JPH0441155A - Wire electric discharge machine - Google Patents

Abstract

PURPOSE:To obtain roundness, by feeding back the error quantity of the circular locus drawn by an X, Y axial table to a control unit on line, and automatically correcting the error quantity with the use of the graphic processing unit, memory device, arithmetic processing unit, etc., inside the control unit. CONSTITUTION:When an X axial table 3 and a Y axial table 4 draw a circular arcuated shape in a constant size, the error quantity (locus error against roundness) that a two-dimensional analog probe 19a detects is fed back to a control unit 18 on line, input to the graphic processing unit 18d of the control unit 18 inside and stored once to a memory device 18b with correction data being prepared by the graphic processing unit 18d. The command including the correction process is then output from the processing unit 18a inside the control unit 18 to an X axial motor 14 and Y axial motor 15. The correction of a circular locus is thus performed automatically so as to become the circular locus closer to roundness than the circular locus initially drawn by the X axial table 3 and Y axial table 4 and an ideal roundness can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a wire electrical discharge machine equipped with an NC (numerical control) device having a table of a coordinate system in which two axes are perpendicular to each other.

[Prior Art] FIGS. 3(a) and 3(b) are a configuration diagram showing a system system excluding a tank system of a conventional wire electric discharge machine, and an enlarged view showing the main parts thereof. In the figure, an initial hole 1a is pre-drilled in a workpiece 1, and a wire electrode 2 is inserted into the initial hole 1a. In order to interpose an insulating machining M9b in the gap between the workpiece 1 and the wire electrode 2, a machining liquid 9b is injected into the gap from a machining liquid nozzle 9a. The relative movement between the workpiece 1 and the wire electrode 2 is performed by moving the X-axis table 3 on which the workpiece 1 is placed. Further, the X-axis table 3 is driven by an X-axis motor 14, and the Y-axis table 4 is driven by a Y-axis motor 15.
and the Y-axis table 4 form an orthogonal coordinate system. With the above configuration, the relative movement between the workpiece 1 and the wire electrode 2 becomes a two-dimensional movement within the X-axis and Y-axis planes.

The wire electrode 2 is supplied by a wire electrode supply bobbin 12, passes through the workpiece l from the upper wire electrode guide 9, reaches the lower wire electrode guide F' 10, and also connects the upper power supply part 9C and the lower part, which are electrical energy sources. The wire electrode is collected by the wire electrode winding and collection roller 13 via the power supply section 10a. At this time, a certain tension is applied to the wire electrode 2 by the brake pulley 11. Control device 1 that drives and controls the X-axis motor 14 and the Y-axis motor 15
8, an NC (numerical control) device is used.

In the figure, 5 is the taper device, 6 is the Z-axis (main axis), 7 is the column, 8 is the lower arm, 16 is the X-axis table guide,
17 indicates a Y-axis table guide.

FIGS. 4(a) and 4(b) are block diagrams showing the relationship between the table drive section and the control device in the wire electrical discharge machine of FIG. 3(a), and an explanatory diagram of its main operations; FIG. 5(a) as well as(
b) is a configuration diagram showing the relationship between the circularity measuring device on the table drive unit and the control device in the wire electric discharge machine of FIG. 3(a), and a diagram illustrating its main operations. In the figure, 3
is an X-axis table, 4 is a Y-axis table, 9 is an upper wire electrode guide, 10 is a lower wire electrode guide, 14 is an X-axis motor, 15 is a Y-axis motor, 18 is a control device (NC device)
, 18a is an arithmetic processing unit (control command device), 18b is a memory device, 18c is a servo amplifier, 19a is a two-dimensional analog probe, 19b is a contact, 20 is a mastering,
21 is an X-Y axis plotter.

Next, the operation of the above-mentioned conventional wire electric discharge machine will be explained. The relative movement between the workpiece 1 and the wire electrode 2 is controlled by the X-axis table 3. Y-axis table 4 and upper wire electrode guide 9. The relative relationship with the lower wire electrode guide 10 is the same, and the geometric movement trajectory such as a circular trajectory, a triangular trajectory, a square trajectory, etc. due to the above-mentioned relative movement is transferred to the workpiece 1. X-axis table 3. Y-axis table 4
The dynamic accuracy of the motion trajectory is a feed condition for a wire electrical discharge machine. Therefore, X-axis table 3. A method is implemented to determine how accurately the dynamic movement of the Y-axis table 4 is executed and whether the command is faithfully executed.

