DE2030657A1 - Method and device for electrolytic etching - Google Patents

Description

MB - 5 (* - 187 C)

IA - 171

Mitsubishi Electric Corporation Tokyo, Japan

Method and device for electrolytic etching

The invention relates to an electrolytic etching process and in particular, a method and apparatus for electrolytically forming a Y / piece.

Electrolytic etching processes generally make use of the phenomenon of electrochemical dissolution or peeling a positive electrode during electrolysis use. A working electrode becomes so relative arranged to a workpiece that in between a Schnaler Working gap remains through which an electrolyte flows at high speed. At the same time a electric current sent through the working gap ", whereby the electrolyte is electrolyzed by the working current so that the workpiece is under the action of electrolysis is processed with training of the desired Porm. It is already known that in this way a Recess or a hole incorporated into a workpiece can be, wherein the shape of the recess or the hole corresponds to the shape of the working electrode. Thus, if a working electrode of a predetermined shape is used, it is possible to etch or incorporate a recess or a hole of the desired shape.

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009883/1492

203065?

When the electrolyte flowing through the working gap at high speed is electrolyzed by the working current, the workpiece is electrochemically dissolved, with part of the workpiece material being removed in a predetermined area of the workpiece, namely the area opposite the working electrode. This electrochemical dissolution or etching takes place for almost the entire duration of the electrolysis, thereby promoting the removal of workpiece material.

The working gap size increases as the workpiece material is loosened to. Accordingly, a feeding device be provided, which moves either the workpiece or the working electrode or both towards each other to a Increase in the distance or the size of the working gap to prevent.

The working accuracy of the electrolytic molding machines of this type is known to depend on the size of the Working gap from "If the size of the working gap is kept constant during the entire processing time, the accuracy of the method is greatest. On the other hand, when the working gap varies during machining, for example in the case of making a hole punch of a predetermined radius in a workpiece, the diameter of the hole produced varies according to the variation of the working gap a. Thus, this improves the machining accuracy degraded. Although it is desirable, the size of the working area throughout the electrolytic ForiDver drive na keep constant, so it succeeds In many cases, however, this is not straightforward, since a large number of factors cause electrolytic etching changes the size of the working gap "

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In the following it will be discussed which factors of the electrolytic etching process influence the size of the working gap and in what way this influence he follows. Bs was previously believed to be the size dc-3 working gap is given by the following formula:

where g is the size of the working gap, V is the working voltage applied to the working gap, ρ is the specific resistance of the electrolyte and J is the electrical working current density in the working gap.

In order to keep the size g of the working gap at a constant value during the etching process, it must be in accordance with the above Formula (1) the feed speed of the Arbeitsselek electrode or the workpiece can be kept constant, from which it follows that the electric working current density J during of the etching process must also be kept constant. On the other hand, the specific resistance varies depending on the density and temperature of the electrolyte used. This is due to the fact that the working current through the electrolyte during the etching process flows and the temperature of the electrolyte increases. The electrolyte liquid and the density of the evaporate Electrolytes change. These operations make it very difficult to determine the resistivity ρ during the Keep etching processing constant. When the changes of the specific resistance P can be determined and used to control the working voltage V, so can the changes in the specific resistance P are compensated. From equation (1) results for Working voltage V the following formula:

V = g J <J (2)

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The electric current density J according to this formula (2) can be kept at a constant value by adjusting the feed rate during the etching processing keeps constant «The size of the working gap is also kept constant during the etching process. If one then assumes that the product gJ = A is a constant, the result is the following formula «

V = A (3)

Thus, if the working voltage V is controlled proportionally to the specific resistance Q , the width g of the working gap can be kept constant during the etching process. Such a process is described in German patent application p. 19 ^ 988 * ""! has been proposed.

It has also been suggested that the size g the working gap is given by the following formula (4) is, which in turn was proposed in German patent application P, 19if9884.1:; ,

(4)

In this formula (4), Vd represents the ElektrolyeeapannungP portion of the Arbeitsspanniuag Y, which must be kept substantially constant * in formula (4), the Arbe itsspannung V is the sum of the voltage Vo corresponding to the Ohm ^1's law obeyed, and the Electrolyzing voltage Vd. Therefore, the relationship V-Vd takes the place of the working voltage V according to formula (1),

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Formula (5) follows from formula (4):

V = gJO »+ Vd (5)

If now the feed rate during the etching process is kept constant, the electric current density J is also kept constant. Because now the width g of the working gap is also kept constant during the etching process, the relationship applies gj = A (constant) and the following formula becomes obtain:

V = A <j> + Vd (6)

From the formula (6) it can be seen that when controlling the Working voltage as the sum of a term AO, which is proportional of the resistivity ^ is and des constant term Vd, which corresponds to the electrolysis voltage, the width g of the working gap with greater accuracy can be maintained at a constant value during the etching processing than according to the formula (3).

Upon further consideration of the conditions innkrfealb des Working gap during the electrolysis process one notices that due to the electrolysis of the electrolyte in the Working gap gas is formed. The gas consists essentially of hydrogen. The formed gas mixes in the working gap with the electrolyte and has a major influence on the electrical equivalent level of the working gap.

In the previously proposed, on the relationships (1) and (4) based devices became the existence of the in the Working gap generated gas not taken into account. Of-

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half is with the proposed devices, even when used the control described, the width of the working gap is not kept constant. Rather, changed the working gap size and thus affects the Accuracy of the etching process.

It is therefore the object of the present invention to provide a method and a device for electrolytic etching of a workpiece, the working gap size being taking into account the gas formation in the working gap during the etching processing is kept constant.

According to the invention, this object is achieved by a method and a device solved, wherein a signal is used for precise control of the working voltage, which proportional to the ratio of the amount of gas generated during electrolysis and the amount flowing through the working gap Amount of electrolyte.

According to the invention there is thus a method for electrolytic insulation Etching created, which comprises the following steps: arranging a working electrode opposite a workpiece with the formation of a narrow working gap; Passing an electrolyte through the Working gap; Electrolyzing the electrolyte in the working gap by applying a working voltage; Feed of the workpiece or the working electrode or both towards each other and at a constant speed; as Control of the work voltage as the sum of a voltage, which is proportional to the specific resistance of the electrolyte introduced into the working area and one Voltage, which is proportional to the ratio of the amount of electrolyte to the amount of gas in the working gap.

009883/1492

According to the invention an apparatus zumelektrolytischen etching is further provided a workpiece, comprising a ^r with formation of a narrow working gap with respect to a workpiece arranged working electrode, and means for supplying an electrolyte into the working gap, a power source to electrolyze the electrolyte in the working gap by applying an operating voltage, a feed for the workpiece and / or the working electrode towards each other and a control device for the working voltage as the sum of a voltage proportional to the specific resistance of the electrolyte introduced into the working gap and a voltage proportional to the ratio of the amount of electrolyte in the working gap to the amount of gas in the working gap *

It is considered as a basic idea of the present invention that the amount of gas generated in the working gap as a ratio of the amount of gas flowing through the working gap Gas amount is taken into account to Elektrolvt amount flowing through the working gap. The amount of gas in the working gap and influencing the flow rate of the gas Equivalent resistance. This is because the gas acts as an electrical insulator and the electrolyte as electrical conductor acts.

When the amount of gas flowing through the working gap is denoted by QH and if the amount of by the Working gap flowing electrolyte is denoted Qe, the following formula results

(7)

which corresponds to the formula (1) and can the formula (4) be written in the following way *

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Y-Vd

ί Q + K ^ WI
The following formulas result from (7)

V = gJ £? * K

V = A

Similarly, from formula (8), the following relationships (10) ί

V = gJ ί y + K (^ f) j + Vd

V = A f 0+ K (S |) i + Vd (10)

If now the working voltage V according to the equations (9) and (10) is controlled and not according to the relationships (3) and (6), the width g of the working gap becomes during of the etching is maintained at a constant value and the accuracy of the etching process is increased.

The control of the working voltage according to the formulas (9)

2
and (10) can be done in ways. The first way is

in the determination of a signal which is proportional to the change in the term (-M) and in the input of these3 signals into the control system for the working voltage V. The second way is to keep the term (Sf) at a constant value and a to generate a signal corresponding to this value and input it into the control system for the working voltage V.

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In the following the invention is based on drawings explained in more detail.

Show it!

Figure 1 is a block diagram of an embodiment of the device according to the invention for performing the method according to the invention;

FIG. 2 shows a detailed block diagram of a section of Figure 1;

FIG. 3 shows a circuit diagram of a section according to FIG. 2;

FIG. 4 is a block diagram of a further embodiment the device for carrying out the invention according to the invention Procedure 5

FIG. 5 shows a block diagram of a section according to Figure 4

Figure 6 is a block diagram of a third embodiment of the device according to the invention for Implementation of the method according to the invention;

Figure 7 is a block diagram of a section according to Figure 6)

Figure 8 is a block diagram of a fourth embodiment of the device according to the invention for Implementation of the method according to the invention and

FIG. 9 shows a block diagram of a section according to FIG. 8.

Figure 1 shows a _. Embodiment of the present invention with a working tank 10 in which the electrical Iy tables is carried out. The working tank IO is shown open at the top 1, however, in practice

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a work tank that is closed on all sides can also be used. On a pad located in the working tank 10 14, a workpiece 12 is fixedly arranged. The workpiece is made of electrically conductive material. Opposite to A working electrode 16 is arranged on the workpiece 12 and has an opening 18 which is open to the workpiece 12 is opposite and allows the passage of an electrolyte. A narrow working gap 20 of size g is located between the workpiece 12 and the working electrode 16. The size g of the working gap 20 can preferably 0.1 mm to 0.5 mm. A tank 22 with an electrolyte 23 is also provided. The electrolyte 23 can for example consist of salt water; however, it can also be a different one depending on the material of the workpiece 12 Electrolyte can be used. The specific resistance of the electrolyte 23 is indicated below with the letter

O are designated. A pump 24 and a pipe 25 are also provided, one end of which is connected to the inlet of the pump 24 and the other end of which is immersed in the electrolyte 23. A pipe 26 is provided for connecting the outlet of the pump 24 and the opening 18, so that the electrolyte 23 can be conducted from the pump 24 into the opening 18, as shown by the arrow in FIG. 1, and then through the area of the working gap 20 can flow. The electrolyte 23 fed into the working gap 20 is under a pressure of sB * 10 to 20 kg / cm so that it can flow through the working gap at high speed. Furthermore, a flow meter 27 is provided in the drilling line 26. For example, a conventional electromagnetic type flow meter can be used to measure the flow rate Qe of the electrolyte fed into the gap 20. The flow meter generates an electrical signal Ve proportional to the flow. A pipe 28 connects the outlet of the pump

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24 with the tank 22 and allows an overflow of the electrolyte 23 from the pump 24. In the branch line or An adjustable valve 29 is provided in the bypass 28. At the bottom of the working tank 10, a pipeline 32 opens which, on the other hand, is immersed in the tank 22. Thus, after flowing through the gap 20, the Electrolyte accumulating at the bottom of the working tank 10 can be returned to the tank 22, as indicated by the arrow shown in FIG.

