DE2153843A1 - Process for the precise electrochemical machining of workpieces of various shapes - Google Patents

Description

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8 MO η c Si'-ϊ π::. . . ~ .i .: >; 7

233-17.736p October 28, 1971

VUMA V ^ skumny ustav mechaniz & cie a automatizacie, Nove Mesto nad Vahom

(CSSR)

Process for the precise electrochemical machining of workpieces of various

shape

The invention relates to a method for the precise electrochemical machining of workpieces of various kinds Shape.

The electrochemical machining of workpieces of various shapes according to the known methods does not have the required accuracy _o An exact shape that corresponds to the shape of the working electrode is not achieved above all where the machined surface is opposite

233- (S 7O68) -Tp-r (8)

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the direction of the mutual advance of the tool and workpiece is inclined.

When processing such components, between the tool - the working electrode - and the Workpiece an equilibrium gap of different sizes in such a way that on surfaces that are opposite to the mutual feed direction are inclined, this gap is larger.

One consequence of this is that after the machining is finished, the working electrode does not exactly fit into the machined Workpiece protrudes, but each has a certain gap on the side surfaces. To the accuracy of the manufactured To increase the workpiece, machining is carried out with very small front gaps, but also by doing this an exact shape cannot be obtained. In order to achieve an exact shape, complicated and cumbersome corrections of the tool - the electrode - are carried out. Through this However, the working electrode gets a different shape than the shape of the workpiece that is to be achieved. To with To achieve the required shape of this working electrode, all working parameters must be precisely observed for which this correction was carried out ο

The invention is based on the object of a method to specify the precise electrochemical machining of such workpieces that no cumbersome corrections of the Tool electrode required

The subject of the invention, with which this object is achieved, is a method for precise electrochemical loading

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work on workpieces of various shapes on which surfaces compared to the mutual feed direction of the tool and workpiece under a constant or continuous variable angle are inclined, which is different from the right angle, with the indication that at these Areas of the workpiece at least one of the processing parameters, voltage E, conductivity H of the electrolyte, Electrode area S, machining time t compared to the parameters when machining areas that correspond to the feed direction are at a right angle, is changed.

One embodiment of the invention consists in applying different voltages to individual parts of the working electrode which have different inclinations with respect to the direction of advance. Another embodiment of the invention provides that at the transition points of the surfaces of the working electrode to a different angle of inclination oC a certain amount of compressed air is supplied in such a way that the mutual ratio of the amount Q _{2 of} the liquid electrolyte to the amount Q ₁ of air

1, 5 sin OC , .. _ _iai amounts,

1 - sin oC

Another embodiment of the invention is that on individual surfaces of the working electrode that form a certain angle with the direction of advance of the working electrode, current is only supplied for a certain time t _{1 of} the time interval t, the processing of the

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Front face corresponds to that is shorter than the time during which the working gap of the front face is halved decreased so that

t = · 60 see and

where de is the size of the front gap between the tool and Workpiece,

Ve is the speed of the tool feed and oC is the angle of inclination of the electrode surface in relation to the feed direction.

One advantage of the method according to the invention is that it results in a high level of accuracy for the finished workpiece is achieved. Another advantage is that this reduces the influence of the majority of the remaining parameters on the accuracy of the machined workpiece is eliminated, the complicated correction of the tool and its simple shape is achieved.

The method according to the invention for electrochemical machining is explained with the aid of examples which are shown in FIG the drawing are shown; show in it!

Fig. 1 shows the state after completion of the invention Working method;

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Fig. 2 shows the course of processing with time-limited Current effect · on the side surfaces;

3 shows a working electrode, the individual parts of which are either have different voltage or different working time;

4 shows an example of a conical electrode with an isolated surface part; and

Fig. 5 shows an arrangement of an electrode for changing the Conductivity in the working gap «,

If you want to work according to this method when machining and want to achieve an exact shape of the workpiece according to the working electrode (Fig. 1), that is, after finishing of machining the working electrode exactly into the generated one Shape fits into it, the working gap between the workpiece and the working electrode must be on surfaces that are under a a certain angle with respect to the direction of advance have a precisely defined size, which depends on the size of the frontal gap, according to the equation

d _b = d _c sin0C, (1)

where d, the size of the lateral working gap and d is the size of the frontal gap »

