JP3032336B2 - EDM method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining method for rough machining a desired NC program shape and then finishing the same shape as the NC program shape.

[0002]

2. Description of the Related Art When a workpiece is machined into a predetermined shape using a wire cut electric discharge machine, electrical conditions are compared in order to obtain a discharge energy sufficient to remove a machined portion by electric discharge. High. For this reason, the processing surface becomes rough and the processing gap is widened, so that it is difficult to obtain a desired shape and the processing accuracy is low. Therefore, after roughing the shape set by the NC program under the relatively high electric conditions as described above, the shape is set lower than the electric conditions of the rough processing, and the end face is processed by a small amount. Finishing is performed.

[0003] At the time of this finishing processing, since a portion of the workpiece to be removed is small (small amount), a strong discharge energy is not required, the processing surface is not roughened, and the processing gap is narrow. The shape can be made closer to the desired shape, and high processing accuracy can be obtained. In addition, the number of times of finishing is not limited to one, but is often performed a plurality of times. In this case, the electrical conditions are gradually set lower and the finishing is repeated.

FIG. 7 is an explanatory view of a conventional apparatus for executing the above-mentioned conventional processing method. FIG. 1 (1) is a front view thereof, and FIG. 2 (2) is a left side view thereof.

In this conventional apparatus, a wire electrode 1 is moved relative to a workpiece 2 to perform electric discharge machining. An upper nozzle 3 and a lower nozzle 4 of a machining liquid jet are formed by a machining liquid supply device (not shown). To supply the machining fluid to the machine.

The workpiece 2 is placed on an X-axis table 5 and a Y-axis table 6. The wire electrode 1 is provided in a column 11 via an upper arm 10, and a U-axis and V-axis table (not shown) is provided in a UV-axis moving device 12 which can be moved up and down by a Z-axis drive motor 13. 14, the U-axis and V-axis tables are horizontally moved by the V-axis drive motor 15, whereby the wire electrode 1 is inclined. The wire electrode 1 is configured to be supplied from a wire feed roller 16 to a processing gap via a guide roller 17 and collected from a wire winding roller (not shown) via a lower arm 9.

FIG. 8 is a plan view of the workpiece 2 and shows an example of processing.

[0008] The NC program shape (a) input and set in advance is the final desired machining shape and is the NC program locus. The wire electrode path (b) at the time of rough machining is indicated by a dashed-dotted line, and the wire electrode path (c) at the time of finish machining is indicated by a broken line. Although there are various definitions of roughing and finishing, in this specification, the first working is called rough working, and the second and subsequent workings are called finishing.

The processing start through hole P1 is a hole formed in the workpiece 2 in advance, and the wire electrode 1 is inserted and connected by a wire electrode insertion connection device (not shown) or the like. The wire electrode 1 moves on a path (so-called offset rough machining path (b)) shifted from the NC program shape (a) in consideration of the diameter of the wire electrode, a discharge gap, a margin for preventing overcut, and the like. In the drawing, processing is performed while proceeding in a counterclockwise direction. Although the offset value is often set on the NC program, in the present case, for the sake of explanation, the final desired shape excluding the offset value is referred to as “NC program shape”, and the locus on the plane is referred to as the “NC program shape”. It is called "trajectory", and both are used properly.

When the end point P2 is reached, electrical conditions or machining conditions such as machining fluid jet pressure are switched, and machining is advanced toward the through-hole P1 on a path with an offset distance shorter than the rough machining offset distance. . If the finishing process is performed once, the process is terminated when it reaches the through hole P1, but when performing the finishing process a plurality of times, the electrical conditions or the processing conditions such as the working fluid jet pressure are switched again. The wire electrode 1 is advanced toward the end point P2 on a path whose offset distance is shorter than the path (c), and thereafter, the above operation is repeated according to the number of times of finishing.

Here, when the wire electrode 1 travels along the path (b) from the machining start through hole P1 and reaches the end point P2, the wire electrode 1 is deflected by the influence of the machining fluid or the like, and the numerical controller is moved to the current position. The actual machining is later than the position corresponding to the upper and lower guides 17 and 18 which is recognized to be. Further, if the finishing process of the path (c) is performed immediately at the end point P2, a sufficient working gap cannot be obtained, and the wire electrode 1 and the workpiece 2 come into contact with each other. Is lost and a short circuit occurs, so that finishing cannot be performed. In order to prevent this short circuit, there is a method in which the end point P2 is turned back under the electrical conditions used in the roughing, and thereafter, the processing is switched to the electrical conditions for the finishing process. However, in this method, when the amount of processing is reduced, processing is performed under high electrical conditions, so that this effect causes disconnection or the voltage does not return to a predetermined value,
There is a case where an adverse effect that it is not possible to shift to the next processing occurs.

In order to prevent this problem, conventionally, the relative feed between the wire electrode 1 and the workpiece 2 is stopped for a fixed time immediately after the wire electrode 1 reaches the end point P2. Discharge is continued. In this way, the bending of the wire electrode 1 is removed, and the finishing process is performed after the discharge gap is enlarged. Alternatively, after reaching the end point P2, the electric discharge machining is interrupted, the wire electrode 1 is cut, and the wire electrode 1 is inserted and connected again through the machining start through hole P1, and the finishing machining path (c) in the same direction as the rough machining. A method of processing the top is also employed.

[0013]

SUMMARY OF THE INVENTION As in the above conventional example,
In order to continue the discharge for a certain period of time while the relative feed between the wire electrode 1 and the workpiece 2 is stopped, and to shift to the next processing step, the operator needs to stop the relative feed for a while. Must be set each time. In this case, if the stop time is too short, a sufficient discharge gap cannot be obtained, resulting in a short circuit or disconnection of the wire electrode. Further, if the stop time is too long, the shape of the workpiece 2 is damaged, so that the stop time needs to be set appropriately.
Furthermore, since the stop time varies depending on the material and thickness of the workpiece, skilled techniques are required. Therefore, for a normal worker, in reality, the wire electrode 1 and the workpiece are practically used. There is a problem in that it is difficult to accurately set the stop time of the relative feed with the second.

On the other hand, if the wire electrode 1 is cut once at the processing end point P2 and the finishing processing is started from the processing start through hole P1, it is necessary to perform various operations such as cutting, insertion, and connection. In addition to the problem that a large amount of work time and labor is required, there is a problem that it is difficult to execute the next step when insertion or connection work fails or a position shift occurs.

According to the present invention, in an electric discharge machining method in which the same NC program shape is repeatedly machined a plurality of times, it is possible to reliably shift to the next machining without breaking or short-circuiting of a wire electrode. It is an object of the present invention to provide an electric discharge machining method that does not require much work time and labor.

Further, according to the present invention, in the above case, even when the gap voltage does not return, the processing can be shifted to the next processing without interrupting the processing, and the switching from the rough processing to the finishing processing can be smoothly performed. It is an object of the present invention to provide an electric discharge machining method capable of performing the above.

[0017]

According to the present invention, there is provided an electric discharge machining method in which the same NC program shape is repeatedly machined a plurality of times. The gap voltage is detected before starting the machining, and when the detected gap voltage becomes equal to or higher than a predetermined voltage, the process proceeds to the next machining.

Further, in the above case, when the gap voltage does not become equal to or higher than a predetermined voltage after a lapse of a predetermined time from when the wire electrode reaches the processing end point, a block having a predetermined shape is subjected to electric discharge machining. When the electric discharge machining is completed, the process shifts to the next machining.

[0019]

According to the present invention, there is provided an electric discharge machining method in which the same NC program shape is repeatedly machined a plurality of times. When the gap voltage is detected, and when the detected gap voltage becomes equal to or higher than a predetermined voltage, the process shifts to the next process, so that the wire electrode can be reliably disconnected for the next process without disconnection or short circuit. It can be migrated and does not require much work time and labor.

Further, in the above case, according to the present invention, when the gap voltage does not become equal to or higher than a predetermined voltage after a lapse of a predetermined time from when the wire electrode reaches the processing end point, a block having a predetermined shape is subjected to electric discharge machining. When the electric discharge machining is completed, the process proceeds to the next machining, so even if the gap voltage does not return, the wire electrode can be vibrated to obtain the necessary gap for machining. It is possible to shift to the next machining without interruption, and to smoothly switch from rough machining to finish machining.

[0021]

FIG. 1 is a flowchart showing one embodiment of the present invention.

In this embodiment, when processing the shape shown in FIG. 8, first, a reference voltage Vr is set (S1). The reference voltage Vr is, for example, 60 to 70 V (that is, a voltage slightly lower than the no-load voltage). When the wire electrode 1 reaches the processing end point P2, the gap voltage Vg
Is measured, and when the gap voltage is equal to or higher than the reference voltage Vr, the rough machining is terminated, and the reference voltage Vr is required at the time of this determination.

Then, a timer time t is set (S2),
The control flag F is set (S3). Note that a plurality of data relating to the timer time is stored in the storage device in advance, and based on the material or plate thickness of the workpiece input by the operator prior to machining, the stored plurality of timer time data is stored. It is preferable to automatically set one of them. The control flag F is "1" when the gap voltage Vg is compared with the reference voltage Vr before the electric discharge machining is completed.
If the electric discharge machining is terminated without performing the control, the value is set to "0". Note that “1” and “0” may be set in the reverse of the above.