A three-phase AC power source 34 is provided, which operates at a common frequency. This voltage source is used to provide a constant Output voltage for the three-phase step-down transformer used. This three-phase step-down transformer includes a primary winding 38 in a delta connection and a three-phase saturation choke 42 with output or fiutpütwicklungen 44 * 46 and 48, which the Input or input connections of the primary winding 38 with the three-phase alternating current power source 34 connect »Furthermore, a control coil 50 is provided, which a three-phase full-wave rectifier 52 inductively connected to the output windings 44, 46 and 48. The rectifier 52 is connected to the output terminal of the secondary winding 40 of the step-down transformer and serves for full-wave rectification of three-phase alternating current.

• With the positive DC output terminal of the Three phase full wave rectifier 52 is one line connected and connected to the negative DC output terminal a line 56 is connected. The positive connection lead 54 is connected to the workpiece 12, on the other hand and the negative connection line 56 is on the other hand connected to the working electrode 16. The direct current

of the three-phase full-wave rectifier 52 is preferably designed so that it provides a voltage of, for example, 5 to 20 volts at a current of, for example, 3000 to 5 (000 amperes. - -.

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It can thus be seen that the rectifier 52 supplies a working voltage V via the lines 54 and 56 to the Workpiece 12 and the working electrode 16 applies. The working voltage V causes an electric current in the Working gap 20 and thus an electrolysis of the electrolyte 23. This electrolysis leads to an electrochemical one Dissolving effect on the workpiece ^ being out of the range of the workpiece t2, which is opposite the working electrode 16. material is dissolved out «The electrical Current density J in the working gap 20 is given below as the ratio of the current intensity in the working area to Area of the working area specified «,

In the device according to FIG. 1, there is also a feed 58 provided for the electrode 16 »In the embodiment shown here, the feed 58 is used for movement of the working electrode 16 in the direction of the workpiece 12. However, the invention is not limited to this and a feed can also be provided, which the Workpiece 12 moved in the direction of the working electrode 16. In the embodiment shown, there is a feed rod 60 connected to the electrode 16 and mounted displaceably * so that the electrode 16 towards the workpiece 12 and can be moved away from this, along the peripheral surface a row of teeth is provided for the push rod € 0, which look in the same direction as the feed shaft extends. A pinion meshes with the row of teeth 62 64, which is seated on the rotating shaft of an electric motor 66. The motor 66 is a DC hoist motor or a same Βΐίοκ shunt motor with an armature 68 and a pilot coil 70. A power source 72 is provided to feed the motor 76. The power source 72 supplies a single-phase alternating current of constant voltage and with a common frequency, which is converted into a single-phase full-wave '

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V 13 -

rectifier 74 for rectifying the alternating current

is entered. Line 76 is connected to the positive DC output terminal of rectifier 74 and line 78 is connected to the negative DC output terminal of rectifier 74. The armature 68 of the motor 66 lies between the lines 76 and 78 and the field coil 70 is via a variable Resistance or via a potentiometer 80 to regulate the motor speed connected to lines 76 and 78.

When the armature 68 and the field coil 70 a constant Voltage is applied and when the potentiometer 80 is brought to a predetermined position, so operates the motor 66 rotates at a constant speed and thereby moves the working electrode 60 during the Form ™ or itz process at a constant speed on the workpiece 12 to. As a result, the electric current density J in the working gap 20 increases during the etching or molding process held at a constant value. The feed rate of the working electrode 16 can be changed by changing the Potentiometer resistor 80 can be varied slightly; Through this however, the electric current density J also changes and thus the potentiometer 80 should during the molding or etching of a particular product cannot be altered.

It is also a single phase AC power source 82 with constant voltage and a single-phase full-wave rectifier 84 for full path rectification of the alternating current. . .the power source 82. A connecting line 86 is on the one hand with the positive DC connection of the rectifier 84 connected and on the other hand via the Resistor 88 with the control coil 50 of the saturation choke.

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A connection line 90 is on the one hand with the negative DC connection of the rectifier 84 and on the other hand to the control coil 50. The one labeled Ic and electric current proportional to the DC voltage of the rectifier 84 flows through the control coil 50 and determines the reactance of the output coils 44, 46 and 48 of the saturation reactor »There are two thyristors 92 and 94 are provided and connected in parallel to one another and in the opposite direction and with the _ ', alternating current circuit of the rectifier 84 connected so that they in.den corresponding half cycles of the alternating current source 82 are alternately actuated at a predetermined ignition phase, whereby the desired AC voltage as an input voltage is applied to the rectifier 84.

The ignition phase of the thyristors 92 and 94 can be set by the DC voltage of the rectifier 84 by adjusting the amount flowing through the control coil 50 electric current Ic and by adjusting the reactance of the output coils 44, 46 and 48. the Reactance of the output apules 44, 46 and 48 kmη by varying the input voltage of the three-phase transformer 36, by adjusting the DC voltage of the rectifier 52 and by varying the voltage applied to the working gap 20 Working voltage V can be set »

There is also an ignition device 96 for actuation the tyriators 92 and 94 are provided, »This ignition device comprises a braking circuit for setting the ignition phase the tyriators 9§ and 94. An amplifier 98 is used to amplify the input to the ignition device Signals provided, aoöass ö through the stronger markets Signals of the amplifier 98 the trigger phase of the thyristors 92 and 94 are rarely set »It is also a signal Comparison circuit 100 is provided, the signals of which are input to the amplifier 98.

00 9883/1482

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^ß AD

It must be emphasized that two signals V and Vs in the Signal comparison circuit 100 are input and that the difference between these "two signals going into the amplifier 98 entered .. i voltage represents.