The relationships according to this equation are shown in Fig. 1, where after completion of the machining the work

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~ 6

electrode fits exactly into the workpiece, that is, d, =

d = 0. Since in electrochemical machining in this case c

for the gap between the working electrode and the workpiece at a certain angle with respect to the feed direction inclined surfaces, that

d
^d b ⁼ ~ ^isfc '^ ² )

it follows that satisfying equation (i) is fitting one of the machining parameters requires »If one uses the relevant parameters in equation (2) for d, do you get the equation?

EHVsp EH E ₀ HS

Ve.sinoC £ s ± n oC I.sinöC

where E is the voltage,

Vsp the specific removal of the material, S the electrode area,
I the working current and

Ve mean the speed of the electrode advance.

In processing according to the present invention, one must satisfy the condition set by the equation (i) the equation (3) have the following form:

EH * S ρ
d, = sin & L = d ° sin oC, (4)

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- j -

From equation (k) it follows that in order to achieve a precise shape of the workpiece during the electrochemical machining of surfaces which are inclined at a certain angle oC with respect to the direction of advance of the working electrode, one of the parameters, such as the voltage E, the conductivity H or the Electrode area S in parameters E ₁ , H., S ₁ must be changed in such a way that

² oC H HSIn ² OC S Ssin ²

E ₁ = E.sin ² oC, H ₁ = H ₀ SIn ² OC, S ₁ = S.sin ² o6. (5)

If so when machining according to this invention
continues that the working electrode opposite the
Moving the workpiece at a speed Ve, a material layer with a thickness a is removed during the time _t

a = Ve. t (6)

In this machining process, the speed of the electrode feed is opposite to an inclined
Sidewall Vn, and during time t ₁ a layer of material having a thickness a .. is removed, with the proviso that

a ₁ = Vn ο t _r (7)

If one now wants to meet the condition of equation (i), the rate of decrease or of
Electrode feed be on the side wall

Ve

Vn = (8)

sin OC,

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from which it follows that

Ve

a. = a »sin ®C = Vn. t., =. t and

^{1 1} sincC ¹

Vn Ve

It follows from equation (9) that the same result of accurately machining an inclined surface by the action of the working current during the time t ₁ can be obtained. The selected time interval value cannot be arbitrary, but must be less than or equal to the time during which the working gap at the end face is reduced by half, so that

t =. 6o see, (10)

2 units

what a sufficient feeding of the working gap with that Electrolyte guaranteed and with no contact of the working electrode with the workpiece occurs. It goes without saying that when working with larger working gaps, this time interval can also be larger.

The electrochemical machining according to the present invention requires an adaptation of the tool - the electrode - depending on which parameter is changed for the case in question.

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In Fig. 3 shows an arrangement of the working electrode 1 is shown for a change in the · voltage E "The current from the current source is directly supplied to only a portion of the working electrode 1 which processes the front face" to the insulated parts 2 and 3 AEV working electrode current through appropriate resistors R _? and R, or these parts are connected to other power sources having a voltage suitable for the condition

2 2 s

E, E ₂ . . . = E sin OC -i ♦ E sin Ch ^ ο ° '°

A less demanding method is available if the individual parts of the working electrode are switched to the same power source via a time switch (not shown) and this time switch is set to certain parts t ₁ ... t _{p of} the time interval t during which they are connected to the power source are connected so that

2, 2 / ■ t-, ο * ^c * ~~ töSm Cs *** ι> teSin ί ^ Ν-χ p ^β

In the electrochemical machining of workpieces, where a working electrode in the form of a solid of revolution is used can be, for example conical or spherical electrodes, possibly a milled disc electrode, it is advantageous to design the working surface S of the electrode so that

2 2

S .., S_, S " » ,. = S. sin <9C-ι »S. sin oC-o · · ·

In the given case, this parameter remains after the

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fit stable and is not changed, the machining accuracy is not affected by changes to the remaining parameters.