In this determination method, the X-axis table 3 shown in FIG.
．． A circular interpolation command is output from the arithmetic processing unit 18a and the memory device 18b in the control device 18 to the servo amplifier 18c so that the Y-axis table 4 draws an arc shape of a constant size, and the X-axis motor 14. Drive the Y-axis motor 15.

At this time, from the road body position of the upper wire electrode guide 9 or the lower wire electrode guide 10, the X-axis table 3. The coordinate system of the Y-axis table 4 is relatively observed, and the amount of error required to draw a circular arc shape locus with respect to an ideal circular arc shape (perfect circular shape) is measured. Then, based on the numerical value of the error amount, the shape of the trajectory, the quadrant position within the arc shape, etc., the X-axis table 3. It is possible to evaluate and judge the motion characteristics of the Y-axis table 4, problems with the mechanical structure, the processing accuracy of the processing unit 18a in the control device 18, the command processing speed, etc.

In order to implement the above determination method, it can be realized using a known roundness measuring device (disc method, DBB method). The operating principle will be briefly explained. Figure 5 (
As shown in a), a contact 1 is attached to the tip of a two-dimensional analog probe 19a fixed in an absolute position system.
The master ring 20, which is a reference circle that is extremely close to the ideal, is fixed on the X-axis table 3 so that it is in a stationary state at 9b. At this time, the contactor 19b is brought into contact with the inner surface of the master ring 20 so as to apply a constant displacement It (for example, 40 μm). In this state, a circular interpolation command is output from the control bag a1B, and the X-axis motor 14 and Y-axis motor 1
5 to cause the X-axis table 3 and the Y-axis table 4 to perform a circular motion with a radius where the displacement is constant. At this time, the two-dimensional analog probe 19 fixed in the absolute position system
a also X-axis table 3. A circular motion is performed relative to the Y-axis table 4. Therefore, the error detected by the contactor 19b relative to the ideal (the inner surface of the master ring 20) is amplified within the two-dimensional analog probe 19a, and the two-dimensional signal is recorded on the X-Y axis plotter 21.

By determining and analyzing the shape of the circular trajectory recorded in this way and the error/deviation from a perfect circle, the X-axis table 3. Motion characteristics of Y-axis table 4 and control device 18
It is possible to recognize the calculation processing speed, accuracy, etc. by the calculation processing unit 1B&.

[Problems to be Solved by the Invention] Since the above-described conventional wire electric discharge machine is configured as described above, the X-axis table 3. After recording the circular motion of the Y-axis table 4 on the X-Y-axis plotter 21, this
- With respect to the trajectory drawn on the recording paper of the Y-axis plotter 21,
Analyzes such as entering reference lines and error amounts were performed manually by humans. For example, manual work such as drawing a perfect circular trajectory line as a reference with a circular ruler and measuring deviations in the trajectory as an error was performed, which resulted in extremely inefficient work, especially when using a pen to draw the trajectory. Depending on the thickness and concentricity of a perfect circle, the data analysis itself becomes less reliable. Therefore, it is impossible to manually input accurate correction data to the memory device 18b in the control device 18, and there is a problem that it is impossible to correct the movement to a highly accurate circular locus motion.

This invention was made to solve the above-mentioned problems, and provides a wire electrical discharge machine equipped with a table drive system that enables highly accurate circular locus movement of the X-axis table and Y-axis table. With the goal.

[Means for Solving the Problems] A wire electrical discharge machine according to the present invention includes an X-axis table, a Y-axis table, and a Y-axis table.
The amount of error in the circular locus drawn by the axis table is fed back to the control device online, and the graphic processing device, memory device, arithmetic processing device, etc. in this control device are used to automatically correct the amount of error, and the X-axis This is to execute a circular locus movement of the table and the Y-axis table.