Subsequently, the electric discharge machining is started (S4), and when the wire guide reaches the machining end point P2 (S4).
5), check the state of the control flag F set in advance (S
6). If the control flag F is "1", the gap voltage Vg at that time is compared with the already set reference voltage Vr (S7). The counter counts the timer time t from when the wire guide reaches the machining end point P2, and the above voltage comparison is performed until the timer time t elapses (S8), and the gap voltage Vg is changed to the reference voltage Vr.
When the above is completed, the process proceeds to the next processing.

Here, even if the gap voltage Vg does not become higher than the reference voltage Vr, the electric discharge machining is terminated when the timer time t has elapsed. Even if the timer time t elapses, the gap voltage Vg remains at the reference voltage Vr.
If the voltage value does not become higher than this, it is often considered that some abnormality has occurred. In this case, it is meaningless to perform the voltage value comparison operation without limitation, and therefore, the time for performing the voltage value comparison operation is limited. Is provided.

For example, when the workpiece 2 is SKD-11 and its thickness is 40 mm, the timer time t may be about 10 seconds, depending on the strength of the electrical processing conditions. When the workpiece 2 is a cemented carbide, the timer time t may be about 15 seconds for the same plate thickness.
Further, the timer time t may be determined according to the predicted processing speed according to the processing conditions, the material of the workpiece 2, the diameter of the wire electrode 1, and the like.

When the gap voltage Vg becomes higher than the reference voltage Vr, it can be considered that the bending of the wire electrode 1 has disappeared, and it is determined that an appropriate gap has been obtained at the end point P2 of the rough machining. Can be. Therefore, when the finish processing is started from the end point P2, the voltage is reliably restored even under weak processing conditions such as the finish processing, and the risk of disconnection of the wire electrode is low because there is a sufficient gap. .

FIG. 2 is a diagram showing an example of a program in the above embodiment. It should be noted that the numerical values in this example of the program match the shape in FIG.

In this program, G54 is a code for specifying a coordinate system, G92 is a code for setting a coordinate value, G90 is a code for specifying an absolute coordinate command, and G42 is a wire diameter correction (rightward in the traveling direction). ), And H170 indicates an offset value of 170 μm.
M98 is a code indicating a subprogram call, G41 is an offset code, that is, a code for wire diameter correction (leftward in the traveling direction), H120 indicates an offset value of 120 μm, and G01 is a linear interpolation code. G40 is a code for canceling wire diameter correction. Note that P0010 indicates that the subprogram is N00
It is shown that it is 10.

G10 is a code indicating that control relating to the electric discharge machining method is inserted in the electric discharge machining program, and corresponds to the case where the flag F in FIG. 1 is "1". . M99 is a code indicating the end of the subprogram.

FIG. 3 is a flowchart showing another embodiment of the present invention.

First, a shape pattern P is set (S1).
1). The swing width L of the shape pattern P is set (S1
2). When an operator creates a machining NC program, the operator inserts a shape block P, displays a plurality of shape patterns P on a CRT screen, and selects one of them to set the shape pattern P. I do. Alternatively, the processing conditions and the shape corresponding to the material, plate thickness, and electrode diameter of the workpiece 2 may be stored in the storage device, and the shape pattern P may be automatically set according to the stored contents.

In this case, the swing width L is set to its radius in the case of a circle, 1/2 of the swing width in the case of swinging back and forth, right and left, and to the distance from the center to the corner in the case of shaking in a diamond shape. It is. Then, the control flag F is set (S1
3), electric discharge machining is started (S14). After the start of the electric discharge machining, if the wire guide reaches the end point P2 and the flag F is "1" (S15, S16), the shape pattern P is machined with the already set swing width L (S17). Move to the next processing.

FIGS. 4 (1), (2) and (3) are diagrams showing examples of the shape pattern P, respectively.

In order to obtain the necessary gap, FIG.
Any of (3) may be adopted, and other shape patterns P may be adopted as long as the swing width L required to obtain a predetermined gap is sufficiently set.

FIG. 5 is a flowchart showing another embodiment of the present invention.

In this embodiment, the voltage value is compared for a predetermined time, and the wire electrode 1 is vibrated only when the voltage does not return within the predetermined time and a necessary gap is obtained. Thus, it is possible to more reliably move to the next processing.

First, parameters such as a reference voltage Vr, a timer time t, a shape pattern P, a swing width L, and a control flag F are set (S21), and a first processing (rough processing) is performed.
The process ends (S22, S23). The setting method is the same as in the first and second embodiments. Then, the gap voltage Vg is detected, and counting of the timer time t set based on the parameter is started (S24). If the gap voltage Vg is equal to or higher than the reference voltage Vr, the processing conditions are changed and the second processing (finish processing) is performed (S28, S29).

