JPH078457B2 - EDM method - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an electric discharge machining method, and more particularly, to moving an electrode along a circular machining trajectory pattern similar to a final machining shape, and The present invention relates to an electric discharge machining method in which a workpiece is sequentially expanded by a predetermined expansion amount for each electric machining condition.

[Prior art]

Generally, in hole machining by electric discharge machining, a pattern (contour) of a certain shape that matches the desired shape to be machined is
A tool electrode is moved along a trajectory pattern enlarged by m, and finally a workpiece having a desired shape and dimensions is processed. This will be described with reference to FIG.
(1) is a pattern of a constant shape that matches the desired shape to be processed (corner pattern is used as an example, the same applies below), and (2) is a trajectory pattern in the process of enlarging the pattern (1) by several μm. Is. (A) shows a rough machining amount region under a large electric machining condition, and (B) shows a finishing machining amount region under a small electric machining condition.

Next, the operation will be described. When making a hole in a desired shape on a workpiece, in order to perform electric discharge machining using an electrode having the same shape as that of the desired shape or a different shape and smaller than the size of the desired shape, first, At the start of processing, the desired shape in (1) above is determined, then the processing conditions from roughing to finishing and the expansion amount and processing speed are determined, and the expansion amount range of the large electrical processing conditions in (A), The expansion amount region of the small electromachining condition of B) is distinguished, and the expansion amount for one time is determined in accordance with each electromachining condition, and the pattern of the entire machining is programmed. At this time, each shape pattern is successively expanded one by one at a speed set in the program for each machining condition, and the entire pattern as shown in FIG. 1 is completed. After that, a normal electric discharge machining is performed by the program.

In this electric discharge machining, a work piece and a tool electrode are opposed to each other in a machining fluid and crushed, and an electric discharge phenomenon is generated between the work piece and the tool electrode through the machining fluid to make the work piece desired. It is processed into a shape.

In the conventional electric discharge machining method using the shape expansion pattern configured as described above, the expansion amount (the moving distance of the electrode in the expansion direction) is preset for each machining electrical condition, and when the machining electrical condition is changed, The expansion amount will be changed accordingly. Therefore, for example, when the machining electrical condition is changed from the large electromachining condition to the small electromachining condition, the expansion amount of the electrode is also changed to that set in the small electromachining condition, which is larger than the expansion amount of the large electromachining condition. It will be a small expansion amount. On the other hand, since the appropriate discharge gap under the small electromachining condition is smaller than that under the large electromachining condition, the gap between the electrode and the work piece is smaller than the appropriate discharge gap when the expansion amount is small as when the machining electric condition is changed. It becomes considerably wide, and the electrode repeats the circular movement while sequentially enlarging the shape enlarging pattern without processing until an appropriate discharge gap is achieved.
Therefore, especially when the area of the side surface to be machined is large or in the case of finishing, the moving speed of the electrode is slow, so that there is a problem that the non-machining time becomes long and the total processing time becomes long.

[Summary of the Invention] The present invention has been made to solve the above-mentioned problems, and when the electromachining condition is switched from the large electromachining condition to the small electromachining condition, a circular trajectory is left without machining the electrode. It is an object of the present invention to provide an electric discharge machining method with high machining efficiency without causing unnecessary movement such as movement.

The electrical discharge machining method according to the present invention moves the electrode along a circular machining trajectory pattern similar to the final machining shape,
In the electric discharge machining method for machining the workpiece by sequentially enlarging the orbiting machining trajectory pattern by a predetermined enlarging amount for each electromachining condition, when switching the electromachining condition from the large electromachining condition to the small electromachining condition. The electrical condition switching step of changing the preset expansion amount under the large electromachining condition to the expansion amount under the small electromachining condition, and the electrical condition switching process switched over from the large electromachining condition to the small electromachining condition. After that, by comparing the servo voltage value detecting step of detecting the servo voltage value and the servo voltage value detected by the servo voltage value detecting step with a preset reference value, the machining state or the non-machining state is determined. If there is a non-machined state in the comparison and judgment process, it is judged whether there is a large electric machining condition or a small electric machining condition. The electrode is moved in the expansion direction by a preset moving distance when the electrical conditions are switched to a distance equal to the difference in the appropriate discharge gap, and the electrode is moved to perform machining along the revolving machining locus pattern, while it is in the machining state. If it is determined that the processing is performed, an enlarging movement control step of performing processing along the revolving processing trajectory pattern is provided.

[Examples of the invention and effects thereof]

An embodiment of the apparatus used in the method of the present invention will be described below with reference to FIG. 2. (1) is the same desired shape pattern as in FIG. 1, and (2) is also the same as in FIG. It is an enlarged locus pattern when the desired shape pattern is enlarged by several μm. (11) is a servo voltage detection device that detects the servo voltage that controls the gap between the workpiece and the tool electrode during electrical discharge machining, and (12) is the movement of the tool electrode according to the servo voltage value sent from the servo voltage detection device. It is an N / C device that judges control. Further, (H) and (K) respectively indicate the expansion amount for each time and the expansion region from the start to the completion of expansion. P ₀ is the base point of the desired shape pattern, and P _{1 to} P _N are the enlargement amounts of the pattern. (5) is the orbit line in the expansion direction.

Next, the operation of this embodiment will be described. In order to process a desired shape on a work piece, it is the same as the conventional method to process a work piece using an electrode having the same shape as or a different shape from the desired shape and smaller than the desired shape size. When machining the electro-machining condition or the large machining area under the small electro-machining condition, the residual machining amount at the time of the pattern machining before being caused by the minimum limit of (H) of expanding by μm every time is 1 μm is loaded, In order to improve that the processing state was adversely affected, the pattern voltage processing state in each revolution was detected as a servo voltage by the servo voltage detection device, and the detected value was judged to have been set in the N / C device (12). A circuit or program is used to judge whether or not the orbital track machining is completed at each orbital completion point P.
Percentage of set value of servo voltage (+3 to + 6V) in one orbit (time of servo voltage +3 to + 6V ÷ one orbit time)
To make the same orbit or move to the next enlarged orbit.

The above-mentioned +3 to + 6V, which is the reference for determining the servo voltage, can be set to any voltage during this period, and the ratio occupied by the servo voltage can also be set arbitrarily.

Further, in the above embodiment, the case of the servo voltage has been described, but the same action and effect can be obtained even if the machining current value is detected. Furthermore, it goes without saying that the expansion locus direction is the same not only in the direction of the figure but also in any direction of 360 °.

As described above, according to the present embodiment, each encircling process of the shape pattern is surely performed by determining that the encircling process of the desired shape pattern every time when enlarging the desired shape pattern by several μm is monitored by the servo voltage value. It is possible to always maintain a stable processing state. As a result, not only abnormal machining is prevented and machining accuracy is improved, but also there is no effect of complicating the processing on a similar program and deficient prediction.

Next, the operation when the electromachining conditions are changed is shown in Figs.
It will be described based on. In this embodiment, the servo voltage provided for controlling the gap between the workpiece and the tool electrode is used to determine whether the machining state or the non-machining state is based on the servo voltage. When it is determined that the electrode is in a non-processed state, the movement amount of the electrode in the enlargement direction is made different from the normal enlargement movement amount.

(1) common to FIGS. 3 and 4 is a desired shape pattern,
(2) is a locus pattern when the desired shape pattern is expanded by several μm, and the servo voltage during processing is detected by the servo voltage detection device (11), and this voltage value is N / C device (12).
When the machine is judged to be non-machined by the machining state after switching from the large electromachining condition of (A) to the small electromachining condition of (B), the machining within the gear gap range of (C) Is omitted, and the tool electrode is moved in the enlargement direction on the enlargement locus of (5).

FIG. 5 is a schematic diagram concretely showing the difference in the discharge gear gap between the large electromachining condition and the small electromachining condition. (13) is a tool electrode, (14) is a workpiece, and (G ₁ ) is large. The discharge gap (SR ₁ ) generated by machining under the electrical machining conditions represents the surface roughness. In addition, (G ₂ ) represents the discharge gear caused by the small electric machining conditions, and (SR ₂ ) represents the surface roughness. (C) represents the difference between the discharge gears under the above two conditions.

FIG. 6 is a diagrammatic representation of FIGS. 3 and 4, where (3) is the final shape pattern position in the expanded area (A) of the large electromachining condition, and at that time, the workpiece to the position (6). Indicates that is processed. (4) is the final shape pattern position in the expanded area (B) of the small electromachining condition, and indicates that the workpiece is processed up to the position (7) at that time. (5) is an enlarged locus line along which the tool electrode moves when expanding from the center of the machining hole.
In the non-machined state, the tool electrode moves only on the expansion locus line in the expansion direction.

Next, the operation of this embodiment will be described. In order to process a workpiece into a desired shape, it is not possible to process the workpiece using electrodes having the same shape as the desired shape or different shapes and smaller than the desired shape size. As before, in this embodiment, the discharge cap (G ₁ ) of each electrical condition that occurs when the machining condition is switched from the large electrical machining condition to the small electrical machining condition.
The difference (C) of (G ₂ ) is calculated from the tool electrode (13) and the workpiece (14).
The servo voltage detection device (11) that detects the servo voltage that controls the gap between the two is used to compare the voltage value with the level value of the servo voltage in the N / C device, and When there is no machining, the tool electrode (13) is moved only along the enlarged trace (5) in the direction of enlargement, and when it is judged that the detected voltage value is in the machining state (1) The pattern is processed in the expansion range of each electrical condition while drawing the shape pattern with the maximum expansion value expanded up to the present.
As a result, the discharge gear gap difference (C) generated when the electrical condition for machining is switched to a non-machined state, and the movement of the shape pattern trajectory of the tool electrode (13) is omitted.

Further, in the above embodiment, the case of the servo voltage has been described, but the same action and effect can be obtained even if the machining current value is detected.

As described above, in this embodiment, since the machining state is judged based on the servo voltage level, there is no waste in the movement of the tool electrode in the non-machining state, and thereby the machining time is shortened. It is now possible to use a simple program without the need for complicated operations on the program.

〔The invention's effect〕

As is clear from the effects of each of the above-described embodiments of the present invention, according to the present invention, it is possible to always maintain a stable machining state, prevent abnormal machining, and improve machining accuracy. There are various effects such that the movement of the electrodes is not wasted, and the complexity of processing on similar programs and the lack of prediction are eliminated.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a desired shape pattern and its enlarged locus pattern, FIG. 2 is a schematic diagram showing the arrangement of an electric discharge machine of the present invention, and FIGS. 3 to 6 are another embodiment of the present invention. FIG. 3 is a schematic diagram of an enlarged locus pattern, FIG. 4 is a schematic diagram of an arrangement using the device of the present invention, FIG. 5 is a schematic diagram showing a relationship between a tool electrode and a workpiece for each electrical condition, and FIG. Figures are Figures 4 and 5
Schematic diagram in which the figures are integrated, (1) ... desired shape pattern, (2) ... locus pattern, (3) ... final shape pattern position in expanded area (A) of large electrical processing conditions, (4) ... The final shape pattern position in the expanded area (B) of the small electrical processing condition, (5) ... expanded trace line,
(6) (7) …… Machining position, (11) …… Servo voltage detector, (12) …… N / C device, (13) …… Tool electrode, (1
4) …… Workpiece, (A) …… Large electric machining condition expanded range,
(B) …… Expansion range for small electromachining conditions, (C) …… Differential range for discharge gears, (G ₁ ) …… Discharge gears for large electromachining conditions, (G ₂ ) …… Discharge gears for small electromachining conditions , (S
R ₁ ) (SR ₂ ) ... Surface roughness.

Claims (1)

[Claims] 1. An object to be processed by moving an electrode along a circular machining trajectory pattern similar to a final machining shape and sequentially enlarging the circular machining trajectory pattern by a predetermined expansion amount for each electrical machining condition. In the electrical discharge machining method for machining, when changing the electrical machining condition from the large electrical machining condition to the small electrical machining condition, the preset expansion amount under the large electrical machining condition is changed to the expansion amount under the small electrical machining condition. An electrical condition switching step, a servo voltage value detecting step of detecting a servo voltage value after switching from a large electrical processing condition to a small electrical processing condition by the electrical condition switching step, and a servo voltage value detecting step By comparing the servo voltage value with a preset reference value, it is possible to perform a comparison / judgment step of judging whether it is in a machining state or a non-machining state, and If it is determined that the electrode is in the machining state, the electrode is moved in the expansion direction by the preset movement distance when the electrical condition is switched to a distance equal to the difference between the appropriate discharge gaps under the large electric machining condition and the small electric machining condition. Then, after the electrode is moved, processing is performed along the revolving machining trajectory pattern, and on the other hand, when it is determined that the machining state is in effect, the machining is performed along the revolving machining trajectory pattern. An electric discharge machining method characterized by: