SU1756047A1 - Method of extimating errors in electroerosion excision - Google Patents

Abstract

Use: determination of the error of the limb wire electrode-tool with EDM cutting. SUMMARY OF THE INVENTION: Electrode-wire 1 is inserted into the workpiece 2 at a distance of 3-5 mm, then, turning off the power pulses, a small powering pulse pulses are fed and the electrode-wire 1 is moved in the opposite direction until the contact is interrupted. By this displacement, the maximum deflection of the electricdd-prb block e is determined. After that, the driving electrode is retracted over distance Xi and tilted by an angle by moving one of the supports by an amount UL Then guides 4 and 5 simultaneously move to distance X before the electrode-wire 1 of part 2 touches at point C By the magnitude of this displacement Fmin is calculated, and then the required error Lf is determined; min. 2 ill. Ъ Ј VI c o g g Phi.2

Description

The invention relates to the field of mechanical engineering, in particular, to electrocrocessing of materials, and can be used to determine the error of electroerosive cutting with an electrode wire.

There is a method of determining the maximum deflection of the electrode-wire directly on the machine during the machining of the part in order to introduce this error into the microprocessor-based device of numerical program control and its correction.

This method of automatically measuring the maximum deflection consists in disconnecting the power pulses from the erosion gap on the test cut or on the initial straight line section and applying low-voltage low-power probe pulses to it and removing the electrode wire from the groove wall of the workpiece until the contact is eliminated This is caused by the absence of spark discharges. In this case, the difference of coordinates i of the end point of introduction and the point of contact liquidation is calculated. The deflection value of the electrode-wire calculates from the expression:

e h + q. (one)

where q - the value of the interelectrode gap.

The value of q can be determined directly on the wall by touching the electrode-wire of the walls of the groove to be processed or it can be obtained from the microprocessor unit of the numerical program control. The values of q in the latter case are determined in advance during the technological tests of the electroerosive cutting and are then recorded in the memory of the microprocessor device.

The maximum value of the deflection of the electrode-wire g does not give complete information about the errors associated with the deflection, and therefore it does not make it possible to fully compensate for these errors in the optimal way. In the known works and methods, the main error is that the irregularity of the electrode-wire deflection along the height of the workpiece is not taken into account. The conducted research of the electrode-wire deflection made it possible to determine the shape of the electrode-wire and groove wall on the workpiece during processing. The equation for the groove wall profile and Electrode-wire in parts has zid

7

one

- ah + bx + c Outside the parts of the electrode-wire branch are linear. The maximum deflection of the electrode-wire is in the plane passing through the middle of the workpiece.

When processing external corners, a complete correction of the profile of the workpiece is possible. However, when processing internal corners and circular arcs, only a minimal distortion of the groove wall profile can be compensated, which is measured over the surface of the workpiece.

The error A of the workpiece, equal to the difference between the maximum and minimum distortions of the wall profile, cannot be compensated for the cutting operation to be performed, and can only be eliminated on subsequent transitions to softer modes, in which the deflection of the wire electrode is insignificant. The error D when machining the inner corners and arcs of circles should be taken as an allowance for subsequent transitions, which allows for the shortest possible time to make parts.

The aim of the invention is to improve the accuracy of determining the error of machining a part on an electroerosive cutting machine.

Figures 1 and 2 show the positions of the electrode wire.

During the processing by the wire electrode 1, the parts 2 of the wall of the cut-out groove 3 have a vertical profile, shown in FIG. 1, where e is the maximum deflection of the wire electrode; WMBKC - mac- distortion of the profile of the workpiece in the plane A-A, passing through the middle of the workpiece; H min the minimum distortion of the profile pa-,. for at the top (or bottom) surface of the B-B workpiece; d is the diameter of the electrode-wire; H is the thickness of the workpiece; h is the distance between the support of the electrode-wire and the surface of the workpiece; q is the interelectrode gap; a is the angle of inclination of the branch of the electrode-wire with a vertical to the surface of the workpiece in the cutting mode.

Figure 2 shows a schematic representation of the positions of the electrode-wire and its supports 4 and 5 relative to the wall of the cut-out groove 3 in determining the errors arising from the deflection of the electrode-wire, II - the position of the supports of the electrode-wire at the end of the incision section of the deflection of the electrode- wire; HM is the position of the electrode-wire at the time it is removed from its contact with the workpiece to measure the maximum deflection; INN - the position of the electrode-wire after its withdrawal back along the coordinate X; IV - position of the electrode-wire after its inclination at an angle tp by moving along the U coordinate; V-V is the position of the electrode-wire, e, the moment of contact of its wall of the groove at the upper point C located on the plane B-B.

The method is carried out as follows.