On the other hand, in S25, the gap voltage Vg
Is lower than the reference voltage Vr, the gap voltage V
g and the reference voltage Vr (S26), and waits until the timer time t elapses or the gap voltage Vg becomes higher than or equal to the reference voltage Vr. If the gap voltage Vg is lower than the reference voltage Vr even after the elapse of the timer time t, the wire electrode 1 is vibrated in a predetermined shape pattern to widen the gap (S27) and prepare for the second processing. The processing conditions are changed, and the second processing is performed (S28, S29).

In the above embodiment, FIGS.
Although only one of the embodiments shown in FIG. 1 is executed at all times, one of FIG. 1, FIG. 3, and FIG. 5 may be selected prior to electric discharge machining.

The processing conditions are switched at the transition from the first processing to the second processing. At this time, the bending of the wire electrode 1 is removed by waiting for a predetermined time, and thereafter, the processing is switched to the second processing. It is desirable to move.

FIG. 6 is an overall explanatory diagram of the above embodiment.

In this figure, the same members as those shown in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted. The switching element 203 is repeatedly turned on and off in response to a pulse from the pulse generator 101, and a current flows from the processing power supply 202 to the wire electrode 1 via the power supply terminals 201 and 204.

The voltage detecting device 102 is an example of a device which detects a gap voltage before the wire electrode reaches the end point of the predetermined number of processings and before the processing proceeds to the next processing. The drive control device 103 receives a command from the calculation command device 104 and controls the motors 7, 8, 13, 14, and 15. The calculation command device 104 includes a voltage detection device 102, a storage device 105, and a timer circuit. 106, each operation is performed based on a signal from the input device 107, and the pulse generator 10
1. A necessary command is sent to the drive control device 103, and necessary information is displayed on the display device 108. In addition, the drive control device 103 and the operation command device 104 determine that the gap voltage detected before the wire electrode has reached the processing end point of the predetermined number of times and shifted to the next round of processing has become equal to or higher than the predetermined voltage. This is an example of a case where control for shifting to the next processing is performed. In addition, the drive control device 103 and the calculation command device 104 perform electric discharge machining of a block having a predetermined shape when a gap voltage does not become equal to or higher than a predetermined voltage after a predetermined time has elapsed since the wire electrode reached the processing end point,
This is an example of a case in which, when the electric discharge machining of this block is completed, the process is shifted to the next machining.

The above is an example of an apparatus for executing the processing method of the present invention, and it is a matter of course that the apparatus is not limited to such an embodiment.

[0046]

According to the first aspect of the present invention, it is possible to surely shift to the next processing without breaking or short-circuiting of the wire electrode, and it is possible to reduce the working time and labor. .

According to the second aspect of the invention, even if the gap voltage does not return, the wire electrode can be vibrated to obtain a gap required for processing, so that the next processing can be performed without interrupting the processing. It is possible to shift to machining, and it is possible to smoothly switch from roughing to finishing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating a program example of the embodiment.

FIG. 3 is a flowchart showing another embodiment of the present invention.

FIG. 4 is a diagram showing an example of a shape pattern P in the embodiment shown in FIG.

FIG. 5 is a flowchart showing still another embodiment of the present invention.

FIG. 6 is an overall explanatory view of the embodiment.

FIG. 7 is a view showing an example of a conventional electric discharge machining apparatus.

FIG. 8 is an explanatory diagram of an operation of roughing and finishing.

[Explanation of symbols]

 P: shape pattern, P1: processing start through hole, P2: processing end point, L: swing width, Vg: gap voltage, Vr: reference voltage, t: timer time.

Claims (2)

(57) [Claims] An electric discharge machining method in which the same NC program shape is repeatedly machined a plurality of times, wherein the wire electrode reaches a machining end point of a predetermined number of times, and a gap is formed before the wire electrode moves to the next machining. An electric discharge machining method comprising: detecting a voltage; and when the detected gap voltage becomes equal to or higher than a predetermined voltage, the process proceeds to the next machining. 2. An electric discharge machining method in which the same NC program shape is repeatedly machined a plurality of times. In the electric discharge machining method, a gap is set before a wire electrode reaches a machining end point of a predetermined number of times and shifts to the next machining. Voltage is detected, and when the detected gap voltage becomes equal to or more than a predetermined voltage, the process proceeds to the next processing, while a predetermined time has elapsed since the wire electrode reached the processing end point, When the gap voltage does not exceed the predetermined voltage,
An electric discharge machining method comprising: subjecting a block having a predetermined shape to electric discharge machining; and, when the electric discharge machining of the block is completed, shifting to the next machining.