RU2009765C1 - Method for determining tool coordinates when machining cylindrical blanks - Google Patents

Abstract

FIELD: machine tool manufacture. SUBSTANCE: tool is set in mechanical high-frequency and ultrasonic oscillations in the direction of the main cutting movement while machining a blank after the beginning of cutting. The oscillation amplitude is determined on condition of stability of the cutting process. Cutting time τ and linear velocity V of tool vibrations during time t are measured for each cycle of oscillations. This allows the tool coordinate Y in the part coordinate system to be determined from a formula Y=U·τ/2·Πn(T-2τ) where n is the number of blank revolutions. EFFECT: improved accuracy. 2 dwg

Description

 The invention relates to metal cutting machines, mainly to methods for their adjustment, and can be used to automate the tuning of metal cutting machines, for example, a turning group.

 The purpose of the invention is improving accuracy.

 In FIG. 1 shows a diagram of a process for implementing the method; in FIG. 2 is a block diagram of a device for implementing the method. The device comprises a vibrator 1 mounted on a machine support, a cutting tool 2, a piezoelectric vibration sensor 3, a noise and vibration meter 4, designed to measure the linear velocity V of the tool’s vibration during time τ, a 5 time interval meter, designed to measure the current value of the cutting time τ in each cycle of oscillations of the tool, switching unit 6, analog-to-digital converter 7 and control unit 8 (micro-computer) connected to the CNC system 9.

 The second input of the switching unit 6 is connected to the second output of the meter 4, the second input of which is connected to the second input of the meter 5, the output of the CNC system 9 and the input of the sensor 3. A switch 6, a vibrator 1, and the input of the CNC 9 are connected to the control unit 8.

 The method is as follows.

 The tool coordinate OY in the direction of the radial component of the cutting force can be represented by the current value of the machining radius R.

10³мм , (1) где V_{о тек} - текущее значение линейной скорости обработанной поверхности;
n - число оборотов заготовки.It is known that
R =

10 ³ mm, (1) where V _{о tech} is the current value of the linear velocity of the treated surface;
n is the number of revolutions of the workpiece.

The current value _of the linear V _tech preform speed is determined as follows.

Oscillations of the tool (Fig. 1) begin at some point O. When the tool moves in the (+ OZ) direction with a speed of V = + a ω cos ω t in the EA segment, chip 1 is formed during cutting and during the time τ the links form an element of the pair tool part. Moreover, each of the many points of the EA segment passes a path equal to the cutting length in one oscillation cycle
l = (V + V _{o tech} ) τ (2)
With further movement in the direction (- ОZ), the pair element breaks. At a distance from point A to point E, the chip does not contact the front surface of the tool during the time of the shockless movement of the tool τ ^- = (T-τ) and point A will pass the path
l = V _{about tech} (T-τ), (3)
in this case, point B moves to the initial position of point E, and point D, respectively, to position A.

V. (4)
Подставляют правую часть (4) в (1) и окончательно записывают формулу для определения координаты инструмента, с учетом, что R = OY:
OУ =

10³мкм. (5)
В соответствии с блок-схемой (фиг. 2) по команде на проведение измерений система ЧПУ 9 запускает программу обработки. После врезания блок 8 управления запускает программу измерений Блок 8 управления включает вибратор 1, который возбуждает механические высокочастотные или ультразвуковые колебания инструмента в направлении главного движения резания.We proceed from the condition that the rotation angles of the workpiece are equal in each cycle of tool vibrations, equate the right parts of expressions (2) and (3), solve the resulting equation for V _{о tech} and write this value in the form
V _{about tech} =

V. (4)
Substitute the right side of (4) in (1) and finally write down the formula for determining the coordinate of the tool, taking into account that R = OY:
OU =

10 ³ microns. (5)
In accordance with the block diagram (Fig. 2), on the command to take measurements, the CNC system 9 starts the processing program. After plunging, the control unit 8 starts the measurement program. The control unit 8 includes a vibrator 1, which excites mechanical high-frequency or ultrasonic vibrations of the tool in the direction of the main cutting movement.

 The value of the frequency (period T) of the tool vibrations is selected in the range of 18-30 kHz according to the passport of the vibrator mounted on the support of the machine. This frequency range is due to the fact that vibrations below 10 kHz can be transmitted to the cutting tool not only through the contact area with the workpiece, but also through the machine headstock. Oscillations above 30 kHz strongly attenuate when passing through the joints of parts, therefore they require a greater power of the vibrator, which causes an increase in its dimensions.

The amplitude a of the oscillations is determined from the condition of stability and intermittent cutting in the form a ≥ 12.5 V _about T 10 ³ μm. The upper limit of the amplitude is determined by the advisability of the working stroke of the tool, that is, point A, at least, should not go beyond the diameter of the workpiece.

 A vibration sensor 3, which is an accelerometer, is mounted on the tool.

 Mechanical vibrations by means of the sensor 3 are converted into an electrical signal proportional to the acceleration, which is then fed to the input of the noise and vibration meter 4, where they are amplified by a pre-amplifier, converted by an integrator into a signal proportional to the linear velocity V of the vibrational movement of the instrument, and a constant component is isolated signal using detection. At the same time, the isolated constant component of the signal is fed to the input of the meter 5 time intervals, where the time interval of periodic signals is measured in the form of cutting time τ in each cycle of the tool oscillations. The switching unit 6, controlled by a microcomputer, connects the analog-to-digital Converter 7 to the meter 4 noise and vibration and the meter 5 time intervals. The analog-to-digital Converter 7 converts the analog signals of the meter 5 time intervals and the meter 4 noise and vibration into digital codes of micro-computers. The microcomputer processes the signal according to the algorithm (5) and, depending on the calculation result, issues an appropriate command to the CNC system 9 to adjust the processing program.

 PRI me R implementation of the method.

 Processed in the centers of the shaft. Shaft diameter D = 200 mm. Shaft length Z = 2000 mm.

Cutting mode: calculated linear speed of the machined surface V _{о calc} = = 150 m / min (number of workpiece revolutions n = 242, 4908 rpm); cutting depth t = 1.5 mm; feed S ₀ = 0.3 mm / rev; T15K6 through passage cutter; processed material - Art. 45.

The parameters of the vibrational movement of the tool: the oscillation period T = 50 ˙10 ^-6 s. ; the calculated value of the amplitude is a = 93.75 microns. ; the adopted amplitude value is a = 100 microns.

Measured parameters: cutting time in each cycle of tool vibrations τ = 5 ˙ 10 ^-6 s. ; the current value of the speed of the vibrational movement of the tool during the cutting time τ: V = 1199.2 m / min; the current value of the tool coordinate in the workpiece coordinate system OY = 98.4343 mm. (56) Copyright certificate of the USSR N 1685609, cl. B 23 B 1/00, 1990.

Claims (1)

METHOD FOR DETERMINING THE INSTRUMENT COORDINATE DURING THE PROCESSING OF CYLINDRICAL Billets, according to which, when moving the tool relative to the rotating workpiece, the tool is subject to fluctuations in the direction of the main movement with frequency and amplitude, the values of which are measured determine the tool coordinate using the measured values, characterized in that, in order to improve accuracy, measure the linear speed the axis v of the vibrational movement of the tool over the time τ of cutting in one cycle of the oscillations of the tool, and the coordinate Y of the tool is determined by the expression
Y =

,
where n is the number of revolutions of the workpiece;
T is the period of oscillation.

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