JPH0436634A - Controller for cutting machine - Google Patents

Abstract

PURPOSE:To securely detect an unloaded power value even in a short-time machining cycle and to decide an accurate cutting state by providing a circuit which clamps the output signal of a power detector with a constant level for a specific time. CONSTITUTION:The power detector 2 detects the consumed power of the driving motor of the cutting machine. Then a clamp circuit 10 clamps the output signal of the power detector 2 with the constant level for a specific time. Then a smoothing circuit 11 smooths a signal passed through the clamp circuit 10. Further, a power extracting circuit 4 extracts the power value in an unloaded state from the output signal of the smoothing circuit 11. Then a control circuit 6 compares the output signal of an arithmetic circuit 13 with a variable set reference value and outputs a control signal to the cutting machine according to the comparison result. Consequently, the securely unloaded power value is securely detected even in the machining cycle wherein the time from actuation to the start of machining is short, and the accurate cutting state is decided.

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]

Conventionally, in cutting machines, in order to deal with variations in tool life and breakage, etc., the power consumption of the drive motor is detected, and the state of wear of the tool is determined from changes in the power consumption.
A device is used to control the machine's feed speed, replacement timing, etc.

Figure 3 shows the power waveform when the power consumption of the electric motor of a cutting machine is extracted over time.The electric power value rises rapidly when the electric motor is started, and then decreases when no load is applied. After the power value stabilizes, the process of rising and falling is repeated each 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.

This calculation is performed using the conventional control device, which calculates the power value f(to>) during no-load within the time period (T) during which the no-load state stabilizes after the power rise at startup decreases and before the start of the first machining. and subtract it from the consumed power to obtain the machining power f(t1
).

In addition, power consumption includes aperiodic noise components, and due to fluctuations in this noise, no-load power or power consumption during machining may not be accurately detected.
As shown by the broken line in the figure, the power value is detected after smoothing the power consumption and removing noise components.

[Problem to be solved by the invention]

By the way, in the actual machining cycle, in order to shorten the machining time, there is no long no-load stable period between the start of the electric motor and the start of machining, and machining is performed at short time intervals as shown in Figure 4. There are many cases.

However, in such a machining cycle, the time T during which the power is stable during no-load is extremely short, so it is not possible to sample the power value stably, and the no-load power cannot be extracted accurately. There's a problem.

In particular, when the consumed power includes aperiodic noise components, the noise fluctuations are added to the signal, making it extremely difficult to sample the no-load power value.

On the other hand, if smoothing processing is applied to the detected power signal in order to remove non-periodic noise components, 2. There is a large time lag before the power signal at startup, which increases sharply, stabilizes to no-load power, and as a result, the stable period of no-load power overlaps with the first machining period, and no-load power is extracted. There is a problem with not being able to get the timing right.

In addition, because the power rise at startup is large, the power rise due to the first processing occurs before the signal obtained by smoothing the power value decreases to the no-load power, and a situation may occur where the signals overlap, resulting in accurate power consumption. There is a drawback that load power cannot be sampled.

The present invention solves the above problems and provides a control device B that can reliably detect a no-load power value even in a machining cycle where the time from startup to machining start is short, and can accurately determine the cutting state. With the goal.

[Means to solve the problem]

In order to solve the above problems, the present invention includes: a power detector that detects the power consumption of a driving motor of a cutting machine; a clamp circuit that clamps the output signal of the power detector at a predetermined level for a predetermined time; a smoothing circuit that smoothes the signal that has passed through the clamp circuit; a power extraction circuit that extracts a no-load power value from the output signal of the smoothing circuit; and an output signal of the no-load power extraction circuit from the output signal of the power detector. and a control circuit that compares the output signal of the calculation circuit with a variable setting reference value and outputs the ff1HB signal to the cutting machine based on the comparison result. It is.

[Effect]

In the above configuration, the power consumption that increases rapidly after the drive motor is started is clamped at a level slightly higher than the no-load power value, and the clamped output signal is smoothed.

By reducing the power at startup by clamping in this way, the power value to be smoothed becomes smaller, and the time required for smooth charging and discharging becomes shorter. Therefore, the time required for the consumed power to stabilize at no-load power is shortened, and a no-load level without noise fluctuation can be obtained before starting machining.