The electrode wire 1 is inserted into the workpiece 2 on the non-working section or on the straight section of the profile for a distance of at least 3-5 mm. At the indicated displacement amount, the deflection of the electrode-wire is completely formed. Then the voltage is turned off from the erosion gap, low-power low-voltage probe pulses are fed to it, stand for some time, and then the electrode-wire is moved back from the part along the -X coordinate until the contact between the electrode-wire and the wall of the groove 3 of the workpiece 2 disappears. this time, the movement And is measured, and then the maximum deflection of the electrode-wire is determined from the expression

 + q. (3)

After that, the electrode-wire is retracted from the bottom of the groove further by distance Xi and tilted forward by an angle p by moving the upper support of the electrode-wire along the U axis by UL. Then the electrode-wire is moved along the X coordinate by distance + X2 to contact with the bottom of the groove of the workpiece at point C located on the surface of the workpiece (plane B-B). The determination of the quantities and A is carried out as follows. From the relation (FIG. 2)

U2 + X2 + 0.2 C + - Xi + And +1 + q define

Phmin-X1 + And + | + q- (+ Q2C). (four)

From A CQa L (figure 2), we have QiC

2 cos p From the similarity of APiQiN and A P2Q.2N na

H + h

H +2 h Substituting (5), (6) and (1) in (4) we obtain

Hf h

 Х1-И (и1т

d

+ Hg)

(7)

0

+ T- cos p

The angle p must be larger than the angle a in order to clearly fix the point C. Angle (p it is advisable to determine from the expression

2 SG max (p "max. (8)

The value of the angle a is determined from A KML (FIG. 1)

tg a -

KL M L

(9)

Where

K1 t „

(ten)

.

Usually h 5-10 mm. From expressions (9) and (10) we find

(mmn - - - q) and arctgg.

(eleven)

(12)

The maximum predicted slope value "max is determined at the maximum possible value (FmT max.

Omax arctg

 (Pmin) max - tt - q

(13)

thirty

35

40

45

50

55

The range of values (Fmin) max and max is determined experimentally or according to the data given in the technical literature. For example, for thickness of details H 80 mm on coarse modes, max - 2.5 °. The angle of inclination p determines the magnitude of the removal of the electrode wire Xg.

Xi tg y (H + 2h). (14)

Take the value of Xi 2 mm more than calculated by the expression (14)

 p (H + 2h) + 2 mm (15)

The amount of movement of the upper support on Ui for mounting the electrode-wire at an angle is determined from APiQiN by the relation:

Ui (H + 2h) + tg (16)

Thus, using expressions (1). (8), (11) (13), (15) and (16), calculate the minimum FMin value by the formula (17), using the values and Xa counted directly by the microprocessor-based numerical control system. The interelectrode gap q can be measured directly on the machine by moving the wire electrode until it touches the side wall of the groove with the power pulses turned off and low-power probe pulses applied to the interelectrode gap. The q value can also be obtained from the memory of the microprocessor control unit.

In addition, the program also sets the diameter of the electrode-wire. Next, the wall error of the groove L is determined:

A e-4U,. (17)

Equating L to the Allowance for subsequent transitions in the processing of internal angles and arcs of a circle, we obtain the value of the minimum allowance, which ensures the minimum processing time while ensuring the accuracy of processing. The magnitude of the maximum distortion of the profile (Figures 1 and 2) is equal to the deflection €. It is advisable to measure the values of e and fmin in the initial non-working area of the incision into the workpiece. Measurements can be carried out on the Y-axis and V, if it is convenient for the configuration of the part. You can also measure when you move together on the axes X and Y, then the movements are measured by the formulas

l Xi2 + Yi2, X22 + Y22 Vui2 + Vi2, etc.

As an example, we give the experimental data when processing stainless steel with a thickness of 80 80 mm with an electrode-wire with a diameter of мм 0.3 mm on a commercially available machine model A207.86:

% ax Ј 0.53 mm. 0.25 mm, L .0.28 mm, L 5 mm, q 0.03 mm, tg a 0.016, and “1 ° - p 2 °.

Claims (1)

The invention The method of determining the error of electroerosive cutting resulting from the deflection of the electrode-wire in The processing plane includes measuring the maximum deflection of the electrode wire by turning off power pulses and feeding low-power probe pulses followed by retracting the electrodes of the wire wires in the opposite direction of the working feed before interrupting the contact of the electrode wire with the part, In order to improve the accuracy of determining the error, with the symmetrical arrangement of the supports relative to the part following the measurement of the maximum deflection, the supports are retracted by X, then the electrode-wire is tilted by moving one of the supports in the direction of the working feed by Ui, then the supports are moved in the direction of the working feed until the electrode wire touches the part and fix the value of this displacement X2, and then determine the magnitude of the error of processing A from the expression D Ч-Cgmin, MM; where e is the maximum deflection, mm;  + | - (+ + r4v + gm: Xi (H + 2h) tg f, mm; Ui (H + 2h) tg (p. Mm; d is the diameter of the electrode-wire, mm; H - part height, mm; h is the distance between the support and the surface of the part, mm; (p is the pre-calculated maximum possible angle of inclination of the electrode-wire branch for given processing conditions. 1