JPS5853975B2 - Electric discharge machining equipment - Google Patents

Description

Detailed Description of the Invention The present invention is based on electrical discharge machining (electro-erosion machining) in which a machining gap between an electrode and a workpiece is subjected to repeated discharges using machining pulses, and whether the discharge being performed is good or bad. In other words, the purpose is to accurately detect and determine changes in the state of the machining gap, whether it is good or bad, and further to control the machining state optimally thereby.

In electrical discharge machining, machining pulses are controlled according to the gap state (discharge state), flow rate of machining fluid, electrical conductivity are controlled,
When machining debris accumulates, it is necessary to optimally perform electrode vibration, cleaning by pulling up the electrode, and servo control to make the gap length follow machining.

Conventionally, in order to detect the condition of the machining gap and the quality of discharge, the voltage or current in the gap was determined to be above or below a certain value.
In addition, although we try to discriminate and judge whether discharge occurs or not, the accuracy of the detected value is not sufficient for any signal detection, and it is difficult to accurately grasp the current state of discharge state, machining state, change trend, etc. I couldn't do that.

According to research on electric discharge machining, in addition to the DC component in the voltage or current of each pulse discharge, an AC component exists and is included, and these components take the form of a superposition.

The alternating current component changes due to discharge, and when the discharge medium is liquid vapor, gas discharge (Ga55 Phase) occurs,
The detection signal voltage is the highest.

When the medium becomes filled with metal vapor, a metallic discharge (metallic phase) occurs, and the detection signal voltage decreases.

Further, when metallic discharge occurs and the discharge point is heated, an arc is generated, the alternating current component is significantly reduced or disappears, and the direct current component is also reduced.

Furthermore, if the gap becomes filled with cutting powder, a short circuit will occur.

Such changes in the discharge state change over time even during one pulse discharge, and as shown in Figure 1A, gas discharge occurs first at the beginning of discharge, and when metal vapor is mixed with gas vapor, gas - Due to metallic discharge, metal vapor increases and changes to become metallic discharge.

Usually, such a discharge is the best discharge for a large amount of machining.

Also, as shown in Figure 0, metallic discharge occurs when metal vapor increases from the initial stage of discharge, and there is also a pulse discharge, as shown in Figure C, in which metallic discharge initially occurs and then discharge due to gas mixture occurs and ends. The amount of machining decreases due to such metallic discharge.

The amount of machining is as shown in the comparison diagram in Figure 2, with 100% gas discharge.
In this case, metallic discharge is about 50 to 70% of that amount, and arc discharge is even lower to about several percent.

Normal discharge refers to everything from gas discharge that is normally used in machining to metallic discharge, and arcing and short circuits are called abnormal discharge.

Therefore, in determining the discharge state, the present invention distinguishes normal discharge into at least gas discharge and metallic discharge, and performs a logical operation based on the output of this discrimination to detect and discriminate the discharge or machining state.

In addition, it is necessary to distinguish at least arc discharge and short circuit from discharges other than normal discharge, and also perform logic operations to determine the discharge state. In other words, by performing a logical operation on one discrimination output signal with a weight of 100% for gas discharge and 50 to 70% for metallic discharge, for example, an accurate machining amount corresponding to the number of pulse discharges can be calculated. The present invention is characterized by the fact that it can be detected by calculation.

In order to detect and discriminate pulse discharges, even if the DC and AC components of the voltage or current of each pulse discharge are used alone,
A combination thereof may also be used.

Combinations are often used when both DC and AC components are detected and discriminated, or when a superimposed signal of both components is detected and discriminated.
Signals are detected and discriminated based on their magnitude (voltage, current value, etc.), degree of change (temporal), frequency, or a combination thereof.

Further, the detection may be performed at one time point during the pulse discharge, at two or more time points, or by detecting and discriminating based on the degree of change between two or more time points.

For example, when the signal voltage is used for discrimination, according to one embodiment, the DC component of the gas discharge is about 15 to 25V, and the AC component is (P-P
) at about 5 to 20 V, and metallic discharge has a DC component of 1
The voltage is about 0 to 15V, and the AC component is about 2 to 5V.

