JPS6335364B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention controls movement of the relative positions of an electrode and a workpiece along a desired pattern using a drive device that moves the relative positions of an electrode and a workpiece by a predetermined amount for each pulse using a pulse signal. The present invention also relates to an improvement of an electrical processing device for processing the above-mentioned workpiece.

In electrical discharge machining, for example, electrical discharge machining,
The entire electrode is fed in only one direction, and the servo is controlled to keep the voltage between the electrodes constant in that direction in an analog manner. However, recently, even in electric discharge machining, the feed direction of machining is controlled not only in one direction but also in the X, Y, and Z axes, giving three-dimensional movement to the electrode, and performing machining similar to so-called milling. Things are emerging. Milling using electrical discharge machining does not require rotation of the electrode, so it is extremely convenient for machining shapes that require sharp corners, and the three-dimensional movement of the electrode and workpiece is
Control using an NC device is convenient.

Here, when controlling an electrical discharge machining device using an NC device, it is extremely difficult to feed the electrode or the workpiece at a constant feed rate as in a normal machine tool. This is because the machining progress speed (machined volume/machined area per fixed time) in normal electric discharge machining is extremely small, and the area to be machined changes greatly, so if you match the feed rate when the machining area is large, the machining area will be small. In some cases, there is too much margin for machining, resulting in poor machining efficiency. Furthermore, if the feed rate is adjusted to the same feed rate when the machining area is small, if the machining area becomes large, a short circuit will occur in the machining gap, making it impossible to continue machining.

To this end, it is conceivable to detect the voltage in the machining gap and apply a relative feed between the electrode and the workpiece only when the voltage exceeds a certain reference voltage. Figures 1 and 2 are examples of electric discharge machining equipment controlled by an NC device based on this idea. To explain this FIG. 1, the electrode 1 and the workpiece 2
A current pulse supplied from a current pulse supply device 3 is passed between the two and the workpiece 2 is machined.
Relative X, Y, Z between electrode 1 and workpiece 2
The movement in the axial direction is controlled by the output from the NC device 4.
For each X-axis, a number of pulse trains corresponding to the feed amount are output to the X-axis pulse motor 6X through the X-axis pulse motor control circuit 5X, and by transmitting the rotation of the pulse motor 6X to the table feed screw 7X, the table 8 move in the X-axis direction. At this time, the Y-axis is also exactly the same as the X-axis, and the workpiece 2 on the table 8 is moved. Regarding the Z-axis, the Z-axis pulse motor control circuit 5
The Z output pulse drives the Z-axis pulse motor 6Z and sends the electrode 1 through the electrode feed screw 7Z. The average voltage of the machining gap is determined by the comparator 9 as the reference voltage.
V _R is compared and the average voltage of the machining gap is the reference voltage.
When the voltage is equal to or higher than _VR , the comparator 9 outputs a logic level "1" to the output Sc, which is input to the NC device 4.

The NC device 4 is controlled by a computer, and a schematic flow chart thereof is shown in FIG. For example, the NC device 4 outputs the number of pulses △X, △Y, △ in the X, Y, and Z directions every 50 msec during that 50 msec.
It calculates and outputs the result so that Z(√△ ² +△ ² +△ ² =△L). This flowchart starts from START, passes through line 10 every 50 msec, and executes process 11 only when the output Sc of the comparator 9 is "1". Process 11 is sequentially moving distance △L in 50 msec (normally △L is constant)
, determine the relative movement direction of the electrode 1 from the input information of the NC device 4, and calculate the outputs △X ₁ , △Y ₁ , △Z ₁ during that 50 msec from the electrode movement direction and △L. Determine, output, and return to line 12. Sc＝
1? In the case of Sc=0, processing 11 is not executed, the process returns to line 12, and the process waits for the next 50 msec signal. In this way, depending on the state of the machining gap, whether or not to output the electrode movement command pulse from the NC device 4 is switched.

