JPS5820735B2 - wire cutter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wire-cut electrical discharge machining apparatus capable of performing highly accurate contour machining.

Today, contour machining using wire-cut electrical discharge machining equipment is widely used, but when contour machining is performed using conventionally known wire-cut electrical discharge machining equipment, the part machined along the contour line at the final stage of machining is There has been a problem in that the machining accuracy of the meeting part that meets the initially machined part is poorer than the machining accuracy of other parts.

The present invention has been developed from the viewpoint of diagonal topography, and an object of the present invention is to automatically perform complete contour machining at the same precision level over the entire circumference of a desired contour line. The object of the present invention is to provide a wire-cut electrical discharge machining device that can perform the following steps.

Hereinafter, conventionally known machining problems and details of an embodiment of the wire-cut electric discharge machining apparatus according to the present invention will be explained with reference to the drawings.

Fig. 1 is an explanatory diagram of known contour machining, Fig. 2 A and B are enlarged views of the portion W shown in Fig. 1, and Fig. 3 shows variations in the area to be machined and wire cut electric discharge machining according to the present invention. FIG. 4 is a graph showing fluctuations in the average machining current in the device, and is a circuit diagram showing an embodiment of the wire-cut electric discharge machining device according to the present invention.

In FIG. 1, 1 is the workpiece, 2 is the contour line to be machined, 1' and 1'' are the workpiece parts divided into two by the contour line 2, and 3, 2 in FIG. 3' is the center locus of the wire electrode 4, and P, Q, R, S, and T are all points on the center locus 3, 3' of the wire electrode 4.

Therefore, the purpose of machining in this case is to perform electrical discharge machining between the wire electrode 4 and the workpiece 1, and to relatively move the center of the wire electrode 4 along desired trajectories 3 and 3'. , the object is to obtain a workpiece part 1' defined by the desired contour line 2.

Thus, the wire electrode 4 passes through points P, Q, and R on the center locus 3 at the beginning of machining to create the contour line 2, and at the end of the process, passes through points S and T on the center locus 3'. It is assumed that the vehicle is allowed to proceed further until it reaches a point Q on the initial center locus 3.

When the center of the wire electrode 4 reaches point T, the workpiece 1 is cut into three parts 1' and 1'', but at this time, the contour line 2 created at the beginning and the contour line created at the end The contour line 2' is not connected linearly and smoothly, and fan-shaped protrusions Va and 1''a remain between them.

In order to remove these protrusions 1'a and 1''a, when the wire electrode 4 is advanced to point Q and an attempt is made to obtain a contour as shown by the dotted line, excessive machining is performed in the meantime. , defective portions 1'b and 1''b are generated, making it impossible to process according to the intended contour line shown by the dotted line in the figure.

The reason why the defective parts 1'b and 1"b occur due to excessive machining is that after the center of the wire electrode 4 passes point T, machining is performed according to the intended outline shown by the dotted line in the figure. This occurs because the machining feed rate and average machining current are held constant even though the power area changes as shown in FIG.

More specifically, since the actual machining feed rate and the average machining current are held constant, the amount of machining per unit machining feed distance of the wire electrode 4, that is, the amount of machining per unit time of actually machining. This is due to the fact that the area or area of the part that is actually machined becomes smaller after point T, compared to before that point, whereas the area or area of the part that is actually machined is kept constant.

Furthermore, during this period, no discharge occurs over the entire front surface of the wire electrode 4, and the discharge is concentrated on the side surface thereof, so that more arcs and the like occur.

The gist of the present invention is, as shown in FIG. 3, to reduce the average machining current in proportion to the area to be machined.

By doing this, the wire electrode 4 is connected to the workpiece 1.
The machining load on the machining load surface facing the protrusions 1'a and 1"a is made constant, and excessive machining is prevented.

If the feed rate is kept constant during this period, complete contour machining can be performed without excessive machining and the occurrence of arcs and the like.

Next, an example of a wire-cut electric discharge machining apparatus according to the present invention will be explained with reference to FIG.

In the figure, 1 is the aforementioned workpiece, and 4 is a wire electrode.

5.5 is a guide roller, 6 and 6 are energizing rollers, 7 is a main power supply, 8 is a switching element, 9 is an insertion resistor, 10 is a monostable element, 11 is a numerical control circuit, 12 is an inhibit circuit, 13 is a frequency divider instrument, 14 is a ring counter,
14-1 to 14-6° are digit elements of the ring counter 14, 15-1 to 15-6 are AND circuits, 16- to 16-6 are on-delay circuits that define the rest time of the voltage pulse, and 17 is an OR circuit. , 18 is a delay circuit that determines the discharge duration, and 19 controls the switching element 8.

It's a flip-flop.

The workpiece 1 is supported by a support device (not shown) and a processing feed device that responds to command pulses output from output terminals 11-1 and 11-2 of the numerical control device 11.
Processing feed is performed so that processing is performed along the aforementioned contour line.