This method corresponds to a conical working electrode 1 according to FIG. K, the part 5 of which of the circumference is insulated, for example, by polyethylene, so that only the part k of the circumference which is inclined takes part in the machining. With this arrangement of the working surface on rotating working electrodes, this surface can be divided into several parts, but it has at least two parts, one insulated and one non-insulated.

In the event that the workpiece has side walls which are inclined at a constant angle OC with respect to the direction of the mutual advance of the tool and workpiece or in which this angle changes only slightly, a change in the conductivity of the electrolyte can be used on these walls. To keep the shape exactly, the conductivity H = H.sin oC must of course be. By arranging the working electrode according to FIG. 5, the conductivity can be changed as desired or maintained at a precisely determined value. In the middle of this working electrode 1 a channel 6 is provided through which the working fluid with a certain conductivity H enters the working space 7 under the pressure p_ in the amount Q ₂ l / min. Via a side opening 8 of the working electrode 1, compressed air is supplied under a pressure P ₁ in the amount Q ₁ l / min and flows into the working space 7 via a narrow gap (about 0.5 to 1 mm)

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The working fluid flowing through the axial channel 6 of the Working electrode 1 flows, each has a pressure of about 2 to 8 kp higher than the air pressure, so that their flow is secured. The parts of the working electrode created in this way are conductively connected to one another and to a common one Power source connected. The exact preparation of the shape of the workpiece only requires the mutual relationship to control both media flowing into the working space 7 so that it corresponds to the following equation s

Q ₂ 1.5 sin ²

Q ₁ 1 - sin ² CC

The method according to the invention for electrochemical machining guarantees the accuracy of the finished shape of the workpiece in accordance with the working electrode without its shape having to be corrected. Since the method according to the invention for electrochemical machining makes the size of the side gap dependent on the size of the front gap when one of the working parameters is adjusted, it is sufficient during machining to control the mutual relationship or the adjusted parameter, while the other working parameters can be changed over a wide range, without affecting the machining accuracy. If, for example, a groove is machined by means of a disk-shaped working electrode, the angle of inclination χ of the side walls with respect to the feed _{direction is 30, the size of the active area S 1} = S.sin ² (£. 100 = 1. 0.25 = 25 #. The remaining area S - S.sin ² qC = 75 # is iso-

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lates. When changing any parameter (E, H, Ve, Vsp), the size of the front gap or the
Machining speed, the accuracy of the shape obtained remains, however, since the size of the side gap changes so that

d, = d * sin CC .
bc

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Claims (4)

Claims V ^ 1 .A method for precise electrochemical machining of workpieces of different shapes, on their surfaces opposite to the mutual feed direction of the tool and Workpieces are inclined at a constant or continuously changing angle, that of the right angle is different, characterized in that at least one of these surfaces of the workpiece Working parameters, voltage E, conductivity H of the electrolyte, electrode area S, processing time t, opposite changed the parameters when machining surfaces that are at a right angle to the feed direction will. 2. The method according to claim 1, characterized in that on individual parts (2, 3) of the working electrode (i), the have different inclinations with respect to the feed direction, different voltages are applied (Fig. 3) 3. The method according to claim 1, characterized in that at the transition points of the surfaces of the working electrode (1) at a different angle of inclination oC a certain amount of compressed air is supplied such that the mutual ratio of the amount Q _{2 of} the liquid electrolyte to the amount of air Q ₁ Q ₂ 1.5 * C = is (Fig. 5). Q ₁ 1 - sin oC 209826/0567 4. The method according to claim 1, characterized in that on individual surfaces of the working electrode (1) which _{enclose a certain angle with the direction of advance of the working electrode, current is only supplied for a certain time t 1 of} the time interval _t, which corresponds to the machining of the end face , which is shorter than the time during which the working gap of the end face is reduced by half, so that t = 6o see and Ve t = t · sinoC = -TTT— ° 60 · sin oC see, where de is the size of the front gap between the tool and Workpiece, Ve is the speed of the tool feed and O ^ the angle of inclination of the electrode surface opposite mean the direction of advance. 209826/0567 Blank page