JPH0431807B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for controlling a wire electrical discharge machine. When machining a workpiece by numerical control, the movement locus of the wire electrode is determined by the radius of the wire electrode and the distance between discharges with respect to the cutting surface of the workpiece.
This is a movement that takes the amount of offset into consideration, that is, a movement that adds an offset amount, but this correction may cause a cut in the workpiece. The present invention relates to a method of controlling a wire-cut electrical discharge machine that prevents this cutting.

[Prior Art] The trajectory of movement of a wire electrode by a numerical control (hereinafter abbreviated as NC) device of a conventional Yaiya-Cut electrical discharge machine was as shown in FIGS. 1 and 2. In FIGS. 1 and 2, 1, 2, and 3 are cut surfaces of the workpiece and represent NC block commands, and 1 is the currently commanded NC block command. 4, 5, and 6 are the ones with an offset amount added to the cut surface of the workpiece, that is, NC
This is the movement trajectory of the wire electrode (hereinafter referred to as the wire electrode movement trajectory) obtained by adding an offset amount to the block command.

In FIG. 2, 9 is the intersection of the wire electrode movement trajectories. As shown in Fig. 2, in order to determine the wire electrode movement locus 4 of the currently issued NC block command 1, the next movement command block must be
By first reading NC block command 2 into the NC device, a vertical vector 10 corresponding to the wire radius and the distance between discharges, that is, an offset amount, is given to NC block commands 1 and 2. Find straight lines 4 and 5 parallel to 2. By finding the intersection 9 of these straight lines 4 and 5, the wire electrode movement locus 4 of the NC block command 1 was determined.

Applying the wire electrode movement locus determined in the above manner to Fig. 1, we can see that the NC block command 1
The wire electrode movement trajectory is 4, the wire electrode movement trajectory of NC block command 2 is 5, and the wire electrode movement trajectory of NC block command 3 is 6. The NC device executes the wire electrode movement trajectories 4, 5, and 6 of the NC block commands 1, 2, and 3 obtained in this way.
The wire electrodes are moved relative to each other so as to move the wire electrodes.

[Problems to be Solved by the Invention] As described above, when processing a workpiece by moving the wire electrode relatively using a movement trajectory to which an offset amount is added, the conventional method is to obtain the current movement trajectory of the wire electrode. In addition, calculations were performed using only the NC block command one block ahead. For this reason,
When processing as shown in FIG. 1, there is a problem in that cuts 7 and 8 are generated, resulting in unnecessary cuts.

Note that 7 is a cut caused by the wire electrode movement trajectory 4, and 8 is a cut caused by the wire electrode movement trajectory 5.

This invention was made to solve this problem, and when a workpiece is machined by moving the wire electrode based on the movement locus of the wire electrode with an offset amount added to the NC block command, the excessive depth of cut is eliminated. The object of the present invention is to provide a control method for a wire-cut electrical discharge machine that prevents this from occurring.

[Means for Solving the Problems] A method for controlling a wire-cut electric discharge machine according to the present invention includes determining, by a numerical control device, a movement trajectory of a wire electrode by adding an offset amount to a numerical control block command; In a control method for moving a wire electrode relative to a workpiece based on a trajectory, at least two blocks of numerical control block commands are read in advance, and at least two numerical control block commands read in advance and the current movement of the wire electrode are read in advance. Using the numerical control block command, first obtain the movement trajectory and direction of movement of the wire electrode for at least three blocks, and if there is a point where the movement direction of the obtained movement trajectory differs from the command direction of the numerical control block command, , the numerical control block commands in different directions are omitted, and the continuous movement locus of the wire electrode with an offset amount added is determined using the numerical control block commands immediately before and after the omitted numerical control block commands. It is.

[Embodiment] FIG. 3 is an explanatory diagram showing the wire electrode movement locus in response to NC block commands in an embodiment of the present invention, and illustrates an example of preventing cutting using three blocks of NC commands.

In Figure 3, 1 is the NC block command that is about to move, similar to 1 shown in Figure 1, and 2 and 3 are the pre-read commands used to determine the wire electrode movement locus of NC block command 1.
This is an NC block command. Furthermore, the wire electrode movement trajectories obtained by NC block commands 1 and 2 are 14 and 13, and the wire electrode movement trajectory obtained by NC block commands 2 and 3 is 5.
It is. Furthermore, the wire electrode movement trajectories according to NC block command 3 are 12 and 16. here,
The intersection of the wire electrode movement trajectories 13 and 5 is 17, the intersection of the wire electrode movement trajectories 5 and 12 is 18,
Let 11 be the intersection of the wire electrode movement trajectories 14 and 16.

Now, for NC block commands 1, 2, and 3, if the movement locus is determined using the previous block one block at a time, the wire electrode moves to 17 on the wire electrode movement locus 14, and then the wire Move on the electrode movement trajectory 5 from 17 to 18,
The wire electrode further moves on the wire electrode movement trajectory 16 from 18 to process the workpiece. here,
When the wire electrode moves from 11 to 17 to 18 to 11, cuts in the workpiece, ie, cuts 7 and 8 shown in FIG. 1 will occur.

