to the workpiece and expanding technological capabilities through the use of feedback "piezoelectric transducer of the oscillating system with the workpiece - high-frequency ultrasonic generator".

The technical result is achieved in a method of maintaining the maximum permissible technological modes of the system, including measuring the informative parameters of these modes, entering the results into a computer and determining the normalized parameters of technological modes from them, which are compared with acceptable values between the received signal characterizing the most informative parameter, and establish a correlation with surface roughness of the workpiece, for which the critical value of the voltage change of the piezoelectric is determined nical transducer vibrational ultrasonic machining system in the range of 10-35% and if the obtained value is more critical load is reduced, and if less, increase it.

The method is illustrated by drawings, where Fig. 1 shows a diagram of the implementation of the method, Fig. 2 is a schematic diagram of maintaining the maximum permissible technological modes, Fig. 3 shows the dependence of the surface roughness of the workpiece on the voltage change of the piezoelectric transducer of the oscillatory system.

The method of maintaining the maximum permissible technological modes is carried out on gear-milling equipment using an ultrasonic generator UZG 3-0.4 and a high-frequency voltmeter when processing a workpiece - steel 40X, mill - P6M5, V = 0.67 m / s, S = 1 mm / rev, m = 0.8 mm, the number of teeth of the cut wheel is 60, ξ = 4-6 microns. The error in determining the surface roughness does not exceed 10%. The system (figure 1) contains a workpiece 1, mounted on a piezoelectric transducer of an oscillatory system, electrically connected with a high-frequency ultrasonic generator 2, an electronic unit 3, a computer 4 and a metal cutting machine with CNC 5.

The electronic unit 3 includes (Fig. 2) a unit for detecting a change in voltage 6 during machining with superposition of ultrasonic vibrations on the workpiece during cutting.

The change in voltage is determined by the dependence:

where U _bnagr - the excitation voltage of the Converter of the oscillatory system without load;

U _pr.rez - the excitation voltage of the Converter of the oscillatory system in the cutting process.

The change in voltage during ultrasonic cutting is measured by a high-frequency voltmeter of an ultrasonic generator, the results of experiments to determine the dependence of the surface roughness of the sides of the cut gear are shown in the table, and the same graphical dependence is shown in Fig. 3

The introduction of electronic unit 3 provides the ability to control surface roughness in real time and maintains the maximum permissible technological modes, and the introduction of computer 4 - calculation of correction of cutting conditions and the implementation of decisions on changing cutting conditions in the system of a CNC machine 5, provides operational control of surface roughness parameters blanks through a change in cutting conditions.

Figure 2 shows a schematic diagram of maintaining the maximum permissible technological modes, which is made in the form of a metal-cutting machine with CNC 5, in the cutting zone of which a piezoelectric transducer with a workpiece 1, powered by an ultrasonic generator 2, to which an electronic unit 3 is connected, including a unit for recording the assessment of voltage changes 6, the signal from which through an analog-to-digital converter 7, narrow-band low-pass 8 and high-frequency 9 filters is fed to the comparison unit by the parameters of the surface roughness 10 of the computer 4, to the other input of which a signal is sent from the surface roughness modeling unit for ultrasonic cutting 11, and the input signal from the comparison unit according to the surface roughness parameters 10 is supplied to the complex surface roughness assessment unit for workpieces 12.

Information about the state of surface roughness in the form of standardized parameters (Ra, Rmax, Rz) and non-standardized parameters (ρ _indent , ρ _protrusion, α _σ ) obtained after calculation according to a special program is supplied to the electrically connected random-access memory 13, display 14 and a printing device 15 that provides operational information about the process of forming irregularities and to the calculation unit for correcting the cutting conditions 16, electrically connected to the unit for implementing decisions on changing the cutting conditions 17, which are mounted vans in the system of a CNC cutting machine 5 and issue commands to the actuators 18.

The method is as follows (Fig. 2): an ultrasonic generator 2 supplies a high-frequency voltage to a piezoceramic transducer of an oscillating system with a workpiece 1 fixed on it; under the influence of cutting forces, a change in the voltage value occurs, which is recorded and processed by an electronic unit 3, which includes a unit assessment of registration of voltage changes 6, analog-to-digital Converter 7, the signal from which is fed to narrow-band filters of low 8 and high frequencies 9 to highlight the frequency deleterious spectrum characterizing the surface roughness of the workpiece. The comparison unit according to the parameters of surface roughness 10, which is included in the computer, simultaneously receives signals from the narrow-band low-8 and high-frequency 9 filters and the surface roughness modeling block during ultrasonic cutting 11, and the processed signal is transmitted to the complex surface roughness assessment unit 12, which the program calculates standardized parameters (Ra, Rmax, Rz) and non-standardized parameters (ρ _indent , ρ _protrusion , α _σ ) whose values are displayed on the random access memory 13, display 1 4 and a printing device 15, which allows you to quickly monitor the process of forming microroughnesses during the cutting process and the block for calculating the correction of the cutting conditions 16, the block for implementing decisions on changing the cutting conditions 17 combined with the system of a metal cutting machine with CNC 5, issuing commands to the actuators 18, providing operational correction of technological modes.

Concrete implementation example

The roughness of the lateral surface of the teeth of the cut gear wheel z = 60 was determined with the application of ultrasonic vibrations of amplitude 4-6 μm on a billet made of steel 40X with a worm-modular milling cutter from P6M5 with t = 0.8 mm at various cutting conditions. The changes in the voltage of the piezoelectric transducer during mechanical processing were recorded and evaluated by the formula:

where U _bnagr - voltage piezoelectric transducer without load;

U _pr.rez - voltage of the piezoelectric transducer during machining.

For the sixth class of surface roughness, the numerical values, the arithmetic mean value of the profile (Ra) are in the range 1.25-2.5 μm, which corresponds to a change in the voltage of the piezoelectric transducer by 10-35%, as shown in figure 3, if this value more critical value, then the load is reduced, and at a lower increase.

The method allows to optimize technological processing conditions by maintaining the specified surface roughness values on CNC machines and expand the technological capabilities of machining when applying ultrasonic vibrations to the workpiece.

Claims (1)

A method of maintaining the maximum allowable technological conditions on metal cutting machines with superimposed ultrasonic vibrations on the workpiece, including measuring the informative parameters of these modes, entering the results into a computer and determining normalized parameters of technological modes from them, which are compared with acceptable values, characterized in that during cutting the workpiece is superimposed by ultrasonic vibrations with an amplitude of 4-6 microns, while measuring the most informative parameter, for which I take voltage change value ΔU piezoelectric transducer vibrational system is set correlation between it and the surface roughness of the workpiece Ra, determine values of the critical values of the voltage change of the piezoelectric transducer when vibrating system and the value is reduced more than 35% load and at a value less than 10% increases the load.

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