JPH0457656A - Controller for cutting machine - Google Patents

Abstract

PURPOSE:To detect surely working power even if the working is performed during the increase of the power in motor start-up by providing a clamp circuit and charging/discharging circuit in a controller to detect the power change a discharge voltage in the motor start-up. CONSTITUTION:Consumptive power P sample from a driving motor 1 by an electric power detector 2 passes through a noise removing circuit 3 to be clamped at a clamp level (a) by a clamp circuit 10 in a time T1 of operating a time 11 in a working power extracting circuit 4 when consumptive electric power f(t) is increased in the motor start-up. At the same time, a gate 12 is opened to charge the clamp voltage to a charging/discharging circuit 13. When the timer 11 is up and a time setter 14 is operated, the circuit of the charging/ discharging circuit 13 is changed over to the discharge. As soon as electric power charged during a time T2 is discharged, the gate circuit 12 is opened to output the consumptive electric power f(t) to a calculating circuit 15 in which the consumptive electric power f(t) is subtracted from discharge voltage f(e) obtained from a discharge curve to calculate working electric power f(t1).

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a control device that controls the movement of a cutting machine by detecting the wear state of a tool from the power consumption of an electric motor of the cutting machine.

[Conventional technology]

Figure 4 shows the power waveform when the power consumption of the electric motor of the cutting machine is extracted over time. It rises, then stabilizes at the power value under no load, and then rises and falls repeatedly every time machining is performed.

In order to accurately detect the wear state of a cutting tool from changes in power consumption, it is necessary to target only the power during machining when the tool is actually cutting into the workpiece. The machining power is calculated by subtracting the no-load power from the power consumption.

In conventional control devices, such detection is performed by determining the power value f( to
) and subtract it from the power consumption to obtain the machining power f
(tI).

[Problem to be solved by the invention]

However, in the actual machining cycle, in order to shorten the machining time, there is no load stabilization period between the start of the motor and the start of machining, as shown in Figure 3 (N), so that the power increase at startup does not decrease. Processing may be performed in between.

In such a machining cycle, the timing for detecting the no-load power cannot be determined, so the power of the actual load cannot be accurately detected, and there is a problem that changes in the machining power cannot be accurately captured.

Therefore, the present invention solves the above problems and provides a control system that can reliably detect machining power and accurately judge tool wear even when machining is performed during the power increase at startup. The purpose is to provide equipment.

[Means to solve the problem]

In order to solve the above problems, the control device of the present invention includes a power detector that detects the power consumption of the drive motor of a cutting machine, and extracts the machining power involved in cutting from the power consumption detected by the power detector. and a control circuit that compares the output signal of the machining power extraction circuit with a variable setting reference value and outputs a control signal to the cutting machine based on the comparison result. The extraction circuit includes a clamp circuit that clamps the output signal of the power detector at a constant level for a predetermined period of time, a charge/discharge circuit that charges the output signal of the clamp circuit through a variable resistor, and a discharge time of the charge/discharge circuit. It is composed of a time setting device for setting, and a compensating circuit that subtracts the output signal of the charging/discharging circuit from the output signal of the power detector.

C action] In the above configuration, after the driving electric motor is started, the power that increases rapidly is clamped at a level greater than the power consumed during machining in the time range from startup to the start of machining, and the clamped output signal is Charge with a charge/discharge circuit.

Next, this charged power is discharged over a time range that includes the machining period specified by the time setting device, and the discharge curve is matched to the power change curve at the time of starting the electric motor by changing the resistance.

By matching the discharge curve to the power curve in this way, it is possible to determine the change in power under no load, and by subtracting this discharge power from the consumed power, the machining power can be detected.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings.

As shown in FIG. 1, the control device of the embodiment includes a power detector 2 connected to a driving motor 1 of a cutting machine, a noise removal circuit 3 that removes noise components from detected power consumption, and a power consumption An abnormal overload detection circuit 6 and a gear tooth are connected to a basic circuit which sequentially connects a machining power extraction circuit section 4 that extracts machining power while using the machining power, and a control circuit section 5 that determines the wear layer of the tool from the obtained machining power. It is constructed by connecting an eliminator circuit 7.

Next, each of the above-mentioned constituent parts will be sequentially explained.

The driving electric motor Ill is intended for an electric motor involved in cutting, such as an electric motor for rotating a main shaft or an electric motor for punching a feed shaft.

The power detection section 2 detects the power consumption of the drive motor 1 and outputs it to the noise removal circuit 3. The power consumption P detected by the power detection unit 2 includes the machining power f (t) involved in machining, the no-load power r (to ), and periodic power consumption caused by vibrations of the heald and the characteristics of the electric motor. Noise component (asinω.

t,, bsin 2ω+t), and P =
f (t) + f (t, ) + asin ω, t + b
It is expressed as sin 2ω+t.

The noise removal circuit 3 removes low frequency noise (asinω) generated from the motor belt, pulley, or mechanical vibration.

It consists of a low-frequency noise removal filter 8 that removes the The filter 8 can be configured by combining a band r-wave circuit, a level adjustment circuit, a phase inversion circuit, and an adder, as proposed in Japanese Patent Publication No. 57-57223.In this way, power consumption can be reduced. When noise is removed, contact between the cutting tool and the workpiece can be detected accurately without time delay, and changes in machining power can be detected with high precision.

Machining power extraction circuit section 4 connected to the noise removal circuit 3
consists of a clamp circuit 10 including a timer 11, a gate circuit 12 and a charge/discharge circuit 13 connected to the clamp circuit 10, a time setter 14 that outputs a signal to the gate circuit 12 and charge/discharge circuit 13, and a gate circuit. 12, an arithmetic circuit 15 to which signals are input from the charge/discharge circuit 13, and an amplifier circuit 16.

FIG. 2 shows a specific circuit configuration of the above configuration excluding the amplifier circuit 16.

As shown in FIG. 2, the clamp circuit 10 includes a noise removal circuit 3 and a variable setting device 1 for setting the clamp level a.
7 is connected to the comparator 18, and (II
), the signal of power consumption f(t) output from the noise removal circuit 3 is applied to the time (T) set by the timer 11.
, ) is clamped at level a. The above-mentioned clamp level a is usually set to a value larger than all power consumption during machining.

As shown in FIG. 3 (El), the timer 11 includes a comparator 19 to which a signal of a start level S set slightly larger than the zero point and a signal of power consumption f(L) are input, and a comparator 19 that receives the signal of the power consumption f(L), and the clamp level The signal of a and the power consumption f(t
) is input to the comparator 20, and is activated by the trigger signal e output when the power consumption f(t) exceeds the start level S, and the power consumption f(t) is clamped. It is set to be deactivated by a trigger signal g that is output when the level is lower than level a.

This timer 11 includes a clamp circuit 10 and a charge/discharge circuit 13.
The gate 21 interposed between the two is opened to allow clamp power to pass through the charging/discharging circuit 13 only for the period of its operation time. The signal from the timer 11 is also output to the time setter 14.

The time setting device 14 consists of a one-sit timer, and the third
As shown in the figure (DI), the timer 11 is activated by a trigger signal g which is an operation end signal.

This operating time (T2) can be set arbitrarily, and is usually set so that the entire machining time is included within that time.

The signal from the time setting device 14 activates the discharging operation switch 22 of the charging/discharging circuit 14 to perform a discharging operation within a time range (T2), and also activates the discharging operation switch 22 of the charging/discharging circuit 14 to perform a discharging operation within the range of time (T2). The circuit 12 is opened and the power consumption that has passed through the clamp circuit 10 is passed to the arithmetic circuit 15 within the above time range (T2).

The charge/discharge circuit 13 includes a clamp circuit 10 and an arithmetic circuit 1.
5, and is provided with a capacitor 23, a variable resistor 24, a discharge operation switch 22, and the like. In this charge/discharge circuit 13, within the time period (T1) during which the gate 21 is open due to the operation of the timer 11,
Clamp voltage f (c
) is charged, and when the timer 11 goes off and the time setter 14 is activated, the internal circuit is switched and the charged power is discharged within the operating time (T) of the time setter 14. In this case, the resistor 24 By changing the resistance value, the discharge curve can be changed (the range shown by the broken line in Fig. 3 (DI)). Match the power change curve.

The released tt force f (e) obtained in this way is expressed as the buffer 2
5 to an arithmetic circuit 15, which is composed of a differential circuit 26 and a full-wave circuit 27.