In order to prevent this incision, in this invention,
In addition to NC block command 2 to determine the wire electrode movement locus of NC block command 1,
By also pre-reading the NC block command 3, the wire electrode movement trajectories 14, 13, 5, 12, and 16 are obtained, and when the traveling direction of the wire electrode movement trajectory 5 obtained here is different from the command direction of the NC block command 2. is the wire electrode movement trajectory 14, 1 with respect to NC block command 1 using NC block command 2.
Since it is known that a cut will occur if 3 is determined, the wire electrode movement locus 14 of NC block command 1 is determined using NC block command 3 instead of NC block command 2.

Therefore, the wire electrode movement locus for NC block command 3 is 16. That is, using NC block commands 1 and 2, a continuous movement locus of the wire electrode to which offset amounts of 14 and 16 are added is determined.

Next, based on this determined movement locus, the wire electrode moves along the wire electrode movement locus 14 to the intersection 11 for NC block command 1, and since NC block command 2 is omitted, it is moved for NC block command 3. In contrast, the wire electrode movement locus 16 is moved from the intersection 11. This makes it possible to prevent cuts into the workpiece within three blocks.

Note that the above-mentioned intersection 11 will be referred to as a cut prevention point in this specification.

Figure 3 describes the case where NC block commands 1, 2 and 3 are straight lines.
The same goes for the case where each wire electrode is a circular arc, the movement trajectory of each wire electrode is determined from the NC block commands for three blocks, and if the direction of movement of this movement trajectory differs from the commanded direction of the NC block command, the second
By omitting the second block (NC block command 2 in this example) and determining a continuous wire electrode movement trajectory using the first and third blocks, a wire electrode movement trajectory that does not cause cutting can be achieved. can be determined.

In the above embodiment, the occurrence of a cut within three blocks is prevented by determining the wire electrode movement locus using three blocks of NC block commands. 2 or more) Read ahead the block, and read this read-ahead n block command and the currently commanded NC.
Using the block command, first find the wire electrode movement trajectory and the direction of movement, and if there is a place where the direction of movement of the movement path found differs from the commanded direction of the NC block command, change the direction of the block in the different direction. If the command is omitted and a continuous wire electrode movement locus is determined using the NC block commands immediately before and after the omitted block command, all cuts can be prevented.

[Effects of the Invention] As described above, according to the present invention, when processing a workpiece by moving the wire electrode relative to each other using an NC program, at least two blocks of the program are pre-read, and the pre-read NC block commands are Using the current NC block command and the current NC block command, the wire electrode movement locus and traveling direction for at least three blocks are first determined, and a place where the traveling direction of the determined movement locus differs from the commanded direction of the NC block command is found. If the NC is in a different direction,
Since the block command is omitted and the continuous wire electrode movement trajectory is determined using the NC block commands immediately before and after the omitted NC block command, a control method for a wire cut electric discharge machine having the following effects can be achieved. Obtainable.

(b) It is possible to prevent cuts that may occur in the workpiece when the wire electrode is moved relative to the wire electrode movement trajectory by adding an offset amount to the NC block command.

(b) Since the wire electrode can move continuously without temporarily stopping at the cut prevention point, another cut will not occur in the workpiece due to the temporary stop of the wire electrode.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a wire electrode movement locus in response to a conventional NC block command, Fig. 2 is an explanatory diagram showing how to obtain a wire electrode movement locus in response to an NC block command, and Fig. 3 is an embodiment of the present invention. FIG. 2 is an explanatory diagram showing a wire electrode movement locus in response to an NC block command according to the invention. In the figure, 1 is the currently issued NC block command,
2 and 3 are NC block commands read in advance, 4 is the wire electrode movement trajectory obtained by commands 1 and 2, 5 is the wire electrode movement trajectory obtained by commands 2 and 3, and 6 is the wire electrode of command 3. movement trajectory,
7 is the incision generated by the wire electrode movement trajectory 4, 8 is the incision caused by the wire electrode movement trajectory 5, 9 is the intersection of the wire electrode movement trajectory, 10 is a vertical vector equivalent to the offset amount, and 11 is the wire electrode movement trajectory 14. 16, 14 is the wire electrode movement locus for NC block command 1 obtained according to the present invention, and 16 is the wire electrode movement locus for NC block command 3 obtained according to the present invention. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A numerical control device determines the movement trajectory of the wire electrode by adding an offset amount to the numerical control block command, and moves the wire electrode relative to the workpiece based on the determined movement trajectory. In a method of controlling a wire cut electric discharge machine, the numerical control block commands are read in advance by at least two blocks, and the numerical control block commands for the at least two blocks read in advance and the numerical control block command to be moved are used to control at least three blocks. The movement locus and direction of movement of the wire electrode for each period are first determined, and if there is a place where the direction of movement of the determined movement path differs from the command direction of the numerical control block command, the numerical control block in the place where the direction is different is found. Control of a wire-cut electric discharge machine characterized by omitting commands and determining a continuous movement locus of a wire electrode with an offset amount added using numerical control block commands immediately before and after the omitted numerical control block commands. Method.