JPS60259327A - Detection of corner point for work in wire electric discharge machine - Google Patents

Abstract

PURPOSE:To work a workpiece at a correct position by detecting the corner point for the workpiece and positioning an electrode at the work starting position by using the corner point and the revolution angle of a work coordinate system with respect to a machine coordinate system, even if the work coordinate system is not parallel to the machine coordinate system. CONSTITUTION:A work WK is arranged onto a table TBL so that a work coordinate system XW-YW revolves by DELTAtheta with respect to a machine coordinate system XM-YM. The work starting position Ps is in a work starting hole STH, and exists at the position far by lx from the edge surface ESx of a work and by ly from the edge surface ESy of the work. Between two contiguous edge surfaces ESx and ESy of the work, at least two edge points Pi (i=1, 2...) are detected for the edge surface ESx, and the first straight-line for specifying the edge surface ESx is obtained from the position coordinate values of the edge point Pi, and at least two edge points Qi (i=1, 2...) are detected for the edge surface ESy, and the second straight-line for specifying the edge surface ESy is obtained from the position coordinate values of the edge point Qi, and the crossing point between the first and the second straight-lines is set as the corner point Pr for the work WK.

Description

[Detailed Description of the Invention] <Industrial Application> The present invention relates to a workpiece corner point detection method in a wire electrical discharge machine, and is particularly suitable for use in correcting machining errors caused by workpiece placement errors. This article relates to a method for detecting the corner point position of a workpiece.

<Prior Art> The path of a wire electrode in a wire electrical discharge machine is controlled relative to a workpiece based on numerical control data. In this case, the X-axis direction of the machine coordinate system is regarded as the commanded X-axis direction and the movement is controlled, and the Y-axis direction of the machine coordinate system is regarded as the commanded Y-axis direction and the movement is controlled. By the way, the numerical control data is programmed based on a workpiece coordinate system set on the workpiece. Therefore, unless the workpiece is fixed to the workpiece stand so that the workpiece coordinate system is parallel to the machine coordinate system, machining errors will occur during machining.

, Figure 8 shows that the workpiece coordinate system X, l-Y is the machine coordinate system x1.
．． It is an explanatory view when rotated by an angle Δθ with respect to l-YM. Even if the NC data is created to perform wire electrical discharge machining along the solid line path PT from the addition start hole STH, the workpiece coordinate system x1. When ly is rotated by an angle Δθ with respect to the machine coordinate system
#! PT', the path PT' is rotated by an angle Δθ with respect to the desired path PT.

Further, the machining start position may be specified by (a) the center of the machining start hole 5TH (see FIG. 6) or (b) the distance from two mutually adjacent end faces.

When the machining start position is specified as in the latter case, the wire electrode cannot be correctly positioned at the machining start position unless the workpiece is placed parallel to the workpiece table, and machining cannot be performed at the correct position on the workpiece. I can't.

<Disadvantages of the prior art> However, conventionally, it is very difficult to mount a workpiece on a workpiece table so that the workpiece coordinate systems Xu-Y, J are parallel to the machine coordinate system XM-YM, and it is always slightly An error occurred when installing the wire, making it impossible to perform wire electrical discharge machining at the correct location on the workpiece.

<Object of the Invention> An object of the present invention is to provide a workpiece corner point detection method that can be used to correct machining errors caused by errors in mounting the workpiece.

Another object of the present invention is to provide a method for detecting a corner point of a workpiece that can accurately position a wire electrode at a machining start position even if the workpiece coordinate system is not parallel to the machine coordinate system.

Still another object of the present invention is to provide a method for detecting a corner point of a workpiece, which allows machining to be performed at an accurate position on the workpiece even if the workpiece coordinate system is not parallel to the machine coordinate system.

<Summary of the Invention> Fig. 1 is a schematic explanatory diagram of the present invention, and Fig. 1 (A) shows that the workpiece WK is arranged so that the workpiece coordinate system X, -Y is parallel to the machine coordinate system XM-Y□. Stand (table) TBL
The figure (B) shows the case where the workpiece coordinate system
This is a case where the workpiece WK is arranged on the table TBL such that -Yl,l are rotated by Δθ with respect to the machine coordinate system xM-YM. The machining start position Ps is within the machining start hole STH, and is located at a distance of 1 degree from the first workpiece end surface ESX and from the second workpiece end surface ES.

Now, in the first embodiment of the present invention, of the two adjacent workpiece end faces ES, ES, the first end face ES,
Detect two or more endpoints P, (i=11.-1211, see Figure 1) for each endpoint P1, find a straight line specifying the first end surface ES from the position coordinate values of each endpoint P1, and One end point Q is detected for the end surface ES of , and the end point Q is
Find the foot of the perpendicular line drawn from , to the straight line (@plane ESX),
The foot of the perpendicular line is defined as the workpiece corner point P. Furthermore, in the second embodiment of the present invention, two adjacent workpiece end surfaces E
Among S, ESy, two or more end points P, i=1.211, for the first end surface E S8 are detected, and the end points P are detected.

A first straight line that specifies the first end surface ESx is determined from the position coordinate values of the second end surface E3. Detect two or more end points Q (i=1.211, see Figure 1) for The intersection of this line and the second straight line is defined as a corner point P of the workpiece WK.

<Example> Fig. 2 is a side view of a wire electrical discharge machine to which the present invention can be applied. There is a capacitor box 3 for power supply.
is placed. On the base 2, the workpiece is mounted on the base 4.
(T'BL in Fig. 1) is provided, and the workpiece mounting table 4 can be moved two-dimensionally on the base 2 by an X-direction drive motor and a Y-direction drive motor. . A workpiece 6 (WK in FIG. 1) is mounted on a table 4 using a clamp 5. 7 is a wire electrode, which runs in the direction of the arrow during electrical discharge machining. Reference numeral 8 denotes a feed-out reel around which an unused wire electrode is wound, and 9 a brake roller that applies a brake in the pulling direction when the wire electrode is fed out, around which the wire electrode is wound once. 10 is a roller, 11 is a lower guide roller, 12 is an upper guide roller, 13
1 is a roller, and 14 is a feed roller, which is rotated by a drive motor that drives a wire electrode. A pinch roller 15 is pressed against the feed roller 14 by a spring 16. Note that the wire electrode 7 is sandwiched between a feed roller 14 and a pinch roller 15.

Reference numeral 17 denotes a winding coil for winding up used wire electrodes.

FIG. 3 is a block diagram of an embodiment of the present invention, and FIG. 4 is a process flowchart.

Prior to wire electrical discharge machining, when the workpiece WK (Fig. 1) is attached to the table TBL (Fig. 1) of the wire electrical discharge machine, the position coordinate values of the corner point P of the workpiece WK and the end face ES are determined by the machine. Angle θ between X and axis of coordinate system XM-YM
. Detect. Note that the workpiece end surface ES8 is the workpiece coordinate system
1. The angle θ1 between l-Y and the x1 axis is known (90° in the figure).

(a) First, the end face ES is
, two end points P, (i
-1, 2) position coordinate values (x,,y,) are detected. That is, after positioning the wire electrode at the first YM-axis direction position Y1, operate the switch on the operation panel 11 (Fig. 3) to set the end surface mode, and set the direction of the workpiece end surface (the direction of the wire electrode). (direction of movement). As a result, the processor 12 first performs approximate end face position detection under the control of the control program stored in the ROM 1B, and then performs accurate one face position detection. In approximate end face position detection, (a-1) As shown in FIG. 5, feed speed f1 (for example, 50 mm/min) from point A in the positive direction (+XM direction) of the selected axis. to move the wire electrode toward the workpiece. That is, the processor 12 calculates the amount of movement ΔX to be moved in a predetermined period of ΔT seconds using the following formula % (1), and outputs the ΔX to the pulse distributor 14 every 61 seconds. The pulse distributor 14 performs a pulse distribution calculation based on the input ΔX, generates a distribution pulse xP, and generates a distribution pulse xP.
It is input to the axis servo circuit 15X, rotates the X-axis motor 16X, and moves the wire electrode relative to the workpiece.

The processor 12 inputs ΔX to the pulse distributor 14 every ΔT seconds to move the wire electrode toward the workpiece, and calculates X+Δx, x (2) every 61 seconds (the sign indicates movement). direction dependent), RAM
The current position X in the X-axis direction stored in 17 is updated.

(a-2) Through the above process, the wire electrode approaches the workpiece, and when the wire electrode comes into contact with the workpiece, a short circuit signal wss is generated from the short circuit detection $18, and the short circuit signal WSS
is taken into the processor 12 via the interface 19.

(a-3) Due to the generation of the short circuit signal, the processor 12
The input of ΔX to the pulse distribution @14 is stopped to stop the wire electrode at point B (see FIG. 5).

(a-4) Then, until the short circuit is released (up to point C), the same feed speed f1 (=50 mm/m1n
) to retract the wire electrode in the -XM axis direction.