The differential circuit 26 subtracts the clamp power f(c) passing through the gate circuit 12 and the power consumption f(t) from the discharge power f(e) output from the charging/discharging circuit 13, and provides a full-wave The circuit 27 removes the clamp power from the output value of the differential circuit 26 and outputs the signal in an inverted state.

Through the computation of this arithmetic circuit 15, the no-load power value is subtracted from the power consumption f(t), and only the machining power involved in machining is determined, and this determined machining power is shown in FIG. The signal is sent to the amplifier circuit 16 as shown in FIG.

This amplifier circuit 16 doubles the extracted machining power f(tl) (where 1<K), greatly amplifies the change in power, and outputs the result. This output value f(tz)−KXf (
tl) becomes the basic machining power for the next control (see Fig. 3 (VT) and (■)).

The control circuit unit 5, which receives the machining power f(tx) from the amplifier circuit 16, includes an integrating circuit unit 28 that integrates the machining power over the machining time range, and outputs a control signal based on the obtained integral value. It consists of a determination circuit section 29.

The integration circuit section 28 includes a machining time setting circuit 30 that sets a machining time as a control range, and an integrating circuit 31. The machining time setting circuit 30 includes a comparison circuit 32, an OR circuit 33, and a gate circuit 34. It is composed of.

The comparison circuit 32 is inputted with a reference value m set larger than the reference power 4rLf(ta), and the machining power r
(tz) and its reference value m are compared, and when the power fDt) passes the reference value m, a signal is output to the OR circuit 33.

The OR circuit 33 receives a timing signal such as a pulse wave from one terminal connected to an external timing signal source, selects either the timing signal or the signal from the comparison circuit 32, and sends the timing signal to the gate circuit 34. Outputs gate signal.

Further, when the gate circuit 34 receives a signal from the OR circuit 33, the processing power f(t
z) is passed through the integrating circuit 31.

On the other hand, the integrating circuit 31 performs integral calculations on the machining power signal inputted manually from the gate circuit 34 (see FIG.
), this integrated value f(ts) - 5f(tz)
is then output to the determination circuit section 29.

This determination circuit section 29 is composed of a counter 35, an average value calculation circuit 36, and a comparison circuit 37.

The counter 35 counts the signal from the comparison circuit 32 of the above-mentioned integration circuit section 28 N times from immediately after the tool change,
The signals up to the Nth count are output to the average value calculation circuit 36.

The average value calculation circuit 36 sequentially accumulates each output inputted from the counter 35 and the integration circuit section 28, and stores them as the number of processing times N and the total sum Σr(ts) of the integral values. Then, the average value r(ta)-Σf(ts)/N of the integral values is calculated by dividing the total sum of integral values by the number of N machining times, and the calculated average value f(tl) is sent to the comparison circuit 37. Output to.

The comparator circuit 37 amplifies the input average value and then compares it with the integral value f(ti) output from the integrating circuit unit 28, and when the integral value reaches the average value or more, outputs a control signal to the cutting machine. (tertiary output signal).

The control signal from the determination circuit section 29 can be a signal for changing the depth of cut or feed amount in a cutting machine, or a command signal for tool exchange.

On the other hand, an abnormal load detection circuit 6 is connected to the noise removal circuit 3 together with the machining power extraction circuit section 4 .

This detection circuit 6 suddenly increases when there is an abnormal collision between the cutting tool and the workpiece due to a malfunction in loading the workpiece, or when machining is performed without the cutting tool being properly installed. It detects the power consumption, and the power consumption f
When (t) reaches a preset value C (this value is greater than the comparison reference value for control), an output signal is generated to stop the cutting tool's depth of cut and the feeding device (primary output signal).

In addition, a gap eliminator circuit 7 connected to the machining power extraction circuit section 4 extracts the machining power and a preset reference value d.
When the machining power f (t The cutting tool is fed rapidly until it comes into contact with the workpiece, and when the cutting tool and workpiece come into contact, it automatically switches to normal cutting feed, reducing blank time not involved in machining. effective.

The control device of this embodiment has the structure as described above, and its operation will be explained next.

When the power consumption P sampled by the power detector 2 from the target drive motor 1 passes through the noise removal circuit 3, noise components are removed from the inside, resulting in power consumption as shown in the waveform of FIG. 3 (1). f(t) is obtained.