The arc discharge is about 5 to IOV and contains almost no alternating current component.

In addition, the number of short circuits caused by cutting powder chips is less than 5 cm, and of course the current also changes accordingly, making it possible to easily distinguish between each discharge state.

The present invention will be explained below with reference to an example.

FIG. 3 shows a device in which the direct current and alternating current components of normal discharge are separated, detected and discriminated separately, and the discrimination outputs are combined to discriminate between gas discharge and metallic discharge.

1 is an electrode, and 2 is a workpiece, which face each other to form a machining gap, to which pulses are supplied from a pulse power source and machining is performed by repeated electric discharges.

18 is a circuit that detects the voltage (or current) during each discharge due to the supply pulse of the machining gap; 19 is a circuit that discriminates between normal discharge and abnormal discharge, and outputs a discrimination signal when the discharge is other than normal discharge.

Normal discharge is further classified into gas discharge and metallic discharge.

That is, 4 is a detection circuit that detects the DC component of the voltage (or current) during discharge due to the machining pulse, 5 is a detection circuit that detects the AC component, and 6, 7, and 8.9 are the detection circuits 4 and 5. A discrimination circuit 6 discriminates the DC component signal detected by the detection circuit 4, discriminates gas discharge and outputs a signal, and 7 discriminates metallic discharge and outputs a signal.

8 discriminates the direct current component detected by the detection circuit 5, discriminates gas discharge and outputs a signal, and 9 discriminates metallic discharge and outputs a signal.

Numerals 10, 11, 12, and 13 are pulse generating circuits provided corresponding to each discrimination circuit, which convert the discrimination output into pulses and output it.

14 and 15 are AND gates, 14 AND-combines the discrimination outputs of the DC component and AC component to output a gas discharge discrimination signal, and 15 outputs a metallic discharge discrimination signal by AND-coupling.

16 is an OR gate that outputs the sum of the number of gas discharges and the number of metallic discharges, but as mentioned above, the gas discharge has a machining amount of 10
Since the amount of machining for metallic discharge is approximately 50% (let's say 50% now) compared to 0%, the output of the AND gate 15 is divided in half by the flip-flop 17 and given a weight of 50%. In addition to the OR gate 16, the output of the AND gate 14 is added to the OR gate 16 with a 100% weight of 1/1 to output the sum of the number of gas discharges and the number of 1/2 metal discharges.

Then, this OR gate output is input to up/down counter 2.
Count in addition to 1.

The number of discharges other than normal discharges discriminated by the discrimination circuit 19 is converted into pulses and added to the up/down counter 21 from the pulse circuit 20, and up-counting is performed based on the number of normal discharges from the OR gate 16. It is counted down depending on the number of discharges other than the number of discharges.

That is, when the count number increases by this up/down counter 21, it indicates that the discharge state is good, and when the count number decreases, it indicates that the discharge state is poor.

The output of the counter 21 may be displayed on a display device, and this signal may be used to control processing conditions.

The signal by pulse discharge may be detected by the voltage (or current) in the gap where the DC component and the AC component are superimposed.
The average voltage (current) can be detected, and gas discharge, metallic discharge, arc discharge, and short circuit can be detected and discriminated as shown in FIG.

First, normal discharge and other discharges are distinguished, and normal discharge is discriminated into gas discharge and metallic discharge.

Of course, there are other gas/metallic mixed discharges, etc., but if we distinguish them at a certain level, we can at least distinguish them into gas discharges and metallic discharges. For example, A in Figure 1 is a metallic discharge. is included, but this is distinguished from gas discharge, and mouth and ha are distinguished from metallic discharge.

Of course, if the number of discriminations is increased to 3 or 4 stages, the accuracy will be improved accordingly, but at least it is necessary to differentiate into two stages, gas discharge and metallic discharge, and perform logical operations by adding light, heavy, and weight corresponding to the amount of machining. This enables accurate detection of discharge status and machining status.