The circuit for generating the signal V, which is input to the comparison circuit 100, will now be described. This circuit includes a circuit 102 for receiving a voltage which is proportional to the working voltage V. As in Figure 2 shown is the circuit 102 between the lines 54 and 56 and includes a potentiometer 104, which lies parallel to the working gap 20. The potentiometer has a connection 106 and the one adjacent to it Voltage V is proportional to the working voltage V. (V = aV). This voltage applied to terminal 106 becomes inputted as signal V to the signal comparison circuit 100.

A circuit for generating the signal Vs to be input to the comparison circuit 100 will now be described. This circuit comprises a circuit 107 for generating a signal (t) which is proportional to the specific resistance 9 of the electrolyte. This signal-generating circuit 107 comprises a high-frequency oscillator 108, the output of which is input to a measuring device 110 for measuring the specific resistance. The measuring device 110 is immersed in the electrolyte 23 located in the tank 22. It must be emphasized that the measuring device 110 for the specific resistance can also be provided in the pipes 25, 26 or 32 and that it can consist of a pair of electrodes of the same predetermined shape and area. The electrodes face each other at a predetermined distance. The electrolyte 23 is located between

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the electrodes. The electrodes can e.g. * hub platinum black exist. The output of the oscillator 1Θ8 is applied to the electrodes and causes a constant current between the Electrodes, even if the resistance of the electrolyte changes. With a constant flow of current between the electrolytes, any change in the specific resistance leads to it o> of the electrolyte 22 to a change in the terminal voltage of the electrodes. Because the distance between the electrodes is kept constant and because the electrode area is also kept constant, the terminal voltage between the electrodes is proportional to the specific Resistance O of the electrolyte 23. The reason for using a high frequency oscillator 108 and that Applying a high frequency voltage to the electrodes is to be seen in the fact that any formation of a voltage or an electromotive force on the electrodes due to polarization is to be prevented.

The voltage (e) between the electrodes of the meter 110 may if due to the high frequency oscillator 108 current flowing through the electrodes are denoted by 1 and the constant by h ^, by the following formula being represented:

e = Ji ₁ i γ (11)

and since the current strength is kept constant, through

«= ^N 2? J ( ^h 2 = ⁿ l *> · < ¹ ' ² >

It is also a signal conversion and amplification circuit 112 is provided, which picks up the signal (s) coming from the measuring device 110 for the specific resistance.

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The output of circuit 112 goes into the signal addition circuit 114 entered. As shown in Figure 2, the signal conversion and amplification circuit 112 includes an amplifier 116, a rectifier 118 and a primary Delay circuit 120. The amplifier 116 is used for amplification of the signal (e) and the rectifier 118 is used for converting the output of the amplifier 116 into a Direct current. The primary delay circuit 120 includes one Input resistor 122, a shunt resistor 126 and a shunt capacitor 128 and is used for smoothing of the output of rectifier 118. The primary delay circuit 120 generates a signal V at the output terminal and this signal is input to the addition circuit 114.

According to FIG. 1, there is also a circuit 1.29 for generation

vw

of a signal -f ^ §) provided. This signal is proportional to the ratio of the gas flow rate im Working gap 20 to the electrolyte flow rate in the working gap 20. The circuit 129 comprises a circuit 130 for generating a signal which is proportional to the flow rate QH of the gas in the working gap 20 is. The amount of gas that is formed in the working gap 20 during the electrolysis of the electrolyte, is proportional to the electrical current strength for the electrolysis of the electrolyte or to the working current strength, which flows through the working gap 20. Therefore, the signal which is proportional to the flow rate QH of the gas is generated indirectly via the work flow. Accordingly, is a conventional DC transformer 132 is provided, which is inductively coupled to the connecting line 54 in order to increase the flow rate of the gas QH to be determined. As shown in Figure 2, two coils 134 and 136 are connected in series with one another and form the inductive coupling of the direct current

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transformer 132. An alternating current source 138 of constant voltage and common frequency is also provided, which at the input of the DC transformer 132, as well as a single-phase full-wave rectifier 140. At the DC, terminals of the rectifier HO leigt a potentiometer 142 with a sliding · YesConclusion 144. A primary delay circuit 148 is for smoothing the direct current. . -. of the potentiometer 142 is provided. The delay circle 148 is connected via a resistor 146 to its input at the output terminal 144. A reversing amplifier 150 is provided to reverse the polarity of the output of the primary delay circuit 148 and produce a signal VH, which is proportional to the gas flow rate QH. Between the primary delay circuit 148 and the inverter gain 150 is a resistor 152 intended. Resistor 154 is in parallel with primary delay circuit 148. A capacitor 156 is connected in parallel with resistor 154 and a resistor 158 in parallel with inverter amplifier 150.

The flow meter 27 generates a signal Ve which is proportional to the flow rate Qe of the means the pump 24 in the working gap 20 is delivered electrolyte 23. The flow rate of the electrolyte 23, which is measured with the flow meter 27, does not refer to the one through the working gap 20 flowing electrolyte but on the electrolyte flowing through the RohrMr device 26. However, since the Rohrlei -.- g device 26 is connected to the working gap 20 is ~ the flow rate in the working gap 20 is proportional to the flow rate of the electrolyte in of the pipeline 26.

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Ea an arithmetic circuit 160 is also provided, to which the signal VH proportional to the gas flow rate QH and the signal proportional to the electrolyte flow rate Qe are input is and which divides the signals and thereby a

VTT

Signal of the form (w ~) generated. This arithmetic circuit 160 is shown in detail in FIG. According to FIG. 3, the arithmetic circuit 160 includes one Servo motor 162 with a red 164, an excitation coil 166 and a control coil 168. An AC power source 170 of constant voltage, which operates at a usual frequency, is connected to the through a capacitor 172 Excitation coil 166 is connected and supplies an alternating current of constant voltage. The armature 164 of the servo motor 162 rotates according to the magnetic field, which surrounds the same due to the electric current flowing through the excitation coil 168. A first potentiometer 174 and a second potentiometer 176 have

-Connections 178 bew, 180, which both rotate due to a lock: 'rotate with the same angle Ige speed. The taps 178 and 180 are rotated in unison by the armature 164. A direct current source 182 with constant voltage is provided, which supplies a direct current of constant voltage to the first potentiometer 174. A signal comparison circuit or comparator 184 is provided for comparing the signal Ve with the signal coming from the terminal 178. An amplifier 186 amplifies the output signal of the signal comparison circuit 184. A further signal comparison circuit 188 is also provided, which compares the signal VH with the signal of the "" _ '. Terminal 180. An amplifier 190 serves to amplify the signal of the signal comparison circuit 188. The • sMgnal of this amplifier on the one hand forms the

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Signal of arithmetic circuit 16O and is on the other hand fed to the second potentiometer 176.

If the angle of rotation of the first potentiometer 174 is denoted by $ · , then the following applies to the signal Vy appearing at the terminal 178: Vy = 61θ , where G1 is a constant. If the servomotor 162 is rotated in such a way that the signal Vy becomes equal to the signal Ve (Ve = Vy), then θ is equal to Ve / G1. The second potentiometer 176 has the same angle of rotation as the first potentiometer. If one designates the signal appearing at the output of the second potentiometer with Vx and the signal of the amplifier 190 with eo, then the following formula applies

Vx = Gp6o ^ = WT Ve eo (G2 is a proportionality constant ).

If the gain of amplifier 190 is denoted by A1, then the following applies

(VH - Vx) A1 = eo ^

(VH * H Ve eo) Al = eo

eo = A 1 VH

1 + G2 Ve A1

If the gain A1 is chosen to be sufficiently greater than 1 , then the following applies

eo =

and if it is further assumed that the relationship G1 / G2 = 1 applies, then the value VH / Ve results for the output eo,

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The gain of the amplifier 186 μηά 190 of the arithmet: 'Ischen Circuit 130 is at such a high level Value set that the relationship according to formula (13) is applicable. That . ^ ignal of the arithmetic circuit 16O is input to the addition circuit 114 and there is also a signal coming from the amplifier 120 added. The adder circuit 114 includes a signal conditioning point 192 (SignalJunction), as shown in Figure 2. The addition circuit 114 further includes a Resistor 194 between signal junction 192 and the terminal of converter and gain circuit 112. Resistor 196 is between the Signal Union 192 and the. Output connection of the arithmetic circuit 160 is provided. The resistance value of the resistor 194 is denoted by Ri and the Resistance of resistor 196 with Rg, addition circuit 114 further includes a reversing amplifier 198 and a shunt resistor in parallel with amplifier 198 200, the resistance of which is Rf. The gain of the inverting amplifier 198 becomes large enough chosen, so that. Signal from the reverse amplifier 198, expressed by Vz, satisfies the following formula:

Φ} -

When the resistance values of resistors 194 and 200 den have the same value and thus the relationship Rf = Ri applies, and if the relation Rf / Rg = k also applies, then the following relation results:

Vz «- [vf + k

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It also has a reversal stop 202 for reversing the Signals Vz provided. Inverter circuit 302 includes an inverting amplifier 203 and one connected thereto Input resistor 204 and a feedback resistor 206 for generating a 'signal of the value - Vz. Ba ^ Signal - Vz is then passed into the adder circuit 208 entered.

There is also a circuit 210 for generating a signal - Vd ^{1 is} provided. The signal - Vd ^{1 is} proportional to the electrolytic voltage Vd and thus the working ^{voltage Vj (Vd 1} * aVl). The circuit 210 for generating a signal comprises a direct current source 212 and a potentiometer 214. The potentiometer 214 comprises a 4 ** - circuit 216 for providing the signal V Vd ¹ . This signal is then input to the addition circuit 208. As shown in Figure 2, the addition circuit 208 includes a signal combination 218 and an inverting amplifier 220. The addition circuit 208 further includes a variable resistor or potentiometer 222 having a resistance value RJ. This potentiometer lies between the signal junction 21> 8 and the / 4 »circuit of the reversing circuit 2Q2. A resistor 224 with the resistance value Rk is located between the signal junction 218 and the / terminal of the circuit 210 for generating a signal *. The amplifier 220 has a high gain and a resistor 226 with a resistance value Rh is parallel to the amplifier 220.

The output of amplifier 220 serves as signal Vs. entered into the comparison circuit or comparator 100 will. The signal Vs obeys the following formula *.

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Vs = -

where using the formula (14) for Vs, the following relationship can be written

w.

If the resistances are set or chosen so that the relationships Rh '\. . Rk = 1 and - || = A ¹ apply, the following relationship results *

Vs = A fv <> + k ⁽ | §) j + Vd (15)

In the described embodiment, the device controlled in such a way that the signal V «is always equivalent to a signal Vs. If at any time the signal

V is greater iiii dae 'signal Vs. the ignition device works 96 while increasing the ignition phase of the two thyristors 92 and 94 across the amplifier 98 by a value equal to the difference between

V and Vs is. This in turn reduces the equation voltage of the rectifier 84. This has the consequence that the electric current Ic, which.through the control coil 50 of the saturation reactor flows, decreases so that the reactance of the output coils 44, 46 and 48 increases and the working voltage V decreases. When the working tension

V decreases, the signal V projected thereto likewise decreases until it is equal to the signal Vs. If the signal V is smaller than the signal Vs, the reverse process takes place and the operating voltage V is increased while the signal V is increased at the same time until it becomes equal to the signal Vs. If the relation Vs is equal to V ¹ , the following relation is obtained:

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_ 24 - Ψ - A «j Vp" + k (^ f) j + Vd · (16)

If one compares the relationship according to (16) with the relationship according to formula (10), it can be seen that when the working voltage V is substituted by the signal V ¹ · (V = aV) the first and second terms on the right-hand side of the relationship according to formula (16) must be greater by the factor (a) than the corresponding terms on the right-hand side of the relationship according to formula (10).

If the constant A 'is determined as the ratio R ^ / R;), the relationship A ¹ = aA can be easily realized. The signal Vd ¹ is selected as described above in such a way that the relationship Vd ¹ = aVd applies. It can thus be seen that when the relationship according to formula (10) is fulfilled, the working voltage V can be controlled in the manner described.

In an alternative embodiment, the operating voltage V is controlled in such a way that the relationship according to the formula (9) is fulfilled. In such an embodiment, it is advantageous that the circuit 210 for signal generation and the addition circuit 208 are omitted so that the signal - Vz or the output which, if reversed of the polarity thereof is obtained as the signal Vs in the signal comparison circuit or comparator 100 is input according to the relation (14).

In the following, the advantageous or the special effects of the embodiment according to FIGS. 1 and 2 will be described in more detail to be discribed. The QH / Qe value varies as the working range changes as the etching progresses. If the working area increases as the etching progresses, a conical hole can be etched in, for example.

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If the specific resistance P of the electrolyte is 3 Si cm, the electric current density J is 100 amperes / cm, the electrolysis voltage Vd is 1.5 volts, the flow rate Qs of the electrolyte is 70 l / min, the constant K the relationship according to formula (8) has the value 18, the gas flow rate Qr, the value 7 l / min, and the working voltage V has the value 7.5 volts, then the width of the working gap results from the relationship according to equation (8) in the following way:

r _ 7t5 - 1.5 = 0 »0125 cm

100 (3 + 1%) = 0, 125 poss

On the other hand, if the term (§ ») is not taken into account then follows the following value for the working gap in accordance with the relationship of the formula (4);

7.5-1.5

g = = 0, 2 ram.

100 X 3

It can thus be seen that, according to the above formula, if the term QH is neglected, an error of 0.075 mm occurs.

The following is an example according to the present invention will now be shown in which the work area increases and the working gap does not vary. If e.g. the working current increases by a factor of 2, then the gas flow rate QH doubles; i.e. in the above example QH now assumes the value 14 l / min. The working voltage V results from the equation (10) in the following way

+ 18 (^) j +1.5

- 26 -00988371492

sa: original

and since the relationship A ». gJ «0.0125 om 100 amperes / cm = 1.25 amperes / cm, then one obtains the value for V:

V «1.25 x 6.6 + ■ 1.5 * 9.75 volts.

In this pail the width of the working gap g in received in the following way «

9.75 '- 1.5 . = 0.0125 cm

7ü; ■ .. ■ .. * 0.125 mm.

₊
¹⁰ 7ü

You can see that the value g is kept constant, Ibt contrasts with the case when the ratio QH / Qe is neglected

In the following, with reference to FIGS. 4 and 5 Another embodiment of the present invention will be described. In this embodiment a further pipeline 300 is provided, which between the opening 1Θ and the flow meter 27 in the pipe 26 opens and which is on the other hand connected to a gas container 302 «The gas container 302 may contain, for example, compressed air or carbon dioxide. There is a control valve 304 in the pipeline 300 provided. This is used to control the amount of gas, which through the pipe 26 through the Electrolyte 23 is admixed. The gas in the gas container 302 is added because it has a higher pressure has, than the electrolyte 23 at the junction of the pipes 26 and 300. With such an arrangement, scratches in the surface of the workpiece be avoided, as in the TJ, S. Patent No. 3,284,327. In this embodiment, the Flow rate of the gas in the working gap 20 from the sum of the size QH generated by electrolysis Gas flow and the size QG of the gas

00-9883 / 1492 " ²⁷ "

BATH

ter 302 coming through the working gap 20 flowing gas. This gives equation (8) for the width g of the working gap the following form:

V - Vd
g = -

From this it follows for the working voltage V:

_{V = A +} . _K (Si + flS) '"+ Vd (18).

Furthermore, in this embodiment, a signal transmitter 306 is provided, which is one of the gas container to the working gap 20, the amount of gas flowing is proportional Signal generated * As shown in Figure 5, the Signal generator 306 a DC voltage source 308 with constant voltage and a potentiometer 310, which is connected to the voltage source 308 and which is on Output terminal 312 of the potentiometer 310 a signal generated, which is proportional to the amount of gas QG coming from the container 302 * The signal Vg is then transmitted via a Resistor 314 is fed to the input of amplifier 150 in circuit 130. Then the signal VH + Vg in entered the arithmetic circuit 160.

In this embodiment, the term QH + QG / Qe is variable and the operating voltage V changes accordingly to compensate for the change in the term and to change the width g of the working gap avoid.