Further, an output pulse is emitted from the output terminal 11-3 of the numerical control device 11 at a rate of one per unit machining feed distance, and the output from the output terminal 11-4 is such that the center of the wire electrode 4 is at the point T. Point T immediately before.

It is "1" until reaching , and after that it becomes "0".
Set in advance.

Furthermore, the first digit element 14-1 of the ring counter 4 is set to "1" at the beginning of machining, and the frequency divider 13 is reset.

Now, when the flip-flop 19 is set, the switching element 8 becomes conductive, and a discharge occurs between the workpiece 1 and the wire electrode 4.

In such a case, the monostable element 10 emits an output pulse, which passes through the delay circuit 18 and resets the flip-flop 19 after the predetermined delay time τon has elapsed.

In this case, the conduction of the switching element 8 is cut off, and the discharge ends.

The reset output of the flip-flop 19 operates the on-delay circuit 16-1 via the AND circuit 15-1, and after the predetermined delay time τ1 has elapsed, the flip-flop 19 is set again.

Therefore, the above point T.

Until reaching the point, the wire cutting process is repeated by repeating the diagonal upward cycle.

Thus, the center of the wire electrode is point T.

When the machining progresses until reaching 11, the output of the output terminal 11-4 of the numerical control circuit 11 becomes "0", and therefore
The pulse output from -3 passes through the inhibit circuit 12 and can be input to the frequency divider 13.

However, processing is still allowed to proceed according to the cycle described above.

Then, the center of the wire electrode passes point T, and then reaches point T.

When reaching the point T1 at a desired distance from the frequency divider 13
emits an output pulse, so that the ring counter 4
is stepped forward, and the digit element 14-2 becomes "1", and the on-delay circuit 16-2 instead of the on-delay circuit 16-1 determines the rest time of the discharge pulse.

The delay time τ2 of this on-delay circuit 16-2 is 16-1
The delay time .tau.1 is set to 2 to 3 times the delay time .tau.1, so that the subsequent average machining current is reduced to about 7 or less, as shown in FIG.

However, during this period, the area to be machined has been reduced by half, so even if the machining feed rate is controlled to keep the discharge state constant, it is difficult to maintain it at the same level. dripping

As the machining progresses further over the specified distance, the ring counter 14 is sequentially incremented, and the voltage pulse pause time is determined by the delay time prescribed by the corresponding on-delay circuit, and the average As shown in FIG. 3, the machining current is reduced approximately proportionally to the machining area.

When the digit element 14-6 of the ring counter 14 reaches "1", the inhibit circuit 12 is closed again, and from then on, electrical discharge machining is performed according to the voltage pulse pause time specified by the on-delay circuit 16-6 until machining is completed. It will be done.

Note that it is not necessary to continue the processing until the center of the wire electrode 4 reaches the point Q, and it is recommended to terminate the processing at a point T5 before that point.

Since the present invention is constructed in a diagonal manner, it is possible to perform complete contour processing very easily and automatically using the present invention.

It should be noted that the configuration of the present invention is not limited to the actual case of diagonal work. For example, the present invention can also be applied to a wire-cut electric discharge machining device controlled by a line tracer, and the present invention can be applied to a wire-cut electric discharge machining device controlled by a line tracer, and the voltage pulse for controlling the average machining current is The pause time can be directly controlled by the program of the numerical control device, and the average machining current can also be controlled by parameters other than the voltage pulse pause time.

That is, for example, as a machining pulse power source for wire cut electrical discharge machining, the RC type is used.

Capacitor charging/discharging power supplies such as L-C type and R-L-C type are often used, but in the case of such pulse power supplies, the charging resistance and inductance of the capacitor must be changed in order to increase them. , the discharge repetition frequency of the capacitor, that is, the average machining current, can be decreased or changed depending on the purpose.

In this case, the capacitance of the capacitor may be changed as necessary.

Furthermore, it is also possible to accelerate the machining feed rate inversely proportional to the area to be machined in addition to controlling the average machining current on the slant, and the present invention encompasses all of these.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of contour processing, Figure 2 is a partially enlarged diagram,
FIG. 3 is a graph showing the area to be machined and fluctuations in average machining current in the wire-cut electrical discharge machining device according to the present invention, and FIG. 4 is a circuit showing an embodiment of the wire-cut electrical discharge machining device according to the present invention. It is a diagram. 1... Workpiece, 2... Contour line, 4...
...Wire electrode, 11...Numerical control circuit,
12...Inhibit circuit, 13...
Frequency divider.

Claims (1)

[Claims] 1 When contouring the workpiece along a predetermined contour line,
A wire-cut electrical discharge machining device characterized by comprising a control device that starts operating in response to a signal indicating that the contour is about to be completed, and reduces the average machining current in proportion to the machining area by a signal generated in response to a decrease in the machining area. .