In the machining power extraction circuit 4, when the power consumption f<1> increases at startup, the timer 11 is activated, and the clamp circuit 10 reduces the power consumption to the clamp circuit loop a for the time period (T,) during which the timer 11 is activated. (see FIG. 3 (II)). At this time, the gate 21 is simultaneously opened and the charge/discharge circuit 13 is charged with the clamp voltage.

When the timer 11 runs out and the time setter 14 operates, the charging/discharging circuit 13 switches to discharging, and the electric power charged during the time (T2) is discharged. In this case, the resistance of the resistor 17 is changed to match the discharge curve with the power change curve at startup. (FIG. 3 (■)) Furthermore, at the same time as the time setting device 14 is activated, the gate circuit 12 is opened and the power consumption f (t) is output to the arithmetic circuit 15 .

In the arithmetic circuit 15, the machining power fN+) is calculated by subtracting the power consumption f(t) from the discharge voltage f(e) obtained from the discharge curve. The power waveform at this time becomes the waveform shown in FIG. 3 (Vl).

The processing power f(tz) obtained by amplifying this signal is sent to the integrating circuit section 28 of the control circuit section 5.
When the machining power f(ti exceeds the level m set by an external signal, the comparison circuit 32 outputs a signal, the gate circuit 34 opens, and the signal is input to the integration circuit 31. The circuit 31 integrates the output portion of the machining power f(t) that has passed through the gate circuit 34 and exceeds the set level value m.

The average value calculating circuit 36 accumulates the integral values f (ti) inputted from the integrating circuit 31, and each time they are updated, the total value Σf(ti) of the integral values is divided by the number of machining times N to calculate the average of the integral values. A value f(t4) is calculated and output to the comparison circuit 37.

In the comparison circuit 37, the average value is compared with the integrated value from the integration circuit 31, and a control signal corresponding to each wear state of the cutting tool is output.

Note that in the above embodiment, the amount of electric power is used as the power consumption, but the amount of current of the electric motor can also be used as the target power.

Further, although the operating time of the time setter 14 which determines the discharge time is determined by a timer, the timing of starting and ending the discharge may be directly instructed by an external signal.

Furthermore, the obtained machining power can be directly amplified and used for comparison without being subjected to integration processing.

〔Effect of the invention〕

As described above, since the control device of the present invention is equipped with a clamp circuit and a charging/discharging circuit, it is possible to detect the power change at the time of starting the motor as a discharge voltage. Even when the cutting conditions overlap, the machining power can be reliably extracted and the cutting state can be controlled accurately and stably.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the control device of the embodiment, Fig. 2 is a circuit diagram showing a specific example of the machining power extraction circuit as above, and (1) to (■) in Fig. 3 are respectively in the control device as above. FIG. 3 (■) is a diagram showing the voltage waveform obtained, and FIG. 4 is a diagram showing changes in power consumption of the motor. DESCRIPTION OF SYMBOLS 1... Drive electric motor, 2... Power detector, 3... Noise removal circuit, 4... Machining power extraction circuit section, 5... ... Control circuit section, 6 ... Abnormal overload detection circuit, 7 ... Gap eliminator circuit, 10 ...
... Clamp circuit, 11 ... Timer, 1
2...Gate circuit, 13...Charging/discharging circuit, 14...Time setting device, 15.
...Arithmetic circuit, 16...Amplification circuit,
24...Variable resistor, 31...Integrator circuit, 3S...Counter, 36...
. . . Average value calculation circuit, 37 . . . Comparison circuit. (N) (resistant

Claims (1)

[Claims] (1) A power detector that detects the power consumption of a drive motor of a cutting machine, and a machining power extraction circuit that extracts the machining power involved in cutting from the power consumption detected by the power detector;
A control circuit that compares the output signal of the machining power extraction circuit with a variable setting reference value and outputs a control signal to the cutting machine based on the comparison result, and the machining power extraction circuit is connected to a power detector. a clamp circuit that clamps the output signal of the clamp circuit at a constant level for a predetermined period of time, a charge/discharge circuit that charges the output signal of the clamp circuit via a variable resistor, and a time setter that sets the discharge time of the charge/discharge circuit; A control device for a cutting machine comprising an arithmetic circuit that subtracts the output signal of the charge/discharge circuit from the output signal of the power detector.