In the following, with reference to FIGS. 6 and 7, another alternative embodiment of the present invention will be explained. In this embodiment, means are provided around the term QH / Qe

009883 / U92. - 28 -

to keep constant during the etching process. In figure 6, a control device 400 is provided, which the Control valve 29 in the secondary line or overflow line 28 controls automatically. The controller 400 includes a constant pressure pressurized air source 402, one Pipeline 404 for applying air pressure to the Control valve 29. A pressure regulator 406 is provided in the pipeline 404. The pressure regulator 406 responds to input electrical signals and reduces the air pressure generated by the pressure source 402. In this control device 400, the control valve 29 changes the valve opening depending on the pressure exerted on it. In this way, the valve opening is controlled by the pressure regulator 406. The change in the valve opening of the control valve 29 reduces or increases the amount Qe of the electrolyte which is entered into the working gap £ 0 will. If, for example, the valve opening of the regulating valve 29 is increased, then the overflow line increases 28 flowing amount of electrolyte in a corresponding manner and the flow rate Qe of the in the Working gap 20 entered electrolyte is reduced. On the other hand, when the valve opening of the control valve 29 is decreased, the flow rate is increased Qe of the electrolyte introduced into the working gap 20. These increases or decreases the electrolyte flow rate keep the Term QP / Qe at a constant value.

A conventional electric motor can also be provided in the control device 400 and the control valve 29 can be designed such that the valve opening is changed in accordance with the rotation of the engine. The engine can be designed to rotate in response to electrical signals.

-29 009883 / 1.492

The device according to FIG. 6 further comprises a control circuit 410 for providing a suitable electrical signal for the pressure regulator 406. If the control device 400 uses an electric motor, the output signals of the control circuit 410 are used to control this motor. The control circuit 410 comprises a circuit to generate a signal which is proportional to the ratio QH / Qe. In this embodiment, the second signal generator circuit 129 for generating a signal according to the ratio VH / Ve is the same as that described with reference to FIGS. Since the signal is proportional to the value QH / Qe according to the ratio VH / Ve, this signal is input into the signal comparison circuit or comparator 412 of the control circuit 410. The control circuit 410 further comprises means 414 for generating a standard signal, a standard signal (VH / Ve) s being input to the comparator 412. The device 414 for generating a standard signal comprises, according to FIG. 7, a direct current source 416 of constant voltage and a potentiometer 418 connected to it. The standard signal (VH / Ve) s * appears at the output terminal 420 of the potentiometer 418. which is equal to the difference + Δ Ve between the signal Vfl / Ve and the signal (VH / Ve) s. The control circuit 410 further comprises a further signal generator 422. The signal generator 422 comprises a direct current source 424 of constant voltage and a potentiometer 426 connected to it for generating a standard signal Ves for the flow velocity. This signal appears at the output terminal 428 of the potentiometer 426. The signal - Δ Ve at the output of the signal comparison circuit or comparator 42 and the standard signal Ves for the flow rate are input to an addition circuit or summer 430,

009883 / U92

so a signal Ves - A Ve for controlling the pressure regulator 406 is generated. Summer 430 includes; As shown in Figure 7, an amplifier 432, a resistor 434 in parallel with the amplifier 432, a resistor 436 between the amplifier 432 and the signal comparison circuit or comparator 412, a resistor 438 between the amplifier 432 and the signal generator 422. The signal ί / Ι Ve and the signal Veβ are then added at 440.

When the amount of gas generated in the working gap 20 increases, the signal VH / Ve becomes greater than the signal (VH / Ve) s. The signal coming from the signal comparison circuit or comparator 412 then has a positive sign + ^ Ve. The signal Ves hh J Ve is then generated in the summer 430 and causes an increase in the electrolyte content in the working gap 20. If the amount of gas generated in the working gap 20 decreases, the signal VH / Ve becomes smaller than the signal (VH / Ve) s. Then the negative signal - "/ J Ve is generated at the comparison circuit or comparator 412 and the summer or addition circuit 430 generates a signal Ves -Ji Ve. This will reduce the amount of electrolyte in the working gap. degraded. Thus, the ratio QH / Qe is controlled to keep a constant value. The device described is particularly suitable in the case of changing work surfaces, such as for example for etching a hole. During such an etching, the ratio QH / Qe is kept at a constant value when the working area changes. It can also be seen that with this device the feed rate must be kept constant during the etching process, so that the electrical current density J in the working gap is also kept at a constant value.

- 31 009883 / U92

However, if the etching process continues and if, for example, the working area increases, the amount of gas generated in the working gap 20 is increased because the current density J is kept constant. In the previously known or proposed devices, the ratio QH / Qc was increased. Here, the Itzen the "tool / .Stückes-is not performed uniformly / This has _r to the result that the working gap is short-circuited 20 wherein sparks are formed. This sparking caused damage to the workpiece held 12. If however, the ratio QH / qg constant If, as in the present case, these disadvantages do not occur and the etching process can be carried out without damaging the workpiece.

In the device described there, the ratio QH / Qe is kept constant during the etching process in order to keep the width of the working gap g constant. This is done by inputting the signal VH / Ve, which is proportional to the ratio QH / Qe, into the control circuit for the operating voltage V. According to FIGS in the embodiment according to FIG. 2. The circuit for generating a standard signal is designed so that a constant signal appears at the output of the arithmetic circuit 160. Although the signal VH / Ve is essentially constant, it is difficult to keep the width g of the working age constant without inputting the signal VH / Ve into the control circuit for the working direction V. This can be seen from the fact that an error occurs when the term fP + K (QH / Qe)? in formulas 7 and 8 becomes zero. Thus, when the specific resistance γ is changed, changes in the term / f + X (QH / Qe)] · largely depend on the existence or nonexistence of the term (QH / Qe).

009883/1492 -5? -

BATH

-μ-

Furthermore, with the device according to FIGS. 6 and 7 the operating voltage V can be controlled so that the Equation (9) is satisfied. In this case, the signal generator 210 and the adder circuit or summer 208 omitted.

According to FIGS. 8 and 9, in the embodiment According to FIGS. 6 and 7, a further embodiment can be provided by providing a gas container 302. In FIGS. 8 and 9 are the line 300, the gas container 302, the control valve 304 and the signal transmitter 306 the structure and effect of the corresponding components in the embodiment according to the figures 4 and 5 the same. In this case the term QH + QG / Qe is kept constant.

In the various embodiments according to the present invention, a signal was provided in each case whose Value is proportional to the values QH / Qe, QH + QG / Qe. However, the invention is not limited in this respect. and it applies in a similar way to the inverse or reciprocal values.

The described embodiments of the present Invention generate a signal which is proportional to the ratio of the value which the flow rate of the electrolyte in by electrolysis of the electrolyte corresponds to the working gap and the value corresponding to the amount of gas flowing through the working gap Electrolytes. This signal is fed into the control system for the working voltage so that the width of the working gap is kept exactly at a constant value during the Xtz process, whereby increased ' Etching accuracy is achieved.

- 33 -009883 / U92

BATH ORIGINAL

By introducing a mixture of electrolyte and gas into the working gap area, scratches and other Damage to the workpiece in an advantageous manner avoided and at the same time the working gap can be precisely controlled, which is extremely precise machining enables.

- Expectations -

009883 / U92

BATH ORIGINAL

Claims (1)

PATENT CLAIMS 1. Process for electrolytic etching of a workpiece by arranging a working electrode leaving a narrow working gap opposite a workpiece, introducing an electrolyte into the working gap, Electrolyzing the electrolyte in the working gap by applying a working voltage and causing a relative movement between the workpiece and the Working electrode approaching the same, characterized in that the Relative movement is carried out at a constant speed and that the working voltage as the sum of one Voltage is controlled, which is proportional to the resistivity of the input into the working gap Is electrolyte and a voltage, which is proportional to the ratio of the amount of electrolyte in the working gap to the amount of gas in the working gap and preferably a voltage that corresponds to the electrolysis voltage is equivalent to* 2. The method according to the main claim, characterized., that the amount of gas in the working gap consists of gas, which in the electrolysis of the Electrolyte is formed in the working gap, and preferably additionally from gas, which is in the working gap entered electrolyte is admixed. 3. A method according to claim 2, characterized in that the ratio of the electrolyzer tmenge held in the working gap at a constant value in the working gap and amount of gas · A. Do one or more of the foregoing. Claims, thereby marked ^! that with at least one machining of a workpiece 009883 / U9-2 - 2 - BATH ORIGINAL the relative movement is kept constant during the entire etching treatment. 5- Method according to one or more of the preceding Claims, characterized in that that when performing the etching on a large number of workpieces, the relative speed during all Etching is kept constant. 6. Device for electrolytic etching of a workpiece for carrying out the method according to one of the preceding Claims with a working electrode arranged with a narrow working gap opposite a workpiece, a device for conveying an electrolyte in the working gap, a power source for the electrolysis of the electrolyte in the working gap and with a feed to bring about a relative movement between the workpiece and the working electrode Approximation of the same, thereby g e k e η η ζ ei c h η e t that a control device is provided for controlling the working voltage as the sum of one Voltage, which is proportional to the specific resistance of the electrolyte introduced into the working gap 20 14 and a voltage which is proportional to the The ratio of the amount of electrolyte in the working gap 20 to the amount of gas in the working gap 20 is and preferably in addition a voltage which corresponds to the electrolyzing voltage. / Device according to claim 6, characterized g e k e η η ζ e i without t that the control device comprises a first signal generator (102) for generating a first signal which is proportional to the working voltage, a second signal generator (110) for generating a second signal which is proportional to the specific resistance of the in the working gap (20) - 3 009883 / 1A92 " si entered electrolyte, as well as a third signal generator (129) for generating a third signal, which is the ratio of the amount of electrolyte in the working gap is proportional to the amount of gas in the working gap, and preferably a fourth signal generator for generation one of the electrolysing voltage proportional fourth signal and wherein a control device for the Working voltage is provided by which the first signal is equal to the sum of the second and third signals will. S device according to claim /, characterized in that that the second signal transmitter is a measuring device (110) for measuring the specific resistance having, which comprises two opposing electrodes, between which the electrolyte flows and wherein a power source (108) for generating a predetermined electrical current in the measuring device (110) is provided so that the second signal is generated according to the voltage applied to the two electrodes will. 9- device according to claim £, characterized in that that the current source (108) is a high frequency oscillator. 10 · Device according to one of claims 6 to 9, characterized in that the third signal transmitter (129) a first measuring device (27) for determining the amount of electrolyte in the working gap (20) and a second measuring device for determining the amount of gas in the working gap (20) and wherein a device (160) is provided, which forms the quotient from the output signals of the measuring devices and a third, this Forms the quotient proportional signal. - 4 009883/1492 BATH ORIGINAL //. Device according to Claim./ö, characterized in that • k e η η ζ e i c h η e t that the first measuring device (27) is a flow meter, which is in a supply pipe (26) for the electrolyte. /·?.· "Device according to claim / O or //, characterized in that the second measuring device determines the electrical current strength in the working gap (20). / 3. Device according to one of Claims 1 to 2, characterized in that a device (300 to 304) is provided for adding gas to the electrolyte to be introduced into the working gap (20). Device according to one of claims ff bis / 3, _T ge characterized by control means for controlling the ratio of amount of electrolyte in the working gap to gas flow in the working gap (20). 009883 / U92 Blank page