In FIG. 3, if the output of the OR gate 16 is calculated independently with an addition counter, the amount of machining can be immediately determined, and on the other hand, the number of discharges other than normal discharges of the output of the pulse generation circuit 20 is compared with the value counted by another counter. By comparison, the discharge state can be detected in the same way as above.

Further, by comparing the output of the OR gate 16 with a time signal and performing a count, it is possible to detect the amount of processing per unit time.

Note that discharges other than normal discharges include arc discharges, short circuits, and others as shown in Figure 4, and these are separated and discriminated and added to a logic circuit and subjected to logical operations to detect the discharge state and machining state. be able to.

In addition, the detection and discrimination of signals can be performed not only by the peak value but also by the vibration state, frequency, degree of change, or a combination thereof.

In addition, the logic circuit for determining the discharge state and machining state based on the detection discrimination signal uses the total number of discharges, the number of normal discharges, the number of normal discharges, and the number of normal discharges as described above.
Logical operations can be performed using time signals and the like, and various logic circuit configurations can be used.

Based on these logic operation outputs, control of the molecular weight of the machining fluid, concentration control, conductivity control, machining fluid jet flow control, flow rate control, electrode vibration control, vibration frequency and amplitude control, and electrode reciprocating motion control is performed. , servo control, and control of the pulse width, pause, repetition rate, peak value, etc. of the machining pulses allows for optimal control at all times.

For example, especially when applying electrode feed in proportion to repeated discharges or the number of discharges, and in proportion to the number of normal discharges, normal discharges are counted by distinguishing them into gas discharges and metallic discharges, and when counting, the weight of the machining amount is By taking into account the number of discharges, it is possible to accurately detect the amount of machining, which enables optimal electrode feeding and servo control, and ensures stable machining by always maintaining the machining gap normally. Can be done.

Furthermore, supply control of machining pulses can be performed extremely stably, and machining speed and machining efficiency can be significantly improved.

In addition, reciprocating motion control for cleaning the machining gap also generates machining chips depending on the amount of machining, so the amount of generated machining chips can be easily and accurately determined, and reciprocating control can be performed at the optimal time. can be washed by doing
In addition, it is possible to optimally control the time of one stroke of reciprocating, stroke width, etc.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of discharge waveforms, FIG. 2 is an explanatory diagram of a comparison of machining amounts, FIG. 3 is a circuit configuration diagram of an embodiment of the present invention, and FIG. 4 is an explanatory diagram of the principle of the present invention.

Claims (1)

[Scope of Claims] 1. An electric discharge machining device that repeatedly applies pulse discharge to a machining gap and performs machining while monitoring the discharge state or the state of the machining gap by the pulse discharge,
The normal discharge of each pulse discharge is at least a gas discharge (G
a55 Phase) and metallic discharge (Metal
lic Phase ), a logic circuit that adds weight to each of the gas discharge discrimination output and the metallic discharge discrimination output and outputs the sum, and a counting circuit that counts the output of the logic circuit. An electric discharge machining device characterized by the following. 2. In an electrical discharge machining device that repeatedly applies pulse discharge to a machining gap and performs machining while monitoring the discharge state or the state of the machining gap by the pulse discharge,
a circuit for discriminating and outputting discharges other than normal discharges among the pulse discharges; a circuit for discriminating and outputting the normal discharges of the pulse discharges at least into gas discharge and metallic discharge; and the gas discharge discrimination output and metallic discharge discrimination output. a logic circuit that adds and outputs each with weights, and a counting circuit that counts the output of the logic circuit and the output of the circuit that discriminates and outputs discharges other than the normal discharges separately or in an additive/subtractive manner. Electrical discharge machining equipment featuring: 3 The circuit that discriminates between pulse discharges
3. The electric discharge machining apparatus according to claim 1, wherein the electrical discharge machining apparatus detects and discriminates electric discharge at a point in time, at two or more points in time, or at a degree of change between two or more points in time. 4. The circuit for discriminating pulse discharges detects and discriminates discharges based on a DC component, an AC component, or a combination thereof in the voltage or current of each pulse discharge, as claimed in claim 1 or 2. The electrical discharge machining device described in .