Therefore, for example, when the machining area is small, the actual electrode feed rate (ΔL/50 msec) is relatively slower than the machining progress speed, so the machining gap becomes slightly open.
The output Sc of comparator 9 remains "1" for a long time, and every 50 m
sec, an electrode movement command pulse is output, and as a result, the average feeding speed of the electrode 1 becomes faster. In addition, when the machining area becomes large, the electrode feed speed is relatively faster than the machining progress speed, so the machining gap tends to be short-circuited, and the output Sc of the comparator 9 often becomes "0", resulting in the electrode The movement command pulse is not output much, and the average electrode feeding speed becomes slow. In this way, according to this method, the average feed rate of the electrode is controlled in response to the state of the machining gap due to changes in the machining area, etc., so that efficient machining can be performed.

However, with this method, it is possible to process when the machining area is relatively small or when the machining gap is wide as in rough machining, but it is not possible when the machining area is large, the machining depth is deep, or when finishing machining is required. In cases where the machining gap is narrow, such as this, it is difficult to discharge machining debris from the machining gap, and machining debris may get stuck in the machining gap during machining, making it impossible to continue machining. . Therefore, it can be said that it had a major practical drawback.

The present invention takes the above method one step further, and not only controls the average feed rate of the electrode in response to the state of the machining gap, but also controls the electrode feed rate (△L/50m).
sec) is larger than the machining progress speed,
The output of the comparator is actively set to "0", and when the output of the comparator is "0", it not only does not output the electrode movement command pulse, but also outputs the desired pattern in which the electrode has already moved. By reversing the above trajectory, the relative motion between the electrode and the workpiece is configured to advance and reverse repeatedly, thereby promoting the removal of machining debris and shortening machining time. , it is possible to continue machining even in machining where it is difficult to remove machining waste.

The details of the present invention will be explained below. The configuration of the electrical processing device according to the present invention is as shown in FIG. 1, and FIG. 3 shows an example of a flowchart of the NC device 4 in FIG. and FIG. 4 shows an example of a memory table according to the invention for reversing the electrode 1. When the NC device 4 outputs the number of movement command pulses △X, △Y, △Z for moving the electrode, this memory table is written as follows:
The number of electrode advance command pulses is always stored sequentially in the area of backward memory address N=1, and at that time N
The number of pulses already stored in the area of =1 is N =
2 area, N=2 area is transferred to N=3 area,
A retrograde memory is formed. Further, as for the number of movement command pulses for moving the electrode 1 backward, the number of pulses stored in the above-mentioned backward movement memory is sequentially read out and the electrode is moved backward.

The flowchart in FIG. 3 starts from START, passes through line 10 every 50 msec, and judges the output Sc of comparator 9. When the output is "1", it is determined whether the backward memory address N is "0" or not, and if N=0, processing 13 for moving the electrode 1 is executed. In process 13,
Distance △L that electrode 1 should move in 50 msec (△L=
√△ ² +△ ² +△ ² ), determine the direction of electrode movement, and use △L and the direction of electrode movement to
The number of electrode advance movement command pulses △X ₁ , △Y ₁ , △Z ₁ to be output during 50 msec is calculated and determined. Next, the contents already stored in the backward memory table configured as shown in FIG. 4 are sequentially shifted to the area of the next backward memory address. Next, new numbers of electrode movement command pulses ΔX ₁ , ΔY ₁ , ΔZ ₁ are stored in the area of address N=1 in the retrograde memory table.
In other words, the new number of electrode movement command pulses is pushed in from the address N=1 side of the backward memory table. Thereafter, the above △X ₁ , △Y ₁ and △Z ₁ are outputted as the number of electrode movement command pulses △X, △Y and △Z, and the process returns to line 12 to wait for the next 50 msec signal. Here, when the next 50 msec signal is input, the output Sc of the comparator 9 is judged as described above. For example, if the output Sc of the comparator 9 is "0",
Process 14 is performed. Processing 14 adds "1" to the backward memory address N and reads out the contents of the address indicated by N. That is, since the backward memory address is now N=0, it is set to N=1 and the number of electrode movement command pulses stored in the area of N=1 is read out. Next, reverse the sign of the read electrode movement command pulse number (reverse the electrode movement direction),
That is, △X ₁ = +5μm, △Y ₁ = +3μm, △Z ₁ = -2μ
When m, △X=-5μm, △Y=-3μm, △
Set Z=+2 μm, output as the number of electrode backward movement command pulses, and return to line 12. Then 50msec
If the state of Sc = 0 continues for example three times, the number of electrode movement command pulses is read out sequentially from the backward movement memory table, so the electrode continues to move backward for 150 msec on a trajectory along the desired pattern.