Therefore, by extracting the no-load power value from the smoothed signal and subtracting that power value from the power consumption from the power detector, accurate machining power can be determined.

〔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 A machining power extraction circuit section 4 extracts the machining power from the machining power, an integrating circuit section 5 that integrates the machining power over the machining time range, a control circuit section 6 that outputs a control signal based on the obtained integral value, and a control circuit section 6 that outputs a control signal based on the obtained integral value. It is constructed by connecting an overload detection circuit 7 and a gap limit inverter circuit 8.

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

The drive electric motor 1 described above is intended for use in a cutting machine that is involved in cutting, and is used, for example, as a spindle rotation electric motor or a feed axis operation electric motor.

The power detector 2 detects and outputs the power consumption of the drive motor 1 during operation. In this case, the detected power consumption P includes the power consumption f (t) actually caused by machining, low-frequency noise generated from belts, pulleys, etc. that transmit the driving force of the motor, and the characteristics of the AC motor. It includes a periodic noise component Δf (t) such as noise and a non-periodic noise component C(t), and P=f(t)+4f (t
)+C(t).

The noise removal circuit 3 includes a plurality of filter circuits 3a and 3b that remove low frequency noise components coming from the drive system, noise components coming from the characteristics of the electric motor, etc., and removes periodic noise Δr ( t) is removed. By removing the noise component in this way, the point of contact between the cutting tool and the workpiece can be accurately detected without any time delay.

On the other hand, the consumption t, 1 from which the noise component Δf (t) is removed
(t) includes the power increase caused by friction caused by spindle rotation in the idling state with no load, so next, the power consumption f (
t) is passed through the machining power extraction circuit section 4 to remove the power increase during no-load, and extract the machining power r(tl).

The machining power extraction circuit section 4 includes a clamp circuit 10 including a timer 9, a smoothing circuit 11, a sample hold circuit 12, an arithmetic circuit 13, and an amplifier circuit 14.

The clamp circuit 10, as shown in FIG. 2(a) Φ),
The signal of the power consumption f (t) output from the noise removal circuit 3 is clamped at a constant level a within the time period in which the timer S is operating. This clamp level a can be set arbitrarily, and is usually set slightly larger than the no-load power.

The timer 9 is set to operate when a predetermined period of time has elapsed since the electric motor 1 has been started, and to be deactivated when the power increase at the time of starting has decreased.

Further, the activation signal of this timer 9 is manually input to a timer 23, and this timer 23 is connected to the sample and hold circuit 12 via an OR circuit 24 to which an external signal is input. The timer 23 operates for a fixed period of time when the timer 9 is deactivated, and the OR circuit 24 selects either the operation signal of the timer 23 or an external signal to send a hold timing signal to the sample and hold circuit 12. Output.

The activation timing of timer 9, the point at which the increased starting power decreases, and the no-load power value that is the standard for level a can be easily determined by performing trial machining on the workpiece in advance and from the power waveform obtained. can be divided into

The smoothing circuit 11 uses a first-order lag circuit with charging and discharging action, and the clamp signal S1 that has passed through the clamp circuit 10
Smooth processing. Through this smoothing process, the waveform of the clamp signal s1 is smoothed as shown in FIG. 2(C), and a smoothed signal S2 from which the aperiodic noise component C(t) has been removed is obtained.

The sample and hold circuit 12 calculates the no-load reference power f (t) from the power consumption f (t) processed by the smoothing circuit 11.
to ) is extracted and stored, and the reference power is sampled only during the time when the timer 23 is operating or the time specified by an external signal.

When the signal that has passed through the clamp circuit 10 and the signal from the sample-and-hold circuit 11 are input, the arithmetic circuit 13 performs an operation to subtract the reference power r(to) held by the sample-and-hold circuit 12 from the power consumption f, (t). (t, ) = f
(t) -f (to) is executed. This results in
The lower part of the power value is removed and shifted downward, and only the machining power f (tl ) is extracted. (See Figure 2 (B)) The amplifier circuit 14 is designed to greatly amplify and output the change in power by multiplying the extracted machining power f (tl ) by (1<K) f. be. This output value f(tz)-Kx f (t + ) becomes the basic machining power for the next control (see FIG. 2(e)).

On the other hand, an abnormal load detection circuit 7 is connected to the noise removal circuit 3 together with the machining power extraction circuit section 4 .

This detection circuit 7 suddenly increases when there is an abnormal collision between the cutting tool and the workpiece due to a malfunction in the coding of 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 a comparison reference value for control to be described later), an output signal is generated to stop the cutting tool and the feeding device.

Next, the integrating circuit section 5 includes a machining time setting circuit 15 that sets a machining time as a control range, and an integrating circuit 16. The machining time setting circuit 15 includes a comparison circuit 17, an OR circuit 18, and a gate. It is composed of a circuit 19.

The comparison circuit 17 is inputted with a reference value m set larger than the reference power value f(to), and as shown in FIG. In comparison, when the power f(tz) passes the reference value m, OR
A signal is output to the circuit 18.

The OR circuit 18 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 17, and sends the timing signal to the gate circuit 19. Outputs gate signal.

When the gate circuit 19 receives the signal from the OR circuit 18, it increases the machining power f(tz) for the duration of the signal input.
The signal is passed through the integrating circuit 16.

The integrating circuit 16 performs integral calculations on the machining power signal input from the gate circuit 19 .

This integrated value f (ts)=ff (tt) is then output to the control circuit section 7.

In addition, the machining power f output from the machining power extraction circuit section 4
(tz) is also input to the gap eliminator circuit 8. This gap eliminator circuit 8 compares the machining power with a preset reference value d, and compares the machining power r (t,
) reaches the reference value d, a switching signal for switching to the normal feed amount is output to the cutting tool feed device (secondary output signal).

As a result, the cutting tool is fed in rapid traverse until just before it comes into contact with the workpiece, and when the cutting tool and workpiece come into contact, it automatically switches to normal cutting feed, allowing blank time that is not involved in machining. This has the effect of shortening the time.

The control circuit section 6 connected to the integration circuit section 5 is composed of a counter 20, an average value calculation circuit 21, and a comparison circuit 22.

The counter 20 counts the signal from the comparator circuit 17 of the above-mentioned integration circuit section 5 N times immediately after the tool is replaced, and outputs the signal up to the N count to the average value calculation circuit 21.

The average value calculation circuit 21 includes a storage section and a calculation section, and the storage section sequentially accumulates each output inputted from the counter 20 and the integration circuit section 5, and calculates the number of processing times N for each.
and is stored as the total sum Σr (ts) of the integral values. Then, the calculation unit calculates the average value r(ta)=Σf(mu,)/N of the integral values by dividing the total sum of integral values by the number of N machining times, and calculates the average value ``(t4) , the comparison circuit 22
Output to.

After amplifying the input average value, the comparison circuit 22 compares it with the integral value f(t:1) output from the integrating circuit section 5, and when the integral value reaches the average value or more, it sends a control signal to the cutting machine. (tertiary output signal).

The control signal from the control circuit section 6 can be a signal for changing the depth of cut or feed amount in a cutting machine, or a command signal for tool exchange.

The control device of this embodiment has the structure 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. 2(a). f(t) is obtained.

This power consumption is then sent to the abnormal overload detection circuit 7.
If the maximum value exceeds the reference value C, a primary output signal is output from the detection circuit 7, and the cutting device is completely stopped.

This prevents serious accidents due to damage to the cutting tool or incorrect installation.

If the power consumption f(t) does not exceed the reference value C, the signal of the power consumption f(t) is processed by the machining power extraction circuit section 4.

In this extraction circuit section 4, when the power consumption f(1) increases at the time of startup, the timer 9 is activated, and the clamp circuit 10 clamps the power consumption at level a for the length of time that the timer 9 is activated (second Figure (b)).

This clamped clamp signal St is then smoothed by the smoothing circuit 11 to remove non-periodic noise components (FIG. 2(C)). In this case, the power consumption f (t) at startup is reduced because the upper part is cut off by the clamp, so the amount of charging and discharging in the smoothing process becomes smaller, and therefore, the time delay of the signal becomes smaller, and It stabilizes to a smooth, no-load state in a short time. As a result, a waveform clearly indicating no-load power f(to) appears between the time of startup and the start of the first machining.

Therefore, in the next sample and hold circuit 12,
By matching the timing signal from the external or internal timer 23 to the time indicating the above-mentioned no-load power, the no-load power f(t.) can be accurately extracted from the smoothed signal S2.

This no-load power f(to) is then subtracted from the power consumption r(t) in the arithmetic circuit 13, and the machining power fD
1) is calculated. The power waveform at this time is shown in Figure 2(d).
The waveform becomes

The machining power f(tg) obtained by amplifying this signal is sent to the gap eliminator circuit 8 and the integrating circuit section 5, and in the gap eliminator circuit 8, the machining power f(tg) is
> and a preset value (Hid) are compared, and at the moment the machining power becomes larger than the value d, a secondary output signal is output, and the rapid feed speed of the cutting tool is switched to the programmed cutting feed.

On the other hand, in the integrating circuit section 5, as shown in FIG. is opened and a signal is manually input to the integrating circuit 16, and the integrating circuit 16 receives the machining power r(
tz), the output exceeding the set level value m is integrated. Through this integration process, a voltage waveform as shown in FIG. 2(f) is obtained.

On the other hand, in the counter 20, the machining time setting circuit section 1
Based on the signal from 5, the number of machining operations after tool exchange is counted N times, and a signal is output to the average value calculation circuit 21.

The average value calculation circuit 21 accumulates the count input from the counter 20 and stores it as the number of machining times N.
The integral values ((1,) inputted from the integrating circuit 16 are accumulated, and each time they are updated, the total integral value Σf(ts) is divided by the number of processing times N to obtain the average value r(t4) of the integral values.
is calculated and output to the comparison circuit 22.

In the comparison circuit 22, the average value is compared with the integral value from the integration circuit 16, and a control signal corresponding to each wear state of the cutting tool is output (tertiary output signal).

In addition, in the above embodiment, electric power was used as the power consumption, but the electric power! The flow rate can also be used as the target power.

In addition, the control circuit section 6 calculates the average value of the integral values and calculates the average value of the integrated values.
Although the average value and the integral value are compared, a reference value for comparison may be set in advance from the outside, and the reference value and the integral value may be compared.

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

[Effects of the Invention] As described above, since the control device of the present invention includes a clamp circuit and a smoothing circuit, it clamps the increasing power consumption at a low level when starting the electric motor, and smooths the power that has been cut to a low level. By doing so, the time delay of the signal due to smoothing can be reduced, and the power can be stabilized to the no-load level in a short time.

Therefore, even if the time interval between startup and machining start is short, no-load power can be reliably extracted before machining starts, and accurate and stable control can be performed.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the flitJ door device of the embodiment, Figure 2 (a) to (e) are diagrams each showing the power waveforms obtained in the control device, and Figure 2 (f) is the voltage waveform of the same. The diagrams shown in FIG. 3 and FIG. 4 are diagrams showing changes in power consumption of the electric motor. DESCRIPTION OF SYMBOLS 1... Drive electric motor, 2... Power detector, 3... Noise removal circuit, 4... Machining power extraction circuit section, 5... ...Integrator circuit section, 6...Control circuit section, 7...Abnormal overload detection circuit, 8...Gap eliminator circuit, 9...
...Timer, 10...Clamp circuit, 1
1... Smoothing circuit, 12... Sample hold circuit, 13...
...Arithmetic circuit, 16...Integrator circuit, 21...
... Average value calculation circuit, 22 ... Comparison circuit. Figure 3 Figure 4 Figure 2

Claims (1)

[Claims] (1) A power detector that detects the power consumption of the drive motor of the cutting machine; A clamp circuit that clamps the output signal of the power detector at a constant level for a predetermined time; A smoother that smoothes the signal that has passed through this clamp circuit. a power extraction circuit that extracts a no-load power value from the output signal of the smoothing circuit; a calculation circuit that subtracts the output signal of the no-load power extraction circuit from the output signal of the power detector; and the calculation circuit. A control device for a cutting machine, comprising: a control circuit that compares the output signal of the output signal with a variable setting reference value and outputs a control signal to the cutting machine based on the comparison result.