[Function] The wire electrical discharge machine according to the present invention includes an X-axis table,
The amount of error in the geometric circular trajectory detected by the two-dimensional analog probe against the circular trajectory drawn by the Y-axis table is imported online into the control device, and mechanically generated backlash (hysteresis) and X-axis , 2-axis servo follow-up delay on the Y-axis, mechanical right angle dust on the 2-axis, etc. are determined using graphic processing and calculation formulas based on differences in geometric shapes and errors.
By automatically correcting the amount of error, human manual errors and errors are removed.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a configuration diagram showing the relationship between a circularity measuring device on a table driving section and a control device in a wire electric discharge machine that is an embodiment of the present invention. In the figure, 3 is the X-axis table, 4
14 is a Y-axis table, 14 is an X-axis motor, 15 is a Y-axis motor, 18 is a control device (NC device), 18a is an arithmetic processing device (control command device), 18b is a memory device, 18c is a servo amplifier, 18d is a graphic 19a is a two-dimensional analog probe, 19b is a contact, 20 is a mastering device,
21 is an X-Y axis plotter.

FIG. 2 is an explanatory diagram for quantifying and calculating the determination of the dynamic accuracy of the table drive system from the circular locus shapes drawn by the X-axis table and the Y-axis table in the wire electric discharge machine of FIG. 1.

Next, the operation of the wire electric discharge machine according to the embodiment of the present invention will be explained. X-axis table.

When the Y-axis table 4 draws an arc shape of a certain size,
The amount of error (trajectory error relative to a perfect circle) detected by the two-dimensional analog probe 19a is fed back to the control device 18 online, and the graphic processing device 1 in this control device 18
8d, the graphic processing device 18d creates correction data, and stores it in the memory device 18b. here,
In the above correction data creation method, when mechanical backlash (hysteresis) occurs as shown in FIG. 2, the X-axis changes with respect to the perfect circle indicated by the broken line (-11 line).

Since a locus of a step shape appears on the Y-axis, the amount of the step is divided into + side and - example for each X-axis and Y-axis, and the respective step amounts (XI, X21 5'++y2
) into equations (1) and (2) below.

X-axis backlash amount △Bx"l XI+X2 l/2 -...(1
) Y-axis backlash amount △Bv= I yI+ 5'2 l/2...
...(2) Here, x,: X-axis + side step amount, X2:
X-axis − side step amount + y+: Y-axis side step amount * y
2: Y-axis side step amount.

Therefore, the X-axis backlash amount ABX and the Y-axis backlash amount ΔBv are determined from equations (1) and (2) above. Next, if a servo tracking delay occurs due to a discrepancy in the servo gains of each X-axis and Y-axis, the circular trajectory will be ±
It becomes an ellipse in the 45° direction, and the X-axis table 3. When the direction of movement of the circular interpolation of the Y-axis table 4 (CW force direction, CCW direction) is changed, the major axis direction changes. At this time, since the servo gains of the two axes, the X-axis and the Y-axis, do not match between the X-axis and the Y-axis, the following calculation formula (3) is obtained.

ΔG= ((dl-d2) (d3 d4)) /
4・・・・・・(3) Here, ΔG: Delay amount due to mismatch of servo gains between X and Y axes + dl: Short axis length of ellipse during CW, d
2: Length of the major axis of the ellipse in cW, d3: Length of the major axis of the ellipse in CCW, d4: Length of the minor axis of the ellipse in ccw.

The amount of servo follow-up delay due to the discrepancy between the X-axis and Y-axis servo gains is determined by the above equation (3), and the servo gain parameter correction amount, that is, the X-axis.

The amount of delay ΔG due to the mismatch of Y-axis servo gains is determined. If there is an error in the perpendicularity of the two axes, the X-axis and the Y-axis, it will become an ellipse at an angle of ±45° with respect to the perfect circle.
Even if the direction of motion of circular interpolation (CW force direction and CCW direction) is changed, the direction of the major axis of the ellipse does not change. At this time, it is possible to determine whether the perpendicularity error is an acute angle or an obtuse angle depending on the direction of the long axis of the ellipse, and the amount of the error is obtained by the following calculation formula (4).