When the output Sc of the comparator 9 becomes "1" in the next 50 msec signal, the backward memory address N becomes "3" at that time, so N=0? Process 15 is executed based on the judgment. Process 15 needs to proceed again along the backward trajectory, so first read the number of electrode movement command pulses △X 3 , △Y 3 , △Z 3 at the backward memory address N = 3, and then read the number of electrode movement command pulses △X ₃ , △Y ₃ , △Z ₃ at the backward memory address N = 3. is subtracted by "1" to make N=2.
Then, △X ₃ , △Y ₃ , and △Z ₃ are output, and the process returns to line 12. After that, if the state of Sc=1 continues, N
Processing 15 is executed for 150 msec until =0, and the movement returns to the position where it first started moving backwards.

By operating the NC device 4 in this way,
The electrode 1 moves on a trajectory following a desired pattern, and as a result, the machining gap becomes shorter, and the voltage corresponding to the average voltage of the machining gap becomes lower than the reference voltage _VR . Therefore, the output Sc of the comparator 9 becomes "0", and the electrode 1 moves backward along the trajectory that it has traveled in accordance with the above-described operation of the NC device 4. Here, by setting the speed at which the electrode advances (△L/50 msec in Figure 3) greater than the speed at which machining progresses (machining volume/machining area per unit time), the electrode 1 is placed on the trajectory of the desired pattern. Processing is carried out gradually by constantly going forward and backward.

As described above, according to the present invention, the electrode 1 performs machining while repeatedly moving forward and backward along the locus of a desired pattern, so when the machining area is large, the machining depth is deep, and the machining gap is narrow. During machining, there is no inconvenience such as clogging of machining debris, which makes machining impossible, and it also has the effect of stirring the machining liquid in the machining gap, resulting in an increase in the machining current that can be passed through the machining gap, reducing machining time. It is also possible to shorten the time.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an electric discharge machine equipped with an NC device for explaining the present invention, and Fig. 2 is an explanatory diagram showing an electric discharge machine equipped with an NC device to explain the present invention.
FIG. 3 is a flowchart of the NC device according to the present invention, and FIG. 4 is a diagram illustrating the configuration of the backward memory according to the present invention. In the figure, 1 is the electrode, 2 is the workpiece, and 4 is the NC.
1 is a device, 9 is a comparator, 13 is a process for advancing the electrode, 14 is a process for reversing the electrode, 1
5 shows a process for returning the electrode to its original position.

Claims (1)

[Claims] 1 The relative position is moved by a drive device that applies a voltage to the machining gap where the electrode and the workpiece face each other and moves the relative position of the electrode and the workpiece by a predetermined amount for each pulse using a pulse signal. In the electrical processing apparatus that performs the control, a means for generating a pulse for advancing the electrode and the workpiece so as to reduce the relative position thereof along a desired pattern, a means for storing a pattern of output pulses according to the desired pattern, and a means for generating a pulse for advancing the electrode and the workpiece so as to shorten the relative position thereof along a desired pattern; Means for generating a pulse for moving the workpiece backward along the desired pattern so as to widen the relative position of the workpiece, means for detecting a voltage corresponding to the state of the machining gap, and comparing and determining the detected voltage with a reference voltage. means for switching and controlling the output of the pulse generating means for advancing and the output of the pulse generating means for reversing according to the output signal of the comparing means; The above-mentioned means for generating a pulse for advancing the object so as to reduce its relative position is such that the advancing speed is higher than the machining progress speed (machining volume/machining area per unit time). An electrical processing device characterized by the following.