(a-5) After that, in order to ensure that the short circuit is released, d (= 20
μ) Move back (position to point D).

(a-6) After the above processing, in order to accurately detect the position of the end face, the wire is moved to the end face again at a feed rate f, (= 0, 2 mm/m1n) using the same control as above until a short circuit signal is generated. Bring the electrodes close together and locate the short circuit signal generation position (P
, point), and convert the current position coordinate values of each axis (X,, Yl,) stored in RAM 1.7 at the end point P,
Save as coordinate values (X, , Y,).

(a-7) After that, update i by setting i + 1-= i, position the wire electrode at the next i-th position in the Y-axis direction, and repeat the process from step (a-1) onwards. The position coordinate value of the second end point is detected.

(a -8) From the above, if the position coordinate values of the two end points P, (i=1.2) for the first end surface ES, , are combined, then
Similarly, calculate the position coordinate values of one end point Q1 with respect to the second end surface ES.

If all the end points P, (i=1.2), Q, hold, the processor calculates the intersection angle θ at which the first end surface ES intersects with a predetermined axis (for example, the x, axis) of the machine coordinate system by the following process. and calculate the position coordinate value of the corner point P1 of the workpiece.

(b-1) First, find the equation of the straight line passing through the two points P and P2. Note that the obtained linear equation is a −x+by=1 (3).

(b-2) Next, find the position coordinate value of the foot P1 of the perpendicular line drawn from the 91st point to the straight line. Furthermore, the position coordinate value of Q is (X
(0% yO...see FIG. 6), the coordinate values (x, y) of the foot P1 of the perpendicular line are calculated by the following formulas (4) (5).

(b-3) Also, the angle θ that the first end surface ES forms with the predetermined shaft hole axis in the machine coordinate system is calculated using the following formula (%) (6). Now, since the intersection angle θ at which the first end surface ES intersects with the workpiece coordinate system predetermined axis
Gamaru.

As a result of the above, the workpiece corner points P, and Δθ are shifted and stored in RAM1.
7, the following path control will be performed in actual processing. It is assumed that NC data has been created with the workpiece corner point P1 as the origin of the workpiece coordinate system, and that NC data G50 Xξ Yl, ; for setting the coordinate system is inserted at the beginning of the NC data. .

(C-1) Prior to automatic operation using NC data, the wire electrode is moved relative to the workpiece by manual operation (MDI operation) and positioned at the processing start position PS (see FIG. 1).

That is, after positioning the wire electrode at the workpiece corner point P,
The MDI device W20 commands movement in the X direction (and Y direction).The processor 12 executes the calculation of the following formula based on the MDI command, and calculates the amount of movement x' in each axis direction (xM, Y0 axis direction). , y', and using these x' and y', the wire electrode is positioned at the processing start position P8 shown in FIG. 1(B) by simultaneous two-axis control. Note that Δθ is stored in the RAM 17. It is the rotation angle of the workpiece coordinate system with respect to the machine coordinate system.

(c-2) Next, when the start button on the operation panel 11 is pressed to start up, the processor 12 reads one block of NC data from the NG tape 22 by using the NGC data acquisition device 21.

(c-3) The processor 12 determines whether the read NC data is path data under the control of the control program.

(c-4) If the N C data does not include path data, the processor 12 executes normal NC processing and
After executing the G process, read the next NC data and proceed to step (
Perform the process c-3).

(c-5) On the other hand, if the NC data includes path data, for example, if the NC data indicates a straight path GOIXx Yy ;, the processor 12 corrects the path data using the following equation. In addition, XN y is NCC
It is the coordinate value of the end point position of the block given by del,
y' and y' are the coordinate values of the end point position after correction. Also, NC
Data indicates a circular path G02 (also ζyo GO3
) Xx Yy Ii Jj; In addition to equation (9), the following equation is calculated to correct the distance data lz j from the center of the arc to the starting point of the arc to i', y'.

(c-6) After calculating, if it is linear data, the processor uses x' and y' obtained from equation (9) to
If it is circular arc data, normal linear movement or circular arc movement processing is performed using y', y', 1', and y' obtained by equations (9) and (10).

(c-7) When the process in step (c-6) is completed, the processor causes the NG data reading device 21 to read the next NC data and performs the step (c-3) described above.
Repeat the following process.

(c-8) Then, when the M code MO2 or M3d indicating the program end is read out from the NC tape 22, the wire electric discharge machining ends. As a result of the above, the wire electrode moves relative to the workpiece along the path shown by the solid line in Figure 8,
Work coordinate system X, -Y.

Even if the hole is tilted with respect to the machine coordinate system XM-YM, wire electric discharge machining can be performed at an accurate position with respect to the reference hole.

In the above explanation, one end point Q is detected for the second end surface ES (see Fig. 1), and the first end point Q is detected from the end point Q1.
Although the case has been described in which the foot of the perpendicular line drawn to the straight line specifying the end surface ES is determined as the corner point of the workpiece, the corner point of the workpiece may be detected by the following method.

That is, the position coordinate values of the two end points Qi and Q2 are also detected for the second end surface ESV (see FIG. 1 (B)),
A second straight line that specifies the second end surface ES is drawn using the position coordinate values of the two end points Q (i=1.2), and a second straight line that specifies the first end surface and the second straight line that specifies the first end surface are 2 may be set as the workpiece corner point P. As shown in Fig. 7, if the equations of the first and second straight lines are a It is given by the % expression %) ). When detecting the position coordinate values of the corner points of the workpiece using this method, the intersecting angles at which the first and second straight lines intersect with the machine coordinate system predetermined axes xI, YM are determined, and the average value thereof is used. The rotation angle of the workpiece coordinate system with respect to the machine coordinate system can be determined by

Also, in the above explanation, each linear equation was calculated using two endpoints, but it is also possible to detect three or more endpoints and use the position coordinate values of each endpoint to find the linear equation using a statistical method such as the method of least squares. You can do it like this.

<Effects of the Invention> As explained above, according to the present invention, the corner points of the workpiece can be easily detected, and the workpiece can be machined using the corner points and the rotation angle of the workpiece coordinate system with respect to the machine coordinate system. The wire electrode can be accurately positioned at the starting position, and processing can be performed at an accurate position on the workpiece.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of the present invention, Fig. 2 is an external view of a wire electrical discharge machine to which the present invention can be applied, Fig. 3 is a block diagram of a device implementing the present invention, and Fig. 4 is a processing according to the present invention. 5 is an explanatory diagram of the end point detection method, FIGS. 6 and 7 are explanatory diagrams of calculation formulas for calculating the coordinate values of the corner points of the workpiece, and FIG. 8 is an explanatory diagram of the background of the present invention. WK...work, TBL...table ES,, ES
,...first and second end surfaces STH...machining start hole, P
6... Machining start position, Pl, Q, - one end point, xl
, l-Y, d...work coordinate system, xM-Yl, l...
・Machine coordinate system patent applicant Fanuc Co., Ltd. Agent Patent attorney Chiki Saito Figure 1 (A) Figure 1 (B) Figure 2-X□ Figure 6 Figure 7 Figure 8

Claims (6)

[Claims] (1) In a workpiece corner point detection method in a wire electric discharge machine that processes a workpiece by moving a t-wire electrode relative to the workpiece based on numerical control data, Detect two or more end points for the end face, find a straight line specifying the first end face from the position coordinate values of the end points, detect one end point for the second end face, and calculate the line from the end point to the A method for detecting a workpiece corner point in a wire electrical discharge machine, in which the foot of a perpendicular drawn to a straight line is set as a workpiece corner point. (2) A method for detecting a workpiece corner point in a wire electric discharge machine according to claim (1), characterized in that the corner point is set as the origin of the workpiece coordinate system. (3) Move the wire electrode toward the end surface of the workpiece, and
A workpiece corner in a wire electric discharge machine according to claim 1 or 2, wherein the end point position is detected using position data when the wire electrode is short-circuited with the end surface of the workpiece. Point detection method. (4) In a method for detecting a workpiece corner point in a wire electrical discharge machine that processes a workpiece by moving a wire electrode relative to the workpiece based on numerical control data, the first Detecting two or more end points with respect to the end face, finding a first straight line specifying the first end face from the position coordinate values of the end point, and detecting two or more end points with respect to the second end face, The second point is calculated from the position coordinate value of the end point.
A workpiece corner point detection method in which a second straight line that specifies an end face of the workpiece is defined, and the intersection of the first and second straight lines is defined as a workpiece corner point. (5) A workpiece corner point detection method in a wire electric discharge machine according to claim (4), characterized in that the corner point is set as an origin in a workpiece coordinate system. (6) The wire electrode is moved toward the end surface of the workpiece, and the end point position is detected using position data when the wire electrode short-circuits with the end surface of the workpiece. Alternatively, the method for detecting a workpiece corner point in a wire electric discharge machine according to item (5).