△E = d + −d 2 / d・・・・・・
・・・・・・・・・ (4) Here, △E: squareness error, d
: Reference circle diameter (mastering diameter), dl: ±456
Diameter in direction, d2 Diameter in knee 45° direction.

The squareness correction amount of the X-axis and Y-axis is determined by the above equation (4).

Regarding the three phenomena described above, by using the correction amounts determined by the above equations (1) to (4), a command including correction processing is sent from the arithmetic processing unit 18a in the control device 18 to the servo amplifier. 18c to the X-axis motor 14. Output to Y-axis motor 15. This results in
So that the X-axis table 3 and Y-axis table 4 will have a circular locus that is closer to the ideal (perfect circle) than the initially drawn circular locus.
The above circular locus can be automatically corrected. Also,
By repeating this operation (process) several times, it becomes possible to obtain an even more ideal perfect circle.

Note that in the above embodiment, the X-axis table 3. The case is shown in which an automatic correction means for automatically correcting the amount of error in the circular locus drawn by the Y-axis table 4 is applied to a wire electric discharge machine. It can be applied to all machine tools installed, and the same effects as the above embodiment can be achieved.

[Effects of the Invention As described above, according to the wire electrical discharge machine of the present invention,
The amount of error in the circular locus drawn by the X-axis table and Y-axis table is fed back to the control device online, and the amount of error is automatically corrected using the graphic processing device, memory device, arithmetic processing device, etc. in this control device. The X-axis table and the Y-axis table are configured to perform circular locus motion, so the locus of circular motion of a constant radius drawn by the X-axis table and Y-axis table is changed to a circle closer to the ideal (perfect circle). This has the excellent effect of making it possible to easily perform circular trajectory correction processing with higher accuracy and reliability without manual intervention. play.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing the relationship between the circularity measuring device on the table drive unit and the control device in a wire electric discharge machine according to an embodiment of the present invention, and FIG. An explanatory diagram for quantifying and calculating the determination of the dynamic accuracy of the table drive system from the circular locus shapes drawn by the X-axis table and the Y-axis table. Figures 3 (a) and (b) are conventional wire electric discharge machining. A block diagram showing the system system excluding the tank system of the machine and an enlarged view showing its main parts. Figures 4 (a) and (b) show the table drive unit and control in the wire electrical discharge machine of Figure 3 (a). The configuration diagram showing the relationship with the device and its main operation explanatory diagram, Figures 5 (a) and (b) are similar to Figure 3 (a).
) is a configuration diagram showing the relationship between the circularity measuring device on the table drive unit and the control device in the wire electric discharge machine (FIG. 1), and a diagram explaining its main operations. In the figure, 1... Workpiece, 1a... Initial hole, 2... Wire electrode, 3... X-axis table,
4... Y-axis table, 5... Taber device, 6...
Z-axis (main axis), 7... Column, 8... Lower arm,
9... Upper wire electrode guide, 9a... Machining fluid nozzle, 9b... Machining fluid, 9c... Upper power feeding section, 10.
...Lower wire electrode guide, 10a...Lower power supply section,
11...Brake pulley, 12...Wire electrode supply bobbin, 13...Wire electrode winding and recovery roller, 14
...X-axis motor, 15--Y-axis motor, 16-...
X-axis table guide, 17...Y-axis table guide,
18...Control device (NC device), 18a...Arithmetic processing device (control command device), 18b...Memory device, 1
8c... Servo amplifier, 18d... Graphic processing device,
19a...Two-dimensional analog probe, 19b...Contactor, 20...Mastering, 21...-X-Y axis plotter. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] In a wire electrical discharge machine equipped with an NC device that has a table with a coordinate system in which two axes are perpendicular to each other, when the table is moved in a circular motion with a constant radius within the orthogonal coordinate system, it becomes a perfect circle on the same radius. and an automatic correction means for digitizing the circular trajectory error using a graphic processing device and automatically correcting the amount of error by a control device. A wire electrical discharge machine characterized by: